diff --git a/airbyte_cdk/manifest_server/command_processor/utils.py b/airbyte_cdk/manifest_server/command_processor/utils.py
index 3aef171e06..2f8b3c30f0 100644
--- a/airbyte_cdk/manifest_server/command_processor/utils.py
+++ b/airbyte_cdk/manifest_server/command_processor/utils.py
@@ -64,16 +64,7 @@ def build_source(
     page_limit: Optional[int] = None,
     slice_limit: Optional[int] = None,
 ) -> ConcurrentDeclarativeSource:
-    # We enforce a concurrency level of 1 so that the stream is processed on a single thread
-    # to retain ordering for the grouping of the builder message responses.
     definition = copy.deepcopy(manifest)
-    if "concurrency_level" in definition:
-        definition["concurrency_level"]["default_concurrency"] = 1
-    else:
-        definition["concurrency_level"] = {
-            "type": "ConcurrencyLevel",
-            "default_concurrency": 1,
-        }
 
     should_normalize = should_normalize_manifest(manifest)
     if should_normalize:
diff --git a/airbyte_cdk/manifest_server/routers/manifest.py b/airbyte_cdk/manifest_server/routers/manifest.py
index 4fefb21293..0ccf74fb0b 100644
--- a/airbyte_cdk/manifest_server/routers/manifest.py
+++ b/airbyte_cdk/manifest_server/routers/manifest.py
@@ -87,8 +87,19 @@ def test_read(request: StreamTestReadRequest) -> StreamReadResponse:
             "md5": hashlib.md5(request.custom_components_code.encode()).hexdigest()
         }
 
+    # We enforce a concurrency level of 1 so that the stream is processed on a single thread
+    # to retain ordering for the grouping of the builder message responses.
+    manifest = request.manifest.model_dump()
+    if "concurrency_level" in manifest:
+        manifest["concurrency_level"]["default_concurrency"] = 1
+    else:
+        manifest["concurrency_level"] = {
+            "type": "ConcurrencyLevel",
+            "default_concurrency": 1,
+        }
+
     source = safe_build_source(
-        request.manifest.model_dump(),
+        manifest,
         config_dict,
         catalog,
         converted_state,
diff --git a/unit_tests/manifest_server/command_processor/test_utils.py b/unit_tests/manifest_server/command_processor/test_utils.py
index 81b43f3035..708bca8811 100644
--- a/unit_tests/manifest_server/command_processor/test_utils.py
+++ b/unit_tests/manifest_server/command_processor/test_utils.py
@@ -31,61 +31,6 @@ def test_build_catalog_creates_correct_structure(self):
         assert configured_stream.sync_mode == SyncMode.incremental
         assert configured_stream.destination_sync_mode == DestinationSyncMode.overwrite
 
-    @patch("airbyte_cdk.manifest_server.command_processor.utils.ConcurrentDeclarativeSource")
-    def test_build_source_creates_source(self, mock_source_class):
-        """Test that build_source creates a ConcurrentDeclarativeSource with correct parameters."""
-        # Setup mocks
-        mock_source = Mock()
-        mock_source_class.return_value = mock_source
-
-        # Test with complex manifest and config structures
-        manifest = {
-            "version": "0.1.0",
-            "definitions": {"selector": {"extractor": {"field_path": ["data"]}}},
-            "streams": [
-                {
-                    "name": "users",
-                    "primary_key": "id",
-                    "retriever": {
-                        "requester": {
-                            "url_base": "https://api.example.com",
-                            "path": "/users",
-                        }
-                    },
-                }
-            ],
-            "check": {"stream_names": ["users"]},
-        }
-
-        config = {
-            "api_key": "sk-test-123",
-            "base_url": "https://api.example.com",
-            "timeout": 30,
-        }
-
-        # Call build_source with additional parameters
-        catalog = build_catalog("test_stream")
-        state = []
-        result = build_source(manifest, catalog, config, state)
-
-        # Verify ConcurrentDeclarativeSource was created with correct parameters
-        expected_source_config = {
-            **manifest,
-            "concurrency_level": {"type": "ConcurrencyLevel", "default_concurrency": 1},
-        }
-        mock_source_class.assert_called_once_with(
-            catalog=catalog,
-            state=state,
-            source_config=expected_source_config,
-            config=config,
-            normalize_manifest=False,  # Default when flag not set
-            migrate_manifest=False,  # Default when flag not set
-            emit_connector_builder_messages=True,
-            limits=mock_source_class.call_args[1]["limits"],
-        )
-
-        assert result == mock_source
-
     @patch("airbyte_cdk.manifest_server.command_processor.utils.ConcurrentDeclarativeSource")
     def test_build_source_with_normalize_flag(self, mock_source_class):
         """Test build_source when normalize flag is set."""
diff --git a/unit_tests/manifest_server/routers/test_manifest.py b/unit_tests/manifest_server/routers/test_manifest.py
index 4f8a90b933..29940488be 100644
--- a/unit_tests/manifest_server/routers/test_manifest.py
+++ b/unit_tests/manifest_server/routers/test_manifest.py
@@ -109,8 +109,12 @@ def test_test_read_endpoint_success(
 
         assert response.status_code == 200
         # Verify build_source was called with correct arguments
+        expected_source_config = {
+            **sample_manifest,
+            "concurrency_level": {"type": "ConcurrencyLevel", "default_concurrency": 1},
+        }
         mock_build_source.assert_called_once_with(
-            sample_manifest,
+            expected_source_config,
             mock_build_catalog.return_value,
             sample_config,
             [],
@@ -169,8 +173,13 @@ def test_test_read_with_custom_components(
         assert config_arg["__injected_components_py_checksums"]["md5"] == expected_checksum
 
         # Verify other arguments
+        # Verify build_source was called with correct arguments
+        expected_source_config = {
+            **sample_manifest,
+            "concurrency_level": {"type": "ConcurrencyLevel", "default_concurrency": 1},
+        }
         mock_build_source.assert_called_once_with(
-            sample_manifest,
+            expected_source_config,
             mock_build_catalog.return_value,
             config_arg,
             [],