R Session watcher

R session watcher connects vscode-R to a live R session and powers the workspace and data viewers, session-aware hover and completion, plots, help, web viewers, and RStudio API emulation.

Basic usage

The watcher is enabled by default through r.sessionWatcher. Run R: Create R terminal to start a managed terminal. vscode-R connects the session automatically and shows the attached R process in the status bar.

vscode-R 3.0.0 uses the bundled sess R package for this connection. If the package is missing or older than the extension, vscode-R asks whether it may install or update the bundled version. Managed terminals can reconnect after a VS Code window reload.

External and self-managed R sessions

To attach an R process started outside R: Create R terminal, run R: Attach External R Session (Copy command) from the Command Palette. This copies a short source(...) command to the clipboard. Run that command in the target R session.

The generated attach script installs or updates the bundled sess package if needed, then connects that R process to the current VS Code window. This makes it suitable for R sessions running in tmux, screen, or another self-managed terminal. Generate a new command when attaching to a different VS Code window.

To switch between connected sessions, focus the desired terminal and use the status bar item or R: Activate R Session.

The old ~/.vscode-R/init.R startup snippet and R: Attach Active Terminal command were removed in v3.0.0. If your .Rprofile still sources that file from a 2.x installation, remove the obsolete source(...) block.

Configuration

Configure session behavior with VS Code settings rather than R options(vsc.*). In particular:

• r.session.watchGlobalEnvironment controls workspace watching and session-aware hover and completion.
• r.session.emulateRStudioAPI controls RStudio API emulation.
• r.session.viewers.viewColumn controls where R webviews open.
• r.plot.backend selects the plot backend.

The R-side vsc.* options used by vscode-R 2.x are no longer read. See Extension settings for the current settings.

Disabling the watcher

Set r.sessionWatcher to false and restart or reload VS Code. Features that require communication with a live R session will then be unavailable.

How it works

The sess package and vscode-R exchange JSON-RPC messages over a local Unix domain socket on Linux and macOS, or a named pipe on Windows. This replaces the 2.x file-watching protocol based on request.log, globalenv.json, and plot.png.

Each connected R process has a stable session identity. The extension can work with multiple sessions, switch the active session, and reconnect managed terminals after the VS Code window reloads. Session files and local endpoints are created with owner-only permissions.