A child-resistant container cap has: an internally threaded inner sidewall. An outer sidewall surrounds the inner wall and has a cross-section normal to the central axis characterized by an opposite first pair of ends compressable from a relaxed condition to a compressed condition and an opposite second pair of ends, a direction between the second pair of ends being normal to a direction between the first pair of ends. A pair of engagement features are carried by the outer sidewall and engagable with container body engagement features to prevent an unscrewing rotation with the cap in the installed condition and the outer sidewall relaxed. Compression of the first ends from the relaxed condition to the compressed condition shifts the cap engagement features radially outward to permit the unscrewing rotation. The cross-section of the cap is longer between the first ends than the second ends.