diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 5b2256f59..e10ffec2d 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -4,7 +4,7 @@
 #
 # Tuned for MAXIMUM security signal with INTEGRATED AUTOFIX:
 #   - All repo languages covered (Python, JS/TS, GitHub Actions; C/C++ via
-#     manual build when present). HTML is analyzed as part of
+#     buildless analysis). HTML is analyzed as part of
 #     javascript-typescript.
 #   - Query packs: security-extended + security-and-quality + experimental
 #     security queries, plus community security packs (when available).
@@ -118,7 +118,7 @@ jobs:
             os: ubuntu-latest
 
           - language: c-cpp
-            build-mode: autobuild
+            build-mode: none
             os: ubuntu-latest
             timeout-minutes: 360
     timeout-minutes: 360
diff --git a/tests/test_codeql_workflow_paths_ignore.py b/tests/test_codeql_workflow_paths_ignore.py
index 125326db7..665da6902 100644
--- a/tests/test_codeql_workflow_paths_ignore.py
+++ b/tests/test_codeql_workflow_paths_ignore.py
@@ -18,6 +18,20 @@ def test_codeql_workflow_ignores_issue_template_changes() -> None:
     assert ".github/ISSUE_TEMPLATE/**" in workflow["on"]["pull_request"]["paths-ignore"]
 
 
+@pytest.mark.unit
+def test_codeql_c_cpp_uses_buildless_mode() -> None:
+    workflow_path = Path(__file__).resolve().parents[1] / ".github" / "workflows" / "codeql.yml"
+    workflow = yaml.load(workflow_path.read_text(encoding="utf-8"), Loader=yaml.BaseLoader)
+
+    c_cpp_entry = next(
+        entry for entry in workflow["jobs"]["analyze"]["strategy"]["matrix"]["include"] if entry["language"] == "c-cpp"
+    )
+
+    assert (
+        c_cpp_entry["build-mode"] == "none"
+    ), "The c-cpp CodeQL lane must stay buildless so it does not invoke the repo root Makefile via autobuild."
+
+
 @pytest.mark.unit
 def test_codeql_autofix_ref_step_avoids_unbound_shell_vars() -> None:
     workflow_path = Path(__file__).resolve().parents[1] / ".github" / "workflows" / "codeql.yml"
@@ -101,6 +115,6 @@ def test_codeql_config_has_document_start_and_no_trailing_whitespace() -> None:
     content = config_path.read_text(encoding="utf-8")
 
     assert content.startswith("---\n"), "CodeQL config must keep its YAML document start marker."
-    assert all(line == line.rstrip() for line in content.splitlines()), (
-        "CodeQL config should not contain trailing whitespace."
-    )
+    assert all(
+        line == line.rstrip() for line in content.splitlines()
+    ), "CodeQL config should not contain trailing whitespace."