[Proposal] Reasoning part for thinking models

[mbleigh]

There are several models now whose API responses includes their reasoning as part of the response.

I propose a new ReasoningPart:

type ReasoningPart = {reasoning: string};

that can be used to capture reasoning in message responses. So a response might look like:

{
  message: {
    role: "model",
    content: [
      {reasoning: "I am thinking about what I'm going to do..."},
      {text: "This is my actual answer."}
    ]
}

[cabljac]

Hey @mbleigh this seems to be supported now, are there any gotchas or is there anything remaining for this feature, or is it complete? We're keen to use it in plugins we're working on.