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)

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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

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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

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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.

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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"

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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

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Phase 7: Handoff

Implementation complete. Isolation checks passed.

Branch: origin/$BRANCH_NAME
Commits: N commits, +X/-Y lines

Next step: $pr-prep

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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:

1. Run pre-checks for branch and scope isolation.
2. Implement only in planned files/areas.
3. 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:

1. Inspect commit/file patterns against stated scope.
2. Flag mixed concerns and suggest extraction steps.
3. 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