AI Models · Open-Source vs Paid

GPT-6 Astra Pro Paid vs Mistral Medium 3.5 Open

GPT-6 Astra Pro vs Mistral Medium 3.5 compared — price per token, context window, multimodality, openness and which to choose. Can the open-source model replace the paid one? Full 2026 breakdown.

GPT-6 Astra Pro — full profile ›

Prices & specs refreshed from live data · olud.ai

Open-model prices = cheapest provider via OpenRouter; official maker rates may be higher.

GPT-6 Astra ProPaidOpenAI

$10 /M input
$50 /M outputManaged API (no infra to run)

TypeProprietary

Context window1.1M tokens

MultimodalYes

Self-hostNo

Mistral Medium 3.5OpenMistral AI

$1.5 /M input
$7.5 /M outputNo per-token fees if you self-host

TypeOpen-weight

Context window262K tokens

MultimodalYes

Self-hostYes

Choose Mistral Medium 3.5 if you want to self-host, keep your data private and skip per-token fees — it's open-weight and runs on your own hardware. Choose GPT-6 Astra Pro if you want frontier capability through a managed API with zero infrastructure to run.

GPT-6 Astra Pro vs Mistral Medium 3.5 specs

Spec	GPT-6 Astra Pro	Mistral Medium 3.5	Winner
Maker	OpenAI	Mistral AI	–
Type	Proprietary	Open-weight	Mistral Medium 3.5
Context window	1.1M tokens	262K tokens	GPT-6 Astra Pro
Input price	$10/M	$1.5/M · free self-host	Mistral Medium 3.5
Output price	$50/M	$7.5/M · free self-host	Mistral Medium 3.5
Vision / multimodal	Yes	Yes	= Tie
Tool / function calling	Yes	Yes	= Tie
Self-hostable	No (API only)	Yes	Mistral Medium 3.5
License	Proprietary	Apache 2.0	Mistral Medium 3.5

Price gap & when to choose each

6.7×cheaper per output token

Mistral Medium 3.5 is ~6.7× cheaper than GPT-6 Astra Pro on output tokens ($7.5 vs $50 per M tokens).

Choose GPT-6 Astra Pro if…

You want frontier performance through a managed API
You need the longer 1.1M context window
You value reliability & ecosystem
You don't want to manage infrastructure

Choose Mistral Medium 3.5 if…

You want to self-host or run on your cloud
You prioritize data privacy & control
You want the lowest operating costs
You are building open or reproducible AI

Feature comparison

Capability	GPT-6 Astra Pro	Mistral Medium 3.5
Open weights (downloadable)	✗	✓
Self-hostable	✗	✓
Runs fully offline	✗	✓
Vision / multimodal	✓	✓
Tool / function calling	✓	✓
1M+ context window	✓	✗

Benchmarks: GPT-6 Astra Pro vs Mistral Medium 3.5

Independent benchmark scores measured by Artificial Analysis. Higher is better (except latency).

GPT-6 Astra Pro

Mistral Medium 3.5

Intelligence index

–

14.9

Coding index

–

46.9

GPQA

–

74.8%

Humanity's Last Exam

–

13.8%

Long Context Reasoning

–

69.3%

SciCode

–

40.2%

IFBench

–

68.8%

τ²-Bench

–

94.2%

τ-Bench Banking

–

15.1%

Terminal-Bench

–

50.6%

Terminal-Bench Hard

–

33.3%

Speed

–

142.2 tok/s

Latency

–

0.74s

Intelligence per $

–

Benchmark data by Artificial Analysis.

How GPT-6 Astra Pro and Mistral Medium 3.5 score

🏆 Best value & openness: Mistral Medium 3.5 (4.6 vs 2.9 / 5)

Criterion	GPT-6 Astra Pro	Mistral Medium 3.5
Cost-efficiency	2.0	4.0
Context window	5.0	4.0
Openness	1.5	5.0
Self-hosting	1.0	5.0
Multimodality	5.0	5.0

Scores come from live data — output price (cost), context length, open vs closed weights (openness & self-hosting) and vision/tool support (multimodality). Raw task quality isn't scored here; it depends on your benchmark — see the verdict.

What each model is

GPT-6 Astra Pro Paid

OpenAI · Proprietary

GPT-6 Astra Pro is the same underlying model as [GPT-6 Astra](https://openrouter.ai/openai/gpt-6-astra), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. Learn more in OpenAI's docs: https://develope

Mistral Medium 3.5 Open

Mistral AI · Open-weight

Mistral Medium 3.5 is a dense 128B instruction-following model from Mistral AI. It supports text and image inputs with text output, and is designed for agentic workflows, coding, and complex...

Other models in these families

These variants are tracked but not compared here — one page per family keeps the comparison readable.

Other variants tracked

Mistral Medium 3.5 (batch)Mistral Small 4Mistral Small 4 (batch)Mistral Medium 3.1Mistral Medium 3.1 (batch)Mistral Large 3 2512Mistral Large 3 2512 (batch)Devstral 2 2512Mistral Medium 3Mistral Small 3.1 24BMistral Small 3.2 24BMistral LargeMistral Large 2407Mistral Small 3SabaMinistral 3 14B 2512Mixtral 8x22B InstructMinistral 3 8B 2512Ministral 3 8B 2512 (batch)Ministral 3 3B 2512UncensoredCodestral 2508Codestral 2508 (batch)Voxtral Small 24B 2507Mistral Nemo

Frequently asked questions

Is Mistral Medium 3.5 as good as GPT-6 Astra Pro?

Mistral Medium 3.5 is open-weight and competitive on many tasks, but GPT-6 Astra Pro may still lead on the hardest reasoning and agentic work. The gap keeps narrowing — benchmark both on your actual use case before deciding.

Can I run Mistral Medium 3.5 locally?

Yes. Mistral Medium 3.5 has open weights, so you can self-host it on your own GPUs or run it via a low-cost API. GPT-6 Astra Pro is API-only and cannot be self-hosted.

How much cheaper is Mistral Medium 3.5?

Mistral Medium 3.5 costs $7.5/M output vs $50/M for GPT-6 Astra Pro — roughly 7x cheaper via API, and free if you self-host.

GPT-6 Astra Pro vs Mistral Medium 3.5 — which should I pick in 2026?

Choose Mistral Medium 3.5 if you want to self-host, keep your data private and skip per-token fees — it's open-weight and runs on your own hardware. Choose GPT-6 Astra Pro if you want frontier capability through a managed API with zero infrastructure to run.

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