GPT-5.5 accessed via Codex backdoor API with new LLM plugin

GPT-5.5 has launched in OpenAI Codex and is rolling out to paid ChatGPT subscribers, but its API release is delayed while OpenAI works on safety and security requirements for serving it at scale. The article describes how Claude Code was used to reverse-engineer the `openai/codex` repo and build `llm-openai-via-codex`, a plugin for the LLM tool that routes prompts through the Codex subscription endpoint. OpenAI's Romain Huet and Peter Steinberger have both confirmed that using OpenAI subscriptions via this mechanism is officially supported. The article also notes GPT-5.5's pricing — $5 per 1M input tokens and $30 per 1M output tokens — double that of GPT-5.4 — with a Pro tier at $30/$180 per 1M tokens.