AionLabs: Aion-2.0 vs Cohere: Command R+ (08-2024)

AionLabs: Aion-2.0 is a text model from AionLabs, released on 2026-02-23. Cohere: Command R+ (08-2024) is a text model from Cohere, released on 2024-08-30. Both are served through api14 as chat models in the text category, and both accept text as input and return text as output. Neither one handles images, audio or any other modality, so if your workload is purely language, both are candidates.

The two models differ in context length on paper: Aion-2.0 lists 131072 tokens and Command R+ lists 128000 tokens, which is close enough that context size should not decide the choice for you. The more useful differences are in the parameters each model exposes. Aion-2.0 supports reasoning and include_reasoning, so it can surface a reasoning pass, and it also supports tools, tool_choice, response_format, temperature, top_p and max_tokens. Command R+ does not expose a reasoning parameter, but it does support structured_outputs alongside tools, tool_choice, response_format, temperature, top_p, top_k, frequency_penalty, presence_penalty, seed and stop. In short, reasoning is only available on Aion-2.0, and structured outputs are only available on Command R+.

For practical selection, start with the capability you actually need. If your task benefits from a visible reasoning step, or you want to toggle reasoning on and off per request, Aion-2.0 is the one to call, since Command R+ has no equivalent parameter. If you need structured outputs, Command R+ is the one to call, because Aion-2.0 does not list that parameter. Both support tool calling, so agent style workflows with function calls work on either. Aion-2.0 is the cheaper of the two on both input and output, so when a task fits both models and you are optimizing for cost, Aion-2.0 is the default. Command R+ remains a reasonable pick when you want its extra sampling controls, such as seed for repeatable runs, top_k, or the frequency and presence penalties, or when structured outputs are part of your pipeline.

Calling either model through api14 works the same way because the API is OpenAI compatible. You send a chat completions request to the same endpoint with the same request body shape, and the only thing that changes is the model id. Use "aion-labs/aion-2.0" when you want Aion-2.0, and use "cohere/command-r-plus-08-2024" when you want Command R+. Messages, roles and the usual fields carry over unchanged, so switching between the two for an A/B test is a one line edit rather than a rewrite. Keep in mind that parameters are not perfectly interchangeable: sending reasoning to Command R+ or structured_outputs to Aion-2.0 is not supported, so trim the request body to the parameters the target model lists.

There are cases where the older model is still the better pick despite being the more expensive one. If your application depends on structured outputs, or on seed for reproducible sampling, or on top_k and the penalty parameters to shape generation, Command R+ gives you knobs that Aion-2.0 does not expose. In those situations the price difference is secondary to getting the behavior you need, and you should call "cohere/command-r-plus-08-2024" even though Aion-2.0 is cheaper on input and output.