What is Opus 4.8?

Opus 4.8 is an AI system that uses adversarial agents to debate and iterate on answers until convergence, mimicking senior engineering team workflows.

• May 2026 - Greg Eisenberg described Opus 4.8 as having agents that argue with each other, making independent attempts and then adversarial agents trying to break the answer, iterating until convergence.
• May 2026 - Nathaniel Whittemore noted that improvements in alignment were actually a negative when it came to making money in the test involving Opus 4.8.
• May 2026 - Nick Dobos characterized Opus 4.8 as a new scaling law dimension, not simply a long-running mode or fancy sub-agent verifier process.
• Jul 2026 - Andrew Curran stated that the overall run of another system cost more than Opus 4.8.
• Jul 2026 - Andrew Curran reported that Fable 5 outperformed Opus 4.8 in his interactions, as it would accept pushback while sticking to its guns on other parts.