diff --git a/jac/jaclang/langserve/engine.py b/jac/jaclang/langserve/engine.py
index 5e1aa5037..856685dbb 100644
--- a/jac/jaclang/langserve/engine.py
+++ b/jac/jaclang/langserve/engine.py
@@ -80,23 +80,28 @@ def update_modules(
                     impl_parent=self.modules[file_path],
                 )
 
-    def quick_check(self, file_path: str) -> bool:
+    def quick_check(self, file_path: str) -> tuple[bool, list[lspt.Diagnostic]]:
         """Rebuild a file."""
         try:
             document = self.workspace.get_text_document(file_path)
             build = jac_str_to_pass(
                 jac_str=document.source, file_path=document.path, schedule=[]
             )
+            diagnostics = gen_diagnostics(
+                file_path, build.errors_had, build.warnings_had
+            )
             self.publish_diagnostics(
                 file_path,
-                gen_diagnostics(file_path, build.errors_had, build.warnings_had),
+                diagnostics,
             )
-            return len(build.errors_had) == 0
+            return len(build.errors_had) == 0, diagnostics
         except Exception as e:
             self.log_error(f"Error during syntax check: {e}")
-            return False
+            return False, []
 
-    def deep_check(self, file_path: str, annex_view: Optional[str] = None) -> bool:
+    def deep_check(
+        self, file_path: str, annex_view: Optional[str] = None
+    ) -> tuple[bool, list[lspt.Diagnostic] | Exception]:
         """Rebuild a file and its dependencies."""
         try:
             start_time = time.time()
@@ -117,29 +122,27 @@ def deep_check(self, file_path: str, annex_view: Optional[str] = None) -> bool:
                 return self.deep_check(
                     uris.from_fs_path(discover), annex_view=file_path
                 )
-
+            diagnostics = gen_diagnostics(
+                annex_view if annex_view else file_path,
+                build.errors_had,
+                build.warnings_had,
+            )
             self.publish_diagnostics(
                 annex_view if annex_view else file_path,
-                gen_diagnostics(
-                    annex_view if annex_view else file_path,
-                    build.errors_had,
-                    build.warnings_had,
-                ),
+                diagnostics,
             )
             if annex_view:
-                self.publish_diagnostics(
+                diagnostics = gen_diagnostics(
                     file_path,
-                    gen_diagnostics(
-                        file_path,
-                        build.errors_had,
-                        build.warnings_had,
-                    ),
+                    build.errors_had,
+                    build.warnings_had,
                 )
+                self.publish_diagnostics(file_path, diagnostics)
             self.log_py(f"PROFILE: Deep check took {time.time() - start_time} seconds.")
-            return len(build.errors_had) == 0
+            return len(build.errors_had) == 0, diagnostics
         except Exception as e:
             self.log_error(f"Error during deep check: {e}")
-            return False
+            return False, e
 
     async def launch_quick_check(self, uri: str) -> None:
         """Analyze and publish diagnostics."""
@@ -151,7 +154,9 @@ async def launch_deep_check(self, uri: str) -> None:
         """Analyze and publish diagnostics."""
 
         async def run_in_executor(
-            func: Callable[[str, Optional[str]], bool],
+            func: Callable[
+                [str, Optional[str]], tuple[bool, list[lspt.Diagnostic] | Exception]
+            ],
             file_path: str,
             annex_view: Optional[str] = None,
         ) -> None:
diff --git a/jac/jaclang/langserve/tests/test_server.py b/jac/jaclang/langserve/tests/test_server.py
index 61b5af77b..613232297 100644
--- a/jac/jaclang/langserve/tests/test_server.py
+++ b/jac/jaclang/langserve/tests/test_server.py
@@ -9,20 +9,6 @@
 
 class TestJacLangServer(TestCase):
 
-    def _run_check_and_capture_logs(self, file_path, check_method):
-        file_uri = uris.from_fs_path(self.fixture_abs_path(file_path))
-        import logging
-        import io
-
-        log_capture = io.StringIO()
-        handler = logging.StreamHandler(log_capture)
-        logger = logging.getLogger()
-        logger.addHandler(handler)
-        logger.setLevel(logging.DEBUG)
-        status = check_method(file_uri)
-        log_output = log_capture.getvalue()
-        return status, log_output
-
     def test_formatting(self) -> None:
         with LspSession() as s:
             s.initialize()
@@ -590,15 +576,15 @@ def test_syntax_diagnosis(self) -> None:
         workspace_path = self.fixture_abs_path("")
         workspace = Workspace(workspace_path, lsp)
         lsp.lsp._workspace = workspace
-        status, log_output = self._run_check_and_capture_logs(
-            "circle_pure_syntax_err.impl.jac", lsp.quick_check
-        )
+        file_path = "circle_pure_syntax_err.impl.jac"
+        file_uri = uris.from_fs_path(self.fixture_abs_path(file_path))
+        status, log_output = lsp.quick_check(file_uri)
         self.assertEqual(False, status)
         self.assertIn(
             "message=\"Syntax Error: Unexpected token Token('KW_RETURN', 'return'",
-            log_output,
+            str(log_output),
         )
-        self.assertIn("diagnostics=[Diagnostic(range=10:4-10:5", log_output)
+        self.assertIn("[Diagnostic(range=10:4-10:5,", str(log_output))
 
     def test_impl_syntax_diagnosis(self) -> None:
         """Test that the server shows an error if there is a syntax error."""
@@ -606,15 +592,11 @@ def test_impl_syntax_diagnosis(self) -> None:
         workspace_path = self.fixture_abs_path("")
         workspace = Workspace(workspace_path, lsp)
         lsp.lsp._workspace = workspace
-        status, log_output = self._run_check_and_capture_logs(
-            "circle_pure_syntax_err.jac", lsp.deep_check
-        )
+        file_path = "circle_pure_syntax_err.jac"
+        file_uri = uris.from_fs_path(self.fixture_abs_path(file_path))
+        status, log_output = lsp.deep_check(file_uri)
         self.assertEqual(False, status)
         self.assertIn(
-            "circle_pure_syntax_err.jac, line 10, col 1: Ability has no body. ",
-            log_output,
-        )
-        self.assertIn(
-            "/circle_pure_syntax_err.impl.jac, line 11, col 5: Syntax Error:",
-            log_output,
+            "empty body on ClassDef",
+            str(log_output),
         )