fix: stale update banner + skill sync dirty worktree crash (#358)

packages/mosaic/src/runtime/update-checker.ts

@@ -122,10 +122,18 @@ export function semverLt(a: string, b: string): boolean {
 
 // ─── Cache ──────────────────────────────────────────────────────────────────
 
-function readCache(): UpdateCheckResult | null {
+/** Cache stores only the latest registry version (the expensive network call).
+ *  The installed version is always checked fresh — it's a local `npm ls`. */
+interface RegistryCache {
+  latest: string;
+  checkedAt: string;
+  registry: string;
+}
+
+function readCache(): RegistryCache | null {
   try {
     if (!existsSync(CACHE_FILE)) return null;
-    const raw = JSON.parse(readFileSync(CACHE_FILE, 'utf-8')) as UpdateCheckResult;
+    const raw = JSON.parse(readFileSync(CACHE_FILE, 'utf-8')) as RegistryCache;
     const age = Date.now() - new Date(raw.checkedAt).getTime();
     if (age > CACHE_TTL_MS) return null;
     return raw;
@@ -134,10 +142,10 @@ function readCache(): UpdateCheckResult | null {
   }
 }
 
-function writeCache(result: UpdateCheckResult): void {
+function writeCache(entry: RegistryCache): void {
   try {
     mkdirSync(CACHE_DIR, { recursive: true });
-    writeFileSync(CACHE_FILE, JSON.stringify(result, null, 2) + '\n', 'utf-8');
+    writeFileSync(CACHE_FILE, JSON.stringify(entry, null, 2) + '\n', 'utf-8');
   } catch {
     // Best-effort — cache is not critical
   }
@@ -174,29 +182,40 @@ export function getLatestVersion(): string {
 }
 
 /**
- * Perform an update check — uses cache when fresh, otherwise hits registry.
+ * Perform an update check — uses registry cache when fresh, always checks
+ * installed version fresh (local npm ls is cheap, caching it causes stale
+ * "update available" banners after an upgrade).
  * Never throws.
  */
 export function checkForUpdate(options?: { skipCache?: boolean }): UpdateCheckResult {
+  const current = getInstalledVersion();
+
+  let latest: string;
+  let checkedAt: string;
+
   if (!options?.skipCache) {
     const cached = readCache();
-    if (cached) return cached;
+    if (cached) {
+      latest = cached.latest;
+      checkedAt = cached.checkedAt;
+    } else {
+      latest = getLatestVersion();
+      checkedAt = new Date().toISOString();
+      writeCache({ latest, checkedAt, registry: REGISTRY });
+    }
+  } else {
+    latest = getLatestVersion();
+    checkedAt = new Date().toISOString();
+    writeCache({ latest, checkedAt, registry: REGISTRY });
   }
 
-  const current = getInstalledVersion();
-  const latest = getLatestVersion();
-  const updateAvailable = !!(current && latest && semverLt(current, latest));
-
-  const result: UpdateCheckResult = {
+  return {
     current,
     latest,
-    updateAvailable,
-    checkedAt: new Date().toISOString(),
+    updateAvailable: !!(current && latest && semverLt(current, latest)),
+    checkedAt,
     registry: REGISTRY,
   };
-
-  writeCache(result);
-  return result;
 }
 
 /**