Dart LSP fails to initialize

[StrongTheDev]

Caused by:
    Server reset the connection
2026-04-03T10:48:37+03:00 INFO  [lsp] starting language server process. binary path: "C:\\Users\\adhue\\scoop\\apps\\flutter\\current\\bin\\dart.bat", working directory: "C:\\Users\\adhue\\Documents\\Projects\\Flutter\\appainter", args: []
2026-04-03T10:48:39+03:00 ERROR [crates/lsp/src/lsp.rs:531] cannot read LSP message headers
2026-04-03T10:48:39+03:00 ERROR [lsp] Server reset connection for a request "initialize" id 0
2026-04-03T10:48:39+03:00 ERROR [lsp] Shutdown request failure, server dart (id 26): server shut down
2026-04-03T10:48:39+03:00 ERROR [crates/lsp/src/lsp.rs:558] The pipe is being closed. (os error 232)
2026-04-03T10:48:39+03:00 ERROR [project::lsp_store] Failed to start language server "dart": initializing server dart, id 26

That's the log. it has been so for ages - i think since the year started. I thought there would be a fix immediately but i think it has really taken so long, so i'm making the issue now.

i'm using:

> flutter --version
Flutter 3.38.0 • channel stable • https://github.com/flutter/flutter.git
Framework • revision a0e9b9dbf7 (5 months ago) • 2025-11-11 15:00:09 -0600
Engine • hash 9ba28611ee8004751cbf039b10d0720ab4ebe521 (revision cb467e31a5) (4 months ago) • 2025-11-11 19:15:58.000Z
Tools • Dart 3.10.0 (build 3.10.0-290.4.beta) • DevTools 2.51.1

> dart --version
Dart SDK version: 3.10.0-290.4.beta (beta) (Thu Oct 30 11:12:42 2025 -0700) on "windows_x64"

In case of extra information i can provide, let me know.

[tsinis]

Hi @StrongTheDev

How does your settings.json (especially the "lsp" part) look like? You may want to try pointing to dart.exe directly in your Zed settings:

{
  "lsp": {
    "dart": {
      "binary": {
        "path": "C:\\Users\\adhue\\scoop\\apps\\flutter\\current\\bin\\cache\\dart-sdk\\bin\\dart.exe"
      }
    }
  }
}

[StrongTheDev]

\bin\cache\dart-sdk\bin\dart.exe"

Okay let me try with the .exe path instead.

[StrongTheDev]

Okay let me try with the .exe path instead.

Still has the same result:

[tsinis]

Hi @StrongTheDev, well, in that case, there are a few more things to check:

• Verify the LSP works outside Zed — run this in a terminal:

dart language-server --protocol=lsp

It should hang waiting for input (that's normal). If it prints errors or exits immediately, the issue is with the Dart installation itself.

• Check for conflicting extensions — disable other Zed extensions temporarily, especially anything that might also register a Dart language server.

• What is your Zed version? Older Zed versions had Windows pipe handling issues.

• Try a fresh Dart-only project — create an empty folder with a single .dart file to rule out project-specific issues.

If dart language-server --protocol=lsp fails in the terminal, the problem is upstream (Dart SDK or system config), not Zed or this extension. Hope it helps!

[StrongTheDev]

dart language-server --protocol=lsp

This works perfectly. It waits for input as expected.

• Check for conflicting extensions — disable other Zed extensions temporarily, especially anything that might also register a Dart language server.

I really don't have any other extension that is a dart language server, and sadly Zed has no convenience button to enable or disable extensions.

• What is your Zed version? Older Zed versions had Windows pipe handling issues.

I update almost every week. I use:

Zed 0.229.0 
7c07887d9555953bca7fe78417602114092ef8c8

0.229.0+stable.206.7c07887d9555953bca7fe78417602114092ef8c8

• Try a fresh Dart-only project — create an empty folder with a single .dart file to rule out project-specific issues.

Sure let me try this. I'll get back to you.

[StrongTheDev]

2026-04-07T16:23:59+03:00 INFO  [lsp] starting language server process. binary path: "C:\\Users\\adhue\\scoop\\apps\\flutter\\current\\bin\\cache\\dart-sdk\\bin\\dart.exe", working directory: "C:\\Users\\adhue\\Documents\\Projects\\Flutter\\PlainDartTestProject", args: []
2026-04-07T16:24:00+03:00 ERROR [crates/lsp/src/lsp.rs:531] cannot read LSP message headers
2026-04-07T16:24:00+03:00 ERROR [lsp] Server reset connection for a request "initialize" id 0
2026-04-07T16:24:00+03:00 ERROR [lsp] Shutdown request failure, server dart (id 25): server shut down
2026-04-07T16:24:00+03:00 ERROR [crates/lsp/src/lsp.rs:558] The pipe is being closed. (os error 232)
2026-04-07T16:24:00+03:00 ERROR [project::lsp_store] Failed to start language server "dart": initializing server dart, id 25

It still failed to work for a single file.

as a (maybe) bonus, i tried this in the terminal, but no response...

> dart language-server --protocol=lsp
{"jsonrpc":"2.0","id":2,"method":"initialize"}

[tsinis]

@StrongTheDev Looking at that first line args: [] - I assume arguments from extensions are not being forwarded, you may want to try to explicitly list them:

{
  "lsp": {
    "dart": {
      "binary": {
        "path": "C:\\Users\\adhue\\scoop\\apps\\flutter\\current\\bin\\cache\\dart-sdk\\bin\\dart.exe",
        "arguments": ["language-server", "--protocol=lsp"] // <--- add this line
      }
    }
  }
}

If it will not work - args from extensions not being passed through on Windows. I will have to find a Windows machine and try to replicate 🤔

[StrongTheDev]

"arguments": ["language-server", "--protocol=lsp"] // <--- add this line

ok. I have just tried this and it has worked properly with no further issues.

Now i wouldn't know why it stopped passing those args by default - because last year by December, it was fine.

[tsinis]

Glad to hear it's working @StrongTheDev! Those args should be passed by default when not explicitly provided, if I recall correctly. So it sounds like it's partially resolved on your end — but I agree that we should still keep the issue open and investigate why they aren't being passed in the first place.

[StrongTheDev]

Good morning/evening @tsinis .

I think I may have found the issue, and i think it was my fault (mostly).

Analysis

There was a time that dart was not in my path so i explicitly provided the path to the dart binary. That must be where the issue started from - because i did not know or add these arguments.

Reason

I think when you provide the path explicitly, Zed expects you to explicitly pass the arguments.
I don't know if that behavior can be edited via the extension api (e.g. to check if args are empty, then if they are, it tries applying default arguments).

I'm saying this because I recently added dart to path again, and (today) i just commented out the manually defined lsp entry in settings.json, and it worked fine.

Conclusion

So in conclusion, I'm so sorry bro 😅 i hope it has not taken much of your week.

[tsinis]

@StrongTheDev, got you and yep no worries, all good :)