diff --git a/lib/index.js b/lib/index.js
index b27f5ee..3fd3442 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -3,10 +3,15 @@
  * @typedef {import('unist').Position} UnistPosition
  * @typedef {import('vfile-message').VFileMessage} VFileMessage
  * @typedef {import('vscode-languageserver').Connection} Connection
- * @typedef {Pick<
+ * @typedef {Partial<Pick<
  *   import('unified-engine').Options,
- *   'ignoreName' | 'packageField' | 'pluginPrefix' | 'plugins' | 'rcName'
- * >} Options
+ *   | 'ignoreName'
+ *   | 'packageField'
+ *   | 'pluginPrefix'
+ *   | 'plugins'
+ *   | 'processor'
+ *   | 'rcName'
+ * >>} Options
  */
 
 import {PassThrough} from 'node:stream'
@@ -136,7 +141,14 @@ function lspDocumentToVfile(document) {
 export function configureUnifiedLanguageServer(
   connection,
   documents,
-  {ignoreName, packageField, pluginPrefix, plugins, rcName}
+  {
+    ignoreName,
+    packageField,
+    pluginPrefix,
+    plugins,
+    processor = unified(),
+    rcName
+  }
 ) {
   /**
    * Process various LSP text documents using unified and send back the
@@ -156,7 +168,7 @@ export function configureUnifiedLanguageServer(
           packageField,
           pluginPrefix,
           plugins,
-          processor: unified(),
+          processor,
           quiet: false,
           rcName,
           silentlyIgnore: true,
diff --git a/readme.md b/readme.md
index 34d76f4..913c634 100644
--- a/readme.md
+++ b/readme.md
@@ -75,7 +75,8 @@ Create a file names `package.json` with the following content:
   "bin": "./index.js",
   "type": "module",
   "dependencies": {
-    "unified-language-server"
+    "remark": "^14.0.0",
+    "unified-language-server": "^1.0.0"
   }
 }
 ```
@@ -83,6 +84,7 @@ Create a file names `package.json` with the following content:
 Then create `index.js` with the following content:
 
 ```js
+import {remark} from 'remark'
 import {createUnifiedLanguageServer} from 'unified-language-server'
 
 process.title = 'remark-language-server'
@@ -91,7 +93,7 @@ createUnifiedLanguageServer({
   ignoreName: '.remarkignore',
   packageField: 'remarkConfig',
   pluginPrefix: 'remark',
-  plugins: ['remark-parse', 'remark-stringify'],
+  processor: remark,
   rcName: '.remarkrc'
 })
 ```
diff --git a/test/index.js b/test/index.js
index 7eaa3d1..57838a8 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,4 +1,6 @@
 /**
+ * @typedef {import('unified').Processor} Processor
+ * @typedef {import('unified').Plugin} Plugin
  * @typedef {import('./test-plugin').UnifiedTestPluginOptions} UnifiedTestPluginOptions
  */
 
@@ -6,6 +8,7 @@ import {pathToFileURL} from 'node:url'
 
 import {spy, stub} from 'sinon'
 import test from 'tape'
+import {unified} from 'unified'
 import * as exports from 'unified-language-server'
 import {
   CodeActionKind,
@@ -49,6 +52,7 @@ function createMockConnection() {
  * @param {string} uri
  * @param {string} text
  * @param {UnifiedTestPluginOptions} [pluginOptions]
+ * @param {Processor} [processor]
  * @param {string} pluginName
  * @returns {Promise<import('vscode-languageserver').PublishDiagnosticsParams>}
  */
@@ -56,6 +60,7 @@ function getDiagnostic(
   uri,
   text,
   pluginOptions,
+  processor,
   pluginName = './test/test-plugin.js'
 ) {
   const connection = createMockConnection()
@@ -72,7 +77,8 @@ function getDiagnostic(
   })
 
   configureUnifiedLanguageServer(connection, documents, {
-    plugins: [[pluginName, pluginOptions]]
+    plugins: [[pluginName, pluginOptions]],
+    processor
   })
 
   onDidChangeContent.firstCall.firstArg({
@@ -107,6 +113,36 @@ test('onInitialize', (t) => {
   t.end()
 })
 
+test('Custom processor', async (t) => {
+  const uri = String(pathToFileURL('test.md'))
+  const diagnostics = await getDiagnostic(
+    uri,
+    'test',
+    undefined,
+    unified().use(
+      /** @type {Plugin} */ (
+        () => (ast, file) => {
+          file.message('custom processor')
+        }
+      )
+    )
+  )
+
+  t.deepEquals(diagnostics, {
+    uri,
+    version: 0,
+    diagnostics: [
+      {
+        range: {start: {line: 0, character: 0}, end: {line: 0, character: 0}},
+        message: 'custom processor',
+        severity: DiagnosticSeverity.Warning
+      }
+    ]
+  })
+
+  t.end()
+})
+
 test('onDocumentFormatting different', async (t) => {
   const connection = createMockConnection()
   const documents = new TextDocuments(TextDocument)
@@ -220,6 +256,7 @@ test('onDidChangeContent transformer error', async (t) => {
     uri,
     'test',
     undefined,
+    undefined,
     'unresolved-plugin'
   )