diff --git a/app/api/session/dispatch/route.ts b/app/api/session/dispatch/route.ts
index 982817d87..59661c172 100644
--- a/app/api/session/dispatch/route.ts
+++ b/app/api/session/dispatch/route.ts
@@ -20,8 +20,8 @@ export async function POST(req: Request) {
     agent_name?: string;
     sessionId?: string;
     session_id?: string;
-    requireRoomVideoInputReady?: boolean;
-    require_room_video_input_ready?: boolean;
+    requireAgentSessionReady?: boolean;
+    require_agent_session_ready?: boolean;
   };
   try {
     body = await req.json();
@@ -57,8 +57,8 @@ export async function POST(req: Request) {
       sessionId,
       agentName,
       readiness: {
-        requireRoomVideoInputReady:
-          body.requireRoomVideoInputReady === true || body.require_room_video_input_ready === true,
+        requireAgentSessionReady:
+          body.requireAgentSessionReady === true || body.require_agent_session_ready === true,
       },
     });
     return NextResponse.json({ status: 'dispatched', roomName, agentName, sessionId, dispatch });
diff --git a/app/api/session/session-dispatch-service.ts b/app/api/session/session-dispatch-service.ts
index 067468acc..44075ff1d 100644
--- a/app/api/session/session-dispatch-service.ts
+++ b/app/api/session/session-dispatch-service.ts
@@ -75,7 +75,7 @@ const globalForInFlightDispatches = globalThis as typeof globalThis & {
 const inFlightDispatches =
   globalForInFlightDispatches.__liveavatarInFlightDispatches ??
   (globalForInFlightDispatches.__liveavatarInFlightDispatches = new Map());
-const DEFAULT_AGENT_DISPATCH_TIMEOUT_MS = 8_000;
+const DEFAULT_AGENT_DISPATCH_TIMEOUT_MS = 30_000;
 const DEFAULT_PREWARM_TOTAL_TIMEOUT_MS = 45_000;
 
 export type PrewarmPhase = 'room' | 'worker_readiness' | 'dispatch_readiness';
@@ -302,7 +302,6 @@ export async function prewarmRoomSession(
             ...request,
             readiness: {
               requireAgentSessionReady: true,
-              requireRoomInputParticipantsReady: true,
             },
           },
           {
diff --git a/hooks/useChatMessages.ts b/hooks/useChatMessages.ts
index e9b75f5d0..7125e826d 100644
--- a/hooks/useChatMessages.ts
+++ b/hooks/useChatMessages.ts
@@ -1,4 +1,4 @@
-import { useMemo } from 'react';
+import { useEffect, useMemo, useState } from 'react';
 import { Room } from 'livekit-client';
 import {
   type ReceivedChatMessage,
@@ -9,6 +9,7 @@ import {
 } from '@livekit/components-react';
 import { type AppConfig } from '@/app-config';
 import { isRenderableChatMessage } from '@/lib/chat-message-filter';
+import { mergeTranscriptionHistory } from '@/lib/transcription-history';
 
 function transcriptionToChatMessage(
   textStream: TextStreamData,
@@ -76,10 +77,19 @@ export function useChatMessages(
   const chat = useChat();
   const room = useRoomContext();
   const transcriptions: TextStreamData[] = useTranscriptions();
+  const [transcriptionHistory, setTranscriptionHistory] = useState<TextStreamData[]>([]);
+
+  useEffect(() => {
+    setTranscriptionHistory([]);
+  }, [room.name]);
+
+  useEffect(() => {
+    setTranscriptionHistory((previous) => mergeTranscriptionHistory(previous, transcriptions));
+  }, [transcriptions]);
 
   const mergedTranscriptions = useMemo(() => {
     // 处理转录消息
-    const transcriptionMessages = transcriptions.map((transcription) =>
+    const transcriptionMessages = transcriptionHistory.map((transcription) =>
       transcriptionToChatMessage(transcription, room, config)
     );
 
@@ -112,7 +122,7 @@ export function useChatMessages(
     ].filter(isRenderableChatMessage);
 
     return merged.sort((a, b) => a.timestamp - b.timestamp);
-  }, [transcriptions, chat.chatMessages, room, config]);
+  }, [transcriptionHistory, chat.chatMessages, room, config]);
 
   return mergedTranscriptions;
 }
diff --git a/hooks/useRoom.ts b/hooks/useRoom.ts
index d44922f1d..25e023a88 100644
--- a/hooks/useRoom.ts
+++ b/hooks/useRoom.ts
@@ -6,7 +6,6 @@ import { useBrowserSourceClient } from '@/hooks/useBrowserSourceClient';
 import { getVoiceSessionId, resetVoiceSessionId } from '@/lib/browser-room-session';
 import { readConnectionDetailsResponse } from '@/lib/connection-details-response';
 import { isValidConnectionRoomId } from '@/lib/connection-room-id';
-import { usesServerRoomInputDevice } from '@/lib/input-device-config';
 import {
   FRONTEND_EVENTS,
   beginFrontendObservabilitySession,
@@ -27,12 +26,6 @@ import {
   waitForAgentSessionStop,
 } from '@/lib/session-stop-client';
 
