How to configure LSP?

Question

I use opencode for embedded development. and I found LSP report many error and warning to AI assistant.
and assistant always want to fix it. but it is LSP error. LSP haven't found them.
Like below:

Error [5:10] 'FreeRTOS.h' file not found
Error [27:8] Unknown type name 'w25qxx_io_t'
Error [47:18] Call to undeclared library function 'strlen' with type 'unsigned long long (const char *)'; ISO C99 and later do not support implicit function declarations

So my question is how to configure LSP make the LSP report correct information to AI assistant. or can we disable this report?

This issue might be a duplicate of existing issues. Please check:

Run LSP only at session end only, asking to fix errors in a subsequent message #2536: Discusses disabling LSP or running it at session end only, addressing concerns about LSP being too aggressive and noisy
How to get opencode to use LSP? #711: Another question about LSP configuration and usage
[FEATURE]: Disable LSP for external directories #7227: Feature request to disable LSP for external directories, which relates to controlling LSP behavior

Feel free to ignore if none of these address your specific case.

I was wondering as well. The docs say clangd is used as the LSP for C++ projects. I have tried adding .clangd config file into my project root with the contents

CompileFlags:
  CompilationDatabase: build/Debug

and I've finally fixed this issue for myself. For reference see https://clangd.llvm.org/config.html#compilationdatabase

start opencode with

OPENCODE_EXPERIMENTAL_LSP_TOOL=true opencode

Fix opencode solargraph lsp

Based on current codebase, one can configure clangd using the following config:

{
  "$schema": "https://opencode.ai/config.json",
  "lsp": {
    "clangd": {
      "command": ["C:\\msys64\\ucrt64\\bin\\clangd.exe", "--background-index", "--clang-tidy"]
    }
  }
}

You can use a project-level opencode.jsonc to override the global config if your different projects uses different clangd and/or with different clangd configuration. My own use-case is not embedded development but at least for my own use-case (MSYS2 C++ development) it works as intended.

LSP diagnostics are fed to the AI assistant to help it understand your code — but if a particular LSP server is producing noisy or incorrect diagnostics (like missing headers or unknown types for embedded development), you can configure or disable it.

To disable LSP entirely:

{ "lsp": false }

To disable a specific LSP server (e.g. clangd which is likely causing your C errors):

{
  "lsp": {
    "clangd": { "disabled": true }
  }
}

To keep LSP enabled but configure it, you can pass initialization options or environment variables. For clangd specifically, you might want to configure your compile commands (compile_commands.json) to fix the missing header errors at the source.

For full details:
https://opencode.ai/docs/lsp/

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How to configure LSP? #7405

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github-actions commented on Jan 9, 2026

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