diff --git a/src/management/shared-manager.ts b/src/management/shared-manager.ts
index a0b5ec77..730f1ded 100644
--- a/src/management/shared-manager.ts
+++ b/src/management/shared-manager.ts
@@ -936,6 +936,10 @@ class SharedManager {
         }
 
         for (const [name, value] of Object.entries(parsed as Record<string, unknown>)) {
+          if (!this.isMarketplaceRegistryEntry(value)) {
+            continue;
+          }
+
           merged[name] = normalizePluginMetadataValue(value, targetConfigDir).normalized;
         }
       } catch (err) {
@@ -954,13 +958,14 @@ class SharedManager {
       const entry = merged[name];
       if (!(name in discoveredEntries)) {
         delete merged[name];
-      } else if (entry && typeof entry === 'object' && !Array.isArray(entry)) {
+      } else if (this.isMarketplaceRegistryEntry(entry)) {
         merged[name] = {
-          ...(entry as Record<string, unknown>),
+          ...entry,
           installLocation: discoveredEntries[name].installLocation,
         };
+      } else {
+        delete merged[name];
       }
-      // else: entry is in discoveredEntries but has a malformed value — preserve as-is
     }
 
     return JSON.stringify(merged, null, 2);
@@ -981,8 +986,8 @@ class SharedManager {
         continue;
       }
 
-      // Skip hidden dirs and Claude Code's .staging rename-dance work trees.
-      if (entry.name.startsWith('.') || entry.name.endsWith('.staging')) {
+      // Skip hidden dirs and Claude Code rename-dance leftovers (.staging/.bak).
+      if (this.isTransientMarketplaceDirectory(entry.name)) {
         continue;
       }
 
@@ -994,6 +999,14 @@ class SharedManager {
     return discovered;
   }
 
+  private isTransientMarketplaceDirectory(name: string): boolean {
+    return name.startsWith('.') || name.endsWith('.staging') || name.endsWith('.bak');
+  }
+
+  private isMarketplaceRegistryEntry(value: unknown): value is Record<string, unknown> {
+    return Boolean(value) && typeof value === 'object' && !Array.isArray(value);
+  }
+
   private writePluginMetadataFile(
     registryPath: string,
     content: string,
diff --git a/tests/unit/shared-manager.test.ts b/tests/unit/shared-manager.test.ts
index 46feb170..730d2f57 100644
--- a/tests/unit/shared-manager.test.ts
+++ b/tests/unit/shared-manager.test.ts
@@ -360,7 +360,7 @@ describe('SharedManager', () => {
       expect(reconciled.stale).toBeUndefined();
     });
 
-    it('does not register .staging directories left behind by interrupted marketplace auto-updates', () => {
+    it('does not register transient marketplace directories left behind by interrupted auto-updates', () => {
       // Regression: CCS used to write bare { installLocation } entries for marketplace
       // directories with no registry record. Claude Code requires source + lastUpdated,
       // so those entries corrupted known_marketplaces.json and broke /plugin.
@@ -369,24 +369,29 @@ describe('SharedManager', () => {
       fs.mkdirSync(instancePath, { recursive: true });
       manager.linkSharedDirectories(instancePath);
 
-      // Simulate Claude Code leaving a .staging dir behind in both the global claude dir
-      // and the instance dir (discoverMarketplaceEntries scans each independently).
-      fs.mkdirSync(marketplacePath(claudeDir(), 'claude-plugins-official.staging'), {
-        recursive: true,
-      });
-      fs.mkdirSync(marketplacePath(instancePath, 'claude-plugins-official.staging'), {
-        recursive: true,
-      });
+      // Simulate Claude Code leaving rename-dance temp dirs behind in both the
+      // global claude dir and the instance dir (discoverMarketplaceEntries scans
+      // each independently).
+      for (const suffix of ['.staging', '.bak']) {
+        fs.mkdirSync(marketplacePath(claudeDir(), `claude-plugins-official${suffix}`), {
+          recursive: true,
+        });
+        fs.mkdirSync(marketplacePath(instancePath, `claude-plugins-official${suffix}`), {
+          recursive: true,
+        });
+      }
 
       manager.normalizeMarketplaceRegistryPaths(instancePath);
 
       const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
       const global = readJson(globalRegistryPath) as Record<string, unknown>;
       expect(global['claude-plugins-official.staging']).toBeUndefined();
+      expect(global['claude-plugins-official.bak']).toBeUndefined();
 
       const instanceRegistryPath = path.join(instancePath, 'plugins', 'known_marketplaces.json');
       const instance = readJson(instanceRegistryPath) as Record<string, unknown>;
       expect(instance['claude-plugins-official.staging']).toBeUndefined();
+      expect(instance['claude-plugins-official.bak']).toBeUndefined();
     });
 
     it('removes registry entries whose physical marketplace directory no longer exists', () => {
@@ -421,6 +426,29 @@ describe('SharedManager', () => {
       expect(instance['vanished-marketplace']).toBeUndefined();
     });
 
+    it('drops malformed marketplace entries even when the payload directory still exists', () => {
+      const manager = new SharedManager();
+      const instancePath = instanceDir('work');
+      fs.mkdirSync(instancePath, { recursive: true });
+      manager.linkSharedDirectories(instancePath);
+
+      fs.mkdirSync(marketplacePath(claudeDir(), 'claude-code-plugins'), { recursive: true });
+
+      const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+      writeJson(globalRegistryPath, {
+        'claude-code-plugins': 'bad-entry',
+      });
+
+      manager.normalizeMarketplaceRegistryPaths(instancePath);
+
+      const global = readJson(globalRegistryPath) as Record<string, unknown>;
+      expect(global['claude-code-plugins']).toBeUndefined();
+
+      const instanceRegistryPath = path.join(instancePath, 'plugins', 'known_marketplaces.json');
+      const instance = readJson(instanceRegistryPath) as Record<string, unknown>;
+      expect(instance['claude-code-plugins']).toBeUndefined();
+    });
+
     it('warns and skips malformed marketplace registries while keeping valid sources', () => {
       const manager = new SharedManager();
       const instancePath = instanceDir('work');