Best Foundation Models for ChatGPT Agent

GPT-5.6 Terra is OpenAI’s balanced GPT-5.6 model for users who need strong performance across everyday work, development tasks, enterprise workflows, and technical analysis. The model is part of the GPT-5.6 family alongside Sol and Luna, with Terra positioned as the middle tier for capable, cost-efficient use. Terra is described as having competitive performance to GPT-5.5 while being 2x cheaper, making it useful for teams that want advanced capability without always using the flagship model. It supports coding workflows, agentic tasks, cybersecurity-related defensive work, biology workflows, knowledge work, and tool-assisted automation. In benchmark previews, Terra appears alongside Sol and Luna in evaluations for coding, biology, ExploitBench, and ExploitGym. The model benefits from the GPT-5.6 safeguard stack, which includes model-level refusals for prohibited cyber assistance, real-time cyber and biology misuse classifiers, and account-level risk review. These safeguards are designed to preserve access to legitimate work such as code review, debugging, vulnerability research, patch development, security education, and defensive testing. GPT-5.6 Terra is planned for availability through the API, Codex, and broader OpenAI products after the limited preview period. GPT-5.6 Terra helps teams get a balanced model for high-quality AI work when they need strong reasoning and automation at a lower cost than Sol.

GPT-5.6 Luna is OpenAI’s fast, cost-efficient model in the GPT-5.6 lineup. The GPT-5.6 family includes Sol for flagship performance, Terra for balanced everyday work, and Luna for strong capability at the lowest listed price. Luna is designed for users who need scalable AI support for routine tasks, coding assistance, workflow automation, analysis, and production API use cases where speed and cost matter. According to the pasted preview text, Luna is priced below both Sol and Terra, making it the most affordable GPT-5.6 option for high-volume workloads. The model is included in GPT-5.6 benchmark previews across Terminal-Bench 2.1, GeneBench v1, ExploitBench, and ExploitGym, showing that it is part of the same technical family used for coding, biology, and cybersecurity evaluations. Luna benefits from safeguards developed across the GPT-5.6 series, including model-level refusal training, real-time cyber and biology misuse classifiers, account-level signals, differentiated access, monitoring, enforcement, and ongoing testing. These controls are designed to preserve legitimate use cases such as debugging, code review, defensive testing, security education, and productivity automation while constraining prohibited misuse. GPT-5.6 Luna is planned for broader access through ChatGPT, Codex, and the API after the limited preview period. GPT-5.6 Luna helps developers and organizations run useful AI workflows with a practical balance of affordability, responsiveness, and safety.

GPT-5.5 is a next-generation AI system built for execution-heavy workflows across coding, research, business analysis, and scientific tasks. It can interpret complex instructions, break them into actionable steps, and carry them through to completion while interacting with tools and systems. The model supports creating applications, generating reports, analyzing datasets, and navigating software environments seamlessly. It also integrates with workspace agents—custom AI agents that automate recurring and multi-step processes across teams. These agents can handle tasks such as lead research, reporting, and workflow automation, either on demand or on schedules. GPT-5.5 enhances productivity by reducing manual effort and enabling continuous task execution across tools. With enterprise-grade safeguards and monitoring, it ensures secure and controlled automation. It is well-suited for organizations looking to scale operations and improve efficiency through AI-driven workflows.

GPT-4o, with the "o" denoting "omni," represents a significant advancement in the realm of human-computer interaction by accommodating various input types such as text, audio, images, and video, while also producing outputs across these same formats. Its capability to process audio inputs allows for responses in as little as 232 milliseconds, averaging 320 milliseconds, which closely resembles the response times seen in human conversations. In terms of performance, it maintains the efficiency of GPT-4 Turbo for English text and coding while showing marked enhancements in handling text in other languages, all while operating at a much faster pace and at a cost that is 50% lower via the API. Furthermore, GPT-4o excels in its ability to comprehend vision and audio, surpassing the capabilities of its predecessors, making it a powerful tool for multi-modal interactions. This innovative model not only streamlines communication but also broadens the possibilities for applications in diverse fields.

GPT-5.5 Pro is a next-generation AI model built for execution-heavy tasks across coding, research, business analysis, and scientific workflows. It can interpret complex instructions, break them into steps, and carry work through to completion using tools and automation. The model supports tasks such as generating documents, building applications, analyzing datasets, and navigating software environments. It is designed to operate across tools, enabling seamless workflows from idea to output. In addition, GPT-5.5 Pro integrates with workspace agents—customizable AI agents that automate recurring and multi-step processes across teams. These agents can handle tasks like lead research, reporting, and workflow automation, running independently or on schedules. Built with enterprise-grade safeguards, the model ensures secure and controlled automation. It helps organizations improve productivity by reducing manual effort and accelerating decision-making. GPT-5.5 Pro is ideal for teams looking to scale operations and handle complex workloads efficiently.

GPT-5.4 Pro is a high-performance AI model introduced by OpenAI for users who require maximum capability when solving complex problems. It builds on earlier GPT models by integrating advanced reasoning, coding, and workflow automation into a single system. The model is designed to assist professionals with demanding tasks such as data analysis, financial modeling, document generation, and software development. GPT-5.4 Pro can interact directly with computers and applications, allowing AI agents to perform multi-step workflows across different tools and environments. Its extended context window supports up to one million tokens, enabling it to analyze large amounts of information while maintaining accuracy. The model also improves deep web research and long-form reasoning tasks. Developers benefit from improved tool usage and search capabilities that help agents select and operate external tools efficiently. GPT-5.4 Pro delivers stronger coding performance and faster iteration cycles for developers working on complex software projects. It also reduces token usage compared with earlier models, improving cost efficiency and speed. Overall, GPT-5.4 Pro is designed to support advanced professional workflows and AI-powered automation at scale.

GPT-6 is an upcoming OpenAI model and the expected next major step beyond the GPT-5.x generation. OpenAI has not yet announced GPT-6 as a generally available product, and public documentation does not currently include GPT-6 pricing, benchmarks, model cards, API access, context length, modality details, or release timing. The latest official OpenAI model materials instead focus on GPT-5.6 Sol, Terra, and Luna, with Sol positioned as the flagship model for complex reasoning and coding. GPT-6 should therefore be described as a forthcoming model rather than a current production option. If it follows OpenAI’s current roadmap direction, GPT-6 will likely improve performance across reasoning, software engineering, scientific work, enterprise workflows, multimodal tasks, and AI agents. It may also expand capabilities around tool use, computer use, file search, web search, long-context work, structured outputs, and high-reliability automation. For businesses, GPT-6 could eventually become a foundation for customer support agents, internal copilots, coding systems, data analysis workflows, research assistants, and complex knowledge-work automation. Developers should continue using officially documented OpenAI models until GPT-6 is formally released. By positioning GPT-6 as an upcoming model, organizations can discuss the future of OpenAI’s model family without overstating what is currently public.