diff --git a/frontend/src/features/courses/components/CourseDetailDrawer.tsx b/frontend/src/features/courses/components/CourseDetailDrawer.tsx
index edb6aac..0c210bb 100644
--- a/frontend/src/features/courses/components/CourseDetailDrawer.tsx
+++ b/frontend/src/features/courses/components/CourseDetailDrawer.tsx
@@ -17,6 +17,7 @@ interface CourseDetailDrawerProps {
   listCourse?: Course | null
   isFavorite: boolean
   favoriteDisabled?: boolean
+  favoriteLoading?: boolean
   showFavorite?: boolean
   onToggleFavorite: () => void
   onClose: () => void
@@ -27,6 +28,7 @@ export function CourseDetailDrawer({
   listCourse = null,
   isFavorite,
   favoriteDisabled = false,
+  favoriteLoading = false,
   showFavorite = true,
   onToggleFavorite,
   onClose,
@@ -78,7 +80,12 @@ export function CourseDetailDrawer({
           </span>
           <div className="flex items-center gap-1.5">
             {showFavorite ? (
-              <FavStar active={isFavorite} disabled={favoriteDisabled} onToggle={onToggleFavorite} />
+              <FavStar
+                active={isFavorite}
+                disabled={favoriteDisabled}
+                isLoading={favoriteLoading}
+                onToggle={onToggleFavorite}
+              />
             ) : null}
             <button
               type="button"
diff --git a/frontend/src/features/courses/components/Overview.tsx b/frontend/src/features/courses/components/Overview.tsx
index 261aa24..9d14912 100644
--- a/frontend/src/features/courses/components/Overview.tsx
+++ b/frontend/src/features/courses/components/Overview.tsx
@@ -278,7 +278,7 @@ export function CoursesOverview() {
   const { courses, isLoading, error, refreshWarning } = useCatalogCourses(search, CATALOG_LIMIT, ALL_CATALOG_PERIODS)
   const { regulationVersion, isLoadingRegulationVersion, regulationVersionError } =
     useRegulationVersion(user?.profile.regulationVersionCode)
-  const { isFavorite, isLoadingFavorites, isSavingFavorites, favoritesError, toggleFavorite } =
+  const { isFavorite, isLoadingFavorites, isFavoriteSaving, favoritesError, toggleFavorite } =
     useFavorites()
   const { completedCourses } = useTranscript()
   const { progressSnapshot } = useProgressSnapshot()
@@ -840,7 +840,8 @@ export function CoursesOverview() {
                               historicalLecturerLookup,
                             )
                       }
-                      favoriteDisabled={isTourSampleRow || isLoadingFavorites || isSavingFavorites}
+                      favoriteDisabled={isTourSampleRow || isLoadingFavorites}
+                      favoriteLoading={!isTourSampleRow && isFavoriteSaving(course.id)}
                       showFavorite={canShowFavorites}
                       offeringStatus={offeringStatus}
                       seasonTermType={isTourSampleRow ? course.termType : detailSeasonTermTypeByCourseId.get(course.id) ?? course.termType}
@@ -872,7 +873,8 @@ export function CoursesOverview() {
           courseId={openCourseId}
           listCourse={courses.find((course) => course.id === openCourseId) ?? null}
           isFavorite={isFavorite(openCourseId)}
-          favoriteDisabled={isLoadingFavorites || isSavingFavorites}
+          favoriteDisabled={isLoadingFavorites}
+          favoriteLoading={isFavoriteSaving(openCourseId)}
           showFavorite={canShowFavorites}
           onToggleFavorite={() => toggleFavorite(openCourseId)}
           onClose={() => navigate(catalogBasePath)}
diff --git a/frontend/src/features/favorites/FavoritesContext.ts b/frontend/src/features/favorites/FavoritesContext.ts
index ce818f8..9e2e192 100644
--- a/frontend/src/features/favorites/FavoritesContext.ts
+++ b/frontend/src/features/favorites/FavoritesContext.ts
@@ -6,6 +6,7 @@ export interface FavoritesContextValue {
   isSavingFavorites: boolean
   favoritesError: string | null
   isFavorite: (courseId: string) => boolean
+  isFavoriteSaving: (courseId: string) => boolean
   toggleFavorite: (courseId: string) => void
 }
 
