> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apiyi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Claude Fable 5.1

> Claude Fable 5.1 on APIYI: $10 input / $50 output per 1M tokens, 1,000,000 context, 128,000 max output, available in 4 billing groups.

The first iteration of the Mythos-class flagship: input and output prices hold while cache reads drop to a quarter; inputs and outputs are retained for 30 days for abuse detection.

## Specifications

| Item | Value |
| - | - |
| **Model ID** | `claude-fable-5-1` · `claude-fable-5-1-thinking` |
| **Vendor** | Anthropic |
| **Vendor release** | 2026-09-01 |
| **Available on APIYI** | 2026-09-02 |
| **Knowledge cutoff** | Not disclosed |
| **Input modalities** | Text, Image |
| **Output modalities** | Text |
| **Context window** | 1,000,000 tokens |
| **Max output** | 128,000 tokens |
| **Billing** | Usage-based |

## Pricing

Prices in USD per 1M tokens (\$/1M).

| Input | Cached input | Output |
| - | - | - |
| \$10 | \$0.25 | \$50 |

<Info>The table shows **list prices**. Recharge promotions and group discounts **stack**; the console reflects the actual charge in real time. See [Pricing](/en/pricing) and [Recharge promotions](/en/faq/recharge-promotions).</Info>

## Endpoints

| Endpoint | Path | Supported |
| - | - | - |
| `OpenAI Chat Completions` | `POST /v1/chat/completions` | ✅ |
| `OpenAI Responses` | `POST /v1/responses` | — |
| `Anthropic Messages` | `POST /v1/messages` | ✅ |
| `Gemini Generate Content` | `POST /v1beta/models/{model}:generateContent` | — |
| `Image Generations` | `POST /v1/images/generations` | — |
| `Embeddings` | `POST /v1/embeddings` | — |

## Billing groups

| Group | Multiplier | Notes |
| - | - | - |
| `ClaudeCode` | 0.95× | 95% of list price |
| `Claude_Reverse` | 0.5× | 50% of list price |
| `Default` | 1× | List price |
| `SVIP` | 1× | List price |

Some groups carry extra discounts, stackable with recharge bonuses. See [Tokens and groups](/en/faq/token-and-groups).

## Supported features

| Feature | Supported |
| - | - |
| Streaming | ✅ |
| Tool calling | ✅ |
| Structured outputs | ✅ |
| Vision | ✅ |
| Prompt caching | ✅ |
| Extended thinking | Opt-in |

## Variants

| Model ID | Notes |
| - | - |
| `claude-fable-5-1` | Standard call. |
| `claude-fable-5-1-thinking` | Forced-thinking variant; pricing, endpoints and groups all identical to the standard model. |

## Example request

The example below calls `claude-fable-5-1` through OpenAI Chat Completions (`/v1/chat/completions`). Point base\_url at `https://api.apiyi.com/v1` — everything else matches the official API.

```bash theme={null}
curl https://api.apiyi.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $APIYI_API_KEY" \
  -d '{
    "model": "claude-fable-5-1",
    "messages": [{"role": "user", "content": "Hello"}]
  }'
```

<Tip>Read the key from an environment variable, never hard-coded. In production, issue separate tokens per use case so you can revoke and attribute usage individually.</Tip>

## Related docs

<CardGroup cols={2}>
  <Card title="Launch announcement" icon="megaphone" href="/en/news/claude-fable-5-1-launch">
    Background, benchmarks and migration notes for Claude Fable 5.1
  </Card>

  <Card title="Claude API Basics" icon="book-open" href="/en/api-capabilities/claude">
    Parameters, usage and best practices
  </Card>

  <Card title="Effort & Thinking" icon="book-open" href="/en/api-capabilities/claude-effort-thinking">
    Parameters, usage and best practices
  </Card>

  <Card title="Claude Fable 5" icon="git-compare" href="/en/models/claude-fable-5">
    Details for a model in the same family
  </Card>

  <Card title="Claude Opus 5" icon="git-compare" href="/en/models/claude-opus-5">
    Details for a model in the same family
  </Card>

  <Card title="Model pricing directory" icon="table" href="/en/models">
    Live pricing, endpoints and groups for all models
  </Card>
</CardGroup>

<Note>Specs on this page are maintained by hand in `models/data/model-details.json`; pricing and endpoints come from the live pricing API and are refreshed with every rebuild.</Note>


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