fix(sync): keep session renames stable (#2043)

* fix(sync): keep session renames stable

* fix(sync): clarify rename mirror flow

* fix(sync): clarify archive comment

---------

Co-authored-by: bashrusakh <bashrusakh@users.noreply.github.com>
Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/sync/__tests__/event-reducer.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, test } from "bun:test"
+import type { Session } from "@opencode-ai/sdk/v2"
 import type { Event, Part, PermissionRequest, QuestionRequest, SessionStatus } from "@opencode-ai/sdk/v2/client"
 import { applyDirectoryEvent } from "../event-reducer"
 import { INITIAL_STATE, type State } from "../types"
@@ -55,6 +56,14 @@ function topLevelSessionOnlyPartUpdatedEvent(): Event {
   } as Event
 }
 
+function buildSession(title: string, time: Session["time"]): Session {
+  return {
+    id: "ses_1",
+    title,
+    time,
+  } as Session
+}
+
 describe("applyDirectoryEvent", () => {
   test("returns typed materialization when delta arrives before parts", () => {
     const result = applyDirectoryEvent(state(), deltaEvent())
@@ -129,6 +138,20 @@ describe("applyDirectoryEvent", () => {
     })
   })
 
+  test("skips stale session.updated events so a newer title survives", () => {
+    const draft = state({ session: [buildSession("New Title", { created: 1, updated: 20 })] })
+
+    const result = applyDirectoryEvent(draft, {
+      type: "session.updated",
+      properties: {
+        info: buildSession("Old Title", { created: 1, updated: 10 }),
+      },
+    } as Event)
+
+    expect(result).toBe(false)
+    expect(draft.session[0]?.title).toBe("New Title")
+  })
+
   test("applies part update without materialization when owning message exists", () => {
     const draft = state({
       message: { ses_1: [{ id: "msg_1", sessionID: "ses_1", role: "assistant", time: { created: 1 } } as never] },