diff --git a/frontend/app/app/assistant.tsx b/frontend/app/app/assistant.tsx
index 633f5af..3d20005 100644
--- a/frontend/app/app/assistant.tsx
+++ b/frontend/app/app/assistant.tsx
@@ -16,7 +16,7 @@ import {
 } from "@/components/assistant-ui/activity-panel";
 import { Thread } from "@/components/assistant-ui/thread";
 import {
-	fetchLatestRunStatus,
+	type fetchLatestRunStatus,
 	toReplayRepository,
 } from "@/components/assistant-ui/thread-list";
 import { ThreadListSidebar } from "@/components/assistant-ui/threadlist-sidebar";
@@ -35,6 +35,10 @@ import {
 	readPendingWorkspaceSessionId,
 	writeActiveSessionId,
 } from "@/lib/claw-active-session";
+import {
+	fetchSessionReplaySnapshot,
+	readCachedSessionReplay,
+} from "@/lib/claw-session-cache";
 import { ClawSessionReplayProvider } from "@/lib/claw-session-replay";
 import { pushSessionUrl, readSessionIdFromUrl } from "@/lib/claw-session-url";
 import {
@@ -112,23 +116,46 @@ export const Assistant = ({ initialSessionId }: AssistantProps = {}) => {
 		loadedInitialSessionRef.current = sessionId;
 		const targetSessionId = sessionId;
 		let cancelled = false;
+		const abortController = new AbortController();
 
 		async function loadSession() {
 			try {
 				writeActiveSessionId(targetSessionId);
-				const response = await fetch(`/api/claw/sessions/${targetSessionId}`, {
-					cache: "no-store",
-				});
-				if (!response.ok || cancelled) return;
-				const payload = await response.json();
-				const runStatus = await fetchLatestRunStatus(targetSessionId);
+				const cached = readCachedSessionReplay<
+					Parameters<typeof toReplayRepository>[0],
+					Awaited<ReturnType<typeof fetchLatestRunStatus>>
+				>(targetSessionId);
+				if (cached && !cancelled) {
+					replaySession(
+						targetSessionId,
+						toReplayRepository(
+							cached.session,
+							targetSessionId,
+							cached.runStatus,
+						),
+					);
+				}
+				const snapshot = await fetchSessionReplaySnapshot<
+					Parameters<typeof toReplayRepository>[0],
+					Awaited<ReturnType<typeof fetchLatestRunStatus>>
+				>(targetSessionId, { signal: abortController.signal });
 				if (cancelled) return;
-				replaySession(
-					targetSessionId,
-					toReplayRepository(payload, targetSessionId, runStatus),
-				);
+				if (!snapshot) return;
+				if (!cached || snapshot.signature !== cached.signature) {
+					replaySession(
+						targetSessionId,
+						toReplayRepository(
+							snapshot.session,
+							targetSessionId,
+							snapshot.runStatus,
+						),
+					);
+				}
 				pushSessionUrl(targetSessionId);
-			} catch {
+			} catch (error) {
+				if (error instanceof DOMException && error.name === "AbortError") {
+					return;
+				}
 				if (!cancelled) {
 					loadedInitialSessionRef.current = null;
 				}
@@ -138,6 +165,7 @@ export const Assistant = ({ initialSessionId }: AssistantProps = {}) => {
 		void loadSession();
 		return () => {
 			cancelled = true;
+			abortController.abort();
 		};
 	}, [account, initialSessionId, replaySession]);
 
