The four lenses — read before this ships

Load when: a change of consequence is about to land — a release, a merge into the guide, a new capability, a rewritten rule. Also on request: "run the lenses over this."

Four readings, one question each, in this order, by someone who is not the author. They are the compensating control for every prose-only gate — the reason it is honest to write enforced_by: prose-only at all is that these run.

Why four separate readings instead of one careful one. A reader holding four questions holds none of them. Each lens is cheap because it ignores everything except its own question, and the order matters: deleting first means the later lenses read less.

Why not the author. Not distrust — the author's context is invisible to the author. They cannot see what they assumed, because assuming it is what made the text feel complete.

1 · Deletion — what can go?

Fights: additive drift.

• What breaks if this is simply removed?
• Does it restate a rule that already lives somewhere? (If so, one of the two is the home and the other points.)
• Is a new entity doing work an existing one could do with one more value?
• Is this a pattern already named in ./patterns, being paraphrased instead of cited?

The bar is not "is this good" but "would we notice it gone". A change that survives deletion is the smallest version of itself, and that is the only version worth reviewing further.

2 · Adversarial — how does this fail?

Fights: authors test what they intended.

• The unhappy path. Misuse by someone in a hurry.
• Does a failure fail loudly or quietly? A gate that fails open is worse than no gate, because it is believed.
• What does a half-finished write leave behind?
• What is the cheapest way to comply with the letter and violate the rule?
• Who pays for it — in tokens, in attention, in a wait nobody sees?

3 · Contradiction — does this fight anything?

Fights: local correctness.

Against the corpus, not against taste. Name both sides, with locations.

• Does it promise something nothing delivers — a referenced file that does not exist, a check described but not implemented, a capability no door reaches?
• Does it use a glossary term in a second meaning?
• A reversal is legitimate; an unstated one is not. If this overturns an earlier decision, say so and say why, and the earlier decision gets its revisit note.

4 · Cold-read — understandable by someone who was not here?

Fights: the author's context is invisible to the author.

• Does it explain why, not only what?
• Does it depend on context that exists only in a conversation?
• Would a newcomer act correctly from this text alone — or correctly by accident?
• Is the example still an example of the rule, or did the rule move?

Running them

Each lens is stated, including when it found nothing. "Deletion: nothing found" is a result; silence is indistinguishable from a skipped lens. And a lens that ran out of budget is recorded as not completed, never as empty — those two are identical in the report and opposite in fact, so "deletion: nothing found" written over a lens killed at its third tool call is a false clean. Measured 2026-09-10: three rounds in one session lost twelve lens agents to usage limits, with nowhere to record it but prose. A round carrying a not completed has not reported clean, which is the condition the tag waits on.

A finding names its place and its fix: path, line, the defect in one sentence, and what would resolve it. A finding without a location is an opinion.

Findings are not votes. The lenses report; the owner of the change decides, and a rejected finding is answered, not ignored — one line saying why.

They run on this skill and on the user's project alike. The corpus is not more fragile than the work; the same four questions catch the same four failures in a spec, a role's instructions or a pipeline change.

A finding of the shape "X is not there" is checked in the main repository before it is reported. Measured 2026-08-09: a lens running in an isolated worktree read a tree three commits behind and filed a defect against work that was present and verified three ways. Isolation buys a reader who did not write the text; it does not guarantee a reader who sees the current one. Two of four lenses that day noticed the staleness themselves and diffed against the newest ref — which is the habit, not the exception: check git rev-parse HEAD first, and if a finding is an absence, confirm it where the work actually lives.

The repair a lens causes is unread until the round runs again over it. The first round reads text drafted before the findings existed; the repair is drafted after them, at speed, by the person those findings have just persuaded — the condition every lens exists for. Re-run the round once the repair is committed and before the tag is cut: the range is still <last tag>..HEAD, so it already contains the repair, and no new mechanism is needed — the same four questions, a range that grew. It ends when a round reports clean, and in practice the rounds shrink; a third still finding structure is the release telling you something.

Three occasions, and none of them was a fifth reader: 2026-08-23, four lenses read a range before its tag and the worst thing they found was a regression in the repair itself; 2026-09-05, three of four adversarial findings were false refusals the repair had introduced; 2026-09-07, a re-run over the repair found a stopping condition that pointed at a range excluding what it deferred, a half-question unanswerable from the input its own text called sufficient, and a wrong occasion cited for the ladder that promoted it.

Give the second round the findings the first one raised where they survive, because did the repair do what the finding asked cannot be read off a diff. Nothing retains them — a lens reports into a notification, not into a record anything reads back — so when they are gone the round answers the half that can be read and says which half it could not.

Do not tag between the rounds. Cutting the tag first is what puts a repair outside the next range: it becomes an ancestor of the tag, and <last tag>..HEAD excludes it by construction. Measured 2026-09-07 on this repository's own history.

What it costs is one more round per release, and nothing here has measured that. The adversarial lens's own fourth question is who pays for it — in tokens, in attention, in a wait nobody sees — and this rule does not answer it. No form holds it: nothing counts rounds, so a skipped one and a stated-empty one are the same artifact. LATER.md carries the candidate.

Temporary readers. When they run as agents, they are created for the release and archived after — they read, they do not own. Archiving them is part of finishing the release (./patterns → promote what outgrew itself does not apply here: a lens never grows into a role).

What the lenses do not cover

They read text. They do not run the code, walk the links, or measure a number — those are ./checking and the eval suite. Four green lenses over a claim that was never true is exactly the failure mode the corpus names: a statement that parsed perfectly, linked correctly, and was false. The six reading rules in AGENTS.md are the chapter habit for that, and the eval pass-rate is the measurement.