atlas-pca-langgraph

LangGraph guard for Proof-Carrying Authority (PCA): make every LangGraph tool call proof-carrying and policy-gated. A tool only runs when the agent carries a valid, in-plan, resource-correct proof for exactly that action. The adapter delegates all verification to atlas-pca and reimplements no cryptography.

Status: 0.4.1, unaudited.

What is tested

The default test suite runs without the framework, against the shared conformance proofs. A second suite, make test-real (needs the framework installed), runs against the real framework and is pinned to LangGraph 1.2.14 with langchain-core 1.6.9. It covers a real ToolNode and StateGraph: proofs carried in the run config and in graph state, a real StructuredTool, and the interrupt()/Command(resume=...) step-up path (a tampered resume is refused, a valid one proceeds). Each denial test checks that the tool body never ran, and checks the refusal reason wherever the framework surfaces it.

Not covered: other framework versions (only the pinned one is exercised), live model providers (the models are scripted and offline), and any property of the underlying atlas-pca verifier beyond what it already documents. This package has not been independently audited.

Install

pip install atlas-pca-langgraph

This installs atlas-pca>=0.4.1,<0.5 as a dependency.

Use

Entry points: pca_tool / PcaToolNode / pca_guard_node.

from atlas_pca_langgraph import pca_tool

See the module docstrings in atlas_pca_langgraph for the full API, and the PCA specification for the model. The verifier applies the full check order, including grant_ref_bound (the signed grant_ref must equal the root capability id), as of atlas-pca 0.2.0.

Links

• Source: https://github.com/Atlas-Authorization/pca-python
• Specification and docs: https://github.com/Atlas-Authorization/pca

License: MIT