Treesum

Project intro

Treesum is an outline-first planning editor that wants to be "the Excalidraw of Excel": you write your plan as a plain-text tree, and the sums, timelines and statistics compute themselves. Values and formulas go in [square brackets] — [500], [120 * 4 + 20] — start dates and durations in {curly braces}, categories via #tags. Three live views — Calcs, Timeline, Stats — aggregate everything automatically: parent rows auto-sum their children, scheduling emerges from date annotations, and pivot-style stats need no formatting effort. Everything runs locally in the browser; a plan is saved permanently by downloading a human- and AI-readable '.tsum' text file, which can be reopened later. No backend, no account. The author, mallahan, is not a full-time developer. He wrote on Show HN (2026-10-13): "This software is entirely vibe-coded. It had to be — none of my developer friends would help me out. The front end JS on this app is too complex for a part time developer like myself." He had the idea for a while and "was only able to bring it to life because of AI", and he is a happy daily user himself. The live demo loads a full interactive tutorial editor, so you can try the concept in seconds.