diff --git a/eslint.config.mjs b/eslint.config.mjs
index aa94178c..481e88af 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -61,10 +61,15 @@ export default tseslint.config(
       '@typescript-eslint/no-unsafe-call': 'off',
       '@typescript-eslint/no-unsafe-return': 'off',
       '@typescript-eslint/no-unsafe-enum-comparison': 'off',
-      '@typescript-eslint/no-unnecessary-type-assertion': 'off',
-      '@typescript-eslint/no-redundant-type-constituents': 'off',
+    },
+  },
+  {
+    // Test files: `async` test callbacks and `act(async () => {})` wrappers are
+    // idiomatic even when they contain no `await` (async `act` flushes the
+    // microtask queue). Relaxing require-await here avoids churn in test infra.
+    files: ['**/*.spec.{ts,tsx}', '**/*.test.{ts,tsx}'],
+    rules: {
       '@typescript-eslint/require-await': 'off',
-      '@typescript-eslint/no-misused-promises': 'off',
     },
   },
   prettierRecommended,
diff --git a/src/app/[locale]/account/notifications/AccountNotifications.tsx b/src/app/[locale]/account/notifications/AccountNotifications.tsx
index 499a05c6..79dd909c 100644
--- a/src/app/[locale]/account/notifications/AccountNotifications.tsx
+++ b/src/app/[locale]/account/notifications/AccountNotifications.tsx
@@ -315,9 +315,7 @@ export default function AccountNotifications(): React.ReactElement {
             <Select
               value={defaultFrequency}
               onChange={(e) => {
-                setDefaultFrequency(
-                  e.target.value as NotificationSettings['frequency'],
-                );
+                setDefaultFrequency(e.target.value);
               }}
               size='small'
             >
diff --git a/src/app/[locale]/complete-registration/CompleteRegistration.tsx b/src/app/[locale]/complete-registration/CompleteRegistration.tsx
index 2d84892d..e2615cd2 100644
--- a/src/app/[locale]/complete-registration/CompleteRegistration.tsx
+++ b/src/app/[locale]/complete-registration/CompleteRegistration.tsx
@@ -86,7 +86,7 @@ export default function CompleteRegistration(): React.ReactElement {
     validationSchema: CompleteRegistrationSchema,
     validateOnChange: isSubmitted,
     validateOnBlur: true,
-    onSubmit: async (values) => {
+    onSubmit: (values) => {
       if (user != null) {
         dispatch(
           refreshUserInformation({
diff --git a/src/app/[locale]/contribute/FeedSubmission/Form/FirstStep.tsx b/src/app/[locale]/contribute/FeedSubmission/Form/FirstStep.tsx
index a203f336..35893604 100644
--- a/src/app/[locale]/contribute/FeedSubmission/Form/FirstStep.tsx
+++ b/src/app/[locale]/contribute/FeedSubmission/Form/FirstStep.tsx
@@ -107,7 +107,11 @@ export default function FormFirstStep({
 
   return (
     <>
-      <form onSubmit={handleSubmit(onSubmit)}>
+      <form
+        onSubmit={(e) => {
+          void handleSubmit(onSubmit)(e);
+        }}
+      >
         <Grid container direction={'column'} rowSpacing={2}>
           <Grid>
             <FormControl
diff --git a/src/app/[locale]/contribute/FeedSubmission/Form/FourthStep.tsx b/src/app/[locale]/contribute/FeedSubmission/Form/FourthStep.tsx
index 1bad0857..385ddc5d 100644
--- a/src/app/[locale]/contribute/FeedSubmission/Form/FourthStep.tsx
+++ b/src/app/[locale]/contribute/FeedSubmission/Form/FourthStep.tsx
@@ -67,7 +67,11 @@ export default function FormFourthStep({
 
