Claude Sonnet 5 removes manual thinking budgets and sampling parameters

On Sonnet 5, manual extended thinking and non-default temperature, top_p or top_k return a 400 error, and a new tokenizer produces about 30% more tokens for the same text.

Who is affected:

Code moving from Claude Sonnet 4.6 to Sonnet 5.

Action needed:

Remove budget_tokens and sampling parameters, and re-measure token costs.