Claude Mythos 5.1

Available

Limited-availability specialized model.

Access details: Anthropic API

The model ID to use in API requests.

claude-mythos-5-1

Updated Sep 23, 2026

Sources & notes

Capabilities & limits

Context window: 1M
Maximum output: 128K
Image input: Supported
Tool calling: Supported
Structured output: Supported

Pricing

USD / 1M tokens

Input: $10.00
Output: $50.00

Standard rates per million tokens. Discounts and long-context rates, where offered, are on Anthropic's pricing page.

Full rate card 5 rates

All prices in USD.

Base input tokens

$10.00 per 1M tokens

Claude API global standard

Output tokens

$50.00 per 1M tokens

Claude API global standard

Cache hits and refreshes

$0.25 per 1M tokens

prompt caching

5 minute cache writes

$12.50 per 1M tokens

prompt caching
5 minute duration

1 hour cache writes

$20.00 per 1M tokens

prompt caching
1 hour duration

Limited availability (Project Glasswing, by invitation). Cache hits are 0.025x the base input price. Batch API is 50% off ($5 input / $25 output per MTok).

Price history

Sep 23, 2026

Input $10.00 per million tokens

Sep 23, 2026

Output $50.00 per million tokens

Technical details

Parameters: Not published
Active parameters: Not published
Architecture: Not published
Training / knowledge cutoff: Jun 2026
Input modalities: Text, image
Output modalities: Text

From Anthropic

Official announcement ↗

Release & lifecycle

First available: Sep 1, 2026
available: As of Sep 23, 2026