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PLUS ULTRAModel ReleasesTypeSafe AIDiogo AlmeidaJevSystem One

TypeSafe AI Unveils System One Models and Jev for High-Speed Structured Decision-Making

PLUS ULTRA by Amenoyomi

TypeSafe AI, led by founder Diogo Almeida, a former researcher at OpenAI, announced the release of System One models and its first public model, Jev, on September 15, 2026. These models are engineered to facilitate automation by providing fast, structured decisions that software can consume directly.

Unlike traditional large language models (LLMs) that generate text token by token, System One models utilize a new architecture, a parallel sampler, and a training method called Reinforcement Learning for Calibrated Decisions (RLCD). The Jev model is specifically optimized for structured outputs rather than string generation, which allows it to be up to 200 times faster and more efficient than existing frontier models for System One-shaped queries.

Jev provides type-safe structured values, meaning the outputs follow a predefined structure without type errors. Every response includes calibrated probabilities and confidence scores to communicate uncertainty. While Jev sacrifices general text generation, it is designed to eliminate hallucinations in structured decision-making. The model is currently available through an early access program.

PLUS ULTRAby Amenoyomi

The design of System One models is inspired by Daniel Kahneman's dual-process theory, specifically the distinction between fast, intuitive "System 1" thinking and slow, deliberate "System 2" reasoning. While traditional LLMs function as System 2 models by autoregressively generating tokens one by one, Jev is designed to act as a "frontier-intelligence function call" that handles unstructured state as input and produces typed probabilistic decisions as output.

This shift in architecture is driven by a parallel sampler and a training method called Reinforcement Learning for Calibrated Decisions (RLCD). Rather than optimizing for human preference in chat responses, RLCD optimizes for epistemically honest probabilities. Because the model generates all outputs in a single query instead of sequentially, it achieves response times between 70ms and 500ms, making it 40 to 200 times faster than existing frontier models for specific decision-based queries.

The elimination of string generation allows Jev to ensure that outputs are mathematically type-safe. By defining possible outputs and structures in advance, the model removes the risk of type errors and structural hallucinations that often occur in traditional LLM tool calls. Every output is accompanied by a calibrated confidence score, meaning higher confidence directly correlates with higher accuracy, which is a prerequisite for reliable software automation.

These capabilities enable the use of AI as "smart if-statements" within production code, where the model can classify, route, or branch based on fuzzy decision rules. Examples include real-time applications like playing DOOM, where the model reacts to game state at 10 queries per second, and high-cardinality navigation tasks such as traversing Wikipedia links, where the model must choose between hundreds or thousands of options without hallucinating the destination. For choices exceeding a cardinality of 255, the system employs a two-stage process of independent scoring followed by an explicit choice.

Sources

  1. Introducing System One Models and Jev (Hacker News Frontpage, 2026-09-15)
  2. TypeSafe Documentation
1 more sourcesHide sources
  1. ChatGPT共同開発者がLLMとは異なる方法で処理するAIモデル「Jev」を開発、GPT-5.6 Terra級の性能でタスクを安価かつ超高速に実行可能 (GIGAZINE, 2026-09-16)