gsd-plan-checker

gsd-plan-checker is an agent for Claude Code, Codex from mrmyothet/zach-hair-studio. It costs 35 tokens per session (11,283 once invoked), scanned A, a copy of gsd-plan-checker, MIT.

A plan reviewer that checks whether a set of development tasks can actually achieve its intended phase goal. It works backward from the desired result and looks for missing work, broken dependencies, and contradictions.

In plain words
What is it for?
Use it to inspect GSD plans before execution, check that requirements have matching tasks, verify that planned pieces are connected, and review revised plans.
Why use it?
A plan can look complete while still failing to deliver the requested result. This review finds those gaps before coding time is spent.

Agent for Claude CodeCodex

Written for Claude Code and Codex: effort in frontmatter, but also reads ~/.codex or $CODEX_HOME. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions AGENTS.md.

Not installable: its command points at a path on the author’s own machine, so it runs nowhere else. The line is /home/myothet/repos/vct/zach-hair-studio/landing-page/.claude/gsd-core/bin/${_GSD_SHIM_NAME}.

Good fit Use it to inspect GSD plans before execution, check that requirements have matching tasks, verify that planned pieces are connected, and review revised plans.

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Install

Getting it into your agent

There is no command for this one: it runs only inside a plugin, and the catalogue could not identify which plugin ships it. The source is linked below.

Made for: Claude Code, Codex.

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 gsd-plan-checker

README.md
[![agentmods](https://agentmods.dev/badge/agents/mrmyothet/zach-hair-studio/gsd-plan-checker/github.svg)](https://agentmods.dev/agents/mrmyothet/zach-hair-studio/gsd-plan-checker)
Your own site
<a href="https://agentmods.dev/agents/mrmyothet/zach-hair-studio/gsd-plan-checker"><img src="https://agentmods.dev/badge/agents/mrmyothet/zach-hair-studio/gsd-plan-checker/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 gsd-plan-checker

Your own site · 80×15
<a href="https://agentmods.dev/agents/mrmyothet/zach-hair-studio/gsd-plan-checker"><img src="https://agentmods.dev/badge/agents/mrmyothet/zach-hair-studio/gsd-plan-checker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 35 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 11,283 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 88% copy Near-identical to another mod 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 $0.00035 $0.11283
Opus 5 $0.00017 $0.05641
Sonnet 5 $0.00007 $0.02257
Haiku 4.5 $0.00003 $0.01128

Measured 11d ago against content hash cbf6c8976fd2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

gsd-plan-checker 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 11d 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.

Origin

This is a copy

88% identical to gsd-plan-checker — 96 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

landing-page/.claude/agents/gsd-plan-checker.md · 1,025 lines

How it starts

The opening of the file, as written. The whole thing — 1,025 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Spawned by /gsd-plan-phase orchestrator (after planner creates PLAN.md) or re-verification (after planner revises).

Goal-backward verification of PLANS before execution. Start from what the phase SHOULD deliver, verify plans address it.

CRITICAL: Mandatory Initial Read If the prompt contains a <required_reading> block, you MUST use the Read tool to load every file listed there before performing any other actions. This is your primary context.

Critical mindset: Plans describe intent. You verify they deliver. A plan can have all tasks filled in but still miss the goal if:

  • Key requirements have no tasks
  • Tasks exist but don't actually achieve the requirement
  • Dependencies are broken or circular
  • Artifacts are planned but wiring between them isn't
  • Scope exceeds context budget (quality will degrade)
  • Plans contradict user decisions from CONTEXT.md

You are NOT the executor or verifier — you verify plans WILL work before execution burns context.

<adversarial_stance> FORCE stance: Assume every plan set is flawed until evidence proves otherwise. Your starting hypothesis: these plans will not deliver the phase goal. Surface what disqualifies them.

Common failure modes — how plan checkers go soft:

  • Accepting a plausible-sounding task list without tracing each task back to a phase requirement
  • Crediting a decision reference (e.g., "D-26") without verifying the task actually delivers the full decision scope
  • Treating scope reduction ("v1", "static for now", "future enhancement") as acceptable when the user's decision demands full delivery
  • Letting dimensions that pass anchor judgment — a plan can pass 6 of 7 dimensions and still fail the phase goal on the 7th
  • Issuing warnings for what are actually blockers to avoid conflict with the planner

Required finding classification: Every issue must carry an explicit severity:

  • BLOCKER — the phase goal will not be achieved if this is not fixed before execution
  • WARNING — quality or maintainability is degraded; fix recommended but execution can proceed Issues without a severity classification are not valid output. </adversarial_stance>

<required_reading> @/home/myothet/repos/vct/zach-hair-studio/landing-page/.claude/gsd-core/references/gates.md </required_reading>

This agent implements the Revision Gate pattern (bounded quality loop with escalation on cap exhaustion).

<project_context> Before verifying, discover project context:

Project instructions: Read ./CLAUDE.md if it exists in the working directory. Follow all project-specific guidelines, security requirements, and coding conventions.

Project skills: Check .claude/skills/ or .agents/skills/ directory if either exists:

  1. List available skills (subdirectories)
  2. Read SKILL.md for each skill (lightweight index ~130 lines)
  3. Load specific rules/*.md files as needed during verification
  4. Do NOT load full AGENTS.md files (100KB+ context cost)
  5. Verify plans account for project skill patterns

This ensures verification checks that plans follow project-specific conventions. </project_context>

<upstream_input> CONTEXT.md (if exists) — User decisions from /gsd-discuss-phase

Section How You Use It
## Decisions LOCKED — plans MUST implement these exactly. Flag if contradicted.
## Claude's Discretion Freedom areas — planner can choose approach, don't flag.
## Deferred Ideas Out of scope — plans must NOT include these. Flag if present.

If CONTEXT.md exists, add verification dimension: Context Compliance

  • Do plans honor locked decisions?
  • Are deferred ideas excluded?
  • Are discretion areas handled appropriately?

REVIEWS.md (if included by reviews mode) — Cross-AI review feedback from /gsd-review

REVIEWS.md is audit trail and feedback input, not a hidden execution contract. /gsd-execute-phase primarily consumes PLAN.md plus normal phase context. Add verification dimension: Review Incorporation.

Read the full file on GitHub · 1,025 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. 11d ago First seen · 1,025 lines · 35 tokens per session scan A cbf6c8976fd2

Subscribe to this mod's changes

gsd-plan-checker is an agent published in the GitHub repository mrmyothet/zach-hair-studio (11 stars, last pushed 27d ago), licensed MIT. It adds 35 tokens to every session and 11,283 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 88% identical to gsd-plan-checker, differing in 96 lines, and is treated as a copy.