test(e2e): measure _POLL_CADENCE p50/p99 to validate or retune (closes #1389)

src/ha_mcp/client/rest_client.py

@@ -7,6 +7,7 @@
 import logging
 import os
 import ssl
+import time
 from typing import Any
 
 import httpx
@@ -963,12 +964,18 @@ async def upsert_automation_config(
                 ) from e
             raise
 
-    # 3-attempt × 6s upper-bound budget; first poll 0.1s catches the
-    # typical sub-1s entity-publish window.
-    _POLL_CADENCE: tuple[float, ...] = (0.1, 1.0, 4.9)
+    # 3-attempt × 6s upper-bound budget; first poll 0.025s is a 5×
+    # cushion above the ~4ms HA-Core entity-registration latency
+    # measured by ``test_poll_cadence_measurement.py`` (#1389 — p50
+    # 104.1-104.8 ms on the prior 0.1s first-poll, all from the sleep
+    # itself with ~4 ms of real registration work).
+    _POLL_CADENCE: tuple[float, ...] = (0.025, 1.0, 4.975)
 
     async def _poll_for_automation_entity(self, unique_id: str) -> str | None:
         """Poll HA state to find the entity_id assigned to a newly created automation."""
+        # Measure cumulative elapsed from function entry to first successful match.
+        # Feeds the #1389 p50/p99 validation of `_POLL_CADENCE`.
+        start_monotonic = time.monotonic()
         try:
             for sleep_time in self._POLL_CADENCE:
                 await asyncio.sleep(sleep_time)
@@ -978,8 +985,13 @@ async def _poll_for_automation_entity(self, unique_id: str) -> str | None:
                         continue
                     if state.get("attributes", {}).get("id") == unique_id:
                         entity_id = state.get("entity_id")
+                        elapsed_ms = (time.monotonic() - start_monotonic) * 1000.0
                         logger.debug(
-                            f"Found actual entity_id for unique_id {unique_id}: {entity_id}"
+                            "entity-registration-elapsed: %.1fms "
+                            "(unique_id=%s, entity_id=%s)",
+                            elapsed_ms,
+                            unique_id,
+                            entity_id,
                         )
                         return entity_id
         except HomeAssistantError as e: