Introduce pallet-dap-satellite and BurnHandler to make tokens burn configurable #10597

sigurpol · 2025-12-10T10:57:31Z

This PR introduces pallet-dap-satellite, allowing system chains different from AssetHub to collect funds (to be periodically sent to DAP on AssetHub in a future PR) instead of burning them directly.

It also introduces BurnHandler trait to make any burns configurable (direct burn vs redirect to a buffer).
In Westend AH, RC and system chains, all burns and all fees now go to DAP or DAP satellite.

Changes

frame-support: New BurnHandler trait and DirectBurn struct. DirectBurn implements BurnHandler::burn_from to reduce total issuance.
pallet-dap-satellite: New pallet that implements BurnHandler and OnUnbalanced by accumulating funds in a satellite account (total issuance unchanged).
DAP and DAP satellite funds are excluded from active_issuance.
Fee split set to 100% DAP / DAP satellites on Westend system chains.
Redirect all burns to DAP or DAP satellite on Westend system chains

The BurnHandler::burn_from method controls the entire burn operation, including balance reduction and issuance handling.
Runtimes must explicitly configure this:

Non-DAP runtimes: DirectBurn<Balances> — reduces total issuance via set_total_issuance()
DAP-integrated runtimes: pallet_dap::Pallet<Runtime> (AssetHub) or pallet_dap_satellite::Pallet<Runtime> (other system chains) — credits buffer via increase_balance, then deactivate(amount). Total issuance unchanged.

Note: non-native asset burns via pallet-assets use the default fungible implementation, not pallet-balances's BurnHandler.

🔜 Coming next

In a followup PR, we will hook the logic to periodically send funds from the satellite to the main DAP on AssetHub.

When doing so, we will also add related tests under cumulus/parachains/integration-tests/emulated/tests. Doing it now without the XCM transfer, wouldn't provide any additional value vs runtime tests added in the scope of this PR.

Related PRs / issues

Followup of #10576.
Close #10488.

kianenigma · 2026-01-30T10:15:52Z

About #10597 (comment): I think we need to add this fix to the normal DAP pallet as well; any DOT that is stored in DAP is not part of the active issuance.

substrate/frame/balances/src/lib.rs

substrate/frame/balances/src/impl_fungible.rs

substrate/frame/dap-satellite/src/lib.rs

kianenigma · 2026-01-30T10:47:55Z

substrate/frame/dap-satellite/src/lib.rs

+		// Mark funds as inactive so they don't participate in governance voting.
+		// TODO: When implementing XCM transfer to AssetHub, call `reactivate(amount)` before
+		// sending.
+		T::Currency::deactivate(amount);


The original code of pallet-balances in this case will reduce the issuance. Is that correct? We are not increasing it
here, but marking something is inactive 🤔

I think it's the correct behavior and no - we are not reducing the total issuance.
Current flow with BurnHandler = Dap / Dap satellite:

decrease_balance(who) ( here https://github.com/paritytech/polkadot-sdk/blob/sigurpol-dap-satellite/substrate/frame/balances/src/impl_fungible.rs#L203-L203 in burn_from) -> removes from user's balance, does NOT touch total issuance

increase_balance(satellite) - adds to satellite's balance, does NOT touch total issuance

Total issuance: unchanged (funds moved to DAP, nothing created / destroyed)

deactivate(amount) - increases InactiveIssuance storage

or maybe I am not understanding your comment correctly 😓

kianenigma · 2026-01-30T10:50:09Z

substrate/frame/dap-satellite/src/lib.rs

+		);
+
+		// Mark funds as inactive so they don't participate in governance voting.
+		// TODO: When implementing XCM transfer to AssetHub, call `reactivate(amount)` before


The flow of funds that go to DAP should be:

Some pallet burns

They come to satellite

TI is not change (or am I missing sth?)

