diff --git a/src/config/sessions.cache.test.ts b/src/config/sessions.cache.test.ts
index ffc84218f49..190b926ad9b 100644
--- a/src/config/sessions.cache.test.ts
+++ b/src/config/sessions.cache.test.ts
@@ -107,6 +107,40 @@ describe("Session Store Cache", () => {
     expect(loaded2["session:1"].skillsSnapshot?.skills?.[0]?.name).toBe("alpha");
   });
 
+  it("does not cache pre-migration or pre-normalization disk JSON", () => {
+    fs.writeFileSync(
+      storePath,
+      JSON.stringify({
+        "session:1": {
+          sessionId: "id-1",
+          updatedAt: Date.now(),
+          provider: "telegram",
+          room: "room-1",
+          modelProvider: " openai ",
+          model: " gpt-5.4 ",
+        },
+      }),
+    );
+
+    const loaded1 = loadSessionStore(storePath);
+    const entry1 = loaded1["session:1"] as SessionEntry & { provider?: string; room?: string };
+    expect(entry1.channel).toBe("telegram");
+    expect(entry1.groupChannel).toBe("room-1");
+    expect(entry1.provider).toBeUndefined();
+    expect(entry1.room).toBeUndefined();
+    expect(entry1.modelProvider).toBe("openai");
+    expect(entry1.model).toBe("gpt-5.4");
+
+    const loaded2 = loadSessionStore(storePath);
+    const entry2 = loaded2["session:1"] as SessionEntry & { provider?: string; room?: string };
+    expect(entry2.channel).toBe("telegram");
+    expect(entry2.groupChannel).toBe("room-1");
+    expect(entry2.provider).toBeUndefined();
+    expect(entry2.room).toBeUndefined();
+    expect(entry2.modelProvider).toBe("openai");
+    expect(entry2.model).toBe("gpt-5.4");
+  });
+
   it("isolates cached session stores without structuredClone", async () => {
     const structuredCloneSpy = vi.spyOn(globalThis, "structuredClone");
     const testStore = createSingleSessionStore(
diff --git a/src/config/sessions/store-load.ts b/src/config/sessions/store-load.ts
index 40aa884fd8e..e13b335271e 100644
--- a/src/config/sessions/store-load.ts
+++ b/src/config/sessions/store-load.ts
@@ -64,7 +64,8 @@ function normalizeSessionEntryDelivery(entry: SessionEntry): SessionEntry {
   };
 }
 
-export function normalizeSessionStore(store: Record<string, SessionEntry>): void {
+export function normalizeSessionStore(store: Record<string, SessionEntry>): boolean {
+  let changed = false;
   for (const [key, entry] of Object.entries(store)) {
     if (!entry) {
       continue;
@@ -72,8 +73,10 @@ export function normalizeSessionStore(store: Record<string, SessionEntry>): void
     const normalized = normalizeSessionEntryDelivery(normalizeSessionRuntimeModelFields(entry));
     if (normalized !== entry) {
       store[key] = normalized;
+      changed = true;
     }
   }
+  return changed;
 }
 
 export function loadSessionStore(
@@ -123,14 +126,11 @@ export function loadSessionStore(
     }
   }
 
-  if (serializedFromDisk !== undefined) {
-    setSerializedSessionStore(storePath, serializedFromDisk);
-  } else {
-    setSerializedSessionStore(storePath, undefined);
+  const migrated = applySessionStoreMigrations(store);
+  const normalized = normalizeSessionStore(store);
+  if (migrated || normalized) {
+    serializedFromDisk = undefined;
   }
-
-  applySessionStoreMigrations(store);
-  normalizeSessionStore(store);
   const maintenance = opts.maintenanceConfig ?? resolveMaintenanceConfig();
   const beforeCount = Object.keys(store).length;
   if (maintenance.mode === "enforce" && beforeCount > maintenance.maxEntries) {
@@ -145,7 +145,6 @@ export function loadSessionStore(
     const afterCount = Object.keys(store).length;
     if (pruned > 0 || capped > 0) {
       serializedFromDisk = undefined;
-      setSerializedSessionStore(storePath, undefined);
       log.info("applied load-time maintenance to oversized session store", {
         storePath,
         before: beforeCount,
@@ -157,6 +156,8 @@ export function loadSessionStore(
     }
   }
 
+  setSerializedSessionStore(storePath, serializedFromDisk);
+
   if (!opts.skipCache && isSessionStoreCacheEnabled()) {
     writeSessionStoreCache({
       storePath,
diff --git a/src/config/sessions/store-migrations.ts b/src/config/sessions/store-migrations.ts
index 0d161f734d6..945ea603e52 100644
--- a/src/config/sessions/store-migrations.ts
+++ b/src/config/sessions/store-migrations.ts
@@ -1,6 +1,7 @@
 import type { SessionEntry } from "./types.js";
 
-export function applySessionStoreMigrations(store: Record<string, SessionEntry>): void {
+export function applySessionStoreMigrations(store: Record<string, SessionEntry>): boolean {
+  let changed = false;
   // Best-effort migration: message provider → channel naming.
   for (const entry of Object.values(store)) {
     if (!entry || typeof entry !== "object") {
@@ -10,18 +11,23 @@ export function applySessionStoreMigrations(store: Record<string, SessionEntry>)
     if (typeof rec.channel !== "string" && typeof rec.provider === "string") {
       rec.channel = rec.provider;
       delete rec.provider;
+      changed = true;
     }
     if (typeof rec.lastChannel !== "string" && typeof rec.lastProvider === "string") {
       rec.lastChannel = rec.lastProvider;
       delete rec.lastProvider;
+      changed = true;
     }
 
     // Best-effort migration: legacy `room` field → `groupChannel` (keep value, prune old key).
     if (typeof rec.groupChannel !== "string" && typeof rec.room === "string") {
       rec.groupChannel = rec.room;
       delete rec.room;
+      changed = true;
     } else if ("room" in rec) {
       delete rec.room;
+      changed = true;
     }
   }
+  return changed;
 }