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DECIDED 2026-07-20 — Option 1, stay correctly rounded

User's call: 1. crtl's libm keeps correct rounding where glibc is not correctly rounded. We do not reproduce glibc's errors to make differential testing quieter.

Correctness over bug-compatibility. It is also a genuinely strong public claim, and a verifiable one — but state it with claims discipline: "judged against high-precision references", never "matches glibc". The whole point is that we do NOT match glibc in these cases, and phrasing it as a match would be both wrong and self-defeating.

Revisit only if a corpus target's oracle diff drowns in libm noise — i.e. if the cost lands on real differential testing rather than in principle.

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