What happened?

What happened?

On Windows, calling collection.add() with ChromaDB 1.3.5 hangs indefinitely and never returns. The issue is in the Rust bindings (chromadb_rust_bindings.pyd).

Versions

• ChromaDB: 1.3.5
• OS: Windows 10/11
• Python: 3.10 / 3.11

Minimal reproduction

import chromadb
from chromadb.config import Settings

client = chromadb.Client(Settings(anonymized_telemetry=False))
collection = client.create_collection('test', embedding_function=None)

# This hangs indefinitely:
collection.add(ids=['id1'], embeddings=[[0.1, 0.2, 0.3]])

Root cause analysis

Using Python's sys.settrace() for line-by-line tracing, the hang occurs at:

• File: chromadb/api/rust.py, line 441
• Code: return self.bindings.add(...)
• The call into chromadb_rust_bindings.Bindings.add() never returns

Trace output:

TRACE: chromadb\api\rust.py:441 in _add
TRACE: chromadb\api\rust.py:442 in _add
... (hangs here, loops indefinitely)

Workaround

Using SegmentAPI instead of the default Rust bindings works correctly:

from chromadb.config import Settings

settings = Settings(
    anonymized_telemetry=False,
    chroma_api_impl="chromadb.api.segment.SegmentAPI",  # Use Python implementation
)
client = chromadb.Client(settings)
collection = client.create_collection('test', embedding_function=None)
collection.add(ids=['id1'], embeddings=[[0.1, 0.2, 0.3]])  # Works!

Suggested fix

Option 1: Investigate the Rust bindings blocking issue on Windows (may be threading/async related)

Option 2: Default to SegmentAPI on Windows platform until the Rust issue is resolved

import platform

if platform.system() == "Windows":
    default_api_impl = "chromadb.api.segment.SegmentAPI"

Versions

ChromaDB: 1.3.5
OS: Windows 10/11
Python: 3.10 / 3.11

Relevant log output