fix(session-ui): animate appended inline code chunks

test(session-ui): stream inline code in partial chunks
test(session-ui): demonstrate streamed inline code fade
2026-08-25 11:06:12 +00:00 · 2026-08-25 14:07:29 +08:00 · 2026-08-25 14:01:20 +08:00 · 2026-08-25 13:59:37 +08:00 · 2026-08-25 13:55:47 +08:00 · 2026-08-24 22:37:47 -05:00
48 changed files with 1841 additions and 205 deletions
@@ -716,7 +716,7 @@ export const protocol = Protocol.make({
      reasoningSignatures: {},
    }),
    step,
-    onHalt,
+    onHalt: (state) => Effect.succeed(onHalt(state)),
  },
 })

@@ -718,7 +718,7 @@ export const protocol = Protocol.make({
      lifecycle: Lifecycle.initial(),
    }),
    step,
-    onHalt: finish,
+    onHalt: (state) => Effect.succeed(finish(state)),
  },
 })

@@ -285,6 +285,7 @@ export const Event = Schema.StructWithRest(
  Schema.Struct({
    type: Schema.String,
    delta: Schema.optional(Schema.String),
+    arguments: Schema.optional(Schema.String),
    text: Schema.optional(Schema.String),
    item_id: Schema.optional(Schema.String),
    summary_index: Schema.optional(Schema.Number),
@@ -996,12 +997,24 @@ const onFunctionCallArgumentsDelta = Effect.fn("OpenResponses.onFunctionCallArgu
  state: ParserState,
  event: Event,
 ) {
-  if (!event.item_id || !event.delta || !state.tools[event.item_id]) return [state, NO_EVENTS] satisfies StepResult
+  if (!event.item_id) return [state, NO_EVENTS] satisfies StepResult
+  const tool = state.tools[event.item_id]
+  if (!tool) return [state, NO_EVENTS] satisfies StepResult
+  const final = event.type === "response.function_call_arguments.done" ? event.arguments : undefined
+  if (event.type === "response.function_call_arguments.done" && final === undefined)
+    return [state, NO_EVENTS] satisfies StepResult
+  if (final !== undefined && !final.startsWith(tool.input))
+    return [
+      { ...state, tools: ToolStream.start(state.tools, event.item_id, { ...tool, input: final }) },
+      NO_EVENTS,
+    ] satisfies StepResult
+  const delta = final === undefined ? event.delta : final.slice(tool.input.length)
+  if (!delta) return [state, NO_EVENTS] satisfies StepResult
  const result = ToolStream.appendExisting(
    state.id,
    state.tools,
    event.item_id,
-    event.delta,
+    delta,
    `${state.name} tool argument delta is missing its tool call`,
  )
  if (ToolStream.isError(result)) return yield* result
@@ -1212,7 +1225,7 @@ export const step = (state: ParserState, event: Event) => {
      return ProviderShared.eventError(state.id, `${event.type} message is missing id`)
    return Effect.succeed(onOutputItemAdded(state, event))
  }
-  if (event.type === "response.function_call_arguments.delta")
+  if (event.type === "response.function_call_arguments.delta" || event.type === "response.function_call_arguments.done")
    return event.item_id
      ? onFunctionCallArgumentsDelta(state, event)
      : ProviderShared.eventError(state.id, `${event.type} is missing item_id`)
@@ -7,7 +7,10 @@ import { HttpTransport } from "../route/transport/index.js"
 import { Protocol } from "../route/protocol.js"
 import {
  AIError,
+  InvalidProviderOutputReason,
  LLMEvent,
+  ProviderInternalReason,
+  UnknownProviderReason,
  Usage,
  type FinishReason,
  type FinishReasonDetails,
@@ -224,16 +227,22 @@ const OpenAIChatChoice = Schema.StructWithRest(
  [Schema.Record(Schema.String, Schema.Unknown)],
 )

-const OpenAIChatError = Schema.Struct({
-  code: optionalNull(Schema.Union([Schema.String, Schema.Number])),
-  message: Schema.String,
-})
+const OpenAIChatError = Schema.StructWithRest(
+  Schema.Struct({
+    code: optionalNull(Schema.Union([Schema.String, Schema.Number])),
+    message: Schema.String,
+  }),
+  [Schema.Record(Schema.String, Schema.Unknown)],
+)

-export const OpenAIChatEvent = Schema.Struct({
-  choices: optionalNull(Schema.Array(OpenAIChatChoice)),
-  usage: optionalNull(OpenAIChatUsage),
-  error: optionalNull(OpenAIChatError),
-})
+export const OpenAIChatEvent = Schema.StructWithRest(
+  Schema.Struct({
+    choices: optionalNull(Schema.Array(OpenAIChatChoice)),
+    usage: optionalNull(OpenAIChatUsage),
+    error: optionalNull(OpenAIChatError),
+  }),
+  [Schema.Record(Schema.String, Schema.Unknown)],
+)
 export type OpenAIChatEvent = Schema.Schema.Type<typeof OpenAIChatEvent>
 type OpenAIChatRequestMessage = LLMRequest["messages"][number]

@@ -256,6 +265,7 @@ export interface ParserState {
  readonly reasoningEmitted: boolean
  readonly latestToolIndex?: number
  readonly nextToolIndex: number
+  readonly requireFinishReason: boolean
 }

 // =============================================================================
@@ -726,14 +736,40 @@ export const fromRequest = Effect.fn("OpenAIChat.fromRequest")(function* (
 // Streaming parsers are small state machines: every event returns a new state
 // plus the common `LLMEvent`s produced by that event. Tool calls are accumulated
 // because OpenAI streams JSON arguments across multiple deltas.
-const mapFinishReason = (reason: string | null | undefined): FinishReason => {
-  if (reason === "stop") return "stop"
-  if (reason === "length") return "length"
-  if (reason === "content_filter") return "content-filter"
-  if (reason === "function_call" || reason === "tool_calls") return "tool-calls"
-  if (reason === "error") return "error"
-  return "unknown"
-}
+const finishReasonError = (event: OpenAIChatEvent, reason: AIError["reason"]) =>
+  new AIError({
+    module: ADAPTER,
+    method: "stream",
+    body: ProviderShared.encodeJson(event),
+    reason,
+  })
+
+const mapFinishReason = Effect.fn("OpenAIChat.mapFinishReason")(function* (event: OpenAIChatEvent, reason: string) {
+  switch (reason) {
+    case "error":
+      return yield* finishReasonError(
+        event,
+        new UnknownProviderReason({ message: "Provider reported an error (finish_reason: error)" }),
+      )
+    case "network_error":
+      return yield* finishReasonError(
+        event,
+        new ProviderInternalReason({ message: "Provider reported a network error (finish_reason: network_error)" }),
+      )
+    case "stop":
+    case "end":
+      return "stop" as const
+    case "length":
+      return "length" as const
+    case "content_filter":
+      return "content-filter" as const
+    case "function_call":
+    case "tool_calls":
+      return "tool-calls" as const
+    default:
+      return "unknown" as const
+  }
+})

 // OpenAI Chat reports `prompt_tokens` (inclusive total) with a
 // cached-read and cache-write subsets, and `completion_tokens` (inclusive
@@ -846,16 +882,20 @@ const reasoningMetadata = (field: ParserState["reasoningField"], details?: Reado

 const step = (state: ParserState, event: OpenAIChatEvent) =>
  Effect.gen(function* () {
-    if (event.error)
+    if (event.error) {
+      const body = ProviderShared.encodeJson(event)
      return yield* new AIError({
        module: ADAPTER,
        method: "stream",
+        body,
        reason: classifyProviderFailure({
          message: event.error.message,
          code: event.error.code === undefined || event.error.code === null ? undefined : String(event.error.code),
          status: typeof event.error.code === "number" ? event.error.code : undefined,
+          rawBody: body,
        }),
      })
+    }
    const events: LLMEvent[] = []
    const choice = event.choices?.[0]
    // Moonshot (and a few other OpenAI-compatible providers) attach usage to
@@ -864,8 +904,11 @@ const step = (state: ParserState, event: OpenAIChatEvent) =>
    const usage = mapUsage(event.usage) ?? (choiceUsage ? mapUsage(choiceUsage) : undefined) ?? state.usage
    const rawFinishReason = choice?.finish_reason
    const finishReason =
-      rawFinishReason !== undefined && rawFinishReason !== null
-        ? { normalized: mapFinishReason(rawFinishReason), raw: choice?.native_finish_reason ?? rawFinishReason }
+      rawFinishReason
+        ? {
+            normalized: yield* mapFinishReason(event, rawFinishReason),
+            raw: choice?.native_finish_reason ?? rawFinishReason,
+          }
        : state.finishReason
    const delta = choice?.delta
    const toolDeltas = delta?.tool_calls ?? []
@@ -885,7 +928,11 @@ const step = (state: ParserState, event: OpenAIChatEvent) =>
      toolDeltas.some((tool) => Boolean(tool.id) || Boolean(tool.function?.name) || Boolean(tool.function?.arguments))
    if (state.finishReason !== undefined) {
      if (hasLateContent)
-        return yield* ProviderShared.eventError(ADAPTER, "OpenAI Chat received content after the finish reason")
+        return yield* ProviderShared.eventError(
+          ADAPTER,
+          "OpenAI Chat received content after the finish reason",
+          ProviderShared.encodeJson(event),
+        )
      return [{ ...state, usage }, events] as const
    }

@@ -957,14 +1004,19 @@ const step = (state: ParserState, event: OpenAIChatEvent) =>
        { id: id || undefined, name: name || undefined, text },
        "OpenAI Chat tool call delta is missing id or name",
      )
-      if (ToolStream.isError(result)) return yield* result
+      if (ToolStream.isError(result))
+        return yield* ProviderShared.eventError(ADAPTER, result.reason.message, ProviderShared.encodeJson(event))
      tools = result.tools
      if (result.events.length) lifecycle = Lifecycle.stepStart(lifecycle, events)
      events.push(...result.events)
    }

    if (finishReason !== undefined && state.finishReason === undefined && Object.keys(pendingTools).length > 0)
-      return yield* ProviderShared.eventError(ADAPTER, "OpenAI Chat tool call delta is missing id or name")
+      return yield* ProviderShared.eventError(
+        ADAPTER,
+        "OpenAI Chat tool call delta is missing id or name",
+        ProviderShared.encodeJson(event),
+      )

    // Finalize accumulated tool inputs eagerly when finish_reason arrives so
    // valid calls and malformed local calls settle independently.
@@ -987,16 +1039,27 @@ const step = (state: ParserState, event: OpenAIChatEvent) =>
        reasoningEmitted,
        latestToolIndex,
        nextToolIndex,
+        requireFinishReason: state.requireFinishReason,
      },
      events,
    ] as const
  })

-const finishEvents = (state: ParserState): ReadonlyArray<LLMEvent> => {
+const finishEvents = Effect.fn("OpenAIChat.finishEvents")(function* (state: ParserState) {
+  if (state.finishReason === undefined && state.requireFinishReason)
+    return yield* new AIError({
+      module: ADAPTER,
+      method: "stream",
+      reason: new InvalidProviderOutputReason({
+        classification: "incomplete-stream",
+        message: "OpenAI Chat stream ended without finish_reason",
+        route: ADAPTER,
+      }),
+    })
  const events: LLMEvent[] = []
  const toolCallEvents =
    state.finishReason === undefined && Object.keys(state.tools).length > 0
-      ? Effect.runSync(ToolStream.finishAll(ADAPTER, state.tools)).events
+      ? (yield* ToolStream.finishAll(ADAPTER, state.tools)).events
      : state.toolCallEvents
  const hasToolCalls = toolCallEvents.length > 0
  const reason = state.finishReason
@@ -1005,7 +1068,7 @@ const finishEvents = (state: ParserState): ReadonlyArray<LLMEvent> => {
        normalized:
          state.finishReason.normalized === "stop" && hasToolCalls ? "tool-calls" : state.finishReason.normalized,
      }
-    : { normalized: hasToolCalls ? ("tool-calls" as const) : ("unknown" as const) }
+    : { normalized: hasToolCalls ? ("tool-calls" as const) : ("stop" as const) }
  const metadata = reasoningMetadata(
    state.reasoningField,
    state.reasoningDetailsObserved ? state.reasoningDetails : undefined,
@@ -1019,7 +1082,7 @@ const finishEvents = (state: ParserState): ReadonlyArray<LLMEvent> => {
  events.push(...toolCallEvents)
  Lifecycle.finish(lifecycle, events, { reason, usage: state.usage })
  return events
-}
+})

 // =============================================================================
 // Protocol And OpenAI Route
@@ -1048,6 +1111,7 @@ export const protocol = Protocol.make({
      reasoningDetailsObserved: false,
      reasoningEmitted: false,
      nextToolIndex: 0,
+      requireFinishReason: request.model.compatibility?.requireFinishReason ?? true,
    }),
    step,
    onHalt: finishEvents,
@@ -1,8 +1,10 @@
-import { Effect } from "effect"
+import { Effect, Option } from "effect"
 import { AIError, LLMEvent, type ProviderMetadata, type ToolCall, type ToolInputError } from "../../schema/index.js"
 import { eventError, parseToolInput, type ToolAccumulator } from "../shared.js"
+import { parse } from "./partial-json.js"

 type StreamKey = string | number
+const parsePartialInput = Option.liftThrowable(parse)

 /**
 * One pending streamed tool call. Providers emit the tool identity and JSON
@@ -57,12 +59,15 @@ const inputStart = (tool: PendingTool) =>
    providerMetadata: tool.providerMetadata,
  })

-const inputDelta = (tool: PendingTool, text: string) =>
-  LLMEvent.toolInputDelta({
+const inputDelta = (tool: PendingTool, text: string) => {
+  const input = parsePartialInput(tool.input)
+  return LLMEvent.toolInputDelta({
    id: tool.id,
    name: tool.name,
    text,
+    ...(Option.isSome(input) ? { input: input.value } : {}),
  })
+}

 const toolCall = (route: string, tool: PendingTool, inputOverride?: string) => {
  const raw = inputOverride ?? tool.input
@@ -321,12 +321,30 @@ function makeFromTransport<Body, Prepared, Frame, Event, State>(
                Stream.mapEffect(decodeEvent(route)),
                protocol.stream.terminal ? Stream.takeUntil(protocol.stream.terminal) : (stream) => stream,
              )
-              const stream = events.pipe(
-                Stream.mapAccumEffect(
-                  () => protocol.stream.initial(request),
-                  protocol.stream.step,
-                  protocol.stream.onHalt ? { onHalt: protocol.stream.onHalt } : undefined,
-                ),
+              const stream = Stream.suspend(() => {
+                let state = protocol.stream.initial(request)
+                const parsed = events.pipe(
+                  Stream.mapEffect((event) =>
+                    protocol.stream.step(state, event).pipe(
+                      Effect.map(([next, output]) => {
+                        state = next
+                        return output
+                      }),
+                    ),
+                  ),
+                  Stream.flatMap(Stream.fromIterable),
+                )
+                const onHalt = protocol.stream.onHalt
+                return onHalt
+                  ? parsed.pipe(
+                      Stream.concat(
+                        Stream.suspend(() =>
+                          Stream.unwrap(onHalt(state).pipe(Effect.map(Stream.fromIterable))),
+                        ),
+                      ),
+                    )
+                  : parsed
+              }).pipe(
                Stream.catchCause((cause) => Stream.fail(streamError(route, `Failed to read ${route} stream`, cause))),
                requireTerminalEvent(route),
              )
@@ -59,8 +59,8 @@ export interface ProtocolStream<Frame, Event, State> {
  readonly step: (state: State, event: Event) => Effect.Effect<readonly [State, ReadonlyArray<LLMEvent>], AIError>
  /** Optional request-completion signal for transports that do not end naturally. */
  readonly terminal?: (event: Event) => boolean
-  /** Optional flush emitted when the framed stream ends. */
-  readonly onHalt?: (state: State) => ReadonlyArray<LLMEvent>
+  /** Optional effectful flush emitted when the framed stream ends. */
+  readonly onHalt?: (state: State) => Effect.Effect<ReadonlyArray<LLMEvent>, AIError>
 }

 /**
@@ -152,6 +152,8 @@ export const ToolInputDelta = Schema.Struct({
  id: ToolCallID,
  name: Schema.String,
  text: Schema.String,
+  /** Best-effort parse of all input fragments received through this delta. */
+  input: Schema.optional(Schema.Unknown),
 }).annotate({ identifier: "LLM.Event.ToolInputDelta" })
 export type ToolInputDelta = Schema.Schema.Type<typeof ToolInputDelta>

@@ -585,12 +585,11 @@ describe("Anthropic Messages route", () => {

  it.effect("infers empty-signature compatibility across Kimi providers", () =>
    Effect.gen(function* () {
-      const coding = AnthropicMessages.route
-        .with({
-          provider: "kimi-for-coding",
-          endpoint: { baseURL: "https://compatible.test/v1/" },
-          auth: Auth.header("x-api-key", "test"),
-        })
+      const coding = AnthropicMessages.route.with({
+        provider: "kimi-for-coding",
+        endpoint: { baseURL: "https://compatible.test/v1/" },
+        auth: Auth.header("x-api-key", "test"),
+      })
      const moonshot = AnthropicMessages.route
        .with({
          provider: "moonshotai",
@@ -1129,8 +1128,14 @@ describe("Anthropic Messages route", () => {
      expect(response.events).toEqual([
        { type: "step-start", index: 0 },
        { type: "tool-input-start", id: "call_1", name: "lookup" },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"' },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}' },
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"', input: {} },
+        {
+          type: "tool-input-delta",
+          id: "call_1",
+          name: "lookup",
+          text: ':"weather"}',
+          input: { query: "weather" },
+        },
        { type: "tool-input-end", id: "call_1", name: "lookup", providerMetadata: undefined },
        {
          type: "tool-call",
@@ -475,8 +475,14 @@ describe("Bedrock Converse route", () => {
      ])
      const events = response.events.filter((event) => event.type === "tool-input-delta")
      expect(events).toEqual([
-        { type: "tool-input-delta", id: "tool_1", name: "lookup", text: '{"query"' },
-        { type: "tool-input-delta", id: "tool_1", name: "lookup", text: ':"weather"}' },
+        { type: "tool-input-delta", id: "tool_1", name: "lookup", text: '{"query"', input: {} },
+        {
+          type: "tool-input-delta",
+          id: "tool_1",
+          name: "lookup",
+          text: ':"weather"}',
+          input: { query: "weather" },
+        },
      ])
      expect(response.events.at(-1)).toMatchObject({
        type: "finish",
@@ -6,6 +6,7 @@ import { AmazonBedrockMantle } from "../../src/providers.js"
 import { compileRequest, LLMClient } from "../../src/route/client.js"
 import { it } from "../lib/effect.js"
 import { dynamicResponse } from "../lib/http.js"
+import { sseEvents } from "../lib/sse.js"
 import { recordedTests } from "../recorded-test.js"

 const credentials = {
@@ -71,7 +72,9 @@ describe("Amazon Bedrock Mantle provider", () => {
            Effect.gen(function* () {
              const request = yield* HttpClientRequest.toWeb(input.request)
              seen.push({ url: request.url, authorization: request.headers.get("authorization") ?? undefined })
-              return input.respond("", { headers: { "content-type": "text/event-stream" } })
+              return input.respond(sseEvents({ choices: [{ delta: {}, finish_reason: "stop" }] }), {
+                headers: { "content-type": "text/event-stream" },
+              })
            }),
          ),
        ),
@@ -1164,8 +1164,14 @@ describe("OpenAI Chat route", () => {
      expect(response.events).toEqual([
        { type: "step-start", index: 0 },
        { type: "tool-input-start", id: "call_1", name: "lookup", providerMetadata: undefined },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"' },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}' },
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"', input: {} },
+        {
+          type: "tool-input-delta",
+          id: "call_1",
+          name: "lookup",
+          text: ':"weather"}',
+          input: { query: "weather" },
+        },
        { type: "tool-input-end", id: "call_1", name: "lookup", providerMetadata: undefined },
        {
          type: "tool-call",
@@ -1245,6 +1251,11 @@ describe("OpenAI Chat route", () => {
      ).pipe(Effect.provide(fixedResponse(body)), Effect.flip)

      expect(error.message).toContain("OpenAI Chat tool call delta is missing id or name")
+      expect(error.reason._tag).toBe("InvalidProviderOutput")
+      if (error.reason._tag !== "InvalidProviderOutput") return
+      expect(decodeJson(error.reason.raw ?? "")).toMatchObject({
+        choices: [{ finish_reason: "tool_calls" }],
+      })
    }),
  )

@@ -1258,6 +1269,7 @@ describe("OpenAI Chat route", () => {
        deltaChunk({ tool_calls: [{ index: 0, function: { arguments: ':"weather"}' } }] }),
      )
      const input = LLMRequest.update(request, {
+        model: LanguageModel.update(model, { compatibility: { requireFinishReason: false } }),
        tools: [ToolDefinition.make({ name: "lookup", description: "Lookup data", inputSchema: { type: "object" } })],
      })
      const response = yield* LLMClient.generate(input).pipe(Effect.provide(fixedResponse(body)))
@@ -1265,8 +1277,14 @@ describe("OpenAI Chat route", () => {
      expect(response.events).toEqual([
        { type: "step-start", index: 0 },
        { type: "tool-input-start", id: "call_1", name: "lookup", providerMetadata: undefined },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"' },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}' },
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"', input: {} },
+        {
+          type: "tool-input-delta",
+          id: "call_1",
+          name: "lookup",
+          text: ':"weather"}',
+          input: { query: "weather" },
+        },
        { type: "tool-input-end", id: "call_1", name: "lookup", providerMetadata: undefined },
        {
          type: "tool-call",
@@ -353,13 +353,106 @@ describe("OpenAI-compatible Chat route", () => {
    }),
  )

-  it.effect("treats an empty finish reason as terminal", () =>
+  it.effect("rejects a stream without a required finish reason", () =>
    Effect.gen(function* () {
-      const response = yield* LLMClient.generate(request).pipe(
+      const error = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({ content: "Hello" }), deltaChunk({}, "")))),
+        Effect.flip,
+      )
+
+      expect(error.reason).toMatchObject({
+        _tag: "InvalidProviderOutput",
+        classification: "incomplete-stream",
+        message: "OpenAI Chat stream ended without finish_reason",
+      })
+    }),
+  )
+
+  it.effect("infers stop when finish reasons are optional", () =>
+    Effect.gen(function* () {
+      const compatible = OpenAICompatibleChat.route
+        .with({ provider: "custom", endpoint: { baseURL: "https://api.custom.test/v1" } })
+        .model({ id: "custom-model", compatibility: { requireFinishReason: false } })
+      const response = yield* LLMClient.generate(LLMRequest.update(request, { model: compatible })).pipe(
        Effect.provide(fixedResponse(sseEvents(deltaChunk({ content: "Hello" }), deltaChunk({}, "")))),
      )

-      expect(response.finishReason).toEqual({ normalized: "unknown", raw: "" })
+      expect(response.finishReason).toEqual({ normalized: "stop" })
+    }),
+  )
+
+  it.effect("normalizes the end finish reason to stop", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({ content: "Hello" }), deltaChunk({}, "end")))),
+      )
+
+      expect(response.finishReason).toEqual({ normalized: "stop", raw: "end" })
+    }),
+  )
+
+  it.effect("classifies provider error finish reasons", () =>
+    Effect.gen(function* () {
+      const error = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({}, "network_error")))),
+        Effect.flip,
+      )
+
+      expect(error.reason).toMatchObject({
+        _tag: "ProviderInternal",
+        message: "Provider reported a network error (finish_reason: network_error)",
+      })
+      expect(decodeJson(error.body ?? "")).toMatchObject({
+        id: "chatcmpl_fixture",
+        choices: [{ finish_reason: "network_error" }],
+      })
+
+      const generic = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({}, "error")))),
+        Effect.flip,
+      )
+      expect(generic.reason).toMatchObject({
+        _tag: "UnknownProvider",
+        message: "Provider reported an error (finish_reason: error)",
+      })
+    }),
+  )
+
+  it.effect("preserves explicit provider error events", () =>
+    Effect.gen(function* () {
+      const error = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents({
+              id: "chatcmpl_error",
+              error: { code: 502, message: "Provider disconnected", details: { upstream: "vendor" } },
+              trace_id: "trace_1",
+            }),
+          ),
+        ),
+        Effect.flip,
+      )
+
+      expect(error.reason).toMatchObject({ _tag: "ProviderInternal", message: "Provider disconnected", status: 502 })
+      expect(decodeJson(error.body ?? "")).toMatchObject({
+        id: "chatcmpl_error",
+        error: { code: 502, message: "Provider disconnected", details: { upstream: "vendor" } },
+        trace_id: "trace_1",
+      })
+    }),
+  )
+
+  it.effect("preserves provider finish outcomes in the common reason algebra", () =>
+    Effect.gen(function* () {
+      const filtered = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({}, "content_filter")))),
+      )
+      const future = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({}, "future_reason")))),
+      )
+
+      expect(filtered.finishReason).toEqual({ normalized: "content-filter", raw: "content_filter" })
+      expect(future.finishReason).toEqual({ normalized: "unknown", raw: "future_reason" })
    }),
  )

@@ -379,6 +472,11 @@ describe("OpenAI-compatible Chat route", () => {
      )

      expect(error.message).toContain("OpenAI Chat received content after the finish reason")
+      expect(error.reason._tag).toBe("InvalidProviderOutput")
+      if (error.reason._tag !== "InvalidProviderOutput") return
+      expect(decodeJson(error.reason.raw ?? "")).toMatchObject({
+        choices: [{ delta: { tool_calls: [{ id: "call_1" }] } }],
+      })
    }),
  )
 })
@@ -1986,6 +1986,11 @@ describe("OpenAI Responses route", () => {
                item_id: "fc_missing",
                delta: '{"orphaned":true}',
              },
+              {
+                type: "response.function_call_arguments.done",
+                item_id: "fc_missing",
+                arguments: '{"orphaned":true}',
+              },
              { type: "response.completed", response: { id: "resp_1" } },
            ),
          ),
@@ -1998,22 +2003,22 @@ describe("OpenAI Responses route", () => {
    }),
  )

-  it.effect("rejects function argument deltas without the spec-required item id", () =>
+  it.effect("rejects function argument events without the spec-required item id", () =>
    Effect.gen(function* () {
-      const error = yield* LLMClient.generate(request).pipe(
-        Effect.provide(
-          fixedResponse(
-            sseEvents(
-              { type: "response.function_call_arguments.delta", delta: "{}" },
-              { type: "response.completed", response: { id: "resp_1" } },
-            ),
-          ),
-        ),
-        Effect.flip,
-      )
+      const events = [
+        { type: "response.function_call_arguments.delta", delta: "{}" },
+        { type: "response.function_call_arguments.done", arguments: "{}" },
+      ]

-      expect(error.reason._tag).toBe("InvalidProviderOutput")
-      expect(error.message).toContain("response.function_call_arguments.delta is missing item_id")
+      for (const event of events) {
+        const error = yield* LLMClient.generate(request).pipe(
+          Effect.provide(fixedResponse(sseEvents(event, { type: "response.completed", response: { id: "resp_1" } }))),
+          Effect.flip,
+        )
+
+        expect(error.reason._tag).toBe("InvalidProviderOutput")
+        expect(error.message).toContain(`${event.type} is missing item_id`)
+      }
    }),
  )

@@ -2806,12 +2811,14 @@ describe("OpenAI Responses route", () => {
          id: "call_1",
          name: "lookup",
          text: '{"query"',
+          input: {},
        },
        {
          type: "tool-input-delta",
          id: "call_1",
          name: "lookup",
          text: ':"weather"}',
+          input: { query: "weather" },
        },
        {
          type: "tool-input-end",
@@ -2855,6 +2862,172 @@ describe("OpenAI Responses route", () => {
    }),
  )

+  it.effect("emits only missing function arguments from the arguments done event", () =>
+    Effect.gen(function* () {
+      const body = sseEvents(
+        {
+          type: "response.output_item.added",
+          item: { type: "function_call", id: "fc_item_1", call_id: "call_1", name: "lookup", arguments: "" },
+        },
+        { type: "response.function_call_arguments.delta", item_id: "fc_item_1", delta: '{"query"' },
+        {
+          type: "response.function_call_arguments.done",
+          item_id: "fc_item_1",
+          arguments: '{"query":"weather"}',
+        },
+        {
+          type: "response.output_item.done",
+          item: {
+            type: "function_call",
+            id: "fc_item_1",
+            call_id: "call_1",
+            name: "lookup",
+            arguments: '{"query":"weather"}',
+          },
+        },
+        { type: "response.completed", response: { id: "resp_1" } },
+      )
+      const response = yield* LLMClient.generate(request).pipe(Effect.provide(fixedResponse(body)))
+
+      expect(response.events.filter((event) => event.type === "tool-input-delta")).toEqual([
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"', input: {} },
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}', input: { query: "weather" } },
+      ])
+      expect(response.events.filter(LLMEvent.is.toolInputEnd)).toHaveLength(1)
+      expect(response.events.filter(LLMEvent.is.toolCall)).toEqual([
+        {
+          type: "tool-call",
+          id: "call_1",
+          name: "lookup",
+          input: { query: "weather" },
+          providerExecuted: undefined,
+          providerMetadata: { openai: { itemId: "fc_item_1" } },
+        },
+      ])
+    }),
+  )
+
+  it.effect("streams complete function arguments supplied only by the arguments done event", () =>
+    Effect.gen(function* () {
+      const body = sseEvents(
+        {
+          type: "response.output_item.added",
+          item: { type: "function_call", id: "fc_item_1", call_id: "call_1", name: "lookup", arguments: "" },
+        },
+        {
+          type: "response.function_call_arguments.done",
+          item_id: "fc_item_1",
+          arguments: '{"query":"weather"}',
+        },
+        { type: "response.completed", response: { id: "resp_1" } },
+      )
+      const response = yield* LLMClient.generate(request).pipe(Effect.provide(fixedResponse(body)))
+
+      expect(response.events.filter((event) => event.type === "tool-input-delta")).toEqual([
+        {
+          type: "tool-input-delta",
+          id: "call_1",
+          name: "lookup",
+          text: '{"query":"weather"}',
+          input: { query: "weather" },
+        },
+      ])
+      expect(response.events.find(LLMEvent.is.toolCall)).toMatchObject({ input: { query: "weather" } })
+      expect(response.finishReason.normalized).toBe("tool-calls")
+    }),
+  )
+
+  it.effect("does not repeat function arguments already supplied by deltas", () =>
+    Effect.gen(function* () {
+      const body = sseEvents(
+        {
+          type: "response.output_item.added",
+          item: { type: "function_call", id: "fc_item_1", call_id: "call_1", name: "lookup", arguments: "" },
+        },
+        {
+          type: "response.function_call_arguments.delta",
+          item_id: "fc_item_1",
+          delta: '{"query":"weather"}',
+        },
+        {
+          type: "response.function_call_arguments.done",
+          item_id: "fc_item_1",
+          arguments: '{"query":"weather"}',
+        },
+        { type: "response.completed", response: { id: "resp_1" } },
+      )
+      const response = yield* LLMClient.generate(request).pipe(Effect.provide(fixedResponse(body)))
+
+      expect(response.events.filter((event) => event.type === "tool-input-delta")).toHaveLength(1)
+      expect(response.events.find(LLMEvent.is.toolCall)).toMatchObject({ input: { query: "weather" } })
+    }),
+  )
+
+  it.effect("uses authoritative arguments done input without emitting a mismatched delta", () =>
+    Effect.gen(function* () {
+      const body = sseEvents(
+        {
+          type: "response.output_item.added",
+          item: { type: "function_call", id: "fc_item_1", call_id: "call_1", name: "lookup", arguments: "" },
+        },
+        {
+          type: "response.function_call_arguments.delta",
+          item_id: "fc_item_1",
+          delta: '{"query":"streamed"}',
+        },
+        {
+          type: "response.function_call_arguments.done",
+          item_id: "fc_item_1",
+          arguments: '{"query":"final"}',
+        },
+        { type: "response.completed", response: { id: "resp_1" } },
+      )
+      const response = yield* LLMClient.generate(request).pipe(Effect.provide(fixedResponse(body)))
+
+      expect(response.events.filter((event) => event.type === "tool-input-delta")).toEqual([
+        {
+          type: "tool-input-delta",
+          id: "call_1",
+          name: "lookup",
+          text: '{"query":"streamed"}',
+          input: { query: "streamed" },
+        },
+      ])
+      expect(response.events.find(LLMEvent.is.toolCall)).toMatchObject({ input: { query: "final" } })
+    }),
+  )
+
+  it.effect("lets completed output item arguments override the arguments done event", () =>
+    Effect.gen(function* () {
+      const body = sseEvents(
+        {
+          type: "response.output_item.added",
+          item: { type: "function_call", id: "fc_item_1", call_id: "call_1", name: "lookup", arguments: "" },
+        },
+        {
+          type: "response.function_call_arguments.done",
+          item_id: "fc_item_1",
+          arguments: '{"query":"arguments-done"}',
+        },
+        {
+          type: "response.output_item.done",
+          item: {
+            type: "function_call",
+            id: "fc_item_1",
+            call_id: "call_1",
+            name: "lookup",
+            arguments: '{"query":"output-item-done"}',
+          },
+        },
+        { type: "response.completed", response: { id: "resp_1" } },
+      )
+      const response = yield* LLMClient.generate(request).pipe(Effect.provide(fixedResponse(body)))
+
+      expect(response.events.find(LLMEvent.is.toolCall)).toMatchObject({ input: { query: "output-item-done" } })
+      expect(response.events.filter(LLMEvent.is.toolCall)).toHaveLength(1)
+    }),
+  )
+
  it.effect("finalizes a pending function call at response completion", () =>
    Effect.gen(function* () {
      const body = sseEvents(
@@ -23,9 +23,11 @@ describe("ToolStream", () => {

      expect(first.events).toEqual([
        { type: "tool-input-start", id: "call_1", name: "lookup" },
-        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"' },
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"', input: {} },
+      ])
+      expect(second.events).toEqual([
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}', input: { query: "weather" } },
      ])
-      expect(second.events).toEqual([{ type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}' }])
      expect(finished).toEqual({
        tools: {},
        events: [
@@ -36,6 +38,45 @@ describe("ToolStream", () => {
    }),
  )

+  it.effect("exposes cumulative partial string values", () =>
+    Effect.gen(function* () {
+      const result = ToolStream.appendOrStart(
+        ADAPTER,
+        ToolStream.empty<number>(),
+        0,
+        { id: "call_1", name: "lookup", text: '{"query":"wea' },
+        "missing tool",
+      )
+      if (ToolStream.isError(result)) return yield* result
+
+      expect(result.events.at(-1)).toEqual({
+        type: "tool-input-delta",
+        id: "call_1",
+        name: "lookup",
+        text: '{"query":"wea',
+        input: { query: "wea" },
+      })
+    }),
+  )
+
+  it.effect("omits partial input when the accumulated value cannot be parsed", () =>
+    Effect.gen(function* () {
+      const result = ToolStream.appendOrStart(
+        ADAPTER,
+        ToolStream.empty<number>(),
+        0,
+        { id: "call_1", name: "lookup", text: "x" },
+        "missing tool",
+      )
+      if (ToolStream.isError(result)) return yield* result
+
+      expect(result.events).toEqual([
+        { type: "tool-input-start", id: "call_1", name: "lookup" },
+        { type: "tool-input-delta", id: "call_1", name: "lookup", text: "x" },
+      ])
+    }),
+  )
+
  it.effect("keeps accumulated identity when later deltas contain empty strings", () =>
    Effect.gen(function* () {
      const first = ToolStream.appendOrStart(
@@ -0,0 +1,226 @@
+import { expect, test, type Page } from "@playwright/test"
+import type { OpenCodeEvent } from "@opencode-ai/client/promise"
+import { base64Encode } from "@opencode-ai/util/encode"
+import { mockOpenCodeServer } from "../utils/mock-server"
+import { expectAppVisible } from "../utils/waits"
+
+const directory = "C:/OpenCode/SessionQueueRegression"
+const projectID = "proj_session_queue_regression"
+const sessionID = "ses_session_queue_regression"
+const server = `http://${process.env.PLAYWRIGHT_SERVER_HOST ?? "127.0.0.1"}:${process.env.PLAYWRIGHT_SERVER_PORT ?? "4096"}`
+
+type InboxRow = {
+  id: string
+  sessionID: string
+  timeCreated: number
+  type: "user"
+  payload: { text: string; metadata?: Record<string, unknown> }
+  delivery: "steer" | "queue"
+}
+
+function createQueueMock(seed: string[]) {
+  const rows: InboxRow[] = seed.map((text, index) => ({
+    id: `inb_seed_${index + 1}`,
+    sessionID,
+    timeCreated: 1700000000000 + index,
+    type: "user",
+    payload: { text },
+    delivery: "queue",
+  }))
+  const events: OpenCodeEvent[] = []
+  const prompts: Record<string, unknown>[] = []
+  const changes: { inboxID: string; action: "cancel" | "steer" }[] = []
+  const log: string[] = []
+  let sequence = 0
+  const emit = (type: OpenCodeEvent["type"], data: OpenCodeEvent["data"]) => {
+    sequence += 1
+    events.push({
+      id: `evt_queue_${sequence}`,
+      type,
+      created: Date.now(),
+      durable: { aggregateID: sessionID, seq: sequence, version: 1 },
+      data,
+    } as OpenCodeEvent)
+  }
+  return {
+    rows,
+    prompts,
+    changes,
+    log,
+    events: () => events.splice(0),
+    onPrompt: (input: { sessionID: string; body: Record<string, unknown> }) => {
+      prompts.push(input.body)
+      log.push(`prompt:${String(input.body.delivery ?? "steer")}`)
+      const row: InboxRow = {
+        id: typeof input.body.id === "string" ? input.body.id : `inb_mock_${sequence}`,
+        sessionID: input.sessionID,
+        timeCreated: Date.now(),
+        type: "user",
+        payload: {
+          text: typeof input.body.text === "string" ? input.body.text : "",
+          ...(input.body.metadata === undefined ? {} : { metadata: input.body.metadata as Record<string, unknown> }),
+        },
+        delivery: input.body.delivery === "queue" ? "queue" : "steer",
+      }
+      rows.push(row)
+      emit("session.inbox.enqueued", {
+        sessionID: input.sessionID,
+        inboxID: row.id,
+        item: { type: "user", payload: row.payload, delivery: row.delivery },
+      })
+    },
+    onInboxChange: (input: { sessionID: string; inboxID: string; action: "cancel" | "steer" }) => {
+      changes.push({ inboxID: input.inboxID, action: input.action })
+      log.push(`${input.action}:${input.inboxID}`)
+      const index = rows.findIndex((row) => row.id === input.inboxID)
+      const row = rows[index]
+      if (!row) return
+      if (input.action === "cancel") {
+        rows.splice(index, 1)
+        emit("session.inbox.cancelled", { sessionID: input.sessionID, inboxID: input.inboxID })
+        return
+      }
+      row.delivery = "steer"
+      emit("session.inbox.delivery.changed", {
+        sessionID: input.sessionID,
+        inboxID: input.inboxID,
+        delivery: "steer",
+      })
+    },
+  }
+}
+
+async function openSession(page: Page, mock: ReturnType<typeof createQueueMock>, followUpBehavior?: "queue" | "steer") {
+  if (followUpBehavior) {
+    await page.addInitScript(
+      (behavior) => localStorage.setItem("settings.v3", JSON.stringify({ general: { followUpBehavior: behavior } })),
+      followUpBehavior,
+    )
+  }
+  await mockOpenCodeServer(page, {
+    directory,
+    project: {
+      id: projectID,
+      worktree: directory,
+      vcs: "git",
+      name: "session-queue-regression",
+      time: { created: 1700000000000, updated: 1700000000000 },
+      sandboxes: [],
+    },
+    provider: {
+      all: [
+        {
+          id: "opencode",
+          name: "OpenCode",
+          models: { "queue-model": { id: "queue-model", name: "Queue Model", limit: { context: 200_000 } } },
+        },
+      ],
+      connected: ["opencode"],
+      default: { providerID: "opencode", modelID: "queue-model" },
+    },
+    sessions: [
+      {
+        id: sessionID,
+        slug: "session-queue-regression",
+        projectID,
+        directory,
+        title: "Session queue regression",
+        version: "dev",
+        time: { created: 1700000000000, updated: 1700000000000 },
+      },
+    ],
+    pageMessages: () => ({ items: [] }),
+    sessionStatus: () => ({ [sessionID]: { type: "running" } }),
+    inbox: () => mock.rows.map((row) => ({ ...row, payload: { ...row.payload } })),
+    onPrompt: mock.onPrompt,
+    onInboxChange: mock.onInboxChange,
+    events: mock.events,
+  })
+  await page.goto(`/server/${base64Encode(server)}/session/${sessionID}`)
+  const composer = page.locator('[data-component="composer"]')
+  await expectAppVisible(composer)
+  return {
+    composer,
+    input: composer.locator('[data-component="composer-editor"]'),
+    rows: page.locator('[data-component="session-queue-row"]'),
+  }
+}
+
+test("follow-up preference controls Enter while Mod+Enter uses the alternate delivery", async ({ page }) => {
+  const mock = createQueueMock([])
+  const view = await openSession(page, mock, "queue")
+
+  await view.input.fill("queue this follow-up")
+  await expect(view.composer.locator('[data-action="composer-alternate-delivery"]')).toContainText("Steer")
+  await view.input.press("Enter")
+  await expect(view.rows.getByText("queue this follow-up", { exact: true })).toBeVisible()
+
+  await view.input.fill("steer this correction")
+  await view.input.press("ControlOrMeta+Enter")
+  await expect.poll(() => mock.prompts.map((prompt) => prompt.delivery)).toEqual(["queue", "steer"])
+  await expect(view.input).toHaveText("")
+})
+
+test("dragging reorders queued prompts", async ({ page }) => {
+  const mock = createQueueMock(["first queued prompt", "second queued prompt", "third queued prompt"])
+  const view = await openSession(page, mock)
+  await expect(view.rows).toHaveCount(3)
+
+  const first = view.rows.filter({ hasText: "first queued prompt" })
+  const third = view.rows.filter({ hasText: "third queued prompt" })
+  await first.getByRole("button", { name: "Reorder queued prompt" }).hover()
+  await page.mouse.down()
+  const target = await third.boundingBox()
+  if (!target) throw new Error("The target queue row is not visible")
+  await page.mouse.move(target.x + target.width / 2, target.y + target.height / 2, { steps: 10 })
+  await page.mouse.up()
+
+  await expect(view.rows.locator('[data-action="session-queue-edit"]')).toHaveText([
+    "second queued prompt",
+    "third queued prompt",
+    "first queued prompt",
+  ])
+  expect(mock.prompts.map((prompt) => prompt.text)).toEqual([
+    "second queued prompt",
+    "third queued prompt",
+    "first queued prompt",
+  ])
+  expect(mock.changes).toEqual([
+    { inboxID: "inb_seed_1", action: "cancel" },
+    { inboxID: "inb_seed_2", action: "cancel" },
+    { inboxID: "inb_seed_3", action: "cancel" },
+  ])
+})
+
+test("editing restores the existing draft and replaces only the original queue position", async ({ page }) => {
+  const mock = createQueueMock(["first queued prompt", "tighten the error copy", "third queued prompt"])
+  const view = await openSession(page, mock)
+  const original = view.rows.getByText("tighten the error copy", { exact: true })
+  await expect(original).toBeVisible()
+
+  await view.input.fill("my in-progress draft")
+  await original.click()
+  await expect(view.input).toHaveText("tighten the error copy")
+  await view.input.press("Escape")
+  await expect(view.input).toHaveText("my in-progress draft")
+
+  await original.click()
+  await expect(view.input).toHaveText("tighten the error copy")
+  await view.input.fill("tighten the error copy and add a retry hint")
+  await view.input.press("Enter")
+
+  await expect(view.rows.locator('[data-action="session-queue-edit"]')).toHaveText([
+    "first queued prompt",
+    "tighten the error copy and add a retry hint",
+    "third queued prompt",
+  ])
+  await expect(view.input).toHaveText("my in-progress draft")
+  expect(mock.prompts.map((prompt) => prompt.text)).toEqual([
+    "tighten the error copy and add a retry hint",
+    "tighten the error copy and add a retry hint",
+    "third queued prompt",
+  ])
+  expect(mock.prompts.every((prompt) => prompt.delivery === "queue" && prompt.resume === false)).toBe(true)
+  expect(mock.changes.map((change) => change.action)).toEqual(["cancel", "cancel", "cancel"])
+  expect(mock.log[0]).toBe("prompt:queue")
+})
@@ -174,6 +174,39 @@ const Group = HttpApiGroup.make("mock")
      success: Json,
    }),
  )
+  .add(
+    HttpApiEndpoint.post("sessionPrompt", "/api/session/:sessionID/prompt", {
+      params: SessionParams,
+      payload: JsonPayload,
+      success: Json,
+    }),
+  )
+  .add(
+    HttpApiEndpoint.post("sessionSwitchAgent", "/api/session/:sessionID/agent", {
+      params: SessionParams,
+      payload: JsonPayload,
+      success: NoContent,
+    }),
+  )
+  .add(
+    HttpApiEndpoint.post("sessionSwitchModel", "/api/session/:sessionID/model", {
+      params: SessionParams,
+      payload: JsonPayload,
+      success: NoContent,
+    }),
+  )
+  .add(
+    HttpApiEndpoint.delete("sessionInboxCancel", "/api/session/:sessionID/inbox/:inboxID", {
+      params: { ...SessionParams, inboxID: Schema.String },
+      success: NoContent,
+    }),
+  )
+  .add(
+    HttpApiEndpoint.post("sessionInboxSteer", "/api/session/:sessionID/inbox/:inboxID/steer", {
+      params: { ...SessionParams, inboxID: Schema.String },
+      success: NoContent,
+    }),
+  )
  .add(
    HttpApiEndpoint.get("sessionPermission", "/api/session/:sessionID/permission", {
      params: SessionParams,
@@ -35,6 +35,9 @@ export interface MockServerConfig {
  fileContent?: (path: string) => unknown | Promise<unknown>
  findFiles?: (input: { query: string; dirs?: string; limit?: number }) => unknown
  sessionStatus?: Record<string, unknown> | (() => Record<string, unknown>)
+  inbox?: unknown[] | (() => unknown[])
+  onPrompt?: (input: { sessionID: string; body: Record<string, unknown> }) => void
+  onInboxChange?: (input: { sessionID: string; inboxID: string; action: "cancel" | "steer" }) => void
 }

