diff --git a/docs/codebase-summary.md b/docs/codebase-summary.md
index df29f733..17ae9fca 100644
--- a/docs/codebase-summary.md
+++ b/docs/codebase-summary.md
@@ -1,6 +1,6 @@
 # CCS Codebase Summary
 
-Last Updated: 2026-03-17
+Last Updated: 2026-03-18
 
 Comprehensive overview of the modularized CCS codebase structure following the Phase 9 modularization effort (Settings, Analytics, Auth Monitor splits + Test Infrastructure), v7.1 Remote CLIProxy feature, v7.2 Kiro + GitHub Copilot (ghcp) OAuth providers, v7.14 Hybrid Quota Management, v7.34 Image Analysis Hook, and account-context validation hardening.
 
@@ -222,6 +222,13 @@ src/
   - API route rejects `context_group`/`continuity_mode` when mode is not `shared`
   - registry normalization drops malformed persisted `context_group` values
 
+### Shared Plugin Layout
+
+- Shared payload owner: `src/management/shared-manager.ts`.
+- Profile entry point: `src/management/instance-manager.ts`.
+- `plugins/marketplaces/`, `plugins/cache/`, and `installed_plugins.json` stay shared through the `~/.ccs/shared/` topology.
+- `known_marketplaces.json` is now instance-local under `~/.ccs/instances/<profile>/plugins/` so Claude Code validates `installLocation` against the active `CLAUDE_CONFIG_DIR` instead of a last-writer-wins shared file.
+
 ### Target Adapter Module
 
 The targets module provides an extensible interface for dispatching profiles to different CLI implementations.
diff --git a/docs/project-roadmap.md b/docs/project-roadmap.md
index 347851b2..ebaef666 100644
--- a/docs/project-roadmap.md
+++ b/docs/project-roadmap.md
@@ -1,6 +1,6 @@
 # CCS Project Roadmap
 
-Last Updated: 2026-03-17
+Last Updated: 2026-03-18
 
 Forward-looking roadmap documenting current priorities, GitHub issues, and future feature plans.
 
@@ -41,6 +41,7 @@ All major modularization work is complete. The codebase evolved from monolithic
 
 ### Recent Fixes
 
+- **2026-03-18**: **#755** Marketplace refresh no longer reuses one shared `known_marketplaces.json` across isolated instances. CCS now keeps marketplace payload directories shared while reconciling per-instance marketplace metadata so Claude Code validation succeeds for alternating or concurrent profiles, including Windows copy fallback.
 - **2026-03-17**: Deprecated user-facing GLMT discovery across CLI help, completions, presets, and docs. Existing `glmt` profiles now run through a compatibility path that normalizes legacy proxy settings to the direct GLM endpoint.
 - **#748**: API profile creation now keeps provider selection compact by collapsing advanced presets behind an explicit toggle, shrinking chooser cards so the form fields stay visually primary, and giving `llama.cpp` a dedicated provider logo.
 - **#744**: API profile creation now keeps featured providers in a horizontal rail with scroll fallback, moves Anthropic Direct API to the end, reuses the shared Claude logo, and separates the custom-endpoint entry point from advanced template discovery.
diff --git a/docs/system-architecture/index.md b/docs/system-architecture/index.md
index a13cd68e..7de060eb 100644
--- a/docs/system-architecture/index.md
+++ b/docs/system-architecture/index.md
@@ -1,6 +1,6 @@
 # CCS System Architecture
 
-Last Updated: 2026-03-02
+Last Updated: 2026-03-18
 
 High-level architecture overview for the CCS (Claude Code Switch) system.
 
@@ -233,12 +233,27 @@ For detailed provider flows (CLIProxyAPI, legacy GLMT compatibility, quota manag
             +---> commands/        # Claude Code commands
             +---> skills/          # Custom skills
             +---> agents/          # Agent configurations
+            +---> plugins/
+                    |
+                    +---> cache/               # Shared plugin payload/cache data
+                    +---> marketplaces/        # Shared marketplace payload directories
+                    +---> installed_plugins.json
+
+  ~/.ccs/instances/<profile>/
+    |
+    +---> plugins/
+            |
+            +---> known_marketplaces.json      # Instance-local registry for active CLAUDE_CONFIG_DIR validation
 
   ~/.factory/ (Droid CLI)
     |
     +---> settings.json            # Droid config (custom models)
 ```
 
+Plugin ownership note:
+- `commands/`, `skills/`, `agents/`, and `settings.json` remain shared through the existing symlink/copy flow.
+- Marketplace payload directories stay shared, but `known_marketplaces.json` is reconciled per instance so Claude Code can validate `installLocation` against that instance's `CLAUDE_CONFIG_DIR/plugins/marketplaces`.
+
 ### Config Loading Order
 
 ```
diff --git a/src/auth/commands/create-command.ts b/src/auth/commands/create-command.ts
index f9edd2dc..ef59fb60 100644
--- a/src/auth/commands/create-command.ts
+++ b/src/auth/commands/create-command.ts
@@ -163,7 +163,7 @@ export async function handleCreate(ctx: CommandContext, args: string[]): Promise
 
     if (!profileExistedBeforeCreate) {
       try {
-        ctx.instanceMgr.deleteInstance(profileName);
+        await ctx.instanceMgr.deleteInstance(profileName);
       } catch {
         // Best-effort cleanup.
       }
diff --git a/src/auth/commands/remove-command.ts b/src/auth/commands/remove-command.ts
index cfef25cd..b7df32fa 100644
--- a/src/auth/commands/remove-command.ts
+++ b/src/auth/commands/remove-command.ts
@@ -68,7 +68,7 @@ export async function handleRemove(ctx: CommandContext, args: string[]): Promise
     }
 
     // Delete instance
-    ctx.instanceMgr.deleteInstance(profileName);
+    await ctx.instanceMgr.deleteInstance(profileName);
 
     // Delete profile from appropriate config
     if (isUnifiedMode() && existsUnified) {
diff --git a/src/management/instance-manager.ts b/src/management/instance-manager.ts
index 7cdbdc97..576bc828 100644
--- a/src/management/instance-manager.ts
+++ b/src/management/instance-manager.ts
@@ -26,11 +26,13 @@ class InstanceManager {
   private readonly instancesDir: string;
   private readonly sharedManager: SharedManager;
   private readonly contextSyncLock: ProfileContextSyncLock;
+  private readonly pluginLayoutLock: ProfileContextSyncLock;
 
   constructor() {
     this.instancesDir = path.join(getCcsDir(), 'instances');
     this.sharedManager = new SharedManager();
     this.contextSyncLock = new ProfileContextSyncLock(this.instancesDir);
+    this.pluginLayoutLock = new ProfileContextSyncLock(this.instancesDir);
   }
 
   /**
@@ -56,9 +58,17 @@ class InstanceManager {
       // Apply context policy (isolated by default, optional shared group).
       await this.sharedManager.syncProjectContext(instancePath, contextPolicy);
       await this.sharedManager.syncAdvancedContinuityArtifacts(instancePath, contextPolicy);
-    });
 
-    this.sharedManager.normalizeSharedPluginMetadataPaths(instancePath);
+      await this.pluginLayoutLock.withNamedLock('__plugin-layout__', async () => {
+        if (!options.bare) {
+          this.sharedManager.linkSharedDirectories(instancePath);
+          return;
+        }
+
+        this.sharedManager.detachSharedDirectories(instancePath);
+        this.sharedManager.normalizeSharedPluginMetadataPaths();
+      });
+    });
 
     // Sync MCP servers from global ~/.claude.json (unless bare)
     if (!options.bare) {
@@ -82,7 +92,7 @@ class InstanceManager {
   private initializeInstance(
     profileName: string,
     instancePath: string,
-    options: InstanceOptions = {}
+    _options: InstanceOptions = {}
   ): void {
     try {
       // Create base directory
@@ -106,10 +116,7 @@ class InstanceManager {
         }
       });
 
-      // Bare profiles skip shared symlinks (commands, skills, agents, settings.json)
-      if (!options.bare) {
-        this.sharedManager.linkSharedDirectories(instancePath);
-      }
+      // Shared links are created during ensureInstance() under the plugin layout lock.
     } catch (error) {
       throw new Error(
         `Failed to initialize instance for ${profileName}: ${(error as Error).message}`
@@ -146,15 +153,22 @@ class InstanceManager {
   /**
    * Delete instance for profile
    */
-  deleteInstance(profileName: string): void {
+  async deleteInstance(profileName: string): Promise<void> {
     const instancePath = this.getInstancePath(profileName);
 
     if (!fs.existsSync(instancePath)) {
       return;
     }
 
-    // Recursive delete
-    fs.rmSync(instancePath, { recursive: true, force: true });
+    await this.contextSyncLock.withLock(profileName, async () => {
+      await this.pluginLayoutLock.withNamedLock('__plugin-layout__', async () => {
+        if (!fs.existsSync(instancePath)) {
+          return;
+        }
+
+        fs.rmSync(instancePath, { recursive: true, force: true });
+      });
+    });
   }
 
   /**
@@ -166,6 +180,10 @@ class InstanceManager {
     }
 
     return fs.readdirSync(this.instancesDir).filter((name) => {
+      if (name.startsWith('.')) {
+        return false;
+      }
+
       const instancePath = path.join(this.instancesDir, name);
       return fs.statSync(instancePath).isDirectory();
     });
diff --git a/src/management/profile-context-sync-lock.ts b/src/management/profile-context-sync-lock.ts
index c8158bc3..01727405 100644
--- a/src/management/profile-context-sync-lock.ts
+++ b/src/management/profile-context-sync-lock.ts
@@ -106,8 +106,8 @@ class ProfileContextSyncLock {
     return this.tryRemoveLockIfUnchanged(lockPath, snapshot.raw);
   }
 
