diff --git a/lib/components/SchematicViewer.tsx b/lib/components/SchematicViewer.tsx
index ab4fd20..8def5f7 100644
--- a/lib/components/SchematicViewer.tsx
+++ b/lib/components/SchematicViewer.tsx
@@ -6,6 +6,7 @@ import { su } from "@tscircuit/soup-util"
 import { useChangeSchematicComponentLocationsInSvg } from "lib/hooks/useChangeSchematicComponentLocationsInSvg"
 import { useChangeSchematicTracesForMovedComponents } from "lib/hooks/useChangeSchematicTracesForMovedComponents"
 import { useSchematicGroupsOverlay } from "lib/hooks/useSchematicGroupsOverlay"
+import { useSchematicTraceHover } from "lib/hooks/useSchematicTraceHover"
 import { enableDebug } from "lib/utils/debug"
 import { useCallback, useEffect, useMemo, useRef, useState } from "react"
 import {
@@ -353,6 +354,13 @@ export const SchematicViewer = ({
     showGroups: showSchematicGroups && !disableGroups,
   })
 
+  // Highlight same-net traces on hover
+  useSchematicTraceHover({
+    svgDivRef,
+    circuitJson,
+    circuitJsonKey,
+  })
+
   // keep the latest touch handler without re-rendering the svg div
   const handleComponentTouchStartRef = useRef(handleComponentTouchStart)
   useEffect(() => {
diff --git a/lib/hooks/useSchematicTraceHover.ts b/lib/hooks/useSchematicTraceHover.ts
new file mode 100644
index 0000000..1e6cfae
--- /dev/null
+++ b/lib/hooks/useSchematicTraceHover.ts
@@ -0,0 +1,263 @@
+import { useEffect } from "react"
+import type { CircuitJson } from "circuit-json"
+
+interface UseSchematicTraceHoverOptions {
+  svgDivRef: React.RefObject<HTMLDivElement | null>
+  circuitJson: CircuitJson
+  circuitJsonKey: string
+}
+
+const HOVER_CLASS = "schematic-trace-hover-highlight"
+const DIM_CLASS = "schematic-trace-hover-dim"
+
+/**
+ * Builds a map from schematic_trace_id → net group key.
+ *
+ * Priority order:
+ * 1. subcircuit_connectivity_map_key already on the trace
+ * 2. Derived from source_port connectivity keys via schematic_port → source_port chain
+ * 3. Geometric adjacency fallback (shared endpoints between traces)
+ */
+function buildTraceGroupMap(circuitJson: CircuitJson): Map<string, string> {
+  const traceGroupMap = new Map<string, string>()
+
+  // Index source_ports by id
+  const sourcePortById = new Map<string, any>()
+  for (const el of circuitJson as any[]) {
+    if (el.type === "source_port" && el.source_port_id) {
+      sourcePortById.set(el.source_port_id, el)
+    }
+  }
+
+  // Index schematic_ports by id, map to source_port
+  const schematicPortById = new Map<string, any>()
+  for (const el of circuitJson as any[]) {
+    if (el.type === "schematic_port" && el.schematic_port_id) {
+      schematicPortById.set(el.schematic_port_id, el)
+    }
+  }
+
+  // Build port center → net key map from source_port connectivity keys
+  const portCenterToNetKey = new Map<string, string>()
+  for (const schPort of schematicPortById.values()) {
+    const srcPort = sourcePortById.get(schPort.source_port_id)
+    const netKey =
+      srcPort?.subcircuit_connectivity_map_key ??
+      srcPort?.net_id ??
+      srcPort?.source_net_id
+    if (netKey && schPort.center) {
+      const key = `${schPort.center.x},${schPort.center.y}`
+      portCenterToNetKey.set(key, netKey)
+    }
+  }
+
+  // Index source_traces by id for connectivity key lookup
+  const sourceTraceByConnKey = new Map<string, string>()
+  for (const el of circuitJson as any[]) {
+    if (el.type === "source_trace" && el.subcircuit_connectivity_map_key) {
+      sourceTraceByConnKey.set(
+        el.source_trace_id,
+        el.subcircuit_connectivity_map_key,
+      )
+    }
+  }
+
+  // Collect all schematic traces
+  const schematicTraces: any[] = []
+  for (const el of circuitJson as any[]) {
+    if (el.type === "schematic_trace" && el.schematic_trace_id) {
+      schematicTraces.push(el)
+    }
+  }
+
+  // Assign net keys to traces
+  for (const trace of schematicTraces) {
+    const id = trace.schematic_trace_id
+
+    // 1. Already has a connectivity key
+    if (trace.subcircuit_connectivity_map_key) {
+      traceGroupMap.set(id, trace.subcircuit_connectivity_map_key)
+      continue
+    }
+
+    // 2. Derive from port centers
+    let netKey: string | undefined
+    const allPoints: Array<{ x: number; y: number }> = []
+    for (const edge of trace.edges ?? []) {
+      if (edge.from) allPoints.push(edge.from)
+      if (edge.to) allPoints.push(edge.to)
+    }
+    for (const pt of allPoints) {
+      const k = `${pt.x},${pt.y}`
+      if (portCenterToNetKey.has(k)) {
+        netKey = portCenterToNetKey.get(k)
+        break
+      }
+    }
+
+    if (netKey) {
+      traceGroupMap.set(id, netKey)
+    }
+  }
+
+  // 3. Geometric adjacency fallback: union-find for traces sharing endpoints
+  // Build endpoint → trace IDs map
+  const endpointToTraces = new Map<string, string[]>()
+  for (const trace of schematicTraces) {
+    const id = trace.schematic_trace_id
+    const points = new Set<string>()
+    for (const edge of trace.edges ?? []) {
+      if (edge.from) points.add(`${edge.from.x},${edge.from.y}`)
+      if (edge.to) points.add(`${edge.to.x},${edge.to.y}`)
+    }
+    for (const junction of trace.junctions ?? []) {
+      points.add(`${junction.x},${junction.y}`)
+    }
+    for (const pt of points) {
+      if (!endpointToTraces.has(pt)) endpointToTraces.set(pt, [])
+      endpointToTraces.get(pt)!.push(id)
+    }
+  }
+
+  // Union-find
+  const parent = new Map<string, string>()
+  const find = (x: string): string => {
+    if (!parent.has(x)) parent.set(x, x)
+    if (parent.get(x) !== x) parent.set(x, find(parent.get(x)!))
