[wip] XCM executor keeps track and resolves all imbalances created by XCM operations #10384

acatangiu · 2025-11-21T09:16:31Z

TODO

_Context_ Asset Hub currently supports registering following types of assets: 1. Local Assets (also called trust-based assets), with `u32` asset ID, asset creatable by Signed accounts and managed by `PalletInstance(50)`. 2. Foreign Assets, `Location` as asset ID, creatable only by external locations over XCM. For "foreign assets", the current code assumes and enforces that the asset is teleportable with its original location/creator. Some ecosystem parachains would want to register foreign assets on Asset Hub, but not also have them teleportable, not have Asset Hub act as a reserve for the asset. Multiple reserve locations adds reserve management overhead for teams, and some don't want to do it. E.g. for HOLLAR to be registered to Asset Hub, Hydration wants Asset Hub to allow reserve-based foreign assets. _Solution_ This PR adds a new storage item and new call to `pallet-assets` that can be used to configure the trusted reserves (as seen by the local chain) on a per-asset basis. It also adds runtime machinery to use the assets reserves information when reasoning about XCM teleports and XCM reserve-based transfers. For each asset, the base chain described in its asset id location is considered a default reserve chain without it having to be explicitly configured. Any other chain that should be assumed as a trusted reserve needs to be marked as such in `pallet-assets-reserves` by the asset's Owner or Admin. When the local chain is also marked as a reserve (`Here` is added to the list of reserves) for a particular asset, then that asset can be teleported between the local chain and any other reserve location. By default, on asset creation, no explicit reserve chain is configured, this results in foreign assets to be reserve-based assets by default and not teleportable. To make them teleportable with their origin chain, `Here` needs to be added as a reserve (local chain to also be a reserve). _AH considerations_ Since there are already a number of Foreign Assets already registered, and have been teleportable since registration, this PR also adds a migration that adds `Here` as a reserve for existing foreign assets, so as not to change any existing behaviors. Newly registered foreign assets will not be teleportable by default, which is the desired result of this PR. They can be configured to be teleportable by the asset's Owner or Admin, post-creation. Signed-off-by: Adrian Catangiu <[email protected]> move reserves config to pallet-assets

…nce-pallet-assets-with-reserves

…t-hub-westend'

…nce-pallet-assets-with-reserves

Co-authored-by: Francisco Aguirre <[email protected]>

…ime asset-hub-westend'" This reverts commit d6838f3. The benchmark changes pollute the PR too much. We'll add them in a dedicated PR.

Co-authored-by: Branislav Kontur <[email protected]>

…executor-annoyance

muharem

thanks, this is a big effort. looks good to me. It does make things even more complex, though, but I don’t have a fundamentally better idea. I left a few suggestions that might make things a bit safer.

this definitely requires us to write new tests for all affected types to verify the correct total issuance.

muharem · 2025-11-25T14:44:01Z

polkadot/xcm/xcm-executor/src/traits/transact_asset.rs

-				Err(XcmError::AssetNotFound) | Err(XcmError::Unimplemented) => (),
+				// Err((unspent, error)) if error == XcmError::AssetNotFound || error == XcmError::Unimplemented => (),
+				Err((unspent, XcmError::AssetNotFound)) | Err((unspent, XcmError::Unimplemented)) => {
+					what = unspent;


should what be just the last? or sum?

same comment applies to deposit_asset_with_surplus

muharem · 2025-11-25T14:52:59Z

polkadot/xcm/xcm-executor/src/config.rs

 	/// The general asset trap - handler for when assets are left in the Holding Register at the
 	/// end of execution.


and the handler for when there is an instruction to claim assets.

muharem · 2025-11-25T15:13:02Z

polkadot/xcm/xcm-executor/src/assets.rs

-					maybe_failed_bin.as_mut().map(|f| f.non_fungible.insert((class, inst)));
-					None
-				},
+		assets.sort();


why do we start sorting? what if I indexed the fee asset, index might change.

muharem · 2025-11-25T15:21:30Z

polkadot/xcm/xcm-executor/src/assets.rs

+
+	/// Return all inner assets, but interpreted from the perspective of a `target` chain. The local
+	/// chain's `context` is provided.
+	pub fn reanchored_assets(&self, target: &Location, context: &InteriorLocation) -> Assets {


this basically same as reanchor_and_burn_local but does not burn and at the same time still returns Assets. may be also warn comment.

this unfortunately means that Assets might represent amounts and imbalances too

muharem · 2025-11-25T15:37:34Z

polkadot/xcm/xcm-executor/src/assets.rs

-									(*self_amount == 0, amount)
+									// Ok to use `saturating_take()` because we checked with
+									// `self.ensure_contains()` above against `saturate` flag
+									let balance = self_amount.saturating_take(amount);


if amount < self_amount, this wont fail and will remove the self_amount. not sure if this an issue.

muharem · 2025-11-26T10:46:42Z

polkadot/xcm/pallet-xcm/src/lib.rs

+		holding.drop_without_accounting();
 		let versioned = VersionedAssets::from(Assets::from(assets));
 		let hash = BlakeTwo256::hash_of(&(&origin, &versioned));
 		AssetTraps::<T>::mutate(hash, |n| *n += 1);


oh, this is also by itself is a credit, may be worth documenting

muharem · 2025-11-26T10:47:57Z

polkadot/xcm/pallet-xcm/src/lib.rs

 		}
+		let mut claimed = AssetsInHolding::new();
+		for asset in assets.inner() {
+			match <T::XcmExecutor as XcmAssetTransfers>::AssetTransactor::mint_asset(asset, context)


should this be minted? on asset trap above we drop_without_accounting

muharem · 2025-11-26T11:02:34Z

substrate/frame/support/src/traits/tokens/fungible/imbalance.rs

 		self.amount = self.amount.saturating_add(other.amount);
 		core::mem::forget(other);
 	}
+	fn subsume_amount(&mut self, amount: B) {


may be pub (crate) subsume_amount like forget above?
otherwise we make safe trait unsafe.

muharem · 2025-11-26T11:03:42Z

substrate/frame/support/src/traits/tokens/imbalance/imbalance_accounting.rs

+
+/// Helper trait to be used for generic Imbalance, helpful for tracking multiple concrete types of
+/// `Imbalance` using dynamic dispatch of this trait.
+pub trait ImbalanceAccounting<Balance> {


this could be ImbalanceAccounting: Unsafe
where we decouple subsume_amount, unsafe_clone and forget_amount to Unsafe

muharem · 2025-11-26T11:07:41Z

polkadot/xcm/xcm-executor/src/assets.rs

-use core::mem;
-use sp_runtime::{traits::Saturating, RuntimeDebug};
+use core::{fmt::Formatter, mem};
+use frame_support::traits::tokens::imbalance::ImbalanceAccounting;


we break the rule of xcm-executor not depending on frame. to not do it we could have an adapter in the builder. not blocker for me, just heads-up.

This reverts commit e9e5946. This doesn't work because we are actually changing types across the stack, we use UnionOf combinations to combine Fungible and Fungibles types into new "union types" so downcasting to specific types becomes very complex...

…executor-annoyance

acatangiu and others added 30 commits October 7, 2025 15:13

add benchmarking

31b0f1d

fix tests

13f1865

add prdoc

aea83bb

fix weights

f078ab8

fix benchmarks for testnets

7954136

fix benchmarks

b9ec3e8

fix genesis test

d19997b

add foreign assets migration - wip

6b2f1f0

foreign assets migration continued

bf8e939

add try-runtime checks

fb62055

move migration to assets-common

36cbce1

fix migration

b1e1127

Merge branch 'master' of github.com:paritytech/polkadot-sdk into enha…

d1525b8

…nce-pallet-assets-with-reserves

add view functions

df2d506

Merge branch 'master' of github.com:paritytech/polkadot-sdk into enha…

77ee64b

…nce-pallet-assets-with-reserves

Merge branch 'master' of github.com:paritytech/polkadot-sdk into enha…

a5e1503

…nce-pallet-assets-with-reserves

fix pallet-xcm/precompiles benchmarks

9345df5

Update from github-actions[bot] running command 'bench --runtime asse…

d6838f3

…t-hub-westend'

Merge branch 'master' of github.com:paritytech/polkadot-sdk into enha…

501bcbb

…nce-pallet-assets-with-reserves

fix snowbridge test

6233cb0

Merge branch 'master' of github.com:paritytech/polkadot-sdk into enha…

0a3cc9b

…nce-pallet-assets-with-reserves

finish FIXME: fully verify origins

5f7bfd1

add more docs

6da2384

Apply suggestion from @franciscoaguirre

78c0aba

Co-authored-by: Francisco Aguirre <[email protected]>

Apply suggestion from @franciscoaguirre

719f003

Co-authored-by: Francisco Aguirre <[email protected]>

Merge branch 'master' into enhance-pallet-assets-with-reserves

74e5eb3

Revert "Update from github-actions[bot] running command 'bench --runt…

edc6ae9

…ime asset-hub-westend'" This reverts commit d6838f3. The benchmark changes pollute the PR too much. We'll add them in a dedicated PR.

update weights for pallet-assets

008a447

Update substrate/frame/assets/src/lib.rs

9551b13

Co-authored-by: Branislav Kontur <[email protected]>

acatangiu added 8 commits November 19, 2025 12:25

adapt pallet-xcm

da1f5cb

even more cleanup

02e7e49

more cleanup and documentation

77424f4

Merge branch 'master' of github.com:paritytech/polkadot-sdk into xcm-…

e57d0ab

…executor-annoyance

fix merge damage

3a2aa7d

xcm-executor mints assets on teleport in or reserve transfer in

f99604c

fix more mock runtimes

08d325c

fix leftover TODOs and get tests passing

ba57fdf

acatangiu added the T6-XCM This PR/Issue is related to XCM. label Nov 21, 2025

acatangiu added 7 commits November 21, 2025 12:07

add pallet-assets Debt and Credit issue and burn events

4621764

update deposit_asset() to take an imbalance and deposit instead of mint

cac915d

update the erc20_transactor too

93de345

fix integration tests

7f0fffa

Merge branch 'master' into xcm-executor-annoyance

30a60cb

fix RBH build

c9e117a

add docs

fb5b764

muharem reviewed Nov 26, 2025

View reviewed changes

acatangiu added 5 commits November 26, 2025 14:09

experiment with Any trait and automatic downcasting

e9e5946

split to more granular traits and expose safer patterns

200bfbf

fix leftover

4d302ad

improve AssetsInHolding and move some unsafe methods to safe wrappers

f1311eb

acatangiu force-pushed the xcm-executor-annoyance branch from 3f3726e to f1311eb Compare November 27, 2025 09:02

acatangiu added 7 commits November 27, 2025 17:15

simplify code

ef100fb

simplify code more

3a66c97

use safer API

a0195a0

fix asset dropping and claiming

79a122b

fix pallet-xcm tests

c02e625

fix xcm-executor tests

f06778c

Merge branch 'master' of github.com:paritytech/polkadot-sdk into xcm-…

7cc28e9

…executor-annoyance

		/// The general asset trap - handler for when assets are left in the Holding Register at the
		/// end of execution.

[wip] XCM executor keeps track and resolves all imbalances created by XCM operations #10384

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[wip] XCM executor keeps track and resolves all imbalances created by XCM operations #10384

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acatangiu commented Nov 21, 2025

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