Overview
Claude Fable 5 is a Mythos-class model from Anthropic, built for autonomous knowledge work and coding. It supports text, image, and file inputs with text output, with reasoning support and a 1M-token context window. It is suited for long-running, complex, and asynchronous tasks that previously required frequent human check-ins.
It is particularly strong at end-to-end work that would otherwise take a person hours, days, or weeks - taking on problems that are long-running, ambiguous, or highly multi-step. It executes well-scoped tasks with few mistakes, automatically self-correcting through verification loops, and ships with robust safeguards.
#Key Features
- Advanced Reasoning: Suitable for complex analytical, technical, and professional knowledge tasks.
- Software Engineering Workflows: Designed for coding assistance, debugging, refactoring, code review, and multi-step implementation planning.
- Long-Context Tasks: Supports extended analysis across large codebases, long documents, and multi-turn work sessions when enabled by the platform configuration.
- Agentic and Tool-Assisted Workflows: Suitable for workflows that rely on tool use, function calling, code execution, MCP, or compatible agent environments.
- Multimodal Understanding: Supports text and image input for document, screenshot, chart, and diagram understanding where available.
#Best Use Cases
- Complex Software Engineering: Large feature work, repository-scale refactors, migration planning, bug investigation, and code review.
- Extended Agentic Workflows: Multi-step tasks that require planning, tool use, verification, and sustained context over longer sessions.
- Research and Knowledge Work: Analysis and synthesis across technical documents, legal or financial materials, and structured research sources.
- Visual Document Analysis: Understanding screenshots, diagrams, charts, PDFs, and other image-based materials when supported by the workflow.
#Capabilities and Limitations
| Capability | Description |
|---|---|
| Reasoning | Advanced reasoning for complex professional and technical tasks |
| Coding | Strong coding, debugging, refactoring, and code review capabilities |
| Agentic | Suitable for long-running tool workflows and multi-step agent tasks |
| Computer Use | Can support browser and desktop interaction through compatible tools and environments |
| Multimodal | Text and image input; text output |
| Context Window | Up to 1,000,000 tokens, subject to platform configuration |
| Max Output | Up to 128,000 tokens, subject to platform configuration |
| Tool Use | Function calling, code execution, MCP support, adaptive thinking, and compatible agent workflows |
| Multilingual | Strong multilingual performance across major world languages |
Usage example
cURL
curl https://www.namoclaw.ai/api/v1/chat/completions \
-H "Authorization: Bearer $API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "anthropic/claude-5-fable-20260609",
"messages": [{ "role": "user", "content": "Hello!" }]
}'Default parameters
| Name | Type | Default | Description |
|---|---|---|---|
| temperature | number | — | — |
| top_p | number | — | — |
| top_k | number | — | — |
| frequency_penalty | number | — | — |
| presence_penalty | number | — | — |
| repetition_penalty | number | — | — |
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