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ObservabilityWeights & Biases

W&B Weave

Tracing and evaluation for LLM apps, from Weights & Biases.

Categories
ObservabilityEval
Pricing
FREEMIUM
Source
Open core
Hosting
Hybrid
Platforms
APIWeb
Models
BYO key / model
Verified
Jun 8, 2026

An observability and evaluation toolkit for generative-AI applications. A single @weave.op decorator traces every model call — capturing inputs, outputs, latency, token cost, and errors — and the same SDK builds rigorous evaluations using LLM-as-judge and custom scorers. Traces and experiments are organized in the Weights & Biases web platform for side-by-side comparison across prompts and models.

Capabilities 4

What it actually does — grouped by capability family.

  • LLM observability (primary capability)
  • LLM evaluation (primary capability)
  • Guardrails (secondary capability)
  • Prompt management (secondary capability)

Pros & cons

  • Single decorator traces every call
  • Tracing + evaluation in one SDK
  • LLM-as-judge and custom scorers
  • Apache-2.0 SDK
  • Ties into W&B experiment tracking
  • Traces land in W&B hosted platform
  • Best value if already on W&B
  • Free only for solo use

Tags

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