diff --git a/frontend/src/features/favorites/components/FavoritesProvider.tsx b/frontend/src/features/favorites/components/FavoritesProvider.tsx
index e579749..b94cff4 100644
--- a/frontend/src/features/favorites/components/FavoritesProvider.tsx
+++ b/frontend/src/features/favorites/components/FavoritesProvider.tsx
@@ -5,6 +5,7 @@ import { useAuth } from '../../auth'
 import { addCourseToCurrentSemesterPlan } from '../../planner/utils/addCourseToCurrentSemesterPlan.ts'
 import { fetchFavoriteCourseIds, saveFavoriteCourseIds } from '../api'
 import { FavoritesContext } from '../FavoritesContext'
+import { toggleFavoriteId, updateSavingFavoriteIds } from '../utils/favoriteIds.ts'
 
 interface FavoritesProviderProps {
   children: ReactNode
@@ -25,8 +26,9 @@ export function FavoritesProvider({ children }: FavoritesProviderProps): JSX.Ele
   const userCacheKey = user?.username ?? 'anonymous'
   const [favoriteIds, setFavoriteIds] = useState<string[]>([])
   const [isLoadingFavorites, setIsLoadingFavorites] = useState<boolean>(false)
-  const [isSavingFavorites, setIsSavingFavorites] = useState<boolean>(false)
+  const [savingFavoriteCourseIds, setSavingFavoriteCourseIds] = useState<string[]>([])
   const [favoritesError, setFavoritesError] = useState<string | null>(null)
+  const isSavingFavorites = savingFavoriteCourseIds.length > 0
 
   useEffect(() => {
     let isActive = true
@@ -69,21 +71,23 @@ export function FavoritesProvider({ children }: FavoritesProviderProps): JSX.Ele
   }, [token])
 
   const isFavorite = (courseId: string): boolean => favoriteIds.includes(courseId)
+  const isFavoriteSaving = (courseId: string): boolean => savingFavoriteCourseIds.includes(courseId)
 
   const toggleFavorite = (courseId: string): void => {
     if (!token) {
       setFavoritesError('Sign in to save interested courses across devices.')
       return
     }
+    if (savingFavoriteCourseIds.includes(courseId)) {
+      return
+    }
 
     const previousFavoriteIds = favoriteIds
-    const nextFavoriteIds = favoriteIds.includes(courseId)
-      ? favoriteIds.filter((id) => id !== courseId)
-      : [...favoriteIds, courseId]
+    const nextFavoriteIds = toggleFavoriteId(favoriteIds, courseId)
 
     setFavoriteIds(nextFavoriteIds)
     setFavoritesError(null)
-    setIsSavingFavorites(true)
+    setSavingFavoriteCourseIds((current) => updateSavingFavoriteIds(current, courseId, true))
 
     const isAddingFavorite = nextFavoriteIds.length > previousFavoriteIds.length
 
@@ -103,7 +107,7 @@ export function FavoritesProvider({ children }: FavoritesProviderProps): JSX.Ele
         setFavoritesError(normalizeErrorMessage(error))
       })
       .finally(() => {
-        setIsSavingFavorites(false)
+        setSavingFavoriteCourseIds((current) => updateSavingFavoriteIds(current, courseId, false))
       })
   }
 
