mergeTooShort() never merges a short first segment (#2615)

Co-authored-by: Steven Enamakel <enamakel@tinyhumans.ai>

app/src/utils/__tests__/messageSegmentation.test.ts

@@ -33,6 +33,32 @@ describe('segmentMessage', () => {
     expect(segments.every(s => s.length >= 40)).toBe(true);
   });
 
+  it('merges a short first paragraph into the second paragraph', () => {
+    const text =
+      'Ok.\n\n' +
+      'This second paragraph is intentionally long enough to stand alone after merging.';
+    const segments = segmentMessage(text);
+
+    expect(segments.length).toBe(1);
+    expect(segments[0].startsWith('Ok.\n\n')).toBe(true);
+    expect(segments[0].length).toBeGreaterThanOrEqual(40);
+  });
+
+  it('forward-merges a short first paragraph yet keeps the remaining bubbles', () => {
+    // Three paragraphs where only the first is below MIN_SEGMENT_CHARS. This
+    // exercises the forward-merge branch in mergeTooShort while still returning
+    // multiple segments from the paragraph-split strategy (no leading stub).
+    const text =
+      'Ok.\n\n' +
+      'This second paragraph is intentionally long enough to stand alone as a bubble.\n\n' +
+      'And a third paragraph that is also long enough to remain its own standalone bubble.';
+    const segments = segmentMessage(text);
+
+    expect(segments).toHaveLength(2);
+    expect(segments[0].startsWith('Ok.\n\n')).toBe(true);
+    expect(segments.every(s => s.length >= 40)).toBe(true);
+  });
+
   it('splits on sentence boundaries when no paragraph breaks exist', () => {
     const text =
       'This is the first sentence with some content. This is the second sentence with more content. ' +

app/src/utils/messageSegmentation.ts

@@ -59,7 +59,18 @@ export function getSegmentDelay(segment: string): number {
 
 // ─── helpers ─────────────────────────────────────────────────────────────────
 
-/** Merge adjacent items that are shorter than MIN_SEGMENT_CHARS. */
+/**
+ * Merge adjacent items that are shorter than MIN_SEGMENT_CHARS.
+ *
+ * Previously only short segments following a prior segment were merged (into
+ * the preceding one). A short *first* segment was left as-is because the
+ * `result.length > 0` guard prevented it from being absorbed. This caused the
+ * first chat bubble to show fewer than MIN_SEGMENT_CHARS characters while all
+ * subsequent short segments were correctly consolidated.
+ *
+ * Fix: after the normal backward-merge pass, check whether the first segment
+ * is still too short and, if so, forward-merge it into the second segment.
+ */
 function mergeTooShort(parts: string[], joiner: string): string[] {
   const result: string[] = [];
   for (const part of parts) {
@@ -69,6 +80,14 @@ function mergeTooShort(parts: string[], joiner: string): string[] {
       result.push(part);
     }
   }
+
+  // If the first segment is still shorter than the minimum, forward-merge it
+  // into the second segment (if one exists) so no leading stub bubble is shown.
+  if (result.length >= 2 && result[0].length < MIN_SEGMENT_CHARS) {
+    result[1] = result[0] + joiner + result[1];
+    result.shift();
+  }
+
   return result;
 }