Fugu Ultra vs GPT-5.5
Fugu Ultra (2026) and GPT-5.5 (2026) are frontier-tier reasoning models from Sakana AI and OpenAI. Fugu Ultra ships a 1m-token context window, while GPT-5.5 ships a 1.05m-token context window. On SWE-bench Pro, Fugu Ultra leads by 15.1 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Pick Fugu Ultra for coding; token pricing is tied, so keep GPT-5.5 only for already-validated prompts or route constraints.
Decision scorecard
Local evidence first| Signal | Fugu Ultra | GPT-5.5 |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 1.05m |
| Cheapest output | $30/1M tokens | $30/1M tokens |
| Provider routes | 2 tracked | 4 tracked |
| Shared benchmarks | SWE-bench Pro leader | 4 shared |
Decision tradeoffs
- Fugu Ultra holds a shared-benchmark lead on SWE-bench Pro, ahead by 15.1 points.
- Local decision data tags Fugu Ultra for Coding, RAG, and Agents.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 has broader tracked provider coverage for fallback and procurement flexibility.
- GPT-5.5 uniquely exposes Code execution in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Fugu Ultra
$11,500
Cheapest tracked route/tier: Sakana AI <=272K tokens
GPT-5.5
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
Estimated monthly gap: $0.00. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on Vercel AI Gateway; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- GPT-5.5 adds Code execution in local capability data.
- Provider overlap exists on Vercel AI Gateway; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- Check replacement coverage for Code execution before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-06-22 | 2026-04-23 |
| Context window | 1m | 1.05m |
| Parameters | — | — |
| Architecture | Composition of Experts | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | - | 2025-12 |
Pricing and availability
| Pricing attribute | Fugu Ultra | GPT-5.5 |
|---|---|---|
| Input price |
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| Output price |
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| Providers |
Capabilities
| Capability | Fugu Ultra | GPT-5.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Fugu Ultra | GPT-5.5 |
|---|---|---|
| SWE-bench Pro | 73.7 | 58.6 |
| Google-Proof Q&A | 95.5 | 93.6 |
| Humanity's Last Exam | 50.0 | 41.4 |
| Terminal-Bench 2.1 | 82.1 | 78.2 |
Deep dive
On shared benchmark coverage, SWE-bench Pro has Fugu Ultra at 73.7 and GPT-5.5 at 58.6, with Fugu Ultra ahead by 15.1 points; Google-Proof Q&A has Fugu Ultra at 95.5 and GPT-5.5 at 93.6, with Fugu Ultra ahead by 1.9 points; Humanity's Last Exam has Fugu Ultra at 50 and GPT-5.5 at 41.4, with Fugu Ultra ahead by 8.6 points. The largest visible gap is 15.1 points on SWE-bench Pro, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on code execution: GPT-5.5. Both models share vision, multimodal input, reasoning mode, and function calling, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Fugu Ultra lists tiered pricing: <=272K tokens is $5/1M input and $30/1M output; >272K tokens is $10/1M input and $45/1M output, while GPT-5.5 lists tiered pricing: 0-272K input tokens is $5/1M input and $30/1M output; 272K+ input tokens is $8/1M input and $36/1M output. A 70/30 input-output blend is tied on the cheapest tracked routes. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 2 providers versus 4, so concentration risk also matters.
Choose Fugu Ultra when vision-heavy evaluation are central to the workload. Choose GPT-5.5 when coding workflow support, larger context windows, and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Fugu Ultra or GPT-5.5?
GPT-5.5 supports 1.05m tokens, while Fugu Ultra supports 1m tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is cheaper, Fugu Ultra or GPT-5.5?
Neither is cheaper on tracked token pricing. Both list $5/1M input and $30/1M output tokens on the cheapest tracked route. Provider discounts, batch pricing, or route-specific tiers can still change the final bill.
Is Fugu Ultra or GPT-5.5 open source?
Fugu Ultra is listed under Proprietary. GPT-5.5 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Fugu Ultra or GPT-5.5?
Both Fugu Ultra and GPT-5.5 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Fugu Ultra or GPT-5.5?
Both Fugu Ultra and GPT-5.5 expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run Fugu Ultra and GPT-5.5?
Fugu Ultra is available on Sakana AI and Vercel AI Gateway. GPT-5.5 is available on OpenAI API, OpenRouter, Vercel AI Gateway, and AWS Bedrock. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-22. Data sourced from public model cards and provider documentation.