fix(runtime): suppress tool execution when provider safety-terminates with tool_calls (#3035)

* fix(runtime): suppress tool execution when provider safety-terminates with tool_calls

When a provider stops generation for safety reasons (OpenAI/Moonshot
finish_reason=content_filter, Anthropic stop_reason=refusal, Gemini
finish_reason=SAFETY/BLOCKLIST/PROHIBITED_CONTENT/SPII/RECITATION/
IMAGE_SAFETY/...), the response may still carry truncated tool_calls.
LangChain's tool router treats any non-empty tool_calls as executable,
so partial arguments (e.g. write_file with a half-finished markdown)
get dispatched and the agent loops on retry.

Add SafetyFinishReasonMiddleware at after_model: detect safety
termination via a pluggable detector registry, clear both structured
tool_calls and raw additional_kwargs.tool_calls / function_call,
preserve response_metadata.finish_reason for downstream observers,
stamp additional_kwargs.safety_termination for traces, append a
user-facing explanation to message content (list-aware for thinking
blocks), and emit a safety_termination custom stream event so SSE
consumers can reconcile any "tool starting..." UI.

Default detectors cover OpenAI-compatible content_filter, Anthropic
refusal, and Gemini safety enums (text + image). Custom providers are
added via reflection (same pattern as guardrails). Wired into both
lead-agent and subagent runtimes.

Closes #3028

* fix(runtime): persist safety_termination as a middleware audit event

Address review on #3035: the SSE custom event is great for live
consumers but invisible to post-run audit. RunEventStore should carry
its own row so operators can answer "which runs were safety-suppressed
today?" from a single SQL query without joining the message body.

Worker now exposes the run-scoped RunJournal via
runtime.context["__run_journal"] (sentinel key, internal channel).
SafetyFinishReasonMiddleware calls the previously-unused
RunJournal.record_middleware, which emits

  event_type = "middleware:safety_termination"
  category   = "middleware"
  content    = {name, hook, action, changes={
                  detector, reason_field, reason_value,
                  suppressed_tool_call_count,
                  suppressed_tool_call_names,
                  suppressed_tool_call_ids,
                  message_id, extras}}

Tool *arguments* are deliberately excluded — those are the very content
the provider filtered and persisting them would defeat the purpose of
the safety filter (per review note in #3035).

Graceful skips when journal is absent (subagent runtime, unit tests,
no-event-store local dev). Journal exceptions never propagate into the
agent loop.

Refs #3028

* fix(runtime): satisfy ruff format + address Copilot review

- ruff format on safety_finish_reason_config.py and e2e demo (CI lint
  failed on ruff format --check; backend Makefile lint target runs
  ruff check AND ruff format --check).
- Docstring on SafetyFinishReasonConfig now says resolve_variable to
  match the actual loader used in from_config (the wording was
  resolve_class previously; behavior is unchanged — resolve_variable
  mirrors how guardrails.provider is loaded).
- Switch the AIMessage type check in SafetyFinishReasonMiddleware._apply
  from getattr(last, "type") == "ai" to isinstance(last, AIMessage),
  matching TokenUsageMiddleware / TodoMiddleware / ViewImageMiddleware
  / SummarizationMiddleware which are the dominant pattern.

