fix: post-Bareiss follow-up — conway marker removed, polynomial bounds 12 → 128 (unblocks red main)

.github/workflows/krl-verification.yml

@@ -68,9 +68,12 @@ jobs:
           julia --color=yes server/krl/test/seam_test.jl
 
       # server/Project.toml [sources] resolves KnotTheory/Skein/AcceleratorGate
-      # at server/../../../<name>.jl — i.e. two directories above the repo
-      # checkout ($GITHUB_WORKSPACE/../../<name>.jl). actions/checkout cannot
-      # write outside the workspace, so check out under deps/ and symlink.
+      # at server/../../<name>.jl — i.e. one directory above the repo checkout
+      # ($GITHUB_WORKSPACE/../<name>.jl). actions/checkout cannot write outside
+      # the workspace, so check out under deps/ and symlink.
+      # NOTE: keep this in step with server/Project.toml — #83 moved [sources]
+      # from ../../../ to ../../ without updating the symlink here, which broke
+      # every instantiate with "expected package KnotTheory to exist at path".
       - name: Checkout KnotTheory.jl
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v4
         with:
@@ -93,8 +96,19 @@ jobs:
         run: |
           set -euo pipefail
           for p in KnotTheory.jl Skein.jl AcceleratorGate.jl; do
-            ln -sfn "$GITHUB_WORKSPACE/deps/$p" "$GITHUB_WORKSPACE/../../$p"
+            ln -sfn "$GITHUB_WORKSPACE/deps/$p" "$GITHUB_WORKSPACE/../$p"
           done
+          # Fail loudly here rather than inside Pkg.instantiate, whose error
+          # ("expected package ... to exist at path") names the path but not
+          # the cause.
+          julia --project=server -e '
+            using TOML
+            src = TOML.parsefile("server/Project.toml")["sources"]
+            for (name, spec) in src
+                path = normpath(joinpath("server", spec["path"]))
+                isdir(path) || error("[sources] $name -> $(spec["path"]) resolves to $path, which does not exist; the symlink step above is out of step with server/Project.toml")
+            end
+            println("PASS: all [sources] paths resolve")'
 
       - name: Instantiate server project
         run: julia --color=yes --project=server -e 'using Pkg; Pkg.instantiate()'

server/quandle_semantic.jl

@@ -469,15 +469,19 @@ end
 const HOMFLY_MAX_CROSSINGS = 15
 const HOMFLY_DEFERRED_SENTINEL = "deferred:too_many_crossings"
 
-# KnotTheory's alexander_polynomial computes its polynomial-matrix minor
-# determinant by naive cofactor expansion — O(n!) in the minor size, which
-# tracks the crossing count. Measured on (2,n)-torus closures (s1^n, the
-# worst case: no arc merging): n=12 → 12s, n=13 → 106s, n=16 → 6h+ (this
-# hung CI to GitHub's job kill). conway_polynomial CALLS alexander_polynomial
-# internally, so it inherits the same bound. jones_polynomial goes through
-# the Kauffman bracket instead, which KnotTheory itself hard-limits at 20
-# crossings by THROWING — we convert that throw into the same sentinel.
-const ALEXANDER_MAX_CROSSINGS = 12
+# alexander_polynomial's determinant is now fraction-free Bareiss
+# elimination — O(n^3) polynomial operations (KnotTheory.jl#46/#48).
+# Re-measured on (2,n)-torus closures (s1^n, the worst case: no arc
+# merging): n=40 → 0.07s, n=100 → 0.10s, n=140 → 0.61s. The previous
+# bound of 12 was calibrated against the O(n!) cofactor expansion it
+# replaced (n=12 → 12s, n=13 → 106s, n=16 → 6h+ and a CI job killed at
+# GitHub's 6-hour limit), so it is now an order of magnitude too tight.
+# 128 keeps the worst case sub-second while covering every realistic
+# diagram. conway_polynomial calls alexander_polynomial, so it shares
+# the bound. jones_polynomial instead goes through the Kauffman bracket,
+# which is genuinely 2^n and which KnotTheory hard-limits at 20 crossings
+# by THROWING — we convert that throw into the same sentinel.
+const ALEXANDER_MAX_CROSSINGS = 128
 const CONWAY_MAX_CROSSINGS = ALEXANDER_MAX_CROSSINGS
 const JONES_MAX_CROSSINGS = 20
 
