D286 - The argument sweep crosses each slot with a success return

Status: decided Date: 2026-08-26

sweep plants each argument slot both unforced and with the call forced to answer success, keyed (slot, answer) with the unforced run first. An out-parameter finding carries the answer it was found under.

Why: a guest checks the return before reading an out-parameter, so each half alone is a clean negative and two clean negatives read as proof of absence. Only the success value gates that read, so the return is a condition, not a sentinel to difference. A finding needing one intervention is stronger than one needing two, and a finding without its condition cannot be reproduced.

Rejected:

• One axis at a time: cannot see a two-condition dependency.
• Crossing argument sentinels with return sentinels: a product of two differencing questions the guest never asked.