refactor(codemode): make functions program objects with name and length

Co-authored-by: nexxeln <95541290+nexxeln@users.noreply.github.com>

packages/ai/AGENTS.md

@@ -122,13 +122,14 @@ Keep provider facades small and explicit:
 
 ### Provider Package Entrypoints
 
-Catalog-selected native providers use package-like export paths from `@opencode/ai`. They are internal entrypoints in one npm package, not separately published provider packages. Every entrypoint implements `ProviderPackage.Definition` and exposes `model(modelID, settings)`, where settings are serializable provider configuration plus common `headers`, `body`, and `limits` overlays.
+Catalog-selected native providers use package-like export paths from `@opencode/ai`. They are internal entrypoints in one npm package, not separately published provider packages. Every entrypoint implements `ProviderPackage.Definition` and exposes `model(modelID, settings)`, where settings are one flat serializable object: the connection keys the entrypoint declares (`apiKey`, `baseURL`, `region`, …), the common `headers` and `body` overlays, and the protocol's request options (`reasoningEffort`, `thinking`, …) side by side. Each entrypoint destructures its own connection keys and passes the rest to the route as `providerOptions`; there is no nested `providerOptions` at the entrypoint.
 
 ```ts
 import { model } from "@opencode/ai/providers/openai/responses"
 
 const selected = model("gpt-5", {
   apiKey,
+  reasoningEffort: "high",
 })
 ```
 

packages/ai/src/protocols/anthropic-messages.ts

@@ -1708,7 +1708,10 @@ export const transport = <
 }
 
 function requiredBetaHeaders(body: Pick<AnthropicMessagesBody, "messages" | "context_management" | "thinking">) {
-  const betas: string[] = []
+  // Always request interleaved thinking. The API accepts the header on any
+  // model and ignores it where unsupported, while manual-thinking models need
+  // it for thinking between tool calls.
+  const betas: string[] = ["interleaved-thinking-2025-05-14"]
   const requestsCompaction = (body.context_management?.edits.length ?? 0) > 0
   const replaysCompaction = body.messages.some((message) =>
     message.content.some((block) => block.type === "compaction"),

packages/ai/src/protocols/open-responses.ts

@@ -1,4 +1,4 @@
-import { Effect, Option, Schema } from "effect"
+import { Effect, Option, Schema, SchemaGetter } from "effect"
 import type { Content } from "@opencode/schema/tool"
 import { HttpTransport } from "../route/transport/index.js"
 import { Protocol } from "../route/protocol.js"
@@ -325,9 +325,8 @@ export const StreamItem = Schema.StructWithRest(
 export type StreamItem = Schema.Schema.Type<typeof StreamItem>
 export type OutputItem = StreamItem & { readonly id: string }
 
-// The Responses schema puts streaming error details at the top level and
-// response failures under `response.error`. WebSocket failures use an
-// event-level `error` envelope, so accept all three shapes here.
+// Responses-compatible providers put streaming error details at the top level or
+// under `error`, and response failures under `response.error`. Accept all three shapes.
 // https://www.openresponses.org/specification
 const OpenResponsesErrorPayload = Schema.Struct({
   type: optionalNull(Schema.String),
@@ -401,6 +400,17 @@ export const Event = Schema.StructWithRest(
     headers: Schema.optional(Schema.Unknown),
   }),
   [Schema.Record(Schema.String, Schema.Unknown)],
+).pipe(
+  Schema.decode({
+    decode: SchemaGetter.transform((event) => {
+      if (event.type !== "error" || event.error != null) return event
+      const { code, message, param, ...rest } = event
+      if (code === undefined && message === undefined && param === undefined) return event
+      // Flat errors (for example, Meta's) can also arrive through generic Responses endpoints.
+      return { ...rest, error: { code, message, param } }
+    }),
+    encode: SchemaGetter.passthrough(),
+  }),
 )
 export type Event = Schema.Schema.Type<typeof Event>
 export type NormalizedEvent = Event & { readonly item?: OutputItem | null }

packages/ai/src/provider-package.ts

@@ -1,6 +1,10 @@
 import type { LanguageModel, ProviderOptions } from "./schema/index.js"
 import type { CompactionOperations } from "./route/client.js"
 
+/**
+ * Flat, serializable settings for `model(modelID, settings)`. Each entrypoint declares the connection keys it
+ * reads; every other key is a request option for the route's protocol.
+ */
 export interface Settings extends Readonly<Record<string, unknown>> {
   readonly baseURL?: string
   readonly headers?: Readonly<Record<string, string>>

packages/ai/src/providers/alibaba.ts

@@ -1,3 +1,4 @@
+import { Struct } from "effect"
 import type { ProviderPackage } from "../provider-package.js"
 import { AlibabaChat } from "../protocols/alibaba-chat.js"
 import { AlibabaMessages } from "../protocols/alibaba-messages.js"
@@ -6,7 +7,7 @@ import { AuthOptions, type AtLeastOne, type ProviderAuthOption } from "../route/
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
 import { Framing } from "../route/framing.js"
-import { ProviderID, ToolDefinition, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, ToolDefinition, type ModelID } from "../schema/index.js"
 
 export const id = ProviderID.make("alibaba")
 
@@ -34,9 +35,9 @@ export type Config = Location &
     readonly providerOptions?: ChatOptionsInput | MessagesOptionsInput | ResponsesOptionsInput
   }
 export type Settings<Options = ChatOptionsInput> = Location &
-  ProviderPackage.Settings & {
+  ProviderPackage.Settings &
+  Options & {
     readonly apiKey?: string
-    readonly providerOptions?: Options
   }
 
 const hosts = new Map<string, string>([
@@ -82,8 +83,13 @@ export const configure = (input: Config) => {
         ? hosts.get(region)
         : `${workspaceID}.${region}.maas.aliyuncs.com`
   if (baseURL === undefined) {
-    if (region === undefined) throw new Error("Alibaba requires region or baseURL")
-    if (host === undefined) throw new Error(`Alibaba region ${region} requires workspaceID or baseURL`)
+    if (region === undefined)
+      throw new ProviderConfigurationError({ provider: id, message: "Alibaba requires region or baseURL" })
+    if (host === undefined)
+      throw new ProviderConfigurationError({
+        provider: id,
+        message: `Alibaba region ${region} requires workspaceID or baseURL`,
+      })
   }
   const opts = { ...rest, auth: AuthOptions.bearer(input, ["DASHSCOPE_API_KEY", "ALIBABA_API_KEY"]) }
   const common = { ...opts, endpoint: { baseURL: baseURL ?? `https://${host}/compatible-mode/v1` } }
@@ -115,7 +121,11 @@ export const responsesModel: ProviderPackage.Definition<
 
 function fromSettings(input: Settings<Config["providerOptions"]>) {
   const { body, ...rest } = input
-  return configure({ ...rest, http: body === undefined ? undefined : { body } })
+  return configure({
+    ...rest,
+    http: body === undefined ? undefined : { body },
+    providerOptions: Struct.omit(rest, ["apiKey", "baseURL", "headers", "region", "workspaceID"]),
+  })
 }
 
 export const webSearch = () => hostedTool("web_search", "Search the web with Alibaba's hosted search tool.")

packages/ai/src/providers/amazon-bedrock-mantle.ts

@@ -4,7 +4,7 @@ import type { ProviderPackage } from "../provider-package.js"
 import { OpenAIChat } from "../protocols/openai-chat.js"
 import { OpenResponses } from "../protocols/open-responses.js"
 import { BedrockAuth, type Credentials } from "../protocols/utils/bedrock-auth.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import { withOpenAIOptions, type OpenAIProviderOptionsInput } from "./openai-options.js"
 
 export const id = ProviderID.make("amazon-bedrock")
@@ -23,16 +23,16 @@ export type Config = RouteDefaultsInput & {
   readonly providerOptions?: OpenAIProviderOptionsInput
 }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly auth?: "bearer" | "sigv4"
-  readonly baseURL?: string
-  readonly credentials?: Credentials
-  readonly profile?: string
-  readonly region?: string
-  readonly topP?: number
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly auth?: "bearer" | "sigv4"
+    readonly baseURL?: string
+    readonly credentials?: Credentials
+    readonly profile?: string
+    readonly region?: string
+    readonly topP?: number
+  }
 
 const responsesRoute = Route.make({
   id: "bedrock-mantle-responses",
@@ -79,9 +79,12 @@ const defaults = (input: Config) => {
 
 export const configure = (input: Config = {}) => {
   if (input.auth === "bearer" && input.apiKey === undefined && process.env.AWS_BEARER_TOKEN_BEDROCK === undefined)
-    throw new Error("Amazon Bedrock Mantle bearer auth requires apiKey")
+    throw new ProviderConfigurationError({ provider: id, message: "Amazon Bedrock Mantle bearer auth requires apiKey" })
   if (input.auth === "sigv4" && input.apiKey !== undefined)
-    throw new Error("Amazon Bedrock Mantle SigV4 auth does not accept apiKey")
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "Amazon Bedrock Mantle SigV4 auth does not accept apiKey",
+    })
   const configuredResponsesRoute = configuredRoute(responsesRoute, input)
   const configuredChatRoute = configuredRoute(chatRoute, input)
   const modelDefaults = defaults(input)
@@ -105,18 +108,29 @@ export const configure = (input: Config = {}) => {
 
 export const provider = configure()
 
-const fromSettings = (settings: Settings) =>
+const fromSettings = ({
+  apiKey,
+  auth,
+  baseURL,
+  body,
+  credentials,
+  headers,
+  profile,
+  region,
+  topP,
+  ...providerOptions
+}: Settings) =>
   configure({
-    apiKey: settings.apiKey,
-    auth: settings.auth,
-    baseURL: settings.baseURL,
-    credentials: settings.credentials,
-    generation: settings.topP === undefined ? undefined : { topP: settings.topP },
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    profile: settings.profile,
-    providerOptions: settings.providerOptions,
-    region: settings.region,
+    apiKey,
+    auth,
+    baseURL,
+    credentials,
+    generation: topP === undefined ? undefined : { topP },
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    profile,
+    providerOptions,
+    region,
   })
 
 export const chatModel: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (

packages/ai/src/providers/amazon-bedrock.ts

@@ -1,6 +1,6 @@
 import type { RouteDefaultsInput } from "../route/client.js"
 import type { ProviderPackage } from "../provider-package.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import * as BedrockConverse from "../protocols/bedrock-converse.js"
 import type { BedrockCredentials } from "../protocols/bedrock-converse.js"
 import { BedrockAuth } from "../protocols/utils/bedrock-auth.js"
@@ -39,8 +39,9 @@ const bedrockBaseURL = (region: string) => `https://bedrock-runtime.${region}.am
 const configuredRoute = (input: Config) => {
   const { apiKey, auth, credentials, profile, region, baseURL, ...rest } = input
   if (auth === "bearer" && apiKey === undefined && process.env.AWS_BEARER_TOKEN_BEDROCK === undefined)
-    throw new Error("Amazon Bedrock bearer auth requires apiKey")
-  if (auth === "sigv4" && apiKey !== undefined) throw new Error("Amazon Bedrock SigV4 auth does not accept apiKey")
+    throw new ProviderConfigurationError({ provider: id, message: "Amazon Bedrock bearer auth requires apiKey" })
+  if (auth === "sigv4" && apiKey !== undefined)
+    throw new ProviderConfigurationError({ provider: id, message: "Amazon Bedrock SigV4 auth does not accept apiKey" })
   const resolvedRegion = BedrockAuth.resolveRegion(input)
   return BedrockConverse.route.with({
     ...rest,

packages/ai/src/providers/anthropic-compatible.ts

@@ -3,7 +3,7 @@ import { AnthropicMessages } from "../protocols/anthropic-messages.js"
 import { Auth } from "../route/auth.js"
 import type { ProviderAuthOption } from "../route/auth-options.js"
 import type { RouteDefaultsInput } from "../route/client.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 
 export type AnthropicOptionsInput = AnthropicMessages.OptionsInput
 export type AnthropicProviderOptionsInput = AnthropicMessages.ProviderOptionsInput
@@ -19,13 +19,13 @@ export type Config = RouteDefaultsInput &
   }
 
 export type Settings = ProviderPackage.Settings &
+  AnthropicMessages.ProviderOptionsInput &
   (
     | { readonly apiKey?: string; readonly authToken?: never }
     | { readonly apiKey?: never; readonly authToken?: string }
   ) & {
     readonly baseURL: string
     readonly provider?: string
-    readonly providerOptions?: AnthropicMessages.ProviderOptionsInput
   }
 
 export const routes = [AnthropicMessages.route]
@@ -36,8 +36,12 @@ const auth = (input: ProviderAuthOption<"optional">) => {
 }
 
 export const configure = (input: Config) => {
-  if (!input.baseURL) throw new Error("Anthropic-compatible providers require a baseURL")
   const provider = input.provider ?? "anthropic-compatible"
+  if (!input.baseURL)
+    throw new ProviderConfigurationError({
+      provider: ProviderID.make(provider),
+      message: "Anthropic-compatible providers require a baseURL",
+    })
   const { provider: _, baseURL, apiKey: _apiKey, auth: _auth, ...rest } = input
   const route = AnthropicMessages.route.with({
     ...rest,
@@ -59,17 +63,20 @@ export const provider = {
 
 export const model: ProviderPackage.Definition<Settings, AnthropicMessages.ProviderOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, authToken, baseURL, body, headers, provider, ...providerOptions },
 ) => {
-  if (settings.apiKey !== undefined && settings.authToken !== undefined)
-    throw new Error("Anthropic-compatible apiKey cannot be combined with authToken")
+  if (apiKey !== undefined && authToken !== undefined)
+    throw new ProviderConfigurationError({
+      provider: ProviderID.make(provider ?? id),
+      message: "Anthropic-compatible apiKey cannot be combined with authToken",
+    })
   return configure({
-    ...(settings.authToken === undefined ? { apiKey: settings.apiKey } : { auth: Auth.bearer(settings.authToken) }),
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    provider: settings.provider,
-    providerOptions: settings.providerOptions,
+    ...(authToken === undefined ? { apiKey: apiKey } : { auth: Auth.bearer(authToken) }),
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    provider,
+    providerOptions,
   }).model(modelID)
 }
 

packages/ai/src/providers/anthropic.ts

@@ -2,7 +2,7 @@ import type { RouteDefaultsInput } from "../route/client.js"
 import { Auth } from "../route/auth.js"
 import type { ProviderAuthOption } from "../route/auth-options.js"
 import type { ProviderPackage } from "../provider-package.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import { AnthropicMessages } from "../protocols/anthropic-messages.js"
 import { AnthropicCompatible } from "./anthropic-compatible.js"
 
@@ -21,12 +21,12 @@ export type Config = RouteDefaultsInput &
   }
 
 export type Settings = ProviderPackage.Settings &
+  AnthropicMessages.ProviderOptionsInput &
   (
     | { readonly apiKey?: string; readonly authToken?: never }
     | { readonly apiKey?: never; readonly authToken?: string }
   ) & {
     readonly baseURL?: string
-    readonly providerOptions?: AnthropicMessages.ProviderOptionsInput
   }
 
 const auth = (options: ProviderAuthOption<"optional">) => {
@@ -54,15 +54,18 @@ export const configure = (input: Config = {}) => {
 export const provider = configure()
 export const model: ProviderPackage.Definition<Settings, AnthropicMessages.ProviderOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, authToken, baseURL, body, headers, ...providerOptions },
 ) => {
-  if (settings.apiKey !== undefined && settings.authToken !== undefined)
-    throw new Error("Anthropic apiKey cannot be combined with authToken")
+  if (apiKey !== undefined && authToken !== undefined)
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "Anthropic apiKey cannot be combined with authToken",
+    })
   return configure({
-    ...(settings.authToken === undefined ? { apiKey: settings.apiKey } : { auth: Auth.bearer(settings.authToken) }),
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    ...(authToken === undefined ? { apiKey: apiKey } : { auth: Auth.bearer(authToken) }),
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 }

packages/ai/src/providers/azure.ts

@@ -3,7 +3,7 @@ import { Auth } from "../route/auth.js"
 import { type AtLeastOne, type ProviderAuthOption } from "../route/auth-options.js"
 import type { Route, RouteDefaultsInput, CompactionOperations } from "../route/client.js"
 import type { ProviderPackage } from "../provider-package.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import * as OpenAIChat from "../protocols/openai-chat.js"
 import * as OpenAIResponses from "../protocols/openai-responses.js"
 import { ProviderShared } from "../protocols/shared.js"
@@ -28,12 +28,12 @@ export type LanguageModelOptions = AzureURL &
 export type Config = LanguageModelOptions
 
 export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput &
   AzureURL & {
     readonly apiKey?: string
     readonly apiVersion?: string
     readonly queryParams?: Readonly<Record<string, string>>
     readonly useDeploymentBasedUrls?: boolean
-    readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
 const resourceBaseURL = (resourceName: string) => `https://${resourceName.trim()}.openai.azure.com/openai`
@@ -151,19 +151,29 @@ export const provider = {
   configure,
 }
 
-const config = (settings: Settings): Config => {
+const config = ({
+  apiKey,
+  apiVersion,
+  baseURL,
+  body,
+  headers,
+  queryParams,
+  resourceName,
+  useDeploymentBasedUrls,
+  ...providerOptions
+}: Settings): Config => {
   const common = {
-    apiKey: settings.apiKey,
-    apiVersion: settings.apiVersion,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
-    queryParams: settings.queryParams === undefined ? undefined : { ...settings.queryParams },
-    useDeploymentBasedUrls: settings.useDeploymentBasedUrls,
+    apiKey,
+    apiVersion,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
+    queryParams: queryParams === undefined ? undefined : { ...queryParams },
+    useDeploymentBasedUrls,
   }
-  if (settings.baseURL !== undefined) return { ...common, baseURL: settings.baseURL }
-  if (settings.resourceName !== undefined) return { ...common, resourceName: settings.resourceName }
-  throw new Error("Azure requires resourceName or baseURL")
+  if (baseURL !== undefined) return { ...common, baseURL }
+  if (resourceName !== undefined) return { ...common, resourceName }
+  throw new ProviderConfigurationError({ provider: id, message: "Azure requires resourceName or baseURL" })
 }
 
 export const responsesModel: ProviderPackage.Definition<

packages/ai/src/providers/baseten.ts

@@ -15,11 +15,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = Route.make({
   id: "baseten-chat",
@@ -48,13 +48,16 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as Baseten from "./baseten.js"

packages/ai/src/providers/cerebras.ts

@@ -15,11 +15,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = Route.make({
   id: "cerebras-chat",
@@ -52,11 +52,14 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)

packages/ai/src/providers/cloudflare-ai-gateway.ts

@@ -5,7 +5,7 @@ import { Auth } from "../route/auth.js"
 import type { AtLeastOne, ProviderAuthOption } from "../route/auth-options.js"
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import type { OpenAIProviderOptionsInput } from "./openai-options.js"
 
 export const id = ProviderID.make("cloudflare-ai-gateway")
@@ -27,15 +27,19 @@ export type LanguageModelOptions = GatewayURL &
   }
 
 export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput &
   GatewayURL & {
     readonly apiKey?: string
     readonly gatewayApiKey?: string
-    readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
 export const baseURL = (input: GatewayURL) => {
   if (input.baseURL) return input.baseURL
-  if (!input.accountId) throw new Error("CloudflareAIGateway.configure requires accountId unless baseURL is supplied")
+  if (!input.accountId)
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "CloudflareAIGateway.configure requires accountId unless baseURL is supplied",
+    })
   return `https://gateway.ai.cloudflare.com/v1/${encodeURIComponent(input.accountId)}/${encodeURIComponent(input.gatewayId?.trim() || "default")}/compat`
 }
 
@@ -85,14 +89,25 @@ export const configure = (input: LanguageModelOptions) => {
 
 export const provider = { id, configure }
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
-  configure({
-    apiKey: settings.apiKey,
-    gatewayApiKey: settings.gatewayApiKey,
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) => {
+  const {
+    accountId: _,
+    apiKey,
+    baseURL: _url,
+    body,
+    gatewayApiKey,
+    gatewayId: _id,
+    headers,
+    ...providerOptions
+  } = settings
+  return configure({
+    apiKey,
+    gatewayApiKey,
     baseURL: baseURL(settings),
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
+}
 
 export * as CloudflareAIGateway from "./cloudflare-ai-gateway.js"

packages/ai/src/providers/cloudflare-workers-ai.ts

@@ -3,7 +3,7 @@ import { OpenAIChat } from "../protocols/openai-chat.js"
 import { AuthOptions, type AtLeastOne, type ProviderAuthOption } from "../route/auth-options.js"
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import type { OpenAIProviderOptionsInput } from "./openai-options.js"
 
 export const id = ProviderID.make("cloudflare-workers-ai")
@@ -21,14 +21,18 @@ export type LanguageModelOptions = WorkersAIURL &
   }
 
 export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput &
   WorkersAIURL & {
     readonly apiKey?: string
-    readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
 export const baseURL = (input: WorkersAIURL) => {
   if (input.baseURL) return input.baseURL
-  if (!input.accountId) throw new Error("CloudflareWorkersAI.configure requires accountId unless baseURL is supplied")
+  if (!input.accountId)
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "CloudflareWorkersAI.configure requires accountId unless baseURL is supplied",
+    })
   return `https://api.cloudflare.com/client/v4/accounts/${encodeURIComponent(input.accountId)}/ai/v1`
 }
 
@@ -59,13 +63,15 @@ export const configure = (input: LanguageModelOptions) => {
 
 export const provider = { id, configure }
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
-  configure({
-    apiKey: settings.apiKey,
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) => {
+  const { accountId: _, apiKey, baseURL: _url, body, headers, ...providerOptions } = settings
+  return configure({
+    apiKey,
     baseURL: baseURL(settings),
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
+}
 
 export * as CloudflareWorkersAI from "./cloudflare-workers-ai.js"

packages/ai/src/providers/deepinfra.ts

@@ -15,11 +15,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = Route.make({
   id: "deepinfra-chat",
@@ -55,11 +55,14 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)

packages/ai/src/providers/deepseek.ts

@@ -15,11 +15,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = Route.make({
   id: "deepseek-chat",
@@ -52,13 +52,16 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as DeepSeek from "./deepseek.js"

packages/ai/src/providers/fireworks.ts

@@ -15,11 +15,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = Route.make({
   id: "fireworks-chat",
@@ -48,13 +48,16 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as Fireworks from "./fireworks.js"

packages/ai/src/providers/google-vertex-chat.ts

@@ -2,7 +2,7 @@ import type { ProviderPackage } from "../provider-package.js"
 import { OpenAIChat } from "../protocols/openai-chat.js"
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import { GoogleVertexShared } from "./google-vertex-shared.js"
 import type { OpenAIProviderOptionsInput } from "./openai-options.js"
 
@@ -16,14 +16,14 @@ export type Config = RouteDefaultsInput &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly accessToken?: string
-  readonly apiKey?: never
-  readonly baseURL?: string
-  readonly location?: string
-  readonly project?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly accessToken?: string
+    readonly apiKey?: never
+    readonly baseURL?: string
+    readonly location?: string
+    readonly project?: string
+  }
 
 const route = Route.make({
   id: "google-vertex-chat",
@@ -37,7 +37,8 @@ const route = Route.make({
 export const routes = [route]
 
 const configuredRoute = (input: Config) => {
-  if ("apiKey" in input && input.apiKey !== undefined) throw new Error("Google Vertex Chat does not support API keys")
+  if ("apiKey" in input && input.apiKey !== undefined)
+    throw new ProviderConfigurationError({ provider: id, message: "Google Vertex Chat does not support API keys" })
   const {
     accessToken: _accessToken,
     auth: _auth,
@@ -73,15 +74,19 @@ export const provider = {
   configure,
 }
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) => {
-  if (settings.apiKey !== undefined) throw new Error("Google Vertex Chat does not support API keys")
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { accessToken, apiKey, baseURL, body, headers, location, project, ...providerOptions },
+) => {
+  if (apiKey !== undefined)
+    throw new ProviderConfigurationError({ provider: id, message: "Google Vertex Chat does not support API keys" })
   return configure({
-    accessToken: settings.accessToken,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    location: settings.location,
-    project: settings.project,
-    providerOptions: settings.providerOptions,
+    accessToken,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    location,
+    project,
+    providerOptions,
   }).model(modelID)
 }

packages/ai/src/providers/google-vertex-messages.ts

@@ -5,7 +5,7 @@ import { Auth } from "../route/auth.js"
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
 import { Protocol } from "../route/protocol.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import { GoogleVertexShared } from "./google-vertex-shared.js"
 
 export type AnthropicOptionsInput = AnthropicMessages.OptionsInput
@@ -25,14 +25,14 @@ export type Config = RouteDefaultsInput &
     readonly providerOptions?: AnthropicMessages.ProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly accessToken?: string
-  readonly apiKey?: never
-  readonly baseURL?: string
-  readonly location?: string
-  readonly project?: string
-  readonly providerOptions?: AnthropicMessages.ProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  AnthropicMessages.ProviderOptionsInput & {
+    readonly accessToken?: string
+    readonly apiKey?: never
+    readonly baseURL?: string
+    readonly location?: string
+    readonly project?: string
+  }
 
 const route = Route.make({
   id: "google-vertex-messages",
@@ -67,7 +67,7 @@ export const routes = [route]
 
 const configuredRoute = (input: Config) => {
   if ("apiKey" in input && input.apiKey !== undefined)
-    throw new Error("Google Vertex Messages does not support API keys")
+    throw new ProviderConfigurationError({ provider: id, message: "Google Vertex Messages does not support API keys" })
   const {
     accessToken: _accessToken,
     auth: _auth,
@@ -105,16 +105,17 @@ export const provider = {
 
 export const model: ProviderPackage.Definition<Settings, AnthropicMessages.ProviderOptionsInput>["model"] = (
   modelID,
-  settings,
+  { accessToken, apiKey, baseURL, body, headers, location, project, ...providerOptions },
 ) => {
-  if (settings.apiKey !== undefined) throw new Error("Google Vertex Messages does not support API keys")
+  if (apiKey !== undefined)
+    throw new ProviderConfigurationError({ provider: id, message: "Google Vertex Messages does not support API keys" })
   return configure({
-    accessToken: settings.accessToken,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    location: settings.location,
-    project: settings.project,
-    providerOptions: settings.providerOptions,
+    accessToken,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    location,
+    project,
+    providerOptions,
   }).model(modelID)
 }

packages/ai/src/providers/google-vertex-responses.ts

@@ -2,7 +2,7 @@ import type { ProviderPackage } from "../provider-package.js"
 import { OpenResponses } from "../protocols/open-responses.js"
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
-import { ProviderID, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type ModelID } from "../schema/index.js"
 import { GoogleVertexShared } from "./google-vertex-shared.js"
 import type { OpenResponsesProviderOptionsInput } from "./open-responses-options.js"
 
