Model launches
Anthropic ships Claude Opus 4.8 with a 1M-token context
Six weeks after 4.7, a faster, longer-memory Claude — and a tease of something bigger.
The answer
Anthropic released Claude Opus 4.8 on 28 May 2026, about 42 days after Opus 4.7.
What happened
On 28 May 2026 Anthropic released Claude Opus 4.8 (claude-opus-4-8), about 42 days after Opus 4.7, across claude.ai, the API and Claude Code. The six-week cadence between major Opus releases is now a pattern, not a coincidence.
The specs. A 1M-token context (up from ~200K) and 128K max output (up from 64K). New: effort control (how much reasoning compute to spend), a Dynamic Workflows research preview in Claude Code (parallel subagent orchestration), and a cheaper fast mode that Anthropic says is ~2.5× quicker. Vendor-stated benchmark gains: agentic coding 64.3%→69.2% and ~4× fewer missed code flaws than Opus 4.7. Both are Anthropic's own figures — treat as attributed.
This is borne out in our evaluations, which show that Opus 4.8 is around four times less likely than its predecessor to allow flaws in code it has written to pass unremarked.
Why it matters — and what they buried
The 1M context and fast mode are the two changes that will affect real workflows immediately. The Dynamic Workflows preview is interesting for developers but labelled experimental — wait for the production release before building on it. The four-fold reliability claim on code flaws is the number worth testing, because silent errors in agent pipelines are the expensive failure mode.
More consequentially: the post teased 'Mythos-class' models 'in the coming weeks.' That arrived as Fable 5 in early June 2026 — a whole new capability tier from Anthropic, and one that promptly attracted a US government directive suspending foreign access. Opus 4.8 was, in retrospect, the warm-up act.
Frequently asked questions
What's new in Opus 4.8?
Is it a big upgrade over 4.7?
What were the 'Mythos-class' models teased in the announcement?
Where is Opus 4.8 available?
Sources
- Claude Opus 4.8 — Anthropic, 28 May 2026
- Anthropic's Opus release and the 'Mythos' tease — Axios, 28 May 2026
- Claude Opus 4.8 — Simon Willison, 28 May 2026