diff --git a/CHANGELOG.md b/CHANGELOG.md
index d41ef3c..b769a27 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,16 @@ ADR-007 and ADR-002.
 
 ### Added
 
+- Relationship propagation, wired and data-driven: relationship types
+  declare propagation-through pairs (relationshiptypepropagations M:N,
+  replacing the never-consumed single column); creating a controls link on
+  one Dualpath bay auto-creates it on the partner bay, and
+  `flask relationships propagate` backfills existing data.
+- Employee photos, mode-aware: self-hosted directory employees support
+  upload/replace/delete (admin), served publicly for kiosk cards; external
+  directory mode passes the HR-supplied picture URL through read-only. One
+  resolver feeds the shopfloor recognition/recert cards and the employee
+  detail hero in either mode.
 - Vendor-model photo management. New admin-gated core endpoints
   `POST /api/models/<modelid>/image` (multipart `file`, png/jpg/jpeg/gif/webp/svg,
   one image per model, replace semantics) and
@@ -66,6 +76,9 @@ ADR-007 and ADR-002.
 
 ### Fixed
 
+- Following a relationship link between two assets of the same type now loads
+  the destination page instead of stale content (router-view keyed on path;
+  query-only URL changes still avoid a remount).
 - Asset relationships card no longer lists a symmetric peer twice. Relationship
   types gain `relationshiptypes.isdirectional` (migration
   `7d19_relationshiptype_directional`; seeded false for the connection-like
diff --git a/frontend/src/components/AssetRelationships.vue b/frontend/src/components/AssetRelationships.vue
index a8e19c2..9f4a95f 100644
--- a/frontend/src/components/AssetRelationships.vue
+++ b/frontend/src/components/AssetRelationships.vue
@@ -18,30 +18,32 @@
     </div>
 
     <template v-else>
-      <!-- Outgoing relationships (this asset controls/connects to...) -->
-      <div v-if="outgoing.length > 0" class="relationship-group">
-        <h4 class="group-title">Outgoing</h4>
+      <!-- Symmetric connections: one direction-blind entry per peer -->
+      <div v-if="connectedItems.length > 0" class="relationship-group">
+        <h4 class="group-title">Connected</h4>
         <div class="relationship-list">
           <div
-            v-for="rel in outgoing"
-            :key="rel.relationshipid"
+            v-for="item in connectedItems"
+            :key="item.key"
             class="relationship-item"
           >
-            <div class="rel-icon"><component :is="getAssetIcon(rel.targetasset?.assettypename || rel.targetasset?.assettype)" :size="16" /></div>
+            <div class="rel-icon"><component :is="getAssetIcon(item.peer?.assettypename || item.peer?.assettype)" :size="16" /></div>
             <div class="rel-content">
-              <router-link :to="getAssetRoute(rel.targetasset)" class="rel-name">
-                {{ rel.targetasset?.name || rel.targetasset?.assetnumber || 'Unknown' }}
-              </router-link>
-              <div class="rel-meta">
-                <span class="badge" :style="colorStyle(colorForType(rel.relationshiptypename))">{{ rel.relationshiptypename }}</span>
-                <span class="rel-type-badge">{{ rel.targetasset?.assettypename || rel.targetasset?.assettype }}</span>
+              <div class="rel-line">
+                <router-link :to="getAssetRoute(item.peer)" class="rel-name">
+                  {{ item.peer?.name || item.peer?.assetnumber || 'Unknown' }}
+                </router-link>
+                <span class="badge" :style="colorStyle(colorForType(item.relationshiptypename))">{{ item.relationshiptypename }}</span>
               </div>
-              <div v-if="rel.notes" class="rel-notes">{{ rel.notes }}</div>
+              <div class="rel-meta">
+                <span class="rel-type-badge">{{ item.peer?.assettypename || item.peer?.assettype }}</span>
+              </div>
+              <div v-if="item.notes" class="rel-notes">{{ item.notes }}</div>
             </div>
             <button
               v-if="authStore.isAuthenticated"
               class="btn-icon delete"
-              @click="deleteRelationship(rel.relationshipid)"
+              @click="deleteItem(item)"
               title="Remove relationship"
             >
               &times;
@@ -50,30 +52,42 @@
         </div>
       </div>
 
-      <!-- Incoming relationships (...controls/connects to this asset) -->
-      <div v-if="incoming.length > 0" class="relationship-group">
-        <h4 class="group-title">Incoming</h4>
+      <!-- Directional relationships: natural per-row phrasing, no jargon -->
+      <div v-if="directionalItems.length > 0" class="relationship-group">
         <div class="relationship-list">
           <div
-            v-for="rel in incoming"
-            :key="rel.relationshipid"
+            v-for="item in directionalItems"
+            :key="item.key"
             class="relationship-item"
           >
-            <div class="rel-icon"><component :is="getAssetIcon(rel.sourceasset?.assettypename || rel.sourceasset?.assettype)" :size="16" /></div>
+            <div class="rel-icon"><component :is="getAssetIcon(item.peer?.assettypename || item.peer?.assettype)" :size="16" /></div>
             <div class="rel-content">
-              <router-link :to="getAssetRoute(rel.sourceasset)" class="rel-name">
-                {{ rel.sourceasset?.name || rel.sourceasset?.assetnumber || 'Unknown' }}
-              </router-link>
-              <div class="rel-meta">
-                <span class="badge" :style="colorStyle(colorForType(rel.relationshiptypename))">{{ rel.relationshiptypename }}</span>
-                <span class="rel-type-badge">{{ rel.sourceasset?.assettypename || rel.sourceasset?.assettype }}</span>
+              <div class="rel-line">
+                <template v-if="item.direction === 'outgoing'">
+                  <span class="badge" :style="colorStyle(colorForType(item.relationshiptypename))">{{ item.relationshiptypename }}</span>
+                  <span class="rel-arrow">-&gt;</span>
+                  <router-link :to="getAssetRoute(item.peer)" class="rel-name">
+                    {{ item.peer?.name || item.peer?.assetnumber || 'Unknown' }}
+                  </router-link>
+                </template>
+                <template v-else>
+                  <span class="rel-arrow">&lt;-</span>
+                  <span class="badge" :style="colorStyle(colorForType(item.relationshiptypename))">{{ item.relationshiptypename }}</span>
+                  <span class="rel-from">from</span>
+                  <router-link :to="getAssetRoute(item.peer)" class="rel-name">
+                    {{ item.peer?.name || item.peer?.assetnumber || 'Unknown' }}
+                  </router-link>
+                </template>
               </div>
-              <div v-if="rel.notes" class="rel-notes">{{ rel.notes }}</div>
+              <div class="rel-meta">
+                <span class="rel-type-badge">{{ item.peer?.assettypename || item.peer?.assettype }}</span>
+              </div>
+              <div v-if="item.notes" class="rel-notes">{{ item.notes }}</div>
             </div>
             <button
               v-if="authStore.isAuthenticated"
               class="btn-icon delete"
-              @click="deleteRelationship(rel.relationshipid)"
+              @click="deleteItem(item)"
               title="Remove relationship"
             >
               &times;
@@ -225,6 +239,71 @@ let searchTimeout = null
 
 const hasRelationships = computed(() => outgoing.value.length > 0 || incoming.value.length > 0)
 
