What this model error usually means
Anthropic: Claude Sonnet 4.6 returning 400 / model capability unsupported means you should first confirm whether model ID anthropic/claude-sonnet-4.6 is visible for this Anthropic key, then separate permission, context, capability, rate limit, or route issues.
- Model: anthropic/claude-sonnet-4.6
- Provider: Anthropic
- Status code: 400