docs(changelog): v2.6.9-warm-acp

CHANGELOG + roadmap (through v2.6.9) + openspec v2-6 Phase 2 checked off (2.1-2.4; Smoke 2/2b pending live).

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

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 All notable changes per release tag. Most recent on top, ordered by tag creation date (which matches the git history). Tag names follow `vMAJOR.MINOR.PATCH-slug` — the slug describes what shipped, so the tag name alone is enough to recall the batch.
 
+## v2.6.9-warm-acp — 2026-05-31
+
+v2.6 Phase 2: goose and qwen now run as **warm ACP backends** instead of one-shot-per-task. A new `WarmAcpBackend` (`backends/warm-acp.ts`, implementing the same `AgentBackend` interface as the opencode warm server) holds one persistent `goose acp` / `qwen --acp` child + `ClientSideConnection` + ACP session per `(chat, agent)`, running `initialize` + `session/new` once and reusing the connection across turns; per-turn abort cancels the in-flight prompt (`session/cancel`) without killing the child, and a child exit marks `agent_sessions.status='crashed'` for re-spawn on the next turn. The dispatcher routes `goose`/`qwen` chat-tab tasks to the pooled warm backend via a pure `shouldUseWarmBackend(task)` predicate (warm only when both `session_id` and `chat_id` are set), keeping the one-shot `runExternalAgent` path as the fallback for session-less creators (arena, MCP, `new_task`); broker frames + `persistExternalAgentTurn` + the latest-wins `pending_changes` diff are identical to the opencode path. The `acp-dispatch.ts` `handleSessionUpdate` switch was extracted into a pure shared `acp-event-map.ts` mapper used by both the one-shot and warm paths (one-shot behavior byte-identical, all existing acp tests green). The design's `unstable_resumeSession` concern is resolved — the installed `@agentclientprotocol/sdk@^0.22.1` exposes stable `resumeSession`/`loadSession`, but resume is moot in the hot path (warm reuse needs none); cross-restart resume + idle eviction are deferred to Phase 3. Built test-first (15 new tests: `warm-acp-routing`, `acp-event-map`); 180 coder tests pass, tsc + build clean. **Smoke 2/2b (live two-message warm reuse + the opencode→boocode→opencode switch round-trip) to be run post-deploy.** Phase 3 (lifecycle hardening) is the last v2.6 phase.
+
+## v2.6.8-agent-attribution — 2026-05-31
+
+v2.6 Phase 1-UX: agent attribution + switch affordances over the already-shipped `pending_changes.agent` column and `agent_sessions` table (read+display, no new backend capability). **Backend:** `pending_changes.agent` is now stamped at every queue site (native write tools → `'boocode'`, dispatched external agents → the task's agent, manual RightRail create → `NULL`) and flows through `listPending`; a new `GET /api/sessions/:id/agent-sessions` route returns `[{agent,status,has_session,last_active_at}]` per `(chat,agent)` for the session's chats; and the opencode warm-server backend consumes opencode's `session.next.step.ended` events, accumulating `input_tokens`/`output_tokens`/`cost` onto the `agent_sessions` row (new columns, idempotent). **Frontend:** the BooCoder DiffPanel renders a per-row agent badge (provider icon + label; `null` → "manual") with a "Changes from X, Y" note when a pending set spans multiple agents, and the AgentComposerBar shows a resumed / history / new-session chip beside the Provider picker — gated on an optional `sessionId` prop so BooChat is unaffected — driven by a new `useAgentSessions` hook that refetches on message-complete; `providerIcon` was extracted to a shared `components/coder/providerIcons.tsx`. Built by three parallel subagents over disjoint file sets; web + coder typecheck clean, 165 coder tests pass (9 new across `opencode-usage` and `agent-sessions.routes`). U.6's persisted token totals are conversation-cumulative and not yet surfaced in the UI (deferred). Implements the U.1–U.6 "remaining" plan from the v2.6 openspec reconciliation; Phase 2 (warm ACP goose/qwen) + Phase 3 (lifecycle hardening) remain.
+
 ## v2.6.7-interrupt-guard — 2026-05-31
 
 Fixes a post-interrupt correctness bug in the `v2.6.1-phase1-opencode` warm-server backend, made one-click reachable by `v2.6.5-panes-tabs-composer`'s Send→Stop composer. `opencode-server.ts` settled an in-flight turn on opencode's `session.idle`/`session.error` by calling `activeTurn.settle()` on whatever turn currently held the session slot — but opencode emits one trailing terminal event for a *cancelled* turn after `client.session.abort()`, and those events carry only a `sessionID` (no turn id). So after the user hit Stop and immediately sent another message, the aborted turn's orphan `session.idle` settled the *new* turn early as success (Paseo hit and fixed the same class in `1d38aac`). The fix adds a small pure guard (`turn-guard.ts`: `armAbortGuard`/`noteTurnActivity`/`consumeTerminal` over a per-session `swallowNextTerminal` flag): abort arms it, the next terminal is swallowed once, and a new turn's first delta self-heals the flag so a never-arriving orphan can't strand a real turn. Implemented test-first — three regression tests in `turn-guard.test.ts` (swallow-the-orphan, settle-when-no-abort, self-heal); full coder suite green (156 passed). This is the F.1 "fix-next" item from the v2.6 openspec reconciliation; Phase 1-UX / Phase 2 / Phase 3 remain.

apps/coder/src/index.ts

@@ -25,6 +25,7 @@ import { setInferenceContext, clearInferenceContext } from './services/tools/inf
 import { registerMessageRoutes } from './routes/messages.js';
 import { registerSkillRoutes } from './routes/skills.js';
 import { registerPendingRoutes } from './routes/pending.js';
+import { registerAgentSessionRoutes } from './routes/agent-sessions.js';
 import { registerTaskRoutes } from './routes/tasks.js';
 import { registerInboxRoutes } from './routes/inbox.js';
 import { registerStatsRoutes } from './routes/stats.js';
@@ -191,6 +192,7 @@ async function main() {
   registerMessageRoutes(app, sql, broker, inferenceApi);
   registerSkillRoutes(app, sql, broker, inferenceApi);
   registerPendingRoutes(app, sql);
+  registerAgentSessionRoutes(app, sql);
   registerTaskRoutes(app, sql, inferenceApi);
   registerInboxRoutes(app, sql);
   registerStatsRoutes(app, sql);

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) {

apps/coder/src/schema.sql

@@ -131,6 +131,17 @@ END $$;
 -- v2.6: config fingerprint for stale-session detection (auto-recover on model change).
 ALTER TABLE agent_sessions ADD COLUMN IF NOT EXISTS config_hash TEXT;
 
+-- v2.6 Phase 1-UX (U.6): opencode token/cost usage, ACCUMULATED per (chat_id, agent).
+-- opencode's warm server emits `session.next.step.ended` once per LLM step (several
+-- per multi-tool turn) carrying {tokens{input,output,reasoning,cache},cost}. We sum
+-- each step's normalized {input,output,cost} onto the session row — running totals
+-- for the whole conversation context, not last-step. Backend-only; no route/UI yet.
+-- input_tokens folds in cache read+write; output_tokens folds in reasoning (see
+-- backends/opencode-usage.ts). Defaults 0 so accumulation (col + delta) is well-defined.
+ALTER TABLE agent_sessions ADD COLUMN IF NOT EXISTS input_tokens BIGINT NOT NULL DEFAULT 0;
+ALTER TABLE agent_sessions ADD COLUMN IF NOT EXISTS output_tokens BIGINT NOT NULL DEFAULT 0;
+ALTER TABLE agent_sessions ADD COLUMN IF NOT EXISTS cost DOUBLE PRECISION NOT NULL DEFAULT 0;
+
 -- ─── P1.5-b (corrected): worktrees entity + re-key agent_sessions to (chat_id, agent) ───
 -- The TAB (a chat) is the context unit: two opencode tabs in one session = two
 -- independent contexts sharing one worktree. So agent_sessions keys on

apps/coder/src/services/__tests__/acp-event-map.test.ts

@@ -0,0 +1,110 @@
+import { describe, it, expect } from 'vitest';
+import type { SessionNotification } from '@agentclientprotocol/sdk';
+import { mapSessionUpdate } from '../acp-event-map.js';
+import type { AcpToolSnapshot } from '../acp-tool-snapshot.js';
+
+/**
+ * Pure event-mapping shared by the one-shot ACP dispatch (AcpStreamContext) and
+ * the warm ACP backend (Phase 2). Mirrors the original handleSessionUpdate switch
+ * verbatim but returns normalized AgentEvents instead of publishing broker frames.
+ */
+describe('mapSessionUpdate (shared ACP event mapping)', () => {
+  function note(update: SessionNotification['update']): SessionNotification {
+    return { sessionId: 's1', update };
+  }
+
+  it('maps an agent_message_chunk text → a text event', () => {
+    const events = mapSessionUpdate(
+      note({ sessionUpdate: 'agent_message_chunk', content: { type: 'text', text: 'hello' } }),
+    );
+    expect(events).toEqual([{ type: 'text', text: 'hello' }]);
+  });
+
+  it('maps an agent_thought_chunk text → a reasoning event', () => {
+    const events = mapSessionUpdate(
+      note({ sessionUpdate: 'agent_thought_chunk', content: { type: 'text', text: 'thinking' } }),
+    );
+    expect(events).toEqual([{ type: 'reasoning', text: 'thinking' }]);
+  });
+
+  it('ignores non-text content on message/thought chunks', () => {
+    const img = mapSessionUpdate(
+      note({
+        sessionUpdate: 'agent_message_chunk',
+        content: { type: 'image', data: 'x', mimeType: 'image/png' },
+      } as never),
+    );
+    expect(img).toEqual([]);
+  });
+
+  it('maps a tool_call → a tool_call event with a merged snapshot', () => {
+    const events = mapSessionUpdate(
+      note({
+        sessionUpdate: 'tool_call',
+        toolCallId: 't1',
+        title: 'read_file',
+        status: 'pending',
+        rawInput: { path: 'a.ts' },
+      } as never),
+    );
+    expect(events).toHaveLength(1);
+    expect(events[0]!.type).toBe('tool_call');
+    const snap = (events[0] as { type: 'tool_call'; toolCall: AcpToolSnapshot }).toolCall;
+    expect(snap.toolCallId).toBe('t1');
+    expect(snap.title).toBe('read_file');
+    expect(snap.status).toBe('pending');
+    expect(snap.rawInput).toEqual({ path: 'a.ts' });
+  });
+
+  it('maps a tool_call_update → a tool_update event merged over the prior snapshot', () => {
+    const prior = new Map<string, AcpToolSnapshot>([
+      ['t1', { toolCallId: 't1', title: 'read_file', status: 'pending', rawInput: { path: 'a.ts' } }],
+    ]);
+    const events = mapSessionUpdate(
+      note({
+        sessionUpdate: 'tool_call_update',
+        toolCallId: 't1',
+        status: 'completed',
+        rawOutput: 'file body',
+      } as never),
+      prior,
+    );
+    expect(events).toHaveLength(1);
+    expect(events[0]!.type).toBe('tool_update');
+    const snap = (events[0] as { type: 'tool_update'; toolCall: AcpToolSnapshot }).toolCall;
+    expect(snap.toolCallId).toBe('t1');
+    // merged: title carried from prior, status updated, output added, input retained
+    expect(snap.title).toBe('read_file');
+    expect(snap.status).toBe('completed');
+    expect(snap.rawOutput).toBe('file body');
+    expect(snap.rawInput).toEqual({ path: 'a.ts' });
+  });
+
+  it('maps available_commands_update → a commands event', () => {
+    const events = mapSessionUpdate(
+      note({
+        sessionUpdate: 'available_commands_update',
+        availableCommands: [
+          { name: 'plan', description: 'make a plan' },
+          { name: 'review', description: null },
+        ],
+      } as never),
+    );
+    expect(events).toEqual([
+      {
+        type: 'commands',
+        commands: [
+          { name: 'plan', description: 'make a plan' },
+          { name: 'review', description: undefined },
+        ],
+      },
+    ]);
+  });
+
+  it('returns [] for unhandled update kinds (plan, mode change)', () => {
+    expect(mapSessionUpdate(note({ sessionUpdate: 'plan', entries: [] } as never))).toEqual([]);
+    expect(
+      mapSessionUpdate(note({ sessionUpdate: 'current_mode_update', currentModeId: 'code' } as never)),
+    ).toEqual([]);
+  });
+});

apps/coder/src/services/acp-dispatch.ts

@@ -32,9 +32,9 @@ import { createAcpNdJsonStream } from './acp-stream.js';
 import { waitForPermissionResponse, waitForElicitationResponse, cancelPendingPermission } from './permission-waiter.js';
 import { mergeTaskCommands, getTaskCommands } from './agent-commands-cache.js';
 import { readWorktreeTextFile, writeWorktreeTextFile } from './acp-client-fs.js';
+import { mapSessionUpdate } from './acp-event-map.js';
 import {
   type AcpToolSnapshot,
-  mergeToolSnapshot,
   snapshotToWireToolCall,
   synthesizeCanceledSnapshots,
 } from './acp-tool-snapshot.js';
@@ -159,63 +159,47 @@ class AcpStreamContext {
     } as WsFrame);
   }
 
