Upgraded embedding model to voyage-3.5, updated README.md

Reviewed-on: #3

README.md

@@ -8,11 +8,15 @@ In kongruity, the artifacts become "sticky notes." A board full of them looks ch
 
 With a click, they are semantically evaluated, grouped into thematic clusters with descriptive headers, rankable and exportable to project planning and execution tools.
 
+## Voyage AI voyage-3.5
+
+![Embedding model benchmarking.](Voyage.jpg)
+
 ## Clustering and evaluation: methodology
 
 Two models run in parallel, and neither sees the other's work. Anthropic's `claude-sonnet-5` (`backend/services/clustering.service.js`) reads the raw text of every note and groups them into labeled thematic clusters. 
 
-At the same time, Voyage AI's voyage-3 model (`backend/services/embedding.service.js`) converts each note's text into a numeric representation of its semantic meaning aka vector. 
+At the same time, Voyage AI's voyage-3.5 model (`backend/services/embedding.service.js`) converts each note's text into a numeric representation of its semantic meaning aka vector. 
 
 Once the LLM returns, kongruity scores that grouping (`backend/services/validation.service.js`) using an established silhouette coefficient, with cosine distance rather than Euclidean as the proximity metric. 
 
@@ -30,14 +34,18 @@ Average silhouette width is a widely-used measure of clustering quality. Higher
 
 2. How well-separated each cluster is from its nearest neighboring cluster.
 
+Although the coefficient is mathematically bounded by [−1, 1], cosine distance between high-dimensional text embeddings is compressed: unrelated notes sit close to orthogonal, so both the within-cluster and nearest-cluster distances land near 0.8. Because silhouette divides the gap between them by the larger of the two, the practical range on embedding data is roughly [−0.05, 0.10] rather than the full interval.
+
+The bands below are therefore calibrated against that observed range. On the seed board, the five ideal thematic clusters score 0.09; swapping a few notes between clusters drops it to 0.06; a scrambled assignment falls below zero.
+
 The score appears above the results with a plain-language band:
 
-- **0.70 and above** — Strong
-- **0.40 to 0.69** — Moderate
-- **0.10 to 0.39** — Weak
-- **Below 0.10** — Poor
+- **0.07 and above** — Strong
+- **0.04 to 0.06** — Moderate
+- **0.01 to 0.03** — Weak
+- **Below 0.01** — Poor
 
-Silhouette values are archetypically bounded below 1.0 for real-world data, so the number is best read as a relative measure. See Hugo Sträng, Tai Dinh. An upper bound on the silhouette evaluation metric for clustering. Pattern Recognition, Volume 178, 2026, 113402, ISSN 0031-3203.
+A score near 0.00 means the grouping is no better than chance. Bands are specific to `voyage-3` cosine distance and would need recalibration behind a different embedding model. See Hugo Sträng, Tai Dinh. An upper bound on the silhouette evaluation metric for clustering. Pattern Recognition, Volume 178, 2026, 113402, ISSN 0031-3203.
 
 ## Organizing clusters, exporting to workflow software
 

backend/services/embedding.service.js

@@ -27,7 +27,7 @@ export const embedNotes = async (notes) => {
             for await (const chunk of batches) {
                 const response = await client.embed({
                     input: chunk.map((n) => n.text),
-                    model: "voyage-3",
+                    model: "voyage-3.5",
                 });
 
                 response.data.forEach((item, i) => {

frontend/src/components/stickies.tsx

@@ -6,132 +6,136 @@ import Sticky from './sticky';
 import Button from './button';
 import '../styles/stickies.css';
 
+// In practice, silhouette on cosine distance between text embeddings occupies roughly
+// [-0.05, 0.10], not strict theoretical [-1, 1]: near-orthogonal vectors put both the within- and
+// nearest-cluster distances close to 0.8, and the coefficient divides their gap
+// by the larger. These bands are calibrated to that range for voyage-3. see README, Reading the cohesion score
 const scoreLabel = (score: number): string => {
-  if (score >= 0.7) return 'Strong';
-  if (score >= 0.4) return 'Moderate';
-  if (score >= 0.1) return 'Weak';
-  return 'Poor';
+    if (score >= 0.07) return 'Strong';
+    if (score >= 0.04) return 'Moderate';
+    if (score >= 0.01) return 'Weak';
+    return 'Poor';
 };
 
 const Stickies = () => {
-  const { data: stickies, isLoading, error } = useGetStickies();
-  const { mutate: cluster, data: clusterResponse, isPending } = useClusterStickies();
+    const { data: stickies, isLoading, error } = useGetStickies();
+    const { mutate: cluster, data: clusterResponse, isPending } = useClusterStickies();
 
