Receipts and verification

A receipt is the record’s account of one event. You, or a reviewer who isn’t you, use receipts to check that the record says what it says and that nobody changed it afterwards.

Events with receipts

Event	The receipt records
A posting	Which entry was posted, through which lane, by whom.
An answer	The hash of the context packet, the lines it cited and the model lane that answered.
An abstention	Whether the record was silent or the reader wasn’t cleared, and the scope Syderial searched.
A tool decision	The tool, a hash of its arguments, the decision and the reason.

Receipts store hashes of content, never the content. A tool receipt stores the hash of the arguments. A reviewer can confirm the sequence of events is intact without clearance to read what those events contained.

How the chain is built

• Syderial serializes each receipt and each entry to a canonical form and hashes it with SHA-256.
• Each one includes the hash of the one before it, which forms an append-only hash chain.
• Syderial signs each hash with Ed25519.

The chain doesn’t depend on the database that serves queries, so you can check it on its own.

Verifying

Verification checks three properties in order.

1. The hash. Recompute the SHA-256 of the canonical form and compare it with the recorded hash.
2. The signature. Check the Ed25519 signature over that hash against the verification key issued with your deployment.
3. The link. Check that the recorded previous hash matches the hash of the receipt before it.

A failed check marks the exact receipt where the record and its receipts disagree.

Reference verifier

We intend to publish the receipt format and a reference verifier as open source, so anyone can check a chain without depending on the service that wrote it. See Open source.

Where you’ll see receipts

• The model doors return a receipt reference with each answer, next to the standard response fields.
• The MCP door records a receipt for each proposal, commit and tool decision.
• Design partners evaluating Syderial verify the receipts themselves before any commitment.