How do I share a fantasy with my partner?

Choose a low-stakes moment - walking, driving, lights off - not mid-intimacy. Start one size smaller than the real thing and see how it lands; trust builds in steps. Frame it as invitation, not verdict: 'something I've been curious about' rather than 'something missing.' And decide beforehand that a hesitant reaction isn't rejection of you - surprise needs processing time. Ask about theirs too. Curiosity in both directions is what makes this safe.