diff --git a/documentation/audits/SESSION-C-2026-07-29.md b/documentation/audits/SESSION-C-2026-07-29.md
index 39509b2..1464253 100644
--- a/documentation/audits/SESSION-C-2026-07-29.md
+++ b/documentation/audits/SESSION-C-2026-07-29.md
@@ -153,14 +153,23 @@ The drive is represented by **two `/disks` rows**, and the flag and the guest pa
 | the `felhom-backup` storage | Observe path, `felhom-agent/internal/localapi/disks.go:211` (`t.Name == primaryTargetID`) | **true** | set only when role is user-data |
 | the registry drive | union path, `disks.go:265-267` — **never assigns `BackupTarget` at all** | **false** | `/mnt/felhom-drives/mentes` |
 
-While the device is absent the target-flagged row loses the classification that gives it a guest path,
-so `out["/mnt/felhom-drives/mentes"]` is written **false** by the union row and the specific branch is
-skipped. On **return** the rows rejoin and the specific event fires — which is exactly the asymmetry
-observed. v0.184.1 fixed the *keying* (both keys are mapped); it did not fix the flag being absent from
-the row that carries the guest path.
+> **CORRECTION 2026-07-29 (R-116 Phase 0).** This section originally said the union row *"writes
+> `false`"*. **That is wrong**, and the real mechanism is worse — the union row is not written at all.
+>
+> The step left un-isolated above has now been isolated: `RoleForStorage` returns `RoleSystem` whenever
+> `backingDevice == ""` (`felhom-agent/internal/storage/role.go:180-181`). So when the device vanishes,
+> Observe's `exactMountDevice` fails, `t.BackingDevice` becomes `""`, the row's role flips to system and
+> it loses its guest path — **but it keeps its `MountPath`**. The union loop skips any drive whose
+> `MountPath` is already `seen` (`disks.go:263`), so the registry row is **DEDUPED AWAY ENTIRELY**.
+>
+> `/disks` therefore carries **no row with that guest path at all**: `isTarget[guestPath]` is a
+> **missing key**, not a `false` value. The practical difference is decisive — the obvious fix (set
+> `BackupTarget` on the union row) **could not have worked**, because that row is not emitted in the
+> state where the alarm is needed.
 
-*(The precise role-classification step that drops the guest path while absent was not isolated — the
-two-row split and the observed absent/return asymmetry are the evidence.)*
+On **return** the rows rejoin and the specific event fires — which is exactly the asymmetry observed.
+v0.184.1 fixed the *keying* (both keys are mapped); it did not fix the flag being absent from the row
+that carries the guest path.
 
 **Filed as R-116.** Not fixed: a defect found in a validation run is a finding.