plan-check

plan-check is a skill for Claude Code from vasuag09/harness-claude. It costs 75 tokens per session (752 once invoked), scanned A, original, MIT.

A read-only review step that checks an implementation plan against its specification before coding starts. It uses an adversarial review, meaning it actively looks for ways the plan could fail.

In plain words
What is it for?
It checks that every acceptance criterion is covered, flags scope creep, and verifies that parallel tasks edit separate files.
Why use it?
It catches missing requirements, unnecessary work, and conflicting parallel tasks while the plan is still cheap to change.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the harness-claude plugin — 32 skills, 8 agents, 6 hooks, 3 MCP servers shipped together

Good fit It checks that every acceptance criterion is covered, flags scope creep, and verifies that parallel tasks edit separate files.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/vasuag09/harness-claude/plan-check
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add vasuag09/harness-claude --skill plan-check
Clone the repo
git clone --depth 1 https://github.com/vasuag09/harness-claude

Made for: Claude Code.

Or install harness-claude, the plugin that ships this one along with the rest of its 32 skills, 8 agents, 6 hooks, 3 MCP servers.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for plan-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/vasuag09/harness-claude/plan-check/github.svg)](https://agentmods.dev/skills/vasuag09/harness-claude/plan-check)
Your own site
<a href="https://agentmods.dev/skills/vasuag09/harness-claude/plan-check"><img src="https://agentmods.dev/badge/skills/vasuag09/harness-claude/plan-check/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for plan-check

Your own site · 80×15
<a href="https://agentmods.dev/skills/vasuag09/harness-claude/plan-check"><img src="https://agentmods.dev/badge/skills/vasuag09/harness-claude/plan-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 75 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 752 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00075 $0.00752
Opus 5 $0.00037 $0.00376
Sonnet 5 $0.00015 $0.00150
Haiku 4.5 $0.00007 $0.00075

Measured 8d ago against content hash 2e3a6cccd856, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

plan-check scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/plan-check/SKILL.md · 55 lines

How it starts

The opening of the file, as written. The whole thing — 55 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/plan-check — gate the plan before building

Goal: catch a broken plan before an executor acts on it. An ambiguous or incomplete plan produces an executor that guesses; parallel executors guessing differently about the same file produce conflicts. Cheaper to fix the plan now than to unwind code later.

This is the plan-phase counterpart to /harness-claude:review — same adversarial stance, one step earlier. It is read-only: it reports, it does not edit the plan.

Do this

  1. Load the artifacts: .claude/planning/<slug>/PLAN.md and SPEC.md (slug is in .claude/STATE.md). If there's no PLAN.md on disk (trivial/inline work), review the plan from the conversation instead — the checks are the same.
  2. Delegate to the harness-claude:planner agent in a check pass (read-only — pass it the plan, the spec, and the objective: "find why this plan fails before we build it"). Get back a summary with severities, not a raw dump.
  3. Check the plan across three dimensions:
    • Criteria coverage — does every AC-n in SPEC.md map to at least one task's addresses:? Name any uncovered criterion.
    • Scope — does any task do work no criterion asked for (scope creep), or is any in-scope item unplanned? Flag both directions.
    • Task independence — for tasks meant to run in parallel (same wave / no depends_on between them), are the write-sets pairwise disjoint? Are depends_on edges acyclic and complete (no task reads another's output without declaring it)? Overlapping write-sets or a missing edge is a correctness bug.
  4. Red-team it: assume the plan already failed in execution and ask why. Attack hidden assumptions, not just the obvious risks.
  5. If findings warrant a revision, hand them back to /harness-claude:plan and re-check — loop ≤ 3 times (per rules/agents.md), then accept or escalate to the user.

Output

A findings list, most-severe first, each with a severity:

Severity Meaning Action
Critical The plan cannot satisfy a criterion, or parallel tasks collide on a file BLOCK — fix the plan before /harness-claude:implement
High Likely bug or significant gap Fix before building
Medium Maintainability / clarity concern Fix when reasonable
Low Minor suggestion Optional

Read the full file on GitHub · 55 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 55 lines · 75 tokens per session scan A 2e3a6cccd856

Subscribe to this mod's changes

plan-check is a skill published in the GitHub repository vasuag09/harness-claude (2 stars, last pushed 2mo ago), licensed MIT. It adds 75 tokens to every session and 752 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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