What Happened
Simon Willison, a prominent technologist, tweeted that GPT-5.5—a model not officially listed in the OpenAI API—is accessible through what he describes as an "apparently approved-of Codex API backdoor." He used this to generate pelican images, sharing results in both default and "xhigh" resolutions. The tweet includes links to the generated images, though the exact endpoint or method isn't detailed.
Context
OpenAI's API typically lists models like GPT-4, GPT-4 Turbo, and GPT-5 in its official documentation. The appearance of GPT-5.5 via the Codex API—a separate service for code generation—suggests either an internal testing channel or a deliberate but unannounced release. Codex, originally for code completion, now appears to support image generation, indicating a broader multimodal expansion.
This isn't the first time OpenAI has used unofficial channels. Previous models like GPT-4.5 were first spotted in early access or third-party integrations before official launch. The "approved-of" qualifier implies OpenAI is aware of this access, possibly as a limited preview for developers.
What This Means in Practice
For developers, GPT-5.5 via Codex offers a sneak peek at capabilities not yet in the main API. However, reliance on unofficial endpoints risks instability or sudden changes. The image generation feature—pelicans in this case—hints at multimodal improvements, but without benchmarks or official documentation, performance remains speculative.
Frequently Asked Questions
Is GPT-5.5 officially available?
No, GPT-5.5 is not listed in the official OpenAI API documentation. It's accessible only through the Codex API, which Simon Willison calls a "backdoor." OpenAI has not announced its release.
What can GPT-5.5 do that GPT-5 cannot?
Based on this report, GPT-5.5 appears to support image generation through the Codex API, a capability not publicly documented for GPT-5. The "xhigh" resolution option suggests enhanced output quality.
How can I access GPT-5.5?
Access requires using the Codex API endpoint, likely with specific parameters. Simon Willison's tweet doesn't provide exact instructions, but developers familiar with Codex might replicate his approach. Note that this is unofficial and may violate OpenAI's terms.
Will OpenAI officially release GPT-5.5?
Unclear. The "approved-of" language suggests OpenAI is aware of this access, possibly as a limited preview. An official release may follow if testing proves successful, but no timeline is available.
