diff --git a/src/api/artist-notes/types.ts b/src/api/artist-notes/types.ts
index 5ada6a05..263b1389 100644
--- a/src/api/artist-notes/types.ts
+++ b/src/api/artist-notes/types.ts
@@ -7,8 +7,8 @@ export type SetNote = {
   note_content: string;
   created_at: string;
   updated_at: string;
-  author_username?: string;
-  author_email?: string;
+  author_username?: string | undefined;
+  author_email?: string | undefined;
 };
 
 // Query key factory
diff --git a/src/api/auth/useSignInWithOtpMutation.ts b/src/api/auth/useSignInWithOtpMutation.ts
index 46346246..85372dc4 100644
--- a/src/api/auth/useSignInWithOtpMutation.ts
+++ b/src/api/auth/useSignInWithOtpMutation.ts
@@ -4,7 +4,7 @@ import { useToast } from "@/components/ui/use-toast";
 
 interface SignInWithOtpParams {
   email: string;
-  inviteToken?: string;
+  inviteToken?: string | undefined;
 }
 
 export function useSignInWithOtpMutation() {
diff --git a/src/api/auth/useUpdateProfile.ts b/src/api/auth/useUpdateProfile.ts
index ea7b8f57..4acbe373 100644
--- a/src/api/auth/useUpdateProfile.ts
+++ b/src/api/auth/useUpdateProfile.ts
@@ -1,8 +1,12 @@
 import { useMutation, useQueryClient } from "@tanstack/react-query";
 import { useToast } from "@/hooks/use-toast";
 import { supabase } from "@/integrations/supabase/client";
+import type { Database } from "@/integrations/supabase/types";
 import { profileKeys } from "./types";
 
+type ValidateProfileUpdateArgs =
+  Database["public"]["Functions"]["validate_profile_update"]["Args"];
+
 // Mutation function
 async function updateProfile(variables: {
   userId: string;
@@ -11,12 +15,14 @@ async function updateProfile(variables: {
   const { userId, updates } = variables;
 
   // Validate username uniqueness before attempting update
+  const trimmedUsername = updates.username?.trim();
+  const rpcArgs: ValidateProfileUpdateArgs = { user_id: userId };
+  if (trimmedUsername !== undefined) {
+    rpcArgs.new_username = trimmedUsername;
+  }
   const { data: validationResult, error: validationError } = await supabase.rpc(
     "validate_profile_update",
-    {
-      user_id: userId,
-      new_username: updates.username?.trim(),
-    },
+    rpcArgs,
   );
 
   if (validationError) {
diff --git a/src/api/editions/types.ts b/src/api/editions/types.ts
index 29341d98..fdd18269 100644
--- a/src/api/editions/types.ts
+++ b/src/api/editions/types.ts
@@ -8,7 +8,7 @@ export type FestivalEdition =
 export const editionsKeys = {
   root: (festivalId: string) =>
     [...festivalsKeys.root(), festivalId, "editions"] as const,
-  all: (festivalId: string, { all }: { all?: boolean } = {}) =>
+  all: (festivalId: string, { all }: { all?: boolean | undefined } = {}) =>
     [...editionsKeys.root(festivalId), { all }] as const,
   item: ({
     editionId,
diff --git a/src/api/editions/useFestivalEditionsForFestival.ts b/src/api/editions/useFestivalEditionsForFestival.ts
index 9c9f93dc..7f7b04e3 100644
--- a/src/api/editions/useFestivalEditionsForFestival.ts
+++ b/src/api/editions/useFestivalEditionsForFestival.ts
@@ -4,7 +4,7 @@ import { FestivalEdition, editionsKeys } from "./types";
 
 export async function fetchFestivalEditions(
   festivalId: string,
-  { all }: { all?: boolean } = {},
+  { all }: { all?: boolean | undefined } = {},
 ): Promise<FestivalEdition[]> {
   let query = supabase
     .from("festival_editions")
@@ -31,7 +31,7 @@ export async function fetchFestivalEditions(
 
 export function editionsForFestivalQuery(
   festivalId: string,
-  { all }: { all?: boolean } = {},
+  { all }: { all?: boolean | undefined } = {},
 ) {
   return queryOptions({
     queryKey: editionsKeys.all(festivalId, { all }),
@@ -41,7 +41,7 @@ export function editionsForFestivalQuery(
 
 export function useFestivalEditionsForFestivalQuery(
   festivalId: string | undefined,
-  { all }: { all?: boolean } = {},
+  { all }: { all?: boolean | undefined } = {},
 ) {
   return useQuery({
     ...editionsForFestivalQuery(festivalId!, { all }),
diff --git a/src/api/festivals/types.ts b/src/api/festivals/types.ts
index 7d096669..47e129b0 100644
--- a/src/api/festivals/types.ts
+++ b/src/api/festivals/types.ts
@@ -5,7 +5,7 @@ export type Festival = Database["public"]["Tables"]["festivals"]["Row"];
 // Query key factory for festivals
 export const festivalsKeys = {
   root: () => ["festivals"] as const,
-  all: ({ all }: { all?: boolean } = {}) =>
+  all: ({ all }: { all?: boolean | undefined } = {}) =>
     [...festivalsKeys.root(), { all }] as const,
   item: (festivalId: string) => [...festivalsKeys.root(), festivalId] as const,
   bySlug: (festivalSlug: string) =>
diff --git a/src/api/festivals/useFestivals.ts b/src/api/festivals/useFestivals.ts
index e6d7e6af..ebdf05f9 100644
--- a/src/api/festivals/useFestivals.ts
+++ b/src/api/festivals/useFestivals.ts
@@ -6,7 +6,9 @@ import { isTimeoutError, withTimeout } from "@/lib/timeout";
 async function fetchFestivals({
   all,
   signal,
-}: { all?: boolean; signal?: AbortSignal } = {}): Promise<Festival[]> {
+}: { all?: boolean | undefined; signal?: AbortSignal } = {}): Promise<
+  Festival[]
+> {
   let query = supabase
     .from("festivals")
     .select("*")
@@ -32,7 +34,7 @@ async function fetchFestivals({
 export function festivalsQuery({
   all,
   timeoutMs = 10000,
-}: { all?: boolean; timeoutMs?: number } = {}) {
+}: { all?: boolean | undefined; timeoutMs?: number } = {}) {
   return queryOptions({
     queryKey: festivalsKeys.all({ all }),
     queryFn: ({ signal }) =>
diff --git a/src/api/groups/types.ts b/src/api/groups/types.ts
index 1f25bf67..98268a93 100644
--- a/src/api/groups/types.ts
+++ b/src/api/groups/types.ts
@@ -11,8 +11,8 @@ export type Group = Database["public"]["Tables"]["groups"]["Row"] & {
 export type GroupMember =
   Database["public"]["Tables"]["group_members"]["Row"] & {
     profiles?: {
-      username?: string;
-      email?: string;
+      username?: string | undefined;
+      email?: string | undefined;
     };
   };
 
