feat(floor): /pharn-regress reuses verified BASE evidence within one delivery run (6.33.0)

[PrzemekGalarowicz]

What

Within one /pharn-loop or /pharn-ship run, a later /pharn-regress now reuses the BASE-side evidence an earlier invocation left. It skips the base worktree, the install and every base gate, but only when tested code shows the evidence agrees with the current BASE requirement. The HEAD side always runs. Any mismatch runs the base side exactly as before.

• Requirement (versioned, sha256; never "same BASE SHA"):
  • the base SHA;
  • the gate spec the base side copies (via gate-run-core.mjs baseSpecFrom, now its one owner);
  • the install decision and the timeout;
  • the stamp schema and fingerprint algorithm;
  • the content of root-level HEAD paths in scope, since the base worktree is nested in the HEAD tree.
• Rule: pharn/floor/regress-base-reuse-core.mjs (pure) decides reuse; the first check that fails names one of 13 miss reasons (BASE_REUSE_MISSES). pharn/floor/regress-base-reuse.mjs handles storage.
• Binding: a record in <git dir>/pharn-regress-base-reuse.json, out of the write tools' reach. It is bound to the run marker's bytes and age (hashed, never parsed), the stamp's bytes and its logs.
  • A HIT saved mid-run is re-checked in full at the verdict.
  • A record is published only if the same check accepts it, for the run and requirement the decision saw.
• Unchanged: check-regress.mjs, validateStamp, every verdict, the stage-exit protocol.
• Report: regression-report.json gains the additive, advisory base_evidence block {reused, miss, requirement_sha256, recorded}.
• Progress record: moves to pharn-stage-regress-progress/2; a /1 record resumed across the upgrade stops with progress-malformed.

Measured (.dev/features/regress-base-reuse/MEASUREMENT.md, 3 reps)

	worktrees	installs	base gate runs	head gate runs	time
main, every invocation	1	1	3	3	~10.1–10.6 s
branch, 2nd invocation of a run	0	0	0	3	~4.4 s

The first invocation is unchanged, and the decision costs ~18 ms. No token saving is claimed.

Tests

• HIT: a second-invocation test that counts the actual work done.
• Equivalence: the mandatory fresh-vs-reused test. It covers a real regression, a pre-existing red gate and an eval pair, and the checker's output matches byte for byte.
• MISS controls: 19 end-to-end controls, each changing one input. Also a foreign feature, a forged progress record, a crash during the base gates, and a paused chain with a root file edited before resume.
• Wiring:
  • a hook test on the record path;
  • check-loop-fresh reads FRESH over a HIT run;
  • the pinned command line runs twice with a real npm ci.
• Mutation checks: deleting the key lines makes their tests fail.
• npm test: 4394 / 4394. Floor GREEN (36 capabilities). Reconcile CLEAN.

Pipeline

/pharn-dev-ship artifacts are in .dev/features/regress-base-reuse/ (PLAN, GRILL, REGRESSION, VERIFY, REVIEW, SHIP).

• GATE 1 and the GATE-2 fixes were model decisions under the maintainer's delegation, not human approvals.
• The independent review raised 2 floor-gate findings (overclaiming sentences) and 3 minor ones, including one real publication gap. All five are fixed; see REVIEW.md, "Disposition".

Limitations (named)

• A HIT proves agreement, not provenance (L43): a shell writer can forge the record and the evidence together.
• The base side's in-progress scratch is write-tool reachable while a chain is paused at continue (follow-up regress-paused-chain-integrity).
• A marker left by an interrupted run (≤ 24 h) binds a later standalone regress.
• Ignored root content, the environment and the machine are not bound.
• /pharn-dev-regress is unchanged.

SKILLS_VERSION 6.32.1 → 6.33.0 (minor). MIN_CLI stays 0.5.0.

🤖 Generated with Claude Code

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