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Sakana AI

Fugu Ultra

Fugu Ultra is Sakana AI's quality-maximizing multi-agent system released June 21, 2026. Behind a single model API, Fugu Ultra coordinates a pool of expert agents to solve hard, multi-step problems. Available through AI Gateway with unified billing, observability, and provider routing.

Vision (Image)Tool UseReasoning
index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'sakana/fugu-ultra',
  prompt: 'Why is the sky blue?'
})
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About Fugu Ultra

Fugu Ultra was released June 21, 2026 as Sakana AI's premium tier in the Fugu line. Instead of answering with a single network, Fugu Ultra runs a multi-agent system behind one model API. A lightweight coordinator assigns Thinker, Worker, and Verifier roles across a pool of frontier models, then routes between one and three agents depending on the problem. The approach builds on Sakana AI's published TRINITY and Conductor research.

Sakana AI tuned Fugu Ultra for maximum answer quality rather than low latency, drawing on a deeper, fixed agent pool and spending more compute per request. Early users applied Fugu Ultra to AI research, paper reproduction, cybersecurity analysis, and literature and patent investigations. In Sakana AI's published evaluations, Fugu Ultra scores 73.7 on SWE-Bench Pro, 95.5 on GPQA-Diamond, and 50.0 on Humanity's Last Exam.

Fugu Ultra supports a context window of 1M tokens with output up to 1M tokens, plus prompt caching for repeated context. Through AI Gateway, you call Fugu Ultra with a unified API key, automatic retries, and built-in observability, using the AI SDK, Chat Completions API, Responses API, Messages API, or other API formats.