Claude Fable 5
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Claude Fable 5 is a large language model developed by Anthropic and released on June 9, 2026, as the first publicly available model in a new "Mythos class" that the company describes as "a tier of Claude models that sit above our Opus class in capability." [1] It is the most capable generally available member of the Claude family, and Anthropic states that "Fable 5's capabilities exceed those of any model we've ever made generally available." [1] The model is served through the Claude API under the identifier claude-fable-5 at $10 per million input tokens and $50 per million output tokens, roughly twice the price of the previous flagship, Claude Opus 4.8. [1][6]
What is Claude Fable 5?
Claude Fable 5 is a reasoning-oriented, multimodal large language model that accepts text and image input and returns text. [4] It inaugurated Anthropic's Claude 5 generation and launched alongside a restricted sibling, Claude Mythos 5, with which it shares the same underlying weights (see below). Anthropic positions the Mythos class as its first tier of models to exceed the Opus class, and frames the release around both capability and risk, writing that "Mythos-class models have reached a threshold where they present significant risks." [1] The company reports state-of-the-art results on nearly all tested benchmarks, with particular strength in software engineering, knowledge work, vision, and scientific research; one customer said the model "accelerated aspects of the drug design process by around 10 times." [1]
The model supports a context window of 1,000,000 tokens and can return up to 128,000 tokens in a single response. [4][8] On the Artificial Analysis Intelligence Index, an aggregate of evaluations that includes GPQA Diamond, Humanity's Last Exam, and Terminal-Bench, Claude Fable 5 scored 60, the highest of any model tracked at launch. [4]
| Attribute | Detail |
|---|---|
| Developer | Anthropic |
| Released | June 9, 2026 (redeployed July 1, 2026) |
| Model ID | claude-fable-5 |
| Model class | Mythos class (above Opus) |
| Type | Reasoning, multimodal (text and image in, text out) |
| Context window | 1,000,000 tokens |
| Maximum output | 128,000 tokens |
| API price | $10 per 1M input, $50 per 1M output |
| Prompt caching | $12.50 write, $1.00 read per 1M tokens |
| Artificial Analysis Intelligence Index | 60 (ranked first at launch) |
What is the difference between Fable 5 and Mythos 5?
Fable 5 and Claude Mythos 5 are the same underlying model; the difference is safety configuration. Fable 5 runs with all safeguards in place, while Mythos 5 is "the same underlying model as Fable 5, but with the safeguards lifted in some areas" and is available only to approved organizations. [1] Because the raw model has dual-use capabilities, Fable 5 uses classifiers that reroute sensitive requests, for example in cybersecurity and in biology and chemistry, to Claude Opus 4.8. Anthropic reports that "more than 95% of Fable sessions involve no fallback at all." [1] The company explains the split by noting that "the same queries that are beneficial in the hands of cybersecurity professionals and biology researchers could be dangerous if available to malicious actors," and that "without safeguards, Fable 5's capabilities in areas like cybersecurity could be misused to cause serious damage." [1]
Mythos 5 is not generally available. At launch it was restricted to partners in Anthropic's Project Glasswing (with cybersecurity safeguards lifted) and, subsequently, to select biology researchers (with biology and chemistry safeguards lifted), pending a broader trusted-access program. [1] Both models are priced identically at $10 and $50 per million input and output tokens. [1]
How does Fable 5 compare to Opus 4.8?
Claude Fable 5 sits one tier above Claude Opus 4.8, which had been Anthropic's most capable generally available model and now serves as the fallback target for Fable 5's safeguards. [1] On SWE-bench Pro, a test of difficult software-engineering tasks, Anthropic reports Fable 5 at 80.3%, compared with 69.2% for Opus 4.8 and 58.6% for OpenAI's GPT-5.5. [1][6] Fable 5 also leads the SWE-bench Verified leaderboard at about 95.0% and scores 92.6% on GPQA Diamond. [5][8]
| Benchmark | Claude Fable 5 | Claude Opus 4.8 | GPT-5.5 |
|---|---|---|---|
| SWE-bench Pro | 80.3% | 69.2% | 58.6% |
| SWE-bench Verified | ~95.0% | not reported | not reported |
| GPQA Diamond | 92.6% | not reported | not reported |
| Artificial Analysis Intelligence Index | 60 | not reported | not reported |
Anthropic's Claude 5 generation also includes Claude Sonnet 5, a lower-cost everyday model released at the end of June 2026 that sits below Fable 5 in capability and price. Opus 4.8 remains available and, at $5 and $25 per million tokens, is half the price of Fable 5. [6]
How much does Claude Fable 5 cost?
Claude Fable 5 costs $10 per million input tokens and $50 per million output tokens, double the $5 and $25 charged for Claude Opus 4.8. [1][6] Prompt caching reduces costs substantially: cached input reads are billed at $1.00 per million tokens, a 90% discount, while cache writes cost $12.50 per million tokens. [4] Requests routed to US-only inference carry a 1.1x price multiplier, and Anthropic requires 30-day data retention for safety monitoring when the model is used. [2] Billing is identical whether the model is accessed as Fable 5 or, for approved organizations, as Mythos 5. [1]
What is the availability of Claude Fable 5?
At launch, Claude Fable 5 was available on the web to Pro, Max, Team, and Enterprise subscribers, through the Claude API, and via Amazon Bedrock, Google Cloud, and Microsoft Foundry, with free introductory access on subscription plans from June 9 to June 22, 2026. [1][2]
The rollout was interrupted by an export-control episode. On June 12, 2026, after researchers at Amazon documented a prompting technique that bypassed Fable 5's safeguards to identify software vulnerabilities and, in one case, produce exploit code, the US government applied export controls requiring access to be restricted from foreign nationals. [3][7] Unable to verify user nationality in real time, Anthropic suspended access to both Fable 5 and Mythos 5 for all users. [3] The controls were lifted on June 30, 2026, and Anthropic redeployed Fable 5 on July 1, 2026 across the Claude Platform, Claude.ai, Claude Code, and Claude Cowork, after training a new cybersecurity classifier that it says blocks the specific technique described in the Amazon report in over 99% of cases and reroutes flagged requests to Opus 4.8. [3][7] The model was offline for roughly 19 days. [3]
References
- Anthropic. "Claude Fable 5 and Claude Mythos 5." June 9, 2026. https://www.anthropic.com/news/claude-fable-5-mythos-5 ↩
- Anthropic. "Claude Fable" (model overview). https://www.anthropic.com/claude/fable ↩
- Anthropic. "Redeploying Claude Fable 5." July 1, 2026. https://www.anthropic.com/news/redeploying-fable-5 ↩
- Artificial Analysis. "Claude Fable 5" model page. https://artificialanalysis.ai/models/claude-fable-5 ↩
- SWE-bench Verified leaderboard. LLM Stats. https://llm-stats.com/benchmarks/swe-bench-verified ↩
- Finout. "Claude Fable 5 and Mythos 5: Pricing, API Costs, and Benchmark Comparison vs Opus 4.8 and GPT-5.5." June 2026. https://www.finout.io/blog/claude-fable-5-mythos-5-pricing-benchmarks ↩
- CNBC. "Anthropic says Trump admin has lifted export controls on Claude Fable 5 and Mythos 5." June 30, 2026. https://www.cnbc.com/2026/06/30/anthropic-says-trump-admin-has-lifted-export-controls-on-claude-fable-5-and-mythos-5.html ↩
- Requesty. "Anthropic claude-fable-5 API Pricing, Context Window and Benchmarks." https://www.requesty.ai/models/anthropic/claude-fable-5 ↩
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