OpenAI shut down four legacy models on September 28: gpt-3.5-turbo-instruct, babbage-002, davinci-002 and gpt-3.5-turbo-1106, with developers pointed at gpt-5.6-terra as the replacement. It is one notch in a long published shutdown calendar: October 1 brings the end of gpt-5.4-cyber (→ gpt-5.6-cyber), October 14 sees GPT-5.5 retire from ChatGPT and Codex, and a larger wave on October 23 retires gpt-4-0613, gpt-4-turbo, o1, o3-mini, o4-mini and more.

The consolidation continues into December: custom GPTs go away on December 11 (moving to plugins and skills), followed by the gpt-5 and o3 snapshot families, and the v1/prompts API and reusable prompts are retired at the end of November. For developers still on old snapshots, the message is the same each time: migrate now or be migrated.