diff --git a/src/stores/chat.ts b/src/stores/chat.ts
index 9c455c9..033e0fc 100644
--- a/src/stores/chat.ts
+++ b/src/stores/chat.ts
@@ -9,6 +9,7 @@ import { useGatewayStore } from './gateway';
 import { useAgentsStore } from './agents';
 import { buildBaselineRunKey, captureBaseline, clearBaselines } from './baseline-cache';
 import { buildCronSessionHistoryPath, isCronSessionKey } from './chat/cron-session-utils';
+import { pickStartupSessionFallback } from './chat/session-selection';
 import {
   CHAT_HISTORY_DISK_FALLBACK_TIMEOUT_MS,
   CHAT_HISTORY_STARTUP_RETRY_DELAYS_MS,
@@ -1463,6 +1464,13 @@ function buildSessionSwitchPatch(
   nextSessionKey: string,
 ): Partial<ChatState> {
   captureSessionRunState(state.currentSessionKey, state);
+  if (state.messages.length > 0) {
+    cacheSessionHistory(
+      state.currentSessionKey,
+      cloneHistoryMessages(state.messages),
+      state.thinkingLevel ?? null,
+    );
+  }
   // Only treat sessions with no history records and no activity timestamp as empty.
   // Relying solely on messages.length is unreliable because switchSession clears
   // the current messages before loadHistory runs, creating a race condition that
@@ -1970,6 +1978,31 @@ function postUserSegmentMessages(filteredMessages: RawMessage[]): RawMessage[] {
   return [];
 }
 
+/** Only treat inbound runs as user-visible for this long after the last user send. */
+const USER_INITIATED_RUN_MAX_AGE_MS = 10 * 60 * 1000;
+
+function hasCachedActiveUserRun(sessionKey: string): boolean {
+  const cached = getCachedSessionRunState(sessionKey);
+  return cached.sending || cached.activeRunId != null || cached.pendingFinal;
+}
+
+function shouldTrackInboundRunLifecycle(
+  state: Pick<ChatState, 'lastUserMessageAt' | 'sending' | 'activeRunId' | 'pendingFinal'>,
+  sessionKey?: string,
+): boolean {
+  if (state.sending || state.activeRunId != null || state.pendingFinal) return true;
+  if (sessionKey && hasCachedActiveUserRun(sessionKey)) return true;
+  if (!state.lastUserMessageAt) return false;
+  return Date.now() - toMs(state.lastUserMessageAt) <= USER_INITIATED_RUN_MAX_AGE_MS;
+}
+
+function isFailedAssistantTurnMessage(message: RawMessage | unknown): boolean {
+  if (!message || typeof message !== 'object') return false;
+  const msg = message as RawMessage;
+  if (msg.role !== 'assistant') return false;
+  return /\[assistant turn failed/i.test(getMessageText(msg.content));
+}
+
 function segmentHasOpenToolRun(segmentMessages: RawMessage[]): boolean {
   if (segmentMessages.length === 0) return false;
   const hasToolActivity = segmentMessages.some(
@@ -2094,7 +2127,10 @@ export const useChatStore = create<ChatState>((set, get) => ({
             // default ghost key (`agent:main:main`) should yield to real history.
             const hasLocalPendingSession = localSessions.some((session) => session.key === nextSessionKey);
             if (!hasLocalPendingSession) {
-              nextSessionKey = dedupedSessions[0].key;
+              const fallbackKey = pickStartupSessionFallback(nextSessionKey, dedupedSessions);
+              if (fallbackKey) {
+                nextSessionKey = fallbackKey;
+              }
             }
           }
 
@@ -2111,15 +2147,33 @@ export const useChatStore = create<ChatState>((set, get) => ({
               .map((session) => [session.key, session.updatedAt!]),
           );
 
