---
name: spt-mantle-is-engine-room-anchor
description: "SPT_MANTLE subnet = the anchor point for SPT nodes' engine rooms (operator, 2026-08-05); closed mode; not an R&D surface"
metadata: 
  node_type: memory
  type: project
  originSessionId: 216e10e1-fcfa-4d44-92a0-bde68cc8696f
  modified: 2026-08-05T21:35:31.601Z
---

**SPT_MANTLE** (operator-stated 2026-08-05): the anchor point for SPT nodes' **engine rooms** —
a closed subnet (3 nodes as of 2026-08-05, roster dynamic like [[spt-rnd-stays-on-spt-dev-nodes]]).
It is fleet plumbing, not an R&D surface: do not target it with instruments, census, or rolls,
and do not treat its membership as the R&D population. Engine-room access posture and the
ER advertisement whitelist (REQ-ER-NOT-ADVERTISED, the DISCOVER conjunction in releases#163)
are the relevant mechanisms when ER visibility questions arise across it.