TLDR Dev 2026-05-04

Harness engineering 🛠, costs of abstractions 🫣, security through obscurity 🥷

Now you can prove your QA team is moving the needle (Sponsor)

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Articles & Tutorials

A Couple Million Lines of Haskell: Production Engineering at Mercury (43 minute read)

The Agent Harness Belongs Outside the Sandbox (11 minute read)

Harness Engineering: How OpenAI Ships Without Writing Code (11 minute read)

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Opinions & Advice

The 'Hidden' Costs of Great Abstractions (3 minute read)

Agentic Coding is a Trap (13 minute read)

LLMs Are Not a Higher Level of Abstraction (4 minute read)

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Launches & Tools

Acai (GitHub Repo)

Agent Desktop (GitHub Repo)

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Miscellaneous

How fast is a macOS VM, and how small could it be? (11 minute read)

Why TUIs are back (7 minute read)

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Quick Links

Understand Anything (GitHub Repo)

Open Design (GitHub Repo)