.

frontend/src/components/AdminPanel.tsx

@@ -439,7 +439,18 @@ function EditUserDialog({ user, onClose, onSaved }: { user: User | null; onClose
     e.preventDefault();
     if (!user) return;
     try {
-      await api.adminPatch(user.id, { username: username.trim().toLowerCase(), displayName: displayName.trim(), avatarUrl: avatarUrl.trim(), email: email.trim(), theme });
+      const patch: { username?: string; displayName?: string; avatarUrl?: string; theme?: string; email?: string } = {};
+      const normalizedUsername = username.trim().toLowerCase();
+      if (normalizedUsername !== (user.username ?? "").toLowerCase()) patch.username = normalizedUsername;
+      if (displayName.trim() !== (user.displayName ?? "")) patch.displayName = displayName.trim();
+      if (avatarUrl.trim() !== (user.avatarUrl ?? "")) patch.avatarUrl = avatarUrl.trim();
+      if (email.trim() !== (user.email ?? "")) patch.email = email.trim();
+      if (theme !== (user.theme ?? "auto")) patch.theme = theme;
+      if (Object.keys(patch).length === 0) {
+        onClose();
+        return;
+      }
+      await api.adminPatch(user.id, patch);
       onSaved();
       onClose();
     } catch (err) {

frontend/src/components/dialogs.tsx

@@ -388,7 +388,21 @@ export function SettingsModal({
         }
         discardStaged();
       }
-      const res = await api.updateMe({ username: username.trim().toLowerCase(), displayName: displayName.trim(), avatarUrl: url, email: email.trim(), theme });
+      const normalizedUsername = username.trim().toLowerCase();
+      // Only send fields that actually changed: this isolates a
+      // username error (e.g. admin rename guard) from the rest of the
+      // profile so one rejected field can't block the whole save.
+      const patch: { username?: string; displayName?: string; avatarUrl?: string; email?: string; theme?: string } = {};
+      if (normalizedUsername !== (user.username ?? "").toLowerCase()) patch.username = normalizedUsername;
+      if (displayName.trim() !== (user.displayName ?? "")) patch.displayName = displayName.trim();
+      if (url !== (user.avatarUrl ?? "")) patch.avatarUrl = url;
+      if (email.trim() !== (user.email ?? "")) patch.email = email.trim();
+      if (theme !== (user.theme ?? "auto")) patch.theme = theme;
+      if (Object.keys(patch).length === 0) {
+        onClose();
+        return;
+      }
+      const res = await api.updateMe(patch);
       onSaved(res.user);
       onClose();
     } catch (err) {

src/index.ts

@@ -628,6 +628,11 @@ const server = Bun.serve<{ ticketId: string | null; isAdmin: boolean }>({
         if (!ok) return json({ error: "invalid JSON" }, 400);
         const patch: { username?: string; displayName?: string; avatarUrl?: string; theme?: string; email?: string } = {};
         if (body.username !== undefined) {
+          // No-op when unchanged (settings forms send the whole profile):
+          // don't fail the entire save for the admin account when the
+          // username field just echoes the current value.
+          const raw = typeof body.username === "string" ? body.username.trim().toLowerCase() : "";
+          if (raw !== user.username) {
             if (user.username === "admin") return json({ error: "the admin account cannot be renamed" }, 403);
             if (!await isUsernameChangeEnabled()) return json({ error: "username changes are disabled" }, 403);
             const u = validUsername(body.username);
@@ -636,6 +641,7 @@ const server = Bun.serve<{ ticketId: string | null; isAdmin: boolean }>({
             if (taken && taken.id !== user.id) return json({ error: "username taken" }, 409);
             patch.username = u;
           }
+        }
         if (body.displayName !== undefined) {
           const d = cleanStr(body.displayName, 60);
           if (d === null) return json({ error: "displayName: 1-60 chars" }, 400);
@@ -813,6 +819,8 @@ const server = Bun.serve<{ ticketId: string | null; isAdmin: boolean }>({
           if (!ok) return json({ error: "invalid JSON" }, 400);
           const patch: { username?: string; displayName?: string; avatarUrl?: string; theme?: string; email?: string } = {};
           if (body.username !== undefined) {
+            const raw = typeof body.username === "string" ? body.username.trim().toLowerCase() : "";
+            if (raw !== target.username) {
               if (target.username === "admin") return json({ error: "the admin account cannot be renamed" }, 403);
               const u = validUsername(body.username);
               if (!u) return json({ error: "username: 2-32 chars [a-z0-9._-], 'admin' reserved" }, 400);
@@ -820,6 +828,7 @@ const server = Bun.serve<{ ticketId: string | null; isAdmin: boolean }>({
               if (taken && taken.id !== target.id) return json({ error: "username taken" }, 409);
               patch.username = u;
             }
+          }
           if (body.displayName !== undefined) {
             const d = cleanStr(body.displayName, 60);
             if (d === null) return json({ error: "displayName: 1-60 chars" }, 400);