A cache is an accelerator, never a dependencyA cache may shorten a derivation, never be the only copy of one; switching it off changes a duration, never an answer. A copy can be the right answerMerge duplicates only when they share semantics, knobs and bugs; otherwise keep the copy, with one line saying why. A harness is not an agent thingThe checks, formatters, linters, compiler errors and gates around a change are one harness, and they hold a person to the green path the same way they hold an agent. A record of refusalsCapabilities magus could have had and does not, or had and removed, with what decided each and where to check it. A refusal carries its reasonA refusal names the mechanism and a next step; an error that leaves you with no next step is a design bug. Abstract at the right layer, or not at allA package, module or layer earns its boundary by what it hides; a thin one that renames a function makes every reader open five files to follow one call. Agents propose, humans disposeAn agent integration can suggest work but never accept it; authorship comes from the transport, never the writer's claim. Automation you can interrogateEach automated verdict ships with a lens that shows its inputs, and each step magus runs is expressible as the tool call it made. Behavior is code, facts are dataA target is a Buzz function you can read top to bottom; configuration holds only facts with no algorithm in them. Break now, hold still laterBefore 1.0 a wrong name or format is fixed without a migration path; after it, the tool that works the way it worked last year is the product. Built for the expensive eraMove what a model would have to work out into deterministic, checked answers, so a smaller model can do the work. Built for the largest monoreposmagus is aimed at the largest monorepos that exist; at that scale performance is the feature, and every hot path is measured. Capability is not a reasonThe default answer to a new capability is no; the burden of proof is a failure removed, never a preference enabled. Clear is better than cleverWrite to the need in front of you, one way, the obvious way; clever earns its place only where a measurement says it must, and then it says why. Corrective competenceThe skill this section protects is your ability to fix the thing yourself when the agent is wrong, or gone. Delete before you addThe best code is still no code; before adding code to keep something working, check whether removing the old path reaches the goal. Design principlesHow magus is built and why: the principles, the judgment calls it leaves to you, the standard it is measured against, and what it refused to build. Determinism at chosen pointsmagus fixes a step where it can prove the answer and leaves the rest to the model; a person chooses which steps are fixed. Enforcement, not pinky promisesA rule written only as prose in an agent's context is a pinky promise; each rule lives at the lowest layer that can enforce it, and skills teach rather than guard. Event stream design notesWhy the magus event stream is outbound only, why it needs no daemon, and what building the first clients changed about the design. Every answer has an addressA run's output ref is derived from the hash of everything it declared, the way a Nix store path is; the same inputs name the same run on any machine. Everything is a fileLocal state is JSON Lines a person reads with cat, grep and diff; one entry per line, the last line per key wins, every rewrite a rename. Friction that carries meaningKeep resistance where the resistance is the information; friction that tells every caller the same sentence is a toll, and a toll is removed. Human in the loopAn agent proposes and does bounded work; a person decides at named points, each explicit, reasoned and recorded. Human-first is the AI integrationNothing is designed for an agent first; an interface legible to a person is legible to anything. Inform people, contain the engineGuardrails live in the engine (the sandbox and the cache), not in a schema that predicts you; magus is strict about what it tells a person and permissive about what it lets them do. Manual on purposeAutomate a repetition, never a rep; each act that forms judgment stays a person's keystroke. Measured, not assertedA claim that something is better, or that a rule holds, needs an artifact someone else can check; a measurement that kills an idea is kept. No generated code in the build pathScaffolding hands you a file and leaves; a generator that must run for the tool to work never leaves, so magus has none. No news is good newsA passing run says almost nothing; output is spent on what failed, what changed and what to do next, because every line costs a reader's attention and an agent's context. No silent defaultsA default that changes what happens without saying so is a bug; misconfiguration is an error, never a warning. One source, every doorA capability lives once, in the layer every caller reaches; the CLI, a magusfile, a script and the MCP tools are doors onto it, never copies of it. Optimize the loop that verifies, never the loop that generatesEvery mechanism makes knowing and trusting a change cheaper; nothing in magus exists to make producing code faster. Provider I/O is BuzzA CI or VCS provider is reached only by a Buzz op that names the act; Go opens no provider socket of its own. ScopeThe claim magus is built on: that a correct incremental build already requires a precise model of your repo, and everything else is a read of it. Includes the test for what belongs, the boundaries, and where the claim is strained. Sit next to the tools, never in front of themA build tool runs other tools; it stays thin enough that you can always see which command ran and reach the tool directly. The Go proverbs, beyond GoRob Pike's Go proverbs hold in every language here; where one has an enforcement point the page names it, and where it has none that is a debt. The host wiring is yoursmagus owns the guard rules and the verdict; the part that knows your agent host is a template you copy and edit. The loop keeps you able to noticeWhat reaches a person is the deviation, the batch and the absence, never a confirmation of a pattern they already trust. The orchestrator plans, workers work, the integrator landsDelegated work has three roles; the orchestrator plans and coordinates, workers read, edit and check, and the integrator builds, regenerates and commits. The outer harness stays outsidemagus judges and informs, and never transforms what reaches the model; the host owns the loop. The standardWendell Berry's nine standards for a new tool, held against magus in both directions. Told, never guessedmagus never sniffs where it runs to change what it does; a caller that needs different behavior asks for it. Unix survives at the verb, not the binaryEach verb answers one question, deterministically, from declared sources, and stops; the binary is as big as the monorepo problem. Verdicts are provenance-blind; disposition is notNo gate conditions on who or what wrote a change; accepting, sending and landing one carries a true name. What we do not build is the productWhen anyone can generate any feature, the tool is defined by what it refuses; the least code is the most secure code, and some capabilities must not be possible at all. Where this is strainedWhere the principles cost more than they claim, and the rules that live only in prose so far. Worth cloningAssume magus can be reproduced; build what is better when copied, and publish the judgment a clone cannot recover.