Comment by blueflow

They are not special cased:

  https://github.com/webpro/ANSI.tools/blob/main/packages/parser/src/parsers/csi.ts#L12

The comment correctly identifies the 0x30-0x3f range as parameter bytes and the following as intermediate bytes. Both the range and the names for the bytes are matching ECMA-48 Chapter 5.4.

But you seem to think that everyone except yourself is incompetent, are you trying to make up for something?