tl;dr: JetBrains has released ThinkRail, an agentic IDE built around the pi coding agent that runs parallel work in isolated git-worktree workspaces, each with its own branch, chats, and Monaco-based editor. It uses "living specs" (SPEC.md files) as persistent project context, supports Agent Skills, MCP servers, and bring-your-own model providers (JetBrains AI or others), and ships as either an Electrobun desktop app or a CLI. The project is Apache 2.0 licensed, developed spec-first, with planned extension support so the agent can build its own tools.