@@ -16,14 +16,14 @@ export type Config = RouteDefaultsInput &
     readonly providerOptions?: OpenResponsesProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly accessToken?: string
-  readonly apiKey?: never
-  readonly baseURL?: string
-  readonly location?: string
-  readonly project?: string
-  readonly providerOptions?: OpenResponsesProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenResponsesProviderOptionsInput & {
+    readonly accessToken?: string
+    readonly apiKey?: never
+    readonly baseURL?: string
+    readonly location?: string
+    readonly project?: string
+  }
 
 const route = Route.make({
   id: "google-vertex-responses",
@@ -39,7 +39,7 @@ export const routes = [route]
 
 const configuredRoute = (input: Config) => {
   if ("apiKey" in input && input.apiKey !== undefined)
-    throw new Error("Google Vertex Responses does not support API keys")
+    throw new ProviderConfigurationError({ provider: id, message: "Google Vertex Responses does not support API keys" })
   const {
     accessToken: _accessToken,
     auth: _auth,
@@ -77,16 +77,17 @@ export const provider = {
 
 export const model: ProviderPackage.Definition<Settings, OpenResponsesProviderOptionsInput>["model"] = (
   modelID,
-  settings,
+  { accessToken, apiKey, baseURL, body, headers, location, project, ...providerOptions },
 ) => {
-  if (settings.apiKey !== undefined) throw new Error("Google Vertex Responses does not support API keys")
+  if (apiKey !== undefined)
+    throw new ProviderConfigurationError({ provider: id, message: "Google Vertex Responses does not support API keys" })
   return configure({
-    accessToken: settings.accessToken,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    location: settings.location,
-    project: settings.project,
-    providerOptions: settings.providerOptions,
+    accessToken,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    location,
+    project,
+    providerOptions,
   }).model(modelID)
 }

packages/ai/src/providers/google-vertex-shared.ts

@@ -1,8 +1,10 @@
 import type { AnyAuthClient } from "google-auth-library"
 import { Effect, Redacted } from "effect"
 import { Auth, MissingCredentialError } from "../route/auth.js"
+import { ProviderConfigurationError, ProviderID } from "../schema/index.js"
 
 const SCOPE = "https://www.googleapis.com/auth/cloud-platform"
+const id = ProviderID.make("google-vertex")
 
 export type OAuthOptions =
   | { readonly accessToken?: string; readonly auth?: never }
@@ -35,12 +37,18 @@ export const host = (location: string) => {
 
 export const requireProject = (value: string | undefined) => {
   if (value) return value
-  throw new Error("Google Vertex requires a project when baseURL is not configured")
+  throw new ProviderConfigurationError({
+    provider: id,
+    message: "Google Vertex requires a project when baseURL is not configured",
+  })
 }
 
 export const apiKey = (input: ApiKeyOptions) => {
   if (input.apiKey !== undefined && (input.accessToken !== undefined || input.auth !== undefined))
-    throw new Error("Google Vertex apiKey cannot be combined with accessToken or auth")
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "Google Vertex apiKey cannot be combined with accessToken or auth",
+    })
   if (input.accessToken !== undefined || input.auth !== undefined) return undefined
   return input.apiKey ?? process.env.GOOGLE_VERTEX_API_KEY
 }
@@ -68,7 +76,10 @@ const adc = (project?: string) => {
 
 export const oauth = (input: OAuthOptions, project?: string) => {
   if (input.accessToken !== undefined && input.auth !== undefined)
-    throw new Error("Google Vertex accessToken cannot be combined with auth")
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "Google Vertex accessToken cannot be combined with auth",
+    })
   if (input.auth) return input.auth
   if (input.accessToken !== undefined) return Auth.bearer(input.accessToken)
   return adc(project)

packages/ai/src/providers/google-vertex.ts

@@ -6,7 +6,7 @@ import { Auth } from "../route/auth.js"
 import { Route, type RouteDefaultsInput } from "../route/client.js"
 import { Endpoint } from "../route/endpoint.js"
 import { Framing } from "../route/framing.js"
-import { ProviderID, type LLMRequest, type ModelID } from "../schema/index.js"
+import { ProviderConfigurationError, ProviderID, type LLMRequest, type ModelID } from "../schema/index.js"
 import { GoogleVertexShared } from "./google-vertex-shared.js"
 
 export interface GeminiOptionsInput extends Gemini.OptionsInput {
@@ -26,6 +26,7 @@ export type Config = RouteDefaultsInput &
   }
 
 export type Settings = ProviderPackage.Settings &
+  GeminiProviderOptionsInput &
   (
     | { readonly accessToken?: string; readonly apiKey?: never }
     | { readonly accessToken?: never; readonly apiKey?: string }
@@ -33,7 +34,6 @@ export type Settings = ProviderPackage.Settings &
     readonly baseURL?: string
     readonly location?: string
     readonly project?: string
-    readonly providerOptions?: GeminiProviderOptionsInput
   }
 
 const fromRequest = Effect.fn("GoogleVertex.fromRequest")(function* (request: LLMRequest) {
@@ -93,7 +93,10 @@ const configuredRoute = (input: Config, modelID: string | ModelID) => {
   const apiKey = GoogleVertexShared.apiKey(input)
   const endpointModel = String(modelID).startsWith("endpoints/")
   if (apiKey !== undefined && endpointModel)
-    throw new Error("Google Vertex tuned models do not support Express Mode API keys")
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "Google Vertex tuned models do not support Express Mode API keys",
+    })
   const location = GoogleVertexShared.location(inputLocation, "us-central1")
   const project = GoogleVertexShared.project(inputProject)
   const endpoint =
@@ -121,16 +124,22 @@ export const provider = {
   id,
   configure,
 }
-export const model: ProviderPackage.Definition<Settings, GeminiProviderOptionsInput>["model"] = (modelID, settings) => {
-  if (settings.apiKey !== undefined && settings.accessToken !== undefined)
-    throw new Error("Google Vertex apiKey cannot be combined with accessToken or auth")
+export const model: ProviderPackage.Definition<Settings, GeminiProviderOptionsInput>["model"] = (
+  modelID,
+  { accessToken, apiKey, baseURL, body, headers, location, project, ...providerOptions },
+) => {
+  if (apiKey !== undefined && accessToken !== undefined)
+    throw new ProviderConfigurationError({
+      provider: id,
+      message: "Google Vertex apiKey cannot be combined with accessToken or auth",
+    })
   return configure({
-    ...(settings.apiKey === undefined ? { accessToken: settings.accessToken } : { apiKey: settings.apiKey }),
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    location: settings.location,
-    project: settings.project,
-    providerOptions: settings.providerOptions,
+    ...(apiKey === undefined ? { accessToken: accessToken } : { apiKey: apiKey }),
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    location,
+    project,
+    providerOptions,
   }).model(modelID)
 }

packages/ai/src/providers/google.ts

@@ -20,11 +20,11 @@ export type Config = RouteDefaultsInput &
     readonly providerOptions?: Gemini.ProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: Gemini.ProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  Gemini.ProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const auth = (options: ProviderAuthOption<"optional">) => {
   if ("auth" in options && options.auth) return options.auth
@@ -57,13 +57,16 @@ export const configure = (input: Config = {}) => {
 }
 
 export const provider = configure()
-export const model: ProviderPackage.Definition<Settings, Gemini.ProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, Gemini.ProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export const image = provider.image

packages/ai/src/providers/groq.ts

@@ -26,11 +26,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ProviderOptions
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: ProviderOptions
-}
+export type Settings = ProviderPackage.Settings &
+  ProviderOptions & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const Options = Schema.Struct({
   includeReasoning: Schema.optional(Schema.Boolean),
@@ -103,13 +103,16 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, ProviderOptions>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, ProviderOptions>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as Groq from "./groq.js"

packages/ai/src/providers/meta.ts

@@ -79,11 +79,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: ProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  ProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const responsesRoute = Route.make({
   id: "meta-responses",
@@ -169,13 +169,13 @@ export const chatModel: ProviderPackage.Definition<Settings, OpenResponsesProvid
 export const messagesModel: ProviderPackage.Definition<Settings, MessagesOptionsInput>["model"] = (modelID, settings) =>
   fromSettings(settings).messages(modelID)
 
-function fromSettings(settings: Settings) {
+function fromSettings({ apiKey, baseURL, body, headers, ...providerOptions }: Settings) {
   return configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   })
 }
 

packages/ai/src/providers/minimax.ts

@@ -40,11 +40,11 @@ export type Config = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ProviderOptionsInput
   }
 
-export interface Settings<Options = MessagesOptionsInput> extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: Options
-}
+export type Settings<Options = MessagesOptionsInput> = ProviderPackage.Settings &
+  Options & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const ChatOptions = Schema.Struct({
   thinking: Schema.optional(Schema.Struct({ type: Schema.String })),
@@ -127,14 +127,14 @@ export const provider = configure()
 
 export const model: ProviderPackage.Definition<Settings<MessagesOptionsInput>, MessagesOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export const messages = provider.messages

packages/ai/src/providers/minimax/chat.ts

@@ -3,11 +3,14 @@ import { MiniMax } from "../minimax.js"
 
 export type Settings = MiniMax.Settings<MiniMax.ChatOptionsInput>
 
-export const model: ProviderPackage.Definition<Settings, MiniMax.ChatOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, MiniMax.ChatOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   MiniMax.configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).chat(modelID)

packages/ai/src/providers/minimax/responses.ts

@@ -5,12 +5,12 @@ export type Settings = MiniMax.Settings<MiniMax.ResponsesOptionsInput>
 
 export const model: ProviderPackage.Definition<Settings, MiniMax.ResponsesOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   MiniMax.configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).responses(modelID)

packages/ai/src/providers/mistral.ts

@@ -14,11 +14,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ProviderOptions
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: ProviderOptions
-}
+export type Settings = ProviderPackage.Settings &
+  ProviderOptions & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = MistralChat.route
 export const routes = [route]
@@ -39,13 +39,16 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, ProviderOptions>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, ProviderOptions>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as Mistral from "./mistral.js"

packages/ai/src/providers/moonshot.ts

@@ -42,11 +42,11 @@ export type Config = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ChatOptionsInput | MessagesOptionsInput | ResponsesOptionsInput
   }
 
-export interface Settings<Options = ChatOptionsInput> extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: Options
-}
+export type Settings<Options = ChatOptionsInput> = ProviderPackage.Settings &
+  Options & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const ChatOptions = Schema.Struct({
   reasoningEffort: Schema.optional(Schema.String),
@@ -133,13 +133,16 @@ export const chat = provider.chat
 export const messages = provider.messages
 export const responses = provider.responses
 
-export const model: ProviderPackage.Definition<Settings, ChatOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, ChatOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as Moonshot from "./moonshot.js"

packages/ai/src/providers/moonshot/messages.ts

@@ -5,12 +5,12 @@ export type Settings = Moonshot.Settings<Moonshot.MessagesOptionsInput>
 
 export const model: ProviderPackage.Definition<Settings, Moonshot.MessagesOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   Moonshot.configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).messages(modelID)

packages/ai/src/providers/moonshot/responses.ts

@@ -5,12 +5,12 @@ export type Settings = Moonshot.Settings<Moonshot.ResponsesOptionsInput>
 
 export const model: ProviderPackage.Definition<Settings, Moonshot.ResponsesOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   Moonshot.configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).responses(modelID)

packages/ai/src/providers/openai-compatible-responses.ts

@@ -16,12 +16,12 @@ export type Config = RouteDefaultsInput &
     readonly providerOptions?: OpenResponsesProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL: string
-  readonly provider?: string
-  readonly providerOptions?: OpenResponsesProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenResponsesProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL: string
+    readonly provider?: string
+  }
 
 export const routes = [OpenAICompatibleResponses.route]
 
@@ -48,13 +48,13 @@ export const provider = {
 
 export const model: ProviderPackage.Definition<Settings, OpenResponsesProviderOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, provider, ...providerOptions },
 ) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    provider: settings.provider,
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    provider,
+    providerOptions,
   }).model(modelID)

packages/ai/src/providers/openai-compatible.ts

@@ -14,12 +14,12 @@ type GenericModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL: string
-  readonly provider?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL: string
+    readonly provider?: string
+  }
 
 export const routes = [OpenAICompatibleChat.route]
 
@@ -45,14 +45,17 @@ export const provider = {
   configure,
 }
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, provider, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    provider: settings.provider,
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    provider,
+    providerOptions,
   }).model(modelID)
 
 export * as OpenAICompatible from "./openai-compatible.js"

packages/ai/src/providers/openai.ts

@@ -57,14 +57,14 @@ export const imageGeneration = (options: ImageGenerationOptions = {}) =>
     },
   })
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly organization?: string
-  readonly project?: string
-  readonly queryParams?: Readonly<Record<string, string>>
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+    readonly organization?: string
+    readonly project?: string
+    readonly queryParams?: Readonly<Record<string, string>>
+  }
 
 const auth = (options: ProviderAuthOption<"optional">) => AuthOptions.bearer(options, "OPENAI_API_KEY")
 
@@ -116,19 +116,28 @@ export const configure = (input: Config = {}) => {
 
 export const provider = configure()
 
-const config = (settings: Settings): Config => {
+const config = ({
+  apiKey,
+  baseURL,
+  body,
+  headers: given,
+  organization,
+  project,
+  queryParams,
+  ...providerOptions
+}: Settings): Config => {
   const headers = {
-    ...(settings.organization === undefined ? {} : { "OpenAI-Organization": settings.organization }),
-    ...(settings.project === undefined ? {} : { "OpenAI-Project": settings.project }),
-    ...settings.headers,
+    ...(organization === undefined ? {} : { "OpenAI-Organization": organization }),
+    ...(project === undefined ? {} : { "OpenAI-Project": project }),
+    ...given,
   }
   return {
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
+    apiKey,
+    baseURL,
     headers: Object.keys(headers).length === 0 ? undefined : headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
-    queryParams: settings.queryParams === undefined ? undefined : { ...settings.queryParams },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
+    queryParams: queryParams === undefined ? undefined : { ...queryParams },
   }
 }
 

packages/ai/src/providers/openrouter.ts

@@ -77,11 +77,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenRouterProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenRouterProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenRouterProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const OpenRouterBody = Schema.StructWithRest(Schema.Struct(OpenAIChat.bodyFields), [
   Schema.Record(Schema.String, Schema.Any),
@@ -191,12 +191,12 @@ export const configure = (input: LanguageModelOptions = {}) => {
 export const provider = configure()
 export const model: ProviderPackage.Definition<Settings, OpenRouterProviderOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)

packages/ai/src/providers/togetherai.ts

@@ -15,11 +15,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: OpenAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: OpenAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  OpenAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export const route = Route.make({
   id: "togetherai-chat",
@@ -52,11 +52,14 @@ export const configure = (input: LanguageModelOptions = {}) => {
 
 export const provider = configure()
 
-export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, OpenAIProviderOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers === undefined ? undefined : { ...settings.headers },
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers: headers === undefined ? undefined : { ...headers },
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)

packages/ai/src/providers/xai.ts

@@ -20,11 +20,11 @@ export type LanguageModelOptions = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: XAIProviderOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: XAIProviderOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  XAIProviderOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export type { XAIImageOptions } from "../protocols/xai-images.js"
 
@@ -110,13 +110,13 @@ export const model: ProviderPackage.Definition<
   Settings,
   XAIProviderOptionsInput,
   typeof responsesRoute.compact
->["model"] = (modelID, settings) =>
+>["model"] = (modelID, { apiKey, baseURL, body, headers, ...providerOptions }) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 export const responses = provider.responses
 export const chat = provider.chat

packages/ai/src/providers/zai-coding-plan.ts

@@ -23,11 +23,11 @@ export type Config = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ChatOptionsInput | MessagesOptionsInput | ResponsesOptionsInput
   }
 
-export interface Settings<Options = ChatOptionsInput> extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: Options
-}
+export type Settings<Options = ChatOptionsInput> = ProviderPackage.Settings &
+  Options & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 const chatRoute = Route.make({
   id: "zai-coding-chat",
@@ -80,13 +80,16 @@ export const chat = provider.chat
 export const messages = provider.messages
 export const responses = provider.responses
 
-export const model: ProviderPackage.Definition<Settings, ChatOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, ChatOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as ZAICodingPlan from "./zai-coding-plan.js"

packages/ai/src/providers/zai-coding-plan/messages.ts

@@ -5,12 +5,12 @@ export type Settings = ZAICodingPlan.Settings<ZAICodingPlan.MessagesOptionsInput
 
 export const model: ProviderPackage.Definition<Settings, ZAICodingPlan.MessagesOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   ZAICodingPlan.configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).messages(modelID)

packages/ai/src/providers/zai-coding-plan/responses.ts

@@ -5,12 +5,12 @@ export type Settings = ZAICodingPlan.Settings<ZAICodingPlan.ResponsesOptionsInpu
 
 export const model: ProviderPackage.Definition<Settings, ZAICodingPlan.ResponsesOptionsInput>["model"] = (
   modelID,
-  settings,
+  { apiKey, baseURL, body, headers, ...providerOptions },
 ) =>
   ZAICodingPlan.configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).responses(modelID)

packages/ai/src/providers/zai.ts

@@ -17,11 +17,11 @@ export type Config = Omit<RouteDefaultsInput, "providerOptions"> &
     readonly providerOptions?: ChatOptionsInput
   }
 
-export interface Settings extends ProviderPackage.Settings {
-  readonly apiKey?: string
-  readonly baseURL?: string
-  readonly providerOptions?: ChatOptionsInput
-}
+export type Settings = ProviderPackage.Settings &
+  ChatOptionsInput & {
+    readonly apiKey?: string
+    readonly baseURL?: string
+  }
 
 export type { ZAIImageOptions } from "../protocols/zai-images.js"
 
@@ -70,13 +70,16 @@ export const provider = configure()
 export const image = provider.image
 export const chat = provider.chat
 
-export const model: ProviderPackage.Definition<Settings, ChatOptionsInput>["model"] = (modelID, settings) =>
+export const model: ProviderPackage.Definition<Settings, ChatOptionsInput>["model"] = (
+  modelID,
+  { apiKey, baseURL, body, headers, ...providerOptions },
+) =>
   configure({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL,
-    headers: settings.headers,
-    http: settings.body === undefined ? undefined : { body: { ...settings.body } },
-    providerOptions: settings.providerOptions,
+    apiKey,
+    baseURL,
+    headers,
+    http: body === undefined ? undefined : { body: { ...body } },
+    providerOptions,
   }).model(modelID)
 
 export * as ZAI from "./zai.js"

packages/ai/src/route/client.ts

@@ -23,6 +23,7 @@ import {
   LanguageModel,
   LLMEvent,
   InvalidProviderOutputError,
+  ProviderConfigurationError,
   ProviderID,
   mergeGenerationOptions,
   mergeHttpOptions,
@@ -128,7 +129,10 @@ const makeRouteLanguageModel = <Options extends ProviderOptions, Compact extends
   const provider = route.provider ?? ("provider" in mapped ? mapped.provider : undefined)
   if (!provider) throw new Error(`Route.model(${route.id}) requires a provider`)
   if (!endpointBaseURL(route.endpoint))
-    throw new Error(`Route.model(${route.id}) requires an endpoint baseURL — configure it on the route first`)
+    throw new ProviderConfigurationError({
+      provider: ProviderID.make(provider),
+      message: `Route.model(${route.id}) requires an endpoint baseURL — configure it on the route first`,
+    })
   return LanguageModel.make<Options, Compact>({
     ...mapped,
     provider,

packages/ai/src/schema/errors.ts

@@ -50,6 +50,19 @@ export class UnsupportedOperationError extends Schema.TaggedError<UnsupportedOpe
   route: Schema.optional(RouteID),
 }) {}
 
+/**
+ * Provider settings that are missing, conflicting, or unsupported, such as
+ * Azure without `resourceName` or `baseURL`. Thrown synchronously while a
+ * provider facade or package entrypoint configures a model, before any
+ * request exists, so it is not an `AIError` reason.
+ */
+export class ProviderConfigurationError extends Schema.TaggedError<ProviderConfigurationError>(
+  "AI.Error.ProviderConfiguration",
+)("ProviderConfiguration", {
+  provider: ProviderID,
+  message: Schema.String,
+}) {}
+
 export class NoRouteError extends Schema.TaggedError<NoRouteError>("AI.Error.NoRoute")("NoRoute", {
   ...ReasonFields,
   route: RouteID,

packages/ai/test/provider-package.test.ts

@@ -3,6 +3,9 @@ import { model } from "@opencode/ai/providers/openai"
 import { LLM } from "../src/index.js"
 import { Endpoint } from "../src/route/endpoint.js"
 
+const configuration = (provider: string, message: string) =>
+  expect.objectContaining({ _tag: "ProviderConfiguration", provider, message })
+
 describe("provider package entrypoints", () => {
   test("semantic API aliases expose the same contract", async () => {
     const modules = await Promise.all([
@@ -185,13 +188,13 @@ describe("provider package entrypoints", () => {
       baseURL: "https://provider.example.test/v1/",
       headers: { "x-application": "opencode" },
       body: { service_tier: "priority" },
-      providerOptions: { reasoningEffort: "high" as const },
+      reasoningEffort: "high" as const,
     }
     const deepinfra = DeepInfra.model("google/gemma-3-27b-it", settings)
 
     expect(deepinfra.route.id).toBe("deepinfra-chat")
     expect(deepinfra.route.endpoint.baseURL).toBe("https://provider.example.test/v1/openai")
-    expect(deepinfra.route.defaults.providerOptions).toEqual(settings.providerOptions)
+    expect(deepinfra.route.defaults.providerOptions).toEqual({ reasoningEffort: "high" })
     expect(deepinfra.route.defaults.headers).toEqual(settings.headers)
     expect(deepinfra.route.defaults.http?.body).toEqual(settings.body)
   })
@@ -207,7 +210,7 @@ describe("provider package entrypoints", () => {
         apiKey: "fixture",
         headers: { "x-application": "opencode" },
         body: { custom: true },
-        providerOptions: { reasoningEffort: "high" },
+        reasoningEffort: "high",
       })
       expect(selected.provider).toBe(provider.id)
       expect(selected.route.endpoint.baseURL).toBe(provider.baseURL({ accountId: "account" }))
@@ -228,11 +231,11 @@ describe("provider package entrypoints", () => {
     }
     const openrouter = OpenRouter.model("anthropic/claude-sonnet-4", {
       ...settings,
-      providerOptions: { usage: true },
+      usage: true,
     })
     const xai = XAI.model("grok-4", {
       ...settings,
-      providerOptions: { reasoningEffort: "high" },
+      reasoningEffort: "high",
     })
 
     for (const selected of [openrouter, xai]) {
@@ -266,7 +269,8 @@ describe("provider package entrypoints", () => {
       provider: "example",
       headers: { "x-application": "opencode" },
       body: { service_tier: "priority" },
-      providerOptions: { reasoningEffort: "low", store: true },
+      reasoningEffort: "low",
+      store: true,
     })
 
     expect(String(selected.provider)).toBe("example")
@@ -292,7 +296,7 @@ describe("provider package entrypoints", () => {
       provider: "example",
       headers: { "x-application": "opencode" },
       body: { metadata: { user_id: "user_1" } },
-      providerOptions: { effort: "low" },
+      effort: "low",
     })
 
     expect(String(selected.provider)).toBe("example")
@@ -312,7 +316,7 @@ describe("provider package entrypoints", () => {
     const Anthropic = await import("@opencode/ai/providers/anthropic")
     const selected = Anthropic.model("claude-sonnet-4-6", {
       apiKey: "fixture",
-      providerOptions: { thinking: { type: "adaptive" } },
+      thinking: { type: "adaptive" },
     })
 
     expect(selected.route.defaults.providerOptions).toEqual({ thinking: { type: "adaptive" } })
@@ -322,7 +326,7 @@ describe("provider package entrypoints", () => {
     const AnthropicCompatible = await import("@opencode/ai/providers/anthropic-compatible")
     expect(() =>
       Reflect.apply(AnthropicCompatible.model, undefined, ["compatible-model", { apiKey: "fixture" }]),
-    ).toThrow("Anthropic-compatible providers require a baseURL")
+    ).toThrow(configuration("anthropic-compatible", "Anthropic-compatible providers require a baseURL"))
   })
 
   test("rejects conflicting Anthropic-compatible auth settings at runtime", async () => {
@@ -337,10 +341,10 @@ describe("provider package entrypoints", () => {
           baseURL: "https://messages.example.test/v1",
         },
       ]),
-    ).toThrow("Anthropic-compatible apiKey cannot be combined with authToken")
+    ).toThrow(configuration("anthropic-compatible", "Anthropic-compatible apiKey cannot be combined with authToken"))
     expect(() =>
       Reflect.apply(Anthropic.model, undefined, ["claude-sonnet-4-6", { apiKey: "fixture", authToken: "token" }]),
-    ).toThrow("Anthropic apiKey cannot be combined with authToken")
+    ).toThrow(configuration("anthropic", "Anthropic apiKey cannot be combined with authToken"))
   })
 
   test("maps legacy OpenAI organization and project settings to headers", () => {
@@ -406,7 +410,7 @@ describe("provider package entrypoints", () => {
       baseURL: "https://generativelanguage.test/v1beta",
       headers: { "x-application": "opencode" },
       body: { safetySettings: [] },
-      providerOptions: { thinkingConfig: { thinkingBudget: 1_024 } },
+      thinkingConfig: { thinkingBudget: 1_024 },
     })
 
     expect(selected.route.id).toBe("gemini")
@@ -490,43 +494,45 @@ describe("provider package entrypoints", () => {
         "gemini-3.5-flash",
         { accessToken: "token", apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex apiKey cannot be combined with accessToken or auth")
+    ).toThrow(configuration("google-vertex", "Google Vertex apiKey cannot be combined with accessToken or auth"))
     const configured = Reflect.apply(GoogleVertex.configure, undefined, [
       { accessToken: "token", auth: {}, project: "vertex-project" },
     ])
-    expect(() => configured.model("gemini-3.5-flash")).toThrow("Google Vertex accessToken cannot be combined with auth")
+    expect(() => configured.model("gemini-3.5-flash")).toThrow(
+      configuration("google-vertex", "Google Vertex accessToken cannot be combined with auth"),
+    )
     expect(() =>
       Reflect.apply(GoogleVertexMessages.model, undefined, [
         "claude-sonnet-4-6",
         { apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex Messages does not support API keys")
+    ).toThrow(configuration("google-vertex", "Google Vertex Messages does not support API keys"))
     expect(() =>
       Reflect.apply(Providers.GoogleVertexMessages.configure, undefined, [
         { apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex Messages does not support API keys")
+    ).toThrow(configuration("google-vertex", "Google Vertex Messages does not support API keys"))
     expect(() =>
       Reflect.apply(GoogleVertexChat.model, undefined, [
         "deepseek-ai/deepseek-v3.2-maas",
         { apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex Chat does not support API keys")
+    ).toThrow(configuration("google-vertex", "Google Vertex Chat does not support API keys"))
     expect(() =>
       Reflect.apply(Providers.GoogleVertexChat.configure, undefined, [
         { apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex Chat does not support API keys")
+    ).toThrow(configuration("google-vertex", "Google Vertex Chat does not support API keys"))
     expect(() =>
       Reflect.apply(GoogleVertexResponses.model, undefined, [
         "xai/grok-4.20-reasoning",
         { apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex Responses does not support API keys")
+    ).toThrow(configuration("google-vertex", "Google Vertex Responses does not support API keys"))
     expect(() =>
       Reflect.apply(Providers.GoogleVertexResponses.configure, undefined, [
         { apiKey: "fixture", project: "vertex-project" },
       ]),
-    ).toThrow("Google Vertex Responses does not support API keys")
+    ).toThrow(configuration("google-vertex", "Google Vertex Responses does not support API keys"))
   })
 })

packages/ai/test/provider/alibaba.test.ts

@@ -76,7 +76,13 @@ it.effect("Alibaba owns regional shared and workspace-specific endpoints", () =>
 
 test("Alibaba requires explicit placement and supports complete base URL overrides", () => {
   for (const region of ["eu-central-1", "ap-northeast-1", "future-region"])
-    expect(() => Alibaba.configure({ region })).toThrow("requires workspaceID or baseURL")
+    expect(() => Alibaba.configure({ region })).toThrow(
+      expect.objectContaining({
+        _tag: "ProviderConfiguration",
+        provider: "alibaba",
+        message: `Alibaba region ${region} requires workspaceID or baseURL`,
+      }),
+    )
   for (const config of [
     { baseURL: "https://gateway.example/prefix" },
     { region: "future-region", workspaceID: "ignored", baseURL: "https://gateway.example/prefix" },

packages/ai/test/provider/anthropic-compaction.test.ts

@@ -69,7 +69,9 @@ for (const model of [
       dynamicResponse(({ request, text, respond }) =>
         Effect.sync(() => {
           const body = JSON.parse(text)
-          expect(request.headers["anthropic-beta"]).toBe("existing-beta,compact-2026-01-12")
+          expect(request.headers["anthropic-beta"]).toBe(
+            "existing-beta,interleaved-thinking-2025-05-14,compact-2026-01-12",
+          )
           if (body.messages.length === 1) {
             expect(body.context_management.edits).toEqual([
               {

packages/ai/test/provider/anthropic-thinking-binding.test.ts

@@ -32,7 +32,9 @@ for (const [id, enabled] of [
         enabled ? { type: "adaptive", block_binding: { prefix_mismatch_behavior: "drop_block" } } : undefined,
       )
       expect(prepared.request.headers["anthropic-beta"]).toBe(
-        enabled ? "existing-beta,thinking-binding-controls-2026-08-01" : "existing-beta",
+        enabled
+          ? "existing-beta,interleaved-thinking-2025-05-14,thinking-binding-controls-2026-08-01"
+          : "existing-beta,interleaved-thinking-2025-05-14",
       )
     }),
   )
@@ -53,7 +55,9 @@ it.effect("preserves explicit thinking settings and combines required beta heade
       const prepared = yield* AnthropicMessages.route.prepareTransport(compiled.body, request)
       expect(compiled.body.thinking).toEqual(thinking)
       expect(prepared.request.headers["anthropic-beta"]).toBe(
-        thinking.type === "disabled" ? "compact-2026-01-12" : "compact-2026-01-12,thinking-binding-controls-2026-08-01",
+        thinking.type === "disabled"
+          ? "interleaved-thinking-2025-05-14,compact-2026-01-12"
+          : "interleaved-thinking-2025-05-14,compact-2026-01-12,thinking-binding-controls-2026-08-01",
       )
     }
   }),

packages/ai/test/provider/bedrock-converse.test.ts

@@ -1458,7 +1458,13 @@ describe("Bedrock Converse route", () => {
         expect(headers.get("authorization")).toContain("Credential=AKIACHAINEXAMPLE/")
         expect(headers.get("authorization")).toContain("/ap-southeast-2/bedrock/aws4_request")
       }
-      expect(() => AmazonBedrock.configure({ auth: "sigv4", apiKey: "k" })).toThrow("does not accept apiKey")
+      expect(() => AmazonBedrock.configure({ auth: "sigv4", apiKey: "k" })).toThrow(
+        expect.objectContaining({
+          _tag: "ProviderConfiguration",
+          provider: "amazon-bedrock",
+          message: "Amazon Bedrock SigV4 auth does not accept apiKey",
+        }),
+      )
     }).pipe(
       withProcessEnv({
         ...noAmbientAWS,

packages/ai/test/provider/google-vertex.test.ts

@@ -378,7 +378,11 @@ describe("Google Vertex providers", () => {
 
   test("rejects tuned Gemini models in express mode", () => {
     expect(() => GoogleVertex.configure({ apiKey: "fixture" }).model("endpoints/1234567890")).toThrow(
-      "Google Vertex tuned models do not support Express Mode API keys",
+      expect.objectContaining({
+        _tag: "ProviderConfiguration",
+        provider: "google-vertex",
+        message: "Google Vertex tuned models do not support Express Mode API keys",
+      }),
     )
   })
 })

packages/ai/test/provider/groq.test.ts

@@ -34,12 +34,10 @@ it.effect("Groq lowers its own options for custom catalog identities and endpoin
         baseURL: "https://gateway.example/v1",
         headers: { "x-client": "test" },
         body: { custom: "value" },
-        providerOptions: {
-          reasoningEffort: "default",
-          parallelToolCalls: true,
-          serviceTier: "flex",
-          user: "test-user",
-        },
+        reasoningEffort: "default",
+        parallelToolCalls: true,
+        serviceTier: "flex",
+        user: "test-user",
       }),
       { provider: "custom-groq" },
     )

packages/ai/test/provider/meta.test.ts

@@ -87,7 +87,7 @@ it.effect("Meta package selectors preserve overrides and Chat token policy on cu
         baseURL: "https://gateway.example/v1",
         headers: { "x-client": "test" },
         body: { custom: "value" },
-        providerOptions: { reasoningEffort: "future-effort" },
+        reasoningEffort: "future-effort",
       })
       expect(model.route.endpoint.baseURL).toBe("https://gateway.example/v1")
       expect(model.route.defaults.headers).toEqual({ "x-client": "test" })

packages/ai/test/provider/native-providers.test.ts

@@ -99,7 +99,7 @@ describe("native OpenAI-compatible providers", () => {
         const settings = {
           apiKey: "fixture",
           baseURL: "https://gateway.example/v1",
-          providerOptions: { reasoningEffort: "high" },
+          reasoningEffort: "high",
         }
         const selected = provider.configure(settings).model("test-model")
         expect(selected.provider).toBe(provider.id)
@@ -143,7 +143,7 @@ describe("native OpenAI-compatible providers", () => {
           tools: [
             ToolDefinition.make({ name: "lookup", description: "Look up data", inputSchema: { type: "object" } }),
           ],
-          providerOptions: { store: true },
+          store: true,
         }),
       )
 