-  async withLock<T>(profileName: string, callback: () => Promise<T>): Promise<T> {
-    const lockPath = this.getLockPath(profileName);
+  async withNamedLock<T>(lockName: string, callback: () => Promise<T>): Promise<T> {
+    const lockPath = this.getLockPath(lockName);
     const retryDelayMs = 50;
     const staleLockMs = 30000;
     const timeoutMs = staleLockMs + 5000;
@@ -159,7 +159,7 @@ class ProfileContextSyncLock {
         }
 
         if (Date.now() - start > timeoutMs) {
-          throw new Error(`Timed out waiting for profile context lock: ${profileName}`);
+          throw new Error(`Timed out waiting for profile context lock: ${lockName}`);
         }
 
         await new Promise((resolve) => setTimeout(resolve, retryDelayMs));
@@ -172,6 +172,85 @@ class ProfileContextSyncLock {
       this.tryRemoveLockIfUnchanged(lockPath, ownerPayloadRaw);
     }
   }
+
+  async withLock<T>(profileName: string, callback: () => Promise<T>): Promise<T> {
+    return this.withNamedLock(profileName, callback);
+  }
+
+  withNamedLockSync<T>(lockName: string, callback: () => T): T {
+    const lockPath = this.getLockPath(lockName);
+    const retryDelayMs = 50;
+    const staleLockMs = 30000;
+    const timeoutMs = staleLockMs + 5000;
+    const start = Date.now();
+    const ownerPayload: ContextSyncLockPayload = {
+      version: 1,
+      pid: process.pid,
+      nonce: createHash('sha1')
+        .update(`${process.pid}:${Date.now()}:${Math.random()}`)
+        .digest('hex')
+        .slice(0, 16),
+      acquiredAtMs: Date.now(),
+    };
+    const ownerPayloadRaw = JSON.stringify(ownerPayload);
+
+    fs.mkdirSync(this.locksDir, { recursive: true, mode: 0o700 });
+
+    while (true) {
+      try {
+        const fd = fs.openSync(lockPath, 'wx', 0o600);
+        fs.writeFileSync(fd, ownerPayloadRaw, 'utf8');
+        fs.closeSync(fd);
+        break;
+      } catch (error) {
+        const err = error as NodeJS.ErrnoException;
+        if (err.code !== 'EEXIST') {
+          throw error;
+        }
+
+        const lockSnapshot = this.readContextSyncLockSnapshot(lockPath);
+        if (lockSnapshot) {
+          if (this.tryRemoveDeadOwnerLock(lockPath, lockSnapshot)) {
+            continue;
+          }
+
+          if (!lockSnapshot.owner) {
+            try {
+              const lockStats = fs.statSync(lockPath);
+              if (Date.now() - lockStats.mtimeMs > staleLockMs) {
+                if (this.tryRemoveLockIfUnchanged(lockPath, lockSnapshot.raw)) {
+                  continue;
+                }
+              }
+            } catch {
+              // Best-effort stale lock cleanup.
+            }
+          }
+        }
+
+        if (Date.now() - start > timeoutMs) {
+          throw new Error(`Timed out waiting for profile context lock: ${lockName}`);
+        }
+
+        const until = Date.now() + retryDelayMs;
+        while (Date.now() < until) {
+          // Sync callers need a synchronous retry path here.
+          // This lock only guards short local filesystem normalization work, so
+          // contention should be brief and limited to profile/bootstrap edges.
+        }
+      }
+    }
+
+    try {
+      return callback();
+    } finally {
+      this.tryRemoveLockIfUnchanged(lockPath, ownerPayloadRaw);
+    }
+  }
+
+  withLockSync<T>(profileName: string, callback: () => T): T {
+    return this.withNamedLockSync(profileName, callback);
+  }
 }
 
 export default ProfileContextSyncLock;
diff --git a/src/management/shared-manager.ts b/src/management/shared-manager.ts
index cc617d3b..b4054c22 100644
--- a/src/management/shared-manager.ts
+++ b/src/management/shared-manager.ts
@@ -9,6 +9,7 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import * as os from 'os';
+import ProfileContextSyncLock from './profile-context-sync-lock';
 import { ok, info, warn } from '../utils/ui';
 import { AccountContextPolicy, DEFAULT_ACCOUNT_CONTEXT_GROUP } from '../auth/account-context';
 import { getCcsDir } from '../utils/config-manager';
@@ -18,23 +19,64 @@ interface SharedItem {
   type: 'directory' | 'file';
 }
 
-export function normalizePluginMetadataPathString(input: string): string {
-  return input.replace(
-    /([\\/])\.ccs\1instances\1[^\\/]+\1/g,
-    (_match, separator: string) => `${separator}.claude${separator}`
+const DEFAULT_INSTALLED_PLUGIN_REGISTRY = JSON.stringify(
+  {
+    version: 2,
+    plugins: {},
+  },
+  null,
+  2
+);
+
+function getPluginPathModule(
+  targetConfigDir: string,
+  input: string
+): typeof path.posix | typeof path.win32 {
+  return targetConfigDir.includes('\\') || input.includes('\\') ? path.win32 : path.posix;
+}
+
+function normalizeTargetConfigDir(targetConfigDir: string, input: string): string {
+  const pathModule = getPluginPathModule(targetConfigDir, input);
+  return pathModule.normalize(
+    pathModule === path.win32
+      ? targetConfigDir.replace(/\//g, '\\')
+      : targetConfigDir.replace(/\\/g, '/')
   );
 }
 
-function normalizePluginMetadataValue(value: unknown): { normalized: unknown; changed: boolean } {
+export function normalizePluginMetadataPathString(
+  input: string,
+  targetConfigDir = path.join(os.homedir(), '.claude')
+): string {
+  const match = input.match(
+    /^(.*?)([\\/])(?:\.claude|\.ccs\2shared|\.ccs\2instances\2[^\\/]+)\2plugins(?:(\2.*))?$/
+  );
+
+  if (!match) {
+    return input;
+  }
+
+  const pathModule = getPluginPathModule(targetConfigDir, input);
+  const normalizedTargetConfigDir = normalizeTargetConfigDir(targetConfigDir, input);
+  const suffix = match[3] ?? '';
+  const suffixSegments = suffix.split(/[\\/]+/).filter(Boolean);
+
+  return pathModule.join(normalizedTargetConfigDir, 'plugins', ...suffixSegments);
+}
+
+function normalizePluginMetadataValue(
+  value: unknown,
+  targetConfigDir: string
+): { normalized: unknown; changed: boolean } {
   if (typeof value === 'string') {
-    const normalized = normalizePluginMetadataPathString(value);
+    const normalized = normalizePluginMetadataPathString(value, targetConfigDir);
     return { normalized, changed: normalized !== value };
   }
 
   if (Array.isArray(value)) {
     let changed = false;
     const normalized = value.map((item) => {
-      const result = normalizePluginMetadataValue(item);
+      const result = normalizePluginMetadataValue(item, targetConfigDir);
       changed = changed || result.changed;
       return result.normalized;
     });
@@ -45,7 +87,7 @@ function normalizePluginMetadataValue(value: unknown): { normalized: unknown; ch
     let changed = false;
     const normalized = Object.fromEntries(
       Object.entries(value as Record<string, unknown>).map(([key, item]) => {
-        const result = normalizePluginMetadataValue(item);
+        const result = normalizePluginMetadataValue(item, targetConfigDir);
         changed = changed || result.changed;
         return [key, result.normalized];
       })
@@ -56,9 +98,12 @@ function normalizePluginMetadataValue(value: unknown): { normalized: unknown; ch
   return { normalized: value, changed: false };
 }
 
-export function normalizePluginMetadataContent(original: string): string {
+export function normalizePluginMetadataContent(
+  original: string,
+  targetConfigDir = path.join(os.homedir(), '.claude')
+): string {
   const parsed = JSON.parse(original) as unknown;
-  const result = normalizePluginMetadataValue(parsed);
+  const result = normalizePluginMetadataValue(parsed, targetConfigDir);
   return result.changed ? JSON.stringify(result.normalized, null, 2) : original;
 }
 
@@ -70,7 +115,14 @@ class SharedManager {
   private readonly sharedDir: string;
   private readonly claudeDir: string;
   private readonly instancesDir: string;
+  private readonly pluginLayoutLock: ProfileContextSyncLock;
   private readonly sharedItems: SharedItem[];
+  private readonly sharedPluginEntries: readonly SharedItem[] = [
+    { name: 'cache', type: 'directory' },
+    { name: 'marketplaces', type: 'directory' },
+    { name: 'installed_plugins.json', type: 'file' },
+  ];
+  private readonly instanceLocalPluginMetadataFiles = new Set(['known_marketplaces.json']);
   private readonly advancedContinuityItems: readonly string[] = [
     'session-env',
     'file-history',
@@ -84,6 +136,7 @@ class SharedManager {
     this.sharedDir = path.join(ccsDir, 'shared');
     this.claudeDir = path.join(this.homeDir, '.claude');
     this.instancesDir = path.join(ccsDir, 'instances');
+    this.pluginLayoutLock = new ProfileContextSyncLock(this.instancesDir);
     this.sharedItems = [
       { name: 'commands', type: 'directory' },
       { name: 'skills', type: 'directory' },
@@ -148,6 +201,8 @@ class SharedManager {
       fs.mkdirSync(this.sharedDir, { recursive: true, mode: 0o700 });
     }
 
