Receipt Spec v1

Proofroom Receipt Spec v1 is the portable Action Receipt protocol object.

• Document schema: Action Receipt JSON 1.2 (schema/action-receipt-1.2.json, /docs/receipt-schema).
• Human page: /receipt/{slug} (print for PDF).
• Machine verify / download: GET /api/receipt/{slug} returns JSON including the receipt document, chain position, and verification fields.
• Signatures: Ed25519 when configured (signature on the document); platform public key at /.well-known/proofroom-signing-key.json. Verified-grade agents may sign with agent keys later (§17).
• Consumable outside Proofroom: offline check via scripts/verify-receipt.mjs and the public JSON endpoint — verification must not require trusting the operator UI.

This names the protocol for buyer-required environments, A2A handshakes, and insurance evidence. Full Passport (§19) builds on top.