The first witness (Windows-generated hash 89704bfd…) failed on Linux CI
with a different hash (b36741bf…). Root cause: hashing `re`/`im` parts of
top-5 taps at 1e-6 precision is too tight against libm differences in
sin/cos/sqrt across glibc, MSVC, and Apple-clang. The previous
"top-5 sorted by magnitude" form also suffered from rank instability when
taps are near-tied — libm jitter could shuffle the ordering even when the
algorithm is unchanged.
New canonical form: full per-tap quantised-magnitude profile in natural
index order, no sort.
- 156 taps × 2 bytes (u16 le) per frame = 312 bytes/frame.
- Quantisation 1e-2 — robust to ~1e-3 float drift while still tripping
on real algorithmic changes (e.g., a 10× lambda shift moves magnitudes
by >1e-2).
- No top-K selection — eliminates the unstable magnitude-sort step.
Regenerated expected_cir_features.sha256 — new hash 120bd7b1…
If the next CI run still mismatches, the cause is structural (rustfft SIMD
code path selection or NeumannSolver internal ordering), not magnitudes,
and the witness needs further coarsening or to be made platform-tagged.
Co-Authored-By: claude-flow <ruv@ruv.net>
d1e6d28a4a