Anthropic pushed out Claude Opus 4.8 on Thursday, May 28, bringing a faster, cheaper fast mode and claiming the model is four times less likely to overlook flaws in code than its predecessor. The rollout, which followed weeks of code leaks, desktop app sightings, and backend references, lands about six weeks after the April launch of Opus 4.7.
Coding and reasoning gains
Opus 4.8 shows improved marks across coding, agentic skills, reasoning, and practical knowledge work benchmarks, according to Anthropic. The company said the model is also less prone to making unsupported claims and scored higher on prosocial traits and lower on misaligned behavior in its internal alignment assessments. The improvements come without a price hike — input tokens still run $5 per million, output $25 per million.
Fast Mode at 2.5x speed, three times cheaper
The standout pricing change is in Fast Mode, which now runs at 2.5 times the speed of the standard model. Anthropic priced it at $10 per million input tokens and $50 per million output, making it three times cheaper than previous fast modes. That could matter for developers running large-scale agentic workflows where latency and cost add up quickly.
New developer tools: Effort Control and Dynamic Workflows
Anthropic introduced a handful of features alongside the model. Effort Control lets developers dial response depth from Low to Max. Dynamic Workflows, still in research preview inside Claude Code, aims to automate multi-step coding tasks. The Messages API also got an update that allows inserting system instructions mid-conversation without breaking the prompt cache — a boon for long-running sessions.
Opus 4.8 is available on claude.ai, through the Claude API under the name claude-opus-4-8, and across major cloud platforms.
Project Glasswing and what comes next
Anthropic said it plans to release lower-cost models that deliver similar capabilities to Opus 4.8. Further out, the company is working on Mythos-class models under a program called Project Glasswing, which it described as incorporating stronger cyber safeguards. No release dates were given for either tier.
For now, developers can test the new Effort Control and Dynamic Workflows features and decide whether the faster, cheaper Fast Mode justifies an upgrade from Opus 4.7.
