Vibe Check

Vibe Check: GPT-5.5 Has It All

OpenAI’s new model is a top-end senior engineer—and easy to talk to

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Frontier models usually take a while to get used to. You have to learn their slow spots, when they need extra prompting, and when to keep a close eye on the output.

GPT-5.5, out today, feels easier to settle into. It’s fast enough to use constantly, personable enough to collaborate with, and assertive enough to carry a plan through serious engineering work. It’s better at writing than any OpenAI model we’ve used in about a year, and it produced the strongest result we’ve seen on our new Senior Engineer Benchmark, which measures how well models can rewrite a messy production codebase the way a senior engineer would. It’s rare for a model to feel easier and stronger at the same time.

The big insights from our testing:

Best on senior-engineer coding. GPT-5.5 scored 62.5 on our Senior Engineer Benchmark versus 33.5 for Opus 4.7. Humans still score in the high 80s and low 90s. The twist: GPT-5.5’s best run used an Opus-written plan.
A real writing comeback. It’s the strongest OpenAI model we’ve tested in a year, with cleaner structure and smoother logical progression than Opus 4.7.
Strong everyday knowledge work. GPT-5.5 beat Opus 4.7 on dashboards and felt dependable for creating client deliverables or customer support replies.
Best with structure. GPT-5.5 shines with a plan, an existing system, or a tight feedback loop. Opus 4.7 still has advantages on one-shot vibe coding, PowerPoint, Ruby, and some broad product-design tasks.

The full Vibe Check has the benchmark results, Reach Test ratings, pricing, screenshots, and advice on when to reach for GPT-5.5 versus Opus 4.7.

Read the full Vibe Check

And watch our video Vibe Check with Dan Shipper:

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Katie Parrott is a staff writer at Every. You can read more of her work in her newsletter.

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