diff --git a/atlas/templates/atlas/collection_case_priors.html b/atlas/templates/atlas/collection_case_priors.html
index 089cfd32..e75a2fcd 100644
--- a/atlas/templates/atlas/collection_case_priors.html
+++ b/atlas/templates/atlas/collection_case_priors.html
@@ -38,73 +38,7 @@
 
     <div class="row g-3">
         {% for case, added, relation, visibility in available_priors %}
-            <div class="col-12 col-md-6 col-lg-4" data-case="{{case.id}}">
-                <div class="card h-100 shadow-sm {% if added %}border-success{% else %}border-secondary{% endif %}">
-                    <div class="card-body d-flex flex-column">
-                        <div class="d-flex justify-content-between align-items-start mb-2">
-                            <h5 class="card-title mb-0">{{case.title}}</h5>
-                            <div>
-                                {% if added %}
-                                    <span class="badge bg-success">Added</span>
-                                {% else %}
-                                    <span class="badge bg-secondary">Available</span>
-                                {% endif %}
-                            </div>
-                        </div>
-
-                        <p class="card-text small text-muted mb-2">Relation: <span class="fw-medium">{{ relation }}</span></p>
-
-                        <div class="mb-3 small">{{case.get_series_blocks|safe}}</div>
-
-                        <div class="mt-auto">
-                            <div class="d-flex gap-2 mb-2">
-                                <a href="{% url 'atlas:case_detail' case.id %}" class="btn btn-sm btn-outline-primary">View case</a>
-                            </div>
-
-                            {% if not added %}
-                                <form class="row g-2" hx-post="{% url 'atlas:collection_case_priors' collection.id case_detail.case.pk %}"
-                                      hx-target="#htmx-response-{{case.id}}">
-                                    {% csrf_token %}
-                                    <input type="hidden" name="prior_case_id" value="{{case.id}}" />
-                                    <div class="col-12">
-                                        <input class="form-control form-control-sm" type="text" name="relation" value="{{relation}}" placeholder="Relation to case" />
-                                    </div>
-                                    <div class="col-8">
-                                        <select class="form-select form-select-sm" name="prior_visibility" id="prior_visibility_{{case.id}}">
-                                            <option value="AL" {% if visibility == 'AL' %}selected{% endif %}>Always</option>
-                                            <option value="RE" {% if visibility == 'RE' %}selected{% endif %}>Review</option>
-                                            <option value="NO" {% if visibility == 'NO' %}selected{% endif %}>None</option>
-                                        </select>
-                                    </div>
-                                    <div class="col-4 d-grid">
-                                        <button class="btn btn-sm btn-primary" type="submit">Add</button>
-                                    </div>
-                                </form>
-                            {% else %}
-                                <form hx-post="{% url 'atlas:collection_case_priors' collection.id case_detail.case.pk %}"
-                                      hx-target="#htmx-response-{{case.id}}">
-                                    {% csrf_token %}
-                                    <input type="hidden" name="remove" value="{{case.id}}" />
-                                    <div class="mb-2 small text-muted">Current relation: <strong>{{relation}}</strong></div>
-                                    <div class="d-flex gap-2">
-                                        <select class="form-select form-select-sm w-50" name="prior_visibility" id="prior_visibility_{{case.id}}" disabled>
-                                            <option value="AL" {% if visibility == 'AL' %}selected{% endif %}>Always</option>
-                                            <option value="RE" {% if visibility == 'RE' %}selected{% endif %}>Review</option>
-                                            <option value="NO" {% if visibility == 'NO' %}selected{% endif %}>None</option>
-                                        </select>
-                                        <button class="btn btn-sm btn-danger" type="submit">Remove</button>
-                                    </div>
-                                </form>
-                            {% endif %}
-
-                        </div>
-                    </div>
-
-                    <div class="card-footer bg-transparent">
-                        <span id="htmx-response-{{case.id}}" class="small"></span>
-                    </div>
-                </div>
-            </div>
+            {% include 'atlas/partials/_prior_card.html' with case=case added=added relation=relation visibility=visibility case_detail=case_detail collection=collection %}
         {% endfor %}
     </div>
 
