my-pi/pi-permission-system/docs/retro/0033-fix-findsection-greedy-end.md

issue, issue_title

issue	issue_title
33	sanitizeAvailableToolsSection silently removes content after the last recognised section header

Retro: #33 — sanitizeAvailableToolsSection silently removes content after the last recognised section header

Final Retrospective (2026-05-03T06:15:00Z)

Session summary

Planned, implemented, and shipped a bug fix for findSection in src/system-prompt-sanitizer.ts. The function defaulted end to lines.length when no subsequent section header followed, silently deleting all content after the last section. The fix uses a two-pass strategy: use the next section header as the boundary when one exists, otherwise stop at the first non-body line via a new isSectionBodyLine helper. Released as v3.0.3.

Observations

What went well

• The plan correctly identified the bug, the affected module, and the general approach (body-line scanning).
• The test.fails → test flip pattern worked cleanly as a red-phase entry point.

What caused friction (agent side)

• premature-convergence — The plan proposed a single-pass isSectionBodyLine-only approach without checking tests/permission-system.test.ts, which exercises sanitizeAvailableToolsSection with a realistic multi-section prompt containing prose between Available tools: and Guidelines:. The naive implementation passed all 16 sanitizer-specific tests but broke the integration test at line 446. Impact: required pivoting to a two-pass strategy and a messy git commit --amend + git rebase -i cleanup that consumed ~5 minutes of rework.

• wrong-abstraction — Used git commit --amend intending to update commit 828c907 (the intermediate fix), but --amend always operates on HEAD, which at that point was the edge-case test commit 2c994d5. This left a broken intermediate commit in the ancestry, requiring an interactive rebase to drop it. The rebase itself hit two obstacles: neovim launching as $EDITOR (needed GIT_SEQUENCE_EDITOR), and a merge conflict because isSectionBodyLine was defined in the dropped commit. Impact: ~3 minutes of git archaeology; no code-quality impact on the final result.

What caused friction (user side)

None observed. The user's issue description was thorough (root cause, reproducer, proposed fix, impact analysis), which made planning and implementation straightforward.

Changes made

1. Added rule to AGENTS.md § Testing: run the full test suite before committing when shared helpers change.
2. Created docs/retro/0033-fix-findsection-greedy-end.md (this file).