`GET /bgp/peers/{peerID}/impact-summary`

Lightweight blast-radius summary for a single BGP peer — a fast, static RIB re-run of the RFC 4271 decision process answering "what breaks if this peering session is lost". No Monte Carlo, no SPF (target response time < 50 ms). Backs the peer-detail impact widget.

Auth: all authenticated roles

Path params:

Param	Type	Required	Description
`peerID`	UUID	Yes	The BGP peer whose failure impact to assess

Query params:

at (string, RFC 3339, optional) — Assess the blast radius as-of-T against the full-RIB history instead of live data. Requires a BMP target recording history_mode="full" covering the peer's AS at T; if none exists, the response is a 200 with all counts 0 and a notice. If the peer had no recorded session at T, likewise 200 + notice.

Response: 200 OK

{
  "prefix_count": 150000,
  "surviving_peer_count": 6,
  "unreachable_count": 12
}

prefix_count — total prefixes whose current best path is via this peer (the blast radius being assessed).
surviving_peer_count — number of distinct alternate peers that would absorb the shifted prefixes (one per best-path transition group after re-running selection without this peer).
unreachable_count — of those prefixes, how many have no alternate path and would become unreachable.
notice (string, optional) — Present only in historical mode when the assessment could not run (no full-RIB history at T, or no session at T).

Errors: 404 if the peer is not found (live mode only); 500 on store error.