fix: prevent hang in CI by flushing print statements and redirecting embedding server output

- Add flush=True to all print statements in convert_to_csr.py to prevent buffer deadlock
- Redirect embedding server stdout/stderr to DEVNULL in CI environment (CI=true)
- Fix timeout in embedding_server_manager.stop_server() final wait call

packages/leann-backend-hnsw/leann_backend_hnsw/convert_to_csr.py

@@ -1,5 +1,6 @@
 import argparse
 import gc  # Import garbage collector interface
+import logging
 import os
 import struct
 import sys
@@ -7,6 +8,12 @@ import time
 
 import numpy as np
 
+# Set up logging to avoid print buffer issues
+logger = logging.getLogger(__name__)
+LOG_LEVEL = os.getenv("LEANN_LOG_LEVEL", "WARNING").upper()
+log_level = getattr(logging, LOG_LEVEL, logging.WARNING)
+logger.setLevel(log_level)
+
 # --- FourCCs (add more if needed) ---
 INDEX_HNSW_FLAT_FOURCC = int.from_bytes(b"IHNf", "little")
 # Add other HNSW fourccs if you expect different storage types inside HNSW
@@ -243,6 +250,12 @@ def convert_hnsw_graph_to_csr(input_filename, output_filename, prune_embeddings=
         output_filename: Output CSR index file
         prune_embeddings: Whether to prune embedding storage (write NULL storage marker)
     """
+    # Disable buffering for print statements to avoid deadlock in CI/pytest
+    import functools
+
+    global print
+    print = functools.partial(print, flush=True)
+
     print(f"Starting conversion: {input_filename} -> {output_filename}")
     start_time = time.time()
     original_hnsw_data = {}

packages/leann-core/src/leann/embedding_server_manager.py

@@ -305,15 +305,23 @@ class EmbeddingServerManager:
         project_root = Path(__file__).parent.parent.parent.parent.parent
         logger.info(f"Command: {' '.join(command)}")
 
-        # Let server output go directly to console
-        # The server will respect LEANN_LOG_LEVEL environment variable
-        # IMPORTANT: Use a new session so we can manage the whole process group reliably,
-        # and detach stdio to avoid lingering output keeping CI steps noisy/alive.
+        # In CI environment, redirect output to avoid buffer deadlock
+        # Embedding servers use many print statements that can fill buffers
+        is_ci = os.environ.get("CI") == "true"
+        if is_ci:
+            stdout_target = subprocess.DEVNULL
+            stderr_target = subprocess.DEVNULL
+            logger.info("CI environment detected, redirecting embedding server output to DEVNULL")
+        else:
+            stdout_target = None  # Direct to console for visible logs
+            stderr_target = None  # Direct to console for visible logs
+
+        # IMPORTANT: Use a new session so we can manage the whole process group reliably
         self.server_process = subprocess.Popen(
             command,
             cwd=project_root,
-            stdout=None,  # Direct to console for visible logs
-            stderr=None,  # Direct to console for visible logs
+            stdout=stdout_target,
+            stderr=stderr_target,
             start_new_session=True,
         )
         self.server_port = port