TLDR Dev 2026-05-04
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Articles & Tutorials
A Couple Million Lines of Haskell: Production Engineering at Mercury (43 minute read)
Mercury's successful operation of a two-million-line Haskell codebase in fintech shows the language's viability at scale despite a team largely new to the language. Haskell has an ability to encode important operational knowledge and institutional memory directly into type-safe interfaces, making the "right thing easy." They treat purity as a boundary, design for introspection with records of functions, and use types for critical invariants.
The Agent Harness Belongs Outside the Sandbox (11 minute read)
AI agent harnesses, the control loops driving LLMs, can be architected either inside or outside the execution sandbox, each with distinct implications for security and multi-user environments. Mendral, building multi-user agents, chose to run the harness outside the sandbox to improve security by keeping credentials separate, have efficient sandbox lifecycle management, and simplify shared state.
Harness Engineering: How OpenAI Ships Without Writing Code (11 minute read)
Harness engineering is where engineers focus more on building the environment and βharnessesβ (like OpenAI's Codex) around AI agents, so that they can build software without manually written code. OpenAI's approach involved making applications legible for agents to query runtime states and structuring documentation with progressive disclosure using an AGENTS.md table of contents. To manage high agent throughput, OpenAI adopted a merge philosophy prioritizing fast corrections over perfect prevention, and continuously addressed technical debt through "golden principles" enforced by background cleanup agents.
The 'Hidden' Costs of Great Abstractions (3 minute read)
In computing, abstracting away complexity has reduced developers' understanding, leading to a decline in software quality over time. Historically, deep knowledge of machine operation was necessary, but as resources grew, reliance on pre-built libraries led to less rigorous development practices. The advent of LLMs now allows almost anyone to generate functional but often poor-quality software, making expertise even more necessary.
Agentic Coding is a Trap (13 minute read)
The shift toward agentic coding risks atrophying developers' critical thinking and implementation skills while increasing system complexity and vendor lock-in. Instead of abdicating full control to AI, developers should maintain active engagement in manual coding to preserve their technical expertise and maintain software quality.
LLMs Are Not a Higher Level of Abstraction (4 minute read)
LLMs don't represent a higher level of programming abstraction. Traditional programming abstractions are characterized by a deterministic function where a specific input consistently yields a specific desired output. However, LLMs operate probabilistically, providing only the chance of getting a desired output, P(y), rather than a guaranteed result.
Acai (GitHub Repo)
Acai is an open-source toolkit for spec-driven software development. It provides a simple `feature.yaml` spec format, a CLI, and a dashboard to organize requirements and track their implementation, coverage, and acceptance status. By introducing unique "ACID" requirement IDs, Acai allows for deep traceability from spec to code and tests.
Agent Desktop (GitHub Repo)
Agent Desktop is a native desktop automation CLI built with Rust, designed for AI agents to interact with any application via OS accessibility trees. It provides structured JSON output and deterministic element references, removing the need for screenshots or pixel matching. The tool has 53 commands for observation and interaction, including progressive skeleton traversal to optimize token usage for AI models.
How fast is a macOS VM, and how small could it be? (11 minute read)
Recent performance benchmarks on Apple silicon show that virtual machines maintain nearly native CPU and GPU speeds, making them great for daily tasks. Even with minimal resources like 4 GB of RAM, these environments are functional for lightweight usage on modern hardware like the MacBook Neo.
Why TUIs are back (7 minute read)
Native GUI development across Windows, Linux, and macOS has become fragmented and inconsistent, leading to the widespread adoption of Electron apps that often lack essential keyboard-driven workflows. Terminal User Interfaces (TUIs) are experiencing a resurgence as fast, automatable, and consistently functional alternatives that transcend these operating system-specific limitations, though AI is allowing native desktop apps to also make a comeback as they get better at developing them.
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