+    this.ensureSharedPluginLayoutDefaults();
+
     // Create symlinks ~/.ccs/shared/* → ~/.claude/*
     for (const item of this.sharedItems) {
       const claudePath = path.join(this.claudeDir, item.name);
@@ -221,17 +276,15 @@ class SharedManager {
     this.ensureSharedDirectories();
 
     for (const item of this.sharedItems) {
+      if (item.name === 'plugins') {
+        this.linkInstancePlugins(instancePath);
+        continue;
+      }
+
       const linkPath = path.join(instancePath, item.name);
       const targetPath = path.join(this.sharedDir, item.name);
 
-      // Remove existing file/directory/link
-      if (fs.existsSync(linkPath)) {
-        if (item.type === 'directory') {
-          fs.rmSync(linkPath, { recursive: true, force: true });
-        } else {
-          fs.unlinkSync(linkPath);
-        }
-      }
+      this.removeExistingPath(linkPath, item.type);
 
       // Create symlink
       try {
@@ -257,6 +310,151 @@ class SharedManager {
     this.normalizeSharedPluginMetadataPaths(instancePath);
   }
 
+  detachSharedDirectories(instancePath: string): void {
+    this.ensureSharedDirectories();
+
+    for (const item of this.sharedItems) {
+      const managedPath = path.join(instancePath, item.name);
+      if (!fs.existsSync(managedPath)) {
+        continue;
+      }
+
+      if (item.name === 'plugins') {
+        this.detachManagedPluginLayout(instancePath);
+        continue;
+      }
+
+      const stats = fs.lstatSync(managedPath);
+      if (!stats.isSymbolicLink()) {
+        continue;
+      }
+
+      if (this.symlinkPointsTo(managedPath, path.join(this.sharedDir, item.name))) {
+        this.removeExistingPath(managedPath, item.type);
+      }
+    }
+  }
+
+  private ensureSharedPluginLayoutDefaults(): void {
+    const pluginsDir = path.join(this.claudeDir, 'plugins');
+    fs.mkdirSync(pluginsDir, { recursive: true, mode: 0o700 });
+
+    for (const entry of this.sharedPluginEntries) {
+      const entryPath = path.join(pluginsDir, entry.name);
+      if (fs.existsSync(entryPath)) {
+        continue;
+      }
+
+      if (entry.type === 'directory') {
+        fs.mkdirSync(entryPath, { recursive: true, mode: 0o700 });
+        continue;
+      }
+
+      fs.writeFileSync(entryPath, DEFAULT_INSTALLED_PLUGIN_REGISTRY, 'utf8');
+    }
+
+    const marketplaceRegistryPath = path.join(pluginsDir, 'known_marketplaces.json');
+    if (!fs.existsSync(marketplaceRegistryPath)) {
+      fs.writeFileSync(marketplaceRegistryPath, JSON.stringify({}, null, 2), 'utf8');
+    }
+  }
+
+  private linkInstancePlugins(instancePath: string): void {
+    const linkPath = path.join(instancePath, 'plugins');
+    const targetPath = path.join(this.sharedDir, 'plugins');
+    let linkStats: fs.Stats | null = null;
+
+    try {
+      linkStats = fs.lstatSync(linkPath);
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code !== 'ENOENT') {
+        throw err;
+      }
+    }
+
+    if (linkStats?.isSymbolicLink() || (linkStats && !linkStats.isDirectory())) {
+      this.removeExistingPath(linkPath, linkStats.isDirectory() ? 'directory' : 'file');
+    }
+
+    if (!linkStats || !linkStats.isDirectory()) {
+      fs.mkdirSync(linkPath, { recursive: true, mode: 0o700 });
+    }
+
+    for (const item of this.getSharedPluginLinkItems()) {
+      const targetEntryPath = path.join(targetPath, item.name);
+      const linkEntryPath = path.join(linkPath, item.name);
+
+      this.removeExistingPath(linkEntryPath, item.type);
+
+      try {
+        const symlinkType = item.type === 'directory' ? 'dir' : 'file';
+        fs.symlinkSync(targetEntryPath, linkEntryPath, symlinkType);
+      } catch (_err) {
+        if (process.platform === 'win32') {
+          if (item.type === 'directory') {
+            this.copyDirectoryFallback(targetEntryPath, linkEntryPath);
+          } else {
+            fs.copyFileSync(targetEntryPath, linkEntryPath);
+          }
+          console.log(
+            warn(`Symlink failed for plugins/${item.name}, copied instead (enable Developer Mode)`)
+          );
+        } else {
+          throw _err;
+        }
+      }
+    }
+  }
+
+  private getSharedPluginLinkItems(): SharedItem[] {
+    const sharedPluginsPath = path.join(this.sharedDir, 'plugins');
+    const items = new Map<string, SharedItem>(
+      this.sharedPluginEntries.map((entry) => [entry.name, { ...entry }])
+    );
+
+    for (const entry of fs.readdirSync(sharedPluginsPath, { withFileTypes: true })) {
+      if (items.has(entry.name) || this.instanceLocalPluginMetadataFiles.has(entry.name)) {
+        continue;
+      }
+
+      const entryPath = path.join(sharedPluginsPath, entry.name);
+      const stats = fs.statSync(entryPath);
+      items.set(entry.name, {
+        name: entry.name,
+        type: stats.isDirectory() ? 'directory' : 'file',
+      });
+    }
+
+    return [...items.values()];
+  }
+
+  private removeExistingPath(targetPath: string, typeHint: SharedItem['type']): void {
+    try {
+      const stats = fs.lstatSync(targetPath);
+      if (stats.isDirectory() && !stats.isSymbolicLink()) {
+        fs.rmSync(targetPath, { recursive: true, force: true });
+        return;
+      }
+
+      if (stats.isSymbolicLink() || typeHint === 'file') {
+        fs.unlinkSync(targetPath);
+        return;
+      }
+
+      fs.rmSync(targetPath, { recursive: true, force: true });
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+        return;
+      }
+
+      if (typeHint === 'directory') {
+        fs.rmSync(targetPath, { recursive: true, force: true });
+      } else {
+        fs.rmSync(targetPath, { force: true });
+      }
+    }
+  }
+
   /**
    * Sync project workspace context based on account policy.
    *
@@ -583,13 +781,19 @@ class SharedManager {
   }
 
   /**
-   * Normalize shared plugin metadata files to canonical ~/.claude/ paths.
+   * Normalize plugin metadata and reconcile marketplace metadata for the active config dir.
    */
   normalizeSharedPluginMetadataPaths(configDir?: string): void {
     this.normalizePluginRegistryPaths(configDir);
     this.normalizeMarketplaceRegistryPaths(configDir);
   }
 
+  normalizeSharedPluginMetadataPathsLocked(configDir?: string): void {
+    this.pluginLayoutLock.withNamedLockSync('__plugin-layout__', () => {
+      this.normalizeSharedPluginMetadataPaths(configDir);
+    });
+  }
+
   /**
    * Normalize plugin registry paths to use canonical ~/.claude/ paths
    * instead of instance-specific ~/.ccs/instances/<name>/ paths.
@@ -607,19 +811,31 @@ class SharedManager {
   }
 
   /**
-   * Normalize marketplace registry paths to use canonical ~/.claude/ paths
-   * instead of instance-specific ~/.ccs/instances/<name>/ paths.
-   *
-   * This ensures known_marketplaces.json is consistent regardless of
-   * which CCS instance added the marketplace.
+   * Reconcile marketplace registry content into the active config dir while
+   * keeping the global ~/.claude copy up to date for non-instance flows.
    */
   normalizeMarketplaceRegistryPaths(configDir?: string): void {
-    this.normalizePluginMetadataFiles(
-      'known_marketplaces.json',
-      configDir,
-      'Normalized marketplace registry paths',
-      'marketplace registry'
-    );
+    const successMessage = 'Synchronized marketplace registry paths';
+    const warningLabel = 'marketplace registry';
+
+    try {
+      const sourcePaths = this.getMarketplaceRegistrySourcePaths(configDir);
+      this.writePluginMetadataFile(
+        path.join(this.claudeDir, 'plugins', 'known_marketplaces.json'),
+        this.buildMarketplaceRegistryContent(sourcePaths, this.claudeDir),
+        successMessage
+      );
+
+      if (configDir && path.resolve(configDir) !== path.resolve(this.claudeDir)) {
+        this.writePluginMetadataFile(
+          path.join(configDir, 'plugins', 'known_marketplaces.json'),
+          this.buildMarketplaceRegistryContent(sourcePaths, configDir),
+          successMessage
+        );
+      }
+    } catch (err) {
+      console.log(warn(`Could not synchronize ${warningLabel}: ${(err as Error).message}`));
+    }
   }
 
   private normalizePluginMetadataFiles(
@@ -676,6 +892,117 @@ class SharedManager {
     }
   }
 
