Why does max_tokens now behave differently on Claude Sonnet 5?

On Sonnet 4.6, an unconfigured request produced no thinking tokens at all, so the full max_tokens budget was effectively reserved for the visible response text by default.

On Sonnet 5, because adaptive thinking now runs by default on the same kind of unconfigured request, thinking tokens draw from that same max_tokens budget before the visible response gets its share - so the identical max_tokens value now has to cover both.

The practical risk is that a max_tokens setting comfortably sized for Sonnet 4.6's text-only output can leave too little room for Sonnet 5's response once thinking tokens are subtracted from the same shared budget, potentially truncating the answer even though nothing about the request itself changed.

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