OpenAI's deliberate mode — GPT-5.5 with far more thinking time, at 6× the price.
GPT-5.5 pro is the same April 2026 flagship family as GPT-5.5, run in extended-compute mode: the model thinks longer, explores more branches, and self-checks before answering. OpenAI charges accordingly — $30 input and $180 output per 1M tokens, six times the standard rate and the most expensive line on our entire API table.
The honest framing: this is a "correctness budget" product. You pay the premium when a wrong answer costs more than the tokens — competition math, hard debugging, research-grade analysis. It is also noticeably slower than standard GPT-5.5 at most query lengths, so it doesn't belong in interactive products.
Pro mode posts the strongest results in the GPT family on the hardest reasoning benchmarks, and that's the entire pitch: same knowledge, same 1M window, same multimodal surface as GPT-5.5 — more deliberation. For most production work the standard model is the right call; OpenAI itself routes ChatGPT traffic to standard GPT-5.5 and reserves pro for the $200/mo Pro tier.
Since June 2026 the value question got sharper: Anthropic's Claude Fable 5 claims state-of-the-art on most benchmarks at $10/$50 — a third of pro's input rate. If you're paying for ceiling capability, compare those two on your actual workload before defaulting to either.
| Model | Input / 1M | Output / 1M | Context |
|---|---|---|---|
| GPT-5.5 pro | $30 | $180 | 1M |
| GPT-5.5 | $5 | $30 | 1M |
| GPT-5.4 | $2.50 | $15 | 272K |
| Claude Fable 5 | $10 | $50 | 1M |
| Claude Opus 4.8 | $5 | $25 | 200K |
The decision tree: start with GPT-5.5 or Opus 4.8 at $5 input. If they're not good enough, Fable 5 at $10/$50 is the next rung. GPT-5.5 pro is the last resort — worth it when a single correct answer justifies dollars of spend, wasteful everywhere else.