diff --git a/src/agentbox/http-server.test.ts b/src/agentbox/http-server.test.ts
index 53a8a87c7..66509008b 100644
--- a/src/agentbox/http-server.test.ts
+++ b/src/agentbox/http-server.test.ts
@@ -403,6 +403,7 @@ describe("http-server — /health + /api/sessions + /api/models", () => {
         schemaVersion: AGENT_SYNC_STATUS_SCHEMA_VERSION,
         knowledge: {
           syncedAt: "2026-08-18T08:00:00.000Z",
+          sessionRefresh: { policy: "next_prompt", residentSessions: 0, pendingSessions: 0 },
           repos: [{ id: "kb-1", name: "hardware", version: 2, sha256: "abc", fileCount: 12 }],
         },
         skills: { names: ["k8s-debug"] },
diff --git a/src/agentbox/http-server.ts b/src/agentbox/http-server.ts
index 5ca2f26d9..4ff453295 100644
--- a/src/agentbox/http-server.ts
+++ b/src/agentbox/http-server.ts
@@ -41,7 +41,7 @@ import {
   readBoxSyncStatus,
   type KnowledgeSyncHandler,
 } from "./sync-handlers.js";
-import type { ObservedMcpServer } from "../shared/agentbox-sync-status.js";
+import { knowledgeSessionRefresh, type ObservedMcpServer } from "../shared/agentbox-sync-status.js";
 import { GATEWAY_SYNC_DESCRIPTORS, type AgentBoxSyncHandler, type GatewaySyncType } from "../shared/gateway-sync.js";
 import { detectLanguage } from "../shared/detect-language.js";
 import { stripLanguageDirective } from "../shared/strip-language-directive.js";
@@ -833,6 +833,7 @@ export function createHttpServer(
     const servers = liveManager ? liveManager.getServerConnections() : observedMcpServers;
     sendJson(res, 200, {
       ...inventory,
+      knowledge: { ...inventory.knowledge, sessionRefresh: knowledgeSessionRefresh(sessionManager.list()) },
       mcp: { ...inventory.mcp, ...(servers ? { servers } : {}) },
       model: observedModel,
       harness: observedHarness,
diff --git a/src/shared/agentbox-sync-status.test.ts b/src/shared/agentbox-sync-status.test.ts
index dc3cf46b5..88d1bedc4 100644
--- a/src/shared/agentbox-sync-status.test.ts
+++ b/src/shared/agentbox-sync-status.test.ts
@@ -8,7 +8,7 @@
  * ways of "saying nothing" mean opposite things.
  */
 import { describe, it, expect } from "vitest";
-import { AGENT_SYNC_STATUS_SCHEMA_VERSION, normalizeBoxSyncStatus } from "./agentbox-sync-status.js";
+import { AGENT_SYNC_STATUS_SCHEMA_VERSION, knowledgeSessionRefresh, normalizeBoxSyncStatus } from "./agentbox-sync-status.js";
 
 const REV_A = "a".repeat(64);
 const REV_B = "b".repeat(64);
@@ -165,3 +165,19 @@ describe("mcp.servers observation", () => {
     expect(status.mcp.servers?.[0].error).toEqual({ kind: "unknown", message: "boom" });
   });
 });
+
+
+describe("knowledge session refresh evidence", () => {
+  it("reports invalidated sessions separately from installed files", () => {
+    const refresh = knowledgeSessionRefresh([{ _invalidated: true }, { _invalidated: false }]);
+    expect(refresh).toEqual({ policy: "next_prompt", residentSessions: 2, pendingSessions: 1 });
+    const status = normalizeBoxSyncStatus(payload({ knowledge: { repos: [], sessionRefresh: refresh } }));
+    expect(status.knowledge.sessionRefresh).toEqual(refresh);
+  });
+  it("preserves missing legacy evidence and rejects inconsistent counts", () => {
+    expect(normalizeBoxSyncStatus(payload()).knowledge.sessionRefresh).toBeUndefined();
+    expect(normalizeBoxSyncStatus(payload({ knowledge: { repos: [], sessionRefresh: {
+      policy: "next_prompt", residentSessions: 1, pendingSessions: 2,
+    } } })).knowledge.sessionRefresh).toBeUndefined();
+  });
+});
diff --git a/src/shared/agentbox-sync-status.ts b/src/shared/agentbox-sync-status.ts
index e81de9c27..d7eca07ba 100644
--- a/src/shared/agentbox-sync-status.ts
+++ b/src/shared/agentbox-sync-status.ts
@@ -30,7 +30,26 @@ export interface ObservedKnowledgeRepo {
  * session has initialized MCP; a v3 box cannot, so a consumer must not read an
  * absent `servers` as "all connected".
  */
-export const AGENT_SYNC_STATUS_SCHEMA_VERSION = 4;
+// 5 adds knowledge.sessionRefresh: materialized files and deferred warm-session
+// invalidation are distinct; older boxes leave this evidence absent.
+export const AGENT_SYNC_STATUS_SCHEMA_VERSION = 5;
+
+/** Installed files and warm-session refresh are separate observations. */
+export interface KnowledgeSessionRefresh {
+  policy: "next_prompt";
+  residentSessions: number;
+  pendingSessions: number;
+}
+
+export function knowledgeSessionRefresh(
+  sessions: ReadonlyArray<{ _invalidated: boolean }>,
+): KnowledgeSessionRefresh {
+  return {
+    policy: "next_prompt",
+    residentSessions: sessions.length,
+    pendingSessions: sessions.filter((session) => session._invalidated).length,
+  };
+}
 
 /** Closed vocabulary shared with core/mcp-client.ts; see McpConnectErrorKind. */
 export type ObservedMcpErrorKind =
@@ -64,6 +83,7 @@ export interface BoxSyncStatus {
   knowledge: {
     syncedAt: string | null;
     repos: ObservedKnowledgeRepo[];
+    sessionRefresh?: KnowledgeSessionRefresh;
   };
   skills: { names: string[] };
   mcp: {
@@ -193,6 +213,11 @@ export function normalizeBoxSyncStatus(value: unknown): BoxSyncStatus {
   if (!root) throw new Error("invalid AgentBox sync status");
 
   const knowledge = record(root.knowledge);
+  const refresh = record(knowledge?.sessionRefresh);
+  const validRefresh = refresh?.policy === "next_prompt"
+    && Number.isSafeInteger(refresh.residentSessions) && (refresh.residentSessions as number) >= 0
+    && Number.isSafeInteger(refresh.pendingSessions) && (refresh.pendingSessions as number) >= 0
+    && (refresh.pendingSessions as number) <= (refresh.residentSessions as number);
   const repos = Array.isArray(knowledge?.repos)
     ? knowledge.repos.flatMap((item): ObservedKnowledgeRepo[] => {
         const repo = record(item);
@@ -229,6 +254,11 @@ export function normalizeBoxSyncStatus(value: unknown): BoxSyncStatus {
     knowledge: {
       syncedAt: typeof knowledge?.syncedAt === "string" ? knowledge.syncedAt : null,
       repos,
+      ...(validRefresh ? { sessionRefresh: {
+        policy: "next_prompt" as const,
+        residentSessions: refresh!.residentSessions as number,
+        pendingSessions: refresh!.pendingSessions as number,
+      } } : {}),
     },
     skills: { names: strings(record(root.skills)?.names) },
     mcp: normalizeObservedMcp(record(root.mcp)),