Very long inputs
Choose Claude Mythos 5.1
Claude Mythos 5.1 reads up to 1M tokens per request, against 200k for Claude Opus 4.1.
Claude Mythos 5.1 vs Claude Opus 4.1: price, context and capabilities
Choose Claude Mythos 5.1 for very long inputs and the latest release; on the other points the two are level or the data is missing.
In short
- Claude Opus 4.1 has been retired; Claude Mythos 5.1 is the one you can still call.
- A price comparison is not possible: one of them has no comparable published price.
- Claude Mythos 5.1 reads more per request: 1M tokens against 200k.
- Claude Mythos 5.1 is the newer model (September 2026, against August 2025).
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Latest release
Choose Claude Mythos 5.1
Claude Mythos 5.1 is the newer release (September 2026, against August 2025 for Claude Opus 4.1).
Specifications side by side
| Claude Mythos 5.1 | Claude Opus 4.1 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Category | Language models | Language models |
| Status | Generally available · Limited access | Retired |
| Headline price | $20.00 / 1M tokens | $30.00 / 1M tokens |
| Input | $10.00 / 1M tokens | $15.00 / 1M tokens |
| Output | $50.00 / 1M tokens | $75.00 / 1M tokens |
| Cached input | $0.25 / 1M tokens | $1.50 / 1M tokens |
| Context window | 1M | 200k |
| Max output | 128k | No data |
| Released | September 2026 | August 2025 |
| Knowledge cutoff | No data | No data |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | claude-mythos-5-1 | claude-opus-4-1-20250805 |
Frequently asked questions
Should I choose Claude Mythos 5.1 or Claude Opus 4.1?
Choose Claude Mythos 5.1 for very long inputs and the latest release; on the other points the two are level or the data is missing.
Which is cheaper, Claude Mythos 5.1 or Claude Opus 4.1?
A price comparison is not possible: one of them has no comparable published price.
Which has the larger context window, Claude Mythos 5.1 or Claude Opus 4.1?
Claude Mythos 5.1 reads more per request: 1M tokens against 200k.
What is the difference between Claude Mythos 5.1 and Claude Opus 4.1?
Claude Mythos 5.1 is made by Anthropic and Claude Opus 4.1 by Anthropic. Claude Opus 4.1 has been retired; Claude Mythos 5.1 is the one you can still call. A price comparison is not possible: one of them has no comparable published price. Claude Mythos 5.1 reads more per request: 1M tokens against 200k. Claude Mythos 5.1 is the newer model (September 2026, against August 2025).
Which is newer, Claude Mythos 5.1 or Claude Opus 4.1?
Claude Mythos 5.1 was released on September 2026 and Claude Opus 4.1 on August 2025.