Refs #3028
This commit is contained in:
Xinmin Zeng
2026-05-22 21:20:28 +08:00
committed by GitHub
parent 253542ea0d
commit be0eae9825
14 changed files with 1936 additions and 5 deletions
@@ -29,6 +29,7 @@ from deerflow.agents.memory.summarization_hook import memory_flush_hook
from deerflow.agents.middlewares.clarification_middleware import ClarificationMiddleware
from deerflow.agents.middlewares.loop_detection_middleware import LoopDetectionMiddleware
from deerflow.agents.middlewares.memory_middleware import MemoryMiddleware
from deerflow.agents.middlewares.safety_finish_reason_middleware import SafetyFinishReasonMiddleware
from deerflow.agents.middlewares.subagent_limit_middleware import SubagentLimitMiddleware
from deerflow.agents.middlewares.summarization_middleware import BeforeSummarizationHook, DeerFlowSummarizationMiddleware
from deerflow.agents.middlewares.title_middleware import TitleMiddleware
@@ -338,6 +339,15 @@ def _build_middlewares(
if custom_middlewares:
middlewares.extend(custom_middlewares)
# SafetyFinishReasonMiddleware — suppress tool execution when the provider
# safety-terminated the response. Registered after custom middlewares so
# that LangChain's reverse-order after_model dispatch runs Safety first;
# cleared tool_calls then flow through Loop/Subagent accounting without
# firing extra alarms. See safety_finish_reason_middleware.py docstring.
safety_config = resolved_app_config.safety_finish_reason
if safety_config.enabled:
middlewares.append(SafetyFinishReasonMiddleware.from_config(safety_config))
# ClarificationMiddleware should always be last
middlewares.append(ClarificationMiddleware())
return middlewares
@@ -0,0 +1,317 @@
"""Suppress tool execution when the provider safety-terminated the response.
Background — see issue bytedance/deer-flow#3028.
Some providers (OpenAI ``finish_reason='content_filter'``, Anthropic
``stop_reason='refusal'``, Gemini ``finish_reason='SAFETY'`` ...) can stop
generation mid-stream while still returning partially-formed ``tool_calls``.
LangChain's tool router treats any AIMessage with a non-empty ``tool_calls``
field as "go execute these", so half-truncated arguments — e.g. a markdown
``write_file`` that stops in the middle of a sentence — get dispatched as if
they were complete. The agent then sees the truncated file, tries to fix it,
gets filtered again, and loops.
This middleware sits at ``after_model`` and gates that behaviour: when a
configured ``SafetyTerminationDetector`` fires *and* the AIMessage carries
tool calls, we strip the tool calls (both structured and raw provider
payloads), append a user-facing explanation, and stash observability fields
in ``additional_kwargs.safety_termination`` so logs, traces, and SSE
consumers can see what happened.
Hook choice: ``after_model`` (not ``wrap_model_call``) because the response
is a *normal* return — not an exception — and we want to participate in the
same after-model chain as ``LoopDetectionMiddleware``, with which we share
the same tool-call-suppression mechanic but a different trigger.
Placement: register *after* ``LoopDetectionMiddleware`` in the middleware
list. LangChain factory wires ``after_model`` edges in reverse list order
(``langchain/agents/factory.py:add_edge("model", middleware_w_after_model[-1])``,
then walks ``range(len-1, 0, -1)``), so the *last* registered middleware is
the *first* to observe the model output. Registering Safety after Loop
means Safety sees the raw response first, clears tool calls if it fires,
and Loop then accounts against the cleaned message.
"""
from __future__ import annotations
import logging
from typing import TYPE_CHECKING, override
from langchain.agents import AgentState
from langchain.agents.middleware import AgentMiddleware
from langchain_core.messages import AIMessage
from langgraph.runtime import Runtime
from deerflow.agents.middlewares.safety_termination_detectors import (
SafetyTermination,
SafetyTerminationDetector,
default_detectors,
)
from deerflow.agents.middlewares.tool_call_metadata import clone_ai_message_with_tool_calls
if TYPE_CHECKING:
from deerflow.config.safety_finish_reason_config import SafetyFinishReasonConfig
logger = logging.getLogger(__name__)
_USER_FACING_MESSAGE = (
"The model provider stopped this response with a safety-related signal "
"({reason_field}={reason_value!r}, detector={detector!r}). Any tool "
"calls produced in this turn were suppressed because their arguments "
