Description

When the assetsUnifyState feature flag is enabled, the UI reads token balances from AssetsController.assetsBalance instead of TokenBalancesController. After a swap (e.g. QuickBuy), balances did not update in the simulator until the 30s poll, even though the real-time websocket push arrived almost immediately.

Root cause: both AccountActivityService and the controller's internal BackendWebsocketDataSource open a separate websocket subscription to the same account-activity channel. The backend routes each notification to a single subscriptionId, so only one subscriber receives the push. AccountActivityService wins that race, starving the data source's subscription — so AssetsController.assetsBalance is never merged with the fresh balance until the periodic poll.

Solution: bridge the AccountActivityService:balanceUpdated event (which reliably receives the push) into the controller's own public handleAssetsUpdate merge entrypoint. The push payload is transformed into the merge shape by a pure, unit-tested helper (buildAssetsBalanceUpdateFromPush) that mirrors the data source's own raw-amount → human-readable-decimal conversion, skipping malformed rows so a single bad entry can't drop the whole push. The bridge is gated behind assetsUnifyState, and the 30s poll remains as a fallback.

Why it wasn't noticeable before (and surfaced via QuickBuy)

This bug affects every balance update under assetsUnifyState, not just QuickBuy — which is why the fix lives at the controller-bridge layer rather than in QuickBuy. It was surfaced by the QuickBuy because of how each flow ends:

• Regular Swaps (Bridge): on completion the confirm flow navigates to Routes.TRANSACTIONS_VIEW (useBridgeConfirm). Navigating away and back re-mounts the wallet token list, which under unify force-refreshes AssetsController.getAssets({ forceUpdate: true }) (useRefreshTokens). That forced read masked the starved websocket path, so balances looked instant.
• QuickBuy: by design it stays on TraderPositionView and only shows lifecycle toasts — no navigation, no re-mount, no forced refresh. With nothing to mask it, the starved real-time path was exposed and balances only updated on the 30s poll (consistent with "pull-to-refresh fixes it" and "waiting eventually updates").

Both flows submit through the same BridgeStatusController.submitTx; the difference is purely the post-submit navigation side effect. This fix repairs the real-time path itself, so balances update live for all flows without relying on navigation or pull-to-refresh.

Changelog

CHANGELOG entry: Fixed token balances not updating immediately after a swap when the unified assets state is enabled.

Related issues

Fixes:

Manual testing steps

```gherkin
Feature: Real-time balance refresh after swap

Scenario: user completes a swap with unified assets state enabled
Given the assetsUnifyState feature flag is enabled
And the user is on a screen displaying their token balances

When the user completes a swap (e.g. via QuickBuy)
Then the source and destination token balances update within a couple of seconds
And the user does not need to pull-to-refresh or wait for the 30s poll

```

Screenshots/Recordings

Before

After

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