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Sweep 01 Oct 2026 · 17:27Z Build v2.1.287 508 read Stable v2.1.285 Latest v2.1.287 Next v2.1.287 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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How the agent loop works changedagent-sdk/agent-loop

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288288A few strategies for long-running agents:
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290* **Use subagents for subtasks.** Each subagent starts with a fresh conversation (no prior message history, though it does load its own system prompt and project-level context like CLAUDE.md). It does not see the parent's turns, and only its final response returns to the parent as a tool result. The main agent's context grows by that summary, not by the full subtask transcript. See [What subagents inherit](/docs/en/agent-sdk/subagents#what-subagents-inherit) for details.
290* **Use subagents for subtasks.** Each subagent starts with a fresh conversation (no prior message history, though it does load its own system prompt and project-level context like CLAUDE.md). It does not see the parent's turns, and only its final response returns to the parent. The main agent's context grows by that summary, not by the full subtask transcript. See [What subagents inherit](/docs/en/agent-sdk/subagents#what-subagents-inherit) for details.
291291* **Be selective with tools.** Every tool definition takes context space. Use the `tools` field on [`AgentDefinition`](/docs/en/agent-sdk/subagents#agentdefinition-configuration) to scope subagents to the minimum set they need.
292292* **Watch MCP server costs.** [MCP tool search](/docs/en/agent-sdk/mcp#mcp-tool-search) defers MCP tool schemas by default and loads them on demand. When tool search is off or has fallen back to upfront loading, each MCP server adds all its tool schemas to every request, so a few servers with many tools can consume significant context before the agent does any work. See [Configure tool search](/docs/en/agent-sdk/tool-search#configure-tool-search) for the configurations where the fallback applies.
293293* **Use lower effort for routine tasks.** Set [effort](#effort-level) to `"low"` for agents that only need to read files or list directories. This reduces token usage and cost.
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