GPT-5.6 Cyber vs Fugu Ultra v2 vs Claude Mythos 5
Too close to call on our weighted score (Fugu Ultra v2 33, Claude Mythos 5 33, GPT-5.6 Cyber 30). The right pick depends on what you value most.
OpenAIGPT-5.6 Cyber
30/100- ECI—
- Price$12.50 / $75.00
- Context400K
Sakana AIFugu Ultra v2
33/100- ECI—
- Price$5.00 / $30.00
- Context1M
AnthropicClaude Mythos 5
33/100- ECI—
- Price$10.00 / $50.00
- Context1M
Too close to call
It is close. Our weighted score puts them within a point (Fugu Ultra v2 33/100, Claude Mythos 5 33/100, GPT-5.6 Cyber 30/100), so choose by what matters most for your work: Fugu Ultra v2 on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceFugu Ultra v2Fugu Ultra v2 $11.25 · Claude Mythos 5 $20.00 · GPT-5.6 Cyber $28.13 per 1M tokens (3:1 blend)
- Longest contextFugu Ultra v2 and Claude Mythos 5Fugu Ultra v2 1,000,000 · Claude Mythos 5 1,000,000 · GPT-5.6 Cyber 400,000 tokens
- Widest inputsFugu Ultra v2 and Claude Mythos 5GPT-5.6 Cyber: Text, Images · Fugu Ultra v2: Text, Images, PDFs · Claude Mythos 5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.6 Cyber | Fugu Ultra v2 | Claude Mythos 5 |
|---|---|---|---|---|
| Price | 50% | 0 | 0 | 0 |
| Inputs & features | 30% | 70 | 70 | 70 |
| Context window | 20% | 44 | 60 | 60 |
| Overall | 100% | 30/100 | 33/100 | 33/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.6 CyberOpenAI | Fugu Ultra v2Sakana AI | Claude Mythos 5Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $12.50 | $5.00 (best) | $10.00 |
| Output | $75.00 | $30.00 (best) | $50.00 |
| Cached input | $1.25 | — | — |
| Blended (3:1) | $28.13 | $11.25 (best) | $20.00 |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official OpenAI API | Median of 6 providers | Median of 2 providers |
| Limits | |||
| Context window | 400,000 tokens | 1,000,000 tokens (best) | 1,000,000 tokens (best) |
| Max output | 128,000 tokens | 128,000 tokens | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | No | Yes | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yes | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | No | No |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-daybreak-red-latest | — | — |
| API providers | 1 | 6 (best) | 2 |
| Released | Aug 7, 2026 | Sep 11, 2026 | Jun 9, 2026 |
| Knowledge cutoff | Feb 16, 2026 | Aug 28, 2026 | Jan 31, 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-5.6 Cyber$275.00
- Fugu Ultra v2$110.00
- Claude Mythos 5$200.00
Which should you choose?
Which is better: GPT-5.6 Cyber, Fugu Ultra v2 or Claude Mythos 5?
It is close. Our weighted score puts them within a point (Fugu Ultra v2 33/100, Claude Mythos 5 33/100, GPT-5.6 Cyber 30/100), so choose by what matters most for your work: Fugu Ultra v2 on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, GPT-5.6 Cyber, Fugu Ultra v2 or Claude Mythos 5?
Fugu Ultra v2 is cheaper at $5.00 input / $30.00 output per million tokens (median across 6 API providers). Claude Mythos 5 costs $10.00 input / $50.00 output per million tokens (median across 2 API providers); GPT-5.6 Cyber costs $12.50 input / $75.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $11.25 per million tokens for Fugu Ultra v2 versus $20.00 for Claude Mythos 5 (1.8× as much) and $28.13 for GPT-5.6 Cyber (2.5× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. GPT-5.6 Cyber has not been scored yet, Fugu Ultra v2 has not been scored yet and Claude Mythos 5 has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.6 Cyber, Fugu Ultra v2 and Claude Mythos 5 yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. All three support tool calling for agent workflows.
Which has the bigger context window?
Fugu Ultra v2 and Claude Mythos 5 have the largest context windows (1,000,000 and 1,000,000 tokens), against 400,000 for GPT-5.6 Cyber. Maximum output per response: GPT-5.6 Cyber up to 128,000, Fugu Ultra v2 up to 128,000, Claude Mythos 5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.6 Cyber accepts text and images; Fugu Ultra v2 accepts text, images and PDFs; Claude Mythos 5 accepts text, images and PDFs. Fugu Ultra v2 handles the widest range of inputs.
Are any of these open source?
No. GPT-5.6 Cyber, Fugu Ultra v2 and Claude Mythos 5 are proprietary and only available through APIs and apps.
Which is newer?
Fugu Ultra v2 is the newest, released Sep 11, 2026. GPT-5.6 Cyber came out Aug 7, 2026; Claude Mythos 5 came out Jun 9, 2026. Knowledge cutoff: GPT-5.6 Cyber Feb 16, 2026, Fugu Ultra v2 Aug 28, 2026, Claude Mythos 5 Jan 31, 2026.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Nov 2, 2026.
