Function min_protocol_version 

pub const fn min_protocol_version(network: Network) -> u32

Per-network default seed used only when an unpinned SDK has no explicit initial version.

Mainnet, testnet and regtest seed at protocol version 13, the lowest version any of those networks still runs. Devnets seed at 14: they are cut from the current development line, and their contracts use index grammar that version 13 cannot deserialize, so a lower seed would fail the very first proved request instead of ratcheting (the ratchet only runs after a proof verifies).

Not a runtime clamp: SdkBuilder::with_initial_version can seed an unpinned SDK below this value (no construction-time floor), and auto-detect (Sdk::maybe_update_protocol_version) only ratchets the stored version upward via fetch_max when the network reports a newer one.