Blindly concatenating any two byte-streams, irrespective of encodings, would also be an invalid assumption; however at that point you've got massive design issu

Blindly concatenating any two byte-streams, irrespective of encodings, would also be an invalid assumption; however at that point you've got massive design issues. You cannot concatenate any random 16 or 32 bit character sequences as the underlying byte forms might be Little or Big Endian stored. UTF-8 does not need that consideration, BUT you must know (or at least contractually expect) valid UTF-8 input; anything else is garbage in garbage out. The LTR RTL issue... depends on if all RTL strings _must_ end with an LTR character; in your use case. https://en.wikipedia.org/wiki/Bidirectional_text https://en.wikipedia.org/wiki/Bidirectional_text Your suggestion of delegating all concatenation operations to that is a safe default. Other options might also be valid, depending on the exact context of inputs and use case.