"may be truncated and unsafe to execute. Please rephrase the request "
"or ask for a narrower output."
)
class SafetyFinishReasonMiddleware(AgentMiddleware[AgentState]):
"""Strip tool_calls from AIMessages flagged by a SafetyTerminationDetector."""
def __init__(self, detectors: list[SafetyTerminationDetector] | None = None) -> None:
super().__init__()
# Copy so caller mutations after construction don't leak into us.
self._detectors: list[SafetyTerminationDetector] = list(detectors) if detectors else default_detectors()
@classmethod
def from_config(cls, config: SafetyFinishReasonConfig) -> SafetyFinishReasonMiddleware:
"""Construct from validated Pydantic config, honouring the
reflection-loaded detector list when provided.
An explicit empty list is intentionally rejected — it would silently
disable detection while leaving the middleware in the chain, which
is the worst of both worlds. Use ``enabled: false`` instead.
"""
if config.detectors is None:
return cls()
if not config.detectors:
raise ValueError("safety_finish_reason.detectors must be omitted (use built-ins) or contain at least one entry; use enabled=false to disable the middleware entirely.")
from deerflow.reflection import resolve_variable
detectors: list[SafetyTerminationDetector] = []
for entry in config.detectors:
detector_cls = resolve_variable(entry.use)
kwargs = dict(entry.config) if entry.config else {}
detector = detector_cls(**kwargs)
if not isinstance(detector, SafetyTerminationDetector):
raise TypeError(f"{entry.use} did not produce a SafetyTerminationDetector (got {type(detector).__name__}); ensure it has a `name` attribute and a `detect(message)` method")
detectors.append(detector)
return cls(detectors=detectors)
# ----- detection -------------------------------------------------------
def _detect(self, message: AIMessage) -> SafetyTermination | None:
for detector in self._detectors:
try:
hit = detector.detect(message)
except Exception: # noqa: BLE001 - never let a buggy detector break the agent run
logger.exception("SafetyTerminationDetector %r raised; treating as no-match", getattr(detector, "name", type(detector).__name__))
continue
if hit is not None:
return hit
return None
# ----- message rewriting ----------------------------------------------
@staticmethod
def _append_user_message(content: object, text: str) -> str | list:
"""Append a plain-text explanation to AIMessage content.
Mirrors ``LoopDetectionMiddleware._append_text`` so list-content
responses (Anthropic thinking blocks, vLLM reasoning splits) keep
their structure instead of being string-coerced into a TypeError.
"""
if content is None or content == "":
return text
if isinstance(content, list):
return [*content, {"type": "text", "text": f"\n\n{text}"}]
if isinstance(content, str):
return content + f"\n\n{text}"
return str(content) + f"\n\n{text}"
def _build_suppressed_message(
self,
message: AIMessage,
termination: SafetyTermination,
) -> AIMessage:
suppressed_names = [tc.get("name") or "unknown" for tc in (message.tool_calls or [])]
explanation = _USER_FACING_MESSAGE.format(
reason_field=termination.reason_field,
reason_value=termination.reason_value,
detector=termination.detector,
)
new_content = self._append_user_message(message.content, explanation)
# clone_ai_message_with_tool_calls handles structured tool_calls,
# raw additional_kwargs.tool_calls, and function_call in one shot.
# It only rewrites finish_reason when the old value was "tool_calls",
# which is not our case — content_filter / refusal / SAFETY stay put
# so downstream SSE / converters keep seeing the real provider reason.
cleared = clone_ai_message_with_tool_calls(message, [], content=new_content)
# Re-clone additional_kwargs so we don't accidentally mutate the
# dict returned by clone_ai_message_with_tool_calls (which already
# made a shallow copy, but downstream model_copy still references
# it). Then stamp the observability record.
kwargs = dict(getattr(cleared, "additional_kwargs", None) or {})
kwargs["safety_termination"] = {
"detector": termination.detector,
"reason_field": termination.reason_field,
"reason_value": termination.reason_value,
"suppressed_tool_call_count": len(suppressed_names),
"suppressed_tool_call_names": suppressed_names,
"extras": dict(termination.extras) if termination.extras else {},
}
return cleared.model_copy(update={"additional_kwargs": kwargs})
# ----- observability ---------------------------------------------------
def _emit_event(
self,
