Weave

Weave is Weights & Biases' toolkit for LLM development: trace every model call, score outputs with evaluations, and iterate on prompts and models — integrated with the W&B platform teams already use for ML experiment tracking. 817k PyPI downloads/month, Apache-2.0. The GitHub star count (1.1k) understates its reach — it ships as a library, not a destination repo. Choose it if you're already in the W&B ecosystem; otherwise Langfuse or Opik have larger standalone communities.

```bash

pip install weave

```

```python

import weave

weave.init("my-project")

@weave.op()

def call_llm(prompt: str) -> str: ...

```

Docs: weave-docs.wandb.ai.