Context: #575

Nobody has used vested transfers on Polkadot or Kusama Asset Hub so far
and disabling it until the Migration would avoid insertion conflicts.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Bastian Köcher <info@kchr.de>
Co-authored-by: fellowship-merge-bot[bot] <151052383+fellowship-merge-bot[bot]@users.noreply.github.com>

A high-level look of the migration is this:

<img width="1204" height="745" alt="Screenshot 2025-09-17 at 18 23 57"
src="https://github.com/user-attachments/assets/1fb39ef8-5efa-4db2-81db-6dd775af3a39"
/>

You can see the main components being the `pallet_rc_migrator` and
`pallet_ah_migrator`. The RC migrator pallet takes data out of the RC
storage and enqueues it for AH through XCM::Transact calls to the AH
migrator pallet.
Each pallet on the RC side has a migrator module that handles the
removal of the old data and creation of the messages for AH. AH then
processes these messages through the MQ pallet and acknowledges back to
RC that they were processed (not shown in the graphic).

There is rate-limiting code in place to prevent it from overloading the
DMP queue or Asset Hub.

## For Reviewers

The review comments are being addressed in
#915.
We need eyes on the Core part that is described below.

## Core STM

The main stage transitions look like this. The only manual part is the
scheduling call by the fellowship that kicks off the procedure:

* `Pending` wait for Fellowship to call `schedule_migration(when)` ->
Scheduled
* `Scheduled` waiting for scheduled block -> `WaitingForAH`
* `WaitingForAH` AH replies that it is ready -> `WarmUp`
* `WarmUp`  waiting for warm-up end -> `Starting`
* `Starting` doing some startup initialization -> `DataMigration`
* `DataMigration` MAIN PART **all pallet migrations finish** ->
`CoolOff`
* `CoolOff` waiting for cool-off to end -> `SignalMigrationFinish`
* `SignalMigrationFinish` send signal to AH that we are done ->
`MigrationDone`
* `MigrationDone` finished, unlock all Pallets.

### State Machine

The core State Machine lives in the `RcMigrator` pallet in its
`on_initialize`:


https://github.com/polkadot-fellows/runtimes/blob/8ef1cc739d756b109dc93eaf3b9da00e3dcf1383/pallets/rc-migrator/src/lib.rs#L1338-L1342

On each block the Rc Migrator checks the current state and possibly
progresses to the next one. It will only do a single state transition
per block to reduce complexity of the code. Generally, there are three
states per pallet (called
[*stages*](https://github.com/polkadot-fellows/runtimes/blob/8ef1cc739d756b109dc93eaf3b9da00e3dcf1383/pallets/rc-migrator/src/lib.rs#L190-L389)
in the code). Some pallets have more then three, but it is generally
still a multiple of three and always follows the pattern of
`PalletInit`, `PalletOngoing { cursor }`, `PalletDone`:


https://github.com/polkadot-fellows/runtimes/blob/8ef1cc739d756b109dc93eaf3b9da00e3dcf1383/pallets/rc-migrator/src/lib.rs#L239-L244

Each pallet then has one migrator struct (eg. `MultisigMigrator<T>`)
that migrates the storage items from the Relay side. It lives in the
module of its name `rc-migrator/src/multisig.rs` respectively.
Taking Multisigs as an example; you can find two functions in the
migrator struct: `migrate_many` and `migrate_single`. The former one is
from the [`PalletMigration`
trait](https://github.com/polkadot-fellows/runtimes/blob/715dbb4455a127066d0118ce7a096c72200e1126/pallets/rc-migrator/src/types.rs#L209-L221).
The `migrate_single` function is done by convention to keep the code
readable. The `migrate_many` does the following:
- Weight accounting for the RC side: Normal weight tracking to not have
overtime RC blocks
- Weight accounting for the AH side: Ensuring to not send messages that
would take up too much weight on AH processing
- Ensure that DMP messages are sensibly sized by using the
`XcmBatchAndMeter`
- Taking the data out from the Relay chain (deleting it)
- Including the data into a DMP message and sending it towards AH

