← Back to Writing

Build What Frustrates You: Reflections from YC's GStack Hackathon

May 2026

Short demo, two browsers, one session.

It's easy to spend 12 hours of a hackathon building the wrong thing. The hardest part isn't the building, it's the picking. Most projects die in the first hour of "what would be cool?" because cool is a terrible filter; you end up with a clever demo nobody, including you, will use again on Monday.

At YC's GStack x GBrain Hackathon, Boris Jabes, one of the visiting partners, offered the cleanest replacement I've heard for that question:

"Build what frustrates you."

It's a deceptively rigorous filter. If you're frustrated by something this week, the problem is real, the user (you) is reachable, and the success criterion is honest. You'll know if the fix works because you'll feel it relax in your own week. It cuts past the trap of building for an imaginary audience.

I'd just started my full-time job and the bulk of my day-to-day was inside Claude Code and Cursor CLI. Both made me dramatically faster on my own, but the moment I wanted to actually collaborate, the experience fell off a cliff. Everyone on a team tends to have a different preferred CLI (one of you wants Claude, the other Cursor, a third Gemini), and the "collaborative layer" doesn't exist for any of them. Even at hackathons, where the whole point is to build with people, working synchronously in a group should be easier with coding agents, not harder.

So that's what I built: nunu. A collaborative layer for any coding agent CLI. Pair programming, evolved into pair prompting.

nunu landing page with Docs-style tile grid (New session, From repo, Template, Join link) and a Recent grid below — The landing page. Start blank, from a GitHub repo, from a template, or join an existing link.

The flow is intentionally Google-Docs-simple. Open nunu in your browser, type a name (no email, no password), pick any CLI (Claude, Cursor, OpenCode, or Gemini), optionally clone a GitHub repo to start from, and you're in a session. You get a link to share.

An active nunu session with three collaborators, Claude editing files in the terminal, presence rail on the right — An active session. Three of us in the same room, Claude editing in the terminal, presence rail on the right showing who's where.

Send the link, your coworker opens it, types a name, and they're in the same terminal you are. You see each other's avatars, who's idle, who's typing in real time. Each session has its own tab strip. Anyone can hit +, pick a CLI, and spawn their own agent in the same workspace. So you can be running Claude while your coworker runs Cursor, both editing different files in the same repo, and everyone in the session sees both tabs live.

From a repo screen with paste URL on the left and pick from GitHub on the right — Starting from a repo. Paste any URL on the left, or pick straight from your GitHub on the right.

I'm planning to keep building nunu past the hackathon and ship a fully open-source initial version by the end of this month. If you live inside Claude Code or Cursor at work and you've felt the same frustration, that being a faster solo developer hasn't actually made it easier to collaborate, that's who I'm building it for.

Resources: github (coming soon)·gstack on GitHub·GStack x GBrain Hackathon