diff --git a/tests/test_server_rest.py b/tests/test_server_rest.py
new file mode 100644
index 0000000..413a3ec
--- /dev/null
+++ b/tests/test_server_rest.py
@@ -0,0 +1,484 @@
+#!/usr/bin/env python3
+"""
+Tests for the REST API server (server_rest.py)
+
+This test suite covers:
+- Health check endpoints (GET /, GET /health)
+- API key authentication (valid/invalid keys, Bearer format)
+- Conversation creation (POST /v1/conversations)
+- Chat endpoint (POST /v1/chat) - streaming and non-streaming
+- Message creation (POST /v1/conversations/{id}/messages) - streaming and non-streaming
+- Memory deletion (DELETE /v1/memory, DELETE /v1/conversations/{id}/memory)
+- Edge cases and error handling
+
+Run with: pytest tests/test_server_rest.py -v
+"""
+import os
+import pytest
+import json
+from unittest.mock import AsyncMock, MagicMock, patch
+from fastapi.testclient import TestClient
+from langgraph.checkpoint.memory import MemorySaver
+
+# Set up test environment before importing the server
+os.environ["FAST_AUTH_KEYS"] = "test-key-1,test-key-2,test-key-3"
+
+# Import after setting environment
+import sys
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from fastapi_server.server_rest import app
+
+
+@pytest.fixture
+def mock_pipeline():
+    """Create a mock Pipeline instance."""
+    pipeline = MagicMock()
+    
+    # Mock async generator for streaming
+    async def mock_achat_stream(inp, as_stream=True, thread_id="test"):
+        chunks = ["Hello", " ", "world", "!"]
+        for chunk in chunks:
+            yield chunk
+    
+    # Mock async function that returns async generator for streaming or string for non-streaming
+    async def mock_achat(inp, as_stream=False, thread_id="test"):
+        if as_stream:
+            # Return async generator for streaming
+            async def gen():
+                chunks = ["Hello", " ", "world", "!"]
+                for chunk in chunks:
+                    yield chunk
+            return gen()
+        else:
+            # Return string for non-streaming
+            return "Hello world!"
+    
+    async def mock_aclear_memory():
+        return None
+    
+    pipeline.achat = AsyncMock(side_effect=mock_achat)
+    pipeline.aclear_memory = AsyncMock(return_value=None)
+    
+    # Mock graph with memory
+    mock_graph = MagicMock()
+    mock_memory = MagicMock(spec=MemorySaver)
+    mock_memory.delete_thread = MagicMock()
+    mock_graph.memory = mock_memory
+    pipeline.graph = mock_graph
+    
+    return pipeline
+
+
+@pytest.fixture
+def client(mock_pipeline):
+    """Create a test client with mocked pipeline."""
+    with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+        with TestClient(app) as test_client:
+            yield test_client
+
+
+@pytest.fixture
+def auth_headers():
+    """Return valid authentication headers."""
+    return {"Authorization": "Bearer test-key-1"}
+
+
+@pytest.fixture
+def invalid_auth_headers():
+    """Return invalid authentication headers."""
+    return {"Authorization": "Bearer invalid-key"}
+
+
+class TestHealthCheck:
+    """Tests for health check endpoint."""
+    
+    def test_root_endpoint(self, client):
+        """Test root endpoint returns API information."""
+        response = client.get("/")
+        assert response.status_code == 200
+        data = response.json()
+        assert "message" in data
+        assert "endpoints" in data
+        assert isinstance(data["endpoints"], list)
+    
+    def test_health_endpoint(self, client):
+        """Test health endpoint returns healthy status."""
+        response = client.get("/health")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["status"] == "healthy"
+
+
+class TestAuthentication:
+    """Tests for API key authentication."""
+    
+    def test_missing_auth_header(self, client):
+        """Test that missing auth header returns 401."""
+        response = client.post("/v1/conversations")
+        assert response.status_code == 401
+    
+    def test_invalid_api_key(self, client, invalid_auth_headers):
+        """Test that invalid API key returns 401."""
