diff --git a/src/agent/skills/index.ts b/src/agent/skills/index.ts
index 0397f79c..7ea7115c 100644
--- a/src/agent/skills/index.ts
+++ b/src/agent/skills/index.ts
@@ -129,6 +129,19 @@ export {
   SerializeKeys,
 } from "./serialize.js";
 
+// Export plugin module
+export {
+  PLUGIN_MANIFEST_FILENAME,
+  loadPluginManifest,
+  loadPluginRegistry,
+  resolvePluginSkillDirs,
+  getPluginRegistry,
+  type PluginManifest,
+  type PluginRecord,
+  type PluginDiagnostic,
+  type PluginRegistry,
+} from "./plugin.js";
+
 /**
  * SkillManager - Loads and manages skills
  *
diff --git a/src/agent/skills/loader.ts b/src/agent/skills/loader.ts
index e16d2c01..7201c376 100644
--- a/src/agent/skills/loader.ts
+++ b/src/agent/skills/loader.ts
@@ -2,6 +2,7 @@
  * Skills Loader
  *
  * Multi-source loading with precedence handling
+ * Supports bundled skills, user-installed skills, profile skills, and plugin skills
  */
 
 import { existsSync, readdirSync, statSync } from "node:fs";
@@ -11,6 +12,7 @@ import type { Skill, SkillSource, SkillManagerOptions } from "./types.js";
 import { SKILL_FILE, SKILL_SOURCE_PRECEDENCE } from "./types.js";
 import { parseSkillFile } from "./parser.js";
 import { DATA_DIR } from "../../shared/index.js";
+import { resolvePluginSkillDirs } from "./plugin.js";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
@@ -118,8 +120,9 @@ export function getProfileSkillsDir(profileId: string, profileBaseDir?: string):
  * Loading order (lowest to highest precedence):
  * 1. bundled - Package bundled skills
  * 2. extra - User-configured extra directories
- * 3. managed - ~/.super-multica/skills/ (user-installed via `skills add`)
- * 4. profile - ~/.super-multica/agent-profiles/<profileId>/skills/
+ * 3. plugins - Skills from npm packages with multica.plugin.json
+ * 4. managed - ~/.super-multica/skills/ (user-installed via `skills add`)
+ * 5. profile - ~/.super-multica/agent-profiles/<profileId>/skills/
  *
  * @param options - Loader options
  * @returns Map of skill ID to Skill
@@ -127,12 +130,20 @@ export function getProfileSkillsDir(profileId: string, profileBaseDir?: string):
 export function loadAllSkills(options: SkillManagerOptions = {}): Map<string, Skill> {
   const skillMap = new Map<string, Skill>();
 
+  // Discover plugin skill directories
+  const pluginSkillDirs = resolvePluginSkillDirs({
+    workspaceDir: options.workspaceDir ?? process.cwd(),
+    extraPaths: options.pluginPaths ?? [],
+  });
+
   // Define sources in order of precedence (lowest first)
   const sources: Array<[string, SkillSource]> = [
     // Bundled skills (lowest precedence)
     [BUNDLED_DIR, "bundled"],
     // Extra directories (treated as bundled)
     ...(options.extraDirs ?? []).map((d): [string, SkillSource] => [d, "bundled"]),
+    // Plugin skills (between extra and managed)
+    ...pluginSkillDirs.map((d): [string, SkillSource] => [d, "bundled"]),
     // Managed skills (user-installed via `skills add`)
     [MANAGED_DIR, "profile"],
   ];
diff --git a/src/agent/skills/plugin.ts b/src/agent/skills/plugin.ts
new file mode 100644
index 00000000..6dbcec22
--- /dev/null
+++ b/src/agent/skills/plugin.ts
@@ -0,0 +1,412 @@
+/**
+ * Plugin System
+ *
+ * Discovers and loads skills from npm packages that contain a multica.plugin.json manifest.
+ * This enables users to install skill packages via npm and have them automatically discovered.
+ *
+ * Design inspired by OpenClaw's plugin system.
