diff --git a/internal/detector/mcp_discovery.go b/internal/detector/mcp_discovery.go
index de77359..fbe1129 100644
--- a/internal/detector/mcp_discovery.go
+++ b/internal/detector/mcp_discovery.go
@@ -119,7 +119,8 @@ func (d *MCPDetector) allConfigLocations(homeDir string, searchDirs []string) []
 // discoverWalkedMCPConfigs walks the configured search dirs and the per-user
 // IDE dotfile roots, recognizing MCP configs by basename. It never enters
 // ~/Library (TCC skipper), skips dependency/cache/build dirs and directory
-// symlinks, and is bounded by maxMCPWalkFiles.
+// symlinks, and is bounded by maxMCPWalkFiles. Hits inside an agent plugin
+// package go through classifyWalkedMCPConfig, which drops catalog templates.
 func (d *MCPDetector) discoverWalkedMCPConfigs(searchDirs []string, homeDir string) []mcpConfigSpec {
 	roots := make([]string, 0, len(searchDirs)+6)
 	roots = append(roots, searchDirs...)
@@ -163,11 +164,13 @@ func (d *MCPDetector) discoverWalkedMCPConfigs(searchDirs []string, homeDir stri
 				c := filepath.Clean(path)
 				if !seen[c] {
 					seen[c] = true
-					specs = append(specs, mcpConfigSpec{
-						SourceName: "discovered_mcp",
-						ConfigPath: c,
-						Vendor:     mcpVendorForPath(c),
-					})
+					if source, vendor, keep := classifyWalkedMCPConfig(c, root); keep {
+						specs = append(specs, mcpConfigSpec{
+							SourceName: source,
+							ConfigPath: c,
+							Vendor:     vendor,
+						})
+					}
 				}
 			}
 			return nil
diff --git a/internal/detector/mcp_plugins.go b/internal/detector/mcp_plugins.go
new file mode 100644
index 0000000..790de5e
--- /dev/null
+++ b/internal/detector/mcp_plugins.go
@@ -0,0 +1,84 @@
+package detector
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+// mcpPluginManifest describes one agent's plugin-package layout: the manifest
+// directory that marks a package root, and how a config found there is
+// reported.
+type mcpPluginManifest struct {
+	dir        string
+	sourceName string
+	vendor     string
+}
+
+var mcpPluginManifests = []mcpPluginManifest{
+	{".claude-plugin", "claude_plugin", "Anthropic"},
+	{".codex-plugin", "codex_plugin", "OpenAI"},
+}
+
+// pluginMCPBasename is the only MCP surface a plugin package declares. Any
+// other MCP-shaped file inside a package is vendored from the plugin's own
+// repo, not a config the host agent loads.
+const pluginMCPBasename = ".mcp.json"
+
+// maxPluginRootLookup bounds the upward search for a package root.
+const maxPluginRootLookup = 8
+
+// classifyWalkedMCPConfig decides what a walked hit is. Plugin marketplaces are
+// clones of a catalog repo that ship one package — and one template .mcp.json —
+// per catalog entry, none of which any agent loads (issue #201). So a
+// plugin-scoped config counts only when it is the package's own .mcp.json and
+// the package is installed.
+func classifyWalkedMCPConfig(path, root string) (sourceName, vendor string, keep bool) {
+	dir := filepath.Dir(path)
+	pluginRoot, manifest, isPlugin := pluginPackageRoot(dir, root)
+	if !isPlugin {
+		return "discovered_mcp", mcpVendorForPath(path), true
+	}
+	if filepath.Base(path) != pluginMCPBasename || dir != pluginRoot {
+		return "", "", false // vendored inside the plugin payload
+	}
+	if !isInstalledPluginPath(pluginRoot) {
+		return "", "", false // marketplace catalog template
+	}
+	return manifest.sourceName, manifest.vendor, true
+}
+
+// pluginPackageRoot walks up from dir looking for a plugin manifest, stopping at
+// the walk root.
+func pluginPackageRoot(dir, root string) (string, mcpPluginManifest, bool) {
+	cleanRoot := filepath.Clean(root)
+	for i := 0; i < maxPluginRootLookup; i++ {
+		for _, m := range mcpPluginManifests {
+			if info, err := os.Stat(filepath.Join(dir, m.dir, "plugin.json")); err == nil && !info.IsDir() {
+				return dir, m, true
+			}
+		}
+		parent := filepath.Dir(dir)
+		if dir == cleanRoot || parent == dir {
+			break
+		}
+		dir = parent
+	}
+	return "", mcpPluginManifest{}, false
+}
+
+// isInstalledPluginPath reports whether a plugin package sits in an agent's
+// installed-plugin tree (<agent dir>/plugins/cache/...). Both Claude Code and
+// Codex install there and keep their catalog clones elsewhere
+// (~/.claude/plugins/marketplaces, ~/.codex/.tmp/plugins), so the segment pair
+// separates installed packages from catalog entries for either agent without a
+// per-vendor path list.