+// Symmetric types collapse to one entry per {peer, type} unordered pair. All
+// stored direction rows (both directions, plus any legacy duplicates) fold
+// into one displayed entry; its rowIds carries every collapsed relationshipid
+// so a delete removes them all.
+const connectedItems = computed(() => {
+  const byPair = new Map()
+  const rows = [
+    ...outgoing.value.map(rel => ({ rel, peer: rel.targetasset })),
+    ...incoming.value.map(rel => ({ rel, peer: rel.sourceasset })),
+  ]
+  for (const { rel, peer } of rows) {
+    if (rel.isdirectional !== false) continue
+    const selfid = resolvedAssetId.value
+    const peerid = peer?.assetid
+    const lo = Math.min(selfid, peerid)
+    const hi = Math.max(selfid, peerid)
+    const key = `${rel.relationshiptypeid}:${lo}:${hi}`
+    const existing = byPair.get(key)
+    if (existing) {
+      existing.rowIds.push(rel.relationshipid)
+      if (!existing.notes && rel.notes) existing.notes = rel.notes
+    } else {
+      byPair.set(key, {
+        key,
+        rowIds: [rel.relationshipid],
+        peer,
+        relationshiptypeid: rel.relationshiptypeid,
+        relationshiptypename: rel.relationshiptypename,
+        notes: rel.notes || null,
+      })
+    }
+  }
+  return Array.from(byPair.values())
+})
+
+// Directional types keep one entry per stored row with arrow phrasing.
+const directionalItems = computed(() => {
+  const items = []
+  for (const rel of outgoing.value) {
+    if (rel.isdirectional === false) continue
+    items.push({
+      key: `out-${rel.relationshipid}`,
+      rowIds: [rel.relationshipid],
+      peer: rel.targetasset,
+      direction: 'outgoing',
+      relationshiptypeid: rel.relationshiptypeid,
+      relationshiptypename: rel.relationshiptypename,
+      notes: rel.notes || null,
+    })
+  }
+  for (const rel of incoming.value) {
+    if (rel.isdirectional === false) continue
+    items.push({
+      key: `in-${rel.relationshipid}`,
+      rowIds: [rel.relationshipid],
+      peer: rel.sourceasset,
+      direction: 'incoming',
+      relationshiptypeid: rel.relationshiptypeid,
+      relationshiptypename: rel.relationshiptypename,
+      notes: rel.notes || null,
+    })
+  }
+  return items
+})
+
 const canSave = computed(() => {
   return newRel.value.relationshiptypeid && newRel.value.targetAssetId && resolvedAssetId.value
 })
@@ -356,11 +435,12 @@ async function saveRelationship() {
   }
 }
 
-async function deleteRelationship(relationshipId) {
+// Delete every collapsed direction row behind a displayed entry.
+async function deleteItem(item) {
   if (!confirm('Remove this relationship?')) return
 
   try {
-    await assetsApi.deleteRelationship(relationshipId)
+    await Promise.all(item.rowIds.map(id => assetsApi.deleteRelationship(id)))
     await loadRelationships()
     emit('updated')
   } catch (error) {
@@ -499,6 +579,24 @@ function getAssetRoute(asset) {
   text-decoration: underline;
 }
 
+.rel-line {
+  display: flex;
+  align-items: center;
+  gap: 0.4rem;
+  flex-wrap: wrap;
+}
+
+.rel-arrow {
+  font-family: monospace;
+  font-weight: 600;
+  color: var(--text-light);
+}
+
+.rel-from {
+  font-size: 0.8rem;
+  color: var(--text-light);
+}
+
 .rel-meta {
   display: flex;
   align-items: center;
diff --git a/frontend/src/views/settings/RelationshipTypesList.vue b/frontend/src/views/settings/RelationshipTypesList.vue
index 3615c23..9ed6ef6 100644
--- a/frontend/src/views/settings/RelationshipTypesList.vue
+++ b/frontend/src/views/settings/RelationshipTypesList.vue
@@ -16,6 +16,7 @@
                 <th>Relationship Type</th>
                 <th>Description</th>
                 <th>Color</th>
+                <th>Directional</th>
                 <th>Actions</th>
               </tr>
             </thead>
@@ -24,6 +25,7 @@
                 <td><span class="badge" :style="colorStyle(t.color)">{{ t.relationshiptype }}</span></td>
                 <td class="cell-truncate" :title="t.description">{{ t.description || '-' }}</td>
                 <td><span class="mono">{{ t.color || 'auto' }}</span></td>
+                <td>{{ t.isdirectional === false ? 'connection' : 'yes' }}</td>
                 <td class="actions">
                   <span v-if="t.isactive === false" class="badge badge-secondary" style="margin-right:6px;">inactive</span>
                   <button class="btn btn-secondary btn-sm" @click="openModal(t)">Edit</button>
@@ -31,7 +33,7 @@
                 </td>
               </tr>
               <tr v-if="visibleItems.length === 0">
-                <td colspan="4" style="text-align: center; color: var(--text-light);">No relationship types found</td>
+                <td colspan="5" style="text-align: center; color: var(--text-light);">No relationship types found</td>
               </tr>
             </tbody>
           </table>
@@ -56,6 +58,10 @@
               <label>Color <span class="hint">(relationship badges; blank = auto)</span></label>
               <ColorSwatchPicker v-model="form.color" />
             </div>
+            <div class="form-group">
+              <label class="checkbox-label"><input type="checkbox" v-model="form.isdirectional" /> Directional</label>
+              <span class="hint">off = shown as a plain connection, no direction</span>
+            </div>
             <div class="form-group">
               <label class="checkbox-label"><input type="checkbox" v-model="form.isactive" /> Active</label>
             </div>
@@ -88,7 +94,7 @@ const showModal = ref(false)
 const editing = ref(null)
 const saving = ref(false)
 const error = ref('')
-const form = ref({ relationshiptype: '', description: '', color: '', isactive: true })
+const form = ref({ relationshiptype: '', description: '', color: '', isactive: true, isdirectional: true })
 
 onMounted(loadData)
 
