doctrine.engineering

Agent confinement is part of the 2026 development workflow. Understanding and managing confinement is a core skill when working with agents, comparable to knowing Git - and probably a better way to separate “vibe coding” from engineering.

Confinement is an engineering concern.

The risks are well-rehearsed. What’s undersupplied is practical, maintainable mitigation advice.

The thesis I’ll advance here: Nix + native OS sandboxing is a sleeper for ergonomic agent confinement. It’s not always enough for long-duration unattended sessions running in parallel - but it’s pretty good, most of the time.

To clarify: this is about using nix to define a declarative shell for your project. Enter the shell, and the stuff you declared is set up. You don’t have to install NixOS (the linux distro) or nix-darwin (managing your Mac system with nix) or home-manager (managing your userland with nix).

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When asked a question of the form “What’s the best X?”, every software architect is duty-bound to answer “It depends. What are you optimising for?”. The “best” choice depends strongly on the criteria you’re using to evaluate the options.

If you’re not clear on those, how can you be confident you’ve found the right set of tradeoffs? Moreover, how can you possibly engage in a rational debate with other people about a decision, if everyone involved is proceeding from a private set of unexamined biases? The best you can hope for is to agree by accident. More likely, you’ll spend a lot of time talking past each other, because you’ve entered the conversation with completely different foundational assumptions.

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Doctrine is an evolving, ambitious, pragmatic approach to agentic engineering, expressed as a Rust CLI tool.

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Steve Jobs famously called the computer a “bicycle for the mind”. Would that make LLMs a “motorcycle for the mind”? They’re certainly less effort than pedalling yourself …

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