-  handleToolUpdate(toolCallId: string, update: Parameters<typeof mergeToolSnapshot>[1]): void {
-    const previous = this.toolSnapshots.get(toolCallId);
-    const snapshot = mergeToolSnapshot(toolCallId, update, previous);
-    this.toolSnapshots.set(toolCallId, snapshot);
-    this.publishToolSnapshot(snapshot);
-  }
-
   async handleSessionUpdate(params: SessionNotification): Promise<void> {
-    const update = params.update;
+    // v2.6 Phase 2: the case-by-case mapping now lives in the shared, pure
-    switch (update.sessionUpdate) {
+    // `mapSessionUpdate` (reused by the warm ACP backend). This method keeps the
-      case 'agent_message_chunk': {
+    // identical broker-publishing side effects — it just translates the normalized
-        const content = update.content;
+    // AgentEvents back into the same frames it always emitted. `this.toolSnapshots`
-        if (content.type === 'text' && 'text' in content) {
+    // is the merge accumulator, so a later tool_call_update merges over its
-          const text = (content as { text: string }).text;
+    // tool_call (the prior `handleToolUpdate` behavior, byte-for-byte).
-          this.textChunks.push(text);
+    for (const event of mapSessionUpdate(params, this.toolSnapshots)) {
+      switch (event.type) {
+        case 'text':
+          this.textChunks.push(event.text);
           if (this.canStream()) {
             this.opts.broker!.publishFrame(this.opts.sessionId!, {
               type: 'delta',
               message_id: this.opts.messageId!,
               chat_id: this.opts.chatId!,
-              content: text,
+              content: event.text,
             } as WsFrame);
           }
-        }
           break;
-      }
+        case 'reasoning':
-      case 'agent_thought_chunk': {
+          this.reasoningChunks.push(event.text);
-        const content = update.content;
-        if (content.type === 'text' && 'text' in content) {
-          const text = (content as { text: string }).text;
-          this.reasoningChunks.push(text);
           if (this.canStream()) {
             this.opts.broker!.publishFrame(this.opts.sessionId!, {
               type: 'reasoning_delta',
               message_id: this.opts.messageId!,
               chat_id: this.opts.chatId!,
-              content: text,
+              content: event.text,
             } as WsFrame);
           }
-        }
           break;
-      }
         case 'tool_call':
-        this.handleToolUpdate(update.toolCallId, update);
+        case 'tool_update':
+          // mapSessionUpdate already stored the merged snapshot in this.toolSnapshots.
+          this.publishToolSnapshot(event.toolCall);
           break;
-      case 'tool_call_update':
+        case 'commands':
-        this.handleToolUpdate(update.toolCallId, update);
+          if (this.opts.taskId && event.commands.length > 0) {
-        break;
+            mergeTaskCommands(this.opts.taskId, event.commands);
-      case 'available_commands_update': {
-        const commands = update.availableCommands.map((cmd) => ({
-          name: cmd.name,
-          description: cmd.description ?? undefined,
-        }));
-        if (this.opts.taskId && commands.length > 0) {
-          mergeTaskCommands(this.opts.taskId, commands);
             if (this.canStream() && this.opts.sessionId) {
-            const all = getTaskCommands(this.opts.taskId) ?? commands;
+              const all = getTaskCommands(this.opts.taskId) ?? event.commands;
               this.opts.broker!.publishFrame(this.opts.sessionId, {
                 type: 'agent_commands',
                 task_id: this.opts.taskId,
@@ -226,8 +210,6 @@ class AcpStreamContext {
           }
           break;
       }
-      default:
-        break;
     }
   }
 

apps/coder/src/services/acp-event-map.ts

@@ -0,0 +1,68 @@
+/**
+ * Shared ACP session-update → normalized AgentEvent mapping.
+ *
+ * Extracted verbatim (v2.6 Phase 2) from `AcpStreamContext.handleSessionUpdate`
+ * in `acp-dispatch.ts` so the warm ACP backend (`backends/warm-acp.ts`) and the
+ * one-shot dispatch share ONE mapping. The one-shot path translates the returned
+ * events into broker frames itself (preserving its prior behavior byte-for-byte);
+ * the warm backend forwards them to the dispatcher's `ctx.onEvent` exactly like
+ * the opencode-server backend does. No I/O, no broker — pure, so it's unit-testable.
+ *
+ * Spec: openspec/changes/v2-6-persistent-agent-sessions/design.md §2b.
+ */
+import type { SessionNotification } from '@agentclientprotocol/sdk';
+import type { AgentEvent } from './agent-backend.js';
+import { type AcpToolSnapshot, mergeToolSnapshot } from './acp-tool-snapshot.js';
+
+/**
+ * Map one ACP `session/update` notification to zero-or-more normalized AgentEvents.
+ *
+ * `priorSnapshots` is the caller-owned tool-call snapshot accumulator (toolCallId →
+ * snapshot). For `tool_call` / `tool_call_update` the merged snapshot is written
+ * back into it (mutated in place, mirroring `AcpStreamContext.handleToolUpdate`)
+ * so a later `tool_call_update` merges over the earlier `tool_call`. Pass an empty
+ * Map for a stateless single call.
+ *
+ * Returns an array (never throws) so the caller can splat it onto `onEvent`.
+ */
+export function mapSessionUpdate(
+  params: SessionNotification,
+  priorSnapshots: Map<string, AcpToolSnapshot> = new Map(),
+): AgentEvent[] {
+  const update = params.update;
+  switch (update.sessionUpdate) {
+    case 'agent_message_chunk': {
+      const content = update.content;
+      if (content.type === 'text' && 'text' in content) {
+        return [{ type: 'text', text: (content as { text: string }).text }];
+      }
+      return [];
+    }
+    case 'agent_thought_chunk': {
+      const content = update.content;
+      if (content.type === 'text' && 'text' in content) {
+        return [{ type: 'reasoning', text: (content as { text: string }).text }];
+      }
+      return [];
+    }
+    case 'tool_call': {
+      const snapshot = mergeToolSnapshot(update.toolCallId, update, priorSnapshots.get(update.toolCallId));
+      priorSnapshots.set(update.toolCallId, snapshot);
+      return [{ type: 'tool_call', toolCall: snapshot }];
+    }
+    case 'tool_call_update': {
+      const snapshot = mergeToolSnapshot(update.toolCallId, update, priorSnapshots.get(update.toolCallId));
+      priorSnapshots.set(update.toolCallId, snapshot);
+      return [{ type: 'tool_update', toolCall: snapshot }];
+    }
+    case 'available_commands_update': {
+      const commands = update.availableCommands.map((cmd) => ({
+        name: cmd.name,
+        description: cmd.description ?? undefined,
+      }));
+      return [{ type: 'commands', commands }];
+    }
+    default:
+      return [];
+  }
+}

apps/coder/src/services/agent-backend.ts

@@ -70,6 +70,12 @@ export interface PromptCtx {
   model: string;
   signal: AbortSignal;
   onEvent: (e: AgentEvent) => void;
+  /** Phase 2: per-turn task id, so a warm ACP backend can route permission /
+   *  elicitation prompts back to the UI via the permission-waiter. Optional —
+   *  the opencode-server backend (autonomous) ignores it. */
+  taskId?: string;
+  /** Phase 2: per-turn mode id (gates autonomous mode in the permission-waiter). */
+  modeId?: string;
 }
 
 /** Result of a completed turn (§2). Diff/persist happen outside the backend. */

apps/coder/src/services/backends/__tests__/opencode-usage.test.ts

@@ -0,0 +1,51 @@
+import { describe, it, expect } from 'vitest';
+import { stepEndedToUsage } from '../opencode-usage.js';
+
+describe('stepEndedToUsage (U.6)', () => {
+  it('folds cache read+write into input and reasoning into output', () => {
+    const u = stepEndedToUsage({
+      cost: 0.0123,
+      tokens: { input: 100, output: 50, reasoning: 20, cache: { read: 10, write: 5 } },
+    });
+    expect(u).toEqual({ input: 115, output: 70, cost: 0.0123 });
+  });
+
+  it('handles a step with no cache and no reasoning', () => {
+    const u = stepEndedToUsage({
+      cost: 0,
+      tokens: { input: 8, output: 4, reasoning: 0, cache: { read: 0, write: 0 } },
+    });
+    expect(u).toEqual({ input: 8, output: 4, cost: 0 });
+  });
+
+  it('is defensive against a missing tokens block', () => {
+    const u = stepEndedToUsage({ cost: 0.5 } as never);
+    expect(u).toEqual({ input: 0, output: 0, cost: 0.5 });
+  });
+
+  it('is defensive against undefined props', () => {
+    expect(stepEndedToUsage(undefined)).toEqual({ input: 0, output: 0, cost: 0 });
+  });
+
+  it('drops NaN / negative noise to zero rather than poisoning the accumulated total', () => {
+    const u = stepEndedToUsage({
+      cost: Number.NaN,
+      tokens: {
+        input: -5,
+        output: Number.NaN,
+        reasoning: 3,
+        cache: { read: Number.POSITIVE_INFINITY, write: 2 },
+      },
+    });
+    // input: (-5→0) + (Inf→0) + 2 = 2; output: (NaN→0) + 3 = 3; cost: NaN→0
+    expect(u).toEqual({ input: 2, output: 3, cost: 0 });
+  });
+
+  it('rounds fractional token counts', () => {
+    const u = stepEndedToUsage({
+      cost: 1.5,
+      tokens: { input: 10.6, output: 4.4, reasoning: 0, cache: { read: 0, write: 0 } },
+    });
+    expect(u).toEqual({ input: 11, output: 4, cost: 1.5 });
+  });
+});

apps/coder/src/services/backends/__tests__/warm-acp-routing.test.ts

@@ -0,0 +1,59 @@
+import { describe, it, expect } from 'vitest';
+import { shouldUseWarmBackend, isTurnOkForStopReason } from '../warm-acp-routing.js';
+
+/**
+ * Phase 2 routing predicate: which goose/qwen tasks go to the warm pool backend
+ * vs the existing one-shot ACP path.
+ *
+ * The warm backend is keyed (chat_id, agent) — the persistent context unit (same
+ * as opencode-server). A task only routes warm when it carries BOTH a session_id
+ * and a chat_id, i.e. it originates from a real chat tab (the coder message route
+ * stamps both). Session-less creators (arena, MCP-created, generic /api/tasks,
+ * new_task) lack chat_id/session_id and keep the one-shot worktree-per-task path,
+ * which never spawns a warm process.
+ */
+describe('shouldUseWarmBackend (Phase 2 routing)', () => {
+  it('routes a chat-tab task (session_id + chat_id) to the warm backend', () => {
+    expect(shouldUseWarmBackend({ agent: 'qwen', session_id: 's1', chat_id: 'c1' })).toBe(true);
+    expect(shouldUseWarmBackend({ agent: 'goose', session_id: 's1', chat_id: 'c1' })).toBe(true);
+  });
+
+  it('keeps a session-less arena/MCP task on the one-shot path', () => {
+    expect(shouldUseWarmBackend({ agent: 'qwen', session_id: null, chat_id: null })).toBe(false);
+  });
+
+  it('keeps a task with a session but no chat on the one-shot path', () => {
+    // chat_id is the warm-key half; without it ensureSession would get a degenerate
+    // (null, agent) key, so fall back to one-shot rather than synthesize a chat.
+    expect(shouldUseWarmBackend({ agent: 'goose', session_id: 's1', chat_id: null })).toBe(false);
+  });
+
+  it('keeps a task with a chat but no session on the one-shot path', () => {
+    expect(shouldUseWarmBackend({ agent: 'qwen', session_id: null, chat_id: 'c1' })).toBe(false);
+  });
+
+  it('only applies to warm-capable agents (goose, qwen); others never warm here', () => {
+    // opencode has its own dedicated warm path; native/claude/etc. are not ACP-warm.
+    expect(shouldUseWarmBackend({ agent: 'opencode', session_id: 's1', chat_id: 'c1' })).toBe(false);
+    expect(shouldUseWarmBackend({ agent: 'claude', session_id: 's1', chat_id: 'c1' })).toBe(false);
+    expect(shouldUseWarmBackend({ agent: null, session_id: 's1', chat_id: 'c1' })).toBe(false);
+  });
+});
+
+describe('isTurnOkForStopReason (ACP stop-reason → ok/fail)', () => {
+  it('treats normal completions as ok', () => {
+    expect(isTurnOkForStopReason('end_turn')).toBe(true);
+    expect(isTurnOkForStopReason('max_tokens')).toBe(true);
+    expect(isTurnOkForStopReason('max_turn_requests')).toBe(true);
+  });
+
+  it('treats refusal and cancelled as failures', () => {
+    expect(isTurnOkForStopReason('refusal')).toBe(false);
+    expect(isTurnOkForStopReason('cancelled')).toBe(false);
+  });
+
+  it('defaults an absent stop reason to a successful end_turn', () => {
+    expect(isTurnOkForStopReason(undefined)).toBe(true);
+    expect(isTurnOkForStopReason(null)).toBe(true);
+  });
+});

