diff --git a/internal/ingestion/component/chunker/token_batch1_test.go b/internal/ingestion/component/chunker/token_batch1_test.go
index a9f33ed792..0c79927f9c 100644
--- a/internal/ingestion/component/chunker/token_batch1_test.go
+++ b/internal/ingestion/component/chunker/token_batch1_test.go
@@ -81,20 +81,36 @@ func TestMergeByTokenSizeFromJSON_OverlapStripsTags(t *testing.T) {
 // threshold. Out-of-range values must not panic and must behave identically to
 // their clamped-in-range equivalent (150 == 100, -5 == 0, and the same for
 // huge magnitudes that would otherwise overflow the float->int slice index).
-func TestMergeByTokenSizeFromJSON_ClampsOverlappedPct(t *testing.T) {
-	items := [][]schema.ChunkDoc{
+// clampOverlapFixture returns a fresh input for mergeByTokenSizeFromJSON.
+// A new slice must be built per invocation: mergeByTokenSizeFromJSON mutates
+// its perItem argument in place (token.go: perItem[idx] = merged) and returns
+// the same backing array. Reusing one fixture across calls lets later calls
+// reprocess already-merged chunks, and — because the result aliases the input
+// — silently overwrites earlier results, making the clamp assertions vacuous
+// (see code review on PR #17396).
+//
+// The first chunk carries TKNums 130 — just above chunk_token_size 128 — so
+// the two clamp directions are both exercised: at pct=0 (threshold 128) the
+// chunks stay split, while an UNCLAMPED negative pct raises the threshold
+// (e.g. -5 -> 134.4) and merges them. With TKNums=100 both cases merge
+// identically, so the lower-clamp assertions would pass even if the clamp
+// were removed (review: coderabbitai on PR #17416).
+func clampOverlapFixture() [][]schema.ChunkDoc {
+	return [][]schema.ChunkDoc{
 		{
-			{Text: strings.Repeat("word ", 20), DocType: "text", CKType: "text", TKNums: intPtr(100)},
+			{Text: strings.Repeat("word ", 20), DocType: "text", CKType: "text", TKNums: intPtr(130)},
 			{Text: "body", DocType: "text", CKType: "text", TKNums: intPtr(5)},
 		},
 	}
+}
 
-	at100 := mergeByTokenSizeFromJSON(items, 128, 100)
+func TestMergeByTokenSizeFromJSON_ClampsOverlappedPct(t *testing.T) {
+	at100 := mergeByTokenSizeFromJSON(clampOverlapFixture(), 128, 100)
 	if at100 == nil || len(at100) == 0 {
 		t.Fatalf("overlappedPct=100: nil/empty result")
 	}
-	at150 := mergeByTokenSizeFromJSON(items, 128, 150)
-	atHuge := mergeByTokenSizeFromJSON(items, 128, 1e300)
+	at150 := mergeByTokenSizeFromJSON(clampOverlapFixture(), 128, 150)
+	atHuge := mergeByTokenSizeFromJSON(clampOverlapFixture(), 128, 1e300)
 	if !reflect.DeepEqual(at100, at150) {
 		t.Errorf("overlappedPct=150 should clamp to 100; output differs from 100")
 	}
@@ -102,12 +118,12 @@ func TestMergeByTokenSizeFromJSON_ClampsOverlappedPct(t *testing.T) {
 		t.Errorf("overlappedPct=1e300 should clamp to 100; output differs from 100")
 	}
 
-	at0 := mergeByTokenSizeFromJSON(items, 128, 0)
+	at0 := mergeByTokenSizeFromJSON(clampOverlapFixture(), 128, 0)
 	if at0 == nil || len(at0) == 0 {
 		t.Fatalf("overlappedPct=0: nil/empty result")
 	}
-	atNeg := mergeByTokenSizeFromJSON(items, 128, -5)
-	atNegHuge := mergeByTokenSizeFromJSON(items, 128, -1e300)
+	atNeg := mergeByTokenSizeFromJSON(clampOverlapFixture(), 128, -5)
+	atNegHuge := mergeByTokenSizeFromJSON(clampOverlapFixture(), 128, -1e300)
 	if !reflect.DeepEqual(at0, atNeg) {
 		t.Errorf("overlappedPct=-5 should clamp to 0; output differs from 0")
 	}