fix: safe encode json events

Author: ranst91

python-sdk/ag_ui/encoder/encoder.py

@@ -1,7 +1,8 @@
 """
 This module contains the EventEncoder class
 """
-
+from typing import Any
+import json
 from ag_ui.core.events import BaseEvent
 
 AGUI_MEDIA_TYPE = "application/vnd.ag-ui.event+proto"
@@ -25,8 +26,55 @@ def encode(self, event: BaseEvent) -> str:
         """
         return self._encode_sse(event)
 
+    def make_json_safe(self, value: Any) -> Any:
+        """
+        Recursively convert a value into a JSON-serializable structure.
+
+        - Handles Pydantic models via `model_dump`.
+        - Handles LangChain messages via `to_dict`.
+        - Recursively walks dicts, lists, and tuples.
+        - For arbitrary objects, falls back to `__dict__` if available, else `repr()`.
+        """
+        # Pydantic models
+        if hasattr(value, "model_dump"):
+            try:
+                return self.make_json_safe(value.model_dump(by_alias=True, exclude_none=True))
+            except Exception:
+                pass
+
+        # LangChain-style objects
+        if hasattr(value, "to_dict"):
+            try:
+                return self.make_json_safe(value.to_dict())
+            except Exception:
+                pass
+
+        # Dict
+        if isinstance(value, dict):
+            return {key: self.make_json_safe(sub_value) for key, sub_value in value.items()}
+
+        # List / tuple
+        if isinstance(value, (list, tuple)):
+            return [self.make_json_safe(sub_value) for sub_value in value]
+
+        # Already JSON safe
+        if isinstance(value, (str, int, float, bool)) or value is None:
+            return value
+
+        # Arbitrary object: try __dict__ first, fallback to repr
+        if hasattr(value, "__dict__"):
+            return {
+                "__type__": type(value).__name__,
+                **self.make_json_safe(value.__dict__),
+            }
+
+        return repr(value)
+
     def _encode_sse(self, event: BaseEvent) -> str:
         """
         Encodes an event into an SSE string.
         """
-        return f"data: {event.model_dump_json(by_alias=True, exclude_none=True)}\n\n"
+        event_dict = event.model_dump(by_alias=True, exclude_none=True)
+        json_ready = self.make_json_safe(event_dict)
+        json_string = json.dumps(json_ready)
+        return f"data: {json_string}\n\n"