 type MockStreamWindow = Window & {
@@ -397,7 +400,39 @@ function mockHandlers(config: MockServerConfig, state: { cursors: Map<string, st
        sessionFormReply: () => noContent,
        sessionFormCancel: () => noContent,
        sessionBackground: () => noContent,
-        sessionInbox: () => Effect.succeed({ data: [] }),
+        sessionInbox: () =>
+          Effect.sync(() => ({ data: typeof config.inbox === "function" ? config.inbox() : (config.inbox ?? []) })),
+        sessionPrompt: (ctx) =>
+          Effect.sync(() => {
+            const body = record(ctx.payload) ? ctx.payload : {}
+            config.onPrompt?.({ sessionID: ctx.params.sessionID, body })
+            return {
+              data: {
+                id: typeof body.id === "string" ? body.id : `inb_mock_${Date.now()}`,
+                sessionID: ctx.params.sessionID,
+                timeCreated: Date.now(),
+                type: "user",
+                payload: {
+                  text: typeof body.text === "string" ? body.text : "",
+                  ...(body.files === undefined ? {} : { files: body.files }),
+                  ...(body.agents === undefined ? {} : { agents: body.agents }),
+                  ...(body.skills === undefined ? {} : { skills: body.skills }),
+                  ...(body.metadata === undefined ? {} : { metadata: body.metadata }),
+                },
+                delivery: body.delivery === "queue" ? "queue" : "steer",
+              },
+            }
+          }),
+        sessionInboxCancel: (ctx) =>
+          Effect.sync(() =>
+            config.onInboxChange?.({ sessionID: ctx.params.sessionID, inboxID: ctx.params.inboxID, action: "cancel" }),
+          ).pipe(Effect.andThen(noContent)),
+        sessionInboxSteer: (ctx) =>
+          Effect.sync(() =>
+            config.onInboxChange?.({ sessionID: ctx.params.sessionID, inboxID: ctx.params.inboxID, action: "steer" }),
+          ).pipe(Effect.andThen(noContent)),
+        sessionSwitchAgent: () => noContent,
+        sessionSwitchModel: () => noContent,
        sessionPermission: (ctx) => {
          const permissions =
            typeof config.permissions === "function" ? config.permissions() : (config.permissions ?? [])
@@ -39,6 +39,26 @@ export type ComposerSelection = {
  variant?: string
 }

+export type ComposerDelivery = "steer" | "queue"
+
+// Contract between the composer and the session prompt queue. The session
+// owns the queue (pending inbox items); the composer only asks which delivery
+// a submit should use and delegates edit confirmation while a queued prompt
+// is loaded in the editor.
+export type ComposerQueue = {
+  count: Accessor<number>
+  // Delivery a plain submit uses right now.
+  delivery: Accessor<ComposerDelivery>
+  // Delivery offered on Mod+Enter and the toolbar hint button; undefined hides the hint.
+  alternate: Accessor<ComposerDelivery | undefined>
+  // Inbox ID of the queued prompt currently loaded in the composer for editing.
+  editing: Accessor<string | undefined>
+  confirmEdit: (delivery: ComposerDelivery) => void
+  cancelEdit: () => void
+  // Loads the first queued prompt into the composer. Returns false when the queue is empty.
+  editFirst: () => boolean
+}
+
 export type ComposerSession = {
  id: string
  directory: string
@@ -8,7 +8,7 @@ import { Tooltip } from "@opencode-ai/ui/tooltip"
 import { ComposerEditor } from "./editor/editor"
 import { ModelSelectorPopover } from "@/providers/models/select-dialog"
 import { DialogSelectModelUnpaid } from "@/providers/models/unpaid"
-import { useCommand } from "@/shell/commands/command"
+import { formatKeybind, useCommand } from "@/shell/commands/command"
 import { useLanguage } from "@/runtime/i18n/language"
 import type { ComposerModel } from "./model"

@@ -32,6 +32,7 @@ export function Composer(props: {
        modelControlsVisible={!props.model.model.loading}
        attachKeybind={command.keybindParts("file.attach")}
        attachShortcut={command.keybind("file.attach")}
+        alternateKeybind={[formatKeybind("mod", language.t), formatKeybind("enter", language.t)]}
        modelControl={
          <ComposerModelControl
            loading={props.model.model.loading}
@@ -45,6 +45,7 @@ export type ComposerEditorProps = {
  modelControlsVisible?: boolean
  attachKeybind?: string[]
  attachShortcut?: string
+  alternateKeybind?: string[]
 }

 export function ComposerEditor(props: ComposerEditorProps) {
@@ -177,10 +178,15 @@ export function ComposerEditor(props: ComposerEditorProps) {
            }}
            onKeyDown={(event) => {
              if (props.controller.onKeyDown(event)) return
+              const mod = event.metaKey || event.ctrlKey
+              if (mod && event.key === "ArrowUp" && !event.shiftKey && !event.altKey) {
+                if (view.submit.queue?.editFirst()) event.preventDefault()
+                return
+              }
              if (event.key === "Enter" && !event.shiftKey && !event.isComposing) {
                event.preventDefault()
                if (event.repeat) return
-                props.controller.submit()
+                props.controller.submit(mod ? { alternate: true } : undefined)
              }
            }}
            onKeyUp={updateCursor}
@@ -248,6 +254,12 @@ export function ComposerEditor(props: ComposerEditorProps) {
              </Show>
            </Show>
          </div>
+          <Show when={state.mode === "normal"}>
+            <ComposerEditorAlternateDelivery
+              controller={props.controller}
+              keybind={props.alternateKeybind ?? ["Mod", "Enter"]}
+            />
+          </Show>
          <ComposerEditorSubmitButton
            mode={state.mode}
            stopping={view.submit.stopping()}
@@ -255,7 +267,7 @@ export function ComposerEditor(props: ComposerEditorProps) {
            accent={props.accentSubmit}
            sendLabel={i18n.t("ui.promptInput.send")}
            stopLabel={i18n.t("ui.promptInput.stop")}
-            onSubmit={props.controller.submit}
+            onSubmit={() => props.controller.submit()}
            onStop={props.controller.stop}
          />
        </div>
@@ -691,6 +703,42 @@ export function ComposerEditorPopover(props: {
  )
 }

+// "Steer ⌘⏎" / "Queue ⌘⏎" hint next to the submit button: submits with the
+// delivery opposite to what plain Enter does. Visible only while the queue
+// exposes an alternate (turn running and composer holding a value), so it
+// disappears on its own when the current turn ends.
+function ComposerEditorAlternateDelivery(props: { controller: ComposerEditorModel; keybind: string[] }) {
+  const i18n = useI18n()
+  const view = props.controller.view
+  const action = createMemo(() => {
+    const queue = view.submit.queue
+    if (!queue || !props.controller.canSubmit()) return undefined
+    if (queue.editing()) return "steer" as const
+    return queue.alternate()
+  })
+  return (
+    <Show when={action()} keyed>
+      {(delivery) => (
+        <Tooltip placement="top" inactive={delivery !== "steer"} value={i18n.t("ui.promptInput.steerHint")}>
+          <Button
+            data-action="composer-alternate-delivery"
+            type="button"
+            variant="ghost-muted"
+            size="small"
+            class="me-3 gap-1.5 px-1.5 text-v2-text-text-muted ![font-weight:530]"
+            onClick={() => props.controller.submit({ alternate: true })}
+          >
+            {delivery === "steer" ? i18n.t("ui.promptInput.steer") : i18n.t("ui.promptInput.queue")}
+            <span class="hidden sm:block">
+              <Keybind keys={props.keybind} variant="neutral" />
+            </span>
+          </Button>
+        </Tooltip>
+      )}
+    </Show>
+  )
+}
+
 export function ComposerEditorSubmitButton(props: {
  mode: ComposerMode
  stopping: boolean
@@ -19,6 +19,7 @@ import {
  type ComposerInteractionEvent,
 } from "../suggestions/machine"
 import { clonePrompt, promptLength } from "../prompt-parts"
+import type { ComposerQueue } from "../adapter"

 export type ComposerSelectControl = {
  options: Accessor<ComposerOption[]>
@@ -37,7 +38,8 @@ export type ComposerEditorView = {
  submit: {
    stopping: Accessor<boolean>
    working?: Accessor<boolean>
-    onSubmit: () => void
+    queue?: ComposerQueue
+    onSubmit: (options?: { alternate?: boolean }) => void
    onStop: () => void
  }
  shell?: {
@@ -212,6 +214,11 @@ export function createComposerEditor(input: {
      )
    }
    if (handled) return true
+    if (event.key === "Escape" && input.view.submit.queue?.editing()) {
+      event.preventDefault()
+      input.view.submit.queue.cancelEdit()
+      return true
+    }
    const stop =
      input.view.submit.working?.() &&
      ((event.ctrlKey && !event.metaKey && !event.altKey && !event.shiftKey && event.key.toLowerCase() === "g") ||
@@ -354,8 +361,8 @@ export function createComposerEditor(input: {
    openShell() {
      dispatch({ type: "mode.shell" })
    },
-    submit() {
-      input.view.submit.onSubmit()
+    submit(options?: { alternate?: boolean }) {
+      input.view.submit.onSubmit(options)
      dispatch({ type: "popover.close" })
    },
    stop() {
@@ -16,7 +16,7 @@ import { createSessionTabs } from "@/session/helpers"
 import { showToast } from "@/shell/notifications/toast"
 import { formatServerError } from "@/runtime/server/errors"
 import { Skill } from "@opencode-ai/schema/skill"
-import type { ComposerAdapter, ComposerControls } from "./adapter"
+import type { ComposerAdapter, ComposerControls, ComposerQueue } from "./adapter"
 import type { ImageAttachmentPart } from "./state"
 import type { PromptHistoryComment } from "./history/entry"
 import { createComposerHistory } from "./history/store"
@@ -27,7 +27,7 @@ export type ComposerModel = ComposerEditorModel & {
  readonly model: ComposerControls["model"]
 }

-export function createComposerModel(adapter: ComposerAdapter): ComposerModel {
+export function createComposerModel(adapter: ComposerAdapter, options?: { queue?: ComposerQueue }): ComposerModel {
  const sdk = useWorkspaceLocation()
  const data = useData()
  const files = useFile()
@@ -80,7 +80,11 @@ export function createComposerModel(adapter: ComposerAdapter): ComposerModel {
  })
  const stopping = createMemo(() => adapter.working() && blank())
  const placeholder = () =>
-    composerPlaceholder(mode(), (key, params) => language.t(key as Parameters<typeof language.t>[0], params as never))
+    composerPlaceholder(
+      mode(),
+      (key, params) => language.t(key as Parameters<typeof language.t>[0], params as never),
+      adapter.working() || (options?.queue?.count() ?? 0) > 0,
+    )

  const historyComments = () => {
    const byID = new Map(comments.all().map((item) => [`${item.file}\n${item.id}`, item] as const))
@@ -253,6 +257,11 @@ export function createComposerModel(adapter: ComposerAdapter): ComposerModel {
    resetHistory: () => controller.resetHistory(),
    setMode: (next) => controller.dispatch({ type: next === "shell" ? "mode.shell" : "mode.normal" }),
    closePopover: () => controller.dispatch({ type: "popover.close" }),
+    delivery: (alternate) => {
+      const queue = options?.queue
+      if (!queue) return "steer"
+      return (alternate ? queue.alternate() : queue.delivery()) ?? "steer"
+    },
    notify: {
      missingSelection: () =>
        showToast({
@@ -360,7 +369,18 @@ export function createComposerModel(adapter: ComposerAdapter): ComposerModel {
      submit: {
        stopping,
        working: adapter.working,
-        onSubmit: () => void submission.submit(new Event("submit")),
+        queue: options?.queue,
+        onSubmit: (submitOptions) => {
+          const queue = options?.queue
+          // Confirming an edit re-admits the queued prompt instead of sending
+          // the composer value as a new prompt. Enter keeps it queued in
+          // place; the alternate action sends it as a steer.
+          if (queue?.editing()) {
+            queue.confirmEdit(submitOptions?.alternate ? "steer" : "queue")
+            return
+          }
+          void submission.submit(new Event("submit"), submitOptions)
+        },
        onStop: () => void submission.stop(),
      },
    },
@@ -12,4 +12,12 @@ describe("Composer placeholder", () => {
  test("uses the command and context hint in normal mode", () => {
    expect(composerPlaceholder("normal", t)).toBe("ui.promptInput.placeholder.normal/@")
  })
+
+  test("uses the follow-up copy while a turn runs or prompts are queued", () => {
+    expect(composerPlaceholder("normal", t, true)).toBe("ui.promptInput.placeholder.followUp/@")
+  })
+
+  test("keeps the shell placeholder while a turn runs", () => {
+    expect(composerPlaceholder("shell", t, true)).toBe("prompt.placeholder.shell:git status")
+  })
 })
@@ -1,7 +1,9 @@
 export function composerPlaceholder(
  mode: "normal" | "shell",
  t: (key: string, params?: Record<string, string>) => string,
+  followUp?: boolean,
 ) {
  if (mode === "shell") return t("prompt.placeholder.shell", { example: "git status" })
+  if (followUp) return t("ui.promptInput.placeholder.followUp", { slash: "/", at: "@" })
  return t("ui.promptInput.placeholder.normal", { slash: "/", at: "@" })
 }
@@ -5,7 +5,7 @@ import type { Accessor } from "solid-js"
 import type { PromptHistoryComment } from "./history/entry"
 import type { ImageAttachmentPart, Prompt } from "./state"
 import { clonePrompt, promptLength } from "./prompt-parts"
-import type { ComposerAdapter, ComposerSelection, ComposerSession } from "./adapter"
+import type { ComposerAdapter, ComposerDelivery, ComposerSelection, ComposerSession } from "./adapter"
 import { createComposerSubmission } from "./submission-state"
 import { buildPromptRequest } from "./request"
 import { setCursorPosition } from "./editor/dom"
@@ -21,7 +21,7 @@ type ComposerSubmission = {
  text: string
  images: ImageAttachmentPart[]
  selection: ComposerSelection
-  delivery: "steer"
+  delivery: ComposerDelivery
 }

