Queue concurrency assessment

Score each gate 0 missing/incorrect, 1 partial or prompted, 2 independently correct with inspectable evidence, 3 fresh-case transfer with limitations. Every gate must reach 2; strong scores cannot compensate for missing evidence.

• CQ1 — Protected state: state the capacity invariant, both wait predicates and the lock protecting queue contents and closure. Explain why notification is not item ownership.
• CQ2 — Close contract: trace accepted versus rejected puts, draining, idempotent close and waking all waiters. Identify linearization points.
• CQ3 — Implementation: own starter passes supplied checks and an independent shutdown case; explain loops and exception outcomes without reading the reference.
• CQ4 — Controlled faults: reject an if-instead-of-while or missing-close-notification fault with a reproducible reached state and repair; classify safety versus progress failure.
• CQ5 — Evidence limits: explain the six lost-update schedules, distinguish sequential histories from concurrent tests, and reject claims of fairness, proof of race freedom or exactly-once external processing.
• CQ6 — Retained transfer: after 48 hours, solve a new producer/close race and connect queue shutdown to a future network-service worker pool, including producer coordination and consumer joining.

Budget 6–8 hours including delayed repair; elapsed waiting is not study time. Record initial score, evidence, feedback, fresh repair case and final score. Failed gates remain incomplete. Automated tests cannot establish independence. Consult calibration after attempting the work; all original module requirements remain required.

Required native parallel-work clinic

Complete Partition, reduce and measure, including PC1–PC4 at level 2. It adds 18–26 hours; this module totals 98–141 hours. Preserve queue-close CQ1–CQ6 and all original concurrency work.