List bulk AP migrations

Detected bulk migrations between Access Points, largest first. A cohort is a gap-≤3-day island of (from_provider, to_provider) mover days that clears three thresholds: at least 25 participants, at least 40 % of them on the busiest day (which rejects a steady drip), and at most 20 active days for the pair over the trailing 40 days (which rejects a recurring partnership).

Every day is the PROBE-OBSERVATION day — the day the change scan saw the SMP record change, not the day the migration was executed — so a cohort is always a [first_day, last_day] range and peak_day is the busiest observation day. Render the range, never a single date.

top_country is derived from the ICD prefix of the participant identifiers, not from business-card country fields. merge_suspect marks a cohort large enough (or whose source provider no longer resolves in the directory) to be a provider merge or a renamed provider rather than that many independent customer decisions — the canonical case is Sovos → Sage, 10,574 participants. Such rows are data events, not customer decisions; verify one before quoting it. The flag is a CURRENT judgment, re-evaluated on every recompute, not frozen at detection.

PLATFORM MOVES. A mover is a platform move when the platform that serves the participant stayed and only the certificate Seat changed: it is not a customer decision. The verdict is per DIRECTED provider pair (from → to), over all its movers since 2026-08-02, with one of two reasons (same_host, sub_provider): at least 90% of the movers whose endpoint host can be compared (5 or more, and at least 50% of all movers of the pair) kept their endpoint host, or at least 90% of 25 or more movers still carry, at the new provider, the sub-provider brand of the provider they left. It is a CURRENT judgment, computed again on every rollup cycle. A cohort of such a pair has platform_move: true. It stays in the list. A Vendor's cohorts (provider=v-<slug>) are not changed and have no platform_move.

from/to are OVERLAP bounds (a cohort counts when its range intersects the window), defaulting to the trailing 90 days the detector re-clusters. Mover history begins 2026-07-24, so no cohort predates it. id is a request-lifetime handle for the participant drill-down — never persist one.