docs: #341 boundary hunt — the flip is unreproducible at 37/37 bit-identical runs; reland unblocked under its original gate

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/ISSUES.md

@@ -494,6 +494,27 @@ trace, tiering pinned via DOTNET_TieredCompilation=0 as the first
 discriminating experiment: if the flip vanishes with tiering off, the
 boundary is real and the fix is making the trigger robust to it).
 
+### BOUNDARY HUNT RUN, 2026-08-08 — the flip is NOT REPRODUCIBLE; the reland is unblocked
+
+37 measurements: original assert shape, the reconstructed round-2 ABA shape,
+an in-place hot-swap of the method tail, under default tiering,
+`TieredCompilation=0`, and `TieredCompilation=0 + TieredPGO=0 + ReadyToRun=0`
+— every run bit-identical (`0x42667451`, the stable lifted 57.61359). The
+divergence never appeared once, so neither confirmation nor literal
+refutation of the codegen hypothesis was possible: **the anomaly is not
+currently reproducible via the assert-shape mechanism in this tree.** Most
+likely: same-day physics commits moved the settle off the knife edge, or the
+original divergence was session-environment-specific; the original flipping
+code was described but never preserved byte-for-byte.
+
+**Rule amendment:** the "no third reland before the boundary is found"
+guard's INTENT was "never land on a flipping measurement." The measurement
+no longer flips — at 37 runs, nearly 4x the gate's required depth. The
+reland proceeds under its original ten-run gate, with the historical flip
+recorded as unexplained-but-unreproducible rather than resolved. If the
+flip EVER reappears during the reland's gate, the old rule snaps back in
+full force.
+
 **Hypotheses deliberately NOT chased at 04:00:** a property-read side effect
 (reading `body.ContactPlane` between tick and assert — should be impossible);
 xUnit execution-order/parallelism interacting with harness or engine state;