January 2026 Summaries

The author reflects on their experience with a coding agent named Claude at exe.dev, emphasizing the importance of maintaining a clean and consistent codebase as a means of influencing the agent's output. Initially, when Claude wrote undesirable code by directly accessing the database in end-to-end tests, the author realized that the agent was simply mimicking existing patterns in the codebase, which included similar direct queries. Instead of blaming the agent, the author corrected the underlying tests and improved the test infrastructure to prevent such patterns. The key lesson is that prompts given to coding agents are temporary, but the codebase serves as a lasting prompt that guides the agent's coding style. Therefore, enhancing the codebase is crucial for achieving desirable results from state-of-the-art coding agents.

The challenge of implementing SSH access for virtual machines (VMs) at exe.dev is addressed by using a pool of public IPv4 addresses due to the high cost of assigning individual IP addresses and the limitations of IPv6. While web traffic can share IP addresses by using the Host header, SSH lacks a similar feature, complicating the routing of connections. To overcome this, exe.dev assigns each VM a unique IP address relative to its owner, allowing the {user, IP} tuple to uniquely identify connections. The process involves careful IP allocation and requires bespoke management software, as public IPs are often NATed in cloud environments. This system was specifically developed to ensure uniform domain name behavior for exe.dev, though it is not recommended as a general solution for others seeking to multiplex SSH access.

Start-ups often develop ad hoc processes, and at exe.dev, using emoji reactions to communicate with bots has proven to be an effective method. These reactions are efficient, intuitive, and visible, providing a low-noise way to interact within the exact context of an action, such as using 🪲 to auto-file an issue or 💡 for feature requests. The bots also communicate back using emoji, with 👀 for ongoing requests, ✅ for success, and 💥 for failure. For example, granting invite codes is streamlined by responding with an emoji indicating the number of invites, resulting in a ✅ when completed successfully. Despite the perceived complexity of deploying bots, exe.dev facilitates this process, supporting a range of hosted applications like Discord and Slack bots, a link shortener, a query-my-logs agent, and a blog, indicating a growing and adaptable platform.

Shelley is an open-source, mobile-friendly coding agent developed by exe.dev, designed to operate efficiently on a variety of platforms and accommodate multiple conversations and models, while running seamlessly on a user's virtual machine. It offers a web-based interface that is preferred for its user-friendly features, such as the ability to scroll, view images, and copy-paste, which contrasts with the limitations of terminal interfaces. Shelley maintains its state in a SQLite database, allowing users to access previous conversations and debug issues, enhancing its utility as a coding tool. The system's architecture enables rapid setup and deployment of internal tools, allowing for easy modifications and testing, which is facilitated by features like proxy support and a code review interface. With its design prioritizing flexibility and accessibility, Shelley is positioned as a practical solution for developers, and it is supported by an active community on platforms like GitHub and Discord.