-          set((state) => ({
-            sessions: sessionsWithCurrent,
-            currentSessionKey: nextSessionKey,
-            currentAgentId: getAgentIdFromSessionKey(nextSessionKey),
-            sessionLastActivity: {
-              ...state.sessionLastActivity,
-              ...discoveredActivity,
-            },
-          }));
+          const previousSessionKey = currentSessionKey;
+          if (previousSessionKey !== nextSessionKey) {
+            // Mirror switchSession: stop in-flight history polls and swap cached
+            // history/run state immediately. Without this, a background loadSessions
+            // can retarget currentSessionKey (e.g. to a cron heartbeat session)
+            // while messages[] still holds the prior conversation until
+            // chat.history returns — which looks like cross-session contamination.
+            clearHistoryPoll();
+            set((state) => ({
+              ...buildSessionSwitchPatch(state, nextSessionKey),
+              sessions: sessionsWithCurrent,
+              sessionLastActivity: {
+                ...state.sessionLastActivity,
+                ...discoveredActivity,
+              },
+            }));
+          } else {
+            set((state) => ({
+              sessions: sessionsWithCurrent,
+              currentSessionKey: nextSessionKey,
+              currentAgentId: getAgentIdFromSessionKey(nextSessionKey),
+              sessionLastActivity: {
+                ...state.sessionLastActivity,
+                ...discoveredActivity,
+              },
+            }));
+          }
           applySessionBackendLabels(set, sessionsWithCurrent);
 
           // Background: fetch first user message for every non-main session to populate labels upfront.
@@ -2181,7 +2235,7 @@ export const useChatStore = create<ChatState>((set, get) => ({
             })();
           }
 
-          if (currentSessionKey !== nextSessionKey) {
+          if (previousSessionKey !== nextSessionKey) {
             void get().loadHistory();
           }
         }
@@ -2455,11 +2509,11 @@ export const useChatStore = create<ChatState>((set, get) => ({
       const applyLoadFailure = (errorMessage: string | null) => {
         if (!isCurrentSession()) return;
         set((state) => {
-          const hasMessages = state.messages.length > 0;
+          const mergedMessages = mergePendingOptimisticUserMessages(currentSessionKey, state.messages);
           return {
             loading: false,
             error: shouldShowForegroundLoading && errorMessage ? errorMessage : state.error,
-            ...(hasMessages ? {} : { messages: [] as RawMessage[] }),
+            ...(mergedMessages.length > 0 ? { messages: mergedMessages } : { messages: [] as RawMessage[] }),
           };
         });
       };
@@ -2515,11 +2569,15 @@ export const useChatStore = create<ChatState>((set, get) => ({
             }
             return filteredMessages;
           })();
-      const lastAssistantAfterBoundary = [...postBoundaryMessages].reverse().find((msg) => msg.role === 'assistant');
-      const latestTerminalAssistantErrorMessage = lastAssistantAfterBoundary
-        && getMessageStopReason(lastAssistantAfterBoundary) === 'error'
-        ? getMessageErrorMessage(lastAssistantAfterBoundary)
-        : null;
+        const lastAssistantAfterBoundary = [...postBoundaryMessages].reverse().find((msg) => msg.role === 'assistant');
+        const latestTerminalAssistantErrorMessage = lastAssistantAfterBoundary
+          && (getMessageStopReason(lastAssistantAfterBoundary) === 'error'
+            || isFailedAssistantTurnMessage(lastAssistantAfterBoundary))
+          ? (getMessageErrorMessage(lastAssistantAfterBoundary)
+            ?? (isFailedAssistantTurnMessage(lastAssistantAfterBoundary)
+              ? getMessageText(lastAssistantAfterBoundary.content)
+              : null))
+          : null;
       const historyErrorIsTransient = Boolean(
         latestTerminalAssistantErrorMessage
         && isSendingNow
@@ -2632,11 +2690,11 @@ export const useChatStore = create<ChatState>((set, get) => ({
         }
       }
 
