diff --git a/packages/context-engine/src/engine/index.ts b/packages/context-engine/src/engine/index.ts
index 1d2a11f4b3..f0f50a7889 100644
--- a/packages/context-engine/src/engine/index.ts
+++ b/packages/context-engine/src/engine/index.ts
@@ -4,3 +4,5 @@ export * from './skills';
 export * from './tools';
 // Messages Engine
 export * from './messages';
+// Topic Reference
+export * from './topicReference';
diff --git a/packages/context-engine/src/engine/messages/MessagesEngine.ts b/packages/context-engine/src/engine/messages/MessagesEngine.ts
index 2e520dcbe5..d593ddd187 100644
--- a/packages/context-engine/src/engine/messages/MessagesEngine.ts
+++ b/packages/context-engine/src/engine/messages/MessagesEngine.ts
@@ -41,6 +41,7 @@ import {
   SystemRoleInjector,
   ToolDiscoveryProvider,
   ToolSystemRoleProvider,
+  TopicReferenceContextInjector,
   UserMemoryInjector,
 } from '../../providers';
 import type { ContextProcessor } from '../../types';
@@ -147,6 +148,7 @@ export class MessagesEngine {
       initialContext,
       stepContext,
       pageContentContext,
+      topicReferences,
       enableSystemDate,
       timezone,
     } = this.params;
@@ -316,6 +318,16 @@ export class MessagesEngine {
       // 17. GTD Todo injection (conditionally added, at end of last user message)
       ...(isGTDTodoEnabled ? [new GTDTodoInjector({ enabled: true, todos: gtd.todos })] : []),
 
+      // 18. Topic Reference context injection (inject referenced topic summaries to last user message)
+      ...(topicReferences && topicReferences.length > 0
+        ? [
+            new TopicReferenceContextInjector({
+              enabled: true,
+              topicReferences,
+            }),
+          ]
+        : []),
+
       // =============================================
       // Phase 4: Message Transformation
       // =============================================
diff --git a/packages/context-engine/src/engine/messages/index.ts b/packages/context-engine/src/engine/messages/index.ts
index cfee0de556..f2af6187b8 100644
--- a/packages/context-engine/src/engine/messages/index.ts
+++ b/packages/context-engine/src/engine/messages/index.ts
@@ -18,6 +18,7 @@ export type {
   ToolDiscoveryConfig,
   ToolDiscoveryMeta,
   ToolsConfig,
+  TopicReferenceItem,
   UIChatMessage,
   UserMemoryActivityItem,
   UserMemoryConfig,
diff --git a/packages/context-engine/src/engine/messages/types.ts b/packages/context-engine/src/engine/messages/types.ts
index f45313ea9a..bf507d776a 100644
--- a/packages/context-engine/src/engine/messages/types.ts
+++ b/packages/context-engine/src/engine/messages/types.ts
@@ -19,6 +19,7 @@ import type { GTDPlan } from '../../providers/GTDPlanInjector';
 import type { GTDTodoList } from '../../providers/GTDTodoInjector';
 import type { SkillMeta } from '../../providers/SkillContextProvider';
 import type { ToolDiscoveryMeta } from '../../providers/ToolDiscoveryProvider';
+import type { TopicReferenceItem } from '../../providers/TopicReferenceContextInjector';
 import type { PipelineContextMetadata } from '../../types';
 import type { LobeToolManifest } from '../tools/types';
 
@@ -281,6 +282,10 @@ export interface MessagesEngineParams {
   /** User memory configuration */
   userMemory?: UserMemoryConfig;
 
+  // ========== Topic References ==========
+  /** Topic reference summaries to inject into last user message */
+  topicReferences?: TopicReferenceItem[];
+
   // ========== Page Editor context ==========
   /**
    * Initial context captured at operation start (frontend runtime usage)
@@ -330,5 +335,6 @@ export { type GTDPlan } from '../../providers/GTDPlanInjector';
 export { type GTDTodoItem, type GTDTodoList } from '../../providers/GTDTodoInjector';
 export { type SkillMeta } from '../../providers/SkillContextProvider';
 export { type ToolDiscoveryMeta } from '../../providers/ToolDiscoveryProvider';
+export { type TopicReferenceItem } from '../../providers/TopicReferenceContextInjector';
 export { type OpenAIChatMessage, type UIChatMessage } from '@/types/index';
 export { type FileContent, type KnowledgeBaseInfo } from '@lobechat/prompts';
diff --git a/packages/context-engine/src/engine/topicReference/__tests__/resolveTopicReferences.test.ts b/packages/context-engine/src/engine/topicReference/__tests__/resolveTopicReferences.test.ts
new file mode 100644
index 0000000000..4afdf8a3d7
--- /dev/null
+++ b/packages/context-engine/src/engine/topicReference/__tests__/resolveTopicReferences.test.ts
@@ -0,0 +1,236 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import { parseReferTopicTags, resolveTopicReferences } from '../resolveTopicReferences';
+
+// ============ parseReferTopicTags ============
+
+describe('parseReferTopicTags', () => {
+  it('should parse refer_topic tags with name before id', () => {
+    const result = parseReferTopicTags([
+      { content: '<refer_topic name="My Topic" id="topic-1" />' },
+    ]);
+    expect(result).toEqual([{ topicId: 'topic-1', topicTitle: 'My Topic' }]);
+  });
+
+  it('should parse refer_topic tags with id before name', () => {
+    const result = parseReferTopicTags([
+      { content: '<refer_topic id="topic-2" name="Other Topic" />' },
+    ]);
+    expect(result).toEqual([{ topicId: 'topic-2', topicTitle: 'Other Topic' }]);
+  });
+
+  it('should deduplicate topic IDs across messages', () => {
+    const result = parseReferTopicTags([
+      { content: '<refer_topic name="A" id="topic-1" />' },
+      { content: '<refer_topic name="A" id="topic-1" />' },
+    ]);
+    expect(result).toHaveLength(1);
+    expect(result[0].topicId).toBe('topic-1');
+  });
+
