In mid-September, developers reported that Claude Code was quietly routing some Opus 5 requests to a newer backend checkpoint the community dubbed "Opus 5.2." The "claude-opus-5-2" slug even surfaced in Microsoft Foundry configs with reasoning-effort tiers.

Anthropic never announced such a model: no model card, API identifier, pricing or benchmarks ever appeared. Instead, Anthropic shipped Claude Opus 5.5 on September 22 with a dated release note, model page, callable ID, documented prices and a migration guide.

Whether the September routing reports were early traffic on what became Opus 5.5, Anthropic has not said. But "Opus 5.2" remains a community label, not a real product: no 5.2 was ever released, and 5.1 never existed on the Opus tier at all.