feat(mobile): add session.tabs.list handler to mock server (#9293)

* feat(mobile): add session.tabs.list handler to mock server

The mock WebSocket server had no handler for session.tabs.list, so the
session screen of a paired dev client hung on 'Loading tabs' forever —
the terminal pane, live input, and command input could never be
exercised against the mock. Respond with a single ready terminal tab
wired to the existing term-1 fixture so the whole session surface works
offline.

* fix(mobile): complete the session.tabs.list mock contract

The new mock response omitted four non-optional fields of
RuntimeMobileSessionTabsResult: publicationEpoch and activeGroupId on the
result, and parentTabId and leafId on the terminal tab. Nothing caught it —
the object literal had no type annotation, and MobileSessionTabsStreamHealth
is generic over both result and tab. A shape-incomplete mock yields
untrustworthy repros for exactly the bugs it gets used for (session tabs,
split panes, pane-to-tab attribution).

Fill the fields with host-realistic values: a per-process publisher epoch, a
layout UUID leaf id, and the `${parentTabId}::${leafId}` surface id
mobileTerminalSurfaceId actually emits. Pin the shape with an explicit return
type so a future required field fails typecheck instead of silently drifting.

Move the fixture into its own module: inlining it pushed
mock-server-rpc-handlers.ts to 317 lines against a 300-line max-lines cap,
which broke `pnpm lint` on the parent commit. It registers through the file's
existing delegation chain, after the native-chat scenario so MOCK_NATIVE_CHAT=1
keeps ownership of the method.

Co-authored-by: Hanjoon Choe <hanjoonchoe@gmail.com>

* test(mobile): pin session tabs mock fidelity

Normalize the selector-backed worktree ID like the real runtime and cover the complete terminal surface response so future contract drift fails the mobile suite.

* fix(mobile): share terminal.list worktree resolution with session tabs

Main added `terminalListWorktreeId`, which the rebased session-tabs fixture
duplicated with a different no-selector fallback — `terminal.list` resolved to
the active fake worktree while `session.tabs.list` returned a literal 'mock',
so a session repro saw two different worktree ids for one screen.

* test(mobile): cover the bare session-tabs worktree selector

Answers the review note that only the `id:`-prefixed path was exercised.

* fix(mobile): make the mock publication epoch unique per process

Date.now() can repeat across a sub-millisecond restart, so the epoch did not
actually guarantee the fresh-publisher identity its comment claimed.

---------

Co-authored-by: Brennan Benson <79079362+brennanb2025@users.noreply.github.com>

mobile/scripts/mock-server-rpc-handlers.ts

@@ -12,6 +12,7 @@ import { handleMockFilePreviewRequest } from './mock-server-file-preview-data'
 import { handleMockGitRequest } from './mock-server-git-state'
 import { handleMockAccountRequest } from './mock-server-account-rpc'
 import { handleMockNativeChatRequest } from './mock-server-native-chat-scenario'
+import { handleMockSessionTabsRequest } from './mock-server-session-tabs-fixture'
 import {
   createMockTerminals,
   FAKE_SCROLLBACK,
@@ -124,7 +125,8 @@ export function handleRequest(
     handleMockGitRequest(request, respond, success) ||
     handleMockFilePreviewRequest(request, respond, success, error) ||
     handleMockAccountRequest(request, respond, success, error) ||
-    handleMockNativeChatRequest(request, respond, success, error, ws)
+    handleMockNativeChatRequest(request, respond, success, error, ws) ||
+    handleMockSessionTabsRequest(request, respond, success, terminalListWorktreeId)
   ) {
     return
   }

