diff --git a/README.md b/README.md
index 53b0472..b6d314b 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,9 @@ This repository implements a minimal, Python-based MVP of GridVerse: a modular,
 - Core concepts: Objects, Morphisms, Functors
 - Lightweight Registry for contracts and adapters
 - Starter DER adapter and a small adapter marketplace scaffold
+- Marketplace and Registry: lightweight in-process components for adapter discovery and contract validation.
+  - AdapterMarketplace (gridverse_open_low_code_platform_for_cro.marketplace) registers and lists adapters.
+  - ContractRegistry (gridverse_open_low_code_platform_for_cro.registry) validates and stores contract schemas.
 - End-to-end tests and packaging skeleton
 
 How to run
diff --git a/gridverse_open_low_code_platform_for_cro/marketplace.py b/gridverse_open_low_code_platform_for_cro/marketplace.py
new file mode 100644
index 0000000..54dfb6f
--- /dev/null
+++ b/gridverse_open_low_code_platform_for_cro/marketplace.py
@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+from typing import Dict, List
+
+from .adapter import Adapter
+
+
+class AdapterMarketplace:
+    """Minimal in-process marketplace for adapters.
+
+    This lightweight scaffold allows registering adapters and querying them
+    by id. It is intentionally tiny to serve as a stepping stone toward a
+    fuller registry/marketplace without affecting the core MVP surface.
+    """
+
+    def __init__(self) -> None:
+        self._adapters: Dict[str, Adapter] = {}
+
+    def register_adapter(self, adapter: Adapter) -> None:
+        if not isinstance(adapter, Adapter):  # type: ignore[unreachable]
+            raise TypeError("adapter must be an instance of Adapter")
+        self._adapters[adapter.adapter_id] = adapter
+
+    def list_adapters(self) -> List[str]:
+        return list(self._adapters.keys())
+
+    def get_adapter(self, adapter_id: str) -> Adapter:
+        return self._adapters[adapter_id]
diff --git a/gridverse_open_low_code_platform_for_cro/marketplace/__init__.py b/gridverse_open_low_code_platform_for_cro/marketplace/__init__.py
index c934244..d7340be 100644
--- a/gridverse_open_low_code_platform_for_cro/marketplace/__init__.py
+++ b/gridverse_open_low_code_platform_for_cro/marketplace/__init__.py
@@ -13,3 +13,22 @@ class Marketplace:
 
     def get_entry(self, adapter_id: str) -> Dict[str, Any]:
         return self.entries[adapter_id]
+
+
+class AdapterMarketplace:
+    """Lightweight in-process adapter marketplace compatible with tests."""
+    def __init__(self) -> None:
+        self._adapters: Dict[str, Any] = {}
+
+    def register_adapter(self, adapter) -> None:
+        # Accept any object that provides an 'adapter_id' attribute
+        if not hasattr(adapter, "adapter_id"):
+            raise TypeError("adapter must expose an 'adapter_id' attribute")
+        self._adapters[adapter.adapter_id] = adapter
+
+    def list_adapters(self) -> List[str]:  # type: ignore[override]
+        from typing import List  # local import to avoid top-level import in small file
+        return list(self._adapters.keys())
+
+    def get_adapter(self, adapter_id: str):  # type: ignore[return-type]
+        return self._adapters[adapter_id]
diff --git a/tests/test_marketplace.py b/tests/test_marketplace.py
new file mode 100644
index 0000000..a1555c2
--- /dev/null
+++ b/tests/test_marketplace.py
@@ -0,0 +1,11 @@
+from gridverse_open_low_code_platform_for_cro.marketplace import AdapterMarketplace
+from gridverse_open_low_code_platform_for_cro.adapters.starter_der_adapter import StarterDERAdapter
+
+
+def test_marketplace_register_and_list_and_get():
+    marketplace = AdapterMarketplace()
+    adapter = StarterDERAdapter()
+    marketplace.register_adapter(adapter)
+    assert marketplace.list_adapters() == [adapter.adapter_id]
+    retrieved = marketplace.get_adapter(adapter.adapter_id)
+    assert isinstance(retrieved, StarterDERAdapter)