Codios

A2A AI Agent Security Layer — open source enforcement core

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Codios adds signed capability contracts to AI agent communication. Every action an agent takes is governed by a cryptographic contract that specifies exactly what it is allowed to do, for how long, and how many times — verified offline in ~0ms.

What's in this repo

Package	Description
backend/	FastAPI enforcement gateway — agents, contracts, audit, policies
sdk-js/	TypeScript SDK (@codios/sdk) — Ed25519 identity + middleware
cli/	codios CLI — keygen, register, issue, verify

The commercial SaaS (codios.midlantics.com) adds a dashboard UI, Stripe billing, SSO, and managed hosting. Everything in this repo is Apache 2.0 and runs fully self-hosted.

Quick start (Docker)

git clone https://github.com/Midlantics/codios
cd codios
./backend/setup-vpc.sh

One command generates Ed25519 keys, starts Postgres + Redis + the API, and prints your platform public key and first API key.

How it works

Agent A  ──(X-Codios-Contract: <signed contract>)──▶  Agent B service
                                                           │
                                                    codiosGuard() middleware
                                                           │
                                                    1. Verify Ed25519 sig  (~0ms, offline)
                                                    2. Check expiry + scope (~0ms, offline)
                                                    3. Consume nonce       (~1ms, Redis)
                                                    4. Evaluate OPA policy (~0ms, Python)
                                                    5. Log to audit trail  (async, non-blocking)

TypeScript SDK

npm install @codios/sdk

import { generateAgentKeyPair, issueContract, verifyContract, codiosGuard } from "@codios/sdk"

// Generate agent identity
const agent = await generateAgentKeyPair()
console.log(agent.did)  // did:key:z6Mk...

// Issue a signed contract (server-side, uses platform key)
const contract = await issueContract(
  { issuer_did: callerDid, subject_did: serviceDid, actions: ["transfer"], ttl_seconds: 3600 },
  platformPrivateKey,
)

// Protect an Express endpoint
app.post("/transfer", codiosGuard({ action: "transfer", publicKey, gatewayUrl }), handler)

// Verify offline (no network)
const result = await verifyContract(encoded, platformPublicKey, "transfer")

Python SDK

pip install codios-sdk

from codios import verify_contract
from codios.middleware.fastapi import require_contract

# FastAPI dependency — reads X-Codios-Contract header
@app.post("/transfer")
async def transfer(contract = Depends(require_contract("transfer", PUBLIC_KEY))):
    return {"authorized_by": contract["issuer_did"]}

CLI

codios keygen --save .env
codios register --name my-agent --public-key <key>
codios issue --issuer <did> --subject <did> --actions transfer,quote
codios verify --contract <b64> --action transfer

Self-hosted environment variables

Variable	Required	Description
DATABASE_URL	✅	PostgreSQL connection string
REDIS_URL	✅	Redis connection string
CODIOS_PRIVATE_KEY	✅	Ed25519 platform private key (base64)
CODIOS_PUBLIC_KEY	✅	Ed25519 platform public key (base64)
CODIOS_DID	✅	Platform DID (did:key:z6Mk...)
SUPABASE_JWT_SECRET	✅	JWT secret for API session tokens
GATEWAY_SECRET	✅	Internal shared secret
RESEND_API_KEY	☐	Email alerts via Resend
SMTP_HOST	☐	Email alerts via SMTP (alternative to Resend)
S3_AUDIT_BUCKET	☐	S3 bucket for immutable audit exports

Run ./backend/setup-vpc.sh to generate all secrets automatically.

Architecture

┌─────────────────────────────────────────────────────┐
│                    Your VPC                         │
│                                                     │
│  ┌──────────┐    ┌──────────┐    ┌───────────────┐  │
│  │ Agent A  │───▶│ Codios   │───▶│ Agent B       │  │
│  │ (caller) │    │ Gateway  │    │ (service)     │  │
│  └──────────┘    │ FastAPI  │    │ +codiosGuard  │  │
│                  └────┬─────┘    └───────────────┘  │
│                       │                             │
│               ┌───────┴────────┐                    │
│               │   PostgreSQL   │   Redis            │
│               │   audit_logs   │   nonces           │
│               └───────────────┘   call counters     │
└─────────────────────────────────────────────────────┘

ISO 27001 alignment

Control	Implementation
A.9 Access control	Ed25519 signed contracts + API keys
A.10 Cryptography	Ed25519 + RFC 8785 canonical JSON
A.12.4 Audit logging	Append-only log with DB-level immutability trigger
A.12.4 Evidence preservation	SHA-256 signed exports to S3 WORM
A.16 Incident response	Email alert rules with cooldown
A.14.2 OPA policies	Custom Rego policy evaluation

Contributing

See CONTRIBUTING.md. Security issues → security@midlantics.com.

License

Apache 2.0 — see LICENSE.

Built by Midlantics. Copyright Sensart Technologies LLC 2026.