Capability to forward tx fees and swap fees to block builder by gztensor · Pull Request #2426 · opentensor/subtensor

gztensor · 2026-02-16T19:09:09Z

Description

Currently the transaction fees are burned and swap fees go to swap pool. This PR enables:

Forwarding of transaction fees to the block producer
Forwarding fraction of swap fees to the block producer

Also, this PR will raise transaction fees by 10x.

Closes #2424

Type of Change

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work as expected)
Documentation update
Other (please describe):

Checklist

I have performed a self-review of my own code
I have commented my code, particularly in hard-to-understand areas
I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
I have made corresponding changes to the documentation
My changes generate no new warnings
I have added tests that prove my fix is effective or that my feature works
New and existing unit tests pass locally with my changes
Any dependent changes have been merged and published in downstream modules

…lock author

…ck builders

…uilder

l0r1s · 2026-02-18T13:24:04Z

runtime/src/lib.rs

+pub struct BlockAuthorFromAura<F>(core::marker::PhantomData<F>);
+
+impl<F: FindAuthor<u32>> BlockAuthorFromAura<F> {
+    pub fn get_block_author() -> Option<AccountId32> {
+        let binding = frame_system::Pallet::<Runtime>::digest();
+        let digest_logs = binding.logs();
+        let author_index = F::find_author(digest_logs.iter().filter_map(|d| d.as_pre_runtime()))?;
+        let authority_id = pallet_aura::Authorities::<Runtime>::get()
+            .get(author_index as usize)?
+            .clone();
+        Some(AccountId32::new(authority_id.to_raw_vec().try_into().ok()?))
+    }
+}
+
+impl AuthorshipInfo<AccountId32> for Runtime {
+    fn author() -> Option<AccountId32> {
+        BlockAuthorFromAura::<Aura>::get_block_author()
+    }
+}
+
+impl<F: FindAuthor<u32>> AuthorshipInfo<sp_runtime::AccountId32> for BlockAuthorFromAura<F> {
+    fn author() -> Option<sp_runtime::AccountId32> {
+        Self::get_block_author()
+    }
+}
+


This looks like a reimplementation of FindAccountFromAuthorIndex, no?

If we add the pallet_authorship to the runtime, this becomes a single line in the config, we could have pallet_authorship::Config be a supertrait of pallet_subtensor::Config and access author directly, just adding a pallet helper to derive the AccountId32 from the AuthorityId.

In your tests you would just have to set the pallet_autorship::Author storage value to what you want.

Wdyt?

Pallet transaction-fee doesn't have config, so we would still have to implement AuthorshipInfo for Runtime. Seems like the trade off is ~15 lines of code vs. including pallet-authorship. IMO this is better, but I'm open to discuss. Let's talk about it in the Nucleus standup.

l0r1s · 2026-02-18T13:50:39Z

pallets/swap-interface/src/lib.rs

    pub fee_paid: PaidIn,
+    pub fee_to_block_author: PaidIn,


Shouldn't these two be the same? Or if I understand correctly you can only pay a part of the fee to the block author and rest goes to the pool?

Correct: Part of the fee may be paid to the block author.

0xcacti · 2026-02-18T15:59:25Z

pallets/subtensor/src/staking/stake_utils.rs

        });

        // Decrease Alpha outstanding.
-        // TODO: Deprecate, not accurate in v3 anymore


off topic, but this removed comment is still true.

0xcacti · 2026-02-18T16:11:46Z

pallets/subtensor/src/staking/stake_utils.rs

+        // Swap (in a fee-less way) the block builder alpha fee
+        let mut fee_outflow = 0_u64;
+        let maybe_block_author_coldkey = T::AuthorshipProvider::author();
+        if let Some(block_author_coldkey) = maybe_block_author_coldkey {


okay, this took me forever to come to the conclusion that it is correct, but it is correct. I would have taken fees on the claim_fees event that the protocol position calls at each block step because then it's super obivous that accounting is correct, but the accounting here is in fact correct. Just took me a long time to realize it.

0xcacti · 2026-02-18T16:14:04Z

pallets/subtensor/src/staking/stake_utils.rs

+        } else {
+            // Block author is not found - burn this TAO
+            // Pallet balances total issuance was taken care of when balance was withdrawn for this swap
+            TotalIssuance::<T>::mutate(|ti| {


nit: probably should use the burning utils we have.

0xcacti · 2026-02-18T16:14:30Z

pallets/subtensor/src/staking/stake_utils.rs


+        // Increase the balance of the block author
+        let maybe_block_author_coldkey = T::AuthorshipProvider::author();
+        if let Some(block_author_coldkey) = maybe_block_author_coldkey {


symmetric to alpha case except we don't have to swap back to TAO.