@@ -115,6 +119,7 @@ export function FavoritesProvider({ children }: FavoritesProviderProps): JSX.Ele
         isSavingFavorites,
         favoritesError,
         isFavorite,
+        isFavoriteSaving,
         toggleFavorite,
       }}
     >
diff --git a/frontend/src/features/favorites/utils/favoriteIds.ts b/frontend/src/features/favorites/utils/favoriteIds.ts
new file mode 100644
index 0000000..7c71616
--- /dev/null
+++ b/frontend/src/features/favorites/utils/favoriteIds.ts
@@ -0,0 +1,18 @@
+export function toggleFavoriteId(favoriteIds: string[], courseId: string): string[] {
+  return favoriteIds.includes(courseId)
+    ? favoriteIds.filter((id) => id !== courseId)
+    : [...favoriteIds, courseId]
+}
+
+export function updateSavingFavoriteIds(
+  savingFavoriteIds: string[],
+  courseId: string,
+  isSaving: boolean,
+): string[] {
+  if (isSaving) {
+    return savingFavoriteIds.includes(courseId)
+      ? savingFavoriteIds
+      : [...savingFavoriteIds, courseId]
+  }
+  return savingFavoriteIds.filter((id) => id !== courseId)
+}
diff --git a/frontend/src/features/planner/components/ManualSlotDialog.tsx b/frontend/src/features/planner/components/ManualSlotDialog.tsx
index 555100e..1b7d631 100644
--- a/frontend/src/features/planner/components/ManualSlotDialog.tsx
+++ b/frontend/src/features/planner/components/ManualSlotDialog.tsx
@@ -49,7 +49,7 @@ export function ManualSlotDialog({ courses, onClose, onAdd }: ManualSlotDialogPr
         role="dialog"
         aria-modal="true"
         aria-labelledby="manual-slot-title"
-        className="w-full max-w-md rounded-[12px] border border-border bg-surface p-5 shadow-xl"
+        className="w-full max-w-md min-w-0 overflow-hidden rounded-[12px] border border-border bg-surface p-5 shadow-xl"
       >
         <h2 id="manual-slot-title" className="text-[15px] font-semibold text-fg">
           Add manual time slot
@@ -58,13 +58,13 @@ export function ManualSlotDialog({ courses, onClose, onAdd }: ManualSlotDialogPr
           Place a course without catalog times — or a custom appointment — on the weekly grid.
         </p>
 
-        <div className="mt-4 grid gap-3">
-          <label className="grid gap-1">
+        <div className="mt-4 grid min-w-0 gap-3">
+          <label className="grid min-w-0 gap-1">
             <span className="text-[11px] font-semibold uppercase tracking-[0.08em] text-fg-muted">Course</span>
             <select
               value={courseId}
               onChange={(event) => setCourseId(event.target.value)}
-              className="rounded-md border border-border bg-surface px-2.5 py-2 text-[13px] text-fg outline-none focus:border-primary"
+              className="w-full min-w-0 max-w-full truncate rounded-md border border-border bg-surface px-2.5 py-2 text-[13px] text-fg outline-none focus:border-primary"
             >
               {sortedCourses.map((course) => (
                 <option key={course.id} value={course.id}>
@@ -74,7 +74,7 @@ export function ManualSlotDialog({ courses, onClose, onAdd }: ManualSlotDialogPr
             </select>
           </label>
 
-          <label className="grid gap-1">
+          <label className="grid min-w-0 gap-1">
             <span className="text-[11px] font-semibold uppercase tracking-[0.08em] text-fg-muted">Day</span>
             <div className="flex flex-wrap gap-1.5">
               {DAY_ORDER.map((weekday) => (
@@ -94,24 +94,24 @@ export function ManualSlotDialog({ courses, onClose, onAdd }: ManualSlotDialogPr
             </div>
           </label>
 
-          <label className="grid gap-1">
+          <label className="grid min-w-0 gap-1">
             <span className="text-[11px] font-semibold uppercase tracking-[0.08em] text-fg-muted">Time</span>
             <input
               type="text"
               value={time}
               onChange={(event) => setTime(event.target.value)}
               placeholder="10:00 - 12:00"
-              className="rounded-md border border-border bg-surface px-2.5 py-2 text-[13px] text-fg outline-none focus:border-primary"
+              className="w-full min-w-0 max-w-full rounded-md border border-border bg-surface px-2.5 py-2 text-[13px] text-fg outline-none focus:border-primary"
             />
           </label>
 