+ */
+
+import { existsSync, readdirSync, readFileSync, statSync } from "node:fs";
+import { join, dirname, resolve } from "node:path";
+
+// ============================================================================
+// Types
+// ============================================================================
+
+/**
+ * Plugin manifest file name
+ */
+export const PLUGIN_MANIFEST_FILENAME = "multica.plugin.json";
+
+/**
+ * Plugin manifest schema
+ * Stored in multica.plugin.json at the package root
+ */
+export interface PluginManifest {
+  /** Unique plugin identifier (required) */
+  id: string;
+  /** Human-readable plugin name */
+  name?: string | undefined;
+  /** Plugin description */
+  description?: string | undefined;
+  /** Plugin version */
+  version?: string | undefined;
+  /** Relative paths to skill directories within the package */
+  skills?: string[] | undefined;
+}
+
+/**
+ * Loaded plugin record with resolved paths
+ */
+export interface PluginRecord {
+  /** Plugin ID from manifest */
+  id: string;
+  /** Plugin name */
+  name?: string | undefined;
+  /** Plugin description */
+  description?: string | undefined;
+  /** Plugin version */
+  version?: string | undefined;
+  /** Absolute path to package root */
+  rootDir: string;
+  /** Absolute path to manifest file */
+  manifestPath: string;
+  /** Resolved absolute paths to skill directories */
+  skillDirs: string[];
+  /** Source of discovery */
+  source: "node_modules" | "custom";
+}
+
+/**
+ * Plugin discovery diagnostic
+ */
+export interface PluginDiagnostic {
+  level: "error" | "warn" | "info";
+  pluginId?: string | undefined;
+  source: string;
+  message: string;
+}
+
+/**
+ * Plugin registry result
+ */
+export interface PluginRegistry {
+  plugins: PluginRecord[];
+  diagnostics: PluginDiagnostic[];
+}
+
+// ============================================================================
+// Manifest Loading
+// ============================================================================
+
+/**
+ * Check if a value is a plain object
+ */
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return Boolean(value && typeof value === "object" && !Array.isArray(value));
+}
+
+/**
+ * Normalize a string array from unknown input
+ */
+function normalizeStringList(value: unknown): string[] {
+  if (!Array.isArray(value)) return [];
+  return value
+    .map((entry) => (typeof entry === "string" ? entry.trim() : ""))
+    .filter(Boolean);
+}
+
+/**
+ * Load and parse a plugin manifest from a directory
+ *
+ * @param rootDir - Package root directory
+ * @returns Parsed manifest or error
+ */
+export function loadPluginManifest(
+  rootDir: string,
+): { ok: true; manifest: PluginManifest; manifestPath: string } | { ok: false; error: string; manifestPath: string } {
+  const manifestPath = join(rootDir, PLUGIN_MANIFEST_FILENAME);
+
+  if (!existsSync(manifestPath)) {
+    return { ok: false, error: `manifest not found: ${manifestPath}`, manifestPath };
+  }
+
+  let raw: unknown;
+  try {
+    raw = JSON.parse(readFileSync(manifestPath, "utf-8")) as unknown;
+  } catch (err) {
+    return {
+      ok: false,
+      error: `failed to parse manifest: ${String(err)}`,
+      manifestPath,
+    };
+  }
+
+  if (!isRecord(raw)) {
+    return { ok: false, error: "manifest must be an object", manifestPath };
+  }
+
+  const id = typeof raw.id === "string" ? raw.id.trim() : "";
+  if (!id) {
+    return { ok: false, error: "manifest requires id field", manifestPath };
+  }
+
+  const manifest: PluginManifest = {
+    id,
+    name: typeof raw.name === "string" ? raw.name.trim() : undefined,
+    description: typeof raw.description === "string" ? raw.description.trim() : undefined,
+    version: typeof raw.version === "string" ? raw.version.trim() : undefined,
+    skills: normalizeStringList(raw.skills),
+  };
+
+  return { ok: true, manifest, manifestPath };
+}
+
+// ============================================================================
