FiftyOne + Playwright Automation

Session notes for driving the FiftyOne App via the Playwright MCP. The App is a React/MUI SPA backed by a Python session over a WebSocket — most pitfalls come from that lifecycle.

1. The #1 Rule: Never browser_navigate or location.reload() after an operator that calls ctx.ops.reload_dataset()

Symptom. The FiftyOne server dies silently (curl localhost:5151 → HTTP 000; ps shows no PID). Dataset on disk is fine — the crash is session-layer. nohup/disown do NOT prevent it; the trigger is inside FiftyOne's own loop.

Cause. The navigate closes the active WebSocket while the remote session is mid-reload; session.wait() exits.

Fixes — ranked by cost.

A. session.refresh() via trigger-file IPC (best)

Neither session.refresh() nor dataset.reload() closes the WebSocket. They require a live handle, so replace session.wait() with a watcher loop. The bundled scripts/launch_app.py implements exactly this — clone a source dataset, launch remote=True, then poll a trigger file and reload() + refresh() whenever it appears: