diff --git a/src/components/AddressChangeRequestModal.tsx b/src/components/AddressChangeRequestModal.tsx
index 0dc590a..5d81cc8 100644
--- a/src/components/AddressChangeRequestModal.tsx
+++ b/src/components/AddressChangeRequestModal.tsx
@@ -2,6 +2,7 @@
 
 import { useState } from 'react';
 import type { AddressChangeRequestInput } from '@/types/addressChangeRequest';
+import { useAddressValidation } from '@/hooks/useAddressValidation';
 
 interface AddressChangeRequestModalProps {
   invoiceId: string;
@@ -25,15 +26,30 @@ export default function AddressChangeRequestModal({
   });
   const [error, setError] = useState<string | null>(null);
   const [success, setSuccess] = useState(false);
+  const [hasAttemptedSubmit, setHasAttemptedSubmit] = useState(false);
+  const {
+    validateAddress,
+    isValid: isAddressValid,
+    isLoading: isAddressValidating,
+    error: addressError,
+  } = useAddressValidation();
 
   const handleChange = (e: React.ChangeEvent<HTMLInputElement | HTMLTextAreaElement>) => {
     const { name, value } = e.target;
     setFormData((prev) => ({ ...prev, [name]: value }));
+    if (name === 'newAddress' && hasAttemptedSubmit) {
+      validateAddress(value);
+    }
+  };
+
+  const handleAddressBlur = (e: React.FocusEvent<HTMLInputElement>) => {
+    validateAddress(e.target.value);
   };
 
   const handleSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
     e.preventDefault();
     setError(null);
+    setHasAttemptedSubmit(true);
 
     // Validate new address is different from old address
     if (formData.newAddress === formData.oldAddress) {
@@ -41,9 +57,9 @@ export default function AddressChangeRequestModal({
       return;
     }
 
-    // Validate new address format (basic check for Stellar address)
-    if (!formData.newAddress.startsWith('G') || formData.newAddress.length !== 56) {
-      setError('Invalid Stellar address format');
+    // Validate new address using Stellar address validation (state populated via blur/change)
+    if (!formData.newAddress.trim() || !isAddressValid) {
+      setError(addressError || 'Invalid Stellar address format');
       return;
     }
 
@@ -119,11 +135,16 @@ export default function AddressChangeRequestModal({
               name="newAddress"
               value={formData.newAddress}
               onChange={handleChange}
+              onBlur={handleAddressBlur}
               placeholder="G..."
               className="w-full bg-gray-800 border border-gray-700 rounded-lg px-4 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-500"
               required
             />
-            <p className="text-xs text-gray-500 mt-1">Must be a valid Stellar address starting with G</p>
+            {addressError ? (
+              <p className="text-xs text-red-400 mt-1">{addressError}</p>
+            ) : (
+              <p className="text-xs text-gray-500 mt-1">Must be a valid Stellar address starting with G</p>
+            )}
           </div>
 
           {/* Justification */}
@@ -158,7 +179,11 @@ export default function AddressChangeRequestModal({
             </button>
             <button
               type="submit"
-              disabled={isLoading}
+              disabled={
+                isLoading ||
+                !formData.newAddress.trim() ||
+                (hasAttemptedSubmit && (!isAddressValid || isAddressValidating))
+              }
               className="flex-1 px-4 py-2 bg-indigo-600 hover:bg-indigo-500 text-white rounded-lg text-sm font-medium transition-colors disabled:opacity-50"
             >
               {isLoading ? 'Submitting...' : 'Submit Request'}
diff --git a/src/components/LanguageSwitcher.tsx b/src/components/LanguageSwitcher.tsx
index de53947..e41e1ac 100644
--- a/src/components/LanguageSwitcher.tsx
+++ b/src/components/LanguageSwitcher.tsx
@@ -1,15 +1,41 @@
 "use client";
 
+import { useEffect } from "react";
 import { useI18n } from "@/components/I18nProvider";
 import type { Locale } from "@/lib/i18nTypes";
 