+        response = client.post(
+            "/v1/conversations",
+            headers=invalid_auth_headers
+        )
+        assert response.status_code == 401
+        assert "Invalid API key" in response.json()["detail"]
+    
+    def test_valid_api_key_bearer_format(self, client, auth_headers):
+        """Test that valid API key with Bearer prefix works."""
+        response = client.post(
+            "/v1/conversations",
+            headers=auth_headers
+        )
+        assert response.status_code == 200
+    
+    def test_valid_api_key_without_bearer(self, client):
+        """Test that valid API key without Bearer prefix works."""
+        response = client.post(
+            "/v1/conversations",
+            headers={"Authorization": "test-key-1"}
+        )
+        assert response.status_code == 200
+    
+    def test_multiple_valid_keys(self, client):
+        """Test that any of the configured keys work."""
+        for key in ["test-key-1", "test-key-2", "test-key-3"]:
+            response = client.post(
+                "/v1/conversations",
+                headers={"Authorization": f"Bearer {key}"}
+            )
+            assert response.status_code == 200
+
+
+class TestConversationCreation:
+    """Tests for conversation creation endpoint."""
+    
+    def test_create_conversation(self, client, auth_headers):
+        """Test creating a new conversation."""
+        response = client.post(
+            "/v1/conversations",
+            headers=auth_headers
+        )
+        assert response.status_code == 200
+        data = response.json()
+        assert "id" in data
+        assert "created_at" in data
+        assert data["id"].startswith("c_")
+        assert len(data["id"]) > 2
+    
+    def test_conversation_id_format(self, client, auth_headers):
+        """Test that conversation IDs follow expected format."""
+        response = client.post(
+            "/v1/conversations",
+            headers=auth_headers
+        )
+        data = response.json()
+        conv_id = data["id"]
+        # Should start with "c_" and have hex characters
+        assert conv_id.startswith("c_")
+        assert len(conv_id) > 2
+
+
+class TestChatEndpoint:
+    """Tests for the /v1/chat endpoint."""
+    
+    def test_chat_non_streaming(self, client, auth_headers, mock_pipeline):
+        """Test non-streaming chat request."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.post(
+                "/v1/chat",
+                headers=auth_headers,
+                json={
+                    "input": "Hello, how are you?",
+                    "stream": False
+                }
+            )
+            assert response.status_code == 200
+            data = response.json()
+            assert "conversation_id" in data
+            assert "output" in data
+            assert data["output"] == "Hello world!"
+            mock_pipeline.achat.assert_called_once()
+            call_kwargs = mock_pipeline.achat.call_args.kwargs
+            assert call_kwargs["inp"] == "Hello, how are you?"
+            assert call_kwargs["as_stream"] is False
+    
+    def test_chat_with_existing_conversation_id(self, client, auth_headers, mock_pipeline):
+        """Test chat with existing conversation ID."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            conv_id = "c_test123"
+            response = client.post(
+                "/v1/chat",
+                headers=auth_headers,
+                json={
+                    "input": "Hello",
+                    "conversation_id": conv_id,
+                    "stream": False
+                }
+            )
+            assert response.status_code == 200
+            data = response.json()
+            assert data["conversation_id"] == conv_id
+            call_kwargs = mock_pipeline.achat.call_args.kwargs
+            assert call_kwargs["thread_id"] == conv_id
+    
+    def test_chat_creates_new_conversation_id(self, client, auth_headers, mock_pipeline):
+        """Test chat creates new conversation ID when not provided."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.post(
+                "/v1/chat",
+                headers=auth_headers,
+                json={
+                    "input": "Hello",
+                    "stream": False
+                }
+            )
+            assert response.status_code == 200
+            data = response.json()
+            assert "conversation_id" in data
+            assert data["conversation_id"].startswith("c_")
+    
+    def test_chat_streaming(self, client, auth_headers, mock_pipeline):
+        """Test streaming chat request."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.post(
+                "/v1/chat",
+                headers=auth_headers,
+                json={
+                    "input": "Hello",
+                    "stream": True
+                }
+            )
+            assert response.status_code == 200
+            assert "text/event-stream" in response.headers["content-type"]
+            
+            # Read streaming response
+            lines = response.text.split("\n")
+            data_lines = [line for line in lines if line.startswith("data: ")]
+            
+            # Should have delta events and a done event
+            assert len(data_lines) > 0
+            
+            # Parse first delta event
+            first_data = json.loads(data_lines[0][6:])  # Remove "data: " prefix
+            assert first_data["type"] == "delta"
+            assert "conversation_id" in first_data
+            assert "delta" in first_data
+            
+            # Check that achat was called with as_stream=True
+            mock_pipeline.achat.assert_called_once()
+            call_kwargs = mock_pipeline.achat.call_args.kwargs
+            assert call_kwargs["as_stream"] is True
+
+
+class TestMessageEndpoint:
+    """Tests for the /v1/conversations/{conversation_id}/messages endpoint."""