 type ComposerSubmitInput = {
@@ -33,6 +33,7 @@ type ComposerSubmitInput = {
  resetHistory: () => void
  setMode: (mode: "normal" | "shell") => void
  closePopover: () => void
+  delivery?: (alternate: boolean) => ComposerDelivery
  notify: {
    missingSelection: () => void
    failed: (kind: "shell" | "command" | "prompt", error: unknown) => void
@@ -45,7 +46,7 @@ type ComposerSubmitInput = {
 }

 export function createComposerSubmit(input: ComposerSubmitInput) {
-  const submit = async (event: globalThis.Event) => {
+  const submit = async (event: globalThis.Event, options?: { alternate?: boolean }) => {
    event.preventDefault()

    const submission = createComposerSubmission({
@@ -56,7 +57,7 @@ export function createComposerSubmit(input: ComposerSubmitInput) {
        selection: item.selection ? { ...item.selection } : undefined,
      })),
    })
-    const value = readSubmission(input, submission.prompt, submission.context)
+    const value = readSubmission(input, submission.prompt, submission.context, options?.alternate ?? false)
    if (!value) {
      if (input.adapter.working() && input.adapter.kind === "active-session") void input.adapter.interrupt()
      return
@@ -113,7 +114,10 @@ export function createComposerSubmit(input: ComposerSubmitInput) {

      if (command) {
        clearSubmission(input, submission)
-        void sendCommand(session, value, command).catch((error) =>
+        // Commands always steer: the server applies a command's configured
+        // agent and model immediately at admission, so queueing one would
+        // reconfigure the turn it is supposed to wait behind.
+        void sendCommand(session, { ...value, delivery: "steer" }, command).catch((error) =>
          failSubmission(input, session, "command", error, restore, value.id),
        )
        return
@@ -157,6 +161,7 @@ function readSubmission(
  input: ComposerSubmitInput,
  prompt: Prompt,
  context: ComposerSubmission["context"],
+  alternate: boolean,
 ): ComposerSubmission | undefined {
  const text = prompt.map((part) => ("content" in part ? part.content : "")).join("")
  const mode = input.mode()
@@ -195,7 +200,7 @@ function readSubmission(
      model: { modelID: model.id, providerID: model.provider.id },
      variant,
    },
-    delivery: "steer",
+    delivery: input.delivery?.(alternate) ?? "steer",
  }
 }

@@ -285,23 +290,30 @@ async function sendCommand(

 async function sendPrompt(session: ComposerSession, value: ComposerSubmission) {
  const request = await buildSubmissionRequest(session, value)
-  const current = session.current()
-  if (current?.agent !== value.selection.agent) {
-    await session.api.switchAgent({ sessionID: session.id, agent: value.selection.agent })
-  }
-  if (
-    current?.model?.providerID !== value.selection.model.providerID ||
-    current.model.id !== value.selection.model.modelID ||
-    (current.model.variant ?? "default") !== (value.selection.variant ?? "default")
-  ) {
-    await session.api.switchModel({
-      sessionID: session.id,
-      model: {
-        id: value.selection.model.modelID,
-        providerID: value.selection.model.providerID,
-        variant: value.selection.variant,
-      },
-    })
+  // Switching agent or model reconfigures the session immediately, and with it
+  // the remainder of a running turn. A steer targets that turn, so its
+  // selection applies now; a queued follow-up must not reconfigure the turn it
+  // waits behind, so it runs with the session selection at delivery time (the
+  // intended selection stays recorded in its metadata).
+  if (value.delivery === "steer") {
+    const current = session.current()
+    if (current?.agent !== value.selection.agent) {
+      await session.api.switchAgent({ sessionID: session.id, agent: value.selection.agent })
+    }
+    if (
+      current?.model?.providerID !== value.selection.model.providerID ||
+      current.model.id !== value.selection.model.modelID ||
+      (current.model.variant ?? "default") !== (value.selection.variant ?? "default")
+    ) {
+      await session.api.switchModel({
+        sessionID: session.id,
+        model: {
+          id: value.selection.model.modelID,
+          providerID: value.selection.model.providerID,
+          variant: value.selection.variant,
+        },
+      })
+    }
  }