+const STORAGE_KEY = "split_app_locale";
+const VALID_LOCALES: Locale[] = ["en", "es", "pt", "fr"];
+
 export default function LanguageSwitcher() {
   const { locale, setLocale } = useI18n();
 
+  useEffect(() => {
+    try {
+      const stored = localStorage.getItem(STORAGE_KEY) as Locale | null;
+      if (stored && VALID_LOCALES.includes(stored) && stored !== locale) {
+        setLocale(stored);
+      }
+    } catch {
+      // localStorage unavailable; keep default locale
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  const handleChange = (e: React.ChangeEvent<HTMLSelectElement>) => {
+    const newLocale = e.target.value as Locale;
+    setLocale(newLocale);
+    try {
+      localStorage.setItem(STORAGE_KEY, newLocale);
+    } catch {
+      // localStorage unavailable; selection still applies for this session
+    }
+  };
+
   return (
     <select
       value={locale}
-      onChange={(e) => setLocale(e.target.value as Locale)}
+      onChange={handleChange}
       className="text-sm text-gray-400 hover:text-gray-200 px-2 py-1 rounded bg-gray-900 border border-gray-800 transition-colors min-h-11 inline-flex items-center"
       aria-label="Select language"
     >
diff --git a/src/components/ProofViewer.tsx b/src/components/ProofViewer.tsx
index 195b279..e958456 100644
--- a/src/components/ProofViewer.tsx
+++ b/src/components/ProofViewer.tsx
@@ -1,6 +1,6 @@
 "use client";
 
-import { useState } from "react";
+import { useRef, useState } from "react";
 import { splitClient } from "@/lib/stellar";
 import { formatAmount, truncateAddress } from "@stellar-split/sdk";
 
@@ -8,17 +8,46 @@ interface VerifiedProof {
   payer: string;
   amount: bigint;
   ledger: number;
+  imageUrl?: string;
 }
 
 interface Props {
   invoiceId: string;
 }
 
+const MIN_ZOOM = 0.5;
+const MAX_ZOOM = 4;
+const ZOOM_STEP = 0.25;
+
 export default function ProofViewer({ invoiceId }: Props) {
   const [proofHash, setProofHash] = useState("");
   const [verifying, setVerifying] = useState(false);
   const [verified, setVerified] = useState<VerifiedProof | null>(null);
   const [error, setError] = useState<string | null>(null);
+  const [zoom, setZoom] = useState(1);
+  const [pan, setPan] = useState({ x: 0, y: 0 });
+  const [isDragging, setIsDragging] = useState(false);
+  const dragStartRef = useRef({ x: 0, y: 0 });
+
+  const zoomIn = () => setZoom((z) => Math.min(MAX_ZOOM, +(z + ZOOM_STEP).toFixed(2)));
+  const zoomOut = () => setZoom((z) => Math.max(MIN_ZOOM, +(z - ZOOM_STEP).toFixed(2)));
+  const resetZoom = () => {
+    setZoom(1);
+    setPan({ x: 0, y: 0 });
+  };
+
+  const handlePointerDown = (e: React.PointerEvent<HTMLDivElement>) => {
+    if (zoom <= 1) return;
+    setIsDragging(true);
+    dragStartRef.current = { x: e.clientX - pan.x, y: e.clientY - pan.y };
+  };
+
+  const handlePointerMove = (e: React.PointerEvent<HTMLDivElement>) => {
+    if (!isDragging) return;
+    setPan({ x: e.clientX - dragStartRef.current.x, y: e.clientY - dragStartRef.current.y });
+  };
+
+  const handlePointerUp = () => setIsDragging(false);
 
   const handleVerify = async () => {
     if (!proofHash.trim()) return;
@@ -103,11 +132,63 @@ export default function ProofViewer({ invoiceId }: Props) {
             </div>
           </div>
 
