Quoting Romain Huet

Simon Willison· April 25, 2026 at 12:06 PM ·1 min read · 0 reactions · 0 comments · 3 views

#gpt-5.5#ai models#coding#unified system#autonomous agents

⚡ TL;DR · AI summary

With GPT-5.4, Codex and the main model were merged into one system, eliminating the separate coding line. GPT-5.5 builds on this integration, showing significant improvements in agentic coding, computer use, and general computer-based tasks. The unified model enhances performance across a broader range of technical workflows. Advancements suggest a shift toward more autonomous, code-capable AI systems.

Key facts

▪GPT-5.4 unified Codex and the main model into a single system.
▪There is no longer a separate coding-specific model line.
▪GPT-5.5 shows strong improvements in agentic coding and computer use.
▪The integration supports better performance on computer-based tasks.
▪The advancements reflect progress toward more autonomous AI behavior.

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Since GPT-5.4, we’ve unified Codex and the main model into a single system, so there’s no separate coding line anymore. GPT-5.5 takes this further, with strong gains in agentic coding, computer use, and any task on a computer.

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Quoting Romain Huet

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