diff --git a/flake.nix b/flake.nix
index 4c458aee..7841752f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,20 +1,25 @@
 {
   inputs = {
-    flake-utils.url = "github:numtide/flake-utils";
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
   };
 
   outputs =
-    inputs:
-    inputs.flake-utils.lib.eachDefaultSystem (
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }:
+    flake-utils.lib.eachDefaultSystem (
       system:
       let
-        pkgs = (import (inputs.nixpkgs) { inherit system; });
+        pkgs = (import nixpkgs { inherit system; });
       in
       {
         formatter = pkgs.nixfmt-rfc-style;
 
-        devShell = pkgs.mkShell {
+        devShells.default = pkgs.mkShell {
+          name = "utrp-dev";
           buildInputs = with pkgs; [
             nodejs_20 # v20.19.4
             pnpm_10 # v10.14.0
diff --git a/public/database/grade_distributions.db b/public/database/grade_distributions.db
index fdd3b058..556dc43e 100644
Binary files a/public/database/grade_distributions.db and b/public/database/grade_distributions.db differ
diff --git a/src/views/components/CourseCatalogMain.tsx b/src/views/components/CourseCatalogMain.tsx
index 073c117b..06e95973 100644
--- a/src/views/components/CourseCatalogMain.tsx
+++ b/src/views/components/CourseCatalogMain.tsx
@@ -15,6 +15,8 @@ import type { SiteSupportType } from '@views/lib/getSiteSupport';
 import { populateSearchInputs } from '@views/lib/populateSearchInputs';
 import React, { useEffect, useRef, useState } from 'react';
 
+import DialogProvider from './common/DialogProvider/DialogProvider';
+
 interface Props {
     support: Extract<SiteSupportType, 'COURSE_CATALOG_DETAILS' | 'COURSE_CATALOG_LIST'>;
 }
@@ -82,28 +84,30 @@ export default function CourseCatalogMain({ support }: Props): JSX.Element | nul
 
     return (
         <ExtensionRoot>
-            <NewSearchLink />
-            <RecruitmentBanner />
-            <TableHead>Plus</TableHead>
-            {rows.map(
-                row =>
-                    row.course && (
-                        <TableRow
-                            key={row.course.uniqueId}
-                            row={row}
-                            isSelected={row.course.uniqueId === selectedCourse?.uniqueId}
-                            activeSchedule={activeSchedule}
-                            onClick={handleRowButtonClick(row.course)}
-                        />
-                    )
-            )}
-            <CourseCatalogInjectedPopup
-                course={selectedCourse!} // always defined when showPopup is true
-                show={showPopup}
-                onClose={() => setShowPopup(false)}
-                afterLeave={() => setSelectedCourse(null)}
-            />
-            {enableScrollToLoad && <AutoLoad addRows={addRows} />}
+            <DialogProvider>
+                <NewSearchLink />
+                <RecruitmentBanner />
+                <TableHead>Plus</TableHead>
+                {rows.map(
+                    row =>
+                        row.course && (
+                            <TableRow
+                                key={row.course.uniqueId}
+                                row={row}
+                                isSelected={row.course.uniqueId === selectedCourse?.uniqueId}
+                                activeSchedule={activeSchedule}
+                                onClick={handleRowButtonClick(row.course)}
+                            />
+                        )
+                )}
+                <CourseCatalogInjectedPopup
+                    course={selectedCourse!} // always defined when showPopup is true
+                    show={showPopup}
+                    onClose={() => setShowPopup(false)}
+                    afterLeave={() => setSelectedCourse(null)}
+                />
+                {enableScrollToLoad && <AutoLoad addRows={addRows} />}
+            </DialogProvider>
         </ExtensionRoot>
     );
 }
diff --git a/src/views/components/common/ExtensionRoot/ExtensionRoot.module.scss b/src/views/components/common/ExtensionRoot/ExtensionRoot.module.scss
index d9221ddb..992b63c3 100644
--- a/src/views/components/common/ExtensionRoot/ExtensionRoot.module.scss
+++ b/src/views/components/common/ExtensionRoot/ExtensionRoot.module.scss
@@ -15,6 +15,11 @@
     @apply font-sans;
     color: #303030;
 
+    // fix font-family on injected pages
+    * {
+        @apply font-sans;
+    }
+
     [data-rfd-drag-handle-context-id=':r1:'] {
         cursor: move;
     }
diff --git a/src/views/components/injected/CourseCatalogInjectedPopup/HeadingAndActions.tsx b/src/views/components/injected/CourseCatalogInjectedPopup/HeadingAndActions.tsx
index 9c49e9ff..38879a94 100644
--- a/src/views/components/injected/CourseCatalogInjectedPopup/HeadingAndActions.tsx
+++ b/src/views/components/injected/CourseCatalogInjectedPopup/HeadingAndActions.tsx
@@ -1,3 +1,5 @@
+import createSchedule from '@pages/background/lib/createSchedule';
+import switchSchedule from '@pages/background/lib/switchSchedule';
 import {
     ArrowUpRight,
     CalendarDots,
@@ -14,8 +16,10 @@ import { background } from '@shared/messages';
 import type { Course } from '@shared/types/Course';
 import type Instructor from '@shared/types/Instructor';
 import type { UserSchedule } from '@shared/types/UserSchedule';
+import { englishStringifyList } from '@shared/util/string';
 import { Button } from '@views/components/common/Button';
 import { Chip, coreMap, flagMap } from '@views/components/common/Chip';
+import { usePrompt } from '@views/components/common/DialogProvider/DialogProvider';
 import Divider from '@views/components/common/Divider';
 import Link from '@views/components/common/Link';
 import Text from '@views/components/common/Text/Text';
@@ -60,7 +64,7 @@ export default function HeadingAndActions({ course, activeSchedule, onClose }: H
 
     const [isCopied, setIsCopied] = useState<boolean>(false);
     const lastCopyTime = useRef<number>(0);
-
+    const showDialog = usePrompt();
     const getInstructorFullName = (instructor: Instructor) => instructor.toString({ format: 'first_last' });
 
     const handleCopy = async (e: React.MouseEvent<HTMLButtonElement, MouseEvent>) => {
@@ -112,10 +116,78 @@ export default function HeadingAndActions({ course, activeSchedule, onClose }: H
         }
     };
 
+    const handleAddToNewSchedule = async (close: () => void) => {
+        const newScheduleId = await createSchedule(`${course.semester.season} ${course.semester.year}`);
+        switchSchedule(newScheduleId);
+        addCourse({ course, scheduleId: newScheduleId });
+        close();
+    };
+
     const handleAddOrRemoveCourse = async () => {
+        const uniqueSemesterCodes = [
+            ...new Set(
+                activeSchedule.courses
+                    .map(course => course.semester.code)
+                    .filter((code): code is string => code !== undefined)
+            ),
+        ];
+        uniqueSemesterCodes.sort();
+        const codeToReadableMap: Record<string, string> = {};
+        activeSchedule.courses.forEach(course => {
+            const { code } = course.semester;
+            if (code) {
+                const readable = `${course.semester.season} ${course.semester.year}`;
+                codeToReadableMap[code] = readable;
+            }
+        });
+        const sortedSemesters = uniqueSemesterCodes
+            .map(code => codeToReadableMap[code])
+            .filter((value): value is string => value !== undefined);
+        const activeSemesters = englishStringifyList(sortedSemesters);
+
         if (!activeSchedule) return;
         if (!courseAdded) {
-            addCourse({ course, scheduleId: activeSchedule.id });
+            const currentSemesterCode = course.semester.code;
+            // Show warning if this course is for a different semester than the selected schedule
+            if (
+                activeSchedule.courses.length > 0 &&
+                activeSchedule.courses.every(otherCourse => otherCourse.semester.code !== currentSemesterCode)
+            ) {
+                const dialogButtons = (close: () => void) => (
+                    <>
+                        <Button variant='minimal' color='ut-black' onClick={close}>
+                            Cancel
+                        </Button>
+                        <Button
+                            variant='filled'
+                            color='ut-burntorange'
+                            onClick={() => {
+                                handleAddToNewSchedule(close);
+                            }}
+                        >
+                            Start a new schedule
+                        </Button>
+                    </>
+                );
+
+                showDialog({
+                    title: 'This course section is from a different semester!',
+                    description: (
+                        <>
+                            The section you&apos;re adding is for{' '}
+                            <span className='text-ut-burntorange'>
+                                {course.semester.season} {course.semester.year}
+                            </span>
+                            , but your current schedule contains sections in{' '}
+                            <span className='text-ut-burntorange'>{activeSemesters}</span>. Mixing semesters in one
+                            schedule may cause confusion.
+                        </>
+                    ),
+                    buttons: dialogButtons,
+                });
+            } else {
+                addCourse({ course, scheduleId: activeSchedule.id });
+            }
         } else {
             removeCourse({ course, scheduleId: activeSchedule.id });
         }