fix(backend): add semaphore to executor cost log tasks; fix type annotation

- Add `_log_semaphore = asyncio.Semaphore(50)` to cost_tracking.py to bound
  concurrent DB inserts (mirrors platform_cost.py's existing semaphore)
- Narrow `_extract_model_name` param type from `Any` to `str | dict | None`
- Add `test_get_dashboard_cache_hit` to verify TTL cache deduplicates DB calls
- Add `scope="col"` to all table `<th>` elements for screen-reader accessibility
- Add `(local time)` labels to date filter inputs to clarify timezone behaviour

autogpt_platform/backend/backend/api/features/admin/platform_cost_routes_test.py

@@ -168,3 +168,25 @@ def test_get_dashboard_invalid_date_format() -> None:
     """Malformed start date must be rejected with 422."""
     response = client.get("/platform-costs/dashboard", params={"start": "not-a-date"})
     assert response.status_code == 422
+
+
+def test_get_dashboard_cache_hit(
+    mocker: pytest_mock.MockerFixture,
+) -> None:
+    """Second identical request returns cached result without calling the DB again."""
+    real_dashboard = PlatformCostDashboard(
+        by_provider=[],
+        by_user=[],
+        total_cost_microdollars=42,
+        total_requests=1,
+        total_users=1,
+    )
+    mock_fn = mocker.patch(
+        "backend.api.features.admin.platform_cost_routes.get_platform_cost_dashboard",
+        AsyncMock(return_value=real_dashboard),
+    )
+
+    client.get("/platform-costs/dashboard")
+    client.get("/platform-costs/dashboard")
+
+    mock_fn.assert_awaited_once()  # second request hit the cache

autogpt_platform/backend/backend/executor/cost_tracking.py

@@ -34,6 +34,8 @@ _WALLTIME_BILLED_PROVIDERS = frozenset(
 # Hold strong references to in-flight log tasks so the event loop doesn't
 # garbage-collect them mid-execution. Tasks remove themselves on completion.
 _pending_log_tasks: set[asyncio.Task] = set()
+# Bound concurrent DB inserts to avoid unbounded queue growth under load.
+_log_semaphore = asyncio.Semaphore(50)
 
 
 async def drain_pending_cost_logs(timeout: float = 5.0) -> None:
@@ -79,26 +81,27 @@ def _schedule_log(
     db_client: "DatabaseManagerAsyncClient", entry: PlatformCostEntry
 ) -> None:
     async def _safe_log() -> None:
-        try:
-            await db_client.log_platform_cost(entry)
-        except Exception:
-            logger.exception(
-                "Failed to log platform cost for user=%s provider=%s block=%s",
-                entry.user_id,
-                entry.provider,
-                entry.block_name,
-            )
+        async with _log_semaphore:
+            try:
+                await db_client.log_platform_cost(entry)
+            except Exception:
+                logger.exception(
+                    "Failed to log platform cost for user=%s provider=%s block=%s",
+                    entry.user_id,
+                    entry.provider,
+                    entry.block_name,
+                )
 
     task = asyncio.create_task(_safe_log())
     _pending_log_tasks.add(task)
     task.add_done_callback(_pending_log_tasks.discard)
 
 
-def _extract_model_name(raw: Any) -> str | None:
+def _extract_model_name(raw: str | dict | None) -> str | None:
     """Return a string model name from a block input field, or None.
 
     Handles str (returned as-is), dict (e.g. an enum wrapper, skipped), and
-    any other type (coerced to str as a best-effort fallback).
+    None (no model field). Unexpected types are coerced to str as a fallback.
     """
     if raw is None:
         return None

autogpt_platform/frontend/src/app/(platform)/admin/platform-costs/components/LogsTable.tsx