+  it('should parse multiple different topics', () => {
+    const result = parseReferTopicTags([
+      { content: '<refer_topic name="A" id="t1" />\n<refer_topic name="B" id="t2" />' },
+    ]);
+    expect(result).toHaveLength(2);
+    expect(result.map((r) => r.topicId)).toEqual(['t1', 't2']);
+  });
+
+  it('should return empty array when no tags found', () => {
+    const result = parseReferTopicTags([{ content: 'Hello world' }]);
+    expect(result).toEqual([]);
+  });
+
+  it('should skip non-string content', () => {
+    const result = parseReferTopicTags([{ content: ['array', 'content'] }]);
+    expect(result).toEqual([]);
+  });
+
+  it('should parse markdown-escaped refer_topic tags', () => {
+    const result = parseReferTopicTags([
+      { content: 'hi \\<refer\\_topic name="新对话开始" id="tpc\\_867aVIS5Av2G" />' },
+    ]);
+    expect(result).toEqual([{ topicId: 'tpc_867aVIS5Av2G', topicTitle: '新对话开始' }]);
+  });
+
+  it('should parse markdown-escaped tags at start of content', () => {
+    const result = parseReferTopicTags([
+      { content: '\\<refer\\_topic name="Greeting Message" id="tpc\\_EH0s0KrwpJN2" />讲了啥' },
+    ]);
+    expect(result).toEqual([{ topicId: 'tpc_EH0s0KrwpJN2', topicTitle: 'Greeting Message' }]);
+  });
+
+  it('should parse mixed escaped and non-escaped tags', () => {
+    const result = parseReferTopicTags([
+      { content: '\\<refer\\_topic name="A" id="tpc\\_1" />' },
+      { content: '<refer_topic name="B" id="tpc_2" />' },
+    ]);
+    expect(result).toHaveLength(2);
+    expect(result.map((r) => r.topicId)).toEqual(['tpc_1', 'tpc_2']);
+  });
+});
+
+// ============ resolveTopicReferences ============
+
+describe('resolveTopicReferences', () => {
+  it('should return undefined when no refer_topic tags found', async () => {
+    const lookup = vi.fn();
+    const result = await resolveTopicReferences([{ content: 'Hello' }], lookup);
+    expect(result).toBeUndefined();
+    expect(lookup).not.toHaveBeenCalled();
+  });
+
+  it('should resolve topics with summaries', async () => {
+    const lookup = vi.fn().mockResolvedValue({
+      historySummary: 'Topic summary content',
+      title: 'DB Title',
+    });
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="UI Title" id="topic-1" />' }],
+      lookup,
+    );
+
+    expect(result).toEqual([
+      { summary: 'Topic summary content', topicId: 'topic-1', topicTitle: 'DB Title' },
+    ]);
+    expect(lookup).toHaveBeenCalledWith('topic-1');
+  });
+
+  it('should resolve topics without summaries', async () => {
+    const lookup = vi.fn().mockResolvedValue({ historySummary: null, title: 'Some Topic' });
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="Fallback" id="topic-2" />' }],
+      lookup,
+    );
+
+    expect(result).toEqual([{ summary: undefined, topicId: 'topic-2', topicTitle: 'Some Topic' }]);
+  });
+
+  it('should fallback to parsed title when lookup returns null', async () => {
+    const lookup = vi.fn().mockResolvedValue(null);
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="Parsed Title" id="topic-3" />' }],
+      lookup,
+    );
+
+    expect(result).toEqual([
+      { summary: undefined, topicId: 'topic-3', topicTitle: 'Parsed Title' },
+    ]);
+  });
+
+  it('should handle lookup errors gracefully', async () => {
+    const lookup = vi.fn().mockRejectedValue(new Error('DB error'));
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="Error Topic" id="topic-err" />' }],
+      lookup,
+    );
+
+    expect(result).toEqual([{ topicId: 'topic-err', topicTitle: 'Error Topic' }]);
+  });
+
+  it('should handle mixed results', async () => {
+    const lookup = vi.fn().mockImplementation(async (id: string) => {
+      if (id === 't1') return { historySummary: 'Has summary', title: 'Topic 1' };
+      return null;
+    });
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="A" id="t1" />\n<refer_topic name="B" id="t2" />' }],
+      lookup,
+    );
+
+    expect(result).toHaveLength(2);
+    expect(result![0]).toEqual({ summary: 'Has summary', topicId: 't1', topicTitle: 'Topic 1' });
+    expect(result![1]).toEqual({ summary: undefined, topicId: 't2', topicTitle: 'B' });
+  });
+
+  it('should fetch recent messages as fallback when no summary and lookupMessages provided', async () => {
+    const lookup = vi.fn().mockResolvedValue({ historySummary: null, title: 'No Summary Topic' });
+    const lookupMessages = vi.fn().mockResolvedValue([
+      { content: 'Hello', role: 'user' },
+      { content: 'Hi there!', role: 'assistant' },
+      { content: '', role: 'tool' },
+      { content: 'Follow up', role: 'user' },
+    ]);
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="T" id="t1" />' }],
+      lookup,
+      lookupMessages,
+    );
+
+    expect(lookupMessages).toHaveBeenCalledWith('t1');
+    expect(result).toHaveLength(1);
+    expect(result![0].recentMessages).toHaveLength(3);
+    expect(result![0].recentMessages).toEqual([
+      { content: 'Hello', role: 'user' },
+      { content: 'Hi there!', role: 'assistant' },
+      { content: 'Follow up', role: 'user' },
+    ]);
+    expect(result![0].summary).toBeUndefined();
+  });
+
+  it('should truncate long message content to 300 chars', async () => {
+    const longContent = 'x'.repeat(500);
+    const lookup = vi.fn().mockResolvedValue({ historySummary: null, title: 'T' });
+    const lookupMessages = vi.fn().mockResolvedValue([{ content: longContent, role: 'user' }]);
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="T" id="t1" />' }],
+      lookup,
+      lookupMessages,
+    );
+
+    expect(result![0].recentMessages![0].content).toHaveLength(303); // 300 + '...'
