We kept hitting the same failure mode with coding agents: you hand over a vague plan, the agent fills the gaps with guesses, and the back-and-forth that explains why a decision was made lives in a linear chat you can't navigate later. So we built inplan: a Markdown editor where you and the agent edit one plan document together.

The part we care most about: you can select any sentence and open a threaded comment on it — ask a question, get the agent's take, make the call — and that exchange stays anchored to that line as a durable record. When the agent changes the plan it comes back as a diff you review and apply, instead of silently rewriting the doc. It installs as a Claude Code skill (also Codex/Pi), so a "plan X" prompt opens the editor: the agent drafts, you refine inline, it revises.

It's open-core (AGPL-3.0) and runs fully locally — npm i -g inplan. There's a hosted edition (inplan.ai) for live multi-person collaboration, which is how we intend to fund it; nothing in the demo needs an account.

Where it's still young: it's an Electron desktop app, the diff is line-based, and it's built around one plan doc at a time — multi-doc and richer agent loops are next. The Windows install path was rough until last week.

60-second demo: https://github.com/melly-lgtm/inplan/releases/download/v0.1.18/inplan-demo.mp4

Would genuinely love feedback — especially where the workflow gets in your way.