diff --git a/src/channels/direct-dm-guard-policy.ts b/src/channels/direct-dm-guard-policy.ts
index 3f816b496972..af0c649d4675 100644
--- a/src/channels/direct-dm-guard-policy.ts
+++ b/src/channels/direct-dm-guard-policy.ts
@@ -1,3 +1,5 @@
+import { resolveIntegerOption } from "../shared/number-coercion.js";
+
 export type DirectDmPreCryptoGuardPolicy = {
   allowedKinds: readonly number[];
   maxFutureSkewSec: number;
@@ -21,16 +23,43 @@ export type DirectDmPreCryptoGuardPolicyOverrides = Partial<
 export function createDirectDmPreCryptoGuardPolicy(
   overrides: DirectDmPreCryptoGuardPolicyOverrides = {},
 ): DirectDmPreCryptoGuardPolicy {
+  const defaultMaxFutureSkewSec = 120;
+  const defaultMaxCiphertextBytes = 16 * 1024;
+  const defaultMaxPlaintextBytes = 8 * 1024;
+  const defaultWindowMs = 60_000;
+  const defaultMaxPerSenderPerWindow = 20;
+  const defaultMaxGlobalPerWindow = 200;
+  const defaultMaxTrackedSenderKeys = 4096;
   return {
     allowedKinds: overrides.allowedKinds ?? [4],
-    maxFutureSkewSec: overrides.maxFutureSkewSec ?? 120,
-    maxCiphertextBytes: overrides.maxCiphertextBytes ?? 16 * 1024,
-    maxPlaintextBytes: overrides.maxPlaintextBytes ?? 8 * 1024,
+    maxFutureSkewSec: resolveIntegerOption(overrides.maxFutureSkewSec, defaultMaxFutureSkewSec, {
+      min: 0,
+    }),
+    maxCiphertextBytes: resolveIntegerOption(
+      overrides.maxCiphertextBytes,
+      defaultMaxCiphertextBytes,
+      { min: 1 },
+    ),
+    maxPlaintextBytes: resolveIntegerOption(overrides.maxPlaintextBytes, defaultMaxPlaintextBytes, {
+      min: 1,
+    }),
     rateLimit: {
-      windowMs: overrides.rateLimit?.windowMs ?? 60_000,
-      maxPerSenderPerWindow: overrides.rateLimit?.maxPerSenderPerWindow ?? 20,
-      maxGlobalPerWindow: overrides.rateLimit?.maxGlobalPerWindow ?? 200,
-      maxTrackedSenderKeys: overrides.rateLimit?.maxTrackedSenderKeys ?? 4096,
+      windowMs: resolveIntegerOption(overrides.rateLimit?.windowMs, defaultWindowMs, { min: 1 }),
+      maxPerSenderPerWindow: resolveIntegerOption(
+        overrides.rateLimit?.maxPerSenderPerWindow,
+        defaultMaxPerSenderPerWindow,
+        { min: 1 },
+      ),
+      maxGlobalPerWindow: resolveIntegerOption(
+        overrides.rateLimit?.maxGlobalPerWindow,
+        defaultMaxGlobalPerWindow,
+        { min: 1 },
+      ),
+      maxTrackedSenderKeys: resolveIntegerOption(
+        overrides.rateLimit?.maxTrackedSenderKeys,
+        defaultMaxTrackedSenderKeys,
+        { min: 1 },
+      ),
     },
   };
 }
diff --git a/src/plugin-sdk/direct-dm.test.ts b/src/plugin-sdk/direct-dm.test.ts
index 0457e197796f..cbd89c421863 100644
--- a/src/plugin-sdk/direct-dm.test.ts
+++ b/src/plugin-sdk/direct-dm.test.ts
@@ -186,6 +186,30 @@ describe("plugin-sdk/direct-dm", () => {
     expect(policy.rateLimit.maxGlobalPerWindow).toBe(200);
   });
 
+  it("defaults non-finite shared pre-crypto guard numeric overrides", () => {
+    const policy = createDirectDmPreCryptoGuardPolicy({
+      maxFutureSkewSec: Number.NaN,
+      maxCiphertextBytes: Number.POSITIVE_INFINITY,
+      maxPlaintextBytes: Number.NEGATIVE_INFINITY,
+      rateLimit: {
+        windowMs: Number.NaN,
+        maxPerSenderPerWindow: Number.POSITIVE_INFINITY,
+        maxGlobalPerWindow: Number.NEGATIVE_INFINITY,
+        maxTrackedSenderKeys: Number.NaN,
+      },
+    });
+
+    expect(policy.maxFutureSkewSec).toBe(120);
+    expect(policy.maxCiphertextBytes).toBe(16 * 1024);
+    expect(policy.maxPlaintextBytes).toBe(8 * 1024);
+    expect(policy.rateLimit).toEqual({
+      windowMs: 60_000,
+      maxPerSenderPerWindow: 20,
+      maxGlobalPerWindow: 200,
+      maxTrackedSenderKeys: 4096,
+    });
+  });
+
   it("dispatches direct DMs through the standard route/session/reply pipeline", async () => {
     const { recordInboundSession, dispatchReplyWithBufferedBlockDispatcher, runtime } =
       createDirectDmRuntime();