LLM observability & evaluation · Weights & Biases

W&B Weave

LLM tracing and evaluation toolkit from Weights & Biases, sharing billing and infrastructure with its ML experiment-tracking platform.

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Weave is Weights & Biases' toolkit for tracing, evaluating, and monitoring generative AI applications, extending the company's existing experiment-tracking platform to LLM-specific workflows: capturing traces of calls and agent steps, running evaluations with custom scorers or LLM-as-judge, and tracking datasets and prompts in a versioned registry. Because it is built into the broader W&B platform, teams already using Weights & Biases for traditional ML experiment tracking get LLM observability under the same account, seats, and billing rather than a separate tool. Weave functionality is available across all W&B plans, including a free tier; what differs by tier is monthly data-ingestion allowance, storage, and enterprise controls such as SSO and single-tenant deployment. Self-hosted (Personal, free for non-commercial use) and Advanced Enterprise self-managed options exist alongside the hosted cloud service.

At a glance

Vendor Weights & Biases
Pricing model Free tier + paid plans
Free tier Yes
Deployment Cloud, Self-hosted
Open source No
Best for Teams already using Weights & Biases for ML experiment tracking who want LLM tracing under the same platform.

Pricing

Weave tracing, evaluation, and monitoring are included on every W&B plan, including the free tier; paid Pro and Enterprise plans raise seat, storage, and monthly data-ingestion limits and add enterprise security controls, billed with metered overage for extra storage/ingestion.

Plan Price Notes
Free $0/month Up to 5 model seats, 5 GB/mo storage, 1 GB/mo Weave data ingestion
Pro From $60/month Up to 10 model seats, 100 GB/mo storage, 1.5 GB/mo Weave ingestion; overage $0.03/GB storage, $0.10/MB ingestion
Enterprise Custom Single-tenant deployment, HIPAA compliance, SSO, audit logs, dedicated support

Prices read from the vendor's own page on September 21, 2026. Vendors change prices; check the source before you budget.

Features

  • Tracing for LLM calls and multi-step agent workflows
  • Evaluation with custom scorers and LLM-as-judge metrics
  • Versioned dataset and prompt registry
  • Shared account/billing with W&B's ML experiment tracking
  • Self-hosted Personal (free, non-commercial) and Advanced Enterprise options
  • Production monitoring dashboards

Integrations

Profile last reviewed September 21, 2026

Alternatives

Arize Phoenix Open-source, local-first tracing and evaluation library for LLM and agent applications, with an optional path to Arize's commercial platform. LangSmith Tracing, evaluation, and deployment platform for LLM applications, built by the team behind LangChain and LangGraph. Braintrust Evaluation-first platform for testing, scoring, and comparing LLM application changes, with production tracing built in.

W&B Weave in the index now

Terms to know

Data observability Continuous automated monitoring of pipelines and datasets to catch freshness, volume and quality problems early. Machine learning Building models that learn patterns from data to make predictions or decisions, rather than following hand-coded rules. LLM observability Monitoring a language model's live behavior in production, tracking its inputs, outputs, latency, cost, and failure patterns.

Related guides

How to choose an LLM observability tool Pick an LLM tool by whether you need tracing, scoring or a gateway first — most teams eventually need all three, rarely from one vendor.