Accumulated dead weight — old files, unused functions, settings nobody remembers setting. Not broken, just there.

An inelegant fix that works. Pronounced klooj. Implies the author knew it was ugly and shipped it anyway.

Two opposite meanings. A hack = an ugly shortcut. A nice hack = an elegant, clever solution. Tone and article decide which.

Only the ugly sense. Works, but by a route nobody would choose twice.

Unreliable, poorly made, liable to behave oddly. Broader than code — a janky UI, a janky build.

Complex in an unpleasant way. Many interacting parts, no clean seam to cut along.

A surface signal that something deeper is wrong. Not a bug — a shape that usually indicates one is coming.

Works now, breaks at the smallest change. The opposite of robust.

Control flow so tangled you can't trace what runs when.

Code you must write but that carries no decision — the same twenty lines every project needs. Neutral, occasionally a complaint about the tool.

Behaviour that happens without visible cause. "Too much magic" means you can't see why it works, so you can't fix it when it doesn't.

A feature that makes it easy to injure yourself. Not a bug — a design that invites misuse.

The parts of a tool that cut you if handled wrong. Softer than footgun; often said affectionately about a tool worth the risk.

Code that stops working though nobody touched it — the world around it moved. A dependency updated, an API changed, a certificate expired.

An elaborate mechanism for a simple job. British and Danish equivalent: a Heath Robinson contraption.

Shipping something expedient now and paying interest on it later, in slower changes and more bugs. The metaphor's power is that the debt is sometimes worth taking.

Change the structure without changing the behaviour. If behaviour changed, it wasn't a refactor — a distinction people are strict about.

Adding polish and capability nobody asked for, usually because it was more interesting than the actual task.

"You Aren't Gonna Need It." Don't build for the requirement you're anticipating; build for the one you have.

"Don't Repeat Yourself." Each piece of knowledge should live in exactly one place. The joke inverse is WET — "Write Everything Twice."

"Keep It Simple, Stupid." Simplicity as a design constraint, not an aesthetic preference.

Making code fast before you know what's slow. Cited constantly, usually as a stop sign.

Copying the form of something that works without understanding the mechanism, and expecting the result to follow.

Don't remove something until you understand why it was put there. The most useful single phrase for directing an AI that wants to tidy your codebase.

Building from nothing versus building into something that already exists and has commitments. Brownfield is harder and is the normal case.

Written the way that language's community writes it. Working code can be unidiomatic; it reads as translated from another language.

Achieves the result with less machinery than you expected. The highest ordinary compliment.

Release to real users. Ship it as an exclamation means "good enough, stop polishing."

Work in progress. Marking something WIP signals "look, but don't judge it as finished."

Minimum viable product — the smallest thing that tests whether the idea works. Widely abused to mean "the version we cut corners on."

A short throwaway build done purely to answer a question — is this possible, how hard is it. The output is knowledge, not code.

Proof of concept. Demonstrates feasibility. Not built to survive contact with users, and shouldn't be promoted into production — though it constantly is.

Generated starting structure — folders, config, empty functions. Support for building, not the building.

A placeholder function that returns something plausible so the rest can be built and tested around it.

A fake stand-in for a real dependency during testing — a pretend database, a pretend API. Lets you test your code without calling anything expensive or slow.

The route through your code where everything is as expected. Most AI-generated code handles the happy path well and the rest thinly — which is where you should look first.

An input at the boundary of what you planned for — empty file, zero rows, a name with an apostrophe, a date in February.

Two or more edge conditions at once. Strictly distinct from edge case, though used interchangeably by most people.

The task quietly growing while you work on it. The dominant failure mode when directing an agent that is eager to help.

The minimum to be taken seriously at all. Not a differentiator — the price of entry.

Take the 80% of the value available for 20% of the effort and stop.

How much breaks if this change is wrong. The single most useful question to ask before letting an agent execute anything.

The three environments. Local is your machine, staging is a rehearsal copy, prod is where real users are. "Don't test in prod" is the joke and the rule.

Releasing to a small slice of traffic first and watching before going wider.

A switch that turns new behaviour on or off without redeploying. Lets you ship code dark and enable it later — or kill it instantly.

Return to the previous working state. Revert usually means undoing a specific change in version control; rollback means returning a whole deployment.

An urgent fix applied straight to production, skipping the usual process. Always a decision with a cost.

A fix that stops the symptom without touching the cause. Sometimes correct — at 3am it's usually correct — but it's understood as deferred work.

