agenttrace-langchain 0.2.1

AgentTrace middleware for LangChain deepagents / create_agent

agenttrace-langchain

Published on PyPI: pypi.org/project/agenttrace-langchain

AgentTraceMiddleware — an AgentMiddleware for LangChain's create_agent / deepagents' create_deep_agent that streams a run to an AgentTrace instance as a live sequence diagram. Also ships AsyncAgentTraceClient/AsyncAgentTraceRun for servers that cache and reuse a compiled agent across requests — see "Servers with a cached/reused agent" below.

Install

pip install agenttrace-langchain

For local development against this checkout instead: pip install -e integrations/agenttrace-langchain.

Usage

from agenttrace_langchain import AgentTraceMiddleware
from deepagents import create_deep_agent

agent = create_deep_agent(
    model=model,
    tools=[...],
    middleware=[AgentTraceMiddleware(run_name="research run")],
)
agent.invoke({"messages": [{"role": "user", "content": "..."}]})

Works the same with await agent.ainvoke(...) — the middleware's async hooks fire automatically. See examples/ for full sync and async runnable projects.

Configure the target instance and project API key (from the AgentTrace Integration tab, prefixed atr_) via environment variables, or pass them explicitly to the middleware:

Env var	Default	Purpose
AGENTTRACE_URL	http://localhost:3000/api/events	Ingestion endpoint
AGENTTRACE_KEY	—	Project API key

middleware = AgentTraceMiddleware(
    run_name="research run",
    url="https://your-deployment/api/events",
    api_key="atr_...",
    timeout=10.0,
)

Reliability

The middleware is built to never affect the agent it instruments:

• Non-blocking — every event is pushed onto a queue drained by a background thread; wrap_model_call/wrap_tool_call never wait on the AgentTrace HTTP call.
• Never fatal — a missing API key or the first network/HTTP failure disables tracing for that run (one warning logged via the standard logging module), the agent keeps running normally.
• Bounded payloads — tool args/results, LLM output previews and the final answer are truncated (agenttrace_langchain.run.truncate/compact) before being sent, so a single large value can't blow up an event body.

AgentTraceRun (run.py) implements this contract and can be reused directly if you're not going through the middleware (e.g. to trace a custom orchestration loop):

from agenttrace_langchain import AgentTraceClient, AgentTraceRun

run = AgentTraceRun("custom run", client=AgentTraceClient(api_key="atr_..."))
run.emit(source="Orchestrator", target="LLM", type="llm_call", label="step")
run.end("completed")
run.close()  # bounded wait for the queue to drain

AgentTraceClient (client.py) itself stays a thin, fail-loud HTTP primitive (raises on a missing key or a failed request) — the right behavior when called directly; AgentTraceRun is the layer that adds the non-blocking/never-fatal guarantees on top.

Servers with a cached/reused agent (don't use the middleware)

AgentTraceMiddleware is baked into the agent graph at create_deep_agent(..., middleware=[...]) build time. If your server compiles the agent once and reuses it across many requests (e.g. a per-user compiled-graph cache with a TTL), a single middleware instance would span multiple runs — the first run's after_agent closes the AgentTrace run, and every later request on that cached agent silently traces into an already-closed run. The middleware is only correct when the agent is (re)built per invocation.

For a cached-agent server there are two options: attach a callback handler per request (recommended — least code), or drive an AsyncAgentTraceRun from your own stream projection (below).

Recommended: AgentTraceCallbackHandler (one callback, minimal wiring)

AgentTraceCallbackHandler is a LangChain AsyncCallbackHandler. You attach a fresh one per request via config={"callbacks": [handler]} on your astream_events/ainvoke call — nothing is baked into the cached graph, so reuse across requests is safe. One top-level handler fires for the main agent and every deepagents sub-agent (LangGraph propagates callbacks down the ambient RunnableConfig), so you don't hand-map the stream at all:

from agenttrace_langchain import AgentTraceCallbackHandler, AsyncAgentTraceClient

handler = AgentTraceCallbackHandler(
    "chat run",
    client=AsyncAgentTraceClient(api_key="atr_..."),
    anonymizer=my_scrubber,        # optional; applied to EVERY event payload
    phrases={"final_answer": "réponse finale"},   # optional label overrides
)
handler.on_user_message(user_text)

config = {"configurable": {"thread_id": tid}, "callbacks": [handler]}
async for event in agent.astream_events(payload, version="v2", config=config):
    ...                            # your own UI dispatch — untouched by tracing

