It does, but it's very poorly documented and quite unstable (on purpose i think). What the other commenter said about the VSCode BYOK seems to be the more reliable way.

I tried adding a Foundry LLM as Github Copilot custom model and failed miserably. But with VSCode BYOK (and Github Copilot as the interfact) i did get it working, and i can now use Deepseek V4 Flash with Copilot.

AFAIK you can already use custom models in VSCode Copilot, but probably not for cloud workloads yet.

It has supported custom, local, any BYOM for quite a while.

I work at GitHub but even then I often use OpenRouter models in the CLI and Copilot App

Copilot Chat supports BYOK since Oct 2025 for the VSCode plugin: https://code.visualstudio.com/blogs/2026/06/18/byok-vscode