+  });
+
+  it('should take only last 5 messages', async () => {
+    const lookup = vi.fn().mockResolvedValue({ historySummary: null, title: 'T' });
+    const messages = Array.from({ length: 10 }, (_, i) => ({
+      content: `msg ${i}`,
+      role: i % 2 === 0 ? 'user' : 'assistant',
+    }));
+    const lookupMessages = vi.fn().mockResolvedValue(messages);
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="T" id="t1" />' }],
+      lookup,
+      lookupMessages,
+    );
+
+    expect(result![0].recentMessages).toHaveLength(5);
+    expect(result![0].recentMessages![0].content).toBe('msg 5');
+  });
+
+  it('should skip lookupMessages when topic has summary', async () => {
+    const lookup = vi.fn().mockResolvedValue({ historySummary: 'Has summary', title: 'T' });
+    const lookupMessages = vi.fn();
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="T" id="t1" />' }],
+      lookup,
+      lookupMessages,
+    );
+
+    expect(lookupMessages).not.toHaveBeenCalled();
+    expect(result![0].summary).toBe('Has summary');
+  });
+
+  it('should fall through to no-context when lookupMessages returns empty', async () => {
+    const lookup = vi.fn().mockResolvedValue({ historySummary: null, title: 'T' });
+    const lookupMessages = vi.fn().mockResolvedValue([]);
+
+    const result = await resolveTopicReferences(
+      [{ content: '<refer_topic name="T" id="t1" />' }],
+      lookup,
+      lookupMessages,
+    );
+
+    expect(result![0].summary).toBeUndefined();
+    expect(result![0].recentMessages).toBeUndefined();
+  });
+});
diff --git a/packages/context-engine/src/engine/topicReference/index.ts b/packages/context-engine/src/engine/topicReference/index.ts
new file mode 100644
index 0000000000..aa68fcca34
--- /dev/null
+++ b/packages/context-engine/src/engine/topicReference/index.ts
@@ -0,0 +1,6 @@
+export type {
+  ParsedTopicReference,
+  TopicLookupResult,
+  TopicMessageItem,
+} from './resolveTopicReferences';
+export { parseReferTopicTags, resolveTopicReferences } from './resolveTopicReferences';
diff --git a/packages/context-engine/src/engine/topicReference/resolveTopicReferences.ts b/packages/context-engine/src/engine/topicReference/resolveTopicReferences.ts
new file mode 100644
index 0000000000..bddbdaeff6
--- /dev/null
+++ b/packages/context-engine/src/engine/topicReference/resolveTopicReferences.ts
@@ -0,0 +1,127 @@
+import type { TopicReferenceItem } from '../../providers/TopicReferenceContextInjector';
+
+/**
+ * Parsed refer_topic tag info
+ */
+export interface ParsedTopicReference {
+  topicId: string;
+  topicTitle?: string;
+}
+
+/**
+ * Topic lookup result (common interface for both client store and server DB)
+ */
+export interface TopicLookupResult {
+  historySummary?: string | null;
+  title?: string | null;
+}
+
+/**
+ * Message item returned by lookupMessages
+ */
+export interface TopicMessageItem {
+  content?: string | null;
+  role: string;
+}
+
+/** Max recent messages to fetch as fallback */
+const MAX_RECENT_MESSAGES = 5;
+/** Max characters per message content */
+const MAX_MESSAGE_LENGTH = 300;
+
+/**
+ * Parse <refer_topic> tags from message contents
+ */
+export function parseReferTopicTags(
+  messages: Array<{ content: string | unknown }>,
+): ParsedTopicReference[] {
+  const topicIds = new Set<string>();
+  const topicNames = new Map<string, string>();
+
+  for (const msg of messages) {
+    // Strip markdown escape backslashes (e.g. \< → <, \_ → _) before parsing
+    const raw = typeof msg.content === 'string' ? msg.content : '';
+    const content = raw.replaceAll(/\\([<>_*[\]()#`~|])/g, '$1');
+    const tagRegex = /<refer_topic\s([^>]*)>/g;
+    let tagMatch;
+    while ((tagMatch = tagRegex.exec(content)) !== null) {
+      const attrs = tagMatch[1];
+      const idMatch = /id="([^"]+)"/.exec(attrs);
+      const nameMatch = /name="([^"]*)"/.exec(attrs);
+      if (idMatch) {
+        topicIds.add(idMatch[1]);
+        if (nameMatch) topicNames.set(idMatch[1], nameMatch[1]);
+      }
+    }
+  }
+
+  return [...topicIds].map((topicId) => ({
+    topicId,
+    topicTitle: topicNames.get(topicId),
+  }));
+}
+
+function truncate(text: string, max: number): string {
+  if (text.length <= max) return text;
+  return text.slice(0, max) + '...';
+}
+
+/**
+ * Resolve topic references by looking up each topic via the provided function.
