T-303: sector heuristic on HSJ/XFORM — guard verification + regression test#247
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…sion test build_reduced_dataset() omits hierarchy_blocks/tip_labels/n_orig_chars/ hsj_alpha/sankoff_* fields, so rss_search/xss_search are already guarded to fall back under HSJ/XFORM (commit e5ff294, same class as the T-275 guard). css_search needs no guard: it never builds a reduced dataset — it runs tbr_search() with a sector_mask against the full ds, so score_tree() dispatches hsj_score()/Sankoff with complete data and the sector-internal heuristic is correct for every scoring mode. Documented this with an in-code comment so it is not re-flagged. Approach (b) (copy the fields into the reduced dataset) is not tractable: the HTU pseudo-tip is a Fitch from_above state-set with no valid HSJ tip_labels or Sankoff tip_costs representation, so the reduced dataset cannot be made correct for those modes without new from-above machinery in both scoring kernels. Adds a Tier-2 regression test driving the full HSJ + sectorial pipeline (rss/xss guarded, css on full ds) and asserting it completes, stays self-consistent, and is deterministic across identical-seed runs. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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T-303 (P2): Sector heuristic degrades silently on HSJ/XFORM datasets
build_reduced_dataset()insrc/ts_sector.cppdoes not copyhierarchy_blocks,tip_labels,n_orig_chars,hsj_alpha, orsankoff_*into the reduced dataset. Sincerd.data.scoring_modeis copied, an unguarded sector would dispatchhsj_score()/Sankoff against empty hierarchy/Sankoff data and silently degrade to Fitch-only — a wrong internal accept/reject heuristic (missed improvements, accept-then-revert churn). Final acceptance scores are unaffected (recomputed on the full dataset). EW, IW, PROFILE are fine.What this PR does
rss_searchandxss_search(the only two routines that callbuild_reduced_dataset) are already oncpp-search(commite5ff2942), mirroring the existing T-275 guard. No change needed there.css_searchdocumented as safe. It is the third sector routine but is not affected: it never builds a reduced dataset — it runstbr_search()with asector_maskagainst the fullds, soscore_tree()dispatcheshsj_score()/Sankoff with complete data and its internal heuristic is correct for every scoring mode. Added an in-code comment so it is not re-flagged. (Guarding it would wrongly disable a working HSJ/XFORM path.)Why not approach (b) (copy the fields)
Not tractable here. The HTU pseudo-tip is a Fitch
from_abovestate-set with no valid HSJtip_labels(original-character tokens) or Sankofftip_costsrepresentation, so the reduced dataset cannot be made correct for those modes without new from-above machinery in both scoring kernels. Approach (a) is the conservative, T-275-consistent fix.Note on testability
T-303 is silent by construction: final scores are always recomputed on the full dataset, so a guard regression cannot be caught by an absolute-score assertion. The test therefore locks in pipeline stability/determinism (it would catch a crash or score desync introduced by the guarded sector path).
Dispatched agent t303. GHA agent-check: run 27398557784. Found by /red-team area 5 (2026-05-26). PROFILE+IW are fine.
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