Saxon

Saxon reports this error in response to a StackOverflow exception coming from Java. You can increase the permitted recursion depth by configuring the Java stack size, but there's nothing you can do about it at the Saxon level.

If it works in 8.9 and not in 9.8 that suggests we're using more stack space, which is a little unfortunate, but these things happen. I don't remember exactly what's changed that might cause this, but new functionality comes along from time to time, like tunnel parameters, that means the internals have to change.

If you hit this kind of problem there are several solutions:

(a) rewrite the code so it isn't recursive. The problem you describe can probably be tacked these days using xsl:analyze-string.

(b) make sure it's tail-recursive, so the recursive call is the last thing that happens, in which case Saxon re-uses the same stack frame for the recursive call

(c) instead of head-tail recursion, where the recursion depth is O(n), use divide-and-conquer recursion, where the maximum depth is O(log n). That typically means splitting a string into two and processing each half separately. Divide and conquer is also better for parallelism if that's ever needed.