Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial
One change · claude-code

How the agent loop works changed

agent-sdk/agent-loop

Nearest release: v2.1.273, published 2 hours before this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

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199199The budget cap covers [subagents](/docs/en/agent-sdk/subagents): their spend counts toward the total. Once spend reaches the cap, spawning another subagent fails with `Budget limit reached`, and Claude Code stops any background subagents still running. The cap-enforcement behaviors require Claude Code v2.1.217 or later.
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201With [streaming input](/docs/en/agent-sdk/streaming-vs-single-mode), a message that is still queued when a turn ends at the max-turns limit stays queued. Claude Code doesn't add it to that turn's last model call. It starts a new turn for the message, and the max-turns count starts over for that turn.
201With [streaming input](/docs/en/agent-sdk/streaming-vs-single-mode), a message that is still queued when a turn ends at the max-turns limit stays queued. Claude Code doesn't add it to that turn's last model call. It starts a new turn for the message, and the max-turns count starts over for that turn. The budget total keeps accumulating across messages, and once spend reaches `maxBudgetUsd`, later messages in the same conversation end with the `error_max_budget_usd` result. A [`/clear`](/docs/en/agent-sdk/cost-tracking) starts the budget over.
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203203### Effort level
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238238### Model
239239 
240If you don't set `model`, the SDK uses Claude Code's default, which depends on your authentication method and subscription. Set it explicitly (for example, `model="claude-sonnet-5"`) to pin a specific model or to use a smaller model for faster, cheaper agents. See [models](https://platform.claude.com/docs/en/about-claude/models) for available IDs.
240Set the `model` option to choose which model runs the session. For more information, see [Choose a model](/docs/en/agent-sdk/configuration#choose-a-model).
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242242## The context window
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