diff --git a/frontend/src/components/ui/ComposeCanvas.tsx b/frontend/src/components/ui/ComposeCanvas.tsx
index 6fbe3b9..e716751 100644
--- a/frontend/src/components/ui/ComposeCanvas.tsx
+++ b/frontend/src/components/ui/ComposeCanvas.tsx
@@ -3,7 +3,11 @@ import { forwardRef, useEffect, useImperativeHandle, useRef } from "react";
 
 const PAD = 36;
 
-export const ComposeCanvas = forwardRef((_props, ref) => {
+export type CanvasTools = {
+  addImage: (url: string) => void;
+};
+
+export const ComposeCanvas = forwardRef<CanvasTools>((_props, ref) => {
   const wrapperRef = useRef<HTMLDivElement>(null);
   const canvasRef = useRef<HTMLCanvasElement>(null);
   const fabricRef = useRef<fabric.Canvas | null>(null);
@@ -137,6 +141,8 @@ export const ComposeCanvas = forwardRef((_props, ref) => {
         fabricRef.current?.add(img);
         fabricRef.current?.setActiveObject(img);
         fabricRef.current?.requestRenderAll();
+
+        URL.revokeObjectURL(url); // cleanup browser upload
       });
     },
   }));
@@ -155,3 +161,4 @@ export const ComposeCanvas = forwardRef((_props, ref) => {
     </div>
   );
 });
+ComposeCanvas.displayName = "ComposeCanvas";
diff --git a/frontend/src/hooks/useAuth.ts b/frontend/src/hooks/useAuth.ts
index 1e67da8..1515067 100644
--- a/frontend/src/hooks/useAuth.ts
+++ b/frontend/src/hooks/useAuth.ts
@@ -1,13 +1,7 @@
 import { useCallback } from "react";
 import { api, publicApi } from "../api/apiClient";
 import { endpoints } from "../config/endpoints";
-import { useAuthStore } from "../store/useAuthStore";
-
-interface UserProfile {
-  public_id: string;
-  email: string;
-  full_name: string;
-}
+import { type UserProfile, useAuthStore } from "../store/useAuthStore";
 
 export const useAuth = () => {
   const { accessToken, user, isInitializing, setAuth, clearAuth } =
@@ -15,7 +9,7 @@ export const useAuth = () => {
 
   const isAuthenticated = !!accessToken;
 
-  const login = async (access: string, profile: UserProfile) => {
+  const login = (access: string, profile: UserProfile) => {
     setAuth(access, profile);
   };
 
diff --git a/frontend/src/pages/Editor.tsx b/frontend/src/pages/Editor.tsx
index 363ca15..651a5d1 100644
--- a/frontend/src/pages/Editor.tsx
+++ b/frontend/src/pages/Editor.tsx
@@ -1,15 +1,18 @@
 import { ImageIcon, LockIcon, TrayIcon } from "@phosphor-icons/react";
 import { useRef, useState } from "react";
-import { ComposeCanvas } from "../components/ui/ComposeCanvas";
+import {
+  type CanvasTools,
+  ComposeCanvas,
+} from "../components/ui/ComposeCanvas";
 import DateDisplay from "../components/ui/DateDisplay";
 
 export default function Editor() {
   const [recipient, setRecipient] = useState("");
 
-  const canvasRef = useRef<any>(null);
-  const _fileInputRef = useRef<HTMLInputElement>(null);
-  const _handleImageUpload = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const file = e.target.files?.[0];
+  const canvasRef = useRef<CanvasTools>(null);
+  const fileInputRef = useRef<HTMLInputElement>(null);
+  const handleImageUpload = (e: React.ChangeEvent<HTMLInputElement>) => {
+    const file = e.target.files?.[0]; // pick one file at a time
     if (file) {
       const url = URL.createObjectURL(file);
       canvasRef.current?.addImage(url);
@@ -47,14 +50,14 @@ export default function Editor() {
             <button
               type="button"
               className="btn btn-ghost btn-sm"
-              onClick={() => _fileInputRef.current?.click()}
+              onClick={() => fileInputRef.current?.click()}
             >
               <ImageIcon size={18} weight="bold" />
             </button>
             <input
               type="file"
-              ref={_fileInputRef}
-              onChange={_handleImageUpload}
+              ref={fileInputRef}
+              onChange={handleImageUpload}
               accept="image/*"
               className="hidden"
             />
diff --git a/frontend/src/pages/Register.tsx b/frontend/src/pages/Register.tsx
index efb1d92..c6dfaed 100644
--- a/frontend/src/pages/Register.tsx
+++ b/frontend/src/pages/Register.tsx
@@ -9,6 +9,7 @@ import { publicApi } from "../api/apiClient";
 import Logo from "../components/Logo";
 import FormField from "../components/ui/FormField";
 import { endpoints } from "../config/endpoints";
+import { ROUTES } from "../config/routes";
 
 // validation logic
 const registerSchema = z
@@ -47,7 +48,7 @@ export default function Register() {
         email: data.email,
         password: data.password,
       });
-      navigate("/verify-email");
+      navigate(ROUTES.VERIFY_EMAIL);
     } catch (err) {
       console.error("Registration error:", err);
       let message = "Registration failed. Please try again.";
diff --git a/frontend/src/pages/VerifyEmail.tsx b/frontend/src/pages/VerifyEmail.tsx
index cc7d230..52d1557 100644
--- a/frontend/src/pages/VerifyEmail.tsx
+++ b/frontend/src/pages/VerifyEmail.tsx
@@ -29,13 +29,14 @@ export default function VerifyEmail() {
         </p>
       </div>
 
-      <p
+      <button
+        type="button"
         className="text-xs italic opacity-40 cursor-pointer underline"
         onClick={() => window.close()}
         onKeyDown={(e) => e.key === "Enter" && window.close()}
       >
         You can close this window now.
-      </p>
+      </button>
     </div>
   );
 }
diff --git a/frontend/src/store/useAuthStore.ts b/frontend/src/store/useAuthStore.ts
index b805a59..d9ee990 100644
--- a/frontend/src/store/useAuthStore.ts
+++ b/frontend/src/store/useAuthStore.ts
@@ -1,6 +1,6 @@
 import { create } from "zustand";
 
-interface UserProfile {
+export interface UserProfile {
   public_id: string;
   email: string;
   full_name: string;
diff --git a/frontend/src/utils/crypto.ts b/frontend/src/utils/crypto.ts
index bdd6b1e..dc66b80 100644
--- a/frontend/src/utils/crypto.ts
+++ b/frontend/src/utils/crypto.ts
@@ -66,7 +66,8 @@ export async function encryptLetter(plaintext: string, masterKey: CryptoKey) {
   const rawKey = await crypto.subtle.exportKey("raw", dek);
 
   // conversion to base64 for transit
-  const toBase64 = (buffer: Uint8Array) => btoa(String.fromCharCode(...buffer));
+  const toBase64 = (buf: Uint8Array) =>
+    btoa(buf.reduce((acc, b) => acc + String.fromCharCode(b), ""));
 
   return {
     // This goes to the server