Recently LSP has stopped working for me.

I'm getting this message for all files in my project.

LSP :: example_filename.c not in project or it is blacklisted.

How can I investigate this, if it's blacklisted, how can I reset the blacklist?

  • LSP is a protocol so it neither works nor can stop working. You're presumably talking about some implementation of this protocol, so please say which implementation you're using (probably lsp-mode or eglot on Emacs's side, and some LSP server on the other side but I can't begin to guess about that other side).
    – Stefan
    Dec 17, 2019 at 15:32
  • The question is tagged lsp-mode, but I could have included that in the title (will edit).
    – ideasman42
    Dec 17, 2019 at 23:37
  • 2
    I had to manually add the folder to the workspace by lsp-workspace-folders-add
    – capitrane
    Feb 3, 2021 at 9:08

3 Answers 3


I somehow managed to blacklist my own project, removing .lsp-session-v1 resolved the issue.

This could be located in either:

  • ~/.emacs.d/.lsp-session-v1
  • ~/.config/emacs/.lsp-session-v1

Although I might have been able to solve this using lsp-workspace-blacklist-remove

  • I don't have folder name called ~/.emacs.d/.lsp-session-* could it be located in somewhere else?
    – alper
    Mar 22, 2022 at 9:20
  • Updated answer to show two possible locations.
    – ideasman42
    Mar 22, 2022 at 10:41
  • I was able to find a file called ~/var/lsp/session.el , could it be the related file?
    – alper
    Mar 22, 2022 at 11:25

@capitrane comment had the answer for me: M-x lsp-workspace-folders-add from within the project, and it started to work.

  • Please don't add "thank you" as an answer. Instead, vote up the answers that you find helpful. - From Review
    – erikstokes
    Jun 16, 2021 at 23:02
  • 1
    There was no such answer -- it was an old comment which deserves to be an answer. Jun 17, 2021 at 21:15
  • 1
    But you shouldn't just copy the comment: make it useful for naive users. E.g. I don't know much about lsp, so I have no idea whether what you quote is a function or a variable. I also have no idea how exactly to call the function/set the variable to add the folder. I can guess and I know how to get around the docs to figure out how to use it, but a noob might not. So by all means, credit @capitrane, make his/her comment an answer, but don't just copy the comment: you spent some time to make it work for you, so explain it in enough detail to enable a naive user to use it.
    – NickD
    Jun 25, 2021 at 14:16
  • Answer updated appropriately. Jul 6, 2021 at 17:17

M-x lsp works for me. ("Entry point for the server startup.")

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