v2.3.2-coder-answer-endpoint: fix ask_user_input submit in CoderPane

The CoderPane runs its own inference runner and broker on the boocoder
service. The AskUserInputCard was calling /api/chats/:id/answer_user_input
on the main BooChat server, which has a different inference runner — the
answer was accepted but the next turn was enqueued on the wrong runner,
so nothing happened.

Fix: register the same answer_user_input endpoint on the boocoder, and
add an apiPrefix prop to AskUserInputCard so the CoderPane routes
through /api/coder/chats/:id/answer_user_input. BooChat's MessageList
continues to use the default (no prefix) path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/coder/src/routes/messages.ts

@@ -5,6 +5,33 @@ import type { Broker } from '@boocode/server/broker';
 import type { WsFrame } from '@boocode/server/ws-frames';
 import { resolveChatId } from './chat-resolve.js';
 
+const AnswerUserInputBody = z.object({
+  tool_call_id: z.string().min(1),
+  answers: z
+    .array(
+      z.object({
+        question: z.string(),
+        selected_options: z.array(z.string()),
+        free_text: z.string().nullable(),
+      }),
+    )
+    .min(1)
+    .max(3),
+});
+
+const AskUserInputArgs = z.object({
+  questions: z
+    .array(
+      z.object({
+        question: z.string(),
+        type: z.enum(['single_select', 'multi_select']),
+        options: z.array(z.string()).min(1),
+      }),
+    )
+    .min(1)
+    .max(3),
+});
+
 const SendBody = z.object({
   content: z.string().min(1).max(64_000),
   pane_id: z.string().min(1).max(200),
@@ -219,6 +246,138 @@ export function registerMessageRoutes(
     },
   );
 
+  // POST /api/chats/:id/answer_user_input — answer a pending ask_user_input
+  app.post<{ Params: { id: string } }>(
+    '/api/chats/:id/answer_user_input',
+    async (req, reply) => {
+      const parsed = AnswerUserInputBody.safeParse(req.body);
+      if (!parsed.success) {
+        reply.code(400);
+        return { error: 'invalid_body', details: parsed.error.flatten() };
+      }
+      const { tool_call_id, answers } = parsed.data;
+
+      const chatRows = await sql<{ id: string; session_id: string }[]>`
+        SELECT id, session_id FROM chats WHERE id = ${req.params.id} AND status = 'open'
+      `;
+      if (chatRows.length === 0) {
+        reply.code(404);
+        return { error: 'chat_not_found' };
+      }
+      const chat = chatRows[0]!;
+      const sessionId = chat.session_id;
+
+      const callerRows = await sql<{
+        message_id: string;
+        payload: { id: string; name: string; args: Record<string, unknown> };
+      }[]>`
+        SELECT p.message_id, p.payload
+        FROM message_parts p
+        JOIN messages m ON m.id = p.message_id
+        WHERE m.chat_id = ${chat.id}
+          AND m.role = 'assistant'
+          AND p.kind = 'tool_call'
+          AND p.payload->>'id' = ${tool_call_id}
+        ORDER BY m.created_at DESC
+        LIMIT 1
+      `;
+      if (!callerRows[0]) {
+        reply.code(404);
+        return { error: 'unknown_tool_call_id' };
+      }
+      const foundCall = callerRows[0].payload;
+      if (foundCall.name !== 'ask_user_input') {
+        reply.code(400);
+        return { error: 'tool_call_not_ask_user_input' };
+      }
+
+      const argsParsed = AskUserInputArgs.safeParse(foundCall.args);
+      if (!argsParsed.success) {
+        reply.code(400);
+        return { error: 'mismatched_answer_shape', detail: 'tool_call args invalid' };
+      }
+      const questions = argsParsed.data.questions;
+      if (answers.length !== questions.length) {
+        reply.code(400);
+        return { error: 'mismatched_answer_shape', detail: `expected ${questions.length} answer(s), got ${answers.length}` };
+      }
+      for (let i = 0; i < questions.length; i++) {
+        const q = questions[i]!;
+        const a = answers[i]!;
+        for (const sel of a.selected_options) {
+          if (!q.options.includes(sel)) {
+            reply.code(400);
+            return { error: 'mismatched_answer_shape', detail: `answer ${i + 1} option not in question: ${sel}` };
+          }
+        }
+        if (q.type === 'single_select' && a.selected_options.length > 1) {
+          reply.code(400);
+          return { error: 'mismatched_answer_shape', detail: `answer ${i + 1} multi on single_select` };
+        }
+        if (a.selected_options.length === 0 && (!a.free_text || !a.free_text.trim())) {
+          reply.code(400);
+          return { error: 'mismatched_answer_shape', detail: `answer ${i + 1} is empty` };
+        }
+      }
+
+      const toolRows = await sql<{
+        message_id: string;
+        payload: { tool_call_id: string; output: unknown };
+      }[]>`
+        SELECT p.message_id, p.payload
+        FROM message_parts p
+        JOIN messages m ON m.id = p.message_id
+        WHERE m.chat_id = ${chat.id}
+          AND m.role = 'tool'
+          AND p.kind = 'tool_result'
+          AND p.payload->>'tool_call_id' = ${tool_call_id}
+        ORDER BY m.created_at DESC
+        LIMIT 1
+      `;
+      if (!toolRows[0]) {
+        reply.code(404);
+        return { error: 'unknown_tool_call_id', detail: 'tool message not found' };
+      }
+      if (toolRows[0].payload?.output !== null) {
+        reply.code(409);
+        return { error: 'tool_call_already_answered' };
+      }
+
+      const answerSet = { answers };
+      const newToolResults = { tool_call_id, output: answerSet, truncated: false };
+      const toolMessageId = toolRows[0].message_id;
+
+      const result = await sql.begin(async (tx) => {
+        await tx`DELETE FROM message_parts WHERE message_id = ${toolMessageId} AND kind = 'tool_result'`;
+        await tx`
+          INSERT INTO message_parts (message_id, sequence, kind, payload)
+          VALUES (${toolMessageId}, 0, 'tool_result', ${tx.json(newToolResults as never)})
+        `;
+        const [assistantMsg] = await tx<{ id: string }[]>`
+          INSERT INTO messages (session_id, chat_id, role, content, status, created_at)
+          VALUES (${sessionId}, ${chat.id}, 'assistant', '', 'streaming', clock_timestamp())
+          RETURNING id
+        `;
+        await tx`UPDATE sessions SET updated_at = clock_timestamp() WHERE id = ${sessionId}`;
+        await tx`UPDATE chats SET updated_at = clock_timestamp() WHERE id = ${chat.id}`;
+        return { tool_message_id: toolMessageId, assistant_message_id: assistantMsg!.id };
+      });
+
+      broker.publishFrame(sessionId, {
+        type: 'tool_result',
+        tool_message_id: result.tool_message_id,
+        tool_call_id,
+        chat_id: chat.id,
+        output: answerSet,
+        truncated: false,
+      } as unknown as WsFrame);
+      inference.enqueue(sessionId, chat.id, result.assistant_message_id, 'default');
+
+      reply.code(202);
+      return result;
+    },
+  );
+
   // POST /api/sessions/:sessionId/stop — cancel active inference
   app.post<{ Params: { sessionId: string } }>(
     '/api/sessions/:sessionId/stop',