diff --git a/gui_agents/s3/core/mllm.py b/gui_agents/s3/core/mllm.py
index fb49e4b0..58beb93c 100644
--- a/gui_agents/s3/core/mllm.py
+++ b/gui_agents/s3/core/mllm.py
@@ -35,6 +35,69 @@ def __init__(self, engine_params=None, system_prompt=None, engine=None):
                     self.engine = LMMEngineOpenRouter(**engine_params)
                 elif engine_type == "parasail":
                     self.engine = LMMEngineParasail(**engine_params)
+                elif engine_type == "ollama":
+                    # Reuse LMMEngineOpenAI for Ollama
+                    if not engine_params.get("base_url"):
+                        import os
+
+                        base_url = os.getenv("OLLAMA_HOST")
+                        if base_url:
+                            if not base_url.endswith("/v1"):
+                                base_url = base_url.rstrip("/") + "/v1"
+                            engine_params["base_url"] = base_url
+                        else:
+                            # RAISE ERROR instead of default
+                            raise ValueError(
+                                "Ollama endpoint must be provided via 'base_url' parameter or 'OLLAMA_HOST' environment variable."
+                            )
+                    if not engine_params.get("api_key"):
+                        engine_params["api_key"] = "ollama"
+                    self.engine = LMMEngineOpenAI(**engine_params)
+                elif engine_type == "deepseek":
+                    if "base_url" not in engine_params:
+                        import os
+
+                        base_url = os.getenv("DEEPSEEK_ENDPOINT_URL")
+                        if not base_url:
+                            base_url = "https://api.deepseek.com"
+                        if not base_url.endswith("/v1"):
+                            base_url = base_url.rstrip("/") + "/v1"
+                        engine_params["base_url"] = base_url
+
+                    if not engine_params.get("api_key"):
+                        import os
+
+                        api_key = os.getenv("DEEPSEEK_API_KEY")
+                        if not api_key:
+                            raise ValueError(
+                                "DeepSeek API key must be provided via 'api_key' parameter or 'DEEPSEEK_API_KEY' environment variable."
+                            )
+                        engine_params["api_key"] = api_key
+
+                    self.engine = LMMEngineOpenAI(**engine_params)
+                elif engine_type == "qwen":
+                    if not engine_params.get("base_url"):
+                        import os
+
+                        base_url = os.getenv("QWEN_ENDPOINT_URL")
+                        if not base_url:
+                            base_url = (
+                                "https://dashscope.aliyuncs.com/compatible-mode/v1"
+                            )
+                        if not base_url.endswith("/v1"):
+                            base_url = base_url.rstrip("/") + "/v1"
+                        engine_params["base_url"] = base_url
+
+                    if not engine_params.get("api_key"):
+                        import os
+
+                        api_key = os.getenv("QWEN_API_KEY")
+                        if not api_key:
+                            raise ValueError(
+                                "Qwen API key must be provided via 'api_key' parameter or 'QWEN_API_KEY' environment variable."
+                            )
+                        engine_params["api_key"] = api_key
+                    self.engine = LMMEngineOpenAI(**engine_params)
                 else:
                     raise ValueError(f"engine_type '{engine_type}' is not supported")
             else:
diff --git a/tests/test_providers.py b/tests/test_providers.py
new file mode 100644
index 00000000..2e1b24d2
--- /dev/null
+++ b/tests/test_providers.py
@@ -0,0 +1,72 @@
+import os
+import unittest
+from unittest.mock import patch, MagicMock
+from gui_agents.s3.core.mllm import LMMAgent
+from gui_agents.s3.core.engine import LMMEngineOpenAI
+
+
+class TestProviders(unittest.TestCase):
+    def setUp(self):
+        # Clear env vars before each test
+        if "OLLAMA_HOST" in os.environ:
+            del os.environ["OLLAMA_HOST"]
+        if "DEEPSEEK_API_KEY" in os.environ:
+            del os.environ["DEEPSEEK_API_KEY"]
+        if "QWEN_API_KEY" in os.environ:
+            del os.environ["QWEN_API_KEY"]
+        if "DEEPSEEK_ENDPOINT_URL" in os.environ:
+            del os.environ["DEEPSEEK_ENDPOINT_URL"]
+        if "QWEN_ENDPOINT_URL" in os.environ:
+            del os.environ["QWEN_ENDPOINT_URL"]
+
+    def test_ollama_missing_config(self):
+        """Test that Ollama raises ValueError if no endpoint is provided"""
+        with self.assertRaises(ValueError) as cm:
+            LMMAgent(engine_params={"engine_type": "ollama", "model": "llama3"})
+        self.assertIn("Ollama endpoint must be provided", str(cm.exception))
+
+    def test_ollama_valid_config_param(self):
+        """Test Ollama init with base_url param"""
+        agent = LMMAgent(
+            engine_params={
+                "engine_type": "ollama",
+                "model": "llama3",
+                "base_url": "http://example.com/v1",
+            }
+        )
+        self.assertIsInstance(agent.engine, LMMEngineOpenAI)
+        self.assertEqual(agent.engine.base_url, "http://example.com/v1")
+
+    def test_ollama_valid_config_env(self):
+        """Test Ollama init with OLLAMA_HOST env var"""
+        with patch.dict(os.environ, {"OLLAMA_HOST": "http://env-host:11434"}):
+            agent = LMMAgent(engine_params={"engine_type": "ollama", "model": "llama3"})
+            self.assertIsInstance(agent.engine, LMMEngineOpenAI)
+            # Check for /v1 addition
+            self.assertEqual(agent.engine.base_url, "http://env-host:11434/v1")
+
+    def test_deepseek_init(self):
+        """Test DeepSeek initialization"""
+        with patch.dict(os.environ, {"DEEPSEEK_API_KEY": "sk-test"}):
+            agent = LMMAgent(
+                engine_params={"engine_type": "deepseek", "model": "deepseek-coder"}
+            )
+            self.assertIsInstance(agent.engine, LMMEngineOpenAI)
+            # Default URL
+            self.assertEqual(agent.engine.base_url, "https://api.deepseek.com/v1")
+            # (Note: engine.py logic resolves default at generate() time or if client created,
+            # but init just stores what's passed. Let's verify prompt generation to ensure it doesn't crash on init)
+
+    def test_qwen_init(self):
+        """Test Qwen initialization"""
+        with patch.dict(os.environ, {"QWEN_API_KEY": "sk-qwen"}):
+            agent = LMMAgent(engine_params={"engine_type": "qwen", "model": "qwen-max"})
+            self.assertIsInstance(agent.engine, LMMEngineOpenAI)
+            self.assertEqual(
+                agent.engine.base_url,
+                "https://dashscope.aliyuncs.com/compatible-mode/v1",
+            )
+
+
+if __name__ == "__main__":
+    unittest.main()