Write an implementation plan as one interactive HTML page - a tree of claims (why › what › how › where), each proved by one exhibit (UI mockup, state machine, call stack, schema or code), with the decisions the user has to make placed on the claim they change. Use when the user types /html-plan, or asks for a plan, RFC or design before building something that touches more than a couple of files.
Install
npx skills add anthropics/claude-plugins-community --skill html-plannpx skills add anthropics/claude-plugins-community --skill html-plan -a claude-code -gnpx skills add anthropics/claude-plugins-community --skill html-plan -a codex -ggemini skills install https://github.com/anthropics/claude-plugins-community.git --path html-plan/skills/html-plangh skill install anthropics/claude-plugins-community html-plangit clone --depth 1 https://github.com/anthropics/claude-plugins-community /tmp/anthropics__claude-plugins-community
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/anthropics__claude-plugins-community/html-plan/skills/html-plan ~/.claude/skills/html-plan # Claude Code
cp -R /tmp/anthropics__claude-plugins-community/html-plan/skills/html-plan ~/.agents/skills/html-plan # Codex, Cursor, Gemini CLI, Copilot, OpenCode