fix(config): reset config-backed singletons on hot reload (#2588)

* Fix stale config singletons on reload

* fix(config): update checkpointer imports after runtime move

* Fix config reload singleton mutation on validation failure

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/packages/harness/deerflow/config/app_config.py

@@ -1,5 +1,6 @@
 import logging
 import os
+from collections.abc import Mapping
 from contextvars import ContextVar
 from pathlib import Path
 from typing import Any, Self
@@ -157,56 +158,54 @@ class AppConfig(BaseModel):
         config_data = cls.resolve_env_variables(config_data)
         cls._apply_database_defaults(config_data)
 
-        # Load title config if present
-        if "title" in config_data:
-            load_title_config_from_dict(config_data["title"])
-
-        # Load summarization config if present
-        if "summarization" in config_data:
-            load_summarization_config_from_dict(config_data["summarization"])
-
-        # Load memory config if present
-        if "memory" in config_data:
-            load_memory_config_from_dict(config_data["memory"])
-
-        # Always refresh agents API config so removed config sections reset
-        # singleton-backed state to its default/disabled values on reload.
-        load_agents_api_config_from_dict(config_data.get("agents_api") or {})
-
-        # Load subagents config if present
-        if "subagents" in config_data:
-            load_subagents_config_from_dict(config_data["subagents"])
-
-        # Load tool_search config if present
-        if "tool_search" in config_data:
-            load_tool_search_config_from_dict(config_data["tool_search"])
-
-        # Load guardrails config if present
-        if "guardrails" in config_data:
-            load_guardrails_config_from_dict(config_data["guardrails"])
-
         # Load circuit_breaker config if present
         if "circuit_breaker" in config_data:
             config_data["circuit_breaker"] = config_data["circuit_breaker"]
 
-        # Load checkpointer config if present
-        if "checkpointer" in config_data:
-            load_checkpointer_config_from_dict(config_data["checkpointer"])
-
-        # Load stream bridge config if present
-        if "stream_bridge" in config_data:
-            load_stream_bridge_config_from_dict(config_data["stream_bridge"])
-
-        # Always refresh ACP agent config so removed entries do not linger across reloads.
-        load_acp_config_from_dict(config_data.get("acp_agents", {}))
-
         # Load extensions config separately (it's in a different file)
         extensions_config = ExtensionsConfig.from_file()
         config_data["extensions"] = extensions_config.model_dump()
 
         result = cls.model_validate(config_data)
+        acp_agents = cls._validate_acp_agents(config_data.get("acp_agents", {}))
+        cls._apply_singleton_configs(result, acp_agents)
         return result
 
+    @classmethod
+    def _validate_acp_agents(
+        cls,
+        config_data: Mapping[str, Mapping[str, object]] | None,
+    ) -> dict[str, ACPAgentConfig]:
+        if config_data is None:
+            config_data = {}
+        return {name: ACPAgentConfig(**cfg) for name, cfg in config_data.items()}
+
+    @classmethod
+    def _apply_singleton_configs(cls, config: Self, acp_agents: dict[str, ACPAgentConfig]) -> None:
+        from deerflow.config.checkpointer_config import get_checkpointer_config
+
+        previous_checkpointer_config = get_checkpointer_config()
+
+        load_title_config_from_dict(config.title.model_dump())
+        load_summarization_config_from_dict(config.summarization.model_dump())
+        load_memory_config_from_dict(config.memory.model_dump())
+        load_agents_api_config_from_dict(config.agents_api.model_dump())
+        load_subagents_config_from_dict(config.subagents.model_dump())
+        load_tool_search_config_from_dict(config.tool_search.model_dump())
+        load_guardrails_config_from_dict(config.guardrails.model_dump())
+        load_checkpointer_config_from_dict(config.checkpointer.model_dump() if config.checkpointer is not None else None)
+        load_stream_bridge_config_from_dict(config.stream_bridge.model_dump() if config.stream_bridge is not None else None)
+        load_acp_config_from_dict({name: agent.model_dump() for name, agent in acp_agents.items()})
+
+        if previous_checkpointer_config != config.checkpointer:
+            # These runtime singletons derive their backend from checkpointer config.
+            # Keep imports local to avoid cycles: both providers import get_app_config.
+            from deerflow.runtime.checkpointer import reset_checkpointer
+            from deerflow.runtime.store import reset_store
+
+            reset_checkpointer()
+            reset_store()
+
     @classmethod
     def _apply_database_defaults(cls, config_data: dict[str, Any]) -> None:
         """Apply config.yaml defaults for persistence when the section is absent."""

backend/packages/harness/deerflow/config/checkpointer_config.py

@@ -40,7 +40,10 @@ def set_checkpointer_config(config: CheckpointerConfig | None) -> None:
     _checkpointer_config = config
 
 
-def load_checkpointer_config_from_dict(config_dict: dict) -> None:
+def load_checkpointer_config_from_dict(config_dict: dict | None) -> None:
     """Load checkpointer configuration from a dictionary."""
     global _checkpointer_config
+    if config_dict is None:
+        _checkpointer_config = None
+        return
     _checkpointer_config = CheckpointerConfig(**config_dict)

backend/packages/harness/deerflow/config/stream_bridge_config.py

@@ -40,7 +40,10 @@ def set_stream_bridge_config(config: StreamBridgeConfig | None) -> None:
     _stream_bridge_config = config
 
 
-def load_stream_bridge_config_from_dict(config_dict: dict) -> None:
+def load_stream_bridge_config_from_dict(config_dict: dict | None) -> None:
     """Load stream bridge configuration from a dictionary."""
     global _stream_bridge_config
+    if config_dict is None:
+        _stream_bridge_config = None
+        return
     _stream_bridge_config = StreamBridgeConfig(**config_dict)

backend/packages/harness/deerflow/config/subagents_config.py

@@ -179,9 +179,3 @@ def load_subagents_config_from_dict(config_dict: dict) -> None:
             overrides_summary or "none",
             custom_agents_names or "none",
         )
-    else:
-        logger.info(
-            "Subagents config loaded: default timeout=%ss, default max_turns=%s, no per-agent overrides",
-            _subagents_config.timeout_seconds,
-            _subagents_config.max_turns,
-        )