Hello atnak,
I used your sample program, and reproduce the issue. I found that EmEditor always outputs EOF (0x1a) when the “Selection” or “Document” is selected for the Input in the External Tool Properties.To work around this, you can select the “Custom” for the Input, and then enter “$(DocText)” for the “Custom” text box, and make sure the “Add EOF” check box is cleared.
On the next version, I will make the “Add EOF” check box enabled even when “Selection” or “Document” is selected.
Thanks!