Function canUseTool

src/cli/print.ts:4186–4295

(
    tool,
    input,
    toolUseContext,
    assistantMessage,
    toolUseId,
    forceDecision,
  )

  permissionPromptTool: PermissionPromptTool,
): CanUseToolFn {
  const canUseTool: CanUseToolFn = async (
    tool,
    input,
    toolUseContext,
    assistantMessage,
    toolUseId,
    forceDecision,
  ) => {
    const mainPermissionResult =
      forceDecision ??
      (await hasPermissionsToUseTool(
        tool,
        input,
        toolUseContext,
        assistantMessage,
        toolUseId,
      ))

    // If the tool is allowed or denied, return the result
    if (
      mainPermissionResult.behavior === 'allow' ||
      mainPermissionResult.behavior === 'deny'
    ) {
      return mainPermissionResult
    }

    // Race the permission prompt tool against the abort signal.
    //
    // Why we need this: The permission prompt tool may block indefinitely waiting
    // for user input (e.g., via stdin or a UI dialog). If the user triggers an
    // interrupt (Ctrl+C), we need to detect it even while the tool is blocked.
    // Without this race, the abort check would only run AFTER the tool completes,
    // which may never happen if the tool is waiting for input that will never come.
    //
    // The second check (combinedSignal.aborted) handles a race condition where
    // abort fires after Promise.race resolves but before we reach this check.
    const { signal: combinedSignal, cleanup: cleanupAbortListener } =
      createCombinedAbortSignal(toolUseContext.abortController.signal)

    // Check if already aborted before starting the race
    if (combinedSignal.aborted) {
      cleanupAbortListener()
      return {
        behavior: 'deny',
        message: 'Permission prompt was aborted.',
        decisionReason: {
          type: 'permissionPromptTool' as const,
          permissionPromptToolName: tool.name,
          toolResult: undefined,
        },
      }
    }

    const abortPromise = new Promise<'aborted'>(resolve => {
      combinedSignal.addEventListener('abort', () => resolve('aborted'), {
        once: true,
      })
    })