-      // After session switch (or cold load) the renderer may have reset run
-      // lifecycle flags even though the Gateway is still executing tools.
-      // Re-arm from authoritative history when the latest user turn has tool
-      // activity but no final reply yet.
-      if (!get().sending && !latestTerminalAssistantErrorMessage) {
+      // After session switch the renderer may have reset run lifecycle flags even
+      // though the Gateway is still executing a user-initiated turn. Re-arm only
+      // when this session had an active cached run (e.g. user switched away
+      // mid-send). Do not re-arm from stale :main heartbeat/tool history alone.
+      if (!get().sending && !latestTerminalAssistantErrorMessage && hasCachedActiveUserRun(currentSessionKey)) {
         const openSegment = postUserSegmentMessages(filteredMessages);
         if (segmentHasOpenToolRun(openSegment)) {
           const lastUser = findLastRealUserMessage(filteredMessages);
@@ -2649,6 +2707,20 @@ export const useChatStore = create<ChatState>((set, get) => ({
           captureSessionRunState(currentSessionKey, get());
         }
       }
+
+      if (
+        get().sending
+        && !latestTerminalAssistantErrorMessage
+        && !shouldTrackInboundRunLifecycle(get(), currentSessionKey)
+      ) {
+        clearHistoryPoll();
+        set({
+          sending: false,
+          activeRunId: null,
+          pendingFinal: false,
+          lastUserMessageAt: null,
+        });
+      }
       return true;
       };
 
@@ -3107,19 +3179,18 @@ export const useChatStore = create<ChatState>((set, get) => ({
       || resolvedState === 'error' || resolvedState === 'aborted';
     if (hasUsefulData) {
       clearHistoryPoll();
-      // Adopt run started from another client (e.g. console at 127.0.0.1:18789):
-      // show loading/streaming in the app when this session has an active run.
+      // Adopt run started from another client only for user-initiated turns.
+      // Background :main heartbeat runs must not surface "Thinking..." in the UI.
       const { sending } = get();
-      if (!sending && runId) {
-          set({ sending: true, activeRunId: runId, error: null, runError: null });
+      if (!sending && runId && shouldTrackInboundRunLifecycle(get(), currentSessionKey)) {
+        set({ sending: true, activeRunId: runId, error: null, runError: null });
       }
     }
 
     switch (resolvedState) {
       case 'started': {
-        // Run just started (e.g. from console); show loading immediately.
         const { sending: currentSending } = get();
-        if (!currentSending && runId) {
+        if (!currentSending && runId && shouldTrackInboundRunLifecycle(get(), currentSessionKey)) {
           set({ sending: true, activeRunId: runId, error: null, runError: null });
         }
         break;
diff --git a/src/stores/chat/session-actions.ts b/src/stores/chat/session-actions.ts
index 0f04bea..c9b5081 100644
--- a/src/stores/chat/session-actions.ts
+++ b/src/stores/chat/session-actions.ts
@@ -1,5 +1,6 @@
 import { invokeIpc } from '@/lib/api-client';
 import { clearPendingOptimisticUserMessages, getCanonicalPrefixFromSessions, getMessageText, toMs } from './helpers';
+import { pickStartupSessionFallback } from './session-selection';
 import { DEFAULT_CANONICAL_PREFIX, DEFAULT_SESSION_KEY, type ChatSession, type RawMessage } from './types';
 import type { ChatGet, ChatSet, SessionHistoryActions } from './store-api';
 
@@ -115,10 +116,12 @@ export function createSessionActions(
             }
           }
           if (!dedupedSessions.find((s) => s.key === nextSessionKey) && dedupedSessions.length > 0) {
-            // Current session not found in the backend list
             const isNewEmptySession = get().messages.length === 0;
             if (!isNewEmptySession) {
-              nextSessionKey = dedupedSessions[0].key;
+              const fallbackKey = pickStartupSessionFallback(nextSessionKey, dedupedSessions);
+              if (fallbackKey) {
+                nextSessionKey = fallbackKey;
+              }
             }
           }
 
