What version of Oxlint are you using?

1.67.0 (also reproduced with 1.66.0)

What command did you run?

oxlint --lsp (launched by neovim's nvim-lspconfig oxlint server, but reproduces with any LSP client). CLI comparison: oxlint app/path/to/file.ts from the child config directory.

What does your .oxlintrc.json (or oxlint.config.ts) config file look like?

Workspace root : .oxlintrc.json:

{
  "$schema": "./node_modules/oxlint/configuration_schema.json",
  "plugins": ["import", "promise", "node"],
  "categories": {
    "correctness": "error",
    "suspicious": "warn",
    "perf": "warn"
  },
  "rules": {
    "typescript/consistent-type-imports": ["warn", { "prefer": "type-imports" }]
  }
}

Child : apps/api/.oxlintrc.json:

{
  "$schema": "../../node_modules/oxlint/configuration_schema.json",
  "extends": ["../../.oxlintrc.json"],
  "ignorePatterns": ["database/schema.ts", ".adonisjs"],
  "rules": {
    "unicorn/filename-case": ["error", { "case": "snakeCase" }]
  }
}

What happened?

When the root config declares an explicit plugins array, the default-on plugins (typescript, unicorn, oxc) are dropped from that config : --print-config from the root confirms this. The child config has no plugins field, so via extends the defaults are merged back in, and --print-config from apps/api/ correctly shows all six plugins.

CLI behaves consistently with --print-config:

# From apps/api/  (extends merges defaults back in)
$ oxlint app/auth/guard/firebase.ts
app/auth/guard/firebase.ts:5:1: warning typescript(consistent-type-imports): ...
app/auth/guard/firebase.ts:6:1: warning typescript(consistent-type-imports): ...
app/auth/guard/firebase.ts:8:1: warning typescript(consistent-type-imports): ...
app/auth/guard/firebase.ts:11:30: error typescript(no-wrapper-object-types): ...

LSP does not:

Launching oxlint --lsp with cwd = apps/api and sending textDocument/diagnostic for the exact same file returns:

{ "items": [], "kind": "full" }

Verified via /proc//cwd that the LSP process really is running in apps/api, and via --print-config from that same cwd that the resolved config includes the typescript/unicorn/oxc plugins. So the LSP is reading the right config on disk, but is not applying the plugins that were re-added through extends. it behaves as if it were using the parent config's literal plugins array.

Expected Behavior

oxlint --lsp should produce the same diagnostics as the CLI when given the same cwd, the same binary, and the same config tree, in particular, plugins re-added via extends (by virtue of the child config omitting plugins) should be active.

Actual Behavior

LSP returns zero diagnostics; CLI returns four. --print-config agrees with the CLI.

Workaround

Add the default plugins explicitly to the root config so neither path relies on the extends merge:

"plugins": ["import", "promise", "node", "typescript", "unicorn", "oxc"]

Related

Possibly the same root cause as the (closed) #21030, which also reports --print-config disagreeing with lint-time behavior under nested/extended configs. That issue was closed without a stated fix and the underlying mismatch still reproduces on 1.67.0.