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Vetro Attest vs. W&B Weave

*Engineering comparison, not legal advice. Weave features change quickly; check the Weights & Biases documentation for the current state.*

Weave comes from the experiment-tracking world: it records what your LLM application did so you can compare, evaluate and improve it. Vetro Attest takes one of those records and makes it checkable by someone outside your team.

What Weave does well

Weave is the LLM toolkit of Weights & Biases. Teams use it to:

• Trace functions, LLM calls and agent steps with a decorator, capturing inputs, outputs, latency and cost;
• Evaluate models and prompts against datasets with scorers, and compare runs in the same workspace as their other ML experiments;
• Version datasets, prompts and models as tracked objects;
• Collect feedback on production calls.

For teams already on W&B, keeping LLM work next to training runs is a real advantage.

What an experiment-tracking tool does not give you

Evidence for a regulator, an auditor or a customer must convince someone who does not trust you.

• The operator controls the data. Traces live in a project your organisation administers and can edit or delete, so an export is a claim, not proof.
• Built for comparison, not for disputes. Experiment tracking answers "which version is better". A disputed decision needs "this is exactly what happened in that run, unchanged since".
• No independent timestamp or signature. An export shows what the workspace held when you exported it, not what it held at the time of the incident.
• No mapping onto the AI Act. Logging duties (Art. 12, 19, 26) ask what the logs make traceable, not only what they contain.

None of this is a flaw in Weave; it is outside what the tool is for.

What Vetro Attest adds

Vetro Attest accepts an OTLP/JSON trace with the OpenTelemetry GenAI semantic conventions, or a natively signed Vetro ledger, rebuilds it into a hash-chained ledger and checks it for free. For 49 USD, one-off, you get:

• a full EU AI Act report (Markdown and HTML) mapping the trace onto logging obligations;
• an ed25519 countersignature over the digest, event count and timestamp, verifiable by anyone against our published public key, no account needed.

The countersignature attests that the trace verified at a time. It does not attest that the events are true; the report is a structured aid, not legal advice or certification.

When to use both

• Keep Weave to trace, evaluate and version your LLM application.
• When a run matters, export its trace as OTLP/JSON (or record it with the Vetro SDK) and get it countersigned. Store the attestation next to the trace.
• On an audit or dispute, hand over the trace plus the attestation. The recipient checks the signature themselves.

Weave tells you what your application did and whether it improved. The countersignature lets someone else believe it.

Try it

• Run the free EU AI Act Art. 12/14 checker.
• Paste an OTLP trace on the Vetro Attest home page and verify it free. The full report plus countersignature is 49 USD, no subscription.

See a sample ledger verified in one click, check your own logs free or get the countersigned EU AI Act report.