-  const [rankedClusters, setRankedClusters] = useState<RankedCluster[]>([]);
-  const dragIndex = useRef<number | null>(null);
-  const [dragOverIndex, setDragOverIndex] = useState<number | null>(null);
+    const [rankedClusters, setRankedClusters] = useState<RankedCluster[]>([]);
+    const dragIndex = useRef<number | null>(null);
+    const [dragOverIndex, setDragOverIndex] = useState<number | null>(null);
 
-  useEffect(() => {
-    if (clusterResponse?.clusters) {
-      setRankedClusters(
-        clusterResponse.clusters.map((c, i) => ({ ...c, rank: i + 1 }))
-      );
-    }
-  }, [clusterResponse]);
+    useEffect(() => {
+        if (clusterResponse?.clusters) {
+            setRankedClusters(
+                clusterResponse.clusters.map((c, i) => ({ ...c, rank: i + 1 }))
+            );
+        }
+    }, [clusterResponse]);
 
-  if (isLoading) return <div>Loading...</div>;
-  if (error) return <div>Error: {error.message}</div>;
+    if (isLoading) return <div>Loading...</div>;
+    if (error) return <div>Error: {error.message}</div>;
 
-  const score = clusterResponse?.score;
+    const score = clusterResponse?.score;
 
-  const handleCluster = () => {
-    cluster();
-  };
+    const handleCluster = () => {
+        cluster();
+    };
 
-  const buildStickyMap = (): Map<string, StickyType> => {
-    const map = new Map<string, StickyType>();
-    stickies?.forEach((s) => map.set(s.id, s));
-    return map;
-  };
+    const buildStickyMap = (): Map<string, StickyType> => {
+        const map = new Map<string, StickyType>();
+        stickies?.forEach((s) => map.set(s.id, s));
+        return map;
+    };
 
-  const stickyMap = buildStickyMap();
+    const stickyMap = buildStickyMap();
 
-  const renderStickies = (items: StickyType[]) =>
-    items?.map((sticky) => <Sticky key={sticky.id} sticky={sticky} />);
+    const renderStickies = (items: StickyType[]) =>
+        items?.map((sticky) => <Sticky key={sticky.id} sticky={sticky} />);
 
-  const handleDragStart = (index: number) => {
-    dragIndex.current = index;
-  };
+    const handleDragStart = (index: number) => {
+        dragIndex.current = index;
+    };
 
-  const handleDragOver = (e: DragEvent, index: number) => {
-    e.preventDefault();
-    setDragOverIndex(index);
-  };
+    const handleDragOver = (e: DragEvent, index: number) => {
+        e.preventDefault();
+        setDragOverIndex(index);
+    };
 
-  const handleDragLeave = () => {
-    setDragOverIndex(null);
-  };
+    const handleDragLeave = () => {
+        setDragOverIndex(null);
+    };
 
-  const handleDrop = (targetIndex: number) => {
-    const sourceIndex = dragIndex.current;
-    if (sourceIndex === null || sourceIndex === targetIndex) {
-      dragIndex.current = null;
-      setDragOverIndex(null);
-      return;
-    }
+    const handleDrop = (targetIndex: number) => {
+        const sourceIndex = dragIndex.current;
+        if (sourceIndex === null || sourceIndex === targetIndex) {
+            dragIndex.current = null;
+            setDragOverIndex(null);
+            return;
+        }
 
-    const reordered = [...rankedClusters];
-    const [moved] = reordered.splice(sourceIndex, 1);
-    reordered.splice(targetIndex, 0, moved);
+        const reordered = [...rankedClusters];
+        const [moved] = reordered.splice(sourceIndex, 1);
+        reordered.splice(targetIndex, 0, moved);
 
-    setRankedClusters(reordered.map((c, i) => ({ ...c, rank: i + 1 })));
-    dragIndex.current = null;
-    setDragOverIndex(null);
-  };
+        setRankedClusters(reordered.map((c, i) => ({ ...c, rank: i + 1 })));
+        dragIndex.current = null;
+        setDragOverIndex(null);
+    };
 
