Elixir — LSP setup

• Builtin server: elixir-ls — elixir-ls
• Extensions: .ex .exs
• Install hint: https://github.com/elixir-lsp/elixir-ls

Install

ElixirLS needs Erlang/OTP and Elixir installed first. Build the release from https://github.com/elixir-lsp/elixir-ls and put the elixir-ls launcher script on PATH.

• macOS: brew install elixir-ls (Homebrew provides the launcher), or build the release manually
• Linux: clone elixir-ls, run mix deps.get && mix compile && mix elixir_ls.release2 -o release, then add release/ to PATH
• Windows: build the release and add the release dir (use the .bat launcher) to PATH

Confirm it resolves:

command -v elixir-ls

Configure

Builtin — usually NO config needed (auto-resolved by extension). Configure only to set priority, init options, override extensions, or disable. Same JSON shape in .codex/lsp-client.json (Codex) AND .opencode/lsp.json (OpenCode/omo):

{ "lsp": { "elixir-ls": { "priority": 100 } } }

For builtin ids in a PROJECT config, command is supplied automatically — only set priority/initialization/extensions/disabled/env. A fully custom (non-builtin) server with its own command must go in the USER config (~/.codex/lsp-client.json).

Initialization options (only if commonly needed)

None commonly required.

Alternatives

• lexical (not builtin): lexical — fast, modern alternative LSP.
• next-ls (not builtin): nextls --stdio — from the elixir-tools project.

Troubleshooting

• PATH: elixir-ls must be on PATH; reopen the shell after install.
• asdf users: the launcher is a shim — after asdf install, run asdf reshim elixir so the elixir-ls shim resolves, and ensure the Erlang/Elixir versions match the build.
• First start is slow: ElixirLS compiles your deps on first run; initial diagnostics can take a while on large projects.
• OTP mismatch: build elixir-ls with the same Erlang/Elixir versions you use for the project to avoid bytecode errors.

Verify

bun ../../scripts/verify-lsp.ts path/to/file.ex