ToolOutput component is wrongly hidden when the tool message result is a empty string

[BHznJNs]

Currently the ToolOutput component implementation has a guard statement:

export const ToolOutput = ({
  className,
  output,
  errorText,
  ...props
}: ToolOutputProps) => {
  if (!(output || errorText)) {
    return null;
  }
  ...

The expression !(output || errorText) will wrongly returns true when the output is an empty string.
And for example, I have a read_file tool, and the agent use it to read a empty text file, sometimes the tool implementation will return an empty string here, and this expression will make the tool result be hidden.

[JiwaniZakir]

The root cause is JavaScript's falsy evaluation — an empty string "" is falsy, so output || errorText short-circuits to errorText (which is also likely undefined/falsy when there's no error), causing the entire expression to evaluate as if no output exists. The guard in ToolOutput should distinguish between "no output provided" (output == null) and "output is an empty string" (output === ""), since an empty string is a valid and meaningful result (e.g., reading an empty file). A more precise check like !(output != null || errorText) or !(output !== undefined || errorText) would correctly treat "" as a renderable value while still returning null when output is genuinely absent.