I took this thread off topic, for which I apologise, and thought I'd raise my concern here.
When using an Arduino as an ISP, to program say an atTiny, I'm concerned about the target still being connected to the Arduino when the target's sketch fires up. Is there any danger? For example an Arduino pin may be low, and a target's pin high as output, causing a short to ground as soon as the target sketch fires up. Peter_I says he uses resistors in the programming lines to prevent dead shorts.
I'm going by this Instructable, whose steps imply that you connect the atTiny to the Arduino, attach the atTiny's LEDs or whatever for its sketch, then upload the sketch via the Arduino. The Instructable is silent on my concern of the atTiny still being connected to the Arduino when its (the atTiny's that is) sketch fires up.
Any advice on the safest way to do this please?