If you get this error message, the Internets may lead you to believe that you have no option but to change magic numbers in the source code and recompile flex. Reader, it is not so. Try the -Ca option, before doing anything else.

No, I don’t know why an option that’s documented to be all about size/speed tradeoffs in the generated, DFA, scanner also has the effect of raising the hard limit on the number of NFA states (from 32000 to about 2³¹), but I already feel dirty just having looked at the code enough to discover this, so I’m going to stop digging while I’m ahead.