We’ve had bug reports about this in the past, but I finally managed to dig a bit deeper.

CSFLE doesn’t work when mongosh was installed via homebrew. homebrew will provide npm with --build-from-source when creating bottles, which means that addons should be built from source.

However, the mongodb-client-encryption addon can’t be built from source in a default environment, since it has external dependencies on libmongocrypt and parts of the C driver.

Consequently, mongodb-client-encryption is never installed successfully in the homebrew bottles and cannot be used by mongosh.