Chromium processes leak on MCP client disconnect (macOS, VSCode)

Environment

• OS: macOS 14 (darwin 25.5.0)
• MCP server: @playwright/mcp@latest invoked via npm exec @playwright/mcp@latest --isolated
• MCP client: Claude Code VSCode extension
• Node: v20.x (system)

Observed

After a normal day of coding sessions, ~82 Playwright-related processes were alive on the machine — a mix of npm exec @playwright/mcp wrappers, node …/playwright-mcp binaries, and Chromium processes under ~/Library/Caches/ms-playwright/. None were tied to an active MCP session; they had reparented to launchd.

$ pgrep -f '@playwright/mcp|playwright-mcp|ms-playwright' | wc -l
82

Killing them all was safe (no user session was using them) and immediately freed ~4 GB RAM.

Expected

When an MCP client disconnects, the @playwright/mcp server should tear down its browser context and exit, releasing its Chromium subprocess. --isolated should make this per-session cleanup automatic.

Actual

Some subset of disconnect paths leaves the Chromium child alive. Because the Chromium child inherits stdio pipes but is not otherwise session-bound, when the node parent dies (or is killed by the MCP client's cleanup) Chromium is reparented to launchd and lingers until reboot.

Not reliably reproducible on demand

The leak seems tied to abnormal disconnects (VSCode window closed with a session running, extension host restart, session compaction mid-tool-call). Clean end-of-session — where the model calls browser_close and then the client disconnects — does NOT appear to leak.

Ask

1. Is the intended contract that clients MUST call browser_close before disconnect, or should --isolated auto-close on transport disconnect?
2. If the former, is there a plan to add a --auto-close-on-disconnect flag or make it default under --isolated?
3. If the latter, would you accept a repro-focused issue with a synthetic disconnect test?

Happy to package a minimal repro if item 3 is the answer — or if it's item 1, I'll update the caller's docs and close this out.

Workaround in place (in case useful to others)

A narrow-pattern reaper that matches ONLY Playwright's own footprint (@playwright/mcp, playwright-mcp, ms-playwright, @playwright+test, /playwright/test) — will not touch Chrome, Chromium, or IDE crashpad handlers. Runs on SessionStart via a Claude Code hook.