stitchgraph v3.27.1 — release notes

stitchgraph v3.27.1 — release notes

The second dogfood patch. v3.27.0 was run on itself with the full battery
(research/15-dogfood-v3.27.md) — a controlled before/after of the D2 dedup, since
research/14 measured the same codebase pre-refactor.

Fixed

• structure_common.parse_tree was dead on arrival. The D2 stage-2 patch added the shared
  walk-guard helper but the transformation script never wired the nine _walk functions to call
  it, and ruff --fix then removed the unused imports — hiding the slip from every
  output-equivalence gate, because dead code has no outputs. find_stale caught it statically;
  find_gaps corroborated at runtime (untested_dead = exactly this + the one known advisory).
  It now guards all nine walk entries as intended, and the seven remaining _walk-local text
  helpers delegate to the shared node_text (closing the residual clone hubs orient still
  ranked at fan_in 97).

What the run verified (the interesting part)

• Behaviour-preservation, measured at runtime: intrinsic dimensionality 27 → 27 across a
  ~400-line refactor — the strongest runtime statement of "behaviour-preserving" available,
  complementing the byte-identical output oracles.
• coverage_drift's first real cross-release use narrated the dedup from coverage alone:
  lost = the nine deleted per-language iterator/closure copies; gained = structure_common.*.
  A behavioural changelog derived without reading the diff.
• The refactor is visible in the static graph exactly where intended: nodes 899 → 866, the
  frontend subsystem cluster 329 → 320, scan findings 192 → 167 (evaporated name-ambiguity
  artifacts), the same three verified-deliberate oranges.

Gate

Byte-identical fingerprint/VFG/PDG baseline over the 9-language corpus; the full 1,618-test
oracle battery; ruff + mypy. Post-patch find_stale is back to the single known advisory.