diff --git a/atlas/templates/atlas/partials/_prior_card.html b/atlas/templates/atlas/partials/_prior_card.html
new file mode 100644
index 00000000..f013a78b
--- /dev/null
+++ b/atlas/templates/atlas/partials/_prior_card.html
@@ -0,0 +1,67 @@
+<div id="prior-card-{{case.id}}" class="col-12 col-md-6 col-lg-4" data-case="{{case.id}}">
+    <div class="card h-100 shadow-sm {% if added %}border-success{% else %}border-secondary{% endif %}">
+        <div class="card-body d-flex flex-column">
+            <div class="d-flex justify-content-between align-items-start mb-2">
+                <h5 class="card-title mb-0">{{case.title}}</h5>
+                <div>
+                    {% if added %}
+                        <span class="badge bg-success">Added</span>
+                    {% else %}
+                        <span class="badge bg-secondary">Available</span>
+                    {% endif %}
+                </div>
+            </div>
+
+            <p class="card-text small text-muted mb-2">Relation: <span class="fw-medium">{{ relation }}</span></p>
+
+            <div class="mb-3 small">{{case.get_series_blocks|safe}}</div>
+
+            <div class="mt-auto">
+                <div class="d-flex gap-2 mb-2">
+                    <a href="{% url 'atlas:case_detail' case.id %}" class="btn btn-sm btn-outline-primary">View case</a>
+                </div>
+
+                {% if not added %}
+                    <form class="row g-2" hx-post="{% url 'atlas:collection_case_priors' collection.id case_detail.case.pk %}"
+                          hx-target="#prior-card-{{case.id}}" hx-swap="outerHTML">
+                        {% csrf_token %}
+                        <input type="hidden" name="prior_case_id" value="{{case.id}}" />
+                        <div class="col-12">
+                            <input class="form-control form-control-sm" type="text" name="relation" value="{{relation}}" placeholder="Relation to case" />
+                        </div>
+                        <div class="col-8">
+                            <select class="form-select form-select-sm" name="prior_visibility" id="prior_visibility_{{case.id}}">
+                                <option value="AL" {% if visibility == 'AL' %}selected{% endif %}>Always</option>
+                                <option value="RE" {% if visibility == 'RE' %}selected{% endif %}>Review</option>
+                                <option value="NO" {% if visibility == 'NO' %}selected{% endif %}>None</option>
+                            </select>
+                        </div>
+                        <div class="col-4 d-grid">
+                            <button class="btn btn-sm btn-primary" type="submit">Add</button>
+                        </div>
+                    </form>
+                {% else %}
+                    <form hx-post="{% url 'atlas:collection_case_priors' collection.id case_detail.case.pk %}"
+                          hx-target="#prior-card-{{case.id}}" hx-swap="outerHTML">
+                        {% csrf_token %}
+                        <input type="hidden" name="remove" value="{{case.id}}" />
+                        <div class="mb-2 small text-muted">Current relation: <strong>{{relation}}</strong></div>
+                        <div class="d-flex gap-2">
+                            <select class="form-select form-select-sm w-50" name="prior_visibility" id="prior_visibility_{{case.id}}" disabled>
+                                <option value="AL" {% if visibility == 'AL' %}selected{% endif %}>Always</option>
+                                <option value="RE" {% if visibility == 'RE' %}selected{% endif %}>Review</option>
+                                <option value="NO" {% if visibility == 'NO' %}selected{% endif %}>None</option>
+                            </select>
+                            <button class="btn btn-sm btn-danger" type="submit">Remove</button>
+                        </div>
+                    </form>
+                {% endif %}
+
+            </div>
+        </div>
+
+        <div class="card-footer bg-transparent">
+            <small class="text-muted">Case ID: {{ case.id }}</small>
+        </div>
+    </div>
+</div>
diff --git a/atlas/views.py b/atlas/views.py
index 740fd600..776da8a3 100755
--- a/atlas/views.py
+++ b/atlas/views.py
@@ -2758,33 +2758,71 @@ def collection_take_start(request, pk, cid=None, passcode=None):
 @user_is_collection_author_or_atlas_editor
 def collection_case_priors(request, exam_id, case_id):
     case_detail = CaseDetail.objects.get(case=case_id, collection=exam_id)
+    collection = case_detail.collection
 
     if request.htmx:
+        # Ensure we can render the updated single-card partial and return it so HTMX
+        # can swap the card on the client side.
         if "remove" in request.POST:
-            p = CasePrior.objects.get(
-                case_detail=case_detail, prior_case=request.POST["remove"]
+            prior_pk = request.POST["remove"]
+            try:
+                p = CasePrior.objects.get(case_detail=case_detail, prior_case=prior_pk)
+                p.delete()
+            except CasePrior.DoesNotExist:
+                # Already removed; continue and render the not-added card
+                pass
+
+            prior_case = Case.objects.get(pk=prior_pk)
+            added = False
+            relation = ""
+            visibility = "AL"
+
+            html = render_to_string(
+                "atlas/partials/_prior_card.html",
+                {
+                    "case": prior_case,
+                    "added": added,
+                    "relation": relation,
+                    "visibility": visibility,
+                    "case_detail": case_detail,
+                    "collection": collection,
+                },
+                request=request,
             )
-            p.delete()
-            return HttpResponse(f"Case removed")
+            return HttpResponse(html)
         elif "prior_case_id" in request.POST:
-            if not request.POST["relation"]:
+            if not request.POST.get("relation"):
                 return HttpResponse(
-                    "You need to enter text to describe the relationship between the cases"
+                    "You need to enter text to describe the relationship between the cases",
+                    status=400,
                 )
             prior_case = Case.objects.get(pk=request.POST["prior_case_id"])
             p, created = CasePrior.objects.get_or_create(
                 case_detail=case_detail, prior_case=prior_case
             )
-            p.relation_text = request.POST["relation"]
-
-            p.prior_visibility = request.POST["prior_visibility"]
-
+            p.relation_text = request.POST.get("relation", "")
+            p.prior_visibility = request.POST.get("prior_visibility", "AL")
             p.save()
 
-            return HttpResponse(f"Case added")
+            added = True
+            relation = p.relation_text
+            visibility = p.prior_visibility
+
+            html = render_to_string(
+                "atlas/partials/_prior_card.html",
+                {
+                    "case": prior_case,
+                    "added": added,
+                    "relation": relation,
+                    "visibility": visibility,
+                    "case_detail": case_detail,
+                    "collection": collection,
+                },
+                request=request,
+            )
+            return HttpResponse(html)
         else:
-            return HttpResponse("False")
-            raise Http404()
+            return HttpResponse("False", status=400)
 
     collection = case_detail.collection