@@ -168,7 +168,7 @@ describe("native OpenAI-compatible providers", () => {
             ]),
             Message.user("Continue."),
           ],
-          providerOptions: { store: true },
+          store: true,
         }),
       )
 
@@ -206,7 +206,7 @@ describe("native OpenAI-compatible providers", () => {
         baseURL: "https://gateway.example/v1",
         headers: { "x-application": "opencode" },
         body: { service_tier: "priority" },
-        providerOptions: { reasoningEffort: "high" },
+        reasoningEffort: "high",
       })
 
       expect(selected.route.endpoint.baseURL).toBe("https://gateway.example/v1")

packages/ai/test/provider/open-responses-errors.test.ts

@@ -0,0 +1,78 @@
+import { expect } from "bun:test"
+import { Effect, Schema } from "effect"
+import { LLM, LLMClient } from "../../src/index.js"
+import { OpenResponses } from "../../src/protocols/open-responses.js"
+import { Meta } from "../../src/providers/index.js"
+import { configure } from "../../src/providers/openai-compatible-responses.js"
+import { it } from "../lib/effect.js"
+import { fixedResponse } from "../lib/http.js"
+import { sseEvents } from "../lib/sse.js"
+
+const decodeEvent = Schema.decodeUnknownEffect(OpenResponses.protocol.stream.event)
+
+it.effect("normalizes flat errors in shared SSE and WebSocket decoding", () =>
+  Effect.gen(function* () {
+    const frame = {
+      type: "error",
+      sequence_number: 4,
+      code: "server_shutting_down",
+      message: "Server is shutting down. Please retry your request.",
+      param: null,
+    }
+    for (const decode of [decodeEvent, OpenResponses.decodeChannelEvent]) {
+      const event = yield* decode(JSON.stringify(frame))
+      expect(event).toEqual({
+        type: "error",
+        sequence_number: 4,
+        error: { code: frame.code, message: frame.message, param: null },
+      })
+
+      for (const unchanged of [
+        event,
+        { type: "error" },
+        {
+          type: "response.failed",
+          response: { id: "resp_failed", error: { code: "server_error", message: "Internal server error" } },
+        },
+        { type: "response.output_text.delta", item_id: "msg_text", delta: "Hello" },
+      ]) {
+        expect(yield* decode(JSON.stringify(unchanged))).toEqual(unchanged)
+      }
+    }
+  }),
+)
+
+it.effect("continues to normalize untyped xAI WebSocket errors", () =>
+  Effect.gen(function* () {
+    const frame = { error: { type: "api_error", message: "gRPC error: Response with id=resp_missing not found" } }
+    expect(yield* OpenResponses.decodeChannelEvent(JSON.stringify(frame))).toEqual({ ...frame, type: "error" })
+  }),
+)
+
+it.effect("retains classification and original error bodies through Meta and generic Responses routes", () =>
+  Effect.gen(function* () {
+    const raw = `{
+  "type": "error",
+  "sequence_number": 4,
+  "code": "server_shutting_down",
+  "message": "Server is shutting down. Please retry your request.",
+  "param": null,
+  "diagnostic": "retain-original-frame"
+}`
+    for (const model of [
+      Meta.configure({ apiKey: "fixture" }).responses("muse-spark-1.3"),
+      configure({ apiKey: "fixture", provider: "gateway", baseURL: "https://responses.example.test/v1" }).model(
+        "example-model",
+      ),
+    ]) {
+      const error = yield* LLMClient.generate(LLM.request({ model, prompt: "Hello" })).pipe(
+        Effect.provide(fixedResponse(sseEvents(raw.replaceAll("\n", "\ndata: ")))),
+        Effect.flip,
+      )
+      expect(error.reason._tag).toBe("ProviderInternal")
+      expect(error.message).toBe("server_shutting_down: Server is shutting down. Please retry your request.")
+      expect(error.reason.body).toBe(raw)
+      expect(error.reason.http?.status).toBe(200)
+    }
+  }),
+)

packages/app/component-tests/ssh-reconnect.spec.ts

@@ -19,11 +19,13 @@ story("cancelling a version mismatch permits reconnecting again", async ({ mount
   const component = await mount("app-dialog-ssh--incompatible-session")
   await component.getByRole("button", { name: "Reconnect", exact: true }).click()
   const dialog = page.getByRole("dialog")
-  await expect(dialog.getByRole("alert")).toBeVisible()
+  await expect(dialog.getByRole("status")).toContainText("Server update required")
+  await expect(dialog.getByRole("textbox")).toHaveCount(0)
   await dialog.getByRole("button", { name: "Cancel", exact: true }).click()
   await expect(dialog).toHaveCount(0)
   await component.getByRole("button", { name: "Reconnect", exact: true }).click()
-  await expect(dialog.getByRole("alert")).toBeVisible()
+  await expect(dialog.getByRole("status")).toContainText("Server update required")
+  await expect(dialog.getByRole("textbox")).toHaveCount(0)
   await dialog.getByRole("button", { name: "Cancel", exact: true }).click()
   await expect(dialog).toHaveCount(0)
 })
@@ -43,6 +45,17 @@ story("adding a server keeps all SSH challenges in the original connection dialo
   await expect(dialog).toHaveCount(0)
 })
 
+story("adding an incompatible server advances to a dedicated update step", async ({ mount, page }) => {
+  await mount("app-dialog-ssh--incompatible-host")
+  const dialog = page.getByRole("dialog")
+  await dialog.getByRole("textbox", { name: "Host or SSH command" }).fill("ssh devbox")
+  await dialog.getByRole("button", { name: "Add server", exact: true }).click()
+  await expect(dialog.getByRole("status")).toContainText("Server update required")
+  await expect(dialog.getByRole("textbox")).toHaveCount(0)
+  await expect(dialog.getByRole("alert")).toHaveCount(0)
+  await expect(dialog.getByRole("button", { name: "Update and reconnect", exact: true })).toBeVisible()
+})
+
 story("updating an incompatible connection continues authentication in the same dialog", async ({ mount, page }) => {
   const component = await mount("app-dialog-ssh--incompatible-session")
   await component.getByRole("button", { name: "Reconnect", exact: true }).click()

packages/app/e2e/regression/session-timeline-reducer-projection.spec.ts

@@ -115,7 +115,7 @@ test("combines follow-up patches into one three-file stack inside Used", async (
   })
   const group = page.locator('[data-component="collapsed-tool-group"]')
   await group.getByRole("button", { name: "Used 2 Shell, Patch", exact: true }).click()
-  await expect(group.getByText("2 files", { exact: true })).toBeVisible()
+  await expect(group.locator('[data-slot="apply-patch-filename"]')).toHaveText(["a.ts", "b.ts"])
   await timeline.send(
     partUpdated(
       toolPart(
@@ -134,7 +134,6 @@ test("combines follow-up patches into one three-file stack inside Used", async (
     "true",
   )
   await expect(group.locator('[data-component="apply-patch-tool"]')).toHaveCount(1)
-  await expect(group.getByText("3 files", { exact: true })).toBeVisible()
   await expect(group.locator('[data-slot="apply-patch-filename"]')).toHaveText(["a.ts", "b.ts", "c.ts"])
 })
 

packages/app/src/runtime/platform/web.ts

@@ -54,8 +54,12 @@ export function createWebPlatform(version: string) {
 
 function getCurrentServerUrl() {
   if (import.meta.env.VITE_OPENCODE_SERVER_MODE === "none") return undefined
-  if (import.meta.env.DEV)
-    return `http://${import.meta.env.VITE_OPENCODE_SERVER_HOST ?? "localhost"}:${import.meta.env.VITE_OPENCODE_SERVER_PORT ?? "4096"}`
+  if (import.meta.env.DEV) {
+    const loopback =
+      location.hostname === "localhost" || location.hostname === "[::1]" || location.hostname.startsWith("127.")
+    const host = import.meta.env.VITE_OPENCODE_SERVER_HOST ?? (loopback ? location.hostname : "localhost")
+    return `http://${host}:${import.meta.env.VITE_OPENCODE_SERVER_PORT ?? "4096"}`
+  }
   return location.origin
 }
 

packages/app/src/runtime/server/runtime.tsx

@@ -10,6 +10,7 @@ import { createData } from "@opencode/client/solid"
 import type { ServerScope } from "@/runtime/server/scope"
 import { createPermissionAutoApprover } from "@/session/requests/auto-approve"
 import { createServerNotificationState } from "@/shell/notifications/notification"
+import { createNotificationCoordinator } from "@/shell/notifications/coordinator"
 import { Persist, persisted } from "@/runtime/persistence/storage"
 import { createDesktopData } from "./data"
 import { ModelState } from "./persistence"
@@ -33,6 +34,7 @@ export const { use: useGlobal, provider: GlobalProvider } = createSimpleContext(
       },
     })
     const models = createGlobalModels()
+    const notificationCoordinator = createNotificationCoordinator()
 
     const settingsServer = createMemo(() => {
       const list = server.list
@@ -57,7 +59,7 @@ export const { use: useGlobal, provider: GlobalProvider } = createSimpleContext(
       if (existing) return existing
       const serverCtx = createRoot((dispose) => {
         serverCtxDisposers.set(key, dispose)
-        return createServerController(conn, server.scope(key), server.projects.forServer(key))
+        return createServerController(conn, server.scope(key), server.projects.forServer(key), notificationCoordinator)
       }, owner)
       serverCtxs.set(key, serverCtx)
       return serverCtx
@@ -131,6 +133,7 @@ function createServerController(
   conn: ServerConnection.Any,
   scope: ServerScope,
   projects: ReturnType<typeof createServerProjects>,
+  notificationCoordinator: ReturnType<typeof createNotificationCoordinator>,
 ) {
   const language = useLanguage()
   const settings = useSettings()
@@ -159,7 +162,7 @@ function createServerController(
   })
   const sync = createServerSyncContext(sdk, data)
   createPermissionAutoApprover({ sdk, data })
-  const notification = createServerNotificationState({ sdk, data, key: connKey })
+  const notification = createServerNotificationState({ sdk, data, key: connKey, coordinator: notificationCoordinator })
 
   function enrich(project: { worktree: string; expanded: boolean }) {
     const [childStore] = sync.child(project.worktree, { bootstrap: false })

packages/app/src/servers/ssh/dialog.stories.tsx

@@ -278,6 +278,7 @@ function Open(props: { initial?: string }) {
 export default { title: "App/Dialogs/SSH", id: "app-dialog-ssh" }
 export const AuthenticationRequired = { render: () => <Fixture initial="required" /> }
 export const SettingsReconnect = { render: () => <Fixture initial="required" settings connectionDelay={200} /> }
+export const IncompatibleHost = { render: () => <Fixture incompatible /> }
 export const IncompatibleSession = { render: () => <Fixture initial="required" session incompatible /> }
 export const InactiveSession = { render: () => <Fixture initial="required" session connectionDelay={3000} /> }
 export const KeyReconnect = { render: () => <Fixture initial="required" session keyOnly connectionDelay={3000} /> }

packages/app/src/servers/ssh/dialog.tsx

@@ -120,7 +120,13 @@ export function DialogSsh(props: {
       <Divider />
       <DialogBody class="flex w-full min-w-0 flex-1 flex-col px-4 pt-4 pb-2">
         <div class="flex w-full min-w-0 flex-col gap-6">
-          <Show when={!props.promptOnly && (!state.prompted || (!!error() && !prompt()))}>
+          <Show
+            when={
+              !props.promptOnly &&
+              item()?.stage !== "incompatible" &&
+              (!state.prompted || (!!error() && !prompt()))
+            }
+          >
             <div class="flex w-full min-w-0 flex-col gap-2">
               <label class="settings-server-dialog-label" for="ssh-target">
                 {language.t("ssh.target")}
@@ -160,6 +166,12 @@ export function DialogSsh(props: {
               />
             </div>
           </Show>
+          <Show when={item()?.stage === "incompatible"}>
+            <div class="flex w-full min-w-0 flex-col gap-2" role="status" aria-live="polite">
+              <span class="text-14-medium text-v2-text-text-base">{language.t("ssh.stage.incompatible")}</span>
+              <span class="text-13-regular text-v2-text-text-muted">{language.t("ssh.error.version")}</span>
+            </div>
+          </Show>
           <Show when={prompt()} keyed>
             {(prompt) => (
               <div class="flex w-full min-w-0 flex-col gap-2">
@@ -195,7 +207,7 @@ export function DialogSsh(props: {
               </div>
             )}
           </Show>
-          <Show when={error()}>
+          <Show when={item()?.stage !== "incompatible" && error()}>
             {(error) => (
               <span class="settings-server-dialog-error !leading-[var(--line-height-compact)]" role="alert">
                 {error()}

packages/app/src/session/files/session-file-browser-tab.tsx

@@ -1,6 +1,6 @@
 import { createMemo, createUniqueId, Show } from "solid-js"
 import { createStore } from "solid-js/store"
-import { createQuery } from "@tanstack/solid-query"
+import { createQuery, keepPreviousData } from "@tanstack/solid-query"
 import { Icon } from "@opencode/ui/icon"
 import { SessionFilePanelV2, SessionFilePanelV2Empty } from "@opencode/session-ui/v2/session-file-panel-v2"
 import { SessionReviewV2Sidebar } from "@opencode/session-ui/v2/session-review-v2"
@@ -56,6 +56,7 @@ export function SessionFileBrowserTab(props: {
       queryKey: [serverSDK.scope, "session-open-file", workspaceKey(), value] as const,
       enabled: serverSDK.connection.status() === "connected" && value.length > 0,
       queryFn: ({ signal }) => file.searchFiles(value, { limit: 200, signal }),
+      placeholderData: keepPreviousData,
     }
   })
   const files = createMemo(() => {

packages/app/src/shell/notifications/coordinator.ts

@@ -0,0 +1,93 @@
+import { onCleanup } from "solid-js"
+
+const FOCUS_LOCK = "opencode:notification-focus"
+const MAX_CLAIMED = 500
+
+export function createNotificationCoordinator() {
+  const locks = typeof navigator === "undefined" ? undefined : navigator.locks
+  const claimed = new Set<string>()
+  const focus = { pending: false, release: undefined as (() => void) | undefined }
+
+  const updateFocus = () => {
+    if (typeof document === "undefined" || !document.hasFocus()) {
+      focus.release?.()
+      return
+    }
+    if (!locks || focus.pending || focus.release) return
+
+    focus.pending = true
+    void locks
+      .request(FOCUS_LOCK, { mode: "shared" }, async () => {
+        focus.pending = false
+        if (!document.hasFocus()) return
+        await new Promise<void>((resolve) => {
+          focus.release = resolve
+        })
+        focus.release = undefined
+      })
+      .catch(() => {
+        focus.pending = false
+      })
+  }
+
+  if (typeof window !== "undefined") {
+    window.addEventListener("focus", updateFocus)
+    window.addEventListener("blur", updateFocus)
+    document.addEventListener("visibilitychange", updateFocus)
+    updateFocus()
+    onCleanup(() => {
+      window.removeEventListener("focus", updateFocus)
+      window.removeEventListener("blur", updateFocus)
+      document.removeEventListener("visibilitychange", updateFocus)
+      focus.release?.()
+    })
+  }
+
+  const once = async (kind: "sound" | "system", eventID: string, run: () => Promise<unknown> | void) => {
+    const key = `${kind}:${eventID}`
+    const execute = async () => {
+      if (!claim(kind, key, claimed)) return
+      await run()
+    }
+    if (!locks) return execute()
+    await locks.request(`opencode:notification:${key}`, execute)
+  }
+
+  return {
+    sound(eventID: string, run: () => Promise<unknown> | void) {
+      return once("sound", eventID, run)
+    },
+    system(eventID: string, run: () => Promise<unknown> | void) {
+      return once("system", eventID, async () => {
+        if (typeof document !== "undefined" && document.hasFocus()) return
+        if (!locks) return run()
+        await locks.request(FOCUS_LOCK, { mode: "exclusive", ifAvailable: true }, async (lock) => {
+          if (!lock) return
+          await run()
+        })
+      })
+    },
+  }
+}
+
+function claim(kind: "sound" | "system", eventID: string, claimed: Set<string>) {
+  if (claimed.has(eventID)) return false
+
+  if (typeof localStorage !== "undefined") {
+    try {
+      const storageKey = `opencode:notification-${kind}`
+      const value: unknown = JSON.parse(localStorage.getItem(storageKey) ?? "[]")
+      const events = Array.isArray(value) ? value.filter((item): item is string => typeof item === "string") : []
+      if (events.includes(eventID)) {
+        claimed.add(eventID)
+        return false
+      }
+      localStorage.setItem(storageKey, JSON.stringify([...events, eventID].slice(-MAX_CLAIMED)))
+    } catch {
+      // The in-memory claim still prevents duplicates in this renderer when storage is unavailable.
+    }
+  }
+
+  claimed.add(eventID)
+  return true
+}

packages/app/src/shell/notifications/notification.tsx

@@ -11,7 +11,8 @@ import { useSettings } from "@/settings/model"
 import { decode64 } from "@/runtime/persistence/base64"
 import { Persist, persisted } from "@/runtime/persistence/storage"
 import { Persistence } from "@/runtime/persistence/schema"
-import { playSoundByIdOnce } from "@/shell/notifications/sound"
+import { playSoundById } from "@/shell/notifications/sound"
+import type { createNotificationCoordinator } from "@/shell/notifications/coordinator"
 import { useGlobal } from "@/runtime/server/runtime"
 import { ServerConnection, useServers } from "@/runtime/server/registry"
 import { sessionIDHasOpenTab, useTabs } from "@/shell/tabs/tabs"
@@ -114,7 +115,12 @@ function buildNotificationIndex(list: Notification[]) {
   return index
 }
 
-export function createServerNotificationState(input: { sdk: ServerSDK; data: Data; key: ServerConnection.Key }) {
+export function createServerNotificationState(input: {
+  sdk: ServerSDK
+  data: Data
+  key: ServerConnection.Key
+  coordinator: ReturnType<typeof createNotificationCoordinator>
+}) {
   const platform = usePlatform()
   const settings = useSettings()
   const language = useLanguage()
@@ -223,7 +229,7 @@ export function createServerNotificationState(input: { sdk: ServerSDK; data: Dat
       if (session.parentID) return
 
       if (sessionIDHasOpenTab(tabs.store, input.key, sessionID) && settings.sounds.agentEnabled()) {
-        void playSoundByIdOnce(settings.sounds.agent(), `${input.key}\0${eventID}`)
+        void input.coordinator.sound(`${input.key}\0${eventID}`, () => playSoundById(settings.sounds.agent()))
       }
 
       append({
@@ -235,8 +241,10 @@ export function createServerNotificationState(input: { sdk: ServerSDK; data: Dat
       })
 
       if (settings.notifications.agent()) {
-        void platform.notify(language.t("notification.session.responseReady.title"), session.title ?? sessionID, () =>
-          openNotificationSession(tabs, input.key, sessionID),
+        void input.coordinator.system(`${input.key}\0${eventID}`, () =>
+          platform.notify(language.t("notification.session.responseReady.title"), session.title ?? sessionID, () =>
+            openNotificationSession(tabs, input.key, sessionID),
+          ),
         )
       }
     })
@@ -248,7 +256,7 @@ export function createServerNotificationState(input: { sdk: ServerSDK; data: Dat
       if (session?.parentID) return
 
       if (sessionIDHasOpenTab(tabs.store, input.key, sessionID) && settings.sounds.errorsEnabled()) {
-        void playSoundByIdOnce(settings.sounds.errors(), `${input.key}\0${eventID}`)
+        void input.coordinator.sound(`${input.key}\0${eventID}`, () => playSoundById(settings.sounds.errors()))
       }
 
       append({
@@ -263,8 +271,10 @@ export function createServerNotificationState(input: { sdk: ServerSDK; data: Dat
         session?.title ??
         (typeof error === "string" ? error : language.t("notification.session.error.fallbackDescription"))
       if (settings.notifications.errors()) {
-        void platform.notify(language.t("notification.session.error.title"), description, () =>
-          openNotificationSession(tabs, input.key, sessionID),
+        void input.coordinator.system(`${input.key}\0${eventID}`, () =>
+          platform.notify(language.t("notification.session.error.title"), description, () =>
+            openNotificationSession(tabs, input.key, sessionID),
+          ),
         )
       }
     })

packages/app/src/shell/notifications/sound.ts

@@ -74,9 +74,6 @@ function getLoads() {
 }
 
 const cache = new Map<SoundID, Promise<string | undefined>>()
-const claimed = new Set<string>()
-const CLAIMED_STORAGE_KEY = "opencode:notification-sounds"
-const MAX_CLAIMED = 500
 
 export function soundSrc(id: string | undefined) {
   const loads = getLoads()
@@ -103,34 +100,3 @@ export function playSound(src: string | undefined) {
 export function playSoundById(id: string | undefined) {
   return soundSrc(id).then((src) => playSound(src))
 }
-
-export async function playSoundByIdOnce(id: string | undefined, eventID: string) {
-  const play = async () => {
-    if (!claim(eventID)) return
-    await playSoundById(id)
-  }
-
-  if (typeof navigator === "undefined" || !navigator.locks) return play()
-  await navigator.locks.request(`${CLAIMED_STORAGE_KEY}:${eventID}`, play)
-}
-
-function claim(eventID: string) {
-  if (claimed.has(eventID)) return false
-
-  if (typeof localStorage !== "undefined") {
-    try {
-      const value: unknown = JSON.parse(localStorage.getItem(CLAIMED_STORAGE_KEY) ?? "[]")
-      const events = Array.isArray(value) ? value.filter((item): item is string => typeof item === "string") : []
-      if (events.includes(eventID)) {
-        claimed.add(eventID)
-        return false
-      }
-      localStorage.setItem(CLAIMED_STORAGE_KEY, JSON.stringify([...events, eventID].slice(-MAX_CLAIMED)))
-    } catch {
-      // The in-memory claim still prevents duplicates in this renderer when storage is unavailable.
-    }
-  }
-
-  claimed.add(eventID)
-  return true
-}

packages/cli/src/acp/config-option.ts

@@ -76,7 +76,10 @@ export function buildEffortSelectOption(input: {
     category: "thought_level",
     type: "select",
     currentValue: selectVariant(input.currentVariant, input.variants),
-    options: input.variants.map((variant) => ({ value: variant, name: formatVariantName(variant) })),
+    options: [...new Set([...input.variants, DEFAULT_VARIANT_VALUE])].map((variant) => ({
+      value: variant,
+      name: formatVariantName(variant),
+    })),
   }
 }
 
@@ -125,6 +128,7 @@ export function formatVariantName(variant: string) {
 }
 
 function selectVariant(variant: string | undefined, variants: readonly string[]) {
+  if (!variant || variant === DEFAULT_VARIANT_VALUE) return DEFAULT_VARIANT_VALUE
   if (variant && variants.includes(variant)) return variant
   if (variants.includes(DEFAULT_VARIANT_VALUE)) return DEFAULT_VARIANT_VALUE
   return variants[0] ?? DEFAULT_VARIANT_VALUE

packages/cli/src/acp/event.ts

@@ -201,7 +201,7 @@ export async function streamTurn(input: {
         if (!child) assistantMessageID = event.data.assistantMessageID
         await send({
           sessionUpdate: "agent_thought_chunk",
-          messageId: event.data.assistantMessageID,
+          messageId: `${event.data.assistantMessageID}:reasoning:${event.data.ordinal}`,
           content: { type: "text", text: event.data.delta },
         })
         continue
@@ -455,6 +455,8 @@ async function replayMessage(
     return
   }
   if (message.type !== "assistant") return
+  // Live reasoning ordinals count only reasoning parts, not the mixed content array.
+  let reasoningOrdinal = 0
   for (const part of message.content) {
     if (part.type === "text") {
       await connection.sessionUpdate({
@@ -472,7 +474,7 @@ async function replayMessage(
         sessionId: sessionID,
         update: {
           sessionUpdate: "agent_thought_chunk",
-          messageId: message.id,
+          messageId: `${message.id}:reasoning:${reasoningOrdinal++}`,
           content: { type: "text", text: part.text },
         },
       })

packages/cli/src/acp/service.ts

@@ -41,7 +41,12 @@ import type {
 } from "@agentclientprotocol/sdk"
 import { OPENCODE_VERSION } from "../version"
 import { SessionMessage } from "@opencode/schema/session-message"
-import { buildConfigOptions, parseModelSelection, type ConfigOptionProvider } from "./config-option"
+import {
+  buildConfigOptions,
+  DEFAULT_VARIANT_VALUE,
+  parseModelSelection,
+  type ConfigOptionProvider,
+} from "./config-option"
 import { promptContentToParts } from "./content"
 import {
   ChildSessionUpdateMethod,
@@ -275,7 +280,7 @@ export function make(input: { readonly client: OpenCodeClient; readonly connecti
       if (typeof params.value !== "string") throw new ACPError.InvalidConfigOptionError({ configId: params.configId })
       switch (params.configId) {
         case "model": {
-          const selected = requireModel(state.catalog, params.value)
+          const selected = requireModel(state.catalog, params.value, state.model)
           state.model = selected
           await input.client.session.switchModel({ sessionID: state.id, model: selected })
           break
@@ -284,7 +289,10 @@ export function make(input: { readonly client: OpenCodeClient; readonly connecti
           const model = state.catalog.models.find(
             (item) => item.providerID === state.model.providerID && item.id === state.model.id,
           )
-          if (!model?.variants.some((variant) => variant.id === params.value))
+          if (
+            !model ||
+            (params.value !== DEFAULT_VARIANT_VALUE && !model.variants.some((variant) => variant.id === params.value))
+          )
             throw new ACPError.InvalidEffortError({ effort: params.value })
           state.model = { ...state.model, variant: params.value }
           await input.client.session.switchModel({ sessionID: state.id, model: state.model })
@@ -453,7 +461,7 @@ function providers(models: readonly ModelInfo[]): ConfigOptionProvider[] {
     }))
 }
 
