Interrupt Handling

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Overview

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Sending an Interrupt

// Cancel current operation (agent stays alive)
handle.interrupt().await?;

// Can continue with new input after interrupting
handle.send_input("New task").await?;

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The Three Scenarios

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1. During LLM Streaming

• Preserves partial text already streamed
• Discards incomplete thinking blocks
• Removes all tool calls (both completed and partial)
• Adds <system>User interrupted this message</system> to response

let handle_clone = handle.clone();
tokio::spawn(async move {
    cancel_signal.await;
    handle_clone.interrupt().await.ok();
});

let mut rx = handle.subscribe();
handle.send_input("Write an essay").await?;

while let Ok(chunk) = rx.recv().await {
    match chunk {
        OutputChunk::TextDelta(text) => print!("{}", text),
        OutputChunk::Done => {
            println!("\nCompleted (or interrupted)");
            break;
        }
        _ => {}
    }
}

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2. During Permission Waiting

• Returns ToolResult::error("Interrupted") for the pending tool
• Adds interrupt marker to history
• Ends the turn (does not retry)

OutputChunk::PermissionRequest { tool_name, action, .. } => {
    match ui.show_permission_dialog(&tool_name, &action).await {
        PermissionResult::Allow => {
            handle.send_permission_response(tool_name, true, false).await?;
        }
        PermissionResult::Cancel => {
            handle.interrupt().await?;
        }
    }
}

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3. During Tool Execution

• Lets the current tool complete (avoids half-written files or resource leaks)
• Returns actual results for completed tools
• Returns ToolResult::error("Interrupted") for unexecuted tools

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Limitations

• Non-streaming mode: Interrupts are not detected during the LLM call itself when streaming is disabled. The interrupt is processed after the full response arrives.
• Long-running tools: Tools that take a long time complete fully before the interrupt is detected.
• Double interrupt: Sending multiple interrupts is safe — subsequent ones are no-ops if already interrupted.

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Next Steps