Retained canonical change record
Anthropic removes non-default sampling controls starting with Claude Opus 4.7
Starting with the April 16, 2026 launch of Claude Opus 4.7, non-default temperature, top_p, and top_k values return HTTP 400; Anthropic recommends omitting them and using prompting.
Required action
Remove temperature, top_p and top_k overrides from affected requests and use prompting to guide behavior.
Scope and evidence limits
Claude API behavior for affected models
Anthropic documents this as model behavior on its API; partner-platform behavior should be checked separately.
not_tested
Official sources
Affected components
temperature, top_p and top_k on Claude Opus 4.7
Affected users
Developers setting non-default sampling parameters on Claude Opus 4.7 or later models, including Claude Mythos Preview.
Migration guidance
Omit temperature, top_p and top_k on affected models and use explicit prompting to guide response behavior.
Correction history
- 2026-09-21: Narrow the legacy model scope to the exact model admitted by the typed record. Current evidence does not support a blanket claim about every later model.