Vibe Check: GPT-5.5 Has It All

April 24, 2026

TL;DR

GPT-5.5 offers improved speed, agency, and code quality with fewer tradeoffs compared to previous models.
It performs well on a Senior Engineer Benchmark for rewriting codebases and is considered a strong workhorse for professional tasks.
Key features include a 1 million-token context window, prompt caching, and a default to medium reasoning.
GPT-5.5 is more expensive than GPT-5.4 but aims to reduce cost per completed task due to better reasoning and fewer retries.
The model is built on a new pre-train, differentiating it from previous GPT-5.x models and signaling OpenAI's strategy to maintain pressure on competitors.
It is effective at transforming messy inputs into usable outputs like dashboards and consulting prose, but can still be bland and struggle with certain tasks.
User feedback highlights its utility for coding, knowledge work, and writing, though some find Opus 4.7 superior for high-stakes tasks or design-focused work.

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