diff --git a/server/src/wled_controller/static/js/core/command-palette.js b/server/src/wled_controller/static/js/core/command-palette.js
index bb0e164..125f849 100644
--- a/server/src/wled_controller/static/js/core/command-palette.js
+++ b/server/src/wled_controller/static/js/core/command-palette.js
@@ -61,8 +61,8 @@ function _buildItems(results, states = {}) {
                 name: tgt.name, detail: t('search.action.stop'), group: 'actions', icon: '■',
                 action: async () => {
                     const resp = await fetchWithAuth(`/output-targets/${tgt.id}/stop`, { method: 'POST' });
-                    if (resp.ok) showToast(t('device.stopped'), 'success');
-                    else showToast(t('target.error.stop_failed'), 'error');
+                    if (resp.ok) { showToast(t('device.stopped'), 'success'); }
+                    else { const err = await resp.json().catch(() => ({})); const d = err.detail || err.message || ''; const ds = Array.isArray(d) ? d.map(x => x.msg || x).join('; ') : String(d); showToast(ds || t('target.error.stop_failed'), 'error'); }
                 },
             });
         } else {
@@ -70,8 +70,8 @@ function _buildItems(results, states = {}) {
                 name: tgt.name, detail: t('search.action.start'), group: 'actions', icon: '▶',
                 action: async () => {
                     const resp = await fetchWithAuth(`/output-targets/${tgt.id}/start`, { method: 'POST' });
-                    if (resp.ok) showToast(t('device.started'), 'success');
-                    else showToast(t('target.error.start_failed'), 'error');
+                    if (resp.ok) { showToast(t('device.started'), 'success'); }
+                    else { const err = await resp.json().catch(() => ({})); const d = err.detail || err.message || ''; const ds = Array.isArray(d) ? d.map(x => x.msg || x).join('; ') : String(d); showToast(ds || t('target.error.start_failed'), 'error'); }
                 },
             });
         }
@@ -92,8 +92,8 @@ function _buildItems(results, states = {}) {
                 name: a.name, detail: t('search.action.disable'), group: 'actions', icon: ICON_AUTOMATION,
                 action: async () => {
                     const resp = await fetchWithAuth(`/automations/${a.id}/disable`, { method: 'POST' });
-                    if (resp.ok) showToast(t('search.action.disable') + ': ' + a.name, 'success');
-                    else showToast(t('search.action.disable') + ' failed', 'error');
+                    if (resp.ok) { showToast(t('search.action.disable') + ': ' + a.name, 'success'); }
+                    else { const err = await resp.json().catch(() => ({})); const d = err.detail || err.message || ''; const ds = Array.isArray(d) ? d.map(x => x.msg || x).join('; ') : String(d); showToast(ds || (t('search.action.disable') + ' failed'), 'error'); }
                 },
             });
         } else {
@@ -101,8 +101,8 @@ function _buildItems(results, states = {}) {
                 name: a.name, detail: t('search.action.enable'), group: 'actions', icon: ICON_AUTOMATION,
                 action: async () => {
                     const resp = await fetchWithAuth(`/automations/${a.id}/enable`, { method: 'POST' });
-                    if (resp.ok) showToast(t('search.action.enable') + ': ' + a.name, 'success');
-                    else showToast(t('search.action.enable') + ' failed', 'error');
+                    if (resp.ok) { showToast(t('search.action.enable') + ': ' + a.name, 'success'); }
+                    else { const err = await resp.json().catch(() => ({})); const d = err.detail || err.message || ''; const ds = Array.isArray(d) ? d.map(x => x.msg || x).join('; ') : String(d); showToast(ds || (t('search.action.enable') + ' failed'), 'error'); }
                 },
             });
         }
@@ -153,8 +153,8 @@ function _buildItems(results, states = {}) {
             name: sp.name, detail: t('search.action.activate'), group: 'actions', icon: '⚡',
             action: async () => {
                 const resp = await fetchWithAuth(`/scene-presets/${sp.id}/activate`, { method: 'POST' });
-                if (resp.ok) showToast(t('scenes.activated'), 'success');
-                else showToast(t('scenes.error.activate_failed'), 'error');
+                if (resp.ok) { showToast(t('scenes.activated'), 'success'); }
+                else { const err = await resp.json().catch(() => ({})); const d = err.detail || err.message || ''; const ds = Array.isArray(d) ? d.map(x => x.msg || x).join('; ') : String(d); showToast(ds || t('scenes.error.activate_failed'), 'error'); }
             },
         });
     });
diff --git a/server/src/wled_controller/static/js/features/advanced-calibration.js b/server/src/wled_controller/static/js/features/advanced-calibration.js
index 53d7d66..2633dcd 100644
--- a/server/src/wled_controller/static/js/features/advanced-calibration.js
+++ b/server/src/wled_controller/static/js/features/advanced-calibration.js
@@ -172,11 +172,13 @@ export async function saveAdvancedCalibration() {
             _modal.forceClose();
         } else {
             const err = await resp.json().catch(() => ({}));
-            showToast(err.message || t('calibration.error.save_failed'), 'error');
+            const detail = err.detail || err.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            showToast(detailStr || t('calibration.error.save_failed'), 'error');
         }
     } catch (error) {
         if (error.isAuth) return;
-        showToast(t('calibration.error.save_failed'), 'error');
+        showToast(error.message || t('calibration.error.save_failed'), 'error');
     }
 }
 
