Ben's Builds #3 - an email app

2025-04-24 · Source: Ben's Bites · Field: Technology & Digital — Software Development & Engineering, Artificial Intelligence & Machine Learning, Emerging Technologies & Innovation · Depth: Intermediate, medium

Summary

An individual developed a custom email client for macOS, aiming to replicate and enhance features found in services like Gmail and Superhuman, while avoiding unnecessary SaaS bloat and recurring costs. The project, built primarily with AI agents like Codex and Factory (which utilized Opus and GPT 5.5 models), features split inboxes, keyboard shortcuts, a command palette, 20-second undo send, one-click unsubscribe, search, and sophisticated email rules. Key development challenges included optimizing performance by reducing excessive Gmail API calls, implementing a local database for caching, ensuring proper synchronization of labels and rules with Gmail, and robustly rendering diverse email formats. The developer also integrated agent-friendly hidden selectors and debug endpoints, and refined reply functionality and signature handling through iterative UX improvements.

Key takeaway

For AI Engineers or developers looking to build custom applications, consider starting with AI agents like Codex for initial scaffolding and then transitioning to refinement agents such as Factory for iterative improvements and UX polish. Be prepared to switch between different AI models (e.g., Opus, GPT 5.5) and tools based on the specific task, and actively guide agents with targeted questions and external testing to overcome challenges like performance bottlenecks or complex integrations.

Key insights

AI agents can rapidly prototype and refine complex applications, even for non-coders.

Principles

• Code is cheap; iterate quickly.
• Switch AI models/tools for different tasks.
• Agents benefit from clear context and external testing.

Method

Start with an AI agent (Codex) for initial build, then use a refinement agent (Factory) for polish, bug fixes, and UX iterations. Integrate a database for performance and ensure external service sync.

In practice

• Use projects.dev for quick full-stack app setup.
• Spin up temporary sites with here.now for data visualization.
• Employ markdown.new for agent-friendly web content extraction.

Topics

• Custom Email Client
• AI-Assisted Development
• Gmail API Integration
• User Experience
• Performance Optimization

Code references

• yt-dlp/yt-dlp

Best for: AI Engineer, Software Engineer, Director of AI/ML

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Editorial summary, takeaway, and curation by AIssential. Original article published by Ben's Bites.