diff --git a/mateclaw-ui/src/i18n/locales/en-US.ts b/mateclaw-ui/src/i18n/locales/en-US.ts
index ba0e18c1..ffb59e5d 100644
--- a/mateclaw-ui/src/i18n/locales/en-US.ts
+++ b/mateclaw-ui/src/i18n/locales/en-US.ts
@@ -2656,6 +2656,8 @@ export default {
     empty: 'No skills found',
     emptyDesc: 'Add skills to enhance your agents\' capabilities',
     noDescription: 'No description',
+    // Issue #83: shown on the padlock that replaces the toggle for MCP/ACP virtual skills.
+    virtualReadonlyHint: 'MCP/ACP-derived skills can\'t be toggled here — manage the underlying service in Settings ▸ Connections.',
     modal: {
       configureTitle: 'Configure Skill',
       newTitle: 'New Skill',
diff --git a/mateclaw-ui/src/i18n/locales/zh-CN.ts b/mateclaw-ui/src/i18n/locales/zh-CN.ts
index 3b00afd1..65404185 100644
--- a/mateclaw-ui/src/i18n/locales/zh-CN.ts
+++ b/mateclaw-ui/src/i18n/locales/zh-CN.ts
@@ -2660,6 +2660,8 @@ export default {
     empty: '暂无技能',
     emptyDesc: '添加技能以增强 Agent 的能力',
     noDescription: '暂无描述',
+    // Issue #83: shown on the padlock that replaces the toggle for MCP/ACP virtual skills.
+    virtualReadonlyHint: 'MCP / ACP 衍生技能不能在此切换，请到 Settings ▸ 连接页面操作对应的服务',
     modal: {
       configureTitle: '配置技能',
       newTitle: '新建技能',
diff --git a/mateclaw-ui/src/views/SkillMarket.vue b/mateclaw-ui/src/views/SkillMarket.vue
index 1eb1430f..8df27f2a 100644
--- a/mateclaw-ui/src/views/SkillMarket.vue
+++ b/mateclaw-ui/src/views/SkillMarket.vue
@@ -98,10 +98,25 @@
                 <!-- RFC-042 §2.2.4 — slug under display name when they differ -->
                 <div v-if="hasI18nName(skill)" class="skill-slug">{{ skill.name }}</div>
               </div>
-              <label class="toggle-switch" @click.stop>
+              <!-- Issue #83: virtual MCP/ACP skills are view-only mirrors of the
+                   underlying MCP/ACP server row, with no mate_skill row to flip.
+                   Hiding the toggle here matches how the configure / delete
+                   buttons are gated below; users enable/disable from the
+                   Settings ▸ MCP connection page instead. -->
+              <label v-if="!isSkillRowVirtual(skill)" class="toggle-switch" @click.stop>
                 <input type="checkbox" :checked="skill.enabled" @change="toggleSkill(skill)" />
                 <span class="toggle-slider"></span>
               </label>
+              <span
+                v-else
+                class="virtual-toggle-hint"
+                :title="$t('skills.virtualReadonlyHint')"
+              >
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+                  <rect x="3" y="11" width="18" height="11" rx="2" ry="2"/>
+                  <path d="M7 11V7a5 5 0 0 1 10 0v4"/>
+                </svg>
+              </span>
             </div>
 
             <p class="skill-desc">{{ skill.description || t('skills.noDescription') }}</p>
@@ -467,7 +482,12 @@
             <span v-if="detailSkill.securityScanTime" class="scan-findings-time">
               · {{ formatScanTime(detailSkill.securityScanTime) }}
             </span>
+            <!-- Issue #83 follow-up: virtual MCP/ACP skills can't be rescanned —
+                 backend rejects with err.skill.virtual_readonly. Hide the button
+                 so users don't trigger a guaranteed 4xx; the readonly banner
+                 already tells them where to go. -->
             <button
+              v-if="!isVirtualSkill"
               class="scan-rescan-btn"
               :disabled="rescanning[String(detailSkill.id)]"
               @click="rescanSkill(detailSkill)"
@@ -1197,6 +1217,14 @@ async function deleteSkill(idOrSkill: string | number | Skill) {
 }
 
 async function toggleSkill(skill: Skill) {
+  // Issue #83: short-circuit if a programmatic caller reaches this for a
+  // virtual skill (the UI hides the toggle, but defense-in-depth keeps the
+  // toast accurate when the backend would otherwise return err.skill.not_found
+  // on builds that pre-date the rejectVirtualSkillMutation guard).
+  if (isSkillRowVirtual(skill)) {
+    ElMessage.warning(t('skills.virtualReadonlyHint'))
+    return
+  }
   try {
     await skillApi.toggle(skill.id, !skill.enabled)
     await loadAll()
@@ -1746,6 +1774,19 @@ html.dark .scan-finding-item { background: rgba(255, 255, 255, 0.05); }
 .toggle-slider::before { content: ''; position: absolute; width: 14px; height: 14px; left: 3px; top: 3px; background: var(--mc-bg-elevated); border-radius: 50%; transition: 0.2s; }
 .toggle-switch input:checked + .toggle-slider { background: var(--mc-primary); }
 .toggle-switch input:checked + .toggle-slider::before { transform: translateX(16px); }
+/* Issue #83: padlock placeholder where the toggle would be on virtual MCP/ACP rows. */
+.virtual-toggle-hint {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 36px;
+  height: 20px;
+  color: var(--mc-text-quaternary);
+  cursor: help;
+  flex-shrink: 0;
+  border-radius: 6px;
+}
+.virtual-toggle-hint:hover { color: var(--mc-text-tertiary); background: var(--mc-bg-sunken); }
 .skill-desc { font-size: 13px; color: var(--mc-text-secondary); margin: 0 0 10px; line-height: 1.5; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; flex: 1; }
 
 /* Runtime Status */