Bug: LANGUAGE_EXTENSIONS map has bare makefile key and is missing common extensions #15859

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1. github-actions

   assigned

   thdxr

   on Mar 3, 2026
2. github-actions

   added

   coreAnything pertaining to core functionality of the application (opencode server stuff)Anything pertaining to core functionality of the application (opencode server stuff)

   on Mar 3, 2026
3. github-actions commented on Mar 3, 2026

   

   github-actionsBot

   on Mar 3, 2026 – with GitHub Actions

   Contributor

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

   • Support C++ header file extensions (.hpp, .hh, .hxx, .h++) in LSP language detection #12660: Covers the same missing C++ header file extensions (.hpp, .hh, .hxx, .h++) in LSP language detection in LANGUAGE_EXTENSIONS

   The current issue is broader (also covering the bare makefile key bug and other missing extensions), so it may make sense to reference or consolidate with that existing issue.
4. xiong-ZH-zq commented on Mar 22, 2026

   

   xiong-ZH-zq

   on Mar 22, 2026

   Last edited by xiong-ZH-zq

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   +1, It would be helpful if support R LSP
5. thdxr

   assigned

   rekram1-node

   and unassigned

   thdxr

   on Apr 26, 2026
6. thdxr

   removed

   coreAnything pertaining to core functionality of the application (opencode server stuff)Anything pertaining to core functionality of the application (opencode server stuff)

   on May 3, 2026
7. github-actions commented on Jul 3, 2026

   

   github-actionsBot

   on Jul 3, 2026 – with GitHub Actions

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   To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.
8. github-actions

   closed this as not plannedon Jul 3, 2026
9. Bearmancer commented on Sep 13, 2026

   

   Bearmancer

   on Sep 13, 2026

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   Still reproducible on 1.18.30 (Windows, "lsp": true): the .jsonc entry named in this issue is still missing from LANGUAGE_EXTENSIONS, and the effect is silence, not an error.

   Mechanism

   .jsonc is absent from LANGUAGE_EXTENSIONS, so the didOpen languageId falls back to "plaintext". Biome's built-in server does list .jsonc in its extensions (so opencode routes the file to Biome), but Biome emits no diagnostics for languageId: "plaintext" — the file silently skips diagnostics.

   Source at dev:

   • packages/opencode/src/lsp/language.ts:1 — export const LANGUAGE_EXTENSIONS: Record<string, string> = {
   • packages/opencode/src/lsp/language.ts:53 — ".json": "json", — and no .jsonc key anywhere in the map
   • packages/opencode/src/lsp/client.ts:560 — const languageId = LANGUAGE_EXTENSIONS[extension] ?? "plaintext"

   Steps to reproduce

   1. Set "lsp": true in ~/.config/opencode/opencode.jsonc.
   2. Create a directory that contains a Biome root marker (e.g. package-lock.json).
   3. Write two files with identical bytes — broken.json and broken.jsonc:

   {
     "a": 1,
     "b":
   }

   4. Write each and read the tool result's <diagnostics> block.

   Expected vs actual

   Expected: both .json and .jsonc report the parse error.
   Actual: only .json reports; .jsonc produces no diagnostics for that file.

   Verbatim tool output after writing broken.json:

   LSP errors detected in this file, please fix:
   <diagnostics file="...\jsonc-bug-probe\broken.json">
   ERROR [4:1] Expected an array, an object, or a literal but instead found '}'.
   </diagnostics>
   

   Writing broken.jsonc (same bytes, same directory) produced no <diagnostics> block for it.

   Independent check that the server can parse it: the same .jsonc bytes report error[biome] (parse) at 4:0: Expected an array, an object, or a literal but instead found '}'. when routed through oh-my-openagent's own lsp_diagnostics path — so Biome handles .jsonc; only opencode's languageId is wrong.

   Proposed fix

   Add the missing entries to LANGUAGE_EXTENSIONS, at minimum:

   ".jsonc": "jsonc",

   plus the other omissions already listed in this issue (.toml, .mdx, .pyi, .h/.hpp/.hh/.hxx/.h++, .R, and the bare makefile key).

   ---

   Environment: opencode 1.18.30 · Windows · plugin oh-my-openagent 4.19.4 · verified 2026-09-13.
10. Bearmancer commented on Sep 13, 2026

    

    Bearmancer

    on Sep 13, 2026

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    ---

    Environment (software)

    item	value
    OS	Microsoft Windows 10 Pro — 10.0.19045 (Build 19045), 64-bit
    Shell	PowerShell 7.6.6 (+ Windows Terminal)
    opencode	1.18.30
    plugins	oh-my-openagent 4.19.4 · @cortexkit/opencode-antigravity-auth 2.2.1
    runtimes	Node v24.19.0 · npm 11.17.0 · Bun 1.4.2
    LSP binaries	biome 2.5.13 · basedpyright 1.40.1 · roslyn-language-server 5.12.0-1.26426.8 · bash-language-server 5.6.0 · shellcheck 0.11.0 · vscode-langservers-extracted 4.10.0 · PowerShellEditorServices 4.7.0 · PSScriptAnalyzer 1.25.0
    logs	~/.local/share/opencode/log/opencode.log · ~/.omo/agent/OmO-debug.log · ~/.omo/agent/logs/config-reload.log

    OS facts collected with:

    Get-CimInstance Win32_OperatingSystem | Select-Object Caption,Version,BuildNumber,OSArchitecture

    No hardware, hostname, username, or credentials included.