23 concepts

Glossary

The ideas underneath the lessons, one screen each, so they carry over to your own setup.

• Allowlist vs denylist A list of what may pass versus a list of what may not, and why failing closed beats failing open.
• Backplane The board every card plugs into so that none talks to another directly, and why enjambre has none: Windows reaches the Mac over SSH and the Mac listens only on its own loopback.
• Budget per job A spending cap that belongs to one job, not to the account: when the agent reaches it, it stops by itself, leaves what it did and says why. A turn limit is not enough, because each turn costs more than the last.
• DHCP, reservations and the private Wi-Fi MAC How the router hands out IP addresses, why a reservation keeps the Mac's address stable, and what the private Wi-Fi address changes.
• Git as a bus Why results travel between machines as branches pushed and fetched through git instead of a shared folder.
• Heartbeat and resumption A long job nobody watches has to answer two questions on its own: is it still alive, and if it died, can it pick up where it left off?
• Idempotence An operation is idempotent if running it twice leaves the system as running it once; why unattended remote commands need that.
• Inherited console on Windows Every command-line program on Windows inherits its parent's console; when there is none, a visible one pops up. Why that matters for background watchers.
• Job queue Why jobs for an unavailable node wait in a queue of files, and what validating the contract before queuing buys you.
• Least privilege for agents Giving an agent only the tools it needs, no sudo, and a file for whatever only the owner can do.
• Living architecture: C4 + reproducible flows One page per project that shows how information flows: the C4 container diagram, plus use cases you can play step by step over it. How to read it, and the rule that keeps it honest.
• Observability Logs, metrics and traces: gather what already exists and do not invent the metric that is missing.
• One-shot vs persistent session An agent that is born, reads the brief, works and dies, against a conversation that survives between messages. What each one needs in the brief and what it keeps.
• Policy and mechanism A rule written in a document is policy; a hook that enforces it is mechanism. Why you need both.
• Polling vs heartbeat Asking each node whether it is alive versus waiting for it to say so, and what each approach can and cannot detect.
• Priorities: admission, pause, eviction and resumption What the scheduler does with a job's class (high > normal > low > night) before launch, while it runs and afterwards: why pausing frees no memory, why only a job with a checkpoint is evicted, and why only high preempts.
• Pull vs push Who starts the conversation, the node that asks or the one that announces, and when each is the better choice.
• Routing How a table plus live state pick the machine for each job, and explain the choice in one line.
• SSH host fingerprint What the host key fingerprint proves the first time you connect, and what it means when it changes.
• The 3-2-1 rule Three copies, two media, one off-site: how the backup of repos and photos measures up and where it falls short.
• TLS fingerprint (Deskflow) Deskflow uses self-signed certificates and trust on first use: each side shows a fingerprint and the other remembers it, like known_hosts in SSH.
• Worktrees Several working directories from one repository, so parallel jobs never fight over the same checkout.
• zsh startup: .zshenv, .zprofile, .zshrc Which startup file zsh reads depends on whether the shell is interactive or login, and that decides whether your PATH exists over SSH.