Hyperparameters

immunity_period

Blocks a newly registered neuron is protected from being pruned as the lowest-scoring UID on a full subnet.

View as Markdown

immunity_period is the number of blocks a freshly registered neuron cannot be pruned to make room for a new registration. Subnet owners tune it to give new miners time to earn emission before they compete for their slot; miners care because it is their grace window to prove themselves.

How it works

When a subnet is at max_allowed_uids, each new registration must recycle an existing slot. get_neuron_to_prune (pallets/subtensor/src/subnets/registration.rs) scans every UID and treats a neuron as immune while current_block − registration_block is less than immunity_period. It picks the lowest-emission non-immune neuron (ties broken by older registration, then lower UID). Owner-immune UIDs (see owner_immune_neuron_limit) are skipped entirely.

Immunity is not absolute: if pruning a non-immune neuron would leave MinNonImmuneUids (default 10) or fewer non-immune UIDs, the chain instead prunes the lowest-emission immune neuron. If no candidate exists at all, registration fails with NoNeuronIdAvailable.

The default is 4096 blocks, about 13.7 hours at 12-second blocks. Longer periods shelter newcomers but shrink the pool of prunable slots; with heavy registration churn, most of the subnet can end up immune.

UID lifecycle playground

A subnet's slot grid, shaded by emission. When it is full, registering prunes the lowest-emission prunable uid. I = inside immunity_period, O = owner-immune, dashed outline = next prune target. Pruning falls back onto immune uids when 2 or fewer non-immune uids remain (chain default: 10). Focused on immunity_period: each immune slot shows how many registrations remain before its protection expires and it joins the prunable pool.

0O
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29I1
30I2
31I3

Press a register button to add a neuron.

Filled / capacity

32 / 32

Immune (new)

3

Within immunity_period

Owner-immune

1 / 1

Never pruned

Next pruned

uid 29

Lowest emission, prunable

32 slots
6 regs
1

Reading and setting

btcli sudo get --netuid N --name immunity_period

The value is a plain block count:

btcli sudo set --netuid N --name immunity_period --value 4096

max_allowed_uids, owner_immune_neuron_limit, serving_rate_limit, min_burn, max_regs_per_block