Parallelize the /v1/models and /api/oauth/usage calls using asyncio.gather in _do_fetch_provider_usage

backend/app/services/provider_usage.py

@@ -1022,22 +1022,38 @@ async def _do_fetch_provider_usage(
                 checked_at=utcnow(), reachable=False,
                 error="No API key configured.",
             )
+
+        elif api_key and effective_session_key:
+            # Fire both calls concurrently — halves latency and eliminates the
+            # sequential back-to-back requests to api.anthropic.com that caused
+            # the subscription endpoint to 429 on every initial load.
+            subscription_attempted = True
+            result, sub_windows = await asyncio.gather(
+                _fetch_anthropic(api_key, base_url),
+                _fetch_anthropic_subscription(effective_session_key),
+            )
+            if result.reachable is not False:
+                if sub_windows:
+                    result.subscription_windows = sub_windows
+                    result.reachable = True
+                else:
+                    result.error = result.error or "No subscription data returned."
+
         elif api_key:
             result = await _fetch_anthropic(api_key, base_url)
+
         else:
+            # OAuth token only — no API key configured
+            subscription_attempted = True
             result = ProviderUsageLive(
                 provider=provider, account_key=account_key,
                 checked_at=utcnow(), reachable=True,
             )
-        # 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
-                result.reachable = True
             else:
-                result.error = result.error or "No subscription data returned."
+                result.error = "No subscription data returned."
 
     elif provider in ("openai", "codex"):
         if not api_key and not session_key: