Update transaction priority

[shamil-gadelshin]

This PR changes Subtensor transaction priority algorithm. Here is the current algorithm description.

Transaction Priority

Overview

In Subtensor, transaction priority is determined by custom transaction extensions, which alter or override the default Substrate SDK behavior. Extensions affecting transaction priority are:

• ChargeTransactionPaymentWrapper (wraps ChargeTransactionPayment)
• SubtensorTransactionExtension

Substrate SDK combines priorities from all transaction extensions using addition.

---

1. ChargeTransactionPaymentWrapper

In the Substrate SDK, ChargeTransactionPayment normally calculates transaction priority based on:

• Tip — an extra fee paid by the sender.
• Weight — computational complexity of the transaction.
• Dispatch class — category of the transaction (Normal, Operational, Mandatory).

However, in Subtensor, ChargeTransactionPaymentWrapper overrides this logic.
It replaces the dynamic calculation with a flat priority scale based only on the dispatch class.

Current priority values:

Dispatch Class	Priority Value	Notes
Normal	1	Standard transactions
Mandatory	1	Rarely used, same as Normal
Operational	10_000_000_000	Reserved for critical system extrinsics (e.g., sudo calls, drand pulses)

---

2. SubtensorTransactionExtension

This extension introduces special priority rules for certain extrinsics, such as:

• commit_weights
• reveal_weights
• etc.

For these, priority is boosted using a time-sensitive factor:

1. Retrieve the current block number.
2. Retrieve the block number from the map LastUpdate.
3. Calculate the difference between them.
4. Add this difference to the transaction’s priority.

---

Additional changes

• staking transactions have no additional priorities now
• DRAND extrinsics will get DispatchClass::Operational
• utility batching extrinsics will have DispatchClass::Normal even if they contain extrinsics with other dispatch classes
• following extrinsics have their dispatch class changed from Operational to Normal:
  • pallet_registry::set_identity
  • pallet_commitments::set_commitment
  • pallet_subtensor::swap_hotkey
  • pallet_subtensor::register_network
  • pallet_subtensor::set_childen
  • pallet_subtensor::schedule_swap_coldkey
  • pallet_subtensor::schedule_dissove_network
  • pallet_subtensor::register_network_with_identity
  • pallet_subtensor::unstake_all
  • pallet_subtensor::unstake_all_alpha
  • pallet_subtensor::swap_stake
  • pallet_subtensor::swap_stake_limit
  • pallet_subtensor::move_stake
  • pallet_subtensor::transfer_stake
  • pallet_subtensor::try_associate_hotkey
  • pallet_subtensor::start_call
  • pallet_subtensor::associate_evm_key
  • pallet_subtensor::recycle_alpha
  • pallet_subtensor::burn_alpha

The absolute majority of the remaining extrinsics with DispatchClass::Operational have ensure_root or similar origin verification now.

[camfairchild]

This could possibly be two extensions with one checking for the coldkey swap to invalidate. The other one handles just this priority logic

[ppolewicz]

@shamil-gadelshin In fact, coldkey swap check should be done in validation, not in transaction extension (in a separate PR)

[shamil-gadelshin]

I removed the second (priority) extension after the discussion with @ppolewicz

[camfairchild]

Put drand below sudo

[camfairchild]

.

[shamil-gadelshin]

I added a special transaction extension for write_pulse priority. Other extrinsics from drand pallet have sudo origin check.

[camfairchild]

Please see comment

[ppolewicz]

Drand pulse submission has to have a check in validation (when inserting into mempool) to see if it's signed by the designated offline worker - if we don't do that then someone can spam these and flood out weight setting, staking, transfers etc

[ppolewicz]

After a discussion with Shamil, we found out that it should be made slightly simpler and the transaction priority for setting weights should be removed until further notice (due to newly found attack vectors)

EDIT: after an even longer discussion with Vune, it was agreed to remove the priority for setting weights

[shamil-gadelshin]

Last updates:

• remove weights extrinsics periory
• new extension for DRAND pulse priority