[Agricola] AGR-2026-045: Body-aware verification failures omit the fresh challenge

[mpp-agricola]

AGR-2026-045 — Body-aware verification failures omit the fresh challenge

Last observed by the head-to-head audit at 2026-08-10T09:38:20.026276Z.

Audited heads

Target	Repository	Commit	Conformance	Semantic review
typescript	wevm/mppx	b7ab48e38e3d	Complete	Reference
rust	tempoxyz/mpp-rs	28c704988b3d	Complete	Complete
go	tempoxyz/mpp-go	266810add451	Complete	Complete
java	stripe/mpp-java	bc52e0f5c77b	Complete	Complete
python	tempoxyz/pympp	09b449739221	Complete	Complete
ruby	stripe/mpp-rb	58a98bbf6820	Complete	Complete

Finding

• Fingerprint: semantic:http-verification/failure-returns-fresh-challenge
• Source: semantic
• Affected SDKs: rust
• Clean SDKs: none
• Not reported by semantic review: go, java, python, ruby
• Canonical reference: draft-httpauth-payment-00 § Payment-Receipt Header / Receipt Status Semantics; § Caching
• Severity: medium
• Confidence: high

Evidence

SDK	Canonical evidence	SDK evidence	Suggested test
rust	http().respondChallenge — Constructs verification-failure responses with the serialized challenge in WWW-Authenticate, Cache-Control: no-store, and status 402 or the payment error status.	PaymentBodyService::call — On verify_with_body failure, calls error_response with status 402; that helper only sets the status and supplies neither a fresh WWW-Authenticate challenge nor no-store.	Send a body-bound request carrying an invalid Payment credential through PaymentBodyLayer and assert that the 402 response contains a newly generated, parseable WWW-Authenticate: Payment challenge and Cache-Control: no-store.

rust: When body-bound credential verification fails, the target returns a bare 402 without WWW-Authenticate or Cache-Control. Canonical behavior returns the failure through the challenge response path, including a fresh challenge and no-store. Automatic clients therefore cannot obtain a replacement challenge and retry the failed body-bound request.

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Target	Automation	Status	Pull request
rust	pr	Recorded	tempoxyz/mpp-rs#380

Quick action

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/ag fix

Command	What it does
/ag fix	Opens or retries draft fixes for every affected PR-enabled SDK.
/ag fix rust	Opens or retries the draft fix for rust only.
/ag fix "instruction"	Applies the instruction to affected fixes; recorded PRs also incorporate unresolved review feedback and failed CI.
/ag status	Reports the current state of linked remediation pull requests.

[brendanjryan]

/ag fix

[mpp-agricola]

Queued remediation for rust.

View fix run

[mpp-agricola]

Opened draft PR for rust: tempoxyz/mpp-rs#380.

View fix run