diff --git a/bloom_lims/api/v1/worksets.py b/bloom_lims/api/v1/worksets.py
index 4534ee3..d20495b 100644
--- a/bloom_lims/api/v1/worksets.py
+++ b/bloom_lims/api/v1/worksets.py
@@ -98,14 +98,18 @@ async def get_workset(euid: str, user: APIUser = Depends(require_api_auth)):
         bdb = get_bdb(user.email)
         bob = get_bob(bdb)
 
-        workset = bob.get_by_euid(euid)
+        try:
+            workset = bob.get_by_euid(euid)
+        except Exception:
+            workset = None
+
         if not workset:
             raise HTTPException(status_code=404, detail=f"Workset not found: {euid}")
 
         if workset.category != "subject" or workset.type != "workset":
             raise HTTPException(status_code=404, detail=f"Not a workset: {euid}")
 
-        props = workset.json_addl.get("properties", {})
+        props = workset.json_addl.get("properties", {}) if workset.json_addl else {}
         members = subjecting.list_members_for_subject(bob, euid)
 
         return {
@@ -181,7 +185,11 @@ async def add_workset_members(
         bob = get_bob(bdb)
 
         # Verify workset exists
-        workset = bob.get_by_euid(euid)
+        try:
+            workset = bob.get_by_euid(euid)
+        except Exception:
+            workset = None
+
         if not workset:
             raise HTTPException(status_code=404, detail=f"Workset not found: {euid}")
 
@@ -217,7 +225,11 @@ async def get_workset_members(euid: str, user: APIUser = Depends(require_api_aut
         bob = get_bob(bdb)
 
         # Verify workset exists
-        workset = bob.get_by_euid(euid)
+        try:
+            workset = bob.get_by_euid(euid)
+        except Exception:
+            workset = None
+
         if not workset:
             raise HTTPException(status_code=404, detail=f"Workset not found: {euid}")
 
@@ -254,7 +266,11 @@ async def complete_workset(
         bob = get_bob(bdb)
 
         # Verify workset exists
-        workset = bob.get_by_euid(euid)
+        try:
+            workset = bob.get_by_euid(euid)
+        except Exception:
+            workset = None
+
         if not workset:
             raise HTTPException(status_code=404, detail=f"Workset not found: {euid}")
 
diff --git a/templates/legacy/workflow_details.html b/templates/legacy/workflow_details.html
index 71b5824..5f99279 100644
--- a/templates/legacy/workflow_details.html
+++ b/templates/legacy/workflow_details.html
@@ -155,9 +155,10 @@
                                         <!-- Recursive call for child steps -->     
                                                                                       
 
+                                        {# Query both container_instance AND content_instance lineages per Rule 6 #}
                                         {% if step.parent_of_lineages %}
                                             <div>
-                                                {% for child_step in step.get_sorted_parent_of_lineages(['container_instance']) %}
+                                                {% for child_step in step.get_sorted_parent_of_lineages(['container_instance', 'content_instance']) %}
                                                 {% if child_step.child_instance.category != 'workflow_step' and udat.get('wf_filter','off') == 'off' %}
                                                         <ul>
                                                         {% else %}
diff --git a/templates/modern/workflow_details.html b/templates/modern/workflow_details.html
index 15c1e46..db2a1f3 100644
--- a/templates/modern/workflow_details.html
+++ b/templates/modern/workflow_details.html
@@ -470,11 +470,12 @@ <h3 class="card-title"><i class="fas fa-play-circle"></i> Workflow Actions</h3>
 {% set is_open = accordion_states.get(step.euid, 'closed') == 'open' %}
 
