moltrust-langchain

Add trust verification to LangChain 1.x agents in one line.

moltrust-langchain plugs into LangChain 1.x's AgentMiddleware hook system to check MolTrust trust scores before an agent reasons and before it calls out to other agents/tools. Below-threshold agents are blocked (or warned/logged).

Install

pip install moltrust-langchain

Usage

from langchain.agents import create_agent
from moltrust_langchain import MolTrustMiddleware

agent = create_agent(
    model="anthropic:claude-sonnet-4-6",
    tools=[...],
    middleware=[MolTrustMiddleware(min_score=60)],
)

This example matches the real langchain.agents.create_agent signature (middleware: Sequence[AgentMiddleware] = ()), verified against langchain 1.3.11.

Usage tiers

Tier 1 — no account required (default):

MolTrustMiddleware(min_score=60)          # keyless; reads scores rate-limited

Tier 2 — free account (higher limits):

MolTrustMiddleware(min_score=60, api_key="mt_...")   # or MOLTRUST_API_KEY env

The API key is sent as the X-API-Key header only when present.

What it does

MolTrustMiddleware is a langchain.agents.middleware.AgentMiddleware. It uses two hook points (verified against langchain 1.3.11):

• before_model(state, runtime) — checks this agent's own DID (agent_did=...) before it reasons. A blocked check raises TrustCheckFailed (halts the agent) when action="block".
• wrap_tool_call(request, handler) — checks the target of a tool / A2A call (DID from the tool-call args under did_key, or agent_did_map by tool name). A blocked call returns an error ToolMessage (the agent can react) instead of raising.

min_score is on the 0–100 MolTrust trust score (trust_score from GET /skill/trust-score/{did}) — the behavioral score, not a 0–5 rating. Scores are recomputable: verify the on-chain solvency component of any agent yourself at

https://api.moltrust.ch/credits/solvency/{did}

Options

MolTrustMiddleware(
    min_score=60,               # 0-100 trust score threshold
    action="block",             # "block" | "warn" | "log"
    agent_did="did:moltrust:…",  # this agent's DID (before_model self-check)
    agent_did_map={"call_agent": "did:moltrust:…"},  # tool → target DID
    did_key="did",              # DID key in tool-call args / runtime context
    pass_without_did=True,       # allow calls with no resolvable DID
    check_model=True, check_tools=True,
)

Difference from Microsoft AGT

Microsoft's Agent Governance Toolkit enforces policies — what an agent may do (scope, sandboxing, zero-trust identity). MolTrust verifies behavioral trust — is this agent trustworthy, based on verifiable history. Complementary, not competing: AGT bounds authority; MolTrust decides who has earned it.

Honest limitations (0.1.0)

• LangChain agents have no MolTrust DID by default — supply agent_did (for the self-check) and/or a did in tool-call args or agent_did_map (for targets).
• A withheld score (registered agent, too few endorsements → API returns trust_score: null) is treated like an unregistered agent: fail-closed in block, fail-open in warn/log.
• On a registry/transport error the middleware fails open (logs, allows) so a MolTrust hiccup never breaks your agent.
• Synchronous hooks only. For fully async agents (ainvoke/astream), async abefore_model/awrap_tool_call are a follow-up.

License

MIT © CryptoKRI GmbH — see LICENSE.