+ * Works with both sync (client store) and async (server DB) data sources.
+ *
+ * When a topic has no historySummary and lookupMessages is provided,
+ * fetches the last 5 user/assistant messages as fallback context (each truncated to 300 chars).
+ */
+export async function resolveTopicReferences(
+  messages: Array<{ content: string | unknown }>,
+  lookupTopic: (topicId: string) => Promise<TopicLookupResult | null | undefined>,
+  lookupMessages?: (topicId: string) => Promise<TopicMessageItem[]>,
+): Promise<TopicReferenceItem[] | undefined> {
+  const parsed = parseReferTopicTags(messages);
+  if (parsed.length === 0) return undefined;
+
+  const refs: TopicReferenceItem[] = [];
+
+  for (const { topicId, topicTitle } of parsed) {
+    try {
+      const topic = await lookupTopic(topicId);
+      const title = topic?.title || topicTitle;
+
+      if (topic?.historySummary) {
+        refs.push({ summary: topic.historySummary, topicId, topicTitle: title });
+        continue;
+      }
+
+      // Fallback: fetch recent messages
+      if (lookupMessages) {
+        try {
+          const allMessages = await lookupMessages(topicId);
+
+          // Filter to user/assistant only, take last N, truncate content
+          const recent = allMessages
+            .filter((m) => m.role === 'user' || m.role === 'assistant')
+            .filter((m) => m.content?.trim())
+            .slice(-MAX_RECENT_MESSAGES)
+            .map((m) => ({
+              content: truncate(m.content!.trim(), MAX_MESSAGE_LENGTH),
+              role: m.role,
+            }));
+
+          if (recent.length > 0) {
+            refs.push({ recentMessages: recent, topicId, topicTitle: title });
+            continue;
+          }
+        } catch {
+          // fallthrough to no-context
+        }
+      }
+
+      refs.push({ topicId, topicTitle: title });
+    } catch {
+      refs.push({ topicId, topicTitle });
+    }
+  }
+
+  return refs.length > 0 ? refs : undefined;
+}
diff --git a/packages/context-engine/src/providers/TopicReferenceContextInjector.ts b/packages/context-engine/src/providers/TopicReferenceContextInjector.ts
new file mode 100644
index 0000000000..cfe7ea7ee6
--- /dev/null
+++ b/packages/context-engine/src/providers/TopicReferenceContextInjector.ts
@@ -0,0 +1,152 @@
+import debug from 'debug';
+
+import { BaseLastUserContentProvider } from '../base/BaseLastUserContentProvider';
+import type { PipelineContext, ProcessorOptions } from '../types';
+
+declare module '../types' {
+  interface PipelineContextMetadataOverrides {
+    topicReferenceCount?: number;
+    topicReferenceInjected?: boolean;
+  }
+}
+
+const log = debug('context-engine:provider:TopicReferenceContextInjector');
+
+/**
+ * Topic reference item
+ */
+export interface TopicReferenceItem {
+  /** Recent messages as fallback when no summary available */
+  recentMessages?: Array<{ content: string; role: string }>;
+  /** The topic's history summary (undefined if no summary available) */
+  summary?: string;
+  /** The topic ID */
+  topicId: string;
+  /** The topic title */
+  topicTitle?: string;
+}
+
+export interface TopicReferenceContextInjectorConfig {
+  /** Whether topic reference context injection is enabled */
+  enabled?: boolean;
+  /** Referenced topics (with or without summaries) */
+  topicReferences?: TopicReferenceItem[];
+}
+
+/**
+ * Format topic references for injection
+ * Topics with summaries are inlined; topics without summaries prompt the agent to use the tool
+ */
+function formatRecentMessages(messages: Array<{ content: string; role: string }>): string {
+  return messages
+    .map((msg) => {
+      const role = msg.role === 'user' ? 'User' : msg.role === 'assistant' ? 'Assistant' : msg.role;
+      return `**${role}**: ${msg.content}`;
+    })
+    .join('\n\n');
+}
+
+function formatTopicReferences(items: TopicReferenceItem[]): string | null {
+  if (items.length === 0) return null;
+
+  const withContext = items.filter((item) => item.summary || item.recentMessages?.length);
+  const withoutContext = items.filter((item) => !item.summary && !item.recentMessages?.length);
+
+  const lines: string[] = [
+    '<referred_topics hint="The following are brief summaries or excerpts of referenced topics. For complete conversation history, use the getTopicContext tool.">',
+  ];
+
+  for (const item of withContext) {
+    const title = item.topicTitle ? ` title="${item.topicTitle}"` : '';
+    const type = item.summary ? 'summary' : 'recent_messages';
+    lines.push(`<topic id="${item.topicId}"${title} type="${type}">`);
+    if (item.summary) {
+      lines.push(item.summary);
+    } else {
+      lines.push(formatRecentMessages(item.recentMessages!));
+    }
+    lines.push('</topic>');
+  }
+
+  if (withoutContext.length > 0) {
+    lines.push(
+      '<pending_topics hint="No context available for the following topics. Use the getTopicContext tool to retrieve their conversation history.">',
+    );
+    for (const item of withoutContext) {
+      const title = item.topicTitle ? ` title="${item.topicTitle}"` : '';
+      lines.push(`<topic id="${item.topicId}"${title} />`);
+    }
+    lines.push('</pending_topics>');
+  }
+
+  lines.push('</referred_topics>');
+
+  return lines.join('\n');
+}
+
+/**
+ * Topic Reference Context Injector
+ *
+ * When user messages contain <refer_topic> tags referencing other topics,
+ * this injector appends the referenced topics' context to the last user message.