-function requireModel(catalog: Catalog, modelID: string): ModelRef {
+function requireModel(catalog: Catalog, modelID: string, current: ModelRef): ModelRef {
   const selected = parseModelSelection(modelID, catalog.providers)
   const model = catalog.models.find(
     (item) => item.providerID === selected.model.providerID && item.id === selected.model.modelID,
@@ -461,7 +469,14 @@ function requireModel(catalog: Catalog, modelID: string): ModelRef {
   if (!model) throw new ACPError.InvalidModelError({ providerId: selected.model.providerID, modelId: modelID })
   if (selected.variant && !model.variants.some((variant) => variant.id === selected.variant))
     throw new ACPError.InvalidEffortError({ effort: selected.variant })
-  return { providerID: model.providerID, id: model.id, variant: selected.variant }
+  const variant =
+    selected.variant ??
+    (current.providerID === model.providerID &&
+    current.id === model.id &&
+    (current.variant === DEFAULT_VARIANT_VALUE || model.variants.some((variant) => variant.id === current.variant))
+      ? current.variant
+      : undefined)
+  return { providerID: model.providerID, id: model.id, variant }
 }
 
 async function selectMode(client: OpenCodeClient, state: Attached, modeID: string) {

packages/cli/test/acp/config-options.subprocess.test.ts

@@ -50,11 +50,11 @@ describe("acp config option subprocess", () => {
     const effort = requireSelectOption((await newSession(acp, fixture.home)).configOptions, "effort")
 
     expect(effort.category).toBe("thought_level")
-    expect(effort.currentValue).toBe("low")
-    expect(flattenSelectOptions(effort).map((option) => option.value)).toEqual(["low", "high"])
+    expect(effort.currentValue).toBe("default")
+    expect(flattenSelectOptions(effort).map((option) => option.value)).toEqual(["low", "high", "default"])
   }, 60_000)
 
-  test("effort switch updates currentValue", async () => {
+  test("effort survives model synchronization and can be reset to default", async () => {
     await using fixture = await createAcpFixture()
     const acp = fixture.spawn()
     await initialize(acp)
@@ -70,5 +70,23 @@ describe("acp config option subprocess", () => {
     )
 
     expect(selectConfigOption(updated.configOptions, "effort")?.currentValue).toBe(nextEffort)
+
+    const synchronized = expectOk(
+      await acp.request<SetSessionConfigOptionResponse>("session/set_config_option", {
+        sessionId: session.sessionId,
+        configId: "model",
+        value: requireSelectOption(session.configOptions, "model").currentValue,
+      }),
+    )
+    expect(selectConfigOption(synchronized.configOptions, "effort")?.currentValue).toBe(nextEffort)
+
+    const reset = expectOk(
+      await acp.request<SetSessionConfigOptionResponse>("session/set_config_option", {
+        sessionId: session.sessionId,
+        configId: "effort",
+        value: "default",
+      }),
+    )
+    expect(selectConfigOption(reset.configOptions, "effort")?.currentValue).toBe("default")
   }, 60_000)
 })

packages/cli/test/acp/event-behavior.test.ts

@@ -91,7 +91,7 @@ describe("acp event behavior", () => {
     }
   })
 
-  test("preserves text and reasoning order before returning the terminal response", async () => {
+  test("preserves reasoning boundaries and update order during streaming and replay", async () => {
     const firstUpdate = Promise.withResolvers<void>()
     const releaseUpdate = Promise.withResolvers<void>()
     const allUpdates = Promise.withResolvers<void>()
@@ -108,6 +108,14 @@ describe("acp event behavior", () => {
             delta: "think-1",
           }),
         )
+        send(
+          ephemeralEvent("session.reasoning.delta", {
+            sessionID: "ses_order",
+            assistantMessageID: "msg_order",
+            ordinal: 0,
+            delta: " continued",
+          }),
+        )
         send(
           ephemeralEvent("session.text.delta", {
             sessionID: "ses_order",
@@ -120,7 +128,7 @@ describe("acp event behavior", () => {
           ephemeralEvent("session.reasoning.delta", {
             sessionID: "ses_order",
             assistantMessageID: "msg_order",
-            ordinal: 2,
+            ordinal: 1,
             delta: "think-2",
           }),
         )
@@ -144,7 +152,7 @@ describe("acp event behavior", () => {
           firstUpdate.resolve()
           await releaseUpdate.promise
         }
-        if (updates.length === 3) allUpdates.resolve()
+        if (updates.length === 4) allUpdates.resolve()
       },
       requestPermission: async () => ({ outcome: { outcome: "cancelled" } }),
     } satisfies Connection
@@ -171,18 +179,48 @@ describe("acp event behavior", () => {
           ) {
             return [
               item.update.sessionUpdate,
+              item.update.messageId,
               item.update.content.type === "text" ? item.update.content.text : undefined,
             ]
           }
           return [item.update.sessionUpdate, undefined]
         }),
       ).toEqual([
-        ["agent_thought_chunk", "think-1"],
-        ["agent_message_chunk", "answer"],
-        ["agent_thought_chunk", "think-2"],
+        ["agent_thought_chunk", "msg_order:reasoning:0", "think-1"],
+        ["agent_thought_chunk", "msg_order:reasoning:0", " continued"],
+        ["agent_message_chunk", "msg_order", "answer"],
+        ["agent_thought_chunk", "msg_order:reasoning:1", "think-2"],
       ])
       expect(fixture.requests.at(-1)?.path).toBe("/api/session/ses_order/message/msg_order")
       expect(response).toMatchObject({ stopReason: "end_turn", usage: { totalTokens: 2 } })
+
+      const replayed: SessionUpdateParams[] = []
+      await replayMessages(recordingConnection(replayed), "ses_order", "/workspace", [
+        {
+          id: "msg_order",
+          type: "assistant",
+          agent: "build",
+          model: { providerID: "test", id: "test-model" },
+          time: { created: 1 },
+          content: [
+            { type: "reasoning", text: "think-1 continued" },
+            { type: "text", text: "answer" },
+            { type: "reasoning", text: "think-2" },
+          ],
+        },
+      ])
+      expect(replayed).toEqual([
+        {
+          sessionId: "ses_order",
+          update: {
+            sessionUpdate: "agent_thought_chunk",
+            messageId: "msg_order:reasoning:0",
+            content: { type: "text", text: "think-1 continued" },
+          },
+        },
+        updates[2],
+        updates[3],
+      ])
     } finally {
       releaseUpdate.resolve()
       releaseSubmit.resolve()

packages/cli/test/acp/service-directory.test.ts

@@ -222,7 +222,7 @@ describe("acp service directory behavior", () => {
     await fixture.service.setSessionMode({ sessionId: session.sessionId, modeId: "build" })
 
     expect(currentValue(selectedModel, "model")).toBe("test/second-model")
-    expect(currentValue(selectedModel, "effort")).toBe("low")
+    expect(currentValue(selectedModel, "effort")).toBe("default")
     expect(currentValue(selectedEffort, "effort")).toBe("medium")
     expect(currentValue(selectedMode, "mode")).toBe("plan")
     expect(

packages/cli/test/acp/service-lifecycle.test.ts

@@ -32,7 +32,7 @@ describe("acp service lifecycle", () => {
         model: { providerID: "test", id: "second-model" },
       },
     })
-    expect(currentValue(created, "effort")).toBe("none")
+    expect(currentValue(created, "effort")).toBe("default")
   })
 
   test("loads and forks with paginated replay while resume does not replay", async () => {

packages/codemode/interpreter-support.md

@@ -9,7 +9,8 @@ standard-library surface that programs can use today, plus concrete gaps that ma
 - Intentional boundaries are not listed as compatibility work.
 
 When behavior changes, update this file and the tests in the same change. The implementation and tests remain the
-ultimate source of truth.
+ultimate source of truth. Upstream test262 files run verbatim from `test/test262`; a failing file is listed in
+`test/test262/skipped.txt` and its gap is an unchecked item here (see `test/test262/README.md`).
 
 ## Source and execution model
 
@@ -25,6 +26,10 @@ ultimate source of truth.
 - [x] The global `search(...)` built-in: synchronous tool discovery that counts as an admitted tool call and is
       shadowable by program declarations like other globals.
 - [x] Cooperative timeout, an optional total tool-call limit, output bounding, and unrestricted tool-call concurrency.
+- [ ] Strict-mode early errors: duplicate parameter names, `yield` as an identifier, and a trailing comma after a
+      rest parameter are accepted unless the program itself begins with `"use strict"`.
+- [ ] Valid JavaScript rejected by TypeScript transpilation before interpretation, such as `in` inside a destructuring
+      default in a `for...of` head and Unicode-escaped keywords.
 
 ## Values and literals
 
@@ -64,6 +69,11 @@ ultimate source of truth.
 - [x] Array binding and assignment destructuring from strings, Maps, Sets, URLSearchParams, custom synchronous
       iterators, and synchronous generators, including stepwise elisions/rest and `IteratorClose` on early completion
       or binding/default failure.
+- [ ] Object destructuring from primitives follows ToObject (`const { length } = "abc"`, `const {} = 1`); non-object
+      sources are rejected.
+- [ ] Destructuring a key that member access resolves through the owning built-in, such as
+      `const { constructor } = error`, reads `undefined`.
+- [ ] Member expressions as `for...in` targets (`for (x.y in obj)`).
 
 ## Statements and control flow
 
@@ -111,6 +121,15 @@ ultimate source of truth.
 - [ ] User-defined constructor calls.
 - [ ] `Function.prototype.call`, `apply`, and `bind` for CodeMode functions.
 - [ ] Classes and private fields.
+- [x] Functions are objects: they hold own properties (`fn.count = 1`), enumerate them, and expose read-only `name`
+      and `length`. Names follow JavaScript's NamedEvaluation: declarations, named expressions, bindings,
+      assignments, object literal keys, and destructuring or parameter defaults.
+- [ ] `name` and `length` of built-in functions such as `Math.max` or `"a".includes`.
+- [ ] A named function expression's name is not bound inside its own body.
+- [ ] Redeclaring a function in the same scope is rejected; in JavaScript the last declaration wins.
+- [ ] A line terminator between `async function` and the function name.
+- [ ] Async generator functions evaluate parameter defaults and destructuring at the first `next()` rather than at the
+      call, so their errors are not thrown synchronously.
 - [x] Synchronous and async generator declarations/expressions, `yield`, and `yield*`, including lazy bodies,
       `next(value)`, `return(value)`, `throw(value)`, exhaustion, promise adoption, async request ordering,
       `try`/`catch`/`finally`, and sync/async iterator symbols. Async `yield*` awaits values while adapting a sync
@@ -154,6 +173,8 @@ ultimate source of truth.
 - [x] Plain, arithmetic, bitwise, and logical assignment operators.
 - [x] Property deletion on plain data objects and arrays, including computed and optional forms; deleting an array index
       creates a hole without changing its length.
+- [ ] Operators, `switch` discriminants, and coercion helpers such as `String` and `isNaN` applied to functions and
+      namespaces; JavaScript coerces them, the interpreter rejects non-data operands.
 
 ## Promises and tools
 
@@ -225,7 +246,8 @@ ultimate source of truth.
 - [x] Circular references are rejected when created (`o.self = o`, `array.push(array)`), not at serialization as in JS.
 - [x] `Object.is` for supported data values.
 - [x] `Object.groupBy` over finite collections and custom synchronous iterators/generators, with string-key coercion
-      and null-prototype results.
+      and plain-object results.
+- [ ] `Object.prototype` methods on values: `toString`, `toLocaleString`, `valueOf`, and `hasOwnProperty`.
 
 ## Arrays
 
@@ -245,10 +267,18 @@ ultimate source of truth.
 - [x] `length`, numeric indexing, index assignment, spread, and `for...of`.
 - [x] The `thisArg` argument of `Array.from` is accepted and ignored, like JS arrows.
 - [x] `Array.prototype.toSpliced`.
-- [x] Canonical array/string index parsing: keys such as `"01"` remain non-index properties rather than aliasing index
-      `1`; arbitrary array-property assignment remains unsupported.
+- [x] Canonical array/string index parsing: keys such as `"01"` are ordinary properties rather than aliases of index
+      `1`.
 - [x] `Array.prototype.sort` preserves trailing holes, while `toSorted` densifies holes into `undefined` elements,
       like JavaScript.
+- [x] Assigning `length` to truncate or extend an array; invalid lengths throw `RangeError`.
+- [x] Non-index own properties on arrays (`arr.foo = 1`, `arr.constructor = null`). They are excluded from the JSON
+      form, like `JSON.stringify`.
+- [ ] Argument coercion for `indexOf`, `lastIndexOf`, `includes`, `fill`, `flat`, `copyWithin`, and the `join`
+      separator: JavaScript applies ToIntegerOrInfinity/ToString (including `valueOf`, strings, and `undefined`), the
+      interpreter requires numbers and strings; `includes()`/`indexOf()` with no argument should search for
+      `undefined`.
+- [ ] Iterator objects from `keys`, `values`, and `entries` with a live `next()`.
 
 ## Strings
 
@@ -332,7 +362,7 @@ ultimate source of truth.
 - [x] `test`, `exec`, and `toString`.
 - [x] Readable `source`, `flags`, `lastIndex`, `hasIndices`, `global`, `ignoreCase`, `multiline`, `sticky`, `unicode`,
       `unicodeSets`, and `dotAll`.
-- [x] Captures, named groups, match `.index`, and stateful global matching.
+- [x] Captures, named groups, match `.index` and `.input`, and stateful global matching.
 - [x] Integration with supported String methods, including function replacers.
 - [x] Writable `lastIndex`.
 - [x] Match `indices` metadata for the `d` flag, including named groups on `exec`, `match`, and `matchAll` results.
@@ -391,3 +421,5 @@ ultimate source of truth.
 - [x] Caught errors do not distinguish user throws, interpreter failures, and tool failures; a program sees one
       Error-shaped value with `name` and `message` in `catch`, rejection handlers, and `Promise.allSettled` reasons.
       This is deliberate: the program should handle a failure the same way regardless of where it originated.
+- [ ] Failures raised by the interpreter itself carry the generic `Error` name where JavaScript throws a `TypeError`,
+      `RangeError`, or `ReferenceError`, so `e instanceof TypeError` and `e.constructor === TypeError` are false.

packages/codemode/script/sync-test262.ts

@@ -0,0 +1,62 @@
+// Copies the manifest's test262 directories from a local checkout into test/test262, verbatim.
+// Files needing unsupported flags, features, or harness includes, or whose code crosses one of the
+// interpreter's intentional boundaries, are not copied, so the vendored tree is exactly what
+// test/test262.test.ts runs.
+//
+// Usage: bun run script/sync-test262.ts /path/to/test262
+import path from "node:path"
+import { rm } from "node:fs/promises"
+
+type Frontmatter = { flags?: Array<string>; features?: Array<string>; includes?: Array<string> }
+
+const root = path.resolve(import.meta.dir, "../test/test262")
+const manifest = (await Bun.file(path.join(root, "manifest.json")).json()) as {
+  revision: string
+  directories: Array<string>
+  harness: Array<string>
+  flags: Array<string>
+  features: Array<string>
+  boundaries: Record<string, string>
+}
+const boundaries = Object.entries(manifest.boundaries).map(([name, pattern]) => [name, new RegExp(pattern)] as const)
+const checkout = process.argv[2]
+if (checkout === undefined) {
+  console.error("usage: bun run script/sync-test262.ts /path/to/test262")
+  process.exit(1)
+}
+const head = (await Bun.$`git -C ${checkout} rev-parse HEAD`.text()).trim()
+if (head !== manifest.revision) {
+  console.error(`checkout is at ${head}; manifest pins ${manifest.revision}`)
+  process.exit(1)
+}
+
+const excluded = new Map<string, number>()
+let copied = 0
+for (const dir of manifest.directories) {
+  await rm(path.join(root, dir), { recursive: true, force: true })
+  const from = path.join(checkout, "test", dir)
+  for await (const file of new Bun.Glob("**/*.js").scan({ cwd: from })) {
+    if (file.endsWith("_FIXTURE.js")) continue
+    const source = await Bun.file(path.join(from, file)).text()
+    const start = source.indexOf("/*---")
+    const end = source.indexOf("---*/", start)
+    const meta = start === -1 ? {} : (Bun.YAML.parse(source.slice(start + 5, end)) as Frontmatter)
+    const code = start === -1 ? source : source.slice(end + 5)
+    const reason =
+      meta.flags?.find((flag) => manifest.flags.includes(flag)) ??
+      meta.features?.find((feature) => manifest.features.includes(feature)) ??
+      meta.includes?.find((include) => !manifest.harness.includes(include)) ??
+      boundaries.find(([, pattern]) => pattern.test(code))?.[0]
+    if (reason !== undefined) {
+      excluded.set(reason, (excluded.get(reason) ?? 0) + 1)
+      continue
+    }
+    await Bun.write(path.join(root, dir, file), Bun.file(path.join(from, file)))
+    copied++
+  }
+}
+
+console.log(`copied ${copied} files`)
+for (const [reason, count] of [...excluded].sort((a, b) => b[1] - a[1])) {
+  console.log(`  excluded ${String(count).padStart(5)}  ${reason}`)
+}

packages/codemode/script/test262-report.ts

@@ -0,0 +1,55 @@
+// Runs every vendored test262 file, including skipped ones, and groups failures by cause. Pass
+// --write to regenerate test/test262/skipped.txt from the current failures.
+//
+// Usage: bun run script/test262-report.ts [--write] [path-prefix]
+import path from "node:path"
+import { root, run, skipped } from "../test/test262/run.js"
+
+const write = process.argv.includes("--write")
+const prefix = process.argv.slice(2).find((arg) => !arg.startsWith("--")) ?? ""
+const files = [...new Bun.Glob("**/*.js").scanSync({ cwd: root })].filter((file) => file.startsWith(prefix)).sort()
+
+const failures: Array<{ file: string; reason: string }> = []
+const recovered: Array<string> = []
+for (const file of files) {
+  const outcome = await run(file)
+  if (outcome.status === "fail") failures.push({ file, reason: outcome.reason })
+  if (outcome.status === "pass" && skipped.has(file)) recovered.push(file)
+}
+
+// Collapse a reason to the part that identifies the cause rather than the test.
+const bucket = (reason: string) => {
+  const syntax = reason.match(/Syntax '([A-Za-z]+)' is not supported/)
+  if (syntax) return `unsupported syntax ${syntax[1]}`
+  if (reason.startsWith("expected ")) return reason.replace(/ but got .*/, " but the program ran")
+  return reason
+    .replace(/^(\$DONE: |ExecutionFailure: |InvalidDataValue: |ParseError: |Uncaught: |Test262Error: |Error: )+/, "")
+    .replace(/ \(line \d+, col \d+\)/, "")
+    .replace(/^[\w$]+\.(\w+) is not a function/, ".$1 is not a function")
+    .replace(/^[\w$]+ cannot be constructed/, "… cannot be constructed")
+    .replace(/'[^']*'/g, "'…'")
+    .slice(0, 100)
+}
+
+const buckets = new Map<string, Array<string>>()
+for (const failure of failures) {
+  const key = bucket(failure.reason)
+  buckets.set(key, [...(buckets.get(key) ?? []), failure.file])
+}
+
+console.log(`${files.length - failures.length} pass, ${failures.length} fail of ${files.length}\n`)
+for (const [key, list] of [...buckets].sort((a, b) => b[1].length - a[1].length)) {
+  console.log(`${String(list.length).padStart(5)}  ${key}`)
+  for (const file of list.slice(0, 3)) console.log(`         ${file}`)
+  if (list.length > 3) console.log(`         … ${list.length - 3} more`)
+}
+if (recovered.length > 0) {
+  console.log(`\n${recovered.length} skipped files pass now; remove them from skipped.txt:`)
+  for (const file of recovered) console.log(`         ${file}`)
+}
+
+if (write) {
+  const lines = failures.map((failure) => `${failure.file}  # ${bucket(failure.reason)}`)
+  await Bun.write(path.join(root, "skipped.txt"), `${lines.join("\n")}\n`)
+  console.log(`\nwrote ${lines.length} entries to skipped.txt`)
+}

packages/codemode/src/data.ts

@@ -1,11 +1,16 @@
 export * as Data from "./data.js"
 
 import type { DiagnosticKind } from "./codemode.js"
+import {
+  ownEntries,
+  parseArrayIndex,
+  ProgramArray,
+  ProgramFunction,
+  ProgramObject,
+  set,
+} from "./interpreter/objects.js"
 import { Values } from "./values.js"
 
-/** A null-prototype object owned by the program. */
-export type SafeObject = Record<string, unknown>
-
 const MAX_VALUE_DEPTH = 32
 
 export class ToolRuntimeError extends Error {
@@ -23,15 +28,15 @@ export class ToolRuntimeError extends Error {
 }
 
 /**
- * Brings a host-produced runtime value into the program: runtime values pass through, their host
- * counterparts (Date, RegExp, Map, Set, URL, URLSearchParams) are wrapped, and objects become
- * null-prototype copies. Arrays keep extra enumerable properties such as `index` and `groups`.
+ * Brings a host-produced value into the program: program and runtime values pass through, their
+ * host counterparts (Date, RegExp, Map, Set, URL, URLSearchParams) are wrapped, and host objects
+ * and arrays are copied.
  */
 export const toProgram = (value: unknown, label: string): unknown => copy(value, label, "program", 0, new Set())
 
 /**
  * Brings host data into the program: Date and URL become strings, other host collections become
- * empty objects, and objects become null-prototype copies. Used for tool results and parsed JSON.
+ * empty objects, and objects become program copies. Used for tool results and parsed JSON.
  */
 export const fromData = (value: unknown, label: string): unknown => copy(value, label, "data", 0, new Set())
 
@@ -44,8 +49,7 @@ export const fromData = (value: unknown, label: string): unknown => copy(value,
 export const toData = (value: unknown, label: string, undefinedAs: "json" | "result" = "json"): unknown =>
   copy(value, label, undefinedAs, 0, new Set())
 
-// "program" and "data" build program-owned null-prototype objects; "json" and "result" build
-// ordinary objects for the host.
+// "program" and "data" build program objects; "json" and "result" build ordinary objects for the host.
 type Mode = "program" | "data" | "json" | "result"
 
 const copy = (value: unknown, label: string, mode: Mode, depth: number, seen: Set<object>): unknown => {
@@ -64,9 +68,13 @@ const copy = (value: unknown, label: string, mode: Mode, depth: number, seen: Se
       `${label} contains an un-awaited Promise; await tool calls (e.g. \`const result = await tools.ns.tool(...)\`) before using their results.`,
     )
   }
+  if (value instanceof ProgramFunction && mode !== "program") {
+    throw new ToolRuntimeError("InvalidDataValue", `${label} must contain data only.`)
+  }
 
+  const plain = mode === "program" || mode === "data"
   if (mode === "program") {
-    if (Values.isValue(value)) return value
+    if (value instanceof ProgramObject || Values.isValue(value)) return value
     if (value instanceof Date) return new Values.Date(value.getTime())
     if (value instanceof RegExp) return new Values.RegExp(value.source, value.flags)
     if (value instanceof Map) {
@@ -85,7 +93,6 @@ const copy = (value: unknown, label: string, mode: Mode, depth: number, seen: Se
     if (value instanceof URLSearchParams) return new Values.URLSearchParams(new URLSearchParams(value))
   }
 
-  const plain = mode === "program" || mode === "data"
   if (value instanceof Values.Date) return Number.isFinite(value.time) ? new Date(value.time).toISOString() : null
   if (value instanceof Date) return Number.isFinite(value.getTime()) ? value.toISOString() : null
   if (value instanceof Values.URL) return value.url.href
@@ -98,7 +105,7 @@ const copy = (value: unknown, label: string, mode: Mode, depth: number, seen: Se
     value instanceof Set ||
     value instanceof URLSearchParams
   ) {
-    return plain ? (Object.create(null) as SafeObject) : {}
+    return plain ? new ProgramObject() : {}
   }
 
   if (seen.has(value)) {
@@ -106,27 +113,48 @@ const copy = (value: unknown, label: string, mode: Mode, depth: number, seen: Se
   }
   seen.add(value)
 
-  if (Array.isArray(value)) {
-    // Host output densifies holes to null like JSON; program copies keep them.
-    const copied = plain
-      ? value.map((item) => copy(item, label, mode, depth + 1, seen))
-      : Array.from(value, (item) => copy(item, label, mode, depth + 1, seen) ?? null)
-    if (mode === "program") {
-      for (const [key, item] of Object.entries(value)) {
-        if (Object.hasOwn(copied, key)) continue
-        define(copied, key, copy(item, label, mode, depth + 1, seen))
-      }
+  if (value instanceof ProgramArray) {
+    const copied = Array.from(value.items, (item) => copy(item, label, mode, depth + 1, seen) ?? null)
+    seen.delete(value)
+    return copied
+  }
+  if (value instanceof ProgramObject) {
+    const copied: Record<string, unknown> = {}
+    for (const [key, item] of ownEntries(value)) {
+      const next = copy(item, label, mode, depth + 1, seen)
+      if (next === undefined && mode === "json") continue
+      define(copied, key, next)
     }
     seen.delete(value)
     return copied
   }
 
+  if (Array.isArray(value)) {
+    if (plain) {
+      const copied = new ProgramArray(value.map((item) => copy(item, label, mode, depth + 1, seen)))
+      for (const [key, item] of Object.entries(value)) {
+        if (parseArrayIndex(key) === undefined) set(copied, key, copy(item, label, mode, depth + 1, seen))
+      }
+      seen.delete(value)
+      return copied
+    }
+    const copied = Array.from(value, (item) => copy(item, label, mode, depth + 1, seen) ?? null)
+    seen.delete(value)
+    return copied
+  }
+
   const prototype = Object.getPrototypeOf(value)
   if (prototype !== Object.prototype && prototype !== null) {
     throw new ToolRuntimeError("InvalidDataValue", `${label} must contain plain objects only.`)
   }
 
-  const copied: SafeObject = plain ? (Object.create(null) as SafeObject) : {}
+  if (plain) {
+    const copied = new ProgramObject()
+    for (const [key, item] of Object.entries(value)) set(copied, key, copy(item, label, mode, depth + 1, seen))
+    seen.delete(value)
+    return copied
+  }
+  const copied: Record<string, unknown> = {}
   for (const [key, item] of Object.entries(value)) {
     const next = copy(item, label, mode, depth + 1, seen)
     if (next === undefined && mode === "json") continue
@@ -136,8 +164,8 @@ const copy = (value: unknown, label: string, mode: Mode, depth: number, seen: Se
   return copied
 }
 
-// Own data property regardless of the target's prototype, so a "__proto__" key on a host object or
-// array never reaches the Object.prototype setter.
+// Own data property regardless of the target's prototype, so a "__proto__" key on a host object
+// never reaches the Object.prototype setter.
 const define = (target: object, key: string, value: unknown): void => {
   Object.defineProperty(target, key, { value, enumerable: true, writable: true, configurable: true })
 }

packages/codemode/src/interpreter/errors.ts

@@ -1,10 +1,11 @@
 import { Effect } from "effect"
 import type { Diagnostic } from "../codemode.js"
 import { ToolError } from "../tool-error.js"
-import { type SafeObject, toData, ToolRuntimeError } from "../data.js"
+import { toData, ToolRuntimeError } from "../data.js"
 import { type AstNode, formatLocation, InterpreterRuntimeError, ProgramThrow, sourceLocation } from "./model.js"
 import { containsRuntimeReference } from "./references.js"
 import { type HostCall, HostFunction } from "./host.js"
+import { get, ProgramError, ProgramObject } from "./objects.js"
 import { type Runner } from "./runner.js"
 import {
   coerceToString,
@@ -44,12 +45,8 @@ export const normalizeError = (error: unknown): Diagnostic => {
       message = "a non-data value"
     } else if (typeof value === "string") {
       message = value
-    } else if (
-      value !== null &&
-      typeof value === "object" &&
-      typeof (value as { message?: unknown }).message === "string"
-    ) {
-      message = (value as { message: string }).message
+    } else if (value instanceof ProgramObject && typeof get(value, "message") === "string") {
+      message = get(value, "message") as string
     } else {
       try {
         message = JSON.stringify(toData(value, "Thrown value")) ?? String(value)
@@ -87,14 +84,14 @@ export const caughtErrorValue = (thrown: unknown): unknown => {
   return createErrorValue(name, normalizeError(thrown).message)
 }
 
