David Crawshaw argues devtools must be open source for AI personalization

The era of rigid plugin APIs and bloated configuration files is ending because source code itself has become the universal customization interface for AI agents.

• –**AI as the Automated Maintenance Engine**: By using scheduled agent workflows to rebase local changes onto upstream releases, developers no longer suffer the historical tax of maintaining custom software forks.
• –**Obsolescence of Extension Architectures**: Designing complex plugin frameworks or extension hooks is no longer worth the engineering overhead when LLM agents can refactor core application code to fit specific user needs.
• –**Open Source as an Agent Imperative**: Closed-source tools like Claude Code restrict users to vendor-provided extension points, whereas open-source agents allow AI to seamlessly restructure the entire codebase.
• –**Bespoke Workflows Over Rigid SaaS**: Engineers and small teams can now generate and maintain highly specialized internal tools—such as integrating diff-minimizer meat.dev into Shelley—rather than forcing their workflows into generic software products.