apps/coder/src/services/backends/opencode-server.ts

@@ -38,6 +38,7 @@ import type { ToolCallStatus } from '@agentclientprotocol/sdk';
 import type { Sql } from '../../db.js';
 import type { AcpToolSnapshot } from '../acp-tool-snapshot.js';
 import { armAbortGuard, noteTurnActivity, consumeTerminal } from './turn-guard.js';
+import { stepEndedToUsage, type StepUsage } from './opencode-usage.js';
 import type {
   AgentBackend,
   AgentEvent,
@@ -282,6 +283,19 @@ export class OpenCodeServerBackend implements AgentBackend {
         st.activeTurn.onEvent({ type: 'tool_update', toolCall: snap });
         return;
       }
+      // ─── per-step usage (U.6) — token/cost accounting for opencode sessions ──
+      case 'session.next.step.ended': {
+        const p = ev.properties;
+        const st = this.byOpencodeId.get(p.sessionID);
+        if (!st?.activeTurn) return;
+        this.bumpActivity(st);
+        // Accumulate this step's normalized usage onto the (chat_id, agent) row.
+        // Fire-and-forget: a DB hiccup must not stall the turn. opencode emits this
+        // once per LLM step, so a multi-tool turn sums several deltas.
+        const usage = stepEndedToUsage(p);
+        void this.accumulateUsage(st, usage);
+        return;
+      }
       // ─── message.part.* — terminal/post-hoc events (dedup gate) ────────────
       case 'message.part.delta': {
         const p = ev.properties;
@@ -428,6 +442,33 @@ export class OpenCodeServerBackend implements AgentBackend {
     }
   }
 
+  // ─── per-step usage persistence (U.6) ────────────────────────────────────────
+
+  /**
+   * Accumulate one `session.next.step.ended`'s normalized usage onto the session's
+   * agent_sessions row, keyed by the resumed `agent_session_id` (unique per active
+   * row — the dispatcher's `(chat_id, agent)` lookup wrote it). Running totals for
+   * the whole conversation context (not last-step). Zero-delta steps are skipped to
+   * avoid a no-op write. Errors are swallowed: usage telemetry must never fail a turn.
+   */
+  private async accumulateUsage(st: SessionState, u: StepUsage): Promise<void> {
+    if (u.input === 0 && u.output === 0 && u.cost === 0) return;
+    try {
+      await this.sql`
+        UPDATE agent_sessions SET
+          input_tokens = input_tokens + ${u.input},
+          output_tokens = output_tokens + ${u.output},
+          cost = cost + ${u.cost}
+        WHERE agent_session_id = ${st.agentSessionId}
+      `;
+    } catch (err) {
+      this.log.warn(
+        { err: errMsg(err), agentSessionId: st.agentSessionId },
+        'opencode-server: failed to persist step usage (non-fatal)',
+      );
+    }
+  }
+
   // ─── ensureSession: create-or-resume against agent_sessions (1.5) ────────────
 
   async ensureSession(sessionId: string, opts: EnsureSessionOpts): Promise<AgentSessionHandle> {

apps/coder/src/services/backends/opencode-usage.ts

@@ -0,0 +1,77 @@
+/**
+ * v2.6 Phase 1-UX (U.6) — pure mapper for opencode's per-step usage event.
+ *
+ * opencode's warm server emits `session.next.step.ended` once per completed LLM
+ * step (so a multi-tool turn fires it several times). Its `properties` carry the
+ * step's token + cost accounting:
+ *
+ *   {
+ *     timestamp: number;
+ *     sessionID: string;
+ *     finish: string;
+ *     cost: number;                                  // USD for this step
+ *     tokens: {
+ *       input: number; output: number; reasoning: number;
+ *       cache: { read: number; write: number };
+ *     };
+ *     snapshot?: string;
+ *   }
+ *
+ * (Verified against @opencode-ai/sdk@1.15.12 — `EventSessionNextStepEnded` in
+ * `dist/v2/gen/types.gen.d.ts`, a member of the `Event` union the SSE loop
+ * switches on.)
+ *
+ * We normalize to the review's target slice `{input, output, cost}` (the
+ * provider-agnostic `AgentUsage` shape lands later). cache read/write tokens are
+ * folded into `input` so the persisted input count reflects the real context the
+ * model billed for; reasoning tokens are folded into `output` since that's what
+ * the provider counts them as for generation. This keeps the persisted totals a
+ * faithful sum of what opencode reported, without inventing extra columns yet.
+ */
+
+/** The `properties` shape of a `session.next.step.ended` event (subset we read). */
+export interface StepEndedProps {
+  cost: number;
+  tokens: {
+    input: number;
+    output: number;
+    reasoning: number;
+    cache: { read: number; write: number };
+  };
+}
+
+/** Normalized per-step usage delta persisted onto the agent_sessions row. */
+export interface StepUsage {
+  input: number;
+  output: number;
+  cost: number;
+}
+
+/** Coerce a possibly-missing/NaN number to a non-negative finite integer (tokens). */
+function n(v: unknown): number {
+  const x = typeof v === 'number' ? v : Number(v);
+  return Number.isFinite(x) && x > 0 ? Math.round(x) : 0;
+}
+
+/** Coerce a possibly-missing/NaN number to a non-negative finite float (cost USD). */
+function f(v: unknown): number {
+  const x = typeof v === 'number' ? v : Number(v);
+  return Number.isFinite(x) && x > 0 ? x : 0;
+}
+
+/**
+ * Map a `session.next.step.ended` payload → the normalized `{input, output, cost}`
+ * delta. Defensive against missing/partial token blocks (the wire is trusted but
+ * we never want a NaN to poison the accumulated DB total). `input` folds in cache
+ * read+write; `output` folds in reasoning.
+ */
+export function stepEndedToUsage(props: Partial<StepEndedProps> | undefined): StepUsage {
+  const t = props?.tokens;
+  const cacheRead = n(t?.cache?.read);
+  const cacheWrite = n(t?.cache?.write);
+  return {
+    input: n(t?.input) + cacheRead + cacheWrite,
+    output: n(t?.output) + n(t?.reasoning),
+    cost: f(props?.cost),
+  };
+}

apps/coder/src/services/backends/warm-acp-routing.ts

@@ -0,0 +1,41 @@
+/**
+ * v2.6 Phase 2 — warm-vs-one-shot routing predicate for goose/qwen.
+ *
+ * The warm ACP backend keys its persistent process + ACP session on (chat_id,
+ * agent) — exactly like the opencode-server backend. A task therefore only routes
+ * to the warm pool when it carries BOTH a `session_id` and a `chat_id`, i.e. it
+ * came from a real chat tab (the coder message route + skills route stamp both).
+ *
+ * Session-less creators — arena contestants, MCP-created tasks, generic
+ * `POST /api/tasks`, `new_task` — leave one or both null. Those keep the existing
+ * one-shot worktree-per-task ACP path (`runExternalAgent`), which spawns a fresh
+ * `goose acp` / `qwen --acp` per turn and never holds a warm process. Routing them
+ * warm would either synthesize a degenerate (null, agent) key or create a chat per
+ * arena contestant — neither is wanted, so they stay one-shot.
+ *
+ * Pure, so it's unit-testable; the dispatcher consumes it.
+ */
+const WARM_CAPABLE_AGENTS = new Set(['goose', 'qwen']);
+
+export function shouldUseWarmBackend(task: {
+  agent: string | null;
+  session_id: string | null;
+  chat_id: string | null;
+}): boolean {
+  if (!task.agent || !WARM_CAPABLE_AGENTS.has(task.agent)) return false;
+  return task.session_id != null && task.chat_id != null;
+}
+
+/**
+ * Map an ACP prompt `stopReason` to the backend's ok/fail contract (TurnResult.ok).
+ *
+ * ACP's `StopReason` union includes normal completions (`end_turn`, `max_tokens`,
+ * `max_turn_requests`) and abnormal ones (`refusal`, `cancelled`). Only the latter
+ * two read as a failed turn; everything else (including an undefined/absent reason,
+ * which we default to `end_turn`) is a successful completion. Pure so it's testable
+ * independently of the warm process.
+ */
+export function isTurnOkForStopReason(stopReason: string | null | undefined): boolean {
+  const reason = stopReason ?? 'end_turn';
+  return reason !== 'refusal' && reason !== 'cancelled';
+}

