JetBrains puts its coding agent in separate worktrees: one branch per workspace, specs kept beside the code
Synopsis
JetBrains released ThinkRail, an agentic IDE that wraps the pi coding agent in a splittable editor workbench and puts each change in its own git worktree workspace with a separate branch and working directory, so agents work in parallel without touching your checkout. Project intent lives in a connected graph of SPEC.md files beside the code, which the agent reads, searches and maintains through dedicated tools so it survives the session. Full extension support is planned next, letting ThinkRail create the tools it needs from how you actually work.
Interpretation
A coding agent no longer edits your checkout directly; each one works in its own workspace cut from the repository. Previously an agent's edits sat in the same place as the developer's current checkout, so parallel tasks interfered with each other. ThinkRail opens any git repo as a project and cuts git worktrees from it as workspaces, each with its own branch and working directory; merge the good branch and delete the rest.
Project intent no longer lives only in the conversation but in a set of connected spec files beside the code. When a session ended, the agent's understanding of the project went with it and had to be rebuilt next time. A connected graph of SPEC.md files sits beside the code, and the agent reads, searches and maintains it through dedicated spec_* tools; a read-only Specs tool renders the graph as a tree in the workbench.
A UI change the agent proposes in chat appears as a before-and-after mockup that can be commented on. Previously such proposals arrived only as text or code, so a reviewer could not see the before and after side by side. Diagrams, option comparisons and file previews render inline in the chat; when the agent proposes a UI change it shows a before/after mockup commentable like a diff.
External tools the agent can call are confirmed before the call. Connecting external servers means the agent could otherwise take actions with side effects without your knowledge. For calls a server does not mark read-only, ThinkRail asks in the chat first; servers a repository defines stay off until you approve them; OAuth servers are signed in from Settings.
Perspective
The introduction addresses developers who use git repositories and want to run coding agents in parallel, covering workspace isolation, spec files, skills and workflows, MCP server connections, and both desktop-app and browser entry points; full extension support is described as a next step and is not yet included.
The material lists full extension support as a next step, at which point the agent will create tools based on how you work; that capability is not yet available, and the material gives no data on how isolated workspaces or spec files perform in real projects.