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Jev & System One models

Jev vs Claude, ChatGPT, Grok and Gemini: which to use for what

A decision model and four chat families, priced on the same job and matched to the work each one is actually good at.

By Warren Leow 2026-09-21 9 min read
Cost per million decisions across Jev, Claude, ChatGPT, Grok and Gemini

Short answer: Jev is not really competing with Claude, ChatGPT, Grok or Gemini. Those are chat models that write, reason and explain. Jev refuses to write anything and returns a typed decision instead. For a million routine decisions it costs about $21 against roughly $112 on GPT-5.6 Luna, $175 on Gemini 3.5 Flash-Lite, $550 on Claude Haiku 4.5, $1,060 on Grok 4.6 and $5,500 on GPT-6 Astra. But only the chat models can tell you why, and only they can produce text at all.

So the useful question is not “which model is best”. It is which of your jobs are decisions and which are language. Most systems have both.

What a million decisions costs on each

ModelInput $/MTokOutput $/MTok1M decisions*Explains itself?Notes
Jev (TypeSafe)$0.042Free~$21NoTyped decisions only
GPT-5.6 Luna$0.20$1.20~$112YesOpenAI's cheap tier
Gemini 3.5 Flash-Lite$0.30$2.50~$175YesGoogle's high-volume tier
Gemini 3.8 Flash$0.75$3.75~$413YesPromotional rate to 31 Dec 2026
Claude Haiku 4.5$1.00$5.00~$550YesAnthropic's fast tier
Grok 4.6$2.00$6.00~$1,060YesxAI flagship; $0.50 cached input
Claude Sonnet 5$2.00$10.00~$1,100YesBalanced workhorse
GPT-5.6 Terra$2.00$12.00~$1,120YesMid tier
Claude Opus 5$5.00$25.00~$2,750YesFrontier reasoning
GPT-6 Astra$10.00$50.00~$5,500YesOpenAI flagship

*One decision = ~500 input tokens and a short output. Jev's output tokens are free. List prices from Anthropic, OpenAI, xAI and Google, checked 21 September 2026; promotional rates and cached-input discounts are noted where they apply.

Two things stand out. The gap between Jev and a frontier model is enormous, roughly 260x against GPT-6 Astra. But the gap against the cheap tiers is far less dramatic: Luna and Flash-Lite come in at five to eight times Jev's price while still writing text and explaining themselves. At 50,000 decisions a month that difference is a few dollars. It only becomes an argument in the millions.

What each family is actually for

  • Claude (Anthropic) — Opus 5 for hard reasoning and long agentic work, Sonnet 5 as the workhorse, Haiku 4.5 when speed and cost matter. Strong on following instructions and structured output, which is why it is the usual baseline when teams test a decision model. See Claude vs ChatGPT.
  • ChatGPT / OpenAI — GPT-6 Astra at the top, the GPT-5.6 tiers below it, and Luna as the genuinely cheap option for high-volume work. The widest ecosystem, and the tier most likely to be your real alternative to a decision model on price.
  • Grok (xAI) — Grok 4.6 and 4.5 at $2 input and $6 output, with heavy caching discounts and very large context windows. Its differentiator is real-time access to X data rather than price.
  • Gemini (Google) — Flash-Lite is the cheap high-volume tier, the Flash models sit above it, and everything is wired into Google Cloud and Workspace. If your data already lives there, that integration usually outweighs a small price gap. See our Gemini training.
  • Jev (TypeSafe) — not a chat model at all. One job: return a typed decision with a calibrated probability, in 70 to 500 milliseconds, with an output shape that cannot be malformed.

For a fuller comparison of the chat families themselves, see the frontier model comparison.

Which one for which job

The jobWhat to useWhy
Draft a reply to a customerA chat modelJev cannot produce a single word of text
Decide which queue that customer goes toJev, or a cheap chat tierA label is the whole answer
Summarise a 40-page reportA chat model with a long contextJev's window is 32k and it does not write
Decide whether the summary is on policyJevA yes/no with a probability, thousands of times a day
Explain a decision to a regulatorA chat model, or a humanJev returns no rationale at all
Gate a risky tool call inside an agentJevNeeds milliseconds, and the answer is binary
Work out why a campaign underperformedA frontier modelOpen-ended reasoning across messy inputs
Score 50,000 survey responsesJev or a cheap chat tierVolume makes the price difference real

On accuracy, nobody has the clean answer yet

Published third-party tests since launch are small and mixed. On synthetic phishing emails, one broad Jev question scored 62.6% against Claude Haiku 4.5's 81.3%; the same judgement split into five narrow questions put Jev at 95.0% against Haiku's 93.2%. On a 50-case event-screening set, Jev scored 96% against Gemini 3.5 Flash-Lite's 86%. On spam, Jev's 98.33% was level with a plain TF-IDF baseline at 98.39%. Sample sizes are small, several datasets were synthetic, and TypeSafe has published no calibration curves.

The honest summary: on narrow, well-framed questions a decision model is competitive with a cheap chat model and much faster. On one broad question it is worse. Nothing here justifies replacing a working system without testing on your own labelled data. Our detailed comparison includes the fine-tuned-classifier and plain-rules baselines too, which matter more than most vendor benchmarks admit.

The practical setup

A stack that uses each model where it is strongest

  1. 1
    Rules first
    Whatever can be decided by a keyword, a domain match or an amount threshold should never reach a model. Free, instant, auditable.
  2. 2
    A decision model for the repeated judgement
    Routing, triage, scoring, guardrails. Ask several narrow questions, not one broad one, and keep the confidence value.
  3. 3
    A cheap chat tier for the grey zone
    Luna, Flash-Lite or Haiku when the case is uncertain and you want a short explanation in the log.
  4. 4
    A frontier model for the genuinely hard work
    Writing, multi-step reasoning, anything a person will read. This is where the quality difference is worth the price.
  5. 5
    A human for anything you must justify
    Regulated decisions, dismissals, credit, medical. Models prioritise the queue; people decide.

One caution on availability

Claude, ChatGPT, Grok and Gemini are generally available, with published rate limits and support. Jev is in early access behind a waitlist, its architecture is undisclosed, it offers no fine-tuning, and TypeSafe says openly it cannot prove the price is unsubsidised. That is a fine basis for a pilot and a weak basis for a dependency. Build the decision layer so the model behind it can be swapped, and you keep the option either way.

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Frequently Asked Questions

Not better, different. Jev only returns typed decisions such as a category, a score or a yes/no probability, and cannot write, summarise or explain. Claude, ChatGPT, Grok and Gemini do all of that. For high-volume routine decisions Jev is far cheaper and faster; for anything involving language or a rationale it cannot do the job at all. Most production systems end up using both.

On list prices in September 2026, Jev at $0.042 per million input tokens with free output is the cheapest hosted option: about $21 per million decisions of roughly 500 tokens each. The cheap chat tiers follow at about $112 on GPT-5.6 Luna and $175 on Gemini 3.5 Flash-Lite, then $550 on Claude Haiku 4.5. A rule you write yourself is still cheaper than all of them, and a self-hosted classifier can be cheaper at very high volume.

Grok 4.6 and 4.5 are listed at $2 per million input tokens and $6 per million output, which puts a million decisions around $1,060, with cached input as low as $0.50 per million. Prices double for prompts of 200,000 tokens or more. Grok's advantage is its very large context and real-time access to X data rather than cost, so for plain classification the cheaper tiers from OpenAI and Google make more sense.

Yes, and that is the intended pattern. Use the decision model for the many small judgements in your workflow, such as routing, screening and gating tool calls, and pass only the cases that need language or reasoning to a chat model. LangChain's own write-up frames Jev as the fast layer inside an agent loop, deciding when the expensive model is needed rather than replacing it.

Only after testing. Published third-party results are mixed: Jev beat Claude Haiku 4.5 when the judgement was split into several narrow questions, and lost badly on one broad question. It is also in early access behind a waitlist, offers no fine-tuning, gives no explanations, and the vendor says the price may be subsidised. Pilot it in parallel with your current setup on a few hundred labelled cases before anything depends on it.

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