Tip: Copilot's `/btw` Side Chat Shares the Prompt Cache With the Primary Conversation
GitHub Changelog·medium signal
Copilot's new `/btw` command opens a side chat to ask a question without interrupting the agent's current turn, and the changelog is explicit that the side chat shares both the context and the prompt cache of the primary conversation. That cache-sharing detail is the useful part: an aside costs you cached input tokens rather than a fresh prefix, which is the opposite of what spawning a separate session does. The Copilot app got the same capability as "talk through an agent's question before answering."