We’ve added Claude Opus 5.5, Anthropic’s new AI model, to Zeno. Before the release, we evaluated it on Dutch and EU legal research questions, assessing both the substance of the answers and their supporting citations.
The update brings Opus 5.5 into Zeno’s legal research environment, where you can review an analysis alongside the authorities supporting it.
What the update means for legal research
When preparing advice, the usefulness of an AI-generated analysis depends on whether you can examine how it reaches a conclusion. The relevant provision, the authority of a judgment and the facts of the matter all deserve scrutiny.
Zeno connects legal analysis to supporting sources, including relevant passages where available. That gives you a starting point for checking the reasoning, identifying gaps and deciding what needs further research before the analysis informs your advice.
Our assessment of Opus 5.5 therefore looked at its answers within Zeno’s research workflows. Testing the model with the legal sources and tools around it helps us understand how it behaves in that setting.
How we evaluated Claude Opus 5.5
Our internal evaluation covered 60 Dutch and EU legal questions. The model configurations tested answered the same questions and were assessed against the same predefined criteria, covering substantive legal analysis and supporting citations.
Each configuration generated one answer per question. We used automated scoring against those criteria to compare the answers. The assessment covered both what an answer said and its citations; a fluent explanation alone was not enough.
This was a focused internal comparison. Automated scoring has limitations, and one answer per question does not capture the variation between repeated attempts. The evaluation does not establish performance across all legal matters or replace professional review.
Working with Opus 5.5 in Zeno
For a first look, revisit a legal question where you already know the relevant authorities. Read the answer alongside its sources, check whether the reasoning fits the facts and consider what you would still need to resolve before using it in a memo or advice.
That review remains part of the work. Opus 5.5 provides groundwork for your assessment; the legal judgement and final advice remain yours.
New to Zeno? Book a demo to discuss your firm’s legal research workflow.