termination: SafetyTermination,
suppressed_names: list[str],
runtime: Runtime,
) -> None:
"""Notify SSE consumers (e.g. the web UI) that a tool turn was
suppressed so they can reconcile any "tool starting..." placeholders
already streamed to the user. Failures are logged at debug and
ignored — this is a best-effort signal."""
try:
from langgraph.config import get_stream_writer
writer = get_stream_writer()
except Exception: # noqa: BLE001
logger.debug("get_stream_writer unavailable; skipping safety_termination event", exc_info=True)
return
thread_id = None
if runtime is not None and getattr(runtime, "context", None):
thread_id = runtime.context.get("thread_id") if isinstance(runtime.context, dict) else None
try:
writer(
{
"type": "safety_termination",
"detector": termination.detector,
"reason_field": termination.reason_field,
"reason_value": termination.reason_value,
"suppressed_tool_call_count": len(suppressed_names),
"suppressed_tool_call_names": suppressed_names,
"thread_id": thread_id,
}
)
except Exception: # noqa: BLE001
logger.debug("Failed to emit safety_termination stream event", exc_info=True)
def _record_audit_event(
self,
termination: SafetyTermination,
message,
tool_calls: list[dict],
runtime: Runtime,
) -> None:
"""Write a ``middleware:safety_termination`` record to RunEventStore
for post-run auditability.
The custom stream event in ``_emit_event`` is consumed by live SSE
clients and disappears after the run; this event is persisted so an
operator can answer "which runs were safety-suppressed today?" from
a single SQL query without joining the message body. Worker exposes
the run-scoped ``RunJournal`` via ``runtime.context["__run_journal"]``;
absent in unit-test / subagent / no-event-store paths, in which case
we silently skip.
Tool **arguments** are deliberately **not** recorded — those are the
very content the provider filtered; persisting them would defeat the
purpose of the safety filter. Names / count / ids are sufficient for
audit and debugging (issue #3028 review).
"""
journal = None
if runtime is not None and getattr(runtime, "context", None):
context = runtime.context
if isinstance(context, dict):
journal = context.get("__run_journal")
if journal is None:
return
suppressed_names = [tc.get("name") or "unknown" for tc in tool_calls]
suppressed_ids = [tc.get("id") for tc in tool_calls if tc.get("id")]
changes = {
"detector": termination.detector,
"reason_field": termination.reason_field,
"reason_value": termination.reason_value,
"suppressed_tool_call_count": len(tool_calls),
"suppressed_tool_call_names": suppressed_names,
"suppressed_tool_call_ids": suppressed_ids,
"message_id": getattr(message, "id", None),
"extras": dict(termination.extras) if termination.extras else {},
}
try:
journal.record_middleware(
tag="safety_termination",
name=type(self).__name__,
hook="after_model",
action="suppress_tool_calls",
changes=changes,
)
except Exception: # noqa: BLE001
# Audit-event persistence must never break agent execution.
logger.debug("Failed to record middleware:safety_termination event", exc_info=True)
# ----- main apply ------------------------------------------------------
def _apply(self, state: AgentState, runtime: Runtime) -> dict | None:
messages = state.get("messages", [])
if not messages:
return None
last = messages[-1]
if not isinstance(last, AIMessage):
return None
# Issue scope: only intervene when there's something to suppress.
# ``content_filter`` without tool_calls is allowed through unchanged
# so the partial text response (if any) reaches the user naturally.
tool_calls = last.tool_calls
if not tool_calls:
return None
termination = self._detect(last)
if termination is None:
return None
patched = self._build_suppressed_message(last, termination)
thread_id = None
if runtime is not None and getattr(runtime, "context", None):
thread_id = runtime.context.get("thread_id") if isinstance(runtime.context, dict) else None
logger.warning(
"Provider safety termination detected — suppressed %d tool call(s)",
len(tool_calls),
extra={
"thread_id": thread_id,
"detector": termination.detector,
"reason_field": termination.reason_field,
"reason_value": termination.reason_value,
"suppressed_tool_call_names": [tc.get("name") for tc in tool_calls],
},
)
self._emit_event(termination, [tc.get("name") or "unknown" for tc in tool_calls], runtime)
self._record_audit_event(termination, last, list(tool_calls), runtime)
return {"messages": [patched]}
