occ-gemini

OCC cryptographic proof signing for Google Gemini.

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

Install

pip install occ-gemini

Quick Start

Wrap a Client (recommended)

from google import genai
from occ_gemini import wrap_client

client = genai.Client(api_key="...")
safe_client = wrap_client(client)
response = safe_client.models.generate_content(
    model="gemini-2.0-flash",
    contents="What's the weather?",
)
# proof.jsonl now contains signed proof entries for any function calls

Decorate Individual Tools

from occ_gemini import occ_tool

@occ_tool
def get_weather(location: str) -> str:
    return f"Sunny in {location}"

Custom Signer

from occ_gemini import OCCSigner, wrap_client

signer = OCCSigner(state_dir="/tmp/.occ", proof_file="audit.jsonl")
safe_client = wrap_client(client, signer=signer)

Legacy API (wrap_model)

wrap_model also accepts a google.genai.Client or a legacy google.generativeai.GenerativeModel:

from occ_gemini import wrap_model

safe_client = wrap_model(client)

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": "get_weather",
    "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