Summary

Add five terminal management tools to the VSCode MCP Server extension, enabling AI assistants to create, control, and read output from VS Code integrated terminals via MCP.

This builds on the existing tool patterns (debug_tools, focus_editor) and adds a frequently requested capability: programmatic terminal access for AI-powered development workflows.

New Tools

Design Decisions & Trade-offs

Output Capture: Why Shell Execution Events (not file-based)

We explored three approaches for reading terminal output before settling on the current design:

Approach A: Passive capture via onDidWriteTerminalData (rejected)

• Captures raw terminal data stream to temp files on disk
• Pros: Captures everything, works without shell integration
• Cons: onDidWriteTerminalData is a proposed API, not available in stable @types/vscode. Also raises security concerns — terminal output (which may contain environment variables, API keys, passwords) would be persisted to disk files, creating a larger attack surface than xterm.js's in-memory scrollback buffer.

Approach B: File-based storage (rejected)

• Append-only files in os.tmpdir() with get_terminal_output(name, offset, limit, stripAnsi) pagination
• While this is memory-efficient (OS page cache handles caching) and suits the write-heavy/read-occasional pattern, the security concern remains: sensitive terminal data on disk survives terminal closure and VS Code restarts, is readable by other processes, and could be forensically recovered after deletion.
• Note: We considered that xterm.js already holds the same data in memory, and ~/.zsh_history persists commands to disk — so the threat model isn't dramatically different. Still, adding a new persistence vector seemed unnecessary when a better stable API exists.

Approach C: Shell execution events (chosen) ✅

• Uses onDidStartTerminalShellExecution + TerminalShellExecution.read() (stable since VS Code 1.93)
• Per-command structured output, already stripped of ANSI escape codes
• In-memory only (max 50 commands per terminal), auto-cleaned on terminal close
• Zero disk persistence = zero security concern
• Requires shell integration (enabled by default in VS Code 1.93+)

Architecture

terminal_output_capture.ts (utils)
  └─ onDidStartTerminalShellExecution listener
  └─ Per-command output stored in Map<terminalName, CommandRecord[]>
  └─ Auto-cleanup on terminal close + extension deactivation

terminal_tools.ts (tools)
  └─ create_terminal, list_terminals, send_terminal_text, close_terminal
  └─ get_terminal_output (reads from capture module)

extension.ts
  └─ Tool registration + capture initialization

Expected Impact

• AI-assisted terminal workflows: AI assistants can create terminals, run commands, and read results — enabling automated build/test/deploy cycles
• Debugging support: Read command output to diagnose build failures, test results, or runtime errors without manual copy-paste
• Multi-terminal orchestration: Manage multiple terminals programmatically (e.g., start a dev server in one, run tests in another, read both outputs)

Files Changed

Testing

• TypeScript compilation (tsc): passing
• Webpack build: passing
• Schema validation tests: passing
• Runtime testing requires VS Code Extension Development Host (F5)