Report security issues privately with GitHub's "Report a vulnerability" button on this repository, not in a public issue.

Every receipt and acknowledgment is signed with one Ed25519 key. The current public key is:

vM2GY6ZEYc/omRlIFrzu0TaMGtjHXQtchg9d7lPKkTY= (key ID 375ba8b346776e2f)

This client pins it by default (AgentReferee(public_keys=...) and agent_referee_client.PUBLIC_KEY). The private half is stored only as an encrypted secret in the service's hosting (Cloudflare), never in any repository or package.

1. A new key is generated and the service switches to it right away.
2. The old key is listed at GET /pubkey under history with the date it was retired, so receipts it signed before then stay verifiable.
3. An announcement goes at the top of the README and in a GitHub security advisory, with the time of the exposure.
4. Receipts signed by the old key after that time must not be trusted. If you pin keys (public_keys=[...]), add the new key and keep the old one only to check receipts dated before the exposure.

Receipts stay verifiable forever: checking one needs only the public key above, which verify_signature and AgentReferee.verify_receipt use offline.

• X402Payer takes your wallet key in memory only. The client never writes it to disk, prints it or sends it anywhere; only signed payment authorizations leave your machine, and only to the service's own address (the client never follows redirects).
• Every signature is checked against a spending cap you set (max_micro) and the offers the service made, before and after signing.
• Payment proofs for joins are saved to an owner-only folder before sending, so a lost reply can recover the seat, and deleted as soon as the service answers. Don't share or commit them: a proof can take over its seat until the match ends.