  const admission = {
@@ -677,6 +677,14 @@ export const dict = {
  "session.background.subagent.one": "{{count}} subagent",
  "session.background.subagent.other": "{{count}} subagents",
  "command.session.background": "Move to background",
+  "session.queue.count.one": "{{count}} queued",
+  "session.queue.count.other": "{{count}} queued",
+  "session.queue.steer": "Steer",
+  "session.queue.send": "Send",
+  "session.queue.steerTooltip": "Send without interrupting",
+  "session.queue.remove": "Remove",
+  "session.queue.reorder": "Reorder queued prompt",
+  "session.queue.attachments": "+ attachments",
  "session.timeline.notice.finished": "{{actor}} finished",
  "session.timeline.notice.failed": "{{actor}} failed",
  "session.timeline.notice.cancelled": "{{actor}} cancelled",
@@ -961,6 +969,11 @@ export const dict = {
  "settings.general.row.showCustomAgents.title": "Show agent",
  "settings.general.row.showCustomAgents.description":
    "Switch between agents in the composer. When hidden, defaults to Build agent.",
+  "settings.general.row.followUpBehavior.title": "Follow-up behavior",
+  "settings.general.row.followUpBehavior.description":
+    "Choose whether to queue follow-ups or steer the current turn. Use {{keybind}} to switch.",
+  "settings.general.row.followUpBehavior.queue": "Queue",
+  "settings.general.row.followUpBehavior.steer": "Steer",
  "settings.general.row.reasoningSummaries.title": "Show reasoning summaries",
  "settings.general.row.reasoningSummaries.description": "Display model reasoning summaries in the timeline",
  "settings.general.row.shellToolPartsExpanded.title": "Expand shell tool parts",
@@ -0,0 +1,186 @@
+import { createMemo, For, Show } from "solid-js"
+import { DragDropProvider, PointerSensor } from "@dnd-kit/solid"
+import { isSortable, useSortable } from "@dnd-kit/solid/sortable"
+import { AutoScroller, Feedback, PointerActivationConstraints } from "@dnd-kit/dom"
+import { RestrictToVerticalAxis } from "@dnd-kit/abstract/modifiers"
+import { RestrictToElement } from "@dnd-kit/dom/modifiers"
+import { arrayMove } from "@dnd-kit/helpers"
+import { Button } from "@opencode-ai/ui/button"
+import { Icon } from "@opencode-ai/ui/icon"
+import { IconButton } from "@opencode-ai/ui/icon-button"
+import { Tooltip } from "@opencode-ai/ui/tooltip"
+import { useLanguage } from "@/runtime/i18n/language"
+import type { SessionQueueView } from "./queue"
+
+// Pullout above the composer listing the prompts queued behind the current
+// turn. The panel slides under the composer card (negative margin, opaque
+// composer background) so the two read as one attached surface.
+export function SessionQueuePanel(props: { queue: SessionQueueView }) {
+  const language = useLanguage()
+  const count = () => props.queue.rows().length
+  let listRef!: HTMLDivElement
+  return (
+    <Show when={count() > 0}>
+      <div
+        data-component="session-queue-panel"
+        class="relative z-0 -mb-3 rounded-xl bg-v2-background-bg-base px-1.5 pt-1.5 pb-[18px] shadow-[inset_0_0_0_0.5px_var(--v2-border-border-base)]"
+      >
+        <Show when={count() > 3}>
+          <div class="px-1.5 pb-px text-[11px] font-[530] uppercase leading-[var(--line-height-tight)] tracking-[0.05px] text-v2-text-text-muted [font-variant-numeric:tabular-nums]">
+            {language.plural("session.queue.count", count())}
+          </div>
+        </Show>
+        <DragDropProvider
+          sensors={(defaults) => [
+            ...defaults.filter((sensor) => sensor !== PointerSensor),
+            PointerSensor.configure({
+              activationConstraints: [new PointerActivationConstraints.Distance({ value: 4 })],
+            }),
+          ]}
+          modifiers={[RestrictToVerticalAxis, RestrictToElement.configure({ element: () => listRef })]}
+          plugins={(defaults) => [
+            ...defaults.filter((plugin) => plugin !== AutoScroller && plugin !== Feedback),
+            AutoScroller.configure({ acceleration: 8, threshold: { x: 0, y: 0.05 } }),
+            Feedback.configure({ dropAnimation: null }),
+          ]}
+          onDragEnd={(event) => {
+            const source = event.operation.source
+            if (event.canceled || !isSortable(source)) return
+            if (source.initialIndex === source.index) return
+            void props.queue.reorder(
+              arrayMove(
+                props.queue.rows().map((row) => row.id),
+                source.initialIndex,
+                source.index,
+              ),
+            )
+          }}
+        >
+          {/* Keyed on row IDs so store updates move row elements instead of
+              remounting them, which would kill an in-flight drag. */}
+          <div
+            ref={listRef}
+            class="flex flex-col gap-px"
+            classList={{ "max-h-[131px] overflow-y-auto": count() > 3 }}
+          >
+            <For each={props.queue.rows().map((row) => row.id)}>
+              {(id, index) => <SessionQueueRow queue={props.queue} id={id} index={index()} />}
+            </For>
+          </div>
+        </DragDropProvider>
+      </div>
+    </Show>
+  )
+}
+
+function SessionQueueRow(props: { queue: SessionQueueView; id: string; index: number }) {
+  const language = useLanguage()
+  const row = createMemo(() => props.queue.rows().find((entry) => entry.id === props.id))
+  const editing = () => props.queue.editing() === props.id
+  // While the turn is stopped the queue stays parked, so the first prompt
+  // shows its actions without hover and its label reads Send: that is how a
+  // parked queue resumes.
+  const active = () => !props.queue.working() && props.index === 0
+  const sortable = useSortable({
+    get id() {
+      return props.id
+    },
+    get index() {
+      return props.index
+    },
+    get disabled() {
+      return props.queue.busy()
+    },
+  })
+  return (
+    <Show when={row()} keyed>
+      {(entry) => (
+        <div
+          ref={sortable.ref}
+          data-component="session-queue-row"
+          class="group/queue-row flex items-center justify-between gap-2 rounded-md py-1 ps-1 pe-2"
+          classList={{
+            "bg-v2-overlay-simple-overlay-hover": editing(),
+            "opacity-60": sortable.isDragSource(),
+          }}
+        >
+          <div class="flex min-w-0 flex-1 items-center gap-2">
+            <button
+              ref={sortable.handleRef}
+              type="button"
+              class="grid shrink-0 cursor-grab touch-none grid-cols-2 gap-x-[2px] gap-y-[2.25px] p-1"
+              aria-label={language.t("session.queue.reorder")}
+            >
+              <For each={Array.from({ length: 6 })}>
+                {() => <span class="size-[2px] bg-v2-background-bg-layer-04" />}
+              </For>
+            </button>
+            <div class="flex min-w-0 flex-col">
+              <button
+                type="button"
+                data-action="session-queue-edit"
+                dir="auto"
+                disabled={props.queue.busy()}
+                class="max-w-full min-w-0 self-start truncate rounded-sm text-start text-[13px] font-[440] leading-[var(--line-height-compact)]"
+                classList={{
+                  "text-v2-text-text-faint": editing(),
+                  "cursor-text text-v2-text-text-base hover:bg-v2-overlay-simple-overlay-hover": !editing(),
+                }}
+                onClick={() => props.queue.edit(props.id)}
+              >
+                {entry.text || (entry.attachments ? language.t("session.queue.attachments") : "")}
+              </button>
+              <Show when={entry.attachments && entry.text}>
+                <span class="text-[13px] font-[440] leading-[var(--line-height-compact)] text-v2-text-text-muted">
+                  {language.t("session.queue.attachments")}
+                </span>
+              </Show>
+            </div>
+          </div>
+          <div
+            data-slot="session-queue-actions"
+            class="flex shrink-0 items-center gap-1.5"
+            classList={{
+              "opacity-0 focus-within:opacity-100 group-hover/queue-row:opacity-100 [@media(hover:none)]:opacity-100":
+                !active() && !editing(),
+              "pointer-events-none": props.queue.busy(),
+            }}
+          >
+            <Show when={!editing()}>
+              <Tooltip
+                placement="top"
+                inactive={!props.queue.working()}
+                value={language.t("session.queue.steerTooltip")}
+              >
+                <Button
+                  data-action="session-queue-steer"
+                  type="button"
+                  size="small"
+                  variant="ghost-muted"
+                  icon="arrow-up"
+                  disabled={props.queue.busy()}
+                  class="text-v2-text-text-muted ![font-weight:530]"
+                  onClick={() => void props.queue.steer(props.id)}
+                >
+                  {props.queue.working() ? language.t("session.queue.steer") : language.t("session.queue.send")}
+                </Button>
+              </Tooltip>
+            </Show>
+            <Tooltip placement="top" value={language.t("session.queue.remove")}>
+              <IconButton
+                data-action="session-queue-remove"
+                type="button"
+                size="small"
+                variant="ghost-muted"
+                icon={<Icon name="outline-xmark" />}
+                disabled={props.queue.busy()}
+                aria-label={language.t("session.queue.remove")}
+                onClick={() => void props.queue.remove(props.id)}
+              />
+            </Tooltip>
+          </div>
+        </div>
+      )}
+    </Show>
+  )
+}
@@ -0,0 +1,275 @@
+import { createEffect, createMemo, onCleanup, type Accessor } from "solid-js"
+import { createStore } from "solid-js/store"
+import type { SessionInboxInfo } from "@opencode-ai/client/promise"
+import type { ComposerDelivery } from "@/composer/adapter"
+import type { ComposerModel } from "@/composer/model"
+import type { ComposerStateTarget } from "@/composer/submission-state"
+import type { ImageAttachmentPart, Prompt } from "@/composer/state"
+import { clonePrompt, promptLength } from "@/composer/prompt-parts"
+import { buildPromptRequest } from "@/composer/request"
+import { blobDataUrl } from "@/runtime/persistence/drafts"
+import { useData } from "@/runtime/server/current"
+import { useServerSDK } from "@/runtime/server/client"
+import { useWorkspaceLocation } from "@/workspaces/location"
+import { useLanguage } from "@/runtime/i18n/language"
+import { showToast } from "@/shell/notifications/toast"
+
+export type QueuedPrompt = Extract<SessionInboxInfo, { type: "user" }>
+
+type EditStash = {
+  prompt: Prompt
+  cursor: number
+  mode: "normal" | "shell"
+  retry: ReturnType<ComposerStateTarget["retry"]["current"]>
+}
+
+export function createSessionQueue(input: {
+  sessionID: string
+  draft: ComposerStateTarget
+  working: Accessor<boolean>
+  behavior: Accessor<ComposerDelivery>
+  composer: Accessor<ComposerModel | undefined>
+}) {
+  const data = useData()
+  const server = useServerSDK()
+  const location = useWorkspaceLocation()
+  const language = useLanguage()
+  const [state, setState] = createStore<{ editing?: { id: string; stash: EditStash }; busy: boolean }>({ busy: false })
+
+  const queued = createMemo(() =>
+    data.session.pending
+      .list(input.sessionID)
+      .filter((item): item is QueuedPrompt => item.type === "user" && item.delivery === "queue"),
+  )
+  const rows = createMemo(() =>
+    queued().map((item) => ({
+      id: item.id,
+      text: queuedPromptText(item),
+      attachments: (item.payload.files?.length ?? 0) > 0,
+    })),
+  )
+
+  createEffect(() => {
+    const editing = state.editing
+    if (!editing || state.busy || queued().some((item) => item.id === editing.id)) return
+    setState("editing", undefined)
+  })
+  onCleanup(() => cancelEdit())
+
+  const notify = () => showToast({ title: language.t("common.requestFailed") })
+  const run = (work: () => Promise<unknown>) => {
+    setState("busy", true)
+    return work()
+      .catch(() => notify())
+      .finally(async () => {
+        await data.session.pending.sync(input.sessionID).catch(() => undefined)
+        setState("busy", false)
+      })
+  }
+
+  const rewrite = async (inboxIDs: string[]) => {
+    const pending = await server.api.session.inbox.list({ sessionID: input.sessionID })
+    if (pending.some((item) => item.delivery === "queue" && item.type !== "user"))
+      throw new Error("Queued control items block reordering")
+    const current = pending.filter((item): item is QueuedPrompt => item.type === "user" && item.delivery === "queue")
+    const ordered = inboxIDs.flatMap((id) => current.filter((item) => item.id === id))
+    if (ordered.length !== current.length) throw new Error("Queued prompts changed before reordering")
+    const changed = ordered.findIndex((item, index) => item.id !== current[index]?.id)
+    if (changed < 0) return
+
+    // Existing inbox APIs cannot reorder rows, so replace only the changed suffix.
+    for (const item of ordered.slice(changed)) {
+      await data.session.prompt({
+        sessionID: input.sessionID,
+        text: item.payload.text,
+        files: item.payload.files?.map((file) => ({
+          uri: `data:${file.mime};base64,${file.data}`,
+          name: file.name,
+          description: file.description,
+          mention: file.mention,
+        })),
+        agents: item.payload.agents,
+        skills: item.payload.skills,
+        metadata: item.payload.metadata,
+        delivery: "queue",
+        resume: false,
+      })
+    }
+    for (const item of current.slice(changed)) {
+      await server.api.session.inbox.cancel({ sessionID: input.sessionID, inboxID: item.id })
+    }
+  }
+  const steer = (id: string) => {
+    if (state.editing?.id === id) cancelEdit()
+    return server.api.session.inbox.steer({ sessionID: input.sessionID, inboxID: id }).catch(() => notify())
+  }
+  const remove = (id: string) => {
+    if (state.editing?.id === id) cancelEdit()
+    return server.api.session.inbox.cancel({ sessionID: input.sessionID, inboxID: id }).catch(() => notify())
+  }
+  const reorder = (inboxIDs: string[]) => {
+    if (state.busy) return Promise.resolve()
+    return run(() => rewrite(inboxIDs))
+  }
+
+  const edit = (id: string) => {
+    if (state.busy) return false
+    if (state.editing?.id === id) return true
+    const item = queued().find((entry) => entry.id === id)
+    if (!item) return false
+    if (state.editing) cancelEdit()
+    const draft = input.draft.current()
+    setState("editing", {
+      id,
+      stash: {
+        prompt: clonePrompt(draft),
+        cursor: input.draft.cursor() ?? promptLength(draft),
+        mode: input.draft.mode.current(),
+        retry: input.draft.retry.current(),
+      },
+    })
+    const text = queuedPromptText(item)
+    input.composer()?.dispatch({ type: "mode.normal" })
+    input.draft.set([{ type: "text", content: text, start: 0, end: text.length }], text.length)
+    input.composer()?.restoreFocus(text.length)
+    return true
+  }
+  const cancelEdit = () => {
+    const editing = state.editing
+    if (!editing) return
+    setState("editing", undefined)
+    // Mode first, then prompt, then retry: mode and prompt writes both clear
+    // the retry marker.
+    input.composer()?.dispatch({ type: editing.stash.mode === "shell" ? "mode.shell" : "mode.normal" })
+    input.draft.set(editing.stash.prompt, editing.stash.cursor)
+    if (editing.stash.retry) input.draft.retry.set(editing.stash.retry)
+    input.composer()?.restoreFocus(editing.stash.cursor)
+  }
+  const confirmEdit = (delivery: ComposerDelivery) => {
+    const editing = state.editing
+    if (!editing || state.busy) return
+    const prompt = clonePrompt(input.draft.current())
+    const text = prompt.map((part) => ("content" in part ? part.content : "")).join("")
+    if (!text.trim() && !prompt.some((part) => part.type === "image")) return cancelEdit()
+    const item = queued().find((entry) => entry.id === editing.id)
+    const pristine = item && text.trim() === queuedPromptText(item) && !prompt.some((part) => part.type === "image")
+    if (pristine && delivery === "queue") return cancelEdit()
+    const inboxIDs = queued().map((entry) => entry.id)
+    void run(async () => {
+      const replacement = await editedPromptInput(input.sessionID, location().directory, item, prompt, text)
+      // Admit before cancelling so a failed replacement never discards the original.
+      const admitted = await data.session.prompt({
+        ...replacement,
+        delivery,
+        ...(delivery === "queue" ? { resume: false } : {}),
+      })
+      await server.api.session.inbox.cancel({ sessionID: input.sessionID, inboxID: editing.id })
+      cancelEdit()
+      if (delivery === "queue") await rewrite(inboxIDs.map((id) => (id === editing.id ? admitted.id : id)))
+    })
+  }
+  const editFirst = () => {
+    const first = queued()[0]
+    if (!first) return false
+    return edit(first.id)
+  }
+
+  return {
+    count: () => queued().length,
+    delivery: () => (input.working() ? input.behavior() : "steer"),
+    alternate: () => {
+      if (state.editing) return "steer"
+      if (!input.working()) return undefined
+      return input.behavior() === "queue" ? "steer" : "queue"
+    },
+    editing: () => state.editing?.id,
+    confirmEdit,
+    cancelEdit,
+    editFirst,
+    rows,
+    busy: () => state.busy,
+    working: input.working,
+    steer,
+    remove,
+    edit,
+    reorder,
+  }
+}
+
+export type SessionQueue = ReturnType<typeof createSessionQueue>
+
+// The slice of the queue the panel renders and drives.
+export type SessionQueueView = Pick<
+  SessionQueue,
+  "rows" | "editing" | "working" | "busy" | "steer" | "remove" | "edit" | "reorder"
+>
+
+export function queuedPromptText(item: QueuedPrompt) {
+  const display = item.payload.metadata?.["displayText"]
+  return typeof display === "string" && display.length > 0 ? display : item.payload.text
+}
+
+// Confirming an edit submits the current composer content as the replacement:
+// mentions and images added during the edit are parsed like a normal
+// submission, the original's stored attachments are preserved, and the
+// review-comment notes appended to the original's model-visible text survive.
+// Ambient composer context (open review comments) stays out: it belongs to
+// the next fresh prompt, not to a queued edit.
+async function editedPromptInput(
+  sessionID: string,
+  directory: string,
+  item: QueuedPrompt | undefined,
+  prompt: Prompt,
+  text: string,
+) {
+  const images = await Promise.all(
+    prompt
+      .filter((part): part is ImageAttachmentPart => part.type === "image")
+      .map(async (part) => ({ ...part, dataUrl: await blobDataUrl(part.blob, part.mime) })),
+  )
+  const request = buildPromptRequest({ prompt, context: [], images, text, sessionDirectory: directory })
+  const payload = item?.payload
+  const display = item ? queuedPromptText(item) : ""
+  const notes = payload && display && payload.text.startsWith(display) ? payload.text.slice(display.length) : ""
+  const mention = (value: { start: number; end: number; text: string } | undefined) => {
+    if (!value) return undefined
+    const start = text.indexOf(value.text)
+    if (start < 0) return undefined
+    return { text: value.text, start, end: start + value.text.length }
+  }
+  // Structured mentions degrade to plain text in the editor, so an original
+  // agent or skill reference survives the edit as long as its mention text
+  // still appears; newly typed structured mentions come from the request.
+  const agents = [
+    ...(payload?.agents?.filter(
+      (agent) =>
+        agent.mention &&
+        text.includes(agent.mention.text) &&
+        !request.agents.some((entry) => entry.name === agent.name),
+    ) ?? []),
+    ...request.agents,
+  ]
+  const skills = [
+    ...(payload?.skills?.filter(
+      (skill) =>
+        skill.mention && text.includes(skill.mention.text) && !request.skills.some((entry) => entry.id === skill.id),
+    ) ?? []),
+    ...request.skills,
+  ]
+  return {
+    sessionID,
+    text: request.text + notes,
+    files: [
+      ...(payload?.files?.map((file) => ({
+        uri: `data:${file.mime};base64,${file.data}`,
+        name: file.name,
+        description: file.description,
+        mention: mention(file.mention),
+      })) ?? []),
+      ...request.files.map((file) => ({ uri: file.uri, name: file.name, mention: file.mention })),
+    ],
+    agents: agents.map((agent) => ({ name: agent.name, mention: mention(agent.mention) })),
+    skills: skills.map((skill) => ({ id: skill.id, mention: mention(skill.mention) })),
+    metadata: { ...payload?.metadata, displayText: request.displayText },
+  }
+}
@@ -6,7 +6,7 @@ import { makeEventListener } from "@solid-primitives/event-listener"
 import { useNavigate } from "@solidjs/router"
 import { createEffect, on, onMount } from "solid-js"
 import { Composer } from "@/composer/composer"
-import { createComposerModel } from "@/composer/model"
+import { createComposerModel, type ComposerModel } from "@/composer/model"
 import { useComposerState } from "@/composer/persistence"
 import { createComposerControls } from "@/composer/selection"
 import { setCursorPosition } from "@/composer/editor/dom"
@@ -27,8 +27,11 @@ import { createSessionRevert } from "../revert"
 import { SessionComposerRegion } from "./session-composer-region"
 import { createSessionComposerRegionController } from "./session-composer-region-controller"
 import { createActiveComposerAdapter } from "./adapter"
+import { createSessionQueue } from "./queue"
+import { SessionQueuePanel } from "./queue-panel"
 import { resolveSessionComposerSelection } from "./selection"
 import { createSessionRequestModel } from "../requests/model"
+import { useSettings } from "@/settings/model"

 export function createActiveSessionRegion(input: {
  session: SessionModel
@@ -216,6 +219,7 @@ export function ActiveSessionComposerRegion(props: {
  accentSubmit: boolean
  onResponseSubmit: () => void
 }) {
+  const settings = useSettings()
  const region = createSessionComposerRegionController({
    state: props.model.region.state,
    parentID: props.session.data.parentID,
@@ -231,11 +235,32 @@ export function ActiveSessionComposerRegion(props: {
    submitted: props.model.submitted,
    setEditor: props.model.input.setPromptRef,
  })
-  const composer = createComposerModel(adapter)
+  let composer: ComposerModel | undefined
+  const queue = createSessionQueue({
+    sessionID: requireSessionID(props.session),
+    draft: adapter.state,
+    working: adapter.working,
+    behavior: settings.general.followUpBehavior,
+    composer: () => composer,
+  })
+  composer = createComposerModel(adapter, { queue })
  return (
    <SessionComposerRegion
      controller={region}
-      composer={<Composer model={composer} borderUnderlay accentSubmit={props.accentSubmit} />}
+      composer={
+        <div class="relative">
+          <SessionQueuePanel queue={queue} />
+          <div class="relative z-10">
+            <Composer model={composer} borderUnderlay accentSubmit={props.accentSubmit} />
+          </div>
+        </div>
+      }
    />
  )
 }
+
+function requireSessionID(session: SessionModel) {
+  const id = session.identity.params.id
+  if (!id) throw new Error("Active Composer requires a Session ID")
+  return id
+}
@@ -55,6 +55,28 @@ export function createSessionRevert(input: {
      await server.api.session.interrupt({ sessionID }).catch(() => undefined)
    }
    if (!(await request(() => server.api.session.revert.stage({ sessionID, messageID: message.id })))) return
+    // Reverting to a previous prompt discards the pending queue (and pending
+    // steers): they were written against the history being rewound. Cancel
+    // the authoritative inbox merged with the local snapshot, fire-and-forget
+    // so a slow request cannot delay restoring the composer. The cutoff keeps
+    // the asynchronous sweep away from prompts admitted after the revert; an
+    // old admission still in flight when the list is fetched can survive it,
+    // and fully closing that race needs a server-side revert-discards-inbox
+    // rule.
+    const cutoff = Date.now()
+    const local = data.session.pending
+      .list(sessionID)
+      .filter((item) => item.type === "user")
+      .map((item) => item.id)
+    void server.api.session.inbox
+      .list({ sessionID })
+      .then((rows) => rows.filter((row) => row.type === "user" && row.timeCreated <= cutoff).map((row) => row.id))
+      .catch(() => [])
+      .then((authoritative) => {
+        new Set([...local, ...authoritative]).forEach(
+          (inboxID) => void server.api.session.inbox.cancel({ sessionID, inboxID }).catch(() => undefined),
+        )
+      })
    restore(target, message)
    owner.run(() => input.setActiveMessage(previous))
  }
@@ -7,7 +7,13 @@ import { TextInput } from "@opencode-ai/ui/text-input"
 import { useLanguage } from "@/runtime/i18n/language"
 import { usePlatform } from "@/runtime/platform/platform"
 import { useUpdaterAction } from "@/shell/updates/action"
-import { type TerminalPlacement, type WorkspaceDefaultDestination, useSettings } from "@/settings/model"
+import {
+  type FollowUpBehavior,
+  type TerminalPlacement,
+  type WorkspaceDefaultDestination,
+  useSettings,
+} from "@/settings/model"
+import { formatKeybind } from "@/shell/commands/command"
 import { ExternalLink } from "@/runtime/platform/external-link"
 import { SettingsList } from "@/settings/list"
 import { SettingsRow } from "@/settings/row"
@@ -148,6 +154,35 @@ const TerminalPlacementSetting: Component = () => {
  )
 }

