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__/session-event-freshness.test.ts

@@ -0,0 +1,33 @@
+import { describe, expect, test } from "bun:test"
+import type { Session } from "@opencode-ai/sdk/v2"
+
+import { shouldSkipStaleSessionEvent } from "../session-event-freshness"
+
+const buildSession = (title: string, time: Partial<NonNullable<Session["time"]>>): Session => ({
+  id: "ses_1",
+  title,
+  time: time as Session["time"],
+} as Session)
+
+describe("shouldSkipStaleSessionEvent", () => {
+  test("skips a stale SSE session update after a newer local rename", () => {
+    const current = buildSession("New Title", { created: 1, updated: 20 })
+    const incoming = buildSession("Old Title", { created: 1, updated: 10 })
+
+    expect(shouldSkipStaleSessionEvent(current, incoming)).toBe(true)
+  })
+
+  test("allows a fresher SSE update to apply", () => {
+    const current = buildSession("Old Title", { created: 1, updated: 10 })
+    const incoming = buildSession("New Title", { created: 1, updated: 20 })
+
+    expect(shouldSkipStaleSessionEvent(current, incoming)).toBe(false)
+  })
+
+  test("falls back to created timestamp when updated is missing", () => {
+    const current = buildSession("Current", { created: 20 })
+    const incoming = buildSession("Incoming", { created: 10 })
+
+    expect(shouldSkipStaleSessionEvent(current, incoming)).toBe(true)
+  })
+})