Yesterday, 26 August 2026, was a busy day in AI land, two far-reaching OpenAI changes took effect at the same time. Below are the facts at a glance, plus what this means for Dutch professionals.
Assistants API discontinued: no grace period
The OpenAI Assistants API went permanently offline on 26 August. All calls to `/v1/assistants`, `/v1/threads` and `/v1/runs` now return a hard error. There is no grace period and no automated migration tool.
Is your production code running on the Assistants API? Then that code is now broken. OpenAI's recommended migration path is the new Responses API + Conversations API: you rebuild assistants as Responses API calls and recreate threads yourself. The main advantages of the Responses API over its predecessor are better performance and support for deep research, MCP and computer use.
What to do now if you use the Assistants API:
- Check immediately which services run on it (search your codebase for `v1/assistants` or `v1/threads`).
- Migrate to the Responses API; the OpenAI migration guide is your starting point.
- Note: Azure OpenAI has its own retirement timeline, consult the Microsoft Q&A.
o3 disappears from ChatGPT; o3-pro remains
At the same time, o3 has been removed from the ChatGPT product following an announced phase-out of 90 days. The API follows a different timeline: the snapshots `o3-2025-04-16` and `o3-pro-2025-06-10` only leave the API on 11 December 2026. If you use o3-pro through a Pro, Team, Enterprise or Edu subscription, you can carry on working as normal, that model remains available in ChatGPT.
For everyday professional use, GPT-5.6 Terra or Luna is the logical successor for most tasks people currently use o3 for.
GPT-5.6 Sol: 20% cheaper than a week ago
Better news on pricing: on 21 August, OpenAI cut the API price of GPT-5.6 Sol by more than 20% for the next three months. GPT-5.6 Luna had already become 80% cheaper on 30 July. The result: the most capable model in the GPT-5.6 family is now more accessible to teams who until recently only looked at the lighter variants.
For comparison, with the new discount GPT-5.6 Sol costs less per token than Claude Sonnet 4.6, while in capability it sits in the upper regions of the Chatbot Arena leaderboard. For cost-conscious organisations, it is worth working through the new prices for your specific usage pattern.
AI Act Article 50, three weeks live, much still to do
Meanwhile, the EU AI Act transparency obligation (Article 50) has now been in force for three weeks. The core requirement: chatbots and voice assistants must identify themselves as AI in every conversation. Plain text you have edited with AI does not need to be labelled, but deepfakes and AI-generated media do, in a machine-readable format.
In practical terms: for small organisations, most adjustments are one afternoon's work. Larger organisations with their own AI interfaces or AI customer service bots that have not yet addressed this are now at risk. Fines can reach €15 million or 3% of worldwide annual turnover. See our safety overview for the GDPR profile per model and the overview of AI Act-related updates.
Does your organisation operate in a regulated sector? Also see the sector pages for sector-specific considerations on AI use and compliance.
Sources: OpenAI – Assistants API migration · AI Weekly – o3 and GPT-4.5 phase-out · OpenAI GPT-5.6 August updates (PDF) · WerkenmetAI – AI Act transparency obligation for SMEs · Computable – AI Act transparency requirements