gsd-plan-checker

An agent that checks whether a software project plan is likely to achieve its stated phase goal before implementation begins.

In plain words
What is it for?
Use it to review implementation plans and verify that their tasks, dependencies, and outputs cover the requirements.
Why use it?
It helps find missing tasks, broken dependencies, disconnected deliverables, contradictions, or plans that are too large to execute reliably.

Agent for Claude Code

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.

agentmods
npx agentmods add agents/bitflight-devops/skilllint/gsd-plan-checker
Clone the repo
git clone --depth 1 https://github.com/bitflight-devops/skilllint

Made for: Claude Code.

Per session 36 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 5,703 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 97% 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 $0.00036 $0.05703
Opus 5 $0.00018 $0.02851
Sonnet 5 $0.00007 $0.01141
Haiku 4.5 $0.00004 $0.00570

Measured 2d ago against content hash b8617b338bc8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 2d 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

97% identical to gsd-plan-checker — 12 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.

.claude/agents/gsd-plan-checker.md · 709 lines

How it starts

The opening of the file, as written. The whole thing — 709 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 <files_to_read> 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.

<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? </upstream_input>

<core_principle> Plan completeness =/= Goal achievement

A task "create auth endpoint" can be in the plan while password hashing is missing. The task exists but the goal "secure authentication" won't be achieved.

Goal-backward verification works backwards from outcome:

  1. What must be TRUE for the phase goal to be achieved?
  2. Which tasks address each truth?
  3. Are those tasks complete (files, action, verify, done)?
  4. Are artifacts wired together, not just created in isolation?
  5. Will execution complete within context budget?

Then verify each level against the actual plan files.

The difference:

  • gsd-verifier: Verifies code DID achieve goal (after execution)
  • gsd-plan-checker: Verifies plans WILL achieve goal (before execution)

Same methodology (goal-backward), different timing, different subject matter. </core_principle>

<verification_dimensions>

Dimension 1: Requirement Coverage

Question: Does every phase requirement have task(s) addressing it?

Process:

  1. Extract phase goal from ROADMAP.md
  2. Extract requirement IDs from ROADMAP.md **Requirements:** line for this phase (strip brackets if present)
  3. Verify each requirement ID appears in at least one plan's requirements frontmatter field
  4. For each requirement, find covering task(s) in the plan that claims it
  5. Flag requirements with no coverage or missing from all plans' requirements fields

FAIL the verification if any requirement ID from the roadmap is absent from all plans' requirements fields. This is a blocking issue, not a warning.

Read the full file on GitHub · 709 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. 2d ago First seen · 709 lines · 36 tokens per session scan A b8617b338bc8

Subscribe to this mod's changes

gsd-plan-checker is an agent published in the GitHub repository bitflight-devops/skilllint (6 stars, last pushed 2d ago), licensed MIT. It adds 36 tokens to every session and 5,703 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to gsd-plan-checker, differing in 12 lines, and is treated as a copy.