Claude Opus 5 (Fast)

The anthropic/claude-opus-5-fast row was dropped from the OpenRouter catalog in the 2026-09-02 snapshot. It was active, without an expiry date, in the 2026-09-01 snapshot before it, and the bound facts above still render their last-known values as of that day. The router withdrew the fast rows for Claude Opus 4.8 and Claude Opus 4.7 in the same snapshot.

Fast mode is still on sale for this model. Anthropic's Opus 5 launch post describes the model as "also offered in Fast mode, where it runs around 2.5 times the default speed" at twice the base price, and its fast-mode documentation still names Opus 5 as a supported model. OpenRouter now serves the option as an "Anthropic Fast" provider on the standard anthropic/claude-opus-5 row, at $10 / $50 per million tokens — the rates this row's last-known facts above record.

The old anthropic/claude-opus-5-fast slug is deprecated, not broken. OpenRouter's notice on its page dates the change to September 1, 2026: the dedicated fast model is deprecated, and fast mode is now served by the fast service tier endpoint on Claude Opus 5 — "Requests to this model keep working and are served by the same fast tier capacity, so no action is required, but new integrations should target the regular model" (model page; service-tier docs). An empty endpoints list on the old slug proves nothing about routing. GET /api/v1/models/anthropic/claude-opus-5-fast/endpoints answered HTTP 200 with "endpoints":[] on 2026-09-02, where the same call on the standard row returns a populated list. No published source explains the difference, and whether requests still route is answered by the deprecation notice above, not by the listing. For new work, call anthropic/claude-opus-5 with service_tier: "fast" or speed: "fast", or on Anthropic's own API speed: "fast" with the fast-mode-2026-02-01 beta header, per its fast-mode documentation. The tier was folded into the parent row, not retired.