+ * - Topics with summaries: summary is inlined directly
+ * - Topics without summaries: a hint is added prompting the agent to call the getTopicContext tool
+ */
+export class TopicReferenceContextInjector extends BaseLastUserContentProvider {
+  readonly name = 'TopicReferenceContextInjector';
+
+  constructor(
+    private config: TopicReferenceContextInjectorConfig,
+    options: ProcessorOptions = {},
+  ) {
+    super(options);
+  }
+
+  protected async doProcess(context: PipelineContext): Promise<PipelineContext> {
+    log('doProcess called');
+    log('config.enabled:', this.config.enabled);
+
+    const clonedContext = this.cloneContext(context);
+
+    if (
+      !this.config.enabled ||
+      !this.config.topicReferences ||
+      this.config.topicReferences.length === 0
+    ) {
+      log('Topic reference not enabled or no references, skipping injection');
+      return this.markAsExecuted(clonedContext);
+    }
+
+    const formattedContent = formatTopicReferences(this.config.topicReferences);
+
+    if (!formattedContent) {
+      log('No topic reference content to inject');
+      return this.markAsExecuted(clonedContext);
+    }
+
+    log('Formatted content length:', formattedContent.length);
+
+    const lastUserIndex = this.findLastUserMessageIndex(clonedContext.messages);
+
+    log('Last user message index:', lastUserIndex);
+
+    if (lastUserIndex === -1) {
+      log('No user messages found, skipping injection');
+      return this.markAsExecuted(clonedContext);
+    }
+
+    const hasExistingWrapper = this.hasExistingSystemContext(clonedContext);
+    const contentToAppend = hasExistingWrapper
+      ? this.createContextBlock(formattedContent, 'topic_reference_context')
+      : this.wrapWithSystemContext(formattedContent, 'topic_reference_context');
+
+    this.appendToLastUserMessage(clonedContext, contentToAppend);
+
+    clonedContext.metadata.topicReferenceInjected = true;
+    clonedContext.metadata.topicReferenceCount = this.config.topicReferences.length;
+
+    log('Topic reference context appended to last user message');
+
+    return this.markAsExecuted(clonedContext);
+  }
+}
diff --git a/packages/context-engine/src/providers/__tests__/TopicReferenceContextInjector.test.ts b/packages/context-engine/src/providers/__tests__/TopicReferenceContextInjector.test.ts
new file mode 100644
index 0000000000..ab7f5c7c39
--- /dev/null
+++ b/packages/context-engine/src/providers/__tests__/TopicReferenceContextInjector.test.ts
@@ -0,0 +1,207 @@
+import { describe, expect, it } from 'vitest';
+
+import type { PipelineContext } from '../../types';
+import { TopicReferenceContextInjector } from '../TopicReferenceContextInjector';
+
+const createContext = (messages: any[] = []): PipelineContext => ({
+  initialState: {
+    messages: [],
+    model: 'gpt-4',
+    provider: 'openai',
+  },
+  isAborted: false,
+  messages,
+  metadata: {
+    maxTokens: 4096,
+    model: 'gpt-4',
+  },
+});
+
+describe('TopicReferenceContextInjector', () => {
+  it('should skip when not enabled', async () => {
+    const injector = new TopicReferenceContextInjector({ enabled: false });
+    const context = createContext([{ content: 'Hello', id: 'user-1', role: 'user' }]);
+    const result = await injector.process(context);
+
+    expect(result.messages[0].content).toBe('Hello');
+    expect(result.metadata.topicReferenceInjected).toBeUndefined();
+  });
+
+  it('should skip when no topic references provided', async () => {
+    const injector = new TopicReferenceContextInjector({ enabled: true, topicReferences: [] });
+    const context = createContext([{ content: 'Hello', id: 'user-1', role: 'user' }]);
+    const result = await injector.process(context);
+
+    expect(result.messages[0].content).toBe('Hello');
+    expect(result.metadata.topicReferenceInjected).toBeUndefined();
+  });
+
+  it('should inject topic summaries into the last user message', async () => {
+    const injector = new TopicReferenceContextInjector({
+      enabled: true,
+      topicReferences: [
+        {
+          summary: 'This topic discussed React hooks and state management.',
+          topicId: 'topic-1',
+          topicTitle: 'React Hooks Discussion',
+        },
+      ],
+    });
+
+    const context = createContext([
+      { content: 'Earlier message', id: 'user-1', role: 'user' },
+      { content: 'Reply', id: 'assistant-1', role: 'assistant' },
+      {
+        content: '<refer_topic name="React Hooks Discussion" id="topic-1" />\nTell me more',
+        id: 'user-2',
+        role: 'user',
+      },
+    ]);
+
+    const result = await injector.process(context);
+
+    expect(result.messages).toHaveLength(3);
+    const lastContent = result.messages[2].content as string;
+    expect(lastContent).toContain('<referred_topics hint=');
+    expect(lastContent).toContain('getTopicContext tool');
+    expect(lastContent).toContain(
+      '<topic id="topic-1" title="React Hooks Discussion" type="summary">',
+    );
+    expect(lastContent).toContain('This topic discussed React hooks and state management.');
+    expect(lastContent).toContain('</referred_topics>');
+    expect(result.metadata.topicReferenceInjected).toBe(true);
+    expect(result.metadata.topicReferenceCount).toBe(1);
