diff --git a/frontend/src/lib/cybersigil.ts b/frontend/src/lib/cybersigil.ts
index 44c4590..2d697a2 100644
--- a/frontend/src/lib/cybersigil.ts
+++ b/frontend/src/lib/cybersigil.ts
@@ -146,6 +146,16 @@ export function buildCybersigil(opts: SigilOptions = {}): string {
 		const pts: Pt[] = [[ox, oy], mid, peak, hook, tail];
 		emit(spline(pts, 5.5), 'cs-sig-main');
 
+		// Bifurcation: split at the mid point with a secondary branch
+		if (depth > 0 && rng() < 0.45) {
+			const bAng = ang + (rng() < 0.5 ? 0.8 : -0.8) + rnd(-0.3, 0.3);
+			const bL = L * rnd(0.4, 0.7);
+			const bPeak: Pt = [mid[0] + Math.cos(bAng) * bL, mid[1] + Math.sin(bAng) * bL];
+			const bPts: Pt[] = [mid, bPeak, [bPeak[0] + rnd(-10, 10), bPeak[1] + rnd(10, 20)]];
+			emit(spline(bPts, 4), 'cs-sig-main');
+			if (rng() < 0.3) ornament(bPeak, bAng, 0.6);
+		}
+
 		// terminal spike off the outermost point
 		barb(peak, ang + rnd(-0.4, 0.4), scale * rnd(10, 22));
 
@@ -198,15 +208,31 @@ export function buildCybersigil(opts: SigilOptions = {}): string {
 		if (depth === 0 && rng() < 0.35) ornament(peak, ang, 0.9);
 	};
 
-	// ── Wavering spine: a curve from top to bottom, gently bowing in +x.
-	const spineNodes = 6 + Math.floor(rng() * 3);
+	// ── Harmonic spine: a weighted wave from top to bottom
+	const spineNodes = 8 + Math.floor(rng() * 4);
 	const spinePts: Pt[] = [];
+	const sFreq = rnd(0.8, 1.8);
+	const sAmp = rnd(8, 15);
 	for (let i = 0; i <= spineNodes; i++) {
-		const y = (H * i) / spineNodes;
-		const x = i === 0 || i === spineNodes ? 0 : rnd(0, 14);
+		const t = i / spineNodes;
+		const y = H * t;
+		const x = (i === 0 || i === spineNodes) ? 0 : 
+			Math.sin(t * Math.PI * sFreq) * sAmp + 
+			Math.sin(t * Math.PI * sFreq * 2.3) * (sAmp * 0.4);
 		spinePts.push([x, y]);
 	}
 	emit(spline(spinePts, 5), 'cs-sig-main cs-sig-spine');
+	
+	// ── Vascular Filaments: high-frequency "shiver" paths tracking the spine
+	for (let j = 0; j < 2; j++) {
+		const vPts = spinePts.map(([x, y], i) => {
+			const t = i / spineNodes;
+			const off = Math.sin(t * 22 + rng() * 6) * 1.8;
+			return [x + off + (j === 0 ? -2.5 : 2.5), y] as Pt;
+		});
+		emit(spline(vPts, 6.5), 'cs-sig-vessel');
+	}
+
 	// ── Chromatic Aberration: two faint, offset echoes of the spine
 	emit(spline(spinePts.map(([x, y]) => [x - 1.5, y] as Pt), 5), 'cs-sig-spine-ab cs-sig-spine-ab--1');
 	emit(spline(spinePts.map(([x, y]) => [x + 1.5, y] as Pt), 5), 'cs-sig-spine-ab cs-sig-spine-ab--2');
diff --git a/frontend/src/styles/partials/70-cybersigil.css b/frontend/src/styles/partials/70-cybersigil.css
index 536d612..f7f317d 100644
--- a/frontend/src/styles/partials/70-cybersigil.css
+++ b/frontend/src/styles/partials/70-cybersigil.css
@@ -241,6 +241,13 @@ html.cybersigil body::after {
   opacity: 0.6;
 }
 
+/* Vascular Vessels */
+.cybersigil .cs-sig-vessel {
+  stroke: var(--sky);
+  stroke-width: 0.2;
+  opacity: 0.25;
+}
+
 /* Stroke-weight tiers — heavy growth, hair filaments, prickly barbs, motifs. */
 .cybersigil .cs-sigil .cs-sig-main { stroke-width: 2.8; }
 .cybersigil .cs-sigil .cs-sig-spine {