@@ -107,8 +113,8 @@ async function loadData() {
 function openModal(item = null) {
   editing.value = item
   form.value = item
-    ? { relationshiptype: item.relationshiptype || '', description: item.description || '', color: item.color || '', isactive: item.isactive !== false }
-    : { relationshiptype: '', description: '', color: '', isactive: true }
+    ? { relationshiptype: item.relationshiptype || '', description: item.description || '', color: item.color || '', isactive: item.isactive !== false, isdirectional: item.isdirectional !== false }
+    : { relationshiptype: '', description: '', color: '', isactive: true, isdirectional: true }
   error.value = ''
   showModal.value = true
 }
diff --git a/migrations/versions/7d19_relationshiptype_directional.py b/migrations/versions/7d19_relationshiptype_directional.py
new file mode 100644
index 0000000..c3bbd78
--- /dev/null
+++ b/migrations/versions/7d19_relationshiptype_directional.py
@@ -0,0 +1,70 @@
+"""Relationship types get isdirectional; flip symmetric legacy types
+
+Adds relationshiptypes.isdirectional (default true). The asset relationships
+card uses it: directional types keep a source->target reading, symmetric types
+(physical links, network connections) collapse both stored direction rows into
+one direction-blind "connected" entry per peer.
+
+Seeds isdirectional=false for the connection-like types present pre-1.0:
+Dualpath, connectedto, Cluster Member, Serial Cable, Direct Ethernet, USB,
+WiFi. Everything else (controls, Controlled By, Backup For, Master-Slave,
+partof, defaultprinter) stays directional.
+
+Idempotent guards so it is safe on a partially-migrated box.
+
+Revision ID: 7d19_relationshiptype_directional
+Revises: 7d18_supportteamcontacts
+Create Date: 2026-07-11
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '7d19_relationshiptype_directional'
+down_revision = '7d18_supportteamcontacts'
+branch_labels = None
+depends_on = None
+
+
+# names seeded symmetric (isdirectional=false)
+SYMMETRIC_TYPES = [
+    'Dualpath',
+    'connectedto',
+    'Cluster Member',
+    'Serial Cable',
+    'Direct Ethernet',
+    'USB',
+    'WiFi',
+]
+
+
+def _has_column(insp, table, column):
+    return column in [c['name'] for c in insp.get_columns(table)]
+
+
+def upgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+
+    if not _has_column(insp, 'relationshiptypes', 'isdirectional'):
+        op.add_column(
+            'relationshiptypes',
+            sa.Column('isdirectional', sa.Boolean(), nullable=False,
+                      server_default='1'))
+
+    # flip the known symmetric types. re-running just re-sets the same values.
+    placeholders = ', '.join([f':n{i}' for i in range(len(SYMMETRIC_TYPES))])
+    params = {f'n{i}': name for i, name in enumerate(SYMMETRIC_TYPES)}
+    bind.execute(
+        sa.text(
+            "UPDATE relationshiptypes SET isdirectional = 0 "
+            f"WHERE relationshiptype IN ({placeholders})"),
+        params)
+
+
+def downgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+    if _has_column(insp, 'relationshiptypes', 'isdirectional'):
+        op.drop_column('relationshiptypes', 'isdirectional')
diff --git a/migrations/versions/7d20_relationshiptypepropagations.py b/migrations/versions/7d20_relationshiptypepropagations.py
new file mode 100644
index 0000000..c22498b
--- /dev/null
+++ b/migrations/versions/7d20_relationshiptypepropagations.py
@@ -0,0 +1,109 @@
+"""Relationship-type propagation goes M:N (relationshiptypepropagations)
+
+Replaces the single-valued relationshiptypes.propagatesthroughid with a join
+table so one type can propagate through several through-types at once. On this
+DB `controls` needs both `partof` (declared) and `Dualpath` (consumed: a
+dual-bay pair is one physical machine with a single controller, so both bays
+must carry the controls link to that PC).
+
+Upgrade: create relationshiptypepropagations, migrate the existing
+propagatesthroughid value into a row, drop the column, then seed the
+controls -> Dualpath row (resolved by name, skipped if either type missing).
+Downgrade: recreate the column from the first propagation row per type (best
+effort) and drop the table.
+
+Idempotent guards so it is safe on a partially-migrated box.
+
+Revision ID: 7d20_relationshiptypepropagations
+Revises: 7d19_relationshiptype_directional
+Create Date: 2026-07-11
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '7d20_relationshiptypepropagations'
+down_revision = '7d19_relationshiptype_directional'
+branch_labels = None
+depends_on = None
+
+
+def _has_column(insp, table, column):
+    return column in [c['name'] for c in insp.get_columns(table)]
+
+
+def upgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+
+    if 'relationshiptypepropagations' not in insp.get_table_names():
+        op.create_table(
+            'relationshiptypepropagations',
+            sa.Column('propagationid', sa.Integer(), primary_key=True),
+            sa.Column('relationshiptypeid', sa.Integer(), nullable=False),
+            sa.Column('throughtypeid', sa.Integer(), nullable=False),
+            sa.ForeignKeyConstraint(['relationshiptypeid'],
+                                    ['relationshiptypes.relationshiptypeid']),
+            sa.ForeignKeyConstraint(['throughtypeid'],
+                                    ['relationshiptypes.relationshiptypeid']),
+            sa.UniqueConstraint('relationshiptypeid', 'throughtypeid',
+                                name='uq_reltype_propagation'),
+        )
+
+    if _has_column(insp, 'relationshiptypes', 'propagatesthroughid'):
+        # migrate the single-FK value into a row (dedup guard for re-runs)
+        bind.execute(sa.text(
+            "INSERT INTO relationshiptypepropagations "
+            "(relationshiptypeid, throughtypeid) "
+            "SELECT rt.relationshiptypeid, rt.propagatesthroughid "
+            "FROM relationshiptypes rt "
+            "WHERE rt.propagatesthroughid IS NOT NULL AND NOT EXISTS ("
+            "  SELECT 1 FROM relationshiptypepropagations p "
+            "  WHERE p.relationshiptypeid = rt.relationshiptypeid "
+            "    AND p.throughtypeid = rt.propagatesthroughid)"))
+        # drop the self-FK (known name from 7a01, else reflect) then the column
+        fk_names = [fk['name'] for fk in insp.get_foreign_keys('relationshiptypes')
+                    if fk.get('constrained_columns') == ['propagatesthroughid']
+                    and fk.get('name')]
+        for name in fk_names:
+            op.drop_constraint(name, 'relationshiptypes', type_='foreignkey')
+        op.drop_column('relationshiptypes', 'propagatesthroughid')
+
+    # seed controls -> Dualpath by name; skip if either type is missing
+    rows = bind.execute(sa.text(
+        "SELECT relationshiptypeid, relationshiptype FROM relationshiptypes")).fetchall()
+    byname = {r[1]: r[0] for r in rows}
+    controls = byname.get('controls')
+    dualpath = byname.get('Dualpath')
+    if controls and dualpath:
+        exists = bind.execute(sa.text(
+            "SELECT 1 FROM relationshiptypepropagations "
+            "WHERE relationshiptypeid = :c AND throughtypeid = :d"),
+            {'c': controls, 'd': dualpath}).fetchone()
+        if not exists:
+            bind.execute(sa.text(
+                "INSERT INTO relationshiptypepropagations "
+                "(relationshiptypeid, throughtypeid) VALUES (:c, :d)"),
+                {'c': controls, 'd': dualpath})
+
+
+def downgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+
+    if not _has_column(insp, 'relationshiptypes', 'propagatesthroughid'):
+        op.add_column('relationshiptypes',
+                      sa.Column('propagatesthroughid', sa.Integer(), nullable=True))
+        op.create_foreign_key('fk_relationshiptype_propagation',
+                              'relationshiptypes', 'relationshiptypes',
+                              ['propagatesthroughid'], ['relationshiptypeid'])
+
+    if 'relationshiptypepropagations' in insp.get_table_names():
+        # best effort: restore the first propagation row per type
+        bind.execute(sa.text(
+            "UPDATE relationshiptypes rt SET propagatesthroughid = ("
+            "  SELECT p.throughtypeid FROM relationshiptypepropagations p "
+            "  WHERE p.relationshiptypeid = rt.relationshiptypeid "
+            "  ORDER BY p.propagationid LIMIT 1)"))
+        op.drop_table('relationshiptypepropagations')
diff --git a/shopdb/cli/__init__.py b/shopdb/cli/__init__.py
index 034e9ff..8ca1bbf 100644
--- a/shopdb/cli/__init__.py
+++ b/shopdb/cli/__init__.py
@@ -196,12 +196,14 @@ def seed_reference_data():
     # Connection types (pre-1.0 legacy; kept for backward compat with
     # existing relationship rows. New ADR-001 code reasons about the three
     # canonical types below via free-text label.)
+    # all symmetric physical/network links -> isdirectional=False so the
+    # relationships card shows one direction-blind "connected" entry per peer.
     connection_types = [
-        {'relationshiptype': 'Serial Cable', 'description': 'RS-232 or similar serial connection'},
-        {'relationshiptype': 'Direct Ethernet', 'description': 'Direct network cable (airgapped)'},
-        {'relationshiptype': 'USB', 'description': 'USB connection'},
-        {'relationshiptype': 'WiFi', 'description': 'Wireless network connection'},
-        {'relationshiptype': 'Dualpath', 'description': 'Redundant/failover network path'},
+        {'relationshiptype': 'Serial Cable', 'description': 'RS-232 or similar serial connection', 'isdirectional': False},
+        {'relationshiptype': 'Direct Ethernet', 'description': 'Direct network cable (airgapped)', 'isdirectional': False},
+        {'relationshiptype': 'USB', 'description': 'USB connection', 'isdirectional': False},
+        {'relationshiptype': 'WiFi', 'description': 'Wireless network connection', 'isdirectional': False},
+        {'relationshiptype': 'Dualpath', 'description': 'Redundant/failover network path', 'isdirectional': False},
     ]
 
     for ct_data in connection_types:
@@ -210,9 +212,9 @@ def seed_reference_data():
             ct = RelationshipType(**ct_data)
             db.session.add(ct)
 
