fix(mobile): restore pending native chat transcripts

Restore the existing transcriptPending capability and preserve pending snapshots through the shared chat presentation seam. A new agent can show its empty chat while keeping draft reconciliation gated until the real transcript arrives. Exercise capability negotiation and the pending-to-ready transition through the native adapter and React hook.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

mobile/src/session/mobile-native-chat-stream-frame.ts

@@ -10,6 +10,7 @@ export type MobileNativeChatStreamFrame = {
   messages?: NativeChatMessage[]
   hasMore?: boolean
   beforeOffset?: number
+  pending?: boolean
   error?: string
   message?: string
   lifecycle?: NativeChatTurnLifecycle
@@ -26,6 +27,7 @@ export type AppliedMobileNativeChatFrame =
       cursorInvalidated?: boolean
       lifecycle?: NativeChatTurnLifecycle
       windowReplaced?: boolean
+      pending?: boolean
     }
 
 function replayRetainedTailStart(
@@ -82,6 +84,7 @@ export function applyMobileNativeChatStreamFrame(args: {
   if (!Array.isArray(frame.messages)) {
     return { kind: 'ignored' }
   }
+  const pending = frame.type === 'snapshot' && frame.pending === true
   const replayStartIndex =
     frame.type === 'snapshot' && !replaceSnapshot && merger.list.length > 0
       ? replayRetainedTailStart(merger, frame.messages, frame.hasMore)
@@ -93,6 +96,7 @@ export function applyMobileNativeChatStreamFrame(args: {
       messages: merger.list,
       hasMore: frame.hasMore,
       windowReplaced: true,
+      ...(pending ? { pending: true } : {}),
       ...(frame.beforeOffset == null ? {} : { beforeOffset: frame.beforeOffset }),
       ...(frame.lifecycle === undefined ? {} : { lifecycle: frame.lifecycle })
     }
@@ -104,6 +108,7 @@ export function applyMobileNativeChatStreamFrame(args: {
   return {
     kind: 'messages',
     messages,
+    ...(pending ? { pending: true } : {}),
     // Why: once the bounded live window drops its oldest row, the snapshot's
     // byte cursor no longer describes the oldest retained message.
     ...(cursorInvalidated ? { cursorInvalidated: true } : {}),

mobile/src/session/native-chat-transcript-pending.test.ts

@@ -0,0 +1,55 @@
+import { createElement } from 'react'
+import { act, create } from 'react-test-renderer'
+import { describe, expect, it, vi } from 'vitest'
+import type { RpcClient } from '../transport/rpc-client'
+import { nativeHostSessionNativeChatOperations } from './native-host-session-native-chat-operations'
+import {
+  useMobileNativeChatSession,
+  type MobileNativeChatSession
+} from './use-mobile-native-chat-session'
+
+describe('native chat before the first transcript flush', () => {
+  it('negotiates pending snapshots and waits for the authoritative transcript', async () => {
+    let state: MobileNativeChatSession | null = null
+    let emit: (frame: unknown) => void = () => {}
+    const subscribe: RpcClient['subscribe'] = vi.fn((_method, params, onData) => {
+      emit = onData
+      if (
+        (params as { capabilities?: { transcriptPending?: number } }).capabilities
+          ?.transcriptPending === 1
+      ) {
+        onData({ type: 'snapshot', messages: [], hasMore: false, pending: true })
+      }
+      return () => {}
+    })
+    const operations = nativeHostSessionNativeChatOperations({ subscribe } as unknown as RpcClient)
+    function Harness() {
+      state = useMobileNativeChatSession({
+        operations,
+        workspaceId: 'workspace',
+        agent: 'claude',
+        sessionId: 'session',
+        transcriptPath: null,
+        terminalId: 'terminal',
+        clientId: 'device'
+      })
+      return null
+    }
+    let renderer: ReturnType<typeof create> | undefined
+    try {
+      await act(async () => {
+        renderer = create(createElement(Harness))
+      })
+      expect(state).toMatchObject({
+        status: 'awaiting-transcript',
+        transcriptLoading: true,
+        messages: []
+      })
+      await act(async () => emit({ type: 'snapshot', messages: [], hasMore: false }))
+      expect(state).toMatchObject({ status: 'ready', transcriptLoading: false, messages: [] })
+      expect(subscribe).toHaveBeenCalledTimes(1)
+    } finally {
+      act(() => renderer?.unmount())
+    }
+  })
+})

mobile/src/session/native-host-session-native-chat-operations.ts

@@ -46,6 +46,7 @@ export function nativeHostSessionNativeChatOperations(
         'nativeChat.subscribe',
         {
           ...nativeChatReadParams(target, limit),
+          capabilities: { transcriptPending: 1 },
           subscriptionId: buildNativeChatSubscriptionId(target.agent, target.sessionId)
         },
         (value) => onEvent(value as Parameters<typeof onEvent>[0])

mobile/src/session/use-mobile-native-chat-session.ts

@@ -218,7 +218,7 @@ export function useMobileNativeChatSession(args: {
           setLoadingEarlier(false)
           beforeOffsetRef.current = null
         }
-        setRead({ operations, identity, status: 'ready' })
+        setRead({ operations, identity, status: applied.pending ? 'awaiting-transcript' : 'ready' })
       },
       () => {
         if (!cancelled) {
@@ -317,7 +317,7 @@ export function useMobileNativeChatSession(args: {
     messages: visibleMessages,
     lifecycle,
     status,
-    transcriptLoading: status === 'loading',
+    transcriptLoading: status === 'loading' || status === 'awaiting-transcript',
     error,
     hasMore,
     loadingEarlier,