# U2 acquisition evidence

2026-10-01. Deterministic package RED before implementation: `SamplingStatistics` had no member `calculate`; complete output `/tmp/rideform-u2-red.log`. GREEN after implementation: three focused tests, zero failures, `/tmp/rideform-u2-green.log`.

Command: `DEVELOPER_DIR=/Applications/Xcode-beta.app/Contents/Developer swift test --package-path Packages/RideFormCore --scratch-path /tmp/rideform-u2-build --disable-sandbox --filter SamplingStatisticsTests`.

Fixtures cover eleven samples/100 Hz, empty/single data, duplicate/backward order, positive interval population SD, nearest-rank p95/p99, gap count/percentage/estimated missing intervals, and delayed delivery ages requiring validated mapping. Sensor timestamps/order remain unchanged.

App tests are supplied for coordinator-authoritative simulator execution: clock validation failure/reset; independent fused/raw timestamps written to a JSON artifact and reloaded with stop count/sequence reconciliation; noncommuting quaternion/matrix and gravity fixtures select both identity/conjugate; identity remains unverified. Simulator fixtures are not hardware evidence. Artifact path is generated in temporary directory per test.

API sources retrieved read-only: Apple timestamp JSON `/tmp/u2-apple-timestamp.json`, manager JSON `/tmp/u2-apple-manager.json`; installed SDK CMLogItem.h explicitly says Mach absolute validity time and CMDeviceMotion.h declares headingAccuracy iOS 27. URLs and decisions in `docs/sensor-api-decisions.md` and verification matrix.

Pending: coordinator app build/tests, full portable suite, real iPhone sustained clock validation/interruption, combined-versus-fused matched trials and exported independent statistics calculations. Physical mounting/sign checks and garage transitions remain human gates.