diff --git a/sumd/pipeline.py b/sumd/pipeline.py
index ca90e18..76f1adf 100644
--- a/sumd/pipeline.py
+++ b/sumd/pipeline.py
@@ -60,6 +60,11 @@ def _map_module_count(text: str) -> int:
     return int(m.group(1)) if m else -1
 
 
+def _is_code2llm_owned_map(text: str) -> bool:
+    """Return whether the canonical map declares code2llm ownership."""
+    return "# producer: code2llm | artifact: map.toon.yaml" in text[:2048]
+
+
 def _refresh_map_toon(proj_dir: Path) -> None:
     """Regenerate project/map.toon.yaml and project/logic.pl from current source before embedding.
 
@@ -82,7 +87,9 @@ def _refresh_map_toon(proj_dir: Path) -> None:
             regresses = False
             if map_path.exists():
                 existing = map_path.read_text(encoding="utf-8", errors="ignore")
-                regresses = _map_module_count(existing) > _map_module_count(content)
+                regresses = _is_code2llm_owned_map(existing) or (
+                    _map_module_count(existing) > _map_module_count(content)
+                )
             if not regresses:
                 map_path.parent.mkdir(parents=True, exist_ok=True)
                 map_path.write_text(content, encoding="utf-8")
diff --git a/tests/test_pipeline.py b/tests/test_pipeline.py
index def2bdc..73f2f1b 100644
--- a/tests/test_pipeline.py
+++ b/tests/test_pipeline.py
@@ -130,6 +130,22 @@ def test_refresh_map_toon_writes_file(tmp_path: Path):
     assert True  # no exception = pass
 
 
+def test_refresh_map_toon_preserves_code2llm_owned_artifact(tmp_path: Path):
+    project_dir = tmp_path / "project"
+    project_dir.mkdir()
+    map_path = project_dir / "map.toon.yaml"
+    canonical = (
+        "# demo | 2f 10L | python:2 | 2026-07-18\n"
+        "# producer: code2llm | artifact: map.toon.yaml | schema: 1\n"
+        "M[2]:\n  app.py,5\n  lib.py,5\nD:\n  app.py:\n    main()\n"
+    )
+    map_path.write_text(canonical, encoding="utf-8")
+
+    _refresh_map_toon(tmp_path)
+
+    assert map_path.read_text(encoding="utf-8") == canonical
+
+
 def test_refresh_analysis_files_noop_without_tools(tmp_path: Path):
     # No .sumd-tools/venv → must complete without raising
     _refresh_analysis_files(tmp_path, "refactor")