fix(skill): make skill prompt cache refresh nonblocking (#1924)

* fix: make skill prompt cache refresh nonblocking

* fix: harden skills prompt cache refresh

* chore: add timeout to skills cache warm-up

backend/packages/harness/deerflow/agents/lead_agent/prompt.py

@@ -1,20 +1,114 @@
+import asyncio
 import logging
+import threading
 from datetime import datetime
 from functools import lru_cache
 
 from deerflow.config.agents_config import load_agent_soul
 from deerflow.skills import load_skills
+from deerflow.skills.types import Skill
 from deerflow.subagents import get_available_subagent_names
 
 logger = logging.getLogger(__name__)
 
+_ENABLED_SKILLS_REFRESH_WAIT_TIMEOUT_SECONDS = 5.0
+_enabled_skills_lock = threading.Lock()
+_enabled_skills_cache: list[Skill] | None = None
+_enabled_skills_refresh_active = False
+_enabled_skills_refresh_version = 0
+_enabled_skills_refresh_event = threading.Event()
+
+
+def _load_enabled_skills_sync() -> list[Skill]:
+    return list(load_skills(enabled_only=True))
+
+
+def _start_enabled_skills_refresh_thread() -> None:
+    threading.Thread(
+        target=_refresh_enabled_skills_cache_worker,
+        name="deerflow-enabled-skills-loader",
+        daemon=True,
+    ).start()
+
+
+def _refresh_enabled_skills_cache_worker() -> None:
+    global _enabled_skills_cache, _enabled_skills_refresh_active
+
+    while True:
+        with _enabled_skills_lock:
+            target_version = _enabled_skills_refresh_version
+
+        try:
+            skills = _load_enabled_skills_sync()
+        except Exception:
+            logger.exception("Failed to load enabled skills for prompt injection")
+            skills = []
+
+        with _enabled_skills_lock:
+            if _enabled_skills_refresh_version == target_version:
+                _enabled_skills_cache = skills
+                _enabled_skills_refresh_active = False
+                _enabled_skills_refresh_event.set()
+                return
+
+            # A newer invalidation happened while loading. Keep the worker alive
+            # and loop again so the cache always converges on the latest version.
+            _enabled_skills_cache = None
+
+
+def _ensure_enabled_skills_cache() -> threading.Event:
+    global _enabled_skills_refresh_active
+
+    with _enabled_skills_lock:
+        if _enabled_skills_cache is not None:
+            _enabled_skills_refresh_event.set()
+            return _enabled_skills_refresh_event
+        if _enabled_skills_refresh_active:
+            return _enabled_skills_refresh_event
+        _enabled_skills_refresh_active = True
+        _enabled_skills_refresh_event.clear()
+
+    _start_enabled_skills_refresh_thread()
+    return _enabled_skills_refresh_event
+
+
+def _invalidate_enabled_skills_cache() -> threading.Event:
+    global _enabled_skills_cache, _enabled_skills_refresh_active, _enabled_skills_refresh_version
+
+    _get_cached_skills_prompt_section.cache_clear()
+    with _enabled_skills_lock:
+        _enabled_skills_cache = None
+        _enabled_skills_refresh_version += 1
+        _enabled_skills_refresh_event.clear()
+        if _enabled_skills_refresh_active:
+            return _enabled_skills_refresh_event
+        _enabled_skills_refresh_active = True
+
+    _start_enabled_skills_refresh_thread()
+    return _enabled_skills_refresh_event
+
+
+def prime_enabled_skills_cache() -> None:
+    _ensure_enabled_skills_cache()
+
+
+def warm_enabled_skills_cache(timeout_seconds: float = _ENABLED_SKILLS_REFRESH_WAIT_TIMEOUT_SECONDS) -> bool:
+    if _ensure_enabled_skills_cache().wait(timeout=timeout_seconds):
+        return True
+
+    logger.warning("Timed out waiting %.1fs for enabled skills cache warm-up", timeout_seconds)
+    return False
+
 
 def _get_enabled_skills():
-    try:
-        return list(load_skills(enabled_only=True))
-    except Exception:
-        logger.exception("Failed to load enabled skills for prompt injection")
-        return []
+    with _enabled_skills_lock:
+        cached = _enabled_skills_cache
+
+    if cached is not None:
+        return list(cached)
+
+    _ensure_enabled_skills_cache()
+    return []
 
 
 def _skill_mutability_label(category: str) -> str:
@@ -22,7 +116,36 @@ def _skill_mutability_label(category: str) -> str:
 
 
 def clear_skills_system_prompt_cache() -> None:
+    _invalidate_enabled_skills_cache()
+
+
+async def refresh_skills_system_prompt_cache_async() -> None:
+    await asyncio.to_thread(_invalidate_enabled_skills_cache().wait)
+
+
+def _reset_skills_system_prompt_cache_state() -> None:
+    global _enabled_skills_cache, _enabled_skills_refresh_active, _enabled_skills_refresh_version
+
     _get_cached_skills_prompt_section.cache_clear()
+    with _enabled_skills_lock:
+        _enabled_skills_cache = None
+        _enabled_skills_refresh_active = False
+        _enabled_skills_refresh_version = 0
+        _enabled_skills_refresh_event.clear()
+
+
+def _refresh_enabled_skills_cache() -> None:
+    """Backward-compatible test helper for direct synchronous reload."""
+    try:
+        skills = _load_enabled_skills_sync()
+    except Exception:
+        logger.exception("Failed to load enabled skills for prompt injection")
+        skills = []
+
+    with _enabled_skills_lock:
+        _enabled_skills_cache = skills
+        _enabled_skills_refresh_active = False
+        _enabled_skills_refresh_event.set()
 
 
 def _build_skill_evolution_section(skill_evolution_enabled: bool) -> str: