you need to contact someone on the plugin support or Anthropic!

The plugin is built by Firefox...It's part of the sidebar.

Hi Naviathan,

To my knowledge, there's no additional plugin associated with the sidebar. If you have trouble logging in from the sidebar, try to login to Claude from a normal window. If you still can't log in from a normal window, please share a screenshot of the message so we can troubleshoot further.

I don't understand why so many people don't know about this feature. Settings -> General -> Browser Layout -> Show sidebar. Right click inside sidebar and select Customize Sidebar. Check AI chatbot under Firefox Tools.

This happens because Anthropic no longer uses verification codes or passwords—only magic-link emails—so third-party plugins that expect a code can’t complete the login flow. The AI Chatbots sidebar can’t open or follow the magic link, so Claude sign-in simply won’t work there. The only fix is to use Claude directly in its supported interfaces (Anthropic’s site or official integrations) or ask the plugin developer to add support for magic-link authentication, since it can’t be done on the user side.

Hi Naviathan, if you are already signed into Claude in a regular tab, do you still need to sign in separately in the chatbot sidebar? Firefox does isolate cookies in some places (such as address bar search engine suggestions), but when I test with ChatGPT, the login from the regular tab carries over to the sidebar.