+  private getMarketplaceRegistrySourcePaths(configDir?: string): string[] {
+    const sourcePaths = new Set<string>([
+      path.join(this.claudeDir, 'plugins', 'known_marketplaces.json'),
+    ]);
+
+    if (fs.existsSync(this.instancesDir)) {
+      for (const entry of fs.readdirSync(this.instancesDir, { withFileTypes: true })) {
+        if (!entry.isDirectory() || entry.name.startsWith('.')) {
+          continue;
+        }
+
+        sourcePaths.add(
+          path.join(this.instancesDir, entry.name, 'plugins', 'known_marketplaces.json')
+        );
+      }
+    }
+
+    if (configDir && path.resolve(configDir) !== path.resolve(this.claudeDir)) {
+      sourcePaths.add(path.join(configDir, 'plugins', 'known_marketplaces.json'));
+    }
+
+    return [...sourcePaths];
+  }
+
+  private buildMarketplaceRegistryContent(sourcePaths: string[], targetConfigDir: string): string {
+    const merged: Record<string, unknown> = {};
+
+    for (const registryPath of sourcePaths) {
+      if (!fs.existsSync(registryPath)) {
+        continue;
+      }
+
+      try {
+        const parsed = JSON.parse(fs.readFileSync(registryPath, 'utf8')) as unknown;
+        if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) {
+          continue;
+        }
+
+        for (const [name, value] of Object.entries(parsed as Record<string, unknown>)) {
+          merged[name] = normalizePluginMetadataValue(value, targetConfigDir).normalized;
+        }
+      } catch (err) {
+        console.log(
+          warn(`Skipping malformed marketplace registry ${registryPath}: ${(err as Error).message}`)
+        );
+      }
+    }
+
+    const discoveredEntries = this.discoverMarketplaceEntries(targetConfigDir);
+
+    for (const [name, value] of Object.entries(discoveredEntries)) {
+      const existing = merged[name];
+      if (existing && typeof existing === 'object' && !Array.isArray(existing)) {
+        merged[name] = {
+          ...(existing as Record<string, unknown>),
+          installLocation: value.installLocation,
+        };
+        continue;
+      }
+
+      merged[name] = value;
+    }
+
+    for (const name of Object.keys(merged)) {
+      if (!(name in discoveredEntries)) {
+        delete merged[name];
+      }
+    }
+
+    return JSON.stringify(merged, null, 2);
+  }
+
+  private discoverMarketplaceEntries(
+    targetConfigDir: string
+  ): Record<string, { installLocation: string }> {
+    const marketplacesDir = path.join(targetConfigDir, 'plugins', 'marketplaces');
+    if (!fs.existsSync(marketplacesDir)) {
+      return {};
+    }
+
+    const discovered: Record<string, { installLocation: string }> = {};
+
+    for (const entry of fs.readdirSync(marketplacesDir, { withFileTypes: true })) {
+      if (!entry.isDirectory()) {
+        continue;
+      }
+
+      discovered[entry.name] = {
+        installLocation: path.join(targetConfigDir, 'plugins', 'marketplaces', entry.name),
+      };
+    }
+
+    return discovered;
+  }
+
+  private writePluginMetadataFile(
+    registryPath: string,
+    content: string,
+    successMessage: string
+  ): void {
+    fs.mkdirSync(path.dirname(registryPath), { recursive: true, mode: 0o700 });
+    const current = fs.existsSync(registryPath) ? fs.readFileSync(registryPath, 'utf8') : null;
+
+    if (current === content) {
+      return;
+    }
+
+    fs.writeFileSync(registryPath, content, 'utf8');
+    console.log(ok(successMessage));
+  }
+
   /**
    * Migrate from v3.1.1 (copied data in ~/.ccs/shared/) to v3.2.0 (symlinks to ~/.claude/)
    * Runs once on upgrade
@@ -1157,6 +1484,118 @@ class SharedManager {
     return candidate;
   }
 
+  private symlinkPointsTo(linkPath: string, expectedTarget: string): boolean {
+    try {
+      const currentTarget = fs.readlinkSync(linkPath);
+      const resolvedCurrentTarget = path.resolve(path.dirname(linkPath), currentTarget);
+      return (
+        this.resolveCanonicalPath(resolvedCurrentTarget) ===
+        this.resolveCanonicalPath(expectedTarget)
+      );
+    } catch {
+      return false;
+    }
+  }
+
+  private detachManagedPluginLayout(instancePath: string): void {
+    const pluginsPath = path.join(instancePath, 'plugins');
+    if (!fs.existsSync(pluginsPath)) {
+      return;
+    }
+
+    const stats = fs.lstatSync(pluginsPath);
+    const sharedPluginsPath = path.join(this.sharedDir, 'plugins');
+
+    if (stats.isSymbolicLink()) {
+      if (this.symlinkPointsTo(pluginsPath, sharedPluginsPath)) {
+        this.removeExistingPath(pluginsPath, 'directory');
+      }
+      return;
+    }
+
+    if (!stats.isDirectory()) {
+      return;
+    }
+
+    let removedManagedEntries = false;
+
+    for (const item of this.getSharedPluginLinkItems()) {
+      const pluginEntryPath = path.join(pluginsPath, item.name);
+      if (!fs.existsSync(pluginEntryPath)) {
+        continue;
+      }
+
+      const entryStats = fs.lstatSync(pluginEntryPath);
+      if (!entryStats.isSymbolicLink()) {
+        continue;
+      }
+
+      if (this.symlinkPointsTo(pluginEntryPath, path.join(sharedPluginsPath, item.name))) {
+        this.removeExistingPath(pluginEntryPath, item.type);
+        removedManagedEntries = true;
+      }
+    }
+
+    if (!removedManagedEntries) {
+      return;
+    }
+
+    this.reconcileLocalMarketplaceRegistry(instancePath);
+
+    if (fs.readdirSync(pluginsPath).length === 0) {
+      fs.rmSync(pluginsPath, { recursive: true, force: true });
+    }
+  }
+
+  private reconcileLocalMarketplaceRegistry(configDir: string): void {
+    const registryPath = path.join(configDir, 'plugins', 'known_marketplaces.json');
+    if (!fs.existsSync(registryPath)) {
+      return;
+    }
+
+    const discoveredEntries = this.discoverMarketplaceEntries(configDir);
+    if (Object.keys(discoveredEntries).length === 0) {
+      this.removeExistingPath(registryPath, 'file');
+      return;
+    }
+
+    let parsed: Record<string, unknown> = {};
+    try {
+      const raw = JSON.parse(fs.readFileSync(registryPath, 'utf8')) as unknown;
+      if (raw && typeof raw === 'object' && !Array.isArray(raw)) {
+        parsed = raw as Record<string, unknown>;
+      }
+    } catch {
+      parsed = {};
+    }
+
+    const reconciled = Object.fromEntries(
+      Object.entries(discoveredEntries).map(([name, value]) => {
+        const existing = parsed[name];
+        if (existing && typeof existing === 'object' && !Array.isArray(existing)) {
+          return [
+            name,
+            {
+              ...(normalizePluginMetadataValue(existing, configDir).normalized as Record<
+                string,
+                unknown
+              >),
+              installLocation: value.installLocation,
+            },
+          ];
+        }
+
+        return [name, value];
+      })
+    );
+
+    this.writePluginMetadataFile(
+      registryPath,
+      JSON.stringify(reconciled, null, 2),
+      'Synchronized marketplace registry paths'
+    );
+  }
+
   private resolveCanonicalPath(targetPath: string): string {
     try {
       return fs.realpathSync.native(targetPath);
diff --git a/src/shared/claude-extension-setup.ts b/src/shared/claude-extension-setup.ts
index 784c8560..9f6a9385 100644
--- a/src/shared/claude-extension-setup.ts
+++ b/src/shared/claude-extension-setup.ts
@@ -168,7 +168,7 @@ async function resolveExtensionEnv(
       profileType: result.type,
       target: 'claude',
     });
-    new SharedManager().normalizeSharedPluginMetadataPaths(continuity.claudeConfigDir);
+    new SharedManager().normalizeSharedPluginMetadataPathsLocked(continuity.claudeConfigDir);
     if (continuity.claudeConfigDir) {
       notes.push(`Default profile inherits continuity from account "${continuity.sourceAccount}".`);
       return {
@@ -250,7 +250,7 @@ async function resolveExtensionEnv(
     );
   }
 
-  new SharedManager().normalizeSharedPluginMetadataPaths(env.CLAUDE_CONFIG_DIR);
+  new SharedManager().normalizeSharedPluginMetadataPathsLocked(env.CLAUDE_CONFIG_DIR);
 
   if (result.type === 'copilot') {
     warnings.push(
diff --git a/src/utils/shell-executor.ts b/src/utils/shell-executor.ts
index 16861f00..ff96458e 100644
--- a/src/utils/shell-executor.ts
+++ b/src/utils/shell-executor.ts
@@ -125,7 +125,7 @@ export function execClaude(
 
   if (profileType !== 'account') {
     try {
-      new SharedManager().normalizeSharedPluginMetadataPaths(env.CLAUDE_CONFIG_DIR);
+      new SharedManager().normalizeSharedPluginMetadataPathsLocked(env.CLAUDE_CONFIG_DIR);
     } catch {
       // Best-effort normalization should never block Claude launch.
     }
diff --git a/src/web-server/routes/account-routes.ts b/src/web-server/routes/account-routes.ts
index daa9c71a..147de4c8 100644
--- a/src/web-server/routes/account-routes.ts
+++ b/src/web-server/routes/account-routes.ts
@@ -324,7 +324,7 @@ router.delete('/reset-default', (_req: Request, res: Response): void => {
 /**
  * DELETE /api/accounts/:name - Delete an account
  */
-router.delete('/:name', (req: Request, res: Response): void => {
+router.delete('/:name', async (req: Request, res: Response): Promise<void> => {
   try {
     const { name } = req.params;
 
@@ -371,7 +371,7 @@ router.delete('/:name', (req: Request, res: Response): void => {
     }
 
     // Match CLI remove ordering: delete instance first, metadata second.
-    instanceMgr.deleteInstance(name);
+    await instanceMgr.deleteInstance(name);
 
     if (existsUnified) {
       registry.removeAccountUnified(name);
diff --git a/tests/unit/instance-manager-mcp-sync.test.ts b/tests/unit/instance-manager-mcp-sync.test.ts
index 1a39e803..8eec45a7 100644
--- a/tests/unit/instance-manager-mcp-sync.test.ts
+++ b/tests/unit/instance-manager-mcp-sync.test.ts
@@ -11,6 +11,16 @@ describe('InstanceManager MCP sync', () => {
   let originalCcsHome: string | undefined;
   let originalCcsDir: string | undefined;
 
