The Rung Contract

Last week I argued that cutting juniors solves this quarter’s demand at the price of a senior famine three years out , and named the work the new apprenticeship should teach. Several readers agreed and asked the fair question: structured how? Every company already has a competency matrix, and competency matrices demonstrably don’t produce seniors. So before the what, the form.

A competency matrix describes skills: “demonstrates growing judgment in reviews.” Nobody can act on it, because it grants nothing and nothing tests it. What apprenticeship actually runs on is a contract per rung, four clauses, written where the team can read them. Permission: the real work this person may now do, with its boundaries. Supervised, dual-controlled, rollback-limited, but real. Evidence: the artifacts that show they’re doing it well, countable ones. Reviewer: the named person whose corrections they receive, because feedback with no owner is noise. Promotion rule: a decision rule specific enough that two managers reading the same record would make the same call. Miss any clause and you don’t have a rung, you have a vibe, and vibes are what apprenticeship consisted of when juniors learned by osmosis from work that no longer exists.

Here’s the contract I’d write for the first rung, in full, because the format is the point. Permission: first-pass review of agent-generated changes, verdict delivered as a written rejection or approval with reasons; no merge authority. Evidence: the rejection log, and a miss rate, meaning defects the apprentice approved that their reviewer caught, measured over a sample. Reviewer: a named senior who re-reviews a fixed sample, weighted toward approvals, because the dangerous failure here is the miss, not the false alarm. Promotion rule, concretely: thirty sampled reviews across six weeks, zero critical misses, noncritical miss rate under an agreed bar, sign-off from two seniors rather than one. Numbers your org would tune. But numbers, or the rung isn’t checkable.

How can juniors catch defects in code they’ve never been able to write? Alone, they can’t, which is why rung one has an entry gate as well as an exit gate. Before their verdicts count, the apprentice calibrates on seeded cases: changes with known defects, where the job is to find the flaw, reproduce it with a failing test, and propose the repair, shadowing a senior’s real reviews until their recall on the seeded set clears a threshold. Review-first learning works only when someone builds the reviewer’s mental model deliberately; the seeded set is that construction. It also answers whether this rung reduces senior load. Initially it doesn’t, since sampled re-review plus teaching costs more senior minutes than it saves. That’s an investment with a measurable payback: track senior review-minutes per merged change and escaped defects, and expect the crossover in months, not weeks. The review queue can afford it ; the bench can’t afford its absence.

The later rungs get the same four-clause treatment, and their order can flex by job family. Owned failure: one production failure mode end to end (alert, runbook, rotation, postmortem) under dual control until an incident shows the senior was informed rather than needed. Defended decisions: real design calls, written with alternatives and costs, scored when made, with assumptions explicit, rollback stated, escalation named, and production outcomes used as later calibration rather than the gate, because outcomes carry luck in both directions. Authored verification: the eval set and drift tripwire for something new, the benchmark only your org can build . Clearing that last contract is the crossing the whole pipeline exists to produce: unsupervised ownership, the numerator in the replacement-rate metric I argued you should track against senior attrition.

And write the failure clause with the same discipline, because a curriculum that can’t fail people honestly fails them dishonestly. An apprentice stalled at a rung gets a diagnosis first (wrong rung order for their role, wrong reviewer, insufficient reps), then a changed assignment and a documented reassessment, before anyone reaches for performance machinery. The contract cuts both ways: it’s how they know exactly what’s asked, and how you know exactly what you owe them. Four clauses, per rung, on one page. Everything else is a vibe.