feat(skills): support recursive nested skill loading (#950)

* feat(skills): support recursive nested skill loading

* Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

backend/CLAUDE.md

@@ -231,7 +231,7 @@ Proxied through nginx: `/api/langgraph/*` → LangGraph, all other `/api/*` →
 
 - **Location**: `deer-flow/skills/{public,custom}/`
 - **Format**: Directory with `SKILL.md` (YAML frontmatter: name, description, license, allowed-tools)
-- **Loading**: `load_skills()` scans directories, parses SKILL.md, reads enabled state from extensions_config.json
+- **Loading**: `load_skills()` recursively scans `skills/{public,custom}` for `SKILL.md`, parses metadata, and reads enabled state from extensions_config.json
 - **Injection**: Enabled skills listed in agent system prompt with container paths
 - **Installation**: `POST /api/skills/install` extracts .skill ZIP archive to custom/ directory
 

backend/README.md

@@ -77,6 +77,7 @@ Per-thread isolated execution with virtual path translation:
 - **Providers**: `LocalSandboxProvider` (filesystem) and `AioSandboxProvider` (Docker, in community/)
 - **Virtual paths**: `/mnt/user-data/{workspace,uploads,outputs}` → thread-specific physical directories
 - **Skills path**: `/mnt/skills` → `deer-flow/skills/` directory
+- **Skills loading**: Recursively discovers nested `SKILL.md` files under `skills/{public,custom}` and preserves nested container paths
 - **Tools**: `bash`, `ls`, `read_file`, `write_file`, `str_replace`
 
 ### Subagent System

backend/src/skills/loader.py

@@ -1,3 +1,4 @@
+import os
 from pathlib import Path
 
 from .parser import parse_skill_file
@@ -59,16 +60,16 @@ def load_skills(skills_path: Path | None = None, use_config: bool = True, enable
         if not category_path.exists() or not category_path.is_dir():
             continue
 
-        # Each subdirectory is a potential skill
-        for skill_dir in category_path.iterdir():
-            if not skill_dir.is_dir():
+        for current_root, dir_names, file_names in os.walk(category_path):
+            # Keep traversal deterministic and skip hidden directories.
+            dir_names[:] = sorted(name for name in dir_names if not name.startswith("."))
+            if "SKILL.md" not in file_names:
                 continue
 
-            skill_file = skill_dir / "SKILL.md"
-            if not skill_file.exists():
-                continue
+            skill_file = Path(current_root) / "SKILL.md"
+            relative_path = skill_file.parent.relative_to(category_path)
 
-            skill = parse_skill_file(skill_file, category=category)
+            skill = parse_skill_file(skill_file, category=category, relative_path=relative_path)
             if skill:
                 skills.append(skill)
 

backend/src/skills/parser.py

@@ -4,7 +4,7 @@ from pathlib import Path
 from .types import Skill
 
 
-def parse_skill_file(skill_file: Path, category: str) -> Skill | None:
+def parse_skill_file(skill_file: Path, category: str, relative_path: Path | None = None) -> Skill | None:
     """
     Parse a SKILL.md file and extract metadata.
 
@@ -55,6 +55,7 @@ def parse_skill_file(skill_file: Path, category: str) -> Skill | None:
             license=license_text,
             skill_dir=skill_file.parent,
             skill_file=skill_file,
+            relative_path=relative_path or Path(skill_file.parent.name),
             category=category,
             enabled=True,  # Default to enabled, actual state comes from config file
         )

backend/src/skills/types.py

@@ -11,13 +11,15 @@ class Skill:
     license: str | None
     skill_dir: Path
     skill_file: Path
+    relative_path: Path  # Relative path from category root to skill directory
     category: str  # 'public' or 'custom'
     enabled: bool = False  # Whether this skill is enabled
 
     @property
     def skill_path(self) -> str:
-        """Returns the relative path from skills root to this skill's directory"""
-        return self.skill_dir.name
+        """Returns the relative path from the category root (skills/{category}) to this skill's directory"""
+        path = self.relative_path.as_posix()
+        return "" if path == "." else path
 
     def get_container_path(self, container_base_path: str = "/mnt/skills") -> str:
         """
@@ -29,7 +31,11 @@ class Skill:
         Returns:
             Full container path to the skill directory
         """
-        return f"{container_base_path}/{self.category}/{self.skill_dir.name}"
+        category_base = f"{container_base_path}/{self.category}"
+        skill_path = self.skill_path
+        if skill_path:
+            return f"{category_base}/{skill_path}"
+        return category_base
 
     def get_container_file_path(self, container_base_path: str = "/mnt/skills") -> str:
         """
@@ -41,7 +47,7 @@ class Skill:
         Returns:
             Full container path to the skill's SKILL.md file
         """
-        return f"{container_base_path}/{self.category}/{self.skill_dir.name}/SKILL.md"
+        return f"{self.get_container_path(container_base_path)}/SKILL.md"
 
     def __repr__(self) -> str:
         return f"Skill(name={self.name!r}, description={self.description!r}, category={self.category!r})"

backend/tests/test_skills_loader.py

@@ -0,0 +1,57 @@
+"""Tests for recursive skills loading."""
+
+from pathlib import Path
+
+from src.skills.loader import load_skills
+
+
+def _write_skill(skill_dir: Path, name: str, description: str) -> None:
+    """Write a minimal SKILL.md for tests."""
+    skill_dir.mkdir(parents=True, exist_ok=True)
+    content = f"---\nname: {name}\ndescription: {description}\n---\n\n# {name}\n"
+    (skill_dir / "SKILL.md").write_text(content, encoding="utf-8")
+
+
+def test_load_skills_discovers_nested_skills_and_sets_container_paths(tmp_path: Path):
+    """Nested skills should be discovered recursively with correct container paths."""
+    skills_root = tmp_path / "skills"
+
+    _write_skill(skills_root / "public" / "root-skill", "root-skill", "Root skill")
+    _write_skill(skills_root / "public" / "parent" / "child-skill", "child-skill", "Child skill")
+    _write_skill(skills_root / "custom" / "team" / "helper", "team-helper", "Team helper")
+
+    skills = load_skills(skills_path=skills_root, use_config=False, enabled_only=False)
+    by_name = {skill.name: skill for skill in skills}
+
+    assert {"root-skill", "child-skill", "team-helper"} <= set(by_name)
+
+    root_skill = by_name["root-skill"]
+    child_skill = by_name["child-skill"]
+    team_skill = by_name["team-helper"]
+
+    assert root_skill.skill_path == "root-skill"
+    assert root_skill.get_container_file_path() == "/mnt/skills/public/root-skill/SKILL.md"
+
+    assert child_skill.skill_path == "parent/child-skill"
+    assert child_skill.get_container_file_path() == "/mnt/skills/public/parent/child-skill/SKILL.md"
+
+    assert team_skill.skill_path == "team/helper"
+    assert team_skill.get_container_file_path() == "/mnt/skills/custom/team/helper/SKILL.md"
+
+
+def test_load_skills_skips_hidden_directories(tmp_path: Path):
+    """Hidden directories should be excluded from recursive discovery."""
+    skills_root = tmp_path / "skills"
+
+    _write_skill(skills_root / "public" / "visible" / "ok-skill", "ok-skill", "Visible skill")
+    _write_skill(
+        skills_root / "public" / "visible" / ".hidden" / "secret-skill",
+        "secret-skill",
+        "Hidden skill",
+    )
+
+    skills = load_skills(skills_path=skills_root, use_config=False, enabled_only=False)
+    names = {skill.name for skill in skills}
+
+    assert "ok-skill" in names
+    assert "secret-skill" not in names