Claude Fable 5
Claude Fable 5 is the publicly accessible Mythos-class Claude model for extended software engineering, visual reasoning, knowledge work, and research. It uses adaptive thinking and can maintain progress through tool-driven tasks with file-based memory. Claude Mythos 5 is the same underlying model with different safeguards and restricted trusted access, represented here as a variant. Fable access was suspended June 12 and restored July 1; the first release remains June 9.
2026-06-09
Unreleased
Undisclosed proprietary architecture
Proprietary
Specifications
- Parameters
- Unreleased
- Architecture
- Undisclosed proprietary architecture
- License
- Proprietary
- Context Window
- 1,000,000 tokens
- Max Output
- 128,000 tokens
- Training Data Cutoff
- 2026-01
- Type
- multimodal
- Modalities
- textimage
Benchmark Scores
Advanced Specifications
- Model Family
- Claude
- API Access
- Available
- Chat Interface
- Available
- Multilingual Support
- Yes
- Variants
- claude-fable-5Claude Mythos 5 (same underlying model; trusted access)
Capabilities & Limitations
- Capabilities
- deep reasoningagentic codingvisionadaptive thinkingcomputer usetool use
- Known Limitations
- Can make factual or coding errors; tool results and important outputs require verification.Longer reasoning and agent work increase latency and token consumption.Sensitive requests may be blocked or routed to another model; Mythos safeguards require trusted access.
- Notable Use Cases
- large software migrationslong research workflowsprofessional knowledge work
- Function Calling Support
- Yes
- Tool Use Support
- Yes