PROVIDER MIGRATION PATH
Claude Sonnet 5.5
Anthropic's announced successor.
Claude Sonnet 4 is retired.
What replaces Claude Sonnet 4?
For a direct Anthropic API replacement for Claude Sonnet 4, compare Claude Sonnet 5.5 first. As of 2026-11-02, its verified Standard blended price is $4.00 per 1M tokens at a 75% input / 25% output mix. ECI is an estimated general-capability measure; this is not a task-performance guarantee.
Historical ECI 141.6 · Current direct API price unavailable
REPLACEMENT DECISION
Provider migration path.
Direct API prices at 75% input / 25% output. ECI is estimated general capability, not task success.
ECI intervals can overlap; no choice guarantees task results or API compatibility.
Replacement questions
Which replacement did Anthropic announce for Claude Sonnet 4?
Anthropic announced Claude Sonnet 5.5. As of 2026-11-02, its verified Standard blended price is $4.00 per 1M tokens at a 75% input / 25% output mix. This historical provider advice can differ from today's price-and-ECI screening choice. Provider notice.
Is the replacement for Claude Sonnet 4 API compatible?
API compatibility has not been verified. Check the provider's migration guidance and test your integration before switching.
Prices verified 2026-11-02; ECI snapshot 2026-11-01. Retirement applies to the Anthropic direct API; seller routes need separate evidence. Retirement notice · ECI data · Browse current models.