# Anthropic Claude Fable 5 API

> 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.

Source: https://www.sandbase.ai/models/anthropic/claude-fable-5
API reference: https://www.sandbase.ai/models/anthropic/claude-fable-5/docs

## Facts

- Provider: Anthropic
- Type: Language model
- Model ID: `anthropic/claude-fable-5`
- Price: $8.50 per 1M input tokens, $42.50 per 1M output tokens (15% off list price)
- Context window: 1M tokens, up to 128K output tokens
- Capabilities: chat, vision, reasoning, structured output, function calling
- Billing: pay per use from one SandBase balance; no provider account or subscription needed

## Call it

- Chat Completions API: `POST https://api.sandbase.ai/v1/chat/completions`
- Messages API: `POST https://api.sandbase.ai/v1/messages`

```bash
curl -X POST https://api.sandbase.ai/v1/chat/completions \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "anthropic/claude-fable-5",
  "messages": [
    {
      "role": "user",
      "content": "Hello"
    }
  ],
  "max_tokens": 2048
}'
```

## FAQ

### How do I call Anthropic Claude Fable 5 through SandBase?

Create a SandBase API key, then send requests with the model ID "anthropic/claude-fable-5" to Chat Completions API (/v1/chat/completions) or Messages API (/v1/messages) at https://api.sandbase.ai. The request examples on this page show the exact payload.

### How much does Anthropic Claude Fable 5 cost?

$8.50 per 1M input tokens and $42.50 per 1M output tokens with the current 15% discount (list price $10 / $50), billed per request from your SandBase balance.

### What is the context window of Anthropic Claude Fable 5?

1M tokens of context, with up to 128K output tokens per response.

### How does Anthropic Claude Fable 5 score on benchmarks?

Anthropic Claude Fable 5 scores 49.6 on the Artificial Analysis Intelligence Index (v4.3), ranking #7 of 83 models on SandBase; Coding Index 76.5, Agentic Index 50.7. Source: Artificial Analysis, measured as Claude Fable 5 (Max, Opus 4.8 Fallback).

### Which features does Anthropic Claude Fable 5 support?

Anthropic Claude Fable 5 supports vision (image input), reasoning, function calling, structured output. See Specifications above for the full list.

### Do I need a separate Anthropic account?

No. One SandBase API key and balance gives you access to Anthropic Claude Fable 5 and the other models in the catalog; you do not need to sign up with Anthropic separately.