Mununu, a formal verification tool, has deleted its maze of SystemVerilog import fallbacks. Every production run now uses the yosys-slang reader, which handled 99 percent of the project's test files, instead of trying an older reader first and switching only after an error. The command-line and application programming interfaces also lose the knobs that selected parsers and preprocessors.
Parser choice looks like configuration flexibility, but it creates two designs from one source file when the front ends interpret an edge case differently. Mununu now plans one import attempt, records that tool in its cache key, and keeps the old conversion path only as a test oracle. The same change adds randomly generated small transition systems whose exact answers are compared with the main proof engines, giving the simplified path an independent check.
This is the right kind of breaking change for a verification tool: fewer accepted configurations and a clearer answer to which source the solver actually saw. Teams with scripts that pass the removed options will have migration work, but they can pin one tool image and reproduce a failed proof without reconstructing an automatic fallback sequence.