AionLabs · language model
Aion 3.5: pricing, context and benchmarks
Aion 3.5 is AionLabs's model released on September 23, 2026. It costs $3 per million input tokens and $6 per million output tokens, with a 262.1K-token context window. No independent score has been published for it so far.
What you need to know about Aion 3.5
AionLabs put Aion 3.5 online on September 23, 2026. It accepts text as input and produces text. Its context window reaches 262,144 tokens, larger than 58 % of the models in the registry, and it can write up to 32,768 tokens in one go.
It is a recent model: real-world feedback and independent scores are still scarce.
Aion 3.5 pricing
On OpenRouter, Aion 3.5 costs $3 per million input tokens and $6 per million output tokens. Counting three tokens read for every token written, its average price is $3.75 per million, more expensive than 82 % of paid models (4.9 times the median of $0.76).
A concrete example: a task that sends 2,000 tokens (about 1,500 words) and receives a 500-token answer costs $0.009. At 1,000 tasks a day, budget $270 a month. The price calculator redoes this with your own volumes.
Tokens already sent and cached are billed at $0.75 per million.
Performance and benchmarks
Epoch AI does not yet publish a capabilities index for Aion 3.5. We therefore show no made-up performance rating: only price, context and features count towards its score.
Features, privacy and local use
- It supports tool calling, so it can drive an AI agent, call APIs or MCP servers.
- It can answer in an enforced JSON format (structured outputs).
- It is a reasoning model: it "thinks" before answering, which helps on hard tasks but uses more output tokens.
Its weights are not published: it can only be used through the AionLabs API or a broker such as OpenRouter, which means sending your data off your machines.
Other AionLabs models
| Model | Released | Avg. price | ECI |
|---|---|---|---|
| Aion 3.5 Mini | Sep 23, 2026 | $0.88 | — |
| Aion-3.0-Mini | Jul 7, 2026 | $0.88 | — |
| Aion-3.0 | Jul 7, 2026 | $3.75 | — |
| Aion-2.0 | Feb 23, 2026 | $1 | — |
| Aion-RP 1.0 (8B) | Feb 4, 2025 | $1 | — |
Verdict
Computed score: 42/100, from public data (performance, price, context, features).
Strengths
- Agent-ready: tool calling and structured JSON output.
Limitations
- Expensive: costlier than 82 % of paid models.
- No independent score published: performance cannot be verified.
- Text only: reads neither images nor files.
Avoid if…
- you process large volumes on a tight budget;
- your data must not leave your servers;
- your tasks are mostly simple: a non-reasoning model will cost less.
Alternatives
- Pareto 26.9$3.75
- GPT-5$3.44
- GPT-5.1$3.44
- Mistral Medium 3.5$3
- GPT-5.1-Codex-Max$3.44
- GPT-5.1-Codex$3.44
Comparisons and tools
Learn more
Frequently asked questions
How much does Aion 3.5 cost?
$3 per million input tokens and $6 per million output tokens on OpenRouter (checked October 25, 2026). A task with 2,000 tokens read and 500 written costs $0.009.
How big is Aion 3.5's context window?
262,144 tokens, roughly 197,000 words, with a maximum of 32,768 output tokens.
Can Aion 3.5 run locally?
No, AionLabs does not publish its weights: it is API-only.
Is Aion 3.5 suitable for an AI agent?
Technically yes: it supports tool calling and structured outputs. Then check its cost for your volume.
What are the alternatives to Aion 3.5?
The closest models on price and performance are Pareto 26.9, GPT-5, and GPT-5.1.
Related articles
- Mistral AI: models, pricing and agentsOctober 25, 2026
- LLM benchmarks: how to read model rankingsOctober 24, 2026
- Running a local LLM: hardware, software, and limitationsOctober 24, 2026
- Open-source or closed models for your AI agents?October 5, 2026
Neutrality. No affiliate links. No vendor pays to be reviewed, rated or ranked. Reviews are directed by François Chollet, neutral and factual, and every data point is dated and sourced. How we score