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fix(mcp,langchain): Add mechanism to captured exceptions #7226

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test(langchain, mcp): Validate error mechanism type and handling in e…
gmassello Aug 22, 2026
f5fcb50
Add mechanism to captured exceptions.
gmassello Aug 22, 2026
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12 changes: 11 additions & 1 deletion sentry_sdk/integrations/langchain.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
)
from sentry_sdk.utils import (
capture_internal_exceptions,
event_from_exception,
has_data_collection_enabled,
logger,
)
Expand Down Expand Up @@ -265,6 +266,15 @@ def setup_once() -> None:
_patch_embeddings_provider(OllamaEmbeddings)


def _capture_exception(exc: "Any", scope: "Optional[Any]" = None) -> None:
event, hint = event_from_exception(
exc,
client_options=sentry_sdk.get_client().options,
mechanism={"type": "langchain", "handled": False},
)
sentry_sdk.capture_event(event, hint=hint, scope=scope)


class SentryLangchainCallback(BaseCallbackHandler):
"""Callback handler that creates Sentry spans."""

Expand Down Expand Up @@ -293,7 +303,7 @@ def _handle_error(self, run_id: "UUID", error: "Any") -> None:
if is_ignored:
span.__exit__(None, None, None)
else:
sentry_sdk.capture_exception(
_capture_exception(
error, span._scope if isinstance(span, StreamedSpan) else span.scope
)
span.__exit__(type(error), error, error.__traceback__)
Expand Down
29 changes: 23 additions & 6 deletions sentry_sdk/integrations/mcp.py
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,8 @@
from sentry_sdk.traces import StreamedSpan
from sentry_sdk.tracing_utils import has_span_streaming_enabled
from sentry_sdk.utils import (
capture_internal_exceptions,
event_from_exception,
has_data_collection_enabled,
nullcontext,
package_version,
Expand Down Expand Up @@ -100,6 +102,15 @@ def setup_once() -> None:
_patch_fastmcp()


def _capture_exception(exc: "Any") -> None:
event, hint = event_from_exception(
exc,
client_options=sentry_sdk.get_client().options,
mechanism={"type": "mcp", "handled": False},
)
sentry_sdk.capture_event(event, hint=hint)


@contextmanager
def _active_http_scopes(
ctx: "Any",
Expand Down Expand Up @@ -394,7 +405,8 @@ async def _tool_handler_wrapper(
result = await result

except Exception as e:
sentry_sdk.capture_exception(e)
with capture_internal_exceptions():
_capture_exception(e)
raise

if result is None:
Expand Down Expand Up @@ -490,7 +502,8 @@ async def _instrument_v2_tool_call(
result = await call_next(ctx)

except Exception as e:
sentry_sdk.capture_exception(e)
with capture_internal_exceptions():
_capture_exception(e)
raise

if not isinstance(result, dict):
Expand Down Expand Up @@ -615,7 +628,8 @@ async def _prompt_handler_wrapper(
result = await result

except Exception as e:
sentry_sdk.capture_exception(e)
with capture_internal_exceptions():
_capture_exception(e)
raise

if result is None:
Expand Down Expand Up @@ -764,7 +778,8 @@ async def _instrument_v2_prompt_get(
try:
result = await call_next(ctx)
except Exception as e:
sentry_sdk.capture_exception(e)
with capture_internal_exceptions():
_capture_exception(e)
raise

if not isinstance(result, dict):
Expand Down Expand Up @@ -919,7 +934,8 @@ async def _resource_handler_wrapper(
result = await result

except Exception as e:
sentry_sdk.capture_exception(e)
with capture_internal_exceptions():
_capture_exception(e)
raise

return result
Expand Down Expand Up @@ -984,7 +1000,8 @@ async def _instrument_v2_resource_read(
result = await call_next(ctx)

except Exception as e:
sentry_sdk.capture_exception(e)
with capture_internal_exceptions():
_capture_exception(e)
raise

return result
Expand Down
79 changes: 79 additions & 0 deletions tests/integrations/langchain/test_langchain.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3621,6 +3621,8 @@ def _llm_type(self) -> str:

error = events[0]
assert error["level"] == "error"
assert error["exception"]["values"][0]["mechanism"]["type"] == "langchain"
assert not error["exception"]["values"][0]["mechanism"]["handled"]


@pytest.mark.parametrize("span_streaming", [True, False])
Expand Down Expand Up @@ -3691,6 +3693,8 @@ def _llm_type(self) -> str:

(error,) = (item.payload for item in items if item.type == "event")
assert error["level"] == "error"
assert error["exception"]["values"][0]["mechanism"]["type"] == "langchain"
assert not error["exception"]["values"][0]["mechanism"]["handled"]
sentry_sdk.flush()
spans = [item.payload for item in items if item.type == "span"]
assert spans[0]["status"] == "error"
Expand Down Expand Up @@ -3728,6 +3732,8 @@ def _llm_type(self) -> str:

(error,) = (item.payload for item in items if item.type == "event")
assert error["level"] == "error"
assert error["exception"]["values"][0]["mechanism"]["type"] == "langchain"
assert not error["exception"]["values"][0]["mechanism"]["handled"]
sentry_sdk.flush()
spans = [item.payload for item in items if item.type == "span"]
assert spans[0]["status"] == "error"
Expand Down Expand Up @@ -3766,10 +3772,83 @@ def _llm_type(self) -> str:

