Add event-payload context resolver

src/activity_core/activities.py

@@ -11,6 +11,7 @@ activities that need DB access.
 
 from __future__ import annotations
 
+import json
 import uuid
 from datetime import datetime, timezone
 from typing import Any
@@ -65,6 +66,24 @@ def _bind_resolver_result(bind_key: str, result: Any) -> Any:
     return result
 
 
+def _parse_event_envelope(event_envelope_json: str | None) -> dict[str, Any] | None:
+    """Parse an event envelope JSON string for context resolvers."""
+    if not event_envelope_json:
+        return None
+    try:
+        payload = json.loads(event_envelope_json)
+    except (TypeError, json.JSONDecodeError) as exc:
+        activity.logger.warning("Invalid event envelope JSON - %s", exc)
+        return None
+    if not isinstance(payload, dict):
+        activity.logger.warning(
+            "Invalid event envelope JSON - expected object, got %s",
+            type(payload).__name__,
+        )
+        return None
+    return payload
+
+
 # ── Activities ─────────────────────────────────────────────────────────────────
 
 @activity.defn
@@ -124,6 +143,7 @@ async def resolve_context(
     from activity_core.context_resolvers.base import CONTEXT_RESOLVER_REGISTRY
 
     snapshot: dict = {}
+    event_envelope = _parse_event_envelope(event_envelope_json)
     for source in context_sources:
         source_type = source.get("type", "")
         query = source.get("query", "")
@@ -152,7 +172,7 @@ async def resolve_context(
             continue
 
         try:
-            resolved = resolver_cls().resolve(query, None, params)
+            resolved = resolver_cls().resolve(query, event_envelope, params)
             snapshot[bind_key] = _bind_resolver_result(bind_key, resolved)
         except Exception as exc:
             if required: