The latest OpenAI GPT models at a glance
(Last updated: October 2026)
What makes GPT-5 stand out?
OpenAI’s GPT-5 ushered in a new generation of powerful large language models. The first official flagship model in OpenAI’s GPT-5 family was released in August 2025. This was followed by updates such as GPT-5.1, GPT-5.4 and, in July 2026, the GPT-5.6 family comprising Sol, Terra and Luna. The models have different functions and performance modes (fast, strong reasoning, high-performance). GPT-5 was at times used as a model name, but is primarily the designation for a family of models. The new Frontier models promise improved token efficiency and enhanced cybersecurity and coding performance.
OpenAI’s aim is to make advanced intelligence more widely available and affordable. According to OpenAI, GPT-5.6 Luna in particular offers cutting-edge intelligence at a fraction of the cost of comparable high-performance models. The model promises shorter response times and more stable performance, whilst also enabling longer dialogue sessions and personalised responses. With these expanded model variants, the GPT-5 series can be used in a wide variety of fields, ranging from content creation and programming to complex analytical tasks and cost-effective real-time applications.
Versions and use of the GPT models
(Last updated: October 2026)
The latest flagship is the GPT-5.6 family (Sol, Terra, Luna), which was fully released on 9 July 2026. Sol is the most powerful model for complex workflows, coding, science and cyber security; Terra is a well-balanced model for everyday use; and Luna is the cost-effective option. GPT-5.5 Instant continues to serve as the standard model for everyday queries in ChatGPT, complemented by GPT-5.5 Thinking and GPT-5.5 Pro for more in-depth reasoning. Parts of the GPT-5.4 range (Thinking, Pro, mini, nano) as well as GPT-5.3 remain in use within the routing system.
GPT-5 represents the ongoing evolution of OpenAI’s AI models. GPT-4 laid the foundations with advanced text and image processing and reliable accuracy in everyday tasks. GPT-4o, as a turbo-optimised variant, operated faster and more accurately, whilst also experimenting with audio and video processing, as well as empathetic and emotional tone. As the next generation, GPT-5 combines the highest level of accuracy with native multimodality for text, images, audio and video, an extremely large context window, and an integrated thinking mode. The choice of model depends on the required accuracy and capacity for each specific use case.
Discontinued Models
Several older models have since been removed from ChatGPT: GPT-4o and the rest of the GPT-4 range (including GPT-4.1, GPT-4.1 mini, o4-mini and GPT-5 Instant/Thinking) as early as February 2026, GPT-5.1 (Instant, Thinking, Pro) in March 2026, GPT-5.2 in June 2026 and, most recently, GPT-4.5 at the end of June 2026. OpenAI is thus clearly focusing on the GPT-5.x and 6 generations and a more system-based model architecture.
GPT-5.6 vs. GPT-5.5
Whilst GPT-5.5 already represented a major leap forward in terms of accuracy, reliability and suitability for everyday use, GPT-5.6 sets even higher standards in precisely these areas of performance. As the standard model in ChatGPT, GPT-5.5 continues to offer developers and businesses a powerful platform for text processing, chatbots, content generation and everyday knowledge work. GPT-5.6 significantly expands on these capabilities: Sol, in particular, offers significantly improved capabilities in coding, scientific analysis and cyber security compared to GPT-5.5 and, according to OpenAI, is considered the most powerful model to date for demanding, multi-stage tasks. Furthermore, GPT-5.6 Sol introduces new control mechanisms such as a customisable ‘Max Reasoning Effort’ level and an ‘Ultra’ mode with multiple sub-agents working in parallel, making complex programming and analysis tasks noticeably more efficient than with the previous model.
Rapid model development and intense competition
The rapid succession of releases, from GPT-5 right through to version 5.6, within the space of just a few months is causing increasing confusion amongst users and developers. The discussions that have emerged have centred primarily on the following questions:
- Are smaller, specialised variants more useful?
- Are new generations of models being released and replaced too soon?
- What about the quality and ethical considerations of the new models?
At the same time, competitive pressure is mounting. In its own benchmarks, OpenAI compares GPT-5.6 directly with models from Anthropic and Google, including Claude Fable 5, Claude Opus 4.8 and Gemini 3.1 Pro. OpenAI is also under scrutiny when it comes to trust: since 24 August, Free and Go users in Germany have been seeing adverts below ChatGPT’s responses, which are not personalised at launch. Perplexity and Anthropic do not display adverts in their chatbots, and Google has also kept Gemini advert-free so far.
Assessment and Outlook
From a technical perspective, OpenAI has made significant strides with the GPT-5 family, particularly in coding and agent-based tasks: on the Artificial Analysis Coding Agent Index, GPT-5.6 outperforms Anthropic’s Fable 5. At the same time, the focus is shifting from raw performance to efficiency: Terra is said to be competitive with GPT-5.5, yet costs only half as much. The GPT-5 family is also firmly established in developer and enterprise platforms, such as GitHub Copilot – where all three GPT-5.6 variants are available – and Azure OpenAI. For businesses, this means more choice, but also greater maintenance effort. Anyone integrating GPT models directly must plan for regular migrations.
GPT-5 hat vor allem seine Stärken in den agentischen Anwendungen, besonders im Bereich der tieferen Recherche und als Assistent beim Programmieren.
OpenAI has already unveiled the next generation, GPT-6, in September 2026. Within the GPT-5 family, GPT-5.6 remains the current generation.
What about gpt-oss?
It may not be making the headlines, but it’s particularly exciting for us here at moinAI: gpt-oss. gpt-oss-120b and gpt-oss-20b are OpenAI’s ‘Open Weight’ models. OpenAI deliberately uses the term ‘Open Weight’ rather than ‘Open Source’ because the training data is not made public. The models are licensed under the Apache 2.0 licence, which is considered particularly open, and gpt-oss-120b runs efficiently on a single 80 GB GPU.
For moinAI, this is precisely the advantage, as we can run gpt-oss entirely on servers in Germany, without relying on non-European providers such as OpenAI or Azure. Customer data remains within our infrastructure and is not passed on to any other third parties. This is digital sovereignty in practice.
Conclusion
In just over a year, GPT-5 has evolved from a single model into an entire family, with GPT-5.6 Sol, Terra and Luna comprising the current generation. The models have become more powerful and efficient. At the same time, short model lifecycles, advertising in ChatGPT and unresolved security issues indicate that trust and reliability are becoming key challenges.
For businesses, therefore, it is not the model that matters, but whether the AI operates in a controlled manner. With moinAI, your AI agents respond using verified sources, operate within clearly defined guardrails and are GDPR-compliant, hosted in Germany – regardless of which model comes next.
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