-const constructErrorValue = (name: string, args: Array<unknown>): SafeObject =>
+const constructErrorValue = (name: string, args: Array<unknown>): ProgramError =>
   createErrorValue(name, args[0] === undefined ? "" : coerceToString(args[0]))
 
 const constructAggregateErrorValue = <R>(
   runner: Runner<R>,
   args: Array<unknown>,
   node: AstNode,
-): Effect.Effect<SafeObject, unknown, R> =>
+): Effect.Effect<ProgramError, unknown, R> =>
   Effect.gen(function* () {
     const cursor = yield* runner.syncIterator(args[0], node)
     if (cursor === undefined) {

packages/codemode/src/interpreter/execute.ts

@@ -7,6 +7,7 @@ import type { DataValue, Diagnostic, ResolvedExecutionLimits, Result } from "../
 import { toData } from "../data.js"
 import { ToolRuntime } from "../tool-runtime.js"
 import { normalizeError } from "./errors.js"
+import type { Host } from "./globals.js"
 import { InterpreterRuntimeError } from "./model.js"
 import { PromiseRuntime } from "./promises.js"
 import { Runtime } from "./runtime.js"
@@ -16,6 +17,7 @@ export const executeProgram = <R>(
   prepared: ToolRuntime.Prepared<R>,
   limits: ResolvedExecutionLimits,
   hooks: ToolRuntime.ToolCallHooks<R>,
+  extraGlobals?: (host: Host<R>) => ReadonlyArray<readonly [string, unknown]>,
 ): Effect.Effect<Result, never, R> => {
   if (code.trim().length === 0) {
     return Effect.succeed({
@@ -39,7 +41,14 @@ export const executeProgram = <R>(
         Effect.gen(function* () {
           const program = parseProgram(code)
           const promises = new PromiseRuntime<R>(scope)
-          const value = yield* new Runtime<R>(tools.execute, tools.search, tools.keys, promises, logs).run(program)
+          const value = yield* new Runtime<R>(
+            tools.execute,
+            tools.search,
+            tools.keys,
+            promises,
+            logs,
+            extraGlobals,
+          ).run(program)
           const result = toData(value, "Execution result", "result") as DataValue
           returned = { value: result, promises }
           const warnings = yield* promises.interrupt()

packages/codemode/src/interpreter/methods.ts

@@ -1,13 +1,14 @@
 import { Effect } from "effect"
-import { type SafeObject, toProgram } from "../data.js"
+import { toProgram } from "../data.js"
 import { dateSetterArgumentCount, invokeDateMethod } from "../stdlib/date.js"
 import { invokeNumberMethod } from "../stdlib/number.js"
 import { invokeRegExpMethod, matchToValue, toHostRegex } from "../stdlib/regexp.js"
 import { invokeURLMethod, uriArgument } from "../stdlib/url.js"
-import { coerceToNumber, coerceToString, errorBrandName } from "../stdlib/value.js"
+import { coerceToNumber, coerceToString } from "../stdlib/value.js"
 import { compareText } from "../tool-runtime.js"
 import { Values } from "../values.js"
 import { type AstNode, IntrinsicReference, InterpreterRuntimeError } from "./model.js"
+import { get, ProgramArray, ProgramObject, record } from "./objects.js"
 import { containsOpaqueReference, rejectCircularInsertion, typeofValue } from "./references.js"
 import { applyCollectionCallback, isSupportedCallback, type Runner, toPrimitive } from "./runner.js"
 
@@ -16,6 +17,14 @@ export const invokeIntrinsic = <R>(
   ref: IntrinsicReference,
   args: Array<unknown>,
   node: AstNode,
+): Effect.Effect<unknown, unknown, R> =>
+  Effect.map(invoke(runner, ref, args, node), (result) => (Array.isArray(result) ? new ProgramArray(result) : result))
+
+const invoke = <R>(
+  runner: Runner<R>,
+  ref: IntrinsicReference,
+  args: Array<unknown>,
+  node: AstNode,
 ): Effect.Effect<unknown, unknown, R> => {
   if (typeof ref.receiver === "string") {
     if (ref.name === "replace" || ref.name === "replaceAll") {
@@ -32,7 +41,7 @@ export const invokeIntrinsic = <R>(
   if (typeof ref.receiver === "number") {
     return Effect.succeed(invokeNumberMethod(ref.receiver, ref.name, args, node))
   }
-  if (Array.isArray(ref.receiver)) {
+  if (ref.receiver instanceof ProgramArray) {
     return invokeArrayMethod(runner, ref.receiver, ref.name, args, node)
   }
   if (ref.receiver instanceof Values.Date) {
@@ -215,7 +224,7 @@ const invokeStringMethod = (value: string, name: string, args: Array<unknown>, n
           node,
         )
       }
-      return Array.from(value.matchAll(pattern), matchToValue)
+      return new ProgramArray(Array.from(value.matchAll(pattern), matchToValue))
     }
     case "search": {
       result = value.search(toHostRegex(args[0], name, node))
@@ -288,13 +297,7 @@ const invokeStringReplacer = <R>(
     if (typeof match !== "string" || typeof offset !== "number") {
       throw new InterpreterRuntimeError(`String.${name} produced an invalid replacement match.`, node)
     }
-    if (hasGroups) {
-      const safeGroups: SafeObject = Object.create(null) as SafeObject
-      for (const [key, group] of Object.entries(groups)) {
-        safeGroups[key] = group
-      }
-      callbackArgs[callbackArgs.length - 1] = safeGroups
-    }
+    if (hasGroups) callbackArgs[callbackArgs.length - 1] = record(groups as Record<string, unknown>)
     matches.push({ match, offset, args: callbackArgs })
     return match
   }
@@ -320,14 +323,11 @@ const invokeStringReplacer = <R>(
     let end = 0
     for (const match of matches) {
       const replacement = yield* apply(match.args)
-      // Error values are branded plain objects; toProgram would strip the brand before coercion.
       output.push(
         value.slice(end, match.offset),
         replacement instanceof Values.Promise
           ? "[object Promise]"
-          : errorBrandName(replacement)
-            ? coerceToString(replacement)
-            : coerceToString(toProgram(replacement, `String.${name} replacer result`)),
+          : coerceToString(toProgram(replacement, `String.${name} replacer result`)),
       )
       end = match.offset + match.match.length
     }
@@ -365,7 +365,7 @@ const invokeMapMethod = <R>(
     case "values":
       return Effect.sync(() => Array.from(target.map.values()))
     case "entries":
-      return Effect.sync(() => Array.from(target.map.entries(), ([key, item]): Array<unknown> => [key, item]))
+      return Effect.sync(() => Array.from(target.map.entries(), ([key, item]) => new ProgramArray([key, item])))
     case "forEach": {
       const apply = applyCollectionCallback(runner, args[0], "Map.forEach", node)
       return Effect.gen(function* () {
@@ -404,7 +404,7 @@ const invokeSetMethod = <R>(
     case "values":
       return Effect.sync(() => Array.from(target.set.values()))
     case "entries":
-      return Effect.sync(() => Array.from(target.set.values(), (item): Array<unknown> => [item, item]))
+      return Effect.sync(() => Array.from(target.set.values(), (item) => new ProgramArray([item, item])))
     case "forEach": {
       const apply = applyCollectionCallback(runner, args[0], "Set.forEach", node)
       return Effect.gen(function* () {
@@ -518,28 +518,27 @@ const loadSetRecord = <R>(runner: Runner<R>, source: unknown, name: string, node
       keys: () => Effect.succeed(source.map.keys()),
     })
   }
-  if (source === null || typeof source !== "object" || Values.isValue(source)) {
+  if (!(source instanceof ProgramObject)) {
     throw new InterpreterRuntimeError(`Set.${name} expects a Set-like object.`, node).as("TypeError")
   }
-  const object = source as Record<string, unknown>
   return Effect.gen(function* () {
-    const size = yield* coerceNumericArgument(runner, object.size, node)
+    const size = yield* coerceNumericArgument(runner, get(source, "size"), node)
     if (Number.isNaN(size)) {
       throw new InterpreterRuntimeError(`Set.${name} received a Set-like object with an invalid size.`, node).as(
         "TypeError",
       )
     }
-    if (!isSupportedCallback(object.has) || !isSupportedCallback(object.keys)) {
+    const has = get(source, "has")
+    const keys = get(source, "keys")
+    if (!isSupportedCallback(has) || !isSupportedCallback(keys)) {
       throw new InterpreterRuntimeError(`Set.${name} expects callable 'has' and 'keys' methods.`, node).as("TypeError")
     }
-    const has = object.has
-    const keys = object.keys
     return {
       size: Math.max(Math.trunc(size), 0),
       has: (item: unknown) => Effect.map(runner.invokeCallable(has, [item], node), Boolean),
       keys: () =>
         Effect.flatMap(runner.invokeCallable(keys, [], node), (result) => {
-          if (Array.isArray(result)) return Effect.succeed(result)
+          if (result instanceof ProgramArray) return Effect.succeed(result.items)
           throw new InterpreterRuntimeError(`Set.${name} expected 'keys' to return an iterator.`, node).as("TypeError")
         }),
     }
@@ -604,7 +603,7 @@ const invokeURLSearchParamsMethod = <R>(
     case "values":
       return Effect.sync(() => Array.from(target.params.values()))
     case "entries":
-      return Effect.sync(() => Array.from(target.params.entries(), ([key, value]): Array<unknown> => [key, value]))
+      return Effect.sync(() => Array.from(target.params.entries(), ([key, value]) => new ProgramArray([key, value])))
     case "toString":
       return Effect.sync(() => target.params.toString())
     case "forEach": {
@@ -622,11 +621,12 @@ const invokeURLSearchParamsMethod = <R>(
 
 const invokeArrayMethod = <R>(
   runner: Runner<R>,
-  target: Array<unknown>,
+  receiver: ProgramArray,
   name: string,
   args: Array<unknown>,
   node: AstNode,
 ): Effect.Effect<unknown, unknown, R> => {
+  const target = receiver.items
   const optNumber = (value: unknown, label: string): number | undefined => {
     if (value === undefined) return undefined
     if (typeof value !== "number")
@@ -638,9 +638,8 @@ const invokeArrayMethod = <R>(
       if (args.length > 1 || (args.length === 1 && typeof args[0] !== "string")) {
         throw new InterpreterRuntimeError("Array.join expects zero arguments or one string separator.", node)
       }
-      const input = toProgram(target, "Array.join input") as Array<unknown>
       return Effect.succeed(
-        input.map((item) => coerceToString(item ?? "")).join(args.length === 0 ? "," : (args[0] as string)),
+        target.map((item) => coerceToString(item ?? "")).join(args.length === 0 ? "," : (args[0] as string)),
       )
     }
     case "includes":
@@ -660,11 +659,15 @@ const invokeArrayMethod = <R>(
     case "slice":
       return Effect.succeed(target.slice(optNumber(args[0], "start"), optNumber(args[1], "end")))
     case "concat":
-      return Effect.succeed(target.concat(...args))
-    case "flat":
-      return Effect.succeed(target.flat(optNumber(args[0], "depth") ?? 1))
+      return Effect.succeed(target.concat(...args.map((item) => (item instanceof ProgramArray ? item.items : item))))
+    case "flat": {
+      const flatten = (items: Array<unknown>, depth: number): Array<unknown> =>
+        items.flatMap((item) => (item instanceof ProgramArray && depth > 0 ? flatten(item.items, depth - 1) : [item]))
+      return Effect.succeed(flatten(target, optNumber(args[0], "depth") ?? 1))
+    }
     case "reverse":
-      return Effect.succeed(target.reverse())
+      target.reverse()
+      return Effect.succeed(receiver)
     case "sort": {
       const length = target.length
       const holeCount = Array.from({ length }, (_, index) => Object.hasOwn(target, index)).filter((own) => !own).length
@@ -676,7 +679,7 @@ const invokeArrayMethod = <R>(
         Array.from({ length: holeCount }, (_, index) => itemCount + index).forEach((index) => {
           Reflect.deleteProperty(target, index)
         })
-        return target
+        return receiver
       })
     }
     case "toSorted":
@@ -695,12 +698,12 @@ const invokeArrayMethod = <R>(
     }
     case "push": {
       // Validate all insertions before mutating to avoid partial cyclic updates.
-      for (const item of args) rejectCircularInsertion(target, item, "Array.push result", node)
+      for (const item of args) rejectCircularInsertion(receiver, item, "Array.push result", node)
       target.push(...args)
       return Effect.succeed(target.length)
     }
     case "unshift": {
-      for (const item of args) rejectCircularInsertion(target, item, "Array.unshift result", node)
+      for (const item of args) rejectCircularInsertion(receiver, item, "Array.unshift result", node)
       target.unshift(...args)
       return Effect.succeed(target.length)
     }
@@ -714,7 +717,7 @@ const invokeArrayMethod = <R>(
       if (args.length === 1) return Effect.succeed(target.splice(start))
       const deleteCount = optNumber(args[1], "delete count") ?? 0
       const inserted = args.slice(2)
-      for (const item of inserted) rejectCircularInsertion(target, item, "Array.splice result", node)
+      for (const item of inserted) rejectCircularInsertion(receiver, item, "Array.splice result", node)
       return Effect.succeed(target.splice(start, deleteCount, ...inserted))
     }
     case "toSpliced": {
@@ -731,23 +734,23 @@ const invokeArrayMethod = <R>(
       return Effect.succeed(copied)
     }
     case "fill": {
-      rejectCircularInsertion(target, args[0], "Array.fill result", node)
-      return Effect.succeed(target.fill(args[0], optNumber(args[1], "start"), optNumber(args[2], "end")))
+      rejectCircularInsertion(receiver, args[0], "Array.fill result", node)
+      target.fill(args[0], optNumber(args[1], "start"), optNumber(args[2], "end"))
+      return Effect.succeed(receiver)
     }
     case "copyWithin":
-      return Effect.succeed(
-        target.copyWithin(
-          optNumber(args[0], "target index") ?? 0,
-          optNumber(args[1], "start") ?? 0,
-          optNumber(args[2], "end"),
-        ),
+      target.copyWithin(
+        optNumber(args[0], "target index") ?? 0,
+        optNumber(args[1], "start") ?? 0,
+        optNumber(args[2], "end"),
       )
+      return Effect.succeed(receiver)
     case "keys":
       return Effect.succeed(Array.from(target.keys()))
     case "values":
       return Effect.succeed([...target])
     case "entries":
-      return Effect.succeed(Array.from(target.entries(), ([index, item]): Array<unknown> => [index, item]))
+      return Effect.succeed(Array.from(target.entries(), ([index, item]) => new ProgramArray([index, item])))
   }
 
   const apply = applyCollectionCallback(runner, args[0], `Array.${name}`, node)
@@ -760,7 +763,7 @@ const invokeArrayMethod = <R>(
         values.length = length
         for (let index = 0; index < length; index += 1) {
           if (!(index in target)) continue
-          values[index] = yield* apply([target[index], index, target])
+          values[index] = yield* apply([target[index], index, receiver])
         }
         return values
       }
@@ -768,8 +771,8 @@ const invokeArrayMethod = <R>(
         const values: Array<unknown> = []
         for (let index = 0; index < length; index += 1) {
           if (!(index in target)) continue
-          const mapped = yield* apply([target[index], index, target])
-          if (Array.isArray(mapped)) values.push(...mapped)
+          const mapped = yield* apply([target[index], index, receiver])
+          if (mapped instanceof ProgramArray) values.push(...mapped.items)
           else values.push(mapped)
         }
         return values
@@ -779,36 +782,36 @@ const invokeArrayMethod = <R>(
         for (let index = 0; index < length; index += 1) {
           if (!(index in target)) continue
           const item = target[index]
-          if (yield* apply([item, index, target])) values.push(item)
+          if (yield* apply([item, index, receiver])) values.push(item)
         }
         return values
       }
       case "find":
         for (let index = 0; index < length; index += 1) {
           const item = target[index]
-          if (yield* apply([item, index, target])) return item
+          if (yield* apply([item, index, receiver])) return item
         }
         return undefined
       case "findIndex":
         for (let index = 0; index < length; index += 1) {
-          if (yield* apply([target[index], index, target])) return index
+          if (yield* apply([target[index], index, receiver])) return index
         }
         return -1
       case "some":
         for (let index = 0; index < length; index += 1) {
           if (!(index in target)) continue
-          if (yield* apply([target[index], index, target])) return true
+          if (yield* apply([target[index], index, receiver])) return true
         }
         return false
       case "every":
         for (let index = 0; index < length; index += 1) {
           if (!(index in target)) continue
-          if (!(yield* apply([target[index], index, target]))) return false
+          if (!(yield* apply([target[index], index, receiver]))) return false
         }
         return true
       case "forEach":
         for (let index = 0; index < length; index += 1) {
-          if (index in target) yield* apply([target[index], index, target])
+          if (index in target) yield* apply([target[index], index, receiver])
         }
         return undefined
       case "reduce": {
@@ -825,7 +828,7 @@ const invokeArrayMethod = <R>(
         }
         for (let index = start; index < length; index += 1) {
           if (!(index in target)) continue
-          accumulator = yield* apply([accumulator, target[index], index, target])
+          accumulator = yield* apply([accumulator, target[index], index, receiver])
         }
         return accumulator
       }
@@ -843,19 +846,19 @@ const invokeArrayMethod = <R>(
         }
         for (let index = start; index >= 0; index -= 1) {
           if (!(index in target)) continue
-          accumulator = yield* apply([accumulator, target[index], index, target])
+          accumulator = yield* apply([accumulator, target[index], index, receiver])
         }
         return accumulator
       }
       case "findLast":
         for (let index = length - 1; index >= 0; index -= 1) {
           const item = target[index]
-          if (yield* apply([item, index, target])) return item
+          if (yield* apply([item, index, receiver])) return item
         }
         return undefined
       case "findLastIndex":
         for (let index = length - 1; index >= 0; index -= 1) {
-          if (yield* apply([target[index], index, target])) return index
+          if (yield* apply([target[index], index, receiver])) return index
         }
         return -1
     }

packages/codemode/src/interpreter/model.ts

@@ -1,7 +1,7 @@
-import type { BlockStatement, Expression, Node, Pattern } from "acorn"
+import type { Node } from "acorn"
 import type { Effect } from "effect"
 import type { DiagnosticKind } from "../codemode.js"
-import type { SafeObject } from "../data.js"
+import type { ProgramObject } from "./objects.js"
 import type { Values } from "../values.js"
 
 /** Any parsed node; the interpreter narrows on `type` and reads `loc` for diagnostics. */
@@ -20,20 +20,10 @@ export type StatementResult =
   | { kind: "continue"; label?: string }
 
 export type MemberReference = {
-  target: SafeObject | Array<unknown> | Values.RegExp | Values.URL
+  target: ProgramObject | Values.RegExp | Values.URL
   key: PropertyKey
 }
 
-export class CodeModeFunction {
-  constructor(
-    readonly parameters: ReadonlyArray<Pattern>,
-    readonly body: BlockStatement | Expression,
-    readonly capturedScopes: ReadonlyArray<Map<string, Binding>>,
-    readonly async: boolean,
-    readonly generator: boolean,
-  ) {}
-}
-
 export type GeneratorRequestKind = "next" | "return" | "throw"
 
 export class CodeModeGenerator {

packages/codemode/src/interpreter/objects.ts

@@ -0,0 +1,145 @@
+import type { BlockStatement, Expression, Pattern } from "acorn"
+import { AsyncIteratorSymbol, type Binding, IteratorSymbol } from "./model.js"
+
+/** An object owned by the program: own properties plus a prototype link. */
+export class ProgramObject {
+  readonly props = new Map<PropertyKey, unknown>()
+  constructor(public proto: ProgramObject | null = null) {}
+}
+
+export class ProgramArray extends ProgramObject {
+  constructor(readonly items: Array<unknown> = []) {
+    super()
+  }
+}
+
+export class ProgramError extends ProgramObject {
+  constructor(readonly errorName: string) {
+    super()
+  }
+}
+
+export class ProgramFunction extends ProgramObject {
+  readonly length: number
+  constructor(
+    readonly name: string,
+    readonly parameters: ReadonlyArray<Pattern>,
+    readonly body: BlockStatement | Expression,
+    readonly capturedScopes: ReadonlyArray<Map<string, Binding>>,
+    readonly async: boolean,
+    readonly generator: boolean,
+  ) {
+    super()
+    const optional = parameters.findIndex((p) => p.type === "AssignmentPattern" || p.type === "RestElement")
+    this.length = optional === -1 ? parameters.length : optional
+  }
+}
+
+const MAX_ARRAY_LENGTH = 4_294_967_295
+
+export const parseArrayIndex = (key: string | number): number | undefined => {
+  const property = String(key)
+  if (!/^(0|[1-9]\d*)$/.test(property)) return undefined
+  const index = Number(property)
+  return index < MAX_ARRAY_LENGTH ? index : undefined
+}
+
+const canonical = (key: PropertyKey): string | symbol => (typeof key === "symbol" ? key : String(key))
+
+const index = (target: ProgramObject, key: string | symbol): number | undefined =>
+  target instanceof ProgramArray && typeof key === "string" ? parseArrayIndex(key) : undefined
+
+// Non-enumerable built-in properties: array length, function name and length.
+const builtin = (target: ProgramObject, name: string | symbol): boolean =>
+  (name === "length" && target instanceof ProgramArray) ||
+  ((name === "name" || name === "length") && target instanceof ProgramFunction)
+
+export const hasOwn = (target: ProgramObject, key: PropertyKey): boolean => {
+  const name = canonical(key)
+  const at = index(target, name)
+  if (at !== undefined) return at in (target as ProgramArray).items
+  return builtin(target, name) || target.props.has(name)
+}
+
+export const getOwn = (target: ProgramObject, key: PropertyKey): unknown => {
+  const name = canonical(key)
+  const at = index(target, name)
+  if (at !== undefined) return (target as ProgramArray).items[at]
+  if (target instanceof ProgramArray && name === "length") return target.items.length
+  if (target instanceof ProgramFunction && name === "name") return target.name
+  if (target instanceof ProgramFunction && name === "length") return target.length
+  return target.props.get(name)
+}
+
+export const get = (target: ProgramObject, key: PropertyKey): unknown => {
+  for (let current: ProgramObject | null = target; current !== null; current = current.proto) {
+    if (hasOwn(current, key)) return getOwn(current, key)
+  }
+  return undefined
+}
+
+export const has = (target: ProgramObject, key: PropertyKey): boolean => {
+  for (let current: ProgramObject | null = target; current !== null; current = current.proto) {
+    if (hasOwn(current, key)) return true
+  }
+  return false
+}
+
+export const set = (target: ProgramObject, key: PropertyKey, value: unknown): boolean => {
+  const name = canonical(key)
+  const at = index(target, name)
+  if (at !== undefined) {
+    ;(target as ProgramArray).items[at] = value
+    return true
+  }
+  if (name === "length" && target instanceof ProgramArray) {
+    const length = typeof value === "number" ? value : Number(value)
+    if (!Number.isInteger(length) || length < 0 || length > 4_294_967_295) return false
+    target.items.length = length
+    return true
+  }
+  if (builtin(target, name)) return false
+  target.props.set(name, value)
+  return true
+}
+
+export const remove = (target: ProgramObject, key: PropertyKey): boolean => {
+  const name = canonical(key)
+  const at = index(target, name)
+  if (at !== undefined) return delete (target as ProgramArray).items[at]
+  if (name === "length" && target instanceof ProgramArray) return false
+  if (builtin(target, name)) return true
+  target.props.delete(name)
+  return true
+}
+
+// JS order: array indexes, integer-like keys ascending, other strings, then symbols.
+export const ownKeys = (target: ProgramObject): Array<string | symbol> => {
+  const strings = [...target.props.keys()].filter((key): key is string => typeof key === "string")
+  const symbols = [...target.props.keys()].filter((key): key is symbol => typeof key === "symbol")
+  return [
+    ...(target instanceof ProgramArray ? Object.keys(target.items) : []),
+    ...strings.filter((key) => parseArrayIndex(key) !== undefined).sort((a, b) => Number(a) - Number(b)),
+    ...strings.filter((key) => parseArrayIndex(key) === undefined),
+    ...symbols,
+  ]
+}
+
+export const ownEntries = (target: ProgramObject): Array<[string, unknown]> =>
+  ownKeys(target)
+    .filter((key): key is string => typeof key === "string")
+    .map((key) => [key, getOwn(target, key)])
+
+export const record = (entries: Record<string, unknown>): ProgramObject => {
+  const target = new ProgramObject()
+  for (const [key, value] of Object.entries(entries)) set(target, key, value)
+  return target
+}
+
+export const assign = (target: ProgramObject, source: ProgramObject, skip?: ReadonlySet<PropertyKey>): void => {
+  for (const key of ownKeys(source)) {
+    if (skip?.has(key)) continue
+    if (typeof key === "symbol" && key !== IteratorSymbol && key !== AsyncIteratorSymbol) continue
+    set(target, key, getOwn(source, key))
+  }
+}

packages/codemode/src/interpreter/promises.ts

@@ -1,13 +1,7 @@
 import { Cause, Deferred, Effect, Exit, Fiber, Scope } from "effect"
 import type { Diagnostic } from "../codemode.js"
-import type { SafeObject } from "../data.js"
-import {
-  type AstNode,
-  CodeModeFunction,
-  InterpreterRuntimeError,
-  ProgramThrow,
-  PromiseInstanceMethodReference,
-} from "./model.js"
+import { type AstNode, InterpreterRuntimeError, ProgramThrow, PromiseInstanceMethodReference } from "./model.js"
+import { get, ProgramArray, ProgramFunction, ProgramObject, record } from "./objects.js"
 import { HostFunction, requiresNew, sync } from "./host.js"
 import { caughtErrorValue, normalizeError } from "./errors.js"
 import { typeofValue } from "./references.js"
@@ -111,8 +105,8 @@ export const resolvePromiseValue = <R>(
 ): Effect.Effect<unknown, unknown, R> => {
   if (own?.promise !== undefined && value === own.promise) return Effect.fail(selfResolutionError(node))
   if (value instanceof Values.Promise) return runner.settlePromise(value)
-  if (value === null || typeof value !== "object" || !Object.hasOwn(value, "then")) return Effect.succeed(value)
-  const then = (value as SafeObject).then
+  if (!(value instanceof ProgramObject)) return Effect.succeed(value)
+  const then = get(value, "then")
   if (typeofValue(then) !== "function") return Effect.succeed(value)
 
   return Effect.gen(function* () {
@@ -174,10 +168,12 @@ const invokePromiseMethod = <R>(
       }
 
       if (name === "all") {
-        return yield* settleAfterTurn(
-          Effect.all(
-            items.map((item) => Effect.flatten(promises.await(item))),
-            { concurrency: "unbounded" },
+        return new ProgramArray(
+          yield* settleAfterTurn(
+            Effect.all(
+              items.map((item) => Effect.flatten(promises.await(item))),
+              { concurrency: "unbounded" },
+            ),
           ),
         )
       }
@@ -186,19 +182,14 @@ const invokePromiseMethod = <R>(
         for (const item of items) {
           const exit = yield* promises.await(item)
           if (Exit.isSuccess(exit)) {
-            outcomes.push(Object.assign(Object.create(null) as SafeObject, { status: "fulfilled", value: exit.value }))
+            outcomes.push(record({ status: "fulfilled", value: exit.value }))
             continue
           }
           if (Cause.hasInterruptsOnly(exit.cause)) return yield* Effect.failCause(exit.cause)
-          outcomes.push(
-            Object.assign(Object.create(null) as SafeObject, {
-              status: "rejected",
-              reason: caughtErrorValue(Cause.squash(exit.cause)),
-            }),
-          )
+          outcomes.push(record({ status: "rejected", reason: caughtErrorValue(Cause.squash(exit.cause)) }))
         }
         yield* Effect.yieldNow
-        return outcomes
+        return new ProgramArray(outcomes)
       }
       if (name === "race") {
         if (items.length === 0) {
@@ -253,7 +244,7 @@ const constructPromise = <R>(
   executor: unknown,
   node: AstNode,
 ): Effect.Effect<Values.Promise, unknown, R> => {
-  if (!(executor instanceof CodeModeFunction)) {
+  if (!(executor instanceof ProgramFunction)) {
     throw new InterpreterRuntimeError(
       "new Promise(...) expects an executor function (e.g. new Promise((resolve, reject) => { ... })).",
       node,

packages/codemode/src/interpreter/references.ts

@@ -3,20 +3,18 @@ import { Values } from "../values.js"
 import { HostFunction, HostNamespace } from "./host.js"
 import {
   type AstNode,
-  AsyncIteratorSymbol,
-  CodeModeFunction,
   CodeModeGenerator,
   GeneratorMethodReference,
   InterpreterRuntimeError,
   IntrinsicReference,
-  IteratorSymbol,
   PromiseInstanceMethodReference,
 } from "./model.js"
+import { getOwn, ownKeys, ProgramArray, ProgramFunction, ProgramObject } from "./objects.js"
 
 export const isRuntimeReference = (value: unknown): boolean =>
   value instanceof HostFunction ||
   value instanceof HostNamespace ||
-  value instanceof CodeModeFunction ||
+  value instanceof ProgramFunction ||
   value instanceof CodeModeGenerator ||
   value instanceof GeneratorMethodReference ||
   value instanceof ToolReference ||
@@ -26,11 +24,8 @@ export const isRuntimeReference = (value: unknown): boolean =>
   Values.isValue(value)
 
 function* childValues(value: object): Generator {
-  for (const key of Reflect.ownKeys(value)) {
-    if (!Object.prototype.propertyIsEnumerable.call(value, key)) continue
-    if (typeof key === "symbol" && key !== AsyncIteratorSymbol && key !== IteratorSymbol) continue
-    yield Reflect.get(value, key)
-  }
+  if (!(value instanceof ProgramObject)) return
+  for (const key of ownKeys(value)) yield getOwn(value, key)
 }
 
