Root stake and childkey delegation

Root network (netuid 0) stake is what makes a single position count on more than one subnet at once — see stake-weight for the underlying formula. Childkey delegation is the mechanism that actually routes a share of that root position outward to specific hotkeys on specific subnets.

What set_children does

A parent hotkey calls set_children(netuid, children), where children is a list of (proportion, child_hotkey) pairs — up to 5 children per call, scoped to that one subnet (ensure_childkey_count enforces the per-call limit). This creates a ChildKeys entry for (parent, netuid), naming which child hotkeys get a cut of that parent's inherited weight on that specific subnet, and how large a cut each gets.

Critically, what a child inherits is the parent's root stake specifically — the same root_tao_stake term from the stake-weight formula, read fresh at computation time — not whatever the parent happens to hold directly on that subnet. A parent with zero Alpha stake on a given subnet can still back a child there, purely off its root position.

Source: pallets/subtensor/src/staking/set_children.rs, stake_utils.rs.

The gate: StakeThreshold

set_children isn't available to just any hotkey — the parent must clear get_total_stake_for_hotkey(parent) >= StakeThreshold. Two things worth being precise about here:

• StakeThreshold is live-queryable and currently 1000 TAO — governance-adjustable, always re-check rather than assuming this figure holds indefinitely.
• The threshold check sums the parent's stake across every subnet it holds any stake on at all (root included), each converted to a TAO-equivalent value at that subnet's current Alpha price — not just root stake in isolation. A parent could in principle clear the threshold through Alpha stake spread across several subnets, though only the root-stake component actually gets inherited by children (per the formula above).

There is no requirement that the parent be registered on the target subnet at all — set_children has no is_hotkey_registered_on_network(parent, netuid) check anywhere in the extrinsic. A parent can back children on subnets it has never registered a UID on itself.

The cooldown

set_children doesn't take effect immediately. PendingChildKeyCooldown — currently ~7200 blocks, roughly 24 hours — delays when a new or changed ChildKeys entry actually starts affecting stake-weight calculations. Budget this into any rollout timeline: a child isn't earning from the inherited pool the moment the set_children transaction lands, only after the cooldown clears.

No cap on how many subnets one root position can back

Each (parent, netuid) ChildKeys entry is independent, and every subnet's stake_weight calculation reads the same root position fresh, on its own. There's no cross-subnet ledger that depletes the parent's root stake as it gets allocated to more children across more subnets — the same 1000 TAO root position (as a concrete example) can back a child on ten different subnets simultaneously, each computing its own inherited share independently, with no accounting mechanism that treats the pool as "spent" by being counted more than once. This is the core reason root delegation scales more efficiently than splitting a fixed pool of capital N ways across N subnets: each subnet's calculation gets the (discounted) full root value, not a shrinking 1/N fraction of it.

What delegation does not replace

A child hotkey still needs its own UID registration on the target subnet. Delegation shares stake-weight; it does not substitute for having a registered neuron in the first place. The sequence is always: register the child hotkey on the subnet (paying that subnet's own recycle-burn cost), then set_children on the parent to route it a share of root stake, then wait out the cooldown before the inherited weight actually counts. Skip the registration step and there's no UID for the inherited stake-weight to attach to at all.

The inherited stake-weight is also not merely a permit-eligibility bump — it flows into active_stake and from there directly into the Yuma Consensus dividends calculation covered on weight-setting and rewards. A child earning inherited weight earns real, proportional emissions from it, the same as if it held that stake directly.