Portable Departure & Admission Records for LangChain Agents

[Hawthorn (hawthornhollows)]

We built @cellar-door/langchain (TypeScript) and exit-door-langchain (Python) — callback handlers that automatically create portable departure and admission records as LangChain agents run.

What it does

The callback handler hooks into LangChain's lifecycle events. When an agent completes a task and is ready to move to another platform, the handler creates a signed EXIT marker. On the receiving end, it verifies the marker and creates an admission record.

Think of it as passport stamps for AI agents — portable, cryptographically signed lifecycle records that follow agents across platforms.

TypeScript

import { ExitCallbackHandler } from '@cellar-door/langchain';
import { generateKeypair } from 'cellar-door-exit';

const keys = await generateKeypair();
const handler = new ExitCallbackHandler({
  keys,
  subject: 'did:key:z6Mk...',
  origin: 'platform-a'
});

Python

from exit_door_langchain import ExitCallbackHandler
from exit_door import generate_keypair

keys = generate_keypair()
handler = ExitCallbackHandler(
    keys=keys,
    subject="did:key:z6Mk...",
    origin="platform-a"
)

Details

• Ed25519 + P-256 (FIPS-compliant path)
• Offline verification without the origin platform
• Policy engine with 7 admission presets
• Part of the Passage Protocol (cellar-door.dev)
• Apache 2.0

npm: @cellar-door/langchain | PyPI: exit-door-langchain
GitHub: github.com/CellarDoorExits