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AI Choice Engine

Model comparison

Claude Fable 5.1 vs Mistral Medium 3.5

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

Catalog record checked September 26, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

Anthropic

Claude Fable 5.1

Frontier

vs

Mistral

Mistral Medium 3.5

Frontier · Open weights

AI model capability comparison
SpecificationClaude Fable 5.1Mistral Medium 3.5
ProviderAnthropicMistral
TierFrontierFrontier
Context windowWinner: 1M262K
Max output128KNot verifiedUnverified
Input / 1M tokens$10Winner: $1.50
Output / 1M tokens$50Winner: $7.50
WeightsClosedOpen
ParametersNot disclosedUnverified128B dense
Reasoning levelsadaptiveNot verifiedUnverified
Modalitiestext, imagetext, image
LicenseNot disclosedUnverifiedModified MIT
API model idclaude-fable-5-1mistral-medium-3-5
ReleasedSeptember 1, 2026April 28, 2026
Artificial Analysis Intelligence Index [max] (2026-09-26)53.4Not verifiedUnverified
Artificial Analysis Intelligence Index (2026-09-26)Not verifiedUnverified14.2
Humanity's Last Exam (2026-09-01)65Not verifiedUnverified
Terminal-Bench 2.1 (2026-09-26)91.4Not verifiedUnverified
Terminal-Bench 4.0 [max] (2026-09-26)52Not verifiedUnverified
DeepSWE 1.1 (2026-09-03)67.4Not verifiedUnverified

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

Where each score comes from, and how far it can be compared across models.

Pricing tiers

Claude Fable 5.1: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day.

Mistral Medium 3.5: Mistral first-party API $1.50/$7.50 per MTok; Mistral advertises up to 90% off cached input (exact cached rate not verified). Open weights under a Modified MIT licence. 128B dense.

FrontierRecord checked September 26, 2026

Claude Fable 5.1

Claude Fable 5.1 is Anthropic's model for the most demanding reasoning and long-horizon agentic work at $10/$50 — Anthropic now recommends Opus 5.5 as the default for most workloads.

Best for

  • Frontier agents
  • Hardest reasoning work
  • Fable 5 workloads at the same price

Watch out

Costs 2.5x Opus 5.5 per token and trails it on the Artificial Analysis Intelligence Index (53.4 vs 57.6, v4.3.2); reserve it for the hardest long-horizon work.

FrontierOpen weightsRecord checked September 26, 2026

Mistral Medium 3.5

Mistral Medium 3.5 is the model Mistral calls its new flagship — a 128B dense open-weight model with a 256K context, powering its Vibe remote agents.

Best for

  • EU-hosted frontier work
  • Open-weight self-hosting
  • Mistral Vibe agents

Watch out

Far behind US and Chinese frontier models on the Artificial Analysis index; max output is not published. Check the Modified MIT terms before redistribution.

When the cheaper one wins

Mistral Medium 3.5 is cheaper on output at $7.50 per million tokens against $50 for Claude Fable 5.1 — about 6.7×. 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: High

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: max output, parameter count, reasoning levels.
  • 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
  • Verified within the last 90 days — Newest catalog check was 2 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.

Related comparisons

Diving deeper on one model? Claude Fable 5.1 · Mistral Medium 3.5

Common questions

Claude Fable 5.1 vs Mistral Medium 3.5

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

Is Claude Fable 5.1 or Mistral Medium 3.5 cheaper for input?
Mistral Medium 3.5 is cheaper at $1.50 per million input tokens, against $10 for Claude Fable 5.1 — roughly 6.7× 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 Fable 5.1 has tiered pricing: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. Mistral Medium 3.5 has tiered pricing: Mistral first-party API $1.50/$7.50 per MTok; Mistral advertises up to 90% off cached input (exact cached rate not verified). Open weights under a Modified MIT licence. 128B dense.
Is Claude Fable 5.1 or Mistral Medium 3.5 cheaper for output?
Mistral Medium 3.5 is cheaper at $7.50 per million output tokens, against $50 for Claude Fable 5.1 — roughly 6.7× 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 Fable 5.1 has tiered pricing: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. Mistral Medium 3.5 has tiered pricing: Mistral first-party API $1.50/$7.50 per MTok; Mistral advertises up to 90% off cached input (exact cached rate not verified). Open weights under a Modified MIT licence. 128B dense.
Which has the larger context window, Claude Fable 5.1 or Mistral Medium 3.5?
Claude Fable 5.1 accepts 1M tokens against 262K for Mistral Medium 3.5. This only matters if you routinely send very long documents or large codebases.
Should I use Claude Fable 5.1 or Mistral Medium 3.5?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Fable 5.1 suits frontier agents; Mistral Medium 3.5 suits eu-hosted frontier work.
Can I self-host Claude Fable 5.1 or Mistral Medium 3.5?
Mistral Medium 3.5 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Claude Fable 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 Medium 3.5 costs $1.50 per 1M tokens versus $10 for Claude Fable 5.1 — a 6.7x difference at the headline tier.
  • Context: Claude Fable 5.1 takes 1M against 262K for Mistral Medium 3.5 — only decisive if your prompts approach the smaller window.
  • Measured capability: Claude Fable 5.1 leads Artificial Analysis Intelligence Index 53.4 to 14.2 (measured 2026-09-26).
  • Deployment: Mistral Medium 3.5 publishes weights you can self-host; the other is API-only.
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