Receipt for proof_loop_check

The proof_loop_check tool files a proof loop check entry, a labelled observation inside a running proof loop. Every call to it files a receipt. In plain terms, an agent receipt is a record of one ai agent tool call that anyone can check: it keeps the exact saved bytes and their sha-256 digest, and it proves the result was not changed since it was saved, not that it was right.

Examples on this page are real receipts pulled from the public Zambo receipts API on 2026-10-24. proof_loop_check appeared 7 times in the 1,600 most recent public receipts checked that day. See the full set at receipt examples by tool.

What a proof_loop_check receipt records

A proof_loop_check receipt is one AER-1 record (receipt schema version 0.4, hosted profile zambo-hosted-receipt/1) for one call. Read from a real proof_loop_check payload, it records:

  • Receipt id: a full UUID. The id is the address of the record: the human page is https://zambo.dev/run/ followed by the id.
  • Tool: name proof_loop_check, version 4.0.0, scope public.
  • Timestamps: the record creation time, and inside the step list a started_at and a completed_at for the call itself.
  • Step status: one step per call, with the tool name and its status. On the first example below the step status is success.
  • The saved output: the exact output object the call returned, kept as canonical bytes. The saved output carries schema, type, label, ai, check, an observation_commitment and an observation_note. Where an observation is withheld, the record says so with an observation_withheld field and still files the commitment.
  • Output digest: output_hash, the SHA-256 digest of those canonical bytes, with the canonical byte length recorded too (956 bytes on the first example below).
  • Caller and provenance: a caller type (session on the first example) and a provenance class of EXECUTED BY ZAMBO, which states how the record was produced.
  • Declared side effects: the record declares its side effects, none on the first example.
  • Verification status: the API carries a verification_status field for the record. On the first example below, the verify API reported verification_status commitment_matches, its wording for a record whose digest still matches the saved bytes.

Live proof_loop_check receipt examples

Each example below is a real proof_loop_check receipt. Open one and you see the saved result, when it was saved, and its digest, the same fields described above.

zambo.dev/run/433c4460-3b32-465e-9241-cddc7e212368

Saved: 2026-10-24T13:53:22.454Z

Output SHA-256 digest: sha256:d1d8b7b76321e2c91ebd1e46ed5c0c77132089be785670c514f6258ae5daefd0

Checked live on 2026-10-24: this URL returned HTTP 200 with this receipt on the page.

zambo.dev/run/c4b6f20b-6587-4d96-a95b-a444e5fbb8d5

Saved: 2026-10-24T13:53:21.542Z

Output SHA-256 digest: sha256:c4de81d590764d0123f1bc4c3be439f3f3f0aebef20ec5ed8baa76ef67d5142d

Checked live on 2026-10-24: this URL returned HTTP 200 with this receipt on the page.

zambo.dev/run/b828cebf-0c76-402d-9e0a-10ba345bbf03

Saved: 2026-10-24T13:53:20.778Z

Output SHA-256 digest: sha256:c14521f8c93d737d4e7c24a3e9ac5a0d2e2c2aa787035656058392670f7585a6

Checked live on 2026-10-24: this URL returned HTTP 200 with this receipt on the page.

How to verify a proof_loop_check receipt

  1. Open zambo.dev/verify/ and paste the receipt link or the receipt id. The checker recomputes the SHA-256 digest over the saved bytes and reports whether the record still matches.
  2. Or call the API directly: GET https://zambo.dev/api/v2/receipt/{receipt-id}/verify returns the record as JSON, including its output_hash and verification_status.
  3. The format is AER-1, an open IETF Internet-Draft: draft-zambo-aer1-26. Anyone can implement the check; it does not need a Zambo account.

Verification answers one question: is this the record that was saved, byte for byte? It does not answer whether the result inside was right.

Get receipts for your own calls

Add Zambo to your AI once, at zambo.dev/add/, and every tool call after that files a receipt like the ones above. Every account starts with 20 free calls per day, and free calls file receipts too. The background is at AI agent receipts, and more worked examples are indexed at receipt examples by tool.