### AH Side

The main logic on Asset Hub lives in the `AhMigrator` pallet. It
contains at least one extrinsic per pallet to receive the incoming data
from the RC. We are using extrinsics since RC is wrapping the data into
XCM::Transacts:


https://github.com/polkadot-fellows/runtimes/blob/9a20b12e22b019c1c0b15b9af897567a559e424c/pallets/ah-migrator/src/lib.rs#L650-L653

This calls into the [`multisig`
module](https://github.com/polkadot-fellows/runtimes/blob/6b603ca47e5c49b3a898be3f8f6b078c424f42a0/pallets/ah-migrator/src/multisig.rs#L37)
to integrate the data into the storage. Per convention we are emitting
events for each item and the whole batch.
The main task of the AH side is to integrate the data. In the example of
the multisig it is special since we do not migrate the multisig, but
only the reserved account which will be unreserved on AH.

## Messaging Logic

The messaging is ACK based. The Relay sends message to Asset Hub up to a
specified limit (50). The limit can be adjusted on the fly through a
dedicated dispatchable call, restricted to Admin and Manager roles. The
limit may be overstepped by the configured batch-size (10), so in total
there should never be more than 60 DMPs queued. Each DMP is set to at
most
[50KB](https://github.com/polkadot-fellows/runtimes/blob/8ef1cc739d756b109dc93eaf3b9da00e3dcf1383/pallets/rc-migrator/src/lib.rs#L131).

The Relay Chain migrator creates a query for each XCM data message using
the XCM query–response primitives and attaches a response status request
from Asset Hub to the message. The XCM executor on Asset Hub then sends
back the response status for every message with such a request.

The Relay migrator stores each data message sent to Asset Hub until it
receives confirmation of successful processing. It also provides a
dispatchable call, available only to Admin and Manager roles, to resend
any unconfirmed messages.

A bug that prevented certain messages from being accounted for during a
particulat pallet migration caused the Westend AHM stall. The system was
queuing too many DMPs, which forced WAH to author an overweight block
while attempting to process them all at once.

## Call Filtering

Pallet calls are filtered during the migration for three reasons:
- prevent malicious users from spamming the chain with cheap TX and
slowing down the migration
- prevent users from sending many UMPs out of AH to clog up the UMP
queue
- prevent interference with pallets that are being migrated to avoid
messing up their storage invariants

Both RC and AH provide call filters for `Before`, `During` and `After`
the migration. As you can see, most things are disabled during the
migration on both chains. After the migration, Relay chain keeps pretty
much everything disabled since it was now enabled on AH:
- Before: RC everything enabled, AH all new pallets disabled (staking,
gov etc)
- During: RC mostly everything disabled, AH mostly everything disabled
- After: RC mostly everything disabled (staking, gov etc), AH everything
enabled (staking, gov etc)

This is implemented  by returning three bools, one for each phase:  

https://github.com/polkadot-fellows/runtimes/blob/88f4aaf62236fbee9cfb9183e44333bac45b1371/system-parachains/asset-hubs/asset-hub-polkadot/src/ah_migration/call_filter.rs#L81-L83

## Testing and Dry-Runs

https://github.com/paritytech/ahm-dryrun is the repository for testing
infrastructure for AHM. As of now, the following is being tested there
(as a part of "[AHM Flow (all
steps)](https://github.com/paritytech/ahm-dryrun/actions/workflows/zombie-bite.yml)"
nightly action):
* Dry-running a migration on a fork of Kusama
* Re-running the rust unit tests introduced in this branch
* Re-running a subset of the same tests, re-written in TS
* Re-running PET tests.

Each action produces a table with the summary of the test results: 

<img width="682" height="357" alt="Screenshot 2025-09-19 at 09 03 20"
src="https://github.com/user-attachments/assets/69c1e37d-6f8f-4b57-b97f-75781a1e1a3a"
/>

And 4 snapshot files (2 real databases, 2 try-runtime snapshots) which
can be used to re-run any of the tests, or run the pre/post migration
chain, locally.