 // Depth-first search over a value tree. `match` stops the walk; `skip` prunes a subtree without matching it.
@@ -79,7 +74,7 @@ export const rejectCircularInsertion = (
 
 export const describeValue = (value: unknown): string => {
   if (value === null) return "null"
-  if (Array.isArray(value)) return "an array"
+  if (value instanceof ProgramArray) return "an array"
   if (value instanceof Values.Promise) return "an un-awaited Promise"
   if (value instanceof ToolReference) return "a tool reference"
   if (value instanceof Values.Date) return "a Date"
@@ -97,7 +92,7 @@ export const describeValue = (value: unknown): string => {
 export const typeofValue = (value: unknown): string => {
   if (
     value instanceof HostFunction ||
-    value instanceof CodeModeFunction ||
+    value instanceof ProgramFunction ||
     value instanceof GeneratorMethodReference ||
     value instanceof IntrinsicReference ||
     value instanceof PromiseInstanceMethodReference
@@ -108,12 +103,3 @@ export const typeofValue = (value: unknown): string => {
   if (value instanceof ToolReference) return value.path.length > 0 ? "function" : "object"
   return typeof value
 }
-
-const MAX_ARRAY_LENGTH = 4_294_967_295
-
-export const parseArrayIndex = (key: string | number): number | undefined => {
-  const property = String(key)
-  if (!/^(0|[1-9]\d*)$/.test(property)) return undefined
-  const index = Number(property)
-  return index < MAX_ARRAY_LENGTH ? index : undefined
-}

packages/codemode/src/interpreter/runner.ts

@@ -2,7 +2,8 @@ import { Effect, Exit } from "effect"
 import { Values } from "../values.js"
 import { coerceToString } from "../stdlib/value.js"
 import { HostFunction } from "./host.js"
-import { type AstNode, CodeModeFunction, InterpreterRuntimeError, IntrinsicReference } from "./model.js"
+import { type AstNode, InterpreterRuntimeError, IntrinsicReference } from "./model.js"
+import { get, has, ProgramFunction, ProgramObject } from "./objects.js"
 import { typeofValue } from "./references.js"
 
 export type IteratorCursor<R> = {
@@ -12,7 +13,7 @@ export type IteratorCursor<R> = {
 
 /** Everything a host function needs to call back into the program. */
 export type Runner<R> = {
-  readonly invokeFunction: (fn: CodeModeFunction, args: Array<unknown>) => Effect.Effect<unknown, unknown, R>
+  readonly invokeFunction: (fn: ProgramFunction, args: Array<unknown>) => Effect.Effect<unknown, unknown, R>
   readonly invokeCallable: (
     callable: unknown,
     args: Array<unknown>,
@@ -42,13 +43,14 @@ export const toPrimitive = <R>(
   if (Values.isValue(value)) {
     return Effect.succeed(value instanceof Values.Date && hint === "number" ? value.time : coerceToString(value))
   }
-  const object = value as Record<string, unknown>
+  if (!(value instanceof ProgramObject)) return Effect.succeed(value)
   const order = hint === "number" ? ["valueOf", "toString"] : ["toString", "valueOf"]
   return Effect.gen(function* () {
     for (const method of order) {
-      if (method === "toString" && !Object.hasOwn(object, "toString")) return coerceToString(value)
-      if (!Object.hasOwn(object, method) || typeofValue(object[method]) !== "function") continue
-      const result = yield* runner.invokeCallable(object[method], [], node)
+      if (method === "toString" && !has(value, "toString")) return coerceToString(value)
+      const callable = get(value, method)
+      if (typeofValue(callable) !== "function") continue
+      const result = yield* runner.invokeCallable(callable, [], node)
       if (result === null || (typeof result !== "object" && typeof result !== "function")) return result
     }
     throw new InterpreterRuntimeError("Cannot convert object to primitive value.", node).as("TypeError")
@@ -59,10 +61,10 @@ export const toPrimitive = <R>(
 // Array.from mappers, and promise reactions all admit exactly these callables.
 // Admission means dispatchable, not necessarily invocable: new-requiring
 // constructors pass the gate and throw a TypeError on call, like JS.
-export type SupportedCallback = CodeModeFunction | HostFunction<unknown> | IntrinsicReference
+export type SupportedCallback = ProgramFunction | HostFunction<unknown> | IntrinsicReference
 
 export const isSupportedCallback = (value: unknown): value is SupportedCallback =>
-  value instanceof CodeModeFunction ||
+  value instanceof ProgramFunction ||
   (value instanceof HostFunction && value.callback) ||
   value instanceof IntrinsicReference
 

packages/codemode/src/interpreter/runtime.ts

@@ -1,6 +1,7 @@
 import type {
   ArrayExpression,
   ArrayPattern,
+  AssignmentPattern,
   ArrowFunctionExpression,
   AssignmentExpression,
   AssignmentProperty,
@@ -41,13 +42,12 @@ import type {
   YieldExpression,
 } from "acorn"
 import { Cause, Deferred, Effect, Exit } from "effect"
-import { ToolRuntimeError, type SafeObject, toProgram } from "../data.js"
+import { ToolRuntimeError, toProgram } from "../data.js"
 import { ToolReference } from "../tool-runtime.js"
 import {
   type AstNode,
   AsyncIteratorSymbol,
   type Binding,
-  CodeModeFunction,
   CodeModeGenerator,
   ComputedValue,
   GeneratorMethodReference,
@@ -55,9 +55,7 @@ import {
   type GeneratorRequestKind,
   IntrinsicReference,
   InterpreterRuntimeError,
-  isRecord,
   IteratorSymbol,
-  IteratorSymbols,
   type MemberReference,
   OptionalShortCircuit,
   PromiseInstanceMethodReference,
@@ -66,16 +64,28 @@ import {
   unsupportedSyntax,
 } from "./model.js"
 import { caughtErrorValue } from "./errors.js"
-import { globals } from "./globals.js"
+import { globals, type Host } from "./globals.js"
 import { HostFunction, HostNamespace } from "./host.js"
 import { invokeIntrinsic } from "./methods.js"
+import {
+  assign,
+  get,
+  has,
+  ownKeys,
+  parseArrayIndex,
+  ProgramArray,
+  ProgramFunction,
+  ProgramObject,
+  record,
+  remove,
+  set,
+} from "./objects.js"
 import { preserveConsumerError, type Runner } from "./runner.js"
 import { invokePromiseInstanceMethod, PromiseRuntime, resolvePromise, resolvePromiseValue } from "./promises.js"
 import {
   containsOpaqueReference,
   describeValue,
   isRuntimeReference,
-  parseArrayIndex,
   rejectCircularInsertion,
   typeofValue,
 } from "./references.js"
@@ -118,14 +128,11 @@ const calleeDescription = (callee: Expression | Super | undefined): string => {
   return "The called value"
 }
 
-const hasOwn = (value: unknown, key: PropertyKey): boolean =>
-  value !== null && typeof value === "object" && Object.hasOwn(value, key)
-
 const constructorName = (value: unknown): string | undefined => {
   if (typeof value === "string") return "String"
   if (typeof value === "number") return "Number"
   if (typeof value === "boolean") return "Boolean"
-  if (Array.isArray(value)) return "Array"
+  if (value instanceof ProgramArray) return "Array"
   if (value instanceof Values.Date) return "Date"
   if (value instanceof Values.RegExp) return "RegExp"
   if (value instanceof Values.Map) return "Map"
@@ -133,7 +140,7 @@ const constructorName = (value: unknown): string | undefined => {
   if (value instanceof Values.URL) return "URL"
   if (value instanceof Values.URLSearchParams) return "URLSearchParams"
   if (value instanceof Values.Promise) return "Promise"
-  if (value === null || typeof value !== "object" || isRuntimeReference(value)) return undefined
+  if (!(value instanceof ProgramObject) || value instanceof ProgramFunction) return undefined
   return errorBrandName(value) ?? "Object"
 }
 
@@ -230,7 +237,7 @@ const loopDeclaration = (left: VariableDeclaration | Pattern, statement: "for...
 }
 
 type CustomIterator = {
-  iterator: SafeObject | CodeModeGenerator
+  iterator: ProgramObject | CodeModeGenerator
   next: unknown
   asynchronous: boolean
 }
@@ -247,13 +254,6 @@ const isOpaqueMemberReference = (value: unknown): value is OpaqueMemberReference
   value instanceof IntrinsicReference ||
   value instanceof GeneratorMethodReference
 
-const copyIteratorSymbols = (source: object, target: object, consumed?: ReadonlySet<PropertyKey>): void => {
-  for (const symbol of IteratorSymbols) {
-    if (!consumed?.has(symbol) && Object.hasOwn(source, symbol))
-      Reflect.set(target, symbol, Reflect.get(source, symbol))
-  }
-}
-
 type GeneratorRequest = {
   kind: GeneratorRequestKind
   value: unknown
@@ -285,6 +285,7 @@ export class Runtime<R> {
     readonly toolKeys: (path: ReadonlyArray<string>) => ReadonlyArray<string>,
     readonly promises: PromiseRuntime<R>,
     readonly logs: Array<string> = [],
+    extraGlobals: (host: Host<R>) => ReadonlyArray<readonly [string, unknown]> = () => [],
   ) {
     const globalScope = new Map<string, Binding>()
     // Calling back into the program never reads frame state, so any frame serves; the root is always alive.
@@ -295,7 +296,7 @@ export class Runtime<R> {
       settlePromise: (promise) => this.root.settlePromise(promise),
       syncIterator: (value, node) => this.root.syncIterator(value, node),
     }
-    this.builtins = new Map(globals(this))
+    this.builtins = new Map([...globals(this), ...extraGlobals(this)])
     for (const [name, value] of this.builtins) globalScope.set(name, { mutable: false, value })
   }
 
@@ -434,8 +435,19 @@ class Frame<R> {
     }).pipe(Effect.ensuring(Effect.sync(() => self.scopes.pop())))
   }
 
-  private createFunction(node: FunctionDeclaration | FunctionExpression | ArrowFunctionExpression): CodeModeFunction {
-    return new CodeModeFunction(node.params, node.body, this.scopes.capture(), node.async, node.generator)
+  private createFunction(
+    node: FunctionDeclaration | FunctionExpression | ArrowFunctionExpression,
+    name = node.type === "ArrowFunctionExpression" ? "" : (node.id?.name ?? ""),
+  ): ProgramFunction {
+    return new ProgramFunction(name, node.params, node.body, this.scopes.capture(), node.async, node.generator)
+  }
+
+  // NamedEvaluation: an anonymous function definition takes the name of what it is assigned to.
+  private evaluateNamed(node: Expression, name: string): Effect.Effect<unknown, unknown, R> {
+    if (node.type === "ArrowFunctionExpression" || (node.type === "FunctionExpression" && !node.id)) {
+      return Effect.sync(() => this.createFunction(node, name))
+    }
+    return this.evaluateExpression(node)
   }
 
   private hoistFunctions(statements: ReadonlyArray<Statement | ModuleDeclaration>): void {
@@ -722,22 +734,26 @@ class Frame<R> {
   }
 
   syncIterator(value: unknown, node: AstNode) {
-    const iterator = Array.isArray(value)
-      ? value[Symbol.iterator]()
-      : typeof value === "string"
-        ? value[Symbol.iterator]()
-        : value instanceof Values.Map
-          ? value.map.entries()
-          : value instanceof Values.Set
-            ? value.set.values()
-            : value instanceof Values.URLSearchParams
-              ? value.params.entries()
-              : undefined
+    const iterator =
+      value instanceof ProgramArray
+        ? value.items[Symbol.iterator]()
+        : typeof value === "string"
+          ? value[Symbol.iterator]()
+          : value instanceof Values.Map
+            ? value.map.entries()
+            : value instanceof Values.Set
+              ? value.set.values()
+              : value instanceof Values.URLSearchParams
+                ? value.params.entries()
+                : undefined
     if (iterator !== undefined) {
       return Effect.succeed({
         next: Effect.sync(() => {
           const step = iterator.next()
-          return { done: Boolean(step.done), value: step.value }
+          return {
+            done: Boolean(step.done),
+            value: Array.isArray(step.value) ? new ProgramArray(step.value) : step.value,
+          }
         }),
         close: Effect.void,
       })
@@ -762,9 +778,9 @@ class Frame<R> {
         asynchronous: value.asynchronous,
       })
     }
-    if (!isRecord(value) || isRuntimeReference(value)) return Effect.undefined
-    const asyncMethod = allowAsync ? Reflect.get(value, AsyncIteratorSymbol) : undefined
-    const method = asyncMethod ?? Reflect.get(value, IteratorSymbol)
+    if (!(value instanceof ProgramObject)) return Effect.undefined
+    const asyncMethod = allowAsync ? get(value, AsyncIteratorSymbol) : undefined
+    const method = asyncMethod ?? get(value, IteratorSymbol)
     if (method === undefined || method === null) return Effect.undefined
     const self = this
     return Effect.map(
@@ -776,7 +792,7 @@ class Frame<R> {
           next:
             object instanceof CodeModeGenerator
               ? new GeneratorMethodReference(object, "next")
-              : self.requireIteratorMethod(object.next, "Iterator next", node),
+              : self.requireIteratorMethod(get(object, "next"), "Iterator next", node),
           asynchronous: asyncMethod !== undefined && asyncMethod !== null,
         }
       },
@@ -792,7 +808,7 @@ class Frame<R> {
           "Iterator next() result",
           node,
         )
-        return { done: Boolean(object.done), value: object.value }
+        return { done: Boolean(get(object, "done")), value: get(object, "value") }
       }
 
       const called = yield* Effect.exit(self.invokeCallable(iterator.next, [], node))
@@ -803,7 +819,7 @@ class Frame<R> {
       const captured = yield* Effect.exit(
         Effect.sync(() => {
           const object = self.requireIteratorObject(called.value, "Iterator next() result", node)
-          return { done: Boolean(object.done), value: object.value }
+          return { done: Boolean(get(object, "done")), value: get(object, "value") }
         }),
       )
       if (!Exit.isSuccess(captured)) {
@@ -823,7 +839,7 @@ class Frame<R> {
     const close =
       iterator.iterator instanceof CodeModeGenerator
         ? new GeneratorMethodReference(iterator.iterator, "return")
-        : iterator.iterator.return
+        : get(iterator.iterator, "return")
     if (close === undefined || close === null) return iterator.asynchronous || !awaiting ? Effect.void : Effect.yieldNow
     const self = this
     return Effect.gen(function* () {
@@ -843,7 +859,7 @@ class Frame<R> {
         return yield* Effect.failCause(called.cause)
       }
       const captured = yield* Effect.exit(
-        Effect.sync(() => self.requireIteratorObject(called.value, "Iterator return() result", node).value),
+        Effect.sync(() => get(self.requireIteratorObject(called.value, "Iterator return() result", node), "value")),
       )
       if (!Exit.isSuccess(captured)) {
         if (awaiting) yield* Effect.yieldNow
@@ -853,12 +869,12 @@ class Frame<R> {
     })
   }
 
-  private requireIteratorObject(value: unknown, context: string, node: AstNode): SafeObject {
-    if (isRecord(value) && !isRuntimeReference(value)) return value
+  private requireIteratorObject(value: unknown, context: string, node: AstNode): ProgramObject {
+    if (value instanceof ProgramObject) return value
     throw new InterpreterRuntimeError(`${context} must be an object.`, node).as("TypeError")
   }
 
-  private requireIterator(value: unknown, node: AstNode): SafeObject | CodeModeGenerator {
+  private requireIterator(value: unknown, node: AstNode): ProgramObject | CodeModeGenerator {
     return value instanceof CodeModeGenerator
       ? value
       : this.requireIteratorObject(value, "Iterator method result", node)
@@ -873,7 +889,7 @@ class Frame<R> {
   private enumerableKeys(value: unknown, node: AstNode): Array<string> {
     if (value instanceof ToolReference) return [...this.runtime.toolKeys(value.path)]
     if (value === null || value === undefined) return []
-    return Object.keys(enumerableSource("for...in", value, node))
+    return ownKeys(enumerableSource("for...in", value, node)).filter((key): key is string => typeof key === "string")
   }
 
   private evaluateForInStatement(
@@ -1019,11 +1035,14 @@ class Frame<R> {
 
         const init = declaration.init
         // `var x` alone is a no-op: the binding was hoisted on function entry.
+        const id = declaration.id
+        const evaluate = (init: Expression) =>
+          id.type === "Identifier" ? self.evaluateNamed(init, id.name) : self.evaluateExpression(init)
         if (kind === "var") {
-          if (init) yield* self.assignPattern(declaration.id, yield* self.evaluateExpression(init), declaration)
+          if (init) yield* self.assignPattern(id, yield* evaluate(init), declaration)
           continue
         }
-        const value = init ? yield* self.evaluateExpression(init) : undefined
+        const value = init ? yield* evaluate(init) : undefined
         yield* self.declarePattern(declaration.id, value, kind !== "const", declaration, true)
       }
     })
@@ -1046,13 +1065,13 @@ class Frame<R> {
       }
 
       if (pattern.type === "AssignmentPattern") {
-        const resolved = value === undefined ? yield* self.evaluateExpression(pattern.right) : value
+        const resolved = value === undefined ? yield* self.evaluateDefault(pattern) : value
         yield* self.declarePattern(pattern.left, resolved, mutable, node, initialize)
         return
       }
 
       if (pattern.type === "ObjectPattern") {
-        if (value === null || typeof value !== "object" || isRuntimeReference(value)) {
+        if (!(value instanceof ProgramObject)) {
           throw new InterpreterRuntimeError(
             `Object destructuring requires a data object or array value, received ${describeValue(value)}.`,
             pattern,
@@ -1063,11 +1082,8 @@ class Frame<R> {
         const consumed = new Set<PropertyKey>()
         for (const property of pattern.properties) {
           if (property.type === "RestElement") {
-            const rest: SafeObject = Object.create(null) as SafeObject
-            for (const [key, item] of Object.entries(value as SafeObject)) {
-              if (!consumed.has(key)) rest[key] = item
-            }
-            copyIteratorSymbols(value, rest, consumed)
+            const rest = new ProgramObject()
+            assign(rest, value, consumed)
             yield* self.declarePattern(property.argument, rest, mutable, property, initialize)
             continue
           }
@@ -1076,7 +1092,7 @@ class Frame<R> {
           consumed.add(typeof key === "symbol" ? key : String(key))
           yield* self.declarePattern(
             property.value,
-            self.destructuringPropertyValue(value as SafeObject | Array<unknown>, key),
+            self.destructuringPropertyValue(value, key),
             mutable,
             property,
             initialize,
@@ -1109,13 +1125,13 @@ class Frame<R> {
       }
 
       if (pattern.type === "AssignmentPattern") {
-        const resolved = value === undefined ? yield* self.evaluateExpression(pattern.right) : value
+        const resolved = value === undefined ? yield* self.evaluateDefault(pattern) : value
         yield* self.assignPattern(pattern.left, resolved, node)
         return
       }
 
       if (pattern.type === "ObjectPattern") {
-        if (value === null || typeof value !== "object" || isRuntimeReference(value)) {
+        if (!(value instanceof ProgramObject)) {
           throw new InterpreterRuntimeError(
             `Object destructuring requires a data object or array value, received ${describeValue(value)}.`,
             pattern,
@@ -1123,21 +1139,17 @@ class Frame<R> {
           )
         }
 
-        const source = value as SafeObject | Array<unknown>
         const consumed = new Set<PropertyKey>()
         for (const property of pattern.properties) {
           if (property.type === "RestElement") {
-            const rest: SafeObject = Object.create(null) as SafeObject
-            for (const [key, item] of Object.entries(source)) {
-              if (!consumed.has(key)) rest[key] = item
-            }
-            copyIteratorSymbols(source, rest, consumed)
+            const rest = new ProgramObject()
+            assign(rest, value, consumed)
             yield* self.assignPattern(property.argument, rest, property)
             continue
           }
           const key = yield* self.destructuringPropertyKey(property)
           consumed.add(typeof key === "symbol" ? key : String(key))
-          yield* self.assignPattern(property.value, self.destructuringPropertyValue(source, key), property)
+          yield* self.assignPattern(property.value, self.destructuringPropertyValue(value, key), property)
         }
         return
       }
@@ -1152,6 +1164,12 @@ class Frame<R> {
     })
   }
 
+  private evaluateDefault(pattern: AssignmentPattern): Effect.Effect<unknown, unknown, R> {
+    return pattern.left.type === "Identifier"
+      ? this.evaluateNamed(pattern.right, pattern.left.name)
+      : this.evaluateExpression(pattern.right)
+  }
+
   private destructureArrayPattern(
     pattern: ArrayPattern,
     value: unknown,
@@ -1171,7 +1189,7 @@ class Frame<R> {
           if (element === null) continue
           yield* consume(
             element.type === "RestElement" ? element.argument : element,
-            element.type === "RestElement" ? [] : undefined,
+            element.type === "RestElement" ? new ProgramArray() : undefined,
             element,
           )
           if (element.type === "RestElement") return
@@ -1188,7 +1206,7 @@ class Frame<R> {
             done = next.done
             if (!done) rest.push(next.value)
           }
-          yield* consume(element.argument, rest, element)
+          yield* consume(element.argument, new ProgramArray(rest), element)
           return
         }
         const consumed = consume(element, step.done ? undefined : step.value, pattern)
@@ -1211,11 +1229,9 @@ class Frame<R> {
     throw unsupportedSyntax(keyNode.type, keyNode)
   }
 
-  private destructuringPropertyValue(source: SafeObject | Array<unknown>, key: PropertyKey): unknown {
-    if (!Array.isArray(source)) return Reflect.get(source, key)
-    if (key === "length") return source.length
-    if (typeof key === "number") return source[key]
-    if (Object.hasOwn(source, key)) return Reflect.get(source, key)
+  private destructuringPropertyValue(source: ProgramObject, key: PropertyKey): unknown {
+    if (!(source instanceof ProgramArray)) return get(source, key)
+    if (has(source, key)) return get(source, key)
     if (typeof key === "string" && arrayMethods.has(key)) return new IntrinsicReference(source, key)
     return undefined
   }
@@ -1293,7 +1309,7 @@ class Frame<R> {
         // otherwise; say `new` is unsupported for them and point at the plain call.
         const name = calleeDescription(node.callee)
         const message =
-          callee instanceof CodeModeFunction
+          callee instanceof ProgramFunction
             ? `${name} cannot be constructed: user-defined constructors and classes are not supported. Call it as a function that returns a plain object instead.`
             : callee instanceof HostFunction
               ? `new ${name}(...) is not supported; call ${name}(...) without new instead.`
@@ -1321,6 +1337,9 @@ class Frame<R> {
   private applyBinaryOperator(operator: string, lhs: unknown, rhs: unknown, node: AstNode): unknown {
     if (operator === "===") return lhs === rhs
     if (operator === "!==") return lhs !== rhs
+    if (operator === "in" && rhs instanceof ProgramObject && !containsOpaqueReference(lhs)) {
+      return has(rhs, lhs !== null && typeof lhs === "object" ? coerceToString(lhs) : (lhs as PropertyKey))
+    }
     if (containsOpaqueReference(lhs) || containsOpaqueReference(rhs)) {
       throw new InterpreterRuntimeError("Binary operators require data values.", node, "InvalidDataValue")
     }
@@ -1373,11 +1392,10 @@ class Frame<R> {
       case ">>>":
         return (l as number) >>> (r as number)
       case "in":
-        if (rhs === null || typeof rhs !== "object") {
+        if (!(rhs instanceof ProgramObject)) {
           throw new InterpreterRuntimeError("The 'in' operator requires a data object on the right-hand side.", node)
         }
-        // Never expose properties inherited from host prototypes.
-        return Object.hasOwn(rhs as object, coerceOperand(lhs) as PropertyKey)
+        return has(rhs, coerceOperand(lhs) as PropertyKey)
       default:
         throw new InterpreterRuntimeError(`Unsupported binary operator '${operator}'.`, node)
     }
@@ -1454,7 +1472,7 @@ class Frame<R> {
           const next = toProgram(self.applyCompoundAssignment(operator, current, rightValue, node), "Assignment result")
           return self.scopes.set(name, next, left)
         }
-        const rightValue = yield* self.evaluateExpression(node.right)
+        const rightValue = yield* self.evaluateNamed(node.right, name)
         return self.scopes.set(name, rightValue, left)
       }
       if (left.type === "MemberExpression") {
@@ -1486,7 +1504,7 @@ class Frame<R> {
       return Effect.gen(function* () {
         const current = self.scopes.get(name, left)
         if (!shouldAssign(current)) return current
-        const rightValue = yield* self.evaluateExpression(node.right)
+        const rightValue = yield* self.evaluateNamed(node.right, name)
         return self.scopes.set(name, rightValue, left)
       })
     }
@@ -1575,7 +1593,7 @@ class Frame<R> {
         }
         return yield* self.createToolCallPromise(callable.path, args)
       }
-      if (callable instanceof CodeModeFunction) {
+      if (callable instanceof ProgramFunction) {
         return yield* self.invokeFunction(callable, args)
       }
       if (callable instanceof GeneratorMethodReference) {
@@ -1626,7 +1644,7 @@ class Frame<R> {
     })
   }
 
-  invokeFunction(fn: CodeModeFunction, args: Array<unknown>): Effect.Effect<unknown, unknown, R> {
+  invokeFunction(fn: ProgramFunction, args: Array<unknown>): Effect.Effect<unknown, unknown, R> {
     const invocation = new Frame(this.runtime, new ScopeStack([...fn.capturedScopes, new Map()]))
     const run = Effect.gen(function* () {
       // Seed all parameters first so defaults cannot fall through to same-named outer bindings.
@@ -1638,7 +1656,13 @@ class Frame<R> {
       }
       for (const [index, parameter] of fn.parameters.entries()) {
         if (parameter.type === "RestElement") {
-          yield* invocation.declarePattern(parameter.argument, args.slice(index), true, parameter, true)
+          yield* invocation.declarePattern(
+            parameter.argument,
+            new ProgramArray(args.slice(index)),
+            true,
+            parameter,
+            true,
+          )
           break
         }
         yield* invocation.declarePattern(parameter, args[index], true, parameter, true)
@@ -1690,12 +1714,12 @@ class Frame<R> {
       }
       if (state.completed) {
         if (kind === "throw") return Effect.fail(new ProgramThrow(value))
-        return Effect.succeed({ value: kind === "return" ? value : undefined, done: true })
+        return Effect.succeed(record({ value: kind === "return" ? value : undefined, done: true }))
       }
       if (!state.started && kind !== "next") {
         state.completed = true
         if (kind === "throw") return Effect.fail(new ProgramThrow(value))
-        return Effect.succeed({ value, done: true })
+        return Effect.succeed(record({ value, done: true }))
       }
 
       state.pending.push(request)
@@ -1725,7 +1749,7 @@ class Frame<R> {
           if (active) {
             Deferred.doneUnsafe(
               active.response,
-              Exit.isSuccess(exit) ? Exit.succeed({ value: exit.value, done: true }) : exit,
+              Exit.isSuccess(exit) ? Exit.succeed(record({ value: exit.value, done: true })) : exit,
             )
           }
           yield* invocation.completeGeneratorRequests(state, asynchronous)
@@ -1752,13 +1776,13 @@ class Frame<R> {
           const resolved = yield* Effect.exit(self.awaitValue(pending.value))
           Deferred.doneUnsafe(
             pending.response,
-            Exit.isSuccess(resolved) ? Exit.succeed({ value: resolved.value, done: true }) : resolved,
+            Exit.isSuccess(resolved) ? Exit.succeed(record({ value: resolved.value, done: true })) : resolved,
           )
           continue
         }
         Deferred.doneUnsafe(
           pending.response,
-          Exit.succeed({ value: pending.kind === "return" ? pending.value : undefined, done: true }),
+          Exit.succeed(record({ value: pending.kind === "return" ? pending.value : undefined, done: true })),
         )
       }
     })
@@ -1803,7 +1827,7 @@ class Frame<R> {
   private suspendGenerator(value: unknown, node: AstNode): Effect.Effect<unknown, unknown, R> {
     const state = this.generatorState
     if (!state?.active) throw new InterpreterRuntimeError("Generator has no active request.", node)
-    Deferred.doneUnsafe(state.active.response, Exit.succeed({ value, done: false }))
+    Deferred.doneUnsafe(state.active.response, Exit.succeed(record({ value, done: false })))
     state.active = undefined
     return Effect.flatMap(this.takeGeneratorRequest(state), (request) => {
       state.active = request
@@ -1819,7 +1843,7 @@ class Frame<R> {
     const self = this
     return Effect.gen(function* () {
       if (
-        Array.isArray(value) ||
+        value instanceof ProgramArray ||
         typeof value === "string" ||
         value instanceof Values.Map ||
         value instanceof Values.Set ||
@@ -1860,7 +1884,7 @@ class Frame<R> {
             ? iterator.next
             : iterator.iterator instanceof CodeModeGenerator
               ? new GeneratorMethodReference(iterator.iterator, kind)
-              : iterator.iterator[kind]
+              : get(iterator.iterator, kind)
         if (method === undefined || method === null) {
           if (kind === "return") return yield* Effect.fail(new GeneratorReturn(input))
           yield* self.closeIterator(iterator, node, self.generatorAsync)
@@ -1878,11 +1902,11 @@ class Frame<R> {
           `Iterator ${kind}() result`,
           node,
         )
-        const done = Boolean(result.done)
+        const done = Boolean(get(result, "done"))
         const resultValue: unknown =
           self.generatorAsync && !iterator.asynchronous
-            ? yield* self.awaitAsyncFromSyncValue(iterator, result.value, node, kind !== "return" && !done)
-            : result.value
+            ? yield* self.awaitAsyncFromSyncValue(iterator, get(result, "value"), node, kind !== "return" && !done)
+            : get(result, "value")
         if (done) {
           if (kind === "return") return yield* Effect.fail(new GeneratorReturn(resultValue))
           return resultValue
@@ -1904,17 +1928,15 @@ class Frame<R> {
     })
   }
 
