Claude task budgets give agents a visible countdown

Anthropic's task-budgets beta adds an advisory token cap spanning a whole agentic loop instead of a single call, per the platform docs. The cap gets injected server-side as a countdown only the model sees. The model paces itself and wraps up before running out, instead of getting cut off mid-response by max_tokens.

That matters for anyone running multi-step agents, where a single step's token ceiling says nothing about how much work is left in the loop.

Task budgets now support Opus 5, per the docs. Effort controls how deep the model goes on any single step; budget controls how much room it has across the whole loop. Two dials, two jobs.

The docs flag two failure modes worth knowing before this goes into production. Set the budget too small for the task, and the model may show refusal-like behavior. It declines the work, or scopes it down, rather than starting something it can't finish. That's not a truncated response, it's a different failure, and the fix is raising the budget, not tuning some other parameter.

The second gotcha is subtler. Decrement remaining yourself client-side instead of letting the server track it, and two things break. Your prompt cache invalidates. And the budget gets under-reported, which makes the agent quit early for no real reason.