HL Opposing Force user created patch for single player maps.
Info and patch can be found here.
Valve should include these patches in an update for Half-Life and Opposing force I mean it saves them time.
You’d think so, but It’s just VALVe turning their valve off.
I’m sure It’d be far more effort to sort out the legalities and technicals of including this guy’s fixes than to fix a few bugs themselves.