There is a flag Auto Cast On that is default to off for SCV - Repair
Target Filters section
Issue may be because repair bot your making is immobile. Think repair require the unit to move towards it's target before it gets activated since melee range.
Have you tried remaking science vessel ability Nano Repair? Edit it to drain minerals instead of energy somehow.
They have an auto cast for repairing machines similar to what medics do to bio units.
Messing around I added this to a Reaper and for ability target flag set Structure as allowed. Now reapers auto heal buildings as a SCV builds it.
Edit: Though this doesn't make the building be built any faster like I thought it would.
There is a flag Auto Cast On that is default to off for SCV - Repair
Target Filters section
Issue may be because repair bot your making is immobile. Think repair require the unit to move towards it's target before it gets activated since melee range.
Have you tried remaking science vessel ability Nano Repair? Edit it to drain minerals instead of energy somehow.
They have an auto cast for repairing machines similar to what medics do to bio units.
Messing around I added this to a Reaper and for ability target flag set Structure as allowed. Now reapers auto heal buildings as a SCV builds it.
Edit: Though this doesn't make the building be built any faster like I thought it would.