# ----- hooks -----------------------------------------------------------
@override
def after_model(self, state: AgentState, runtime: Runtime) -> dict | None:
return self._apply(state, runtime)
@override
async def aafter_model(self, state: AgentState, runtime: Runtime) -> dict | None:
return self._apply(state, runtime)
@@ -0,0 +1,237 @@
"""Detectors for provider-side safety termination signals.
Different LLM providers signal "I stopped this response for safety reasons"
through different fields with different values. This module defines a small
strategy interface and three built-in detectors that cover the major
providers DeerFlow supports today. New providers (Wenxin, Hunyuan, Bedrock
adapters, in-house gateways, ...) can be added by implementing
``SafetyTerminationDetector`` and wiring it through
``config.yaml: safety_finish_reason.detectors``.
The middleware that consumes these detectors lives in
``safety_finish_reason_middleware.py``.
"""
from __future__ import annotations
from dataclasses import dataclass, field
from typing import Any, Protocol, runtime_checkable
from langchain_core.messages import AIMessage
@dataclass(frozen=True)
class SafetyTermination:
"""A detected safety-related termination signal.
Attributes:
detector: Name of the detector that produced this result. Used for
observability so operators can see which provider rule fired.
reason_field: The message metadata field that carried the signal
(e.g. ``finish_reason``, ``stop_reason``).
reason_value: The actual value of that field
(e.g. ``content_filter``, ``refusal``, ``SAFETY``).
extras: Provider-specific metadata that may help downstream
consumers (e.g. Azure OpenAI content_filter_results, Gemini
safety_ratings). Detectors are free to populate or skip this.
"""
detector: str
reason_field: str
reason_value: str
extras: dict[str, Any] = field(default_factory=dict)
@runtime_checkable
class SafetyTerminationDetector(Protocol):
"""Strategy interface for provider safety termination detection."""
name: str
def detect(self, message: AIMessage) -> SafetyTermination | None:
"""Return a SafetyTermination if *message* indicates provider safety
termination, otherwise return ``None``.
Implementations must be side-effect free and tolerant of missing or
oddly-typed metadata — detectors run on every model response.
"""
...
def _get_metadata_value(message: AIMessage, field_name: str) -> str | None:
"""Read a string-typed value from either ``response_metadata`` or
``additional_kwargs``.
LangChain provider adapters are inconsistent about where they stash
provider stop signals. Most modern adapters use ``response_metadata``,
but some legacy / passthrough paths still surface them via
``additional_kwargs``. We check both, in that order, and only accept
string values — Pydantic enums or dicts are ignored so we never raise
on malformed inputs.
"""
for container_name in ("response_metadata", "additional_kwargs"):
container = getattr(message, container_name, None) or {}
if not isinstance(container, dict):
continue
value = container.get(field_name)
if isinstance(value, str) and value:
return value
return None
class OpenAICompatibleContentFilterDetector:
"""OpenAI-compatible content_filter signal.
Covers OpenAI, Azure OpenAI, Moonshot/Kimi, DeepSeek, Mistral, vLLM,
Qwen (OpenAI-compatible mode), and any other adapter that follows the
OpenAI ``finish_reason`` convention.
Some Chinese providers ship custom OpenAI-compatible gateways that use
alternative tokens like ``sensitive`` or ``violation``. Extend the set
via the ``finish_reasons`` kwarg in config.
"""
name = "openai_compatible_content_filter"
def __init__(self, finish_reasons: list[str] | tuple[str, ...] | None = None) -> None:
configured = finish_reasons if finish_reasons is not None else ("content_filter",)
self._finish_reasons: frozenset[str] = frozenset(r.lower() for r in configured)
def detect(self, message: AIMessage) -> SafetyTermination | None:
value = _get_metadata_value(message, "finish_reason")
if value is None or value.lower() not in self._finish_reasons:
return None
extras: dict[str, Any] = {}
# Azure OpenAI ships a structured content_filter_results block; carry it
# through so operators can see *what* was filtered without re-tracing.
response_metadata = getattr(message, "response_metadata", None) or {}
if isinstance(response_metadata, dict):
filter_results = response_metadata.get("content_filter_results")
if filter_results:
extras["content_filter_results"] = filter_results
