Anthropic logo

Claude Fable 5

AnthropicProprietaryPending Human Review

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

Related Models