Capstone

The capstone: one real feature, verify-first

Goal: complete one real feature with an agent under a verify-first discipline -- a specified prompt, tests as the tripwire, reviewed diffs, and a written record of what was trusted versus verified -- landing a change fully understood by the human who accepted it, not just the agent that generated it.

Concepts exercised: a specified prompt with constraints and acceptance criteria (co-05); a tests-as-tripwire verification loop (co-13, co-14); a trust/verify decision log (co-17, co-24); context management (co-04); catching and rejecting a wrong generation (co-15, co-16); small reversible steps (co-12).

The feature itself is parse_duration(s: str) -> int -- a small, real, testable utility that converts a compact duration string ("1h30m") into a total whole-second count. It is deliberately small: the point of this capstone is not the feature's complexity, it is that every single change along the way -- including one genuinely wrong generation -- was run and reviewed before anything built on top of it.

• Step 1 -- The prompt: the goal, constraints, one example, seven acceptance criteria, and the failing tripwire test, captured failing before any implementation existed.
• Step 2 -- The session: three small, independently revertible steps -- a first generation that is confidently, plausibly wrong; its rejection with a specific reason; the one-line fix; and a small behavior-preserving refactor -- every step run against the real test suite, never accepted on inspection alone.
• Step 3 -- The trust/verify log: every change in the session mapped to an explicit trust-or-verify decision with a stated rationale, plus the final acceptance-criteria checklist.

Acceptance criteria: the feature passes its tests; every accepted change was verified before being built on; the log justifies each trust/verify call; no unreviewed agent output reached the final diff.

Done bar: runnable end-to-end -- python3 -m pytest test_parse_duration.py -q against learning/capstone/code/ reproduces the final 7 passed transcript -- and web-verified per this topic's syllabus Accuracy notes.

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