# Plan Lock

> Use when creating or executing implementation plans to ensure plan integrity via SHA-256 attestation. Prevents mid-execution plan drift.

- Skill: `johnnylin2121/plan-lock` (Agent Skill)
- Install (CLI): `npx skillmds@latest add johnnylin2121/plan-lock`
- Raw SKILL.md: https://api.skillmd.com/api/skills/johnnylin2121/plan-lock/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: Johnnylin2121 (https://skillmd.com/u/johnnylin2121)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/johnnylin2121/plan-lock

---


# Plan Attestation

Ensures implementation plans are not modified during execution without detection.

## Workflow

### 1. After Creating a Plan

```bash
# Compute hash of plan file
shasum -a 256 plans/your-plan.md | awk '{print $1}'
```

Store the hash in your notes.md or the plan file header:

```markdown
<!-- ATTESTATION: sha256=<hash> -->
```

### 2. Before Each Task Execution

Re-compute the hash and compare:

```bash
hash=$(shasum -a 256 plans/your-plan.md | awk '{print $1}')
attested="<stored-hash>"
if [ "$hash" != "$attested" ]; then
  echo "WARNING: Plan hash mismatch! Plan may have been modified."
  # Pause and verify with user
fi
```

### 3. If Mismatch Detected

- Warn the user immediately
- Show what changed (git diff if in git repo)
- Do NOT proceed until user confirms the changes are intentional

## When to Use

- Plans longer than 5 tasks
- Multi-day implementation projects
- Any plan where integrity matters

## Quick Commands

- **Attest**: `shasum -a 256 <plan-file>`
- **Verify**: Compare stored hash with current hash
- **Log**: Record hash + timestamp in notes.md

## Limitations

- This is a soft lock (skill-based, not enforced by hook)
- Agent must follow the workflow — it's a discipline, not a hard gate
- For hard enforcement, use the completion-gate hook instead