diff --git a/.changeset/fix-admin-meta-access.md b/.changeset/fix-admin-meta-access.md
new file mode 100644
index 00000000000..4698edbb3eb
--- /dev/null
+++ b/.changeset/fix-admin-meta-access.md
@@ -0,0 +1,5 @@
+---
+'@keystone-6/core': patch
+---
+
+Fixes `ui.isAccessAllowed` when `undefined`, to prevent access to the `adminMeta` GraphQL query, akin to the behaviour for the default AdminUI `pageMiddleware`
diff --git a/packages/core/src/admin-ui/system/generateAdminUI.ts b/packages/core/src/admin-ui/system/generateAdminUI.ts
index 1c22ccd8d8f..44ab0292a00 100644
--- a/packages/core/src/admin-ui/system/generateAdminUI.ts
+++ b/packages/core/src/admin-ui/system/generateAdminUI.ts
@@ -7,7 +7,7 @@ import { Entry, walk as _walk } from '@nodelib/fs.walk';
 import type { KeystoneConfig, AdminFileToWrite } from '../../types';
 import { writeAdminFiles } from '../templates';
 import { serializePathForImport } from '../utils/serializePathForImport';
-import type { AdminMetaRootVal } from './createAdminMeta';
+import type { AdminMetaRootVal } from '../../lib/create-admin-meta';
 
 const walk = promisify(_walk);
 
diff --git a/packages/core/src/admin-ui/system/index.ts b/packages/core/src/admin-ui/system/index.ts
index 73ca4fe2e14..40f22ecb86e 100644
--- a/packages/core/src/admin-ui/system/index.ts
+++ b/packages/core/src/admin-ui/system/index.ts
@@ -1,2 +1 @@
 export { generateAdminUI } from './generateAdminUI';
-export { KeystoneMeta } from './adminMetaSchema';
diff --git a/packages/core/src/admin-ui/templates/app.ts b/packages/core/src/admin-ui/templates/app.ts
index 9667af1134a..90ede20ae2c 100644
--- a/packages/core/src/admin-ui/templates/app.ts
+++ b/packages/core/src/admin-ui/templates/app.ts
@@ -12,7 +12,7 @@ import {
   Kind,
 } from 'graphql';
 import { staticAdminMetaQuery, StaticAdminMetaQuery } from '../admin-meta-graphql';
-import type { AdminMetaRootVal } from '../system/createAdminMeta';
+import type { AdminMetaRootVal } from '../../lib/create-admin-meta';
 
 type AppTemplateOptions = { configFileExists: boolean };
 
diff --git a/packages/core/src/admin-ui/templates/index.ts b/packages/core/src/admin-ui/templates/index.ts
index d6e5164083b..05bfa8e9ff5 100644
--- a/packages/core/src/admin-ui/templates/index.ts
+++ b/packages/core/src/admin-ui/templates/index.ts
@@ -1,7 +1,7 @@
 import * as Path from 'path';
 import type { GraphQLSchema } from 'graphql';
 import type { KeystoneConfig, AdminFileToWrite } from '../../types';
-import type { AdminMetaRootVal } from '../system/createAdminMeta';
+import type { AdminMetaRootVal } from '../../lib/create-admin-meta';
 import { appTemplate } from './app';
 import { homeTemplate } from './home';
 import { listTemplate } from './list';
diff --git a/packages/core/src/fields/types/relationship/index.ts b/packages/core/src/fields/types/relationship/index.ts
index 6d143ea7abb..c8e36c26233 100644
--- a/packages/core/src/fields/types/relationship/index.ts
+++ b/packages/core/src/fields/types/relationship/index.ts
@@ -1,6 +1,6 @@
 import { BaseListTypeInfo, FieldTypeFunc, CommonFieldConfig, fieldType } from '../../../types';
 import { graphql } from '../../..';
-import { getAdminMetaForRelationshipField } from '../../../admin-ui/system/createAdminMeta';
+import { getAdminMetaForRelationshipField } from '../../../lib/create-admin-meta';
 
 // This is the default display mode for Relationships
 type SelectDisplayConfig = {
diff --git a/packages/core/src/admin-ui/system/adminMetaSchema.ts b/packages/core/src/lib/admin-meta-resolver.ts
similarity index 95%
rename from packages/core/src/admin-ui/system/adminMetaSchema.ts
rename to packages/core/src/lib/admin-meta-resolver.ts
index 0f2800dc309..672a606e1b6 100644
--- a/packages/core/src/admin-ui/system/adminMetaSchema.ts
+++ b/packages/core/src/lib/admin-meta-resolver.ts
@@ -7,7 +7,7 @@ import type {
   ListMetaRootVal,
   AdminMetaRootVal,
   FieldGroupMeta,
-} from './createAdminMeta';
+} from './create-admin-meta';
 
 type Context = KeystoneContext | { isAdminUIBuildProcess: true };
 
@@ -228,19 +228,25 @@ const adminMeta = graphql.object<AdminMetaRootVal>()({
   },
 });
 