+const FollowUpBehaviorSetting: Component = () => {
+  const language = useLanguage()
+  const settings = useSettings()
+  const options = createMemo((): { value: FollowUpBehavior; label: string }[] => [
+    { value: "queue", label: language.t("settings.general.row.followUpBehavior.queue") },
+    { value: "steer", label: language.t("settings.general.row.followUpBehavior.steer") },
+  ])
+
+  return (
+    <SettingsRow
+      title={language.t("settings.general.row.followUpBehavior.title")}
+      description={language.t("settings.general.row.followUpBehavior.description", {
+        keybind: formatKeybind("mod+enter", language.t),
+      })}
+    >
+      <Select
+        data-action="settings-follow-up-behavior"
+        options={options()}
+        current={options().find((option) => option.value === settings.general.followUpBehavior())}
+        value={(option) => option.value}
+        label={(option) => option.label}
+        placement="bottom-end"
+        gutter={6}
+        onSelect={(option) => option && settings.general.setFollowUpBehavior(option.value)}
+      />
+    </SettingsRow>
+  )
+}
+
 const AppearanceSection: Component<{ controller: AppearanceSettingsController }> = (props) => {
  const language = useLanguage()
  return (
@@ -294,6 +329,7 @@ export const SettingsGeneral: Component<{

        <ShellSetting controller={shell} />
        <TerminalPlacementSetting />
+        <FollowUpBehaviorSetting />

        <SettingsRow
          title={language.t("settings.general.row.reasoningSummaries.title")}
@@ -7,6 +7,7 @@ import { ScopedKey, type ServerScope } from "@/runtime/server/scope"
 export type WorkspaceDefaultDestination = "last-used" | "local" | "new"
 export type WorkspaceLastUsed = "local" | "workspace"
 export type TerminalPlacement = "side" | "bottom"
+export type FollowUpBehavior = "queue" | "steer"

 export interface NotificationSettings {
  agent: boolean
@@ -39,6 +40,7 @@ export interface Settings {
    showCustomAgents: boolean
    mobileTitlebarPosition: "top" | "bottom"
    terminalPlacement: TerminalPlacement
+    followUpBehavior: FollowUpBehavior
  }
  appearance: {
    fontSize: number
@@ -126,6 +128,7 @@ const defaultSettings: Settings = {
    showCustomAgents: false,
    mobileTitlebarPosition: "top",
    terminalPlacement: "side",
+    followUpBehavior: "steer",
  },
  appearance: {
    fontSize: 14,
@@ -256,6 +259,10 @@ export const { use: useSettings, provider: SettingsProvider } = createSimpleCont
        setTerminalPlacement(value: TerminalPlacement) {
          setStore("general", "terminalPlacement", value)
        },
+        followUpBehavior: withFallback(() => store.general?.followUpBehavior, defaultSettings.general.followUpBehavior),
+        setFollowUpBehavior(value: FollowUpBehavior) {
+          setStore("general", "followUpBehavior", value)
+        },
      },
      visibility: {
        fileTree: showFileTree,
@@ -237,9 +237,8 @@ export default function PrivacyPolicy() {
                      </td>
                      <td>
                        <ul>
-                          <li>Providing, Customizing and Improving the Services</li>
-                          <li>Marketing the Services</li>
-                          <li>Corresponding with You</li>
+                          <li>Passing through to upstream provider to provide services</li>
+                          <li>Not stored</li>
                        </ul>
                      </td>
                      <td>
@@ -1,7 +1,9 @@
 import type { ToolDefinition } from "@opencode-ai/ai"
 import { Tool } from "@opencode-ai/schema/tool"
 import type { StandardJSONSchemaV1, StandardSchemaV1 } from "@standard-schema/spec"
-import { Cache, Effect, JsonSchema, Schema, SchemaRepresentation } from "effect"
+import { Cache, Effect, JsonSchema, Schema, SchemaIssue, SchemaRepresentation } from "effect"
+
+const formatEffectIssues = SchemaIssue.makeFormatterStandardSchemaV1()

 const jsonSchemas = Effect.runSync(
  Cache.make<JsonSchema.JsonSchema, Schema.Codec<unknown> | undefined>({
@@ -23,7 +25,7 @@ export const definition = (tool: Tool.Info<any, any>): ToolDefinition => ({

 export const execute = (tool: Tool.Info<any, any>, input: unknown, context: Tool.Context) =>
  Effect.gen(function* () {
-    const decoded = yield* decodeInput(tool.input, input)
+    const decoded = yield* decodeInput(tool, input)
    // Tool implementations declare `Tool.Error` but plugins can fail with anything at
    // runtime. A foreign typed failure would slip past every `catchTag("Tool.Error")`
    // downstream and leave its call permanently unsettled, so the declared contract is
@@ -55,18 +57,43 @@ export const execute = (tool: Tool.Info<any, any>, input: unknown, context: Tool
    }
  })

-const decodeInput = (schema: Tool.ValueSchema<any>, value: unknown) => {
-  if (Schema.isSchema(schema))
-    return Schema.decodeUnknownEffect(schema)(value).pipe(
-      Effect.mapError((error) => new Tool.Error({ message: `Invalid tool input: ${error.message}` })),
+const decodeInput = (tool: Tool.Info<any, any>, value: unknown) =>
+  Effect.gen(function* () {
+    const result = yield* validateInput(tool.input, value)
+    if (result.issues)
+      return yield* new Tool.Error({ message: formatInputIssues(effectiveName(tool), result.issues, value) })
+    return result.value
+  })
+
+const validateInput = (
+  schema: Tool.ValueSchema<any>,
+  value: unknown,
+): Effect.Effect<StandardSchemaV1.Result<unknown>> => {
+  if (isStandardSchema(schema)) return validateStandard(schema, value)
+  return Effect.gen(function* () {
+    const codec = Schema.isSchema(schema) ? schema : yield* Cache.get(jsonSchemas, schema)
+    if (codec === undefined) return { value }
+    return yield* Schema.decodeUnknownEffect(codec)(value, { errors: "all" }).pipe(
+      Effect.match({
+        onFailure: (error) => formatEffectIssues(error.issue),
+        onSuccess: (value) => ({ value }),
+      }),
    )
-  if (isStandardSchema(schema)) return validateStandard(schema, value, "Invalid tool input")
-  return Cache.get(jsonSchemas, schema).pipe(
-    Effect.flatMap((schema) =>
-      schema === undefined ? Effect.succeed(value) : Schema.decodeUnknownEffect(schema)(value),
-    ),
-    Effect.mapError((error) => new Tool.Error({ message: `Invalid tool input: ${error.message}` })),
-  )
+  })
+}
+
+const formatInputIssues = (tool: string, issues: ReadonlyArray<StandardSchemaV1.Issue>, value: unknown) => {
+  const details = issues.slice(0, 5).map((issue) => {
+    const path =
+      issue.path?.reduce<string>((path, segment) => {
+        const key = typeof segment === "object" ? segment.key : segment
+        if (typeof key === "number") return `${path}[${key}]`
+        return path === "" ? String(key) : `${path}.${String(key)}`
+      }, "") || "root"
+    return `- ${path}: ${issue.message}`
+  })
+  if (issues.length > 5) details.push(`- ...and ${issues.length - 5} more ${issues.length === 6 ? "issue" : "issues"}`)
+  return `Invalid arguments for tool "${tool}":\n${details.join("\n")}\n\nArguments provided:\n${JSON.stringify(value, null, 2)}\n\nUpdate the arguments and call the tool again.`
 }

 const jsonSchema = (schema: JsonSchema.JsonSchema) => {
@@ -86,7 +113,15 @@ const encodeOutput = (schema: Tool.ValueSchema<any>, value: unknown) => {
      ),
    )
  if (isStandardSchema(schema))
-    return validateStandard(schema, value, "Tool returned an invalid value for its output schema")
+    return validateStandard(schema, value).pipe(
+      Effect.flatMap((result) =>
+        result.issues
+          ? new Tool.Error({
+              message: `Tool returned an invalid value for its output schema: ${result.issues.map((issue) => issue.message).join(", ")}`,
+            })
+          : Effect.succeed(result.value),
+      ),
+    )
  return Schema.decodeUnknownEffect(Schema.Json)(value).pipe(
    Effect.mapError(
      (error) => new Tool.Error({ message: `Tool returned a non-JSON value for its output schema: ${error.message}` }),
@@ -102,26 +137,16 @@ const isStandardSchema = (
 const validateStandard = (
  schema: StandardSchemaV1<any, any> & StandardJSONSchemaV1<any, any>,
  value: unknown,
-  prefix: string,
-) =>
+): Effect.Effect<StandardSchemaV1.Result<unknown>> =>
  Effect.gen(function* () {
-    const pending = yield* Effect.try({
-      try: () => schema["~standard"].validate(value),
-      catch: (error) => standardFailure(prefix, error),
-    })
-    const result =
-      pending instanceof Promise
-        ? yield* Effect.tryPromise({ try: () => pending, catch: (error) => standardFailure(prefix, error) })
-        : pending
-    if (result.issues)
-      return yield* new Tool.Error({
-        message: `${prefix}: ${result.issues.map((issue) => issue.message).join(", ")}`,
-      })
-    return result.value
-  })
-
-const standardFailure = (prefix: string, error: unknown) =>
-  new Tool.Error({ message: `${prefix}: ${error instanceof Error ? error.message : String(error)}` })
+    const result = yield* Effect.try({ try: () => schema["~standard"].validate(value), catch: (error) => error })
+    return result instanceof Promise ? yield* Effect.tryPromise({ try: () => result, catch: (error) => error }) : result
+  }).pipe(
+    Effect.match({
+      onFailure: (error) => ({ issues: [{ message: error instanceof Error ? error.message : String(error) }] }),
+      onSuccess: (result) => result,
+    }),
+  )

 const inputJsonSchema = (schema: Tool.ValueSchema<any>): JsonSchema.JsonSchema => {
  if (schema === undefined || schema === null) return {}
@@ -511,7 +511,11 @@ describe("Tool", () => {
        }),
      ).toMatchObject({
        status: "error",
-        error: { type: "tool.execution", message: expect.stringContaining("Invalid tool input") },
+        error: {
+          type: "tool.execution",
+          message:
+            'Invalid arguments for tool "transformed":\n- value: Expected boolean\n\nArguments provided:\n{\n  "value": "yes"\n}\n\nUpdate the arguments and call the tool again.',
+        },
      })
      expect(executed).toEqual(["yes"])

@@ -100,7 +100,11 @@ describe("QuestionTool", () => {
        }),
      ).toMatchObject({
        status: "error",
-        error: { type: "tool.execution", message: expect.stringContaining("Invalid tool input") },
+        error: {
+          type: "tool.execution",
+          message:
+            'Invalid arguments for tool "question":\n- questions: Expected a value with a length of at least 1\n\nArguments provided:\n{\n  "questions": []\n}\n\nUpdate the arguments and call the tool again.',
+        },
      })
      expect(capturedInput()).toBeUndefined()
    }),
@@ -144,7 +144,12 @@ test("portable schema failures become tool failures", async () => {
    "~standard": {
      version: 1,
      vendor: "test",
-      validate: (_value: unknown) => ({ issues: [{ message: "expected a string" }] }),
+      validate: (_value: unknown) => ({
+        issues: [
+          { path: ["value"], message: "expected a string" },
+          { path: [{ key: "nested" }, { key: "count" }], message: "expected a positive integer" },
+        ],
+      }),
      jsonSchema: {
        input: () => ({ type: "string" }),
        output: () => ({ type: "string" }),
@@ -166,7 +171,62 @@ test("portable schema failures become tool failures", async () => {
      ),
    ),
  )
-  expect(error).toEqual(new Tool.Error({ message: "Invalid tool input: expected a string" }))
+  expect(error).toEqual(
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "invalid":\n- value: expected a string\n- nested.count: expected a positive integer\n\nArguments provided:\n1\n\nUpdate the arguments and call the tool again.',
+    }),
+  )
+})
+
+test("Effect schema failures use normalized input issues", async () => {
+  const tool: Info = {
+    name: "effect",
+    description: "Effect tool",
+    input: Schema.Struct({
+      value: Schema.String,
+      nested: Schema.Struct({ count: Schema.Int.check(Schema.isGreaterThanOrEqualTo(1)) }),
+    }),
+    execute: () => Effect.succeed({ content: "unused" }),
+  }
+
+  expect(
+    await Effect.runPromise(Effect.flip(execute(tool, { value: 1, nested: { count: 0 } }, {} as Tool.Context))),
+  ).toEqual(
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "effect":\n- value: Expected string\n- nested.count: Expected a value greater than or equal to 1\n\nArguments provided:\n{\n  "value": 1,\n  "nested": {\n    "count": 0\n  }\n}\n\nUpdate the arguments and call the tool again.',
+    }),
+  )
+})
+
+test("input error prompts limit normalized issues", async () => {
+  const input = {
+    "~standard": {
+      version: 1,
+      vendor: "test",
+      validate: (_value: unknown) => ({
+        issues: Array.from({ length: 6 }, (_, index) => ({ message: `issue ${index + 1}` })),
+      }),
+      jsonSchema: {
+        input: () => ({}),
+        output: () => ({}),
+      },
+    },
+  }
+  const tool: Info = {
+    name: "limited",
+    description: "Limited issues",
+    input,
+    execute: () => Effect.succeed({ content: "unused" }),
+  }
+
+  expect(await Effect.runPromise(Effect.flip(execute(tool, {}, {} as Tool.Context)))).toEqual(
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "limited":\n- root: issue 1\n- root: issue 2\n- root: issue 3\n- root: issue 4\n- root: issue 5\n- ...and 1 more issue\n\nArguments provided:\n{}\n\nUpdate the arguments and call the tool again.',
+    }),
+  )
 })

 test("canonical results carry metadata with typed output", async () => {
@@ -219,16 +279,31 @@ test("raw JSON schemas validate and decode tool input", async () => {
    content: [{ type: "text", text: '{"value":"ok"}' }],
  })
  expect(await Effect.runPromise(Effect.flip(execute(tool, { value: 1 }, {} as Tool.Context)))).toEqual(
-    new Tool.Error({ message: 'Invalid tool input: Expected string\n  at ["value"]' }),
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "raw":\n- value: Expected string\n\nArguments provided:\n{\n  "value": 1\n}\n\nUpdate the arguments and call the tool again.',
+    }),
  )
  expect(await Effect.runPromise(Effect.flip(execute(tool, {}, {} as Tool.Context)))).toEqual(
-    new Tool.Error({ message: 'Invalid tool input: Missing key\n  at ["value"]' }),
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "raw":\n- value: Missing key\n\nArguments provided:\n{}\n\nUpdate the arguments and call the tool again.',
+    }),
  )
  expect(
    await Effect.runPromise(Effect.flip(execute(tool, { value: "ok", nested: { count: 0 } }, {} as Tool.Context))),
  ).toEqual(
    new Tool.Error({
-      message: 'Invalid tool input: Expected a value greater than or equal to 1\n  at ["nested"]["count"]',
+      message:
+        'Invalid arguments for tool "raw":\n- nested.count: Expected a value greater than or equal to 1\n\nArguments provided:\n{\n  "value": "ok",\n  "nested": {\n    "count": 0\n  }\n}\n\nUpdate the arguments and call the tool again.',
+    }),
+  )
+  expect(
+    await Effect.runPromise(Effect.flip(execute(tool, { value: 1, nested: { count: 0 } }, {} as Tool.Context))),
+  ).toEqual(
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "raw":\n- value: Expected string\n- nested.count: Expected a value greater than or equal to 1\n\nArguments provided:\n{\n  "value": 1,\n  "nested": {\n    "count": 0\n  }\n}\n\nUpdate the arguments and call the tool again.',
    }),
  )
 })
@@ -250,7 +325,10 @@ test("raw JSON schemas resolve draft-07 definitions", async () => {
    content: [{ type: "text", text: '{"value":"ok"}' }],
  })
  expect(await Effect.runPromise(Effect.flip(execute(tool, { value: 1 }, {} as Tool.Context)))).toEqual(
-    new Tool.Error({ message: 'Invalid tool input: Expected value\n  at ["value"]' }),
+    new Tool.Error({
+      message:
+        'Invalid arguments for tool "draft-07":\n- value: Expected value\n\nArguments provided:\n{\n  "value": 1\n}\n\nUpdate the arguments and call the tool again.',
+    }),
  )
 })

