diff --git a/FABRIC.md b/FABRIC.md
index a043d6f..e72b59f 100644
--- a/FABRIC.md
+++ b/FABRIC.md
@@ -1535,8 +1535,33 @@ settle that.
 
 **Chosen: one global array of cells, one global index space.** Nesting becomes a
 *partition* of that index set rather than separate allocations. A VM's quota is a **count,
-not a contiguous range**, so cells are drawn from a shared free list, there is no adjacency
-requirement, no fragmentation, and index links keep working because indices are global.
+not a contiguous range**, so there is no adjacency requirement, no fragmentation, and index
+links keep working because indices are global.
+
+#### Free lists are per-VM, not shared
+
+An earlier draft of this section said cells are drawn from a **shared free list**. That was
+wrong, and it quietly undercut the argument that decided §21.
+
+§21.3's decisive discriminator is the SMP row: *messages are the only boundary-crossers, so
+no shared memory and still no locks.* A shared free list is shared mutable state, touched by
+every VM on every admission and every reap. Under SMP it would need a lock or atomics —
+exactly what that row claims nesting avoids permanently. The defence offered there, that
+"VMs never touch each other's cells," does not reach it: **the free list is nobody's cell,
+and allocation touches it.**
+
+The fix costs essentially nothing:
+
+> **Each VM holds its own free-list head index into the global array.** Hera hands a VM its
+> cells when she grants quota; the VM allocates and frees only within what it holds.
+
+One head index per VM instead of one global head. One index space is preserved, one datatype
+is preserved, §13 is unaffected — and disjointness becomes **total** rather than nearly
+total. No mutable structure is shared between VMs at all, which is what §21.3 actually
+promised.
+
+Transfer of capacity is then Hera moving cells from one VM's free list to another's, which
+is still arithmetic plus a list splice, and still arbitrated at a known point (§22.5 #2).
 
 Two reasons this is the right trade: