fix(btw): strip replayed tool calls from side-question context

src/agents/btw.test.ts

@@ -581,4 +581,64 @@ describe("runBtwSideQuestion", () => {
       expect.arrayContaining([expect.objectContaining({ role: "toolResult" })]),
     );
   });
+
+  it("strips assistant tool calls from BTW context so no-tool side questions stay tool-free", async () => {
+    getActiveEmbeddedRunSnapshotMock.mockReturnValue({
+      transcriptLeafId: "assistant-1",
+      messages: [
+        {
+          role: "user",
+          content: [{ type: "text", text: "seed" }],
+          timestamp: 1,
+        },
+        {
+          role: "assistant",
+          content: [
+            { type: "text", text: "Let me check." },
+            { type: "toolCall", id: "call_1", name: "read", arguments: { path: "README.md" } },
+            { type: "toolUse", id: "call_legacy", name: "read", input: { path: "README.md" } },
+          ],
+          provider: DEFAULT_PROVIDER,
+          api: "anthropic-messages",
+          model: DEFAULT_MODEL,
+          stopReason: "toolUse",
+          usage: {
+            input: 1,
+            output: 2,
+            cacheRead: 0,
+            cacheWrite: 0,
+            totalTokens: 3,
+            cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+          },
+          timestamp: 2,
+        },
+      ],
+    });
+    mockDoneAnswer(MATH_ANSWER);
+
+    await runMathSideQuestion();
+
+    const [, context] = streamSimpleMock.mock.calls[0] ?? [];
+    expect(context).toMatchObject({
+      messages: [
+        expect.objectContaining({ role: "user" }),
+        expect.objectContaining({
+          role: "assistant",
+          content: [{ type: "text", text: "Let me check." }],
+        }),
+        expect.objectContaining({ role: "user" }),
+      ],
+    });
+    expect(
+      (context as { messages?: Array<{ role?: string; content?: Array<{ type?: string }> }> })
+        .messages,
+    ).not.toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          role: "assistant",
+          content: expect.arrayContaining([expect.objectContaining({ type: "toolCall" })]),
+        }),
+      ]),
+    );
+  });
 });

src/agents/btw.ts

@@ -83,13 +83,48 @@ function buildBtwQuestionPrompt(question: string, inFlightPrompt?: string): stri
   return lines.join("\n");
 }
 
+const BTW_TOOL_BLOCK_TYPES = new Set(["toolCall", "toolUse", "functionCall"]);
+
+function sanitizeBtwAssistantMessage(
+  message: Extract<Message, { role: "assistant" }>,
+): Extract<Message, { role: "assistant" }> | undefined {
+  const originalContent = Array.isArray(message.content) ? message.content : [];
+  const content = originalContent.filter((block) => {
+    if (!block || typeof block !== "object") {
+      return true;
+    }
+    return !BTW_TOOL_BLOCK_TYPES.has((block as { type?: unknown }).type as string);
+  });
+  if (content.length === originalContent.length) {
+    return message;
+  }
+  if (content.length === 0) {
+    return undefined;
+  }
+  return {
+    ...message,
+    content,
+  };
+}
+
 function toSimpleContextMessages(messages: unknown[]): Message[] {
-  const contextMessages = messages.filter((message): message is Message => {
+  const contextMessages = messages.flatMap((message): Message[] => {
     if (!message || typeof message !== "object") {
-      return false;
+      return [];
     }
     const role = (message as { role?: unknown }).role;
-    return role === "user" || role === "assistant";
+    if (role === "user") {
+      return [message as Extract<Message, { role: "user" }>];
+    }
+    if (role !== "assistant") {
+      return [];
+    }
+    // BTW is a no-tools path, so strip replay-only tool calls from assistant
+    // context before handing history to strict providers like Bedrock.
+    const sanitizedMessage = sanitizeBtwAssistantMessage(
+      message as Extract<Message, { role: "assistant" }>,
+    );
+    return sanitizedMessage ? [sanitizedMessage] : [];
   });
   return stripToolResultDetails(
     contextMessages as Parameters<typeof stripToolResultDetails>[0],