-function requiresRoomVideoInputReady(appConfig: AppConfig) {
-  return appConfig.visionInputDevice
-    ? usesServerRoomInputDevice(appConfig.visionInputDevice)
-    : false;
-}
-
 export function useRoom(appConfig: AppConfig) {
   const aborted = useRef(false);
   const sessionIdRef = useRef<string | null>(null);
@@ -212,7 +205,6 @@ export function useRoom(appConfig: AppConfig) {
       await recoverFromStartError(error);
     };
 
-    setIsSessionActive(true);
     beginFrontendObservabilitySession(room);
 
     const dispatchAgentSession = async () => {
@@ -220,7 +212,7 @@ export function useRoom(appConfig: AppConfig) {
       dispatchSessionId = sessionId;
       const signal = beginAgentSessionStart(room.name, sessionId);
       const dispatchPromise = requestAgentSessionDispatch(appConfig.agentName, sessionId, {
-        requireRoomVideoInputReady: requiresRoomVideoInputReady(appConfig),
+        requireAgentSessionReady: usesManagedRoomInput,
         signal,
       });
       registerAgentSessionDispatch(room.name, sessionId, dispatchPromise);
@@ -310,6 +302,7 @@ export function useRoom(appConfig: AppConfig) {
       if (!usesSandboxConcurrentStartup) {
         await dispatchAgentSession();
       }
+      setIsSessionActive(true);
     } catch (error) {
       await handleStartError(error);
     }
diff --git a/lib/session-dispatch-client.ts b/lib/session-dispatch-client.ts
index 0d6b7ef1b..06fa7c93d 100644
--- a/lib/session-dispatch-client.ts
+++ b/lib/session-dispatch-client.ts
@@ -1,6 +1,6 @@
 type DispatchOptions = {
   signal?: AbortSignal;
-  requireRoomVideoInputReady?: boolean;
+  requireAgentSessionReady?: boolean;
 };
 
 export class AgentSessionDispatchCancelledError extends Error {
@@ -27,7 +27,7 @@ export async function requestAgentSessionDispatch(
     body: JSON.stringify({
       agentName: normalizedAgentName,
       sessionId: normalizedSessionId,
-      ...(options.requireRoomVideoInputReady ? { requireRoomVideoInputReady: true } : {}),
+      ...(options.requireAgentSessionReady ? { requireAgentSessionReady: true } : {}),
     }),
     signal: options.signal,
   });
diff --git a/lib/session-dispatch-readiness.ts b/lib/session-dispatch-readiness.ts
index 2c6026cc3..51cb58e47 100644
--- a/lib/session-dispatch-readiness.ts
+++ b/lib/session-dispatch-readiness.ts
@@ -16,6 +16,8 @@ export type ReusableAgentParticipantOptions = AgentParticipantMatchOptions & {
 };
 
 export const AGENT_SESSION_READY_ATTRIBUTE = 'liveavatar.agent.session_ready';
+// livekit-server-sdk maps protobuf attribute keys to camelCase object keys.
+const AGENT_SESSION_READY_ATTRIBUTE_CAMEL = 'liveavatarAgentSessionReady';
 
 const ROOM_AUDIO_INPUT_IDENTITY = 'room_audio_input';
 const ROOM_VIDEO_INPUT_IDENTITY = 'room_video_input';
@@ -127,7 +129,11 @@ function isExpectedAgentParticipant(participant: ParticipantInfo, agentName: str
 }
 
 function isAgentSessionReady(participant: ParticipantInfo) {
-  return participant.attributes?.[AGENT_SESSION_READY_ATTRIBUTE] === 'true';
+  const attributes = participant.attributes ?? {};
+  return (
+    attributes[AGENT_SESSION_READY_ATTRIBUTE] === 'true' ||
+    attributes[AGENT_SESSION_READY_ATTRIBUTE_CAMEL] === 'true'
+  );
 }
 