-    # ADR-001 canonical relationship types. Created first without propagation
-    # FKs, then patched with propagatesthroughid since `controls` points at
-    # `partof` (same table). All three are idempotent.
+    # ADR-001 canonical relationship types. Created first, then their
+    # propagation rails are seeded as relationshiptypepropagations rows (M:N).
+    # All idempotent.
     #
     # MySQL collation is case-insensitive by default, which would let a
     # legacy capitalized row (e.g. "Controls") match the lowercase
@@ -229,21 +231,38 @@ def seed_reference_data():
         return RelationshipType.query.filter_by(relationshiptype=name).first()
 
     adr_types = [
-        {'relationshiptype': 'partof', 'description': 'Composition / sub-assembly (ADR-001)'},
-        {'relationshiptype': 'controls', 'description': 'Operational authority over another asset (ADR-001)'},
-        {'relationshiptype': 'connectedto', 'description': 'Network or data link without authority (ADR-001)'},
+        {'relationshiptype': 'partof', 'description': 'Composition / sub-assembly (ADR-001)', 'isdirectional': True},
+        {'relationshiptype': 'controls', 'description': 'Operational authority over another asset (ADR-001)', 'isdirectional': True},
+        {'relationshiptype': 'connectedto', 'description': 'Network or data link without authority (ADR-001)', 'isdirectional': False},
     ]
     for at in adr_types:
         if not _lookup_binary(at['relationshiptype']):
             db.session.add(RelationshipType(**at))
     db.session.flush()
 
-    # Wire `controls` -> `partof` propagation rail. partof + connectedto stay
-    # null (no propagation).
-    partof = _lookup_binary('partof')
-    controls = _lookup_binary('controls')
-    if partof and controls and controls.propagatesthroughid != partof.relationshiptypeid:
-        controls.propagatesthroughid = partof.relationshiptypeid
+    # Seed `controls` propagation rails as M:N rows. controls -> partof
+    # (declared; directional rail, not consumed yet) and controls -> Dualpath
+    # (consumed; a dual-bay pair shares one controller so both bays carry
+    # controls). Idempotent, resolved by name, skipped if a type is missing.
+    from shopdb.core.models.relationship import RelationshipTypePropagation
+
+    def _seed_propagation(sourcename, throughname):
+        source = _lookup_binary(sourcename)
+        through = _lookup_binary(throughname)
+        if not source or not through:
+            return
+        exists = RelationshipTypePropagation.query.filter_by(
+            relationshiptypeid=source.relationshiptypeid,
+            throughtypeid=through.relationshiptypeid,
+        ).first()
+        if not exists:
+            db.session.add(RelationshipTypePropagation(
+                relationshiptypeid=source.relationshiptypeid,
+                throughtypeid=through.relationshiptypeid,
+            ))
+
+    _seed_propagation('controls', 'partof')
+    _seed_propagation('controls', 'Dualpath')
 
     # Default-printer link: a PC asset -> its default printer asset. Read by the
     # printer-installer endpoint (parity with classic apipcdefaultprinter.asp).
@@ -332,6 +351,109 @@ def seed_admin(username, email, password):
         click.echo(click.style('=' * 52, fg='cyan'))
 
 
+@click.group('relationships')
+def relationships_cli():
+    """Asset-relationship maintenance commands."""
+    pass
+
+
+@relationships_cli.command('propagate')
+@with_appcontext
+def propagate_relationships():
+    """Backfill propagated relationship rows across symmetric rails.
+
+    Scans every existing relationship of a type that propagates through a
+    symmetric through-type (e.g. controls through Dualpath) and creates the
+    missing fanned-out rows. Idempotent. Also serves the legacy-import flow:
+    the import creates controls links on primary bays, this fans them out to
+    the Dualpath partner bays.
+    """
+    from shopdb.extensions import db
+    from shopdb.core.models.relationship import RelationshipType, AssetRelationship
+    from shopdb.core.api.assets import propagate_relationship
+
+    # types that actually propagate through at least one symmetric through-type
+    propagating_ids = [
+        t.relationshiptypeid for t in RelationshipType.query.all()
+        if any(not through.isdirectional for through in t.propagatesthrough)
+    ]
+
+    total = 0
+    if propagating_ids:
+        rels = AssetRelationship.query.filter(
+            AssetRelationship.relationshiptypeid.in_(propagating_ids),
+            AssetRelationship.isactive == True,
+        ).all()
+        for rel in rels:
+            total += len(propagate_relationship(rel))
+        db.session.commit()
+
+    click.echo(click.style(f"Propagated {total} relationship row(s).", fg='green'))
+
+
+@relationships_cli.command('fix-controls-direction')
+@with_appcontext
+def fix_controls_direction():
+    """Flip reversed legacy controls rows to PC -> machine.
+
+    Legacy import stores controls as machine -> PC, which reads as the machine
+    having authority over the PC. In reality the PC is the controller (it
+    sends programs to the machine and receives logs), so per ADR-001 the PC
+    must be the source. Flips every active controls row whose source is a
+    machine asset and target is a computer asset. If the flipped row already
+    exists, the reversed duplicate is deactivated instead. Idempotent.
+    """
+    from sqlalchemy.orm import aliased
+    from shopdb.extensions import db
+    from shopdb.core.models import Asset, AssetType
+    from shopdb.core.models.relationship import RelationshipType, AssetRelationship
+
+    controls = RelationshipType.query.filter_by(relationshiptype='controls').first()
+    if not controls:
+        click.echo(click.style("No 'controls' relationship type; nothing to do.", fg='yellow'))
+        return
+
+    sourceasset = aliased(Asset)
+    targetasset = aliased(Asset)
+    sourcetype = aliased(AssetType)
+    targettype = aliased(AssetType)
+
+    reversed_rows = (
+        AssetRelationship.query
+        .join(sourceasset, AssetRelationship.sourceassetid == sourceasset.assetid)
+        .join(targetasset, AssetRelationship.targetassetid == targetasset.assetid)
+        .join(sourcetype, sourceasset.assettypeid == sourcetype.assettypeid)
+        .join(targettype, targetasset.assettypeid == targettype.assettypeid)
+        .filter(
+            AssetRelationship.relationshiptypeid == controls.relationshiptypeid,
+            AssetRelationship.isactive == True,
+            sourcetype.assettype == 'machine',
+            targettype.assettype == 'computer',
+        )
+        .all()
+    )
+
+    flipped = 0
+    deactivated = 0
+    for row in reversed_rows:
+        duplicate = AssetRelationship.query.filter_by(
+            sourceassetid=row.targetassetid,
+            targetassetid=row.sourceassetid,
+            relationshiptypeid=controls.relationshiptypeid,
+        ).first()
+        if duplicate:
+            row.isactive = False  # flipped row already exists, retire this one
+            deactivated += 1
+        else:
+            row.sourceassetid, row.targetassetid = row.targetassetid, row.sourceassetid
+            flipped += 1
+    db.session.commit()
+
+    click.echo(click.style(
+        f"Flipped {flipped} controls row(s) to PC -> machine"
+        f" ({deactivated} reversed duplicate(s) deactivated).", fg='green'))
+
+
 @seed_cli.command('permissions')
 @with_appcontext
 def seed_permissions():
diff --git a/shopdb/core/api/assets.py b/shopdb/core/api/assets.py
index a5915ea..cd16d15 100644
--- a/shopdb/core/api/assets.py
+++ b/shopdb/core/api/assets.py
@@ -237,12 +237,7 @@ def delete_asset_status(status_id: int):
 def list_relationship_types():
     """List all asset relationship types."""
     types = RelationshipType.query.order_by(RelationshipType.relationshiptype).all()
-    return success_response([{
-        'relationshiptypeid': t.relationshiptypeid,
-        'relationshiptype': t.relationshiptype,
-        'description': t.description,
-        'color': t.color
-    } for t in types])
+    return success_response([_rel_type_dict(t) for t in types])
 
