diff --git a/tools/loop-cost/dist/estimator.js b/tools/loop-cost/dist/estimator.js
index 8e83acf5..90146650 100644
--- a/tools/loop-cost/dist/estimator.js
+++ b/tools/loop-cost/dist/estimator.js
@@ -47,7 +47,11 @@ export function parseInterval(token) {
     if (!m)
         throw new Error(`Invalid cadence interval: ${token}`);
     const unit = m[2];
-    return Number(m[1]) * INTERVAL_MS[unit];
+    const value = Number(m[1]);
+    if (value <= 0) {
+        throw new Error(`Invalid cadence interval: ${token}. The interval value must be greater than zero.`);
+    }
+    return value * INTERVAL_MS[unit];
 }
 /** Runs per day for a single interval like 15m or 1d. */
 export function runsPerDayForInterval(interval) {
diff --git a/tools/loop-cost/src/estimator.ts b/tools/loop-cost/src/estimator.ts
index a7fd91ac..83415846 100644
--- a/tools/loop-cost/src/estimator.ts
+++ b/tools/loop-cost/src/estimator.ts
@@ -113,7 +113,11 @@ export function parseInterval(token: string): number {
   const m = token.match(/^(\d+)([mhd])$/);
   if (!m) throw new Error(`Invalid cadence interval: ${token}`);
   const unit = m[2] as keyof typeof INTERVAL_MS;
-  return Number(m[1]) * INTERVAL_MS[unit];
+  const value = Number(m[1]);
+  if (value <= 0) {
+    throw new Error(`Invalid cadence interval: ${token}. The interval value must be greater than zero.`);
+  }
+  return value * INTERVAL_MS[unit];
 }
 
 /** Runs per day for a single interval like 15m or 1d. */
diff --git a/tools/loop-cost/test/estimator.test.mjs b/tools/loop-cost/test/estimator.test.mjs
index cd65a869..992839cc 100644
--- a/tools/loop-cost/test/estimator.test.mjs
+++ b/tools/loop-cost/test/estimator.test.mjs
@@ -30,6 +30,10 @@ test('runsPerDayForInterval: 1d = 1', () => {
   assert.equal(runsPerDayForInterval('1d'), 1);
 });
 
+test('runsPerDayForInterval rejects a zero cadence', () => {
+  assert.throws(() => runsPerDayForInterval('0m'), /greater than zero/);
+});
+
 test('cadenceToRunsPerDay: range uses fastest by default', () => {
   assert.equal(cadenceToRunsPerDay('5m-15m'), 288);
 });