+  });
+
+  it('should inject pending hint for topics without summaries', async () => {
+    const injector = new TopicReferenceContextInjector({
+      enabled: true,
+      topicReferences: [
+        {
+          topicId: 'topic-no-summary',
+          topicTitle: 'Old Chat',
+        },
+      ],
+    });
+
+    const context = createContext([{ content: 'Check this topic', id: 'user-1', role: 'user' }]);
+
+    const result = await injector.process(context);
+    const lastContent = result.messages[0].content as string;
+
+    expect(lastContent).toContain('<pending_topics');
+    expect(lastContent).toContain('getTopicContext');
+    expect(lastContent).toContain('<topic id="topic-no-summary" title="Old Chat" />');
+    expect(lastContent).not.toContain('</topic>');
+    expect(result.metadata.topicReferenceInjected).toBe(true);
+  });
+
+  it('should handle mixed topics (some with summaries, some without)', async () => {
+    const injector = new TopicReferenceContextInjector({
+      enabled: true,
+      topicReferences: [
+        {
+          summary: 'Summary of topic A.',
+          topicId: 'topic-a',
+          topicTitle: 'Topic A',
+        },
+        {
+          topicId: 'topic-b',
+          topicTitle: 'Topic B',
+        },
+      ],
+    });
+
+    const context = createContext([
+      { content: 'Refer to both topics', id: 'user-1', role: 'user' },
+    ]);
+
+    const result = await injector.process(context);
+    const lastContent = result.messages[0].content as string;
+
+    expect(lastContent).toContain('<topic id="topic-a" title="Topic A" type="summary">');
+    expect(lastContent).toContain('Summary of topic A.');
+    expect(lastContent).toContain('<pending_topics');
+    expect(lastContent).toContain('<topic id="topic-b" title="Topic B" />');
+    expect(result.metadata.topicReferenceCount).toBe(2);
+  });
+
+  it('should reuse existing system context wrapper', async () => {
+    const injector = new TopicReferenceContextInjector({
+      enabled: true,
+      topicReferences: [
+        {
+          summary: 'Topic summary.',
+          topicId: 'topic-1',
+        },
+      ],
+    });
+
+    const context = createContext([
+      {
+        content: `My question
+
+<!-- SYSTEM CONTEXT (NOT PART OF USER QUERY) -->
+<existing_context>
+some context
+</existing_context>
+<!-- END SYSTEM CONTEXT -->`,
+        id: 'user-1',
+        role: 'user',
+      },
+    ]);
+
+    const result = await injector.process(context);
+    const content = result.messages[0].content as string;
+
+    expect(content.match(/<!-- SYSTEM CONTEXT \(NOT PART OF USER QUERY\) -->/g)).toHaveLength(1);
+    expect(content).toContain('<existing_context>');
+    expect(content).toContain('<topic_reference_context>');
+  });
+
+  it('should inject recent messages when no summary available', async () => {
+    const injector = new TopicReferenceContextInjector({
+      enabled: true,
+      topicReferences: [
+        {
+          recentMessages: [
+            { content: 'What is React?', role: 'user' },
+            { content: 'React is a JS library.', role: 'assistant' },
+          ],
+          topicId: 'topic-recent',
+          topicTitle: 'React Q&A',
+        },
+      ],
+    });
+
+    const context = createContext([
+      { content: 'Tell me about that topic', id: 'user-1', role: 'user' },
+    ]);
+
+    const result = await injector.process(context);
+    const lastContent = result.messages[0].content as string;
+
+    expect(lastContent).toContain(
+      '<topic id="topic-recent" title="React Q&A" type="recent_messages">',
+    );
+    expect(lastContent).toContain('**User**: What is React?');
+    expect(lastContent).toContain('**Assistant**: React is a JS library.');
+    expect(lastContent).not.toContain('<pending_topics');
+  });
+
+  it('should skip injection when no user messages exist', async () => {
+    const injector = new TopicReferenceContextInjector({
+      enabled: true,
+      topicReferences: [{ summary: 'Summary', topicId: 'topic-1' }],
+    });
+
+    const context = createContext([
+      { content: 'Assistant only', id: 'assistant-1', role: 'assistant' },
+    ]);
+
+    const result = await injector.process(context);
+
+    expect(result.messages[0].content).toBe('Assistant only');
+    expect(result.metadata.topicReferenceInjected).toBeUndefined();
+  });
+});
diff --git a/packages/context-engine/src/providers/index.ts b/packages/context-engine/src/providers/index.ts
index d3a0bd2080..bcc7f75464 100644
--- a/packages/context-engine/src/providers/index.ts
+++ b/packages/context-engine/src/providers/index.ts
@@ -18,6 +18,7 @@ export { SystemDateProvider } from './SystemDateProvider';
 export { SystemRoleInjector } from './SystemRoleInjector';
 export { ToolDiscoveryProvider } from './ToolDiscoveryProvider';
 export { ToolSystemRoleProvider } from './ToolSystemRole';
+export { TopicReferenceContextInjector } from './TopicReferenceContextInjector';
 export { UserMemoryInjector } from './UserMemoryInjector';
 
 // Re-export types
@@ -58,4 +59,8 @@ export type { SystemDateProviderConfig } from './SystemDateProvider';
 export type { SystemRoleInjectorConfig } from './SystemRoleInjector';
