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Jev Pong

Pong where the ball advances one segment per model decision, run as four lanes so you can watch a typed-decision model keep up with a court that structured-output chat models cannot.

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1
Language
TypeScript
License
APACHE-2.0
Published by
Community
Author
ably-labs
Last verified
Oct 2026

ably-labs/jev-pong

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Pong where the ball moves one step per model decision. Jev vs LLMs via Vercel AI Gateway, every player and agent on an Ably channel.

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3
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Updated Oct 2026

Repo stats from the GitHub API, cached Oct 2026.Homepage

About this project

Pong where the ball moves one step per model decision. Slow model, slow ball. Play it: jev-pong.ably.dev, arrow keys or W/S, drag on a phone. The how page shows the real state and the real question every model gets. I'm Matt, co-founder of Ably. 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.

Quoted from the project's README. Read the full README.

Highlights

  • One decision moves the ball one segment; eight segments cross the court and nothing is sped up or skipped.
  • The model sees about 125 bytes of numbers and answers up, down or stay from one shared question.
  • The agent is a channel member alongside the player, publishing state after every decision instead of sitting behind a request.
  • Spectators attach to the same Ably channel, so human versus human needs no extra code.

Watch out

The author calls it a latency demo rather than an intelligence demo: in their runs the chat models answered the same question correctly 95 to 100 percent of the time and were slow because they answer in language. Model choice is therefore part of what you are looking at. In any mode where a human plays, a ball step never completes faster than 260 ms even if the model answers sooner, and the published latency is still the real round trip; only demo mode is unpaced. The browser predicts your own paddle the moment a key goes down and reconciles it only once a frame acknowledges your latest input, so what you see is not purely wire state. Jev reaches this through Vercel AI Gateway as typesafe-ai/jev with AI SDK 7.0.105 or later, and the record and compare endpoints require an admin token. Copy reviewed against the repository README on 2026-10-04, not from running it.

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