Using your own product in real work before asking anyone else to. Your learning plan is structured around this.

Running it twice has the same effect as running it once. Critical for anything scheduled or retried — the difference between a safe automation and one that sends four copies of the same email.

To get a change merged into the main branch. "It landed yesterday."

Defer deliberately. Punt carries a slight sense of giving up on solving it properly; park is neutral.

Pull request — a proposed set of changes, offered for review before merging. MR (merge request) is the same thing on GitLab.

The set of lines added and removed. "Reading the diff" is the core evaluation act — and the one you're building toward.

"Looks good to me." Approval. LGTM with nits means approved, fix the small things at your discretion.

A prefix marking a comment as trivial and non-blocking — spelling, naming, formatting. Prefixing it is a courtesy: it tells the author they may ignore you.

Whether your comment must be resolved before merge. Saying which you mean is the whole etiquette of review.

"Please take another look" — sent after addressing review comments.

"Sounds good to me." Agreement with a plan, as opposed to LGTM's agreement with code.

Approving without actually reading. The named failure mode of AI-assisted development — and the exact thing your evaluation threshold exists to prevent.

A quick unsolicited comment or fix from someone not otherwise involved. Can be generous or irritating depending on delivery.

Handing work to the next person without the context they need to carry it.

Explaining your problem aloud to something that can't help — traditionally a rubber duck on the desk — and finding the answer in the act of explaining.

Spending disproportionate time on the trivial part, because it's the part everyone feels qualified to have a view on.

The chain of unrelated prerequisite tasks standing between you and the thing you sat down to do. You wanted to fix one line; six hours later you're updating a package manager.

How many people would have to be hit by a bus before the project stops. A bus factor of one is a warning, and describes most solo-built internal tools.

Something preventing progress that you can't resolve alone. Naming blockers is the entire point of a standup.

A short daily status meeting, historically held standing so it stays short.

Written proposals circulated before building. RFC = request for comments; ADR = architecture decision record, which captures what was decided and why, so future readers don't remove the fence.

Two people, one piece of work, in real time. What you're doing with an agent is structurally closer to pairing than to delegation.

Two meanings. Bump a thread = nudge for a response. Bump a version = increase a dependency's version number.

Stop discussing this here; two of us will resolve it separately. Corporate rather than technical, but constant in engineering meetings.

A defect. The general term for anything the code does that it shouldn't.

The system does the wrong thing and reports nothing. No crash, no error, no failed test. Retrieval returns the wrong documents and the answer reads perfectly. This is the failure class that behaviour-based checking cannot catch, and the reason evaluation sets exist.

Something that used to work and now doesn't. Distinct from a new bug: it means a change broke existing behaviour.

A test that passes and fails on identical input. Usually timing or ordering. Corrosive, because it trains people to ignore failures.

A bug that disappears when you try to observe it — the act of adding logging changes the timing enough to hide it.

Two things happen concurrently and the result depends on which finishes first. Intermittent by nature, and the usual cause of flakiness.

Two processes each waiting for the other to release something. Neither moves. Nothing errors — it just stops.

Counting from the wrong end, or one too many or few. Ubiquitous enough to be a joke: "the two hardest problems in computing are cache invalidation, naming things, and off-by-one errors."

A behaviour that is technically documented but surprising, and catches everyone once.

Short for reproduce. Repro steps = the exact sequence that triggers the bug. "I can't repro" means it doesn't happen for them.

Minimal reproducible example — the smallest piece of code that still shows the problem. Producing one usually reveals the cause before anyone else reads it.

Said ironically. Means the environments differ and nobody has established how. The reason containers exist.

The chain of calls that led to an error. Read it bottom-up: the last lines say what broke and where.

Informal for crashed. Choked on names the input: "it choked on the empty rows."

Working hard, making no progress — a machine swapping memory endlessly, or a person changing approach every ten minutes.

Lost in detail, no longer tracking the goal.

An investigation that keeps going deeper and stops being worth it. Distinct from yak shaving: yak shaving is necessary prerequisites, a rabbit hole is curiosity.

Something broken in production, with a severity level. Sev 1 is the whole thing is down.

Written analysis after an incident. Blameless postmortem is the norm: the discipline of asking what made the mistake likely rather than who made it.

Digging past the proximate failure to the condition that allowed it. Contested: the premise that complex failures have a single root cause is disputed in modern resilience engineering.

Being the person a system wakes at 3am. "I got paged" — from the pagers this was done with.