 function isAnonymousLiveKitAgentParticipant(participant: ParticipantInfo) {
diff --git a/lib/transcription-history.ts b/lib/transcription-history.ts
new file mode 100644
index 000000000..2a16a8da8
--- /dev/null
+++ b/lib/transcription-history.ts
@@ -0,0 +1,23 @@
+import { type TextStreamData } from '@livekit/components-react';
+
+const DEFAULT_TRANSCRIPTION_HISTORY_SIZE = 100;
+
+/**
+ * Keep completed text streams even when LiveKit replaces the current entry for
+ * the same speech segment. A tool preamble and its final answer can share one
+ * segment id while still arriving as distinct text streams.
+ */
+export function mergeTranscriptionHistory(
+  previous: TextStreamData[],
+  current: TextStreamData[],
+  maxEntries = DEFAULT_TRANSCRIPTION_HISTORY_SIZE
+): TextStreamData[] {
+  if (current.length === 0) return previous;
+
+  const byStreamId = new Map(previous.map((entry) => [entry.streamInfo.id, entry]));
+  current.forEach((entry) => byStreamId.set(entry.streamInfo.id, entry));
+
+  return Array.from(byStreamId.values())
+    .sort((a, b) => a.streamInfo.timestamp - b.streamInfo.timestamp)
+    .slice(-maxEntries);
+}
diff --git a/tests/chat-message-filter.test.mjs b/tests/chat-message-filter.test.mjs
index 9f3074b99..632df3fcd 100644
--- a/tests/chat-message-filter.test.mjs
+++ b/tests/chat-message-filter.test.mjs
@@ -3,6 +3,19 @@ import { readFile } from 'node:fs/promises';
 import { test } from 'node:test';
 
 const { isRenderableChatMessage } = await import('../lib/chat-message-filter.ts');
+const { mergeTranscriptionHistory } = await import('../lib/transcription-history.ts');
+
+function transcription(id, segmentId, timestamp, text) {
+  return {
+    text,
+    participantInfo: { identity: 'frontdesk-agent' },
+    streamInfo: {
+      id,
+      timestamp,
+      attributes: { 'lk.segment_id': segmentId },
+    },
+  };
+}
 
 test('chat message filter hides empty transcription messages', () => {
   assert.equal(isRenderableChatMessage({ message: '' }), false);
@@ -19,3 +32,33 @@ test('chat message hook filters empty merged messages before sorting', async ()
   assert.match(source, /isRenderableChatMessage/);
   assert.match(source, /\.filter\(isRenderableChatMessage\)/);
 });
+
+test('transcription history preserves a tool preamble replaced by the final stream', () => {
+  const preamble = transcription('stream-preamble', 'speech-1', 100, '我查一下。');
+  const final = transcription('stream-final', 'speech-1', 200, '已经设置好了。');
+
+  const history = mergeTranscriptionHistory([preamble], [final]);
+
+  assert.deepEqual(
+    history.map(({ text }) => text),
+    ['我查一下。', '已经设置好了。']
+  );
+});
+
+test('transcription history updates partial text without duplicating one stream', () => {
+  const partial = transcription('stream-1', 'speech-1', 100, '我查');
+  const completed = transcription('stream-1', 'speech-1', 100, '我查一下。');
+
+  const history = mergeTranscriptionHistory([partial], [completed]);
+
+  assert.equal(history.length, 1);
+  assert.equal(history[0].text, '我查一下。');
+});
+
+test('transcription history survives a transient empty snapshot', () => {
+  const preamble = transcription('stream-1', 'speech-1', 100, '我查一下。');
+
+  const history = mergeTranscriptionHistory([preamble], []);
+
+  assert.deepEqual(history, [preamble]);
+});
diff --git a/tests/session-dispatch-client.test.mjs b/tests/session-dispatch-client.test.mjs
index 09bb1e45a..3e0c9a8c2 100644
--- a/tests/session-dispatch-client.test.mjs
+++ b/tests/session-dispatch-client.test.mjs
@@ -43,7 +43,7 @@ test('agent session dispatch sends only canonical session id to Next API', async
   }
 });
 
-test('agent session dispatch can require room video input readiness', async () => {
+test('agent session dispatch can require authoritative session readiness', async () => {
   const originalFetch = globalThis.fetch;
   let postedBody;
   globalThis.fetch = async (_url, init) => {
@@ -55,13 +55,13 @@ test('agent session dispatch can require room video input readiness', async () =
     const { requestAgentSessionDispatch } = await loadSessionDispatchClientModule();
 
     await requestAgentSessionDispatch('agent-a', '11111111-2222-4333-8444-555555555555', {
-      requireRoomVideoInputReady: true,
+      requireAgentSessionReady: true,
     });
 
     assert.deepEqual(postedBody, {
       agentName: 'agent-a',
       sessionId: '11111111-2222-4333-8444-555555555555',
-      requireRoomVideoInputReady: true,
+      requireAgentSessionReady: true,
     });
   } finally {
     globalThis.fetch = originalFetch;
diff --git a/tests/session-dispatch-readiness.test.mjs b/tests/session-dispatch-readiness.test.mjs
index 7977a5d74..93567c1d6 100644
--- a/tests/session-dispatch-readiness.test.mjs
+++ b/tests/session-dispatch-readiness.test.mjs
@@ -62,6 +62,24 @@ test('dispatch can require room video input readiness before reusing an agent',
   );
 });
 