-          <label className="grid gap-1">
+          <label className="grid min-w-0 gap-1">
             <span className="text-[11px] font-semibold uppercase tracking-[0.08em] text-fg-muted">Room (optional)</span>
             <input
               type="text"
               value={room}
               onChange={(event) => setRoom(event.target.value)}
-              className="rounded-md border border-border bg-surface px-2.5 py-2 text-[13px] text-fg outline-none focus:border-primary"
+              className="w-full min-w-0 max-w-full rounded-md border border-border bg-surface px-2.5 py-2 text-[13px] text-fg outline-none focus:border-primary"
             />
           </label>
         </div>
diff --git a/frontend/src/features/planner/components/PlannerFavoritesPanel.tsx b/frontend/src/features/planner/components/PlannerFavoritesPanel.tsx
index 026ed5f..6c2d9d9 100644
--- a/frontend/src/features/planner/components/PlannerFavoritesPanel.tsx
+++ b/frontend/src/features/planner/components/PlannerFavoritesPanel.tsx
@@ -2,7 +2,6 @@ import { Link } from 'react-router-dom'
 import type { CompletedCourse, Course } from '../../courses'
 import { cleanCourseTitle, formatCourseTypeLabel } from '../../courses'
 import { buildCourseAreaTags } from '../../courses/utils/courseCardDisplay.ts'
-import { encodeCatalogDetailSegment } from '../../courses/utils/catalogDetailRoute.ts'
 import { ROUTES } from '../../routes'
 import type { RegulationRuleGroup } from '../../../shared/utils/regulation'
 import { AreaBadge } from '../../../shared/components/AreaBadge'
@@ -26,7 +25,9 @@ function CandidateCard({
   activeSemesterLabel,
   hiddenSlotIds,
   onAddCourse,
+  onOpenCourse,
   onToggleFavorite,
+  isFavoriteSaving,
   onSelectTutorialSlot,
 }: {
   candidate: PlannerFavoriteCandidate
@@ -34,7 +35,9 @@ function CandidateCard({
   activeSemesterLabel: string
   hiddenSlotIds: string[]
   onAddCourse: (courseId: string, areaCode: string | null) => void
+  onOpenCourse: (courseId: string) => void
   onToggleFavorite: (courseId: string) => void
+  isFavoriteSaving: (courseId: string) => boolean
   onSelectTutorialSlot: (courseId: string, selectedSlotId: string) => void
 }) {
   const { t } = useTranslation()
@@ -147,14 +150,19 @@ function CandidateCard({
         </div>
 
         <div className="flex shrink-0 items-start gap-1" onClick={(event) => event.stopPropagation()}>
-          <Link
-            to={`${ROUTES.catalog}/${encodeCatalogDetailSegment(course.id)}`}
+          <button
+            type="button"
+            onClick={() => onOpenCourse(course.id)}
             aria-label={t('planner.favorites.openCourseDetail')}
             className="flex items-center justify-center rounded-md p-1 text-fg-muted transition-colors hover:bg-surface-hover hover:text-primary"
           >
             <InfoIcon size={15} />
-          </Link>
-          <FavStar active onToggle={() => onToggleFavorite(course.id)} />
+          </button>
+          <FavStar
+            active
+            isLoading={isFavoriteSaving(course.id)}
+            onToggle={() => onToggleFavorite(course.id)}
+          />
         </div>
       </div>
     </div>
@@ -178,7 +186,9 @@ interface PlannerFavoritesPanelProps {
   catalogTo?: string
   onSetAssignment: (courseId: string, areaCode: string | null) => void
   onAddCourse: (courseId: string, areaCode: string | null) => void
+  onOpenCourse: (courseId: string) => void
   onToggleFavorite: (courseId: string) => void
+  isFavoriteSaving: (courseId: string) => boolean
   hiddenSlotIds: string[]
   onSelectTutorialSlot: (courseId: string, selectedSlotId: string) => void
 }
@@ -200,7 +210,9 @@ export function PlannerFavoritesPanel({
   catalogTo = ROUTES.catalog,
   onSetAssignment,
   onAddCourse,
+  onOpenCourse,
   onToggleFavorite,
+  isFavoriteSaving,
   hiddenSlotIds,
   onSelectTutorialSlot,
 }: PlannerFavoritesPanelProps) {
@@ -259,7 +271,9 @@ export function PlannerFavoritesPanel({
                   activeSemesterLabel={activeSemesterLabel}
                   hiddenSlotIds={hiddenSlotIds}
                   onAddCourse={onAddCourse}
+                  onOpenCourse={onOpenCourse}
                   onToggleFavorite={onToggleFavorite}
+                  isFavoriteSaving={isFavoriteSaving}
                   onSelectTutorialSlot={onSelectTutorialSlot}
                 />
               </div>
diff --git a/frontend/src/features/planner/components/SemesterPlanner.tsx b/frontend/src/features/planner/components/SemesterPlanner.tsx
index 0933714..bb4a434 100644
--- a/frontend/src/features/planner/components/SemesterPlanner.tsx
+++ b/frontend/src/features/planner/components/SemesterPlanner.tsx
@@ -68,7 +68,7 @@ export function SemesterPlanner({
   const { isAuthenticated, token, user } = useAuth()
   const { t } = useTranslation()
   const { isOpen: isOnboardingOpen, activeStepId } = useOnboarding()
-  const { favoriteIds, toggleFavorite } = useFavorites()
+  const { favoriteIds, isFavoriteSaving, toggleFavorite } = useFavorites()
   const {
     completedCourses,
     isLoadingCompletedCourses,
@@ -290,6 +290,13 @@ export function SemesterPlanner({
     }
   }
 