   return (
     <>
-      <form onSubmit={handleSubmit(onSubmit)}>
+      <form
+        onSubmit={(e) => {
+          void handleSubmit(onSubmit)(e);
+        }}
+      >
         <Grid container direction={'column'} rowSpacing={2}>
           <Grid>
             <FormControl component='fieldset' fullWidth>
diff --git a/src/app/[locale]/contribute/FeedSubmission/Form/SecondStep.tsx b/src/app/[locale]/contribute/FeedSubmission/Form/SecondStep.tsx
index 76fccaa4..2e5ba37f 100644
--- a/src/app/[locale]/contribute/FeedSubmission/Form/SecondStep.tsx
+++ b/src/app/[locale]/contribute/FeedSubmission/Form/SecondStep.tsx
@@ -59,7 +59,11 @@ export default function FormSecondStep({
   return (
     <>
       <Typography gutterBottom>{t('gtfsScheduleFeed')}</Typography>
-      <form onSubmit={handleSubmit(onSubmit)}>
+      <form
+        onSubmit={(e) => {
+          void handleSubmit(onSubmit)(e);
+        }}
+      >
         <Grid container direction={'column'} rowSpacing={2}>
           <Grid>
             <FormControl
diff --git a/src/app/[locale]/contribute/FeedSubmission/Form/SecondStepRealtime.tsx b/src/app/[locale]/contribute/FeedSubmission/Form/SecondStepRealtime.tsx
index c062e5e8..525c1e0d 100644
--- a/src/app/[locale]/contribute/FeedSubmission/Form/SecondStepRealtime.tsx
+++ b/src/app/[locale]/contribute/FeedSubmission/Form/SecondStepRealtime.tsx
@@ -111,7 +111,11 @@ export default function FormSecondStepRT({
       >
         {t('gtfsRealtimeFeed')}
       </Typography>
-      <form onSubmit={handleSubmit(onSubmit)}>
+      <form
+        onSubmit={(e) => {
+          void handleSubmit(onSubmit)(e);
+        }}
+      >
         <Grid container direction={'column'} rowSpacing={2}>
           <Grid>
             <FormControl
diff --git a/src/app/[locale]/contribute/FeedSubmission/Form/ThirdStep.tsx b/src/app/[locale]/contribute/FeedSubmission/Form/ThirdStep.tsx
index 66b94782..357f380d 100644
--- a/src/app/[locale]/contribute/FeedSubmission/Form/ThirdStep.tsx
+++ b/src/app/[locale]/contribute/FeedSubmission/Form/ThirdStep.tsx
@@ -74,7 +74,11 @@ export default function FormThirdStep({
 
   return (
     <>
-      <form onSubmit={handleSubmit(onSubmit)}>
+      <form
+        onSubmit={(e) => {
+          void handleSubmit(onSubmit)(e);
+        }}
+      >
         <Grid container direction={'column'} rowSpacing={2}>
           {/* Show required emptyLicenseUsage if official producer and no license provided */}
           {isOfficialProducer && noLicenseProvided && (
diff --git a/src/app/[locale]/feeds/[feedDataType]/[feedId]/static/layout.tsx b/src/app/[locale]/feeds/[feedDataType]/[feedId]/static/layout.tsx
index 2beedda2..7d92a7dd 100644
--- a/src/app/[locale]/feeds/[feedDataType]/[feedId]/static/layout.tsx
+++ b/src/app/[locale]/feeds/[feedDataType]/[feedId]/static/layout.tsx
@@ -24,9 +24,9 @@ interface Props {
  * from the clean URLs like /feeds/gtfs/mdb-123.
  * TODO: Now that legacy catch-all route is removed, change this to a private route `_static` and update proxy and links accordingly.
  */
-export default async function StaticFeedLayout({
+export default function StaticFeedLayout({
   children,
   params,
-}: Props): Promise<React.ReactElement> {
+}: Props): React.ReactElement {
   return <>{children}</>;
 }
diff --git a/src/app/[locale]/layout.tsx b/src/app/[locale]/layout.tsx
index 03610522..93b769e0 100644
--- a/src/app/[locale]/layout.tsx
+++ b/src/app/[locale]/layout.tsx
@@ -84,7 +84,7 @@ export default async function LocaleLayout({
   }
 
   // At this point, locale is guaranteed to be a valid Locale type
-  const validLocale = locale as Locale;
+  const validLocale = locale;
 