+    return parent.get(x)!
+  }
+  const union = (a: string, b: string) => {
+    parent.set(find(a), find(b))
+  }
+
+  for (const traces of endpointToTraces.values()) {
+    for (let i = 1; i < traces.length; i++) {
+      union(traces[0], traces[i])
+    }
+  }
+
+  // Assign fallback group keys to traces without a net key
+  for (const trace of schematicTraces) {
+    const id = trace.schematic_trace_id
+    if (!traceGroupMap.has(id)) {
+      const root = find(id)
+      traceGroupMap.set(id, `schematic_trace_group_${root}`)
+    }
+  }
+
+  return traceGroupMap
+}
+
+export const useSchematicTraceHover = ({
+  svgDivRef,
+  circuitJson,
+  circuitJsonKey,
+}: UseSchematicTraceHoverOptions) => {
+  useEffect(() => {
+    const container = svgDivRef.current
+    if (!container) return
+
+    const traceGroupMap = buildTraceGroupMap(circuitJson)
+
+    // Build reverse map: groupKey → [traceId, ...]
+    const groupToTraces = new Map<string, string[]>()
+    for (const [traceId, groupKey] of traceGroupMap) {
+      if (!groupToTraces.has(groupKey)) groupToTraces.set(groupKey, [])
+      groupToTraces.get(groupKey)!.push(traceId)
+    }
+
+    const svg = container.querySelector("svg")
+    if (!svg) return
+
+    // Inject hover CSS once
+    const styleId = "schematic-trace-hover-style"
+    if (!svg.querySelector(`#${styleId}`)) {
+      const style = document.createElementNS(
+        "http://www.w3.org/2000/svg",
+        "style",
+      )
+      style.id = styleId
+      style.textContent = `
+        .${HOVER_CLASS} path,
+        .${HOVER_CLASS} line,
+        .${HOVER_CLASS} polyline,
+        .${HOVER_CLASS} circle {
+          stroke: #f5a623 !important;
+          stroke-width: 2.5 !important;
+          filter: drop-shadow(0 0 3px rgba(245, 166, 35, 0.6));
+        }
+        .${DIM_CLASS} {
+          opacity: 0.3;
+        }
+      `
+      svg.insertBefore(style, svg.firstChild)
+    }
+
+    const cleanups: Array<() => void> = []
+
+    for (const [traceId, groupKey] of traceGroupMap) {
+      const el = svg.querySelector(
+        `[data-schematic-trace-id="${traceId}"]`,
+      ) as SVGElement | null
+      if (!el) continue
+
+      el.style.cursor = "pointer"
+
+      const siblingIds = groupToTraces.get(groupKey) ?? []
+
+      const onEnter = () => {
+        // Highlight all traces in the same group
+        for (const sid of siblingIds) {
+          const sibling = svg.querySelector(
+            `[data-schematic-trace-id="${sid}"]`,
+          )
+          sibling?.classList.add(HOVER_CLASS)
+        }
+        // Dim all traces NOT in this group
+        for (const [otherId, otherGroup] of traceGroupMap) {
+          if (otherGroup !== groupKey) {
+            const other = svg.querySelector(
+              `[data-schematic-trace-id="${otherId}"]`,
+            )
+            other?.classList.add(DIM_CLASS)
+          }
+        }
+      }
+
+      const onLeave = () => {
+        for (const sid of siblingIds) {
+          const sibling = svg.querySelector(
+            `[data-schematic-trace-id="${sid}"]`,
+          )
+          sibling?.classList.remove(HOVER_CLASS)
+        }
+        for (const [otherId] of traceGroupMap) {
+          const other = svg.querySelector(
+            `[data-schematic-trace-id="${otherId}"]`,
+          )
+          other?.classList.remove(DIM_CLASS)
+        }
+      }
+
+      el.addEventListener("mouseenter", onEnter)
+      el.addEventListener("mouseleave", onLeave)
+      cleanups.push(() => {
+        el.removeEventListener("mouseenter", onEnter)
+        el.removeEventListener("mouseleave", onLeave)
+        el.style.cursor = ""
+      })
+    }
+
+    return () => {
+      for (const cleanup of cleanups) cleanup()
+      // Remove injected style
+      svg.querySelector(`#${styleId}`)?.remove()
+      // Remove any lingering classes
+      for (const el of svg.querySelectorAll(
+        `.${HOVER_CLASS}, .${DIM_CLASS}`,
+      )) {
+        el.classList.remove(HOVER_CLASS, DIM_CLASS)
+      }
+    }
+  }, [svgDivRef, circuitJsonKey, circuitJson])
+}