+  const claudeDir = () => path.join(tempRoot, '.claude');
+  const marketplacePath = (configDir: string, name = 'claude-code-plugins') =>
+    path.join(configDir, 'plugins', 'marketplaces', name);
+  const readJson = (filePath: string) =>
+    JSON.parse(fs.readFileSync(filePath, 'utf8')) as Record<string, unknown>;
+
+  function ensureMarketplacePayload(configDir: string, name = 'claude-code-plugins'): void {
+    fs.mkdirSync(marketplacePath(configDir, name), { recursive: true });
+  }
+
   function writeMarketplaceRegistry(registryPath: string, installLocation: string): void {
     fs.mkdirSync(path.dirname(registryPath), { recursive: true });
     fs.writeFileSync(
@@ -28,6 +38,33 @@ describe('InstanceManager MCP sync', () => {
     );
   }
 
+  function writeMarketplaceRegistryWithMetadata(
+    registryPath: string,
+    installLocation: string,
+    metadata: Record<string, unknown>
+  ): void {
+    fs.mkdirSync(path.dirname(registryPath), { recursive: true });
+    fs.writeFileSync(
+      registryPath,
+      JSON.stringify(
+        {
+          'claude-code-plugins': {
+            installLocation,
+            ...metadata,
+          },
+        },
+        null,
+        2
+      ),
+      'utf8'
+    );
+  }
+
+  function expectMarketplaceLocation(registryPath: string, expectedLocation: string): void {
+    const parsed = readJson(registryPath) as Record<string, { installLocation?: string }>;
+    expect(parsed['claude-code-plugins']?.installLocation).toBe(expectedLocation);
+  }
+
   beforeEach(() => {
     tempRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-instance-mcp-test-'));
     originalHome = process.env.HOME;
@@ -95,9 +132,10 @@ describe('InstanceManager MCP sync', () => {
     const synced = manager.syncMcpServers(instancePath);
     expect(synced).toBe(true);
 
-    const instanceContent = JSON.parse(
-      fs.readFileSync(path.join(instancePath, '.claude.json'), 'utf8')
-    );
+    const instanceContent = readJson(path.join(instancePath, '.claude.json')) as {
+      otherKey: string;
+      mcpServers: Record<string, { command: string }>;
+    };
     expect(instanceContent.otherKey).toBe('keep-me');
     expect(instanceContent.mcpServers).toEqual({
       globalOnly: { command: 'global-cmd' },
@@ -121,6 +159,17 @@ describe('InstanceManager MCP sync', () => {
     expect(String(warnSpy.mock.calls[0]?.[0] || '')).toContain('MCP sync skipped');
   });
 
+  it('does not list lock housekeeping as an instance', async () => {
+    spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
+    spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
+    spyOn(InstanceManager.prototype, 'syncMcpServers').mockImplementation(() => false);
+
+    const manager = new InstanceManager();
+    await manager.ensureInstance('work', { mode: 'isolated' });
+
+    expect(manager.listInstances()).toEqual(['work']);
+  });
+
   it('skips shared symlinks and MCP sync for bare instance creation', async () => {
     const linkSharedSpy = spyOn(
       SharedManager.prototype,
@@ -134,9 +183,10 @@ describe('InstanceManager MCP sync', () => {
 
     const manager = new InstanceManager();
     const instancePath = manager.getInstancePath('sandbox');
-    const sharedRegistryPath = path.join(tempRoot, '.claude', 'plugins', 'known_marketplaces.json');
+    const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+    ensureMarketplacePayload(claudeDir());
     writeMarketplaceRegistry(
-      sharedRegistryPath,
+      globalRegistryPath,
       path.join(
         tempRoot,
         '.ccs',
@@ -150,20 +200,100 @@ describe('InstanceManager MCP sync', () => {
 
     await manager.ensureInstance('sandbox', { mode: 'isolated' }, { bare: true });
 
-    const normalized = JSON.parse(fs.readFileSync(sharedRegistryPath, 'utf8'));
-
     expect(linkSharedSpy).not.toHaveBeenCalled();
     expect(fs.existsSync(instancePath)).toBe(true);
-    expect(normalized['claude-code-plugins'].installLocation).toBe(
-      path.join(tempRoot, '.claude', 'plugins', 'marketplaces', 'claude-code-plugins')
-    );
+    expectMarketplaceLocation(globalRegistryPath, marketplacePath(claudeDir()));
     expect(fs.existsSync(path.join(instancePath, 'plugins', 'known_marketplaces.json'))).toBe(
       false
     );
     expect(syncMcpSpy).not.toHaveBeenCalled();
   });
 
-  it('normalizes shared plugin metadata for existing non-bare instances', async () => {
+  it('detaches existing shared layout when an instance is reopened as bare', async () => {
+    spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
+    spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
+    const syncMcpSpy = spyOn(InstanceManager.prototype, 'syncMcpServers').mockImplementation(
+      () => false
+    );
+
+    const manager = new InstanceManager();
+    const instancePath = await manager.ensureInstance('work', { mode: 'isolated' });
+    syncMcpSpy.mockClear();
+
+    await manager.ensureInstance('work', { mode: 'isolated' }, { bare: true });
+
+    expect(fs.existsSync(path.join(instancePath, 'settings.json'))).toBe(false);
+    expect(fs.existsSync(path.join(instancePath, 'commands'))).toBe(false);
+    expect(fs.existsSync(path.join(instancePath, 'skills'))).toBe(false);
+    expect(fs.existsSync(path.join(instancePath, 'agents'))).toBe(false);
+    expect(fs.existsSync(path.join(instancePath, 'plugins'))).toBe(false);
+    expect(syncMcpSpy).not.toHaveBeenCalled();
+  });
+
+  it('restores the shared layout when a bare-reopened instance is switched back to non-bare', async () => {
+    spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
+    spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
+    const syncMcpSpy = spyOn(InstanceManager.prototype, 'syncMcpServers').mockImplementation(
+      () => false
+    );
+
+    const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+    ensureMarketplacePayload(claudeDir());
+    writeMarketplaceRegistry(globalRegistryPath, marketplacePath(claudeDir()));
+
+    const manager = new InstanceManager();
+    const instancePath = await manager.ensureInstance('work', { mode: 'isolated' });
+    await manager.ensureInstance('work', { mode: 'isolated' }, { bare: true });
+    syncMcpSpy.mockClear();
+
+    await manager.ensureInstance('work', { mode: 'isolated' });
+
+    expect(fs.lstatSync(path.join(instancePath, 'settings.json')).isSymbolicLink()).toBe(true);
+    expectMarketplaceLocation(
+      path.join(instancePath, 'plugins', 'known_marketplaces.json'),
+      marketplacePath(instancePath)
+    );
+    expect(syncMcpSpy).toHaveBeenCalledWith(instancePath);
+  });
+
+  it('preserves genuine bare-local content when re-ensuring a bare instance', async () => {
+    spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
+    spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
+    const syncMcpSpy = spyOn(InstanceManager.prototype, 'syncMcpServers').mockImplementation(
+      () => false
+    );
+
+    const manager = new InstanceManager();
+    const instancePath = manager.getInstancePath('sandbox');
+    fs.mkdirSync(path.join(instancePath, 'plugins', 'marketplaces', 'custom-market'), {
+      recursive: true,
+    });
+    fs.mkdirSync(path.join(instancePath, 'commands'), { recursive: true });
+    fs.writeFileSync(
+      path.join(instancePath, 'settings.json'),
+      JSON.stringify({ local: true }, null, 2),
+      'utf8'
+    );
+    fs.writeFileSync(path.join(instancePath, 'commands', 'local.md'), '# local', 'utf8');
+    writeMarketplaceRegistry(
+      path.join(instancePath, 'plugins', 'known_marketplaces.json'),
+      marketplacePath(instancePath, 'custom-market')
+    );
+
+    await manager.ensureInstance('sandbox', { mode: 'isolated' }, { bare: true });
+
+    expect(readJson(path.join(instancePath, 'settings.json'))).toEqual({ local: true });
+    expect(fs.readFileSync(path.join(instancePath, 'commands', 'local.md'), 'utf8')).toBe(
+      '# local'
+    );
+    expectMarketplaceLocation(
+      path.join(instancePath, 'plugins', 'known_marketplaces.json'),
+      marketplacePath(instancePath, 'custom-market')
+    );
+    expect(syncMcpSpy).not.toHaveBeenCalled();
+  });
+
+  it('rewrites existing non-bare instance marketplace metadata to the instance-local plugin dir', async () => {
     spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
     spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
     const syncMcpSpy = spyOn(InstanceManager.prototype, 'syncMcpServers').mockImplementation(
@@ -172,40 +302,32 @@ describe('InstanceManager MCP sync', () => {
 
     const manager = new InstanceManager();
     const instancePath = manager.getInstancePath('work');
+    ensureMarketplacePayload(claudeDir());
     writeMarketplaceRegistry(
       path.join(instancePath, 'plugins', 'known_marketplaces.json'),
-      path.join(
-        tempRoot,
-        '.ccs',
-        'instances',
-        'work',
-        'plugins',
-        'marketplaces',
-        'claude-code-plugins'
-      )
+      path.join(tempRoot, '.claude', 'plugins', 'marketplaces', 'claude-code-plugins')
     );
 
     await manager.ensureInstance('work', { mode: 'isolated' });
 
