What's the relevant difference between apache2handler and other SAPIs here? Can you add a code comment for why it has special handling?

Actually, that may only be relevant for mpm_winnt, where the control process attaches to SHM, and afterwards the handler process reattaches, although it needs to do the JIT initialization. I wonder if the proper solution would be to suppress OPcache initialization (or at least JIT initialization) for the control process in the first place. I have no idea how to do that, and what would need to be done for Linux, especially for worker and event (although these are not recommended according to the PHP manual).

Well, after more debugging I found that there is no relevant difference between the SAPIs here at all. The problem is just that we need to initialize the tracing JIT handlers for tracing even when reattaching on Windows. The new patch does this in the most simple way, namely by ignoring ZEND_VM_KIND_HYBRID which is not available on Windows anyway, and by doing the initialization on Windows only (I don't think this initialization is ever needed on other OSs).

Note that it was sufficient for the OP to just revert 2a545ba, because they had opcache.jit=1205 (= "function").

I don't think this initialization is ever needed on other OSs

Why is this? The handlers are defaulted to NULL, and only inited currently in zend_jit_make_stubs() - I don't see any other place where they are initialized, nor any special behaviour for *nix - am I missing something here?

@dktapps, I think that re-attaching is a Windowes only thing.

I eventually managed to answer my own question - fork() is used everywhere except Windows, and SHM reattach is only done from forked subprocess on non-Windows. In a forked subprocess these handlers would already be initialized anyway because of the forking.