-  const handleDragEnd = () => {
-    dragIndex.current = null;
-    setDragOverIndex(null);
-  };
-
-  return (
-    <div className="stickies-container">
-      <Button onClick={handleCluster} isLoading={isPending} label="Group Stickies By Topic" />
-      {rankedClusters.length > 0 ? (
-        <div className="clusters-container">
-          {score != null && (
-            <div className="cohesion-score">
-              Cluster cohesion: <strong>{score.toFixed(2)}</strong> — {scoreLabel(score)}
-            </div>
-          )}
-          {rankedClusters.map((group, index) => (
-            <div
-              key={group.label}
-              className={`cluster-group cluster-draggable${dragOverIndex === index ? ' cluster-drag-over' : ''}`}
-              draggable
-              onDragStart={() => handleDragStart(index)}
-              onDragOver={(e) => handleDragOver(e, index)}
-              onDragLeave={handleDragLeave}
-              onDrop={() => handleDrop(index)}
-              onDragEnd={handleDragEnd}
-            >
-              <div className="cluster-header">
-                <span className="cluster-rank" aria-label={`Priority ${group.rank}`}>
-                  {group.rank}
-                </span>
-                {group.rank === 1 && (
-                  <span className="cluster-reorder-hint">Drag and drop to reorganize cluster priority</span>
-                )}
-                <h3 className="cluster-label">{group.label}</h3>
-                <span className="cluster-drag-handle" aria-hidden="true">⠿</span>
-              </div>
-              <div className="stickies-grid">
-                {renderStickies(
-                  group?.noteIds
-                    .map((id) => stickyMap?.get(id))
-                    .filter((s): s is StickyType => !!s)
-                )}
-              </div>
-            </div>
-          ))}
+    const handleDragEnd = () => {
+        dragIndex.current = null;
+        setDragOverIndex(null);
+    };
+    console.log(score?.toFixed(2))
+    return (
+        <div className="stickies-container">
+            <Button onClick={handleCluster} isLoading={isPending} label="Group Stickies By Topic" />
+            {rankedClusters.length > 0 ? (
+                <div className="clusters-container">
+                    {score != null && (
+                        <div className="cohesion-score">
+                            Cluster cohesion: <strong>{scoreLabel(score)}</strong>
+                        </div>
+                    )}
+                    {rankedClusters.map((group, index) => (
+                        <div
+                            key={group.label}
+                            className={`cluster-group cluster-draggable${dragOverIndex === index ? ' cluster-drag-over' : ''}`}
+                            draggable
+                            onDragStart={() => handleDragStart(index)}
+                            onDragOver={(e) => handleDragOver(e, index)}
+                            onDragLeave={handleDragLeave}
+                            onDrop={() => handleDrop(index)}
+                            onDragEnd={handleDragEnd}
+                        >
+                            <div className="cluster-header">
+                                <span className="cluster-rank" aria-label={`Priority ${group.rank}`}>
+                                    {group.rank}
+                                </span>
+                                {group.rank === 1 && (
+                                    <span className="cluster-reorder-hint">Drag and drop to reorganize cluster priority</span>
+                                )}
+                                <h3 className="cluster-label">{group.label}</h3>
+                                <span className="cluster-drag-handle" aria-hidden="true">⠿</span>
+                            </div>
+                            <div className="stickies-grid">
+                                {renderStickies(
+                                    group?.noteIds
+                                        .map((id) => stickyMap?.get(id))
+                                        .filter((s): s is StickyType => !!s)
+                                )}
+                            </div>
+                        </div>
+                    ))}
+                </div>
+            ) : (
+                <div className="stickies-grid">
+                    {renderStickies(stickies ?? [])}
+                </div>
+            )}
         </div>
-      ) : (
-        <div className="stickies-grid">
-          {renderStickies(stickies ?? [])}
-        </div>
-      )}
-    </div>
-  );
+    );
 };
 
 export default Stickies;

frontend/src/styles/stickies.css

@@ -1,100 +1,107 @@
 .stickies-grid {
-  display: flex;
-  flex-wrap: wrap;
-  gap: 16px;
-  justify-content: center;
-  margin-top: 18px;
-  padding: 24px;
+    display: flex;
+    flex-wrap: wrap;
+    gap: 16px;
+    justify-content: center;
+    margin-top: 18px;
+    padding: 24px;
 }
 
