Claude Opus 4.8

Claude Opus 4.8 (`claude-opus-4-8`) was Anthropic's most capable Opus-tier model at its May 28, 2026 launch and the recommended default for complex reasoning, long-horizon agentic coding, and high-autonomy work until Claude Opus 5.5 replaced it on September 22, 2026. It keeps Opus 4.7 pricing at $5 per million input tokens and $25 per million output tokens, with a 1M token context window, 128K max output, and a January 2026 knowledge cutoff. Anthropic reports it is around four times less likely than its predecessor to let flaws in its own code pass unremarked, and the `effort` parameter defaults to high on all surfaces including the Claude API and Claude Code. It also serves as the fallback model that handles requests Fable 5's safety classifiers decline. At half of Fable 5's price, it was the workhorse choice for most production agent stacks through the summer of 2026.