Introducing System One Models and Jev - TypeSafe AI Blog

Diogo Almeida, founder, TypeSafeModels have been superhuman at chat for years, so where is all the automation?This has been my driving question for the last four years. At OpenAI, I helped build the methods that made language models useful at following instructions and talking with people. That work ended up as the research behind ChatGPT.  At the time, I thought maybe chat models would lead to AGI, but despite the hype it became obvious to me that there was something really big missing.After two years in stealth, countless technical challenges, and research breakthroughs… I am beyond excited to announce that today, TypeSafe AI is releasing our first System One Model: a new class of frontier models built to make fast, structured decisions that software can use directly.We built a new stack entirely focused on automation: with a new model architecture, parallel sampler for maximum efficiency, and training method we call Reinforcement Learning for Calibrated Decisions (RLCD).Our first public model is Jev, available today in early access. Jev achieves similar levels of intelligence on System One tasks compared to existing LLMs, while being two orders of magnitude faster and more efficient. While Jev gives up string generation, it’s optimized for structured outputs and can’t hallucinate. Think of Jev as a frontier-intelligence function call: unstructured state in, typed probabilistic decisions out. Extraordinary claims require extraordinary evidence so see below for the receipts. 💅Frontiers, Old and NewExisting LLMsSystem One + JevOptimized withReinforcement Learning with Human Feedback (RLHF) / Reinforcement Learning with Verifiable Rewards (RLVR)Reinforcement Learning for Calibrated Decisions (RLCD)Optimizes forHuman preference: writeups and chat responses that human raters prefer.Verifiable rewards: outputs that can be programmatically verified.Calibrated decisions: answers with epistemically honest probabilities on System One tasks.InputsUnstructured data (e.g. text) with an emphasis on sequential messages.Unstructured data (e.g. text) with an emphasis on structured program state.OutputsStrings / generated text. Strings are flexible and can be anything: chat responses, code, hallucinations, refusals, or even type-safe structured values. To be used by software, responses need to be parsed + validated. There is also always some risk that the AI goes off the rails.Type-safe structured values. Possible outputs and structure are defined in advance. The model never makes type errors. All answers are accompanied with calibrated probabilities and confidence scores.SamplingSequential. Generates one token at a time, each conditioned on the last.Parallel. Generates all outputs in a single query. Incredibly efficient and hardware-aware.CostInput tokens: from $0.20 to $10 / MTok.Output tokens: ~5x more expensive than input tokens.Input tokens: $0.042 / MTok ($42 per billion tokens).Output tokens: FREE (too cheap to meter).SpeedEnd-to-end response time is 3 to 329 seconds for frontier models.  Fast enough for interfacing with humans, but a big bottleneck when integrated in code.End-to-end response time is 70ms-500ms for TypeSafe. This can range from 40x-200x faster for the same levels of frontier intelligence for System One shaped queries.ConfidenceEven if prompted for a confidence estimate, models tend to be overconfident and inconsistent. If a model can do a task 95% of the time but doesn’t say when it’s in the 5%, it can’t automate that task.Always communicates confidence and uncertainty with every output. Calibrated: higher confidence means higher accuracy. More consistent: returns similar answers for similar inputs.Use casesHuman-in-the-loop tasks (chatbots, copilots, coding agents). General and powerful, but requires human oversight because their freedom also means they might go off the rails.Verifiable problems (math proofs, kernel optimization). When correctness can be checked cheaply and automatically, LLMs can generate, test, and iterate until they find something that works.Demos. The flexibility of strings allows it to be incredible for quickly making prototypes that only work sometimes.AI-Powered Workflows / smart if-statements. Structured outputs slot into ordinary software as fuzzy decision rules: classify, route, score, extract, or branch where hand-written logic is too brittle. The surrounding code constrains their freedom, making them easier to compose into reliable systems.Map-reducing over big data. Turn petabytes of data into features and insights.Real-time applications. 