diff --git a/src/stores/chat/session-selection.ts b/src/stores/chat/session-selection.ts
new file mode 100644
index 0000000..346e723
--- /dev/null
+++ b/src/stores/chat/session-selection.ts
@@ -0,0 +1,39 @@
+import { isCronSessionKey } from './cron-session-utils';
+import type { ChatSession } from './types';
+
+function getAgentIdFromSessionKey(sessionKey: string): string {
+  if (!sessionKey.startsWith('agent:')) return 'main';
+  const [, agentId] = sessionKey.split(':');
+  return agentId || 'main';
+}
+
+function sortByUpdatedAtDesc(sessions: ChatSession[]): ChatSession[] {
+  return [...sessions].sort((a, b) => (b.updatedAt ?? 0) - (a.updatedAt ?? 0));
+}
+
+/**
+ * When the current session key is missing from `sessions.list`, pick a safer
+ * replacement than `sessions[0]`. Cron/heartbeat sessions must never become
+ * the implicit startup target just because they sort first in the gateway list.
+ */
+export function pickStartupSessionFallback(
+  currentSessionKey: string,
+  sessions: ChatSession[],
+): string | null {
+  if (sessions.length === 0) return null;
+
+  const agentId = getAgentIdFromSessionKey(currentSessionKey);
+  const agentMainKey = `agent:${agentId}:main`;
+  const agentMain = sessions.find((session) => session.key === agentMainKey);
+  if (agentMain) return agentMain.key;
+
+  const agentNonCron = sortByUpdatedAtDesc(
+    sessions.filter((session) => session.key.startsWith(`agent:${agentId}:`) && !isCronSessionKey(session.key)),
+  );
+  if (agentNonCron.length > 0) return agentNonCron[0]!.key;
+
+  const nonCron = sortByUpdatedAtDesc(sessions.filter((session) => !isCronSessionKey(session.key)));
+  if (nonCron.length > 0) return nonCron[0]!.key;
+
+  return null;
+}
diff --git a/tests/unit/chat-load-sessions-startup.test.ts b/tests/unit/chat-load-sessions-startup.test.ts
new file mode 100644
index 0000000..872ee83
--- /dev/null
+++ b/tests/unit/chat-load-sessions-startup.test.ts
@@ -0,0 +1,156 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+const runtimeStatus = {
+  state: 'running',
+  port: 18789,
+  connectedAt: 0,
+};
+
+const { gatewayRpcMock } = vi.hoisted(() => ({
+  gatewayRpcMock: vi.fn(),
+}));
+
+vi.mock('@/stores/gateway', () => ({
+  useGatewayStore: {
+    getState: () => ({
+      status: runtimeStatus,
+      rpc: gatewayRpcMock,
+    }),
+  },
+}));
+
+vi.mock('@/stores/agents', () => ({
+  useAgentsStore: {
+    getState: () => ({ agents: [] }),
+  },
+}));
+
+vi.mock('@/lib/host-api', () => ({
+  hostApiFetch: vi.fn().mockResolvedValue({ success: true, summaries: [] }),
+}));
+
+describe('chat store loadSessions startup selection', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    gatewayRpcMock.mockReset();
+    runtimeStatus.connectedAt = Date.now();
+  });
+
+  afterEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('opens the latest non-cron session instead of a cron heartbeat session', async () => {
+    gatewayRpcMock.mockImplementation(async (method: string) => {
+      if (method === 'sessions.list') {
+        return {
+          sessions: [
+            {
+              key: 'agent:main:cron:heartbeat',
+              label: 'Main Agent heartbeat',
+              updatedAt: 9_000,
+            },
+            {
+              key: 'agent:main:session-a',
+              displayName: 'PDF summary',
+              updatedAt: 5_000,
+            },
+          ],
+        };
+      }
+      if (method === 'chat.history') {
+        return { messages: [] };
+      }
+      throw new Error(`Unexpected gateway RPC: ${method}`);
+    });
+
+    const { useChatStore } = await import('@/stores/chat');
+    useChatStore.setState({
+      currentSessionKey: 'agent:main:main',
+      currentAgentId: 'main',
+      sessions: [],
+      messages: [],
+      sessionLabels: {},
+      sessionLastActivity: {},
+    });
+
+    await useChatStore.getState().loadSessions();
+
+    expect(useChatStore.getState().currentSessionKey).toBe('agent:main:session-a');
+  });
+
+  it('clears the prior conversation when loadSessions retargets to another session', async () => {
+    gatewayRpcMock.mockImplementation(async (method: string) => {
+      if (method === 'sessions.list') {
+        return {
+          sessions: [
+            {
+              key: 'agent:main:cron:heartbeat',
+              label: 'Main Agent heartbeat',
+              updatedAt: 9_000,
