Help Logging stdio Output from a TypeScript LSP in Helix

[babucarr32]

I am trying to follow a tutorial on how to create an LSP using typescript.
But unfortunately I am not able to have my lsp log the the output to a file /tmp/lsp.log.
Any help will be appreciated.

languages.toml

[language-server.lsp-demo]
command = "npx"
args = ["ts-node", "/Users/USER/Documents/programs/javaScript/lsp-demo/server/src/server.ts"]

Running hx ~/.cache/helix/helix.log I can see the following.

2025-05-25T18:43:57.487 helix_lsp::transport [ERROR] typos err <- "2025-05-25T18:43:57.487409Z DEBUG typos_lsp::lsp: initialize: {\"processId\":18255,\"rootPath\":\"/Users/USER/Documents/programs/javaScript/lsp-demo\",\"rootUri\":\"file:///Users/USER/Documents/programs/javaScript/lsp-demo\",\"initializationOptions\":{\"diagnosticSeverity\":\"Error\"},\"capabilities\":{\"workspace\":{\"applyEdit\":true,\"workspaceEdit\":{\"documentChanges\":true,\"resourceOperations\":[\"create\",\"rename\",\"delete\"],\"failureHandling\":\"abort\",\"normalizesLineEndings\":false},\"didChangeConfiguration\":{\"dynamicRegistration\":false},\"didChangeWatchedFiles\":{\"dynamicRegistration\":true,\"relativePatternSupport\":false},\"symbol\":{\"dynamicRegistration\":false},\"executeCommand\":{\"dynamicRegistration\":false},\"workspaceFolders\":true,\"configuration\":true,\"fileOperations\":{\"didRename\":true,\"willRename\":true},\"inlayHint\":{\"refreshSupport\":false}},\"textDocument\":{\"completion\":{\"completionItem\":{\"snippetSupport\":true,\"deprecatedSupport\":true,\"tagSupport\":{\"valueSet\":[1]},\"insertReplaceSupport\":true,\"resolveSupport\":{\"properties\":[\"documentation\",\"detail\",\"additionalTextEdits\"]}},\"completionItemKind\":{}},\"hover\":{\"contentFormat\":[\"markdown\"]},\"signatureHelp\":{\"signatureInformation\":{\"documentationFormat\":[\"markdown\"],\"parameterInformation\":{\"labelOffsetSupport\":true},\"activeParameterSupport\":true}},\"formatting\":{\"dynamicRegistration\":false},\"codeAction\":{\"codeActionLiteralSupport\":{\"codeActionKind\":{\"valueSet\":[\"\",\"quickfix\",\"refactor\",\"refactor.extract\",\"refactor.inline\",\"refactor.rewrite\",\"source\",\"source.organizeImports\"]}},\"isPreferredSupport\":true,\"disabledSupport\":true,\"dataSupport\":true,\"resolveSupport\":{\"properties\":[\"edit\",\"command\"]}},\"rename\":{\"dynamicRegistration\":false,\"prepareSupport\":true,\"honorsChangeAnnotations\":false},\"publishDiagnostics\":{\"tagSupport\":{\"valueSet\":[1,2]},\"versionSupport\":true},\"inlayHint\":{\"dynamicRegistration\":false}},\"window\":{\"workDoneProgress\":true},\"general\":{\"positionEncodings\":[\"utf-8\",\"utf-32\",\"utf-16\"]}},\"workspaceFolders\":[{\"uri\":\"file:///Users/USER/Documents/programs/javaScript/lsp-demo\",\"name\":\"lsp-demo\"}],\"clientInfo\":{\"name\":\"helix\",\"version\":\"25.01.1 (523e8aa7)\"}}\n"

Repo: https://github.com/babucarr32/helix-typescript-lsp-help

[the-mikedavis]

You can run helix with hx -v to increase the log verbosity. That will show the communication to and from the language server. Helix also logs an error line for anything a server prints on stderr.