langchain-alex

Verify signed ALEX Evidence Packages inside LangChain and LangGraph workflows. The verifier checks the package against a public key obtained separately from the evidence bundle and fails closed on unsupported schemas, signature failures, incomplete evidence, or inconsistent declared outcomes.

valid=True means that the evidence package passed verification and carries a verified outcome. Authentic bundles documenting failed or inconclusive runs remain rejected; inspect reason and outcome separately.

Requirements

• Python 3.10 or newer
• OpenSSL available as openssl on PATH

Install

pip install langchain-alex

Verify an Evidence Package

from langchain_alex import AlexEvidenceVerifier

verifier = AlexEvidenceVerifier.from_key_files("alex-public-key.pem")
result = verifier.verify_file("evidence-bundle.json")

print(result.valid, result.reason, result.outcome)

The trust anchor is intentionally supplied separately. A public key embedded only in the bundle is not trusted.

LangChain tool

tool = verifier.as_tool()
result = tool.invoke({"bundle": evidence_bundle})

The tool returns a JSON-serializable object with valid, reason, bundle_id, schema_version, outcome, and claim_ladder.

LangGraph node

from typing_extensions import TypedDict
from langgraph.graph import END, START, StateGraph


class State(TypedDict):
    evidence_bundle: dict
    alex_verification: dict


graph = StateGraph(State)
graph.add_node("alex_verify", verifier.as_langgraph_node())
graph.add_edge(START, "alex_verify")
graph.add_edge("alex_verify", END)
app = graph.compile()

result = app.invoke({"evidence_bundle": evidence_bundle})
assert result["alex_verification"]["valid"] is True

The node returns a state update and does not mutate its input state. Route on both valid and outcome when the graph controls a consequential action.

Development

python -m pip install -e ".[dev]"
python -m pytest
ruff check .
python -m build

The verifier implementation is also used by the repository's standalone Python CLI at tools/verify-bundle/verify.py; the integration does not maintain a second verdict algorithm.

Public evidence

The public ALEX record shows a human-readable projection of a signed Evidence Package plus the verifier path and explicit limits of the claim. It is evidence of the recorded execution and controls, not proof that the underlying work is professionally correct.