Introduction to GPT-5.1
OpenAI has released GPT-5.1 Instant and GPT-5.1 Thinking, two updated versions of its flagship AI models now available in ChatGPT. The company describes these models as warmer, more conversational, and better at following instructions. This release comes after complaints earlier this year that its previous models were excessively cheerful and sycophantic, as well as controversy over how OpenAI modified the default GPT-5 output style following several suicide lawsuits.
Background and Context
The company now faces intense scrutiny from lawyers and regulators that could threaten its future operations. In this environment, releasing a new AI model requires careful consideration. The basics of the new models are as follows: GPT-5.1 Instant will serve as ChatGPT’s faster default option for most tasks, while GPT-5.1 Thinking is a simulated reasoning model designed to handle more complex problem-solving tasks.
Model Capabilities and Improvements
OpenAI claims that both models perform better on technical benchmarks such as math and coding evaluations (including AIME 2025 and Codeforces) than GPT-5, which was released in August. Improved benchmarks may win over some users, but the biggest change with GPT-5.1 is in its presentation. OpenAI has introduced eight preset options for simulating different communication styles, including Professional, Friendly, Candid, Quirky, Efficient, Cynical, and Nerdy, alongside a Default setting. These presets alter the instructions fed into each prompt to simulate different personality styles, but the underlying model capabilities remain the same across all settings.
Adaptive Reasoning and Rollout Plans
In addition to the new personality styles, the company trained GPT-5.1 Instant to use “adaptive reasoning,” meaning that the model decides when to spend more computational time processing a prompt before generating output. The company plans to roll out the models gradually over the next few days, starting with paid subscribers before expanding to free users. OpenAI plans to bring both GPT-5.1 Instant and GPT-5.1 Thinking to its API later this week. GPT-5.1 Instant will appear as gpt-5.1-chat-latest, and GPT-5.1 Thinking will be released as GPT-5.1 in the API, both with adaptive reasoning enabled. The older GPT-5 models will remain available in ChatGPT under the legacy models dropdown for paid subscribers for three months.
Conclusion
The release of GPT-5.1 Instant and GPT-5.1 Thinking marks a significant update to OpenAI’s flagship models, with a focus on improved performance, versatility, and user experience. As the AI landscape continues to evolve, it will be interesting to see how these models are received by users and how they impact the broader conversation around AI development and regulation.
FAQs
- Q: What are the main differences between GPT-5.1 Instant and GPT-5.1 Thinking?
A: GPT-5.1 Instant is designed for faster performance on most tasks, while GPT-5.1 Thinking is focused on handling more complex problem-solving tasks. - Q: How do the new personality styles in GPT-5.1 work?
A: The personality styles (e.g., Professional, Friendly, Candid) alter the instructions fed into each prompt to simulate different communication styles, without changing the underlying model capabilities. - Q: When will GPT-5.1 models be available to all users?
A: The models will be rolled out gradually, starting with paid subscribers before being made available to free users. - Q: What happens to the older GPT-5 models?
A: They will remain available in ChatGPT under the legacy models dropdown for paid subscribers for three months.
