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AI Choice Engine

Model comparison

GPT-5.6 Luna vs Mistral Small 4

OpenAI 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

OpenAI

GPT-5.6 Luna

Budget

vs

Mistral

Mistral Small 4

Budget · Open weights

AI model capability comparison
SpecificationGPT-5.6 LunaMistral Small 4
ProviderOpenAIMistral
TierBudgetBudget
Context windowWinner: 1.05M262K
Max output128KNot verifiedUnverified
Input / 1M tokens$0.20Winner: $0.15
Output / 1M tokens$1.20Winner: $0.60
WeightsClosedOpen
Parametersprevious-generation GPT-5.6 small tier119B total / 6.5B active (MoE)
Reasoning levelsnone, low, medium, high, xhigh, maxNot verifiedUnverified
Modalitiestext, imagetext, image
LicenseNot disclosedUnverifiedApache 2.0
API model idgpt-5.6-lunamistral-small-2603
ReleasedJuly 9, 2026March 16, 2026
Artificial Analysis Intelligence Index [max] (2026-09-26)37.3Not verifiedUnverified
Artificial Analysis Intelligence Index (2026-09-26)Not verifiedUnverified11.3
SWE-bench Verified (2026-09-01)93Not verifiedUnverified
Terminal-Bench 2.1 (2026-07-09)84.7Not verifiedUnverified
LiveBench (2026-09-05)73.6Not 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

GPT-5.6 Luna: Launch list was $1/$6; cut to $0.20/$1.20 on 2026-07-30. Above 272K input the whole request bills 2x input / 1.5x output. Cached input $0.02/MTok; cache writes 1.25x input; batch $0.10/$0.60.

Mistral Small 4: Mistral first-party API $0.15/$0.60 per MTok. Open weights (Apache 2.0). 119B total / 6.5B active MoE.

BudgetRecord checked September 26, 2026

GPT-5.6 Luna

GPT-5.6 Luna was OpenAI's cheapest GPT-5.6 tier; GPT-6 Luna replaced it on 2026-09-22 at half the price ($0.10/$0.50).

Best for

  • Classification
  • High-volume chat
  • Latency-sensitive pipelines

Watch out

Superseded by GPT-6 Luna, which costs half as much and matches it on the Artificial Analysis index; still served, not deprecated.

BudgetOpen weightsRecord checked September 26, 2026

Mistral Small 4

Mistral Small 4 is Mistral's low-cost Apache-2.0 MoE — 6.5B active parameters with a 256K context and image input.

Best for

  • Cheap EU-hosted inference
  • Open-weight self-hosting
  • High-volume extraction

Watch out

Small active size: not for hard reasoning or agentic coding; max output is not published.

When the cheaper one wins

Mistral Small 4 is cheaper on output at $0.60 per million tokens against $1.20 for GPT-5.6 Luna — about 2.0×. 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.
  • 3/5 core specs verified on both sides — Not published for at least one side: max output, 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? GPT-5.6 Luna · Mistral Small 4

Common questions

GPT-5.6 Luna vs Mistral Small 4

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

Is GPT-5.6 Luna or Mistral Small 4 cheaper for input?
Mistral Small 4 is cheaper at $0.15 per million input tokens, against $0.20 for GPT-5.6 Luna — roughly 1.3× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.6 Luna has tiered pricing: Launch list was $1/$6; cut to $0.20/$1.20 on 2026-07-30. Above 272K input the whole request bills 2x input / 1.5x output. Cached input $0.02/MTok; cache writes 1.25x input; batch $0.10/$0.60. Mistral Small 4 has tiered pricing: Mistral first-party API $0.15/$0.60 per MTok. Open weights (Apache 2.0). 119B total / 6.5B active MoE.
Is GPT-5.6 Luna or Mistral Small 4 cheaper for output?
Mistral Small 4 is cheaper at $0.60 per million output tokens, against $1.20 for GPT-5.6 Luna — roughly 2.0× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.6 Luna has tiered pricing: Launch list was $1/$6; cut to $0.20/$1.20 on 2026-07-30. Above 272K input the whole request bills 2x input / 1.5x output. Cached input $0.02/MTok; cache writes 1.25x input; batch $0.10/$0.60. Mistral Small 4 has tiered pricing: Mistral first-party API $0.15/$0.60 per MTok. Open weights (Apache 2.0). 119B total / 6.5B active MoE.
Which has the larger context window, GPT-5.6 Luna or Mistral Small 4?
GPT-5.6 Luna accepts 1.05M tokens against 262K for Mistral Small 4. This only matters if you routinely send very long documents or large codebases.
Should I use GPT-5.6 Luna or Mistral Small 4?
Both sit in the budget tier, so the choice usually comes down to price and context rather than capability. GPT-5.6 Luna suits classification; Mistral Small 4 suits cheap eu-hosted inference.
Can I self-host GPT-5.6 Luna or Mistral Small 4?
Mistral Small 4 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. GPT-5.6 Luna 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 Small 4 costs $0.15 per 1M tokens versus $0.20 for GPT-5.6 Luna — a 1.3x difference at the headline tier.
  • Context: GPT-5.6 Luna takes 1.05M against 262K for Mistral Small 4 — only decisive if your prompts approach the smaller window.
  • Deployment: Mistral Small 4 publishes weights you can self-host; the other is API-only.
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