(error, transaction) = events
assert error["level"] == "error"
assert error["exception"]["values"][0]["mechanism"]["type"] == "langchain"
assert not error["exception"]["values"][0]["mechanism"]["handled"]
assert transaction["spans"][0]["status"] == "internal_error"
assert transaction["spans"][0]["tags"]["status"] == "internal_error"


@tool
def failing_tool(word: str) -> int:
"""Raises instead of returning a length."""
raise ValueError("Tool execution failed")


def test_langchain_tool_error(
sentry_init,
capture_events,
get_model_response,
nonstreaming_responses_tool_call_model_responses,
):
sentry_init(
integrations=[LangchainIntegration(include_prompts=True)],
disabled_integrations=[StdlibIntegration],
traces_sample_rate=1.0,
)

responses = nonstreaming_responses_tool_call_model_responses(
tool_name="failing_tool",
arguments='{"word": "eudca"}',
response_model="gpt-4-0613",
response_text="",
response_ids=iter(["resp_1"]),
usages=iter(
[
ResponseUsage(
input_tokens=0,
input_tokens_details=InputTokensDetails(
cached_tokens=0,
cache_write_tokens=0,
),
output_tokens=0,
output_tokens_details=OutputTokensDetails(
reasoning_tokens=0,
),
total_tokens=0,
),
]
),
)
tool_response = get_model_response(
next(responses),
serialize_pydantic=True,
request_headers={
"X-Stainless-Raw-Response": "True",
},
)

llm = ChatOpenAI(
model_name="gpt-4",
temperature=0,
openai_api_key="badkey",
use_responses_api=True,
)
agent = create_agent(model=llm, tools=[failing_tool], name="failing_agent")

events = capture_events()

with patch.object(
llm.client._client._client, "send", side_effect=[tool_response]
), start_transaction(name="tx"), pytest.raises(ValueError):
agent.invoke({"messages": [HumanMessage(content="hi")]})

error_events = [event for event in events if event.get("level") == "error"]
assert len(error_events) == 1
assert error_events[0]["exception"]["values"][0]["type"] == "ValueError"
assert error_events[0]["exception"]["values"][0]["mechanism"]["type"] == "langchain"
assert not error_events[0]["exception"]["values"][0]["mechanism"]["handled"]

@cursor cursor Bot Aug 22, 2026

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Missing LangChain version skip

Medium Severity

test_langchain_tool_error uses create_agent, which is only imported for LangChain 1.0+, but it lacks the @pytest.mark.skipif(LANGCHAIN_VERSION < (1,), ...) guard that sibling tests such as test_langchain_create_agent and test_tool_execution_span already apply. On tox envs still in the matrix (langchain-base-v0.1.20, v0.3.30), collection succeeds while the test raises NameError at runtime.

Fix in Cursor Fix in Web

Reviewed by Cursor Bugbot for commit f5fcb50. Configure here.



def test_manual_callback_no_duplication(sentry_init):
"""
Test that when a user manually provides a SentryLangchainCallback,
Expand Down
14 changes: 14 additions & 0 deletions tests/integrations/mcp/test_mcp.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -618,6 +618,8 @@ def failing_tool(tool_name, arguments):
assert (
error_payload["exception"]["values"][0]["value"] == "Tool execution failed"
)
assert error_payload["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_payload["exception"]["values"][0]["mechanism"]["handled"]

assert span["status"] == "error"
else:
Expand Down Expand Up @@ -647,6 +649,8 @@ def failing_tool(tool_name, arguments):
assert error_event["level"] == "error"
assert error_event["exception"]["values"][0]["type"] == "ValueError"
assert error_event["exception"]["values"][0]["value"] == "Tool execution failed"
assert error_event["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_event["exception"]["values"][0]["mechanism"]["handled"]

# Check transaction and span
assert tx["type"] == "transaction"
Expand Down Expand Up @@ -944,6 +948,8 @@ async def failing_prompt(name, arguments):

assert error_payload["level"] == "error"
assert error_payload["exception"]["values"][0]["type"] == "RuntimeError"
assert error_payload["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_payload["exception"]["values"][0]["mechanism"]["handled"]
assert span["status"] == "error"
else:
events = capture_events()
Expand All @@ -966,6 +972,8 @@ async def failing_prompt(name, arguments):

assert error_event["level"] == "error"
assert error_event["exception"]["values"][0]["type"] == "RuntimeError"
assert error_event["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_event["exception"]["values"][0]["mechanism"]["handled"]

# Check transaction and span
assert tx["type"] == "transaction"
Expand Down Expand Up @@ -1229,6 +1237,8 @@ def failing_resource(uri):

assert error_payload["level"] == "error"
assert error_payload["exception"]["values"][0]["type"] == "FileNotFoundError"
assert error_payload["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_payload["exception"]["values"][0]["mechanism"]["handled"]
assert span["status"] == "error"
else:
events = capture_events()
Expand All @@ -1248,6 +1258,8 @@ def failing_resource(uri):

assert error_event["level"] == "error"
assert error_event["exception"]["values"][0]["type"] == "FileNotFoundError"
assert error_event["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_event["exception"]["values"][0]["mechanism"]["handled"]

# Check transaction and span
assert tx["type"] == "transaction"
Expand Down Expand Up @@ -2008,6 +2020,8 @@ def failing_tool(tool_name, arguments):

error_event = error_events[0]
assert error_event["exception"]["values"][0]["type"] == "ValueError"
assert error_event["exception"]["values"][0]["mechanism"]["type"] == "mcp"
assert not error_event["exception"]["values"][0]["mechanism"]["handled"]

# The captured error shares the trace of the MCP transaction, proving the
# handler executed under the propagated request scope.
Expand Down