Jev · System One model · Real-time decisions

Decisions, not strings.

The game runs at 60 FPS in your browser. Every obstacle gets serialised into eight numbers and sent to Jev, which answers JUMP, DUCK or NONE. Nothing ever waits for the reply.

70–500ms

End-to-end

193.6×

Faster

444.6×

Cheaper

0

Hallucinations

Jev’s published figures. This page shows the part you can watch.

One question, two shapeslive
Jev0.000s
$ jev decide --frame 1042
Sending request to the parallel Jev API...
LLM0.000s
$ jev decide --frame 1042
Sending request to an autoregressive API.
Waiting for the first token...

Real time, not sped up. Jev’s and the chat model’s published completion times on the same System One task.

What Jev is

A frontier-intelligence function call: unstructured state in, typed decisions out. Named for Kahneman’s fast System 1 — and for Jevons, whose paradox says making something radically cheaper only multiplies its use.

 Chat modelSystem One
OutputA string you must parseA typed decision
SamplingToken by tokenEvery field in parallel
TrainingRLHF — human preferenceRLCD — calibrated decisions
FailureCan hallucinate anythingConstrained to the type
Zero hallucinationspublished
Structured output error ratelower is better
Jev-1.0Jev0.00%
GPT-5.6 LunaOpenAI0.49%
Gemini 3.1 ProGoogle1.92%
Claude Opus 5Anthropic3.76%
Claude Fable 5.1Anthropic7.99%
Claude Sonnet 5Anthropic12.60%
0%5%10%15%
How a jump happens
  1. 01Detect

    An obstacle crosses the decision zone.

  2. 02Serialise

    The world becomes eight numbers — no history, no pixels.

  3. 03Ask

    Once per obstacle, never per frame. The server owns the prompt.

  4. 04Answer

    JUMP, DUCK or NONE comes back. Nothing else is accepted.

  5. 05Act

    If the obstacle is still live it fires; if it has passed, the reply is dropped as stale.

You can throw an obstacle at the runner mid-run and watch Jev answer it.

The setup
Decision
JUMP · DUCK · NONE
Payload
Eight numbers
Cadence
One call per obstacle
Round trip
130–290 ms, measured
Inference
Served via Groq
Stack
Next.js 16 · React 19 · Canvas 2D

The runner, cacti and birds are Chrome’s dinosaur at 2× scale, redrawn as rectangles in code — none of Google’s image files are used, so the whole scene repaints when you switch themes.

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