diff --git a/src/api/groups/useCreateGroup.ts b/src/api/groups/useCreateGroup.ts
index 86bade55..2a5f2e9f 100644
--- a/src/api/groups/useCreateGroup.ts
+++ b/src/api/groups/useCreateGroup.ts
@@ -1,25 +1,32 @@
 import { useMutation, useQueryClient } from "@tanstack/react-query";
 import { useToast } from "@/hooks/use-toast";
 import { supabase } from "@/integrations/supabase/client";
+import type { Database } from "@/integrations/supabase/types";
 import { groupsKeys } from "./types";
 import { generateSlug } from "@/lib/slug";
 
+type GroupInsert = Database["public"]["Tables"]["groups"]["Insert"];
+
 // Mutation function
 async function createGroup(variables: {
   name: string;
-  description?: string;
+  description?: string | undefined;
   userId: string;
 }) {
   const { name, description, userId } = variables;
 
+  const groupData: GroupInsert = {
+    name,
+    slug: generateSlug(name),
+    created_by: userId,
+  };
+  if (description !== undefined) {
+    groupData.description = description;
+  }
+
   const { data: group, error } = await supabase
     .from("groups")
-    .insert({
-      name,
-      slug: generateSlug(name),
-      description,
-      created_by: userId,
-    })
+    .insert(groupData)
     .select()
     .single();
 
diff --git a/src/api/invites/useGenerateInviteMutation.ts b/src/api/invites/useGenerateInviteMutation.ts
index 77813585..ce0cba25 100644
--- a/src/api/invites/useGenerateInviteMutation.ts
+++ b/src/api/invites/useGenerateInviteMutation.ts
@@ -1,8 +1,12 @@
 import { useMutation, useQueryClient } from "@tanstack/react-query";
 import { useToast } from "@/components/ui/use-toast";
 import { supabase } from "@/integrations/supabase/client";
+import type { Database } from "@/integrations/supabase/types";
 import { inviteKeys } from "./types";
 
+type GroupInviteInsert =
+  Database["public"]["Tables"]["group_invites"]["Insert"];
+
 async function generateInviteLink(
   groupId: string,
   options?: {
@@ -21,13 +25,17 @@ async function generateInviteLink(
     throw new Error("Authentication required");
   }
 
-  const inviteData = {
+  const inviteData: GroupInviteInsert = {
     group_id: groupId,
     invite_token: token,
     created_by: user.id,
-    expires_at: options?.expiresAt?.toISOString(),
-    max_uses: options?.maxUses,
   };
+  if (options?.expiresAt !== undefined) {
+    inviteData.expires_at = options.expiresAt.toISOString();
+  }
+  if (options?.maxUses !== undefined) {
+    inviteData.max_uses = options.maxUses;
+  }
 
   const { error } = await supabase.from("group_invites").insert(inviteData);
 
diff --git a/src/api/ratings/useRateSet.ts b/src/api/ratings/useRateSet.ts
index 953dad8b..a34170fd 100644
--- a/src/api/ratings/useRateSet.ts
+++ b/src/api/ratings/useRateSet.ts
@@ -12,7 +12,7 @@ async function rateSet({
   setId: string;
   rating: number;
   userId: string;
-  existingRating?: number;
+  existingRating?: number | undefined;
 }) {
   if (existingRating === rating) {
     const { error } = await supabase
diff --git a/src/api/sets/useUpdateSet.ts b/src/api/sets/useUpdateSet.ts
index 952ab571..e2162a57 100644
--- a/src/api/sets/useUpdateSet.ts
+++ b/src/api/sets/useUpdateSet.ts
@@ -24,18 +24,29 @@ export type UpdateSetInput = Partial<
 async function updateSet(variables: { id: string; updates: UpdateSetInput }) {
   const { id, updates } = variables;
 
-  const updateData: SetUpdate = {
-    name: updates.name,
-    description: updates.description,
-    festival_edition_id: updates.festival_edition_id,
-    stage_id: updates.stage_id,
-    time_start: updates.time_start,
-    time_end: updates.time_end,
-    archived: updates.archived,
-  };
+  const updateData: SetUpdate = {};
   if (updates.name !== undefined) {
+    updateData.name = updates.name;
     updateData.slug = generateSlug(updates.name);
   }
+  if (updates.description !== undefined) {
+    updateData.description = updates.description;
+  }
+  if (updates.festival_edition_id !== undefined) {
+    updateData.festival_edition_id = updates.festival_edition_id;
+  }
+  if (updates.stage_id !== undefined) {
+    updateData.stage_id = updates.stage_id;
+  }
+  if (updates.time_start !== undefined) {
+    updateData.time_start = updates.time_start;
+  }
+  if (updates.time_end !== undefined) {
+    updateData.time_end = updates.time_end;
+  }
+  if (updates.archived !== undefined) {
+    updateData.archived = updates.archived;
+  }
 