+          {verified.imageUrl && (
+            <div className="space-y-2">
+              <div
+                className="relative h-64 overflow-hidden rounded-lg border border-gray-700 bg-gray-900"
+                style={{ cursor: zoom > 1 ? (isDragging ? "grabbing" : "grab") : "default" }}
+                onPointerDown={handlePointerDown}
+                onPointerMove={handlePointerMove}
+                onPointerUp={handlePointerUp}
+                onPointerLeave={handlePointerUp}
+              >
+                <img
+                  src={verified.imageUrl}
+                  alt="Payment proof"
+                  draggable={false}
+                  className="h-full w-full object-contain select-none"
+                  style={{
+                    transform: `translate(${pan.x}px, ${pan.y}px) scale(${zoom})`,
+                    transformOrigin: "center center",
+                  }}
+                />
+              </div>
+              <div className="flex gap-2">
+                <button
+                  type="button"
+                  onClick={zoomOut}
+                  disabled={zoom <= MIN_ZOOM}
+                  aria-label="Zoom out"
+                  className="flex-1 px-3 py-1.5 rounded-lg border border-gray-700 text-sm font-medium hover:bg-gray-700 disabled:opacity-50"
+                >
+                  −
+                </button>
+                <button
+                  type="button"
+                  onClick={zoomIn}
+                  disabled={zoom >= MAX_ZOOM}
+                  aria-label="Zoom in"
+                  className="flex-1 px-3 py-1.5 rounded-lg border border-gray-700 text-sm font-medium hover:bg-gray-700 disabled:opacity-50"
+                >
+                  +
+                </button>
+                <button
+                  type="button"
+                  onClick={resetZoom}
+                  className="flex-1 px-3 py-1.5 rounded-lg border border-gray-700 text-sm font-medium hover:bg-gray-700"
+                >
+                  Reset
+                </button>
+              </div>
+            </div>
+          )}
+
           <button
             type="button"
             onClick={() => {
               setVerified(null);
               setProofHash("");
+              resetZoom();
             }}
             className="w-full px-4 py-2 rounded-lg border border-gray-700 text-sm font-medium hover:bg-gray-700"
           >
diff --git a/src/components/ToastContainer.tsx b/src/components/ToastContainer.tsx
index dbaf4ca..ee6e3d0 100644
--- a/src/components/ToastContainer.tsx
+++ b/src/components/ToastContainer.tsx
@@ -9,14 +9,27 @@ export interface ToastMessage {
   type: 'success' | 'error' | 'info';
 }
 
+export type ToastContainerPosition = 'top-right' | 'top-left' | 'bottom-right' | 'bottom-left';
+
+export interface ToastContainerProps {
+  position?: ToastContainerPosition;
+}
+
+const POSITION_CLASSES: Record<ToastContainerPosition, string> = {
+  'top-right': 'top-4 right-4',
+  'top-left': 'top-4 left-4',
+  'bottom-right': 'bottom-4 right-4',
+  'bottom-left': 'bottom-4 left-4',
+};
+
 /**
  * ToastContainer — manages a stack of toast notifications.
- * Renders toasts in the bottom-right corner with auto-dismiss.
- * 
+ * Renders toasts at a configurable corner (default top-right) with auto-dismiss.
+ *
  * Note: The project also has a ToastContext-based toast system.
  * This component provides a lightweight alternative for direct use.
  */
-export default function ToastContainer() {
+export default function ToastContainer({ position = 'top-right' }: ToastContainerProps) {
   const [toasts, setToasts] = useState<ToastMessage[]>([]);
   const dedupeTimersRef = useRef<Map<string, NodeJS.Timeout>>(new Map());
   const dismissTimersRef = useRef<Map<string, NodeJS.Timeout>>(new Map());
@@ -71,7 +84,7 @@ export default function ToastContainer() {
 
   return (
     <div
-      className="fixed bottom-4 right-4 z-50 flex flex-col gap-2 max-w-sm"
+      className={`fixed ${POSITION_CLASSES[position]} z-50 flex flex-col gap-2 max-w-sm`}
       aria-live="polite"
       aria-label="Notifications"
     >