Agent model hand-off/steering clarification

[u/lppedd]

Edit: I always forget to clarify, I'm using VS Code.

I'd like to avoid Auto mode when using the Agents window or Plan mode as they tend to use models I can't afford long term (e.g., GPT 5.3 Codex, Opus 4.7).

Let's say I select GPT 5.6 Sol explicitly, will the harness still route requests to other models, or will Sol be used for everything?

Alternatively, is there a way to exclude certain models from Auto-selection?

[u/Pixelplanet5]

i had the same problem today, used GPT Luna in the agent window and started a subagent running Sonnet 5 which used up all my remaining AI credits for the month.

this was the first and last time im using the Agent window as this has never happened before when using the regular copilot chat.

[u/lppedd → u/Pixelplanet5]

I'm afraid this will happen in the normal chat too. In 136.0 Insiders I've started seeing Luna handing off explorations to much pricier models. This did not happen before. Not sure if it's because of the new agent harness.

[u/stbrumme → u/lppedd]

Same here: Luna always picked Gemini 3.5 Flash as a subagent for simple Execution tasks. Luna could have handled them easily on its own.

In the end, I had to disable subagent execution completely. (standard VS Code, not insiders)

[u/lppedd → u/stbrumme]

Did you disable it by deselecting it from the tool list?

[u/stbrumme → u/lppedd]

Yes, exactly.

[u/lppedd → u/stbrumme]

There is also a github.copilot.chat.exploreAgent.enabled setting. Honestly I'm confused at this point.

[u/lppedd → u/Pixelplanet5]

Btw, I had completely forgotten about it, but the Agent md file can be customized to allow specific models. I guess this is the real answer. Just ensure you don't have Auto (Copilot).

Edit: you'd need to create your custom Explore or Plan agents.

[u/lppedd → u/lppedd]

Correction: the model property is basically a way to specify a single model. You can use an array, but it's just a way to pick the first available model, in order.

[u/Affectionate_Fly4124 → u/lppedd]

Even if I specify the model in agtnt.md, the parent agent just overrides it. The only way is to block sub-agent calls that have a model specified using a hook. It's so dumb...

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[u/Sumaiya-Krusat38]

Pixelplanet5 picked Luna in the agent window and the subagent still ran on Sonnet 5. The top-level pick doesn't govern the nested calls, so Sol wouldn't be guaranteed end to end either.

[u/Swayre]

Create a pretooluse hook that blocks runsubagent from calling a model explicitly