High-volume, cost-sensitive work
Either one
Both cost $20.00 per million tokens on a typical mix of three input tokens for every output token.
Claude Fable 5 vs Claude Mythos 5.1: price, context and capabilities
Choose Claude Mythos 5.1 for reused prompts and documents (RAG, agents) and the latest release; on the other points the two are level or the data is missing.
In short
- Both cost the same at the headline price ($20.00 / 1M tokens).
- Both accept 1M tokens per request.
- Claude Mythos 5.1 is the newer model (September 2026, against June 2026).
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Reused prompts and documents (RAG, agents)
Choose Claude Mythos 5.1
Claude Mythos 5.1 charges $0.25 per million cached input tokens, against $1.00 for Claude Fable 5.
Latest release
Choose Claude Mythos 5.1
Claude Mythos 5.1 is the newer release (September 2026, against June 2026 for Claude Fable 5).
Monthly cost at three volumes
| Volume | Claude Fable 5 | Claude Mythos 5.1 | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $22.50 | $22.50 | = |
| Production: 20M input, 5M output tokens | $450.00 | $450.00 | = |
| Scale: 500M input, 100M output tokens | $10,000 | $10,000 | = |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Claude Fable 5 | Claude Mythos 5.1 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Category | Language models | Language models |
| Status | Legacy | Generally available · Limited access |
| Headline price | $20.00 / 1M tokens | $20.00 / 1M tokens |
| Input | $10.00 / 1M tokens | $10.00 / 1M tokens |
| Output | $50.00 / 1M tokens | $50.00 / 1M tokens |
| Cached input | $1.00 / 1M tokens | $0.25 / 1M tokens |
| Context window | 1M | 1M |
| Max output | 128k | 128k |
| Released | June 2026 | September 2026 |
| 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-fable-5 | claude-mythos-5-1 |
Benchmarks side by side
Leader in bold.
| Benchmark | Claude Fable 5 | Claude Mythos 5.1 |
|---|---|---|
| Intelligence Index | 49.6 | No data |
| Terminal-Bench Hard | 62.9% | No data |
| SciCode | 61% | No data |
| GPQA Diamond | 92.6% | No data |
| Humanity's Last Exam | 55.5% | No data |
| IFBench (instruction following) | 63.5% | No data |
| τ²-Bench (agentic tool use) | 98.5% | No data |
| Long-context reasoning (AA-LCR) | 82.3% | No data |
Independent evaluations by Artificial Analysis, run the same way for every model, at the reasoning setting shown. Percentages unless marked as an index.
Frequently asked questions
Should I choose Claude Fable 5 or Claude Mythos 5.1?
Choose Claude Mythos 5.1 for reused prompts and documents (RAG, agents) and the latest release; on the other points the two are level or the data is missing.
Which is cheaper, Claude Fable 5 or Claude Mythos 5.1?
Both cost the same at the headline price ($20.00 / 1M tokens).
Which has the larger context window, Claude Fable 5 or Claude Mythos 5.1?
Both accept 1M tokens per request.
What is the difference between Claude Fable 5 and Claude Mythos 5.1?
Claude Fable 5 is made by Anthropic and Claude Mythos 5.1 by Anthropic. Both cost the same at the headline price ($20.00 / 1M tokens). Both accept 1M tokens per request. Claude Mythos 5.1 is the newer model (September 2026, against June 2026).
How much do Claude Fable 5 and Claude Mythos 5.1 cost per month?
At 20 million input and 5 million output tokens a month, Claude Fable 5 costs $450.00 and Claude Mythos 5.1 costs $450.00, at standard rates.
Which is newer, Claude Fable 5 or Claude Mythos 5.1?
Claude Mythos 5.1 was released on September 2026 and Claude Fable 5 on June 2026.