diff --git a/src/core/config.py b/src/core/config.py
index 0ac6314..4bf3759 100644
--- a/src/core/config.py
+++ b/src/core/config.py
@@ -22,9 +22,9 @@ class Settings(BaseSettings):
 
     # Retrieval
     top_k: int = 5
-    # Neighbor Expansion for fixed_size (ADR-0023); 0/0 = off
-    neighbor_prev: int = 0
-    neighbor_next: int = 0
+    # Neighbor Expansion for fixed_size (ADR-0023); 3/3 = decision default (see final-chunking-strategy-decision.md)
+    neighbor_prev: int = 3
+    neighbor_next: int = 3
 
     # LLM generation
     temperature: float = 0.0
diff --git a/src/static/index.html b/src/static/index.html
index bd57e89..ad48566 100644
--- a/src/static/index.html
+++ b/src/static/index.html
@@ -1287,8 +1287,8 @@ function RetrievalInspectView({ experiment, onBack }) {
 
 function QueryTab({ documents, strategies, addToast, formatFilter = 'word', hideTitle = false }) {
   const [form, setForm] = useState({
-    document_id: '', strategy: '', question: '', top_k: 5,
-    neighbor_prev: 0, neighbor_next: 0, corpus_model_id: '',
+    document_id: '', strategy: 'fixed_size', question: '', top_k: 5,
+    neighbor_prev: 3, neighbor_next: 3, corpus_model_id: '',
   });
   const [result, setResult] = useState(null);
   const [loading, setLoading] = useState(false);
@@ -1761,9 +1761,9 @@ function ComparisonView({ experiments, addToast, onBack }) {
 function BenchmarksTab({ documents, strategies, addToast, questionsFile, formatFilter = 'word', hideTitle = false }) {
   const [experiments, setExperiments] = useState([]);
   const [form, setForm] = useState({
-    document_id: '', strategies: strategies.map(s => s.name),
+    document_id: '', strategies: ['fixed_size'],
     questions_file: questionsFile, top_k: 5,
-    neighbor_prev: 0, neighbor_next: 0, dry_run: false, corpus_model_id: '',
+    neighbor_prev: 3, neighbor_next: 3, dry_run: false, corpus_model_id: '',
   });
   const [running, setRunning] = useState(false);
   const [embModels, setEmbModels] = useState([]);