# Two things a callback can't derive — the app supplies them:
#   handler.approval_required(interrupt_info)      # HITL pause (read from graph state)
await handler.finish("completed", answer=final_report)   # emits final_answer + closes

The handler captures on its own: LLM input (system + messages) at on_chat_model_start, LLM output + token usage at on_llm_end, tool call/result (with duration), sub-agent handoffs (the task tool and any handoff/delegate tool), and tool/LLM errors — each attributed to the main agent or the emitting sub-agent node (via metadata["langgraph_node"] / checkpoint_ns). It works identically whether you consume astream_events v2 or v3, since callbacks fire at the runnable level, not the stream level.

anonymizer is any Callable[[Any], Any] (e.g. langsmith.anonymizer.create_anonymizer(rules)): it runs on every event payload right before send, once, instead of masking at each call site. It's never fatal — a raising anonymizer logs a warning and the payload passes through rather than breaking the run.

Lower-level: AsyncAgentTraceRun + your own projection

If you already project agent.astream_events(...) into your own typed events and would rather feed those directly, create one AsyncAgentTraceRun per request and call on_stream_event:

from agenttrace_langchain import AsyncAgentTraceClient, AsyncAgentTraceRun

client = AsyncAgentTraceClient(api_key="atr_...")  # reuse across runs; own httpx.AsyncClient optional
run = AsyncAgentTraceRun("chat run", client=client, tool_server=my_mcp_routing_fn)

run.on_user_message(user_text)
async for kind, source, data in my_stream_projection(agent, ...):
    run.on_stream_event(kind, source, data)  # tool_call/tool_result/agent_start/agent_end/approval_required/final
run.end("completed")
await run.aclose()

tool_server is an optional Callable[[str], str] — pass it if you want a payload.server label on tool arrows (e.g. which MCP/backend served a tool call); omit it if you don't need that.

on_stream_event's diagram labels default to English ("delegate → X", "failed"/"done", "final answer", ...) — override any of them with phrases (merged over the defaults in async_run.DEFAULT_PHRASES), e.g. to localize:

run = AsyncAgentTraceRun(
    "chat run",
    client=client,
    phrases={
        "delegate": "délégation → {target}",
        "subagent_failed": "{name} → échec",
        "final_answer": "réponse finale",
    },
)

A stream projection typically doesn't expose LLM call boundaries, so on this lower-level path token usage/llm_call still needs a callback. Prefer AgentTraceCallbackHandler above, which already captures LLM input/output/ tokens and tool/sub-agent arrows in a single handler. AsyncAgentTraceRun also accepts the same optional anonymizer= callable, applied to every emitted payload.

Event mapping

Event type	Emitted from	Diagram arrow
llm_call	wrap_model_call	Orchestrator → LLM (payload: input — system prompt + messages sent — and output_preview)
tool_call	wrap_tool_call (before)	Orchestrator → tool
tool_result	wrap_tool_call (after)	tool → Orchestrator
handoff	wrap_tool_call (tool name matches handoff/delegate)	Orchestrator → Sub-agent
error	wrap_tool_call (exception)	tool → Orchestrator (red)
final_answer	after_agent	Orchestrator → User

Tests

pip install -e ".[dev]"
pytest

Releasing a new version

Published: pypi.org/project/agenttrace-langchain — Trusted Publishing (OIDC) is set up, no API token stored as a GitHub secret.

To ship a new version:

1. Bump version in pyproject.toml.
2. Commit, then push a tag matching agenttrace-langchain-v* (e.g. agenttrace-langchain-v0.1.1) — .github/workflows/publish-agenttrace-langchain.yml (repo root) builds and publishes automatically. A GitHub Release (published event) also triggers it, or run the workflow manually (workflow_dispatch).
3. Locally, verify before tagging: python -m build && twine check dist/* in this directory.

Trusted publisher config on pypi.org (Publishing → Trusted publishers), for reference/if it ever needs re-registering: project agenttrace-langchain, owner CouLiBaLy-B, repo agenttrace, workflow publish-agenttrace-langchain.yml, environment pypi-agenttrace-langchain (kept distinct from deepagents-trace's pypi environment so the two packages' publish permissions stay independent).