apps/cowswap-frontend/src/modules/balancesAndAllowances/updaters/CommonPriorityBalancesAndAllowancesUpdater.tsx (1)

25-61: ⚡ Quick win

Avoid running legacy updater hooks when watcher mode is enabled.

usePriorityTokenAddresses, timer effects, and useOrdersFilledEventsTrigger are executed before the isBwEnabled return, so watcher mode still initializes legacy multicall-path logic. Split the watcher and legacy paths into separate components and branch immediately after reading the flag.

Proposed refactor

 export function CommonPriorityBalancesAndAllowancesUpdater(): ReactNode {
   const sourceChainId = useSourceChainId().chainId
   const { account } = useWalletInfo()
   const balancesContext = useBalancesContext()
   const balancesAccount = balancesContext.account || account
   const { isBwEnabled } = useFeatureFlags()
-
-  const priorityTokenAddresses = usePriorityTokenAddresses()
-  const priorityTokenAddressesAsArray = useMemo(() => {
-    return Array.from(priorityTokenAddresses.values())
-  }, [priorityTokenAddresses])
-  const priorityTokenCount = priorityTokenAddressesAsArray.length
-  const [skipFirstPriorityUpdate, setSkipFirstPriorityUpdate] = useState(true)
-  useEffect(() => {
-    setSkipFirstPriorityUpdate(true)
-  }, [sourceChainId])
-  useEffect(() => {
-    if (!account || !priorityTokenCount) return
-    const timeout = setTimeout(() => {
-      setSkipFirstPriorityUpdate(false)
-    }, PRIORITY_TOKENS_REFRESH_INTERVAL)
-    return () => clearTimeout(timeout)
-  }, [account, priorityTokenCount])
-  const refreshTrigger = useOrdersFilledEventsTrigger()

   if (isBwEnabled) {
     return <BalancesWatcherUpdater account={balancesAccount} chainId={sourceChainId} />
   }
+
+  return <LegacyPriorityBalancesUpdater account={account} balancesAccount={balancesAccount} sourceChainId={sourceChainId} />
+}
+
+function LegacyPriorityBalancesUpdater({
+  account,
+  balancesAccount,
+  sourceChainId,
+}: {
+  account: string | undefined
+  balancesAccount: string | undefined
+  sourceChainId: number
+}): ReactNode {
+  const priorityTokenAddresses = usePriorityTokenAddresses()
+  const priorityTokenAddressesAsArray = useMemo(() => Array.from(priorityTokenAddresses.values()), [priorityTokenAddresses])
+  const priorityTokenCount = priorityTokenAddressesAsArray.length
+  const [skipFirstPriorityUpdate, setSkipFirstPriorityUpdate] = useState(true)
+  const refreshTrigger = useOrdersFilledEventsTrigger()
+  // existing effects and return JSX remain here

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@apps/cowswap-frontend/src/modules/balancesAndAllowances/updaters/CommonPriorityBalancesAndAllowancesUpdater.tsx`
around lines 25 - 61, The legacy updater hooks including
usePriorityTokenAddresses, the timer effects with
PRIORITY_TOKENS_REFRESH_INTERVAL, and useOrdersFilledEventsTrigger are being
executed unconditionally before checking the isBwEnabled flag. Move the check
for isBwEnabled to the top of the component and return the
BalancesWatcherUpdater immediately when watcher mode is enabled, then wrap all
the legacy hook calls and effects (usePriorityTokenAddresses, the two useEffect
blocks, and useOrdersFilledEventsTrigger) in a conditional that only executes
when isBwEnabled is false. This ensures legacy multicall-path logic is not
initialized when watcher mode is active.

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

Finding: Handle watcher errors before the first snapshot as a completed balance load failure

• Location: libs/balances-and-allowances/src/hooks/useBalancesWatcherSession.ts:75 and apps/cowswap-frontend/src/modules/tradeFormValidation/hooks/useTradeFormValidationContext.ts:111
• When isBwEnabled is true, the PR bypasses the RPC updater and relies on the watcher path for EVM chains.
• If createBalancesWatcherSession rejects or the SSE stream terminates before the first balance_update, the hook sets error and isLoading: false, but leaves hasFirstLoad: false.
• The validation context then computes isBalancesLoading: !hasFirstLoad || isBalancesLoading, so the UI stays in BalancesLoading instead of surfacing BalancesNotLoaded. This matches the current Cypress failures on the PR head where swap flows never find #do-trade-button.

Suggested fix

• Make the error path stop the first-load gate, or make validation treat a balance error as not loading. For example, terminal watcher/create-session failures should transition to a state that renders BalancesNotLoaded rather than permanent BalancesLoading.
• Add coverage for both createSession rejection and terminal SSE error before the first snapshot, asserting the downstream validation sees a not-loaded/error state rather than loading forever.

Verify this finding against current PR head. Keep the fix minimal and validate it with focused tests.

Context:
- `CommonPriorityBalancesAndAllowancesUpdater` switches EVM chains to `BalancesWatcherUpdater` when `isBwEnabled` is true.
- `useBalancesWatcherSession` sets `error` and `isLoading: false` on create-session rejection or terminal SSE error, but leaves `hasFirstLoad: false`.
- `useTradeFormValidationContext` computes `isBalancesLoading` as `!hasFirstLoad || isBalancesLoading`, so pre-snapshot watcher failures remain stuck as loading.
- Expected behavior: pre-snapshot watcher failures should render a balance-load error/not-loaded state instead of permanent loading.

Generated using the pr-review skill from the CoW Protocol skills repo.