   const { data, error } = await supabase
     .from("sets")
diff --git a/src/api/voting/useVoteMutation.ts b/src/api/voting/useVoteMutation.ts
index 8ba4614c..7780bc4a 100644
--- a/src/api/voting/useVoteMutation.ts
+++ b/src/api/voting/useVoteMutation.ts
@@ -8,7 +8,7 @@ export async function vote(variables: {
   setId: string;
   voteType: number;
   userId: string;
-  existingVote?: number;
+  existingVote?: number | undefined;
 }) {
   const { setId, voteType, userId, existingVote } = variables;
 
diff --git a/src/components/Admin/ScheduleImport/CsvUploadStep.tsx b/src/components/Admin/ScheduleImport/CsvUploadStep.tsx
index 5c300a3c..4e1150f2 100644
--- a/src/components/Admin/ScheduleImport/CsvUploadStep.tsx
+++ b/src/components/Admin/ScheduleImport/CsvUploadStep.tsx
@@ -10,7 +10,7 @@ import { CsvDropZone } from "./CsvDropZone";
 
 type Props = {
   festivalEditionId: string;
-  defaultTimezone?: string;
+  defaultTimezone?: string | undefined;
   onDiffReady: (diff: DiffResult, timezone: string) => void;
 };
 
diff --git a/src/components/ArtistImageLoader.tsx b/src/components/ArtistImageLoader.tsx
index 57fa5437..f692cade 100644
--- a/src/components/ArtistImageLoader.tsx
+++ b/src/components/ArtistImageLoader.tsx
@@ -2,7 +2,7 @@ import { useState } from "react";
 import { Music } from "lucide-react";
 
 interface ArtistImageLoaderProps {
-  src?: string | null;
+  src?: string | null | undefined;
   alt: string;
   className?: string;
 }
diff --git a/src/components/AuthDialog/AuthDialog.tsx b/src/components/AuthDialog/AuthDialog.tsx
index 38681419..bc9819de 100644
--- a/src/components/AuthDialog/AuthDialog.tsx
+++ b/src/components/AuthDialog/AuthDialog.tsx
@@ -15,8 +15,8 @@ interface AuthDialogProps {
   open: boolean;
   onOpenChange: (open: boolean) => void;
   onSuccess: () => void;
-  inviteToken?: string;
-  groupName?: string;
+  inviteToken?: string | undefined;
+  groupName?: string | undefined;
 }
 
 export function AuthDialog({
diff --git a/src/components/AuthDialog/EmailStep.tsx b/src/components/AuthDialog/EmailStep.tsx
index 7838140e..8c7b5fa3 100644
--- a/src/components/AuthDialog/EmailStep.tsx
+++ b/src/components/AuthDialog/EmailStep.tsx
@@ -5,7 +5,7 @@ import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 
 interface EmailStepProps {
-  inviteToken?: string;
+  inviteToken?: string | undefined;
   onSuccess: (email: string) => void;
 }
 
diff --git a/src/components/AuthDialog/OtpStep.tsx b/src/components/AuthDialog/OtpStep.tsx
index 6130597a..d0385ea1 100644
--- a/src/components/AuthDialog/OtpStep.tsx
+++ b/src/components/AuthDialog/OtpStep.tsx
@@ -11,7 +11,7 @@ import {
 
 interface OtpStepProps {
   email: string;
-  inviteToken?: string;
+  inviteToken?: string | undefined;
   onSuccess: () => void;
 }
 
diff --git a/src/components/ErrorBoundary.tsx b/src/components/ErrorBoundary.tsx
index 4740e0f0..04128c46 100644
--- a/src/components/ErrorBoundary.tsx
+++ b/src/components/ErrorBoundary.tsx
@@ -2,12 +2,15 @@ import React from "react";
 
 interface ErrorBoundaryState {
   hasError: boolean;
-  error?: Error;
+  error?: Error | undefined;
 }
 
 interface ErrorBoundaryProps {
   children: React.ReactNode;
-  fallback?: React.ComponentType<{ error?: Error; retry: () => void }>;
+  fallback?: React.ComponentType<{
+    error?: Error | undefined;
+    retry: () => void;
+  }>;
 }
 
 export class ErrorBoundary extends React.Component<
@@ -46,7 +49,7 @@ function DefaultErrorFallback({
   error,
   retry,
 }: {
-  error?: Error;
+  error?: Error | undefined;
   retry: () => void;
 }) {
   return (
diff --git a/src/components/StageBadge.tsx b/src/components/StageBadge.tsx
index 726d9eb8..1f3993c1 100644
--- a/src/components/StageBadge.tsx
+++ b/src/components/StageBadge.tsx
@@ -2,9 +2,9 @@ import { MapPin } from "lucide-react";
 
 interface StageBadgeProps {
   stageName: string;
-  stageColor?: string;
-  size?: "sm" | "md";
-  showIcon?: boolean;
+  stageColor?: string | undefined;
+  size?: "sm" | "md" | undefined;
+  showIcon?: boolean | undefined;
 }
 
 export function StageBadge({
diff --git a/src/components/filters/FilterToggle.tsx b/src/components/filters/FilterToggle.tsx
index 352c144f..0fe5c7f5 100644
--- a/src/components/filters/FilterToggle.tsx
+++ b/src/components/filters/FilterToggle.tsx
@@ -8,7 +8,7 @@ interface FilterToggleProps {
   hasActiveFilters: boolean;
   activeFilterCount: number;
   label?: string;
-  onClearFilters?: () => void;
+  onClearFilters?: (() => void) | undefined;
 }
 
