Owen Posted on Apr 29 • Originally published at ofox.ai GPT-5.4 Pro API: Complete Developer Guide — Pricing, Setup & When to Use It TL;DR: GPT-5.4 Pro costs $30/M input and $180/M output when you go direct to OpenAI. Via ofox, Pro Plan members pay roughly $24/$144 with the 20% flagship discount. The model scores 75% on OSWorld (above the human expert baseline) and 89.3% on BrowseComp — benchmarks that reflect the long-horizon agentic tasks where it earns that price. Here's exactly how to set it up and when to choose Mini or Nano instead. Why GPT-5.4 Pro Still Matters (Even With GPT-5.5 Out) GPT-5.4 Pro remains OpenAI's most battle-tested model for production agentic workloads — teams running it since March haven't stopped just because GPT-5.5 appeared on April 23. OpenAI has not deprecated GPT-5.4 Pro.…