VS Code agent host runs Copilot, Claude, and Codex in a dedicated process

This release note describes Visual Studio Code's new Agent Host architecture and UI improvements: agents run in separate processes enabling shared sessions across windows, a redesigned single-pane Agents editor integrates files and chat with improved diff support, session-management tools allow agents to list and message sessions and hand off work, and workflow enhancements include remembered defaults, Git worktree isolation for agent changes, command-prefix chat execution, and experimental Modern UI/UI API updates. These are product feature and workflow changes, not a security incident.