+  function handleOpenFavoriteCourse(courseId: string): void {
+    setOpenCourseId(courseId)
+    if (isSmallViewport) {
+      setIsAddDrawerOpen(false)
+    }
+  }
+
   function handleAddManualSlot(slot: ManualPlannerSlot): void {
     if (!plannedCourseIds.includes(slot.courseId)) {
       setPlannedCourseIds([...plannedCourseIds, slot.courseId])
@@ -452,7 +459,9 @@ export function SemesterPlanner({
       maxVisibleCandidates={isPlannerMobileInterestedTour ? 2 : undefined}
       onSetAssignment={setAssignment}
       onAddCourse={handleInterestedCourseAdd}
+      onOpenCourse={handleOpenFavoriteCourse}
       onToggleFavorite={toggleFavorite}
+      isFavoriteSaving={isFavoriteSaving}
       hiddenSlotIds={displayHiddenSlotIds}
       onSelectTutorialSlot={handleTutorialSlotSelect}
     />
diff --git a/frontend/src/index.css b/frontend/src/index.css
index 9314a78..c490d40 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -71,6 +71,88 @@ body {
   overflow: hidden;
 }
 
+@keyframes favorite-save-pop {
+  0% {
+    transform: scale(1);
+  }
+  45% {
+    transform: scale(1.16) translateY(-1px);
+  }
+  78% {
+    transform: scale(0.98);
+  }
+  100% {
+    transform: scale(1);
+  }
+}
+
+@keyframes favorite-save-burst {
+  0% {
+    opacity: 0.55;
+    transform: translate(-50%, -50%) scale(0.55);
+  }
+  100% {
+    opacity: 0;
+    transform: translate(-50%, -50%) scale(1.35);
+  }
+}
+
+@keyframes favorite-remove-pop {
+  0% {
+    transform: scale(1);
+  }
+  45% {
+    transform: scale(0.86);
+  }
+  100% {
+    transform: scale(1);
+  }
+}
+
+@keyframes favorite-remove-ring {
+  0% {
+    opacity: 0.35;
+    transform: translate(-50%, -50%) scale(0.98);
+  }
+  100% {
+    opacity: 0;
+    transform: translate(-50%, -50%) scale(0.72);
+  }
+}
+
+.favorite-add-pop {
+  animation: favorite-save-pop 320ms cubic-bezier(0.22, 1, 0.36, 1);
+}
+
+.favorite-remove-pop {
+  animation: favorite-remove-pop 260ms ease-out;
+}
+
+.favorite-save-burst {
+  animation: favorite-save-burst 380ms ease-out forwards;
+  border: 1px solid color-mix(in srgb, var(--color-primary) 34%, transparent);
+  border-radius: 9999px;
+  box-shadow: 0 0 0 0.12rem color-mix(in srgb, var(--color-primary) 8%, transparent);
+  height: 1.45rem;
+  left: 50%;
+  pointer-events: none;
+  position: absolute;
+  top: 50%;
+  width: 1.45rem;
+}
+
+.favorite-remove-ring {
+  animation: favorite-remove-ring 300ms ease-out forwards;
