PR Implement Skill

Fork-based implementation for open source contributions with mandatory isolation check.

Overview

Execute a contribution plan with fork isolation. Ensures PRs are clean

and focused by running isolation checks before and during implementation.

Input: Plan artifact from $pr-plan or repo URL

When to Use:

• Implementing a planned OSS contribution

• Need isolation enforcement for clean PRs

• After completing $pr-plan

When NOT to Use:

• Internal project work (use $implement)

• Haven't planned yet (run $pr-plan first)

Workflow

-1. Prior Work Check      -> BLOCKING: Check for competing PRs

0.  Input Discovery       -> Find plan artifact or repo

1.  Fork Setup            -> Ensure fork exists and is current

2.  Worktree Creation     -> Create isolated worktree

3.  Isolation Pre-Check   -> BLOCK if mixed concerns

4.  Implementation        -> Execute plan

5.  Isolation Post-Check  -> BLOCK if scope creep

6.  Commit Preparation    -> Stage with proper commit type

7.  Handoff               -> Ready for $pr-prep

Phase -1: Prior Work Check (BLOCKING)

# Search for open PRs on this topic

gh pr list -R <owner/repo> --state open --search "<topic>" --limit 10

# Check target issue status

gh issue view <issue-number> -R <repo> --json state,assignees

Finding

Action

Open PR exists

Coordinate or wait

Issue assigned

Coordinate or find alternative

No competing work

Proceed

Phase 3: Isolation Pre-Check (BLOCKING)

# Commit type analysis

git log --oneline main..HEAD | sed 's/^[^ ]* //' | grep -oE '^[a-z]+(\([^)]+\))?:' | sort -u

# File theme analysis

git diff --name-only main..HEAD | cut -d'/' -f1-2 | sort -u

Check

Pass Criteria

Single commit type

0 or 1 prefix

Thematic files

All match plan scope

Branch fresh

Based on recent main

DO NOT PROCEED IF PRE-CHECK FAILS.

Phase 4: Implementation

Guidelines

Guideline

Why

Single concern

Each commit = one logical change

Match conventions

Follow project style exactly

Test incrementally

Run tests after each change

Commit Convention

git commit -m "type(scope): brief description

Longer explanation if needed.

Related: #issue-number"

Phase 5: Isolation Post-Check (BLOCKING)

# Commit type analysis

git log --oneline main..HEAD | sed 's/^[^ ]* //' | grep -oE '^[a-z]+(\([^)]+\))?:' | sort -u

# Summary stats

git diff --stat main..HEAD

Check

Pass Criteria

Single commit type

All commits share same prefix

Thematic files

All files relate to PR scope

Atomic scope

Can explain in one sentence

Phase 7: Handoff

Implementation complete. Isolation checks passed.

Branch: origin/$BRANCH_NAME

Commits: N commits, +X/-Y lines

Next step: $pr-prep

Anti-Patterns

DON'T

DO INSTEAD

Skip isolation pre-check

Run Phase 3 FIRST

Skip isolation post-check

Run Phase 5 before push

Mix concerns in commits

One type prefix per PR

Implement without plan

Run $pr-plan first

Examples

Implement From Contribution Plan

User says: "Implement this external PR plan with isolation checks."

What happens:

• Run pre-checks for branch and scope isolation.

• Implement only in planned files/areas.

• Run post-checks and prepare handoff for PR prep.

Enforce Single-Concern Commit Set

User says: "Make sure this branch is still single-purpose before I prep the PR."

What happens:

• Inspect commit/file patterns against stated scope.

• Flag mixed concerns and suggest extraction steps.

• Produce a clean handoff to $pr-prep.

Troubleshooting

Problem

Cause

Solution

Isolation check fails

Unrelated changes on branch

Move unrelated edits to separate branch/PR

Commits mix concerns

Implementation drifted from plan

Re-split commits by concern and revalidate

Scope keeps expanding

Weak boundaries in plan

Re-anchor to Out of Scope and stop additional changes

Hard to hand off

Missing summary/test context

Add concise change summary and verification notes