fix(agents): require config.yaml in resolve_agent_dir to skip memory-only directories (#3390) (#3481)

When memory is enabled, the first conversation with a legacy shared agent
creates a per-user agent directory containing only memory.json (no
config.yaml). On the second turn, resolve_agent_dir() returned this
incomplete directory, causing load_agent_config() to fail with
"Agent config not found".

Require config.yaml to exist alongside the directory for both the
per-user and legacy paths, so that memory-only directories fall
through correctly. This aligns resolve_agent_dir with the existing
config.yaml check in list_custom_agents.

Refs: https://github.com/bytedance/deer-flow/issues/3390

backend/tests/test_custom_agent.py

@@ -203,6 +203,79 @@ class TestLoadAgentConfig:
         assert cfg.name == "legacy-agent"
 
 
+# ===========================================================================
+# 3b. resolve_agent_dir — memory-only directory fallback (#3390)
+# ===========================================================================
+
+
+class TestResolveAgentDirMemoryOnlyFallback:
+    """Regression tests for #3390.
+
+    When memory is enabled, the first conversation creates a user-isolated
+    agent directory containing only ``memory.json`` (no ``config.yaml``).
+    On the next turn ``resolve_agent_dir`` must fall through to the legacy
+    shared layout instead of returning the incomplete user directory.
+    """
+
+    def test_user_dir_with_only_memory_falls_back_to_legacy(self, tmp_path):
+        """User dir has memory.json but no config.yaml → use legacy dir."""
+        from deerflow.config.agents_config import resolve_agent_dir
+
+        # Legacy agent with full config
+        legacy_dir = tmp_path / "agents" / "my-agent"
+        legacy_dir.mkdir(parents=True)
+        (legacy_dir / "config.yaml").write_text("name: my-agent\n", encoding="utf-8")
+        (legacy_dir / "SOUL.md").write_text("legacy soul", encoding="utf-8")
+
+        # User dir created by memory write — no config.yaml
+        user_dir = tmp_path / "users" / "u1" / "agents" / "my-agent"
+        user_dir.mkdir(parents=True)
+        (user_dir / "memory.json").write_text("{}", encoding="utf-8")
+
+        with patch("deerflow.config.agents_config.get_paths", return_value=_make_paths(tmp_path)), patch("deerflow.config.agents_config.get_effective_user_id", return_value="u1"):
+            result = resolve_agent_dir("my-agent", user_id="u1")
+
+        assert result == legacy_dir
+
+    def test_user_dir_with_config_takes_priority(self, tmp_path):
+        """User dir with config.yaml should still win over legacy."""
+        from deerflow.config.agents_config import resolve_agent_dir
+
+        # Legacy
+        legacy_dir = tmp_path / "agents" / "my-agent"
+        legacy_dir.mkdir(parents=True)
+        (legacy_dir / "config.yaml").write_text("name: my-agent\n", encoding="utf-8")
+
+        # User dir with full config (migrated)
+        user_dir = tmp_path / "users" / "u1" / "agents" / "my-agent"
+        user_dir.mkdir(parents=True)
+        (user_dir / "config.yaml").write_text("name: my-agent\nmodel: gpt-4\n", encoding="utf-8")
+        (user_dir / "memory.json").write_text("{}", encoding="utf-8")
+
+        with patch("deerflow.config.agents_config.get_paths", return_value=_make_paths(tmp_path)), patch("deerflow.config.agents_config.get_effective_user_id", return_value="u1"):
+            result = resolve_agent_dir("my-agent", user_id="u1")
+
+        assert result == user_dir
+
+    def test_load_config_falls_back_when_user_dir_is_memory_only(self, tmp_path):
+        """End-to-end: load_agent_config works when user dir only has memory.json."""
+        config_dict = {"name": "my-agent", "description": "Legacy agent", "model": "deepseek-v3"}
+        _write_agent(tmp_path, "my-agent", config_dict)
+
+        # Simulate memory write creating user dir without config
+        user_dir = tmp_path / "users" / "u1" / "agents" / "my-agent"
+        user_dir.mkdir(parents=True)
+        (user_dir / "memory.json").write_text("{}", encoding="utf-8")
+
+        with patch("deerflow.config.agents_config.get_paths", return_value=_make_paths(tmp_path)), patch("deerflow.config.agents_config.get_effective_user_id", return_value="u1"):
+            from deerflow.config.agents_config import load_agent_config
+
+            cfg = load_agent_config("my-agent", user_id="u1")
+
+        assert cfg.name == "my-agent"
+        assert cfg.model == "deepseek-v3"
+
+
 # ===========================================================================
 # 4. load_agent_soul
 # ===========================================================================