refactor(core): use nonempty array guards

packages/core/src/session/runner/publish-llm-event.ts

@@ -1,5 +1,6 @@
 import { type LLMEvent, type ProviderMetadata, type ToolResultValue } from "@opencode-ai/ai"
 import { Clock, Effect, Iterable } from "effect"
+import { isArrayNonEmpty, isReadonlyArrayNonEmpty } from "effect/Array"
 import { Bus } from "../../bus.js"
 import { Model } from "../../model.js"
 import { SessionEvent } from "../event.js"
@@ -45,9 +46,6 @@ export interface StepRecord {
 /** Derives canonical model content from a provider-hosted tool result. */
 type NonEmptyContent = readonly [Tool.Content, ...Tool.Content[]]
 
-const nonEmpty = (content: ReadonlyArray<Tool.Content>): NonEmptyContent | undefined =>
-  content.length > 0 ? (content as NonEmptyContent) : undefined
-
 const stringify = (value: unknown) => {
   if (typeof value === "string") return value
   try {
@@ -58,10 +56,7 @@ const stringify = (value: unknown) => {
 }
 
 const hostedContent = (result: ToolResultValue): NonEmptyContent => {
-  if (result.type === "content") {
-    const content = nonEmpty(result.value)
-    if (content !== undefined) return content
-  }
+  if (result.type === "content" && isReadonlyArrayNonEmpty(result.value)) return result.value
   return [{ type: "text", text: stringify(result.value) }]
 }
 
@@ -561,12 +556,12 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
         : result.content === undefined
           ? []
           : [...result.content]
-    if (content.length === 0) return yield* Effect.die(new Error(`Tool execution has no content: ${id}`))
+    if (!isArrayNonEmpty(content)) return yield* Effect.die(new Error(`Tool execution has no content: ${id}`))
     yield* bus.publish(SessionEvent.Tool.Success, {
       sessionID: input.sessionID,
       assistantMessageID,
       id,
-      content: [content[0], ...content.slice(1)],
+      content,
       ...(result.metadata === undefined ? {} : { metadata: result.metadata }),
       executed: tool.providerExecuted,
     })

packages/core/src/session/transfer.ts

@@ -5,6 +5,7 @@ import { Tool } from "@opencode-ai/schema/tool"
 import { Skill } from "@opencode-ai/schema/skill"
 import { eq } from "drizzle-orm"
 import { Context, DateTime, Effect, Layer, Schema } from "effect"
+import { map } from "effect/Array"
 import path from "path"
 import { makeGlobalNode } from "@opencode-ai/util/effect/app-node"
 import { App } from "../app.js"
@@ -304,21 +305,13 @@ function sanitizeToolState(id: string, state: SessionMessage.ToolState): Session
     return {
       ...state,
       input: { redacted: `tool-input:${id}` },
-      content: [
-        sanitizeToolContent(id, state.content[0]),
-        ...state.content.slice(1).map((item) => sanitizeToolContent(id, item)),
-      ],
+      content: map(state.content, (item) => sanitizeToolContent(id, item)),
       metadata: meta,
     }
   return {
     ...state,
     input: { redacted: `tool-input:${id}` },
-    content: state.content
-      ? [
-          sanitizeToolContent(id, state.content[0]),
-          ...state.content.slice(1).map((item) => sanitizeToolContent(id, item)),
-        ]
-      : undefined,
+    content: state.content ? map(state.content, (item) => sanitizeToolContent(id, item)) : undefined,
     metadata: meta,
   }
 }

packages/plugin/src/README.md

@@ -5,9 +5,7 @@ The Promise plugin API at `@opencode-ai/plugin` is the async/await equivalent of
 - `hook` installs behavior at an OpenCode extension point.
 - `reload` reruns every transform hook for a stateful domain.
 
-The Promise API uses Promises instead of Effects for setup, runtime hook
-callbacks, hook registration, `reload`, and `Registration.dispose`. Transform
-draft callbacks remain synchronous.
+The only difference from the Effect API is the async boundary: hook callbacks, hook registration, `reload`, and `Registration.dispose` use Promises instead of Effects.
 
