diff --git a/internal/exporter/html.go b/internal/exporter/html.go
index 752aee9..292ed2e 100644
--- a/internal/exporter/html.go
+++ b/internal/exporter/html.go
@@ -1,7 +1,6 @@
 package exporter
 
 import (
-	"encoding/json"
 	"fmt"
 	"html"
 	"html/template"
@@ -18,7 +17,6 @@ type htmlData struct {
 	Format     string
 	Iterations []htmlIteration
 	Summary    htmlSummary
-	DataJSON   template.JS
 }
 
 type htmlIteration struct {
@@ -117,9 +115,6 @@ func buildHTMLData(t *trace.Trace) htmlData {
 		}
 	}
 
-	jsonBytes, _ := json.Marshal(d.Iterations)
-	d.DataJSON = template.JS(string(jsonBytes))
-
 	return d
 }
 
diff --git a/internal/exporter/html_test.go b/internal/exporter/html_test.go
new file mode 100644
index 0000000..7fc392a
--- /dev/null
+++ b/internal/exporter/html_test.go
@@ -0,0 +1,123 @@
+package exporter
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/loop-eng/looprelay/internal/trace"
+)
+
+func sampleTrace() *trace.Trace {
+	tr := trace.New([]trace.Iteration{
+		{
+			Number: 1,
+			Phase:  trace.PhaseAct,
+			Action: trace.Action{
+				Type:   "Edit",
+				Target: "src/main.go",
+				Diff:   "+func main() {}\n-func Main() {}",
+			},
+			Tokens:     trace.TokenUsage{InputTokens: 100, OutputTokens: 50},
+			CostUSD:    0.0123,
+			Context:    trace.ContextState{FillPct: 42, Compactions: 1},
+			DurationMs: 1200,
+		},
+		{
+			Number: 2,
+			Phase:  trace.PhaseVerify,
+			Verification: &trace.Verification{
+				Status: "success",
+				Output: "ok <script>alert(1)</script>",
+			},
+			Tokens:  trace.TokenUsage{InputTokens: 80, OutputTokens: 20},
+			CostUSD: 0.0045,
+			Context: trace.ContextState{FillPct: 55, Compactions: 1},
+		},
+	})
+	tr.SourceFile = "demo.ltf"
+	tr.SessionID = "sess-42"
+	tr.Agent = "claude"
+	tr.SourceFormat = "ltf"
+	return tr
+}
+
+func TestBuildHTMLData_NoDataJSONField(t *testing.T) {
+	d := buildHTMLData(sampleTrace())
+	if d.Title == "" {
+		t.Fatal("expected title")
+	}
+	if len(d.Iterations) != 2 {
+		t.Fatalf("expected 2 iterations, got %d", len(d.Iterations))
+	}
+	if d.Summary.TotalIterations != 2 {
+		t.Fatalf("expected summary total 2, got %d", d.Summary.TotalIterations)
+	}
+	// Regression for #14: DataJSON was computed via json.Marshal but never
+	// referenced in the template — the field must stay removed.
+	// (Compile-time: htmlData no longer has DataJSON.)
+}
+
+func TestExportHTML_RendersReplayWithoutUnusedJSON(t *testing.T) {
+	dir := t.TempDir()
+	out := filepath.Join(dir, "replay.html")
+	if err := ExportHTML(sampleTrace(), out); err != nil {
+		t.Fatalf("ExportHTML: %v", err)
+	}
+
+	raw, err := os.ReadFile(out)
+	if err != nil {
+		t.Fatalf("read output: %v", err)
+	}
+	html := string(raw)
+
+	for _, want := range []string{
+		"LoopRelay",
+		"sess-42",
+		"claude",
+		"Iteration 1",
+		"Iteration 2",
+		"src/main.go",
+		"diff-add",
+		"status-pass",
+		"ok &lt;script&gt;alert(1)&lt;/script&gt;",
+	} {
+		if !strings.Contains(html, want) {
+			t.Errorf("exported HTML missing %q", want)
+		}
+	}
+
+	// Ensure we did not reintroduce a dumped iterations JSON blob for JS.
+	if strings.Contains(html, `"ActionType"`) || strings.Contains(html, `"PhaseClass"`) {
+		t.Error("exported HTML unexpectedly embeds marshaled iteration JSON (DataJSON dead code)")
+	}
+	if strings.Contains(html, "<script>alert(1)</script>") {
+		t.Error("verification output was not HTML-escaped")
+	}
+}
+
+func TestPhaseAndStatusClass(t *testing.T) {
+	if got := phaseClass("act"); got != "phase-act" {
+		t.Errorf("phaseClass(act)=%q", got)
+	}
+	if got := phaseClass("unknown"); got != "phase-other" {
+		t.Errorf("phaseClass(unknown)=%q", got)
+	}
+	if got := statusClass("success"); got != "status-pass" {
+		t.Errorf("statusClass(success)=%q", got)
+	}
+	if got := statusClass("fail"); got != "status-fail" {
+		t.Errorf("statusClass(fail)=%q", got)
+	}
+}
+
+func TestRenderDiffHTML(t *testing.T) {
+	got := renderDiffHTML("+added\n-removed\n context")
+	if !strings.Contains(got, `class="diff-add"`) || !strings.Contains(got, "+added") {
+		t.Fatalf("missing add span: %s", got)
+	}
+	if !strings.Contains(got, `class="diff-del"`) || !strings.Contains(got, "-removed") {
+		t.Fatalf("missing del span: %s", got)
+	}
+}