 export function FilterToggle({
diff --git a/src/components/layout/AppHeader/FestivalIndicator.tsx b/src/components/layout/AppHeader/FestivalIndicator.tsx
index 7039c799..0d64e412 100644
--- a/src/components/layout/AppHeader/FestivalIndicator.tsx
+++ b/src/components/layout/AppHeader/FestivalIndicator.tsx
@@ -1,7 +1,7 @@
 interface FestivalIndicatorProps {
   isTitleVisible?: boolean;
-  logoUrl?: string | null;
-  festivalName?: string;
+  logoUrl?: string | null | undefined;
+  festivalName?: string | undefined;
 }
 
 export function FestivalIndicator({
diff --git a/src/components/layout/AppHeader/TitleSection.tsx b/src/components/layout/AppHeader/TitleSection.tsx
index 2ac70738..83cc44c4 100644
--- a/src/components/layout/AppHeader/TitleSection.tsx
+++ b/src/components/layout/AppHeader/TitleSection.tsx
@@ -3,7 +3,7 @@ import { Music, Heart } from "lucide-react";
 
 interface TitleSectionProps {
   title: string;
-  logoUrl?: string | null;
+  logoUrl?: string | null | undefined;
   onLogoRefChange?: (ref: HTMLElement | null) => void;
 }
 
diff --git a/src/components/layout/AppHeader/UserAvatar.tsx b/src/components/layout/AppHeader/UserAvatar.tsx
index ac1538de..0480b7e6 100644
--- a/src/components/layout/AppHeader/UserAvatar.tsx
+++ b/src/components/layout/AppHeader/UserAvatar.tsx
@@ -1,8 +1,8 @@
 import { Avatar, AvatarFallback, AvatarImage } from "@/components/ui/avatar";
 
 interface UserAvatarProps {
-  username?: string | null;
-  email?: string | null;
+  username?: string | null | undefined;
+  email?: string | null | undefined;
   size?: "sm" | "md" | "lg";
 }
 
diff --git a/src/components/layout/AppHeader/UserMenu.tsx b/src/components/layout/AppHeader/UserMenu.tsx
index a00db88d..f3993a66 100644
--- a/src/components/layout/AppHeader/UserMenu.tsx
+++ b/src/components/layout/AppHeader/UserMenu.tsx
@@ -18,7 +18,7 @@ type Profile = Database["public"]["Tables"]["profiles"]["Row"];
 
 interface UserMenuProps {
   user: User;
-  profile?: Profile;
+  profile?: Profile | undefined;
   onSignOut: () => void;
   isMobile?: boolean;
 }
diff --git a/src/components/ui/context-menu.tsx b/src/components/ui/context-menu.tsx
index 35559580..61a8a2f3 100644
--- a/src/components/ui/context-menu.tsx
+++ b/src/components/ui/context-menu.tsx
@@ -90,14 +90,13 @@ ContextMenuItem.displayName = ContextMenuPrimitive.Item.displayName;
 const ContextMenuCheckboxItem = React.forwardRef<
   React.ElementRef<typeof ContextMenuPrimitive.CheckboxItem>,
   React.ComponentPropsWithoutRef<typeof ContextMenuPrimitive.CheckboxItem>
->(({ className, children, checked, ...props }, ref) => (
+>(({ className, children, ...props }, ref) => (
   <ContextMenuPrimitive.CheckboxItem
     ref={ref}
     className={cn(
       "relative flex cursor-default select-none items-center rounded-sm py-1.5 pl-8 pr-2 text-sm outline-none focus:bg-accent focus:text-accent-foreground data-[disabled]:pointer-events-none data-[disabled]:opacity-50",
       className,
     )}
-    checked={checked}
     {...props}
   >
     <span className="absolute left-2 flex h-3.5 w-3.5 items-center justify-center">
diff --git a/src/components/ui/dropdown-menu.tsx b/src/components/ui/dropdown-menu.tsx
index 3a7794a2..e1c51542 100644
--- a/src/components/ui/dropdown-menu.tsx
+++ b/src/components/ui/dropdown-menu.tsx
@@ -93,14 +93,13 @@ DropdownMenuItem.displayName = DropdownMenuPrimitive.Item.displayName;
 const DropdownMenuCheckboxItem = React.forwardRef<
   React.ElementRef<typeof DropdownMenuPrimitive.CheckboxItem>,
   React.ComponentPropsWithoutRef<typeof DropdownMenuPrimitive.CheckboxItem>
->(({ className, children, checked, ...props }, ref) => (
+>(({ className, children, ...props }, ref) => (
   <DropdownMenuPrimitive.CheckboxItem
     ref={ref}
     className={cn(
       "relative flex cursor-default select-none items-center rounded-sm py-1.5 pl-8 pr-2 text-sm outline-none transition-colors focus:bg-accent focus:text-accent-foreground data-[disabled]:pointer-events-none data-[disabled]:opacity-50",
       className,
     )}
-    checked={checked}
     {...props}
   >
     <span className="absolute left-2 flex h-3.5 w-3.5 items-center justify-center">
diff --git a/src/components/ui/menubar.tsx b/src/components/ui/menubar.tsx
index f97f0c41..7c2ea6e6 100644
--- a/src/components/ui/menubar.tsx
+++ b/src/components/ui/menubar.tsx
@@ -126,14 +126,13 @@ MenubarItem.displayName = MenubarPrimitive.Item.displayName;
 const MenubarCheckboxItem = React.forwardRef<
   React.ElementRef<typeof MenubarPrimitive.CheckboxItem>,
   React.ComponentPropsWithoutRef<typeof MenubarPrimitive.CheckboxItem>
->(({ className, children, checked, ...props }, ref) => (
+>(({ className, children, ...props }, ref) => (
   <MenubarPrimitive.CheckboxItem
     ref={ref}
     className={cn(
       "relative flex cursor-default select-none items-center rounded-sm py-1.5 pl-8 pr-2 text-sm outline-none focus:bg-accent focus:text-accent-foreground data-[disabled]:pointer-events-none data-[disabled]:opacity-50",
       className,
     )}
-    checked={checked}
     {...props}
   >
     <span className="absolute left-2 flex h-3.5 w-3.5 items-center justify-center">
diff --git a/src/components/ui/multi-select.tsx b/src/components/ui/multi-select.tsx
index 12c4fecc..6f8d7fff 100644
--- a/src/components/ui/multi-select.tsx
+++ b/src/components/ui/multi-select.tsx
@@ -29,7 +29,7 @@ interface MultiSelectProps {
   searchPlaceholder?: string;
   emptyMessage?: string;
   disabled?: boolean;
-  className?: string;
+  className?: string | undefined;
 }
 
