> ## Documentation Index
> Fetch the complete documentation index at: https://docs.retellai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# GPT-4.1 nano model replacement (10/20/2026)

> On 10/20/2026, Retell replaces GPT-4.1 nano (gpt-4.1-nano) with gpt-5.6-luna. Existing configurations will be automatically migrated.

* The following models are being deprecated and replaced with newer versions:
  * **OpenAI models:**
    * `gpt-4.1-nano` → replaced with `gpt-5.6-luna`
  * On 10/20/2026, existing configurations will be automatically migrated to the replacement model.


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