# Claude Fable 5.1 - Core.Today AI API

> Anthropic's top model tier, above Opus. 1M-token context window and 128K max output tokens. Priced at $10/$50 per M tokens with prompt caching — cache reads are only $0.25/M (2.5% of the input price) and 5-minute cache writes $12.50/M — plus web search. Compatible with the Anthropic Messages and OpenAI Chat Completions formats.

- **Provider**: Anthropic
- **Model ID**: claude-fable-5-1
- **Category**: LLM
- **Credits**: 10 per 1K tokens (avg)
- **Speed**: Medium
- **Quality**: Ultra

## Model Specifications
- **Context Window**: 1M tokens
- **Max Output**: 128K tokens
- **Training Cutoff**: Not published
- **Supported Formats**: text, json, markdown
- **Compatible SDK**: Anthropic, OpenAI

### Capabilities
- Vision (image input)
- Function Calling
- Streaming
- JSON Mode
- System Prompt

### Token Pricing (per 1M tokens)
- **Input Tokens**: 18,580 credits ($12.39)
- **Output Tokens**: 92,900 credits ($61.93)
- **Cached Tokens**: 464.5 credits ($0.31)

## Features
- Top Anthropic model tier (above Opus)
- 1M token context window
- 128K max output tokens
- Prompt caching (read 2.5% / 5-min write 125% of input price)
- Web search tool support
- Vision and tool use
- Streaming support

## Use Cases
- Hardest research and analysis tasks
- Long-context document understanding (up to 1M tokens)
- Complex code generation and refactoring
- Long-running agentic workflows with large cached contexts
- Web-grounded question answering

## API Endpoint

Base URL: https://api.core.today
Endpoint: POST /llm/anthropic/v1/messages

## Authentication
Header: Authorization: Bearer YOUR_API_KEY

Note: LLM endpoints use OpenAI-compatible format with Authorization Bearer token.

## Input Parameters

### Required
- **messages**: array - Array of message objects (OpenAI format)

### Optional
- **max_tokens**: integer (default: 4096) - Maximum tokens in response (up to 128000)
- **stream**: boolean (default: false) - Enable Server-Sent Events streaming

## Examples

### Long-context Analysis
Deep multi-step analysis over large documents with Claude Fable 5.1
```json
{
  "model": "claude-fable-5-1",
  "messages": [
    {
      "role": "system",
      "content": "You are a principal research analyst. Provide rigorous, source-aware analysis."
    },
    {
      "role": "user",
      "content": "Given this corpus of quarterly reports, identify the three biggest emerging risks and quantify their exposure."
    }
  ],
  "max_tokens": 8000
}
```

### Production Code Generation
Generate production-ready code with Claude Fable 5.1
```json
{
  "model": "claude-fable-5-1",
  "messages": [
    {
      "role": "system",
      "content": "You are a senior software engineer. Write clean, well-tested, production code."
    },
    {
      "role": "user",
      "content": "Implement an idempotent payment reconciliation worker in Python with retries and unit tests."
    }
  ],
  "max_tokens": 6000
}
```

## Response Format
```json
{
  "id": "chatcmpl-abc123",
  "object": "chat.completion",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Response text here"
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 100,
    "completion_tokens": 50,
    "total_tokens": 150
  }
}
```

## Tips
- Top tier ($10/$50 per M) — use Claude Opus 5.5 ($4/$20) or Sonnet 5.5 ($2/$10) when tasks don't need maximum capability
- Cache reads cost $0.25/M (2.5% of input) — caching large repeated contexts is especially cheap on this model; 5-minute cache writes are $12.50/M
- 1M context window handles very large codebases and document sets in a single request
- Web search costs about 18.6 credits per request ($10 per 1,000 searches) on top of token usage
- Sampling params (`temperature`, `top_p`, `top_k`) are not accepted by Claude 4.7+ models — omit them (the console strips `temperature` automatically)
- Streaming recommended for long responses
- Compatible with both Anthropic Messages and OpenAI SDK formats

## Documentation
https://docs.anthropic.com/en/docs/about-claude/models