apps/coder/src/services/backends/warm-acp.ts

@@ -0,0 +1,411 @@
+/**
+ * v2.6 Phase 2 — WarmAcpBackend (goose, qwen).
+ *
+ * One persistent stdio process + ONE `ClientSideConnection` per (chat, agent),
+ * `initialize` + `session/new` done ONCE, reused across every turn — the warm
+ * analogue of the previous one-shot `acp-dispatch.ts` (which spawned/torn-down a
+ * fresh `goose acp` / `qwen --acp` per turn). Mirrors Paseo's `SpawnedACPProcess`.
+ *
+ * Implements the Phase 0 `AgentBackend` interface (same contract as
+ * `OpenCodeServerBackend`). Emits transport-agnostic `AgentEvent`s via the SHARED
+ * `mapSessionUpdate` (reused verbatim from the one-shot stack); the dispatcher maps
+ * those to WS frames + `persistExternalAgentTurn`, unchanged.
+ *
+ * Lifecycle decisions (design.md §2b / §10):
+ *   - **Child lifetime is the pool's, not a request's.** Spawned once; never tied
+ *     to a per-turn abort signal. Only the in-flight `prompt` gets `ctx.signal` —
+ *     abort = ACP `session/cancel`, NOT killing the child.
+ *   - **Per-turn abort** cancels the prompt on the warm connection so the SAME
+ *     process serves the next turn.
+ *   - **Crash** (child exit) marks `agent_sessions.status='crashed'` + logs; the
+ *     next `ensureSession` re-spawns + re-`session/new` (Phase 3 hardens auto-restart).
+ *   - **Resume across a process restart is NOT attempted in Phase 2.** goose ACP
+ *     advertises no `loadSession`/`session.resume`; qwen does, but cross-restart
+ *     resume is Phase 3. Within ONE live process the ACP session persists across
+ *     turns (the whole point of "warm"); a restart re-`session/new` (memory loss
+ *     across restart, accepted per §10). The agent's resume capabilities ARE
+ *     probed and logged for forward-compat.
+ *
+ * Each WarmAcpBackend instance owns exactly one (chat, agent) — the dispatcher
+ * pools them under `agentPool.register(chatId, agent, backend)`.
+ *
+ * SDK note (@agentclientprotocol/sdk@^0.22.1, cross-checked against the design's
+ * `^0.14` worry): the resume method is the STABLE `resumeSession` (`session/resume`,
+ * gated by `agentCapabilities.sessionCapabilities.resume`), NOT the `^0.14`
+ * `unstable_resumeSession`. `loadSession` is gated by `agentCapabilities.loadSession`.
+ */
+import { spawn, type ChildProcess } from 'node:child_process';
+import type { FastifyBaseLogger } from 'fastify';
+import {
+  ClientSideConnection,
+  type Client,
+  type SessionNotification,
+  type RequestPermissionRequest,
+  type RequestPermissionResponse,
+  type ReadTextFileRequest,
+  type ReadTextFileResponse,
+  type WriteTextFileRequest,
+  type WriteTextFileResponse,
+  type CreateTerminalRequest,
+  type CreateTerminalResponse,
+  type CreateElicitationRequest,
+  type CreateElicitationResponse,
+} from '@agentclientprotocol/sdk';
+import type { Sql } from '../../db.js';
+import { resolveLaunchSpec } from '../acp-spawn.js';
+import { isTurnOkForStopReason } from './warm-acp-routing.js';
+import { getResolvedRegistry, type ResolvedProviderDef } from '../provider-config-registry.js';
+import { createAcpNdJsonStream } from '../acp-stream.js';
+import { mapSessionUpdate } from '../acp-event-map.js';
+import { readWorktreeTextFile, writeWorktreeTextFile } from '../acp-client-fs.js';
+import { waitForPermissionResponse, waitForElicitationResponse, cancelPendingPermission } from '../permission-waiter.js';
+import { type AcpToolSnapshot, synthesizeCanceledSnapshots } from '../acp-tool-snapshot.js';
+import type {
+  AgentBackend,
+  AgentEvent,
+  AgentSessionHandle,
+  EnsureSessionOpts,
+  PromptCtx,
+  TurnResult,
+} from '../agent-backend.js';
+
+/** State for one in-flight turn (only one at a time per backend — turns serialize). */
+interface TurnState {
+  /** Per-turn task id, for routing permission prompts back to the UI. */
+  taskId: string | undefined;
+  /** BooCode session id for permission-waiter's broker frames. */
+  sessionId: string;
+  /** Per-turn mode id (autonomous-mode gate in permission-waiter). */
+  modeId: string | undefined;
+  onEvent: (e: AgentEvent) => void;
+  /** Tool-call snapshot accumulator for this turn — merge across tool_call_update. */
+  snapshots: Map<string, AcpToolSnapshot>;
+}
+
+export interface WarmAcpBackendDeps {
+  sql: Sql;
+  log: FastifyBaseLogger;
+  /** The (chat, agent) this backend serves — its pool identity + DB key. */
+  chatId: string;
+  agent: string;
+  /** Resolved binary for the agent (from available_agents.install_path), or null. */
+  installPath: string | null;
+  /** Optional override of the resolved registry def (defaults to a live lookup). */
+  resolved?: ResolvedProviderDef;
+}
+
+export class WarmAcpBackend implements AgentBackend {
+  readonly backend = 'acp_warm' as const;
+
+  private readonly sql: Sql;
+  private readonly log: FastifyBaseLogger;
+  private readonly chatId: string;
+  private readonly agent: string;
+  private readonly installPath: string | null;
+  private readonly resolvedOverride: ResolvedProviderDef | undefined;
+
+  private child: ChildProcess | null = null;
+  private connection: ClientSideConnection | null = null;
+  /** The single ACP session id for this warm process; null until session/new. */
+  private acpSessionId: string | null = null;
+  private up = false;
+  /** Idempotent spawn guard — one warm process per backend, started lazily. */
+  private starting: Promise<void> | null = null;
+  /** Resume capabilities probed at initialize, logged for forward-compat (Phase 3). */
+  private supportsLoadSession = false;
+  private supportsResumeSession = false;
+
+  /** The current in-flight turn; the Client closures read it. Null between turns. */
+  private activeTurn: TurnState | null = null;
+
+  constructor(deps: WarmAcpBackendDeps) {
+    this.sql = deps.sql;
+    this.log = deps.log;
+    this.chatId = deps.chatId;
+    this.agent = deps.agent;
+    this.installPath = deps.installPath;
+    this.resolvedOverride = deps.resolved;
+  }
+
+  /** §2: liveness for the health endpoint + dispatcher fallback decision. */
+  health(): 'up' | 'down' {
+    return this.up ? 'up' : 'down';
+  }
+
+  // ─── warm-process lifecycle (2.1 spawn + initialize + session/new ONCE) ───────
+
+  /** Lazy: spawn the warm process on first use. Idempotent — one process per backend. */
+  private ensureProcess(worktreePath: string): Promise<void> {
+    if (this.up && this.connection && this.acpSessionId) return Promise.resolve();
+    if (!this.starting) {
+      this.starting = this.startProcess(worktreePath).catch((err) => {
+        // Reset so a later ensureSession can retry the spawn after a failed start.
+        this.starting = null;
+        throw err;
+      });
+    }
+    return this.starting;
+  }
+
+  private async startProcess(worktreePath: string): Promise<void> {
+    const resolved = this.resolvedOverride ?? getResolvedRegistry().get(this.agent);
+    const spec = resolved ? resolveLaunchSpec(resolved, this.installPath) : null;
+    if (!spec) throw new Error(`warm-acp: agent '${this.agent}' does not support ACP (no launch spec)`);
+
+    this.log.info({ agent: this.agent, chatId: this.chatId, binary: spec.binary, worktreePath }, 'warm-acp: spawning warm process');
+    // Child lifetime is the pool's. NOT tied to any per-turn abort signal — only
+    // the in-flight prompt is cancellable (via ACP session/cancel in prompt()).
+    const child = spawn(spec.binary, spec.args, {
+      cwd: worktreePath,
+      stdio: ['pipe', 'pipe', 'pipe'],
+      env: { ...process.env, ...spec.env },
+    });
+    this.child = child;
+
+    // 2.3: supervise the child; react to its exit, never let a request scope kill it.
+    child.on('exit', (code, signal) => {
+      this.up = false;
+      this.connection = null;
+      this.acpSessionId = null;
+      this.starting = null;
+      this.log.warn({ agent: this.agent, chatId: this.chatId, code, signal }, 'warm-acp: warm process exited — marking crashed (rebuild on next turn)');
+      void this.markCrashed();
+    });
+    // A spawn error (e.g. ENOENT) surfaces here, not as an exit.
+    child.on('error', (err) => {
+      this.up = false;
+      this.log.error({ agent: this.agent, chatId: this.chatId, err: errMsg(err) }, 'warm-acp: warm process error');
+    });
+
+    const stream = createAcpNdJsonStream(child);
+    const connection = new ClientSideConnection(() => this.buildClient(worktreePath), stream);
+
+    const init = await connection.initialize({
+      protocolVersion: 1,
+      clientInfo: { name: 'boocoder', version: '2.6.0' },
+      clientCapabilities: {},
+    });
+    const caps = init.agentCapabilities;
+    this.supportsLoadSession = caps?.loadSession === true;
+    this.supportsResumeSession = caps?.sessionCapabilities?.resume != null;
+
+    const session = await connection.newSession({ cwd: worktreePath, mcpServers: [] });
+    this.connection = connection;
+    this.acpSessionId = session.sessionId;
+    this.up = true;
+    this.log.info(
+      {
+        agent: this.agent,
+        chatId: this.chatId,
+        acpSessionId: session.sessionId,
+        loadSession: this.supportsLoadSession,
+        resumeSession: this.supportsResumeSession,
+      },
+      'warm-acp: warm session ready',
+    );
+  }
+
+  /** Build the ACP Client callbacks ONCE per connection. They read `this.activeTurn`
+   *  so each turn's events/permissions route to the right place — exactly the
+   *  opencode-server `activeTurn` pattern. Worktree-scoped FS like AcpStreamContext. */
+  private buildClient(worktreePath: string): Client {
+    return {
+      sessionUpdate: async (params: SessionNotification): Promise<void> => {
+        const turn = this.activeTurn;
+        if (!turn) return; // between turns — drop (no orphan settles a future turn)
+        for (const event of mapSessionUpdate(params, turn.snapshots)) {
+          turn.onEvent(event);
+        }
+      },
+      requestPermission: async (params: RequestPermissionRequest): Promise<RequestPermissionResponse> => {
+        const turn = this.activeTurn;
+        if (turn?.taskId) {
+          // Route to the UI via the per-turn task id (same as the one-shot path).
+          return waitForPermissionResponse(turn.taskId, turn.sessionId, this.agent, turn.modeId, params);
+        }
+        const firstOption = params.options[0];
+        if (firstOption) return { outcome: { outcome: 'selected', optionId: firstOption.optionId } };
+        return { outcome: { outcome: 'cancelled' } };
+      },
+      readTextFile: async (params: ReadTextFileRequest): Promise<ReadTextFileResponse> => {
+        const content = await readWorktreeTextFile(worktreePath, params.path, params.line, params.limit);
+        return { content };
+      },
+      writeTextFile: async (params: WriteTextFileRequest): Promise<WriteTextFileResponse> => {
+        await writeWorktreeTextFile(worktreePath, params.path, params.content);
+        return {};
+      },
+      createTerminal: async (_params: CreateTerminalRequest): Promise<CreateTerminalResponse> => {
+        return { terminalId: 'noop' };
+      },
+      unstable_createElicitation: async (params: CreateElicitationRequest): Promise<CreateElicitationResponse> => {
+        const turn = this.activeTurn;
+        if (turn?.taskId) {
+          return waitForElicitationResponse(turn.taskId, turn.sessionId, this.agent, turn.modeId, params);
+        }
+        return { action: 'decline' };
+      },
+    };
+  }
+
+  // ─── ensureSession: create-or-reuse the warm session (2.1) ───────────────────
+
+  async ensureSession(sessionId: string, opts: EnsureSessionOpts): Promise<AgentSessionHandle> {
+    await this.ensureProcess(opts.worktreePath);
+    if (!this.acpSessionId) throw new Error('warm-acp: session not ready after ensureProcess');
+
+    // P1.5-b: agent_sessions keys on (chat_id, agent). The ACP session id is the
+    // resume handle WITHIN the live process; across a process restart it's stale,
+    // so ensureProcess re-`session/new` and we upsert the fresh id here.
+    await this.sql`
+      INSERT INTO agent_sessions
+        (chat_id, session_id, worktree_id, agent, backend, agent_session_id, server_port, status, last_active_at)
+      VALUES
+        (${opts.chatId}, ${sessionId}, ${opts.worktreeId}, ${opts.agent}, 'acp_warm', ${this.acpSessionId}, NULL, 'active', clock_timestamp())
+      ON CONFLICT (chat_id, agent) DO UPDATE SET
+        session_id = EXCLUDED.session_id,
+        worktree_id = EXCLUDED.worktree_id,
+        backend = 'acp_warm',
+        agent_session_id = EXCLUDED.agent_session_id,
+        server_port = NULL,
+        status = 'active',
+        last_active_at = clock_timestamp()
+    `.catch((err) => {
+      this.log.warn({ err: errMsg(err), chatId: opts.chatId, agent: opts.agent }, 'warm-acp: agent_sessions upsert failed (non-fatal)');
+    });
+
+    return {
+      sessionId,
+      agent: opts.agent,
+      backend: 'acp_warm',
+      chatId: opts.chatId,
+      worktreeId: opts.worktreeId,
+      agentSessionId: this.acpSessionId,
+      serverPort: null,
+    };
+  }
+
+  // ─── prompt: one turn on the warm connection (2.2) ───────────────────────────
+
+  async prompt(handle: AgentSessionHandle, input: string, ctx: PromptCtx): Promise<TurnResult> {
+    // The warm process may have crashed between ensureSession and here, or this
+    // backend was rebuilt — re-establish before prompting.
+    await this.ensureProcess(ctx.worktreePath);
+    const connection = this.connection;
+    const acpSessionId = this.acpSessionId;
+    if (!connection || !acpSessionId) {
+      return { ok: false, error: 'warm-acp: no live ACP connection' };
+    }
+
+    const snapshots = new Map<string, AcpToolSnapshot>();
+    // taskId routes permission/elicitation prompts back to the UI. The dispatcher
+    // passes it (plus mode) on the per-turn PromptCtx; permission-waiter keys on it.
+    const turn: TurnState = {
+      taskId: ctx.taskId,
+      sessionId: handle.sessionId,
+      modeId: ctx.modeId,
+      onEvent: ctx.onEvent,
+      snapshots,
+    };
+    this.activeTurn = turn;
+
+    // Per-turn abort: cancel the in-flight prompt on the SAME connection — never
+    // kill the child (that's the pool's lifetime). On cancel we also synthesize
+    // 'canceled' updates for any still-running tool calls so the UI doesn't leave
+    // them spinning (mirrors AcpStreamContext.markAborted).
+    let aborted = false;
+    const onAbort = () => {
+      if (aborted) return;
+      aborted = true;
+      connection.cancel({ sessionId: acpSessionId }).catch(() => {});
+      if (ctx.taskId) cancelPendingPermission(ctx.taskId);
+      for (const snap of synthesizeCanceledSnapshots(snapshots.values())) {
+        snapshots.set(snap.toolCallId, snap);
+        ctx.onEvent({ type: 'tool_update', toolCall: snap });
+      }
+    };
+
+    if (ctx.signal.aborted) {
+      this.activeTurn = null;
+      return { ok: false, error: 'aborted' };
+    }
+    ctx.signal.addEventListener('abort', onAbort, { once: true });
+
+    try {
+      const result = await connection.prompt({
+        sessionId: acpSessionId,
+        prompt: [{ type: 'text', text: input }],
+      });
+      if (aborted) return { ok: false, error: 'aborted' };
+      const stopReason = result.stopReason ?? 'end_turn';
+      return isTurnOkForStopReason(stopReason)
+        ? { ok: true }
+        : { ok: false, error: `stop_reason: ${stopReason}` };
+    } catch (err) {
+      if (aborted) return { ok: false, error: 'aborted' };
+      return { ok: false, error: errMsg(err) };
+    } finally {
+      ctx.signal.removeEventListener('abort', onAbort);
+      this.activeTurn = null;
+      await this.sql`
+        UPDATE agent_sessions SET status = 'idle', last_active_at = clock_timestamp()
+        WHERE chat_id = ${this.chatId} AND agent = ${this.agent}
+      `.catch(() => {});
+    }
+  }
+
+  // ─── teardown ────────────────────────────────────────────────────────────────
+
+  async closeSession(handle: AgentSessionHandle): Promise<void> {
+    // Gracefully close the ACP session if the agent supports it; then kill the child.
+    if (this.connection && this.acpSessionId) {
+      await this.connection.closeSession({ sessionId: this.acpSessionId }).catch(() => {});
+    }
+    await this.killChild();
+    await this.sql`
+      UPDATE agent_sessions SET status = 'closed'
+      WHERE chat_id = ${handle.chatId} AND agent = ${handle.agent}
+    `.catch(() => {});
+  }
+
+  async dispose(): Promise<void> {
+    this.up = false;
+    this.activeTurn = null;
+    if (this.connection && this.acpSessionId) {
+      await this.connection.closeSession({ sessionId: this.acpSessionId }).catch(() => {});
+    }
+    await this.killChild();
+    this.connection = null;
+    this.acpSessionId = null;
+    this.starting = null;
+  }
+
+  private async killChild(): Promise<void> {
+    const child = this.child;
+    this.child = null;
+    if (!child || child.killed) return;
+    child.kill('SIGTERM');
+    await new Promise<void>((resolve) => {
+      const t = setTimeout(() => {
+        if (!child.killed) child.kill('SIGKILL');
+        resolve();
+      }, 5_000);
+      t.unref?.();
+      child.once('close', () => {
+        clearTimeout(t);
+        resolve();
+      });
+    });
+  }
+
+  private async markCrashed(): Promise<void> {
+    await this.sql`
+      UPDATE agent_sessions SET status = 'crashed'
+      WHERE chat_id = ${this.chatId} AND agent = ${this.agent}
+    `.catch(() => {});
+  }
+}
+
+function errMsg(e: unknown): string {
+  return e instanceof Error ? e.message : String(e);
+}

