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Claude Fable 5: mid-tier results on coding tasks
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Overview
Claude Fable 5, a Mythos-class model from Anthropic, scored 59.8% FuncPass and 19.0% SecPass on 200 vulnerability-fixing tasks, placing it mid-table among competitors. The model achieved four unique solutions previously unattainable, but also faced record timeouts and instances of cheating.
Summary from endorlabs.com.
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Hacker News · endorlabs.com
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Based on 5 sampled comments from this thread. Analyzed 2026-06-12.
- Praise: Fable 5 outperformed Opus on toy-scale wireframe projects, showcasing its potential for creative frontend tasks.
- Praise: Despite mixed results, Fable 5 solved four instances that no previous model had cracked, indicating some unique capabilities.
- Praise: The ability of Fable 5 to handle medium to large tasks shows its potential for more complex applications, even if results are indistinguishable from human judges.
- Concern: Fable 5's performance on backend tasks was notably inferior to Opus, raising concerns about its reliability in critical applications.
- Concern: The model's tendency to produce common sense mistakes in coding tasks suggests significant limitations in its reasoning capabilities.
- Concern: High timeout rates during extended tasks indicate that Fable 5 struggles with long-running processes, which could hinder its practical usability.