feat(coder): Phase 1-UX backend — agent attribution + agent-sessions route + opencode usage

pending_changes.agent stamped at every queue site (native -> 'boocode', dispatched external -> task.agent, manual RightRail -> NULL) + flows through listPending. New GET /api/sessions/:id/agent-sessions -> [{agent,status,has_session,last_active_at}] per (chat,agent). opencode warm server consumes session.next.step.ended, accumulating input_tokens/output_tokens/cost onto agent_sessions (new idempotent columns) via a pure opencode-usage.ts mapper. Tests: agent-sessions.routes (3) + opencode-usage (6); tsc clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/coder/src/routes/__tests__/agent-sessions.routes.test.ts

@@ -0,0 +1,75 @@
+import { describe, it, expect } from 'vitest';
+import Fastify, { type FastifyInstance } from 'fastify';
+import { registerAgentSessionRoutes } from '../agent-sessions.js';
+import type { Sql } from '../../db.js';
+
+// Mock the porsager surface this route uses: a tagged-template `sql` dispatched by
+// query substring. Two queries: the session-existence check and the agent_sessions
+// JOIN. We return post-coercion shapes (booleans/strings) exactly as porsager would
+// hand them to the route — `has_session` already a JS boolean, `last_active_at` a
+// string|null — so the asserted JSON matches the API contract end-to-end.
+interface MockState {
+  sessionExists: boolean;
+  rows: Array<{ agent: string; status: string; has_session: boolean; last_active_at: string | null }>;
+}
+
+function mockSql(state: MockState): Sql {
+  return ((strings: TemplateStringsArray) => {
+    const q = strings.join('');
+    if (q.includes('SELECT id FROM sessions')) {
+      return Promise.resolve(state.sessionExists ? [{ id: 'session-1' }] : []);
+    }
+    if (q.includes('FROM agent_sessions')) {
+      return Promise.resolve(state.rows);
+    }
+    return Promise.resolve([]);
+  }) as unknown as Sql;
+}
+
+function buildApp(state: MockState): FastifyInstance {
+  const app = Fastify();
+  registerAgentSessionRoutes(app, mockSql(state));
+  return app;
+}
+
+describe('GET /api/sessions/:id/agent-sessions', () => {
+  it('returns the per-(chat,agent) rows in the contracted shape', async () => {
+    const app = buildApp({
+      sessionExists: true,
+      rows: [
+        { agent: 'opencode', status: 'active', has_session: true, last_active_at: '2026-05-31T12:00:00.000Z' },
+        { agent: 'goose', status: 'idle', has_session: false, last_active_at: null },
+      ],
+    });
+    const res = await app.inject({ method: 'GET', url: '/api/sessions/session-1/agent-sessions' });
+    expect(res.statusCode).toBe(200);
+    const body = res.json();
+    expect(Array.isArray(body)).toBe(true);
+    expect(body).toEqual([
+      { agent: 'opencode', status: 'active', has_session: true, last_active_at: '2026-05-31T12:00:00.000Z' },
+      { agent: 'goose', status: 'idle', has_session: false, last_active_at: null },
+    ]);
+    // Contract field types.
+    expect(typeof body[0].agent).toBe('string');
+    expect(typeof body[0].status).toBe('string');
+    expect(typeof body[0].has_session).toBe('boolean');
+    expect(body[1].last_active_at).toBeNull();
+    await app.close();
+  });
+
+  it('returns an empty array when the session has no agent_sessions rows', async () => {
+    const app = buildApp({ sessionExists: true, rows: [] });
+    const res = await app.inject({ method: 'GET', url: '/api/sessions/session-1/agent-sessions' });
+    expect(res.statusCode).toBe(200);
+    expect(res.json()).toEqual([]);
+    await app.close();
+  });
+
+  it('404s when the session does not exist', async () => {
+    const app = buildApp({ sessionExists: false, rows: [] });
+    const res = await app.inject({ method: 'GET', url: '/api/sessions/nope/agent-sessions' });
+    expect(res.statusCode).toBe(404);
+    expect(res.json()).toEqual({ error: 'session not found' });
+    await app.close();
+  });
+});

apps/coder/src/routes/agent-sessions.ts

@@ -0,0 +1,51 @@
+import type { FastifyInstance } from 'fastify';
+import type { Sql } from '../db.js';
+
+// v2.6 Phase 1-UX (design §9b): chat-scoped "resumed vs new session" indicator.
+// `agent_sessions` is keyed (chat_id, agent) — the tab/chat is the agent-context
+// unit (P1.5-b). The route param is a SESSION id, so we resolve every chat in the
+// session and return the union of their agent_sessions rows. A session with two
+// opencode tabs yields two rows (one per chat); the frontend keys the chip per
+// chat, but the wire shape is a flat per-(chat,agent) list.
+//
+// has_session = agent_session_id IS NOT NULL — i.e. a native backend session id
+// (opencode/ACP) was created and stored, so switching back resumes rather than
+// starts fresh.
+export interface AgentSessionRow {
+  agent: string;
+  status: string;
+  has_session: boolean;
+  last_active_at: string | null;
+}
+
+export function registerAgentSessionRoutes(app: FastifyInstance, sql: Sql): void {
+  // GET /api/sessions/:sessionId/agent-sessions — list the agent-session rows for
+  // every chat in the session (drives the AgentComposerBar resumed/new chip).
+  app.get<{ Params: { sessionId: string } }>(
+    '/api/sessions/:sessionId/agent-sessions',
+    async (req, reply) => {
+      const sessionId = req.params.sessionId;
+
+      const session = await sql<{ id: string }[]>`SELECT id FROM sessions WHERE id = ${sessionId}`;
+      if (session.length === 0) {
+        reply.code(404);
+        return { error: 'session not found' };
+      }
+
+      // Join through chats so the session-scoped param resolves to its (chat,agent)
+      // rows. last_active_at first → the frontend reads the freshest activity.
+      const rows = await sql<AgentSessionRow[]>`
+        SELECT
+          a.agent AS agent,
+          a.status AS status,
+          (a.agent_session_id IS NOT NULL) AS has_session,
+          a.last_active_at AS last_active_at
+        FROM agent_sessions a
+        JOIN chats c ON c.id = a.chat_id
+        WHERE c.session_id = ${sessionId}
+        ORDER BY a.last_active_at DESC NULLS LAST, a.agent ASC
+      `;
+      return rows;
+    },
+  );
+}

apps/coder/src/routes/pending.ts

@@ -90,6 +90,8 @@ export function registerPendingRoutes(app: FastifyInstance, sql: Sql): void {
           parsed.data.file_path,
           parsed.data.content,
           projectRoot,
+          // Manual RightRail create — no agent staged it; renders as "manual".
+          null,
         );
         return change;
       } catch (err) {