TypeSafe JEV: System One Model Tutorial & Plugin Directory
TypeSafe JEV (released 2026-09-15) is the first "System One" model: instead of generating text, it returns typed decisions with calibrated probabilities. Built by ChatGPT co-inventor Diogo Almeida, JEV is 40-200x faster and 40-400x cheaper than traditional LLMs for code and automation tasks.
What makes JEV different
- No text generation: Returns typed decisions, scores, and probabilities that code can act on directly
- No hallucinations: Calibrated confidence scores mean you know when the model is uncertain
- ~150ms decision time: 40-200x faster than frontier LLMs
- Built for machines: Designed for automated workflows and code integration, not human conversation
- Use cases: Classification, routing, scoring, A/B testing, workflow automation
JEV ecosystem (top plugins by GitHub stars)
| # | Plugin | Stars | Description |
|---|---|---|---|
| 1 | awesome-jev fatwang2/awesome-jev | ⭐ 450 | Source-backed JEV project collection: classification experiments, A/B input comparison, conversation routing |
| 2 | jev-review (MCP Plugin) NiazMorshed2007/jev-review | ⭐ 280 | Local-first MCP plugin: structured feedback for Claude Code, Codex, Cursor, OpenCode |
| 3 | awesome-typesafe AbdelStark/awesome-typesafe | ⭐ 380 | Comprehensive curated list of official resources and community projects for TypeSafe |
Quick start: using JEV in your code
import { TypeSafe } from '@typesafe/client';
const client = new TypeSafe({ apiKey: process.env.TYPESAFE_API_KEY });
// Classification with calibrated confidence
const result = await client.classify({
input: "Is this customer support request urgent?",
labels: ["urgent", "normal", "low"],
});
console.log(result.decision); // "urgent"
console.log(result.confidence); // 0.94
console.log(result.probabilities); // { urgent: 0.94, normal: 0.05, low: 0.01 }When to use JEV vs traditional LLMs
Use JEV for:
- Classification tasks
- Routing decisions
- Scoring and ranking
- A/B testing analysis
- Workflow automation
- Real-time code integration
Use traditional LLMs for:
- Text generation
- Human conversation
- Creative writing
- Complex reasoning chains
- Long-form content
- Exploratory dialogue
Also see our JEV plugins & tools directory and DeepSeek Harness plugin directory for traditional LLM-based coding agents.