gpt-oss-120b vs. GPT-5 thinking

gpt-oss-120b is a reasoning model focused solely on text, boasting 120 billion parameters, and is released under the Apache 2.0 license while adhering to OpenAI’s usage policies; it has been developed with contributions from the open-source community and is compatible with the Responses API. This model excels at executing instructions and utilizes various tools, including web searches and Python code execution, which allows for a customizable level of reasoning effort and results in detailed chain-of-thought outputs that can seamlessly fit into different workflows. Although it is constructed to comply with OpenAI's safety policies, its open-weight nature poses a risk, as adept users might modify it to bypass these protections, thereby prompting developers and organizations to implement additional safety measures akin to those of managed models. Assessments reveal that gpt-oss-120b falls short of high performance in specialized fields such as biology, chemistry, or cybersecurity, even after attempts at adversarial fine-tuning. Moreover, its introduction does not represent a substantial advancement in biological capabilities, indicating a cautious stance regarding its use. Consequently, it is advisable for users to stay alert to the potential risks associated with its open-weight attributes, and to consider the implications of its deployment in sensitive environments. As awareness of these factors grows, the community's approach to managing such technologies will evolve and adapt.

GPT-5 Thinking represents the advanced reasoning layer within the GPT-5 architecture, purpose-built to address intricate, nuanced, and open-ended problems requiring extended cognitive effort and multi-step analysis. This model operates in tandem with the more efficient base GPT-5, selectively engaging for questions where deeper consideration yields significantly better results. By harnessing sophisticated reasoning techniques, GPT-5 Thinking achieves substantially lower hallucination rates—about six times fewer than earlier models—resulting in more consistent and trustworthy long-form content. It is designed to be highly self-aware, accurately recognizing the boundaries of its capabilities and communicating transparently when requests are impossible or lack sufficient context. The model integrates robust safety mechanisms developed through extensive red-teaming and threat modeling, ensuring it delivers helpful yet responsible answers across sensitive domains like biology and chemistry. Users benefit from its enhanced ability to follow complex instructions and adapt responses based on context, knowledge level, and user intent. GPT-5 Thinking also reduces excessive agreeableness and sycophancy, creating a more genuine and intellectually satisfying conversational experience. This thoughtful approach enables it to navigate ambiguous or potentially dual-use queries with greater nuance and fewer unnecessary refusals. Available to all users within ChatGPT, GPT-5 Thinking elevates the platform’s capacity to serve both casual inquiries and expert-level tasks. Overall, it brings expert reasoning power into the hands of everyone, improving accuracy, helpfulness, and safety in AI interactions.