ChatGPT-5.6 Luna shifts to site: search, cites fewer sources
ChatGPT-5.6 Luna, now OpenAI’s default ChatGPT model, runs far more site-targeted searches than its predecessor GPT-5.5, per a Seer Interactive analysis of 346 matched prompts across six industries. Luna used the site: search operator — limiting a query to one website — in 76% of searches, up from 21.6% for GPT-5.5, while consulting 43% fewer sources overall (3,481 versus 6,134) and generating about 13% fewer inline citations, even as total search volume held roughly steady. Seer notes a brand Luna doesn’t search for directly by name may see fewer citations under the new model, and that most AI-visibility trackers measure only citations — the last step in that retrieval process.
Why it matters: As ChatGPT's default retrieval shifts from open web search toward targeted site: queries, showing up among the specific domains a model searches directly — not just ranking broadly on the open web — becomes the lever for AI citation visibility.
Posted to the wire September 24, 2026. Edited by Joe Balewski.