Running a subnet

A subnet owner defines an incentive mechanism: what miners must produce and how validators must score it. The chain side — creating the subnet, tuning its hyperparameters, publishing its identity — is all reachable through the SDK. The mechanism itself is code you write and run off-chain.

Create

register-subnet creates a new subnet owned by your coldkey, with your wallet's hotkey as the subnet-owner hotkey:

btcli query subnet-registration-cost --json   # check the lock cost FIRST
btcli tx register-subnet --dry-run -w my_coldkey
btcli tx register-subnet -w my_coldkey

The cost doubles each time anyone registers a subnet, then decays linearly back over the lock-reduction interval (100,800 blocks, ~2 weeks), floored at NetworkMinLockCost — 1,000 TAO by default. It is only known at execution time, so a Policy spend cap blocks this call until raised; read the live price with subnet-registration-cost. Subnet registrations are also chain-rate-limited to one per 7,200 blocks (~1 day) network-wide.

The lock is not a refundable deposit. The entire lock is transferred into the new subnet's pool as its initial TAO reserve (floored at NetworkMinLockCost); the matching alpha reserve is sized so the starting price equals the median alpha price across subnets. Nothing is recycled at registration. You get it back only by owning a subnet that earns.

Identity can be set atomically at registration: the chain's register_network_with_identity extrinsic takes an optional identity record. register-subnet wraps plain register_network, so the identity variant needs the raw-call escape hatch.

A new subnet is a two-step commitment: register, then activate with start-call — until then it earns nothing.

Activate

Once the chain's activation delay has passed, flip the subnet on with start-call — owner-only, once per subnet:

btcli tx start-call --netuid 42 -w my_coldkey

Check the schedule with subnet-start-schedule.

start-call enables the subnet's token and starts its epochs, but the subnet's share of network TAO emission is a separate root-controlled switch: new subnets register with emission disabled, and only root (via sudo_set_subnet_emission_enabled) turns it on. Until then the subnet earns no TAO emission share.

The subnet economy

Each subnet is an automated market maker with two reserves: TAO in and alpha in. The alpha price is the pool's weighted reserve ratio — exactly TAO-in / alpha-in at the default 0.5/0.5 pool weights — and moves on every stake and unstake; emission injections shift the pool weights instead of the price. The subnet's share of network TAO emissions follows the exponential moving average of that price — stakers vote with their TAO — so a subnet's income is set by market demand for its token, not by governance. See emissions for the full mechanics.

Each tempo the subnet's alpha emission splits three ways: 18% to the owner, ~41% to miners (incentive), ~41% to validators and their stakers (dividends). The owner cut can be auto-locked into a conviction position via the owner_cut_auto_lock_enabled hyperparameter instead of arriving as free stake; conviction locking and its unlock schedule are covered in the staking guide.

Three owner habits worth adopting. Decide your registration_allowed policy before activation — owners pause registration during mechanism upgrades so participants can update without eviction risk, and the toggle is root-gated here, so plan ahead. Run a validator on the owner hotkey: the owner cut and validation rewards land on the same key, and the 18% cut can be staked behind it. Do not mine on the owner hotkey — miner emission directed at owner hotkeys is burned or recycled, never paid.

Tune hyperparameters

Owner-settable hyperparameters go through set-hyperparameter (the equivalent of btcli's sudo set); read them back with subnet-hyperparameters:

btcli query subnet-hyperparameters --netuid 42 --json
btcli tx set-hyperparameter --netuid 42 --name commit_reveal_weights_enabled --value 1 -w my_coldkey

The important owner-settable parameters, with chain defaults:

Parameters marked * have their own extrinsics on chain rather than a name in set-hyperparameter; if the SDK doesn't expose one, use the raw-call escape hatch.

Chain reads also return rho, difficulty, adjustment_interval, adjustment_alpha, and target_regs_per_interval — legacy registration and consensus parameters that still exist as storage but no longer drive neuron admission; the burn price decay/bump mechanism replaced the old PoW and adjustment-interval machinery. (max_registrations_per_block is still enforced.)

Two chain-side constraints on owner changes:

• Rate limit — each hyperparameter can be changed roughly once per two tempos (default OwnerHyperparamRateLimit = 2), tracked independently per parameter, so you can change several different parameters in one tempo but not the same one twice.
• Freeze window — owner admin calls are rejected during the last ~10 blocks of each tempo (AdminFreezeWindow), so parameters can't change while an epoch is being computed.

Root-only parameters — kappa (default 32,767 ≈ 0.5), max_allowed_validators (128), weights_set_rate_limit (100 blocks between weight submissions), tempo outside the owner bounds, registration_allowed, and others — need root privileges and the raw-call escape hatch.

