Access GPT-5.5 via Codex Subscription API Plugin
Install llm-openai-via-codex to run GPT-5.5 prompts against your ChatGPT/Codex subscription, avoiding the unavailable official API. Generates detailed SVGs like pelicans on bikes with high reasoning effort.
Exploit Codex Backdoor for GPT-5.5 API Access
OpenAI released GPT-5.5 to Codex and ChatGPT subscribers but delayed the official API due to safety requirements. Use the semi-official Codex endpoints—originally for their open-source Codex CLI—to access it via subscriptions. OpenAI endorses this for tools like OpenClaw, JetBrains, and Pi, as confirmed by exec Romain Huet and OpenClaw creator Peter Steinberger. Install Codex CLI, log in with your paid OpenAI plan ($20+/month), and the auth tokens enable API calls at subscription rates, cheaper than raw API pricing.
This bypasses ChatGPT's hidden system prompts, ideal for benchmarks. Simon Willison had Claude Code reverse-engineer the openai/codex repo to build llm-openai-via-codex, a plugin for the LLM CLI tool.
Quick Setup and Full LLM Features
Run these steps to prompt GPT-5.5:
- Install Codex CLI and log in with your OpenAI subscription.
uv tool install llmllm install llm-openai-via-codexllm -m openai-codex/gpt-5.5 'prompt'
Supports images (-a filepath.jpg), chats (llm chat -m openai-codex/gpt-5.5), logs (llm logs), and tools (llm --tool). Model alias: openai-codex/gpt-5.5.
Pelican Benchmark Reveals Reasoning Gains
Prompt: 'Generate an SVG of a pelican riding a bicycle.' Default output used 39 reasoning tokens, producing a mangled bike frame and odd body (view SVG). Add -o reasoning_effort xhigh for 9,322 tokens and 4 minutes: results in CSS gradients, better-proportioned body, improved bike (one extra bar), superior overall (SVG). xhigh shifts to CSS-heavy code vs. default paths, showing escalated reasoning trades speed for quality.
GPT-5.5 excels at building requested features but shows jagged frontier—strong in some tasks, unpredictable elsewhere (per Ethan Mollick's tests).
Pricing Trade-offs Favor Subscriptions
API pricing (upcoming): GPT-5.5 at $5/1M input, $30/1M output—double GPT-5.4's $2.5/$15. Pro version: $30/$180. Subscriptions via Codex offer discounted access now. Keep GPT-5.4 for cost-sensitive tasks, like Sonnet to Opus.