Quick answer: Unity build pipeline emitting old binary after adding a new package? Incremental cache misses the dependency - clear Library/Bee or run a clean build.
Added a new Burst-using package. Build doesn't include the Burst-compiled functions; runtime crashes.
Clear Library/Bee
Stop Unity. Delete Library/Bee. Reopen; first build is clean. Subsequent builds incremental from fresh state.
Or trigger via Build Profiles
Unity 2023.3+: Build Profiles > Clean Build button. Same effect; doesn't require manual delete.
Verify package compile
Build Report > Build Steps. Each package should appear; missing = the incremental cache didn't pick it up.
“Incremental builds optimize the common case. Package adds aren't the common case.”
After package changes, do one clean build. The discipline catches the bug class; subsequent incrementals are reliable.