diff --git a/src/feishu/event-handler.ts b/src/feishu/event-handler.ts
index 134d3ba2..01341394 100644
--- a/src/feishu/event-handler.ts
+++ b/src/feishu/event-handler.ts
@@ -1276,7 +1276,7 @@ async function executeClaudeTask(
     // 使用 repo identity（而非带随机后缀的工作区路径）确保同仓库记忆互通
     const repoIdentity = getRepoIdentity(workingDir);
     const memoryContext = config.memory.enabled
-      ? await injectMemories(rawPrompt, { agentId, userId, workspaceDir: repoIdentity })
+      ? await injectMemories(rawPrompt, { agentId, userId, workspaceDir: repoIdentity, chatId })
       : '';
 
     const result = await claudeExecutor.execute({
@@ -1627,7 +1627,7 @@ async function executeDirectTask(
     // 记忆注入（使用 repo identity 确保同仓库记忆互通）
     const repoIdentity = getRepoIdentity(workingDir);
     const memoryContext = config.memory.enabled
-      ? await injectMemories(rawPrompt, { agentId, userId, workspaceDir: repoIdentity })
+      ? await injectMemories(rawPrompt, { agentId, userId, workspaceDir: repoIdentity, chatId })
       : '';
 
     const result = await claudeExecutor.execute({
diff --git a/src/memory/__tests__/injector.test.ts b/src/memory/__tests__/injector.test.ts
index 9a754ee3..5d290f34 100644
--- a/src/memory/__tests__/injector.test.ts
+++ b/src/memory/__tests__/injector.test.ts
@@ -140,7 +140,7 @@ describe('formatMemories', () => {
     ];
 
     const output = formatMemories(results);
-    expect(output).toContain('since 2026-02-15');
+    expect(output).toContain('(2026-02-15');
   });
 
   it('should include date for decisions', () => {
@@ -165,6 +165,32 @@ describe('formatMemories', () => {
     expect(output).toContain('confidence: low');
   });
 
+  it('should tag memories from other chats', () => {
+    const results = [
+      makeResult({ type: 'fact', content: '使用 PostgreSQL' }),
+    ];
+    // memory.chatId defaults to 'chat1', pass a different currentChatId
+    const output = formatMemories(results, 'chat_other');
+    expect(output).toContain('来自其他会话');
+  });
+
+  it('should not tag memories from current chat', () => {
+    const results = [
+      makeResult({ type: 'fact', content: '使用 PostgreSQL' }),
+    ];
+    // memory.chatId defaults to 'chat1', pass same as currentChatId
+    const output = formatMemories(results, 'chat1');
+    expect(output).not.toContain('来自其他会话');
+  });
+
+  it('should not tag memories when no currentChatId provided', () => {
+    const results = [
+      makeResult({ type: 'fact', content: '使用 PostgreSQL' }),
+    ];
+    const output = formatMemories(results);
+    expect(output).not.toContain('来自其他会话');
+  });
+
   it('should not tag high-confidence memories', () => {
     const results = [
       makeResult({ type: 'preference', content: '确定用 React', confidence: 0.9 }),
diff --git a/src/memory/injector.ts b/src/memory/injector.ts
index e8604688..414963a0 100644
--- a/src/memory/injector.ts
+++ b/src/memory/injector.ts
@@ -12,6 +12,7 @@ export interface InjectionContext {
   agentId: string;
   userId?: string;
   workspaceDir?: string;
+  chatId?: string;
 }
 
 /** Type display names */
@@ -54,7 +55,7 @@ export async function injectMemories(
       return '';
     }
 
-    const fragment = formatMemories(results);
+    const fragment = formatMemories(results, context.chatId);
     logger.info(
       { agentId: context.agentId, userId: context.userId, count: results.length, chars: fragment.length },
       'Memories injected into system prompt',
@@ -68,8 +69,9 @@ export async function injectMemories(
 
 /**
  * Format search results into a prompt fragment, respecting maxInjectTokens.
+ * @param currentChatId - When provided, memories are annotated with source context (current vs other chat).
  */
-export function formatMemories(results: MemorySearchResult[]): string {
+export function formatMemories(results: MemorySearchResult[], currentChatId?: string): string {
   const maxChars = config.memory.maxInjectTokens * 3;
 
   // Group by type
@@ -97,20 +99,34 @@ export function formatMemories(results: MemorySearchResult[]): string {
     const itemLines: string[] = [];
     for (const r of group) {
       const mem = r.memory;
-      let line: string;
+
+      // Date tag: for decisions use createdAt (when the decision was made);
+      // for other types prefer validAt (when the fact became true)
+      const dateStr = (type === 'decision'
+        ? (mem.createdAt || mem.validAt || '')
+        : (mem.validAt || mem.createdAt || '')
+      ).split('T')[0];
+
+      // Source tag: annotate whether this memory is from the current chat or another
+      const fromOtherChat = currentChatId && mem.chatId && mem.chatId !== currentChatId;
+
+      // Build annotation parts
+      const annotations: string[] = [];
 
       if (type === 'state' && mem.ttl) {
-        line = `- ${mem.content} (预计到 ${mem.ttl.split('T')[0]})`;
-      } else if (type === 'fact' && mem.validAt) {
-        line = `- ${mem.content} (since ${mem.validAt.split('T')[0]})`;
-      } else if (type === 'decision' && mem.createdAt) {
-        const reason = mem.supersedeReason ? `, 原因: ${mem.supersedeReason}` : '';
-        line = `- ${mem.content} (${mem.createdAt.split('T')[0]}${reason})`;
-      } else {
-        const confidenceTag = mem.confidence < 0.6 ? ' (confidence: low)' : '';
-        line = `- ${mem.content}${confidenceTag}`;
+        annotations.push(`预计到 ${mem.ttl.split('T')[0]}`);
+      } else if (type === 'decision' && mem.supersedeReason) {
+        annotations.push(dateStr, `原因: ${mem.supersedeReason}`);
+      } else if (dateStr) {
+        annotations.push(dateStr);
       }
 
+      if (mem.confidence < 0.6) annotations.push('confidence: low');
+      if (fromOtherChat) annotations.push('来自其他会话');
+
+      const tag = annotations.length > 0 ? ` (${annotations.join(', ')})` : '';
+      const line = `- ${mem.content}${tag}`;
+
       if (totalChars + header.length + 1 + line.length + 1 > maxChars) {
         budgetExhausted = true;
         break;