+    
+    def test_create_message_non_streaming(self, client, auth_headers, mock_pipeline):
+        """Test creating a message (non-streaming)."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            conv_id = "c_test123"
+            response = client.post(
+                f"/v1/conversations/{conv_id}/messages",
+                headers=auth_headers,
+                json={
+                    "role": "user",
+                    "content": "Hello, how are you?",
+                    "stream": False
+                }
+            )
+            assert response.status_code == 200
+            data = response.json()
+            assert data["conversation_id"] == conv_id
+            assert "message" in data
+            assert data["message"]["role"] == "assistant"
+            assert "content" in data["message"]
+            mock_pipeline.achat.assert_called_once()
+            call_kwargs = mock_pipeline.achat.call_args.kwargs
+            assert call_kwargs["inp"] == "Hello, how are you?"
+            assert call_kwargs["thread_id"] == conv_id
+    
+    def test_create_message_streaming(self, client, auth_headers, mock_pipeline):
+        """Test creating a message (streaming)."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            conv_id = "c_test123"
+            response = client.post(
+                f"/v1/conversations/{conv_id}/messages",
+                headers=auth_headers,
+                json={
+                    "role": "user",
+                    "content": "Hello",
+                    "stream": True
+                }
+            )
+            assert response.status_code == 200
+            assert "text/event-stream" in response.headers["content-type"]
+            
+            # Verify achat was called with streaming
+            mock_pipeline.achat.assert_called_once()
+            call_kwargs = mock_pipeline.achat.call_args.kwargs
+            assert call_kwargs["as_stream"] is True
+            assert call_kwargs["thread_id"] == conv_id
+    
+    def test_create_message_invalid_role(self, client, auth_headers):
+        """Test that only 'user' role is accepted."""
+        conv_id = "c_test123"
+        response = client.post(
+            f"/v1/conversations/{conv_id}/messages",
+            headers=auth_headers,
+            json={
+                "role": "assistant",
+                "content": "Hello",
+                "stream": False
+            }
+        )
+        assert response.status_code == 400
+        assert "Only role='user' is supported" in response.json()["detail"]
+
+
+class TestMemoryDeletion:
+    """Tests for memory deletion endpoints."""
+    
+    def test_delete_all_memory(self, client, auth_headers, mock_pipeline):
+        """Test deleting all memory."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.delete(
+                "/v1/memory",
+                headers=auth_headers
+            )
+            assert response.status_code == 200
+            data = response.json()
+            assert data["status"] == "success"
+            assert data["scope"] == "all"
+            mock_pipeline.aclear_memory.assert_called_once()
+    
+    def test_delete_all_memory_error_handling(self, client, auth_headers, mock_pipeline):
+        """Test error handling when deleting all memory fails."""