+            },
+            {
+              key: 'agent:main:session-b',
+              displayName: 'Other chat',
+              updatedAt: 5_000,
+            },
+          ],
+        };
+      }
+      if (method === 'chat.history') {
+        return { messages: [] };
+      }
+      throw new Error(`Unexpected gateway RPC: ${method}`);
+    });
+
+    const { useChatStore } = await import('@/stores/chat');
+    useChatStore.setState({
+      currentSessionKey: 'agent:main:main',
+      currentAgentId: 'main',
+      sessions: [],
+      messages: [{ role: 'user', content: 'question from another chat' }],
+      sessionLabels: {},
+      sessionLastActivity: {},
+    });
+
+    await useChatStore.getState().loadSessions();
+
+    expect(useChatStore.getState().currentSessionKey).toBe('agent:main:session-b');
+    expect(useChatStore.getState().messages).toEqual([]);
+  });
+
+  it('keeps the default main ghost session when only cron sessions exist', async () => {
+    gatewayRpcMock.mockImplementation(async (method: string) => {
+      if (method === 'sessions.list') {
+        return {
+          sessions: [
+            {
+              key: 'agent:main:cron:heartbeat',
+              label: 'Main Agent heartbeat',
+              updatedAt: 9_000,
+            },
+          ],
+        };
+      }
+      if (method === 'chat.history') {
+        return { messages: [] };
+      }
+      throw new Error(`Unexpected gateway RPC: ${method}`);
+    });
+
+    const { useChatStore } = await import('@/stores/chat');
+    useChatStore.setState({
+      currentSessionKey: 'agent:main:main',
+      currentAgentId: 'main',
+      sessions: [],
+      messages: [],
+      sessionLabels: {},
+      sessionLastActivity: {},
+    });
+
+    await useChatStore.getState().loadSessions();
+
+    expect(useChatStore.getState().currentSessionKey).toBe('agent:main:main');
+    expect(useChatStore.getState().sessions.some((session) => session.key === 'agent:main:main')).toBe(true);
+  });
+});
diff --git a/tests/unit/chat-session-selection.test.ts b/tests/unit/chat-session-selection.test.ts
new file mode 100644
index 0000000..33fe431
--- /dev/null
+++ b/tests/unit/chat-session-selection.test.ts
@@ -0,0 +1,41 @@
+import { describe, expect, it } from 'vitest';
+import { pickStartupSessionFallback } from '@/stores/chat/session-selection';
+import type { ChatSession } from '@/stores/chat/types';
+
+describe('pickStartupSessionFallback', () => {
+  it('prefers the agent main session when present', () => {
+    const sessions: ChatSession[] = [
+      { key: 'agent:main:cron:heartbeat', label: 'heartbeat', updatedAt: 9_000 },
+      { key: 'agent:main:main', displayName: 'Main', updatedAt: 1_000 },
+    ];
+
+    expect(pickStartupSessionFallback('agent:main:main', sessions)).toBe('agent:main:main');
+  });
+
+  it('prefers the most recently updated non-cron session for the agent', () => {
+    const sessions: ChatSession[] = [
+      { key: 'agent:main:cron:heartbeat', label: 'heartbeat', updatedAt: 9_000 },
+      { key: 'agent:main:session-old', updatedAt: 2_000 },
+      { key: 'agent:main:session-new', updatedAt: 5_000 },
+    ];
+
+    expect(pickStartupSessionFallback('agent:main:main', sessions)).toBe('agent:main:session-new');
+  });
+
+  it('does not auto-select cron sessions when only cron entries exist', () => {
+    const sessions: ChatSession[] = [
+      { key: 'agent:main:cron:heartbeat', label: 'heartbeat', updatedAt: 9_000 },
+    ];
+
+    expect(pickStartupSessionFallback('agent:main:main', sessions)).toBeNull();
+  });
+
+  it('falls back to non-cron sessions from other agents before cron', () => {
+    const sessions: ChatSession[] = [
+      { key: 'agent:main:cron:heartbeat', updatedAt: 9_000 },
+      { key: 'agent:research:desk', updatedAt: 3_000 },
+    ];
+
+    expect(pickStartupSessionFallback('agent:main:main', sessions)).toBe('agent:research:desk');
+  });
+});
diff --git a/tests/unit/chat-store-history-retry.test.ts b/tests/unit/chat-store-history-retry.test.ts
index da14603..6df544f 100644
--- a/tests/unit/chat-store-history-retry.test.ts
+++ b/tests/unit/chat-store-history-retry.test.ts
@@ -287,6 +287,85 @@ describe('useChatStore startup history retry', () => {
     expect(useChatStore.getState().messages.map((message) => message.content)).toEqual(['cached history']);
   });
 