<img width="1347" height="476" alt="Screenshot 2025-09-19 at 09 03 40"
src="https://github.com/user-attachments/assets/127cbf76-b2fb-467f-8fef-3e93a9a709f6"
/>


<details><summary>Full Changelog</summary>
<p>

- **[AHM] OpenGov for Kusama AH (#877)**
- **Relay Chain Accounts to Asset Hub Migration (#515)**
- **Test Relay<->AH migration through DMP messages (#528)**
- **[AHM] Improve account migration (#532)**
- **[AHM] Add multisig migration (#534)**
- **[AHM] Proxy migration (#542)**
- **[AHM] Cleanup and add Preimage doc (#543)**
- **[AHM] Improve accounts migration (#550)**
- **[AHM] Preimage migration (#545)**
- **[AHM] Add Polkadot call filtering (#559)**
- **[AHM] Nomination pools (#562)**
- **[AHM] referenda pallet (#558)**
- **[AHM] Cleanup (#565)**
- **[AHM] Scheduler Pallet (#569)**
- **[AHM] Fast unstake and Bags list (#563)**
- **[AHM] Pallet claims (#570)**
- **[AHM] Conviction Voting Pallet (#578)**
- **[AHM] Pallet Indices (#577)**
- **[AHM] pause scheduler during migration (#580)**
- **[AHM] Asset rate pallet migration (#581)**
- **[AHM] Bounties data migration (#585)**
- **[AHM] Vesting (#575)**
- **[AHM] fix the rc-migrator call filter (#598)**
- **[AHM] Sovereign Account Translation (#594)**
- **[AHM] Crowdloans (#592)**
- **[AHM] Set up AH migration testing framework for single pallets
(#597)**
- **[AHM] Stage management (#584)**
- **[AHM] Do not pause inherents 🙈 (#609)**
- **[AHM] Relay Chain accounts' reserves (#602)**
- **[AHM] Benchmarks (#589)**
- **[AHM] Pallet testing framework (#612)**
- **[AHM] fix xcm weight at most (#617)**
- **[AHM] Improve weight accounting for accounts migration  (#618)**
- **[AHM] AH acks messages from RC (#620)**
- **[AHM] Pure Proxy Investigation (#621)**
- **[AHM] Remove migrated items for pallet preimage and improve testing
(#619)**
- **[AHM] Referenda metadata (#633)**
- **[AHM] Fix accounts migration failures (#628)**
- **[AHM] refactor events and enable scheduled migration start (#634)**
- **[AHM] Migrating DOT total issuance tracking from RC to AH (#607)**
- **[AHM] Comment faulty checks out (#640)**
- **Account migrator refactor (#639)**
- **[AHM] Rebase (#641)**
- **[AHM] Run AHM test in CI (#642)**
- **[AHM] Vesting test (#615)**
- **[AHM] bags_list and conviction_voting tests  (#632)**
- **[AHM] Treasury pallet migration (#624)**
- **[AHM] Fix tests for pallet preimage (#643)**
- **[AHM] Test Coverage Report (#650)**
- **[AHM] deactivate/reactivate total issuance & weights (#648)**
- **[AHM] add sudo behind feature flag (#657)**
- **[AHM] fast_unstake tests (#658)**
- **[AHM] asset_rate test (#660)**
- **[AHM] Pallet treasury tests (#664)**
- **[AHM] Improve account balances integration tests (#655)**
- **[AHM] Integrate AH migrator weights to RC (#665)**
- **Testing for bounties migration (#669)**
- **[AHM] Westend port adapters (#652)**
- **[AHM] fix checking account and total issuance migration (#636)**
- **[AHM] Bump polkadot relay and AH versions (#667)**
- **[AHM] Fix tests for pallet treasury (#671)**
- **[AHM] Claims and Crowdloan tests (#622)**
- **[AHM] Benchmarks (#663)**
- **[AHM] Add Asset Hub CallFilter (#670)**
- **[AHM] Westend staking migration (#689)**
- **[AHM] Referenda migration storage checks (#672)**
- **[AHM] AH benchmarks cleanup (#690)**
- **[AHM] Westend Async Staking Migration (#691)**
- **[AHM] Relay Chain migrator benchmarks (#692)**
- **[AHM] Asset Hub ops pallet benchmarks (#693)**
- **[AHM] Xcm send weights and Batch helper types (#694)**
- **Finish staking Westend (#695)**
- **[AHM] Account provider/consumer references (#702)**
- **[AHM] Fix westend builds (#704)**
- **[AHM] Generate weights (#706)**
- **[AHM] Proxy fixes and more tests (#707)**
- **[AHM] Docs and simpler events (#699)**
- **[AHM] Test call decoding (#710)**