+        mock_pipeline.aclear_memory = AsyncMock(side_effect=Exception("Memory error"))
+        
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.delete(
+                "/v1/memory",
+                headers=auth_headers
+            )
+            assert response.status_code == 500
+            assert "Memory error" in response.json()["detail"]
+    
+    def test_delete_conversation_memory(self, client, auth_headers, mock_pipeline):
+        """Test deleting memory for a specific conversation."""
+        conv_id = "c_test123"
+        
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.delete(
+                f"/v1/conversations/{conv_id}/memory",
+                headers=auth_headers
+            )
+            assert response.status_code == 200
+            data = response.json()
+            assert data["status"] == "success"
+            assert data["scope"] == "conversation"
+            assert data["conversation_id"] == conv_id
+            # Verify delete_thread was called
+            mock_pipeline.graph.memory.delete_thread.assert_called_once()
+    
+    def test_delete_conversation_memory_with_device_id(self, client, auth_headers, mock_pipeline):
+        """Test deleting memory for conversation with device ID format."""
+        conv_id = "c_test123_device456"
+        
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.delete(
+                f"/v1/conversations/{conv_id}/memory",
+                headers=auth_headers
+            )
+            assert response.status_code == 200
+            # Should normalize to base thread_id
+            mock_pipeline.graph.memory.delete_thread.assert_called_once_with("c_test123")
+    
+    def test_delete_conversation_memory_no_memory_saver(self, client, auth_headers):
+        """Test deleting conversation memory when MemorySaver is not available."""
+        # Create a mock pipeline without MemorySaver
+        mock_pipeline_no_mem = MagicMock()
+        mock_pipeline_no_mem.graph = MagicMock()
+        mock_pipeline_no_mem.graph.memory = None
+        
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline_no_mem):
+            conv_id = "c_test123"
+            response = client.delete(
+                f"/v1/conversations/{conv_id}/memory",
+                headers=auth_headers
+            )
+            assert response.status_code == 501
+            data = response.json()
+            assert data["status"] == "unsupported"
+            assert "not supported" in data["message"].lower()
+
+
+class TestEdgeCases:
+    """Tests for edge cases and error handling."""
+    
+    def test_chat_empty_input(self, client, auth_headers, mock_pipeline):
+        """Test chat with empty input."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            response = client.post(
+                "/v1/chat",
+                headers=auth_headers,
+                json={
+                    "input": "",
+                    "stream": False
+                }
+            )
+            # Should still process (validation would be in Pipeline)
+            assert response.status_code in [200, 400]
+    
+    def test_chat_missing_input(self, client, auth_headers):
+        """Test chat with missing input field."""
+        response = client.post(
+            "/v1/chat",
+            headers=auth_headers,
+            json={
+                "stream": False
+            }
+        )
+        assert response.status_code == 422  # Validation error
+    
+    def test_message_missing_content(self, client, auth_headers):
+        """Test message creation with missing content."""
+        conv_id = "c_test123"
+        response = client.post(
+            f"/v1/conversations/{conv_id}/messages",
+            headers=auth_headers,
+            json={
+                "role": "user",
+                "stream": False
+            }
+        )
+        assert response.status_code == 422  # Validation error
+    
+    def test_invalid_conversation_id_format(self, client, auth_headers, mock_pipeline):
+        """Test that various conversation ID formats are handled."""
+        with patch("fastapi_server.server_rest.pipeline", mock_pipeline):
+            # Test with underscore (device_id format)
+            conv_id = "thread_123_device_456"
+            response = client.post(
+                f"/v1/conversations/{conv_id}/messages",
+                headers=auth_headers,
+                json={
+                    "role": "user",
+                    "content": "Hello",
+                    "stream": False
+                }
+            )
+            # Should normalize thread_id (take first part before _)
+            assert response.status_code == 200
+            call_kwargs = mock_pipeline.achat.call_args.kwargs
+            # The thread_id normalization happens in _normalize_thread_id
+            # but achat receives the full conversation_id
+            assert call_kwargs["thread_id"] == conv_id
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])
+