0xcacti · 2026-02-18T16:16:28Z

pallets/swap/src/pallet/impls.rs


        log::trace!("Delta out: {}", swap_result.delta_out);
        log::trace!("Fees: {}", swap_result.fee_paid);
+        log::trace!("Fees for block author: {}", swap_result.fee_to_block_author);


lets goo, I believe that Greg and I originally added this long block of trace logs, but I never suspected they would make it into the codebase nor that be expanded upon later.

0xcacti · 2026-02-18T16:18:28Z

pallets/swap/src/pallet/swap_step.rs


-            // Hold the fees
-            Self::add_fees(self.netuid, self.fee);
+            // Split fees according to DefaultFeeSplit between liquidity pool and


In this section we comment that if we want to take the whole fee we can just do fee_to_block_author = self.fee.

I'm totally okay with this, we just have to make 100% certain that add_fees is called with 0. If it's a positive value we will be double counting fees and create TAO or alpha out of nothing.

0xcacti · 2026-02-18T16:22:06Z

pallets/swap/src/pallet/swap_step.rs

            fee_paid: self.fee,
            delta_in: self.delta_in,
            delta_out,
+            fee_to_block_author,


Just making a note that units are in Alpha or TAO here. Looks good everywhere, but we can't ever assume fee_to_block_author is in TAO terms when working with the SwapStepResult type.

fee_to_block_author is declared as PaidIn type, so if we're buying, then PaidIn is TaoBalance, and if we're selling, then PaidIn is AlphaBalance. All with type safety.

github-actions · 2026-02-18T16:59:45Z

@opentensor/cerebrum / @opentensor/gyrus / @opentensor/cortex breaking change detected! Please prepare accordingly!

sam0x17 · 2026-02-18T16:59:57Z

marked as breaking change only because some e2es break

gztensor · 2026-02-19T19:25:10Z

Manually tested on a baedeker clone with a transfer. The diff shows:

One account (destination) replenished with 0.1 balance
One account (origin) reduced balance
One account (authority) created with 13756 rao balance (fee)

$ diff accounts-before.json accounts-after-transfer.json 
151434c151434
<   "5H3qhPGzKMNV9fTPuizxzp8azyFRMd4BnheSuwN9Qxb5Cz3u": "0",
---
>   "5H3qhPGzKMNV9fTPuizxzp8azyFRMd4BnheSuwN9Qxb5Cz3u": "100000000",
299743a299744
>   "5G6okTjVk3urYHR1MyJLXmF6AtSvZ9qiwzWhCatNBXV9JMJd": "13756",
332880c332881
<   "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY": "1000000000",
---
>   "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY": "899986244",

gztensor added 5 commits February 13, 2026 16:12

Increaase tx fees 10x, increase swap fees to 1%, forward tx fees to b…

2208d29

…lock author

Move AuthorshipProvider to subtensor pallet, forward swap fees to blo…

f6e2f43

…ck builders

Add block builder fee test

bd0d98f

Fix broken staking tests

e33246a

fmt

3300b1f

gztensor self-assigned this Feb 16, 2026

gztensor added the skip-cargo-audit This PR fails cargo audit but needs to be merged anyway label Feb 16, 2026

gztensor added 4 commits February 17, 2026 11:03

Fix tx weights

280a880

Unstake block builders alpha

0b346d2

Merge branch 'devnet-ready' into feat/tx-fees-swap-fees-go-to-block-b…

b7ce784

…uilder

Set fee split as 1:4

fc31ca5

sam0x17 previously approved these changes Feb 17, 2026

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shamil-gadelshin previously approved these changes Feb 18, 2026

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l0r1s requested changes Feb 18, 2026

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l0r1s reviewed Feb 18, 2026

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Set fee split 100% to block builder

d1bc5cd

gztensor dismissed stale reviews from shamil-gadelshin and sam0x17 via d1bc5cd February 18, 2026 14:46

0xcacti approved these changes Feb 18, 2026

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l0r1s approved these changes Feb 18, 2026

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sam0x17 approved these changes Feb 18, 2026

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sam0x17 added the breaking-change This PR introduces a noteworthy breaking change label Feb 18, 2026

sam0x17 merged commit d147ebd into devnet-ready Feb 18, 2026
189 of 193 checks passed

sam0x17 mentioned this pull request Feb 18, 2026

mainnet deploy 2/20/2026 #2442

Merged

gztensor mentioned this pull request Feb 19, 2026

increase tx fees and credit to block builder #2424

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