occ-anthropic

OCC cryptographic proof signing for the Anthropic Python SDK.

Every tool call produces an Ed25519-signed proof entry in proof.jsonl, creating a tamper-evident audit log of agent actions.

Install

pip install occ-anthropic

Quick Start

Wrap Client

import anthropic
from occ_anthropic import wrap_client

client = anthropic.Anthropic()
client = wrap_client(client)

# Every messages.create() with tool_use responses is now signed
response = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    tools=[{
        "name": "search",
        "description": "Search the web",
        "input_schema": {
            "type": "object",
            "properties": {"query": {"type": "string"}},
            "required": ["query"],
        },
    }],
    messages=[{"role": "user", "content": "Search for OCC proofs"}],
)

Decorator

from occ_anthropic import occ_tool

@occ_tool
def search(query: str) -> str:
    """Search the web."""
    return f"Results for: {query}"

# Call as usual — proof is signed automatically
result = search(query="OCC proofs")

Custom Signer

from occ_anthropic import OCCSigner, wrap_client

signer = OCCSigner(state_dir=".occ", proof_file="audit.jsonl")
client = wrap_client(anthropic.Anthropic(), signer=signer)

Proof Format

Each line in proof.jsonl is a JSON object:

{
  "version": "occ/proof/1",
  "timestamp": "2026-03-20T12:00:00.000Z",
  "signer": "<base64url-ed25519-public-key>",
  "payload": {
    "type": "tool-call",
    "tool": "search",
    "inputHash": "<sha256-hex>",
    "outputHash": "<sha256-hex>"
  },
  "signature": "<base64url-ed25519-signature>",
  "prev": "<sha256-hex-of-previous-proof>"
}

Proofs are chained: each proof's prev field contains the SHA-256 hash of the previous proof's canonical JSON.

Configuration

• State directory: Keypair stored in .occ/signer-state.json (defaults to CWD)
• Proof file: Defaults to proof.jsonl in CWD
• Both configurable via OCCSigner(state_dir=..., proof_file=...)

License

Apache-2.0