@@ -23,16 +23,36 @@ function LogsTable({ logs, pagination, onPageChange }: Props) {
         <table className="w-full text-left text-sm">
           <thead className="border-b text-xs uppercase text-muted-foreground">
             <tr>
-              <th className="px-3 py-3">Time</th>
-              <th className="px-3 py-3">User</th>
-              <th className="px-3 py-3">Block</th>
-              <th className="px-3 py-3">Provider</th>
-              <th className="px-3 py-3">Type</th>
-              <th className="px-3 py-3">Model</th>
-              <th className="px-3 py-3 text-right">Cost</th>
-              <th className="px-3 py-3 text-right">Tokens</th>
-              <th className="px-3 py-3 text-right">Duration</th>
-              <th className="px-3 py-3">Session</th>
+              <th scope="col" className="px-3 py-3">
+                Time
+              </th>
+              <th scope="col" className="px-3 py-3">
+                User
+              </th>
+              <th scope="col" className="px-3 py-3">
+                Block
+              </th>
+              <th scope="col" className="px-3 py-3">
+                Provider
+              </th>
+              <th scope="col" className="px-3 py-3">
+                Type
+              </th>
+              <th scope="col" className="px-3 py-3">
+                Model
+              </th>
+              <th scope="col" className="px-3 py-3 text-right">
+                Cost
+              </th>
+              <th scope="col" className="px-3 py-3 text-right">
+                Tokens
+              </th>
+              <th scope="col" className="px-3 py-3 text-right">
+                Duration
+              </th>
+              <th scope="col" className="px-3 py-3">
+                Session
+              </th>
             </tr>
           </thead>
           <tbody>

autogpt_platform/frontend/src/app/(platform)/admin/platform-costs/components/PlatformCostContent.tsx

@@ -48,7 +48,7 @@ function PlatformCostContent({ searchParams }: Props) {
       <div className="flex flex-wrap items-end gap-3 rounded-lg border p-4">
         <div className="flex flex-col gap-1">
           <label htmlFor="start-date" className="text-sm text-muted-foreground">
-            Start Date
+            Start Date <span className="text-xs">(local time)</span>
           </label>
           <input
             id="start-date"
@@ -60,7 +60,7 @@ function PlatformCostContent({ searchParams }: Props) {
         </div>
         <div className="flex flex-col gap-1">
           <label htmlFor="end-date" className="text-sm text-muted-foreground">
-            End Date
+            End Date <span className="text-xs">(local time)</span>
           </label>
           <input
             id="end-date"

autogpt_platform/frontend/src/app/(platform)/admin/platform-costs/components/ProviderTable.tsx

@@ -21,13 +21,29 @@ function ProviderTable({ data, rateOverrides, onRateOverride }: Props) {
       <table className="w-full text-left text-sm">
         <thead className="border-b text-xs uppercase text-muted-foreground">
           <tr>
-            <th className="px-4 py-3">Provider</th>
-            <th className="px-4 py-3">Type</th>
-            <th className="px-4 py-3 text-right">Usage</th>
-            <th className="px-4 py-3 text-right">Requests</th>
-            <th className="px-4 py-3 text-right">Known Cost</th>
-            <th className="px-4 py-3 text-right">Est. Cost</th>
-            <th className="px-4 py-3 text-right" title="Per-session only">
+            <th scope="col" className="px-4 py-3">
+              Provider
+            </th>
+            <th scope="col" className="px-4 py-3">
+              Type
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Usage
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Requests
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Known Cost
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Est. Cost
+            </th>
+            <th
+              scope="col"
+              className="px-4 py-3 text-right"
+              title="Per-session only"
+            >
               Rate <span className="text-[10px] font-normal">(unsaved)</span>
             </th>
           </tr>

autogpt_platform/frontend/src/app/(platform)/admin/platform-costs/components/UserTable.tsx

@@ -11,11 +11,21 @@ function UserTable({ data }: Props) {
       <table className="w-full text-left text-sm">
         <thead className="border-b text-xs uppercase text-muted-foreground">
           <tr>
-            <th className="px-4 py-3">User</th>
-            <th className="px-4 py-3 text-right">Known Cost</th>
-            <th className="px-4 py-3 text-right">Requests</th>
-            <th className="px-4 py-3 text-right">Input Tokens</th>
-            <th className="px-4 py-3 text-right">Output Tokens</th>
+            <th scope="col" className="px-4 py-3">
+              User
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Known Cost
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Requests
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Input Tokens
+            </th>
+            <th scope="col" className="px-4 py-3 text-right">
+              Output Tokens
+            </th>
           </tr>
         </thead>
         <tbody>