lsp-mode fails to start Vue language server: TypeError: Cannot read properties of undefined (reading 'protocol')

[ParsaJR]

Hello everyone.

I'm trying to setup the vue's language server on emacs using lsp-mode toolkit.

Here is my configuration:

(use-package lsp-mode
  :commands (lsp lsp-deferred)
  :init
  (setq lsp-keymap-prefix "C-c l")
  :config
  (lsp-enable-which-key-integration t))

(use-package lsp-ui
  :hook (lsp-mode . lsp-ui-mode)
  )

(use-package lsp-ivy)

Here is the npm packages that are installed globally in my computer:

@vue/language-server@3.3.7
typescript@6.0.3
typescript-language-server@5.3.0

Now, starting the language server in a *.vue buffer, i recieve the following error from vue's server:

/home/parsajr/.local/share/pnpm/store/v11/links/@vue/language-server/3.3.7/e6429b168f0f896f4f3f1e1b7e2fb73c224aa029e421c1319629d7d41df2d580/node_modules/@vue/language-server/lib/server.js:40
                        projectInfoPromise = sendTsServerRequest('_vue:' + ts.server.protocol.CommandTypes.ProjectInfo, {
                                                                                     ^

TypeError: Cannot read properties of undefined (reading 'protocol')
    at Object.getLanguageService (/home/parsajr/.local/share/pnpm/store/v11/links/@vue/language-server/3.3.7/e6429b168f0f896f4f3f1e1b7e2fb73c224aa029e421c1319629d7d41df2d580/node_modules/@vue/language-server/lib/server.js:40:86)
    at Immediate.<anonymous> (/home/parsajr/.local/share/pnpm/store/v11/links/@volar/language-server/2.4.28/c5d768f1c4e5c46a09828593d218fa4301d7696629ee279576380e7a3933cc71/node_modules/@volar/language-server/lib/features/languageFeatures.js:744:62)
    at process.processImmediate (node:internal/timers:484:21)

Node.js v22.22.2

Process vue-semantic-server stderr finished

Is there any compability issues between vue-language-server and typescript package? I cant really guess anything from this output, suppose i miss something?

[TargiX]

This does not look like a TypeScript 6 compatibility issue by itself. I tested the same package versions locally (@vue/language-server@3.3.7, typescript@6.0.3, and typescript-language-server@5.3.0), and typescript@6.0.3 does expose ts.server.protocol.

The exception instead means that the vue-language-server process is resolving a different/broken TypeScript instance. With pnpm global packages, the peer dependency link can become stale when these packages were installed or upgraded separately.

You can see exactly what that server resolves with:

ROOT="$(pnpm root -g)"

node - "$ROOT" <<'NODE'
const root = process.argv[2]
const vueServer = require.resolve('@vue/language-server', { paths: [root] })
const typescript = require.resolve('typescript', { paths: [vueServer] })
const ts = require(typescript)

console.log({
  vueServer,
  typescript,
  version: ts.version,
  hasServerProtocol: Boolean(ts.server?.protocol),
})
NODE

For the versions in the question, the last value should be true. If it is false, rebuild the global peer links together:

pnpm remove -g @vue/language-server typescript typescript-language-server
pnpm add -g typescript@6.0.3 typescript-language-server@5.3.0 @vue/language-server@3.3.7
hash -r

Then restart Emacs (or at least refresh its exec-path) and confirm that (executable-find "vue-language-server") points to the newly installed binary.

A project-local installation is even less prone to this problem:

pnpm add -D typescript@6.0.3 typescript-language-server@5.3.0 @vue/language-server@3.3.7

One more Emacs-specific detail: current lsp-volar is an add-on client and forwards tsserver/request to the TypeScript LSP client, so both Volar and typescript-language-server must be running after startup. But a missing TypeScript LSP client produces a separate Could not found 'ts-ls' lsp client message; it is not the cause of the ts.server.protocol exception shown here.

[ParsaJR]

Hey. Thank you so much for the detailed answer. I think now i finally managed to solve the issue after some painful debugging.

As you know, typescript version 7.0.0 has been released about two days ago.
And the thing is, the package @vue/language-server describes its typescript dependency like this:

	"peerDependencies": {
		"typescript": "*"
	},

I just manually pinned the version to 6 and after a pnpm install, the problem solved.

The npm/pnpm tools are keep installing the latest release of typescript that actually has some compability issues with the language-server. And this error:

TypeError: Cannot read properties of undefined (reading 'protocol')

Is a first aspect of it.

I'll notice the maintainer.

Thank you.

[ParsaJR]

@KazariEX
Hi.

I believe the package @vue/language-server has some problems after the release of typescript 7.

The package declares:

"peerDependencies": {
"typescript": "*"
}

This allows package managers to install unsupported TypeScript versions such as TypeScript 7.x.

For example, my pnpm resolves:

@vue/language-server@3.3.7
typescript@7.0.2

The language server then fails because it relies on TypeScript APIs that are not compatible with this version.

[KazariEX]

I’m not sure whether we should narrow the version, because Johnson is working on a way to integrate with TS7, and doing so would break this use case.

[ParsaJR]

By the way it was something that i encountered and newcomers will notice this, until the integration happens

[alewis001]

In case this helps someone else... I recently updated to the latest vue-language-server to use with Neovim (Lazyvim) and the lsp started to error on startup, the log contained:

[ERROR][2026-07-16 17:22:19] ...lar/neovim/0.12.4/share/nvim/runtime/lua/vim/lsp/log.lua:150	"rpc"	"vue-language-server"	"stderr"	"/Users/alewis/.local/share/nvim/mason/packages/vue-language-server/node_modules/@vue/language-server/lib/server.js:40\n                        projectInfoPromise = sendTsServerRequest('_vue:' + ts.server.protocol.CommandTypes.ProjectInfo, {\n                                                                                     ^\n\nTypeError: Cannot read properties of undefined (reading 'protocol')\n    at Object.getLanguageService (/Users/alewis/.local/share/nvim/mason/packages/vue-language-server/node_modules/@vue/language-server/lib/server.js:40:86)\n    at Immediate.<anonymous> (/Users/alewis/.local/share/nvim/mason/packages/vue-language-server/node_modules/@vue/language-server/node_modules/@volar/language-server/lib/features/languageFeatures.js:744:62)\n    at process.processImmediate (node:internal/timers:483:21)\n\nNode.js v20.19.2\n"

I had to go to my vue-language-server install (installed via a tool called Mason that's part of the Neovim ecosystem) and set the typescript dependency in the package.json to ^6.0.0which appears to have resolved the issue for me.

I'll see if I can cross post in Lazyvim