diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ef96528..8c2179a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,7 +22,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: "3.11"
-      - run: pip install ruff>=0.4
+      - run: pip install "ruff>=0.4"
       - run: ruff check catchme/
       - run: ruff format --check catchme/
 
diff --git a/catchme/mcp_server.py b/catchme/mcp_server.py
index daf41d9..84c5cbd 100644
--- a/catchme/mcp_server.py
+++ b/catchme/mcp_server.py
@@ -23,6 +23,7 @@
 
 from __future__ import annotations
 
+import asyncio
 import json
 import logging
 
@@ -47,7 +48,7 @@ def serve() -> None:
     from mcp.server.stdio import stdio_server
     from mcp.types import TextContent, Tool
 
-    from .pipelines.retrieve import retrieve, _load_all_trees, _node_index
+    from .pipelines.retrieve import _load_all_trees, _node_index, retrieve
 
     server = Server("catchme")
 
@@ -163,12 +164,14 @@ def _handle_list_days() -> list[TextContent]:
         days = []
         for t in trees:
             node = t.get("tree", {})
-            days.append({
-                "date": t.get("date", node.get("title", "?")),
-                "node_id": node.get("node_id", ""),
-                "summary": (node.get("summary") or "")[:300],
-                "session_count": len(node.get("children", [])),
-            })
+            days.append(
+                {
+                    "date": t.get("date", node.get("title", "?")),
+                    "node_id": node.get("node_id", ""),
+                    "summary": (node.get("summary") or "")[:300],
+                    "session_count": len(node.get("children", [])),
+                }
+            )
         return [TextContent(type="text", text=json.dumps(days, ensure_ascii=False, indent=2))]
 
     # ── get_session ──────────────────────────────────────────────────────────
@@ -197,7 +200,9 @@ def _slim(n: dict, depth: int = 0) -> dict:
                 out["children"] = [_slim(c, depth + 1) for c in n.get("children", [])]
             return out
 
-        return [TextContent(type="text", text=json.dumps(_slim(node), ensure_ascii=False, indent=2))]
+        return [
+            TextContent(type="text", text=json.dumps(_slim(node), ensure_ascii=False, indent=2))
+        ]
 
     # ── get_tree ─────────────────────────────────────────────────────────────
 
@@ -214,8 +219,6 @@ def _handle_get_tree(args: dict) -> list[TextContent]:
 
     # ── run ──────────────────────────────────────────────────────────────────
 
-    import asyncio
-
     async def _run():
         async with stdio_server() as (read_stream, write_stream):
             await server.run(read_stream, write_stream, server.create_initialization_options())