diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a305edc..f00876c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,6 +35,8 @@ jobs:
         run: pytest tests/unit/test_uvicorn_reload_regression.py -q
       - name: Run LLM service final-turn parsing regression
         run: pytest tests/unit/test_llm_service.py::test_create_idea_final_turn_conclusion_parsing tests/unit/test_llm_service.py::test_create_idea_final_turn_fallback_parsing -q
+      - name: Run nested test discovery regression
+        run: pytest tests/unit/test_nested_test_discovery_regression.py -q
       - name: Run unit tests
         # Deselect known-broken tests that are tracked by their own open issues
         # (leave them for those issue-workers; don't scope-creep or race them).
diff --git a/tests/unit/test_nested_test_discovery_regression.py b/tests/unit/test_nested_test_discovery_regression.py
new file mode 100644
index 0000000..288722f
--- /dev/null
+++ b/tests/unit/test_nested_test_discovery_regression.py
@@ -0,0 +1,105 @@
+"""
+Regression tests for issue #23: a `test_*` function nested inside another
+function is unreachable dead code -- pytest only collects module-level
+functions and methods of `Test*` classes, so a nested test silently never
+runs while masquerading as coverage.
+
+Concretely, `test_create_idea_final_turn_fallback_parsing` had been defined
+*inside* `test_create_idea_live_groq_call` in `tests/unit/test_llm_service.py`.
+The nested copy was never collected. These tests parse the AST of every
+`tests/unit/test_*.py` file (offline, no imports of the scanned files) and
+lock in that no `test_*` function is nested inside another function.
+"""
+import ast
+from pathlib import Path
+
+TESTS_UNIT_DIR = Path(__file__).resolve().parent
+
+
+def _find_nested_test_functions(tree):
+    """Return (test_func_name, enclosing_func_name) pairs for nested tests.
+
+    A `test_*` function is a bug when its *nearest enclosing scope* is another
+    function (FunctionDef/AsyncFunctionDef). Module-level functions and methods
+    of a class (e.g. `class Test...`) are fine -- pytest collects those.
+    """
+    offenders = []
+
+    def walk(node, enclosing_func):
+        for child in ast.iter_child_nodes(node):
+            if isinstance(child, (ast.FunctionDef, ast.AsyncFunctionDef)):
+                if enclosing_func is not None and child.name.startswith("test"):
+                    offenders.append((child.name, enclosing_func))
+                # Descend into the function body; its own nearest enclosing
+                # scope is now `child`.
+                walk(child, child.name)
+            elif isinstance(child, ast.ClassDef):
+                # A class body resets the "enclosing function" context: methods
+                # of a `Test*` class are collectable by pytest.
+                walk(child, None)
+            else:
+                walk(child, enclosing_func)
+
+    walk(tree, None)
+    return offenders
+
+
+class TestNoNestedTestFunctions:
+    """No `test_*` function may hide inside another function in tests/unit."""
+
+    def test_no_test_function_nested_in_another_function(self):
+        """Every `test_*` func must be module-level or a class method."""
+        all_offenders = []
+        # Every collectable `test_*.py` file in tests/unit.
+        for path in sorted(TESTS_UNIT_DIR.glob("test_*.py")):
+            tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
+            for test_name, enclosing in _find_nested_test_functions(tree):
+                all_offenders.append((path.name, test_name, enclosing))
+
+        assert not all_offenders, (
+            "Found test function(s) nested inside another function -- pytest "
+            "never collects these, so they are unreachable dead code:\n"
+            + "\n".join(
+                f"  {fname}: {test} is nested inside {enclosing}"
+                for fname, test, enclosing in all_offenders
+            )
+        )
+
+
+class TestFallbackParsingIsTopLevel:
+    """Lock in the exact #23 fix in test_llm_service.py."""
+
+    def _llm_service_tree(self):
+        path = TESTS_UNIT_DIR / "test_llm_service.py"
+        assert path.exists(), f"expected {path} to exist"
+        return ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
+
+    def test_fallback_parsing_defined_exactly_once_at_module_level(self):
+        """`test_create_idea_final_turn_fallback_parsing` is a direct child of Module."""
+        tree = self._llm_service_tree()
+        module_level = [
+            node.name
+            for node in tree.body
+            if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+        ]
+        count = module_level.count("test_create_idea_final_turn_fallback_parsing")
+        assert count == 1, (
+            "test_create_idea_final_turn_fallback_parsing must be defined exactly "
+            f"once at module level in test_llm_service.py; found {count} "
+            f"module-level definition(s)."
+        )
+
+    def test_fallback_parsing_not_nested_in_live_groq_call(self):
+        """It must not be nested inside test_create_idea_live_groq_call (the #23 bug)."""
+        tree = self._llm_service_tree()
+        offenders = _find_nested_test_functions(tree)
+        bad = [
+            (test, enclosing)
+            for test, enclosing in offenders
+            if test == "test_create_idea_final_turn_fallback_parsing"
+        ]
+        assert not bad, (
+            "test_create_idea_final_turn_fallback_parsing is nested inside "
+            f"{bad[0][1]} in test_llm_service.py -- pytest will never collect it. "
+            "It must be a top-level function (issue #23)."
+        )