 export function MultiSelect({
diff --git a/src/components/ui/select.tsx b/src/components/ui/select.tsx
index 9b769ec5..98cc3cd8 100644
--- a/src/components/ui/select.tsx
+++ b/src/components/ui/select.tsx
@@ -4,7 +4,21 @@ import { Check, ChevronDown, ChevronUp } from "lucide-react";
 
 import { cn } from "@/lib/utils";
 
-const Select = SelectPrimitive.Root;
+type SelectProps = Omit<
+  React.ComponentProps<typeof SelectPrimitive.Root>,
+  "value"
+> & {
+  value?: string | undefined;
+};
+
+function Select({ value, ...props }: SelectProps) {
+  return (
+    <SelectPrimitive.Root
+      {...(value !== undefined ? { value } : {})}
+      {...props}
+    />
+  );
+}
 
 const SelectGroup = SelectPrimitive.Group;
 
diff --git a/src/components/ui/sonner.tsx b/src/components/ui/sonner.tsx
index 3bdb4184..b38250ea 100644
--- a/src/components/ui/sonner.tsx
+++ b/src/components/ui/sonner.tsx
@@ -8,7 +8,7 @@ function Toaster({ ...props }: ToasterProps) {
 
   return (
     <Sonner
-      theme={theme as ToasterProps["theme"]}
+      theme={theme as "light" | "dark" | "system"}
       className="toaster group"
       toastOptions={{
         classNames: {
diff --git a/src/components/ui/toggle-group.tsx b/src/components/ui/toggle-group.tsx
index 35ba3feb..37759a1b 100644
--- a/src/components/ui/toggle-group.tsx
+++ b/src/components/ui/toggle-group.tsx
@@ -12,21 +12,42 @@ const ToggleGroupContext = React.createContext<
   variant: "default",
 });
 
+type ToggleGroupProps = (
+  | (Omit<ToggleGroupPrimitive.ToggleGroupSingleProps, "value"> & {
+      value?: string | undefined;
+    })
+  | (Omit<ToggleGroupPrimitive.ToggleGroupMultipleProps, "value"> & {
+      value?: string[] | undefined;
+    })
+) &
+  VariantProps<typeof toggleVariants>;
+
 const ToggleGroup = React.forwardRef<
   React.ElementRef<typeof ToggleGroupPrimitive.Root>,
-  React.ComponentPropsWithoutRef<typeof ToggleGroupPrimitive.Root> &
-    VariantProps<typeof toggleVariants>
->(({ className, variant, size, children, ...props }, ref) => (
-  <ToggleGroupPrimitive.Root
-    ref={ref}
-    className={cn("flex items-center justify-center gap-1", className)}
-    {...props}
-  >
-    <ToggleGroupContext.Provider value={{ variant, size }}>
-      {children}
-    </ToggleGroupContext.Provider>
-  </ToggleGroupPrimitive.Root>
-));
+  ToggleGroupProps
+>(({ className, variant, size, children, value, ...props }, ref) => {
+  // TS can't carry the exactOptionalPropertyTypes-safe shape through a
+  // spread of a destructured union's rest; the cast just restates what
+  // ToggleGroupProps above already guarantees.
+  const rootProps = {
+    ...props,
+    ...(value !== undefined ? { value } : {}),
+  } as
+    | ToggleGroupPrimitive.ToggleGroupSingleProps
+    | ToggleGroupPrimitive.ToggleGroupMultipleProps;
+
+  return (
+    <ToggleGroupPrimitive.Root
+      ref={ref}
+      className={cn("flex items-center justify-center gap-1", className)}
+      {...rootProps}
+    >
+      <ToggleGroupContext.Provider value={{ variant, size }}>
+        {children}
+      </ToggleGroupContext.Provider>
+    </ToggleGroupPrimitive.Root>
+  );
+});
 
 ToggleGroup.displayName = ToggleGroupPrimitive.Root.displayName;
 
diff --git a/src/contexts/FestivalEditionContext.tsx b/src/contexts/FestivalEditionContext.tsx
index 6d493858..697d36cb 100644
--- a/src/contexts/FestivalEditionContext.tsx
+++ b/src/contexts/FestivalEditionContext.tsx
@@ -24,7 +24,7 @@ export function useFestivalEdition() {
 
 interface FestivalEditionProviderProps {
   festival: Festival;
-  editionSlug?: string;
+  editionSlug?: string | undefined;
 }
 
 export function FestivalEditionProvider({
diff --git a/src/hooks/use-toast.ts b/src/hooks/use-toast.ts
index 21a5c5ec..f4e5b0ab 100644
--- a/src/hooks/use-toast.ts
+++ b/src/hooks/use-toast.ts
@@ -39,11 +39,11 @@ type Action =
     }
   | {
       type: ActionType["DISMISS_TOAST"];
-      toastId?: ToasterToast["id"];
+      toastId?: ToasterToast["id"] | undefined;
     }
   | {
       type: ActionType["REMOVE_TOAST"];
-      toastId?: ToasterToast["id"];
+      toastId?: ToasterToast["id"] | undefined;
     };
 