+  border: 1px solid color-mix(in srgb, var(--color-fg-muted) 32%, transparent);
+  border-radius: 9999px;
+  height: 1.25rem;
+  left: 50%;
+  pointer-events: none;
+  position: absolute;
+  top: 50%;
+  width: 1.25rem;
+}
+
 .studyplanner-tour-active [data-app-topbar] {
   pointer-events: none;
 }
diff --git a/frontend/src/shared/components/CourseCard.tsx b/frontend/src/shared/components/CourseCard.tsx
index 345d74e..993270c 100644
--- a/frontend/src/shared/components/CourseCard.tsx
+++ b/frontend/src/shared/components/CourseCard.tsx
@@ -24,6 +24,7 @@ interface CourseCardProps {
   isActive?: boolean
   isCompleted?: boolean
   favoriteDisabled?: boolean
+  favoriteLoading?: boolean
   showFavorite?: boolean
   offeringStatus?: OfferingStatus
   // Overrides the raw course.termType so callers can align season tags with
@@ -57,6 +58,7 @@ export function CourseCard({
   isActive = false,
   isCompleted = false,
   favoriteDisabled = false,
+  favoriteLoading = false,
   showFavorite = true,
   offeringStatus = 'confirmed',
   seasonTermType,
@@ -126,7 +128,12 @@ export function CourseCard({
               }}
               onKeyDown={(event) => event.stopPropagation()}
             >
-              <FavStar active={isFavorite} disabled={favoriteDisabled} onToggle={onToggleFavorite} />
+              <FavStar
+                active={isFavorite}
+                disabled={favoriteDisabled}
+                isLoading={favoriteLoading}
+                onToggle={onToggleFavorite}
+              />
             </div>
           ) : undefined
         }
diff --git a/frontend/src/shared/components/FavStar.tsx b/frontend/src/shared/components/FavStar.tsx
index 9606fe6..58d0396 100644
--- a/frontend/src/shared/components/FavStar.tsx
+++ b/frontend/src/shared/components/FavStar.tsx
@@ -4,12 +4,14 @@ import { BookmarkIcon } from './icons'
 interface FavStarProps {
   active: boolean
   disabled?: boolean
+  isLoading?: boolean
   onToggle: () => void
 }
 
-export function FavStar({ active, disabled = false, onToggle }: FavStarProps) {
+export function FavStar({ active, disabled = false, isLoading = false, onToggle }: FavStarProps) {
   const [isHovered, setIsHovered] = useState<boolean>(false)
-  const showFilled = isHovered ? !active : active
+  const [feedback, setFeedback] = useState<{ key: number; type: 'add' | 'remove' } | null>(null)
+  const showFilled = isLoading ? active : isHovered ? !active : active
 
