intextus

ColBERT embedding and MaxSim scoring without PyTorch. Uses a native C++ extension (ONNX Runtime + tokenizers-cpp) so you don't need to pull in 2 GB of deep learning dependencies just to encode some text.

Install

pip install intextus-embed

Only runtime deps are numpy and huggingface-hub.

Usage

from intextus import LateInteractionEncoder, compute_maxsim

model = LateInteractionEncoder()  # downloads intextus/mxbai-edge-colbert-v0-17m-onnx

q = model.encode_queries("What is late interaction?")
d = model.encode_docs("ColBERT computes token-level similarity.")

score = compute_maxsim(q[0], d[0])
print(score)

You can also point it at a local directory with model.onnx and tokenizer.json:

model = LateInteractionEncoder("./my-model/")

Models

Alias	Repo	Size	Dim	Notes
mxbai-edge-colbert-v0-17m	intextus/mxbai-edge-colbert-v0-17m-onnx	66 MB	48	Default
mxbai-edge-colbert-v0-32m	intextus/mxbai-edge-colbert-v0-32m-onnx	124 MB	64
colbertv2.0	intextus/colbertv2.0-onnx	438 MB	128	Standard ColBERTv2.0 BERT-based model
answerai-colbert-small-v1	intextus/answerai-colbert-small-v1-onnx	135 MB	96	Lightweight, high-performance model
jina-colbert-v2	intextus/jina-colbert-v2-onnx	2.23 GB	128	XLM-RoBERTa multilingual model
lateon	intextus/lateon-onnx	580 MB	128	Case-sensitive: use do_lower_case=False

Any ColBERT ONNX model should work if you put model.onnx and tokenizer.json in a folder and pass the path.

Benchmarks

The following benchmark was run on CPU using 20 queries (max length 32) and 20 documents (max length 256), comparing intextus against fastembed execution:

Performance (Throughput & Speedup)

Model	Operation	intextus Throughput	fastembed Throughput	Speedup (Wall-clock)
ColBERTv2.0	Queries	71.3 QPS	31.6 QPS	2.25x
ColBERTv2.0	Documents	93.8 DPS	66.1 DPS	1.42x
Jina ColBERT v2	Queries	6.2 QPS	5.0 QPS	1.25x
Jina ColBERT v2	Documents	10.1 DPS	5.2 DPS	1.94x

How it works

• Tokenization and inference run in C++ via a nanobind extension
• GIL is released during encode and MaxSim calls, so you can run multiple threads
• Punctuation tokens are masked out of document embeddings (standard ColBERT behavior)
• Embeddings are L2-normalized by default
• CPU only for now

Docker & Alpine Linux Compatibility

Because the underlying precompiled ONNX Runtime library is linked against glibc, this package will not run out-of-the-box on Alpine Linux images (e.g., python:3.10-alpine).

If deploying via Docker, it is highly recommended to use a Debian-based slim image:

FROM python:3.10-slim

If you must use Alpine, you will need to install the compatibility layer: apk add --no-cache gcompat.

Supported Platforms & Architectures

Precompiled wheels are published to PyPI for the following environments:

Operating System	Architecture	Python Versions	Notes
Linux	x86_64, aarch64	3.9, 3.10, 3.11, 3.12, 3.13, 3.14	Built on manylinux_2_28 (glibc-based)
macOS	arm64 (Apple Silicon)	3.9, 3.10, 3.11, 3.12, 3.13, 3.14	SDK/deployment target macOS 13.3+
Windows	AMD64 (x86_64)	3.9, 3.10, 3.11, 3.12, 3.13, 3.14

Note

Other platforms (such as Intel-based macOS or ARM-based Windows) will fall back to compilation from the source distribution (sdist). This requires a local C++ compiler (supporting C++17) and CMake.

License

MIT. See LICENSE.