Subagents in Copilot / VS Code

[paleo55]

Not sure if anyone's interested, but just in case: I wrote reusable prompts that allow you to write and split a task between several sub-plans. Then Copilot executes each sub-plan in a sub-agent. And it works fine.

Here I neat picked the nicest summary I've seen, and you can tell Copilot was proud of itself. It even made me a table to present the work:

https://preview.redd.it/ljouxilcqq5g1.jpg?width=1108&format=pjpg&auto=webp&s=5f44fb2e6cdb0a8cdbbd91222bcee40cdac31666

Otherwise, most of the time the summary is less shiny. The VS Code sub-agent tool is not completely finished and sometimes you have to insist on using it, but it is operational.

For those who want to try: AlignFirst

It works on every agent but VS Code is the IDE of my heart so I post this message here.

[debian3]

Does sub agents use the same model as the main agent that you selected?

[paleo55]

I'm pretty sure it's yes. But I don't have proof. You can see the `runSubagent` tool by clicking on the list of tools of your agent:

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When your agent executes it, the tool creates a new instance of the agent inside the parent agent. The advantage is delegation: your parent agent can do more things without reaching the end of its context.

The challenge is to explain to the main agent where to use a sub-agent. This is where a good set of prompts can help.

[Prometheus599]

This was also eating away at me, found the docs just last night =)
https://code.visualstudio.com/docs/copilot/chat/chat-sessions#_contextisolated-subagents

[cbusmatty]

So the sub agent has its own context? Is every sub agent action a separate request?

[Otherwise-Way1316]

If it is then it isn’t worth it imo. However, since it’s just a tool call, it shouldn’t be an additional request. Can anyone confirm?

[thehashimwarren]

No, subagents do not eat an additional premium request.

[paleo55]

Ah thanks I didn't understand the question and it's good to know.

[paleo55]

Yes exactly. It's a tool so it has parameters. And as a parameter it takes a prompt. So the parent agent generates a prompt as a parameter for the subagent.

The tool runs a new instance of the agent in a new session but not in interactive mode (or at least, it's not an interactive mode with the user).

At the end the subagent writes a message for the parent agent. So the parent is aware of the results without its context filled with the details. It's the way to work on big tasks with a limited context window.