# Track Specification: Advanced Tier 4 QA Auto-Patching (tier4_auto_patching_20260306)

## Overview
Elevate Tier 4 from log summarizer to auto-patcher. When verification tests fail, Tier 4 generates a .patch file. GUI displays side-by-side diff; user clicks Apply Patch to resume pipeline.

## Architectural Constraints
- **Safe Preview**: Patches MUST be previewed before application.
- **Rollback**: Failed patches MUST be revertable.
- **Atomic Application**: Patch application MUST be atomic (all-or-nothing).

## Functional Requirements
- **Patch Generation**: Tier 4 generates .patch file on test failure.
- **Diff Viewer**: GUI shows side-by-side diff of proposed changes.
- **Apply Button**: User confirms patch application.
- **Patch Application**: Apply patch to working directory and verify.

## Acceptance Criteria
- [ ] Tier 4 generates valid .patch file.
- [ ] GUI displays readable side-by-side diff.
- [ ] User can approve/reject patch.
- [ ] Approved patches applied correctly.
- [ ] Rollback available on failure.