diff --git a/server/src/wled_controller/static/js/features/automations.js b/server/src/wled_controller/static/js/features/automations.js
index d61c240..ecd5d89 100644
--- a/server/src/wled_controller/static/js/features/automations.js
+++ b/server/src/wled_controller/static/js/features/automations.js
@@ -721,7 +721,10 @@ export async function toggleAutomationEnabled(automationId, enable) {
         const resp = await fetchWithAuth(`/automations/${automationId}/${action}`, {
             method: 'POST',
         });
-        if (!resp.ok) throw new Error(`Failed to ${action} automation`);
+        if (!resp.ok) {
+            const err = await resp.json().catch(() => ({}));
+            throw new Error(err.detail || `Failed to ${action} automation`);
+        }
         automationsCacheObj.invalidate();
         loadAutomations();
     } catch (e) {
@@ -768,7 +771,10 @@ export async function deleteAutomation(automationId, automationName) {
         const resp = await fetchWithAuth(`/automations/${automationId}`, {
             method: 'DELETE',
         });
-        if (!resp.ok) throw new Error('Failed to delete automation');
+        if (!resp.ok) {
+            const err = await resp.json().catch(() => ({}));
+            throw new Error(err.detail || 'Failed to delete automation');
+        }
         showToast(t('automations.deleted'), 'success');
         automationsCacheObj.invalidate();
         loadAutomations();
diff --git a/server/src/wled_controller/static/js/features/calibration.js b/server/src/wled_controller/static/js/features/calibration.js
index 08d99ee..75a23a3 100644
--- a/server/src/wled_controller/static/js/features/calibration.js
+++ b/server/src/wled_controller/static/js/features/calibration.js
@@ -815,13 +815,15 @@ export async function toggleTestEdge(edge) {
             });
             if (!response.ok) {
                 const errorData = await response.json();
-                error.textContent = t('calibration.error.test_toggle_failed');
+                const detail = errorData.detail || errorData.message || '';
+                const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+                error.textContent = detailStr || t('calibration.error.test_toggle_failed');
                 error.style.display = 'block';
             }
         } catch (err) {
             if (err.isAuth) return;
             console.error('Failed to toggle CSS test edge:', err);
-            error.textContent = t('calibration.error.test_toggle_failed');
+            error.textContent = err.message || t('calibration.error.test_toggle_failed');
             error.style.display = 'block';
         }
         return;
@@ -845,13 +847,15 @@ export async function toggleTestEdge(edge) {
         });
         if (!response.ok) {
             const errorData = await response.json();
-            error.textContent = t('calibration.error.test_toggle_failed');
+            const detail = errorData.detail || errorData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            error.textContent = detailStr || t('calibration.error.test_toggle_failed');
             error.style.display = 'block';
         }
     } catch (err) {
         if (err.isAuth) return;
         console.error('Failed to toggle test edge:', err);
-        error.textContent = t('calibration.error.test_toggle_failed');
+        error.textContent = err.message || t('calibration.error.test_toggle_failed');
         error.style.display = 'block';
     }
 }
@@ -948,13 +952,15 @@ export async function saveCalibration() {
             }
         } else {
             const errorData = await response.json();
-            error.textContent = t('calibration.error.save_failed');
+            const detail = errorData.detail || errorData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            error.textContent = detailStr || t('calibration.error.save_failed');
             error.style.display = 'block';
         }
     } catch (err) {
         if (err.isAuth) return;
         console.error('Failed to save calibration:', err);
-        error.textContent = t('calibration.error.save_failed');
+        error.textContent = err.message || t('calibration.error.save_failed');
         error.style.display = 'block';
     }
 }
diff --git a/server/src/wled_controller/static/js/features/device-discovery.js b/server/src/wled_controller/static/js/features/device-discovery.js
index a1e0f80..533f7f8 100644
--- a/server/src/wled_controller/static/js/features/device-discovery.js
+++ b/server/src/wled_controller/static/js/features/device-discovery.js
@@ -871,13 +871,15 @@ export async function handleAddDevice(event) {
         } else {
             const errorData = await response.json();
             console.error('Failed to add device:', errorData);
-            error.textContent = t('device_discovery.error.add_failed');
+            const detail = errorData.detail || errorData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            error.textContent = detailStr || t('device_discovery.error.add_failed');
             error.style.display = 'block';
         }
     } catch (err) {
         if (err.isAuth) return;
         console.error('Failed to add device:', err);
-        showToast(t('device_discovery.error.add_failed'), 'error');
+        showToast(err.message || t('device_discovery.error.add_failed'), 'error');
     }
 }
 