@@ -498,7 +502,7 @@ end
     _safe_alexander_serialised(pd::KnotTheory.PlanarDiagram) -> String
 
 Alexander polynomial, guarded by `ALEXANDER_MAX_CROSSINGS` (the upstream
-determinant is O(n!) cofactor expansion). Returns the deferred sentinel
+determinant is O(n^3) Bareiss elimination). Returns the deferred sentinel
 above the bound.
 """
 function _safe_alexander_serialised(pd::KnotTheory.PlanarDiagram)::String
@@ -510,7 +514,7 @@ end
     _safe_conway_serialised(pd::KnotTheory.PlanarDiagram) -> String
 
 Conway polynomial, guarded by `CONWAY_MAX_CROSSINGS` (upstream it is
-computed FROM the Alexander polynomial, so it shares the O(n!) cost).
+computed FROM the Alexander polynomial, so it shares that cost).
 Returns the deferred sentinel above the bound.
 """
 function _safe_conway_serialised(pd::KnotTheory.PlanarDiagram)::String

server/test_br5_fuzz.jl

@@ -120,13 +120,23 @@ end
 
 @testset "BR-5: crossing-order invariance on random braid words" begin
     rng = MersenneTwister(BR5_SEED + 1)
-    # KNOWN-BROKEN (upstream): the polynomial segments of quandle_key
-    # (alexander/conway/homfly from KnotTheory.jl) are crossing-order
-    # sensitive on some diagrams — the polynomials are not normalised to a
-    # canonical unit (±t^k), so 25/200 seeded trials disagree. The layers
-    # this repo owns (presentation_hash, colouring counts) are asserted
-    # hard below; the key mismatch count is tracked and marked broken so
-    # the marker must be removed once KnotTheory.jl normalises.
+    # KNOWN-BROKEN (upstream KnotTheory.jl#51): the polynomial segments of
+    # quandle_key are crossing-order sensitive on multi-component LINKS.
+    # Measured over this 200-trial corpus, splitting by Delta(1):
+    #     links (Delta(1)=0):  11 mismatch, 87 agree
+    #     knots (Delta(1)=±1):  0 mismatch, 102 agree
+    # Knots became fully order-invariant when KnotTheory#48 landed the
+    # Delta(1)=+1 normalisation; that fix cannot apply to links, where
+    # Delta(1)=0 and the code falls back to an order-sensitive rule. Worse,
+    # conway_polynomial reconstructs from an assumed symmetry about
+    # exponent 0, which no link satisfies (even span ⟹ half-integer
+    # centre), so it returns genuinely DIFFERENT polynomials for the same
+    # link (e.g. 1 + z² vs 1) — not merely a different unit.
+    # NOTE: this count did NOT move when #48 merged. The earlier
+    # attribution of these mismatches to the alexander/conway sign
+    # convention was wrong; the sign fix was real but orthogonal.
+    # The layers this repo owns (presentation_hash, colouring counts) are
+    # asserted hard below and hold on every trial.
     quandle_key_mismatches = 0
     for trial in 1:BR5_TRIALS
         nstrands = rand(rng, 3:4)

