Phase 16: dataset semantics verified (2451-device fleet, end_time = admin snapshot; no model change)

EXPERIMENTS.md

@@ -512,6 +512,30 @@ for that objective. detect_swaps() and the GHOST_ZERO/QUARANTINE knobs remain
 in the code, inert by default, with the production table and runtime paths
 unchanged. Champion unchanged: panel 1679.2, all-48 Docker 2146.9.
 
+## Phase 16 - dataset semantics (two community observations verified; no model change needed)
+
+**Categorical metadata leak**: the train parquets' device_id dtype carries
+**2,451 categories** while train uses 461 - the held-out fleets total ~1,990
+devices (~4.3x train). Implications: (a) per-split adaptive refits are the
+right architecture (each split has its own large fleet); (b) worker limits
+(fixed 100/day) bind much harder at 4x fleet size - the public leader's
+daily_limit penalties (108/scenario) are rational there; our optimize_days
+prices limits exactly, but local CV never exercises limit-saturated regimes.
+
+**end_time semantics**: locations.end_time is the ADMIN snapshot end, not
+per-device last data - 445/461 devices share 2026-08-01. All 82 dead slots
+keep reporting past EOL (mean 107d, max 305d): replacement batteries under
+the same device_id, invisible to scoring. Verified harmless everywhere:
+master_curve filters tau >= 0 (replacement data never enters), dead devices
+are excluded from planning, and the 15 admin-removed unscoreable devices
+(early end_time, no EOL; e.g. 11 removed 2025-12-26) are scored p42 ~ 0.01
+by the model - the "stale + frozen voltage -> survives" pattern learned from
+exactly these rows (phase 15's load-bearing negatives) keeps them out of
+every plan. The e_far imputation pricing in cost_curves makes them
+prohibitively expensive to the break-even top-up as well (two-sided fix,
+phase 11). Example decoded: d_57e99ff00802 - EOL 2026-02-02 (scored death),
+replacement battery reports until 2026-05-13, admin end_time 2026-08-01.
+
 ## Test-look ledger
 
 8 looks total (now historical - see protocol change above); look 9 = the