GitHub Copilot CLI: Plan Mode Hard-Blocks File Edits

GitHub has updated its Copilot CLI, specifically closing a loophole in its "plan mode." Previously, an AI agent could modify files during the planning phase, even though it was not supposed to. Now, built-in tool calls that would change the workspace are hard-blocked at the tool-call layer when in plan mode. This means the system rejects these actions before they can even reach the execution engine. This architectural change makes it a significant security improvement, rather than just a documentation update. The update arrived shortly after researchers demonstrated a method to bypass Copilot's safety refusals. This new hard-block prevents planning agents from altering files without developer approval, which is especially important in automated workflows. The update also extends the sandbox filesystem policy to cover Language Server Protocol file reads and rename edits.