Claude Fable 5.1
claude-fable-5-1Anthropic's model for the most demanding reasoning and long-horizon agentic work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.
- Price ยท 1M in / out
- $12.00 / $60.00
- Context
- 1,000,000 tokens
- Max. output
- 128,000 tokens
- Input โ output
- Text + Image โ Text
- Developer
- Anthropic
- Updated
- September 23, 2026
Playground
Try Claude Fable 5.1
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This run
at most $0.0615 ยท 6.15 credits reserved
Billed by the tokens actually used; the unused part of the reservation is refunded.
For accounts without a purchase: runs above 2 credits need a top-up.
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5 free credits ($0.05) when you sign up with Google
Usable 24 hours after sign-up, up to 5 runs per day and at most 2 credits per run. Other sign-in methods start without credits.
About Claude Fable 5.1
Claude Fable 5.1 is a model by Anthropic in the Text & chat category. On Railwail, Claude Fable 5.1 costs $12.00 per 1M input tokens and $60.00 per 1M output tokens. The context window holds 1,000,000 tokens, and one response can be up to 128,000 tokens long.
Pricing
| Input | $12.00 / 1M tokens |
|---|---|
| Output | $60.00 / 1M tokens |
- Billed by the tokens each request actually uses.
- 1 credit = $0.01
Cost calculator
Price calculator
Total
$4.20
420 credits
Per request
$0.042 ยท 4.2 credits
Each request is rounded up to 0.01 credits.
API
curl https://railwail.com/api/v1/chat/completions \
-H "Authorization: Bearer $RAILWAIL_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-fable-5-1",
"messages": [
{
"role": "user",
"content": "Explain what a vector database is in two sentences."
}
],
"max_tokens": 1024
}'import os
from openai import OpenAI
client = OpenAI(
api_key=os.environ["RAILWAIL_API_KEY"],
base_url="https://railwail.com/api/v1",
)
completion = client.chat.completions.create(
model="claude-fable-5-1",
messages=[
{
"role": "user",
"content": "Explain what a vector database is in two sentences.",
},
],
max_tokens=1024,
)
print(completion.choices[0].message.content)import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.RAILWAIL_API_KEY,
baseURL: "https://railwail.com/api/v1",
});
const completion = await client.chat.completions.create({
model: "claude-fable-5-1",
messages: [
{
role: "user",
content: "Explain what a vector database is in two sentences."
}
],
max_tokens: 1024
});
console.log(completion.choices[0].message.content);// npm install railwail
import railwail from "railwail";
const rw = railwail(process.env.RAILWAIL_API_KEY);
const res = await rw.chat("claude-fable-5-1", [
{ role: "user", content: "Explain what a vector database is in two sentences." },
], { max_tokens: 1024 });
console.log(res.choices[0].message.content);Specifications
- Model ID
claude-fable-5-1- Developer
- Anthropic
- Category
- Text & chat
- Input
- Text, Image
- Output
- Text
- Context window
- 1,000,000 tokens
- Max. output
- 128,000 tokens
- Billing
- By usage (tokens or GPU time)
- Released
- September 1, 2026
- Lifecycle
- Current version
- Catalog entry updated
- September 23, 2026
Input parameters
Inputs and settings from the model's input schema. The example in the API section shows which of them the API accepts.
promptrequiredUser message
Type: TextDefault: โAllowed values: up to 32,000 charactersstreamType: Yes/noDefault:falseAllowed values: โmax_tokensType: IntegerDefault:4096Allowed values: 1 to 128,000system_promptOptional system instruction
Type: TextDefault: โAllowed values: up to 8,000 characters
Tags
- anthropic
- claude
- fable
- flagship
- reasoning
- agentic
- vision
- long-context
- 1m-context
Use cases
Frequently asked questions
What is Claude Fable 5.1?
Claude Fable 5.1 is a model by Anthropic in the Text & chat category. On Railwail you can call it with an API key through the Railwail API.
How much does Claude Fable 5.1 cost on Railwail?
On Railwail, Claude Fable 5.1 costs $12.00 per 1M input tokens and $60.00 per 1M output tokens. You are charged for what each request actually uses. Usage is paid from prepaid credits; 1 credit equals $0.01.
What is the context window of Claude Fable 5.1?
The context window of Claude Fable 5.1 holds 1,000,000 tokens. One response can be up to 128,000 tokens long.
How fast is Claude Fable 5.1?
There are not enough measured runs of Claude Fable 5.1 on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.
Is Claude Fable 5.1 better than Claude Opus 5.5?
That depends on the task. Claude Fable 5.1 (Anthropic) and Claude Opus 5.5 (Anthropic) are both models in the Text & chat category. The comparison page shows their prices and specifications side by side.
Compare Claude Fable 5.1 and Claude Opus 5.5Can Claude Fable 5.1 process images?
Yes. Claude Fable 5.1 accepts images as input in addition to text.
How do I use Claude Fable 5.1 through the API?
Create a Railwail API key and send your request with the model ID claude-fable-5-1. Code examples for curl, Python and JavaScript are in the API section of this page.
Comparable models
All in this category- Claude Opus 4.8Anthropic
The most capable model of Anthropic's Opus 4 series. State of the art on long-horizon agentic work, coding and knowledge tasks, with a 1M-token context window at standard pricing.
- Claude Opus 5.5Anthropic
Anthropic's current Opus model for long-running agentic coding and knowledge work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.
- Claude Sonnet 5Anthropic
Anthropic's Sonnet model with the best combination of speed and intelligence. 1M-token context window, up to 128K output tokens, adaptive thinking.
Use Claude Fable 5.1 via the API
One API key for every model on Railwail. Usage is charged from prepaid credits, 1 credit = $0.01.