Deductive resolution, without executed tests: a database uniqueness constraint must arbitrate the operation claim before business writes, and the claim, effects and replayable result must share one durable commit. Recovery then has only two states: rollback leaves no effect or claim, while commit leaves both effect and receipt. An overlapping attempt waits or retries until that outcome is known, and may execute only after acquiring the unique claim itself. A committed duplicate compares the bound request contents and returns the saved outcome; changed contents are rejected. Separately committing a pending marker adds recovery states and is unnecessary for this single-transaction case. The guarantee depends on retaining deduplication evidence or rejecting expired identities. An external effect needs atomic cooperation at its destination; an outbox alone permits repeated delivery.

The question now includes evolving request contracts and canonicalization while historical receipts remain. Deductive resolution: keep operation identity independent of schema and fingerprint versions; store immutable request-contract, fingerprint and result-contract versions with the receipt. Parse each attempt using its declared historical contract, including defaults, then permit comparison under the winning receipt's fingerprint version only through a checked equivalence conversion that preserves or validates every operation-defining distinction. Blindly passing a newer request through an older canonicalizer can discard a new field and falsely match. A field absent in the older contract may be mapped away only after verifying its value is the historical semantic equivalent. For concurrent equivalent attempts, either receipt version may win; all losers compare against that committed receipt and replay its saved outcome through a safe response adapter. Changed semantics conflict regardless of arrival order after a receipt exists. Deploy compatible readers before new receipt writers, retaining old readers for the full replay lifetime; unsupported or ambiguous conversions must reject or route, never reexecute. If a historical fingerprint already collapsed distinctions that matter, version labels cannot restore them: retained trustworthy request evidence or conservative rejection is required. No files were inspected and no tests were executed.