Show HN: Inplan – Before Start Coding Inplan, an open-source interactive planning editor for AI-assisted software development, introduces Planning-Driven Development (PDD) to help coding agents and humans collaborate on a versioned Markdown spec before code is written. The tool, available at inplan.ai and via npm as 'inplan', requires Node.js 22 or newer and bundles a desktop editor and agent skill for Claude Code, Pi, and Codex. It aims to reduce implementation drift and improve alignment between intent and code by allowing agents to draft plans, raise open questions inline, and apply revisions like a PR. Plan with your coding agent — before it writes the code. A Markdown workspace where you and your AI coding agent turn a vague ask into a real spec: the agent drafts, raises the open questions inline, you answer them in place, it revises, and you apply the diff like a PR. Think of it as vibe coding with a plan — the agent builds against a versioned spec instead of guessing from a fading chat. The hosted edition lives at inplan.ai ; this repo is the open core you can run yourself. InPlan Interactive Planning Editor brings structure and accountability to AI-assisted software development. While AI coding agents are excellent at generating code quickly, they struggle when requirements evolve, context grows, and decisions accumulate over time. Traditional AI coding workflows are built around linear conversations, making it difficult to track requirements, rationale, implementation status, and changes in a way that remains consistent as a project grows. InPlan introduces Planning-Driven Development PDD , where requirements become a living, collaborative document that evolves alongside the code. Inspired by the collaborative experience of document editors and code reviews, it enables teams to continuously refine plans, capture decisions, manage requirement updates separately from bug fixes, and maintain a reliable source of truth that neither humans nor AI agents can consistently hold in memory. The result is less implementation drift, safer refactoring, better alignment between intent and code, and a development process that remains adaptable without sacrificing correctness. Comment on a specific sentence and discuss it with the agent in a thread; when it revises the plan, review the diff and apply it like a PR. ▶ Watch with narration https://github.com/melly-lgtm/inplan/releases/download/demo-assets/inplan-demo.mp4 You and the agent edit one Markdown plan, like two people in a shared document: Draft the plan. Write requirements in Markdown. The agent proposes structure and raises open questions as inline comments. Refine together. Comment, answer, and revise. Accept the agent's changes automatically Auto-accept or vet each one Review ; work turn-by-turn Turn or in real time Instant . The plan converges into a shared decision record. Build with confidence. The agent implements against the agreed, versioned source of truth — so refactoring is safer and intent stays aligned with the code. Comments live in the document itself, so the plan and its rationale travel together and stay reviewable in Git. Requires Node.js 22 or newer. Install the CLI from npm — it bundles the desktop editor and the agent skill: npm install -g inplan inplan --version This puts the inplan command on your PATH, bundles the desktop editor launched by inplan open , and installs the agent skill into any coding agents it detects Claude Code, Pi, Codex — set INPLAN NO SKILL INSTALL=1 to skip, or run inplan install-skill later . A coding agent can self-install the same way: inplan --version || npm install -g inplan From source TypeScript monorepo, npm workspaces — for development: git clone https://github.com/melly-lgtm/inplan.git cd inplan npm install npm run build Packages: @inplan/core pure, embeddable editor + plan-format logic , @inplan/cli the inplan command — the agent's side of the loop , and @inplan/app the Electron editor — the human's side . Most users never need to configure anything, but for restricted networks, air-gapped/CI, or source checkouts see the environment variables reference /melly-lgtm/inplan/blob/main/docs/environment.md . You don't run inplan yourself — your coding agent does. There are two steps: 1. Install once — this also drops the agent skill into your coding agent Claude Code, Pi, Codex : npm install -g inplan 2. Ask your agent to plan , in plain language — for example: Let's plan a tic-tac-toe game. Plan the auth rewrite with me. The skill triggers on any "plan X" request: your agent writes