 ## Defining A Plugin
 
@@ -48,15 +46,12 @@ await registration.dispose()
 
 ## Transform Hooks
 
-Transform hooks contribute to stateful domains. The draft editor is synchronous,
-so load asynchronous data before registering a transform or reloading its domain:
+Transform hooks contribute to stateful domains. The draft editor is synchronous; the callback may be `async` when it needs to await other work:
 
 ```ts
-const description = await loadReviewerDescription()
-
 await ctx.agent.transform((agent) => {
   agent.update("reviewer", (item) => {
-    item.description = description
+    item.description = "Reviews code for regressions"
     item.mode = "subagent"
   })
 })
@@ -69,12 +64,8 @@ ctx.agent.transform
 ctx.catalog.transform
 ctx.command.transform
 ctx.integration.transform
-ctx.mcp.transform
 ctx.reference.transform
 ctx.skill.transform
-ctx.tool.transform
-ctx.vcs.transform
-ctx.websearch.transform
 ```
 
 ## Runtime Hooks
@@ -90,7 +81,7 @@ await ctx.aisdk.hook("sdk", async (event) => {
 
 await ctx.aisdk.hook("language", (event) => {
   if (event.model.providerID !== "xai") return
-  event.language = event.sdk.responses(event.model.modelID)
+  event.language = event.sdk.responses(event.model.api.id)
 })
 ```
 
@@ -103,15 +94,14 @@ await ctx.session.hook("context", (event) => {
 })
 ```
 
-Promise tools use complete executable tool values with async executors:
+Promise tools use executable tool values with async executors. Registration
+supplies the tool's name and options separately:
 
 ```ts
 import { Schema } from "effect"
 
 await ctx.tool.transform((tools) => {
-  tools.add({
-    name: "echo",
-    options: { codemode: false },
+  tools.add("echo", {
     description: "Echo text",
     input: Schema.Struct({ text: Schema.String }),
     output: Schema.Struct({ text: Schema.String }),
@@ -142,10 +132,6 @@ ctx.agent.reload()
 ctx.catalog.reload()
 ctx.command.reload()
 ctx.integration.reload()
-ctx.mcp.reload()
 ctx.reference.reload()
 ctx.skill.reload()
-ctx.tool.reload()
-ctx.vcs.reload()
-ctx.websearch.reload()
 ```

packages/plugin/src/effect/README.md

@@ -31,9 +31,7 @@ Registrations are owned by the plugin scope. Closing the scope removes them auto
 
 ## Transform Hooks
 
-Transform hooks contribute to stateful domains. Their draft callbacks are
-synchronous, so load effectful data before registering a transform or reloading
-its domain:
+Transform hooks contribute to stateful domains:
 
 ```ts
 yield *
@@ -54,12 +52,8 @@ ctx.agent.transform
 ctx.catalog.transform
 ctx.command.transform
 ctx.integration.transform
-ctx.mcp.transform
 ctx.reference.transform
 ctx.skill.transform
-ctx.tool.transform
-ctx.vcs.transform
-ctx.websearch.transform
 ```
 
 ## Runtime Hooks
@@ -78,12 +72,10 @@ yield *
   )
 
 yield *
-  ctx.aisdk.hook("language", (event) =>
-    Effect.sync(() => {
-      if (event.model.providerID !== "xai") return
-      event.language = event.sdk.responses(event.model.modelID)
-    }),
-  )
+  ctx.aisdk.hook("language", (event) => {
+    if (event.model.providerID !== "xai") return
+    event.language = event.sdk.responses(event.model.api.id)
+  })
 ```
 
 Hooks run sequentially in registration order. Later hooks observe mutations made by earlier hooks.
@@ -125,10 +117,6 @@ ctx.agent.reload()
 ctx.catalog.reload()
 ctx.command.reload()
 ctx.integration.reload()
-ctx.mcp.reload()
 ctx.reference.reload()
 ctx.skill.reload()
-ctx.tool.reload()
-ctx.vcs.reload()
-ctx.websearch.reload()
 ```

packages/util/src/cross-spawn-spawner.ts

@@ -1,4 +1,4 @@
-import type { NonEmptyReadonlyArray } from "effect/Array"
+import { isArrayNonEmpty } from "effect/Array"
 import * as NodeFileSystem from "@effect/platform-node/NodeFileSystem"
 import * as NodePath from "@effect/platform-node/NodePath"
 import * as NodeSink from "@effect/platform-node/NodeSink"
@@ -62,10 +62,9 @@ const flatten = (command: ChildProcess.Command) => {
   }
 
   walk(command)
-  if (commands.length === 0) throw new Error("flatten produced empty commands array")
-  const [head, ...tail] = commands
+  if (!isArrayNonEmpty(commands)) throw new Error("flatten produced empty commands array")
   return {
-    commands: [head, ...tail] as NonEmptyReadonlyArray<ChildProcess.StandardCommand>,
+    commands,
     opts,
   }
 }