-    const normalized = JSON.parse(
-      fs.readFileSync(path.join(instancePath, 'plugins', 'known_marketplaces.json'), 'utf8')
-    );
-    expect(normalized['claude-code-plugins'].installLocation).toBe(
-      path.join(tempRoot, '.claude', 'plugins', 'marketplaces', 'claude-code-plugins')
+    expectMarketplaceLocation(
+      path.join(instancePath, 'plugins', 'known_marketplaces.json'),
+      marketplacePath(instancePath)
     );
     expect(syncMcpSpy).toHaveBeenCalledWith(instancePath);
   });
 
-  it('normalizes shared plugin metadata during new non-bare instance creation', async () => {
+  it('writes new non-bare instance marketplace metadata without clobbering the global copy', async () => {
     spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
     spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
     const syncMcpSpy = spyOn(InstanceManager.prototype, 'syncMcpServers').mockImplementation(
       () => false
     );
 
-    const registryPath = path.join(tempRoot, '.claude', 'plugins', 'known_marketplaces.json');
+    const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+    ensureMarketplacePayload(claudeDir());
     writeMarketplaceRegistry(
-      registryPath,
+      globalRegistryPath,
       path.join(
         tempRoot,
         '.ccs',
@@ -220,20 +342,110 @@ describe('InstanceManager MCP sync', () => {
     const manager = new InstanceManager();
     const instancePath = await manager.ensureInstance('work', { mode: 'isolated' });
 
-    const expected = path.join(
-      tempRoot,
-      '.claude',
-      'plugins',
-      'marketplaces',
-      'claude-code-plugins'
+    expectMarketplaceLocation(globalRegistryPath, marketplacePath(claudeDir()));
+    expectMarketplaceLocation(
+      path.join(instancePath, 'plugins', 'known_marketplaces.json'),
+      marketplacePath(instancePath)
     );
-    const normalizedShared = JSON.parse(fs.readFileSync(registryPath, 'utf8'));
-    const normalizedInstance = JSON.parse(
-      fs.readFileSync(path.join(instancePath, 'plugins', 'known_marketplaces.json'), 'utf8')
-    );
-
-    expect(normalizedShared['claude-code-plugins'].installLocation).toBe(expected);
-    expect(normalizedInstance['claude-code-plugins'].installLocation).toBe(expected);
     expect(syncMcpSpy).toHaveBeenCalledWith(instancePath);
   });
+
+  it('reconciles marketplace metadata across isolated instances without losing refresh fields', async () => {
+    spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
+    spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
+
+    const manager = new InstanceManager();
+    ensureMarketplacePayload(claudeDir());
+    const workPath = await manager.ensureInstance('work', { mode: 'isolated' });
+    const workRegistryPath = path.join(workPath, 'plugins', 'known_marketplaces.json');
+    writeMarketplaceRegistryWithMetadata(workRegistryPath, marketplacePath(workPath), {
+      label: 'Official marketplace',
+      refreshToken: 'refresh-token',
+      metadata: {
+        source: 'refresh-flow',
+        lastSyncedAt: '2026-03-18T00:00:00Z',
+      },
+    });
+
+    const personalPath = await manager.ensureInstance('personal', { mode: 'isolated' });
+    const workRegistry = readJson(workRegistryPath) as Record<
+      string,
+      {
+        installLocation?: string;
+        label?: string;
+        refreshToken?: string;
+        metadata?: Record<string, unknown>;
+      }
+    >;
+    const personalRegistry = readJson(path.join(personalPath, 'plugins', 'known_marketplaces.json')) as Record<
+      string,
+      {
+        installLocation?: string;
+        label?: string;
+        refreshToken?: string;
+        metadata?: Record<string, unknown>;
+      }
+    >;
+
+    expect(workRegistry['claude-code-plugins']).toMatchObject({
+      installLocation: marketplacePath(workPath),
+      label: 'Official marketplace',
+      refreshToken: 'refresh-token',
+      metadata: {
+        source: 'refresh-flow',
+        lastSyncedAt: '2026-03-18T00:00:00Z',
+      },
+    });
+    expect(personalRegistry['claude-code-plugins']).toMatchObject({
+      installLocation: marketplacePath(personalPath),
+      label: 'Official marketplace',
+      refreshToken: 'refresh-token',
+      metadata: {
+        source: 'refresh-flow',
+        lastSyncedAt: '2026-03-18T00:00:00Z',
+      },
+    });
+  });
+
+  it('upgrades a legacy shared plugins symlink to an instance-local layout', async () => {
+    spyOn(SharedManager.prototype, 'syncProjectContext').mockResolvedValue(undefined);
+    spyOn(SharedManager.prototype, 'syncAdvancedContinuityArtifacts').mockResolvedValue(undefined);
+
+    const manager = new InstanceManager();
+    const legacyPath = manager.getInstancePath('legacy');
+    const sharedPluginsPath = path.join(tempRoot, '.ccs', 'shared', 'plugins');
+    fs.mkdirSync(sharedPluginsPath, { recursive: true });
+    fs.mkdirSync(legacyPath, { recursive: true });
+    fs.symlinkSync(sharedPluginsPath, path.join(legacyPath, 'plugins'), 'dir');
+
+    ensureMarketplacePayload(claudeDir());
+    writeMarketplaceRegistryWithMetadata(
+      path.join(claudeDir(), 'plugins', 'known_marketplaces.json'),
+      path.join(tempRoot, '.ccs', 'shared', 'plugins', 'marketplaces', 'claude-code-plugins'),
+      {
+        label: 'Legacy marketplace',
+        refreshToken: 'legacy-refresh-token',
+      }
+    );
+
+    await manager.ensureInstance('legacy', { mode: 'isolated' });
+
+    expect(fs.lstatSync(path.join(legacyPath, 'plugins')).isSymbolicLink()).toBe(false);
+    expectMarketplaceLocation(
+      path.join(legacyPath, 'plugins', 'known_marketplaces.json'),
+      marketplacePath(legacyPath)
+    );
+
+    const legacyRegistry = readJson(
+      path.join(legacyPath, 'plugins', 'known_marketplaces.json')
+    ) as Record<
+      string,
+      { installLocation?: string; label?: string; refreshToken?: string }
+    >;
+    expect(legacyRegistry['claude-code-plugins']).toMatchObject({
+      installLocation: marketplacePath(legacyPath),
+      label: 'Legacy marketplace',
+      refreshToken: 'legacy-refresh-token',
+    });
+  });
 });
diff --git a/tests/unit/profile-context-sync-lock.test.ts b/tests/unit/profile-context-sync-lock.test.ts
new file mode 100644
index 00000000..323810e7
--- /dev/null
+++ b/tests/unit/profile-context-sync-lock.test.ts
@@ -0,0 +1,94 @@
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import { createHash } from 'crypto';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import ProfileContextSyncLock from '../../src/management/profile-context-sync-lock';
+
+describe('ProfileContextSyncLock', () => {
+  let tempRoot = '';
+  let instancesDir = '';
+
+  const getLockPath = (lockName: string): string => {
+    const safeName = lockName.replace(/[^a-zA-Z0-9_-]/g, '-').toLowerCase();
+    const profileHash = createHash('sha1').update(lockName).digest('hex').slice(0, 8);
+    return path.join(instancesDir, '.locks', `${safeName}-${profileHash}.lock`);
+  };
+
+  beforeEach(() => {
+    tempRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-context-lock-test-'));
+    instancesDir = path.join(tempRoot, 'instances');
+    fs.mkdirSync(instancesDir, { recursive: true });
+  });
+
+  afterEach(() => {
+    if (tempRoot && fs.existsSync(tempRoot)) {
+      fs.rmSync(tempRoot, { recursive: true, force: true });
+    }
+  });
+
+  it('acquires and releases synchronous named locks', () => {
+    const lock = new ProfileContextSyncLock(instancesDir);
+    const lockPath = getLockPath('__plugin-layout__');
+
+    let sawLockInsideCallback = false;
+    const result = lock.withNamedLockSync('__plugin-layout__', () => {
+      sawLockInsideCallback = fs.existsSync(lockPath);
+      expect(fs.readFileSync(lockPath, 'utf8')).toContain(`"pid":${process.pid}`);
+      return 'ok';
+    });
+
+    expect(result).toBe('ok');
+    expect(sawLockInsideCallback).toBe(true);
+    expect(fs.existsSync(lockPath)).toBe(false);
+  });
+
+  it('releases synchronous named locks when the callback throws', () => {
+    const lock = new ProfileContextSyncLock(instancesDir);
+    const lockPath = getLockPath('__plugin-layout__');
+
+    expect(() =>
+      lock.withNamedLockSync('__plugin-layout__', () => {
+        throw new Error('boom');
+      })
+    ).toThrow('boom');
+    expect(fs.existsSync(lockPath)).toBe(false);
+  });
+
+  it('reclaims dead-owner locks before entering the callback', () => {
+    const lock = new ProfileContextSyncLock(instancesDir);
+    const lockPath = getLockPath('__plugin-layout__');
+
+    fs.mkdirSync(path.dirname(lockPath), { recursive: true });
+    fs.writeFileSync(
+      lockPath,
+      JSON.stringify({
+        version: 1,
+        pid: 999999,
+        nonce: 'dead-owner',
+        acquiredAtMs: Date.now() - 1000,
+      }),
+      'utf8'
+    );
+
+    const result = lock.withNamedLockSync('__plugin-layout__', () => 'reclaimed');
+
+    expect(result).toBe('reclaimed');
+    expect(fs.existsSync(lockPath)).toBe(false);
+  });
+
+  it('reclaims malformed stale locks before entering the callback', () => {
+    const lock = new ProfileContextSyncLock(instancesDir);
+    const lockPath = getLockPath('__plugin-layout__');
+    const staleDate = new Date(Date.now() - 60_000);
+
+    fs.mkdirSync(path.dirname(lockPath), { recursive: true });
+    fs.writeFileSync(lockPath, 'not-json', 'utf8');
+    fs.utimesSync(lockPath, staleDate, staleDate);
+
+    const result = lock.withNamedLockSync('__plugin-layout__', () => 'stale-reclaimed');
+
+    expect(result).toBe('stale-reclaimed');
+    expect(fs.existsSync(lockPath)).toBe(false);
+  });
+});
diff --git a/tests/unit/shared-manager.test.ts b/tests/unit/shared-manager.test.ts
index 96ee5eee..3cd142f8 100644
--- a/tests/unit/shared-manager.test.ts
+++ b/tests/unit/shared-manager.test.ts
@@ -1,19 +1,12 @@
-/**
- * Unit tests for SharedManager - plugin registry path normalization
- */
-import { describe, it, expect, beforeEach, afterEach, mock, spyOn } from 'bun:test';
+import { afterEach, beforeEach, describe, expect, it, mock, spyOn } from 'bun:test';
 import * as fs from 'fs';
-import * as path from 'path';
 import * as os from 'os';
+import * as path from 'path';
 import SharedManager, {
+  normalizePluginMetadataContent,
   normalizePluginMetadataPathString,
 } from '../../src/management/shared-manager';
 
