Reference playwright mcp shared profile contention

All Playwright MCP instances on Console launch chrome against the same shared profile dir (~/.cache/ms-playwright-mcp/mcp-chrome-<hash>). When several sessions or subagents run at once, whichever grabs the browser first holds the lock; every other browser_navigate fails with "Browser is already in use ... use --isolated". Observed 2026-07-09: 4+ live playwright-mcp servers, one 16h-old chrome holding the lock, an entire 9-item UI smoke test blocked.

How to apply: do not fan out multiple browser-driving agents in parallel; serialize UI verification into ONE agent, or verify at HTTP/SQL/API level instead. Do not kill the lock-holding chrome unless its parent session is confirmed dead (it may be another live session mid-task). Long-term fix worth building: per-session --isolated profiles for the playwright MCP config. See [[reference_browser_mcp_playwright_default]].