mobile/scripts/mock-server-session-tabs-fixture.ts

@@ -0,0 +1,69 @@
+import { randomUUID } from 'node:crypto'
+import type { RuntimeMobileSessionTabsResult } from '../../src/shared/runtime-types'
+import type { RpcRequest, RpcResponse } from './mock-server-rpc-handlers'
+
+// Why: the client's snapshot-acceptance gate keys on the publisher epoch, so it
+// must stay stable for the process and change on restart like a real publisher —
+// hence a uuid, not a clock read two restarts could land on.
+// The `mobile-local:` prefix is reserved for phone-local writes — never use it.
+const PUBLICATION_EPOCH = `mock-server:${randomUUID()}`
+const GROUP_ID = 'group-1'
+const PARENT_TAB_ID = 'tab-1'
+// The host only ever publishes terminal-layout UUIDs here; pane-key parsing
+// rejects any other shape, so a placeholder would mask pane-attribution bugs.
+const LEAF_ID = 'f47ac10b-58cc-4372-a567-0e02b2c3d479'
+// The host publishes terminal surfaces as `${parentTabId}::${leafId}`.
+const SURFACE_TAB_ID = `${PARENT_TAB_ID}::${LEAF_ID}`
+
+/** One ready terminal tab bound to the `term-1` fixture. Mirrors the full
+ *  `session.tabs.list` contract so mock-server repros of tab, split-pane, and
+ *  pane-attribution bugs aren't shape-incomplete. */
+function createMockSessionTabs(worktreeId: string): RuntimeMobileSessionTabsResult {
+  return {
+    worktree: worktreeId,
+    publicationEpoch: PUBLICATION_EPOCH,
+    snapshotVersion: 1,
+    activeGroupId: GROUP_ID,
+    activeTabId: SURFACE_TAB_ID,
+    activeTabType: 'terminal',
+    // Groups track top-level tabs, so they carry parentTabId, not surface ids.
+    tabGroups: [
+      {
+        id: GROUP_ID,
+        activeTabId: PARENT_TAB_ID,
+        tabOrder: [PARENT_TAB_ID],
+        recentTabIds: [PARENT_TAB_ID]
+      }
+    ],
+    tabs: [
+      {
+        type: 'terminal',
+        id: SURFACE_TAB_ID,
+        title: 'zsh',
+        parentTabId: PARENT_TAB_ID,
+        leafId: LEAF_ID,
+        status: 'ready',
+        terminal: 'term-1',
+        isActive: true
+      }
+    ]
+  }
+}
+
+/** Default session-tabs backend: without it the session screen hangs on
+ *  'Loading tabs'. Returns false for methods it does not own. */
+export function handleMockSessionTabsRequest(
+  request: RpcRequest,
+  respond: (response: RpcResponse) => void,
+  success: (id: string, result: unknown, streaming?: boolean) => RpcResponse,
+  // Shared with `terminal.list` so both surfaces agree on which worktree an
+  // absent or `id:`-prefixed selector means.
+  resolveWorktreeId: (selector: unknown) => string | undefined
+): boolean {
+  if (request.method !== 'session.tabs.list') {
+    return false
+  }
+  const worktreeId = resolveWorktreeId(request.params?.worktree) ?? 'mock'
+  respond(success(request.id, createMockSessionTabs(worktreeId)))
+  return true
+}

mobile/src/mock-server-session-tabs-fixture.test.ts

@@ -0,0 +1,77 @@
+import { describe, expect, it } from 'vitest'
+import type { WebSocket } from 'ws'
+import {
+  handleRequest,
+  type RpcRequest,
+  type RpcResponse
+} from '../scripts/mock-server-rpc-handlers'
+
+function callRpc(method: string, params?: Record<string, unknown>): RpcResponse {
+  let response: RpcResponse | undefined
+  const request: RpcRequest = { id: 'request-1', method, ...(params ? { params } : {}) }
+  handleRequest(
+    request,
+    (nextResponse) => {
+      response = nextResponse
+    },
+    {} as WebSocket
+  )
+  expect(response).toBeDefined()
+  return response!
+}
+
+function listSessionTabs(worktree: string): RpcResponse {
+  return callRpc('session.tabs.list', { worktree })
+}
+
+describe('mock server session tabs fixture', () => {
+  it('returns a contract-complete terminal surface for the requested worktree', () => {
+    const response = listSessionTabs('id:repo-1::worktree-1')
+
+    expect(response.result).toEqual({
+      worktree: 'repo-1::worktree-1',
+      publicationEpoch: expect.stringMatching(/^mock-server:/),
+      snapshotVersion: 1,
+      activeGroupId: 'group-1',
+      activeTabId: 'tab-1::f47ac10b-58cc-4372-a567-0e02b2c3d479',
+      activeTabType: 'terminal',
+      tabGroups: [
+        {
+          id: 'group-1',
+          activeTabId: 'tab-1',
+          tabOrder: ['tab-1'],
+          recentTabIds: ['tab-1']
+        }
+      ],
+      tabs: [
+        {
+          type: 'terminal',
+          id: 'tab-1::f47ac10b-58cc-4372-a567-0e02b2c3d479',
+          title: 'zsh',
+          parentTabId: 'tab-1',
+          leafId: 'f47ac10b-58cc-4372-a567-0e02b2c3d479',
+          status: 'ready',
+          terminal: 'term-1',
+          isActive: true
+        }
+      ]
+    })
+  })
+
+  it('passes a bare worktree selector through unprefixed', () => {
+    const response = listSessionTabs('repo-1::worktree-1')
+
+    expect((response.result as { worktree: string }).worktree).toBe('repo-1::worktree-1')
+  })
+
+  it('falls back to the same worktree terminal.list uses when no selector is sent', () => {
+    const terminals = callRpc('terminal.list').result as {
+      terminals: { worktreeId: string }[]
+    }
+    const expected = terminals.terminals[0]?.worktreeId
+    expect(expected).toBeTruthy()
+
+    const tabs = callRpc('session.tabs.list').result as { worktree: string }
+    expect(tabs.worktree).toBe(expected)
+  })
+})