Code Forge — Fixbug

Systematically debug and fix bugs with interactive trace-back to upstream documents (task descriptions, plans, requirements).

When to Use

• Encountered a bug or unexpected behavior in a feature
• Need to diagnose whether the root cause is in code, task description, plan, or requirements
• Want to fix the bug with TDD and keep upstream documents in sync

Workflow

Bug Input → Context Scan → Feature Association → Root Cause Diagnosis → Trace-back Confirmation → TDD Fix → Doc Sync → Summary

Detailed Steps

@../shared/configuration.md

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Step 1: Receive Bug Description

Accept input in two modes:

• Prompt text (e.g., /code-forge:fixbug login page returns 500 error) — use the text as bug description
• File reference (e.g., /code-forge:fixbug @issues/bug-123.md) — read the file for bug details

If no input provided, use AskUserQuestion to ask: "Describe the bug you encountered."

Store the bug description for subsequent steps.

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Step 2: Project Context Scan

Scan the project codebase to understand the context:

1. Use Glob to get project structure overview
2. Use Grep to search for keywords from the bug description in the codebase
3. Identify files and modules likely related to the bug
4. Note the tech stack and testing framework used

Store a concise context summary (~500 words).

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Step 3: Associate Feature (If Exists)

Attempt to associate the bug with an existing code-forge feature:

1. Search {output_dir}/*/state.json for all features
2. For each feature, check if the bug-related files overlap with the feature's task files (read tasks/*.md → "Files Involved" sections)
3. Match found → load the feature's plan.md and relevant tasks/*.md as additional context. Note the feature name.
4. No match found → mark as standalone bug. Skip upstream trace-back (Steps 5 and 7). Proceed with code-only fix.

If multiple features match, use AskUserQuestion to let user select the most relevant one.

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Step 4: Root Cause Diagnosis

Offload to sub-agent for deep analysis.

Spawn a Task tool call with:

• subagent_type: "general-purpose"
• description: "Diagnose bug root cause"

Sub-agent prompt must include:

• Bug description
• Project context summary from Step 2
• Feature context (plan.md, task files) if associated in Step 3
• Instruction to: reproduce the bug, identify the root cause, classify the root cause level

Root cause levels:

Level	Description	Example
1	Code bug	Logic error, boundary miss, typo, wrong variable
2	Incomplete task description	Task.md steps missing a case, wrong acceptance criteria
3	Plan design flaw	Architecture doesn't handle a scenario, missing component
4	Incomplete requirement doc	Original feature doc missing a requirement

Sub-agent must return:

ROOT_CAUSE_LEVEL: <1-4>
ROOT_CAUSE_SUMMARY: <1-2 sentence description>
AFFECTED_FILES:
- path/to/file.ext: <what's wrong>
UPSTREAM_DOCS_AFFECTED: (only if Level >= 2)
- Level 2: tasks/<task>.md — <what's missing/wrong>
- Level 3: plan.md — <what's missing/wrong>
- Level 4: {input_dir}/<feature>.md — <what's missing/wrong>
PROPOSED_FIX: <brief fix description>
REGRESSION_TEST: <what test to write>

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Step 5: Interactive Trace-back Confirmation

This step only runs if Level >= 2 AND the bug is associated with a feature.

Present the root cause analysis to the user, then confirm upstream updates level by level.

5.1 Present Analysis

Display:

Root Cause Analysis

Level: {level} — {level_description}
Summary: {root_cause_summary}

Affected code:
  {affected_files list}

Upstream documents affected:
  {upstream_docs_affected list}

5.2 Per-Level Confirmation

For each affected upstream level (from lowest to highest), use AskUserQuestion:

"Root cause traced to {level_name}: {doc_path} — {what's wrong}. Update this document?"

Options:

• "Yes, update this document" → mark for update in Step 7
• "No, code fix only" → skip this level, do not modify this document
• "Show proposed changes" → display the proposed diff for this document, then re-ask

5.3 Generate Fix Plan

Compile the fix plan:

• Code changes to make (always)
• Upstream documents to update (based on user confirmations)
• Regression test to write

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Step 6: TDD Fix

Execute the fix following TDD methodology:

6.1 Write Regression Test

Write a test that reproduces the bug:

• Test must FAIL with the current code (proving the bug exists)
• Test must describe the expected correct behavior

Run the test to verify it fails.

6.2 Implement Fix

Make the minimal code changes to fix the bug.

Run the regression test to verify it passes.

6.3 Run Full Test Suite

Run the project's full test suite to ensure no regressions:

• If tests pass: continue
• If tests fail: investigate and fix before proceeding

6.4 Commit Fix

Commit the code changes with a descriptive message:

fix: {brief description of bug fix}

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Step 7: Upstream Document Sync

This step only runs if upstream documents were confirmed for update in Step 5.

For each confirmed document update:

7.1 Show Diff Preview

Before modifying each document, show the proposed changes in diff format:

--- a/{doc_path}
+++ b/{doc_path}
@@ ... @@
- old content
+ new content

Ask user: "Apply this change?" (Yes / No / Edit manually)

7.2 Apply Changes

• Level 2 (task.md): Update the task's steps, acceptance criteria, or files involved
• Level 3 (plan.md): Update architecture, task breakdown, or risk sections
• Level 4 (feature doc): Update requirements or scope

7.3 Commit Document Updates

Commit upstream document changes separately from code fix:

docs: update {doc_path} — traced from bug fix

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Step 8: Update state.json

If the bug is associated with a feature:

1. Read the feature's state.json
2. Add a fixes array (if not present) to the feature-level metadata
3. Append a fix record:

   {
     "bug": "brief bug description",
     "root_cause_level": 2,
     "root_cause": "brief root cause",
     "fixed_files": ["path/to/file.ext"],
     "commits": ["abc1234"],
     "doc_updates": ["tasks/auth-logic.md"],
     "fixed_at": "ISO timestamp"
   }
   

4. Update state.json updated timestamp

If standalone bug (no associated feature): skip this step.

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Step 9: Summary

Display fix summary:

Bug Fix Complete

Bug: {description}
Root Cause: Level {level} — {summary}

Code Changes:
  {files changed}

Regression Test:
  {test file and name}

Document Updates:
  {list of updated docs, or "none"}

Commits:
  {commit hashes}

Next steps:
  /code-forge:status {feature}    View updated progress
  /code-forge:review {feature}    Review all changes