return SafetyTermination(
detector=self.name,
reason_field="finish_reason",
reason_value=value,
extras=extras,
)
class AnthropicRefusalDetector:
"""Anthropic ``stop_reason == "refusal"`` signal.
Anthropic models surface safety refusals via a dedicated ``stop_reason``
rather than ``finish_reason``. See:
https://platform.claude.com/docs/en/test-and-evaluate/strengthen-guardrails/handle-streaming-refusals
"""
name = "anthropic_refusal"
def __init__(self, stop_reasons: list[str] | tuple[str, ...] | None = None) -> None:
configured = stop_reasons if stop_reasons is not None else ("refusal",)
self._stop_reasons: frozenset[str] = frozenset(r.lower() for r in configured)
def detect(self, message: AIMessage) -> SafetyTermination | None:
value = _get_metadata_value(message, "stop_reason")
if value is None or value.lower() not in self._stop_reasons:
return None
return SafetyTermination(
detector=self.name,
reason_field="stop_reason",
reason_value=value,
)
class GeminiSafetyDetector:
"""Gemini / Vertex AI safety-related finish reasons.
Gemini uses the same ``finish_reason`` field as OpenAI but with an
enumerated upper-case taxonomy. The default set covers every Gemini
finish_reason that means "the model stopped because the content/image
tripped a safety, blocklist, recitation, or PII filter" — i.e. cases
where any tool_calls returned alongside are likely truncated/
unreliable. Full enum:
https://docs.cloud.google.com/python/docs/reference/aiplatform/latest/google.cloud.aiplatform_v1.types.Candidate.FinishReason
Intentionally **excluded** from the default set:
- ``STOP`` — normal termination.
- ``MAX_TOKENS`` — output length truncation, not safety
(same root failure mode as
content_filter, but issue #3028
scopes it out; expose separately if
desired).
- ``LANGUAGE`` / ``NO_IMAGE`` — capability mismatches, unrelated to
safety; tool_calls would be absent
anyway.
- ``MALFORMED_FUNCTION_CALL`` /
``UNEXPECTED_TOOL_CALL`` — tool-call protocol errors. The
tool_calls are *also* unreliable
here, but the failure category is
distinct from safety filtering;
handle in a dedicated detector to
keep observability records honest.
- ``OTHER`` / ``IMAGE_OTHER`` /
``FINISH_REASON_UNSPECIFIED`` — too broad to enable by default;
opt in via ``finish_reasons=`` if
your provider abuses these.
"""
name = "gemini_safety"
_DEFAULT_FINISH_REASONS = (
# Text safety
"SAFETY",
"BLOCKLIST",
"PROHIBITED_CONTENT",
"SPII",
"RECITATION",
# Image safety (multimodal generation)
"IMAGE_SAFETY",
"IMAGE_PROHIBITED_CONTENT",
"IMAGE_RECITATION",
)
def __init__(self, finish_reasons: list[str] | tuple[str, ...] | None = None) -> None:
configured = finish_reasons if finish_reasons is not None else self._DEFAULT_FINISH_REASONS
self._finish_reasons: frozenset[str] = frozenset(r.upper() for r in configured)
def detect(self, message: AIMessage) -> SafetyTermination | None:
value = _get_metadata_value(message, "finish_reason")
if value is None or value.upper() not in self._finish_reasons:
return None
extras: dict[str, Any] = {}
response_metadata = getattr(message, "response_metadata", None) or {}
if isinstance(response_metadata, dict):
# Gemini surfaces per-category scoring under safety_ratings.
ratings = response_metadata.get("safety_ratings")
if ratings:
extras["safety_ratings"] = ratings
return SafetyTermination(
detector=self.name,
reason_field="finish_reason",
reason_value=value,
extras=extras,
)
def default_detectors() -> list[SafetyTerminationDetector]:
"""Built-in detector set used when no custom detectors are configured."""
return [
OpenAICompatibleContentFilterDetector(),
AnthropicRefusalDetector(),
GeminiSafetyDetector(),
]
__all__ = [
"AnthropicRefusalDetector",
"GeminiSafetyDetector",
"OpenAICompatibleContentFilterDetector",
"SafetyTermination",
"SafetyTerminationDetector",
"default_detectors",
]
@@ -164,4 +164,14 @@ def build_subagent_runtime_middlewares(
middlewares.append(ViewImageMiddleware())
# Same provider safety-termination guard the lead agent uses — subagents
# are equally exposed to truncated tool_calls returned with
# finish_reason=content_filter (and friends), and the bad call would then
# propagate back to the lead agent via the task tool result.
safety_config = app_config.safety_finish_reason
if safety_config.enabled:
from deerflow.agents.middlewares.safety_finish_reason_middleware import SafetyFinishReasonMiddleware
middlewares.append(SafetyFinishReasonMiddleware.from_config(safety_config))
return middlewares