Thinking Mode Retirement Timeline: ChatGPT Product vs. API Lifecycle

This article was first published on August 8, 2025 as a GPT-5 Thinking guide. Its old model-picker instructions are no longer current. The URL and original publication date remain, while this revision records what changed.

This correction records the Thinking Mode retirement timeline by separating the ChatGPT product lifecycle from the API lifecycle.

What was true in August 2025

OpenAI released GPT-5 for developers on August 7, 2025 and documented API controls such as reasoning_effort. The original developer announcement also distinguished the API reasoning model from the non-reasoning model used in ChatGPT.

At the time, Thinking was presented as a choice for additional reasoning. It did not establish that every task improves simply by spending more time.

What changed in February 2026

OpenAI's ChatGPT retirement notice states that GPT-5 Instant and Thinking were retired from ChatGPT on February 13, 2026. Old screenshots and instructions to select “GPT-5 Thinking” therefore do not apply to the current ChatGPT picker.

The same notice says there was no API change from that ChatGPT retirement. ChatGPT and API model lifecycles must be checked separately.

How to check now

1. Open the model choices currently shown in ChatGPT.
2. Check Model Release Notes for launch, update, and retirement dates.
3. For API use, check the official model and deprecation documentation separately.
4. When continuing an old conversation, retest important output because a newer replacement model can respond differently.

Evaluating a current reasoning option

If the current interface offers a Thinking or reasoning-time option:

• start simple transformation or retrieval with the normal setting;
• compare a reasoning setting for multi-constraint planning, evaluation, or code verification;
• use a small task with a known answer and record accuracy, time, and evidence;
• retain primary-source and qualified review for medical, legal, financial, and safety decisions.

Conclusion

The 2025 GPT-5 Thinking guide is a historical record. Because the model was retired from ChatGPT in February 2026, use current release notes and the live interface for present instructions. Check API availability as a separate lifecycle.