max_burn

Caps how expensive a burned registration can get, no matter how many registrations pile in. Miners care because it bounds their worst-case entry cost during a registration rush; owners tune it to decide how hard a rush should be throttled by price.

How it works

The burn price moves in two ways, and both are clamped into [min_burn, max_burn] in pallets/subtensor/src/subnets/registration.rs:

• Each successful registration multiplies the price by burn_increase_mult (bump_registration_price_after_registration). Once the product exceeds max_burn, the price is pinned at max_burn — further registrations in the same burst cost exactly max_burn each.
• Each block, the price decays exponentially with half-life burn_half_life (update_registration_prices_for_networks), pulling it back down from the ceiling toward min_burn.

The value lives in MaxBurn storage as a rao amount (1 TAO = 1e9 rao); the chain default is 100 TAO. The owner-set extrinsic (sudo_set_max_burn in pallets/admin-utils/src/lib.rs) requires the new value to be above 0.1 TAO (MaxBurnLowerBound) and strictly greater than the subnet's current min_burn. A low ceiling makes registration cheap but lets bursts through; a high ceiling makes sustained bursts increasingly expensive.

Reading and setting

btcli sudo get --netuid 12 --name max_burn
btcli sudo set --netuid 12 --name max_burn --value 50.0

Settable by the subnet owner or root. A value with a decimal point is a TAO amount (50.0 = τ50); a plain integer is raw rao.

Related

• min_burn — the matching floor
• burn_increase_mult — how fast a rush drives the price toward this cap
• burn_half_life — how fast it comes back down
• max_regs_per_block — the non-price rate limit