diff --git a/src/infra/heartbeat-schedule.test.ts b/src/infra/heartbeat-schedule.test.ts
index 9f01e459c25..c379aebc4dc 100644
--- a/src/infra/heartbeat-schedule.test.ts
+++ b/src/infra/heartbeat-schedule.test.ts
@@ -61,6 +61,37 @@ describe("heartbeat schedule helpers", () => {
       }),
     ).toBe(nextDueMs);
   });
+
+  it("falls back to finite schedule values for non-finite numeric inputs", () => {
+    expect(
+      resolveHeartbeatPhaseMs({
+        schedulerSeed: "device-a",
+        agentId: "main",
+        intervalMs: Number.NaN,
+      }),
+    ).toBe(0);
+
+    expect(
+      computeNextHeartbeatPhaseDueMs({
+        nowMs: Number.NaN,
+        intervalMs: Number.NaN,
+        phaseMs: Number.NaN,
+      }),
+    ).toBe(1);
+
+    expect(
+      resolveNextHeartbeatDueMs({
+        nowMs: 10,
+        intervalMs: Number.NaN,
+        phaseMs: Number.NaN,
+        prev: {
+          intervalMs: 1,
+          phaseMs: 0,
+          nextDueMs: 20,
+        },
+      }),
+    ).toBe(20);
+  });
 });
 
 describe("seekNextActivePhaseDueMs", () => {
diff --git a/src/infra/heartbeat-schedule.ts b/src/infra/heartbeat-schedule.ts
index 6df73e1e0f0..153542f2f34 100644
--- a/src/infra/heartbeat-schedule.ts
+++ b/src/infra/heartbeat-schedule.ts
@@ -1,4 +1,9 @@
 import { createHash } from "node:crypto";
+import { resolveIntegerOption } from "./numeric-options.js";
+
+function resolvePositiveIntervalMs(value: number): number {
+  return resolveIntegerOption(value, 1, { min: 1 });
+}
 
 function normalizeModulo(value: number, divisor: number) {
   return ((value % divisor) + divisor) % divisor;
@@ -9,7 +14,7 @@ export function resolveHeartbeatPhaseMs(params: {
   agentId: string;
   intervalMs: number;
 }) {
-  const intervalMs = Math.max(1, Math.floor(params.intervalMs));
+  const intervalMs = resolvePositiveIntervalMs(params.intervalMs);
   const digest = createHash("sha256").update(`${params.schedulerSeed}:${params.agentId}`).digest();
   return digest.readUInt32BE(0) % intervalMs;
 }
@@ -19,9 +24,12 @@ export function computeNextHeartbeatPhaseDueMs(params: {
   intervalMs: number;
   phaseMs: number;
 }) {
-  const intervalMs = Math.max(1, Math.floor(params.intervalMs));
-  const nowMs = Math.floor(params.nowMs);
-  const phaseMs = normalizeModulo(Math.floor(params.phaseMs), intervalMs);
+  const intervalMs = resolvePositiveIntervalMs(params.intervalMs);
+  const nowMs = Number.isFinite(params.nowMs) ? Math.floor(params.nowMs) : 0;
+  const phaseMs = normalizeModulo(
+    Number.isFinite(params.phaseMs) ? Math.floor(params.phaseMs) : 0,
+    intervalMs,
+  );
   const cyclePositionMs = normalizeModulo(nowMs, intervalMs);
   let deltaMs = normalizeModulo(phaseMs - cyclePositionMs, intervalMs);
   if (deltaMs === 0) {
@@ -40,8 +48,11 @@ export function resolveNextHeartbeatDueMs(params: {
     nextDueMs: number;
   };
 }) {
-  const intervalMs = Math.max(1, Math.floor(params.intervalMs));
-  const phaseMs = normalizeModulo(Math.floor(params.phaseMs), intervalMs);
+  const intervalMs = resolvePositiveIntervalMs(params.intervalMs);
+  const phaseMs = normalizeModulo(
+    Number.isFinite(params.phaseMs) ? Math.floor(params.phaseMs) : 0,
+    intervalMs,
+  );
   const prev = params.prev;
   if (
     prev &&
@@ -81,7 +92,7 @@ export function seekNextActivePhaseDueMs(params: {
   if (!isActive) {
     return params.startMs;
   }
-  const intervalMs = Math.max(1, Math.floor(params.intervalMs));
+  const intervalMs = resolvePositiveIntervalMs(params.intervalMs);
   const horizonMs = params.startMs + MAX_SEEK_HORIZON_MS;
   let candidateMs = params.startMs;
   let iterations = 0;
diff --git a/src/infra/numeric-options.ts b/src/infra/numeric-options.ts
index 2907881db37..a3934cbfd04 100644
--- a/src/infra/numeric-options.ts
+++ b/src/infra/numeric-options.ts
@@ -1,3 +1,12 @@
 export function resolveNonNegativeIntegerOption(value: number, fallback: number): number {
   return Number.isFinite(value) ? Math.max(0, Math.floor(value)) : fallback;
 }
+
+export function resolveIntegerOption(
+  value: number,
+  fallback: number,
+  params: { min: number },
+): number {
+  const candidate = Number.isFinite(value) ? value : fallback;
+  return Math.max(params.min, Math.floor(candidate));
+}