   return (
     <button
@@ -17,18 +19,37 @@ export function FavStar({ active, disabled = false, onToggle }: FavStarProps) {
       onClick={(event) => {
         event.preventDefault()
         event.stopPropagation()
+        setFeedback((current) => ({
+          key: (current?.key ?? 0) + 1,
+          type: active ? 'remove' : 'add',
+        }))
         onToggle()
       }}
-      disabled={disabled}
-      aria-label={active ? 'Remove from interested' : 'Mark as interested'}
+      disabled={disabled || isLoading}
+      aria-label={isLoading ? 'Saving interested status' : active ? 'Remove from interested' : 'Mark as interested'}
       aria-pressed={active}
+      aria-busy={isLoading}
       onMouseEnter={() => setIsHovered(true)}
       onMouseLeave={() => setIsHovered(false)}
       onFocus={() => setIsHovered(true)}
       onBlur={() => setIsHovered(false)}
-      className="flex shrink-0 items-center justify-center p-1 text-primary transition-colors disabled:cursor-not-allowed disabled:opacity-50"
+      className={`relative flex shrink-0 items-center justify-center overflow-visible rounded-full p-1 text-primary transition-colors disabled:cursor-default disabled:opacity-60 ${
+        isLoading ? 'animate-pulse' : ''
+      }`}
     >
-      <BookmarkIcon filled={showFilled} />
+      {feedback ? (
+        <span
+          key={`favorite-feedback-${feedback.key}`}
+          aria-hidden
+          className={feedback.type === 'add' ? 'favorite-save-burst' : 'favorite-remove-ring'}
+        />
+      ) : null}
+      <span
+        key={`favorite-pop-${feedback?.key ?? 0}`}
+        className={feedback ? `favorite-${feedback.type}-pop` : undefined}
+      >
+        <BookmarkIcon filled={showFilled} />
+      </span>
     </button>
   )
 }
diff --git a/frontend/src/shared/components/catClasses.ts b/frontend/src/shared/components/catClasses.ts
index 8d74206..b28dc59 100644
--- a/frontend/src/shared/components/catClasses.ts
+++ b/frontend/src/shared/components/catClasses.ts
@@ -1,52 +1,52 @@
-import type { MasterCat } from '../../features/courses'
-
-/** Muted area tints — readable category hint without loud saturation. */
-export const CAT_BADGE_CLASSES: Record<MasterCat, string> = {
-  TECH: 'text-cat-tech/45 border-cat-tech/18 bg-cat-tech/5',
-  THEO: 'text-cat-theo/42 border-cat-theo/16 bg-cat-theo/4',
-  PRAK: 'text-cat-prak/45 border-cat-prak/18 bg-cat-prak/5',
-  INFO: 'text-cat-info/55 border-cat-info/25 bg-cat-info/10 dark:text-[#c4a8e8] dark:border-[#9b7cc4]/45 dark:bg-cat-info/20',
-  BASIS: 'text-cat-basis/42 border-cat-basis/16 bg-cat-basis/4',
-}
-
-/** Matches tag intensity — soft fills for credited ECTS in the auto-assign panel. */
-export const CAT_PROGRESS_CREDITED_CLASSES: Record<MasterCat, string> = {
-  TECH: 'bg-cat-tech/18',
-  THEO: 'bg-cat-theo/15',
-  PRAK: 'bg-cat-prak/18',
-  INFO: 'bg-cat-info/15',
-  BASIS: 'bg-cat-basis/15',
-}
-
-export const CAT_PROGRESS_DOT_CLASSES: Record<MasterCat, string> = {
-  TECH: 'bg-cat-tech/40',
-  THEO: 'bg-cat-theo/38',
-  PRAK: 'bg-cat-prak/40',
-  INFO: 'bg-cat-info/38',
-  BASIS: 'bg-cat-basis/38',
-}
-
-export function catProgressPlannedStyle(masterCat: MasterCat | null): {
-  backgroundColor: string
-  backgroundImage: string
-  opacity: number
-} {
-  const baseColor = masterCat === 'TECH'
-    ? 'var(--color-cat-tech)'
-    : masterCat === 'THEO'
-      ? 'var(--color-cat-theo)'
-      : masterCat === 'PRAK'
-        ? 'var(--color-cat-prak)'
-        : masterCat === 'INFO'
-          ? 'var(--color-cat-info)'
-          : masterCat === 'BASIS'