These funds are inactive now

Nothing wrt. active/inactive/issuance changes when they are sent from the satellite account to the main DAP account.

improved the comment. AFAIK here we need to reactivate before sending and on DAP side we need to deactivate when receiving

kianenigma

I have doubts around how TI issuance is handled; Let me recap what I knew before this:

Pallet balances implements fungible::Mutate, which has as burn_from method.
This is used for both the burn transaction, and if another pallet calls T::Currency::burn() (test should cover this too btw)
At the moment, this implementation is hardcoded in pallet-balances, and does what is sensible: burn the funds, reduce TI.
Now we want pallet-balances to allow for customization of its fungible::Mutate::burn_from.
I think in the new model, the whole implementation of BurnFrom should come from a type BurnHandler, not just the destination part.
This will allow our new BurnHandler to manage TI as it wants, while allowing the original DirectBurn to remain exactly as-is.
The PRdoc and PR description should say clearly that all existing users should use type BurnHandler = pallet_balances::DirectBurn and it will be a noop.

sigurpol · 2026-01-30T11:13:41Z

About #10597 (comment): I think we need to add this fix to the normal DAP pallet as well; any DOT that is stored in DAP is not part of the active issuance.

It is part of this PR already after your previous comment. But if we decide NOT to ship this PR for 2.0.6 then yes, we need to add that fix in ad-hoc small PR targeting 2512 / 2.0.6

sigurpol · 2026-01-30T11:40:40Z

I have doubts around how TI issuance is handled; Let me recap what I knew before this:

Pallet balances implements fungible::Mutate, which has as burn_from method.

This is used for both the burn transaction, and if another pallet calls T::Currency::burn() (test should cover this too btw)

At the moment, this implementation is hardcoded in pallet-balances, and does what is sensible: burn the funds, reduce TI.

Now we want pallet-balances to allow for customization of its fungible::Mutate::burn_from.

I think in the new model, the whole implementation of BurnFrom should come from a type BurnHandler, not just the destination part.

This will allow our new BurnHandler to manage TI as it wants, while allowing the original DirectBurn to remain exactly as-is.

The PRdoc and PR description should say clearly that all existing users should use type BurnHandler = pallet_balances::DirectBurn and it will be a noop.

I think the current behavior is correct but your approach is definitely much cleaner so I will go for BurnHandler manage the whole burn_from as per #10597 (comment)

sigurpol · 2026-01-30T12:49:00Z

I think the current behavior is correct but your approach is definitely much cleaner so I will go for BurnHandler manage the whole burn_from as per #10597 (comment)

Implemented here f91cb59

paritytech-workflow-stopper · 2026-01-30T15:04:27Z

All GitHub workflows were cancelled due to failure one of the required jobs.
Failed workflow url: https://github.com/paritytech/polkadot-sdk/actions/runs/21520140321
Failed job name: fmt

kianenigma · 2026-01-30T15:24:29Z

substrate/frame/balances/src/lib.rs

+			/// `DirectBurn<Balances>` or a custom implementation.
+			type BurnHandler = ();


Can't we set this to DirectBurn then a lot of tests and mocks don't need to change.

Other option is to make the impl for () be actually what DirectBurn does.

I am cooking the latter as we speak since I realized we can make things much better assuming default = DirectBurn for all test and non Westend runtimes

kianenigma · 2026-01-30T15:37:17Z

substrate/frame/dap-satellite/src/lib.rs

+			let mut split =
+				fees.ration(dap_percent.deconstruct() as u32, other_percent.deconstruct() as u32);
+			if let Some(tips) = fees_then_tips.next() {
+				// Tips go 100% to other handler.


Is this intentional?

I suppose most runtimes will want to configure this as "everything goes to DAP". In this case the tips still go whatever
is OtherHandler.

