Jev Pong

# Jev Pong

Pong where the ball moves one step per model decision. Slow model, slow ball.



**Play it: [jev-pong.ably.dev](https://jev-pong.ably.dev)**, arrow keys or W/S, drag on a phone. The [how page](https://jev-pong.ably.dev/how) shows the real state and the real question every model gets.

## Why I built this

I'm Matt, co-founder of [Ably](https://ably.com). Jev landed on Vercel AI Gateway on September 16, 2026, and two days later this was playable, because the model is a string id and one AI SDK call.

I wanted to see one thing for myself: whether a model that answers in a couple of hundred milliseconds changes what an agent can be. Everything we've built with AI so far waits. Request and response waits for the answer. Streaming and background agents wait more gracefully. A model that decides inside human reaction time can be a participant in what you're doing right now, and a game is the least forgiving place to test that, because the ball doesn't wait.

This is a latency demo, not an intelligence demo. The chat models answered the same question correctly 95 to 100 percent of the time in our runs. They're slow because they answer with language, and this question doesn't need a paragraph. Jev is a typed-decision model, state in and a typed choice out, so it doesn't generate any. That's the whole difference, and it's enough to make the ball move.

The other half of the demo is how the agent takes part. It isn't behind a request. It's a member of the same Ably channel as the player: present, reading the paddle input, publishing the ball, watchable by anyone with the link. That's the pattern we think live agents need, and it's why the code is open.

## The numbers

Four lanes play the same game with a different model on the right paddle. Same serve, same rules, sa