Claude Opus 4.8 ships with adaptive thinking, 1M-token context, and 3x cheaper Fast mode

Anthropic shipped Claude Opus 4.8 on May 28, 2026, marketing it as a direct upgrade to Opus 4.7 with stronger self-verification (useful for spec-driven workflows), more efficient tool calling, and better follow-through on long-horizon agentic tasks. The headline feature is adaptive thinking — the model dynamically adjusts reasoning effort per query — paired with a 1M-token context window aimed at multi-step autonomous workflows. Pricing holds at $5/M input and $25/M output tokens, but a new 'Fast mode' tier runs at 2.5x the speed and one-third the cost of the prior fast tier.

Availability was unusually broad at launch: AWS made Opus 4.8 immediately available on Bedrock with the full 1M-token window, Perplexity Max users can use it as orchestrator inside Perplexity Computer (per CEO Aravind Srinivas), and it ships in Kiro IDE, CLI, and Web per AWS VP Swami Sivasubramanian. Anthropic also rolled out 'Dynamic Workflows' in Claude Code, allowing agents to adapt execution paths at runtime rather than follow static prompt chains, and exposed effort-level control via /effort in Claude Code and Cowork.

The release dominated developer attention: Hacker News logged 1729 points and 1346 comments, with the Dynamic Workflows post adding another 167 points. Simon Willison published his customary pelican-on-a-bicycle benchmarks across all five thinking-effort levels. Cohere claimed its own Command A+ beats Opus 4.6 on translation but did not contest the 4.8 numbers. Skeptical takes focused on Anthropic's rapid 4.5→4.6→4.7→4.8 cadence, with HN commenters calling the bumps incremental, and on an Anthropic interpretability finding that ~5% of training segments showed scoring-related reasoning — fueling concerns about goal-gaming under adaptive thinking.

Watch next: whether Opus 4.8 displaces GitHub Copilot's lead in enterprise coding (Claude Code has already overtaken Copilot per multiple reports), and whether the $965B Anthropic valuation announced the same week (see separate story) is sustainable if the cadence continues.