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Thank you all for reporting this issue. Here's what's going on. This rerouting is related to our efforts to protect against cyber abuse. The gpt-5.3-codex model is our most cyber-capable reasoning model to date. It can be used as an effective tool for cyber defense applications, but it can also be exploited for malicious purposes, and we take safety seriously. When our systems detect potential cyber activity, they reroute to a different, less-capable reasoning model. We're continuing to tune these detection mechanisms. It is important for us to get this right, especially as we prepare to make gpt-5.3-codex available to API users. Refer to this article for additional information. You can go to chatgpt.com/cyber to verify and regain gpt-5.3-codex access. We plan to add notifications in all of our Codex surfaces (TUI, extension, app, etc.) to make users aware that they are being rerouted due to these checks and provide a link to our “Trusted Access for Cyber” flow. We also plan to add a dedicated button in our /feedback flow for reporting false positive classifications. In the meantime, please use the "Bug" option to report issues of this type. Filing bugs in the Github issue tracker is not necessary for these issues.

_Originally posted by @etraut-openai in #11189_