 export type { ToolDiscoveryMeta, ToolDiscoveryProviderConfig } from './ToolDiscoveryProvider';
 export type { ToolSystemRoleConfig } from './ToolSystemRole';
+export type {
+  TopicReferenceContextInjectorConfig,
+  TopicReferenceItem,
+} from './TopicReferenceContextInjector';
 export type { MemoryContext, UserMemoryInjectorConfig } from './UserMemoryInjector';
diff --git a/src/server/modules/AgentRuntime/RuntimeExecutors.ts b/src/server/modules/AgentRuntime/RuntimeExecutors.ts
index 8f7abc1664..b8b12f0905 100644
--- a/src/server/modules/AgentRuntime/RuntimeExecutors.ts
+++ b/src/server/modules/AgentRuntime/RuntimeExecutors.ts
@@ -14,6 +14,7 @@ import {
   type LobeToolManifest,
   type OperationToolSet,
   type ResolvedToolSet,
+  resolveTopicReferences,
   ToolNameResolver,
   ToolResolver,
 } from '@lobechat/context-engine';
@@ -24,7 +25,8 @@ import { type ChatToolPayload, type MessageToolCall, type UIChatMessage } from '
 import { serializePartsForStorage } from '@lobechat/utils';
 import debug from 'debug';
 
-import { type MessageModel } from '@/database/models/message';
+import { type MessageModel, MessageModel as MessageModelClass } from '@/database/models/message';
+import { TopicModel } from '@/database/models/topic';
 import { type LobeChatDatabase } from '@/database/type';
 import { serverMessagesEngine } from '@/server/modules/Mecha/ContextEngineering';
 import { type EvalContext } from '@/server/modules/Mecha/ContextEngineering/types';
@@ -178,6 +180,33 @@ export const createRuntimeExecutors = (
       if (agentConfig) {
         const { LOBE_DEFAULT_MODEL_LIST } = await import('model-bank');
 
+        // Extract <refer_topic> tags from messages and fetch summaries.
+        // Skip if messages already contain injected topic_reference_context
+        // (e.g., from client-side contextEngineering preprocessing) to avoid double injection.
+        let topicReferences;
+        const alreadyHasTopicRefs = (
+          llmPayload.messages as Array<{ content: string | unknown }>
+        ).some(
+          (m) => typeof m.content === 'string' && m.content.includes('topic_reference_context'),
+        );
+
+        if (!alreadyHasTopicRefs && ctx.serverDB && ctx.userId) {
+          const topicModel = new TopicModel(ctx.serverDB, ctx.userId);
+          const messageModel = new MessageModelClass(ctx.serverDB, ctx.userId);
+          topicReferences = await resolveTopicReferences(
+            llmPayload.messages as Array<{ content: string | unknown }>,
+            async (topicId) => topicModel.findById(topicId),
+            async (topicId) => {
+              const topic = await topicModel.findById(topicId);
+              return messageModel.query({
+                agentId: topic?.agentId ?? undefined,
+                groupId: topic?.groupId ?? undefined,
+                topicId,
+              });
+            },
+          );
+        }
+
         const contextEngineInput = {
           additionalVariables: state.metadata?.deviceSystemInfo,
           userTimezone: ctx.userTimezone,
@@ -235,6 +264,9 @@ export const createRuntimeExecutors = (
           ...(state.metadata?.skillMetas?.length && {
             skillsConfig: { enabledSkills: state.metadata.skillMetas },
           }),
+
+          // Topic reference summaries
+          ...(topicReferences && { topicReferences }),
         };
 
         processedMessages = await serverMessagesEngine(contextEngineInput);
diff --git a/src/server/modules/AgentRuntime/__tests__/RuntimeExecutors.test.ts b/src/server/modules/AgentRuntime/__tests__/RuntimeExecutors.test.ts
index 0a4af1a93f..67aa6abf7e 100644
--- a/src/server/modules/AgentRuntime/__tests__/RuntimeExecutors.test.ts
+++ b/src/server/modules/AgentRuntime/__tests__/RuntimeExecutors.test.ts
@@ -1100,6 +1100,61 @@ describe('RuntimeExecutors', () => {
           name: 'Enabled KB',
         });
       });
+
+      it('should skip topic reference resolution when messages already contain topic_reference_context', async () => {
+        const ctxWithConfig: RuntimeExecutorContext = {
+          ...ctx,
+          agentConfig: { plugins: [], systemRole: 'test' },
+        };
+        const executors = createRuntimeExecutors(ctxWithConfig);
+        const state = createMockState();
+
+        const instruction = {
+          payload: {
+            messages: [
+              {
+                content:
+                  '<refer_topic name="Old topic" id="topic-abc" />\nHello\n<system_context>\n<context type="topic_reference_context">\n<referred_topics>...</referred_topics>\n</context>\n</system_context>',
+                role: 'user',
+              },
+            ],
+            model: 'gpt-4',
+            provider: 'openai',
+          },
+          type: 'call_llm' as const,
+        };
+
+        await executors.call_llm!(instruction, state);
+
+        expect(engineSpy).toHaveBeenCalledTimes(1);
+        const callArgs = engineSpy.mock.calls[0][0];
+        expect(callArgs).not.toHaveProperty('topicReferences');
+      });
+
+      it('should resolve topic references when messages do not contain topic_reference_context', async () => {
+        const ctxWithConfig: RuntimeExecutorContext = {
+          ...ctx,
