diff --git a/internal/ls/lsutil/userpreferences.go b/internal/ls/lsutil/userpreferences.go
index 8fc5146d634..9ce32c8dcdf 100644
--- a/internal/ls/lsutil/userpreferences.go
+++ b/internal/ls/lsutil/userpreferences.go
@@ -1,6 +1,7 @@
 package lsutil
 
 import (
+	"maps"
 	"reflect"
 	"slices"
 	"strings"
@@ -886,7 +887,21 @@ func ParseUserPreferences(items map[string]any) UserPreferences {
 	// editor < javascript < typescript < js/ts
 	if editorItem, ok := items["editor"]; ok && editorItem != nil {
 		if editorSettings, ok := editorItem.(map[string]any); ok {
-			prefs = prefs.withConfig(map[string]any{"unstable": editorSettings})
+			unstableEditorSettings := make(map[string]any, len(editorSettings)+2)
+			maps.Copy(unstableEditorSettings, editorSettings)
+			// VS Code editor settings use "insertSpaces" and "tabSize"; map them to
+			// tsserver raw formatting setting names consumed by "unstable".
+			if tabSize, ok := unstableEditorSettings["tabSize"]; ok {
+				if _, hasIndentSize := unstableEditorSettings["indentSize"]; !hasIndentSize {
+					unstableEditorSettings["indentSize"] = tabSize
+				}
+			}
+			if insertSpaces, ok := unstableEditorSettings["insertSpaces"]; ok {
+				if _, hasConvertTabs := unstableEditorSettings["convertTabsToSpaces"]; !hasConvertTabs {
+					unstableEditorSettings["convertTabsToSpaces"] = insertSpaces
+				}
+			}
+			prefs = prefs.withConfig(map[string]any{"unstable": unstableEditorSettings})
 		}
 	}
 	// Apply javascript, then typescript, then js/ts (highest precedence).
diff --git a/internal/ls/lsutil/userpreferences_test.go b/internal/ls/lsutil/userpreferences_test.go
index 153f737b345..bb597be2bf7 100644
--- a/internal/ls/lsutil/userpreferences_test.go
+++ b/internal/ls/lsutil/userpreferences_test.go
@@ -511,6 +511,34 @@ func TestUserPreferencesParseServerFeaturePreferences(t *testing.T) {
 	})
 }
 
+func TestUserPreferencesParseEditorFormattingSettings(t *testing.T) {
+	t.Parallel()
+
+	t.Run("editor insertSpaces and tabSize apply to format settings", func(t *testing.T) {
+		t.Parallel()
+		prefs := ParseUserPreferences(map[string]any{
+			"editor": map[string]any{
+				"tabSize":      2,
+				"insertSpaces": false,
+			},
+		})
+		assert.Equal(t, prefs.FormatCodeSettings.TabSize, 2)
+		assert.Equal(t, prefs.FormatCodeSettings.IndentSize, 2)
+		assert.Equal(t, prefs.FormatCodeSettings.ConvertTabsToSpaces, core.TSFalse)
+	})
+
+	t.Run("editor raw formatting setting wins over insertSpaces alias", func(t *testing.T) {
+		t.Parallel()
+		prefs := ParseUserPreferences(map[string]any{
+			"editor": map[string]any{
+				"insertSpaces":        false,
+				"convertTabsToSpaces": true,
+			},
+		})
+		assert.Equal(t, prefs.FormatCodeSettings.ConvertTabsToSpaces, core.TSTrue)
+	})
+}
+
 func TestUserPreferencesParseJSDocCompletionPreferences(t *testing.T) {
 	t.Parallel()