diff --git a/apps/cli/src/ai/agent-stream-runner.ts b/apps/cli/src/ai/agent-stream-runner.ts
index a7293ff0..1e70f9ff 100644
--- a/apps/cli/src/ai/agent-stream-runner.ts
+++ b/apps/cli/src/ai/agent-stream-runner.ts
@@ -9,6 +9,7 @@ import {
   SkillManager,
   buildSkillMenuWithBuiltinChart,
   createActivateSkillTool,
+  createDataSnapshotFromOverview,
   getAllowedBuiltinToolsForChartAutoSkill,
   getChartCapabilitySkill,
   getSkillConfigWithBuiltinChart,
@@ -166,19 +167,7 @@ export function createCliRunAgentStream(
     let dataSnapshot: DataSnapshot | undefined
     if (db) {
       try {
-        const overview = getChatOverview(db, 5)
-        if (overview) {
-          dataSnapshot = {
-            name: overview.name,
-            platform: overview.platform,
-            type: overview.type,
-            totalMessages: overview.totalMessages,
-            totalMembers: overview.totalMembers,
-            firstMessageTs: overview.firstMessageTs,
-            lastMessageTs: overview.lastMessageTs,
-            capturedAt: Math.floor(Date.now() / 1000),
-          }
-        }
+        dataSnapshot = createDataSnapshotFromOverview(getChatOverview(db, 10))
       } catch {
         // non-fatal
       }
diff --git a/apps/desktop/main/ai/agent-stream-runner.ts b/apps/desktop/main/ai/agent-stream-runner.ts
index bc65ebe4..69996b80 100644
--- a/apps/desktop/main/ai/agent-stream-runner.ts
+++ b/apps/desktop/main/ai/agent-stream-runner.ts
@@ -13,6 +13,7 @@ import {
   CHART_CAPABILITY_ANALYSIS_TOOLS,
   checkAndCompress,
   createCompressionLlmAdapter,
+  createDataSnapshotFromOverview,
   formatAIError,
   getAllowedBuiltinToolsForChartAutoSkill,
   getChartCapabilitySkill,
@@ -214,19 +215,7 @@ export function createElectronRunAgentStream(): (
 
     let dataSnapshot: ToolContext['dataSnapshot'] | undefined
     try {
-      const overview = await workerManager.getChatOverview(sessionId, 5)
-      if (overview) {
-        dataSnapshot = {
-          name: overview.name,
-          platform: overview.platform,
-          type: overview.type,
-          totalMessages: overview.totalMessages,
-          totalMembers: overview.totalMembers,
-          firstMessageTs: overview.firstMessageTs,
-          lastMessageTs: overview.lastMessageTs,
-          capturedAt: Math.floor(Date.now() / 1000),
-        }
-      }
+      dataSnapshot = createDataSnapshotFromOverview(await workerManager.getChatOverview(sessionId, 10))
     } catch (error) {
       aiLogger.warn('AgentStream', `Failed to load data snapshot: ${requestId}`, { error: String(error) })
     }
diff --git a/apps/desktop/main/worker/query/sessions.ts b/apps/desktop/main/worker/query/sessions.ts
index d4556e26..9a1c534c 100644
--- a/apps/desktop/main/worker/query/sessions.ts
+++ b/apps/desktop/main/worker/query/sessions.ts
@@ -160,6 +160,7 @@ export function getChatOverview(sessionId: string, topN: number = 10) {
 
   const cacheDir = getCacheDir()
   const overview = resolveOverview(db, sessionId, cacheDir)
+  const summaryCount = getSummaryCount(coreDb)
 