+          agentConfig: { plugins: [], systemRole: 'test' },
+        };
+        const executors = createRuntimeExecutors(ctxWithConfig);
+        const state = createMockState();
+
+        const instruction = {
+          payload: {
+            messages: [{ content: 'Just a normal message without any topic refs', role: 'user' }],
+            model: 'gpt-4',
+            provider: 'openai',
+          },
+          type: 'call_llm' as const,
+        };
+
+        await executors.call_llm!(instruction, state);
+
+        expect(engineSpy).toHaveBeenCalledTimes(1);
+        // resolveTopicReferences ran but found no <refer_topic> tags → topicReferences is undefined
+        const callArgs = engineSpy.mock.calls[0][0];
+        expect(callArgs).not.toHaveProperty('topicReferences');
+      });
     });
   });
 
diff --git a/src/server/modules/Mecha/ContextEngineering/index.ts b/src/server/modules/Mecha/ContextEngineering/index.ts
index 432015877a..c334c0a78d 100644
--- a/src/server/modules/Mecha/ContextEngineering/index.ts
+++ b/src/server/modules/Mecha/ContextEngineering/index.ts
@@ -68,6 +68,7 @@ export const serverMessagesEngine = async ({
   evalContext,
   agentManagementContext,
   pageContentContext,
+  topicReferences,
   additionalVariables,
   userTimezone,
 }: ServerMessagesEngineParams): Promise<OpenAIChatMessage[]> => {
@@ -140,6 +141,9 @@ export const serverMessagesEngine = async ({
     // Skills configuration
     ...(skillsConfig?.enabledSkills && skillsConfig.enabledSkills.length > 0 && { skillsConfig }),
 
+    // Topic references
+    ...(topicReferences && topicReferences.length > 0 && { topicReferences }),
+
     // Extended contexts
     ...(agentBuilderContext && { agentBuilderContext }),
     ...(discordContext && { discordContext }),
diff --git a/src/server/modules/Mecha/ContextEngineering/types.ts b/src/server/modules/Mecha/ContextEngineering/types.ts
index 58b08fb76a..fb23ba675b 100644
--- a/src/server/modules/Mecha/ContextEngineering/types.ts
+++ b/src/server/modules/Mecha/ContextEngineering/types.ts
@@ -8,6 +8,7 @@ import type {
   KnowledgeBaseInfo,
   LobeToolManifest,
   SkillMeta,
+  TopicReferenceItem,
   UserMemoryData,
 } from '@lobechat/context-engine';
 import type { PageContentContext } from '@lobechat/prompts';
@@ -120,6 +121,9 @@ export interface ServerMessagesEngineParams {
   // ========== Tools ==========
   /** Tools configuration */
   toolsConfig?: ServerToolsConfig;
+  // ========== Topic References ==========
+  /** Topic reference summaries to inject into last user message */
+  topicReferences?: TopicReferenceItem[];
   // ========== User memory ==========
   /** User memory configuration */
   userMemory?: ServerUserMemoryConfig;
@@ -134,6 +138,7 @@ export {
   type EvalContext,
   type FileContent,
   type KnowledgeBaseInfo,
+  type TopicReferenceItem,
   type UserMemoryData,
 } from '@lobechat/context-engine';
 export type { PageContentContext } from '@lobechat/prompts';
diff --git a/src/services/chat/mecha/contextEngineering.ts b/src/services/chat/mecha/contextEngineering.ts
index ab011108e0..ea1cdda8be 100644
--- a/src/services/chat/mecha/contextEngineering.ts
+++ b/src/services/chat/mecha/contextEngineering.ts
@@ -16,7 +16,7 @@ import type {
   ToolDiscoveryConfig,
   UserMemoryData,
 } from '@lobechat/context-engine';
-import { MessagesEngine } from '@lobechat/context-engine';
+import { MessagesEngine, resolveTopicReferences } from '@lobechat/context-engine';
 import { historySummaryPrompt } from '@lobechat/prompts';
 import type {
   OpenAIChatMessage,
@@ -35,6 +35,7 @@ import { getChatGroupStoreState } from '@/store/agentGroup';
 import { agentGroupSelectors } from '@/store/agentGroup/selectors';
 import { getAiInfraStoreState } from '@/store/aiInfra';
 import { getChatStoreState } from '@/store/chat';
+import { topicSelectors } from '@/store/chat/selectors';
 import { getToolStoreState } from '@/store/tool';
 import {
   builtinToolSelectors,
@@ -515,6 +516,23 @@ export const contextEngineering = async ({
     log('mentionedAgents injected: %d agents', initialContext!.mentionedAgents!.length);
   }
 
+  // Resolve topic references from messages containing <refer_topic> tags
+  const topicReferences = await resolveTopicReferences(
+    messages,
+    async (topicId: string) => {
+      const topic = topicSelectors.getTopicById(topicId)(getChatStoreState());
+      return topic ?? null;
+    },
+    async (topicId: string) => {
+      const { messageService } = await import('@/services/message');
+      const msgs = await messageService.getMessages({ agentId, groupId, topicId });
+      return msgs.map((m) => ({
+        content: typeof m.content === 'string' ? m.content : '',
+        role: m.role,
+      }));
+    },
+  );
+
   // Create MessagesEngine with injected dependencies
   const engine = new MessagesEngine({
     // Agent configuration
@@ -582,6 +600,7 @@ export const contextEngineering = async ({
     ...((isAgentManagementEnabled || hasMentionedAgents) && { agentManagementContext }),
     ...(agentGroup && { agentGroup }),
     ...(gtdConfig && { gtd: gtdConfig }),
+    ...(topicReferences && topicReferences.length > 0 && { topicReferences }),
   });
 
   log('Input messages count: %d', messages.length);