Rectify: Commit Guard Regression Heuristic — Content-Movement Immunity#3895
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Trecek merged 9 commits intoJun 8, 2026
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…unity (#3887) The _check_regression heuristic in _cmd_rpc_guards.py fired on file splits because aggregate net-line-count comparison cannot distinguish content movement from content deletion. Replace the single-signal threshold with multi-signal classification: new-file accounting (subtract lines of nearby untracked destinations from regression_lines), empty-reverted-files guard (no per-file reversion evidence → CLEAR), and a _RegressionVerdict enum for informational classification. commit_guard now passes file_status XY codes to _check_regression via a new file_status dict built alongside files_to_add. Recipes that call commit_guard with base_branch must route regression_detected to an escalation step; the new commit-guard-regression-route-missing semantic rule enforces this and was added to all four bundled recipes. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
…recipe steps Replace on_success with default route entry inside on_result for all four commit_guard steps (implementation, implementation-groups, remediation x2). Fix test_commit_guard_allows_intentional_reduction to assert regression_detected (correct behavior for bulk reduction without content redistribution). Update pyright suppression allowlist line number and recipe/rules file count. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Pass VIRTUAL_ENV to subprocess env and derive it from sys.executable when not already set. This prevents fastmcp import failures when install-worktree rebuilds the venv before test execution under xdist. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The test_ci_dev_config::test_ruff_check_clean test calls `uv run ruff check` which triggers `uv sync`, replacing package files in the shared .venv while xdist workers run concurrently. When the import isolation subprocess starts during this window, fastmcp's package files are mid-swap, causing ImportError or PackageNotFoundError. Pin PYTHONPATH in the subprocess env to the parent's sys.path so module resolution uses the snapshot from process startup rather than the live (potentially mid-sync) venv filesystem. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Root cause: test_ci_dev_config::test_ruff_check_clean calls `uv run ruff check` which triggers `uv sync`, replacing .dist-info directories in the shared .venv while xdist workers run concurrently. When the import isolation subprocess starts during this window, fastmcp's __init__.py hits PackageNotFoundError or ModuleNotFoundError. Add _run_import_subprocess() wrapper that retries once after 1s on import-infrastructure errors (PackageNotFoundError, ModuleNotFoundError). The uv sync race window is typically < 1s, so the retry succeeds after the sync completes. Remove PYTHONPATH pinning (doesn't help since importlib.metadata resolves .dist-info from the same physical dir). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
…tely describe behavior The test name claimed the guard "allows" the reduction, but the assertion checks for regression_detected, indicating the guard does NOT allow it. Rename to test_commit_guard_detects_pure_reduction_as_regression to align the name with the assertion and docstring, which already correctly describe the detection behavior for a 50→20 line single-file reduction. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
… enum members These members were never referenced in code expressions — the early-return paths use `return None` directly. Only POSSIBLE_REVERSION is used. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The function returns a verdict key but skill_contracts.yaml did not declare it, creating a contract validation gap. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Enables Pyright to verify attribute access on the step parameter. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
The
_check_regression()heuristic in_cmd_rpc_guards.pyuses aggregate net-line-count comparison (committed_net - wt_net > 10) to detect accidental reversion of implementation work. This false-positives on any file split, refactor, or dead-code removal because line-count deltas cannot distinguish content movement from content deletion. The architectural weakness is: a binary threshold over a single numeric proxy makes an irreversible decision (abort commit) with no corroborating evidence.The immunity approach replaces the single-signal threshold with a multi-signal classification that distinguishes content-movement from content-reversion, and gates the abort decision on corroborating evidence (git name-status metadata, new-file accounting, per-file balance analysis). The heuristic becomes structurally incapable of false-positiving on file splits because it explicitly detects and compensates for content movement between files.
Requirements
The heuristic either needs to be made substantially more robust or replaced with a mechanism that doesn't rely on line-count proxies. Options to evaluate:
Cross-file awareness: Before declaring regression, check if new/untracked files in the same directory contain the "missing" lines. If
regression_linesfrom file A can be accounted for bynew_linesin sibling files, it's a split, not a reversion.Content-based detection: Instead of counting lines, check if the working tree version has content overlap with the committed version. A reversion would show the working tree matching an older commit; a refactor would show novel organization of the same content.
Test-gated commit: If tests pass after the changes, the regression heuristic should yield. A true reversion of implementation work would likely cause test failures. The guard could be:
regression_lines > threshold AND tests_not_yet_passed.Semantic diffing: Compare the set of function/class definitions between committed and working tree. If the same symbols exist (just in different files), it's a reorganization.
Elimination: If the only scenario this guards against is "session accidentally checks out old file version," that can be detected more precisely by comparing the working tree against known old commits (
git diff --stat HEAD~Nmatching the dirty state exactly). If no old commit matches, it's not a reversion.The current threshold of 10 lines is also concerningly low for a heuristic with no escape valve — any non-trivial refactoring of a file that was modified in the implementation commits will trip it.
Implementation Plan
Plan file:
/home/talon/projects/autoskillit-runs/remediation-20260607-164912-642953/.autoskillit/temp/rectify/rectify_commit_guard_regression_heuristic_2026-06-07_170500.mdCloses #3887
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