   let membersCache = getCache<MembersCache>(sessionId, CACHE_KEY_MEMBERS, cacheDir)
   if (!membersCache) {
@@ -187,5 +188,6 @@ export function getChatOverview(sessionId: string, topN: number = 10) {
     firstMessageTs: overview.firstMessageTs,
     lastMessageTs: overview.lastMessageTs,
     topMembers,
+    summaryCount,
   }
 }
diff --git a/apps/desktop/main/worker/workerManager.ts b/apps/desktop/main/worker/workerManager.ts
index 02f6e2ab..b0a7977c 100644
--- a/apps/desktop/main/worker/workerManager.ts
+++ b/apps/desktop/main/worker/workerManager.ts
@@ -432,6 +432,7 @@ export async function getChatOverview(
   firstMessageTs: number | null
   lastMessageTs: number | null
   topMembers: Array<{ id: number; name: string; count: number }>
+  summaryCount: number
 } | null> {
   return sendToWorker('getChatOverview', { sessionId, topN })
 }
diff --git a/packages/core/src/query/__tests__/session-queries.test.ts b/packages/core/src/query/__tests__/session-queries.test.ts
index 89902328..66932402 100644
--- a/packages/core/src/query/__tests__/session-queries.test.ts
+++ b/packages/core/src/query/__tests__/session-queries.test.ts
@@ -10,7 +10,13 @@
 import { describe, it } from 'node:test'
 import assert from 'node:assert/strict'
 import type { SessionMeta, SessionOverview } from '../session-queries'
-import { buildSessionInfo, getSessionInfo, getSummaryCount, getLastPlatformMessageId } from '../session-queries'
+import {
+  buildSessionInfo,
+  getChatOverview,
+  getSessionInfo,
+  getSummaryCount,
+  getLastPlatformMessageId,
+} from '../session-queries'
 import type { DatabaseAdapter } from '../../interfaces'
 
 // ==================== Mock helpers ====================
@@ -141,6 +147,38 @@ describe('getSessionInfo', () => {
   })
 })
 
+describe('getChatOverview', () => {
+  it('returns summaryCount together with overview and top members', () => {
+    const db = createMockDb({
+      'FROM meta': () => ({
+        name: 'Chat',
+        platform: 'wechat',
+        type: 'group',
+        imported_at: 1700000000,
+        group_id: null,
+        group_avatar: null,
+        owner_id: null,
+      }),
+      'FROM message msg': () => ({ count: 42 }),
+      'FROM member\n       WHERE': () => ({ count: 2 }),
+      'MIN(ts)': () => ({ v: 1600000000 }),
+      'MAX(ts)': () => ({ v: 1700000000 }),
+      sqlite_master: () => ({ cnt: 1 }),
+      'FROM segment': () => ({ count: 5 }),
+      'FROM member m': () => [
+        { memberId: 1, platformId: 'u1', name: 'Alice', avatar: null, messageCount: 30 },
+        { memberId: 2, platformId: 'u2', name: 'Bob', avatar: null, messageCount: 12 },
+      ],
+    })
+
+    const overview = getChatOverview(db, 1)
+
+    assert.ok(overview)
+    assert.equal(overview.summaryCount, 5)
+    assert.deepEqual(overview.topMembers, [{ id: 1, name: 'Alice', count: 30 }])
+  })
+})
+
 describe('getSummaryCount', () => {
   it('returns 0 when segment table does not exist', () => {
     const db = createMockDb({
diff --git a/packages/core/src/query/session-queries.ts b/packages/core/src/query/session-queries.ts
index a1f05867..ca2ed610 100644
--- a/packages/core/src/query/session-queries.ts
+++ b/packages/core/src/query/session-queries.ts
@@ -194,6 +194,7 @@ export interface ChatOverviewData {
   firstMessageTs: number | null
   lastMessageTs: number | null
   topMembers: Array<{ id: number; name: string; count: number }>
+  summaryCount: number
 }
 
 export interface SessionPreviewMessage {
@@ -252,6 +253,7 @@ export function getChatOverview(db: DatabaseAdapter, topN: number = 10): ChatOve
 
   const overview = getSessionOverview(db)
   const members = getMemberActivity(db)
+  const summaryCount = getSummaryCount(db)
 
   const topMembers = members.slice(0, topN).map((m) => ({
     id: m.memberId,
@@ -268,6 +270,7 @@ export function getChatOverview(db: DatabaseAdapter, topN: number = 10): ChatOve
     firstMessageTs: overview.firstMessageTs,
     lastMessageTs: overview.lastMessageTs,
     topMembers,
+    summaryCount,
   }
 }
 
