diff --git a/extension/src/language/form.ts b/extension/src/language/form.ts
index e62a910..0f655d9 100644
--- a/extension/src/language/form.ts
+++ b/extension/src/language/form.ts
@@ -5,6 +5,7 @@
  *--------------------------------------------------------*/
 
 import * as vscode from 'vscode';
+import { InitializeParams } from 'vscode-languageserver-protocol';
 import { LanguageClient, RequestType, ServerOptions, LanguageClientOptions } from 'vscode-languageclient/node';
 
 // ----------------------------------------------------------------------------
@@ -294,6 +295,25 @@
 	}
 
 	/**
+	 * Fills in the LSP initialize parameters during the handshake, and registers
+	 * client capabilities to support interactive refactoring prompts.
+	 *
+	 * @important Subclasses overriding this method must:
+	 * 1. Call `super.fillInitializeParams(params)` first to preserve base client
+	 *    configurations.
+	 * 2. Amend or merge properties into `params.capabilities.experimental`
+	 *    rather than overwriting the entire field, to prevent erasing the
+	 * 		interactive capabilities.
+	 */
+	protected fillInitializeParams(params: InitializeParams): void {
+		super.fillInitializeParams(params);
+
+		const experimental = params.capabilities.experimental || {};
+		experimental.interactiveInputTypes = ['bool', 'file', 'enum', 'lazyEnum', 'number', 'string'];
+		params.capabilities.experimental = experimental;
+	}
+
+	/**
 	 * MAX_RETRY defined the maximum number of user collection allowed for when
 	 * resolving a command.
 	 */
diff --git a/extension/src/language/goLanguageServer.ts b/extension/src/language/goLanguageServer.ts
index 8ca63ce..f6d30e3 100644
--- a/extension/src/language/goLanguageServer.ts
+++ b/extension/src/language/goLanguageServer.ts
@@ -14,7 +14,7 @@
 import semver = require('semver');
 import util = require('util');
 import vscode = require('vscode');
-import { InitializeParams, LSPObject } from 'vscode-languageserver-protocol';
+import { InitializeParams } from 'vscode-languageserver-protocol';
 import {
 	CancellationToken,
 	CloseAction,
@@ -363,10 +363,9 @@
 		// library. Experimental capabilities not used by vscode-languageserver-node
 		// can be used for custom communication between vscode-go and gopls.
 		// See https://github.com/microsoft/vscode-languageserver-node/issues/1607
-		const experimental: LSPObject = {
-			progressMessageStyles: ['log'],
-			interactiveInputTypes: ['bool', 'file', 'enum', 'lazyEnum', 'number', 'string']
-		};
+		const experimental = (params.capabilities.experimental as any) || {};
+		experimental.progressMessageStyles = ['log'];
+
 		params.capabilities.experimental = experimental;
 	}
 }