 interface State {
diff --git a/src/hooks/useScheduleData.ts b/src/hooks/useScheduleData.ts
index 81028817..b3630315 100644
--- a/src/hooks/useScheduleData.ts
+++ b/src/hooks/useScheduleData.ts
@@ -26,8 +26,8 @@ export interface ScheduleArtist {
   name: string;
   slug?: string;
   stageId?: string;
-  startTime?: Date;
-  endTime?: Date;
+  startTime?: Date | undefined;
+  endTime?: Date | undefined;
   votes?: { vote_type: number; user_id: string }[];
   formattedTimeRange?: string | null;
   conflictsWith?: string[];
diff --git a/src/lib/scheduleFilter.ts b/src/lib/scheduleFilter.ts
index c92f48ac..50976b22 100644
--- a/src/lib/scheduleFilter.ts
+++ b/src/lib/scheduleFilter.ts
@@ -19,9 +19,9 @@ export interface ScheduleFilterCriteria {
   voteTypes?: VoteType[];
   voteScope?: VoteScope;
   /** `undefined` (logged out) makes vote filtering inert, not exclusionary. */
-  currentUserId?: string;
+  currentUserId?: string | undefined;
   /** `undefined` (group members still loading, or no group) makes group-scope vote filtering inert. */
-  groupMemberIds?: Set<string>;
+  groupMemberIds?: Set<string> | undefined;
 }
 
 function matchesTimeOfDay(
diff --git a/src/lib/timelineCalculator.ts b/src/lib/timelineCalculator.ts
index 558230ca..9b1a2549 100644
--- a/src/lib/timelineCalculator.ts
+++ b/src/lib/timelineCalculator.ts
@@ -44,7 +44,7 @@ export interface TimelineData {
   timeSlots: Date[];
   stages: Array<{
     name: string;
-    color?: string;
+    color?: string | undefined;
     sets: HorizontalTimelineSet[];
   }>;
   totalWidth: number;
diff --git a/src/lib/timelineMountMoment.ts b/src/lib/timelineMountMoment.ts
index d9f061ef..653b7173 100644
--- a/src/lib/timelineMountMoment.ts
+++ b/src/lib/timelineMountMoment.ts
@@ -3,7 +3,7 @@ import { fromZonedTime } from "date-fns-tz";
 import type { ScheduleWindow } from "@/lib/timelineCalculator";
 
 export interface TimelineMountMomentInput {
-  scrollTo?: string;
+  scrollTo?: string | undefined;
   day: string;
   timezone: string;
   festivalStart: Date;
diff --git a/src/pages/EditionView/EditionHero.tsx b/src/pages/EditionView/EditionHero.tsx
index 1b820f65..085bb14a 100644
--- a/src/pages/EditionView/EditionHero.tsx
+++ b/src/pages/EditionView/EditionHero.tsx
@@ -3,7 +3,7 @@ import { useFestivalPhase } from "@/hooks/useFestivalPhase";
 
 interface EditionHeroProps {
   title: string;
-  logoUrl?: string | null;
+  logoUrl?: string | null | undefined;
   onRowRefChange?: (node: HTMLElement | null) => void;
 }
 
diff --git a/src/pages/EditionView/tabs/InfoTab/EditionTitle.tsx b/src/pages/EditionView/tabs/InfoTab/EditionTitle.tsx
index 4865156a..89b87a82 100644
--- a/src/pages/EditionView/tabs/InfoTab/EditionTitle.tsx
+++ b/src/pages/EditionView/tabs/InfoTab/EditionTitle.tsx
@@ -1,5 +1,5 @@
 interface EditionTitleProps {
-  name?: string;
+  name?: string | undefined;
 }
 
 export function EditionTitle({ name }: EditionTitleProps) {
diff --git a/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageLabels.tsx b/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageLabels.tsx
index d8adfca4..51c21b92 100644
--- a/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageLabels.tsx
+++ b/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageLabels.tsx
@@ -1,7 +1,7 @@
 import { DEFAULT_STAGE_COLOR } from "@/lib/constants/stages";
 
 interface StageLabelsProps {
-  stages: Array<{ name: string; color?: string }>;
+  stages: Array<{ name: string; color?: string | undefined }>;
 }
 
 export function StageLabels({ stages }: StageLabelsProps) {
diff --git a/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageRow.tsx b/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageRow.tsx
index 752cfb44..35fc873a 100644
--- a/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageRow.tsx
+++ b/src/pages/EditionView/tabs/ScheduleTab/horizontal/StageRow.tsx
@@ -4,7 +4,7 @@ import type { HorizontalTimelineSet } from "@/lib/timelineCalculator";
 interface StageRowProps {
   stage: {
     name: string;
-    color?: string;
+    color?: string | undefined;
     sets: HorizontalTimelineSet[];
   };
   totalWidth: number;
diff --git a/src/pages/EditionView/tabs/ScheduleTab/list/ListDayGroup.tsx b/src/pages/EditionView/tabs/ScheduleTab/list/ListDayGroup.tsx
index db04dab3..f2fa952d 100644
--- a/src/pages/EditionView/tabs/ScheduleTab/list/ListDayGroup.tsx
+++ b/src/pages/EditionView/tabs/ScheduleTab/list/ListDayGroup.tsx
@@ -9,7 +9,10 @@ import type { ScheduleSet } from "@/hooks/useScheduleData";
 
 interface TimeSlot {
   time: Date;
-  sets: (ScheduleSet & { stageName: string; stageColor?: string })[];
+  sets: (ScheduleSet & {
+    stageName: string;
+    stageColor?: string | undefined;
+  })[];
 }
 
 interface ListDayGroupProps {
diff --git a/src/pages/EditionView/tabs/ScheduleTab/list/MobileSetCard.tsx b/src/pages/EditionView/tabs/ScheduleTab/list/MobileSetCard.tsx
index fa9082ad..8858413c 100644
--- a/src/pages/EditionView/tabs/ScheduleTab/list/MobileSetCard.tsx
+++ b/src/pages/EditionView/tabs/ScheduleTab/list/MobileSetCard.tsx
@@ -8,8 +8,8 @@ import { StageBadge } from "@/components/StageBadge";
 import type { ScheduleSet } from "@/hooks/useScheduleData";
 