 
 @assets_bp.route('/relationshiptypes', methods=['POST'])
@@ -264,7 +259,8 @@ def create_relationship_type():
     rel_type = RelationshipType(
         relationshiptype=data['relationshiptype'],
         description=data.get('description'),
-        color=data.get('color')
+        color=data.get('color'),
+        isdirectional=data.get('isdirectional', True)
     )
     db.session.add(rel_type)
     db.session.commit()
@@ -278,6 +274,16 @@ def _rel_type_dict(t):
         'relationshiptype': t.relationshiptype,
         'description': t.description,
         'color': t.color,
+        'isdirectional': t.isdirectional,
+        # read-only view of the propagation rails (seed/CLI-managed, no UI)
+        'propagatesthrough': [
+            {
+                'relationshiptypeid': p.relationshiptypeid,
+                'relationshiptype': p.relationshiptype,
+                'isdirectional': p.isdirectional,
+            }
+            for p in t.propagatesthrough
+        ],
     }
 
 
@@ -294,7 +300,7 @@ def update_relationship_type(type_id: int):
         if RelationshipType.query.filter_by(relationshiptype=data['relationshiptype']).first():
             return error_response(ErrorCodes.CONFLICT,
                                   f"Relationship type '{data['relationshiptype']}' already exists", http_code=409)
-    for key in ('relationshiptype', 'description', 'color'):
+    for key in ('relationshiptype', 'description', 'color', 'isdirectional'):
         if key in data:
             setattr(t, key, data[key])
     db.session.commit()
@@ -563,6 +569,97 @@ def lookup_asset_by_number(assetnumber: str):
 # Asset Relationships
 # =============================================================================
 
+def _partners_via(assetid, throughtypeid):
+    """Return the set of asset ids linked to assetid via throughtypeid.
+
+    Direction-blind: matches rows where assetid is source OR target, so a
+    symmetric through-type (Dualpath) stored in either direction is caught.
+    """
+    rows = AssetRelationship.query.filter(
+        AssetRelationship.relationshiptypeid == throughtypeid,
+        AssetRelationship.isactive == True,
+        db.or_(
+            AssetRelationship.sourceassetid == assetid,
+            AssetRelationship.targetassetid == assetid,
+        ),
+    ).all()
+    partners = set()
+    for row in rows:
+        other = row.targetassetid if row.sourceassetid == assetid else row.sourceassetid
+        partners.add(other)
+    return partners
+
+
+def _relationship_exists(sourceid, targetid, typeid):
+    # existence check ignores isactive so a soft-deleted row still blocks a
+    # duplicate insert (the uniqueness constraint spans all rows).
+    return AssetRelationship.query.filter_by(
+        sourceassetid=sourceid,
+        targetassetid=targetid,
+        relationshiptypeid=typeid,
+    ).first() is not None
+
+
+def _add_propagated(sourceid, targetid, rel, created):
+    # idempotent add; skip if source-T->target already exists (any isactive)
+    if sourceid in (targetid,):
+        return
+    if _relationship_exists(sourceid, targetid, rel.relationshiptypeid):
+        return
+    newrel = AssetRelationship(
+        sourceassetid=sourceid,
+        targetassetid=targetid,
+        relationshiptypeid=rel.relationshiptypeid,
+        label=rel.label,
+    )
+    db.session.add(newrel)
+    created.append(newrel)
+
+
+def propagate_relationship(rel):
+    """Fan out rel across the SYMMETRIC through-types of its type.
+
+    A Dualpath pair is one physical dual-bay machine, so a relationship that
+    touches one bay must be mirrored to the partner bay - whichever end (source
+    or target) carries the Dualpath link. For each symmetric through-type P
+    (isdirectional false) in the type's propagation set we mirror BOTH ends,
+    keeping the relationship's direction:
+
+      * for each partner X of the TARGET via P: create source -T-> X
+      * for each partner X of the SOURCE via P: create X -T-> target
+
+    In practice only one end has partners (the bay end of a controls edge,
+    whichever direction the row is stored), so there is no double fan-out.
+    Canonical controls direction is PC -> machine (the PC is the controller:
+    it sends programs to the machine and receives logs); reversed legacy rows
+    are corrected by `flask relationships fix-controls-direction`, and
+    propagation preserves whatever direction the row carries. Same-direction
+    idempotency: controls is directional, so we skip when the same
+    source-T->target row already exists. Returns the newly created
+    AssetRelationship rows (added to the session, not committed).
+
+    Directional through-types (partof) are declared but NOT consumed: the
+    parent/child fan-out direction is ambiguous, so their propagation semantics
+    are deferred and partof stays inert exactly as before.
+    """
+    created = []
+    reltype = rel.relationshiptype or db.session.get(RelationshipType, rel.relationshiptypeid)
+    if not reltype:
+        return created
+    for through in reltype.propagatesthrough:
+        if through.isdirectional:
+            continue  # directional propagation deferred (parent/child ambiguity)
+        # target-side partners inherit being controlled BY the source
+        for partnerid in _partners_via(rel.targetassetid, through.relationshiptypeid):
+            if partnerid != rel.sourceassetid:
+                _add_propagated(rel.sourceassetid, partnerid, rel, created)
+        # source-side partners inherit controlling the target
+        for partnerid in _partners_via(rel.sourceassetid, through.relationshiptypeid):
+            if partnerid != rel.targetassetid:
+                _add_propagated(partnerid, rel.targetassetid, rel, created)
+    return created
+
+
 @assets_bp.route('/<int:asset_id>/relationships', methods=['GET'])
 @jwt_required(optional=True)
 def get_asset_relationships(asset_id: int):
@@ -595,6 +692,8 @@ def get_asset_relationships(asset_id: int):
         r = rel.to_dict()
         r['targetasset'] = rel.targetasset.to_dict() if rel.targetasset else None
         r['relationshiptypename'] = rel.relationshiptype.relationshiptype if rel.relationshiptype else None
+        # directionality drives card display (symmetric collapse vs arrows)
+        r['isdirectional'] = rel.relationshiptype.isdirectional if rel.relationshiptype else True
         outgoing_data.append(r)
 
     incoming_data = []
@@ -602,6 +701,7 @@ def get_asset_relationships(asset_id: int):
         r = rel.to_dict()
         r['sourceasset'] = rel.sourceasset.to_dict() if rel.sourceasset else None
         r['relationshiptypename'] = rel.relationshiptype.relationshiptype if rel.relationshiptype else None
+        r['isdirectional'] = rel.relationshiptype.isdirectional if rel.relationshiptype else True
         incoming_data.append(r)
 
