The Riftbreaker · Mech upgrade
Repair Tools
The guide describes Repair Tools as capable of stacked regeneration modifiers and gives a specific crafted combination as a theorycrafting example.
How it works
The author says Repair Tools have strong possibilities for stacking regeneration and describes a combination of cooldown, build cost, and movement modifiers across four crafted upgrades. They explicitly call the combination theorycrafting and say it took them about 200 attempts to obtain. That is a personal anecdote, not a stated drop rate or guaranteed outcome.
Read the supporting references
Check the edition and source version for patch-specific details. Guide methodology.