# Weave

> Open-source toolkit by Weights & Biases for tracing and evaluating AI agents and LLM applications.

Weave is a toolkit from Weights & Biases for tracing and evaluating AI agents and LLM applications. It ships Python and TypeScript libraries, and the Python library is released under the Apache 2.0 license. Weights & Biases is now part of CoreWeave Forge, and the documentation is hosted on the CoreWeave docs site.

## What It Is

Weave is an observability and evaluation platform for agents and LLM apps. After installing the library and calling `weave.init()` with a project name, it records what your application does and sends the data to your W&B (CoreWeave Forge) account for review.

## Tracing Agents and Functions

For supported agent SDKs, including the OpenAI Agents SDK, Claude Agent SDK and Google ADK, `weave.init()` is enough to trace conversations, turns, LLM calls and tool calls. These appear in the Agents tab. Custom agent loops can be wrapped with `start_conversation`, `start_turn`, `start_llm` and `start_tool`. Agents instrumented with OpenTelemetry can send spans to Weave's OTLP endpoint without installing the Weave SDK.

For non-agent code, the `@weave.op` decorator traces functions into the Calls tab. This suits evaluations, scorers and standalone LLM calls. Plain `openai` calls are also auto-traced after initialization.

## Evaluation and Iteration

The docs describe evaluation pipelines that use LLM judges and custom scorers. They include tutorials for evaluating RAG applications. The platform also covers versioning, prompt and model experimentation, and monitoring with feedback collection.

## Setup Path

Install with `pip install weave` or `npm install weave`, create an account, and set an API key. The Python library requires Python 3.10 or higher. The docs note that CoreWeave Agent Lens is the successor to Weights & Biases Weave for agent tracing workflows. Both services already receive agent tracing data, so nothing needs to be migrated.

## Features
- Agent tracing of conversations, turns, LLM calls and tool calls
- Function tracing with @weave.op
- OpenTelemetry span ingestion
- Evaluations with LLM judges and custom scorers
- RAG application evaluation
- Prompt and model experimentation
- Versioning of objects
- Monitoring and feedback collection
- Python and TypeScript libraries

## Integrations
OpenAI Agents SDK, Claude Agent SDK, Google ADK, OpenAI, LangChain, LlamaIndex, OpenTelemetry

## Platforms
IOS, WEB, API, DEVELOPER_SDK, CLI

## Pricing
Open Source

## Version
v0.53.12

## Links
- Website: https://wandb.me/weave
- Documentation: https://docs.coreweave.com/products/wandb/weave
- Repository: https://github.com/wandb/weave
- EveryDev.ai: https://www.everydev.ai/tools/weave