OpenAI Launches Astra for Law and Its Own Legal Research Index
OpenAI has launched Astra for Law, powered by its GPT-6 Astra model, specifically tailored for legal work. This innovative tool comes with a comprehensive legal research index covering 230 million URLs of US law. Harvey and Legora are among the partners already building on this foundation.
September 18, 2026 - 8:53 am
Credit: OpenAI
“As AI becomes more open and interoperable, the value is not in connectivity alone,” stated Joel Hron, Chief Technology Officer of Thomson Reuters, in a supportive note for OpenAI. “Legal professionals need more than access to information.”
Astra for Law: Features and Capabilities
OpenAI introduced Astra for Law on September 17th. This powerful model offers legal search, instructions for legal analysis and writing, and security controls designed for law firms. A Trusted Access program in ChatGPT and Codex allows select firms early access. The API will follow later as gpt-6-astra-law.
The Legal Research Index
While the specific model configuration matters, what truly matters is the underlying index. OpenAI has built a vast legal search index encompassing:
- United States case law
- Statutes
- Regulations
- Court rules
- Administrative decisions
Spanning over 230 million URLs, the index grows daily with new sources, including significant contributions from the Free Law Project's CourtListener. OpenAI emphasizes this index complements existing licensed content and specialist products offered by providers like Thomson Reuters.
Benchmarking and Performance
OpenAI evaluated Astra for Law using 200 US legal research questions from the private validation set of Vals AI’s Legal Research Bench. At the highest reasoning effort, the configured model passed 54.0% of overall correctness checks. GPT-6 Astra with web search alone achieved 38.7%.
While OpenAI claims a 40% relative improvement, it's important to note that nearly half the questions remained unanswered correctly by the system. It outperformed in identifying relevant case law and retrieving relevant passages from correct opinions, however.
Partner Plugins and Integrations
In conjunction with Astra for Law, OpenAI launched 26 partner-built plugins integrating ChatGPT with existing legal tools used by firms like Relativity, Clio, iManage, Intapp, and DeepJudge. Nine community plugins from LegalQuants, LECG, and Skills.law offer 47 custom skills.
Additionally, ChatGPT for Word became generally available the same day. Several vendors issued press releases announcing their integrations between 16:00 and 16:15 New York time.