Anthropic replaces Opus 4.7 with Opus 4.8, says misalignment rates similar to Mythos Preview

Anthropic rolled out Opus 4.8 on May 28, 2026 as the immediate replacement for Opus 4.7, positioning the update around cost and speed while emphasizing improved alignment. The company says Opus 4.8 reduces misalignment relative to 4.7 and likens its alignment profile to what it has described for Mythos Preview — a claim that matters for customers balancing capability with safety.

Anthropic did not claim Opus 4.8 fully surpasses OpenAI’s GPT-5.5 family on coding, a caveat that echoes the broader competitive backdrop. OpenAI released GPT-5.5 Instant on May 5, 2026 — a lighter, less verbose variant that the company says produced 52.5% fewer hallucinated claims than GPT-5.3 Instant on high‑stakes prompts in medicine, law and finance and was made the default in ChatGPT. NVIDIA published Nemotron 3 Nano Omni on April 28, 2026, positioning it as an open multimodal model for visual, audio and textual perception and reasoning.

For builders, the concrete tradeoffs are clear: Opus 4.8’s cheaper faster modes could materially cut inference spend and reduce latency for throughput‑sensitive applications, while modest coding improvements may speed development workflows. Because Anthropic’s notes show 4.8 does not fully best GPT-5.5 on coding benchmarks and because its alignment claims are framed against Mythos Preview and earlier versions, teams should benchmark task‑specific performance and validate vendor‑reported safety metrics before switching models. Anthropic previously reported a 92% honesty rate for Opus 4.7.

The original coverage points readers to a Model Release Tracker designed to put vendor claims in context: the tracker lists major 2026 releases, captures rollout and pricing details, and includes hands‑on expert tests and an Expert Score where applicable. The tracker will be updated when notable new models arrive, which matters for developers and operators who must weigh raw capability alongside safety and behavioral metrics. Disclosure: the publisher's parent company filed a lawsuit against OpenAI in April 2025 alleging copyright issues, as noted in the original coverage.