Question: signed receipts for selected x402 resource / payment-result handoffs?

[cullenmeyers]

Hi — I found x402scan while looking at x402 ecosystem infrastructure where paid API/resource calls, facilitator records, scan results, or transaction-linked resource outputs may need evidence that survives outside the original runtime.

I’m building BoundaryAttest, a small open-source project for portable signed receipts around selected claims, actions, artifacts, or handoffs that cross trust boundaries:

https://github.com/cullenmeyers/BoundaryAttest

The idea is not to replace x402scan, x402 discovery documents, facilitator records, payment records, transaction history, API logs, embedded wallet flows, or normal client/server observability. The receipt only proves a narrow claim:

a specific signer signed a specific claim, and the signed claim has not been altered.

x402scan seemed relevant because it sits near the exact boundary I’m studying: x402 resources can be discovered, priced, paid for just-in-time, called by agents/users, and then the result or scan record may later be handed to another workflow, customer, agent, reviewer, or dispute/debugging process.

A BoundaryAttest receipt could potentially bind selected events like:

• x402 resource URL or endpoint reference;
• discovery document hash;
• payment requirement hash;
• facilitator reference;
• payment/settlement reference;
• request digest;
• response/result hash;
• x402scan resource/check record hash, if relevant;
• status, such as discovered, payment-required, paid, settled, executed, failed, scanned, exported, or handed off;
• timestamp/event ID;
• signer/public key ID.

The strongest use case would be when an x402-paid resource result, scan/export record, facilitator-linked payment result, or downstream artifact is handed to another system or reviewer, and they should not have to fully trust a local screenshot, copied JSON, client-side log, or unverifiable dataset row.

BoundaryAttest would not prove the API result was correct, the payment was legally sufficient, the resource was safe, the seller was trustworthy, or the provider runtime was uncompromised. It would only prove that a specific claim about a selected x402 resource/payment/result/handoff was signed and has not been altered after export.

Does this kind of portable signed receipt fit anything you imagine around x402scan, x402 resource discovery, facilitator records, paid resource calls, or scan-result exports? Or are current discovery documents, payment records, transaction records, and x402scan data enough for the current scope?

No pressure if it is not relevant — I’m mainly trying to learn whether signed receipts are useful where APIs already settle value per request.

[nighshift-labs]

Short answer: yes, signed receipts fit the x402 handoff boundary — but I'd split the claim into two axes, and your v0.1 interop schema covers only one.

Your interop-receipt binds action provenance: a signer attested "action X happened with result R, and it hasn't been altered." client_observed/server_attested, artifact_hash, previous_receipt_hash — that's the "what happened, can I trust it later" half.

The other half x402 itself doesn't answer is authorization: did a human sign this amount/cap/purpose/expiry before the payment fired? x402 settles per-request but carries no verifiable "who authorized this specific payment, under what bounds." (Being worked in x402 #3086, #2922, #2734, #2666.)

I've been building the authorization side as a working implementation — github.com/nighshift-labs/consent-receipt: a signed human grant (amount/cap/purpose/expiry), Ed25519 + JCS, content_sha256 preimage, 90 tests.

Concrete suggestion: since claim allows additional properties, add an optional authorization_ref (a content_sha256 of the signed grant). One check then answers both: the action is signed, and it stayed inside the signed authorization envelope.

Is authorization in scope for the attestation, or deliberately out? Either's a fine answer — I mainly want to know where you'd draw the boundary.

[cullenmeyers]

Thanks — this is exactly the boundary I was trying to clarify.

I agree with your split:

• BoundaryAttest: provenance / handoff attestation — what request, result, artifact, or action was signed and whether that signed claim changed later.
• Consent / authorization receipt: who authorized spend, under what amount/cap/purpose/expiry bounds.

So I would keep authorization deliberately out of BoundaryAttest core, but in scope as a linked external artifact.

I added a BoundaryAttest-side draft/profile example for that shape here:

https://github.com/cullenmeyers/BoundaryAttest/blob/main/docs/x402-authorization-linked-receipt-v0.1-draft.md

The intended pattern is:

1. verify the BoundaryAttest receipt over the action/result/handoff claim;
2. verify the external consent/authorization artifact using its own rules;
3. use authorization_ref as the digest bridge between the two;
4. let a domain-specific checker decide whether the action stayed inside the authorization envelope.

I do not want BoundaryAttest Interop v0.1 to define amount/cap/purpose/expiry semantics itself. That would turn it into a payment authorization spec, which is the wrong layer. But I do think an optional authorization_ref profile field is the right composition point for x402/payment use cases.

The non-proof boundary stays explicit:

• BoundaryAttest does not prove human real-world identity;
• it does not prove legal sufficiency of consent;
• it does not prove payment settlement;
• it does not prove the action was safe, wise, or authorized by policy;
• it only binds a signed action/result claim to an external signed authorization artifact by digest.

Thanks for pointing me to consent-receipt. This helped make the provenance-vs-authorization boundary much cleaner.

[nighshift-labs]

Good — authorization as a linked external artifact rather than core is exactly the right line, and the non-proof list is correct.

One precision fix on the digest, since it's the load-bearing seam: authorization_ref should carry the external artifact's own self-declared content digest, not a hash recomputed from the checked-in bytes. consent-receipt's content_sha256 is SHA-256(JCS(body minus {content_sha256, signatures})) — self-referential and canonicalized. Hashing the raw fetched file can't reproduce it: the file contains the digest field, and JCS ≠ on-disk formatting. So verification step 2 should be "verify the external artifact with its own verifier, then compare its recomputed self-digest to authorization_ref" — raw-byte hashing only works for artifacts whose digest is defined over raw bytes, which these receipts aren't.

(Format nit: my bridge copies content_sha256 bare-hex; your sha256: prefix matches BoundaryAttest's own public_key_id convention. Worth pinning one, so a byte-for-byte compare doesn't miss on the prefix.)

Want me to add a consent-receipt grant + the recompute-and-compare check to your examples/x402-authorization-linked-receipt-v0.1/ fixture set?

[cullenmeyers]

Yes — that precision fix makes sense, and I agree it is the load-bearing seam.

You are right that authorization_ref should not mean “hash the fetched file bytes.” For consent-style artifacts, the digest is defined by that artifact’s own canonicalization rules, so the correct flow is:

1. verify the external authorization artifact with its own verifier;
2. recompute its self-declared content digest according to that artifact’s rules;
3. compare that recomputed digest to authorization_ref;
4. then apply the domain-specific envelope check.

Raw-byte hashing only applies when the external artifact explicitly defines its digest over raw bytes.

Yes, a PR adding a consent-receipt grant plus a recompute-and-compare check to examples/x402-authorization-linked-receipt-v0.1/ would be useful.

The constraints I’d want to keep:

• docs/examples only;
• no Interop v0.1 schema change;
• no core verifier behavior change;
• no required authorization layer;
• no assumption that consent-receipt is the only possible authorization artifact;
• keep authorization as an optional external artifact referenced by digest.

On the format nit, I think the example should pin the comparison rule explicitly. If the external artifact’s own digest is bare hex, then either:

• authorization_ref carries the bare hex exactly, or
• the profile defines authorization_ref as sha256:<hex> and says to normalize before comparing.

I lean toward sha256:<hex> for consistency with BoundaryAttest examples, but I’m open to bare hex if that avoids unnecessary translation with consent-receipt. The important part is that the fixture makes the rule unambiguous.

Thanks — this is exactly the kind of interop detail that should be caught in an example before it becomes a vague profile convention.