diff --git a/frontend/src/components/AdminPanel.tsx b/frontend/src/components/AdminPanel.tsx
index 065cce8..7c22bb7 100644
--- a/frontend/src/components/AdminPanel.tsx
+++ b/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) {
diff --git a/frontend/src/components/dialogs.tsx b/frontend/src/components/dialogs.tsx
index bf7b82f..5b56810 100644
--- a/frontend/src/components/dialogs.tsx
+++ b/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) {
diff --git a/src/index.ts b/src/index.ts
index a0ae19d..4be527a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -628,13 +628,19 @@ 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) {
-          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);
-          if (!u) return json({ error: "username: 2-32 chars [a-z0-9._-], 'admin' reserved" }, 400);
-          const taken = await getUserByUsername(u);
-          if (taken && taken.id !== user.id) return json({ error: "username taken" }, 409);
-          patch.username = u;
+          // 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);
+            if (!u) return json({ error: "username: 2-32 chars [a-z0-9._-], 'admin' reserved" }, 400);
+            const taken = await getUserByUsername(u);
+            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);
@@ -813,12 +819,15 @@ 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) {
-            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);
-            const taken = await getUserByUsername(u);
-            if (taken && taken.id !== target.id) return json({ error: "username taken" }, 409);
-            patch.username = u;
+            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);
+              const taken = await getUserByUsername(u);
+              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);