STEP 1 — integer spiral-index packing (EXACT): pack_spiral_index/
unpack_spiral_index with corpus-wide base=2·max|c|+1 and offset-encoded
digits, recorded in the codebook JSON header; round-trip verified over
all 250 matrices. Fixes the sign bug in integration_sprint.py's integer
path (unoffset signed packing collapsed (-1,1) with (1,0) in base 2).
STEP 2 — f(n) layout (DECORATIVE): per-entry radius_sq + angle_frac,
computed in decimal arithmetic (indices reach ~1e44 >> 2^52); verified
against VERIFICATION_LOG V007 f(20121); min angular separation ≈4.64e-6
of a turn reported.
STEP 3 — Cartan Δ-floor (--cartan-floor): Δ=17/1792 exact
(CartanConnection.lean:70) as Fisher-distance resolution floor on Δ₇;
13 sub-Δ pairs merge 196 fingerprints into 187 Δ-resolution codewords
vs 9 gap-rule clusters; emitted alongside, not replacing, the 3×-median
rule. Caveat asserted in tests: the |c|/Σ|c| simplex projection is
lossy (one corpus pair at Fisher distance 0) — similarity, not identity.
STEP 4 — torus-winding saturation fix: TorusWinding gains
a_exact/b_exact (plain ℤ, no Q16.16 clamp); torus_to_spiral_index
prefers them, making the round trip lossless (regression-tested at
n=1e9). BraidEigensolid.lean needs the same widening — noted, Lean
untouched.
Also corrects charpoly_codebook.py's stale docstring counts (192/180 →
196/182, cross-checked against the exact Faddeev–LeVerrier fingerprints:
identical on all 250 matrices).
Tests: 43 passed (19 new).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Bug 1: Phinary packing not injective (integration_sprint.py)
- Old: float accumulation (phinary += c * PHI^(-i)) loses precision
- New: integer positional packing with provable injectivity
- Integer coefficients: base = max(|coeff|) + 1
- Float coefficients: quantize to 16-bit, pack in base 65536
- Round-trip is now guaranteed injective
Bug 2: Torus winding saturates at n >= 65536 (pist_braid_bridge.py)
- spiral_to_torus_winding stores b = n//2 as Q16.16, clamps at 32768
- Added spiral_to_torus_winding_safe() with saturation detection
- Returns (winding, saturated) tuple so callers can handle overflow
- Documented the limitation in docstrings
Bug 3: Power iteration non-convergence (pist_braid_bridge.py + MatrixN.lean)
- power_iteration_q16 now returns (eigenvalue, converged) tuple
- Detects oscillation via Rayleigh quotient stability check
- Added exact_eigenvalue_q16() fallback using numpy
- compute_pist_spectral auto-falls-back on non-convergence
- Lean MatrixN.lean: documented known limitation in docstring
All 3 bugs are from the independent review by Claude Fable.
