Small Codex tip: force sub-agents to use Luna too if you want to save usage

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I noticed something while using Codex that might help reduce token/usage consumption.

Even when I select GPT-5.6 Luna as the main model, Codex will sometimes create sub-agents and assign GPT-5.6 Sol to them instead. Since Sol is more expensive in terms of usage, this can burn through your Codex allowance surprisingly fast, especially when several sub-agents are spawned.

A simple workaround is to add an explicit instruction to your Codex prompt/instructions, something like:

«When creating sub-agents, always use GPT-5.6 Luna. Do not use GPT-5.6 Sol for sub-agents unless explicitly requested.»

After adding this constraint, you can keep the main workflow on Luna and prevent automatically spawned sub-agents from silently switching to Sol.

If you use Codex heavily with multi-agent tasks, this can save a noticeable amount of your usage quota.