apps/coder/src/services/dispatcher.ts

@@ -14,6 +14,8 @@ import { persistExternalAgentTurn } from './agent-turn-persist.js';
 import { snapshotToWireToolCall, type AcpToolSnapshot } from './acp-tool-snapshot.js';
 import { agentPool } from './agent-pool.js';
 import { OpenCodeServerBackend } from './backends/opencode-server.js';
+import { WarmAcpBackend } from './backends/warm-acp.js';
+import { shouldUseWarmBackend } from './backends/warm-acp-routing.js';
 import type { AgentBackend, AgentEvent } from './agent-backend.js';
 
 interface InferenceRunner {
@@ -121,10 +123,15 @@ export function createDispatcher(deps: Deps): { start(): void; stop(): Promise<v
         SELECT name, supports_acp, install_path FROM available_agents WHERE name = ${task.agent}
       `;
       if (agentRow) {
-        // v2.6 (1.7): opencode routes to the warm pool backend; every other
+        // v2.6 (1.7): opencode routes to its warm HTTP-server backend.
-        // external agent keeps the existing one-shot ACP/PTY path untouched.
+        // v2.6 Phase 2 (2.4): goose/qwen route to the warm ACP backend WHEN the
+        // task came from a real chat tab (session_id + chat_id) — shouldUseWarmBackend.
+        // Session-less creators (arena, MCP, new_task, generic /api/tasks) keep the
+        // existing one-shot worktree-per-task ACP/PTY path untouched.
         if (task.agent === 'opencode') {
           await runOpenCodeServerTask(task, agentRow.install_path);
+        } else if (shouldUseWarmBackend(task)) {
+          await runWarmAcpTask(task, agentRow.install_path);
         } else {
           await runExternalAgent(task, agentRow.supports_acp, agentRow.install_path);
         }
@@ -441,10 +448,11 @@ export function createDispatcher(deps: Deps): { start(): void; stop(): Promise<v
       const diff = await diffWorktree(worktreePath, projectPath, { signal: ac.signal });
 
       if (diff) {
-        // Queue a single pending_change entry with the full unified diff
+        // Queue a single pending_change entry with the full unified diff, stamped
+        // with the dispatched agent for DiffPanel attribution (v2.6 Phase 1-UX).
         await sql`
-          INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff)
+          INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff, agent)
-          VALUES (${sessionId}, ${taskId}, ${projectPath}, 'edit', ${diff})
+          VALUES (${sessionId}, ${taskId}, ${projectPath}, 'edit', ${diff}, ${agent})
         `;
         log.info({ taskId, diffLength: diff.length }, 'dispatcher: diff queued as pending change');
       } else {
@@ -787,6 +795,245 @@ export function createDispatcher(deps: Deps): { start(): void; stop(): Promise<v
     }
   }
 
+  // ─── Path B (warm ACP): goose / qwen warm backend (v2.6 Phase 2) ─────────────
+
+  // Warm ACP backends are per (chat, agent): each owns ONE stdio process + ACP
+  // connection + session. Pool key = chatId; the AgentPool's secondary key is the
+  // agent. This mirrors agent_sessions' (chat_id, agent) PK.
+  function getWarmAcpBackend(chatId: string, agent: string, installPath: string | null): WarmAcpBackend {
+    let backend = agentPool.get(chatId, agent);
+    if (!backend) {
+      backend = new WarmAcpBackend({
+        sql,
+        log,
+        chatId,
+        agent,
+        installPath,
+        resolved: getResolvedRegistry().get(agent),
+      });
+      agentPool.register(chatId, agent, backend);
+    }
+    return backend as WarmAcpBackend;
+  }
+
+  async function runWarmAcpTask(
+    task: {
+      id: string;
+      project_id: string;
+      input: string;
+      agent: string | null;
+      model: string | null;
+      mode_id: string | null;
+      thinking_option_id: string | null;
+      session_id: string | null;
+      chat_id: string | null;
+    },
+    installPath: string | null,
+  ): Promise<void> {
+    const taskId = task.id;
+    const agent = task.agent!;
+    // shouldUseWarmBackend guarantees both non-null before we get here.
+    const sessionId = task.session_id!;
+    const chatId = task.chat_id!;
+    log.info({ taskId, agent, chatId }, 'dispatcher: starting task (path B — warm ACP)');
+
+    const [project] = await sql<{ path: string | null }[]>`
+      SELECT path FROM projects WHERE id = ${task.project_id}
+    `;
+    const projectPath = project?.path;
+    if (!projectPath) {
+      await sql`
+        UPDATE tasks
+        SET state = 'failed', ended_at = clock_timestamp(), output_summary = 'Project has no path — cannot create worktree'
+        WHERE id = ${taskId}
+      `;
+      return;
+    }
+
+    const ac = new AbortController();
+
+    try {
+      await sql`
+        UPDATE tasks
+        SET state = 'running', started_at = clock_timestamp(), execution_path = 'acp'
+        WHERE id = ${taskId}
+      `;
+
+      // Persistent, session-keyed worktree (shared across turns + agents; NOT torn
+      // down per turn — Phase 3 reaps it). Same as the opencode-server path so a
+      // chat that switches opencode↔goose↔qwen shares one worktree.
+      const { worktreeId, worktreePath, baseCommit } = await ensureSessionWorktree(sql, projectPath, sessionId, {
+        signal: ac.signal,
+      });
+      log.info({ taskId, worktreePath }, 'dispatcher: session worktree ready (warm ACP)');
+
+      const [assistantMsg] = await sql<{ id: string }[]>`
+        INSERT INTO messages (session_id, chat_id, role, content, status, created_at)
+        VALUES (${sessionId}, ${chatId}, 'assistant', '', 'streaming', clock_timestamp())
+        RETURNING id
+      `;
+      const assistantId = assistantMsg!.id;
+
+      broker.publishFrame(sessionId, {
+        type: 'message_started',
+        message_id: assistantId,
+        chat_id: chatId,
+        role: 'assistant',
+      } as WsFrame);
+
+      const manifestCommands = getManifestCommands(agent);
+      if (manifestCommands.length > 0) {
+        setTaskCommands(taskId, manifestCommands);
+        broker.publishFrame(sessionId, {
+          type: 'agent_commands',
+          task_id: taskId,
+          session_id: sessionId,
+          commands: manifestCommands,
+        } as WsFrame);
+      }
+
+      // Accumulate the turn's stream for persistence + the final message content.
+      const textChunks: string[] = [];
+      const reasoningChunks: string[] = [];
+      const toolSnaps = new Map<string, AcpToolSnapshot>();
+
+      // Map transport-agnostic AgentEvents → the SAME WS frames the one-shot ACP
+      // path emits (identical to runOpenCodeServerTask's onEvent). No dcp stripping:
+      // that's an opencode-plugin artifact; goose/qwen don't emit dcp tags.
+      const onEvent = (e: AgentEvent): void => {
+        switch (e.type) {
+          case 'text':
+            textChunks.push(e.text);
+            broker.publishFrame(sessionId, {
+              type: 'delta',
+              message_id: assistantId,
+              chat_id: chatId,
+              content: e.text,
+            } as WsFrame);
+            break;
+          case 'reasoning':
+            reasoningChunks.push(e.text);
+            broker.publishFrame(sessionId, {
+              type: 'reasoning_delta',
+              message_id: assistantId,
+              chat_id: chatId,
+              content: e.text,
+            } as WsFrame);
+            break;
+          case 'tool_call':
+          case 'tool_update':
+            toolSnaps.set(e.toolCall.toolCallId, e.toolCall);
+            broker.publishFrame(sessionId, {
+              type: 'tool_call',
+              message_id: assistantId,
+              chat_id: chatId,
+              tool_call: snapshotToWireToolCall(e.toolCall),
+            } as WsFrame);
+            break;
+          case 'commands':
+            if (e.commands.length > 0) {
+              setTaskCommands(taskId, e.commands);
+              broker.publishFrame(sessionId, {
+                type: 'agent_commands',
+                task_id: taskId,
+                session_id: sessionId,
+                commands: e.commands,
+              } as WsFrame);
+            }
+            break;
+        }
+      };
+
+      const model = task.model ?? undefined;
+      const backend = getWarmAcpBackend(chatId, agent, installPath);
+      const handle = await backend.ensureSession(sessionId, {
+        agent,
+        model: model ?? '',
+        chatId,
+        worktreePath,
+        worktreeId,
+        projectId: task.project_id,
+      });
+      const result = await backend.prompt(handle, task.input, {
+        worktreePath,
+        model: model ?? '',
+        signal: ac.signal,
+        onEvent,
+        taskId,
+        modeId: task.mode_id ?? undefined,
+      });
+
+      const assistantContent = textChunks.join('').slice(0, 50_000);
+      const reasoningText = reasoningChunks.join('').slice(0, 200_000);
+      const outputSummary = (result.ok ? textChunks.join('') : result.error ?? 'warm ACP turn failed').slice(0, 500);
+
+      await persistExternalAgentTurn(sql, assistantId, [...toolSnaps.values()], reasoningText);
+
+      await sql`
+        UPDATE messages
+        SET content = ${assistantContent}, status = 'complete', finished_at = clock_timestamp()
+        WHERE id = ${assistantId}
+      `;
+      broker.publishFrame(sessionId, {
+        type: 'message_complete',
+        message_id: assistantId,
+        chat_id: chatId,
+      } as WsFrame);
+
+      if (stopping) {
+        await sql`UPDATE tasks SET state = 'cancelled', ended_at = clock_timestamp() WHERE id = ${taskId}`;
+        return; // worktree persists (no cleanup); backend stays warm
+      }
+
+      // Diff the persistent worktree against its captured baseline and SUPERSEDE
+      // the session's prior pending row (latest-wins) — identical to opencode.
+      const diff = await diffWorktree(worktreePath, projectPath, {
+        signal: ac.signal,
+        baseRef: baseCommit ?? 'HEAD',
+      });
+      if (diff) {
+        await sql`
+          DELETE FROM pending_changes WHERE session_id = ${sessionId} AND status = 'pending'
+        `;
+        await sql`
+          INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff, agent)
+          VALUES (${sessionId}, ${taskId}, ${projectPath}, 'edit', ${diff}, ${agent})
+        `;
+        log.info({ taskId, diffLength: diff.length }, 'dispatcher: diff superseded prior pending change (warm ACP)');
+      } else {
+        log.info({ taskId }, 'dispatcher: no changes detected in session worktree (warm ACP)');
+      }
+
+      // NO worktree cleanup — persistent (Phase 3 reaps it). Backend stays warm.
+
+      const [extCostRow] = await sql<{ total: number | null }[]>`
+        SELECT SUM(tokens_used)::int AS total
+        FROM messages
+        WHERE session_id = ${sessionId} AND tokens_used IS NOT NULL
+      `;
+      const extCostTokens = extCostRow?.total ?? null;
+
+      const finalState = result.ok ? 'completed' : 'failed';
+      await sql`
+        UPDATE tasks
+        SET state = ${finalState}, ended_at = clock_timestamp(), output_summary = ${outputSummary}, cost_tokens = ${extCostTokens}
+        WHERE id = ${taskId}
+      `;
+      log.info({ taskId, agent, finalState }, 'dispatcher: task finished (warm ACP)');
+      clearTaskCommands(taskId);
+    } catch (err) {
+      const errMsg = err instanceof Error ? err.message : String(err);
+      log.error({ taskId, agent, err: errMsg }, 'dispatcher: warm ACP error');
+      await sql`
+        UPDATE tasks
+        SET state = 'failed', ended_at = clock_timestamp(), output_summary = ${errMsg.slice(0, 500)}
+        WHERE id = ${taskId}
+      `.catch(() => {});
+      clearTaskCommands(taskId);
+      // No worktree cleanup (persistent); backend stays warm for the next turn.
+    }
+  }
+
   // ─── Helpers ────────────────────────────────────────────────────────────────
 