@@ -252,8 +280,7 @@ function AssistantWorkspace() {
 		const handleChanged = (event: Event) => {
 			const customEvent = event as CustomEvent<{ sessionId?: string | null }>;
 			const hasExplicitSession =
-				customEvent.detail &&
-				Object.prototype.hasOwnProperty.call(customEvent.detail, "sessionId");
+				customEvent.detail && Object.hasOwn(customEvent.detail, "sessionId");
 			const next = hasExplicitSession
 				? (customEvent.detail.sessionId ?? null)
 				: (readSessionIdFromUrl() ?? readActiveSessionId());
diff --git a/frontend/app/components/assistant-ui/thread-list.tsx b/frontend/app/components/assistant-ui/thread-list.tsx
index 73e63ea..0e33ae7 100644
--- a/frontend/app/components/assistant-ui/thread-list.tsx
+++ b/frontend/app/components/assistant-ui/thread-list.tsx
@@ -29,6 +29,12 @@ import {
 	writeActiveSessionId,
 	writePendingWorkspaceSessionId,
 } from "@/lib/claw-active-session";
+import {
+	fetchSessionReplaySnapshot,
+	invalidateCachedSessionReplay,
+	readCachedSessionReplay,
+	type SessionReplaySnapshot,
+} from "@/lib/claw-session-cache";
 import { useClawSessionReplay } from "@/lib/claw-session-replay";
 import { pushHomeUrl, pushSessionUrl } from "@/lib/claw-session-url";
 
@@ -113,6 +119,27 @@ type ClawStoredToolCall = {
 	};
 };
 
+type ReplaySessionFn = (
+	sessionId: string,
+	repository: ExportedMessageRepository,
+) => void;
+
+type ClawReplaySnapshot = SessionReplaySnapshot<
+	ClawStoredSession,
+	ClawRunStatus
+>;
+
+function replaySessionSnapshot(
+	replaySession: ReplaySessionFn,
+	sessionId: string,
+	snapshot: ClawReplaySnapshot,
+) {
+	replaySession(
+		sessionId,
+		toReplayRepository(snapshot.session, sessionId, snapshot.runStatus),
+	);
+}
+
 export const ThreadList: FC = () => {
 	return (
 		<ThreadListPrimitive.Root className="aui-root aui-thread-list-root flex min-h-0 flex-1 flex-col gap-1">
@@ -168,7 +195,7 @@ function ensureSidebarWorkspaceSessionId(): {
 }
 
 function workspaceDisplayLabel(entry: JupyterWorkspaceEntry): string {
-	if (entry.label && entry.label.trim()) return entry.label.trim();
+	if (entry.label?.trim()) return entry.label.trim();
 	if (entry.base_url) {
 		try {
 			return new URL(entry.base_url).host;
@@ -243,16 +270,15 @@ const JupyterWorkspaceList: FC = () => {
 			window.dispatchEvent(new Event("claw-sessions-changed"));
 			window.dispatchEvent(new Event("claw-workspaces-changed"));
 		} catch (err) {
-			setError(
-				err instanceof Error ? err.message : "切换工作区时网络异常",
-			);
+			setError(err instanceof Error ? err.message : "切换工作区时网络异常");
 		} finally {
 			setBindingId(null);
 		}
 	};
 
 	const remove = async (entry: JupyterWorkspaceEntry) => {
-		if (!window.confirm(`移除工作区「${workspaceDisplayLabel(entry)}」？`)) return;
+		if (!window.confirm(`移除工作区「${workspaceDisplayLabel(entry)}」？`))
+			return;
 		try {
 			const response = await fetch(
 				`/api/claw/jupyter/workspaces/${encodeURIComponent(entry.id)}`,
@@ -331,6 +357,8 @@ const ClawSessionList: FC = () => {
 		null,
 	);
 	const renameInputRef = useRef<HTMLInputElement | null>(null);
+	const openRequestRef = useRef(0);
+	const openAbortRef = useRef<AbortController | null>(null);
 
 	useEffect(() => {
 		setActiveSessionId(readActiveSessionId());
@@ -394,6 +422,51 @@ const ClawSessionList: FC = () => {
 		setDraftTitle("");
 	};
 
