On the local page, Start reading checks your quota with the official client every 60 seconds. Stop ends it and closes only the program it started. Nothing reads by itself, and other Codex processes are never touched.
Stopped
On this computer
Off by default. When on, readings are written to the companion's journal (its data folder) only when a value changes or every 15 minutes. It is not encrypted.
Off by default. Fixed texts about a window change, reset credits and low remaining. macOS shows them under Script Editor with your notification and Focus settings. Clicking one does not open CodexQuota, and nothing confirms it was shown.