diff --git a/packages/node-runtime/src/ai/agent/__tests__/data-snapshot.test.ts b/packages/node-runtime/src/ai/agent/__tests__/data-snapshot.test.ts
new file mode 100644
index 00000000..30a8e61e
--- /dev/null
+++ b/packages/node-runtime/src/ai/agent/__tests__/data-snapshot.test.ts
@@ -0,0 +1,100 @@
+/**
+ * Tests for DataSnapshot assembly.
+ *
+ * Run: npx tsx --test packages/node-runtime/src/ai/agent/__tests__/data-snapshot.test.ts
+ */
+
+import { describe, it } from 'node:test'
+import assert from 'node:assert/strict'
+import { createDataSnapshotFromOverview } from '../data-snapshot'
+
+describe('createDataSnapshotFromOverview', () => {
+  it('maps overview members and summary count into an extended data snapshot', () => {
+    const snapshot = createDataSnapshotFromOverview({
+      name: 'Team Chat',
+      platform: 'wechat',
+      type: 'group',
+      totalMessages: 200,
+      totalMembers: 3,
+      firstMessageTs: 1735689600,
+      lastMessageTs: 1767225599,
+      summaryCount: 7,
+      topMembers: [
+        { id: 1, name: 'Alice', count: 120 },
+        { id: 2, name: 'Bob', count: 80 },
+      ],
+    })
+
+    assert.deepEqual(snapshot, {
+      version: 2,
+      name: 'Team Chat',
+      platform: 'wechat',
+      type: 'group',
+      totalMessages: 200,
+      totalMembers: 3,
+      firstMessageTs: 1735689600,
+      lastMessageTs: 1767225599,
+      activeMemberHints: [
+        { memberId: 1, displayName: 'Alice', messageCount: 120, share: 60 },
+        { memberId: 2, displayName: 'Bob', messageCount: 80, share: 40 },
+      ],
+      segmentSummaries: { availableCount: 7 },
+    })
+  })
+
+  it('keeps all supplied members for small groups and caps large groups at ten hints', () => {
+    const topMembers = Array.from({ length: 12 }, (_, index) => ({
+      id: index + 1,
+      name: `Member ${index + 1}`,
+      count: 10,
+    }))
+
+    const smallGroup = createDataSnapshotFromOverview({
+      name: 'Small',
+      platform: 'wechat',
+      type: 'group',
+      totalMessages: 120,
+      totalMembers: 10,
+      firstMessageTs: null,
+      lastMessageTs: null,
+      topMembers: topMembers.slice(0, 10),
+    })
+    const largeGroup = createDataSnapshotFromOverview({
+      name: 'Large',
+      platform: 'wechat',
+      type: 'group',
+      totalMessages: 120,
+      totalMembers: 12,
+      firstMessageTs: null,
+      lastMessageTs: null,
+      topMembers,
+    })
+
+    assert.ok(smallGroup?.activeMemberHints)
+    assert.ok(largeGroup?.activeMemberHints)
+    assert.equal(smallGroup.activeMemberHints.length, 10)
+    assert.equal(largeGroup.activeMemberHints.length, 10)
+    assert.equal(largeGroup.activeMemberHints.at(-1)?.memberId, 10)
+  })
+
+  it('returns a usable snapshot without member hints when overview has no topMembers', () => {
+    const snapshot = createDataSnapshotFromOverview({
+      name: 'No Cache',
+      platform: 'wechat',
+      type: 'group',
+      totalMessages: 0,
+      totalMembers: 0,
+      firstMessageTs: null,
+      lastMessageTs: null,
+    })
+
+    assert.ok(snapshot?.segmentSummaries)
+    assert.equal(snapshot.segmentSummaries.availableCount, 0)
+    assert.deepEqual(snapshot?.activeMemberHints, [])
+  })
+
+  it('returns undefined for missing overview', () => {
+    assert.equal(createDataSnapshotFromOverview(null), undefined)
+    assert.equal(createDataSnapshotFromOverview(undefined), undefined)
+  })
+})
diff --git a/packages/node-runtime/src/ai/agent/data-snapshot.ts b/packages/node-runtime/src/ai/agent/data-snapshot.ts
new file mode 100644
index 00000000..c028c373
--- /dev/null
+++ b/packages/node-runtime/src/ai/agent/data-snapshot.ts
@@ -0,0 +1,46 @@
+import type { DataSnapshot } from './prompt-builder'
+
+export interface ChatOverviewForSnapshot {
+  name: string
+  platform: string
+  type: string
+  totalMessages: number
+  totalMembers: number
+  firstMessageTs: number | null
+  lastMessageTs: number | null
+  topMembers?: Array<{ id: number; name: string; count: number }>
+  summaryCount?: number
+}
+
+function roundShare(value: number): number {
+  if (!Number.isFinite(value)) return 0
+  return Math.round(value * 10) / 10
+}
+
+export function createDataSnapshotFromOverview(
+  overview: ChatOverviewForSnapshot | null | undefined
+): DataSnapshot | undefined {
+  if (!overview) return undefined
+
+  const topMembers = overview.topMembers ?? []
+
+  return {
+    version: 2,
+    name: overview.name,
+    platform: overview.platform,
+    type: overview.type,
+    totalMessages: overview.totalMessages,
+    totalMembers: overview.totalMembers,
+    firstMessageTs: overview.firstMessageTs,
+    lastMessageTs: overview.lastMessageTs,
+    activeMemberHints: topMembers.slice(0, 10).map((member) => ({
+      memberId: member.id,
+      displayName: member.name,
+      messageCount: member.count,
+      share: overview.totalMessages > 0 ? roundShare((member.count / overview.totalMessages) * 100) : 0,
+    })),
+    segmentSummaries: {
+      availableCount: overview.summaryCount ?? 0,
+    },
+  }
+}
diff --git a/packages/node-runtime/src/ai/agent/index.ts b/packages/node-runtime/src/ai/agent/index.ts
index bce9b9d6..ffaf379f 100644
--- a/packages/node-runtime/src/ai/agent/index.ts
+++ b/packages/node-runtime/src/ai/agent/index.ts
@@ -4,6 +4,8 @@ export { DEFAULT_MAX_TOOL_ROUNDS } from './constants'
 export { createLlmRouteDecider, decideRequestRoute } from './router'
 export type { LlmRouteDecider, RequestRoute, RouteDecision, RouteDecisionSource, RouterInput } from './routing-types'
 export { buildPlanGuidance, createAnalysisPlanner, createPlanContentBlock } from './planner'
+export { createDataSnapshotFromOverview } from './data-snapshot'
+export type { ChatOverviewForSnapshot } from './data-snapshot'
 export type {
   AnalysisPlanIntent,
   AnalysisPlanner,
diff --git a/packages/node-runtime/src/ai/index.ts b/packages/node-runtime/src/ai/index.ts
index 37dc0f9d..403a2ad5 100644
--- a/packages/node-runtime/src/ai/index.ts
+++ b/packages/node-runtime/src/ai/index.ts
@@ -102,6 +102,7 @@ export type { AgentCoreOptions, AgentCoreEvent, AgentCoreResult, AgentTokenUsage
 export { DEFAULT_MAX_TOOL_ROUNDS, createLlmRouteDecider, decideRequestRoute, runAgentCore } from './agent'
 export type { LlmRouteDecider, RequestRoute, RouteDecision, RouteDecisionSource, RouterInput } from './agent'
 export { buildPlanGuidance, createAnalysisPlanner, createPlanContentBlock } from './agent'
+export { createDataSnapshotFromOverview } from './agent'
 export type {
   AnalysisPlanIntent,
   AnalysisPlanner,
@@ -111,6 +112,7 @@ export type {
   PlannerInput,
   PlanContentBlock,
   PlanDraftContentBlock,
+  ChatOverviewForSnapshot,
 } from './agent'
 