-  private evaluateObjectExpression(node: ObjectExpression): Effect.Effect<Record<string, unknown>, unknown, R> {
-    const objectValue: Record<string, unknown> = Object.create(null) as Record<string, unknown>
+  private evaluateObjectExpression(node: ObjectExpression): Effect.Effect<ProgramObject, unknown, R> {
+    const objectValue = new ProgramObject()
     const self = this
     return Effect.gen(function* () {
       for (const property of node.properties) {
         if (property.type === "SpreadElement") {
           const spread = yield* self.evaluateExpression(property.argument)
           if (spread === null || spread === undefined) continue
-          const from = enumerableSource("Object spread", spread, property)
-          for (const [key, value] of Object.entries(from)) objectValue[key] = value
-          if (typeof from === "object") copyIteratorSymbols(from, objectValue)
+          assign(objectValue, enumerableSource("Object spread", spread, property))
           continue
         }
 
@@ -1936,14 +1958,20 @@ class Frame<R> {
           throw new InterpreterRuntimeError("Unsupported object property key shape.", keyNode)
         }
 
-        Reflect.set(objectValue, key, yield* self.evaluateExpression(property.value))
+        const name =
+          key === IteratorSymbol
+            ? "[Symbol.iterator]"
+            : key === AsyncIteratorSymbol
+              ? "[Symbol.asyncIterator]"
+              : String(key)
+        set(objectValue, key, yield* self.evaluateNamed(property.value, name))
       }
 
       return objectValue
     })
   }
 
-  private evaluateArrayExpression(node: ArrayExpression): Effect.Effect<Array<unknown>, unknown, R> {
+  private evaluateArrayExpression(node: ArrayExpression): Effect.Effect<ProgramArray, unknown, R> {
     const values: Array<unknown> = []
 
     const self = this
@@ -1968,7 +1996,7 @@ class Frame<R> {
           values.push(yield* self.evaluateExpression(element))
         }
       }
-      return values
+      return new ProgramArray(values)
     })
   }
 
@@ -2055,7 +2083,11 @@ class Frame<R> {
       }
 
       // Values have no prototype chain, so `.constructor` resolves to the owning built-in directly.
-      if (operation === "read" && key === "constructor" && !hasOwn(objectValue, key)) {
+      if (
+        operation === "read" &&
+        key === "constructor" &&
+        !(objectValue instanceof ProgramObject && has(objectValue, key))
+      ) {
         const name = constructorName(objectValue)
         if (name !== undefined) return new ComputedValue(self.runtime.builtins.get(name))
       }
@@ -2136,6 +2168,8 @@ class Frame<R> {
         return new ComputedValue(undefined)
       }
 
+      if (objectValue instanceof ProgramObject) return { target: objectValue, key }
+
       if (isRuntimeReference(objectValue)) {
         throw new InterpreterRuntimeError(
           `Cannot read properties of ${describeValue(objectValue)}; only data values expose properties.`,
@@ -2143,42 +2177,27 @@ class Frame<R> {
           "InvalidDataValue",
         )
       }
-
-      if (typeof objectValue !== "object" || objectValue === null) {
-        throw new InterpreterRuntimeError("Cannot access a property on a non-object value.", objectNode)
-      }
-
-      if (Array.isArray(objectValue)) {
-        if (operation === "delete") return { target: objectValue, key }
-        const index = typeof key === "symbol" ? undefined : parseArrayIndex(key)
-        if (key !== "length" && !(typeof key === "string" && arrayMethods.has(key)) && index === undefined) {
-          if (typeof key === "string" && Object.hasOwn(objectValue, key)) {
-            return new ComputedValue((objectValue as Record<string, unknown> & Array<unknown>)[key])
-          }
-          return new ComputedValue(undefined)
-        }
-        return { target: objectValue, key: index ?? key }
-      }
-
-      return { target: objectValue as SafeObject, key }
+      throw new InterpreterRuntimeError("Cannot access a property on a non-object value.", objectNode)
     })
   }
 
   private readMember(node: MemberExpression): Effect.Effect<unknown, unknown, R> {
+    const self = this
     return Effect.map(this.getMemberReference(node), (reference) => {
       if (reference === OptionalShortCircuit) return OptionalShortCircuit
       if (reference instanceof ComputedValue) return reference.value
       if (reference === undefined || isOpaqueMemberReference(reference)) return reference
-      if (Array.isArray(reference.target)) {
-        if (reference.key === "length") return reference.target.length
-        if (typeof reference.key === "string") return new IntrinsicReference(reference.target, reference.key)
-        return Reflect.get(reference.target, reference.key)
+      const value = self.readReferenceValue(reference, reference.key)
+      if (
+        value === undefined &&
+        reference.target instanceof ProgramArray &&
+        typeof reference.key === "string" &&
+        arrayMethods.has(reference.key) &&
+        !has(reference.target, reference.key)
+      ) {
+        return new IntrinsicReference(reference.target, reference.key)
       }
-      if (reference.target instanceof Values.RegExp) return reference.target.lastIndex
-      if (reference.target instanceof Values.URL) {
-        return Reflect.get(reference.target.url, reference.key)
-      }
-      return Reflect.get(reference.target, reference.key)
+      return value
     })
   }
 
@@ -2204,7 +2223,7 @@ class Frame<R> {
       if (reference.target instanceof Values.RegExp) {
         return Reflect.deleteProperty(reference.target.regex, reference.key)
       }
-      return Reflect.deleteProperty(reference.target, reference.key)
+      return remove(reference.target, reference.key)
     })
   }
 
@@ -2224,12 +2243,6 @@ class Frame<R> {
       ) {
         throw new InterpreterRuntimeError("Only data fields may be assigned.", node)
       }
-      if (Array.isArray(reference.target)) {
-        if (reference.key === "length") throw new InterpreterRuntimeError("Array length cannot be assigned.", node)
-        if (typeof reference.key === "string" && arrayMethods.has(reference.key)) {
-          throw new InterpreterRuntimeError("Array methods cannot be assigned.", node)
-        }
-      }
       const key = reference.key
       const { write, next, result } = yield* compute(self.readReferenceValue(reference, key))
       if (write) self.assignToReference(reference, key, next, node)
@@ -2242,23 +2255,10 @@ class Frame<R> {
       return Reflect.get(reference.target.url, key)
     }
     if (reference.target instanceof Values.RegExp) return reference.target.lastIndex
-    return Reflect.get(reference.target, key)
+    return get(reference.target, key)
   }
 
   private assignToReference(reference: MemberReference, key: PropertyKey, next: unknown, node: AstNode): void {
-    if (Array.isArray(reference.target)) {
-      const target = reference.target
-      if (typeof key !== "number" || parseArrayIndex(key) === undefined) {
-        throw new InterpreterRuntimeError(
-          "Array assignment index must be a valid array index.",
-          node,
-          "InvalidDataValue",
-        )
-      }
-      rejectCircularInsertion(target, next, "Array assignment result", node)
-      target[key] = next
-      return
-    }
     if (reference.target instanceof Values.URL) {
       const property = key as string
       if (!urlWritableProperties.has(property)) {
@@ -2277,9 +2277,16 @@ class Frame<R> {
       reference.target.lastIndex = next
       return
     }
-    const target = reference.target as SafeObject
-    rejectCircularInsertion(target, next, "Object assignment result", node)
-    Reflect.set(target, key, next)
+    const target = reference.target
+    rejectCircularInsertion(
+      target,
+      next,
+      target instanceof ProgramArray ? "Array assignment result" : "Object assignment result",
+      node,
+    )
+    if (set(target, key, next)) return
+    if (target instanceof ProgramArray) throw new InterpreterRuntimeError("Invalid array length", node).as("RangeError")
+    throw new InterpreterRuntimeError(`Cannot assign to read only property '${String(key)}'.`, node).as("TypeError")
   }
 
   private toPropertyKey(value: unknown, node: AstNode): PropertyKey {

packages/codemode/src/stdlib/array.ts

@@ -1,28 +1,27 @@
 import { Effect } from "effect"
 import { HostFunction, sync, syncCall } from "../interpreter/host.js"
 import { type AstNode, CodeModeGenerator, InterpreterRuntimeError } from "../interpreter/model.js"
+import { get, ProgramArray, ProgramObject } from "../interpreter/objects.js"
 import { describeValue } from "../interpreter/references.js"
 import { applyCollectionCallback, preserveConsumerError, type Runner } from "../interpreter/runner.js"
 
-const constructArray = (args: Array<unknown>, node: AstNode): Array<unknown> => {
-  if (args.length !== 1) return [...args]
+const constructArray = (args: Array<unknown>, node: AstNode): ProgramArray => {
+  if (args.length !== 1) return new ProgramArray([...args])
   const first = args[0]
-  if (typeof first !== "number") return [first]
+  if (typeof first !== "number") return new ProgramArray([first])
   if (!Number.isInteger(first) || first < 0 || first > 4294967295) {
     throw new InterpreterRuntimeError("Invalid array length.", node).as("RangeError")
   }
   // Sparse like JS: Array(3) has holes, and combinator loops already skip them.
-  return new Array(first)
+  return new ProgramArray(new Array(first))
 }
 
-const arrayLikeSource = (source: unknown, node: AstNode): { readonly length: number; readonly source: object } => {
-  if (
-    source !== null &&
-    typeof source === "object" &&
-    (Object.getPrototypeOf(source) === Object.prototype || Object.getPrototypeOf(source) === null) &&
-    typeof (source as { length?: unknown }).length === "number"
-  ) {
-    const length = (source as { length: number }).length
+const arrayLikeSource = (
+  source: unknown,
+  node: AstNode,
+): { readonly length: number; readonly source: ProgramObject } => {
+  if (source instanceof ProgramObject && typeof get(source, "length") === "number") {
+    const length = get(source, "length") as number
     const normalized = Number.isNaN(length) || length <= 0 ? 0 : Math.trunc(length)
     if (normalized > 4_294_967_295) throw new RangeError("Invalid array length")
     return { length: normalized, source }
@@ -49,16 +48,16 @@ const arrayFrom = <R>(runner: Runner<R>, args: Array<unknown>, node: AstNode): E
       const arrayLike = arrayLikeSource(source, node)
       const values: Array<unknown> = []
       for (let index = 0; index < arrayLike.length; index += 1) {
-        const item = Reflect.get(arrayLike.source, index)
+        const item = get(arrayLike.source, index)
         values.push(apply === undefined ? item : yield* apply([item, index]))
       }
-      return values
+      return new ProgramArray(values)
     }
     const values: Array<unknown> = []
     let index = 0
     while (true) {
       const step = yield* cursor.next
-      if (step.done) return values
+      if (step.done) return new ProgramArray(values)
       values.push(apply === undefined ? step.value : yield* preserveConsumerError(cursor, apply([step.value, index])))
       index += 1
     }
@@ -71,10 +70,10 @@ export const arrayGlobal = <R>(runner: Runner<R>) =>
     name: "Array",
     call: syncCall(constructArray),
     construct: syncCall(constructArray),
-    instanceOf: (value) => Array.isArray(value),
+    instanceOf: (value) => value instanceof ProgramArray,
     members: {
-      isArray: sync("Array.isArray", (args) => Array.isArray(args[0])),
-      of: sync("Array.of", (args) => [...args]),
+      isArray: sync("Array.isArray", (args) => args[0] instanceof ProgramArray),
+      of: sync("Array.of", (args) => new ProgramArray([...args])),
       from: new HostFunction<R>({ name: "Array.from", call: (args, node) => arrayFrom(runner, args, node) }),
     },
   })

packages/codemode/src/stdlib/collections.ts

@@ -1,7 +1,7 @@
 import { Effect } from "effect"
-import type { SafeObject } from "../data.js"
 import { HostFunction, requiresNew } from "../interpreter/host.js"
-import { type AstNode, InterpreterRuntimeError, isRecord } from "../interpreter/model.js"
+import { type AstNode, InterpreterRuntimeError } from "../interpreter/model.js"
+import { getOwn, ProgramArray, ProgramObject, set } from "../interpreter/objects.js"
 import { describeValue, isRuntimeReference } from "../interpreter/references.js"
 import { applyCollectionCallback, preserveConsumerError, type Runner, toPrimitive } from "../interpreter/runner.js"
 import { Values } from "../values.js"
@@ -108,13 +108,13 @@ export const groupBy = <R>(runner: Runner<R>, namespace: "Map" | "Object") =>
             const item = step.value
             const key = yield* preserveConsumerError(cursor, apply([item, index]))
             const group = result.map.get(key)
-            if (group === undefined) result.map.set(key, [item])
-            else (group as Array<unknown>).push(item)
+            if (group === undefined) result.map.set(key, new ProgramArray([item]))
+            else (group as ProgramArray).items.push(item)
             index += 1
           }
         }
 
-        const result: SafeObject = Object.create(null) as SafeObject
+        const result = new ProgramObject()
         let index = 0
         while (true) {
           const step = yield* cursor.next
@@ -124,9 +124,9 @@ export const groupBy = <R>(runner: Runner<R>, namespace: "Map" | "Object") =>
             cursor,
             Effect.flatMap(apply([item, index]), (value) => coerceGroupByPropertyKey(runner, value, node)),
           )
-          const group = result[key]
-          if (group === undefined) result[key] = [item]
-          else (group as Array<unknown>).push(item)
+          const group = getOwn(result, key)
+          if (group === undefined) set(result, key, new ProgramArray([item]))
+          else (group as ProgramArray).items.push(item)
           index += 1
         }
       })
@@ -150,12 +150,12 @@ const constructMap = <R>(runner: Runner<R>, init: unknown, node: AstNode) => {
       yield* preserveConsumerError(
         cursor,
         Effect.sync(() => {
-          if (!isRecord(step.value) || isRuntimeReference(step.value)) {
+          if (!(step.value instanceof ProgramObject)) {
             throw new InterpreterRuntimeError("new Map(...) expects [key, value] pairs as entry objects.", node).as(
               "TypeError",
             )
           }
-          target.map.set(step.value[0], step.value[1])
+          target.map.set(getOwn(step.value, 0), getOwn(step.value, 1))
         }),
       )
     }

packages/codemode/src/stdlib/console.ts

@@ -1,5 +1,6 @@
 import { toData, toProgram } from "../data.js"
 import { HostNamespace, sync } from "../interpreter/host.js"
+import { get, ownEntries, ProgramArray, ProgramObject } from "../interpreter/objects.js"
 import { containsOpaqueReference, containsRuntimeReference, isRuntimeReference } from "../interpreter/references.js"
 import { Values } from "../values.js"
 import { coerceToString } from "./value.js"
@@ -51,8 +52,8 @@ const formatConsoleValue = (value: unknown, seen: Set<object>, depth: number): s
   if (value instanceof Values.Map) {
     seen.add(value)
     try {
-      const entries = Array.from(value.map.entries(), ([key, item]): Array<unknown> => [key, item])
-      return `Map(${value.map.size}) ${formatConsoleValue(entries, seen, depth + 1)}`
+      const entries = Array.from(value.map.entries(), ([key, item]) => new ProgramArray([key, item]))
+      return `Map(${value.map.size}) ${formatConsoleValue(new ProgramArray(entries), seen, depth + 1)}`
     } finally {
       seen.delete(value)
     }
@@ -60,7 +61,7 @@ const formatConsoleValue = (value: unknown, seen: Set<object>, depth: number): s
   if (value instanceof Values.Set) {
     seen.add(value)
     try {
-      return `Set(${value.set.size}) ${formatConsoleValue(Array.from(value.set.values()), seen, depth + 1)}`
+      return `Set(${value.set.size}) ${formatConsoleValue(new ProgramArray([...value.set.values()]), seen, depth + 1)}`
     } finally {
       seen.delete(value)
     }
@@ -68,10 +69,11 @@ const formatConsoleValue = (value: unknown, seen: Set<object>, depth: number): s
   if (isRuntimeReference(value)) return "[opaque reference]"
   seen.add(value)
   try {
-    if (Array.isArray(value)) {
-      return `[${value.map((item) => formatConsoleValue(item, seen, depth + 1)).join(",")}]`
+    if (value instanceof ProgramArray) {
+      return `[${value.items.map((item) => formatConsoleValue(item, seen, depth + 1)).join(",")}]`
     }
-    return `{${Object.entries(value)
+    if (!(value instanceof ProgramObject)) return "[object Object]"
+    return `{${ownEntries(value)
       .map(([key, item]) => `${JSON.stringify(key)}:${formatConsoleValue(item, seen, depth + 1)}`)
       .join(",")}}`
   } finally {
@@ -104,20 +106,19 @@ const consoleTableRows = (
   data: unknown,
   columns: ReadonlyArray<string> | undefined,
 ): Array<{ readonly index: string; readonly values: Record<string, unknown> }> => {
-  if (Array.isArray(data)) {
-    return data.map((item, index) => ({ index: String(index), values: consoleTableValues(item, columns) }))
+  if (data instanceof ProgramArray) {
+    return data.items.map((item, index) => ({ index: String(index), values: consoleTableValues(item, columns) }))
   }
-  if (data !== null && typeof data === "object" && !Values.isValue(data)) {
-    return Object.entries(data).map(([index, item]) => ({ index, values: consoleTableValues(item, columns) }))
+  if (data instanceof ProgramObject) {
+    return ownEntries(data).map(([index, item]) => ({ index, values: consoleTableValues(item, columns) }))
   }
   return [{ index: "0", values: { Value: data } }]
 }
 
 const consoleTableValues = (value: unknown, columns: ReadonlyArray<string> | undefined): Record<string, unknown> => {
-  if (value !== null && typeof value === "object" && !Array.isArray(value) && !Values.isValue(value)) {
-    const source = value as Record<string, unknown>
-    if (columns !== undefined) return Object.fromEntries(columns.map((column) => [column, source[column]]))
-    return Object.fromEntries(Object.entries(source))
+  if (value instanceof ProgramObject && !(value instanceof ProgramArray)) {
+    if (columns !== undefined) return Object.fromEntries(columns.map((column) => [column, get(value, column)]))
+    return Object.fromEntries(ownEntries(value))
   }
   return { Value: value }
 }

packages/codemode/src/stdlib/json.ts

@@ -3,7 +3,8 @@ import { HostFunction, HostNamespace } from "../interpreter/host.js"
 import { applyCollectionCallback, type Runner } from "../interpreter/runner.js"
 import { type AstNode, InterpreterRuntimeError } from "../interpreter/model.js"
 import { typeofValue } from "../interpreter/references.js"
-import { fromData, type SafeObject, toData, toProgram } from "../data.js"
+import { fromData, toData, toProgram } from "../data.js"
+import { get, ownKeys, ProgramArray, ProgramObject, record, remove, set } from "../interpreter/objects.js"
 import { Values } from "../values.js"
 
 export const jsonGlobal = <R>(runner: Runner<R>) =>
@@ -29,28 +30,19 @@ const parse = <R>(runner: Runner<R>, args: Array<unknown>, node: AstNode): Effec
   if (typeofValue(args[1]) !== "function") return Effect.succeed(parsed)
 
   const apply = applyCollectionCallback(runner, args[1], "JSON.parse", node)
-  const root: SafeObject = Object.create(null) as SafeObject
-  root[""] = parsed
-  const visit = (holder: SafeObject | Array<unknown>, key: string): Effect.Effect<unknown, unknown, R> =>
+  const visit = (holder: ProgramObject, key: string): Effect.Effect<unknown, unknown, R> =>
     Effect.gen(function* () {
-      const value = holder[key as keyof typeof holder]
-      if (Array.isArray(value)) {
-        const length = value.length
-        for (let index = 0; index < length; index += 1) {
-          const revived = yield* visit(value, String(index))
-          if (revived === undefined) Reflect.deleteProperty(value, index)
-          else value[index] = revived
-        }
-      } else if (isPlainObject(value)) {
-        for (const name of Object.keys(value)) {
-          const revived = yield* visit(value, name)
-          if (revived === undefined) Reflect.deleteProperty(value, name)
-          else value[name] = revived
+      const value = get(holder, key)
+      if (value instanceof ProgramObject) {
+        for (const name of ownKeys(value)) {
+          const revived = yield* visit(value, name as string)
+          if (revived === undefined) remove(value, name)
+          else set(value, name, revived)
         }
       }
       return yield* apply([key, value])
     })
-  return visit(root, "")
+  return visit(record({ "": parsed }), "")
 }
 
 const stringify = <R>(runner: Runner<R>, args: Array<unknown>, node: AstNode): Effect.Effect<unknown, unknown, R> => {
@@ -59,44 +51,41 @@ const stringify = <R>(runner: Runner<R>, args: Array<unknown>, node: AstNode): E
   const replacer = args[1]
 
   if (typeofValue(replacer) !== "function") {
-    const properties = Array.isArray(replacer)
-      ? replacer
-          .filter((item): item is string | number => typeof item === "string" || typeof item === "number")
-          .map(String)
-      : null
+    const properties =
+      replacer instanceof ProgramArray
+        ? replacer.items
+            .filter((item): item is string | number => typeof item === "string" || typeof item === "number")
+            .map(String)
+        : null
     return Effect.succeed(JSON.stringify(toData(args[0], "JSON.stringify value"), properties, indent))
   }
 
   // Validate up front; the replacer walk below reads the original value.
   toProgram(args[0], "JSON.stringify value")
   const apply = applyCollectionCallback(runner, replacer, "JSON.stringify", node)
-  const root: SafeObject = Object.create(null) as SafeObject
-  root[""] = args[0]
   const stack = new Set<object>()
-  const visit = (holder: SafeObject | Array<unknown>, key: string): Effect.Effect<unknown, unknown, R> =>
+  const visit = (holder: ProgramObject, key: string): Effect.Effect<unknown, unknown, R> =>
     Effect.gen(function* () {
-      const value = yield* apply([key, toJSONValue(holder[key as keyof typeof holder])])
+      const value = yield* apply([key, toJSONValue(get(holder, key))])
       if (value === undefined || typeofValue(value) === "function") return undefined
       toProgram(value, "JSON.stringify replacer result")
       if (typeof value === "number") return Number.isFinite(value) ? value : null
       if (value === null || typeof value === "string" || typeof value === "boolean") return value
-      if (Array.isArray(value)) {
-        if (stack.has(value))
-          throw new InterpreterRuntimeError("Converting circular structure to JSON.", node).as("TypeError")
-        stack.add(value)
+      if (!(value instanceof ProgramObject)) return {}
+      if (stack.has(value))
+        throw new InterpreterRuntimeError("Converting circular structure to JSON.", node).as("TypeError")
+      stack.add(value)
+      if (value instanceof ProgramArray) {
         const result: Array<unknown> = []
-        for (let index = 0; index < value.length; index += 1) {
+        for (let index = 0; index < value.items.length; index += 1) {
           result.push((yield* visit(value, String(index))) ?? null)
         }
         stack.delete(value)
         return result
       }
-      if (!isPlainObject(value)) return {}
-      if (stack.has(value))
-        throw new InterpreterRuntimeError("Converting circular structure to JSON.", node).as("TypeError")
-      stack.add(value)
-      const result: SafeObject = Object.create(null) as SafeObject
-      for (const name of Object.keys(value)) {
+      const result: Record<string, unknown> = Object.create(null)
+      for (const name of ownKeys(value)) {
+        if (typeof name !== "string") continue
         const item = yield* visit(value, name)
         if (item !== undefined) result[name] = item
       }
@@ -104,7 +93,7 @@ const stringify = <R>(runner: Runner<R>, args: Array<unknown>, node: AstNode): E
       return result
     })
 
-  return Effect.map(visit(root, ""), (value) => JSON.stringify(value, null, indent))
+  return Effect.map(visit(record({ "": args[0] }), ""), (value) => JSON.stringify(value, null, indent))
 }
 
 const toJSONValue = (value: unknown): unknown => {
@@ -114,6 +103,3 @@ const toJSONValue = (value: unknown): unknown => {
   if (value instanceof Values.URL) return value.url.href
   return value
 }
-
-const isPlainObject = (value: unknown): value is SafeObject =>
-  value !== null && typeof value === "object" && !Values.isValue(value)

packages/codemode/src/stdlib/object.ts

@@ -2,11 +2,10 @@ import { Effect } from "effect"
 import { toProgram } from "../data.js"
 import { HostFunction, sync, syncCall } from "../interpreter/host.js"
 import { type AstNode, AsyncIteratorSymbol, InterpreterRuntimeError, IteratorSymbol } from "../interpreter/model.js"
+import { getOwn, hasOwn, ownEntries, ownKeys, ProgramArray, ProgramObject, set } from "../interpreter/objects.js"
 import {
   containsOpaqueReference,
   describeValue,
-  isRuntimeReference,
-  parseArrayIndex,
   rejectCircularInsertion,
   typeofValue,
 } from "../interpreter/references.js"
@@ -16,9 +15,8 @@ import { Values } from "../values.js"
 import { groupBy } from "./collections.js"
 import { coerceToString } from "./value.js"
 
