diff --git a/src/agentci/adapters/codegraph.py b/src/agentci/adapters/codegraph.py
index 86c88f7..bcdcf23 100644
--- a/src/agentci/adapters/codegraph.py
+++ b/src/agentci/adapters/codegraph.py
@@ -16,7 +16,8 @@ class CodeGraphError(RuntimeError):
 class CodeGraphClient:
     async def prepare(self, workspace: Path) -> None:
         self._exclude_index(workspace)
-        command = "sync" if (workspace / ".codegraph").is_dir() else "init"
+        index = workspace / ".codegraph" / "codegraph.db"
+        command = "sync" if index.is_file() else "init"
         started = monotonic()
         log.info(
             "CodeGraph index preparation started",
diff --git a/tests/test_codegraph.py b/tests/test_codegraph.py
index 0876496..d8f063d 100644
--- a/tests/test_codegraph.py
+++ b/tests/test_codegraph.py
@@ -10,11 +10,12 @@ class FakeProcess:
         return b"", b""
 
 
-async def test_initializes_index_and_excludes_it_from_git(
+async def test_initializes_incomplete_index_and_excludes_it_from_git(
     tmp_path: Path, monkeypatch
 ) -> None:
     workspace = tmp_path / "repo"
     (workspace / ".git" / "info").mkdir(parents=True)
+    (workspace / ".codegraph").mkdir()
     calls: list[tuple[object, ...]] = []
 
     async def create_subprocess_exec(*args, **_kwargs):
@@ -38,6 +39,7 @@ async def test_syncs_an_existing_index_without_duplicating_exclude(
     workspace = tmp_path / "repo"
     (workspace / ".git" / "info").mkdir(parents=True)
     (workspace / ".codegraph").mkdir()
+    (workspace / ".codegraph" / "codegraph.db").touch()
     exclude = workspace / ".git" / "info" / "exclude"
     exclude.write_text("# local excludes\n.codegraph/\n")
     calls: list[tuple[object, ...]] = []