+	const openSession = async (sessionId: string) => {
+		const requestId = openRequestRef.current + 1;
+		openRequestRef.current = requestId;
+		openAbortRef.current?.abort();
+		const abortController = new AbortController();
+		openAbortRef.current = abortController;
+		const cached = readCachedSessionReplay<ClawStoredSession, ClawRunStatus>(
+			sessionId,
+		);
+
+		writeActiveSessionId(sessionId);
+		pushSessionUrl(sessionId);
+		setActiveSessionId(sessionId);
+		if (cached) {
+			replaySessionSnapshot(replaySession, sessionId, cached);
+			setLoadingSessionId(null);
+		} else {
+			setLoadingSessionId(sessionId);
+		}
+
+		try {
+			const snapshot = await fetchSessionReplaySnapshot<
+				ClawStoredSession,
+				ClawRunStatus
+			>(sessionId, { signal: abortController.signal });
+			if (requestId !== openRequestRef.current) return;
+			if (readActiveSessionId() !== sessionId) return;
+			if (!snapshot) return;
+			if (!cached || snapshot.signature !== cached.signature) {
+				replaySessionSnapshot(replaySession, sessionId, snapshot);
+			}
+		} catch (error) {
+			if (!(error instanceof DOMException && error.name === "AbortError")) {
+				console.warn("[session-list] failed to open session", error);
+			}
+		} finally {
+			if (requestId === openRequestRef.current) {
+				setLoadingSessionId(null);
+			}
+			if (openAbortRef.current === abortController) {
+				openAbortRef.current = null;
+			}
+		}
+	};
+
 	return (
 		<div className="min-h-0 flex-1 overflow-y-auto pr-1">
 			<div className="flex flex-col gap-1">
@@ -443,31 +516,7 @@ const ClawSessionList: FC = () => {
 											preview: session.preview,
 										});
 										setOpenMenuSessionId(null);
-										writeActiveSessionId(session.session_id);
-										pushSessionUrl(session.session_id);
-										setActiveSessionId(session.session_id);
-										setLoadingSessionId(session.session_id);
-										try {
-											const response = await fetch(
-												`/api/claw/sessions/${session.session_id}`,
-											);
-											if (!response.ok) return;
-											const payload =
-												(await response.json()) as ClawStoredSession;
-											const runStatus = await fetchLatestRunStatus(
-												session.session_id,
-											);
-											replaySession(
-												session.session_id,
-												toReplayRepository(
-													payload,
-													session.session_id,
-													runStatus,
-												),
-											);
-										} finally {
-											setLoadingSessionId(null);
-										}
+										await openSession(session.session_id);
 									}}
 								>
 									<span className="truncate">
@@ -525,6 +574,7 @@ const ClawSessionList: FC = () => {
 														(item) => item.session_id !== session.session_id,
 													),
 												);
+												invalidateCachedSessionReplay(session.session_id);
 												setOpenMenuSessionId(null);
 												if (activeSessionId === session.session_id) {
 													clearActiveSessionId();
diff --git a/frontend/app/components/assistant-ui/threadlist-sidebar.tsx b/frontend/app/components/assistant-ui/threadlist-sidebar.tsx
index 91998b0..3e3cf7c 100644
--- a/frontend/app/components/assistant-ui/threadlist-sidebar.tsx
+++ b/frontend/app/components/assistant-ui/threadlist-sidebar.tsx
@@ -14,12 +14,12 @@ import {
 } from "lucide-react";
 import { Popover as PopoverPrimitive } from "radix-ui";
 import type * as React from "react";
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 import type { ClawAccount } from "@/app/claw-account-gate";
 import { ClawLlmSettings } from "@/app/claw-llm-settings";
 import { ClawThemeSwitcher } from "@/app/claw-theme-switcher";
 import {
-	fetchLatestRunStatus,
+	type ClawRunStatus,
 	ThreadList,
 	toReplayRepository,
 } from "@/components/assistant-ui/thread-list";
@@ -49,6 +49,10 @@ import {
 	readActiveSessionId,
 	writeActiveSessionId,
 } from "@/lib/claw-active-session";
+import {
+	fetchSessionReplaySnapshot,
+	readCachedSessionReplay,
+} from "@/lib/claw-session-cache";
 import { useClawSessionReplay } from "@/lib/claw-session-replay";
 import { pushHomeUrl, pushSessionUrl } from "@/lib/claw-session-url";
 