     return success_response({
@@ -614,7 +714,19 @@ def get_asset_relationships(asset_id: int):
 @jwt_required()
 @require_permission('assets.create')
 def create_asset_relationship():
-    """Create a relationship between two assets."""
+    """Create a relationship between two assets.
+
+    After the row is created, the relationship is fanned out across its type's
+    propagation rails (relationshiptypepropagations). For each SYMMETRIC
+    through-type (e.g. Dualpath) the edge is mirrored to the partner of
+    whichever endpoint carries the through-type link, keeping direction.
+    Concretely, `controls` between a bay of a dual-bay machine and its PC is
+    also created for the partner bay, since a Dualpath pair is one physical
+    machine with a single controller. Directional through-types (partof) are
+    declared but not consumed yet. The response carries `propagated` and
+    `propagatedcount`. Propagation pairs are seed/CLI-managed (there is no
+    management UI); backfill legacy data with `flask relationships propagate`.
+    """
     data = request.get_json()
 
     if not data:
@@ -661,16 +773,30 @@ def create_asset_relationship():
 
     db.session.add(rel)
     apply_import_timestamps(rel, data)
+    db.session.flush()
+
+    # fan out across symmetric propagation rails (e.g. Dualpath partner bays)
+    propagated = propagate_relationship(rel)
+    for prop in propagated:
+        apply_import_timestamps(prop, data)
     db.session.commit()
 
-    return success_response(rel.to_dict(), message='Relationship created', http_code=201)
+    payload = rel.to_dict()
+    payload['propagated'] = [prop.to_dict() for prop in propagated]
+    payload['propagatedcount'] = len(propagated)
+    return success_response(payload, message='Relationship created', http_code=201)
 
 
 @assets_bp.route('/relationships/<int:rel_id>', methods=['DELETE'])
 @jwt_required()
 @require_permission('assets.delete')
 def delete_asset_relationship(rel_id: int):
-    """Delete an asset relationship."""
+    """Delete an asset relationship.
+
+    Deletion is manual and per-row: propagated rows (e.g. the mirrored controls
+    link on a Dualpath partner bay) are real independent rows and each is
+    deleted on its own. Removing one bay's link does NOT cascade to the other.
+    """
     rel = db.session.get(AssetRelationship, rel_id)
 
     if not rel:
diff --git a/shopdb/core/models/relationship.py b/shopdb/core/models/relationship.py
index 6290397..9e81e6a 100644
--- a/shopdb/core/models/relationship.py
+++ b/shopdb/core/models/relationship.py
@@ -21,30 +21,78 @@ class RelationshipType(BaseModel):
     description = db.Column(db.Text)
     color = db.Column(db.String(20), comment='CSS color for relationship badges')
 
-    # Sibling propagation (ADR-001): when a relationship of this type is
-    # created/deleted, the framework finds all assets related to the source
-    # via the type at propagatesthroughid and mirrors the change. Null means
-    # no propagation. Seeded values:
-    #   partof       -> null (propagation rail itself)
-    #   controls     -> partof (controls propagates across siblings)
-    #   connectedto  -> null (network paths don't propagate)
-    propagatesthroughid = db.Column(
-        db.Integer,
-        db.ForeignKey('relationshiptypes.relationshiptypeid'),
-        nullable=True,
-        comment='Sibling-propagation rail per ADR-001'
+    # True: edge has a source->target meaning (controls, partof, Backup For).
+    # False: symmetric link (Dualpath, connectedto, USB...) shown on the card
+    # once per peer with no direction, both stored direction rows collapsed.
+    isdirectional = db.Column(
+        db.Boolean,
+        default=True,
+        nullable=False,
+        server_default='1',
+        comment='False = symmetric connection, shown direction-blind'
     )
 
+    # Sibling propagation (ADR-001), WIRED. When a relationship of this type is
+    # created, the create path fans it out across every through-type in this
+    # type's propagation set (relationshiptypepropagations rows). For each
+    # SYMMETRIC through-type P, the source's edge to the target is mirrored to
+    # every asset linked to the target via P. This is M:N so one type can
+    # propagate through several rails at once. Seeded rows on this DB:
+    #   controls -> partof   (declared; directional rail, NOT consumed yet -
+    #                         parent/child fan-out direction is ambiguous)
+    #   controls -> Dualpath (consumed; a dual-bay pair is one physical machine
+    #                         with one controller, so both bays carry controls)
+    # A dual-bay Dualpath pair thus gets the PC's controls link on both bays.
+    # propagatesthrough is the list of through-type RelationshipType rows.
     propagatesthrough = db.relationship(
         'RelationshipType',
-        remote_side=[relationshiptypeid],
-        foreign_keys=[propagatesthroughid],
+        secondary='relationshiptypepropagations',
+        primaryjoin='RelationshipType.relationshiptypeid'
+                    ' == RelationshipTypePropagation.relationshiptypeid',
+        secondaryjoin='RelationshipType.relationshiptypeid'
+                      ' == RelationshipTypePropagation.throughtypeid',
+        viewonly=True,
     )
 
     def __repr__(self):
         return f"<RelationshipType {self.relationshiptype}>"
 