 // Agent Event Handler
diff --git a/packages/node-runtime/src/index.ts b/packages/node-runtime/src/index.ts
index e3d5bbc6..f32435fa 100644
--- a/packages/node-runtime/src/index.ts
+++ b/packages/node-runtime/src/index.ts
@@ -207,7 +207,7 @@ export type { AIChat, AIMessage, AIMessageRole, ContentBlock, TokenUsageData, AI
 export type { AgentCoreOptions, AgentCoreEvent, AgentCoreResult, AgentTokenUsage, SimpleHistoryMessage } from './ai'
 export { DEFAULT_MAX_TOOL_ROUNDS, createLlmRouteDecider, decideRequestRoute, runAgentCore } from './ai'
 export type { LlmRouteDecider, RequestRoute, RouteDecision, RouteDecisionSource, RouterInput } from './ai'
-export { buildPlanGuidance, createAnalysisPlanner, createPlanContentBlock } from './ai'
+export { buildPlanGuidance, createAnalysisPlanner, createDataSnapshotFromOverview, createPlanContentBlock } from './ai'
 export type {
   AnalysisPlanIntent,
   AnalysisPlanner,
@@ -217,6 +217,7 @@ export type {
   PlannerInput,
   PlanContentBlock,
   PlanDraftContentBlock,
+  ChatOverviewForSnapshot,
 } from './ai'
 
 // Summary generation