+test('dispatch accepts the server SDK camel-cased agent ready attribute', () => {
+  const agent = participant({
+    identity: 'agent-AJ_ready',
+    kind: ParticipantInfo_Kind.AGENT,
+    attributes: {
+      lkAgentName: 'frontdesk-agent',
+      liveavatarAgentSessionReady: 'true',
+    },
+  });
+
+  assert.equal(
+    findReusableAgentParticipant([agent], 'frontdesk-agent', {
+      requireAgentSessionReady: true,
+    }),
+    agent
+  );
+});
+
 test('dispatch can reuse an active agent once room video input is publishing', () => {
   const agent = participant({
     identity: 'agent-AJ_running',
diff --git a/tests/session-prewarm.test.mjs b/tests/session-prewarm.test.mjs
index 9a44fdb32..243ac835e 100644
--- a/tests/session-prewarm.test.mjs
+++ b/tests/session-prewarm.test.mjs
@@ -331,7 +331,7 @@ test('missing LiveKit configuration fails before registering a room session', as
   }
 });
 
-test('regular dispatch keeps its 8s timeout while prewarm gets the default 45s total budget', async () => {
+test('regular dispatch keeps its 30s timeout while prewarm gets the default 45s total budget', async () => {
   const originalNow = Date.now;
   const originalTimeout = process.env.AGENT_DISPATCH_TIMEOUT_MS;
   const originalPrewarmTimeout = process.env.LIVEAVATAR_PREWARM_TOTAL_TIMEOUT_MS;
@@ -384,7 +384,7 @@ test('regular dispatch keeps its 8s timeout while prewarm gets the default 45s t
       ),
       /agent dispatch failed/
     );
-    assert.equal(now - regularStartedAt, 8_000);
+    assert.equal(now - regularStartedAt, 30_000);
 
     const prewarmStartedAt = now;
     await assert.rejects(
@@ -1322,7 +1322,7 @@ test('shared dispatch token stays active through per-caller readiness waits', as
   assert.doesNotMatch(readinessSource, /beginRoomSessionDispatch|finishRoomSessionDispatch/);
 });
 
-test('prewarm waits for the agent session and both room input participants', async () => {
+test('prewarm completes when the agent session is ready without waiting for optional video input', async () => {
   const agentName = 'frontdesk-browser-agent-readiness';
   let roomCreated = false;
   let workerReady = false;
@@ -1395,7 +1395,7 @@ test('prewarm waits for the agent session and both room input participants', asy
   assert.deepEqual(result.readiness, {
     agentSessionReady: true,
     audioParticipantReady: true,
-    visionParticipantReady: true,
+    visionParticipantReady: false,
   });
 });
 
diff --git a/tests/session-start-dispatch.test.mjs b/tests/session-start-dispatch.test.mjs
index dca58fa7e..eba6d783f 100644
--- a/tests/session-start-dispatch.test.mjs
+++ b/tests/session-start-dispatch.test.mjs
@@ -175,8 +175,8 @@ test('session dispatch route only accepts anonymous LiveKit agent fallback after
     serviceSource,
     /const alreadyJoined = await findReusableAgentParticipant\(\s*roomClient,\s*roomName,\s*agentName,\s*reusableAgentOptions\s*\);/
   );
-  assert.match(routeSource, /requireRoomVideoInputReady/);
-  assert.match(routeSource, /require_room_video_input_ready/);
+  assert.match(routeSource, /requireAgentSessionReady/);
+  assert.match(routeSource, /require_agent_session_ready/);
   assert.match(readinessSource, /type AgentParticipantMatchOptions/);
   assert.match(readinessSource, /type ReusableAgentParticipantOptions/);
   assert.match(readinessSource, /allowAnonymousLiveKitAgentFallback/);
@@ -207,9 +207,12 @@ test('start call dispatches the agent with a cancellable room session id', async
   assert.match(useRoomSource, /isExpectedStartCancellation/);
   assert.match(useRoomSource, /waitForAgentSessionStop/);
   assert.match(useRoomSource, /requestAgentSessionDispatch\(\s*appConfig\.agentName,\s*sessionId,/);
-  assert.match(
-    useRoomSource,
-    /requireRoomVideoInputReady: requiresRoomVideoInputReady\(appConfig\)/
+  assert.match(useRoomSource, /requireAgentSessionReady: usesManagedRoomInput/);
+  assert.match(useRoomSource, /await Promise\.allSettled\(\[/);
+  assert.ok(
+    useRoomSource.lastIndexOf('setIsSessionActive(true)') >
+      useRoomSource.lastIndexOf('await dispatchAgentSession()'),
+    'session view must become active only after dispatch readiness completes'
   );
   assert.doesNotMatch(useRoomSource, /requestAgentSessionDispatch\(\s*room\.name,/);
 });