Claude Mythos 5.1
Last verified September 7, 2026 · Anthropic pricing ↗$10.00/1M input · $50.00/1M output · 1.0M context · Anthropic
Limited access
Not generally available
Claude Mythos 5.1 is not on Anthropic’s open price list. Access is gated to vetted partners or a waitlist, so the rate below is what those customers pay rather than something you can sign up for. It is excluded from the calculator’s default model list and from every ranking.
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Pricing Details
AnthropicSame model as Fable 5.1 with safeguards lifted, launched September 1, 2026. Access restricted to vetted partners via Project Glasswing; Anthropic's pricing table marks it limited availability. Card is identical to Fable 5.1 to the cent, including the 0.025x cache read at $0.25/MTok - these two are the only rows on Anthropic's price list not using the standard 0.1x multiplier. Scores 60.9 on Terminal-Bench 4.0 against Fable 5.1's 55.8 and Mythos 5's 42.0 (Anthropic-reported), so the cheapest cache reads Anthropic sells sit on the model with the highest score and the shortest access list. RE-VERIFIED 2026-09-05 against the pricing page and the launch post. Anthropic's model page states Mythos 5.1 'is offered separately, by invitation only, as part of Project Glasswing' and 'shares Claude Fable 5.1's specifications and pricing'; the launch post says the two 'are the same model, but with different levels of safeguards' and that Mythos 5.1 'is identical to Fable 5.1'. GATING NUANCE THAT MATTERS: Anthropic names two doors, the Cyber Verification Program and the Life Sciences Verification Program, but the CVP page says it 'currently provides access to certain Opus- and Sonnet-class models' and 'in the near future, this program will also include access to Claude Mythos-class models'. So as of 2026-09-05 the cyber door is a registration of interest, not a purchase path; only the LSVP is described as having enrolled participants, done in partnership with the US government. Access is currently limited to a set of US organisations (the announcement scopes that sentence to Mythos 5.1 overall, NOT specifically to the life sciences programme - do not repeat that misreading), with stated intent to expand to domestic and international partners. Note two distinct US-only concepts that do not cancel: US-organisations-only ACCESS is free, while US-only INFERENCE ROUTING via inference_geo:'us' still costs the standard 1.1x on every token category for Claude 4.6+, giving $11.00 input, $0.275 cache read, $13.75 and $22.00 cache writes, $55.00 output, $5.50 and $27.50 batch. Anthropic does not name Mythos 5.1 individually in that rule; it rests on the generational scope statement. KEEPS ITS DISCOUNTS: unlike OpenAI's gated gpt-5.6-cyber (Responses API only, no Batch endpoint at all), Mythos 5.1 retains the full 50% batch discount at $5.00/$25.00. On a 3:1 blend Red is 1.406x Mythos 5.1 at standard rates but 2.813x once each model uses the cheapest tier it publishes. Model IDs: claude-mythos-5-1 on the Claude API, Google Cloud and Microsoft Foundry; anthropic.claude-mythos-5-1 on Bedrock. Retirement not sooner than 2027-09-01. NOT RESELLABLE: OpenRouter's full catalogue pulled 2026-09-05 (714,005 bytes, 431 models) has zero rows matching mythos, daybreak, cyber or glasswing, while Fable 5.1 is present with a batch variant. Do NOT confuse with claude-mythos-preview, a different and earlier model priced $25/$125 on the Glasswing page.
Input / 1M tokens
$10
Output / 1M tokens
$50
Context Window
1.0M
Max Output
128K
Price History
No price change recorded since 2026-09-07, when this site started tracking this model; it launched on 2026-09-01.
Frequently Asked Questions
Common questions about Claude Mythos 5.1 pricing and usage