# set-mechanism-count (/docs/tx/set-mechanism-count)

Mechanisms are independent incentive sub-markets within one subnet, each
running its own weights and consensus; this owner-only call sets how many
the subnet runs. The count must be greater than zero, and the chain caps
how many mechanisms a subnet may have. Increasing the count opens new
mechanisms; decreasing it removes the highest-numbered ones and the
miner state in them. Any change to the count clears the emission split
back to an even division. Rate-limited and blocked during the
end-of-epoch admin freeze window.

| Signer    | Origin       | Pallet     | Wraps                                                                                     |
| --------- | ------------ | ---------- | ----------------------------------------------------------------------------------------- |
| `coldkey` | subnet owner | AdminUtils | [`AdminUtils.sudo_set_mechanism_count`](/code/pallets/admin-utils/src/lib.rs#L1871-L1893) |

## Parameters [#parameters]

| Parameter         | Type    | Required | Description                                        |
| ----------------- | ------- | -------- | -------------------------------------------------- |
| `netuid`          | integer | yes      | Subnet to configure; the signer must be its owner. |
| `mechanism_count` | integer | yes      | Number of mechanisms the subnet should run.        |

Address parameters (`--hotkey`, `--coldkey`, `--dest`, ...) accept a raw ss58
address, an address-book or proxy-book name, or a local wallet/hotkey name.

## CLI [#cli]

Preview with `--dry-run` (shows fee, effects, and policy result without
submitting), then submit:

```bash
btcli tx set-mechanism-count \
  --netuid <int> \
  --mechanism-count <int> --dry-run
btcli tx set-mechanism-count \
  --netuid <int> \
  --mechanism-count <int> -w my_coldkey
```

## Python [#python]

```python
import bittensor as bt
from bittensor.wallet import Wallet

wallet = Wallet(name="my_coldkey", hotkey="my_hotkey")
intent = bt.SetMechanismCount(netuid=1, mechanism_count=0)

sub = bt.Subtensor()
plan = sub.plan(intent, wallet)   # fee, effects, policy — no submission
result = sub.execute(intent, wallet)
if not result.success:
    print(result.error.code, result.error.remediation)
```

(`bt.Subtensor` is also the async client — `async with bt.Subtensor() as client:`
— see [The client](/docs/concepts/client).) Or build the intent by op name, as
an agent would:

```python
result = sub.execute_tool("set_mechanism_count", {...}, wallet)
```

## On-chain implementation [#on-chain-implementation]

`AdminUtils.sudo_set_mechanism_count` — [`pallets/admin-utils/src/lib.rs#L1873`](/code/pallets/admin-utils/src/lib.rs#L1871-L1893):

```rust
#[pallet::call_index(76)]
#[pallet::weight(<T as Config>::WeightInfo::sudo_set_mechanism_count())]
pub fn sudo_set_mechanism_count(
    origin: OriginFor<T>,
    netuid: NetUid,
    mechanism_count: MechId,
) -> DispatchResult {
    let maybe_owner = pallet_subtensor::Pallet::<T>::ensure_sn_owner_or_root_with_limits(
        origin,
        netuid,
        &[TransactionType::MechanismCountUpdate],
    )?;
    pallet_subtensor::Pallet::<T>::ensure_admin_window_open(netuid)?;

    pallet_subtensor::Pallet::<T>::do_set_mechanism_count(netuid, mechanism_count)?;

    pallet_subtensor::Pallet::<T>::record_owner_rl(
        maybe_owner,
        netuid,
        &[TransactionType::MechanismCountUpdate],
    );
    Ok(())
}
```

Every file is browsable under [/code](/code) exactly as built into the runtime, or as plain text under `/code/raw/<path>` (index: [`/code/index.json`](/code/index.json)).