Claude Mythos 5.1 vs GPT-5.1
At a Glance
| Compare | Claude Mythos 5.1Anthropic |  GPT-5.1OpenAI |
|---|---|---|
| Intelligence, Cost, and Efficiency | ||
| IntelligenceHigher is better · MM Intelligence v2.5 | UnrankedNot in the 46-model eligible cohort | #37 of 4625.7 score · 2/3 sources · provisional · missing LiveBench · full-core range 17.1–50.5 |
| Pricing and Limits | ||
| Input priceFrom · USD / 1M tokens | $10.00Anthropic ↗ · Sep 2, 2026 | $1.25Openai ↗ · Sep 3, 2026 |
| Output priceFrom · USD / 1M tokens | $50.00Anthropic ↗ · Sep 2, 2026 | $10.00Openai ↗ · Sep 3, 2026 |
| Context windowMaximum documented tokens | 1,000K | 400K |
| Model facts checked | Sep 2, 2026View model evidence → | Sep 3, 2026View model evidence → |
Token prices are the lowest available sourced USD rates; input and output may use different providers. Cost ranking estimates output spend on LiveBench, not a full request bill. Ranking methodology →
Available Benchmarks
Side-by-Side Facts
| Field | Claude Mythos 5.1 | GPT-5.1 |
|---|---|---|
| Developer | Anthropic | OpenAI |
| Family | Claude 5 1 | Gpt 5 1 |
| Model | Claude Mythos 5.1 | GPT-5.1 |
| Version | Claude Mythos 5.1 | GPT-5.1 |
| Lifecycle | active | active |
| Released | 2026-09-01 | 2025-11-13 |
| Knowledge cutoff | 2026-06-01 | 2024-09-30 |
| Input modalities | Text, Image | Text, Image |
| Output modalities | Text | Text |
| Context window | 1,000K | 400K |
| Total parameters | Unknown | Unknown |
| Active parameters | Unknown | Unknown |
| License | Unknown | Unknown |
| Open weights | No | No |
| API available | Yes | Yes |
| Self-hostable | No | No |
| Provider access | Anthropic (Project Glasswing) | Openai (Standard), Openrouter (Standard) |
| Capabilities | chat, generation, reasoning, tools | chat, generation, reasoning, structured_outputs, tools |
Claude Mythos 5.1 Capabilities
GPT-5.1 Capabilities
Related Comparisons
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|---|---|---|---|
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Claude Mythos 5.1Anthropic | vs |  Kimi-K3Moonshot AI | cross-developer peersimage, text |
 MiniMax-M3MiniMax | vs | Claude Mythos 5.1Anthropic | cross-developer peersimage, text |
Claude Mythos 5.1Anthropic | vs |  GLM-5.3Z.ai | cross-developer peerstext |
Claude Mythos 5.1Anthropic | vs |  Hy4 previewTencent | cross-developer peerstext |
Claude Mythos 5.1Anthropic | vs | Seed 2.1 ProByteDance Seed | cross-developer peersimage, text |
Claude Mythos 5.1Anthropic | vs |  Mistral Large 3Mistral AI | cross-developer peersimage, text |
Primary Evidence
Sources and Freshness
Questions
Claude Mythos 5.1 vs GPT-5.1 FAQs
Is Claude Mythos 5.1 or GPT-5.1 better for coding?+
This comparison does not currently contain a protocol-matched coding benchmark for both Claude Mythos 5.1 and GPT-5.1, so Model Markets cannot name a coding leader from pricing, context size, or capability labels alone.
Which is cheaper, Claude Mythos 5.1 or GPT-5.1?+
Claude Mythos 5.1 is $10.00 and GPT-5.1 is $1.25 per million tokens, so GPT-5.1 is cheaper on this metric. Claude Mythos 5.1 is $50.00 and GPT-5.1 is $10.00 per million tokens, so GPT-5.1 is cheaper on this metric.
Which has a larger context window, Claude Mythos 5.1 or GPT-5.1?+
Claude Mythos 5.1 has the larger sourced context window. Claude Mythos 5.1 supports 1,000K and GPT-5.1 supports 400K.
Which performs better in benchmarks, Claude Mythos 5.1 or GPT-5.1?+
There is no overall benchmark winner: At least two independently verified, protocol-matched benchmarks are required for an overall winner.
Can Claude Mythos 5.1 or GPT-5.1 be self-hosted?+
Both models have the same recorded self-hosting status: unsupported. Claude Mythos 5.1 is not marked open weight; GPT-5.1 is not marked open weight.
Can Claude Mythos 5.1 and GPT-5.1 understand images?+
Claude Mythos 5.1 is documented with image input; GPT-5.1 is documented with image input. This reflects supported input modalities, not vision quality.
Which can generate longer answers, Claude Mythos 5.1 or GPT-5.1?+
Neither has a larger sourced maximum output. Claude Mythos 5.1 is 128K and GPT-5.1 is 128K.
Do Claude Mythos 5.1 and GPT-5.1 support reasoning and tool use?+
Claude Mythos 5.1: reasoning, tool calling, and image input. GPT-5.1: reasoning, tool calling, and image input. Feature support does not establish relative quality.
Which is available from more inference providers, Claude Mythos 5.1 or GPT-5.1?+
Claude Mythos 5.1 has 1 sourced provider route; GPT-5.1 has 2, so GPT-5.1 has broader tracked availability.
Which offers better value, Claude Mythos 5.1 or GPT-5.1?+
There is no universal value winner. Compare the input and output prices above with the matched benchmark result for your workload: cheaper tokens can be offset by different quality, token usage, latency, or provider availability.