exit-door-langchain 0.1.0

LangChain callback handler for EXIT Protocol departure markers

exit-door-langchain 𓉸

𓉸 Passage Protocol · exit-door · entry-door · mcp · langchain · vercel · eliza · eas · erc-8004 · sign · python

⚠️ Pre-release software -- no formal security audit has been conducted.

LangChain callback handler for EXIT Protocol departure markers. Automatically creates signed departure records when chains or agents complete execution. Thread-safe, fail-safe, works with LCEL and LangGraph.

Quick Start

pip install exit-door-langchain

from exit_door_langchain import ExitCallbackHandler

handler = ExitCallbackHandler(origin="my-app")

# Use with any LangChain chain
chain.invoke({"input": "hello"}, config={"callbacks": [handler]})

# Markers are collected automatically
print(handler.markers[-1].id)  # urn:exit:abc123...

Configuration

from exit_door import ExitType

handler = ExitCallbackHandler(
    origin="my-platform",              # Platform name (default: "langchain")
    exit_type=ExitType.VOLUNTARY,      # Exit type for success (default: VOLUNTARY)
    error_exit_type=ExitType.FORCED,   # Exit type for errors (default: FORCED)
    on_marker=my_callback,             # Called on each new marker
    max_markers=500,                   # Memory limit (default: 1000)
    root_only=True,                    # Skip subchain markers (default: True)
    fail_safe=True,                    # Never break user's chain (default: True)
)

API

Method / Property	Description
handler.markers	Deque of collected ExitMarker objects
handler.markers_to_json()	Export all markers as JSON array
handler.clear()	Remove all stored markers and reset state

How It Works

The handler hooks into LangChain's callback system:

Callback	When	Exit Type
on_chain_end	Chain completes successfully	exit_type (default: VOLUNTARY)
on_chain_error	Chain fails with exception	error_exit_type (default: FORCED)
on_agent_finish	Agent completes (deduplicated)	exit_type (default: VOLUNTARY)

root_only mode (default): Only creates markers for root-level chain completions, not nested subchains. Set root_only=False to get a marker for every chain/subchain.

fail_safe mode (default): Marker creation errors are logged but never propagated to the user's chain. Set fail_safe=False to let exceptions bubble up.

Thread safety: Safe for concurrent chain invocations sharing one handler instance.

Web Server Usage

In web server contexts, create a new handler per request to prevent marker accumulation across users:

@app.post("/chat")
async def chat(request: ChatRequest):
    handler = ExitCallbackHandler(origin="my-api")
    result = chain.invoke(request.input, config={"callbacks": [handler]})
    return {"result": result, "departures": len(handler.markers)}

Ecosystem

Package	Language	Description
exit-door	TypeScript	Core protocol (reference impl)
exit-door	Python	Core protocol
cellar-door-entry	TypeScript	Arrival/entry markers
@cellar-door/langchain	TypeScript	LangChain integration
exit-door-langchain	Python	LangChain integration ← you are here
@cellar-door/vercel-ai-sdk	TypeScript	Vercel AI SDK
@cellar-door/mcp-server	TypeScript	MCP server
@cellar-door/eliza	TypeScript	ElizaOS plugin
@cellar-door/eas	TypeScript	EAS attestation anchoring
@cellar-door/erc-8004	TypeScript	ERC-8004 identity/reputation
@cellar-door/sign-protocol	TypeScript	Sign Protocol attestation

Paper · Website

License

Apache-2.0