 .stickies-container {
-  margin: 36px 0px 36px 0px;
+    margin: 36px 0px 36px 0px;
 }
 
 .clusters-container {
-  display: flex;
-  flex-direction: column;
-  gap: 32px;
-  padding: 24px 0;
+    display: flex;
+    flex-direction: column;
+    gap: 32px;
+    padding: 24px 0;
 }
 
 .cluster-group {
-  border: 1px solid #6dd6f4;
-  border-radius: 8px;
-  padding: 16px;
+    border: 1px solid #6dd6f4;
+    border-radius: 8px;
+    padding: 16px;
 }
 
 .cluster-draggable {
-  cursor: grab;
-  transition: box-shadow 0.2s ease, border-color 0.2s ease, transform 0.15s ease;
+    cursor: grab;
+    transition: box-shadow 0.2s ease, border-color 0.2s ease, transform 0.15s ease;
 }
 
 .cluster-draggable:active {
-  cursor: grabbing;
+    cursor: grabbing;
 }
 
 .cluster-drag-over {
-  border-color: #ffb7ce;
-  box-shadow: 0 0 12px rgba(255, 183, 206, 0.4);
-  transform: scale(1.01);
+    border-color: #ffb7ce;
+    box-shadow: 0 0 12px rgba(255, 183, 206, 0.4);
+    transform: scale(1.01);
 }
 
 .cluster-header {
-  display: flex;
-  align-items: center;
-  gap: 12px;
-  margin-bottom: 16px;
+    position: relative;
+    display: flex;
+    align-items: center;
+    gap: 12px;
+    margin-bottom: 16px;
+    min-height: 32px;
 }
 
 .cluster-rank {
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  width: 32px;
-  height: 32px;
-  border-radius: 50%;
-  background: #6dd6f4;
-  color: #1a1a2e;
-  font-weight: 700;
-  font-size: 0.95em;
-  flex-shrink: 0;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 32px;
+    height: 32px;
+    border-radius: 50%;
+    background: #6dd6f4;
+    color: #1a1a2e;
+    font-weight: 700;
+    font-size: 0.95em;
+    flex-shrink: 0;
 }
 
 .cluster-reorder-hint {
-  font-size: 0.8em;
-  color: #9ca3af;
-  font-style: italic;
-  white-space: nowrap;
-  flex-shrink: 0;
+    font-size: 0.8em;
+    color: #9ca3af;
+    font-style: italic;
+    white-space: nowrap;
+    flex-shrink: 0;
 }
 
 .cluster-label {
-  margin: 0;
-  font-size: 1.2em;
-  font-weight: 600;
-  flex: 1;
+    position: absolute;
+    left: 50%;
+    transform: translateX(-50%);
+    max-width: 50%;
+    margin: 0;
+    font-size: 1.2em;
+    font-weight: 600;
+    pointer-events: none;
 }
 
 .cluster-drag-handle {
-  font-size: 1.4em;
-  color: #6dd6f4;
-  opacity: 0.4;
-  user-select: none;
-  transition: opacity 0.2s ease;
-  flex-shrink: 0;
+    margin-left: auto;
+    font-size: 1.4em;
+    color: #6dd6f4;
+    opacity: 0.4;
+    user-select: none;
+    transition: opacity 0.2s ease;
+    flex-shrink: 0;
 }
 
 .cluster-draggable:hover .cluster-drag-handle {
-  opacity: 0.8;
+    opacity: 0.8;
 }
 
 .cohesion-score {
-  text-align: center;
-  font-size: 0.95em;
-  color: #e0e0e0;
-  padding: 8px 16px;
-  background: rgba(109, 214, 244, 0.1);
-  border-radius: 6px;
-  width: fit-content;
-  margin: 0 auto;
-}
+    text-align: center;
+    font-size: 0.95em;
+    color: #e0e0e0;
+    padding: 8px 16px;
+    background: rgba(109, 214, 244, 0.1);
+    border-radius: 6px;
+    width: fit-content;
+    margin: 0 auto;
+}

frontend/src/tests/stickies.test.tsx

@@ -14,7 +14,7 @@ const MOCK_CLUSTER_RESPONSE = {
     { label: 'Auth Issues', noteIds: ['note_001'] },
     { label: 'Export Issues', noteIds: ['note_002'] },
   ],
-  score: 0.74,
+  score: 0.09,
 };
 
 let fetchMock: ReturnType<typeof vi.fn>;