@@ -384,6 +388,8 @@ function SessionResultButton({
 function useSidebarSessions(open: boolean) {
 	const [sessions, setSessions] = useState<SidebarSession[]>([]);
 	const [loadingSessionId, setLoadingSessionId] = useState<string | null>(null);
+	const openRequestRef = useRef(0);
+	const openAbortRef = useRef<AbortController | null>(null);
 
 	useEffect(() => {
 		if (!open) return;
@@ -417,22 +423,54 @@ function useSidebarSessions(open: boolean) {
 	) {
 		const cleanSessionId = normalizeSessionId(sessionId);
 		if (!cleanSessionId) return;
+		const requestId = openRequestRef.current + 1;
+		openRequestRef.current = requestId;
+		openAbortRef.current?.abort();
+		const abortController = new AbortController();
+		openAbortRef.current = abortController;
+		const cached = readCachedSessionReplay<ReplaySessionPayload, ClawRunStatus>(
+			cleanSessionId,
+		);
 		writeActiveSessionId(cleanSessionId);
 		pushSessionUrl(cleanSessionId);
-		setLoadingSessionId(sessionId);
-		try {
-			const response = await fetch(`/api/claw/sessions/${cleanSessionId}`, {
-				cache: "no-store",
-			});
-			if (!response.ok) return;
-			const payload = (await response.json()) as ReplaySessionPayload;
-			const runStatus = await fetchLatestRunStatus(cleanSessionId);
+		if (cached) {
 			replaySession(
 				cleanSessionId,
-				toReplayRepository(payload, cleanSessionId, runStatus),
+				toReplayRepository(cached.session, cleanSessionId, cached.runStatus),
 			);
-		} finally {
 			setLoadingSessionId(null);
+		} else {
+			setLoadingSessionId(sessionId);
+		}
+		try {
+			const snapshot = await fetchSessionReplaySnapshot<
+				ReplaySessionPayload,
+				ClawRunStatus
+			>(cleanSessionId, { signal: abortController.signal });
+			if (requestId !== openRequestRef.current) return;
+			if (readActiveSessionId() !== cleanSessionId) return;
+			if (!snapshot) return;
+			if (!cached || snapshot.signature !== cached.signature) {
+				replaySession(
+					cleanSessionId,
+					toReplayRepository(
+						snapshot.session,
+						cleanSessionId,
+						snapshot.runStatus,
+					),
+				);
+			}
+		} catch (error) {
+			if (!(error instanceof DOMException && error.name === "AbortError")) {
+				console.warn("[sidebar] failed to open session", error);
+			}
+		} finally {
+			if (requestId === openRequestRef.current) {
+				setLoadingSessionId(null);
+			}
+			if (openAbortRef.current === abortController) {
+				openAbortRef.current = null;
+			}
 		}
 	}
 