-// Test the normalization regex pattern directly
-const normalizePluginPaths = (content: string): string => {
-  return normalizePluginMetadataPathString(content);
-};
-
 describe('SharedManager', () => {
   let tempRoot = '';
   let originalHome: string | undefined;
@@ -21,6 +14,28 @@ describe('SharedManager', () => {
   let originalCcsDir: string | undefined;
   let originalPlatform: PropertyDescriptor | undefined;
 
+  const claudeDir = () => path.join(tempRoot, '.claude');
+  const ccsDir = () => path.join(tempRoot, '.ccs');
+  const instanceDir = (name: string) => path.join(ccsDir(), 'instances', name);
+  const marketplacePath = (configDir: string, name = 'claude-code-plugins') =>
+    path.join(configDir, 'plugins', 'marketplaces', name);
+  const readJson = (filePath: string) =>
+    JSON.parse(fs.readFileSync(filePath, 'utf8')) as Record<string, unknown>;
+
+  function ensureMarketplacePayload(configDir: string, name = 'claude-code-plugins'): void {
+    fs.mkdirSync(marketplacePath(configDir, name), { recursive: true });
+  }
+
+  function writeJson(filePath: string, value: unknown): void {
+    fs.mkdirSync(path.dirname(filePath), { recursive: true });
+    fs.writeFileSync(filePath, JSON.stringify(value, null, 2), 'utf8');
+  }
+
+  function readMarketplaceLocation(filePath: string, name = 'claude-code-plugins'): string {
+    const parsed = readJson(filePath) as Record<string, { installLocation?: string }>;
+    return parsed[name]?.installLocation ?? '';
+  }
+
   beforeEach(() => {
     tempRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-shared-manager-test-'));
     originalHome = process.env.HOME;
@@ -55,218 +70,244 @@ describe('SharedManager', () => {
     }
   });
 
-  describe('normalizePluginRegistryPaths', () => {
-    describe('regex pattern', () => {
-      it('should replace instance paths with canonical claude path', () => {
-        const input = '/home/user/.ccs/instances/ck/plugins/cache/plugin/0.0.2';
-        const expected = '/home/user/.claude/plugins/cache/plugin/0.0.2';
-        expect(normalizePluginPaths(input)).toBe(expected);
-      });
+  describe('plugin metadata path normalization', () => {
+    it('rewrites instance plugin paths to the requested target config dir', () => {
+      const targetConfigDir = path.join('/home/user', '.claude');
+      const input = '/home/user/.ccs/instances/work/plugins/cache/plugin/0.0.2';
 
-      it('should handle different instance names', () => {
-        const inputs = [
-          '/home/user/.ccs/instances/work/plugins/cache/plugin/1.0.0',
-          '/home/user/.ccs/instances/personal/plugins/cache/plugin/1.0.0',
-          '/home/user/.ccs/instances/test-account/plugins/cache/plugin/1.0.0',
-        ];
-        for (const input of inputs) {
-          expect(normalizePluginPaths(input)).toContain('/.claude/');
-          expect(normalizePluginPaths(input)).not.toContain('/.ccs/instances/');
-        }
-      });
+      expect(normalizePluginMetadataPathString(input, targetConfigDir)).toBe(
+        '/home/user/.claude/plugins/cache/plugin/0.0.2'
+      );
+    });
 
-      it('should handle multiple occurrences', () => {
-        const input = JSON.stringify({
+    it('rewrites shared plugin paths to an instance-local target config dir', () => {
+      const targetConfigDir = instanceDir('personal');
+      const input = path.join(tempRoot, '.ccs', 'shared', 'plugins', 'marketplaces', 'official');
+
+      expect(normalizePluginMetadataPathString(input, targetConfigDir)).toBe(
+        marketplacePath(targetConfigDir, 'official')
+      );
+    });
+
+    it('normalizes all matching JSON string values without changing the structure', () => {
+      const targetConfigDir = instanceDir('work');
+      const input = JSON.stringify(
+        {
           plugins: {
-            'plugin-a': [{ installPath: '/home/user/.ccs/instances/ck/plugins/a' }],
-            'plugin-b': [{ installPath: '/home/user/.ccs/instances/work/plugins/b' }],
-          },
-        });
-        const result = normalizePluginPaths(input);
-        expect(result).not.toContain('/.ccs/instances/');
-        expect(result.match(/\.claude/g)?.length).toBe(2);
-      });
-
-      it('should not modify already-canonical paths', () => {
-        const input = '/home/user/.claude/plugins/cache/plugin/0.0.2';
-        expect(normalizePluginPaths(input)).toBe(input);
-      });
-
-      it('should be idempotent', () => {
-        const input = '/home/user/.ccs/instances/ck/plugins/cache/plugin/0.0.2';
-        const first = normalizePluginPaths(input);
-        const second = normalizePluginPaths(first);
-        expect(first).toBe(second);
-      });
-
-      it('should preserve JSON structure', () => {
-        const original = {
-          version: 2,
-          plugins: {
-            'claude-hud@claude-hud': [
+            'plugin-a': [
               {
-                scope: 'user',
-                installPath:
-                  '/home/kai/.ccs/instances/ck/plugins/cache/claude-hud/claude-hud/0.0.2',
-                version: '0.0.2',
+                installPath: path.join(
+                  tempRoot,
+                  '.ccs',
+                  'instances',
+                  'old',
+                  'plugins',
+                  'cache',
+                  'plugin-a'
+                ),
               },
             ],
           },
-        };
-        const input = JSON.stringify(original, null, 2);
-        const result = normalizePluginPaths(input);
-
-        // Should be valid JSON
-        expect(() => JSON.parse(result)).not.toThrow();
-
-        // Should have normalized path
-        const parsed = JSON.parse(result);
-        expect(parsed.plugins['claude-hud@claude-hud'][0].installPath).toBe(
-          '/home/kai/.claude/plugins/cache/claude-hud/claude-hud/0.0.2'
-        );
-      });
-
-      it('should normalize marketplace installLocation values', () => {
-        const original = {
-          'claude-code-plugins': {
-            installLocation:
-              '/home/kai/.ccs/instances/work/plugins/marketplaces/claude-code-plugins',
+          marketplaces: {
+            official: {
+              installLocation: path.join(
+                tempRoot,
+                '.claude',
+                'plugins',
+                'marketplaces',
+                'official'
+              ),
+            },
           },
-        };
-        const input = JSON.stringify(original, null, 2);
-        const result = normalizePluginPaths(input);
+        },
+        null,
+        2
+      );
 
-        expect(() => JSON.parse(result)).not.toThrow();
+      const normalized = JSON.parse(normalizePluginMetadataContent(input, targetConfigDir)) as {
+        plugins: { 'plugin-a': [{ installPath: string }] };
+        marketplaces: { official: { installLocation: string } };
+      };
 
-        const parsed = JSON.parse(result);
-        expect(parsed['claude-code-plugins'].installLocation).toBe(
-          '/home/kai/.claude/plugins/marketplaces/claude-code-plugins'
-        );
-      });
+      expect(normalized.plugins['plugin-a'][0].installPath).toBe(
+        path.join(targetConfigDir, 'plugins', 'cache', 'plugin-a')
+      );
+      expect(normalized.marketplaces.official.installLocation).toBe(
+        marketplacePath(targetConfigDir, 'official')
+      );
     });
 
-    describe('edge cases', () => {
-      it('should handle empty object', () => {
-        const input = JSON.stringify({});
-        expect(normalizePluginPaths(input)).toBe(input);
-      });
+    it('preserves paths already rooted at the target config dir', () => {
+      const targetConfigDir = instanceDir('work');
+      const input = path.join(targetConfigDir, 'plugins', 'cache', 'plugin-a');
 
-      it('should handle plugins without installPath', () => {
-        const input = JSON.stringify({ plugins: {} });
-        expect(normalizePluginPaths(input)).toBe(input);
-      });
+      expect(normalizePluginMetadataPathString(input, targetConfigDir)).toBe(input);
+    });
 
-      it('should handle Windows-style paths (backslash)', () => {
-        const input = 'C:\\Users\\user\\.ccs\\instances\\ck\\plugins\\cache';
-        expect(normalizePluginPaths(input)).toBe('C:\\Users\\user\\.claude\\plugins\\cache');
-      });
+    it('handles Windows path separators', () => {
+      const targetConfigDir = 'C:\\Users\\user\\.claude';
+      const input = 'C:\\Users\\user\\.ccs\\instances\\work\\plugins\\marketplaces\\official';
+
+      expect(normalizePluginMetadataPathString(input, targetConfigDir)).toBe(
+        'C:\\Users\\user\\.claude\\plugins\\marketplaces\\official'
+      );
     });
   });
 
