feat: enhance subscription window handling to avoid stale cache on transient failures

backend/app/services/provider_usage.py

@@ -951,6 +951,10 @@ async def fetch_provider_usage(
         if cached is not None:
             return cached
 
+    # Tracks whether a subscription-window fetch was attempted so we can skip
+    # caching on transient empty-window failures (avoids stale navbar state).
+    _subscription_attempted = False
+
     if provider == "anthropic":
         # Auto-detected local OAuth token (sk-ant-oat01-) takes precedence — it is
         # the correct credential type for the oauth/usage endpoint and is always
@@ -974,6 +978,7 @@ async def fetch_provider_usage(
             )
         # Overlay subscription windows from OAuth token (auto or explicit)
         if effective_session_key and result.reachable is not False:
+            _subscription_attempted = True
             sub_windows = await _fetch_anthropic_subscription(effective_session_key)
             if sub_windows:
                 result.subscription_windows = sub_windows
@@ -1001,6 +1006,7 @@ async def fetch_provider_usage(
         local_codex = _read_codex_local_token()
         effective_codex_key = session_key or local_codex
         if effective_codex_key and result.reachable is not False:
+            _subscription_attempted = True
             sub_windows, plan_label = await _fetch_codex_subscription(effective_codex_key)
             if sub_windows:
                 result.subscription_windows = sub_windows
@@ -1020,7 +1026,16 @@ async def fetch_provider_usage(
         )
 
     result.account_key = account_key
-    _set_cached(credential_id, result)
+    # Skip caching when subscription windows were expected but came back empty —
+    # a transient failure at startup would otherwise be served stale for up to
+    # CACHE_TTL_SECONDS, causing the navbar to show no usage data.
+    if _subscription_attempted and not result.subscription_windows:
+        logger.debug(
+            "provider_usage.skip_cache provider=%s reason=empty_subscription_windows",
+            provider,
+        )
+    else:
+        _set_cached(credential_id, result)
     logger.info(
         "provider_usage.checked provider=%s account=%s reachable=%s error=%s",
         provider, account_key, result.reachable, result.error,