GPT-5.6 Cyber vs Claude Mythos 5 vs Seed 2.1 Pro
Seed 2.1 Pro comes out ahead, 50 to 36 and 30 on our weighted score, and it is the cheaper option too.
OpenAIGPT-5.6 Cyber
30/100- ECI—
- Price$12.50 / $75.00
- Context400K
AnthropicClaude Mythos 5
36/100- ECI—
- Price$10.00 / $50.00
- Context1M
- Our pick
ByteDance SeedSeed 2.1 Pro
50/100- ECI—
- Price$0.891 / $4.45
- Context256K
Seed 2.1 Pro is our pick
Seed 2.1 Pro is the better all-round choice, scoring 50/100 against Claude Mythos 5 (36) and GPT-5.6 Cyber (30). It leads on price. Claude Mythos 5 wins on context window. 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 priceSeed 2.1 ProSeed 2.1 Pro $1.78 · Claude Mythos 5 $20.00 · GPT-5.6 Cyber $28.13 per 1M tokens (3:1 blend)
- Longest contextClaude Mythos 5Claude Mythos 5 1,000,000 · GPT-5.6 Cyber 400,000 · Seed 2.1 Pro 256,000 tokens
- Widest inputsClaude Mythos 5 and Seed 2.1 ProGPT-5.6 Cyber: Text, Images · Claude Mythos 5: Text, Images, PDFs · Seed 2.1 Pro: Text, Images, Video
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.6 Cyber | Claude Mythos 5 | Seed 2.1 Pro |
|---|---|---|---|---|
| Price | 50% | 0 | 0 | 38 |
| Inputs & features | 30% | 70 | 80 | 80 |
| Context window | 20% | 44 | 60 | 36 |
| Overall | 100% | 30/100 | 36/100 | 50/100 |
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 | Seed 2.1 ProByteDance Seed |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $12.50 | $10.00 | $0.891 (best) |
| Output | $75.00 | $50.00 | $4.45 (best) |
| Cached input | $1.25 | — | $0.178 (best) |
| Blended (3:1) | $28.13 | $20.00 | $1.78 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official OpenAI API | Median of 2 providers | Official Volcengine Ark API |
| Limits | |||
| Context window | 400,000 tokens | 1,000,000 tokens (best) | 256,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens | 256,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | No | Yes | No |
| Audio | No | No | No |
| Video | No | No | Yes |
| Reasoning | Yeslow · medium · high · xhigh · max | Yes | Yesminimal · low · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-daybreak-red-latest | — | doubao-seed-2-1-pro-260628 |
| API providers | 1 | 2 (best) | 2 (best) |
| Released | Aug 7, 2026 | Jun 9, 2026 | Jun 23, 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
- Seed 2.1 Pro$17.81
Which should you choose?
Which is better: GPT-5.6 Cyber, Claude Mythos 5 or Seed 2.1 Pro?
Seed 2.1 Pro is the better all-round choice, scoring 50/100 against Claude Mythos 5 (36) and GPT-5.6 Cyber (30). It leads on price. Claude Mythos 5 wins on context window. 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 Seed 2.1 Pro?
Seed 2.1 Pro is cheaper at $0.891 input / $4.45 output per million tokens (official Volcengine Ark 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 $1.78 per million tokens for Seed 2.1 Pro versus $20.00 for Claude Mythos 5 (11× as much) and $28.13 for GPT-5.6 Cyber (16× 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 Seed 2.1 Pro 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 Seed 2.1 Pro 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 has the largest context window at 1,000,000 tokens, against 400,000 for GPT-5.6 Cyber and 256,000 for Seed 2.1 Pro. Maximum output per response: GPT-5.6 Cyber up to 128,000, Claude Mythos 5 up to 128,000, Seed 2.1 Pro up to 256,000 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; Seed 2.1 Pro accepts text, images and video. Claude Mythos 5 handles the widest range of inputs.
Are any of these open source?
No. GPT-5.6 Cyber, Claude Mythos 5 and Seed 2.1 Pro are proprietary and only available through APIs and apps.
Which is newer?
GPT-5.6 Cyber is the newest, released Aug 7, 2026. Seed 2.1 Pro came out Jun 23, 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.