-  describe('normalizeMarketplaceRegistryPaths', () => {
-    it('rewrites known_marketplaces.json on disk', () => {
-      const pluginsDir = path.join(tempRoot, '.claude', 'plugins');
-      fs.mkdirSync(pluginsDir, { recursive: true });
+  describe('marketplace registry ownership', () => {
+    it('writes global and instance registries with different authoritative install locations', () => {
+      const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+      ensureMarketplacePayload(claudeDir());
+      writeJson(globalRegistryPath, {
+        'claude-code-plugins': {
+          installLocation: path.join(
+            tempRoot,
+            '.ccs',
+            'instances',
+            'work',
+            'plugins',
+            'marketplaces',
+            'claude-code-plugins'
+          ),
+        },
+      });
 
-      const registryPath = path.join(pluginsDir, 'known_marketplaces.json');
-      fs.writeFileSync(
-        registryPath,
-        JSON.stringify(
-          {
-            'claude-code-plugins': {
-              installLocation:
-                '/home/kai/.ccs/instances/work/plugins/marketplaces/claude-code-plugins',
-            },
-          },
-          null,
-          2
-        ),
-        'utf8'
-      );
+      const instancePath = instanceDir('personal');
+      fs.mkdirSync(instancePath, { recursive: true });
 
       const manager = new SharedManager();
-      manager.normalizeMarketplaceRegistryPaths();
+      manager.linkSharedDirectories(instancePath);
 
-      const normalized = JSON.parse(fs.readFileSync(registryPath, 'utf8'));
-      expect(normalized['claude-code-plugins'].installLocation).toBe(
-        '/home/kai/.claude/plugins/marketplaces/claude-code-plugins'
-      );
+      const instanceRegistryPath = path.join(instancePath, 'plugins', 'known_marketplaces.json');
+      expect(readMarketplaceLocation(globalRegistryPath)).toBe(marketplacePath(claudeDir()));
+      expect(readMarketplaceLocation(instanceRegistryPath)).toBe(marketplacePath(instancePath));
+      expect(fs.lstatSync(path.join(instancePath, 'plugins')).isSymbolicLink()).toBe(false);
+      expect(fs.lstatSync(instanceRegistryPath).isSymbolicLink()).toBe(false);
     });
 
-    it('rewrites Windows-style known_marketplaces.json paths on disk', () => {
-      const pluginsDir = path.join(tempRoot, '.claude', 'plugins');
-      fs.mkdirSync(pluginsDir, { recursive: true });
-
-      const registryPath = path.join(pluginsDir, 'known_marketplaces.json');
-      fs.writeFileSync(
-        registryPath,
-        JSON.stringify(
-          {
-            'claude-code-plugins': {
-              installLocation:
-                'C:\\Users\\kai\\.ccs\\instances\\work\\plugins\\marketplaces\\claude-code-plugins',
-            },
-          },
-          null,
-          2
-        ),
-        'utf8'
-      );
-
+    it('self-heals missing installLocation from discovered marketplace payloads', () => {
       const manager = new SharedManager();
-      manager.normalizeMarketplaceRegistryPaths();
+      const instancePath = instanceDir('work');
+      fs.mkdirSync(instancePath, { recursive: true });
+      manager.linkSharedDirectories(instancePath);
 
-      const normalized = JSON.parse(fs.readFileSync(registryPath, 'utf8'));
-      expect(normalized['claude-code-plugins'].installLocation).toBe(
-        'C:\\Users\\kai\\.claude\\plugins\\marketplaces\\claude-code-plugins'
-      );
+      fs.mkdirSync(marketplacePath(claudeDir()), { recursive: true });
+      writeJson(path.join(instancePath, 'plugins', 'known_marketplaces.json'), {
+        'claude-code-plugins': {
+          label: 'Official marketplace',
+        },
+      });
+
+      manager.normalizeMarketplaceRegistryPaths(instancePath);
+
+      const repaired = readJson(
+        path.join(instancePath, 'plugins', 'known_marketplaces.json')
+      ) as Record<string, { label?: string; installLocation?: string }>;
+      expect(repaired['claude-code-plugins']).toEqual({
+        label: 'Official marketplace',
+        installLocation: marketplacePath(instancePath),
+      });
     });
 
-    it('normalizes copied shared and instance metadata under Windows fallback', () => {
+    it('prunes stale marketplace entries whose payload directories no longer exist', () => {
+      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 });
+      writeJson(path.join(instancePath, 'plugins', 'known_marketplaces.json'), {
+        'claude-code-plugins': {
+          installLocation: marketplacePath(instancePath, 'claude-code-plugins'),
+          label: 'Official marketplace',
+        },
+        stale: {
+          installLocation: marketplacePath(instancePath, 'stale'),
+          label: 'Stale marketplace',
+        },
+      });
+
+      manager.normalizeMarketplaceRegistryPaths(instancePath);
+
+      const reconciled = readJson(
+        path.join(instancePath, 'plugins', 'known_marketplaces.json')
+      ) as Record<string, { label?: string; installLocation?: string }>;
+      expect(reconciled['claude-code-plugins']).toEqual({
+        installLocation: marketplacePath(instancePath, 'claude-code-plugins'),
+        label: 'Official marketplace',
+      });
+      expect(reconciled.stale).toBeUndefined();
+    });
+
+    it('warns and skips malformed marketplace registries while keeping valid sources', () => {
+      const manager = new SharedManager();
+      const instancePath = instanceDir('work');
+      fs.mkdirSync(instancePath, { recursive: true });
+      manager.linkSharedDirectories(instancePath);
+
+      const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+      ensureMarketplacePayload(claudeDir());
+      writeJson(globalRegistryPath, {
+        'claude-code-plugins': {
+          installLocation: path.join(
+            tempRoot,
+            '.ccs',
+            'instances',
+            'work',
+            'plugins',
+            'marketplaces',
+            'claude-code-plugins'
+          ),
+          label: 'Official marketplace',
+        },
+      });
+
+      const malformedRegistryPath = path.join(instancePath, 'plugins', 'known_marketplaces.json');
+      fs.writeFileSync(malformedRegistryPath, '{invalid-json', 'utf8');
+      const logSpy = spyOn(console, 'log').mockImplementation(() => {});
+
+      manager.normalizeMarketplaceRegistryPaths(instancePath);
+
+      expect(readMarketplaceLocation(malformedRegistryPath)).toBe(marketplacePath(instancePath));
+      expect(
+        logSpy.mock.calls.some(
+          ([message]) =>
+            String(message).includes('Skipping malformed marketplace registry') &&
+            String(message).includes(malformedRegistryPath)
+        )
+      ).toBe(true);
+    });
+
+    it('keeps the instance-local registry valid under Windows copy fallback', () => {
       Object.defineProperty(process, 'platform', { value: 'win32' });
       spyOn(fs, 'symlinkSync').mockImplementation(() => {
         throw Object.assign(new Error('simulated symlink failure'), { code: 'EPERM' });
       });
 
-      const pluginsDir = path.join(tempRoot, '.claude', 'plugins');
-      fs.mkdirSync(pluginsDir, { recursive: true });
+      const globalRegistryPath = path.join(claudeDir(), 'plugins', 'known_marketplaces.json');
+      ensureMarketplacePayload(claudeDir());
+      writeJson(globalRegistryPath, {
+        'claude-code-plugins': {
+          installLocation: path.join(
+            tempRoot,
+            '.claude',
+            'plugins',
+            'marketplaces',
+            'claude-code-plugins'
+          ),
+        },
+      });
 
-      const registryPath = path.join(pluginsDir, 'known_marketplaces.json');
-      fs.writeFileSync(
-        registryPath,
-        JSON.stringify(
-          {
-            'claude-code-plugins': {
-              installLocation:
-                '/home/kai/.ccs/instances/work/plugins/marketplaces/claude-code-plugins',
-            },
-          },
-          null,
-          2
-        ),
-        'utf8'
-      );
+      const instancePath = instanceDir('personal');
+      fs.mkdirSync(instancePath, { recursive: true });
 
       const manager = new SharedManager();
-      const instancePath = path.join(tempRoot, '.ccs', 'instances', 'personal');
-      fs.mkdirSync(instancePath, { recursive: true });
       manager.linkSharedDirectories(instancePath);
 
-      const expected = '/home/kai/.claude/plugins/marketplaces/claude-code-plugins';
-      const claudeRegistry = JSON.parse(fs.readFileSync(registryPath, 'utf8'));
-      const sharedRegistry = JSON.parse(
-        fs.readFileSync(
-          path.join(tempRoot, '.ccs', 'shared', 'plugins', 'known_marketplaces.json'),
-          'utf8'
-        )
-      );
-      const instanceRegistry = JSON.parse(
-        fs.readFileSync(path.join(instancePath, 'plugins', 'known_marketplaces.json'), 'utf8')
-      );
-
-      expect(claudeRegistry['claude-code-plugins'].installLocation).toBe(expected);
-      expect(sharedRegistry['claude-code-plugins'].installLocation).toBe(expected);
-      expect(instanceRegistry['claude-code-plugins'].installLocation).toBe(expected);
+      const instanceRegistryPath = path.join(instancePath, 'plugins', 'known_marketplaces.json');
+      expect(readMarketplaceLocation(globalRegistryPath)).toBe(marketplacePath(claudeDir()));
+      expect(readMarketplaceLocation(instanceRegistryPath)).toBe(marketplacePath(instancePath));
+      expect(fs.existsSync(path.join(instancePath, 'plugins', 'marketplaces'))).toBe(true);
     });
   });
 });