 
+class RelationshipTypePropagation(db.Model):
+    """
+    M:N propagation rails (ADR-001). One row means: a relationship of type
+    relationshiptypeid propagates through the connections of type throughtypeid.
+
+    Replaces the old single-valued relationshiptypes.propagatesthroughid so a
+    type (controls) can propagate through several through-types (partof AND
+    Dualpath) at once. Seed/CLI-managed; no management UI.
+    """
+    __tablename__ = 'relationshiptypepropagations'
+
+    propagationid = db.Column(db.Integer, primary_key=True)
+    relationshiptypeid = db.Column(
+        db.Integer,
+        db.ForeignKey('relationshiptypes.relationshiptypeid'),
+        nullable=False
+    )
+    throughtypeid = db.Column(
+        db.Integer,
+        db.ForeignKey('relationshiptypes.relationshiptypeid'),
+        nullable=False
+    )
+
+    __table_args__ = (
+        db.UniqueConstraint(
+            'relationshiptypeid',
+            'throughtypeid',
+            name='uq_reltype_propagation'
+        ),
+    )
+
+    def __repr__(self):
+        return f"<RelationshipTypePropagation {self.relationshiptypeid} through {self.throughtypeid}>"
+
+
 class AssetRelationship(BaseModel):
     """
     Relationships between assets.
diff --git a/tests/test_core/test_relationship_directional.py b/tests/test_core/test_relationship_directional.py
new file mode 100644
index 0000000..ce59deb
--- /dev/null
+++ b/tests/test_core/test_relationship_directional.py
@@ -0,0 +1,106 @@
+"""Relationship-type directionality: CRUD carries isdirectional and the
+per-asset relationships endpoint tags each row with its type directionality.
+
+The frontend uses isdirectional to collapse symmetric-type rows (Dualpath and
+other physical links) into one direction-blind card entry, and to render
+directional types (controls, partof...) with source->target phrasing. That
+dedupe is view logic verified live; here we lock the backend surface it needs.
+"""
+
+from shopdb.extensions import db
+from shopdb.core.models import Asset, AssetType
+from shopdb.core.models.relationship import RelationshipType, AssetRelationship
+
+
+def _make_asset(assetnumber, typeid):
+    asset = Asset(assetnumber=assetnumber, assettypeid=typeid)
+    db.session.add(asset)
+    db.session.flush()
+    return asset
+
+
+# ---------------------------------------------------------------------------
+# Relationship type CRUD carries isdirectional
+# ---------------------------------------------------------------------------
+
+def test_create_type_defaults_directional(client, db, auth_headers):
+    resp = client.post('/api/assets/relationshiptypes',
+                       json={'relationshiptype': 'Backup For'},
+                       headers=auth_headers)
+    assert resp.status_code == 201, resp.get_json()
+    assert resp.get_json()['data']['isdirectional'] is True
+
+
+def test_create_symmetric_type(client, db, auth_headers):
+    resp = client.post('/api/assets/relationshiptypes',
+                       json={'relationshiptype': 'Dualpath',
+                             'isdirectional': False},
+                       headers=auth_headers)
+    assert resp.status_code == 201, resp.get_json()
+    assert resp.get_json()['data']['isdirectional'] is False
+
+
+def test_update_toggles_directional(client, db, auth_headers):
+    typeid = client.post('/api/assets/relationshiptypes',
+                         json={'relationshiptype': 'USB'},
+                         headers=auth_headers).get_json()['data']['relationshiptypeid']
+    resp = client.put(f'/api/assets/relationshiptypes/{typeid}',
+                      json={'isdirectional': False}, headers=auth_headers)
+    assert resp.status_code == 200
+    assert resp.get_json()['data']['isdirectional'] is False
+
+
+def test_list_includes_directional(client, db, auth_headers):
+    client.post('/api/assets/relationshiptypes',
+                json={'relationshiptype': 'WiFi', 'isdirectional': False},
+                headers=auth_headers)
+    resp = client.get('/api/assets/relationshiptypes')
+    assert resp.status_code == 200
+    row = next(t for t in resp.get_json()['data']
+               if t['relationshiptype'] == 'WiFi')
+    assert row['isdirectional'] is False
+
+
+# ---------------------------------------------------------------------------
+# Per-asset relationships endpoint tags each row with isdirectional
+# ---------------------------------------------------------------------------
+
+def test_relationships_row_carries_isdirectional(client, db, auth_headers):
+    atype = AssetType(assettype='machine')
+    db.session.add(atype)
+    db.session.flush()
+
+    symmetric = RelationshipType(relationshiptype='Dualpath', isdirectional=False)
+    directional = RelationshipType(relationshiptype='controls', isdirectional=True)
+    db.session.add_all([symmetric, directional])
+    db.session.flush()
+
+    a = _make_asset('M-A', atype.assettypeid)
+    b = _make_asset('M-B', atype.assettypeid)
+
+    # symmetric link stored in both directions (legacy shape)
+    db.session.add(AssetRelationship(sourceassetid=a.assetid, targetassetid=b.assetid,
+                                     relationshiptypeid=symmetric.relationshiptypeid))
+    db.session.add(AssetRelationship(sourceassetid=b.assetid, targetassetid=a.assetid,
+                                     relationshiptypeid=symmetric.relationshiptypeid))
+    # directional link a controls b
+    db.session.add(AssetRelationship(sourceassetid=a.assetid, targetassetid=b.assetid,
+                                     relationshiptypeid=directional.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.get(f'/api/assets/{a.assetid}/relationships')
+    assert resp.status_code == 200
+    data = resp.get_json()['data']
+
+    for row in data['outgoing']:
+        assert 'isdirectional' in row
+    for row in data['incoming']:
+        assert 'isdirectional' in row
+
+    # symmetric type reports False both directions; directional reports True
+    sym_rows = [r for r in data['outgoing'] + data['incoming']
+                if r['relationshiptypename'] == 'Dualpath']
+    assert sym_rows and all(r['isdirectional'] is False for r in sym_rows)
+    ctrl_rows = [r for r in data['outgoing']
+                 if r['relationshiptypename'] == 'controls']
+    assert ctrl_rows and all(r['isdirectional'] is True for r in ctrl_rows)
diff --git a/tests/test_core/test_relationship_propagation.py b/tests/test_core/test_relationship_propagation.py
new file mode 100644
index 0000000..da4b84e
--- /dev/null
+++ b/tests/test_core/test_relationship_propagation.py
@@ -0,0 +1,249 @@
+"""Relationship propagation across symmetric rails (ADR-001, wired).
+
+A Dualpath pair is one physical dual-bay machine with a single controller PC
+and a bay-selector switch, so BOTH bay records must carry the controls link to
+that PC. Creating PC controls bayA where bayA has a Dualpath partner bayB
+auto-creates PC controls bayB. The propagation set is M:N
+(relationshiptypepropagations): controls propagates through Dualpath
+(symmetric, consumed) and through partof (directional, declared but inert).
+"""
+
+from shopdb.extensions import db
+from shopdb.core.models import Asset, AssetType
+from shopdb.core.models.relationship import (
+    RelationshipType,
+    RelationshipTypePropagation,
+    AssetRelationship,
+)
+
+
+def _make_asset(assetnumber, typeid):
+    asset = Asset(assetnumber=assetnumber, assettypeid=typeid)
+    db.session.add(asset)
+    db.session.flush()
+    return asset
+
+
+def _setup_types():
+    atype = AssetType(assettype='machine')
+    db.session.add(atype)
+    db.session.flush()
+
+    controls = RelationshipType(relationshiptype='controls', isdirectional=True)
+    dualpath = RelationshipType(relationshiptype='Dualpath', isdirectional=False)
+    partof = RelationshipType(relationshiptype='partof', isdirectional=True)
+    db.session.add_all([controls, dualpath, partof])
+    db.session.flush()
+    return atype, controls, dualpath, partof
+
+
+def _rel_exists(sourceid, targetid, typeid):
+    return AssetRelationship.query.filter_by(
+        sourceassetid=sourceid, targetassetid=targetid, relationshiptypeid=typeid
+    ).first() is not None
+
+
+# ---------------------------------------------------------------------------
+# Symmetric through-type propagates (controls fans across a Dualpath pair)
+# ---------------------------------------------------------------------------
+
+def test_controls_propagates_across_dualpath_pair(client, db, auth_headers):
+    atype, controls, dualpath, partof = _setup_types()
+    db.session.add(RelationshipTypePropagation(
+        relationshiptypeid=controls.relationshiptypeid,
+        throughtypeid=dualpath.relationshiptypeid))
+
+    pc = _make_asset('PC-1', atype.assettypeid)
+    baya = _make_asset('BAY-A', atype.assettypeid)
+    bayb = _make_asset('BAY-B', atype.assettypeid)
+
+    # the two bays are Dualpath partners (one physical machine)
+    db.session.add(AssetRelationship(sourceassetid=baya.assetid, targetassetid=bayb.assetid,
