There is a persistent encoding bug in the Illustrator Scripting API (ExtendScript) when moving Global or Spot swatches into a SwatchGroup. Specifically, the addSpot() method fails to preserve Unicode characters, resulting in corrupted strings for any non-Latin swatch names (Chinese, Japanese, Russian, etc.).

Example:
var doc = app.activeDocument;

// 1. Create a color group
var targetGroup = doc.swatchGroups.add();
targetGroup.name = 'Spot_Test';

// 2. Create a color object
var swatchColor = new CMYKColor();
swatchColor.cyan = 80;

// 3. Create a swatch with a name in Cyrillic or another language
var newSwatch = doc.spots.add();
newSwatch.name = 'Синий';
newSwatch.colorType = ColorModel.SPOT;
newSwatch.color = swatchColor;

// 4. Moving a swatch to a group
targetGroup.addSpot(newSwatch);

Version Range: This issue has been present since CS6 and remains in the current 2026 release.
Platform: Reproducible on both macOS and Windows.
Impact: Affects all automation tools and scripts dealing with brand assets, localized palettes, and pre-press workflows in non-English environments.

Full technical breakdown and details:
https://aiscripts.medium.com/non-latin-spot-color-names-in-swatch-groups-2cd075e6ae82