diff --git a/server/src/wled_controller/static/js/features/devices.js b/server/src/wled_controller/static/js/features/devices.js
index 4d8e07f..cc75709 100644
--- a/server/src/wled_controller/static/js/features/devices.js
+++ b/server/src/wled_controller/static/js/features/devices.js
@@ -516,7 +516,9 @@ export async function saveDeviceSettings() {
 
         if (!deviceResponse.ok) {
             const errorData = await deviceResponse.json();
-            settingsModal.showError(t('device.error.update'));
+            const detail = errorData.detail || errorData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            settingsModal.showError(detailStr || t('device.error.update'));
             return;
         }
 
@@ -527,7 +529,7 @@ export async function saveDeviceSettings() {
     } catch (err) {
         if (err.isAuth) return;
         console.error('Failed to save device settings:', err);
-        settingsModal.showError(t('device.error.save'));
+        settingsModal.showError(err.message || t('device.error.save'));
     }
 }
 
@@ -546,11 +548,14 @@ export async function saveCardBrightness(deviceId, value) {
             body: JSON.stringify({ brightness: bri })
         });
         if (!resp.ok) {
-            showToast(t('device.error.brightness'), 'error');
+            const errData = await resp.json().catch(() => ({}));
+            const detail = errData.detail || errData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            showToast(detailStr || t('device.error.brightness'), 'error');
         }
     } catch (err) {
         if (err.isAuth) return;
-        showToast(t('device.error.brightness'), 'error');
+        showToast(err.message || t('device.error.brightness'), 'error');
     }
 }
 
diff --git a/server/src/wled_controller/static/js/features/scene-presets.js b/server/src/wled_controller/static/js/features/scene-presets.js
index ef54796..5bc1fee 100644
--- a/server/src/wled_controller/static/js/features/scene-presets.js
+++ b/server/src/wled_controller/static/js/features/scene-presets.js
@@ -319,7 +319,10 @@ export async function activateScenePreset(presetId) {
             method: 'POST',
         });
         if (!resp.ok) {
-            showToast(t('scenes.error.activate_failed'), 'error');
+            const errData = await resp.json().catch(() => ({}));
+            const detail = errData.detail || errData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            showToast(detailStr || t('scenes.error.activate_failed'), 'error');
             return;
         }
         const result = await resp.json();
@@ -352,11 +355,14 @@ export async function recaptureScenePreset(presetId) {
             scenePresetsCache.invalidate();
             _reloadScenesTab();
         } else {
-            showToast(t('scenes.error.recapture_failed'), 'error');
+            const errData = await resp.json().catch(() => ({}));
+            const detail = errData.detail || errData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            showToast(detailStr || t('scenes.error.recapture_failed'), 'error');
         }
     } catch (error) {
         if (error.isAuth) return;
-        showToast(t('scenes.error.recapture_failed'), 'error');
+        showToast(error.message || t('scenes.error.recapture_failed'), 'error');
     }
 }
 
@@ -425,11 +431,14 @@ export async function deleteScenePreset(presetId) {
             scenePresetsCache.invalidate();
             _reloadScenesTab();
         } else {
-            showToast(t('scenes.error.delete_failed'), 'error');
+            const errData = await resp.json().catch(() => ({}));
+            const detail = errData.detail || errData.message || '';
+            const detailStr = Array.isArray(detail) ? detail.map(d => d.msg || d).join('; ') : String(detail);
+            showToast(detailStr || t('scenes.error.delete_failed'), 'error');
         }
     } catch (error) {
         if (error.isAuth) return;
-        showToast(t('scenes.error.delete_failed'), 'error');
+        showToast(error.message || t('scenes.error.delete_failed'), 'error');
     }
 }