Bug Origin Checker

Bug Origin Checker

Context

• User is a manual QA tester on the EXAMPLE-PROJ team
• Tests feature branch builds on physical iPhones
• PRs are linked in JIRA story comments
• User has access to RC/main builds for comparison
• Explain everything in plain, simple language

Trigger Phrases

Activate when the user says things like:

• "Is this bug from the branch or was it already there?"
• "Did this branch introduce this bug?"
• "I found a bug while testing [story] — is it pre-existing?"
• "Is this a regression from the feature branch?"
• "Was this bug already in main?"
• "Is this new or existing?"

Step 1: Gather Info

Ask for two things (if not already provided):

1. The story being tested — JIRA key (e.g., EXAMPLE-PROJ-456)
2. The bug found — which screen/area, what happens

Example prompt:

What story were you testing, and what's the bug you found?

Step 2: Find the PR

Fetch the JIRA story to locate the PR link:

CallMcpTool:
  server: user-atlassian-mcp-server
  toolName: jira_get_issue
  arguments:
    issue_key: <story key>
    fields: "*all"
    comment_limit: 50

Look for a GitHub PR link in:

• Issue comments
• Description
• Remote links / linked issues

Extract the PR URL (e.g., https://github.com/your-org/your-mobile-app/pull/1234).

If no PR found

Tell the user:

I couldn't find a linked PR for this story. Without seeing the code changes, I can't determine if the bug is pre-existing.

You can check by installing the latest RC or main build and seeing if the bug happens there too. If it does, it's pre-existing.

Stop here — do not guess.

Step 3: Analyze the PR Diff

Use the GitHub CLI to get the list of changed files:

gh pr diff <PR_NUMBER> --repo <REPO> --name-only

This returns just the file paths that were changed (no code content needed for the initial check).

If more detail is needed, get the full diff:

gh pr diff <PR_NUMBER> --repo <REPO>

If gh CLI fails with auth error

Follow the github-auth-recovery skill to resolve, then retry.

Step 4: Map Files to App Areas

Translate file paths into plain-language app areas the user understands.

Common patterns in the iOS codebase:

If a file path doesn't match known patterns, use the directory name and file name to infer the area. When unsure, list the raw file paths for the user.

Step 5: Compare and Give Verdict

Compare the bug area (from the user's description) against the changed areas (from the PR).

Verdict A: Very Likely Pre-existing

The branch did NOT change any files related to the bug area.

I checked PR #1234 for EXAMPLE-PROJ-456. Here's what the branch changed:

| Area Changed | Files Modified |
|-------------|---------------|
| Checkout / Payment | 4 files |
| Cart | 2 files |

Your bug is on the **profile screen**. The branch **did not change any
profile-related code**.

**Verdict: Very likely pre-existing.**
This bug was probably already there before this branch.

**Recommended next steps:**
1. Check the latest RC build to confirm it happens there too
2. File it as a **separate bug** (not related to EXAMPLE-PROJ-456)

Want me to check for duplicates and file a bug?

Verdict B: Possibly Introduced

The branch DID change files in or near the bug area.

I checked PR #1234 for EXAMPLE-PROJ-456. Here's what the branch changed:

| Area Changed | Files Modified |
|-------------|---------------|
| Profile / Account | 3 files |
| Networking | 1 file |

Your bug is on the **profile screen**. The branch **changed 3 files in the
profile area**.

**Verdict: This bug might be introduced by this branch.**
The code changes touch the same area where you found the bug.

**Recommended next steps:**
1. Check the RC build — if the bug does NOT happen there, the branch likely caused it
2. Add a comment on EXAMPLE-PROJ-456 describing the bug
3. Flag it to the developer on the story

Want me to add a comment on the JIRA story?

Verdict C: Inconclusive (Shared Code Changed)

The branch changed shared/common code that could affect many areas.

I checked PR #1234 for EXAMPLE-PROJ-456. Here's what the branch changed:

| Area Changed | Files Modified |
|-------------|---------------|
| Checkout | 3 files |
| Networking / API (shared) | 2 files |
| Navigation (shared) | 1 file |

Your bug is on the **profile screen**. The branch didn't directly change
profile code, BUT it changed **shared networking and navigation code** that
the profile screen also uses.

**Verdict: Inconclusive — could go either way.**

**Recommended next step:**
Check the latest RC build. If the bug happens on RC too → pre-existing.
If it only happens on this branch → the shared code change likely caused it.

Want me to help after you check?

Step 6: Chain to Next Action

Based on the verdict, offer the appropriate next step:

Carry forward all context so the user doesn't repeat themselves.

Important Rules

• Never guess without PR data — if there's no PR, say so and suggest testing on RC
• Always show what changed — give the user a table of changed areas, not just the verdict
• Plain language only — translate file paths to app areas, never show raw code paths unless necessary
• Connect the dots — after the verdict, link to duplicate-bug-checker or bug filing
• RC build is the ultimate proof — always mention it as the definitive way to confirm, especially for inconclusive cases
• Don't analyze code logic — focus on what areas were changed, not how the code works. Keep it accessible for a non-technical user.