non-blocking read + no import in function

src/kohakuboard/api/runs.py

@@ -4,6 +4,9 @@ Unified API for accessing run data (scalars, media, tables, histograms).
 Works in both local and remote modes with project-based organization.
 """
 
+import asyncio
+import json
+from datetime import datetime, timezone
 from pathlib import Path
 
 from fastapi import APIRouter, Depends, HTTPException, Query
@@ -71,10 +74,12 @@ async def get_run_status(
     # Check metadata for creation time
     metadata_file = run_path / "metadata.json"
     if metadata_file.exists():
-        import json
+        # Use asyncio.to_thread to avoid blocking
+        def read_metadata():
+            with open(metadata_file, "r") as f:
+                return json.load(f)
 
-        with open(metadata_file, "r") as f:
-            metadata = json.load(f)
+        metadata = await asyncio.to_thread(read_metadata)
     else:
         metadata = {}
 
@@ -94,8 +99,6 @@ async def get_run_status(
                 # Convert timestamp ms to ISO string
                 ts_ms = latest_step_info.get("timestamp")
                 if ts_ms:
-                    from datetime import datetime, timezone
-
                     last_updated = datetime.fromtimestamp(
                         ts_ms / 1000, tz=timezone.utc
                     ).isoformat()

src/kohakuboard/api/utils/board_reader_hybrid.py

@@ -11,6 +11,7 @@ import time
 from pathlib import Path
 from typing import Any, Dict, List, Optional
 
+import numpy as np
 from lance.dataset import LanceDataset
 from loguru import logger
 
@@ -451,8 +452,6 @@ class HybridBoardReader:
                     num_bins = len(counts)
 
                     # Reconstruct bin edges from min/max/num_bins
-                    import numpy as np
-
                     bin_edges = np.linspace(min_val, max_val, num_bins + 1).tolist()
 
                     result.append(

src/kohakuboard/client/storage/hybrid.py

@@ -6,6 +6,8 @@ Combines the best of both worlds:
 - Adaptive histograms: Lance with percentile-based range tracking
 """
 
+import time
+from datetime import datetime, timezone
 from pathlib import Path
 from typing import Any, Dict, List, Optional
 
@@ -93,8 +95,6 @@ class HybridStorage:
             caption: Optional caption
         """
         # Record step info (use current timestamp)
-        from datetime import datetime, timezone
-
         timestamp_ms = int(datetime.now(timezone.utc).timestamp() * 1000)
         self.metadata_storage.append_step_info(step, global_step, timestamp_ms)
 
@@ -116,8 +116,6 @@ class HybridStorage:
             table_data: Table dict
         """
         # Record step info
-        from datetime import datetime, timezone
-
         timestamp_ms = int(datetime.now(timezone.utc).timestamp() * 1000)
         self.metadata_storage.append_step_info(step, global_step, timestamp_ms)
 
@@ -143,8 +141,6 @@ class HybridStorage:
             precision: "compact" (uint8) or "exact" (int32)
         """
         # Record step info
-        from datetime import datetime, timezone
-
         timestamp_ms = int(datetime.now(timezone.utc).timestamp() * 1000)
         self.metadata_storage.append_step_info(step, global_step, timestamp_ms)