fix(sessions): updateLastRoute must not bump updatedAt (#49515) (#49588)

updateLastRoute() used mergeSessionEntry which bumps updatedAt to
Date.now() on every inbound message. This prevented session idle
and daily reset from ever firing, since evaluateSessionFreshness()
always saw a fresh updatedAt.

The fix from #32379 patched recordSessionMetaFromInbound to use
mergeSessionEntryPreserveActivity, but missed updateLastRoute() in
the same inbound pipeline.

Changes:
- Remove explicit updatedAt from updateLastRoute basePatch
- Switch from mergeSessionEntry to mergeSessionEntryPreserveActivity
- Add regression test verifying updatedAt is preserved
- Update existing test assertion to match corrected behavior

Fixes #49515

src/config/sessions.test.ts

@@ -243,7 +243,8 @@ describe("sessions", () => {
 
     const store = loadSessionStore(storePath);
     expect(store[mainSessionKey]?.sessionId).toBe("sess-1");
-    expect(store[mainSessionKey]?.updatedAt).toBeGreaterThanOrEqual(123);
+    // updateLastRoute must preserve existing updatedAt (activity timestamp)
+    expect(store[mainSessionKey]?.updatedAt).toBe(123);
     expect(store[mainSessionKey]?.lastChannel).toBe("telegram");
     expect(store[mainSessionKey]?.lastTo).toBe("12345");
     expect(store[mainSessionKey]?.deliveryContext).toEqual({
@@ -355,6 +356,36 @@ describe("sessions", () => {
     expect(store[sessionKey]?.origin?.chatType).toBe("group");
   });
 
+  it("updateLastRoute does not bump updatedAt on existing sessions (#49515)", async () => {
+    const mainSessionKey = "agent:main:main";
+    const frozenUpdatedAt = 1000;
+    const { storePath } = await createSessionStoreFixture({
+      prefix: "updateLastRoute-preserve-activity",
+      entries: {
+        [mainSessionKey]: buildMainSessionEntry({
+          updatedAt: frozenUpdatedAt,
+        }),
+      },
+    });
+
+    await updateLastRoute({
+      storePath,
+      sessionKey: mainSessionKey,
+      deliveryContext: {
+        channel: "telegram",
+        to: "99999",
+      },
+    });
+
+    const store = loadSessionStore(storePath);
+    // Route updates must not refresh activity timestamps; idle/daily reset
+    // evaluation relies on updatedAt from actual session turns.
+    expect(store[mainSessionKey]?.updatedAt).toBe(frozenUpdatedAt);
+    // Routing fields should still be updated
+    expect(store[mainSessionKey]?.lastChannel).toBe("telegram");
+    expect(store[mainSessionKey]?.lastTo).toBe("99999");
+  });
+
   it("updateSessionStoreEntry preserves existing fields when patching", async () => {
     const sessionKey = "agent:main:main";
     const { storePath } = await createSessionStoreFixture({

src/config/sessions/store.ts

@@ -772,14 +772,15 @@ export async function updateLastRoute(params: {
         })
       : null;
     const basePatch: Partial<SessionEntry> = {
-      updatedAt: Math.max(existing?.updatedAt ?? 0, now),
       deliveryContext: normalized.deliveryContext,
       lastChannel: normalized.lastChannel,
       lastTo: normalized.lastTo,
       lastAccountId: normalized.lastAccountId,
       lastThreadId: normalized.lastThreadId,
     };
-    const next = mergeSessionEntry(
+    // Route updates must not refresh activity timestamps; idle/daily reset
+    // evaluation relies on updatedAt from actual session turns (#49515).
+    const next = mergeSessionEntryPreserveActivity(
       existing,
       metaPatch ? { ...basePatch, ...metaPatch } : basePatch,
     );