fix(ai): normalize tool result history

packages/ai/src/route/client.ts

@@ -7,6 +7,7 @@ import { HttpTransport } from "./transport/index.js"
 import type { HttpMiddleware, Transport, TransportRuntime, WebSocketChannelExecutor } from "./transport/index.js"
 import type { Protocol } from "./protocol.js"
 import { applyCachePolicy } from "../cache-policy.js"
+import { normalizeToolHistory } from "../tool-history.js"
 import { sanitizeSurrogates } from "../utils/sanitize.js"
 import * as ProviderShared from "../protocols/shared.js"
 import type { ProtocolID, ProviderOptions } from "../schema/index.js"
@@ -169,17 +170,19 @@ export interface GenerateMethod {
 export class Service extends Context.Service<Service, Interface>()("@opencode/LLMClient") {}
 
 const resolveRequestOptions = (request: LLMRequest) => {
-  const routeDefaults = request.model.route.defaults
-  const modelDefaults = request.model.defaults
-  const generation = mergeGenerationOptions(routeDefaults.generation, modelDefaults?.generation, request.generation)
-  return LLMRequest.update(request, {
+  const messages = normalizeToolHistory(request.messages)
+  const normalized = messages === request.messages ? request : LLMRequest.update(request, { messages })
+  const routeDefaults = normalized.model.route.defaults
+  const modelDefaults = normalized.model.defaults
+  const generation = mergeGenerationOptions(routeDefaults.generation, modelDefaults?.generation, normalized.generation)
+  return LLMRequest.update(normalized, {
     generation: generation ?? new GenerationOptions({}),
     providerOptions: mergeProviderOptions(
       routeDefaults.providerOptions,
       modelDefaults?.providerOptions,
-      request.providerOptions,
+      normalized.providerOptions,
     ),
-    http: mergeHttpOptions(routeDefaults.http, modelDefaults?.http, request.http),
+    http: mergeHttpOptions(routeDefaults.http, modelDefaults?.http, normalized.http),
   })
 }
 

packages/ai/src/tool-history.ts

@@ -0,0 +1,74 @@
+import { Message, ToolResultPart, type ToolCallPart } from "./schema/messages.js"
+
+const EMPTY_TOOL_OUTPUT = "(no tool output)"
+const MISSING_TOOL_RESULT = "Tool result missing"
+
+export function normalizeToolHistory(messages: ReadonlyArray<Message>) {
+  const normalized: Message[] = []
+  const pending = new Map<string, ToolCallPart>()
+  const appendMissingResults = () => {
+    if (pending.size === 0) return
+    normalized.push(missingToolResults(pending.values()))
+    pending.clear()
+  }
+
+  for (const message of messages) {
+    if (message.role === "user" || message.role === "assistant") appendMissingResults()
+
+    if (message.role === "tool") {
+      const tool = normalizeToolMessage(message, pending)
+      if (tool) normalized.push(tool)
+      continue
+    }
+
+    normalized.push(message)
+    if (message.role !== "assistant") continue
+    for (const part of message.content) {
+      if (part.type === "tool-call" && part.providerExecuted !== true) pending.set(part.id, part)
+    }
+  }
+
+  return normalized.length === messages.length && normalized.every((message, index) => message === messages[index])
+    ? messages
+    : normalized
+}
+
+function missingToolResults(calls: Iterable<ToolCallPart>) {
+  return new Message({
+    role: "tool",
+    content: [...calls].map((call) =>
+      ToolResultPart.make({ id: call.id, name: call.name, result: MISSING_TOOL_RESULT, resultType: "error" }),
+    ),
+  })
+}
+
+function normalizeToolMessage(message: Message, pending: Map<string, ToolCallPart>): Message | undefined {
+  const content = message.content.map((part) => {
+    if (part.type !== "tool-result" || part.providerExecuted === true) return part
+    const call = pending.get(part.id)
+    if (call) pending.delete(part.id)
+    return normalizeToolResult(part, call?.name ?? part.name)
+  })
+  if (content.length === 0) return undefined
+  if (content.every((part, index) => part === message.content[index])) return message
+  return new Message({
+    id: message.id,
+    role: message.role,
+    content,
+    metadata: message.metadata,
+    native: message.native,
+  })
+}
+
+function normalizeToolResult(part: ToolResultPart, name: string): ToolResultPart {
+  const named = part.name === name ? part : { ...part, name }
+  if (named.result.type === "text" && named.result.value === "")
+    return { ...named, result: { type: "text", value: EMPTY_TOOL_OUTPUT } }
+  if (named.result.type === "error" && named.result.value === "")
+    return { ...named, result: { type: "error", value: EMPTY_TOOL_OUTPUT } }
+  if (named.result.type !== "content") return named
+  const value = named.result.value.filter((item) => item.type !== "text" || item.text !== "")
+  if (value.length === 0) return { ...named, result: { type: "text", value: EMPTY_TOOL_OUTPUT } }
+  if (value.length === named.result.value.length) return named
+  return { ...named, result: { type: "content", value } }
+}

packages/ai/test/compile.test.ts

@@ -106,6 +106,26 @@ describe("request option precedence", () => {
     }),
   )
 
+  it.effect("normalizes tool history before protocol lowering", () =>
+    Effect.gen(function* () {
+      const prepared = yield* compileRequest(
+        LLM.request({
+          model: OpenAIChat.route.model({ id: "gpt-4o-mini" }),
+          messages: [
+            Message.assistant(ToolCallPart.make({ id: "call_1", name: "lookup", input: {} })),
+            Message.user("Continue."),
+          ],
+        }),
+      )
+
+      expect(prepared.body.messages).toMatchObject([
+        { role: "assistant", tool_calls: [{ id: "call_1", function: { name: "lookup" } }] },
+        { role: "tool", tool_call_id: "call_1", content: "Tool result missing" },
+        { role: "user", content: "Continue." },
+      ])
+    }),
+  )
+
   it.effect("applies model HTTP defaults before request HTTP overlays", () =>
     LLMClient.generate(
       LLM.request({

packages/ai/test/tool-history.test.ts

@@ -0,0 +1,77 @@
+import { describe, expect, test } from "bun:test"
+import { Message, ToolCallPart, ToolResultPart } from "../src/schema/messages.js"
+import { normalizeToolHistory } from "../src/tool-history.js"
+
+const toolCall = (id: string, name = id) => ToolCallPart.make({ id, name, input: {} })
+const toolResult = (id: string, value: unknown, name = id, resultType?: "text" | "content" | "error") =>
+  Message.tool(ToolResultPart.make({ id, name, result: value, resultType }))
+
+describe("tool history normalization", () => {
+  test("fills missing local results before the next step", () => {
+    const normalized = normalizeToolHistory([
+      Message.assistant([toolCall("first"), toolCall("second")]),
+      toolResult("first", "done", "wrong", "text"),
+      Message.user("Continue."),
+      Message.assistant(toolCall("trailing")),
+    ])
+
+    expect(normalized.map((message) => message.role)).toEqual([
+      "assistant",
+      "tool",
+      "tool",
+      "user",
+      "assistant",
+    ])
+    expect(normalized[1]?.content[0]).toMatchObject({ type: "tool-result", id: "first", name: "first" })
+    expect(normalized[2]?.content).toEqual([
+      { type: "tool-result", id: "second", name: "second", result: { type: "error", value: "Tool result missing" } },
+    ])
+    expect(normalized[4]?.content).toEqual([toolCall("trailing")])
+  })
+
+  test("normalizes empty results without changing whitespace or media", () => {
+    const media = { type: "file" as const, uri: "data:image/png;base64,AQID", mime: "image/png" }
+    const normalized = normalizeToolHistory([
+      Message.assistant([
+        toolCall("text"),
+        toolCall("content"),
+        toolCall("error"),
+        toolCall("mixed"),
+        toolCall("whitespace"),
+      ]),
+      toolResult("text", "", "text", "text"),
+      toolResult("content", [], "content", "content"),
+      toolResult("error", "", "error", "error"),
+      toolResult("mixed", [{ type: "text", text: "" }, media], "mixed", "content"),
+      toolResult("whitespace", "   ", "whitespace", "text"),
+    ])
+
+    expect(normalized.slice(1).map((message) => message.content[0])).toEqual([
+      { type: "tool-result", id: "text", name: "text", result: { type: "text", value: "(no tool output)" } },
+      { type: "tool-result", id: "content", name: "content", result: { type: "text", value: "(no tool output)" } },
+      { type: "tool-result", id: "error", name: "error", result: { type: "error", value: "(no tool output)" } },
+      { type: "tool-result", id: "mixed", name: "mixed", result: { type: "content", value: [media] } },
+      { type: "tool-result", id: "whitespace", name: "whitespace", result: { type: "text", value: "   " } },
+    ])
+  })
+
+  test("leaves unmatched and provider-executed history unchanged", () => {
+    const hostedCall = ToolCallPart.make({
+      id: "hosted",
+      name: "web_search",
+      input: {},
+      providerExecuted: true,
+    })
+    const hostedResult = ToolResultPart.make({
+      id: "hosted",
+      name: "web_search",
+      result: "",
+      resultType: "text",
+      providerExecuted: true,
+    })
+    const hosted = Message.assistant([hostedCall, hostedResult])
+    const orphan = toolResult("orphan", "ignored", "orphan", "text")
+
+    expect(normalizeToolHistory([orphan, hosted])).toEqual([orphan, hosted])
+  })
+})