OpenAI API · 28 days left

GPT-5 nano API shutdown: December 11, 2026

OpenAI is removing GPT-5 nano from its API on December 11, 2026. Any request that still uses gpt-5-nano or gpt-5-nano-2025-08-07 will fail from that day. The replacement OpenAI lists is gpt-6-luna.

What to do before December 11

1. Find every place the ID is used. Search your code, environment variables, prompt management tools and scheduled jobs for gpt-5-nano. Fine tuned versions follow the base model's schedule.
2. Run your real prompts on both models. Take ten to fifty real inputs and compare the answers from gpt-5-nano and gpt-6-luna side by side. Look first at anything your code parses: JSON, labels, numbers, tool arguments.
3. Save the old answers. After the shutdown you cannot ask GPT-5 nano anything again. A saved baseline lets you check any later model against it.
4. Switch, then watch. Change the model ID, deploy, and watch latency, token usage and error rates for the first days.

Compare gpt-5-nano with gpt-6-luna now

Free for three prompts. Runs in your browser with your own OpenAI key. Nothing is sent to us.

What usually changes in a model swap

The replacement is normally the stronger model, so quality is rarely the problem. The breaks come from code that expected the old model's habits:

• JSON answers that arrive inside a code fence, or with a key renamed, added or missing.
• Plain text answers that come back with markdown headings, bold text or bullet lists.
• Answers that are much longer or shorter, which shifts cost and can overflow a user interface.
• One word classifications that flip on borderline inputs.
• Refusals or added caveats on inputs the old model answered directly.
• Different latency and output token counts for the same request.

Retired on the same day

GPT-5, GPT-5 mini, GPT-5 pro, o3, o3-pro.

Questions

When is GPT-5 nano shut down?

OpenAI lists December 11, 2026 as the date gpt-5-nano, gpt-5-nano-2025-08-07 are removed from the API. After that date requests to those model IDs fail.

What replaces GPT-5 nano?

OpenAI's deprecation page lists gpt-6-luna as the replacement.

Will my prompts behave the same on gpt-6-luna?

Usually close, and often better, but not identical. The common breaks are structural: JSON that gains a code fence or loses a key, markdown where plain text used to be, longer or shorter answers, a label that flips. The only way to know is to run your own prompts on both models while the old one still answers.

Can I still test against GPT-5 nano after December 11, 2026?

Not against the live model. If you save its answers to your prompts before December 11, 2026, you can compare any later model against that saved baseline.