Rules
- Previous versions: the rule menu keeps the code before each of the last 10 saves; "Restore to editor" opens one unsaved
- Any rule can become the template for new rules ("Use as template for new rules")
- "Upload JSON" lists the file's contents: add only the checked rules and libraries, or "Replace all"

Styles
- The "Style options" menu: turn the Sass preprocessor off, keep styles out of nested frames, apply inside open shadow DOM
- A new or enabled rule's style appears in open tabs without a reload
- Firefox 136–146: on single-page sites, styles follow in-page navigation without a reload
- The "!important" checkbox no longer breaks @import; options toggled during a save are no longer lost

Libraries
- Optional automatic updates, daily or weekly ("Library updates" in the Extension panel)
- An empty response or a login page is treated as a download error; "Download again" keeps the previous file on failure
- The library window shows when the file was downloaded

Other
- If the extension has no access to sites, the settings page and the popup warn and offer an "Allow" button
- The background no longer wakes every 30 seconds when idle
- "What's new" in the About tab covers 4.0–4.2

Full changelog: https://tenrabbits.github.io/user-js-css-docs/changelog

AI agent tools (experimental). Let an agent on your computer — Claude Code, Cursor, Codex, VS Code and other MCP clients — manage your rules. Off by default; enable in Settings → MCP. The connection is local only: the extension connects to ws://127.0.0.1:8767, served by the user-js-css-mcp server your agent starts. Nothing leaves your machine; both sides verify a shared secret. Turn it off with the same switch. Server: https://www.npmjs.com/package/user-js-css-mcp