100ms speeds means you can use AI in your applications where UX is critical.Verify everything. Score, judge, verify, guardrail, and detect jailbreaks of LLM prompts, reasoning traces, and/or outputs.Evidence / Technical ResultsWe love skeptics, and are skeptics ourselves.There are some claims you can easily verify:Speed per call: We truly are that fast, though our published evals are generally run from our laptops on the West Coast (this is where our service is currently based).Cost per call: We make our pricing transparent. We can’t prove it isn’t subsidized; we’ll need the long-term to prove the sustainability of our pricing (which we expect to go down, not up).No type errors: This would be an easy thing to falsify with just a single counter-example, but it is mathematically impossible.For our bolder claims, we want to provide as much nuance as we can.Side-by-side demonstrationOur side-by-side demo shows a key difference between our models and LLMs: Jev outputs all probabilities in parallel instead of autoregressively generating by token. Strings are extremely powerful and general, but costly. “Giving up” strings actually gives us a lot of superpowers!Nuance:For people with early access to TypeSafe, here is the actual query.The query is highly simplified and questions were chosen to have descriptive, human-readable keys so that the output on the screen is understandable.The state is also a short, dense, and detailed paragraph, to emphasize the difference in sampling methodology. The relatively shorter input paints our model in an advantageous light.For the keen eyed, for the recorded run, the only disagreement with GPT-5.6 Terra is on “Churn likelihood level”. The actual answer seems genuinely ambiguous to us.We used GPT-5.6 Terra with default reasoning for this example, because we’ve found it to be the most comparable at intelligence to Jev on average.Fun fact: a similar demo was what convinced us to go all-in in the direction of System One Models!Workflow evalsWe made a new type of evaluation to measure how well AI works within code. We don’t optimize for a ground truth classification orand allow the harness and model to change (potentially allowing for overfitting via harness engineering). Instead, we assume there is a correct compute graph (a “workflow” represented in code) and use the predictions of the largest, smartest, and most expensive external models as reference probabilities.Rephrased: every model gets the same workflow. We test how they compare to the average of the smartest models (in this case, Astra and Fable).Jev is off the charts – owning the Pareto frontier for almost 2 orders of magnitude. We also compare to models with a generated prompt doing all the logic in their chain-of-thought, but this tends to do significantly worse than using the workflow itself.Note that the calls here are significantly more complex than the side-by-side demonstration above. That’s because they’re more representative of the types of production workloads needed for true business automation. Below is the simplest of the 4 workflows we’re publishing:The most reliable real-world workflows tend to have many independent, decomposed questions, with fine-grained behavior that’s dependent on probabilities instead of discrete decisions. The end result is discrete branching, but how we get to a final answer involves a lot of domain-specific engineering that needs to be done highly consistently.See our workflow evals site for all the details: examples, disagreements, full queries, and each workflow.Nuance:This is where the claims of 193.6x faster, 444.6x cheaper on our home page comes from, and we expect that these are on the higher end of real world gains.These content of these workflows were not deliberately chosen nor constructed to make our model look good, and are not in our training distribution. However, they were made by individuals on our model capabilities team, so some bias could exist.We use the average of GPT-6 Astra and Fable 5.1 as the reference answer, which biases answers towards OpenAI and Anthropic’s models. We likely underestimate the relative performance of our model and DeepSeek’s models.The LLMs use our System One LLM wrapper, which constrains LLMs to output structured decisions compatible with our API. We have found this to be the most accurate way to get decisions from LLMs, but this tends to be slower and more expensive than giving decisions without probabilities.Hallucination and Type-safetyHallucination and type-safety are intrinsically related, and we think the latter is table stakes for automation. Having a hallucinated tool call is inconvenient in an agent, but is an absolute deal-breaker if it’s part of a system with latency guarantees or it’s buried several layers deep in a dependency chain. Existing models, no matter how smart, still hallucinate and have type errors.Nuance:The numbers for LLMs are from OpenRouter i.e., there almost certainly is bias here: more complex queries might be routed to better models.Our number is not empirical. Schema matching is guaranteed, thus we can confidently add 0% into the plots.Fun DemosPerhaps the most exciting part of our work is enabling new use cases. We have a lot more to show you, but here are a couple of the team’s favorites:DoomWe love how this doomo doomonstrates real-time intelligence and what can be doone with code + AI. The engineer behind it was worried about making