dawnseeker8 · Oct 19, 2026 · Oct 19, 2026 · Oct 20, 2026 · Oct 22, 2026 · Oct 22, 2026
@@ -897,6 +897,7 @@
 /packages/wallet/src/initialization/instances/accounts-controller/               @MetaMask/accounts-engineers
 /packages/wallet/src/initialization/instances/address-book-controller/           @MetaMask/confirmations
 /packages/wallet/src/initialization/instances/approval-controller/               @MetaMask/confirmations
+/packages/wallet/src/initialization/instances/assets-controller/                 @MetaMask/metamask-assets
 /packages/wallet/src/initialization/instances/claims-controller/                 @MetaMask/web3auth
 /packages/wallet/src/initialization/instances/claims-service/                    @MetaMask/web3auth
 /packages/wallet/src/initialization/instances/client-controller/                 @MetaMask/core-platform @MetaMask/extension-platform @MetaMask/mobile-platform

diff --git a/codeowners.ts b/codeowners.ts
@@ -44,6 +44,7 @@ const config = {
     },
     'assets-controller': {
       teams: ['@MetaMask/metamask-assets'],
+      initializationPath: 'assets-controller',
     },
     'assets-controllers': {
       teams: ['@MetaMask/metamask-assets'],

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add `start()` and the `AssetsController:start` messenger action ([#10885](https://github.com/MetaMask/core/pull/10885))
+  - `start()` reads enabled networks from `NetworkEnablementController:getState`, creates the data sources, subscribes to external events and to `subscribeToBasicFunctionalityChange`, waits for the Accounts API supported networks, runs the unlock cleanups when the keyring is already unlocked, and starts asset tracking when the UI is open, the keyring is unlocked and the account tree is initialized.
+  - Call it once the client has constructed and initialized the controllers `AssetsController` depends on, such as `AccountTreeController` and `SnapController`. Repeated calls return the same promise; calls after `destroy()` do nothing.
+- Export the `AssetsControllerStartAction` type ([#10885](https://github.com/MetaMask/core/pull/10885))
+
+### Changed
+
+- **BREAKING:** The `AssetsController` constructor no longer calls messenger actions, creates data sources or subscribes to external events; asset tracking does not run until `start()` is called ([#10885](https://github.com/MetaMask/core/pull/10885))
+  - Call `start()` (or the `AssetsController:start` action) after the controllers `AssetsController` depends on are registered. Data sources are created in `start()`, so their constructors still read `NetworkController`, `NetworkEnablementController`, `SnapController`, `PermissionController` and `RemoteFeatureFlagController` as before, only later.
+  - `subscribeToBasicFunctionalityChange` is invoked by `start()` instead of the constructor.
+  - Before `start()`, `getAssets` (and the methods built on it) with `forceUpdate: true` return what is already in state without fetching and without changing `assetsLoadingStatus`; `handleAssetsUpdate`, `syncAssetsPrices`, `subscribeAssetsPrice` and `handleBasicFunctionalityChange` do nothing; `setSelectedCurrency` updates state without refreshing prices.
+
 ### Fixed
 
 - Stop removing launchpad tokens as spam: EVM ERC-20s below the occurrence floor are now kept when Token API `/v2/assets` identifies them as launchpad tokens and their security data does not classify them as malicious ([#11251](https://github.com/MetaMask/core/pull/11251))

@@ -5,6 +5,47 @@
 
 import type { AssetsController } from './AssetsController.js';
 
+/**
+ * Start the controller once every controller it depends on is registered.
+ *
+ * The constructor does not touch other controllers. `start()` reads enabled
+ * networks, creates the data sources (whose constructors read network, snap
+ * and feature-flag state), subscribes to external events and to
+ * basic-functionality changes, and begins asset tracking when the UI is
+ * open, the keyring is unlocked and the account tree is initialized.
+ *
+ * Call it after the client has constructed and initialized its own
+ * controllers, such as `AccountTreeController` and `SnapController`.
+ * Until then, asset tracking does not run: forced fetches return what is
+ * already in state, and pushed updates are ignored.
+ *
+ * Repeated calls return the same promise. Calls after `destroy()` do
+ * nothing.
+ *
+ * @returns A promise that resolves once the controller has started.
+ */
+export type AssetsControllerStartAction = {
+  type: `AssetsController:start`;
+  handler: AssetsController['start'];
+};
+
+/**
+ * Get assets for the given accounts, optionally force-fetching them first.
+ *
+ * Before `start()` there are no data sources, so a forced fetch is skipped
+ * and the assets already in state are returned. The loading status of the
+ * accounts is left untouched, so the first fetch after `start()` still
+ * reports them as loading.
+ *
+ * @param accounts - Accounts to get assets for.
+ * @param options - Fetch options.
+ * @param options.chainIds - Chains to include. Defaults to the enabled chains.
+ * @param options.assetTypes - Asset types to include. Defaults to fungible.
+ * @param options.forceUpdate - Fetch from the data sources before reading state.
+ * @param options.bypassServerCache - Also bypass server-side HTTP caches.
+ * @param options.dataTypes - Data types to fetch.
+ * @returns Assets keyed by account ID and asset ID.
+ */
 export type AssetsControllerGetAssetsAction = {
   type: `AssetsController:getAssets`;
   handler: AssetsController['getAssets'];
@@ -217,6 +258,7 @@ export type AssetsControllerSetSelectedCurrencyAction = {
  * Union of all AssetsController action types.
  */
 export type AssetsControllerMethodActions =
+  | AssetsControllerStartAction
   | AssetsControllerGetAssetsAction
   | AssetsControllerSyncAssetsPricesAction
   | AssetsControllerGetAssetsBalanceAction

@@ -82,6 +82,7 @@ async function withController<ReturnValue>(
     queryApiClient,
     isBasicFunctionality: (): boolean => true,
   });
+  await controller.start();
 
   try {
     return await fn({ controller, messenger: rootMessenger });

@@ -70,6 +70,7 @@ async function withController<ReturnValue>(
     queryApiClient,
     isBasicFunctionality: (): boolean => true,
   });
+  await controller.start();
 
   try {
     return await fn({ controller, messenger: rootMessenger });

@@ -109,6 +109,7 @@ async function withController<ReturnValue>(
     queryApiClient,
     isBasicFunctionality: (): boolean => true,
   });
+  await controller.start();
 
   try {
     return await fn({ controller, messenger: rootMessenger });

@@ -102,6 +102,7 @@ async function withController<ReturnValue>(
     isBasicFunctionality,
     captureException,
   });
+  await controller.start();
 
   try {
     return await fn({ controller, messenger: rootMessenger });

@@ -120,6 +120,7 @@ async function withController<ReturnValue>(
     isBasicFunctionality,
     captureException,
   });
+  await controller.start();
 
   try {
     return await fn({ controller, messenger: rootMessenger });

@@ -142,6 +142,7 @@ async function withStaleBalanceController<ReturnValue>(
     queryApiClient,
     isBasicFunctionality: (): boolean => true,
   });
+  await controller.start();
 
   try {
     // `AccountsApiDataSource` loads `/v2/supportedNetworks` asynchronously