v0.20.3 align antigravity agent layering

tests/test_adapter_deploy.py

@@ -57,6 +57,7 @@ def test_deploy_antigravity_writes_workspace_rules_and_skills(tmp_path: Path) ->
     result = deploy_antigravity(target=target, repo_root=REPO_ROOT)
 
     assert result.written
+    assert (target / ".agents" / "agents.md").exists()
     assert (target / ".agents" / "rules" / "deep-research-antigravity.md").exists()
     assert (target / ".agents" / "workflows" / "deep-research-native.md").exists()
     assert (target / ".agents" / "skills" / "antigravity-surface-adapter" / "SKILL.md").exists()
@@ -77,6 +78,19 @@ def test_deploy_antigravity_skips_existing_files_by_default(tmp_path: Path) -> N
     assert not existing.with_name("deep-research-antigravity.md.bak").exists()
 
 
+def test_deploy_antigravity_skips_existing_agents_file_by_default(tmp_path: Path) -> None:
+    target = tmp_path / "workspace"
+    existing = target / ".agents" / "agents.md"
+    existing.parent.mkdir(parents=True)
+    existing.write_text("custom agents\n", encoding="utf-8")
+
+    result = deploy_antigravity(target=target, repo_root=REPO_ROOT)
+
+    assert existing.read_text(encoding="utf-8") == "custom agents\n"
+    assert existing in result.skipped
+    assert not existing.with_name("agents.md.bak").exists()
+
+
 def test_deploy_antigravity_force_backs_up_existing_files(tmp_path: Path) -> None:
     target = tmp_path / "workspace"
     existing = target / ".agents" / "rules" / "deep-research-antigravity.md"