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GPT-3.5 Turbo Instruct

GPT-3.5 Turbo Instruct is an instruction-tuned completion model designed for the legacy Completions endpoint, offering a direct prompt-in, text-out format suited to few-shot tasks, templated generation, and workflows that predate the chat message structure.

index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'openai/gpt-3.5-turbo-instruct',
  prompt: 'Why is the sky blue?'
})
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About GPT-3.5 Turbo Instruct

GPT-3.5 Turbo Instruct launched on September 28, 2023 as part of OpenAI's update that also brought fine-tuning support to the GPT-3.5 Turbo family. While the base GPT-3.5 Turbo targets the Chat Completions API, this variant works with the legacy Completions endpoint, the same interface GPT-3 era models used. That makes it the natural successor for workflows built on that format.

The model follows the instructed-completion paradigm: you write a free-form prompt and the model continues or responds directly, without requiring the message-role structure the chat endpoint demands. This suits few-shot pattern completion, structured data extraction from templated prompts, text transformation tasks, and any integration where a prompt-in, completion-out contract is preferable.

OpenAI positioned the Instruct variant as a bridge for developers who wanted Turbo-family efficiency and pricing without abandoning the Completions interface. For new projects, chat-format models generally offer more capability per token. But for existing pipelines or use cases where single-turn completion is semantically cleaner, GPT-3.5 Turbo Instruct fills a clear slot.