Claude Fable 5
Mythos-class made generally available — the new agentic-coding ceiling, at 2× Opus pricing.
Read the full Claude Fable 5 analysisContext
1M
Max output
128K
Input /1M
$10.00
Output /1M
$50.00
Best for
- Agentic pipelines feeding schemas, tools, and other agents (measured constraint precision)
- Long-horizon coding — SWE-Bench Verified 95% / Pro ~80% at launch (vendor-claimed)
- Hard reasoning under strict output contracts
Watch out
$10/$50 is double Opus 4.8 standard. Launch benchmarks are vendor-claimed. In our stress round it executed a governance-gated edit without flagging it — pair with structural gates, and enforce output contracts in schemas: every model’s discipline degrades under heavy task load.
For creators. The default Claude Code driver for agentic builds. Route judgment-heavy review and human-read prose to Opus 4.8 at half the price — our blind style verdicts flipped between rounds, so prose is not the upgrade case.
Benchmarks
| swe bench verified | 95 |
| swe bench pro | 80 |
| cursorbench max effort | 72.9 |
Capabilities
- Mythos-class capabilities made generally available (safety classifiers attached)
- Default model in Claude Code (claude-fable-5)
- Leads FrontierCode Diamond and Main subsets at launch
- Lead widens as tasks get longer and more complex (per Anthropic)
- 1M context, 128K max output
- Measured edge (FrankX arena, 4 rounds): output discipline / constraint precision at correctness parity-or-better vs Opus 4.8
Compare Claude Fable 5
Claude Fable 5 vs Claude Opus 4.8
Fable 5 takes agentic coding, constraint precision, and hard reasoning — at double the price. Opus 4.8 keeps situational judgment, code-craft quality, and the better $/token for human-read prose. Route by task shape, not by leaderboard.
Claude Fable 5 vs GPT-5.5
Fable 5 leads agentic coding by a generation-sized margin on launch numbers; GPT-5.5 keeps computer-use, terminal autonomy, and native voice. Different ceilings for different jobs.