Constant LNV1_HTLC_EXPIRY_SAFETY_MARGIN 

pub const LNV1_HTLC_EXPIRY_SAFETY_MARGIN: u32 = _; // 30u32

Exclusive remaining-CLTV safety margin for an intercepted LNv1 HTLC.

This reserves the worst-case time to claim the HTLC on-chain after federation funding and threshold decryption. Exactly the margin is rejected; fresh funding requires at least one additional block. The value deliberately matches the route-hint delta advertised by pre-upgrade clients so their invoices remain payable; see LNV1_INCOMING_HTLC_EXPIRY_SAFETY_MARGIN for the plan to raise it.