diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc8e31e..4842273 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,16 @@
 # Changelog
 
+## Unreleased
+
+- **`checkPolicy` allowlists now fail closed.** When a policy set `allowedCodes`
+  or `allowedCustomers`, a request that omitted `metadata.code` /
+  `metadata.customer` (or sent an empty string) skipped the allowlist and was
+  approved if the amount and budget checks passed. Such a request is now denied
+  with `CODE_NOT_ALLOWED` / `CUSTOMER_NOT_ALLOWED`. **Behavior change** for
+  callers that set an allowlist but do not send the field: send it, or drop the
+  allowlist. Policies without allowlists are unaffected. Reported in
+  [#8](https://github.com/goodmeta/agent-verifier/issues/8).
+
 ## 0.6.1
 
 - **`requiredConstraints` now reaches `verifyPaymentChain`.** 0.6.0 added it to
diff --git a/README.md b/README.md
index b907179..d186547 100644
--- a/README.md
+++ b/README.md
@@ -66,10 +66,19 @@ const policy: SpendingPolicy = {
 checkPolicy(policy, {
   agentId: "billing-agent",
   amount: 4_500,
+  metadata: { code: "api_calls" },
   idempotencyKey: "tx-1",
 })
 // → { approved: true, remaining: { budget: 15500, period: "monthly" } }
 
+// ❌ no code, but the policy only allows listed codes (allowlists fail closed)
+checkPolicy(policy, {
+  agentId: "billing-agent",
+  amount: 4_500,
+  idempotencyKey: "tx-3",
+})
+// → { approved: false, reason: "CODE_NOT_ALLOWED", detail: "No code given; this policy only allows listed codes" }
+
 // ❌ over per-event limit
 checkPolicy(policy, {
   agentId: "billing-agent",
diff --git a/src/policy.ts b/src/policy.ts
index a1ace7f..e6b3246 100644
--- a/src/policy.ts
+++ b/src/policy.ts
@@ -88,8 +88,16 @@ export function checkPolicy(
     };
   }
 
-  // Code allowlist
-  if (metadata?.code && constraints.allowedCodes?.length) {
+  // Code allowlist. Fails closed: when the policy lists allowed codes, a request
+  // that omits `metadata.code` (or sends "") is denied, not waved through.
+  if (constraints.allowedCodes?.length) {
+    if (!metadata?.code) {
+      return {
+        approved: false,
+        reason: "CODE_NOT_ALLOWED",
+        detail: "No code given; this policy only allows listed codes",
+      };
+    }
     if (!constraints.allowedCodes.includes(metadata.code)) {
       return {
         approved: false,
@@ -108,8 +116,15 @@ export function checkPolicy(
     };
   }
 
-  // Customer allowlist
-  if (metadata?.customer && constraints.allowedCustomers?.length) {
+  // Customer allowlist. Fails closed, as the code allowlist does.
+  if (constraints.allowedCustomers?.length) {
+    if (!metadata?.customer) {
+      return {
+        approved: false,
+        reason: "CUSTOMER_NOT_ALLOWED",
+        detail: "No customer given; this policy only allows listed customers",
+      };
+    }
     if (!constraints.allowedCustomers.includes(metadata.customer)) {
       return {
         approved: false,
diff --git a/test/policy.test.ts b/test/policy.test.ts
index 0960caa..80ba4b5 100644
--- a/test/policy.test.ts
+++ b/test/policy.test.ts
@@ -12,19 +12,19 @@ const req = (amount: unknown, extra: Record<string, unknown> = {}) =>
   ({ agentId: "billing-agent", amount, idempotencyKey: "k", ...extra }) as never;
 
 test("approves a valid in-budget request and reports remaining", () => {
-  const r = checkPolicy(policy, req(4_500));
+  const r = checkPolicy(policy, req(4_500, { metadata: { code: "api_calls" } }));
   assert.equal(r.approved, true);
   assert.deepEqual(r.remaining, { budget: 15_500, period: "monthly" });
 });
 
 test("denies over per-event max", () => {
-  const r = checkPolicy(policy, req(6_000));
+  const r = checkPolicy(policy, req(6_000, { metadata: { code: "api_calls" } }));
   assert.equal(r.approved, false);
   assert.equal(r.reason, "AMOUNT_EXCEEDED");
 });
 
 test("denies when amount exceeds remaining budget (currentSpend applied)", () => {
-  const r = checkPolicy(policy, req(3_000), 18_000);
+  const r = checkPolicy(policy, req(3_000, { metadata: { code: "api_calls" } }), 18_000);
   assert.equal(r.approved, false);
   assert.equal(r.reason, "BUDGET_EXCEEDED");
 });
@@ -36,7 +36,7 @@ test("denies a code not in the allowlist", () => {
 });
 
 test("denies a blocked customer", () => {
-  const r = checkPolicy(policy, req(1_000, { metadata: { customer: "acme" } }));
+  const r = checkPolicy(policy, req(1_000, { metadata: { code: "api_calls", customer: "acme" } }));
   assert.equal(r.approved, false);
   assert.equal(r.reason, "CUSTOMER_BLOCKED");
 });
@@ -59,3 +59,36 @@ test("rejects a malformed request shape (missing agentId)", () => {
   assert.equal(r.approved, false);
   assert.equal(r.reason, "INVALID_REQUEST");
 });
+
+// #8: an allowlist used to be skipped when the request omitted the field, so a
+// request with no code (or no customer) cleared a policy that restricts it.
+test("denies a request with no code when the policy has a code allowlist", () => {
+  for (const extra of [{}, { metadata: {} }, { metadata: { code: "" } }]) {
+    const r = checkPolicy(policy, req(1_000, extra));
+    assert.equal(r.approved, false);
+    assert.equal(r.reason, "CODE_NOT_ALLOWED");
+  }
+});
+
+const customerScoped: SpendingPolicy = {
+  ...policy,
+  constraints: { maxPerEvent: 5_000, allowedCustomers: ["globex"] },
+};
+
+test("denies a request with no customer when the policy has a customer allowlist", () => {
+  for (const extra of [{}, { metadata: {} }, { metadata: { customer: "" } }]) {
+    const r = checkPolicy(customerScoped, req(1_000, extra));
+    assert.equal(r.approved, false);
+    assert.equal(r.reason, "CUSTOMER_NOT_ALLOWED");
+  }
+});
+
+test("still approves a listed customer, and an unlisted one is still denied", () => {
+  assert.equal(checkPolicy(customerScoped, req(1_000, { metadata: { customer: "globex" } })).approved, true);
+  assert.equal(checkPolicy(customerScoped, req(1_000, { metadata: { customer: "acme" } })).reason, "CUSTOMER_NOT_ALLOWED");
+});
+
+test("a policy with no allowlists does not require code or customer", () => {
+  const open: SpendingPolicy = { ...policy, constraints: { maxPerEvent: 5_000 } };
+  assert.equal(checkPolicy(open, req(1_000)).approved, true);
+});