Whether you can tell what a running system is doing from the outside. Logs, metrics, traces. The discipline that replaces reading code when reading stops scaling.

Building by describing what you want and accepting the output without reading it. Originally descriptive and slightly self-mocking; now used both as a badge and as an accusation.

A system that decides its own next step and acts, rather than answering and stopping. The word carries a lot of marketing weight and often means only "it calls tools in a loop."

Got it right on the first attempt without correction. "Claude one-shotted it." Distinct from the older technical sense of one-shot / few-shot prompting, which means how many examples you gave it.

Running an agent with approval prompts disabled, letting it execute without asking. Named accurately.

Read-only operation — the agent inspects and proposes but writes nothing. Your Phase 1 rule.

A separate agent instance with its own isolated context, given one job by a parent agent. Isolation is the point: a fresh reviewer catches what the author's context biases it against.

A person approves before an action takes effect. Often abbreviated HITL. Worth noting: it describes an architecture, not a guarantee — a human who approves without reading has removed themselves from the loop while remaining in the diagram.

Constraints preventing an agent doing certain things. Usefully concrete when it means permissions and allowlists; near-meaningless when it means "we told it not to."

Standing instructions given to a model before any user message. For an advisory tool, this is where the actual product design lives.

Fluent, confident, wrong. The term is contested: researchers have argued confabulation is more accurate, since hallucination implies false perception rather than false generation. It stuck anyway.

Low-quality AI-generated output produced at volume — text, code, images. Coined as a deliberate parallel to spam.

A long session degrading as the context window fills with stale, contradictory or irrelevant material. The practical argument for starting fresh sessions per task.

How much text a model can hold at once. Everything outside it does not exist to the model, no matter how important it was ten minutes ago.

Instructions hidden in content the model reads — a web page, a document, an email — that the model then treats as commands. The core unsolved security problem for agents with tool access.

Getting a model to ignore its own constraints. Distinct from prompt injection: jailbreaking is done by the user, injection is done to the user.

Consuming context or spend on work that produced nothing. The cost side of running fleets of agents.

A model agreeing with the user rather than being accurate. A measured, named failure mode — and the specific risk in any reflective or advisory tool built on one.

Optimising a model to score on published benchmarks rather than to be useful. The accusation levelled whenever benchmark gains outpace felt improvement.

A fixed set of inputs with known-good answers, run against the system to score it. Evals are to probabilistic systems what tests are to deterministic ones — and they are the thing that replaces reading every line.

The known-correct answer you score against. Assembling it is manual, unglamorous, and the part everyone skips.

The curated collection of cases you always run before shipping a change. Small, hand-checked, stable.

Retrieval-augmented generation — fetch relevant documents first, then answer from them. A retrieval strategy that appears to the model as a callable tool, not an architecture requirement.

Splitting source documents into pieces small enough to retrieve and fit in context. Where you cut determines what can ever be found.

A list of numbers representing a piece of text's meaning, so that similar meanings sit near each other and can be found by proximity rather than by keyword.

Two ways to be wrong. Recall: did you find everything relevant. Precision: was everything you found relevant. Improving one usually costs the other.

How much randomness in the model's choices. Lower is more predictable, higher more varied. Not a creativity dial, though it's described as one.

Model Context Protocol — a standard for wiring external tools to a model. A connection convention, not a runtime component of an agent.

"Too long; didn't read." Introduces a one-line summary, usually written by the same author who wrote the long version.

"If I recall correctly." Signals the claim is from memory and unverified.

"As far as I know" / "as far as I can tell." The second is stronger — it implies they looked.

"In my opinion" / "in my humble opinion." The H is usually ironic.

"For what it's worth." Offers something without insisting on it.

"Your mileage may vary." This worked for me and may not for you.

"It seems to me." Softer than IMO.

"Without loss of generality." Borrowed from mathematics; means the simplification doesn't weaken the argument.

"Read the manual" — with an expletive in the middle. Hostile. Its existence tells you something about the culture it came from.

"Explain like I'm five." A request for the version without jargon. Not an admission of incompetence — used freely by senior people crossing into an unfamiliar domain.

"Today I learned." Prefaces something the writer just found out, usually with mild embarrassment that they didn't know it.

"In case you missed it."

Agreement or objection, without adding argument. In some processes -1 is a formal veto.

"Single source of truth" — the one place a fact lives, so it can't disagree with itself.

Placeholder names in examples, meaning nothing. If you see foo in code, it's illustrative and not real.

Used as a verb: "we bikeshedded the button colour for an hour."