diff --git a/src/components/pet/AvatarUpload.tsx b/src/components/pet/AvatarUpload.tsx
index cf3d180..81222df 100644
--- a/src/components/pet/AvatarUpload.tsx
+++ b/src/components/pet/AvatarUpload.tsx
@@ -8,6 +8,7 @@ import { useTRPC } from "@/trpc/client";
 import { useMutation } from "@tanstack/react-query";
 import { Avatar, AvatarImage, AvatarFallback } from "@/components/ui/avatar";
 import { Progress } from "@/components/ui/progress";
+import { uploadFileWithProgress } from "@/lib/upload-xhr";
 
 /**
  * AvatarUpload — five-state upload zone for pet avatars.
@@ -110,32 +111,10 @@ export function AvatarUpload({
           }
         );
 
-        // Step 2: PUT file directly to R2 using XHR for progress tracking
-        await new Promise<void>((resolve, reject) => {
-          const xhr = new XMLHttpRequest();
-
-          xhr.upload.onprogress = (event) => {
-            if (event.lengthComputable) {
-              const percent = Math.round((event.loaded / event.total) * 100);
-              setUploadProgress(percent);
-            }
-          };
-
-          xhr.onload = () => {
-            if (xhr.status >= 200 && xhr.status < 300) {
-              resolve();
-            } else {
-              reject(new Error(`R2 PUT failed with status ${xhr.status}`));
-            }
-          };
-
-          xhr.onerror = () => reject(new Error("Network error during upload"));
-
-          xhr.open("PUT", presignedUrl);
-          // Content-Type MUST match the contentType sent to getPresignedUrl
-          // Pitfall 4: mismatch causes R2 403 SignatureDoesNotMatch
-          xhr.setRequestHeader("Content-Type", file.type);
-          xhr.send(file);
+        // Step 2: PUT file directly to R2, tracking progress
+        await uploadFileWithProgress(presignedUrl, file, {
+          contentType: file.type,
+          onProgress: setUploadProgress,
         });
 
         // Step 3: Confirm upload — write avatarKey to Pet DB row
diff --git a/src/components/post-creation/MultiImageUpload.tsx b/src/components/post-creation/MultiImageUpload.tsx
index 3cfd11e..9400b18 100644
--- a/src/components/post-creation/MultiImageUpload.tsx
+++ b/src/components/post-creation/MultiImageUpload.tsx
@@ -5,6 +5,7 @@ import { ImagePlus, X, Loader2 } from "lucide-react";
 import { toast } from "sonner";
 import { useTRPC } from "@/trpc/client";
 import { useMutation } from "@tanstack/react-query";
+import { uploadFileWithProgress } from "@/lib/upload-xhr";
 
 /**
  * MultiImageUpload — multi-file upload zone for post images (up to 10).
@@ -112,35 +113,16 @@ export function MultiImageUpload({
           fileSize: file.size,
         });
 
-        // Step 2: PUT file directly to Supabase Storage via XHR (with progress)
-        await new Promise<void>((resolve, reject) => {
-          const xhr = new XMLHttpRequest();
-
-          xhr.upload.onprogress = (event) => {
-            if (event.lengthComputable) {
-              const percent = Math.round((event.loaded / event.total) * 100);
-              setImages((prev) => {
-                const updated = [...prev];
-                updated[index] = { ...updated[index], uploadProgress: percent };
-                return updated;
-              });
-            }
-          };
-
-          xhr.onload = () => {
-            if (xhr.status >= 200 && xhr.status < 300) {
-              resolve();
-            } else {
-              reject(new Error(`Storage PUT failed: ${xhr.status}`));
-            }
-          };
-
-          xhr.onerror = () => reject(new Error("Network error during upload"));
-
-          xhr.open("PUT", presignedUrl);
-          // Pitfall 4: Content-Type MUST exactly match what was sent to getPresignedUrl
-          xhr.setRequestHeader("Content-Type", file.type);
-          xhr.send(file);
+        // Step 2: PUT file directly to Supabase Storage, tracking progress
+        await uploadFileWithProgress(presignedUrl, file, {
+          contentType: file.type,
+          onProgress: (percent) => {
+            setImages((prev) => {
+              const updated = [...prev];
+              updated[index] = { ...updated[index], uploadProgress: percent };
+              return updated;
+            });
+          },
         });
 
