Model comparison

Claude Mythos 5.1 vs Mistral Large 3

Anthropic against Mistral, compared on context, price, and verified benchmark results.

Catalog record checked September 5, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below

Anthropic

Claude Mythos 5.1

Frontier

Mistral

Mistral Large 3

Frontier · Open weights

AI model capability comparison
Specification	Claude Mythos 5.1	Mistral Large 3
Provider	Anthropic	Mistral
Tier	Frontier	Frontier
Context window	Not verifiedUnverified	262K
Max output	Not verifiedUnverified	262K
Input / 1M tokens	$10	Winner: $0.50
Output / 1M tokens	$50	Winner: $1.50
Weights	Closed	Open
Parameters	cyber/bio research variant of Fable 5.1	675B total / 41B active (sparse MoE)
Reasoning levels	adaptive	Not verifiedUnverified
Modalities	text, image	text, image
License	Not disclosedUnverified	Apache 2.0
API model id	claude-mythos-5	mistral-large-3
Released	September 1, 2026	December 1, 2025
Artificial Analysis Intelligence Index (2026-08-14)	Not verifiedUnverified	46
GPQA Diamond (2025-12-02)	Not verifiedUnverified	43.9

Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
2025-12-02: Mistral — Introducing Mistral 3 (vendor, base model, 5-shot no CoT); independent review concursGraduate-level science reasoning: multiple-choice questions written by domain PhDs. Comparability: comparable with caveat — Small question pool: differences under ~2 points are within run-to-run noise. Chain-of-thought vs direct answering must match to compare.

Pricing tiers: Claude Mythos 5.1: Starts at $10/$50 per MTok — priced with Fable 5.1, which shares the same underlying model. API id claude-mythos-5 replaced the deprecated claude-mythos-preview. · Mistral Large 3: Mistral first-party API $0.50/$1.50 per MTok; cached input $0.05/MTok. Open weights (Apache 2.0), EU-hosted.

FrontierRecord checked September 3, 2026

Claude Mythos 5.1

Claude Mythos 5.1 is Anthropic's most capable model for cybersecurity and biology research — the Fable 5.1 model with fewer cyber/bio safeguards, restricted to vetted US organisations.

Best for

Cyber-defence research
Biology research
Claude Security workloads

Watch out

Invite-only (vetted US organisations, verification programmes); 30-day data retention applies by default. Same underlying model as Fable 5.1 — most teams should just use Fable.

FrontierOpen weightsRecord checked September 5, 2026

Mistral Large 3

Mistral Large 3 is Mistral's flagship — 262K-context, multimodal, Apache-2.0 open-weight at $0.50/$1.50.

Best for

Open-weight deployments
Multimodal EU-hosted inference
Balanced frontier work

Watch out

Verify multimodal support and EU data-residency on your endpoint.

When the cheaper one wins

Mistral Large 3 is cheaper on output at $1.50 per million tokens against $50 for Claude Mythos 5.1 — about 33×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.

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Evidence confidence: Medium

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

Pricing verified on both sides — Input and output rates are verified for both models.
2/5 core specs verified on both sides — Not published for at least one side: context window, max output, reasoning levels.
No shared named benchmark — No benchmark has been measured on both models.
Verified within the last 90 days — Newest catalog check was 6 days ago.
Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Claude Mythos 5.1: Anthropic — Claude Mythos (accessed 2026-09-03)
Claude Mythos 5.1: Anthropic — model deprecations (claude-mythos-5) (accessed 2026-09-03)
Mistral Large 3: Mistral docs — mistral-large-2512 (675B total / 41B active, 256K) (accessed 2026-09-05)
Mistral Large 3: Mistral — Introducing Mistral 3 (sparse MoE parameters) (accessed 2026-09-05)

Related comparisons

Diving deeper on one model? Claude Mythos 5.1 · Mistral Large 3

Common questions

Claude Mythos 5.1 vs Mistral Large 3

Answered from the verified figures on this page rather than general guidance.

Is Claude Mythos 5.1 or Mistral Large 3 cheaper for input?

Mistral Large 3 is cheaper at $0.50 per million input tokens, against $10 for Claude Mythos 5.1 — roughly 20× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Mythos 5.1 has tiered pricing: Starts at $10/$50 per MTok — priced with Fable 5.1, which shares the same underlying model. API id claude-mythos-5 replaced the deprecated claude-mythos-preview. Mistral Large 3 has tiered pricing: Mistral first-party API $0.50/$1.50 per MTok; cached input $0.05/MTok. Open weights (Apache 2.0), EU-hosted.

Is Claude Mythos 5.1 or Mistral Large 3 cheaper for output?

Mistral Large 3 is cheaper at $1.50 per million output tokens, against $50 for Claude Mythos 5.1 — roughly 33× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Mythos 5.1 has tiered pricing: Starts at $10/$50 per MTok — priced with Fable 5.1, which shares the same underlying model. API id claude-mythos-5 replaced the deprecated claude-mythos-preview. Mistral Large 3 has tiered pricing: Mistral first-party API $0.50/$1.50 per MTok; cached input $0.05/MTok. Open weights (Apache 2.0), EU-hosted.

Should I use Claude Mythos 5.1 or Mistral Large 3?

Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Mythos 5.1 suits cyber-defence research; Mistral Large 3 suits open-weight deployments.

Can I self-host Claude Mythos 5.1 or Mistral Large 3?

Mistral Large 3 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Claude Mythos 5.1 is a closed model whose supported access paths are controlled by its provider.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

Input price: Mistral Large 3 costs $0.50 per 1M tokens versus $10 for Claude Mythos 5.1 — a 20x difference at the headline tier.
Deployment: Mistral Large 3 publishes weights you can self-host; the other is API-only.

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