diff --git a/frontend/src/core/uploads/api.ts b/frontend/src/core/uploads/api.ts
index 3572551..0d83b6f 100644
--- a/frontend/src/core/uploads/api.ts
+++ b/frontend/src/core/uploads/api.ts
@@ -29,6 +29,16 @@ export interface ListFilesResponse {
   count: number;
 }
 
+async function readErrorDetail(
+  response: Response,
+  fallback: string,
+): Promise<string> {
+  const error = await response
+    .json()
+    .catch(() => ({ detail: fallback }));
+  return error.detail ?? fallback;
+}
+
 /**
  * Upload files to a thread
  */
@@ -51,10 +61,7 @@ export async function uploadFiles(
   );
 
   if (!response.ok) {
-    const error = await response
-      .json()
-      .catch(() => ({ detail: "Upload failed" }));
-    throw new Error(error.detail ?? "Upload failed");
+    throw new Error(await readErrorDetail(response, "Upload failed"));
   }
 
   return response.json();
@@ -71,7 +78,9 @@ export async function listUploadedFiles(
   );
 
   if (!response.ok) {
-    throw new Error("Failed to list uploaded files");
+    throw new Error(
+      await readErrorDetail(response, "Failed to list uploaded files"),
+    );
   }
 
   return response.json();
@@ -92,7 +101,7 @@ export async function deleteUploadedFile(
   );
 
   if (!response.ok) {
-    throw new Error("Failed to delete file");
+    throw new Error(await readErrorDetail(response, "Failed to delete file"));
   }
 
   return response.json();