diff --git a/frontend/app/lib/claw-session-cache.ts b/frontend/app/lib/claw-session-cache.ts
new file mode 100644
index 0000000..e431d79
--- /dev/null
+++ b/frontend/app/lib/claw-session-cache.ts
@@ -0,0 +1,115 @@
+"use client";
+
+export type SessionReplaySnapshot<TSession = unknown, TRun = unknown> = {
+	sessionId: string;
+	session: TSession;
+	runStatus: TRun | null;
+	signature: string;
+	fetchedAt: number;
+};
+
+const MAX_REPLAY_CACHE_SIZE = 50;
+const replayCache = new Map<string, SessionReplaySnapshot>();
+
+export function readCachedSessionReplay<TSession = unknown, TRun = unknown>(
+	sessionId: string,
+): SessionReplaySnapshot<TSession, TRun> | null {
+	const cached = replayCache.get(sessionId);
+	if (!cached) return null;
+	// Refresh recency for LRU behavior.
+	replayCache.delete(sessionId);
+	replayCache.set(sessionId, cached);
+	return cached as SessionReplaySnapshot<TSession, TRun>;
+}
+
+export function invalidateCachedSessionReplay(sessionId: string) {
+	replayCache.delete(sessionId);
+}
+
+export async function fetchSessionReplaySnapshot<
+	TSession = unknown,
+	TRun = unknown,
+>(
+	sessionId: string,
+	options: { signal?: AbortSignal } = {},
+): Promise<SessionReplaySnapshot<TSession, TRun> | null> {
+	const [sessionResponse, runStatus] = await Promise.all([
+		fetch(`/api/claw/sessions/${encodeURIComponent(sessionId)}`, {
+			cache: "no-store",
+			signal: options.signal,
+		}),
+		fetchLatestRunStatusForCache<TRun>(sessionId, options.signal),
+	]);
+	if (!sessionResponse.ok) return null;
+	const session = (await sessionResponse.json()) as TSession;
+	return writeCachedSessionReplay(sessionId, session, runStatus);
+}
+
+function writeCachedSessionReplay<TSession, TRun>(
+	sessionId: string,
+	session: TSession,
+	runStatus: TRun | null,
+): SessionReplaySnapshot<TSession, TRun> {
+	const snapshot: SessionReplaySnapshot<TSession, TRun> = {
+		sessionId,
+		session,
+		runStatus,
+		signature: sessionReplaySignature(session, runStatus),
+		fetchedAt: Date.now(),
+	};
+	replayCache.set(sessionId, snapshot as SessionReplaySnapshot);
+	while (replayCache.size > MAX_REPLAY_CACHE_SIZE) {
+		const oldest = replayCache.keys().next().value;
+		if (!oldest) break;
+		replayCache.delete(oldest);
+	}
+	return snapshot;
+}
+
+async function fetchLatestRunStatusForCache<TRun>(
+	sessionId: string,
+	signal?: AbortSignal,
+): Promise<TRun | null> {
+	try {
+		const url = new URL("/api/claw/runs/latest", window.location.origin);
+		url.searchParams.set("session_id", sessionId);
+		const response = await fetch(url, { cache: "no-store", signal });
+		if (!response.ok) return null;
+		return (await response.json()) as TRun;
+	} catch (error) {
+		if (error instanceof DOMException && error.name === "AbortError") {
+			throw error;
+		}
+		return null;
+	}
+}
+
+function sessionReplaySignature(session: unknown, runStatus: unknown) {
+	const sessionObject = isObject(session) ? session : {};
+	const runObject = isObject(runStatus) ? runStatus : {};
+	const messages = Array.isArray(sessionObject.messages)
+		? sessionObject.messages
+		: [];
+	const lastMessage = messages.at(-1);
+	const lastObject = isObject(lastMessage) ? lastMessage : {};
+	const metadata = isObject(lastObject.metadata) ? lastObject.metadata : {};
+	return [
+		sessionObject.session_id,
+		sessionObject.turns,
+		sessionObject.tool_calls,
+		messages.length,
+		lastObject.role,
+		lastObject.message_id,
+		typeof lastObject.content === "string" ? lastObject.content.length : "",
+		metadata.elapsed_ms,
+		runObject.run_id,
+		runObject.status,
+		runObject.updated_at,
+		runObject.finished_at,
+		runObject.elapsed_ms,
+	].join("|");
+}
+
+function isObject(value: unknown): value is Record<string, unknown> {
+	return Boolean(value) && typeof value === "object" && !Array.isArray(value);
+}