Cubical compatible

The option --cubical-compatible specifies whether the module being type-checked is compatible with Cubical Agda: modules without this flag can not be imported from --cubical modules.


Prior to Agda 2.6.3, the --cubical-compatible flag did not exist, and --without-K also implied the (internal) generation of Cubical Agda-specific code. See Agda issue #5843 for the rationale behind this change.

Compatibility with Cubical Agda consists of:

  • No reasoning principles incompatible with univalent type theory may be used. This behaviour is controlled by the Without K flag (--without-K), which --cubical-compatible implies.

  • Due to specifics of the Cubical Agda implementation, several kinds of Agda definition need internal support code to be generated during their elaboration.

Occasionally, elaborator bugs can result in errors surfacing from these internal definitions, despite the code being type-correct. To avoid showing errors mentioning cubical definitions when the user-written code is independent of Cubical Agda, these internal definitions are now gated behind --cubical-compatible.

Note that code that uses (only) --without-K can not be imported from code that uses --cubical. Thus library developers are encouraged to use --cubical-compatible instead of --without-K, if possible.

Note also that Agda tends to be quite a bit faster if --without-K is used instead of --cubical-compatible.

The --cubical-compatible option is coinfective (see Checking options for consistency): the generated support code for functions may depend on those of importing modules.