Goodbye GPT‑4, Hello o‑Series:

https://openai.com/index/gpt-4-1/?utm_source=chatgpt.com

1 | Why this update matters

On 16 April OpenAI quietly rewired its product stack:
 * o3* — its most advanced “reasoning” model to date — and the lighter o4‑mini entered public preview, while GPT‑4 and GPT‑4.5 began an official sunset. The move signals a pivot from “bigger models” to specialised, tool‑using agents that run cheaper and faster. citeturn0news50

2 | Meet the newcomers

o3: the agent‑ready brain

* Self‑directed tool use* — o3 can decide when to call web search, python execution, file parsers or image generation inside ChatGPT, then chain the results in under a minute.
 * Top of SWE‑Bench* — 69 % verified bug‑fix success, eclipsing GPT‑4o.
 * Vision‑native* — treats screenshots, charts and design mocks as first‑class input. citeturn0news50

o4‑mini: performance per dollar

Roughly 8 B parameters, yet scores within single‑digit points of GPT‑4o on coding and maths while cutting token pricing by ~60 %. Perfect for startups that found GPT‑4.5 financially painful. citeturn0news50

3 | GPT‑4.1 family: long‑context workhorse

Two days earlier, OpenAI unveiled GPT‑4.1, 4.1‑mini and 4.1‑nano for API use only. Headline stats:

OpenAI confirmed GPT‑4.5’s research preview will vanish from the API on 14 July 2025.

4 | Sunsetting GPT‑4 inside ChatGPT

From 30 April the ChatGPT client (web / desktop / mobile) will drop GPT‑4 entirely and default Plus/Pro users to GPT‑4o. If you still rely on GPT‑4‑specific prompts, migrate or pin the API model now. citeturn0search4

5 | Strategic implications

6 | Migration check‑list

1. Audit current prompt library for GPT‑4‑specific quirks (JSON mode, function‑calling IDs).
2. Prototype with GPT‑4.1: verify latency and throttling.
3. Pilot o4‑mini on cost‑sensitive endpoints (FAQ bots, nightly ETL).
4. Stage rollout using traffic splitting; watch hallucination deltas.
5. Update dashboards: token prices and model IDs change.

7 | Forecast: the road to GPT‑5

Sam Altman says GPT‑5 is still on track “within a few months” and will fold o‑series advances into a single, unified release. Expect:

* Native multimodal everywhere
 * Chain‑of‑thought output by default
 * First‑party agent orchestration layer

OpenAI’s message is clear: bigger is passé; smarter and cheaper wins.