By: ValentinHirschi <valentin.hirschi@gmail.com>
Keep the trif2 coefficient c exactly zero at a vanishing invariant The two-mass triangle (trif2) forms c = (s4/s2 - r24)/(s3 s4). At p23 = 0 with unequal masses r24 is s4/s2 analytically, so c vanishes; computed as a difference it was a few-bit residue in Float. The quadratic formula then returned a noise second root and the root term divided by it, so the NinjaRS syn-n6-r6 C0 calls (one complex mass, one massless line) came out with 2-8 tracked bits and wrong leading digits from 248 bits up, at 2048 bits in the interpreted expressions too. c now uses the registered helper rfun_ratio_gap, which returns -delta (the exact zero-momentum root offset, zero at p = 0) when the r-function chose the root s4/s2, and the plain difference otherwise. Checked at 96..1024 bits in steps of 8 and at 2048 bits for all 165 syn-n6-r6 C0 calls, native Float and interpreted expressions: no deviation from the 2048-bit reference, which agrees with OneLOop 3.6 in quadruple precision to 1e-20. Binary64 values are unchanged in the sweeps. tests/float_branch_decisions.rs checks both reported calls at 128-2048 bits on both routes (the old coefficient fails it from 256 bits up). Native C0 code and the C0 SymJIT asset are regenerated. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>