+function defaultIsAccessAllowed({ session, sessionStrategy }: KeystoneContext) {
+  if (!sessionStrategy) return true;
+  return session !== undefined;
+}
+
 export const KeystoneMeta = graphql.object<{ adminMeta: AdminMetaRootVal }>()({
   name: 'KeystoneMeta',
   fields: {
     adminMeta: graphql.field({
       type: graphql.nonNull(adminMeta),
       resolve({ adminMeta }, args, context) {
-        if ('isAdminUIBuildProcess' in context || adminMeta.isAccessAllowed === undefined) {
+        if ('isAdminUIBuildProcess' in context) {
           return adminMeta;
         }
-        return Promise.resolve(adminMeta.isAccessAllowed(context)).then(isAllowed => {
-          if (isAllowed) {
-            return adminMeta;
-          }
+
+        const isAccessAllowed = adminMeta?.isAccessAllowed ?? defaultIsAccessAllowed;
+        return Promise.resolve(isAccessAllowed(context)).then(isAllowed => {
+          if (isAllowed) return adminMeta;
+
           // TODO: ughhhhhh, we really need to talk about errors.
           // mostly unrelated to above: error or return null here(+ make field nullable)?s
           throw new Error('Access denied');
diff --git a/packages/core/src/admin-ui/system/createAdminMeta.ts b/packages/core/src/lib/create-admin-meta.ts
similarity index 98%
rename from packages/core/src/admin-ui/system/createAdminMeta.ts
rename to packages/core/src/lib/create-admin-meta.ts
index f15051fdd15..8b02b13206b 100644
--- a/packages/core/src/admin-ui/system/createAdminMeta.ts
+++ b/packages/core/src/lib/create-admin-meta.ts
@@ -8,9 +8,10 @@ import type {
   JSONValue,
   MaybeItemFunction,
 } from '../../types';
-import { humanize } from '../../lib/utils';
-import type { InitialisedList } from '../../lib/core/initialise-lists';
-import type { FilterOrderArgs } from '../../types/config/fields';
+import type { FilterOrderArgs } from '../types/config/fields';
+
+import { humanize } from './utils';
+import type { InitialisedList } from './core/initialise-lists';
 
 type ContextFunction<Return> = (context: KeystoneContext) => MaybePromise<Return>;
 
diff --git a/packages/core/src/lib/createGraphQLSchema.ts b/packages/core/src/lib/createGraphQLSchema.ts
index b38079f924a..685fae60af9 100644
--- a/packages/core/src/lib/createGraphQLSchema.ts
+++ b/packages/core/src/lib/createGraphQLSchema.ts
@@ -1,9 +1,9 @@
 import { GraphQLNamedType, GraphQLSchema } from 'graphql';
 
-import type { KeystoneConfig } from '../types';
-import { KeystoneMeta } from '../admin-ui/system/adminMetaSchema';
 import { graphql } from '../types/schema';
-import type { AdminMetaRootVal } from '../admin-ui/system/createAdminMeta';
+import type { KeystoneConfig } from '../types';
+import { KeystoneMeta } from './admin-meta-resolver';
+import type { AdminMetaRootVal } from './create-admin-meta';
 import type { InitialisedList } from './core/initialise-lists';
 
 import { getMutationsForList } from './core/mutations';
diff --git a/packages/core/src/lib/createSystem.ts b/packages/core/src/lib/createSystem.ts
index 9b9d1d19221..f61226c74e2 100644
--- a/packages/core/src/lib/createSystem.ts
+++ b/packages/core/src/lib/createSystem.ts
@@ -2,9 +2,9 @@ import { randomBytes } from 'node:crypto';
 import pLimit from 'p-limit';
 import type { FieldData, KeystoneConfig } from '../types';
 
-import { createAdminMeta } from '../admin-ui/system/createAdminMeta';
 import type { PrismaModule } from '../artifacts';
 import { allowAll } from '../access';
+import { createAdminMeta } from './create-admin-meta';
 import { createGraphQLSchema } from './createGraphQLSchema';
 import { createContext } from './context/createContext';
 import { initialiseLists, InitialisedList } from './core/initialise-lists';
diff --git a/packages/core/src/scripts/dev.ts b/packages/core/src/scripts/dev.ts
index 60408ed6c8b..b4476e3f922 100644
--- a/packages/core/src/scripts/dev.ts
+++ b/packages/core/src/scripts/dev.ts
@@ -25,7 +25,7 @@ import {
 import type { KeystoneConfig } from '../types';
 import { initialiseLists } from '../lib/core/initialise-lists';
 import { printPrismaSchema } from '../lib/core/prisma-schema-printer';
-import type { AdminMetaRootVal } from '../admin-ui/system/createAdminMeta';
+import type { AdminMetaRootVal } from '../lib/create-admin-meta';
 import { pkgDir } from '../pkg-dir';
 import { ExitError } from './utils';
 import type { Flags } from './cli';