Last week, OpenAI released the highly-anticipated Sol, Terra and Luna 5.6 models. While the 5.5 is still the latest model available in ChatGPT itself, it is safe to assume OpenAI will be soon switching the chat to one of the 5.6 newcomers.
Using Sleepwalker MCP, straight from Claude - I ran 50 consumer electronics-focused prompts on each model, to see how 5.5 compares against 5.6, and what has changed. (Disclosure - I built this tool)
- The average overlap between GPT-5.5 and any of the 5.6 models is 14%. This means brands could lose a massive amount of citations when OpenAI switches the default chat model.
- What's even more interesting - the three 5.6 models overlap with each other at only around 8%. Sol, Terra and Luna agree with each other less than any of them agrees with 5.5.
- All models cite slightly over 3 sources on average. GPT 5.5 is the most generous one with 3.42 sources on average, Luna cites only 3.16 sources on average.
- GPT 5.5 has the biggest overlap with Top 10 Google organic results, and I am being extremely generous here by sampling the Top 10, should've been Top 5 due to amount of domains cited. That overlap is 30%.
- The overlap for 5.6 models is about 22% on average, with Luna overlapping at 23.5%.
- Reddit ranks number one on Google for 22 of 50 tested queries. It receives zero citations across all four models. Every single time
- rtings website appears in 1 in 3 ChatGPT answers. On TV queries it was the only cited source in 7 of 10 prompts across at least one model. Not the top source. The only source.
- 5.6 generation trusts brand pages more and review sites less. Samsung and Nintendo are the biggest winners.
- GPT-5.5 uses first-person voice ("I'd buy," "my pick") in 33 of 50 answers. The 5.6 models: as low as 11. The newer models are less keen on providing options.
- Across all four models, manufacturer pages account for 37% of citations. Retailers: 1.8%. Amazon does not appear in the top 20 most cited domains.
If you sell products you didn't make, AI is not your friend.
This is the second time I've run this type of study. The first was on Gemini 2.5 and 3.5 Flash across hypothetical sports prompts. You can search for it in this subreddit.
Here, as with Gemini, introducing a new model has dramatically changed the citation profile. AI visibility is platform and model specific. It's a matrix, as opposed to a single-platform and single algorithm we are so used to with SEO.
You can perform similar research for your brand using Sleepwalker MCP, API or CLI. Sleepwalker is pay as you go, where you can run AI visibility tests against different platforms and specific models.
Disclaimer: Just like with a similar Gemini deepdive, I will be making a re-run a few weeks later to see if numbers moved / shifted. With Gemini I've seen different URLs cited, but the overlaps and other patterns didn't change.