+// Plugin Discovery
+// ============================================================================
+
+/**
+ * Find all node_modules directories to search
+ * Walks up from workspaceDir to find all node_modules in the tree
+ */
+function findNodeModulesDirs(workspaceDir: string): string[] {
+  const dirs: string[] = [];
+  let current = resolve(workspaceDir);
+  const root = dirname(current);
+
+  while (current !== root) {
+    const nodeModules = join(current, "node_modules");
+    if (existsSync(nodeModules) && statSync(nodeModules).isDirectory()) {
+      dirs.push(nodeModules);
+    }
+    const parent = dirname(current);
+    if (parent === current) break;
+    current = parent;
+  }
+
+  return dirs;
+}
+
+/**
+ * Discover plugin packages in a node_modules directory
+ *
+ * @param nodeModulesDir - Path to node_modules
+ * @returns Array of package directories containing plugin manifests
+ */
+function discoverPluginsInNodeModules(nodeModulesDir: string): string[] {
+  const candidates: string[] = [];
+
+  try {
+    const entries = readdirSync(nodeModulesDir);
+
+    for (const entry of entries) {
+      // Skip hidden and special directories
+      if (entry.startsWith(".") || entry === "node_modules") continue;
+
+      const entryPath = join(nodeModulesDir, entry);
+
+      try {
+        const stat = statSync(entryPath);
+        if (!stat.isDirectory()) continue;
+
+        // Handle scoped packages (@org/package)
+        if (entry.startsWith("@")) {
+          const scopedEntries = readdirSync(entryPath);
+          for (const scopedEntry of scopedEntries) {
+            if (scopedEntry.startsWith(".")) continue;
+            const scopedPath = join(entryPath, scopedEntry);
+            if (existsSync(join(scopedPath, PLUGIN_MANIFEST_FILENAME))) {
+              candidates.push(scopedPath);
+            }
+          }
+        } else {
+          // Regular package
+          if (existsSync(join(entryPath, PLUGIN_MANIFEST_FILENAME))) {
+            candidates.push(entryPath);
+          }
+        }
+      } catch {
+        // Skip inaccessible directories
+      }
+    }
+  } catch {
+    // Skip inaccessible node_modules
+  }
+
+  return candidates;
+}
+
+/**
+ * Build a plugin record from a manifest and candidate
+ */
+function buildPluginRecord(params: {
+  manifest: PluginManifest;
+  manifestPath: string;
+  rootDir: string;
+  source: "node_modules" | "custom";
+}): PluginRecord {
+  const { manifest, manifestPath, rootDir, source } = params;
+
+  // Resolve skill directories
+  const skillDirs: string[] = [];
+  for (const skillPath of manifest.skills ?? []) {
+    const resolved = resolve(rootDir, skillPath);
+    if (existsSync(resolved)) {
+      skillDirs.push(resolved);
+    }
+  }
+
+  return {
+    id: manifest.id,
+    name: manifest.name,
+    description: manifest.description,
+    version: manifest.version,
+    rootDir,
+    manifestPath,
+    skillDirs,
+    source,
+  };
+}
+
+// ============================================================================
+// Plugin Registry
+// ============================================================================
+
+/**
+ * Discover and load all plugins
+ *
+ * @param options - Discovery options
+ * @returns Plugin registry with all discovered plugins
+ */
+export function loadPluginRegistry(options: {
+  /** Workspace directory to start search from */
+  workspaceDir?: string;
+  /** Additional directories to search for plugins */
+  extraPaths?: string[];
+  /** Skip node_modules scanning */
+  skipNodeModules?: boolean;
+}): PluginRegistry {
+  const { workspaceDir, extraPaths = [], skipNodeModules = false } = options;
+  const plugins: PluginRecord[] = [];
+  const diagnostics: PluginDiagnostic[] = [];
+  const seenIds = new Set<string>();
+
+  // Discover plugins in node_modules
+  if (!skipNodeModules && workspaceDir) {
+    const nodeModulesDirs = findNodeModulesDirs(workspaceDir);
+