   // Enable static rendering for this locale
   setRequestLocale(validLocale);
diff --git a/src/app/api/revalidate/route.spec.ts b/src/app/api/revalidate/route.spec.ts
index 913aba2f..15509aac 100644
--- a/src/app/api/revalidate/route.spec.ts
+++ b/src/app/api/revalidate/route.spec.ts
@@ -43,7 +43,7 @@ describe('GET /api/revalidate', () => {
       },
     });
 
-    const response = await GET(request);
+    const response = GET(request);
     const json = await response.json();
 
     expect(response.status).toBe(500);
@@ -65,7 +65,7 @@ describe('GET /api/revalidate', () => {
       },
     });
 
-    const response = await GET(request);
+    const response = GET(request);
     const json = await response.json();
 
     expect(response.status).toBe(401);
@@ -87,7 +87,7 @@ describe('GET /api/revalidate', () => {
       },
     });
 
-    const response = await GET(request);
+    const response = GET(request);
     const json = await response.json();
 
     expect(response.status).toBe(200);
diff --git a/src/app/api/revalidate/route.ts b/src/app/api/revalidate/route.ts
index 1ffa841d..b004953e 100644
--- a/src/app/api/revalidate/route.ts
+++ b/src/app/api/revalidate/route.ts
@@ -36,7 +36,7 @@ const defaultRevalidateOptions: RevalidateBody = {
  * Vercel automatically passes Authorization: Bearer <CRON_SECRET> with each invocation.
  * Configured in vercel.json under "crons" for 4am UTC Monday-Saturday and 7am UTC Sunday.
  */
-export async function GET(req: Request): Promise<NextResponse> {
+export function GET(req: Request): NextResponse {
   const authHeader = req.headers.get('authorization');
   const cronSecret = process.env.CRON_SECRET;
 
diff --git a/src/app/api/session/route.ts b/src/app/api/session/route.ts
index c7cc109b..258f7972 100644
--- a/src/app/api/session/route.ts
+++ b/src/app/api/session/route.ts
@@ -62,7 +62,7 @@ export async function POST(req: NextRequest): Promise<NextResponse> {
   }
 }
 
-export async function GET(req: NextRequest): Promise<NextResponse> {
+export function GET(req: NextRequest): NextResponse {
   try {
     const cookie = req.cookies.get(COOKIE_NAME)?.value;
     if (cookie == null) {
@@ -88,7 +88,7 @@ export async function GET(req: NextRequest): Promise<NextResponse> {
   }
 }
 
-export async function DELETE(req: NextRequest): Promise<NextResponse> {
+export function DELETE(req: NextRequest): NextResponse {
   // Clear the session cookie so that subsequent requests have no session.
   const response = NextResponse.json({ status: 'logged_out' });
   // Use the built-in delete helper to ensure the cookie is removed.
diff --git a/src/app/components/GtfsVisualizationMap.spec.tsx b/src/app/components/GtfsVisualizationMap.spec.tsx
index 4e61e0b8..db030ed2 100644
--- a/src/app/components/GtfsVisualizationMap.spec.tsx
+++ b/src/app/components/GtfsVisualizationMap.spec.tsx
@@ -94,7 +94,7 @@ describe('generateStopColorExpression', () => {
 
 describe('generateRouteOutlineColorExpression', () => {
   // Helper to safely index into nested unknown arrays
-  type NestedArr = Array<unknown | NestedArr>;
+  type NestedArr = unknown[];
   const at = (arr: NestedArr, ...indices: number[]): NestedArr =>
     indices.reduce<NestedArr>((a, i) => (a as NestedArr[])[i], arr);
   it('returns an array expression starting with "let" and "rgba"', () => {
diff --git a/src/app/components/Map/SelectedRoutesStopsPanel.tsx b/src/app/components/Map/SelectedRoutesStopsPanel.tsx
index 4a259624..bbfe374c 100644
--- a/src/app/components/Map/SelectedRoutesStopsPanel.tsx
+++ b/src/app/components/Map/SelectedRoutesStopsPanel.tsx
@@ -79,7 +79,7 @@ export const SelectedRoutesStopsPanel = (
                 key={s.stopId}
                 role='button'
                 tabIndex={0}
-                aria-selected={isActive ? 'true' : 'false'}
+                aria-pressed={isActive ? 'true' : 'false'}
                 onClick={() => {
                   focusStopFromPanel(s);
                 }}
diff --git a/src/app/components/ThemeToggle.tsx b/src/app/components/ThemeToggle.tsx
index b1ec9cd4..24e246de 100644
--- a/src/app/components/ThemeToggle.tsx
+++ b/src/app/components/ThemeToggle.tsx
@@ -2,13 +2,14 @@ import { IconButton } from '@mui/material';
 import Brightness4Icon from '@mui/icons-material/Brightness4';
 import Brightness7Icon from '@mui/icons-material/Brightness7';
 import { useTheme } from '../context/ThemeProvider';
+import { ThemeModeEnum } from '../Theme';
 