-            ? 'var(--color-cat-basis)'
-            : 'var(--color-border)'
-  return {
-    backgroundColor: baseColor,
-    backgroundImage:
-      'repeating-linear-gradient(135deg, transparent, transparent 3px, rgba(255,255,255,0.5) 3px, rgba(255,255,255,0.5) 6px)',
-    opacity: 0.22,
-  }
-}
-
\ No newline at end of file
+import type { MasterCat } from '../../features/courses'
+
+/** Muted area tints — readable category hint without loud saturation. */
+export const CAT_BADGE_CLASSES: Record<MasterCat, string> = {
+  TECH: 'border-[#B8D9E6] bg-[#EEF8FB] text-[#315F73] dark:border-[#4A6470] dark:bg-[#253239] dark:text-[#A8C7D3]',
+  THEO: 'border-[#EBC3D6] bg-[#FCF0F5] text-[#8A4968] dark:border-[#714B5E] dark:bg-[#382932] dark:text-[#D8A9C0]',
+  PRAK: 'border-[#B7E1DA] bg-[#EFF9F6] text-[#3D6E66] dark:border-[#486B65] dark:bg-[#263633] dark:text-[#A8D2CA]',
+  INFO: 'border-[#D3C4E6] bg-[#F6F1FB] text-[#654F83] dark:border-[#5E526F] dark:bg-[#302A39] dark:text-[#C4B4D9]',
+  BASIS: 'border-[#E8C7C4] bg-[#FCF1EF] text-[#8A504B] dark:border-[#704F4B] dark:bg-[#392B29] dark:text-[#D9ABA6]',
+}
+
+/** Matches tag intensity — soft fills for credited ECTS in the auto-assign panel. */
+export const CAT_PROGRESS_CREDITED_CLASSES: Record<MasterCat, string> = {
+  TECH: 'bg-cat-tech/18',
+  THEO: 'bg-cat-theo/15',
+  PRAK: 'bg-cat-prak/18',
+  INFO: 'bg-cat-info/15',
+  BASIS: 'bg-cat-basis/15',
+}
+
+export const CAT_PROGRESS_DOT_CLASSES: Record<MasterCat, string> = {
+  TECH: 'bg-cat-tech/40',
+  THEO: 'bg-cat-theo/38',
+  PRAK: 'bg-cat-prak/40',
+  INFO: 'bg-cat-info/38',
+  BASIS: 'bg-cat-basis/38',
+}
+
+export function catProgressPlannedStyle(masterCat: MasterCat | null): {
+  backgroundColor: string
+  backgroundImage: string
+  opacity: number
+} {
+  const baseColor = masterCat === 'TECH'
+    ? 'var(--color-cat-tech)'
+    : masterCat === 'THEO'
+      ? 'var(--color-cat-theo)'
+      : masterCat === 'PRAK'
+        ? 'var(--color-cat-prak)'
+        : masterCat === 'INFO'
+          ? 'var(--color-cat-info)'
+          : masterCat === 'BASIS'
+            ? 'var(--color-cat-basis)'
+            : 'var(--color-border)'
+  return {
+    backgroundColor: baseColor,
+    backgroundImage:
+      'repeating-linear-gradient(135deg, transparent, transparent 3px, rgba(255,255,255,0.5) 3px, rgba(255,255,255,0.5) 6px)',
+    opacity: 0.22,
+  }
+}
+
diff --git a/frontend/tests/favorites/favoriteIds.test.ts b/frontend/tests/favorites/favoriteIds.test.ts
new file mode 100644
index 0000000..9a664da
--- /dev/null
+++ b/frontend/tests/favorites/favoriteIds.test.ts
@@ -0,0 +1,23 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import { toggleFavoriteId, updateSavingFavoriteIds } from '../../src/features/favorites/utils/favoriteIds.ts'
+
+test('toggleFavoriteId adds and removes one course without mutating the input', () => {
+  const favoriteIds = ['course-a']
+
+  const withAddedCourse = toggleFavoriteId(favoriteIds, 'course-b')
+  const withRemovedCourse = toggleFavoriteId(favoriteIds, 'course-a')
+
+  assert.deepEqual(withAddedCourse, ['course-a', 'course-b'])
+  assert.deepEqual(withRemovedCourse, [])
+  assert.deepEqual(favoriteIds, ['course-a'])
+})
+
+test('updateSavingFavoriteIds tracks one saving entry per course', () => {
+  const savingFavoriteIds = updateSavingFavoriteIds(['course-a'], 'course-a', true)
+
+  assert.deepEqual(savingFavoriteIds, ['course-a'])
+  assert.deepEqual(updateSavingFavoriteIds(savingFavoriteIds, 'course-b', true), ['course-a', 'course-b'])
+  assert.deepEqual(updateSavingFavoriteIds(savingFavoriteIds, 'course-a', false), [])
+})