+                                     relationshiptypeid=dualpath.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.post('/api/assets/relationships', headers=auth_headers, json={
+        'sourceassetid': pc.assetid,
+        'targetassetid': baya.assetid,
+        'relationshiptypeid': controls.relationshiptypeid,
+    })
+    assert resp.status_code == 201, resp.get_json()
+    assert resp.get_json()['data']['propagatedcount'] == 1
+
+    # PC now controls BOTH bays
+    assert _rel_exists(pc.assetid, baya.assetid, controls.relationshiptypeid)
+    assert _rel_exists(pc.assetid, bayb.assetid, controls.relationshiptypeid)
+
+
+def test_propagation_finds_partner_stored_either_direction(client, db, auth_headers):
+    # Dualpath row stored partner->target; propagation must still catch it.
+    atype, controls, dualpath, partof = _setup_types()
+    db.session.add(RelationshipTypePropagation(
+        relationshiptypeid=controls.relationshiptypeid,
+        throughtypeid=dualpath.relationshiptypeid))
+
+    pc = _make_asset('PC-2', atype.assettypeid)
+    baya = _make_asset('BAY-A2', atype.assettypeid)
+    bayb = _make_asset('BAY-B2', atype.assettypeid)
+    # note: bayb is the SOURCE of the Dualpath row, target is baya
+    db.session.add(AssetRelationship(sourceassetid=bayb.assetid, targetassetid=baya.assetid,
+                                     relationshiptypeid=dualpath.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.post('/api/assets/relationships', headers=auth_headers, json={
+        'sourceassetid': pc.assetid,
+        'targetassetid': baya.assetid,
+        'relationshiptypeid': controls.relationshiptypeid,
+    })
+    assert resp.status_code == 201
+    assert _rel_exists(pc.assetid, bayb.assetid, controls.relationshiptypeid)
+
+
+def test_controls_propagates_when_bay_is_source(client, db, auth_headers):
+    # Matches real dev data: controls is stored bay -> PC (source is the bay).
+    # The bay's Dualpath partner must also get a controls -> PC row.
+    atype, controls, dualpath, partof = _setup_types()
+    db.session.add(RelationshipTypePropagation(
+        relationshiptypeid=controls.relationshiptypeid,
+        throughtypeid=dualpath.relationshiptypeid))
+
+    pc = _make_asset('PC-S', atype.assettypeid)
+    baya = _make_asset('BAY-AS', atype.assettypeid)
+    bayb = _make_asset('BAY-BS', atype.assettypeid)
+    db.session.add(AssetRelationship(sourceassetid=baya.assetid, targetassetid=bayb.assetid,
+                                     relationshiptypeid=dualpath.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.post('/api/assets/relationships', headers=auth_headers, json={
+        'sourceassetid': baya.assetid,
+        'targetassetid': pc.assetid,
+        'relationshiptypeid': controls.relationshiptypeid,
+    })
+    assert resp.status_code == 201, resp.get_json()
+    assert resp.get_json()['data']['propagatedcount'] == 1
+    # partner bay now also controls the PC, same direction (bay -> PC)
+    assert _rel_exists(bayb.assetid, pc.assetid, controls.relationshiptypeid)
+
+
+# ---------------------------------------------------------------------------
+# Idempotent: pre-existing propagated row is not duplicated
+# ---------------------------------------------------------------------------
+
+def test_propagation_idempotent(client, db, auth_headers):
+    atype, controls, dualpath, partof = _setup_types()
+    db.session.add(RelationshipTypePropagation(
+        relationshiptypeid=controls.relationshiptypeid,
+        throughtypeid=dualpath.relationshiptypeid))
+
+    pc = _make_asset('PC-3', atype.assettypeid)
+    baya = _make_asset('BAY-A3', atype.assettypeid)
+    bayb = _make_asset('BAY-B3', atype.assettypeid)
+    db.session.add(AssetRelationship(sourceassetid=baya.assetid, targetassetid=bayb.assetid,
+                                     relationshiptypeid=dualpath.relationshiptypeid))
+    # the mirrored row already exists
+    db.session.add(AssetRelationship(sourceassetid=pc.assetid, targetassetid=bayb.assetid,
+                                     relationshiptypeid=controls.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.post('/api/assets/relationships', headers=auth_headers, json={
+        'sourceassetid': pc.assetid,
+        'targetassetid': baya.assetid,
+        'relationshiptypeid': controls.relationshiptypeid,
+    })
+    assert resp.status_code == 201
+    assert resp.get_json()['data']['propagatedcount'] == 0
+
+    count = AssetRelationship.query.filter_by(
+        sourceassetid=pc.assetid, targetassetid=bayb.assetid,
+        relationshiptypeid=controls.relationshiptypeid).count()
+    assert count == 1
+
+
+# ---------------------------------------------------------------------------
+# Non-propagating type creates no extras
+# ---------------------------------------------------------------------------
+
+def test_non_propagating_type_no_extras(client, db, auth_headers):
+    atype, controls, dualpath, partof = _setup_types()
+    # controls has NO propagation rows here
+
+    pc = _make_asset('PC-4', atype.assettypeid)
+    baya = _make_asset('BAY-A4', atype.assettypeid)
+    bayb = _make_asset('BAY-B4', atype.assettypeid)
+    db.session.add(AssetRelationship(sourceassetid=baya.assetid, targetassetid=bayb.assetid,
+                                     relationshiptypeid=dualpath.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.post('/api/assets/relationships', headers=auth_headers, json={
+        'sourceassetid': pc.assetid,
+        'targetassetid': baya.assetid,
+        'relationshiptypeid': controls.relationshiptypeid,
+    })
+    assert resp.status_code == 201
+    assert resp.get_json()['data']['propagatedcount'] == 0
+    assert not _rel_exists(pc.assetid, bayb.assetid, controls.relationshiptypeid)
+
+
+# ---------------------------------------------------------------------------
+# Directional through-type (partof) does NOT propagate (deferred)
+# ---------------------------------------------------------------------------
+
+def test_directional_through_type_does_not_propagate(client, db, auth_headers):
+    atype, controls, dualpath, partof = _setup_types()
+    # controls propagates only through partof, which is directional -> inert
+    db.session.add(RelationshipTypePropagation(
+        relationshiptypeid=controls.relationshiptypeid,
+        throughtypeid=partof.relationshiptypeid))
+
+    pc = _make_asset('PC-5', atype.assettypeid)
+    parent = _make_asset('PARENT-5', atype.assettypeid)
+    child = _make_asset('CHILD-5', atype.assettypeid)
+    db.session.add(AssetRelationship(sourceassetid=child.assetid, targetassetid=parent.assetid,
+                                     relationshiptypeid=partof.relationshiptypeid))
+    db.session.commit()
+
+    resp = client.post('/api/assets/relationships', headers=auth_headers, json={
+        'sourceassetid': pc.assetid,
+        'targetassetid': parent.assetid,
+        'relationshiptypeid': controls.relationshiptypeid,
+    })
+    assert resp.status_code == 201
+    assert resp.get_json()['data']['propagatedcount'] == 0
+    assert not _rel_exists(pc.assetid, child.assetid, controls.relationshiptypeid)
+
+
+# ---------------------------------------------------------------------------
+# CLI backfill creates missing rows and is idempotent run twice
+# ---------------------------------------------------------------------------
+
+def test_cli_backfill_propagates_and_is_idempotent(client, db, auth_headers, runner):
+    atype, controls, dualpath, partof = _setup_types()
+    db.session.add(RelationshipTypePropagation(
+        relationshiptypeid=controls.relationshiptypeid,
+        throughtypeid=dualpath.relationshiptypeid))
+
+    pc = _make_asset('PC-6', atype.assettypeid)
+    baya = _make_asset('BAY-A6', atype.assettypeid)
+    bayb = _make_asset('BAY-B6', atype.assettypeid)
+    db.session.add(AssetRelationship(sourceassetid=baya.assetid, targetassetid=bayb.assetid,
+                                     relationshiptypeid=dualpath.relationshiptypeid))
+    # legacy-import shape: controls exists only on the primary bay
+    db.session.add(AssetRelationship(sourceassetid=pc.assetid, targetassetid=baya.assetid,
+                                     relationshiptypeid=controls.relationshiptypeid))
+    db.session.commit()
+
+    assert not _rel_exists(pc.assetid, bayb.assetid, controls.relationshiptypeid)
+
+    result = runner.invoke(args=['relationships', 'propagate'])
+    assert result.exit_code == 0, result.output
+    assert 'Propagated 1' in result.output
+    assert _rel_exists(pc.assetid, bayb.assetid, controls.relationshiptypeid)
+
+    # second run creates nothing more
+    result2 = runner.invoke(args=['relationships', 'propagate'])
+    assert result2.exit_code == 0, result2.output
+    assert 'Propagated 0' in result2.output
+    count = AssetRelationship.query.filter_by(
+        sourceassetid=pc.assetid, targetassetid=bayb.assetid,
+        relationshiptypeid=controls.relationshiptypeid).count()
+    assert count == 1