Sol and Terra seems specifically post-trained to handle multi-agent orchestration, I'm guessing OpenAI feels like the trained data of when to do the spawning and what context to include for the new sub-agent is the magic in their new models, so that's what they're aiming to preserve. But, this is all a guess of course.

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resonious 4 hours ago | parent [-]

Right I saw them saying something along the lines of "they're good at subagents". But this seems true even with third party harnesses. So I'm wondering what Codex is hiding.

	▲	embedding-shape 4 hours ago \| parent [-]
		The only thing I've found impacting this, is when you specifically use the "Ultra" thinking/reasoning effort, then codex adds a small part to the system prompt to further get the model to use sub-agents. Any other reasoning/thinking effort than "Ultra" and this piece is no longer in the system prompt. Seemingly mostly a prompting thing it seems on the surface. GPT-5.5 (and maybe even GPT-5.4) already had (experimental?) support for sub-agents, remember using it even with -spark which I think was launched together with GPT-5.4 if I remember correctly, so this whole "use sub-agents" stuff most have been part of the training data for quite some time already, but maybe they've mainly been iterating on the prompt themselves since then.