Bugfix Specs

The Bugfix Spec models how experienced developers approach bug fixes: identify the root cause, understand what should change, and explicitly preserve what shouldn't. Bugfix Specs provide a structured approach using that workflow, guiding you through root cause analysis, fix design, and regression prevention to ensure surgical, reliable fixes.

Key Benefits

Surgical fixes - Explicit constraints ensure only necessary changes are made

Regression prevention - Unchanged behavior is documented and tested

Documentation - Complete record of the bug, fix, and reasoning for future reference

Reliability - Structured workflow prevents common pitfalls of ad-hoc fixes

When to Use Bugfix Specs

Best for:

• Complex bugs requiring root cause analysis
• Bugs in critical code paths where regressions are costly
• Bugs that need documentation for compliance or team knowledge
• Situations where previous fix attempts caused regressions

How It Works

Bugfix Specs follow the same three-phase workflow as Feature Specs (Requirements → Design → Tasks), but with content tailored specifically for surgical bug fixes:

1. Bugfix Analysis Phase

Instead of a requirements document, you create a bugfix.md that captures:

Current Behavior (Defect)

• WHEN [condition] THEN the system [incorrect behavior]

Expected Behavior (Correct)

• WHEN [condition] THEN the system SHALL [correct behavior]

Unchanged Behavior (Regression Prevention)

• WHEN [condition] THEN the system SHALL CONTINUE TO [existing behavior]

This explicit structure ensures Kiro understands not just what's broken, but what must remain working.

2. Design Phase

Kiro explores the codebase to root cause the issue and generates a design.md with:

• Root cause analysis
• Proposed fix approach
• Properties to test for:
  • Current implementation produces incorrect behavior (validates the bug exists)
  • Fixed implementation produces correct behavior (validates the fix works)
  • Unchanged implementation continues working (prevents regressions)

3. Tasks Phase

Implementation tasks are generated with property-based tests (PBTs) that validate:

• The bug is reproducible
• The bug is fixed
• No regressions are introduced

Getting Started

1. Choose Spec from the chat pane.
2. Describe the bug, including:
   • When the bug occurs (reproduction steps)
   • What should happen instead
   • Any constraints (code that shouldn't be modified)
3. Choose Bugfix when Kiro asks what your intent is.
4. Follow the workflow through analysis, design, and implementation.

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