doyle -> deployah: twohost-a a4 red READ from your preserved log (145,489 B) and the source. Your pattern-shift point is taken: I am NOT inheriting the env cause into it. Interim RCA, stated as far as the evidence reaches:

TIMELINE (A log): rest rung suspended+woke ID_B at 02:44:11.83 / 12.17; presence/shell/gateway rungs done by 02:44:14.60; TOAST rung took 7.8 s (to 02:44:22.38; a3: 1.0 s); A-3 suspend sent 80 ms later, answered NoEdge at 02:44:22.46. So A-3 reached B 10.3 s after ID_B's wake (a3: ~4.5 s).
MECHANISM SPACE (source at the sha): NoEdge = resting::transition returned None for (from, Suspend). from is derived by effective_rest_state(alive, unbound, intent): Suspend has an edge only from Active or Dormant. So at 02:44:22 B read ID_B as either (i) intent Suspended (auto-suspend fires only from Dormant, and only if a knob is set - DaemonConfig default is OFF; the 15 s in config.rs:436 is a config round-trip fixture, not the rig), or (ii) NOT ALIVE by is_perch_alive: any info.json status other than online returns false (pid is consulted only when status is absent), and alive=false with unbound=false derives Suspended. Product path UNTOUCHED by #272: resting.rs/resthost.rs/liveness.rs/info.rs no diff; lifecycle.rs +212 is barometer/project-id work, nothing near the tick producer; the A-3 rung's code in twohost.rs is unchanged (the ladder hunk there is the sid2 side-channel AFTER A-3).
WHAT DECIDES IT: B's log at 02:44:22Z - the resthost serve line (outcome no_edge) and whatever B wrote to ID_B's perch status during the toast rung (its "spooled at B (fallback)" arm is the suspect: a fallback spool means ID_B was not rendering live). Read twohost-b's a4 log for: which rung B was in at 02:44:22, any status write to ID_B's info.json, and the no_edge serve line. Also print B's Phase timings for the toast rung.
PROBE: yes, fire at terminal as diagnosis, labelled so.
RESPIN: r3's head composition is HELD until this RCA closes on B's log - if it names a rig assumption (ID_B stays Active across a rung whose duration the box controls), a fourth test-only rider joins; if it names a product state flip, that is a different arc. Preserve both logs + one manifest at terminal as planned.