From 667d33d851448fdec5c2b8f4339f965e91103a3f Mon Sep 17 00:00:00 2001
From: Anas Khan <83116240+anxkhn@users.noreply.github.com>
Date: Sun, 5 Jul 2026 09:37:53 +0530
Subject: [PATCH] fix(bedrock): degrade to empty args on malformed streamed
 tool JSON

In the Bedrock streaming path, tool-call arguments are accumulated across
contentBlockDelta chunks and parsed with json.loads, but without the
JSONDecodeError guard that every sibling provider uses (OpenAI streaming and
non-streaming, SAP AI Core streaming). A truncated or malformed streamed
tool-argument JSON therefore raises inside the generator and aborts the whole
turn as an API_ERROR, instead of degrading to empty args like the other
providers and the Bedrock non-streaming path.

Wrap the json.loads call in try/except json.JSONDecodeError and fall back to
{}, matching the existing behavior across the models package. Add a regression
test that streams a truncated toolUse input and asserts the turn completes with
empty args rather than an error.

Signed-off-by: Anas Khan <83116240+anxkhn@users.noreply.github.com>
---
 .../src/kagent/adk/models/_bedrock.py         |  5 ++-
 .../tests/unittests/models/test_bedrock.py    | 36 +++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/python/packages/kagent-adk/src/kagent/adk/models/_bedrock.py b/python/packages/kagent-adk/src/kagent/adk/models/_bedrock.py
index 5323a7ada8..70ca31b83d 100644
--- a/python/packages/kagent-adk/src/kagent/adk/models/_bedrock.py
+++ b/python/packages/kagent-adk/src/kagent/adk/models/_bedrock.py
@@ -421,7 +421,10 @@ def _produce():
                 if aggregated_text:
                     final_parts.append(types.Part.from_text(text=aggregated_text))
                 for tool_id, tool in tool_uses.items():
-                    args = json.loads(tool["input_json"]) if tool["input_json"] else {}
+                    try:
+                        args = json.loads(tool["input_json"]) if tool["input_json"] else {}
+                    except json.JSONDecodeError:
+                        args = {}
                     part = types.Part.from_function_call(name=tool["name"], args=args)
                     if part.function_call:
                         part.function_call.id = tool_id
diff --git a/python/packages/kagent-adk/tests/unittests/models/test_bedrock.py b/python/packages/kagent-adk/tests/unittests/models/test_bedrock.py
index 08cbfad5b5..d9bd9d2169 100644
--- a/python/packages/kagent-adk/tests/unittests/models/test_bedrock.py
+++ b/python/packages/kagent-adk/tests/unittests/models/test_bedrock.py
@@ -306,6 +306,42 @@ async def fake_to_thread(fn, **kwargs):
         tool_names = [t["toolSpec"]["name"] for t in call_kwargs["toolConfig"]["tools"]]
         assert tool_names == ["fetch_get_url"]
 
+    @pytest.mark.asyncio
+    async def test_streaming_malformed_tool_input_degrades_to_empty_args(self):
+        """A truncated/malformed streamed tool-argument JSON must not abort the
+        turn: it degrades to empty args, matching the OpenAI and SAP AI Core
+        streaming paths."""
+        llm = KAgentBedrockLlm(model="us.anthropic.claude-sonnet-4-20250514-v1:0")
+
+        stream_events = [
+            {"contentBlockStart": {"start": {"toolUse": {"toolUseId": "call-xyz", "name": "get_weather"}}}},
+            {"contentBlockDelta": {"delta": {"toolUse": {"input": '{"city": "Paris"'}}}},
+            {"messageStop": {"stopReason": "tool_use"}},
+        ]
+        mock_client = mock.MagicMock()
+        mock_client.converse_stream.return_value = {"stream": stream_events}
+
+        async def fake_to_thread(fn, **kwargs):
+            return fn(**kwargs)
+
+        request = mock.MagicMock()
+        request.model = "us.anthropic.claude-sonnet-4-20250514-v1:0"
+        request.contents = []
+        request.config = None
+
+        with (
+            mock.patch("kagent.adk.models._bedrock._get_bedrock_client", return_value=mock_client),
+            mock.patch("kagent.adk.models._bedrock.asyncio.to_thread", side_effect=fake_to_thread),
+        ):
+            responses = [r async for r in llm.generate_content_async(request, stream=True)]
+
+        final = responses[-1]
+        assert final.error_code is None
+        fc = final.content.parts[0].function_call
+        assert fc.name == "get_weather"
+        assert fc.id == "call-xyz"
+        assert fc.args == {}
+
     def test_create_llm_from_bedrock_model_config(self):
         from kagent.adk.types import Bedrock, _create_llm_from_model_config