         // Step 3: Mark as done with storage key
diff --git a/src/components/video/VideoUploadForm.tsx b/src/components/video/VideoUploadForm.tsx
index ea95047..5844aa2 100644
--- a/src/components/video/VideoUploadForm.tsx
+++ b/src/components/video/VideoUploadForm.tsx
@@ -6,6 +6,7 @@ import { toast } from "sonner";
 import { useMutation } from "@tanstack/react-query";
 import { useTRPC } from "@/trpc/client";
 import { useActivePet } from "@/context/ActivePetContext";
+import { uploadFileWithProgress } from "@/lib/upload-xhr";
 import { Button } from "@/components/ui/button";
 import { Textarea } from "@/components/ui/textarea";
 import { Label } from "@/components/ui/label";
@@ -78,22 +79,10 @@ export function VideoUploadForm({ onClose }: VideoUploadFormProps) {
         caption: caption.trim() || null,
       });
 
-      // PUT file directly to Mux upload URL
-      await new Promise<void>((resolve, reject) => {
-        const xhr = new XMLHttpRequest();
-        xhr.upload.onprogress = (event) => {
-          if (event.lengthComputable) {
-            setUploadProgress(Math.round((event.loaded / event.total) * 100));
-          }
-        };
-        xhr.onload = () => {
-          if (xhr.status >= 200 && xhr.status < 300) resolve();
-          else reject(new Error(`Upload failed: ${xhr.status}`));
-        };
-        xhr.onerror = () => reject(new Error("Network error during upload"));
-        xhr.open("PUT", uploadUrl ?? "");
-        // Mux direct upload accepts the video without a specific Content-Type header
-        xhr.send(file);
+      // PUT file directly to Mux upload URL, tracking progress
+      // (Mux direct upload accepts the video without a specific Content-Type header)
+      await uploadFileWithProgress(uploadUrl ?? "", file, {
+        onProgress: setUploadProgress,
       });
 
       setUploadState("processing");
diff --git a/src/lib/avatar-url.ts b/src/lib/avatar-url.ts
index 9fd5477..76e5651 100644
--- a/src/lib/avatar-url.ts
+++ b/src/lib/avatar-url.ts
@@ -1,8 +1,8 @@
+import { getMediaUrl } from "@/lib/media-url";
+
 /**
  * Constructs the public CDN URL for a pet avatar stored in Supabase Storage.
- * Safe to use in both server and client components (uses NEXT_PUBLIC_ env var).
+ * Identical bucket/path scheme to getMediaUrl — kept as a separate export
+ * for call-site readability (avatar vs. post/story media).
  */
-export function getAvatarUrl(key: string | null | undefined): string | null {
-  if (!key) return null;
-  return `${process.env.NEXT_PUBLIC_SUPABASE_URL}/storage/v1/object/public/pet-avatars/${key}`;
-}
+export const getAvatarUrl = getMediaUrl;
diff --git a/src/lib/upload-xhr.ts b/src/lib/upload-xhr.ts
new file mode 100644
index 0000000..bc97a6d
--- /dev/null
+++ b/src/lib/upload-xhr.ts
@@ -0,0 +1,42 @@
+/**
+ * PUTs a file directly to a presigned/direct-upload URL via XHR, tracking
+ * progress. Shared by AvatarUpload, MultiImageUpload, and VideoUploadForm —
+ * all three PUT a File straight to storage after obtaining a signed URL
+ * from a tRPC mutation; only the surrounding state management differs.
+ *
+ * contentType is optional because Mux's direct-upload URL doesn't require
+ * a Content-Type header, while Supabase presigned URLs require it to
+ * exactly match what was sent to getPresignedUrl (mismatch → 403/400
+ * SignatureDoesNotMatch — "Pitfall 4").
+ */
+export function uploadFileWithProgress(
+  url: string,
+  file: File,
+  options?: { contentType?: string; onProgress?: (percent: number) => void }
+): Promise<void> {
+  return new Promise<void>((resolve, reject) => {
+    const xhr = new XMLHttpRequest();
+
+    xhr.upload.onprogress = (event) => {
+      if (event.lengthComputable) {
+        options?.onProgress?.(Math.round((event.loaded / event.total) * 100));
+      }
+    };
+
+    xhr.onload = () => {
+      if (xhr.status >= 200 && xhr.status < 300) {
+        resolve();
+      } else {
+        reject(new Error(`Upload failed with status ${xhr.status}`));
+      }
+    };
+
+    xhr.onerror = () => reject(new Error("Network error during upload"));
+
+    xhr.open("PUT", url);
+    if (options?.contentType) {
+      xhr.setRequestHeader("Content-Type", options.contentType);
+    }
+    xhr.send(file);
+  });
+}