Get started

Requirements

• Claude Code or Codex with filesystem access and command execution.
• Git and Python 3.10 or later available on PATH.
• A repository containing an implementation plan and its approved specification.
• Project dependencies already available for any rehearsal commands.
• A fresh independent reviewer for a Ready verdict. Without one, the report records the missing review and remains Not ready.

The initial release is verified on Linux. The manual shell commands below target Linux/macOS shells; native Windows installation has not been verified. The renderer has no third-party Python dependencies, API keys or account of its own. Your agent host may incur normal model charges.

Claude Code plugin

In your terminal:

claude plugin marketplace add snowholt-labs/plan-validation
claude plugin install plan-validation@snowholt-plugins
claude plugin list
claude plugin details plan-validation

Look for all three skills in the component inventory. Start a fresh session in your project. The plugin commands are:

/plan-validation:validation-args
/plan-validation:validate-plan
/plan-validation:revise-prompt

This is the project’s own marketplace, not Anthropic’s official directory. Installation follows the Claude marketplace mechanism.

To inspect locally before installing, clone the repository and run claude plugin validate . from its root. A temporary local session can load it with claude --plugin-dir /absolute/path/to/plan-validation.

Update or remove

claude plugin marketplace update snowholt-plugins
claude plugin update plan-validation@snowholt-plugins

Restart Claude Code after updating.

The repository moved from snowholt/plan-validation to snowholt-labs/plan-validation. Older installations still work through GitHub’s redirect, which stops if the old path is reused. Run claude plugin marketplace list; if snowholt-plugins shows the old source, add it again from the new location:

claude plugin marketplace remove snowholt-plugins
claude plugin marketplace add snowholt-labs/plan-validation
claude plugin install plan-validation@snowholt-plugins

To remove the plugin:

claude plugin uninstall plan-validation@snowholt-plugins

Your project’s plan/spec edits and saved reports remain your files. Review them separately; uninstalling a skill does not undo a validation.

Codex skills

Inside Codex, request all three skills from the built-in installer:

$skill-installer install validate-plan, validation-args and revise-prompt from https://github.com/snowholt-labs/plan-validation, using skills/validate-plan, skills/validation-args and skills/revise-prompt.

Resolve an existing installation instead of overwriting it. If skills do not appear, restart Codex. Invoke with $validation-args, $validate-plan and $revise-prompt. A packaged plugin may expose a namespace; use the exact name shown by its skill picker.

Manual clone and symlinks

Use this alternative when you want an inspectable checkout and straightforward updates. The script stops before creating anything if its destination paths are already in use. It does not replace existing skills.

bash <<'SH'
set -eu
pv_checkout="$HOME/.local/share/plan-validation-skills"
pv_skills="$HOME/.agents/skills"
for pv_path in "$pv_checkout" "$pv_skills/validate-plan" "$pv_skills/validation-args" "$pv_skills/revise-prompt"; do
  if [ -e "$pv_path" ] || [ -L "$pv_path" ]; then
    printf 'Already exists; inspect before installing: %s\n' "$pv_path" >&2
    exit 1
  fi
done
mkdir -p "$HOME/.local/share" "$pv_skills"
git clone https://github.com/snowholt-labs/plan-validation.git "$pv_checkout"
ln -s "$pv_checkout/skills/validate-plan" "$pv_skills/validate-plan"
ln -s "$pv_checkout/skills/validation-args" "$pv_skills/validation-args"
ln -s "$pv_checkout/skills/revise-prompt" "$pv_skills/revise-prompt"
SH

Codex supports user skills at ~/.agents/skills and follows symlinked skill folders. See the official skills documentation. The clone tracks main; inspect changes before updating. For a fixed pilot revision, check out v0.2.0 in the clone instead.

Update or disable

For the manual clone on main:

git -C "$HOME/.local/share/plan-validation-skills" pull --ff-only

A clone made before the move to snowholt-labs/plan-validation can point at the new location first:

git -C "$HOME/.local/share/plan-validation-skills" remote set-url origin https://github.com/snowholt-labs/plan-validation.git

An installer-created copy does not follow that clone. Use the installer to prepare a replacement version after preserving any local changes; do not overwrite a customized skill without reviewing the diff.

To disable a skill without deleting it, add a [[skills.config]] entry to your existing ~/.codex/config.toml, using the exact absolute SKILL.md path shown by Codex, with enabled = false. Preserve the rest of your configuration and restart Codex. Official enable/disable guidance.

To remove the manual symlink installation, first verify that each path is a symlink to this clone. Remove those three symlinks only; keep the clone if it contains changes. Do not delete a skill folder from another installation. The built-in installer route may use a different user skill location; inspect its actual installed path.

Plugin package for Codex

The repository includes .codex-plugin/plugin.json, referencing the same skills/ directory. It is a compatibility package for hosts that support that layout. The first-release quick start uses standalone skills; live Codex plugin installation and public directory acceptance are not claimed. See OpenAI plugin packaging for current host-specific authoring and submission routes.