- **[AHM] Emulated test for migration with async backing (#717)**
- **[AHM] Increase test coverage (#720)**
- **[AHM] Add referenda checks to Westend migration (#713)**
- **[AHM] Nom_pools test (#677)**
- **[AHM] Scheduler storage item checks (#680)**
- **[AHM] Update Polkadot Snapshot (#725)**
- **[AHM] Pallet multisig tests (#666)**
- **[AHM] Adapt XCM configuration to account for changes before and
after migration (#722)**
- **[AHM] document checking account migration (#716)**
- **[AHM] Dependency fixes for integration tests and the Polkadot
runtime (#751)**
- **[AHM] Remove empty conviction voting filter (#750)**
- **[AHM] Missing TODOs and `AccountState` type update (#742)**
- **[AHM] DMP prioritization on AH (#772)**
- **[AHM] Disable #[pallet::hooks] for migrating pallets during
migration (#784)**
- **[AHM] AH messages prioritization on RC (#787)**
- **[AHM] Cache test snapshots and include more tests into CI job
(#788)**
- **[AHM] Cleanup Westend feature (#789)**
- **[AHM] Introducing the Cool-Off stage (#786)**
- **[AHM]  Flow Control System (#780)**
- **[AHM] Migrate pallet delegated-staking to AH (#791)**
- **[AHM] Merge master into dev branch (#793)**
- **[AHM] Disable indirect XCMs from RC to AH and vice versa during
migration (#774)**
- **Rebase**
- **bring back RelayTreasuryLocation to make old tests compiole**
- **[AHM] Missing `RootLocation` for WaivedLocation for AHP (#798)**
- **[AHM] Missing `SecretaryEntities` for AHP (#797)**
- **[AHM] Migration idempotency (#808)**
- **[AHM] Block number providers for migrating pallets (#809)**
- **[AHM] Copy latest ah-ops pallet from the SDK (#810)**
- **[AHM / ah-migrator]: Implement RC->AH account translation `mocked`
migration across all involved pallets (#807)**
- **[AHM] Complete account balances tests (#674)**
- **[AHM] Address TODOs (#815)**
- **[AHM] Async staking config (#812)**
- **[AHM] Optional migration manager account id (#818)**
- **[AHM] Type safe Hold and Freeze-Reason translation (#819)**
- **[AHM] Create new response query on resend and tests (#816)**
- **PolkadotAssetHub: Enable Async Backing (#763)**
- **Ensure no era planned when migration starts (#728)**
- **[AHM] with async backing (#822)**
- **[AHM] Staking migration (#821)**
- **identify with only validator account**
- **[AHM] Tests work for Paseo (#827)**
- **[AHM] Child bounties (#613)**
- **[AHM] Cleanup and linter fixes (#828)**
- **[AHM] Fix snowbridge test - wrong import of
`RelayTreasuryPalletAccount` (instead of AH, it should be BH) (#831)**
- **[AHM] Account Translation mapping (#829)**
- **Fast unstake: remove alias**
- **fmt**
- **[AHM] Max migrated items per block (#834)**
- **[AHM] Record migration timings (#835)**
- **[AHM] Remove storage aliases and cleanup (#832)**
- **[AHM] fix Kusama bags list pallet benchmarks (#836)**
- **[AHM] Unprocessed msg buffer size 50 (#839)**
- **[AHM] Post migration cool off stage (#841)**
- **[AHM] Multisig test and storage_alias cleanup (#842)**
- **[AHM] Remove fast-unstake and test fixes (#846)**
- **Run try-state check for all pallets post AHM rust tests (#833)**
- **[AHM] Preserve on RC manager' account (#843)**
- **[AHM] Filter staking calls before migration starts (#847)**
- **[AHM] State Decode Tests (#848)**
- **[AHM] Send xcm extrinsic within migrator pallets (#851)**
- **Merge and cleanup merge commit**
- #845
- #852
- #862
- #875
- #872
- #877
- #626
- #879
- #885
- #886
- #882
- #883
- #854
- #888
- #895
- #892
- #896
- #889

</p>
</details> 

// only to let all CIs to execute for now
- [ ] Does not require a CHANGELOG entry

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Signed-off-by: Adrian Catangiu <adrian@parity.io>
Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
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