D182 - The compatibility record is derived from runs

Status: decided Date: 2026-08-21

A title's file under compat/ holds its settings and its measured result, in one file and never merged. Every measured field is derived from a trace; the grade ladder uses stages the loader distinguishes and stops at Entered, ranking within it by distinct imports then calls. A run in which unimplemented functions reported success is never recorded, first entry included.

Why: two files would disagree about which was current. A hand-written grade drifts with optimism and nothing checks it. A spin accumulates calls without learning anything, so surviving to the limit is an outcome, not a distance. A contaminated baseline could never be beaten by an honest run.

Rejected:

• Hand-written grades such as "playable": aspirational fiction.
• Merging measurements like settings: a measurement does not override another.
• A Sustained rung: ranks the least informative run first.