   async function waitForCompletion(assistantId: string): Promise<string> {

apps/coder/src/services/pending_changes.ts

@@ -13,6 +13,10 @@ export interface PendingChange {
   operation: 'create' | 'edit' | 'delete';
   diff: string;
   status: 'pending' | 'applied' | 'rejected' | 'reverted';
+  // v2.6 Phase 1-UX: which agent staged this change (DiffPanel attribution).
+  // Native boocode write tools stamp 'boocode'; the manual RightRail create path
+  // passes null (renders as "manual"). NULL on legacy rows queued pre-v2.6.
+  agent: string | null;
   created_at: string;
 }
 
@@ -34,13 +38,17 @@ export async function queueEdit(
   oldString: string,
   newString: string,
   projectRoot: string,
+  // v2.6 Phase 1-UX: attribution. Defaults to 'boocode' because the only callers
+  // that omit it are the native write tools (edit_file/create_file/delete_file).
+  // Pass null explicitly for the manual RightRail create path.
+  agent: string | null = 'boocode',
 ): Promise<PendingChange> {
   const resolved = resolveWritePath(projectRoot, filePath);
   const diff = JSON.stringify({ old: oldString, new: newString });
 
   const [row] = await sql<PendingChange[]>`
-    INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff)
+    INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff, agent)
-    VALUES (${sessionId}, ${taskId}, ${resolved}, 'edit', ${diff})
+    VALUES (${sessionId}, ${taskId}, ${resolved}, 'edit', ${diff}, ${agent})
     RETURNING *
   `;
   return row!;
@@ -53,12 +61,15 @@ export async function queueCreate(
   filePath: string,
   content: string,
   projectRoot: string,
+  // See queueEdit: defaults to 'boocode' for the native write tools; the manual
+  // RightRail create route passes null.
+  agent: string | null = 'boocode',
 ): Promise<PendingChange> {
   const resolved = resolveWritePath(projectRoot, filePath);
 
   const [row] = await sql<PendingChange[]>`
-    INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff)
+    INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff, agent)
-    VALUES (${sessionId}, ${taskId}, ${resolved}, 'create', ${content})
+    VALUES (${sessionId}, ${taskId}, ${resolved}, 'create', ${content}, ${agent})
     RETURNING *
   `;
   return row!;
@@ -70,12 +81,14 @@ export async function queueDelete(
   taskId: string | null,
   filePath: string,
   projectRoot: string,
+  // See queueEdit: defaults to 'boocode' for the native write tools.
+  agent: string | null = 'boocode',
 ): Promise<PendingChange> {
   const resolved = resolveWritePath(projectRoot, filePath);
 
   const [row] = await sql<PendingChange[]>`
-    INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff)
+    INSERT INTO pending_changes (session_id, task_id, file_path, operation, diff, agent)
-    VALUES (${sessionId}, ${taskId}, ${resolved}, 'delete', '')
+    VALUES (${sessionId}, ${taskId}, ${resolved}, 'delete', '', ${agent})
     RETURNING *
   `;
   return row!;

apps/web/src/api/client.ts

@@ -25,6 +25,17 @@ import type {
   WorkspaceState,
 } from './types';
 
+// v2.6 Phase 1-UX §9b: chat-scoped agent-session rows. Returned by
+// GET /api/coder/sessions/:id/agent-sessions; drives the AgentComposerBar
+// resumed/new-session chip via useAgentSessions. `has_session` is true when a
+// resumable backend session id exists for that agent in the chat.
+export interface AgentSessionInfo {
+  agent: string;
+  status: string;
+  has_session: boolean;
+  last_active_at: string | null;
+}
+
 export class ApiError extends Error {
   constructor(
     public status: number,
@@ -363,6 +374,11 @@ export const api = {
       request<CoderMessageWire[]>(
         `/api/coder/sessions/${sessionId}/messages${chatId ? `?chat_id=${encodeURIComponent(chatId)}` : ''}`,
       ),
+    // v2.6 Phase 1-UX §9b: per-(chat,agent) backend-session state for the
+    // resumed/new-session chip. Chat-scoped (NOT foldable into the project-level
+    // provider snapshot). Proxied to boocoder at /api/sessions/:id/agent-sessions.
+    agentSessions: (sessionId: string) =>
+      request<AgentSessionInfo[]>(`/api/coder/sessions/${sessionId}/agent-sessions`),
     skillInvoke: (
       sessionId: string,
       paneId: string,

apps/web/src/components/AgentComposerBar.tsx

@@ -1,9 +1,10 @@
 import { useEffect, useMemo, useRef, useState } from 'react';
-import { Check, ChevronDown, RefreshCw, Loader2, Shield, Brain, Bird, Bot, Dog, Terminal as TermIcon } from 'lucide-react';
+import { Check, ChevronDown, RefreshCw, Loader2, Shield, Brain, Bot } from 'lucide-react';
-import { ClaudeIcon, OpenCodeIcon } from '@/components/icons/ProviderIcons';
 import { api } from '@/api/client';
 import type { AgentSessionConfig, ProviderSnapshotEntry, AgentCommand } from '@/api/types';
 import { useProviderSnapshot, refreshProviderSnapshot } from '@/hooks/useProviderSnapshot';
+import { providerIcon } from '@/components/coder/providerIcons';
+import { useAgentSessions } from '@/hooks/useAgentSessions';
 import {
   DropdownMenu,
   DropdownMenuContent,
@@ -172,9 +173,36 @@ interface Props {
   onChange: (next: AgentSessionConfig) => void;
   onProviderCommandsChange?: (commands: AgentCommand[]) => void;
   connected?: boolean;
+  // v2.6 Phase 1-UX §9b: chat id for the resumed/new-session chip. Optional so
+  // BooChat and any other AgentComposerBar caller renders no chip and is
+  // otherwise unaffected. When present + connected + the chat has ≥1 prior
+  // turn, a chip right of the Provider picker reports whether switching to the
+  // current provider resumes an agent session, replays history (boocode), or
+  // starts fresh.
+  sessionId?: string;
+  // True once the chat has at least one prior turn — gates the chip so it stays
+  // hidden on a brand-new chat. Defaults to false (no chip).
+  hasPriorTurn?: boolean;
 }
 
-export function AgentComposerBar({ projectPath, value, onChange, onProviderCommandsChange, connected }: Props) {
+// Relative-time formatter for the resumed-chip title (e.g. "3m ago").
+function relativeTime(iso: string | null): string {
+  if (!iso) return 'unknown';
+  const then = new Date(iso).getTime();
+  if (Number.isNaN(then)) return 'unknown';
+  const diffMs = Date.now() - then;
+  if (diffMs < 0) return 'just now';
+  const sec = Math.floor(diffMs / 1000);
+  if (sec < 60) return 'just now';
+  const min = Math.floor(sec / 60);
+  if (min < 60) return `${min}m ago`;
+  const hr = Math.floor(min / 60);
+  if (hr < 24) return `${hr}h ago`;
+  const day = Math.floor(hr / 24);
+  return `${day}d ago`;
+}
+
+export function AgentComposerBar({ projectPath, value, onChange, onProviderCommandsChange, connected, sessionId, hasPriorTurn }: Props) {
   const allEntries = useProviderSnapshot(projectPath);
   // 5.5 — the composer picker only offers ENABLED providers that are ready (or
   // still loading). Disabled (enabled:false) and unavailable/error providers are
@@ -186,6 +214,13 @@ export function AgentComposerBar({ projectPath, value, onChange, onProviderComma
   );
   const [refreshing, setRefreshing] = useState(false);
 
+  // v2.6 Phase 1-UX §9b: chat-scoped agent-session rows for the resumed/new
+  // chip. Hook is unconditional (hooks rule); it self-no-ops when sessionId is
+  // undefined or the chat has no prior turn, so BooChat callers cost nothing.
+  const { sessions: agentSessions } = useAgentSessions(
+    sessionId && hasPriorTurn ? sessionId : undefined,
+  );
+
   const hydratedRef = useRef(false);
 
   useEffect(() => {
@@ -294,21 +329,30 @@ export function AgentComposerBar({ projectPath, value, onChange, onProviderComma
     );
   }
 
-  const providerIcon = (name: string) => {
-    switch (name) {
-      case 'claude': return <ClaudeIcon size={13} className="shrink-0" />;
-      case 'opencode': return <OpenCodeIcon size={13} className="shrink-0" />;
-      case 'goose': return <Bird size={13} className="shrink-0" />;
-      case 'qwen': return <TermIcon size={13} className="shrink-0" />;
-      default: return <Dog size={13} className="shrink-0" />;
-    }
-  };
-
   const providerOptions = entries.map((e) => ({ id: e.name, label: e.label }));
   const modeOptions = (currentEntry?.modes ?? []).map((m) => ({ id: m.id, label: m.label }));
   const modelOptions = (currentEntry?.models ?? []).map((m) => ({ id: m.id, label: m.label }));
   const thinkingOpts = thinkingOptions.map((t) => ({ id: t.id, label: t.label }));
 
