diff --git a/src/sdk/client.py b/src/sdk/client.py
index 95b2f5c8c..7361ec586 100644
--- a/src/sdk/client.py
+++ b/src/sdk/client.py
@@ -24,8 +24,13 @@ def _request(self, method: str, path: str, data: Dict = None) -> Dict:
 
         try:
             with urlopen(req) as resp:
-                return json.loads(resp.read().decode())
+                raw = resp.read()
+                if resp.status == 204 or not raw:
+                    return {}
+                return json.loads(raw.decode())
         except HTTPError as e:
+            if e.code == 204:
+                return {}
             return {"error": e.code, "message": e.reason}
 
     def register_agent(self, name: str, agent_type: str, config: Dict = None) -> Dict:
diff --git a/tests/test_sdk_client.py b/tests/test_sdk_client.py
new file mode 100644
index 000000000..1d689ff38
--- /dev/null
+++ b/tests/test_sdk_client.py
@@ -0,0 +1,69 @@
+"""Tests for SDK 204 No Content response handling."""
+
+import json
+from unittest.mock import patch, MagicMock
+from io import BytesIO
+
+from src.sdk.client import OrchestratorClient
+
+
+def make_mock_resp(status=200, body=b""):
+    """Helper to create a mock urllib response."""
+    resp = MagicMock()
+    resp.status = status
+    resp.read.return_value = body
+    resp.__enter__ = MagicMock(return_value=resp)
+    resp.__exit__ = MagicMock(return_value=False)
+    return resp
+
+
+class TestRequest204Handling:
+    """Regression tests for #4086 - Handle 204 responses without JSON decoding."""
+
+    def setup_method(self):
+        self.client = OrchestratorClient(
+            base_url="https://test.example.com", api_key="test-key"
+        )
+
+    @patch("src.sdk.client.urlopen")
+    def test_delete_returns_empty_dict_on_204(self, mock_urlopen):
+        """A 204 No Content response should return an empty dict."""
+        mock_urlopen.return_value = make_mock_resp(status=204, body=b"")
+        result = self.client.delete_agent("agent-123")
+        assert result == {}
+
+    @patch("src.sdk.client.urlopen")
+    def test_delete_returns_empty_dict_on_empty_body(self, mock_urlopen):
+        """An empty response body should return an empty dict even on 200."""
+        mock_urlopen.return_value = make_mock_resp(status=200, body=b"")
+        result = self.client.delete_agent("agent-123")
+        assert result == {}
+
+    @patch("src.sdk.client.urlopen")
+    def test_200_with_json_body_still_parses(self, mock_urlopen):
+        """A 200 with a valid JSON body should still parse normally."""
+        data = json.dumps({"id": "agent-123", "status": "running"}).encode()
+        mock_urlopen.return_value = make_mock_resp(status=200, body=data)
+        result = self.client.get_agent("agent-123")
+        assert result == {"id": "agent-123", "status": "running"}
+
+    @patch("src.sdk.client.urlopen")
+    def test_stop_agent_handles_204(self, mock_urlopen):
+        """Stop endpoint returning 204 should not crash."""
+        mock_urlopen.return_value = make_mock_resp(status=204, body=b"")
+        result = self.client.stop_agent("agent-456")
+        assert result == {}
+
+    @patch("src.sdk.client.urlopen")
+    def test_404_error_still_returns_error_dict(self, mock_urlopen):
+        """Non-204 errors should still return the error dict."""
+        from urllib.error import HTTPError
+        mock_urlopen.side_effect = HTTPError(
+            url="https://test.example.com/api/v2/agents/missing",
+            code=404,
+            msg="Not Found",
+            hdrs=MagicMock(),
+            fp=BytesIO(b""),
+        )
+        result = self.client.get_agent("missing")
+        assert result == {"error": 404, "message": "Not Found"}