 const ThemeToggle = (): React.ReactElement => {
   const { mode, toggleTheme } = useTheme();
 
   return (
     <IconButton onClick={toggleTheme} color='inherit' aria-label='Theme Toggle'>
-      {mode === 'dark' ? <Brightness7Icon /> : <Brightness4Icon />}
+      {mode === ThemeModeEnum.dark ? <Brightness7Icon /> : <Brightness4Icon />}
     </IconButton>
   );
 };
diff --git a/src/app/screens/Feed/components/NotificationSettingsDialog.tsx b/src/app/screens/Feed/components/NotificationSettingsDialog.tsx
index 637e8f44..75b7d8f6 100644
--- a/src/app/screens/Feed/components/NotificationSettingsDialog.tsx
+++ b/src/app/screens/Feed/components/NotificationSettingsDialog.tsx
@@ -121,9 +121,7 @@ export default function NotificationSettingsDialog({
             <Select
               value={frequency}
               onChange={(e) => {
-                setFrequency(
-                  e.target.value as NotificationSettings['frequency'],
-                );
+                setFrequency(e.target.value);
               }}
               size='small'
             >
diff --git a/src/app/screens/FeedSubmitted.tsx b/src/app/screens/FeedSubmitted.tsx
index 6cfa7427..8e265c63 100644
--- a/src/app/screens/FeedSubmitted.tsx
+++ b/src/app/screens/FeedSubmitted.tsx
@@ -1,6 +1,7 @@
 'use client';
 
 import { Typography, Box, Container, useTheme, Button } from '@mui/material';
+import Image from 'next/image';
 
 export default function FeedSubmitted(): React.ReactElement {
   const theme = useTheme();
@@ -21,10 +22,13 @@ export default function FeedSubmitted(): React.ReactElement {
         🚀 Your feed has been submitted!
       </Typography>
       <Box sx={{ display: 'flex', flexDirection: 'row', p: 2 }}>
-        <img
+        <Image
           src='/assets/rocket.gif'
           alt='rocket'
-          style={{ width: '300px', height: '300px', marginRight: '60px' }}
+          width={300}
+          height={300}
+          unoptimized
+          style={{ marginRight: '60px' }}
         />
         <Box sx={{ maxWidth: '615px', justifyContent: 'center' }}>
           <Typography variant='body1' sx={{ mb: 2, fontSize: '20px' }}>
diff --git a/src/app/screens/GbfsValidator/GbfsFeedSearchInput.tsx b/src/app/screens/GbfsValidator/GbfsFeedSearchInput.tsx
index 3fa621d3..cb821691 100644
--- a/src/app/screens/GbfsValidator/GbfsFeedSearchInput.tsx
+++ b/src/app/screens/GbfsValidator/GbfsFeedSearchInput.tsx
@@ -37,7 +37,7 @@ export default function GbfsFeedSearchInput({
     initialFeedUrl ?? '',
   );
   const [requiresAuth, setRequiresAuth] = useState(false);
-  const [authType, setAuthType] = useState<string>('');
+  const [authType, setAuthType] = useState<AuthTypeEnum | ''>('');
   const [basicAuthUsername, setBasicAuthUsername] = useState<
     string | undefined
   >(undefined);
@@ -65,7 +65,9 @@ export default function GbfsFeedSearchInput({
   // Used to keep the auth inputs up to date
   useEffect(() => {
     setRequiresAuth(auth !== undefined);
-    setAuthType(auth == undefined ? '' : (auth.authType ?? ''));
+    setAuthType(
+      auth == undefined ? '' : ((auth.authType as AuthTypeEnum) ?? ''),
+    );
     setBasicAuthUsername(
       auth != null && 'username' in auth ? auth.username : undefined,
     );
@@ -91,7 +93,7 @@ export default function GbfsFeedSearchInput({
   };
 
