What Is GPT-5.4 Thinking?

OpenAI has released its latest frontier reasoning model, GPT-5.4 Thinking, alongside a detailed system card documenting the model's capabilities, safety evaluations, and limitations. The release marks another step in OpenAI's push to develop AI systems capable of tackling complex, multi-step problems through extended reasoning chains before delivering final answers to users.

Unlike standard language models that generate responses token-by-token without deliberation, GPT-5.4 Thinking uses chain-of-thought reasoning — working through problems internally before committing to an output. This architecture enables the model to handle mathematical proofs, complex coding tasks, scientific reasoning, and nuanced logical analysis with substantially greater accuracy than earlier systems.

The system card, which OpenAI publishes for all frontier models, provides a transparent view of how the company evaluates AI before deployment. It covers safety benchmarks, red-team results, potential misuse risks, and the specific mitigations implemented — giving researchers and enterprise customers the information they need to assess appropriate use cases for the new model.

Safety Evaluations and Red-Teaming Results

Safety testing for GPT-5.4 Thinking followed OpenAI's Preparedness Framework, evaluating the model across cybersecurity threats, biological and chemical weapons enablement, radiological risk, and autonomous resource acquisition. The system card places GPT-5.4 Thinking in the Medium overall risk category, meaning it can be deployed with standard safety mitigations in place without triggering additional restrictions.

Red-team evaluations tested the model's resistance to jailbreaks, indirect prompt injection, and multi-step adversarial manipulation. GPT-5.4 Thinking demonstrated improved resistance to many attack vectors compared to prior generations, though it remains imperfect against highly sophisticated adversarial inputs — a caveat that applies to all current AI systems regardless of training sophistication.

Evaluations of persuasion and manipulation capabilities found that the model's safety training substantially reduces its willingness to produce content designed to deceive or coerce users. OpenAI also evaluated behavior in agentic settings, where the model might take sequences of actions with real-world consequences, and found performance within acceptable safety parameters for the Medium classification threshold.