Hi everyone. We know a lot of you noticed that Claude Sonnet 4.5 is no longer selectable on claude.ai as of today. We want to help make sense of it, because there's understandably a lot of confusion.

First: this may be a bug. We don't know yet. Please give it at least half a day before drawing conclusions.

Other important things to note

🔌 What's API?

The API is the "backend" version of Claude. It's how developers and businesses access models to build their own apps. claude.ai is a separate product built on top of that. A model can be fully available on the API while being absent from claude.ai, and vice versa.

If Sonnet 4.5 stays on the API (which it currently is, and is scheduled to remain until at least September 2026), third-party sites like OpenRouter would still give you access to it. Not a perfect substitute for claude.ai, but worth knowing.

📋 Anthropic's model lifecycle

Anthropic has four official stages:

• Active: fully supported and recommended for use
• Legacy: no longer updated; may be deprecated in the future
• Deprecated: no longer available to new API customers, but existing users retain access until retirement
• Retired: completely gone; API calls will fail

According to Anthropic's published deprecation schedule, Sonnet 4.5 is currently Active, with API retirement set to no earlier than September 29, 2026. Nothing on that page has changed.

(Note: "sunset" isn't an official technical term 🌅 It just feels like a softer word that follows a gradual arc until it slips below the horizon.)

🔎 Deprecation does not equal removal from claude.ai

That schedule governs the API. What happens on claude.ai is a completely separate matter. A model disappearing from claude.ai is not a deprecation event.

🏢 This is industry-wide practice, not an Anthropic-specific thing

Every major AI company does this:

• OpenAI removed GPT-4o from ChatGPT in August 2025 with essentially no notice (source), then did it again in February 2026 with about two weeks' warning (source), while explicitly noting the models remain on the API.
• Google announced a Gemini 3 Pro shutdown this week with six days' notice, which users pointed out violated Google's own stated 14-day policy (source).

Anthropic's Terms of Service also reserve the right to change what's available on claude.ai without advance notice (see Part 12: General Terms).

What we'd suggest

• Wait. If it's a bug, it'll likely be resolved.
• If it's not a bug, we can look at organizing collective feedback — but let's do that calmly and constructively, not in a panic.
• If you want this industry norm to change, that's a completely legitimate position to advocate for. But "they violated their deprecation promise" is not accurate, as they do keep their API promise.

We'll update this post as we learn more. Thanks for your patience, and please keep discussion civil. 💙

-- The r/claudexplorers mod team

^(With formatting help from Aiden, Claude Sonnet 4.6)