-// ToObject for enumeration. Strings return themselves: the host's Object.keys/entries/hasOwn index a
-// primitive string directly. Numbers, booleans, wrappers, and functions have no own enumerable keys.
-export const enumerableSource = (label: string, value: unknown, node: AstNode): Record<string, unknown> => {
+// ToObject for enumeration.
+export const enumerableSource = (label: string, value: unknown, node: AstNode): ProgramObject => {
   if (value === null || value === undefined) {
     throw new InterpreterRuntimeError(`${label} cannot convert ${describeValue(value)} to an object.`, node).as(
       "TypeError",
@@ -38,58 +36,41 @@ export const enumerableSource = (label: string, value: unknown, node: AstNode):
       "InvalidDataValue",
     )
   }
-  if (typeof value === "string") return value as unknown as Record<string, unknown>
-  if (typeof value !== "object" || Values.isValue(value) || isRuntimeReference(value)) return {}
-  return value as Record<string, unknown>
+  if (typeof value === "string") return new ProgramArray([...value])
+  if (value instanceof ProgramObject) return value
+  return new ProgramObject()
 }
 
 export const objectAssign = (args: Array<unknown>, node: AstNode): unknown => {
   const target = args[0]
   // JS would box a primitive target; wrappers and primitives cannot hold fields here.
-  if (target === null || typeof target !== "object" || Values.isValue(target) || isRuntimeReference(target)) {
+  if (!(target instanceof ProgramObject)) {
     throw new InterpreterRuntimeError(
       `Object.assign expects a data object or array target, received ${describeValue(target)}.`,
       node,
     ).as("TypeError")
   }
-  const out = target as Record<string, unknown>
   const seen = new Set<object>()
-  const guardedSet = (key: PropertyKey, item: unknown): void => {
-    // Arrays hold only indexed elements, as with direct assignment; Reflect.set would otherwise
-    // reach Array's length and Object.prototype's __proto__ setter.
-    if (Array.isArray(out) && (typeof key === "symbol" || parseArrayIndex(key) === undefined)) {
-      throw new InterpreterRuntimeError(
-        `Object.assign cannot assign '${String(key)}' to an array: only array indexes may be assigned.`,
-        node,
-      ).as("TypeError")
-    }
-    rejectCircularInsertion(out, item, "Object.assign result", node, seen)
-    if (!Reflect.set(out, key, item))
-      throw new InterpreterRuntimeError(`Object.assign could not assign property '${String(key)}'.`, node).as(
-        "TypeError",
-      )
-  }
   for (const source of args.slice(1)) {
     if (source === null || source === undefined) continue
     const from = enumerableSource("Object.assign(...)", source, node)
-    if (typeof from !== "object") {
-      for (const [key, item] of Object.entries(from)) guardedSet(key, item)
-      continue
-    }
-    for (const key of Reflect.ownKeys(from)) {
+    for (const key of ownKeys(from)) {
       if (typeof key === "symbol" && key !== AsyncIteratorSymbol && key !== IteratorSymbol) continue
-      if (Object.prototype.propertyIsEnumerable.call(from, key)) guardedSet(key, Reflect.get(from, key))
+      rejectCircularInsertion(target, getOwn(from, key), "Object.assign result", node, seen)
+      if (!set(target, key, getOwn(from, key))) {
+        throw new InterpreterRuntimeError("Invalid array length", node).as("RangeError")
+      }
     }
   }
-  return out
+  return target
 }
 
 const objectFromEntries = <R>(
   runner: Runner<R>,
   source: unknown,
   node: AstNode,
-): Effect.Effect<Record<string, unknown>, unknown, R> => {
-  const out: Record<string, unknown> = Object.create(null)
+): Effect.Effect<ProgramObject, unknown, R> => {
+  const out = new ProgramObject()
   return Effect.gen(function* () {
     const cursor = yield* runner.syncIterator(source, node)
     if (cursor === undefined) {
@@ -103,21 +84,12 @@ const objectFromEntries = <R>(
       yield* preserveConsumerError(
         cursor,
         Effect.sync(() => {
-          if (
-            step.value === null ||
-            typeof step.value !== "object" ||
-            Values.isValue(step.value) ||
-            containsOpaqueReference(step.value)
-          ) {
+          if (!(step.value instanceof ProgramObject) || containsOpaqueReference(step.value)) {
             throw new InterpreterRuntimeError("Object.fromEntries expects [key, value] entry objects.", node).as(
               "TypeError",
             )
           }
-          const entry = step.value as Record<string, unknown>
-          toProgram(entry[0], "Object.fromEntries key")
-          toProgram(entry[1], "Object.fromEntries value")
-          const key = coerceToString(entry[0])
-          out[key] = entry[1]
+          set(out, coerceToString(getOwn(step.value, 0)), getOwn(step.value, 1))
         }),
       )
     }
@@ -126,7 +98,7 @@ const objectFromEntries = <R>(
 
 const constructObject = (args: Array<unknown>, node: AstNode): unknown => {
   const first = args[0]
-  if (first === null || first === undefined) return Object.create(null)
+  if (first === null || first === undefined) return new ProgramObject()
   if (typeof first === "object") return first
   throw new InterpreterRuntimeError(
     `Object(${typeof first}) wrapper objects are not supported; use the primitive value directly.`,
@@ -147,18 +119,24 @@ export const objectGlobal = <R>(runner: Runner<R>, toolKeys: (path: ReadonlyArra
         toProgram(
           args[0] instanceof ToolReference
             ? [...toolKeys(args[0].path)]
-            : Object.keys(enumerableSource("Object.keys(...)", args[0], node)),
+            : ownKeys(enumerableSource("Object.keys(...)", args[0], node)).filter((key) => typeof key === "string"),
           "Object.keys result",
         ),
       ),
-      values: sync("Object.values", (args, node) =>
-        Object.values(enumerableSource("Object.values(...)", args[0], node)),
+      values: sync(
+        "Object.values",
+        (args, node) =>
+          new ProgramArray(ownEntries(enumerableSource("Object.values(...)", args[0], node)).map((entry) => entry[1])),
       ),
-      entries: sync("Object.entries", (args, node) =>
-        Object.entries(enumerableSource("Object.entries(...)", args[0], node)).map(([key, item]) => [key, item]),
+      entries: sync(
+        "Object.entries",
+        (args, node) =>
+          new ProgramArray(
+            ownEntries(enumerableSource("Object.entries(...)", args[0], node)).map((entry) => new ProgramArray(entry)),
+          ),
       ),
       hasOwn: sync("Object.hasOwn", (args, node) =>
-        Object.hasOwn(
+        hasOwn(
           enumerableSource("Object.hasOwn(...)", args[0], node),
           args[1] === AsyncIteratorSymbol || args[1] === IteratorSymbol ? args[1] : String(args[1]),
         ),

packages/codemode/src/stdlib/regexp.ts

@@ -1,19 +1,9 @@
 import { sync, syncCall } from "../interpreter/host.js"
 import { type AstNode, InterpreterRuntimeError } from "../interpreter/model.js"
-import type { SafeObject } from "../data.js"
+import { ProgramArray, record, set } from "../interpreter/objects.js"
 import { Values } from "../values.js"
 import { coerceToNumber, coerceToString } from "./value.js"
 
-type MatchValue = Array<unknown> & {
-  index?: number
-  groups?: SafeObject
-  indices?: IndicesValue
-}
-
-type IndicesValue = Array<unknown> & {
-  groups?: SafeObject
-}
-
 export const regexpMethods = new Set(["test", "exec", "toString"])
 
 export const regexpProperties = new Set([
@@ -56,17 +46,12 @@ export const toHostRegex = (arg: unknown, method: string, node: AstNode, extraFl
   )
 }
 
-export const matchToValue = (match: RegExpMatchArray): Array<unknown> => {
-  const result: MatchValue = Array.from(match, (group) => group)
-  if (match.index !== undefined) result.index = match.index
-  if (match.groups) {
-    const groups: SafeObject = Object.create(null) as SafeObject
-    for (const [key, group] of Object.entries(match.groups)) {
-      groups[key] = group
-    }
-    result.groups = groups
-  }
-  if (match.indices) result.indices = indicesToValue(match.indices)
+export const matchToValue = (match: RegExpMatchArray): ProgramArray => {
+  const result = new ProgramArray(Array.from(match, (group) => group))
+  if (match.index !== undefined) set(result, "index", match.index)
+  if (match.input !== undefined) set(result, "input", match.input)
+  if (match.groups) set(result, "groups", record(match.groups))
+  if (match.indices) set(result, "indices", indicesToValue(match.indices))
   return result
 }
 
@@ -143,16 +128,16 @@ const toLength = (value: unknown): number => {
   return Math.min(Math.floor(number), Number.MAX_SAFE_INTEGER)
 }
 
-const indicesToValue = (indices: RegExpIndicesArray): IndicesValue => {
-  const result: IndicesValue = Array.from(indices, (range) => (range === undefined ? undefined : [...range]))
-  if (indices.groups) {
-    const groups: SafeObject = Object.create(null) as SafeObject
-    for (const [key, range] of Object.entries(indices.groups)) {
-      groups[key] = range === undefined ? undefined : [...range]
-    }
-    result.groups = groups
-    return result
-  }
-  result.groups = undefined
+const indicesToValue = (indices: RegExpIndicesArray): ProgramArray => {
+  const range = (pair: [number, number] | undefined) => (pair === undefined ? undefined : new ProgramArray([...pair]))
+  const result = new ProgramArray(Array.from(indices, range))
+  const groups = indices.groups
+  set(
+    result,
+    "groups",
+    groups === undefined
+      ? undefined
+      : record(Object.fromEntries(Object.entries(groups).map(([key, pair]) => [key, range(pair)]))),
+  )
   return result
 }

packages/codemode/src/stdlib/url.ts

@@ -2,6 +2,7 @@ import { Effect } from "effect"
 import { toProgram } from "../data.js"
 import { HostFunction, requiresNew, sync, syncCall } from "../interpreter/host.js"
 import { type AstNode, InterpreterRuntimeError } from "../interpreter/model.js"
+import { ownEntries, ProgramObject } from "../interpreter/objects.js"
 import { isRuntimeReference } from "../interpreter/references.js"
 import { preserveConsumerError, type Runner } from "../interpreter/runner.js"
 import { Values } from "../values.js"
@@ -183,15 +184,14 @@ const constructURLSearchParams = <R>(
       ).as("TypeError")
     }
     if (Values.isValue(init)) return new Values.URLSearchParams(new URLSearchParams())
-    const data = toProgram(init, "new URLSearchParams input")
-    if (data === null || typeof data !== "object") {
+    if (!(init instanceof ProgramObject)) {
       throw new InterpreterRuntimeError(
         "new URLSearchParams(...) expects a query string, data object, iterable pairs, or URLSearchParams.",
         node,
       ).as("TypeError")
     }
     return new Values.URLSearchParams(
-      new URLSearchParams(Object.fromEntries(Object.entries(data).map(([key, value]) => [key, coerceToString(value)]))),
+      new URLSearchParams(Object.fromEntries(ownEntries(init).map(([key, value]) => [key, coerceToString(value)]))),
     )
   })
 }

packages/codemode/src/stdlib/value.ts

@@ -1,6 +1,7 @@
 import { type HostFunction, sync, type SyncOptions } from "../interpreter/host.js"
 import { type AstNode, InterpreterRuntimeError } from "../interpreter/model.js"
-import { type SafeObject, toProgram } from "../data.js"
+import { toProgram } from "../data.js"
+import { get, ProgramArray, ProgramError, set } from "../interpreter/objects.js"
 import { Values } from "../values.js"
 
 export const errorConstructors = new Set([
@@ -16,21 +17,21 @@ export const errorConstructors = new Set([
 
 export const compoundOperators = new Set(["+=", "-=", "*=", "/=", "%=", "**=", "&=", "|=", "^=", "<<=", ">>=", ">>>="])
 
-const ErrorBrand: unique symbol = Symbol("codemode.error")
-
-export const createErrorValue = (name: string, message: string): SafeObject => {
-  const value = Object.assign(Object.create(null) as SafeObject, { name, message })
-  Object.defineProperty(value, ErrorBrand, { value: name })
+export const createErrorValue = (name: string, message: string): ProgramError => {
+  const value = new ProgramError(name)
+  set(value, "name", name)
+  set(value, "message", message)
   return value
 }
 
-export const createAggregateErrorValue = (errors: Array<unknown>, message: string): SafeObject =>
-  Object.assign(createErrorValue("AggregateError", message), { errors })
+export const createAggregateErrorValue = (errors: Array<unknown>, message: string): ProgramError => {
+  const value = createErrorValue("AggregateError", message)
+  set(value, "errors", new ProgramArray(errors))
+  return value
+}
 
 export const errorBrandName = (value: unknown): string | undefined =>
-  value !== null && typeof value === "object"
-    ? ((value as Record<PropertyKey, unknown>)[ErrorBrand] as string | undefined)
-    : undefined
+  value instanceof ProgramError ? value.errorName : undefined
 
 export const coerceToString = (value: unknown): string => {
   if (value === null) return "null"
@@ -42,29 +43,27 @@ export const coerceToString = (value: unknown): string => {
   if (value instanceof Values.Set) return "[object Set]"
   if (value instanceof Values.URL) return value.url.href
   if (value instanceof Values.URLSearchParams) return value.params.toString()
-  if (errorBrandName(value) !== undefined) {
+  if (value instanceof ProgramError) {
     // Match Error.prototype.toString: "name: message", or just one when the other is empty.
-    const error = value as { name?: unknown; message?: unknown }
-    const name = typeof error.name === "string" ? error.name : "Error"
-    const message = typeof error.message === "string" ? error.message : ""
-    if (message === "") return name
-    if (name === "") return message
-    return `${name}: ${message}`
+    const name = get(value, "name")
+    const message = get(value, "message")
+    const shownName = typeof name === "string" ? name : "Error"
+    const shownMessage = typeof message === "string" ? message : ""
+    if (shownMessage === "") return shownName
+    if (shownName === "") return shownMessage
+    return `${shownName}: ${shownMessage}`
   }
-  if (typeof value === "object") {
-    return Array.isArray(value)
-      ? value.map((item) => (item === null || item === undefined ? "" : coerceToString(item))).join(",")
-      : "[object Object]"
+  if (value instanceof ProgramArray) {
+    return value.items.map((item) => (item === null || item === undefined ? "" : coerceToString(item))).join(",")
   }
+  if (typeof value === "object") return "[object Object]"
   return String(value)
 }
 
 export const coerceToNumber = (value: unknown): number => {
   if (value instanceof Values.Date) return value.time
   if (Values.isValue(value)) return Number.NaN
-  // Arrays coerce through our own string coercion: host Number(array) joins with host
-  // ToPrimitive, which throws on the null-prototype objects the interpreter produces.
-  if (Array.isArray(value)) return Number(coerceToString(value))
+  if (value instanceof ProgramArray) return Number(coerceToString(value))
   return value !== null && typeof value === "object" ? Number.NaN : Number(value)
 }
 
@@ -78,8 +77,6 @@ const coerce = (name: Coercion, args: Array<unknown>, node: AstNode): unknown =>
     if (name === "String") return ""
   }
   const raw = args[0]
-  // Error values are plain SafeObjects; the toProgram path below would strip their brand.
-  if (name === "String" && errorBrandName(raw) !== undefined) return coerceToString(raw)
   if (Values.isValue(raw)) {
     if (name === "Boolean") return true
     if (name === "Number") return coerceToNumber(raw)

packages/codemode/src/stdlib/web.ts

@@ -5,9 +5,8 @@ import { coerceToString } from "./value.js"
 // WebIDL DOMString conversion: a missing argument is a TypeError, anything else stringifies.
 const base64 = (name: "atob" | "btoa") =>
   sync(name, (args, node) => {
-    if (args.length === 0) {
-      throw new InterpreterRuntimeError(`${name} requires 1 argument, but only 0 were provided.`, node).as("TypeError")
-    }
+    if (args.length === 0)
+      throw new InterpreterRuntimeError(`${name} requires 1 argument (a string)`, node).as("TypeError")
     const input = coerceToString(args[0])
     try {
       return name === "atob" ? atob(input) : btoa(input)

packages/codemode/test/enumeration.test.ts

@@ -98,7 +98,7 @@ describe("Object.keys over arrays", () => {
     )
     expect((await error(`const { a } = new Map(); return a`)).message).toContain("received a Map.")
     expect((await error(`return Array.from(7)`)).message).toContain("received a number.")
-    expect((await error(`return (() => 1).x`)).message).toContain("Cannot read properties of a function")
+    expect(await value(`return [(() => 1).x, Object.keys(() => 1)]`)).toEqual([null, []])
   })
 })
 

packages/codemode/test/object-coercion-test262.test.ts

@@ -167,17 +167,14 @@ describe("Object.assign Test262 parity", () => {
     ).toEqual([true, [1, 8, 9], true, [1, 8, 3], true, 5, true, 0])
   })
 
-  test("array targets accept only array indexes (deviation from target-Array.js)", async () => {
+  test("test/built-ins/Object/assign/target-Array.js", async () => {
     expect(
       await value(`
         const target = [7]
-        const out = []
-        for (const source of [{ length: 0 }, { x: 1 }, { "1.5": 1 }, { "-0": 1 }, { ["__proto__"]: null }]) {
-          try { Object.assign(target, source) } catch (error) { out.push(error.name) }
-        }
-        return [out, [...target], target.length, Object.keys(target)]
+        for (const source of [{ x: 1 }, { "1.5": 1 }, { "-0": 1 }, { 1: 8 }, { length: 1 }]) Object.assign(target, source)
+        return [[...target], target.length, Object.keys(target), target.x]
       `),
-    ).toEqual([["TypeError", "TypeError", "TypeError", "TypeError", "TypeError"], [7], 1, ["0"]])
+    ).toEqual([[7], 1, ["0", "x", "1.5", "-0"], 1])
   })
 
   test("test/built-ins/Object/assign/Target-{Null,Undefined}.js", async () => {

packages/codemode/test/parity.test.ts

@@ -81,27 +81,26 @@ describe("H3: array property access reads as undefined (not a throw)", () => {
     ).toEqual(["b", "b", null, null, "a", null])
   })
 
-  test("noncanonical keys cannot mutate or delete an aliased element", async () => {
+  test("noncanonical keys are ordinary properties that never alias an element", async () => {
     expect(
       await value(`
         const values = ["a", "b"]
-        let writes = 0
-        try { values["01"] = ++writes } catch {}
+        values["01"] = "c"
+        const before = [values["01"], values[1], values.length]
         const removed = delete values["01"]
-        return [writes, removed, values]
+        return [before, removed, values["01"], values]
       `),
-    ).toEqual([0, true, ["a", "b"]])
+    ).toEqual([["c", "b", 2], true, null, ["a", "b"]])
   })
 
-  test("the maximum array length is not accepted as an array index", async () => {
+  test("the maximum array length is a property, not an index", async () => {
     expect(
       await value(`
         const values = []
-        let writes = 0
-        try { values["4294967295"] = ++writes } catch {}
-        return [writes, values.length]
+        values["4294967295"] = 1
+        return [values["4294967295"], values.length]
       `),
-    ).toEqual([0, 0])
+    ).toEqual([1, 0])
   })
 })
 
@@ -246,16 +245,14 @@ describe("property deletion", () => {
     expect(await value(`const values = [1, 2]; return [delete values.length, values.length]`)).toEqual([false, 2])
   })
 
-  test("does not broaden unsupported array property assignment", async () => {
+  test("arrays accept named properties like JS, and they stay out of the JSON form", async () => {
     expect(
       await value(`
-        const values = []
-        let rightHandSideRuns = 0
-        function next() { rightHandSideRuns++; return 1 }
-        try { values.field = next() } catch {}
-        return rightHandSideRuns
+        const values = [1]
+        values.field = 2
+        return [values.field, Object.keys(values), values]
       `),
-    ).toBe(0)
+    ).toEqual([2, ["0", "field"], [1]])
   })
 
   test("optional deletion short-circuits without evaluating the key", async () => {
@@ -916,3 +913,48 @@ describe("coercion parity: unknown static members read as undefined", () => {
     ])
   })
 })
+
+describe("functions are objects", () => {
+  test("name follows NamedEvaluation and length counts required parameters", async () => {
+    expect(
+      await value(`
+        function decl(a, b = 1, ...rest) {}
+        const arrow = () => {}
+        const named = function inner() {}
+        let assigned
+        assigned = (a, b) => {}
+        const { fromDefault = () => {} } = {}
+        const [fromArray = function () {}] = []
+        const obj = { method() {}, key: () => {}, [Symbol.iterator]: () => {} }
+        const passthrough = (0, () => {})
+        return [
+          [decl.name, decl.length],
+          [arrow.name, named.name, assigned.name, assigned.length],
+          [fromDefault.name, fromArray.name],
+          [obj.method.name, obj.key.name, obj[Symbol.iterator].name],
+          passthrough.name,
+        ]
+      `),
+    ).toEqual([
+      ["decl", 1],
+      ["arrow", "inner", "assigned", 2],
+      ["fromDefault", "fromArray"],
+      ["method", "key", "[Symbol.iterator]"],
+      "",
+    ])
+  })
+
+  test("functions hold own properties; name and length are read-only", async () => {
+    expect(
+      await value(`
+        const fn = () => 1
+        fn.count = 2
+        fn.count += 1
+        let renamed = false
+        try { fn.name = "other" } catch (error) { renamed = error instanceof TypeError }
+        const { name, count } = fn
+        return [fn.count, Object.keys(fn), "count" in fn, "name" in fn, name, count, renamed, delete fn.count, fn.count]
+      `),
+    ).toEqual([3, ["count"], true, true, "fn", 3, true, true, null])
+  })
+})

packages/codemode/test/stdlib.test.ts

@@ -17,8 +17,6 @@
 import { describe, expect, test } from "bun:test"
 import { Effect, Schema } from "effect"
 import { CodeMode, Tool } from "../src/index.js"
-import { AsyncIteratorSymbol, IteratorSymbol } from "../src/interpreter/model.js"
-import { objectAssign } from "../src/stdlib/object.js"
 
 // Standard-library value types: Date, RegExp, Map, Set. Programs use them as ordinary JS;
 // intra-CodeMode checkpoints (Object.* helpers, spread, coercion inputs) preserve the live
@@ -770,13 +768,18 @@ describe("stdlib integration", () => {
       ],
     ])
     expect(await value(`const match = /a/.exec("ba"); return [Object.values(match), Object.entries(match)]`)).toEqual([
-      ["a", 1],
+      ["a", 1, "ba"],
       [
         ["0", "a"],
         ["index", 1],
+        ["input", "ba"],
       ],
     ])
-    expect(await value(`return Object.keys(Object.values({ match: /a/.exec("ba") })[0])`)).toEqual(["0", "index"])
+    expect(await value(`return Object.keys(Object.values({ match: /a/.exec("ba") })[0])`)).toEqual([
+      "0",
+      "index",
+      "input",
+    ])
   })
 
   test("Object.fromEntries accepts every supported entry collection", async () => {
@@ -849,86 +852,6 @@ describe("stdlib integration", () => {
     expect(await value(`try { Object.assign(null, { a: 1 }); return false } catch { return true }`)).toBe(true)
   })
 
-  test("Object.assign ignores non-enumerable supported symbols without reading them", () => {
-    const target = {}
-    const reads: Array<boolean> = []
-    const source = Object.defineProperty({}, IteratorSymbol, {
-      get() {
-        reads.push(true)
-        return target
-      },
-    })
-    expect(objectAssign([target, source], { type: "CallExpression", start: 0, end: 0 })).toBe(target)
-    expect(reads).toEqual([])
-    expect(Object.hasOwn(target, IteratorSymbol)).toBe(false)
-  })
-
-  test("Object.assign ignores nested non-enumerable supported symbols during cycle checks", () => {
-    const target = {}
-    const reads: Array<boolean> = []
-    const nested = Object.defineProperty({}, IteratorSymbol, {
-      get() {
-        reads.push(true)
-        return target
-      },
-    })
-    expect(objectAssign([target, { nested }], { type: "CallExpression", start: 0, end: 0 })).toBe(target)
-    expect(reads).toEqual([])
-    expect(target).toEqual({ nested })
-  })
-
-  test("Object.assign rejects cycles through supported symbols on nested arrays", () => {
-    const target = {}
-    const nested = Object.defineProperty([], IteratorSymbol, { enumerable: true, value: target })
-    expect(() => objectAssign([target, { nested }], { type: "CallExpression", start: 0, end: 0 })).toThrow(
-      "Object.assign result contains a circular value.",
-    )
-    expect(Object.hasOwn(target, "nested")).toBe(false)
-  })
-
-  test("Object.assign cycle checks traverse sparse keys lazily", () => {
-    const target = {}
-    const reads: Array<boolean> = []
-    const nested = Object.defineProperties([], {
-      4294967294: { enumerable: true, value: target },
-      later: {
-        enumerable: true,
-        get() {
-          reads.push(true)
-          return null
-        },
-      },
-    })
-    expect(() => objectAssign([target, { nested }], { type: "CallExpression", start: 0, end: 0 })).toThrow(
-      "Object.assign result contains a circular value.",
-    )
-    expect(reads).toEqual([])
-  })
-
-  test("Object.assign stops after a supported symbol write fails", () => {
-    const previous = () => ({ done: true })
-    const target = Object.defineProperty({}, IteratorSymbol, { value: previous })
-    const reads: Array<boolean> = []
-    const source = Object.defineProperties(
-      {},
-      {
-        [IteratorSymbol]: { enumerable: true, value: () => ({ done: false }) },
-        [AsyncIteratorSymbol]: {
-          enumerable: true,
-          get() {
-            reads.push(true)
-            return () => ({ done: true })
-          },
-        },
-      },
-    )
-    expect(() => objectAssign([target, source], { type: "CallExpression", start: 0, end: 0 })).toThrow(
-      "Object.assign could not assign property",
-    )
-    expect(Reflect.get(target, IteratorSymbol)).toBe(previous)
-    expect(reads).toEqual([])
-  })
-
   test("Object.assign rejects direct and nested cycles", async () => {
     expect(
       await value(`
@@ -1000,27 +923,6 @@ describe("stdlib integration", () => {
     ).toEqual([true, true, true, 2])
   })
 
-  test("Object.assign traverses shared aliases once", () => {
-    const reads: Array<boolean> = []
-    const shared = Object.defineProperty({}, "value", {
-      enumerable: true,
-      get() {
-        reads.push(true)
-        return 1
-      },
-    })
-    const target = {}
-    expect(
-      objectAssign([target, { left: shared, right: shared }], {
-        type: "CallExpression",
-        start: 0,
-        end: 0,
-      }),
-    ).toBe(target)
-    expect(target).toEqual({ left: shared, right: shared })
-    expect(reads).toEqual([true])
-  })
-
   test("assignment resolves and reads its left side before evaluating the right side", async () => {
     expect(await value(`let x = 1; x += (x = 5); return x`)).toBe(6)
     expect(await value(`let i = 0; const values = [9]; values[i++] = i; return [values, i]`)).toEqual([[1], 1])
@@ -1199,7 +1101,7 @@ describe("CodeMode values at intra-CodeMode checkpoints", () => {
     const diagnostic = await error(`return Array.from(Promise.resolve([1]))`)
     expect(diagnostic.kind).toBe("InvalidDataValue")
     expect(diagnostic.message).toContain("await")
-    expect((await error(`return Array.from(() => 1)`)).kind).toBe("InvalidDataValue")
+    expect(await value(`return Array.from((a, b) => 1)`)).toEqual([null, null])
   })
 
   test("regexes stay callable through Object.values", async () => {

packages/codemode/test/test262.test.ts

@@ -0,0 +1,20 @@
+/*
+ * Runs the test262 files vendored under test/test262 (see test/test262/README.md) verbatim.
+ * Files listed in test/test262/skipped.txt fail on a known interpreter gap and are skipped;
+ * `bun run script/test262-report.ts` shows current gaps and which skipped files pass again.
+ * Licensed under test/LICENSE.test262.
+ */
+import { test } from "bun:test"
+import { root, run, skipped } from "./test262/run.js"
+
+for (const file of [...new Bun.Glob("**/*.js").scanSync({ cwd: root })].sort()) {
+  const define = skipped.has(file) ? test.skip : test
+  define(
+    file,
+    async () => {
+      const outcome = await run(file)
+      if (outcome.status === "fail") throw new Error(outcome.reason)
+    },
+    10_000,
+  )
+}

packages/codemode/test/test262/.gitignore

@@ -0,0 +1,3 @@
+# Upstream test262 files are populated locally by script/sync-test262.ts and not committed yet.
+built-ins/
+language/

packages/codemode/test/test262/README.md

@@ -0,0 +1,41 @@
+# test262
+
+Runs upstream [test262](https://github.com/tc39/test262) files verbatim through `test/test262.test.ts`. The files
+themselves are not committed yet: populate them from a local checkout with
+
+```sh
+git clone https://github.com/tc39/test262 ~/development/test262
+bun run script/sync-test262.ts ~/development/test262
+```
+
+Without them the runner registers no tests, so CI is unaffected. Licensed under `test/LICENSE.test262`.
+
+## Layout
+
+- `manifest.json` — the pinned upstream revision, which upstream directories are copied, and what is left out.
+- `built-ins/`, `language/` — the copied files, mirroring upstream `test/`; gitignored.
+- `skipped.txt` — vendored files that fail on a known interpreter gap, one `path  # reason` per line. They are
+  skipped, and each gap is listed as unchecked in `interpreter-support.md`.
+- `run.ts` — runs one file: prepends `"use strict"`, provides the harness (`assert`, `Test262Error`,
+  `compareArray`, `$DONE`, `$DONOTEVALUATE`) as host globals, and interprets the file's frontmatter (`negative`,
+  `flags: [async]`).
+
+## What is not vendored
+
+`script/sync-test262.ts` skips a file when its frontmatter declares a `flags`, `features`, or `includes` value the
+manifest marks unsupported, or when its code matches one of the manifest's `boundaries` patterns. The sync checks the
+checkout is at the pinned revision, so every machine runs the same 3993 files. Boundaries are
+intentional limits of the interpreter, not compatibility work: classes, `this`, `arguments`, prototype objects,
+property descriptors, accessors, boxed primitives, sloppy mode, `eval`, `Symbol()`, and the `$262` host API. If one
+of those decisions changes, delete its entry and re-sync; the tests are upstream, not lost.
+
+## Commands
+
+```sh
+bun run script/sync-test262.ts /path/to/test262   # re-copy at the pinned revision; edit manifest.json to change scope
+bun run script/test262-report.ts [--write] [dir]  # run everything, group failures by cause; --write regenerates skipped.txt
+bun test test/test262.test.ts                     # what CI runs
+```
+
+When a fix makes skipped files pass, the report lists them so they can be removed from `skipped.txt`, and the
+matching gap in `interpreter-support.md` is checked in the same change.