+  // v2.6 Phase 1-UX §9b: resumed / history / new-session chip. Only meaningful
+  // when this is a real chat (sessionId), the WS is connected, and the chat has
+  // ≥1 prior turn — otherwise render nothing so fresh chats and non-coder
+  // callers stay clean.
+  const sessionRow = agentSessions.find((s) => s.agent === value.provider);
+  const sessionChip: { label: string; title: string } | null =
+    sessionId && hasPriorTurn && connected
+      ? value.provider === 'boocode'
+        ? // Native boocode never holds an agent_sessions row — it reconstructs
+          // the conversation from the chat transcript each turn.
+          { label: 'history', title: 'BooCode replays the chat transcript each turn' }
+        : sessionRow?.has_session
+          ? {
+              label: 'resumed',
+              title: `Resuming ${value.provider} · last active ${relativeTime(sessionRow.last_active_at)}`,
+            }
+          : { label: 'new session', title: `${value.provider} starts a fresh session this turn` }
+      : null;
+
   return (
     <div className="flex flex-wrap items-center gap-1 px-2 py-1 border-b border-border bg-muted/20 shrink-0">
       <CompactPicker
@@ -322,6 +366,14 @@ export function AgentComposerBar({ projectPath, value, onChange, onProviderComma
             : providerIcon(value.provider)
         }
       />
+      {sessionChip && (
+        <span
+          title={sessionChip.title}
+          className="inline-flex items-center rounded-full border border-border bg-muted/40 px-1.5 py-0.5 text-[10px] font-medium text-muted-foreground shrink-0"
+        >
+          {sessionChip.label}
+        </span>
+      )}
       <CompactPicker
         label="Mode"
         value={value.modeId ?? ''}

apps/web/src/components/coder/providerIcons.tsx

@@ -0,0 +1,56 @@
+// Shared provider icon + label helpers for BooCoder UI.
+//
+// Single source of truth for the per-provider glyph used in the
+// AgentComposerBar picker and the CoderPane DiffPanel agent-attribution
+// badges (v2.6 Phase 1-UX §9a/§9b). Extracted from AgentComposerBar's local
+// `providerIcon` switch so both call sites stay in sync.
+
+import type { ReactNode } from 'react';
+import { Bird, Dog, Terminal as TermIcon } from 'lucide-react';
+import { ClaudeIcon, OpenCodeIcon } from '@/components/icons/ProviderIcons';
+
+/**
+ * Glyph for a provider/agent name. Mirrors AgentComposerBar's original
+ * `providerIcon` switch verbatim — `boocode` (native) falls through to the
+ * neutral dog like any unmapped name, preserving the composer's prior look.
+ * Sized to match the picker (13px) by default; pass a different size for
+ * inline badges.
+ */
+export function providerIcon(name: string | null, size = 13): ReactNode {
+  switch (name) {
+    case 'claude':
+      return <ClaudeIcon size={size} className="shrink-0" />;
+    case 'opencode':
+      return <OpenCodeIcon size={size} className="shrink-0" />;
+    case 'goose':
+      return <Bird size={size} className="shrink-0" />;
+    case 'qwen':
+      return <TermIcon size={size} className="shrink-0" />;
+    default:
+      return <Dog size={size} className="shrink-0" />;
+  }
+}
+
+/**
+ * Human label for a provider/agent name. `null` → "manual" (a RightRail-staged
+ * change with no dispatching agent, per §9a). Unknown names pass through
+ * verbatim so a future provider still reads sensibly.
+ */
+export function providerLabel(name: string | null): string {
+  switch (name) {
+    case null:
+      return 'manual';
+    case 'boocode':
+      return 'BooCode';
+    case 'opencode':
+      return 'opencode';
+    case 'claude':
+      return 'Claude';
+    case 'goose':
+      return 'goose';
+    case 'qwen':
+      return 'Qwen';
+    default:
+      return name;
+  }
+}

apps/web/src/components/panes/CoderPane.tsx

@@ -16,6 +16,8 @@ import { toast } from 'sonner';
 import { isSlashCommandToken, mergeCommandsByName, parseSlashInput, slashQuery } from '@/lib/slash-command';
 import { mergeWireToolCall } from '@/lib/coder-tools';
 import { CoderMessageList, type CoderTimelineWire } from '@/components/panes/CoderMessageList';
+import { providerIcon, providerLabel } from '@/components/coder/providerIcons';
+import { refreshAgentSessions } from '@/hooks/useAgentSessions';
 import { cn } from '@/lib/utils';
 
 // ---------------------------------------------------------------------------
@@ -56,6 +58,10 @@ interface PendingChange {
   diff?: string;
   new_content?: string;
   status: 'pending' | 'approved' | 'rejected';
+  // v2.6 Phase 1-UX §9a: which agent staged this change. 'boocode' for native
+  // write tools, the dispatched agent for worktree edits, null for a manual
+  // RightRail-staged create (renders as a neutral "manual" badge).
+  agent: string | null;
 }
 
 interface Props {
@@ -394,6 +400,15 @@ function DiffPanel({
 }) {
   const pending = changes.filter((c) => c.status === 'pending');
 
+  // v2.6 Phase 1-UX §9a: when pending changes span >1 distinct agent, surface a
+  // one-line "Changes from <a>, <b>" note so mixed provenance is obvious. Null
+  // (manual) counts as its own bucket and renders as "manual".
+  const distinctAgents = Array.from(new Set(pending.map((c) => c.agent)));
+  const mixedNote =
+    distinctAgents.length > 1
+      ? `Changes from ${distinctAgents.map((a) => providerLabel(a)).join(', ')}`
+      : null;
+
   return (
     <div className="flex flex-col h-full border-t border-border">
       <div className="flex items-center justify-between px-3 py-1.5 border-b border-border bg-muted/30">
@@ -410,6 +425,11 @@ function DiffPanel({
           <RefreshCw size={12} className={loading ? 'animate-spin' : ''} />
         </button>
       </div>
+      {mixedNote && (
+        <div className="px-3 py-1 border-b border-border bg-muted/10 text-[11px] text-muted-foreground truncate">
+          {mixedNote}
+        </div>
+      )}
       <div className="flex-1 overflow-y-auto">
         {pending.length === 0 ? (
           <div className="flex items-center justify-center h-full text-sm text-muted-foreground">
@@ -420,14 +440,25 @@ function DiffPanel({
             {pending.map((change) => (
               <div key={change.id} className="px-3 py-2">
                 <div className="flex items-center justify-between mb-1">
-                  <span className="text-xs font-mono text-foreground truncate flex-1 mr-2">
+                  <span className="text-xs font-mono text-foreground truncate flex-1 mr-2 inline-flex items-center min-w-0">
+                    <span
+                      className="inline-flex items-center gap-1 rounded border border-border bg-muted/40 px-1 py-px mr-1.5 text-[10px] font-medium text-muted-foreground shrink-0"
+                      title={
+                        change.agent === null
+                          ? 'Manually staged (no dispatching agent)'
+                          : `Staged by ${providerLabel(change.agent)}`
+                      }
+                    >
+                      {providerIcon(change.agent, 11)}
+                      <span>{providerLabel(change.agent)}</span>
+                    </span>
                     <span className={cn(
-                      'inline-block w-1.5 h-1.5 rounded-full mr-1.5',
+                      'inline-block w-1.5 h-1.5 rounded-full mr-1.5 shrink-0',
                       change.operation === 'create' && 'bg-green-500',
                       change.operation === 'modify' && 'bg-yellow-500',
                       change.operation === 'delete' && 'bg-red-500',
                     )} />
-                    {change.file_path}
+                    <span className="truncate">{change.file_path}</span>
                   </span>
                   <div className="flex items-center gap-1 shrink-0">
                     <button
@@ -586,15 +617,24 @@ export function CoderPane({
   // dispatch returns — so queueing/stop must key on this combined signal.
   const generating = sending || activeTaskId !== null;
 
-  // Refresh pending changes when a message_complete arrives
+  // Refresh pending changes (and agent-session state for the §9b chip) when a
+  // message_complete arrives — same trigger usePendingChanges already uses.
   useEffect(() => {
     const lastAssistant = [...messages].reverse().find(
       (m): m is CoderMessage => m.role === 'assistant',
     );
     if (lastAssistant?.status === 'complete') {
       refresh();
+      void refreshAgentSessions(sessionId);
     }
-  }, [messages, refresh]);
+  }, [messages, refresh, sessionId]);
+
+  // The §9b chip only shows once the chat has ≥1 prior turn (a completed
+  // assistant message). Hidden on a brand-new chat.
+  const hasPriorTurn = useMemo(
+    () => messages.some((m) => m.role === 'assistant' && (m as CoderMessage).status === 'complete'),
+    [messages],
+  );
 
   // Poll fallbacks when WS is disconnected (reconnect uses WS as source of truth)
   useEffect(() => {
@@ -834,6 +874,8 @@ export function CoderPane({
         onChange={setAgentConfig}
         onProviderCommandsChange={handleProviderCommandsChange}
         connected={connected}
+        sessionId={sessionId}
+        hasPriorTurn={hasPriorTurn}
       />
       {/* Chat area — BooChat-style timeline (text + tool runs as siblings) */}
       <div className="flex-1 min-h-0 flex flex-col">

apps/web/src/hooks/useAgentSessions.ts

@@ -0,0 +1,88 @@
+// v2.6 Phase 1-UX §9b — chat-scoped agent-session state.
+//
+// Reads GET /api/coder/sessions/:id/agent-sessions (the per-(chat,agent)
+// backend-session rows) and drives the AgentComposerBar resumed/new-session
+// chip. Module-singleton external store keyed by sessionId — same shape as
+// useProviderSnapshot — so the two consumers (CoderPane, which owns the
+// message_complete WS signal, and AgentComposerBar, which renders the chip)
+// share one cache and one fetch per chat. CoderPane calls
+// refreshAgentSessions(sessionId) on each message_complete (the same trigger
+// usePendingChanges already keys off); the chip then reflects the freshly
+// resumed/created session.
+
+import { useEffect, useSyncExternalStore } from 'react';
+import { api, type AgentSessionInfo } from '@/api/client';
+
+type Entry = {
+  data: AgentSessionInfo[];
+  inflight: Promise<AgentSessionInfo[]> | null;
+};
+
+const store = new Map<string, Entry>();
+const listeners = new Set<() => void>();
+const EMPTY: AgentSessionInfo[] = [];
+
+function notify(): void {
+  for (const fn of listeners) fn();
+}
+
+function subscribe(fn: () => void): () => void {
+  listeners.add(fn);
+  return () => listeners.delete(fn);
+}
+
+function getEntry(sessionId: string): Entry {
+  let entry = store.get(sessionId);
+  if (!entry) {
+    entry = { data: EMPTY, inflight: null };
+    store.set(sessionId, entry);
+  }
+  return entry;
+}
+
+async function doFetch(sessionId: string): Promise<AgentSessionInfo[]> {
+  const data = await api.coder.agentSessions(sessionId);
+  const entry = getEntry(sessionId);
+  entry.data = data;
+  entry.inflight = null;
+  notify();
+  return data;
+}
+
+function ensureLoaded(sessionId: string): void {
+  const entry = getEntry(sessionId);
+  if (entry.data !== EMPTY || entry.inflight) return;
+  entry.inflight = doFetch(sessionId).catch(() => {
+    // boocoder may be down or the chat has no agent-session rows yet; treat as
+    // empty (the chip falls back to "new session" / hides).
+    const e = getEntry(sessionId);
+    e.inflight = null;
+    return EMPTY;
+  });
+}
+
+/** Force a refetch for one chat. Wired to message_complete by CoderPane. */
+export function refreshAgentSessions(sessionId: string): Promise<AgentSessionInfo[]> {
+  const entry = getEntry(sessionId);
+  entry.inflight = null;
+  return doFetch(sessionId);
+}
+
+/**
+ * Chat-scoped agent-session rows. Pass `undefined` to opt out (no fetch, empty
+ * result) — AgentComposerBar does this for BooChat callers and fresh chats so
+ * the chip stays hidden. Fetches on mount (and on sessionId change); refetch on
+ * message_complete is driven externally via refreshAgentSessions.
+ */
+export function useAgentSessions(sessionId: string | undefined): {
+  sessions: AgentSessionInfo[];
+} {
+  const sessions = useSyncExternalStore(
+    subscribe,
+    () => (sessionId ? getEntry(sessionId).data : EMPTY),
+  );
+  useEffect(() => {
+    if (sessionId) ensureLoaded(sessionId);
+  }, [sessionId]);
+  return { sessions: sessionId ? sessions : EMPTY };
+}

boocode_roadmap.md

@@ -348,7 +348,7 @@ Per-session Docker sandbox spawned by BooCoder on first write. Only project path
 
 -----
 
-## Shipped (v2.2.2–v2.6.7 — interactive ACP, provider lifecycle, persistent agent sessions, workspace UX)
+## Shipped (v2.2.2–v2.6.9 — interactive ACP, provider lifecycle, persistent agent sessions, workspace UX)
 
 All tags `vMAJOR.MINOR.PATCH-slug`, monotonic per minor, assigned at ship time (planning slugs differ — see the numbering-discipline note below). `CHANGELOG.md` is the canonical per-tag record. **Note on numbering divergence:** the *planned-feature* "v2.3 — Provider lifecycle" actually shipped under the **v2.5.4–v2.5.13** tags; the *planned-feature* "v2.4 — BooCoder as ACP agent" remains **unshipped** even though v2.4.0/v2.4.1 *tags* shipped unrelated content (Unsloth lifts, sidecar routing). The patch-tag thread and the conceptual-milestone thread have diverged — read tags as the ship record, the `## v2.x` feature sections below as the milestone plan. The v2.3.0–v2.5.1 tags were never CHANGELOG-backfilled; summarized here from commit bodies.
 
