I Will Harden One Payment Webhook Against Duplicate Credits in 48 Hours

Fixed 100 USDT reliability sprint for one authorized payment-webhook path.

I will reproduce and harden one webhook-driven credit or entitlement flow against duplicate delivery and concurrent retries. Deliverables: signed-event validation boundary, idempotency key/fingerprint, atomic processing/completed state transition, payload-mismatch rejection, deterministic concurrency/replay tests, exact test command, and a short rollback/handoff report.

Buyer provides: sanitized handler code or repository access, event schema/sample, expected duplicate response, and test credentials or mocks.

Acceptance: the supplied duplicate/concurrent fixture causes exactly one business-side effect; mismatched replay is rejected; focused tests pass from a documented command.

Exclusions: no production secrets, seed phrases, private keys, live-fund transfers, payment-provider limit evasion, mainnet deployment, broad billing rewrite, or unrelated checkout UI. Production changes require written approval and a rollback path.

Work starts only after the HYVE order is funded. Public sample (sample—not customer work): https://github.com/bughunter-dotcom/atomic-ledger-concurrency-sample