fix: close broker uncertainty audit gaps

trex_core/domain/slot/service.py

@@ -15,10 +15,11 @@ from __future__ import annotations
 from dataclasses import replace
 from datetime import datetime, timezone
 from decimal import Decimal
-from typing import Any, Optional
+from typing import Any, Callable, Optional
 from uuid import UUID
 
 from trex_core.domain.slot.errors import (
+    SlotAdmissionRejectedError,
     SlotNotFoundError,
     SlotStateMismatchError,
     SlotTransitionError,
@@ -87,6 +88,7 @@ class SlotService:
         slippage_pct: Optional[float] = None,
         venue: Optional[str] = None,
         extra: Optional[dict[str, Any]] = None,
+        precondition: Optional[Callable[[Slot], Optional[str]]] = None,
     ) -> Slot:
         """Transition slot from one state to another atomically.
 
@@ -116,6 +118,10 @@ class SlotService:
                     f"slot {slot_id} current state {slot.status.value} "
                     f"!= requested from_state {from_state.value}"
                 )
+            if precondition is not None:
+                rejection_reason = precondition(slot)
+                if rejection_reason is not None:
+                    raise SlotAdmissionRejectedError(rejection_reason)
 
             updated = self._apply_transition_fields(
                 slot,