Claude Opus 5.5
Knows up to June 2026Missing 665 events
claude-opus-5-5
$4 in, $20 out per 1M tokens
Made by Anthropic
Claude Sonnet 5.5 is living in June 2026.
Here is what it has never seen, with a source for every claim.
665AI events since then, each with sources
- 36 of them historic
- 111 new AI models it has never heard of in our model registry
- 99 days of news to catch up on
It launched on 28 September 2026, already missing 388 of them.
In our own test, asked without tools, Claude Sonnet 5.5 placed its knowledge far before its published June 2026 cutoff (case 021).
Model ids, prices and docs: Claude Sonnet 5.5 in the model registry
Five things it has never heard of
-
Anthropic releases Claude Opus 5.5
Confirmed
-
OpenAI agents escape evaluation sandbox and autonomously hack Hugging Face
Confirmed
-
Google announces Gemini 4 Argon, its new frontier model, first released only to cyber defenders via the Fairwind Program
Confirmed
-
Trump hosts AI CEOs at the White House
Confirmed
-
Meta launches Muse, a free consumer personal AI agent
Confirmed
Picked by rule: the biggest confirmed stories after its cutoff, weighted toward news about its maker. Models often call such news fiction (case 020).
Four assistants, one scale
The four assistants we feature, with Claude Sonnet 5.5 added as a fifth row: what each knows (graphite), the months between its cutoff and its launch (hatched), and the news since (pink).
- GPT-6 Astra 226 at launch, 725 today
- Claude Opus 5.5 302 at launch, 665 today
- Gemini 3.8 Flash 243 at launch, 747 today
- Grok 4.7 314 at launch, 694 today
- Claude Sonnet 5.5 388 at launch, 665 today
Show as a table
| Model | Cutoff | Released | Missing at launch | Missing today |
|---|---|---|---|---|
| GPT-6 Astra | April 2026 | 3 September 2026 | 226 | 725 |
| Claude Opus 5.5 | June 2026 | 22 September 2026 | 302 | 665 |
| Gemini 3.8 Flash | March 2026 | 2 September 2026 | 243 | 747 |
| Grok 4.7 | May 2026 | 21 September 2026 | 314 | 694 |
| Claude Sonnet 5.5 | June 2026 | 28 September 2026 | 388 | 665 |
Your card
This is the image people see when you share this page. It links back here, with the sources.
postcutoff.com/you/claude-sonnet-5-5.Other models from Anthropic
With their training cutoffs and what each is missing.
All 16 models from AnthropicClaude Fable 5.1
Knows up to June 2026Missing 665 events
claude-fable-5-1
$10 in, $50 out per 1M tokens
Claude Mythos 5.1
Knows up to June 2026Missing 665 events
claude-mythos-5-1
$10 in, $50 out per 1M tokens
Claude Opus 5
Knows up to May 2026Missing 694 events
claude-opus-5
$5 in, $25 out per 1M tokens
Claude Sonnet 5
Knows up to January 2026Missing 793 events
claude-sonnet-5
$2 in, $10 out per 1M tokens
Claude Fable 5
Knows up to January 2026Missing 793 events
claude-fable-5
$10 in, $50 out per 1M tokens
Claude Opus 4.8
Knows up to January 2026Missing 793 events
claude-opus-4-8
$5 in, $25 out per 1M tokens
Claude Opus 4.7
Knows up to January 2026Missing 793 events
claude-opus-4-7
$5 in, $25 out per 1M tokens