OpenAI Retires GPT-4o and GPT-4.1 API Models on January 14, 2027

Four GPT-4 Models Leave the API

OpenAI is retiring GPT-4o, GPT-4o mini, GPT-4.1, and GPT-4.1 mini from its API on January 14, 2027. A deprecation notice sent to developers on Wednesday covers the base models, their dated snapshots, and every fine-tuned model built on top of them, leaving about three months to migrate production traffic.

GPT-4o arrived on May 13, 2024 as OpenAI's flagship. When GPT-5 replaced it in August 2025, Reddit complaints led OpenAI to bring it back for paying ChatGPT subscribers the next day. That reprieve ended on February 13, 2026, when GPT-4o and GPT-4.1 disappeared from ChatGPT. OpenAI said only 0.1% of daily ChatGPT users were still choosing GPT-4o at that point, though the model kept serving API requests. GPT-4.1, released on April 14, 2025, was an API-only family aimed at developers, with stronger coding, better instruction following, up to a million tokens of context, and more reliable diff formats. OpenAI chief product officer Kevin Weil described the models as trained just for developers during the launch livestream, and Sam Altman said on X that developers seemed very happy with them.

Migrating to GPT-6 Luna

OpenAI's recommended replacement is GPT-6 Luna, the fastest and cheapest tier of GPT-6. It offers a 1.05 million-token context window, structured outputs, and function calling. Pricing is $0.10 per million input tokens and $0.50 per million output tokens, cheaper than GPT-5.6 Luna, which charged twice as much for input and $1.20 per million output tokens. Once a prompt passes 272,000 input tokens, the input rate doubles and the output rate rises by 50% for the entire request, which could eat into savings for RAG pipelines and coding agents working with large codebases.

OpenAI's migration guide says GPT-6 Luna defaults to medium reasoning effort and supports function calling through Chat Completions only with reasoning_effort=none. Combining reasoning and tool calls requires the Responses API. Enabling reasoning also rules out temperature, top_p, top_logprobs, and logprobs, all supported by GPT-4.1. The company recommends using its Docs skill in Codex to update API calls across a project, though those changes will not account for differences in model behavior. Anthropic faced a similar problem last month when Opus 5.5 introduced four breaking changes that caused 400 errors in existing agent integrations, and other changes altered agent behavior without triggering errors.

Fine-tuning Window Closes Earlier

New self-serve fine-tuning jobs end on January 6, 2027, eight days before the GPT-4 models retire. Existing fine-tuned models will continue serving inference requests until January 14, leaving a short window to run replacements alongside them.

Broader Shutdown Schedule

Other deadlines on OpenAI's deprecation schedule include GPT-4.1 nano, the first GPT-4o snapshot, and older GPT-3.5, GPT-4, and o-series models retiring October 23. GPT-5 and o3 snapshots follow on December 11, with selected legacy audio, real-time, and transcription models scheduled for January 20, 2027. GPT-5.1, GPT-5.3-Codex, and GPT-5.4-Nano are set to retire April 1.

The List models API now includes a shutdown_date field, making it possible to check upcoming retirements automatically. Customers who need more time may be able to keep older models running through dedicated capacity, arranged with OpenAI's sales team. The three-month warning falls short of OpenAI's own deprecation policy, which promises at least six months' notice for generally available models. The policy allows exceptions for safety or compliance reasons, but OpenAI has not explained why these models are getting only half that time.

Sources: The New Stack