Jev vs Clef: Which Decision Model Fits Your Workload?

Screenshots, product photos or scanned forms in the state: Clef. Classmethod reports it takes up to four PNG, JPEG or WebP images per request, each up to 4 MiB, and no remote URLs. Jev accepts text and JSON only, so you would need a captioning step first.

Short text states at high volume: Clef Flash. At $0.038 per million tokens it is the cheaper hosted option per token. Its 24,576-token window is the limit to check.

Long text states: Jev. A 100,000-token case file fits Jev's window at $0.0042 per decision. It does not fit any Clef model.

On OpenRouter, Clef's rate is 4.57 times Jev's ($0.192 ÷ $0.042). The models use different tokenizers, so the same comment can count as a different number of tokens on each. The per-request ratio can differ from the rate-card ratio in either direction.

Two write-ups tried to measure it, at Workers AI's early-October Clef price rather than OpenRouter's. Better Stack wrote that, based on average comment length, Jev was 6.5x cheaper per comment than standard Clef. The DEV Community author estimated about 4x per decision after counting tokens. Treat 4x to 6.5x as the range, and count your own tokens.

A DEV Community author ran 117 labelled cases from five production decisions, three calls each. At thresholds set for Jev, Clef scored 92.3%, Jev 88.6% and Clef Flash 82.1%. With each model's own threshold chosen on held-out cases, the scores were 93.2%, 90.9% and 90.6%. The author reports Clef's 3.7-point lead had a 95% interval of -1.1 to +8.8 points, which is not significant.

Better Stack's comparison found the reverse: Jev matched its referee 86% of the time and Clef 83%, with Clef ahead on three of five questions. Neither test is large. Together they say the two models are close, and your questions decide the winner.

Cloudflare's own run of the Jev Decision Index reports median model-side latency of 209.3 ms for Clef, 38.8 ms for Clef Flash and 524.1 ms for Jev. Developers Digest labels these vendor-run figures, and so do we.

Client-side numbers point the other way. Classmethod's author timed five runs from their own machine: Jev 0.238 s, Clef Flash 0.294 s and Clef 0.478 s, and says that is too few to be firm. Better Stack found Jev returned results nearly twice as fast as Clef. If latency matters, time calls from your own region.

The DEV Community test sent each case three times. Clef returned the same probability, to four decimal places, on all 351 calls. Jev's probabilities moved between identical calls by up to 0.10.

That matters if your code acts at a cutoff such as 0.80. With a 0.10 swing, a case near the line can go one way on Monday and the other way on Tuesday. With Jev, keep a band around the threshold that goes to a stronger model or a person.

Classmethod reports Clef's API is compatible with Jev's: change the endpoint, key and model name. On Workers AI's REST API the response wraps results in a result field, so Jev code needs a small change there. Through OpenRouter, both sit behind the same key.

Clef's weights are on Hugging Face under Apache 2.0, and Classmethod notes you can run them on your own GPU. Developers Digest adds that the training data and pipeline are not published. Jev has no weights to download. If leaving a hosted vendor later matters to you, that favours Clef.

At a 500-token state, each model's monthly bill is decisions × 500 tokens × its rate. At 100,000 decisions a month: Clef Flash $1.90, Jev $2.10, Clef $9.60. At 1 million: $19, $21 and $96. At 10 million: $190, $210 and $960. At 50 million: $950, $1,050 and $4,800.

Below a million decisions a month, the gap between Jev and either Clef is too small to drive the choice. At 10 million it is $750 a month between Jev and standard Clef, or $9,000 a year. At that point, check whether Clef's lead on one small test is worth it. These sums assume both models count your text as the same number of tokens. They may not, as the tokenizer section explains.

Thresholds come first. A cutoff tuned on Jev's probabilities will not carry over to Clef, because the two models spread their probabilities differently. The DEV Community test shows how much the threshold matters: Clef Flash scored 82.1% at Jev's thresholds and 90.6% at its own.

Then check what each decision point sends. Any state over 24,576 tokens cannot go to Clef Flash. Any state over 65,537 tokens cannot go to Clef. Any decision with images cannot stay on Jev.