Using Copilot's new agent/subagent feature, you can start a chat with a free model (e.g. GPT-5 Mini), have it spawn a subagent configured to use a premium model (e.g. Opus 4.5), and the expensive model runs without consuming premium credits...

Bug author submitted to MSRC -> was told "billing bypass is out of scope, file on GitHub" -> VSCode bot immediately closed it as "not planned"