 interface MobileSetCardProps {
-  set: ScheduleSet & { stageName: string; stageColor?: string };
-  timezone?: string;
+  set: ScheduleSet & { stageName: string; stageColor?: string | undefined };
+  timezone?: string | undefined;
 }
 
 export function MobileSetCard({ set, timezone }: MobileSetCardProps) {
diff --git a/src/pages/EditionView/tabs/ScheduleTab/list/TimeSlotGroup.tsx b/src/pages/EditionView/tabs/ScheduleTab/list/TimeSlotGroup.tsx
index 7381c20d..5dfc59be 100644
--- a/src/pages/EditionView/tabs/ScheduleTab/list/TimeSlotGroup.tsx
+++ b/src/pages/EditionView/tabs/ScheduleTab/list/TimeSlotGroup.tsx
@@ -6,12 +6,15 @@ import type { ScheduleSet } from "@/hooks/useScheduleData";
 
 interface TimeSlot {
   time: Date;
-  sets: (ScheduleSet & { stageName: string; stageColor?: string })[];
+  sets: (ScheduleSet & {
+    stageName: string;
+    stageColor?: string | undefined;
+  })[];
 }
 
 interface TimeSlotGroupProps {
   timeSlot: TimeSlot;
-  timezone?: string;
+  timezone?: string | undefined;
 }
 
 export function TimeSlotGroup({ timeSlot, timezone }: TimeSlotGroupProps) {
diff --git a/src/pages/EditionView/tabs/VoteTab/filters/FilterSortControls.tsx b/src/pages/EditionView/tabs/VoteTab/filters/FilterSortControls.tsx
index 5da56744..4296c39b 100644
--- a/src/pages/EditionView/tabs/VoteTab/filters/FilterSortControls.tsx
+++ b/src/pages/EditionView/tabs/VoteTab/filters/FilterSortControls.tsx
@@ -22,7 +22,7 @@ interface FilterSortControlsProps {
   onStateChange: (updates: Partial<FilterSortState>) => void;
   onClear: () => void;
   editionId: string;
-  votePerspective?: VotePerspectiveProps;
+  votePerspective?: VotePerspectiveProps | undefined;
 }
 
 export function FilterSortControls({
diff --git a/src/pages/ExploreSetPage/SetExploreCard/SetAudioPlayer.tsx b/src/pages/ExploreSetPage/SetExploreCard/SetAudioPlayer.tsx
index fcff52f2..1ced8013 100644
--- a/src/pages/ExploreSetPage/SetExploreCard/SetAudioPlayer.tsx
+++ b/src/pages/ExploreSetPage/SetExploreCard/SetAudioPlayer.tsx
@@ -1,5 +1,5 @@
 interface SetAudioPlayerProps {
-  soundcloudUrl?: string;
+  soundcloudUrl?: string | undefined;
   isActive?: boolean;
 }
 
diff --git a/src/pages/ExploreSetPage/SetExploreCard/SetCardHeader.tsx b/src/pages/ExploreSetPage/SetExploreCard/SetCardHeader.tsx
index 9d131e9b..e67a56b8 100644
--- a/src/pages/ExploreSetPage/SetExploreCard/SetCardHeader.tsx
+++ b/src/pages/ExploreSetPage/SetExploreCard/SetCardHeader.tsx
@@ -4,7 +4,7 @@ import { StageBadgeById } from "@/components/StageBadgeById";
 import { useScheduleReveal } from "@/hooks/useScheduleReveal";
 
 interface SetCardHeaderProps {
-  stageId?: string;
+  stageId?: string | undefined;
   timeStart: string | null;
 }
 
diff --git a/src/pages/ExploreSetPage/SetExploreCard/SoundCloudBadge.tsx b/src/pages/ExploreSetPage/SetExploreCard/SoundCloudBadge.tsx
index c29e5cc5..9d4288ca 100644
--- a/src/pages/ExploreSetPage/SetExploreCard/SoundCloudBadge.tsx
+++ b/src/pages/ExploreSetPage/SetExploreCard/SoundCloudBadge.tsx
@@ -1,6 +1,6 @@
 interface SoundCloudBadgeProps {
   soundcloudUrl?: string | null;
-  onClick?: (e: React.MouseEvent) => void;
+  onClick?: ((e: React.MouseEvent) => void) | undefined;
 }
 
 export function SoundCloudBadge({
diff --git a/src/pages/ExploreSetPage/useExplorableSets.tsx b/src/pages/ExploreSetPage/useExplorableSets.tsx
index e3bbb7f8..fe8d37e7 100644
--- a/src/pages/ExploreSetPage/useExplorableSets.tsx
+++ b/src/pages/ExploreSetPage/useExplorableSets.tsx
@@ -5,7 +5,7 @@ export function useExplorableSets({
   editionId,
   userVotes,
 }: {
-  editionId?: string;
+  editionId?: string | undefined;
   userVotes: Record<string, number>;
 }) {
   const setsQuery = useSetsByEditionQuery(editionId);
diff --git a/src/pages/admin/festivals/info/FestivalFields/FestivalInfoField.tsx b/src/pages/admin/festivals/info/FestivalFields/FestivalInfoField.tsx
index 8d495b28..dfb4b1c4 100644
--- a/src/pages/admin/festivals/info/FestivalFields/FestivalInfoField.tsx
+++ b/src/pages/admin/festivals/info/FestivalFields/FestivalInfoField.tsx
@@ -8,7 +8,7 @@ import { getTextAlignmentClasses } from "@/lib/textAlignment";
 
 interface FestivalInfoFieldProps {
   festivalId: string;
-  infoText?: string | null;
+  infoText?: string | null | undefined;
 }
 