+    for (const nodeModulesDir of nodeModulesDirs) {
+      const candidates = discoverPluginsInNodeModules(nodeModulesDir);
+
+      for (const candidate of candidates) {
+        const result = loadPluginManifest(candidate);
+
+        if (!result.ok) {
+          diagnostics.push({
+            level: "error",
+            source: result.manifestPath,
+            message: result.error,
+          });
+          continue;
+        }
+
+        const { manifest, manifestPath } = result;
+
+        if (seenIds.has(manifest.id)) {
+          diagnostics.push({
+            level: "warn",
+            pluginId: manifest.id,
+            source: manifestPath,
+            message: `duplicate plugin id; earlier instance takes precedence`,
+          });
+          continue;
+        }
+
+        seenIds.add(manifest.id);
+        plugins.push(
+          buildPluginRecord({
+            manifest,
+            manifestPath,
+            rootDir: candidate,
+            source: "node_modules",
+          }),
+        );
+      }
+    }
+  }
+
+  // Load plugins from extra paths
+  for (const extraPath of extraPaths) {
+    if (!existsSync(extraPath)) {
+      diagnostics.push({
+        level: "warn",
+        source: extraPath,
+        message: "extra plugin path does not exist",
+      });
+      continue;
+    }
+
+    const result = loadPluginManifest(extraPath);
+
+    if (!result.ok) {
+      diagnostics.push({
+        level: "error",
+        source: result.manifestPath,
+        message: result.error,
+      });
+      continue;
+    }
+
+    const { manifest, manifestPath } = result;
+
+    if (seenIds.has(manifest.id)) {
+      diagnostics.push({
+        level: "warn",
+        pluginId: manifest.id,
+        source: manifestPath,
+        message: `duplicate plugin id; earlier instance takes precedence`,
+      });
+      continue;
+    }
+
+    seenIds.add(manifest.id);
+    plugins.push(
+      buildPluginRecord({
+        manifest,
+        manifestPath,
+        rootDir: extraPath,
+        source: "custom",
+      }),
+    );
+  }
+
+  return { plugins, diagnostics };
+}
+
+// ============================================================================
+// Skill Directory Resolution
+// ============================================================================
+
+/**
+ * Get all skill directories from discovered plugins
+ *
+ * This function is the main integration point with SkillManager.
+ * It discovers plugins and returns their skill directories.
+ *
+ * @param options - Discovery options
+ * @returns Array of absolute paths to skill directories
+ */
+export function resolvePluginSkillDirs(options: {
+  workspaceDir?: string;
+  extraPaths?: string[];
+}): string[] {
+  const registry = loadPluginRegistry(options);
+  const dirs: string[] = [];
+  const seen = new Set<string>();
+
+  for (const plugin of registry.plugins) {
+    for (const skillDir of plugin.skillDirs) {
+      if (!seen.has(skillDir)) {
+        seen.add(skillDir);
+        dirs.push(skillDir);
+      }
+    }
+  }
+
+  return dirs;
+}
+
+/**
+ * Get plugin registry with diagnostics for CLI/debugging
+ *
+ * @param options - Discovery options
+ * @returns Full registry with plugins and diagnostics
+ */
+export function getPluginRegistry(options: {
+  workspaceDir?: string;
+  extraPaths?: string[];
+}): PluginRegistry {
+  return loadPluginRegistry(options);
+}
diff --git a/src/agent/skills/types.ts b/src/agent/skills/types.ts
index 0534a3d2..9e9aacb1 100644
--- a/src/agent/skills/types.ts
+++ b/src/agent/skills/types.ts
@@ -224,6 +224,10 @@ export interface SkillManagerOptions {
   platform?: NodeJS.Platform | undefined;
   /** Skills configuration */
   config?: SkillsConfig | undefined;
+  /** Workspace directory for plugin discovery (defaults to cwd) */
+  workspaceDir?: string | undefined;
+  /** Additional paths to search for plugins (directories with multica.plugin.json) */
+  pluginPaths?: string[] | undefined;
 }
 
 /**