pfc-langchain 0.1.0

Thin LangChain adapter for PFC execution-boundary decisions

pfc-langchain

pfc-langchain is a thin execution-boundary wrapper for LangChain-style tools. It asks PFC for a decision before the wrapped callable runs, then returns the tool result together with PFC decision metadata.

What It Does

• Wraps a callable tool with a PFC pre-execution decision
• Preserves a simple callable interface
• Returns the tool result, decision id, and receipt hash in one response

Install

From this monorepo:

pip install -e ./packages/pfc_core
pip install -e ./packages/pfc_langchain

Quick Start

from pfc_langchain import GovernedTool


class EchoTool:
    name = "echo"
    description = "Return the provided value"

    def __call__(self, value):
        return {"echo": value}


tool = GovernedTool(
    EchoTool(),
    policy_id="policy-123",
    pfc_api_key="pfc_test_key",
)

result = tool(value="hello")
print(result)

How It Works

1. GovernedTool builds a PFC execution payload from the wrapped tool call.
2. It sends that payload to PFC before the tool executes.
3. If PFC allows the action, the tool runs and the wrapper returns result, decision_id, and receipt.
4. If PFC blocks the action, the wrapped tool is not executed.

Failure Behavior

• If the wrapped object is not callable, GovernedTool raises TypeError.
• If PFC returns a blocking decision, pfc_core.middleware.PFCBlockedError is raised.
• If the PFC API request fails, the underlying PFC client raises an exception.

Limitations

• This package is intentionally thin and does not manage prompts, chains, or policies.
• It treats the wrapped object as a generic callable rather than depending on specific LangChain internals.
• Positional arguments are represented in the PFC payload under an args list.