@@ -118,7 +118,8 @@ describe("search tools", () => {
              status: "error",
              error: {
                type: "tool.execution",
-                message: 'Invalid tool input: Pattern must not be empty\n  at ["pattern"]',
+                message:
+                  'Invalid arguments for tool "grep":\n- pattern: Pattern must not be empty\n\nArguments provided:\n{\n  "pattern": ""\n}\n\nUpdate the arguments and call the tool again.',
              },
            })
          }),
@@ -41,6 +41,32 @@ test("keeps completed block text compact", () => {
  ])
 })

+test("marks streamed inline code for animation", () => {
+  expect(parseMarkdownNodes("<p><code>file.ts:29-43</code></p>", true, true)).toEqual([
+    {
+      key: "0",
+      type: "element",
+      tag: "p",
+      attributes: {},
+      children: [
+        {
+          key: "0.0",
+          type: "element",
+          tag: "code",
+          attributes: {},
+          children: Array.from("file.ts:29-43", (text, index) => ({
+            key: `0.0.0:${index}`,
+            type: "word",
+            text,
+            animate: true,
+          })),
+          animate: true,
+        },
+      ],
+    },
+  ])
+})
+
 test("marks words for animation only when requested", () => {
  expect(
    parseMarkdownNodes("<p>Hello</p>", true).flatMap((node) => (node.type === "element" ? node.children : [node]))[0],
@@ -3,7 +3,14 @@ import { createStore, reconcile } from "solid-js/store"
 import { Dynamic, render } from "solid-js/web"

 type MarkdownNode =
-  | { key: string; type: "element"; tag: string; attributes: Record<string, string>; children: MarkdownNode[] }
+  | {
+      key: string
+      type: "element"
+      tag: string
+      attributes: Record<string, string>
+      children: MarkdownNode[]
+      animate?: true
+    }
  | { key: string; type: "text"; text: string }
  | { key: string; type: "word"; text: string; animate?: true }

@@ -38,8 +45,12 @@ function MarkdownDomNode(props: { node: MarkdownNode; animate: () => boolean })
      </span>
    )
  }
+  let ref: HTMLElement | undefined
+  onMount(() => {
+    if (props.animate() && node.animate) ref?.setAttribute("data-markdown-enter", "")
+  })
  return (
-    <Dynamic component={node.tag} {...node.attributes}>
+    <Dynamic component={node.tag} ref={ref} {...node.attributes}>
      <For each={node.children}>{(node) => <MarkdownDomNode node={node} animate={props.animate} />}</For>
    </Dynamic>
  )
@@ -51,10 +62,10 @@ export function parseMarkdownNodes(html: string, words: boolean, animate = false
  return Array.from(template.content.childNodes).flatMap((node, index) => parseNode(node, `${index}`, words, animate))
 }

-function parseNode(node: Node, key: string, words: boolean, animate: boolean): MarkdownNode[] {
+function parseNode(node: Node, key: string, words: boolean, animate: boolean, inlineCode = false): MarkdownNode[] {
  if (node instanceof Text) {
    if (!words) return [{ key, type: "text", text: node.data }]
-    return node.data.split(/(\s+)/).flatMap((text, index): MarkdownNode[] => {
+    return (inlineCode ? Array.from(node.data) : node.data.split(/(\s+)/)).flatMap((text, index): MarkdownNode[] => {
      if (!text) return []
      if (/^\s+$/.test(text)) return [{ key: `${key}:${index}`, type: "text", text }]
      return [{ key: `${key}:${index}`, type: "word", text, ...(animate ? { animate: true as const } : {}) }]
@@ -67,7 +78,18 @@ function parseNode(node: Node, key: string, words: boolean, animate: boolean): M
      type: "element",
      tag: node.tagName.toLowerCase(),
      attributes: Object.fromEntries(Array.from(node.attributes).map((attribute) => [attribute.name, attribute.value])),
-      children: Array.from(node.childNodes).flatMap((child, index) => parseNode(child, `${key}.${index}`, words, animate)),
+      children: Array.from(node.childNodes).flatMap((child, index) =>
+        parseNode(
+          child,
+          `${key}.${index}`,
+          words,
+          animate,
+          inlineCode || (node.tagName === "CODE" && node.parentElement?.tagName !== "PRE"),
+        ),
+      ),
+      ...(words && animate && node.tagName === "CODE" && node.parentElement?.tagName !== "PRE"
+        ? { animate: true as const }
+        : {}),
    },
  ]
 }
@@ -20,7 +20,7 @@
    display: inline;
  }

-  [data-markdown-word][data-markdown-enter] {
+  :is([data-markdown-word], code)[data-markdown-enter] {
    animation: markdown-word-enter 180ms ease-out both;
  }

@@ -347,7 +347,7 @@
 }

@media (prefers-reduced-motion: reduce) {
-  [data-component="markdown"] [data-markdown-word][data-markdown-enter] {
+  [data-component="markdown"] :is([data-markdown-word], code)[data-markdown-enter] {
    animation: none;
  }
 }
@@ -52,3 +52,36 @@ export const StreamingResponse = {
    </div>
  ),
 }
+
+function StreamingInlineCodeMarkdown() {
+  const chunks = [
+    "Updated ",
+    "`apps/cloud",
+    "flare/src/",
+    "editor/Cloud",
+    "Auth.ts:29",
+    "-43` and ",
+    "`packages/",
+    "session-ui/src/",
+    "components/markdown",
+    "-solid.tsx`, ",
+    "then verified ",
+    "the changes with ",
+    "`bun type",
+    "check` and ",
+    "`bun te",
+    "st`.",
+  ]
+  const [count, setCount] = createSignal(1)
+  const timer = setInterval(() => setCount((value) => (value >= chunks.length ? 1 : value + 1)), 220)
+  onCleanup(() => clearInterval(timer))
+  return <Markdown text={chunks.slice(0, count()).join("")} streaming />
+}
+
+export const StreamingInlineCode = {
+  render: () => (
+    <div class="mx-auto max-w-[760px] rounded-lg border border-border-weak-base bg-background-base px-5 py-4">
+      <StreamingInlineCodeMarkdown />
+    </div>
+  ),
+}
@@ -131,6 +131,7 @@ const source = {
  "ui.promptInput.label": "Prompt",
  "ui.promptInput.placeholder.shell": "Enter shell command...",
  "ui.promptInput.placeholder.normal": "Ask anything, {{slash}} for commands, {{at}} for context...",
+  "ui.promptInput.placeholder.followUp": "Add follow-up, {{slash}} for commands, {{at}} for context...",
  "ui.promptInput.add": "Add images and files",
  "ui.promptInput.attachments": "Images and files",
  "ui.promptInput.context": "Context",
@@ -140,6 +141,9 @@ const source = {
  "ui.promptInput.chooseVariant": "Choose model variant",
  "ui.promptInput.send": "Send",
  "ui.promptInput.stop": "Stop",
+  "ui.promptInput.steer": "Steer",
+  "ui.promptInput.queue": "Queue",
+  "ui.promptInput.steerHint": "Send without interrupting",

  "ui.tabs.close": "Close tab",

@@ -2,6 +2,10 @@
 title: "Intro"
 ---

+OpenCode is used by millions every day. Build on top of it to create your own
+applications, integrations, and agent experiences without starting from
+scratch.
+
 <CardGroup cols={1}>
  <Card title="Extend OpenCode" href="/build/plugins">
    Build plugins that add tools, integrations, commands, agents, and custom behavior while keeping the rest of OpenCode
@@ -46,16 +46,6 @@ constructor(state: DurableObjectState) {
 }
 ```

-Configuration is a typed JavaScript object, and plugins are imported values bundled with the Worker.
-
-```ts
-await OpenCodeWorkerd.create({
-  storage: state.storage,
-  config: { default_agent: "build" },
-  plugins: [myPlugin],
-})
-```
-
 Wrangler selects OpenCode's Workerd-safe implementations through the `workerd` package condition. Cloudflare may evict
 a Durable Object without running cleanup, so correctness does not depend on `close()` being called.

@@ -65,17 +55,33 @@ a Durable Object without running cleanup, so correctness does not depend on `clo
 }
 ```

-## Effect
+## Customize

-Use the Effect-native entrypoint from `@opencode-ai/sdk/workerd/effect`.
+Customize your OpenCode instance by registering plugins bundled with your
+Worker. Pass plugins to `OpenCodeWorkerd.create()` to customize agents, models,
+tools, and other behavior:

 ```ts
-import { OpenCodeWorkerd } from "@opencode-ai/sdk/workerd/effect"
-import { Effect } from "effect"
+import { Plugin } from "@opencode-ai/plugin"
+import { OpenCodeWorkerd } from "@opencode-ai/sdk/workerd"

-const program = Effect.scoped(
-  Effect.gen(function* () {
-    return yield* OpenCodeWorkerd.create({ storage: state.storage })
-  }),
-)
+const plugin = Plugin.define({
+  id: "customize-agent",
+  async setup(ctx) {
+    await ctx.agent.transform((agents) => {
+      agents.update("build", (agent) => {
+        agent.description = "Builds features and fixes bugs for our team"
+      })
+    })
+  },
+})
+
+await OpenCodeWorkerd.create({
+  storage: state.storage,
+  config: { default_agent: "build" },
+  plugins: [plugin],
+})
 ```
+
+See the [full plugins documentation](/build/plugins) for plugin hooks,
+transforms, tools, and the complete plugin context.
@@ -56,31 +56,33 @@ yield* opencode.events.subscribe().pipe(
 )
 ```

-## Register plugins
+## Customize

-Register Effect plugins through the embedded host. Their registrations remain scoped to the host.
+Customize your OpenCode instance by registering Effect plugins. Use the embedded
+host to customize agents, models, tools, and other behavior:

 ```ts
 import { Plugin } from "@opencode-ai/plugin/effect"
 import { Effect } from "effect"

 const plugin = Plugin.define({
-  id: "example",
+  id: "customize-agent",
  effect: (ctx) =>
    Effect.gen(function* () {
-      const storage = ctx.storage
-      yield* storage.set("embedded", true)
+      const agent = ctx.agent
+      yield* agent.transform((agents) => {
+        agents.update("build", (agent) => {
+          agent.description = "Builds features and fixes bugs for our team"
+        })
+      })
    }),
 })

 yield* opencode.plugin(plugin)
 ```

-See the [Effect plugins guide](/build/plugins/effect) for the complete plugin context.
-
-```ts
-yield* opencode.plugin.list()
-```
+See the [full Effect plugins documentation](/build/plugins/effect) for plugin
+hooks, transforms, tools, and the complete plugin context.

 ## Layer

@@ -50,25 +50,31 @@ for await (const event of opencode.events.subscribe()) {
 Pass an `AbortSignal` through the generated request options, or leave an
 iteration to cancel its response body.

-## Register plugins
+## Customize

-Pass initial Promise plugins to `OpenCode.create()`. Embedded plugins use the
-same discovery and Location-scoped activation path as configured plugins.
+Customize your OpenCode instance by registering plugins. Pass plugins to
+`OpenCode.create()` to customize agents, models, tools, and other behavior when
+the embedded host starts:

 ```ts
-const plugin = {
-  id: "example",
+import { Plugin } from "@opencode-ai/plugin"
+import { OpenCode } from "@opencode-ai/sdk"
+
+const plugin = Plugin.define({
+  id: "customize-agent",
  async setup(ctx) {
    await ctx.agent.transform((agents) => {
-      // Modify the Location's agent catalog.
+      agents.update("build", (agent) => {
+        agent.description = "Builds features and fixes bugs for our team"
+      })
    })
  },
-}
+})

 await using opencode = await OpenCode.create({ plugins: [plugin] })
 ```

 Call `await opencode.plugin(plugin)` to register another plugin after startup.

-See the [Plugins guide](/build/plugins) for the plugin context and available
-hooks.
+See the [full plugins documentation](/build/plugins) for plugin hooks,
+transforms, tools, and the complete plugin context.
Author	SHA1	Message	Date
Brendan Allan	c92d311161	fix(session-ui): animate appended inline code chunks	2026-08-25 14:07:29 +08:00
Brendan Allan	23faebc5bb	test(session-ui): stream inline code in partial chunks	2026-08-25 14:01:20 +08:00
Brendan Allan	95cbdd7cc9	test(session-ui): demonstrate streamed inline code fade	2026-08-25 13:59:37 +08:00
Brendan Allan	80a22790d0	fix(session-ui): fade in streamed inline code	2026-08-25 13:55:47 +08:00
Aiden Cline	895eff09b0	fix(ai): classify missing chat finish reasons as incomplete (#44864 )	2026-08-24 22:37:47 -05:00
Aiden Cline	d0252f7179	fix(ai): handle completed response function arguments (#44862 )	2026-08-24 22:36:43 -05:00
Aiden Cline	d78c13fce3	refactor(core): normalize tool input errors (#44818 )	2026-08-24 22:23:25 -05:00
Aiden Cline	6bb5200464	fix(ai): enforce chat finish reasons (#44743 )	2026-08-24 22:10:21 -05:00
Luke Parker	a02a2f5799	feat(app): queue and steer follow-up prompts (#44683 )	2026-08-25 13:01:04 +10:00
Aiden Cline	63c23c98de	feat(ai): parse partial tool input (#44830 )	2026-08-24 21:56:53 -05:00
Dax Raad	9a90b94921	docs(sdk): align Effect and Cloudflare customization guides	2026-08-24 22:52:30 -04:00
Dax Raad	f03418afde	docs: improve build and SDK customization guides	2026-08-24 22:52:30 -04:00
opencode-agent[bot]thdxr Dax	19d0009891	docs: clarify prompt data handling (#44854 ) Co-authored-by: thdxr <826656+thdxr@users.noreply.github.com> Co-authored-by: Dax <mail@thdxr.com>	2026-08-24 22:29:36 -04:00