For most workflows, Claude Mythos 5.1 is the stronger default — fable 5.1 with the safeguards lifted — partner-only, 60.9% terminal-bench 4.0.
The safest Claude Mythos 5.1 vs Claude Mythos 5 default, the cheaper option worth trying first, and the specialist pick — before you read the detail below.
Claude Mythos 5.1 is the strongest answer here for Claude Mythos 5.1 vs Claude Mythos 5 — pick it when quality of output matters more than the $10.00/1M/1M input you pay for it.
GPT-5.1-Codex-Max handles the same job for about 81% less per token. Start here and only move up if the output is not good enough.
Claude Mythos 5 is the fastest of these for Claude Mythos 5.1 vs Claude Mythos 5 — worth it when latency is what the reader notices, not the last few points of reasoning depth.
Claude Mythos 5.1 leads on coding with a score of 100 vs 100 for Claude Mythos 5.
Both models are similarly priced — the decision comes down to capability, not cost.
Claude Mythos 5.1 is the stronger default for coding tasks.
Choose Claude Mythos 5.1 for vetted frontier cybersecurity and life-sciences research at the absolute capability ceiling. Its coding and research scores are what carry the recommendation here.
Choose Claude Mythos 5 when your work is mostly frontier cybersecurity research and autonomous vulnerability discovery — that is the workload it was tuned for.
Both models serve different primary workflows — Claude Mythos 5.1 for vetted frontier cybersecurity and life-sciences research at the absolute capability ceiling, Claude Mythos 5 for frontier cybersecurity research and autonomous vulnerability discovery — so running each where it has a clear edge often beats forcing one to do both.
Switch the scoring lens to see whether the Claude Mythos 5.1 vs Claude Mythos 5 answer changes when cost, speed, or long-document depth leads the decision.
Anthropic / Premium / Sep 1, 2026
Fable 5.1 with the safeguards lifted — partner-only, 60.9% Terminal-Bench 4.0.
Ranks models by the broadest mix of coding, writing, research, and long-context usefulness.
You don't hold vetted trusted access, or your work never trips Fable 5.1's safeguards — the two models are otherwise identical.
Where the Claude Mythos 5.1 vs Claude Mythos 5 recommendation shifts once you weigh price or latency differently.
Fable 5.1 with the safeguards lifted — partner-only, 60.9% Terminal-Bench 4.0.
The frontier ceiling — same model as Fable 5, safeguards lifted, partner-only.
List prices and published scores — the numbers this page's pick is built from.
| Model | Input | Output | Est. month | Context | Speed | Coding | Writing | Research |
|---|---|---|---|---|---|---|---|---|
| Claude Mythos 5.1Anthropic | $10.00/1M | $50.00/1M | $200 | 1M tokens | Deliberate | 100 | 97 | 99 |
| Claude Mythos 5Anthropic | $10.00/1M | $50.00/1M | $200 | 1M tokens | Deliberate | 100 | 97 | 99 |
Scores out of 100 — how we evaluate models. “Est. month” is 10M in / 2M out at list price: a ceiling, no discounts.
Why each one is on the shortlist for Claude Mythos 5.1 vs Claude Mythos 5, what it is genuinely good at, and where we would steer you away from it.
Ranked first here for Claude Mythos 5.1 vs Claude Mythos 5: 100/100 on coding, with the widest margin of anything in this line-up.
The unrestricted twin of Claude Fable 5.1 — the same model with safeguards lifted in high-risk areas, released September 1, 2026 to vetted cybersecurity and life-sciences organisations under Anthropic's trusted-access programme. Scores 60.9% on Terminal-Bench 4.0, the highest agentic-coding result Anthropic has published.
You don't hold vetted trusted access, or your work never trips Fable 5.1's safeguards — the two models are otherwise identical.
The highest published agentic-coding score anywhere — 60.9% on Terminal-Bench 4.0 — but you almost certainly cannot get it. Mythos 5.1 is Fable 5.1 with safeguards lifted, gated to vetted cybersecurity and life-sciences organisations. Unless you hold trusted access and hit refusals that block real research, Fable 5.1 is the same model at the same price.
Full pricing, benchmark table and release notes on the Claude Mythos 5.1 page.
Here for latency: it answers fastest of anything listed for Claude Mythos 5.1 vs Claude Mythos 5, at 100/100 on coding.
Anthropic's most powerful frontier model — the same underlying model as Fable 5 with safeguards lifted in some areas, restricted to vetted enterprise and research partners. The capability ceiling of mid-2026.
You don't have vetted-partner access or don't need lifted safeguards — Fable 5 is the same model, generally available, at the same price.
The most capable model Anthropic has ever shipped — but access is gated to vetted partners because its safeguards are lifted in high-risk areas. For everyone else, Fable 5 is the same model at the same price with standard safety controls. Choose Mythos 5 only if you have partner access and need its security ceiling.
Full pricing, benchmark table and release notes on the Claude Mythos 5 page.
UseRightAI recommendations are based on practical decision factors people actually feel in day-to-day use.
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Claude Mythos 5.1 wins on more of the categories we score — coding, research, long context — so it is the better default of the two. Claude Mythos 5 is the better pick when your work is mostly frontier cybersecurity research and autonomous vulnerability discovery. Neither is universally "better": Claude Mythos 5.1 is aimed at vetted frontier cybersecurity and life-sciences research at the absolute capability ceiling, Claude Mythos 5 at frontier cybersecurity research and autonomous vulnerability discovery.
Both models are similarly priced at $10/1M input tokens. The decision should come down to capability, not cost.
Both Claude Mythos 5.1 and Claude Mythos 5 have the same 1M context window.
Claude Mythos 5.1 and Claude Mythos 5 are similarly matched on coding. GPT-6 Astra is the overall coding leader in this directory at 100/100.
Both Claude Mythos 5.1 and Claude Mythos 5 have similar speed profiles — rated deliberate. Neither will be the bottleneck if latency is your deciding factor.
Not generally available — restricted to vetted US organisations under Project Glasswing. No advantage for ordinary work; Fable 5.1 is the same model at the same price for everyone else. Same deliberate, high-latency profile and premium pricing as Fable 5.1. Avoid it if you don't hold vetted trusted access, or your work never trips Fable 5.1's safeguards — the two models are otherwise identical. That is the main case for looking at Claude Mythos 5 instead.
Not generally available — limited to vetted partners after Project Glasswing's private preview. Most teams should use Fable 5, which is the same model with standard safeguards. Premium $10/$50 pricing and a deliberate, high-latency profile. Avoid it if you don't have vetted-partner access or don't need lifted safeguards — Fable 5 is the same model, generally available, at the same price. Against Claude Mythos 5.1 specifically, the two are close enough on capability that price and speed decide it.
Take a moderate workload of 10M input and 2M output tokens a month. Claude Mythos 5.1 runs $200.00 (at $10/1M in and $50/1M out); Claude Mythos 5 runs $200.00 (at $10/1M in and $50/1M out). The gap is small enough that price should not decide this one. Output tokens dominate the bill on both, so prompt length matters far less than response length.
Yes, and for most teams that beats picking one. A common split is Claude Mythos 5.1 for vetted frontier cybersecurity and life-sciences research at the absolute capability ceiling, with Claude Mythos 5 handling frontier cybersecurity research and autonomous vulnerability discovery. Since Claude Mythos 5.1 is both the stronger and the cheaper option here, a split mainly makes sense if Claude Mythos 5 covers a capability you specifically need.