 interface InfoFormData {
@@ -50,7 +50,7 @@ function InfoFieldForm({
   onSave,
 }: {
   festivalId: string;
-  infoText?: string | null;
+  infoText?: string | null | undefined;
   onCancel: () => void;
   onSave: () => void;
 }) {
diff --git a/src/pages/admin/festivals/info/FestivalFields/FestivalMapField.tsx b/src/pages/admin/festivals/info/FestivalFields/FestivalMapField.tsx
index ff325c07..3ca0aa04 100644
--- a/src/pages/admin/festivals/info/FestivalFields/FestivalMapField.tsx
+++ b/src/pages/admin/festivals/info/FestivalFields/FestivalMapField.tsx
@@ -8,7 +8,7 @@ import { useMapUpload } from "./shared/useMapUpload";
 
 interface FestivalMapFieldProps {
   festivalId: string;
-  mapImageUrl?: string | null;
+  mapImageUrl?: string | null | undefined;
 }
 
 interface MapFormData {
@@ -51,7 +51,7 @@ function MapFieldForm({
   onSave,
 }: {
   festivalId: string;
-  mapImageUrl?: string | null;
+  mapImageUrl?: string | null | undefined;
   onCancel: () => void;
   onSave: () => void;
 }) {
diff --git a/src/pages/admin/festivals/info/FestivalFields/FestivalSocialField.tsx b/src/pages/admin/festivals/info/FestivalFields/FestivalSocialField.tsx
index 6f86876b..367eecfb 100644
--- a/src/pages/admin/festivals/info/FestivalFields/FestivalSocialField.tsx
+++ b/src/pages/admin/festivals/info/FestivalFields/FestivalSocialField.tsx
@@ -8,8 +8,8 @@ import { useFestivalInfoMutation } from "@/api/festival-info/useFestivalInfoMuta
 
 interface FestivalSocialFieldProps {
   festivalId: string;
-  facebookUrl?: string | null;
-  instagramUrl?: string | null;
+  facebookUrl?: string | null | undefined;
+  instagramUrl?: string | null | undefined;
 }
 
 interface SocialFormData {
@@ -72,8 +72,8 @@ function SocialFieldForm({
   onSave,
 }: {
   festivalId: string;
-  facebookUrl?: string | null;
-  instagramUrl?: string | null;
+  facebookUrl?: string | null | undefined;
+  instagramUrl?: string | null | undefined;
 
   onCancel: () => void;
   onSave: () => void;
diff --git a/src/routes/festivals/$festivalSlug/editions/$editionSlug/schedule/list.tsx b/src/routes/festivals/$festivalSlug/editions/$editionSlug/schedule/list.tsx
index d49178e3..c9b40aa3 100644
--- a/src/routes/festivals/$festivalSlug/editions/$editionSlug/schedule/list.tsx
+++ b/src/routes/festivals/$festivalSlug/editions/$editionSlug/schedule/list.tsx
@@ -33,7 +33,10 @@ export const Route = createFileRoute(
 
 interface TimeSlot {
   time: Date;
-  sets: (ScheduleSet & { stageName: string; stageColor?: string })[];
+  sets: (ScheduleSet & {
+    stageName: string;
+    stageColor?: string | undefined;
+  })[];
 }
 
 interface DayGroup {
@@ -86,7 +89,7 @@ function ListSchedule() {
     // startTime can't be placed into a time slot, so they're dropped here.
     const allSets: (ScheduleSet & {
       stageName: string;
-      stageColor?: string;
+      stageColor?: string | undefined;
     })[] = [];
 
     filteredScheduleDays.forEach((day) => {
@@ -108,7 +111,7 @@ function ListSchedule() {
     // Group sets by start time
     const timeGroups = new Map<
       string,
-      (ScheduleSet & { stageName: string; stageColor?: string })[]
+      (ScheduleSet & { stageName: string; stageColor?: string | undefined })[]
     >();
 
     allSets.forEach((set) => {
diff --git a/src/services/scheduleImport/parseCsv.ts b/src/services/scheduleImport/parseCsv.ts
index 8886548e..dac84f48 100644
--- a/src/services/scheduleImport/parseCsv.ts
+++ b/src/services/scheduleImport/parseCsv.ts
@@ -23,15 +23,22 @@ export function parseScheduleCsv(csvContent: string): CsvRow[] {
           .filter(Boolean),
       );
 
-      return {
-        artists,
-        setName: row["set name"]?.trim() || undefined,
-        stage: row.stage?.trim() || undefined,
-        date: row.date?.trim() || undefined,
-        startTime: row["start time"]?.trim() || undefined,
-        endTime: row["end time"]?.trim() || undefined,
-        description: row.description?.trim() || undefined,
-      };
+      const setName = row["set name"]?.trim() || undefined;
+      const stage = row.stage?.trim() || undefined;
+      const date = row.date?.trim() || undefined;
+      const startTime = row["start time"]?.trim() || undefined;
+      const endTime = row["end time"]?.trim() || undefined;
+      const description = row.description?.trim() || undefined;
+
+      const csvRow: CsvRow = { artists };
+      if (setName !== undefined) csvRow.setName = setName;
+      if (stage !== undefined) csvRow.stage = stage;
+      if (date !== undefined) csvRow.date = date;
+      if (startTime !== undefined) csvRow.startTime = startTime;
+      if (endTime !== undefined) csvRow.endTime = endTime;
+      if (description !== undefined) csvRow.description = description;
+
+      return csvRow;
     })
     .filter((row) => row.artists.length > 0);
 
diff --git a/tsconfig.app.json b/tsconfig.app.json
index 18756ac5..6650053e 100644
--- a/tsconfig.app.json
+++ b/tsconfig.app.json
@@ -16,6 +16,7 @@
 
     /* Linting */
     "strict": true,
+    "exactOptionalPropertyTypes": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
     "noFallthroughCasesInSwitch": true,