 {# Separate workflow step children from container and content children #}
+{# Query both container_instance AND content_instance lineages per Rule 6 (polymorphic identity naming) #}
 {% set workflow_children = [] %}
 {% set container_children = [] %}
 {% set content_children = [] %}
 {% if step.parent_of_lineages %}
-    {% for child_lineage in step.get_sorted_parent_of_lineages(['container_instance']) %}
+    {% for child_lineage in step.get_sorted_parent_of_lineages(['container_instance', 'content_instance']) %}
         {% set child = child_lineage.child_instance %}
         {% if child.category == 'workflow_step' %}
             {% set _ = workflow_children.append(child) %}
diff --git a/tests/test_api_v1.py b/tests/test_api_v1.py
index e38da5d..7846475 100644
--- a/tests/test_api_v1.py
+++ b/tests/test_api_v1.py
@@ -1106,3 +1106,95 @@ def test_task_cancel(self, client):
         """Test task cancel endpoint."""
         response = client.post("/api/v1/tasks/00000000-0000-0000-0000-000000000000/cancel")
         assert response.status_code in [200, 400, 404, 422, 500]
+
+
+class TestWorksetsAPI:
+    """Tests for /api/v1/worksets endpoints."""
+
+    def test_list_worksets(self, client):
+        """Test listing worksets."""
+        response = client.get("/api/v1/worksets/")
+        assert response.status_code == 200
+        data = response.json()
+        assert "items" in data
+        assert "total" in data
+        assert "page" in data
+        assert "page_size" in data
+
+    def test_list_worksets_with_filters(self, client):
+        """Test listing worksets with status filter."""
+        response = client.get("/api/v1/worksets/?status=complete&page_size=10")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["page_size"] == 10
+
+    def test_list_worksets_with_workflow_filter(self, client):
+        """Test listing worksets with workflow filter."""
+        response = client.get("/api/v1/worksets/?workflow_euid=AY1")
+        assert response.status_code == 200
+        data = response.json()
+        assert "items" in data
+
+    def test_get_workset_not_found(self, client):
+        """Test getting non-existent workset."""
+        # Use a truly non-existent EUID pattern that won't match any object
+        response = client.get("/api/v1/worksets/ZZZZZ_DOES_NOT_EXIST_99999")
+        assert response.status_code == 404
+
+    def test_get_workset_not_a_workset(self, client):
+        """Test getting an object that exists but is not a workset."""
+        # GT1 is a template, not a workset
+        response = client.get("/api/v1/worksets/GT1")
+        assert response.status_code == 404
+
+    def test_create_workset_response_structure(self, client):
+        """Test creating workset returns expected response structure."""
+        # Note: This may create a workset even with non-existent anchor
+        # depending on implementation. We just verify the response structure.
+        response = client.post(
+            "/api/v1/worksets/",
+            json={
+                "anchor_euid": "WSX1",  # Use a likely existing workflow step
+                "workset_type": "accession",
+            }
+        )
+        # Should return 200 with success structure or 400/500 on error
+        assert response.status_code in [200, 400, 500]
+        if response.status_code == 200:
+            data = response.json()
+            assert "success" in data
+            assert "euid" in data or "message" in data
+
+    def test_add_members_workset_not_found(self, client):
+        """Test adding members to non-existent workset."""
+        response = client.post(
+            "/api/v1/worksets/ZZZZZ_DOES_NOT_EXIST_99999/members",
+            json={"member_euids": ["CX1", "CX2"]}
+        )
+        assert response.status_code == 404
+
+    def test_get_members_workset_not_found(self, client):
+        """Test getting members of non-existent workset."""
+        response = client.get("/api/v1/worksets/ZZZZZ_DOES_NOT_EXIST_99999/members")
+        assert response.status_code == 404
+
+    def test_complete_workset_not_found(self, client):
+        """Test completing non-existent workset."""
+        response = client.put(
+            "/api/v1/worksets/ZZZZZ_DOES_NOT_EXIST_99999/complete",
+            json={"status": "complete"}
+        )
+        assert response.status_code == 404
+
+    def test_get_workset_by_anchor_response(self, client):
+        """Test finding workset by anchor returns expected structure."""
+        # Use a unique anchor that likely doesn't have a workset
+        import uuid
+        unique_anchor = f"TEST_ANCHOR_{uuid.uuid4().hex[:8]}"
+        response = client.get(f"/api/v1/worksets/by-anchor/{unique_anchor}")
+        # Should return 404 for non-existent anchor, or 200 with workset info
+        assert response.status_code in [200, 404]
+        if response.status_code == 200:
+            data = response.json()
+            assert "euid" in data
+            assert "anchor_euid" in data
\ No newline at end of file