min_burn

Sets the lowest price a subnet can charge for a burned registration. Miners watch it because it is the cost of joining a quiet subnet; owners tune it to keep registration from ever becoming free while still letting the price decay to something affordable.

How it works

Every block, update_registration_prices_for_networks (in pallets/subtensor/src/subnets/registration.rs, run from block_step) decays the current burn price exponentially toward zero — and then clamps it into [min_burn, max_burn]. The same clamp is applied after each registration bumps the price by burn_increase_mult. So with no registrations arriving, the price settles at exactly min_burn and stays there; min_burn is the resting price of an idle subnet.

The value is stored in MinBurn as a rao amount (1 TAO = 1e9 rao). The chain default is 500,000 rao (τ0.0005). The owner-set extrinsic (sudo_set_min_burn in pallets/admin-utils/src/lib.rs) enforces two bounds: the new value must be below 1 TAO (MinBurnUpperBound) and strictly less than the subnet's current max_burn. Registration burns are recycled — they are subtracted from total issuance and can be re-emitted, which pushes halvings out (see emissions).

Reading and setting

btcli sudo get --netuid 12 --name min_burn
btcli sudo set --netuid 12 --name min_burn --value 0.001

Settable by the subnet owner or root. A value with a decimal point is a TAO amount (0.001 = τ0.001); a plain integer is raw rao (1000000 = τ0.001).

Related

• max_burn — the matching ceiling
• burn_half_life — how fast the price decays back to this floor
• burn_increase_mult — the bump per registration
• registration_allowed