Why OpenAI scheduled it for shutdown
gpt-3.5-turbo has been overtaken by newer low-cost tiers that are both cheaper and more capable, so OpenAI scheduled its dated snapshots for shutdown. After the date above, a call naming gpt-3.5-turbo-0125 fails rather than quietly routing to a newer model.
If your code pins the bare alias gpt-3.5-turbo instead of the dated id, OpenAI's alias will point at whatever the current default is — but relying on that means your model can change under you without notice, which is its own reason to move deliberately.
What to move to
The replacement shown above is OpenAI's current low-cost / low-latency tier — the modern equivalent of what gpt-3.5-turbo was for: high-volume, cost-sensitive calls. It is a meaningful quality jump for the same class of task, usually at a lower price per token.
For anything that was straining against gpt-3.5-turbo's limits (longer context, more reliable JSON, better reasoning), this is the point to test whether the low-cost tier now suffices before reaching for a flagship.
Migration notes
The API shape is compatible — same chat-completions interface — so the swap is usually a one-line model-string change. Re-check any prompt that was hand-tuned to gpt-3.5-turbo's quirks, though: newer models follow instructions more literally, so a prompt that over-specifies to compensate for the old model can produce different output.
If you use structured output, the newer tier supports JSON mode and function tools more reliably; a migration is a good moment to replace prompt-coaxed JSON with an enforced structured-output call.