   const handleAuthTypeChange = (event: SelectChangeEvent<string>): void => {
-    setAuthType(event.target.value);
+    setAuthType(event.target.value as AuthTypeEnum);
     setBasicAuthUsername(undefined);
     setBasicAuthPassword(undefined);
     setBearerAuthValue(undefined);
diff --git a/src/app/screens/GbfsValidator/components/ErrorDetailsDialog.tsx b/src/app/screens/GbfsValidator/components/ErrorDetailsDialog.tsx
index e045892e..de866a11 100644
--- a/src/app/screens/GbfsValidator/components/ErrorDetailsDialog.tsx
+++ b/src/app/screens/GbfsValidator/components/ErrorDetailsDialog.tsx
@@ -431,7 +431,7 @@ export function ErrorDetailsDialog({
                                     </Box>
                                   )}
                                   {renderHighlightedObject(
-                                    parentContextData as JSONValue,
+                                    parentContextData,
                                     null,
                                     null,
                                   )}
@@ -439,7 +439,7 @@ export function ErrorDetailsDialog({
                               );
                             }
                             return renderHighlightedObject(
-                              parentContextData as JSONValue,
+                              parentContextData,
                               lastPointerSegment ?? null,
                               lastArrayIndex,
                             );
diff --git a/src/app/services/api-auth-middleware.ts b/src/app/services/api-auth-middleware.ts
index d83ba77b..1f30c393 100644
--- a/src/app/services/api-auth-middleware.ts
+++ b/src/app/services/api-auth-middleware.ts
@@ -25,7 +25,7 @@ export const generateAuthMiddlewareWithToken = (
   userContextJwt?: string,
 ): Middleware => {
   return {
-    async onRequest(req) {
+    onRequest(req) {
       // Always attach the bearer token for IAP/GCIP.
       req.headers.set('Authorization', `Bearer ${accessToken}`);
 
diff --git a/src/app/services/profile-service.ts b/src/app/services/profile-service.ts
index 1835d51f..481c32b1 100644
--- a/src/app/services/profile-service.ts
+++ b/src/app/services/profile-service.ts
@@ -22,7 +22,7 @@ export const sendEmailVerification = async (): Promise<void> => {
 /**
  * Return the current user or null if the user is not logged in.
  */
-export const getUserFromSession = async (): Promise<User | null> => {
+export const getUserFromSession = (): User | null => {
   const currentUser = app.auth().currentUser;
   if (currentUser === null) {
     return null;
diff --git a/src/app/types.ts b/src/app/types.ts
index 5c196f87..a6560598 100644
--- a/src/app/types.ts
+++ b/src/app/types.ts
@@ -78,19 +78,19 @@ export enum LicenseErrorSource {
 }
 
 export interface ProfileError {
-  code: string | 'unknown';
+  code: string;
   message: string;
   source?: ProfileErrorSource;
 }
 
 export interface FeedError {
-  code: string | 'unknown';
+  code: string;
   message: string;
   source?: FeedErrorSource;
 }
 
 export interface LicenseError {
-  code: string | 'unknown';
+  code: string;
   message: string;
   source?: LicenseErrorSource;
 }
diff --git a/src/app/utils/precompute.ts b/src/app/utils/precompute.ts
index 62bce45e..83490aad 100644
--- a/src/app/utils/precompute.ts
+++ b/src/app/utils/precompute.ts
@@ -42,13 +42,7 @@ export interface PrecomputeDeps {
 
 /** Small helper: wait once for a map event */
 async function once(map: maplibregl.Map, ev: string): Promise<void> {
-  await new Promise<void>(
-    // eslint-disable-next-line no-async-promise-executor
-    async (resolve) =>
-      await map.once(ev, () => {
-        resolve();
-      }),
-  );
+  await map.once(ev);
 }
 
 // Extend helpers for [minLng,minLat,maxLng,maxLat]