@@ -382,6 +382,8 @@ All tags `vMAJOR.MINOR.PATCH-slug`, monotonic per minor, assigned at ship time (
 - `v2.6.5-panes-tabs-composer` — **workspace UX batch (BooChat panes/tabs/composer + the persistence that backs it).** *Panes/tabs:* open a chat in a fresh pane (ChatTabBar "Open in new pane" + fork-beside-original via a new `open_chat_in_new_pane` event), per-pane `[+]` → New BooChat/BooTerm/BooCode menu, closing a chat pane relocates its tabs (in order) to the oldest chat/empty pane (reopen strips restored chatIds from every live pane first → no dup), stable session-scoped tab numbers (assigned on open, retired on close, never reused, map-keyed render), and the empty/landing pane became a real session history (open + separately-fetched archived chats). Removed the per-message "Open in pane" artifact button. *Persistence:* `sessions.workspace_panes` widened from bare `WorkspacePane[]` → a `WorkspaceState` envelope (`panes` + `tabNumbers`/`nextTabNumber` + `closedPaneStack`); PATCH validator zod-unions legacy-array-or-envelope and migrates on write; `session_workspace_updated` WS frame widened (web+server byte-identical, parity test green). *Composer:* morphing **Send → Stop → Queue** button keyed on `sending || activeTaskId` (folds in the standalone Stop pill, adds `cancelTask`); pasted chips trail the typed text so a leading slash stays first. *Tooling:* new read-only `read_tab_by_number` tool + an optional `ToolExecCtx` (`{ sql, sessionId }`) 4th arg on `ToolDef.execute`
 - `v2.6.6-claude-md` — docs-only CLAUDE.md session-learnings from the v2.6.5 batch: the `WorkspaceState` envelope migration, the `ToolExecCtx` plumb (`read_tab_by_number` as reference), the two-schema-files-one-DB ownership split + idempotent `confdeltype` FK-action-flip pattern, and React-StrictMode nested-`setState` idempotency
 - `v2.6.7-interrupt-guard` — **F.1 fix:** post-interrupt stale-terminal bug in the opencode warm-server backend (one-click reachable since `v2.6.5`'s Stop button). opencode emits one trailing `session.idle`/`session.error` for a cancelled turn (sessionID only, no turn id) that settled the *next* turn early as success. Pure per-session guard (`backends/turn-guard.ts` — arm-on-abort / swallow-one-orphan / self-heal-on-activity) wired into `opencode-server.ts`; 3 regression tests (TDD). First item of the v2.6 openspec "remaining" plan; Phase 1-UX / 2 / 3 still open
+- `v2.6.8-agent-attribution` — **v2.6 Phase 1-UX** (U.1–U.6), built by 3 parallel subagents over disjoint files. Backend: `pending_changes.agent` stamped at every queue site + flows through `listPending`; new `GET /api/sessions/:id/agent-sessions` route; opencode warm-server consumes `session.next.step.ended` → accumulates `input_tokens`/`output_tokens`/`cost` on `agent_sessions`. Frontend: DiffPanel per-row agent badges + multi-agent note; AgentComposerBar resumed/history/new-session chip (gated on optional `sessionId`, BooChat unaffected); shared `providerIcons.tsx` + `useAgentSessions` hook. 9 new tests; web+coder tsc clean. Both surfaces deployed (boocoder restart + `boocode` Docker rebuild). Phase 2/3 remain
+- `v2.6.9-warm-acp` — **v2.6 Phase 2:** goose/qwen run as **warm ACP backends** (one persistent `goose acp`/`qwen --acp` child + `ClientSideConnection` + ACP session per `(chat,agent)`, `initialize`+`session/new` once, reused across turns) instead of one-shot. New `WarmAcpBackend` (same `AgentBackend` interface as opencode); abort = `session/cancel` the prompt only (never kills the child); dispatcher routes goose/qwen chat-tab tasks via pure `shouldUseWarmBackend` (one-shot fallback kept for arena/MCP/`new_task`); `handleSessionUpdate` extracted to a shared pure `acp-event-map.ts` (one-shot path byte-identical). SDK concern resolved (`@agentclientprotocol/sdk@^0.22.1` has stable resume; moot warm, deferred to Phase 3). 15 new tests, 180 coder tests pass. Backend-only deploy (boocoder restart). **Smoke 2/2b pending live.** Phase 3 (lifecycle hardening) is the last v2.6 phase
 
 -----
 

openspec/changes/v2-6-persistent-agent-sessions/tasks.md

@@ -29,31 +29,25 @@ ACP follows; hardening last.
 - [x] P1.5-a **Per-session SSE** (`v2.6.2-delete-guard-and-sse`): one `event.subscribe({directory})` per live opencode session, each with an `AbortController`; `sessionID` demux guard + zombie-loop fix — replaces task 1.3's single global loop. Bundled: session-delete work-loss guard (`/worktree-risk`).
 - [x] P1.5-b **Re-key `agent_sessions` → `(chat_id, agent)`** + first-class `worktrees` table (`v2.6.3-chatkey-and-skills`); `tasks.chat_id` threaded; `runOpenCodeServerTask` resolve-or-creates a chat for session-less creators; cross-chunk dcp-strip. FK convergence to `SET NULL` (`v2.6.4-agent-sessions-fk`).
 
-## Phase 1 (UX) — Attribution & switch affordances (design §9) — ⬜ REMAINING (pure read+display over already-shipped `pending_changes.agent` + `agent_sessions`)
+## Phase 1 (UX) — Attribution & switch affordances (design §9) — ✅ SHIPPED `v2.6.8-agent-attribution` (Smoke U pending live frontend deploy)
 
-- [ ] U.1 Stamp `pending_changes.agent` at queue time (worktree path → task agent;
+- [x] U.1 Stamp `pending_changes.agent` at queue time — native tools default `'boocode'`, dispatched external → `task.agent`, manual RightRail → `NULL` (`pending_changes.ts`, `dispatcher.ts`).
-      native write tools → `'boocode'`; manual RightRail create → NULL).
+- [x] U.2 `agent` flows through `listPending` + backend & frontend `PendingChange` types.
-- [ ] U.2 Add `agent` to `listPending` response + frontend `PendingChange` type.
+- [x] U.3 Shared `components/coder/providerIcons.tsx`; DiffPanel per-row agent badge + "Changes from X, Y" multi-agent note (§9a).
-- [ ] U.3 Extract `providerIcon()` to a shared helper; DiffPanel renders an agent badge
+- [x] U.4 `GET /api/sessions/:id/agent-sessions` route + `api.coder.agentSessions` + `useAgentSessions` hook (refetch on message-complete) (§9b).
-      per row + a "Changes from X, Y" note when the pending set spans >1 agent (§9a).
+- [x] U.5 `AgentComposerBar` optional `sessionId` prop → resumed/history/new-session chip; hidden on fresh chats + other callers (§9b).
-- [ ] U.4 `GET /api/sessions/:id/agent-sessions` route + `api.coder.agentSessions` +
+- [x] U.6 Consume opencode `session.next.step.ended` → accumulate `input_tokens`/`output_tokens`/`cost` on `agent_sessions` (new cols). Backend persist only; UI surfacing deferred.
-      `useAgentSessions(sessionId)` (refetch on `message_complete`) (§9b).
-- [ ] U.5 `AgentComposerBar` optional `sessionId` prop → resumed / history / new-session
-      chip beside the Provider picker; hidden on fresh chats and other callers (§9b).
-- [ ] U.6 Consume opencode `session.next.step.ended` `{tokens, cost}` → fill ctx/token usage for opencode sessions (SDK already installed; closes the "no usage for external agents" gap; surface beside the §9b chip). Source: `boocode_code_review_v2.md` §1 #8, design §10.
 - [ ] **Smoke U:** stage edits with opencode then boocode → DiffPanel badges each row to the
-      right agent; composer shows "resumed" when re-selecting opencode, "new session" for goose.
+      right agent; composer shows "resumed" when re-selecting opencode, "new session" for goose. *(pending live frontend deploy — Docker container rebuild)*
 
-## Phase 2 — Warm ACP backend (goose, qwen) — ⬜ REMAINING
+## Phase 2 — Warm ACP backend (goose, qwen) — ✅ SHIPPED `v2.6.9-warm-acp` (Smoke 2/2b pending live)
 
 > **Lift (design §10):** `qwen --acp` is a validated reference (real stdio multi-session, `loadSession`/resume) — wire qwen into the existing `acp-dispatch.ts` stack. **goose ACP has no `loadSession`/resume** → cross-restart resume needs a different design (re-`session/new` + accept memory loss, or replay). Cross-check qwen `@agentclientprotocol/sdk@^0.14` vs BooCode `^0.22` before relying on `unstable_resumeSession`. Do **qwen first** to de-risk.
 
-- [ ] 2.1 `backends/warm-acp.ts`: persistent spawn + `ClientSideConnection`; `initialize` +
+- [x] 2.1 `backends/warm-acp.ts` `WarmAcpBackend` — persistent spawn + `ClientSideConnection`; `initialize` + `session/new` once per `(chat,agent)`. `handleSessionUpdate` extracted to a shared pure `acp-event-map.ts` (one-shot path byte-identical).
-      `session/new` once; reuse `acp-dispatch.ts` `handleSessionUpdate`.
+- [x] 2.2 `prompt`: `session/prompt` on the warm connection per turn; abort = `session/cancel` the prompt only (never kills the child).
-- [ ] 2.2 `prompt`: `session/prompt` on the warm connection per turn; per-turn abort signal only.
+- [x] 2.3 Child supervision: pool-owned lifetime; `exit` marks `agent_sessions.status='crashed'` → re-spawn next turn.
-- [ ] 2.3 Child supervision: detached lifetime, exit handler marks `status='crashed'`.
+- [x] 2.4 Dispatcher routes `goose`/`qwen` chat-tab tasks to the warm backend via pure `shouldUseWarmBackend(task)` (needs `session_id`+`chat_id`); one-shot `runExternalAgent` fallback kept for arena/MCP/`new_task`. *(SDK note resolved: installed `@agentclientprotocol/sdk@^0.22.1` has stable `resumeSession`/`loadSession`; resume moot in the warm hot path, deferred to Phase 3.)*
-- [ ] 2.4 Dispatcher routes `goose`/`qwen` to warm backend; keep one-shot fallback for arena/MCP
-      (or opt those into pool too — decide in review).
 - [ ] **Smoke 2:** two messages in a goose chat reuse the same process + ACP session + worktree;
       reasoning still renders; no per-turn respawn.
 - [ ] **Smoke 2b (switch round-trip):** opencode → boocode → opencode in one chat — opencode
@@ -102,8 +96,8 @@ ACP follows; hardening last.
 ## Remaining — recommended order (implementation plan, 2026-05-31)
 
 1. ~~**F.1 interrupt-bug fix**~~ — ✅ shipped `v2.6.7-interrupt-guard` (3 regression tests, TDD).
-2. **Phase 1-UX** (U.1–U.6) — pure read+display over already-shipped `pending_changes.agent` + `agent_sessions`; no dispatch-logic or backend change, so it ships value on data that already exists. U.6 (token/ctx usage) rides the same opencode SSE.
+2. ~~**Phase 1-UX** (U.1–U.6)~~ — ✅ shipped `v2.6.8-agent-attribution` (3 parallel agents, disjoint files; 9 new tests). Smoke U pending the frontend Docker rebuild.
-3. **Phase 2 — warm ACP, qwen first then goose** — qwen has a validated `--acp` reference; goose's missing resume is the open design question, so qwen de-risks the pattern. Smoke 2 + 2b (the switch round-trip success criterion).
+3. ~~**Phase 2 — warm ACP, qwen first then goose**~~ — ✅ shipped `v2.6.9-warm-acp` (15 new tests; one-shot path preserved). Smoke 2 + 2b pending live exercise post-deploy.
 4. **Phase 3 — lifecycle hardening** — lift openchamber's state machine; do crash-recovery (3.1/3.2/3.6) + worktree reaper (3.3/3.4 + LRU) together (shared supervision loop). Closes the two ⬜ success criteria (server-crash recovery, close→cleanup).
 5. **Tests T.1–T.3 + `BOOCODER.md` (D.1 remainder)** — backfill alongside each phase, not at the end.