GPT-5.6 Cyber vs Claude Mythos 5 vs Fugu Ultra
Claude Mythos 5 comes out ahead, 36 to 33 and 30 on our weighted score, though Fugu Ultra is 44% cheaper per token.
OpenAIGPT-5.6 Cyber
30/100- ECI—
- Price$12.50 / $75.00
- Context400K
- Our pick
AnthropicClaude Mythos 5
36/100- ECI—
- Price$10.00 / $50.00
- Context1M
Sakana AI
Fugu Ultra
33/100- ECI—
- Price$5.00 / $30.00
- Context1M
Claude Mythos 5 is our pick
Claude Mythos 5 is the better all-round choice, scoring 36/100 against Fugu Ultra (33) and GPT-5.6 Cyber (30). It leads on inputs & features. 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 UltraFugu Ultra $11.25 · Claude Mythos 5 $20.00 · GPT-5.6 Cyber $28.13 per 1M tokens (3:1 blend)
- Longest contextClaude Mythos 5 and Fugu UltraClaude Mythos 5 1,000,000 · Fugu Ultra 1,000,000 · GPT-5.6 Cyber 400,000 tokens
- Widest inputsClaude Mythos 5GPT-5.6 Cyber: Text, Images · Claude Mythos 5: Text, Images, PDFs · Fugu Ultra: Text, Images
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.6 Cyber | Claude Mythos 5 | Fugu Ultra |
|---|---|---|---|---|
| Price | 50% | 0 | 0 | 0 |
| Inputs & features | 30% | 70 | 80 | 70 |
| Context window | 20% | 44 | 60 | 60 |
| Overall | 100% | 30/100 | 36/100 | 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 | Claude Mythos 5Anthropic | Fugu UltraSakana AI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $12.50 | $10.00 | $5.00 (best) |
| Output | $75.00 | $50.00 | $30.00 (best) |
| Cached input | $1.25 | — | $0.50 (best) |
| Blended (3:1) | $28.13 | $20.00 | $11.25 (best) |
| Long-context rate | Same rate | Same rate | Over 272K: $10.00 / $45.00 |
| Price source | Official OpenAI API | Median of 2 providers | Official Sakana AI API |
| Limits | |||
| Context window | 400,000 tokens | 1,000,000 tokens (best) | 1,000,000 tokens (best) |
| Max output | 128,000 tokens | 128,000 tokens | — |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | No | Yes | No |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yes | Yeshigh · xhigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-daybreak-red-latest | — | fugu-ultra |
| API providers | 1 | 2 | 11 (best) |
| Released | Aug 7, 2026 | Jun 9, 2026 | Jun 15, 2026 |
| Knowledge cutoff | Feb 16, 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
- Claude Mythos 5$200.00
- Fugu Ultra$110.00
Which should you choose?
Which is better: GPT-5.6 Cyber, Claude Mythos 5 or Fugu Ultra?
Claude Mythos 5 is the better all-round choice, scoring 36/100 against Fugu Ultra (33) and GPT-5.6 Cyber (30). It leads on inputs & features. 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, Claude Mythos 5 or Fugu Ultra?
Fugu Ultra is cheaper at $5.00 input / $30.00 output per million tokens (official Sakana AI API price). 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 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, Claude Mythos 5 has not been scored yet and Fugu Ultra has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.6 Cyber, Claude Mythos 5 and Fugu Ultra 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?
Claude Mythos 5 and Fugu Ultra 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, Claude Mythos 5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.6 Cyber accepts text and images; Claude Mythos 5 accepts text, images and PDFs; Fugu Ultra accepts text and images. Claude Mythos 5 handles the widest range of inputs.
Are any of these open source?
No. GPT-5.6 Cyber, Claude Mythos 5 and Fugu Ultra are proprietary and only available through APIs and apps.
Which is newer?
GPT-5.6 Cyber is the newest, released Aug 7, 2026. Fugu Ultra came out Jun 15, 2026; Claude Mythos 5 came out Jun 9, 2026. Knowledge cutoff: GPT-5.6 Cyber Feb 16, 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 Oct 4, 2026.
