feat(event_handler): allow custom serializer on BedrockAgentResolver

BedrockAgentResolver did not expose the `serializer` parameter that its
parent ApiGatewayResolver and its sibling BedrockAgentFunctionResolver
already accept, so there was no way to override the default
`ensure_ascii=True` serialization. Non-ASCII agent responses (e.g.
Korean/Japanese/emoji) were therefore always \uXXXX-escaped in
responseBody.body.

Expose the existing parent `serializer` argument and pass it through to
super().__init__, matching the sibling resolver.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: kimnamu

aws_lambda_powertools/event_handler/bedrock_agent.py

@@ -99,12 +99,17 @@ def lambda_handler(event, context):
 
     current_event: BedrockAgentEvent
 
-    def __init__(self, debug: bool = False, enable_validation: bool = True):
+    def __init__(
+        self,
+        debug: bool = False,
+        enable_validation: bool = True,
+        serializer: Callable[[dict], str] | None = None,
+    ):
         super().__init__(
             proxy_type=ProxyEventType.BedrockAgentEvent,
             cors=None,
             debug=debug,
-            serializer=None,
+            serializer=serializer,
             strip_prefixes=None,
             enable_validation=enable_validation,
             json_body_deserializer=None,

tests/functional/event_handler/_pydantic/test_bedrock_agent.py

@@ -1,4 +1,5 @@
 import json
+from functools import partial
 from typing import Any, Dict, Optional
 
 import pytest
@@ -383,3 +384,37 @@ def run_sql_query(query: Annotated[str, Query()]):
     # THEN the parameter with commas should be correctly passed to the handler
     body = json.loads(result["response"]["responseBody"]["application/json"]["body"])
     assert body["result"] == "SELECT a.source_name, b.thing FROM table"
+
+
+def test_bedrock_agent_with_default_serializer_escapes_non_ascii():
+    # GIVEN a Bedrock Agent resolver using the default serializer
+    app = BedrockAgentResolver()
+
+    @app.get("/claims", description="Gets claims")
+    def claims() -> Dict[str, Any]:
+        return {"output": "잔액은 1,000원입니다 💰"}
+
+    # WHEN calling the event handler
+    result = app(load_event("bedrockAgentEvent.json"), {})
+
+    # THEN the body is valid JSON and non-ASCII characters are escaped (default json.dumps behavior)
+    body = result["response"]["responseBody"]["application/json"]["body"]
+    assert "\\uc794" in body  # "잔" escaped
+    assert json.loads(body) == {"output": "잔액은 1,000원입니다 💰"}
+
+
+def test_bedrock_agent_with_custom_serializer_preserves_non_ascii():
+    # GIVEN a Bedrock Agent resolver initialized with a custom serializer that keeps non-ASCII characters
+    app = BedrockAgentResolver(serializer=partial(json.dumps, ensure_ascii=False))
+
+    @app.get("/claims", description="Gets claims")
+    def claims() -> Dict[str, Any]:
+        return {"output": "잔액은 1,000원입니다 💰"}
+
+    # WHEN calling the event handler
+    result = app(load_event("bedrockAgentEvent.json"), {})
+
+    # THEN the non-ASCII characters are preserved verbatim in the response body
+    body = result["response"]["responseBody"]["application/json"]["body"]
+    assert "잔액은 1,000원입니다 💰" in body
+    assert json.loads(body) == {"output": "잔액은 1,000원입니다 💰"}