OpenAI dropped GPT-5.4 in early April 2026 with a 1-million-token context window and a 33% reduction in factual errors. Here is what actually changed and whether it affects your workflows.
GPT-5.4 consolidates the coding capabilities of the GPT-5.3 Codex specialist model into the general GPT-5.4 architecture ending the need to switch between specialist variants for coding tasks. The headline improvements are a 1-million-token context window matching Claude's 200K expansion strategy with a significantly larger window and a reported 33% reduction in factual errors compared to GPT-5 — the reliability improvement that matters most for production enterprise use cases according to early testers. Response latency is lower than previous GPT-5 variants making it faster for interactive use. The model is available to ChatGPT Plus subscribers and via the OpenAI API with pricing still being established.
On SWE-Bench Pro GPT-5.4 scores 57.7% with integrated Codex capabilities — meaningful progress from earlier GPT-5 variants. Claude Opus 4.6 sits around 80% on comparable benchmarks representing a real gap on the most complex software engineering tasks. For reasoning tasks the intelligence index from Artificial Analysis places GPT-5.4 at the very top tier alongside Gemini 3.1 Pro Preview. Grok 4.20 surprisingly ranked second on ForecastBench ahead of GPT-5.4 on probabilistic forecasting tasks — a result worth monitoring. The extreme reasoning mode for long-horizon tasks is a new capability without direct comparison benchmarks at publication time.
The practical implication of a 1-million-token context window is the ability to load an entire large codebase multiple research papers an entire book or extensive documentation into a single conversation. For Claude users already familiar with 200K context the jump to 1M in GPT-5.4 is significant — roughly five times more context. In testing this context length holding accuracy at 1M tokens varies by task — models generally degrade on very long contexts even when the window technically supports it. GPT-5.4's performance at maximum context length has not yet been independently benchmarked at the scale of Nemotron 3 Super's RULER results making direct comparison difficult.
For ChatGPT Plus subscribers the upgrade is automatic at no additional cost — GPT-5.4 replaces previous GPT-5 variants in the interface. For API users the question is whether the reliability improvements and expanded context justify any pricing changes from GPT-5. For developers currently on GPT-4o the move to GPT-5.4 is a clear upgrade. For developers currently split between Claude for coding and ChatGPT for other tasks GPT-5.4's improved coding reliability may reduce the need to switch. The consolidation of Codex capabilities into the main model is the most practically significant change for developers.
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