diff --git a/backend/app/api/endpoints/steps.py b/backend/app/api/endpoints/steps.py
index d5c8d279..14bc5a7c 100644
--- a/backend/app/api/endpoints/steps.py
+++ b/backend/app/api/endpoints/steps.py
@@ -353,6 +353,12 @@ async def update_step(
     """Update a step (owner or admin only)."""
     step = await get_step_or_404(step_id, db, current_user, check_edit=True)
 
+    if step.is_flow_synced:
+        raise HTTPException(
+            status_code=400,
+            detail="Flow-synced steps are read-only. Fork to customize."
+        )
+
     # Validate category if being updated
     if step_data.category_id:
         cat_result = await db.execute(
diff --git a/backend/app/api/endpoints/trees.py b/backend/app/api/endpoints/trees.py
index dbed1105..ce1ad5ae 100644
--- a/backend/app/api/endpoints/trees.py
+++ b/backend/app/api/endpoints/trees.py
@@ -641,8 +641,8 @@ async def update_tree(
     if "tree_structure" in update_data:
         tree.version += 1
 
-    # Sync steps to step library when publishing
-    if update_data.get("status") == 'published' or tree.status == 'published':
+    # Sync steps to step library on publish transition only
+    if update_data.get("status") == 'published':
         _structure = update_data.get("tree_structure", tree.tree_structure)
         _type = update_data.get("tree_type", tree.tree_type)
         _is_public = update_data.get("is_public", tree.is_public)
diff --git a/backend/tests/test_step_sync.py b/backend/tests/test_step_sync.py
index 8f734f05..63308d64 100644
--- a/backend/tests/test_step_sync.py
+++ b/backend/tests/test_step_sync.py
@@ -138,3 +138,79 @@ class TestExtractStepsForSync:
         }
         results = list(extract_steps_for_sync(tree_structure, tree_type='maintenance'))
         assert len(results) == 1
+
+
+class TestSyncOnPublish:
+    """Integration tests — sync triggered by publishing a tree."""
+
+    @pytest.mark.asyncio
+    async def test_publishing_procedural_tree_creates_library_steps(
+        self, client, auth_headers
+    ):
+        # Create a procedural tree with two steps
+        tree_resp = await client.post("/api/v1/trees", json={
+            "name": "Test Procedure",
+            "tree_type": "procedural",
+            "status": "draft",
+            "tree_structure": {
+                "steps": [
+                    {"id": "step_1", "type": "procedure_step",
+                     "title": "First step", "description": "Do this first"},
+                    {"id": "step_2", "type": "procedure_step",
+                     "title": "Second step", "description": "Do this second"},
+                    {"id": "end_1", "type": "procedure_end", "title": "Done"},
+                ]
+            }
+        }, headers=auth_headers)
+        assert tree_resp.status_code == 201
+        tree_id = tree_resp.json()["id"]
+
+        # Publish the tree
+        pub_resp = await client.put(f"/api/v1/trees/{tree_id}", json={"status": "published"}, headers=auth_headers)
+        assert pub_resp.status_code == 200
+
+        # Check library has synced entries
+        lib_resp = await client.get("/api/v1/steps", headers=auth_headers)
+        assert lib_resp.status_code == 200
+        steps = lib_resp.json()
+        synced = [s for s in steps if s.get("is_flow_synced")]
+        assert len(synced) == 2
+        titles = {s["title"] for s in synced}
+        assert "First step" in titles
+        assert "Second step" in titles
+
+    @pytest.mark.asyncio
+    async def test_republishing_updates_existing_library_steps(
+        self, client, auth_headers
+    ):
+        # Create a draft tree first, then publish
+        tree_resp = await client.post("/api/v1/trees", json={
+            "name": "Update Test",
+            "tree_type": "procedural",
+            "status": "draft",
+            "tree_structure": {"steps": [
+                {"id": "step_1", "type": "procedure_step",
+                 "title": "Original title", "description": "Original desc"},
+                {"id": "end_1", "type": "procedure_end", "title": "Done"},
+            ]}
+        }, headers=auth_headers)
+        tree_id = tree_resp.json()["id"]
+        first_pub = await client.put(f"/api/v1/trees/{tree_id}", json={"status": "published"}, headers=auth_headers)
+        assert first_pub.status_code == 200
+
+        # Republish with updated step title
+        second_pub = await client.put(f"/api/v1/trees/{tree_id}", json={
+            "tree_structure": {"steps": [
+                {"id": "step_1", "type": "procedure_step",
+                 "title": "Updated title", "description": "Updated desc"},
+                {"id": "end_1", "type": "procedure_end", "title": "Done"},
+            ]},
+            "status": "published"
+        }, headers=auth_headers)
+        assert second_pub.status_code == 200
+
+        # Check library shows updated title (not a duplicate)
+        lib_resp = await client.get("/api/v1/steps", headers=auth_headers)
+        synced = [s for s in lib_resp.json() if s.get("is_flow_synced")]
+        assert len(synced) == 1
+        assert synced[0]["title"] == "Updated title"
diff --git a/frontend/src/components/procedural-editor/StepEditor.tsx b/frontend/src/components/procedural-editor/StepEditor.tsx
index 6ce284ac..26225d1c 100644
--- a/frontend/src/components/procedural-editor/StepEditor.tsx
+++ b/frontend/src/components/procedural-editor/StepEditor.tsx
@@ -255,8 +255,8 @@ export function StepEditor({ step, stepNumber, onUpdate, onCollapse, availableVa
               </div>
             </div>
 
-            {/* Library Visibility */}
-            <div>
+            {/* Library Visibility — procedure_step nodes only */}
+            {step.type === 'procedure_step' && <div>
               <label htmlFor="library-visibility" className="mb-1.5 block text-xs font-medium text-muted-foreground">
                 Library Visibility
               </label>
@@ -275,7 +275,7 @@ export function StepEditor({ step, stepNumber, onUpdate, onCollapse, availableVa
               <p className="mt-1 text-[10px] text-muted-foreground">
                 Controls visibility in the step library. Defaults to the flow's own visibility setting.
               </p>
-            </div>
+            </div>}
           </div>
         )}
       </div>
diff --git a/frontend/src/types/step.ts b/frontend/src/types/step.ts
index 08f76383..5be0e87e 100644
--- a/frontend/src/types/step.ts
+++ b/frontend/src/types/step.ts
@@ -10,6 +10,7 @@ export interface StepContent {
   instructions: string
   help_text?: string
   commands?: StepCommand[]
+  group_label?: string
 }
 
 export interface Step {