In a similar vein, while DealWithFeesSplit is useful, am I correct that in most real cases we want to use type DealWithFees = Dap, which directly uses the OnUnbalanced impl below?

kianenigma · 2026-01-30T15:40:59Z

substrate/frame/dap-satellite/src/tests/mod.rs

+mod burn_handler;
+mod deal_with_fees_split;
+mod genesis;
+mod on_unbalanced;


This is a good place to have the tests where:

You create a fake pallet in the mock.rs that has type Currency in it.

It calls T::Currency::burn

Burn ends up in DAP.

sigurpol requested review from a team as code owners December 10, 2025 10:57

sigurpol added T2-pallets This PR/Issue is related to a particular pallet. A4-backport-stable2512 Pull request must be backported to the stable2512 release branch labels Dec 10, 2025

sigurpol changed the title ~~Introduce pallet-dap-satellite for fund collection on relay-chain and system chains~~ 🚧 Introduce pallet-dap-satellite for fund collection on relay-chain and system chains Dec 10, 2025

sigurpol changed the title ~~🚧 Introduce pallet-dap-satellite for fund collection on relay-chain and system chains~~ 🚧 Introduce pallet-dap-satellite and redirect all burns for native tokens to DAP/ DAP satellite on Westend runtimes Dec 10, 2025

sigurpol force-pushed the sigurpol-dap-satellite branch from 4ecbd80 to 5025686 Compare December 10, 2025 22:19

sigurpol mentioned this pull request Dec 15, 2025

Introduce the first version of pallet-dap and collect staking slashes into a buffer on asset-hub-westend #10576

Merged

sigurpol force-pushed the sigurpol-dap-satellite branch from 137b6f5 to ee054ae Compare December 15, 2025 08:34

sigurpol force-pushed the sigurpol-dap-satellite branch from ee054ae to 1ad4d04 Compare December 29, 2025 13:58

sigurpol requested review from a team as code owners December 29, 2025 13:58

sigurpol removed the A4-backport-stable2512 Pull request must be backported to the stable2512 release branch label Dec 29, 2025

sigurpol force-pushed the sigurpol-dap-satellite branch 10 times, most recently from 9d68694 to 85200d8 Compare December 30, 2025 15:55

sigurpol changed the title ~~🚧 Introduce pallet-dap-satellite and redirect all burns for native tokens to DAP/ DAP satellite on Westend runtimes~~ Introduce pallet-dap-satellite and redirect all burns for native tokens to DAP/ DAP satellite on Westend runtimes Dec 30, 2025

sigurpol requested review from Ank4n, kianenigma and seadanda and removed request for a team December 31, 2025 13:12

sigurpol added 2 commits January 29, 2026 13:50

More review comments

7c84c22

Fee split set to 100% DAP on Westend chains

87c55ce

sigurpol added the A4-backport-stable2512 Pull request must be backported to the stable2512 release branch label Jan 29, 2026

sigurpol changed the title ~~Introduce pallet-dap-satellite and redirect all burns for native tokens to DAP/ DAP satellite on Westend runtimes~~ Introduce pallet-dap-satellite and BurnHandler to make tokens burn configurable Jan 30, 2026

sigurpol added 3 commits January 30, 2026 10:49

cleanup

8993417

Merge remote-tracking branch 'origin/master' into sigurpol-dap-satellite

797f913

coretime-westend: cleanup

921f956

coretime: remove unused Timeslice

cd5139e

kianenigma reviewed Jan 30, 2026

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fix review comments

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Introduce BurnHandler

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sigurpol added 6 commits January 30, 2026 13:59

treasury: revert changes

5a8500e

fix treasury config

f0407ee

Merge branch 'master' into sigurpol-dap-satellite

7ab365f

improve comment around transfer to DAP

2db5bf5

fix xcm mock

865ff74

fix more xcm tests

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kianenigma reviewed Jan 30, 2026

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		/// `DirectBurn<Balances>` or a custom implementation.
		type BurnHandler = ();

Introduce pallet-dap-satellite and BurnHandler to make tokens burn configurable #10597

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Introduce pallet-dap-satellite and BurnHandler to make tokens burn configurable #10597

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