Trim UIDs

trim-subnet lowers max_allowed_uids and evicts the excess neurons. Rules:

• Rate-limited to one trim per 216,000 blocks (~30 days).
• Victims are the lowest-emission UIDs; temporally immune UIDs (within immunity_period) and owner-immune UIDs are skipped, and immune UIDs may not exceed 80% of the new maximum.
• You cannot trim below 64 UIDs.
• Surviving UIDs are renumbered consecutively from 0 — a miner's UID can change even if it survives.
• A trimmed UID's on-chain state (hotkey mapping, registration block, weights, bonds, axon info) is permanently deleted.

Mechanisms

A subnet can run multiple scoring mechanisms, each with its own weights. set-mechanism-count and set-mechanism-emission-split configure them; validators target one via the mechid field on set-weights. Read the current count with mechanism-count.

• The chain currently caps subnets at 2 mechanisms.
• Each mechanism runs Yuma Consensus independently, with its own weight matrix and separate bond pools. Miners keep one UID across all mechanisms — no separate registration — and their total emission is the sum across mechanisms.
• The same applies to validators: emission is computed per mechanism from that mechanism's own consensus, then combined according to the emission split.
• Mechanisms were formerly called "subsubnets"; the old name survives in some APIs and code comments.
• max_allowed_uids × mechanism count must stay ≤ 256; reduce max_allowed_uids first if raising the count would exceed it.
• The emission split is a vector of u16 weights summing to 65,535 (e.g. [13107, 52428] is 20%/80%); unset means an even split. Changing the mechanism count resets the split to even.
• Count and split changes are each rate-limited to once per 7,200 blocks (~24 hours).

Deregistration

There is no inactivity-based deregistration; pruning is price-based. When the subnet limit (128) is reached, the next register-subnet prunes the non-immune subnet with the lowest EMA alpha price (ties go to the oldest) and reuses its netuid. New subnets are immune for 1,296,000 blocks (~6 months) from registration; if every subnet is immune the new registration fails instead.

Price-ranked deregistration has history: it existed pre-dTAO (ranked by emission then), was removed at dTAO's launch in February 2025, and returned price-ranked in September 2025.

Deregistering a subnet deregisters all of its neurons with it — every UID's on-chain state is deleted along with the subnet.

On dissolution the subnet's TAO reserve is distributed pro-rata over all alpha — credited directly to each holder's coldkey balance, not restaked. Two caveats: protocol-held alpha (the pool's alpha-in plus alpha bought back by the chain) counts in the denominator and its share returns to the chain, diluting holder payouts; and conviction locks are deleted before liquidation — locked stake is paid out like any other, but accumulated conviction is not compensated. Owners of subnets registered since dTAO get no lock refund. The payout can also cut the other way: liquidation pays the pool's TAO-per-alpha rate, so if that exceeds the market price at dissolution, holders receive more than market value.

Identity and token

• set-subnet-identity — the subnet's public profile (name, links, contact, logo). Public and permanent; each call overwrites the whole record.
• update-symbol — the subnet token's ticker, chosen from a fixed on-chain list of available symbols.

The most common identity mistake: logo_url must point at a raw image file (e.g. a raw.githubusercontent.com URL), not an HTML page that displays the image.

Financing: leases and crowdloans

A subnet can be financed collectively: create a crowdloan (create-crowdloan, contributions via contribute-crowdloan) and register the network under a lease that shares emissions with contributors (register-leased-network, ended with terminate-lease). Inspect with the crowdloans and leases reads.

Economics worth knowing before committing:

• The lease's emissions_share is a percentage of the owner cut (18%), not of total emissions: a 50% share pays contributors 9% of the subnet's emission.
• Contributor dividends are swapped from alpha to TAO and paid automatically during coinbase, on a fixed distribution interval (100 blocks), pro-rata by contribution. If pool liquidity is too thin to swap, the alpha accumulates for a later interval.
• At lease creation, whatever remains of the raised cap after paying the registration cost is refunded to contributors pro-rata (rounding remainder to the beneficiary) — so set the cap above the projected lock cost, not wildly above it.
• Crowdloans must run between 50,400 and 432,000 blocks (7–60 days). Contributions are clipped to the remaining cap rather than rejected. Refunds after a failed raise process at most 50 contributors per refund-crowdloan call, so large campaigns need several.

Bootstrapping validation

A brand-new subnet has no validators, and the owner gets no special treatment: setting weights requires meeting the same stake threshold as any validator (see validating). The common tactic is to ask an established root validator to parent your validator hotkey as a childkey (set-children), lending it stake weight for consensus participation until the subnet attracts its own stake.