June 3, 2026 · By the ToolNav Team · 5 min read OpenAI ChatGPT GPT-4.5 o3 Model Deprecation

OpenAI Retiring GPT-4.5 from ChatGPT on June 27 and o3 on August 26 — Migration Window Now Open

TL;DR

OpenAI confirmed on June 3, 2026 that it will retire GPT-4.5 and o3 from the ChatGPT model picker in two waves: GPT-4.5 on June 27, 2026 (a 30-day sunset) and o3 on August 26, 2026 (a 90-day sunset). Both changes affect the ChatGPT interface only — o3 remains available via the API, so developers face no disruption. Paid ChatGPT users who manually select either model will need to switch to another model in the picker before the deadlines. OpenAI did not name a specific replacement, though its lineup is consolidating on the GPT-5.5 series.

June 27, 2026

GPT-4.5 removed from the ChatGPT model picker — a 30-day sunset; 12 days from today (June 15, 2026)

August 26, 2026

o3 removed from the ChatGPT model picker — a 90-day sunset; affects paid plans

API unaffected

o3 remains available via the OpenAI API with no announced API retirement date — this is a ChatGPT-interface change only

GPT-5.5 series

OpenAI named no specific replacement; the ChatGPT lineup is consolidating on GPT-5.5, with no named one-to-one o3 reasoning equivalent

OpenAI announced on June 3, 2026 that GPT-4.5 and o3 will be removed from the ChatGPT model picker — giving paid users a defined window to migrate before each model becomes unavailable in the interface. The change was posted in OpenAI's ChatGPT release notes, and the two retirements land on different dates.

Two deadlines, two models. GPT-4.5 will be removed from ChatGPT on June 27, 2026, following a 30-day sunset from the June 3 announcement. o3 follows on August 26, 2026, a 90-day sunset. Neither change touches API access: o3 remains available through the OpenAI API with no announced API retirement date, so existing integrations are unaffected — this is a ChatGPT-interface change only.

What to switch to. OpenAI did not designate a specific named replacement in the announcement. Its ChatGPT lineup is consolidating on the GPT-5.5 series — free ChatGPT users are already served by GPT-5.5 models — so GPT-5.5 and its variants in the picker are the practical default for general GPT-4.5 workflows. For o3's reasoning-heavy use cases there is no OpenAI-named one-to-one replacement; affected users will need to evaluate the GPT-5.x options in their own model picker and test before the August 26 cutoff.

Who is affected — and who is not. This retirement is scoped to the ChatGPT interface. Paid ChatGPT users on Plus and Pro plans who manually select GPT-4.5 or o3 in the model picker are the clearly affected group. Whether Team and Enterprise plans share the exact June 27 and August 26 dates or receive extended windows was not specified in the announcement, so admins on those plans should confirm their own timeline. Free ChatGPT users — already on GPT-5.5 — see no change, and developers calling o3 through the OpenAI API are unaffected.

Why OpenAI is retiring them. OpenAI has not published a detailed rationale, but the pattern matches its standard practice of retiring older, lower-usage models as usage concentrates on newer ones. Both GPT-4.5 and o3 have been superseded in the ChatGPT lineup by the GPT-5.5 series, where OpenAI is focusing compute. The announcement appeared in ChatGPT release notes rather than a dedicated blog post, consistent with earlier model retirements in this cycle.

The June 27 deadline is the urgent one. As of today, June 15, GPT-4.5 exits the ChatGPT model picker in 12 days. If your team uses GPT-4.5 in any ChatGPT workflow — shared prompts, team templates, saved conversations defaulting to GPT-4.5, or individual users who have pinned it — those selections become unavailable on June 27 and will route to a different model. Move those workflows to GPT-5.5 before June 27; do not wait. The August 26 o3 deadline is less urgent but benefits from early testing — the GPT-5.x reasoning options behave differently from o3 on extended reasoning chains, so some prompt tuning may be needed.

Why It Matters

Teams that rely on GPT-4.5 in ChatGPT workflows have 12 days to switch before the model disappears from the picker on June 27. This is interface-only — the o3 API is unaffected — but any ChatGPT workflow, shared prompt, or team template pinned to GPT-4.5 will break or silently downgrade on June 27. The o3 deadline on August 26 is less urgent but still requires testing: the GPT-5.x reasoning options handle extended chains differently from o3, and OpenAI named no one-to-one replacement, so plan time to evaluate and tune before swapping production ChatGPT workflows.

Who's Affected

— Paid ChatGPT users on Plus or Pro who manually select GPT-4.5 or o3 — your model selections become unavailable on June 27 and August 26 respectively, and will route to a different model.
— Teams with shared ChatGPT prompts or templates pinned to GPT-4.5 — any workflow depending on that selection will stop working or silently route elsewhere after June 27. Audit team configurations now.
— Team and Enterprise admins — the announcement did not confirm whether your plans share the exact June 27 and August 26 dates or get extended windows; confirm your own timeline rather than assuming the consumer dates apply unchanged.
— Developers calling o3 through the OpenAI API — not affected. o3 remains available via the API with no announced API retirement date; this change is limited to the ChatGPT interface.

What To Do Now

1. Switch ChatGPT workflows off GPT-4.5 now — you have 12 days. Open ChatGPT, find any conversation or team template using GPT-4.5, and switch the model selection to GPT-5.5. Do not wait for June 27.
2. Check Team and Enterprise ChatGPT configurations for pinned models — and confirm your dates. Admins should audit shared spaces, system prompts, and templates that specify GPT-4.5, and verify whether their plan shares the consumer June 27 deadline.
3. For o3 users: start testing a GPT-5.x reasoning replacement before August 26. OpenAI named no one-to-one o3 replacement, so evaluate the reasoning options in your picker against your most sensitive prompts now and tune as needed — you have time, but starting early prevents a last-minute scramble.
4. Note the API boundary. o3 API access is not being retired here — this announcement is ChatGPT-interface-only. Integrations calling o3 via the API are unaffected and continue normally.

Source OpenAI — ChatGPT Release Notes (GPT-4.5 and o3 retirement announced June 3, 2026)

OpenAI Retiring GPT-4.5 from ChatGPT on June 27 and o3 on August 26 — Migration Window Now Open

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