Good piece, but two things work against the thesis:

The Sunsama example actually argues the opposite direction. He spent an afternoon hacking around a closed system with an agent and it worked. If agents are good enough to reverse-engineer and workaround proprietary software today, the urgency to switch to open source decreases, not increases. "Good enough" workarounds are how SaaS stays sticky.

And agents don't eliminate the trust problem, they move it. Today you trust Sunsama with your workflows. In this vision, you trust your agent to correctly interpret your intent, modify code safely, and not introduce security holes. Non-technical users can't audit agent-modified code any better than they could audit the original source. You've traded one black box for another.