Anthropic: Original Claude Sonnet 4 and Opus 4 Models Retired — Migration to Sonnet 4.6 and Opus 4.8

Anthropic has retired the original Claude Sonnet 4 and Claude Opus 4 models from production. According to the Claude Platform release notes, all API requests to the identifiers claude-sonnet-4-20250514 and claude-opus-4-20250514 now return an error.

What exactly changed in the Anthropic API?

Anthropic has discontinued support for the original generation of Claude Sonnet 4 and Claude Opus 4 models. The identifiers claude-sonnet-4-20250514 and claude-opus-4-20250514 no longer route to active models — every call now returns an error. Development teams that embedded those identifiers in production integrations must update their configuration immediately, as calls fail without a silent fallback.

Which models does Anthropic recommend migrating to?

Anthropic recommends switching to Claude Sonnet 4.6 and Claude Opus 4.8, newer iterations within the same family. Migration in practice means replacing the old model identifier with the new one in API calls; the request format remains the same. Sonnet 4.6 and Opus 4.8 bring improved capabilities compared to the original generation from May 2025, which those identifiers with the date suffix 20250514 designated.

Can researchers retain access to the retired models?

Researchers can request access to retired models through Anthropic’s External Researcher Access Program. The program allows academic and independent researchers to retain access to older versions for reproducibility and safety evaluation purposes, even after the models have been removed from the commercial offering.

Why does this retirement matter?

Retiring fixed model identifiers is a normal part of the commercial AI model lifecycle, but it demands attention because calls to a retired ID fail immediately. Teams that depend on Claude models are advised to treat model identifiers as configurable parameters rather than permanent constants, so that future migrations remain painless.