# kappa (/docs/hyperparameters/kappa)

`kappa` is the majority-stake threshold of Yuma Consensus: the fraction of
active stake that must support a weight level for it to count as consensus.
It shapes how much a stake majority can discipline outlier validators, so
validators and subnet designers both care — but only root governance can
change it.

## How it works [#how-it-works]

Each epoch, the chain computes a per-miner consensus score as a stake-weighted
median (`weighted_median_col` in `pallets/subtensor/src/epoch/math.rs`,
called from `epoch/run_epoch.rs` with `kappa` as the majority ratio): the
highest weight level such that validators holding at least `kappa` of active
stake set a weight at or above it. Every weight above that consensus value is
clipped down to it (`inplace_col_clip`), and the clipped matrix drives ranks,
incentive, and validator trust. In the classic sigmoid formulation, `kappa`
is also the midpoint of the trust curve that
[`rho`](/docs/hyperparameters/rho) steepens.

Stored as u16 where 65535 = 1.0; the default 32767 means 0.5 — a simple
stake majority. Raising it demands broader agreement before a weight
survives clipping; lowering it lets smaller stake coalitions set consensus.
The full pipeline is described in
[Yuma Consensus](/docs/concepts/emissions#yuma-consensus).

<HyperparamConsensusSigmoid focus="kappa" />

## Reading and setting [#reading-and-setting]

Inspect with:

```
btcli sudo get --netuid N --name kappa
```

Not settable by the subnet owner — root/governance only
(`sudo_set_kappa` in the AdminUtils pallet requires the root origin). When
set, the raw value is a u16: 32767 ≈ 0.5.

## Related [#related]

[`rho`](/docs/hyperparameters/rho) ·
[`tempo`](/docs/hyperparameters/tempo) ·
[`activity_cutoff`](/docs/hyperparameters/activity-cutoff) ·
[`max_validators`](/docs/hyperparameters/max-validators)