+  it('does not re-arm Thinking state for stale main-session heartbeat tool history', async () => {
+    const { useChatStore } = await import('@/stores/chat');
+
+    gatewayRpcMock.mockResolvedValue({
+      messages: [
+        { id: 'user-old', role: 'user', content: 'old question', timestamp: 1_000 },
+        {
+          id: 'assistant-tool',
+          role: 'assistant',
+          content: [{ type: 'toolCall', id: 'tool-1', name: 'read', arguments: { path: '~/.openclaw/workspace/HEARTBEAT.md' } }],
+          stopReason: 'toolUse',
+          timestamp: 1_100,
+        },
+      ],
+    });
+
+    useChatStore.setState({
+      currentSessionKey: 'agent:main:main',
+      currentAgentId: 'main',
+      sessions: [{ key: 'agent:main:main' }],
+      messages: [],
+      sessionLabels: {},
+      sessionLastActivity: {},
+      sending: false,
+      activeRunId: null,
+      streamingText: '',
+      streamingMessage: null,
+      streamingTools: [],
+      pendingFinal: false,
+      lastUserMessageAt: null,
+      pendingToolImages: [],
+      error: null,
+      loading: false,
+      thinkingLevel: null,
+    });
+
+    await useChatStore.getState().loadHistory(false);
+
+    expect(useChatStore.getState().sending).toBe(false);
+    expect(useChatStore.getState().activeRunId).toBeNull();
+  });
+
+  it('switchSession preserves unsynced optimistic user messages when switching back', async () => {
+    const { useChatStore } = await import('@/stores/chat');
+    const optimisticHello = {
+      id: 'user-hello-opt',
+      role: 'user' as const,
+      content: '你好',
+      timestamp: 1_700_000_000,
+    };
+
+    useChatStore.setState({
+      currentSessionKey: 'agent:main:session-a',
+      currentAgentId: 'main',
+      sessions: [{ key: 'agent:main:session-a' }, { key: 'agent:main:other' }],
+      messages: [optimisticHello],
+      sessionLabels: {},
+      sessionLastActivity: { 'agent:main:session-a': Date.now() },
+      sending: true,
+      activeRunId: 'run-hello',
+      streamingText: '',
+      streamingMessage: null,
+      streamingTools: [],
+      pendingFinal: false,
+      lastUserMessageAt: Date.now(),
+      pendingToolImages: [],
+      error: null,
+      loading: false,
+      thinkingLevel: null,
+    });
+
+    gatewayRpcMock.mockResolvedValue({ messages: [] });
+
+    useChatStore.getState().switchSession('agent:main:other');
+    useChatStore.getState().switchSession('agent:main:session-a');
+
+    expect(useChatStore.getState().messages.map((message) => message.content)).toEqual(['你好']);
+  });
+
   it('switchSession restores in-flight run state so Thinking indicator survives navigation', async () => {
     const { useChatStore } = await import('@/stores/chat');
     useChatStore.setState({