Anthropic: Claude Mythos 5.1

Overview

The same model as Claude Fable 5.1, offered by Anthropic only to organizations verified through its verification programs, such as the Cyber Verification Program.

Provider

Anthropic

Modality

Text and image

Input

text, image

Output

text

Max output

128,000 tokens

Weights

Closed

Tags

reasoning, coding, agents, vision, long-context, security

Docs

Provider documentation

Data policy

Prompts go to

Anthropic (global routing by default)

Retention

Not used for model training without express permission. Claude Mythos 5.1 is a Covered Model that requires 30-day data retention and is not available under ZDR unless Anthropic expressly authorizes it

Zero data retention

Not offered

Region

Global by default, US-only inference via inference_geo at 1.1x pricing (Claude 4.6 and later)

Policy

Anthropic data policy

Summarised from the provider's published terms. The provider's own policy is what applies.

Pricing

Notes

Base price, same as Claude Fable 5.1. Anthropic requires the organization to be verified through one of its programs before use. Cache hits $0.25/1M. Batch 50% off.

Source

Anthropic pricing , last verified October 8, 2026

No markup on model usage: you pay the provider's list price.

API

OpenAI-compatible. Your API key and access to this model are set up for your workspace when you choose Use with Safeguard.

from openai import OpenAI

client = OpenAI(
    base_url="https://api.safeguard.sh/v1",
    api_key="SAFEGUARD_API_KEY",
)

response = client.chat.completions.create(
    model="anthropic/claude-mythos-5-1",
    messages=[{"role": "user", "content": "Hello"}],
)
print(response.choices[0].message.content)

Base URL https://api.safeguard.sh/v1, model anthropic/claude-mythos-5-1.