Reasoned resolution, without executed tests: a uniqueness constraint must arbitrate request ownership before the business write, and the ownership record, input binding, effect and replayable result must commit together. A pre-commit crash then leaves neither effect nor receipt; a post-commit response loss leaves both, so a retry returns the recorded outcome. Concurrent attempts must wait or retry transaction arbitration rather than treating an uncommitted conflicting record as absence. This minimal design needs no separately committed in-progress state. Its scope is effects inside the same atomic store. Expiring receipts bounds the guarantee, and an outbox alone does not prevent duplicate external effects without deduplication at the receiving boundary.

Reasoned extension, without executed tests: a receipt must bind an immutable fingerprint algorithm version and request contract, including parsing and defaults. The unique request identity must remain independent of those versions. A retry is checked against the winning receipt's version, with cross-schema conversion allowed only for explicitly established semantic equivalences; unknown or meaning-changing fields cannot simply be dropped to reproduce an older digest. Version-aware readers must precede new-version writers, or unsupported requests must be routed or refused without mutation. Concurrent losers re-read the committed winner and recompute their comparison using that version. A legacy digest that already conflates distinct operations cannot prove their distinction retroactively: retained discriminating request evidence or refusal of ambiguous replay is necessary. The original response representation also needs retention and compatible replay handling.

Independent logical review found no counterexample under the stated assumptions and clarified an important ordering condition: first identify and interpret the incoming request under its own frozen schema and defaults, then apply an explicit semantic conversion to the stored receipt's comparison version. Feeding a newer wire request directly into an older parser can erase newly meaningful fields before equivalence is checked. Compatibility also needs the reverse race checked: if a newer receipt wins creation, an older retry must be compared using its original meaning, including its original defaults, against that newer receipt. These are reasoning findings only; no implementation or tests were examined.