Log at info level changedagents-and-tools/tool-use/tool-runner
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590590The tool runner is an iterable that yields messages from Claude. On each iteration, the runner checks whether Claude requested a tool use. If so, it runs the tool and sends the result back to Claude automatically, then yields the next message from Claude to continue your loop.
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592You can end the loop at any iteration with a `break` statement. The runner loops until Claude returns a message without a tool use, or until it reaches `max_iterations` if you set it.
592You can end the loop at any iteration with a `break` statement. The runner loops until Claude returns a message without a tool use, or until it reaches `max_iterations` (csharp, java, php: `maxIterations`; go: `MaxIterations`) if you set it.
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594594If you don't need intermediate messages, you can get the final message directly:
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822822You take over by modifying the runner's messages from inside the loop body. The exact method depends on the SDK. See the per-language tabs that follow.
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824When you take over for an iteration, the runner does not append the assistant message or tool results from that turn. You become responsible for keeping the conversation valid: append the assistant message and a tool result yourself (if you want the turn to count), modify state conditionally so the loop can still exit when there are no tool calls, and pass `max_iterations` to bound the loop. All seven SDKs support `max_iterations`.
824When you take over for an iteration, the runner does not append the assistant message or tool results from that turn. You become responsible for keeping the conversation valid: append the assistant message and a tool result yourself (if you want the turn to count), modify state conditionally so the loop can still exit when there are no tool calls, and pass `max_iterations` (csharp, java, php: `maxIterations`; go: `MaxIterations`) to bound the loop. All seven SDKs support `max_iterations` (csharp, java, php: `maxIterations`; go: `MaxIterations`).
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826826<Tabs>
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11071107### Automatic context management
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1109For long-running agentic tasks, the TypeScript and Ruby tool runners support automatic [compaction](https://platform.claude.com/docs/en/build-with-claude/context-editing#client-side-compaction-sdk), which generates summaries when token usage exceeds a threshold so the conversation can continue beyond context window limits. Both SDKs have deprecated this client-side option in favor of [server-side compaction](https://platform.claude.com/docs/en/build-with-claude/compaction-threshold), which works with every SDK's tool runner through the `context_management` request parameter. The Python SDK (v1.0 and later) and the Go, Java, C#, and PHP tool runners don't include client-side compaction. The Python, TypeScript, C#, Go, Java, PHP, and Ruby tool runners have a `compact_before_next_turn()` helper for on-demand compaction, spelled in each language's own casing. See [Compact in a loop](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#compact-in-a-loop). Use it or a `context_management` compaction edit on a runner, not both.
1109For long-running agentic tasks, the TypeScript and Ruby tool runners support automatic [compaction](https://platform.claude.com/docs/en/build-with-claude/context-editing#client-side-compaction-sdk), which generates summaries when token usage exceeds a threshold so the conversation can continue beyond context window limits. Both SDKs have deprecated this client-side option in favor of [server-side compaction](https://platform.claude.com/docs/en/build-with-claude/compaction-threshold), which works with every SDK's tool runner through the `context_management` request parameter. The Python SDK (v1.0 and later) and the Go, Java, C#, and PHP tool runners don't include client-side compaction. The Python, TypeScript, C#, Go, Java, PHP, and Ruby tool runners have a `compact_before_next_turn()` (typescript, java, php: `compactBeforeNextTurn()`; csharp, go: `CompactBeforeNextTurn()`) helper for on-demand compaction. See [Compact in a loop](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#compact-in-a-loop). Use it or a `context_management` compaction edit on a runner, not both.
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11111111### Debugging tool execution
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