+func isInstalledPluginPath(pluginRoot string) bool {
+	p := pluginRoot
+	if runtime.GOOS == "windows" {
+		p = strings.ToLower(p)
+	}
+	sep := string(filepath.Separator)
+	return strings.Contains(p, sep+"plugins"+sep+"cache"+sep)
+}
diff --git a/internal/detector/mcp_plugins_test.go b/internal/detector/mcp_plugins_test.go
new file mode 100644
index 0000000..b276737
--- /dev/null
+++ b/internal/detector/mcp_plugins_test.go
@@ -0,0 +1,102 @@
+package detector
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func gotSpecMap(specs []mcpConfigSpec) map[string]mcpConfigSpec {
+	m := make(map[string]mcpConfigSpec, len(specs))
+	for _, s := range specs {
+		m[s.ConfigPath] = s
+	}
+	return m
+}
+
+// TestDiscoverWalkedMCPConfigs_PluginPackages: marketplace catalog templates and
+// files vendored inside a plugin payload are dropped; an installed plugin's own
+// .mcp.json and ordinary configs are kept (issue #201).
+func TestDiscoverWalkedMCPConfigs_PluginPackages(t *testing.T) {
+	root := t.TempDir()
+
+	// Claude catalog clone: one package per catalog entry, none installed.
+	writeFile(t, root, ".claude/plugins/marketplaces/official/external_plugins/terraform/.claude-plugin/plugin.json")
+	catalogClaude := writeFile(t, root, ".claude/plugins/marketplaces/official/external_plugins/terraform/.mcp.json")
+
+	// Codex catalog clone.
+	writeFile(t, root, ".codex/.tmp/plugins/plugins/linear/.codex-plugin/plugin.json")
+	catalogCodex := writeFile(t, root, ".codex/.tmp/plugins/plugins/linear/.mcp.json")
+
+	// Installed Claude plugin: its own .mcp.json is active, the opencode.json
+	// vendored from the plugin's repo is not.
+	writeFile(t, root, ".claude/plugins/cache/official/ponytail/1.0.0/.claude-plugin/plugin.json")
+	installed := writeFile(t, root, ".claude/plugins/cache/official/ponytail/1.0.0/.mcp.json")
+	vendored := writeFile(t, root, ".claude/plugins/cache/official/ponytail/1.0.0/opencode.json")
+
+	// Ordinary project config, no plugin manifest anywhere above it.
+	project := writeFile(t, root, "proj/.mcp.json")
+
+	d := &MCPDetector{}
+	got := gotSpecMap(d.discoverWalkedMCPConfigs([]string{root}, ""))
+
+	for _, p := range []string{catalogClaude, catalogCodex, vendored} {
+		if _, ok := got[p]; ok {
+			t.Errorf("should not have reported %s", p)
+		}
+	}
+	if s, ok := got[installed]; !ok {
+		t.Errorf("did not find installed plugin config %s", installed)
+	} else if s.SourceName != "claude_plugin" || s.Vendor != "Anthropic" {
+		t.Errorf("installed plugin: got source=%q vendor=%q", s.SourceName, s.Vendor)
+	}
+	if s, ok := got[project]; !ok {
+		t.Errorf("did not find project config %s", project)
+	} else if s.SourceName != "discovered_mcp" {
+		t.Errorf("project config: got source=%q, want discovered_mcp", s.SourceName)
+	}
+	if len(got) != 2 {
+		t.Errorf("expected 2 configs, got %d: %v", len(got), got)
+	}
+}
+
+// TestDiscoverWalkedMCPConfigs_CodexInstalledPlugin: Codex installs under
+// plugins/cache too, so its plugin .mcp.json is reported as codex_plugin.
+func TestDiscoverWalkedMCPConfigs_CodexInstalledPlugin(t *testing.T) {
+	root := t.TempDir()
+	writeFile(t, root, ".codex/plugins/cache/openai-curated-remote/github/.codex-plugin/plugin.json")
+	installed := writeFile(t, root, ".codex/plugins/cache/openai-curated-remote/github/.mcp.json")
+
+	d := &MCPDetector{}
+	got := gotSpecMap(d.discoverWalkedMCPConfigs([]string{root}, ""))
+
+	s, ok := got[installed]
+	if !ok {
+		t.Fatalf("did not find %s: %v", installed, got)
+	}
+	if s.SourceName != "codex_plugin" || s.Vendor != "OpenAI" {
+		t.Errorf("got source=%q vendor=%q", s.SourceName, s.Vendor)
+	}
+}
+
+// TestPluginPackageRoot_NestedAndBounded: a config nested inside a package
+// resolves to the package root; the search stops at the walk root.
+func TestPluginPackageRoot_NestedAndBounded(t *testing.T) {
+	root := t.TempDir()
+	writeFile(t, root, "pkg/.claude-plugin/plugin.json")
+	nested := writeFile(t, root, "pkg/config/deep/mcp.json")
+
+	pluginRoot, manifest, ok := pluginPackageRoot(filepath.Dir(nested), root)
+	if !ok {
+		t.Fatal("expected to find package root")
+	}
+	if want := filepath.Join(root, "pkg"); pluginRoot != want {
+		t.Errorf("pluginRoot = %q, want %q", pluginRoot, want)
+	}
+	if manifest.sourceName != "claude_plugin" {
+		t.Errorf("manifest = %q, want claude_plugin", manifest.sourceName)
+	}
+
+	if _, _, ok := pluginPackageRoot(filepath.Join(root, "other"), root); ok {
+		t.Error("expected no package root outside a plugin package")
+	}
+}