server/test_quandle_axioms.jl

@@ -512,22 +512,32 @@ end
 end
 
 @testset "KT-2 ext: polynomial guards return sentinels above their bounds" begin
-    # Build a synthetic 16-crossing PD by braid word s1^16 — a genuine
-    # (2,16)-torus-link diagram (post KnotTheory#43; before that fix the
-    # broken braid closure made this degenerate and cheap, which is how the
-    # missing guards went unnoticed). 16 crossings exceeds
-    # HOMFLY_MAX_CROSSINGS (15) and ALEXANDER/CONWAY_MAX_CROSSINGS (12,
-    # the O(n!) upstream determinant: 12 → 12s, 13 → 106s, 16 → 6h+ and a
-    # CI job killed at GitHub's 6-hour limit), but not JONES_MAX_CROSSINGS
-    # (20, Kauffman bracket: 2.8s measured at 16).
-    pd_large = from_braid_word(join(["s1" for _ in 1:16], ".")).pd
-    d_large = quandle_descriptor(pd_large)
-    @test d_large.homfly_polynomial == HOMFLY_DEFERRED_SENTINEL
-    @test d_large.alexander_polynomial == HOMFLY_DEFERRED_SENTINEL
-    @test d_large.conway_polynomial == HOMFLY_DEFERRED_SENTINEL
-    # Jones stays real at 16 crossings — a sentinel here would mean the
-    # bound was tightened without re-measuring.
-    @test d_large.jones_polynomial != HOMFLY_DEFERRED_SENTINEL
+    # Each polynomial has its OWN bound, set by its own measured cost model,
+    # so one diagram cannot exercise them all. Both cases below are genuine
+    # (2,n)-torus-link diagrams (post KnotTheory#43 — before that fix the
+    # broken braid closure made them degenerate and cheap, which is how the
+    # missing guards went unnoticed until CI hung for 6 hours).
+
+    # 16 crossings: above HOMFLY's 15 (skein recursion is exponential), but
+    # below Jones' 20 (Kauffman bracket, 2.8s measured here) and far below
+    # alexander/conway's 128 (Bareiss, O(n^3)).
+    pd16 = from_braid_word(join(["s1" for _ in 1:16], ".")).pd
+    d16 = quandle_descriptor(pd16)
+    @test d16.homfly_polynomial == HOMFLY_DEFERRED_SENTINEL
+    @test d16.jones_polynomial != HOMFLY_DEFERRED_SENTINEL
+    @test d16.alexander_polynomial != HOMFLY_DEFERRED_SENTINEL
+    @test d16.conway_polynomial != HOMFLY_DEFERRED_SENTINEL
+
+    # 130 crossings: above every bound — all four defer. This also pins the
+    # alexander/conway bound itself: if someone raises it without raising
+    # this fixture, the test fails rather than silently going quiet.
+    pd_over = from_braid_word(join(["s1" for _ in 1:130], ".")).pd
+    @test length(pd_over.crossings) > ALEXANDER_MAX_CROSSINGS
+    d_over = quandle_descriptor(pd_over)
+    @test d_over.alexander_polynomial == HOMFLY_DEFERRED_SENTINEL
+    @test d_over.conway_polynomial == HOMFLY_DEFERRED_SENTINEL
+    @test d_over.jones_polynomial == HOMFLY_DEFERRED_SENTINEL
+    @test d_over.homfly_polynomial == HOMFLY_DEFERRED_SENTINEL
 end
 
 @testset "KT-2 ext: Jones polynomial distinguishes the test knots" begin
@@ -675,17 +685,14 @@ end
     t = quandle_descriptor(trefoil().pd)
     @test t.conway_polynomial == "0:1,2:1"
 
-    # Figure-eight ∇(z) = 1 - z² → "0:1,2:-1"
-    # KNOWN-BROKEN (upstream KnotTheory.jl#42): the computed value is
-    # "0:-1,2:1" = -(1 - z²). Conway is canonically normalised (∇(unknot)=1,
-    # so there is NO legitimate unit ambiguity) — the sign flip comes from
-    # the Alexander determinant's row/sign convention on mixed-sign
-    # diagrams, the same missing unit normalisation tracked in #42. The
-    # trefoil and cinquefoil (all-positive crossings) are unaffected.
-    # First caught here: this fixture suite (issue #32) merged behind the
-    # 6-hour CI hang and had never actually executed before.
+    # Figure-eight ∇(z) = 1 - z² → "0:1,2:-1". This was @test_broken: the
+    # computed value was -(1 - z²) because alexander normalised its unit by
+    # "leading coefficient positive", the wrong canonical choice on
+    # mixed-sign knots. Fixed upstream (KnotTheory.jl#48) by normalising to
+    # Δ(1) = +1, the Conway normalisation — the marker then reported
+    # "unexpected pass", which is exactly the signal it existed to produce.
     f = quandle_descriptor(figure_eight().pd)
-    @test_broken f.conway_polynomial == "0:1,2:-1"
+    @test f.conway_polynomial == "0:1,2:-1"
 
     # Cinquefoil ∇(z) = 1 + 3z² + z⁴ → "0:1,2:3,4:1"
     c = quandle_descriptor(cinquefoil().pd)