diff --git a/CHANGELOG.md b/CHANGELOG.md
index 374e45d..d86375a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # @longsightgroup/lti-tool
 
+## 0.1.8
+
+### Patch Changes
+
+- Accept absolute HTTPS URI-named extension properties in LTI Deep Linking
+  settings while continuing to reject ordinary unknown, insecure, and
+  malformed property names.
+
 ## 0.1.7
 
 ### Breaking Changes
diff --git a/package-lock.json b/package-lock.json
index ab666d9..4aa9539 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@longsightgroup/lti-tool",
-  "version": "0.1.7",
+  "version": "0.1.8",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@longsightgroup/lti-tool",
-      "version": "0.1.7",
+      "version": "0.1.8",
       "license": "MIT",
       "dependencies": {
         "jose": "^6.2.3",
diff --git a/package.json b/package.json
index 3108980..67ce097 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@longsightgroup/lti-tool",
-  "version": "0.1.7",
+  "version": "0.1.8",
   "description": "LTI 1.3 implementation for Node.js with framework and storage adapters",
   "type": "module",
   "author": "Longsight",
diff --git a/packages/core/src/schemas/lti13/claims/serviceClaims.schema.ts b/packages/core/src/schemas/lti13/claims/serviceClaims.schema.ts
index 49c489b..a5f7903 100644
--- a/packages/core/src/schemas/lti13/claims/serviceClaims.schema.ts
+++ b/packages/core/src/schemas/lti13/claims/serviceClaims.schema.ts
@@ -15,17 +15,37 @@ export const NrpsServiceSchema = z
   })
   .optional();
 
+const DeepLinkingSettingsShape = {
+  deep_link_return_url: z.string(),
+  accept_types: z.array(z.string()),
+  accept_presentation_document_targets: z.array(z.string()),
+  accept_media_types: z.string().optional(),
+  accept_multiple: z.boolean().optional(),
+  accept_lineitem: z.boolean().optional(),
+  auto_create: z.boolean().optional(),
+  title: z.string().optional(),
+  text: z.string().optional(),
+  data: z.string().optional(),
+};
+
+const DeepLinkingSettingsKnownKeys = new Set(Object.keys(DeepLinkingSettingsShape));
+const DeepLinkingSettingsExtensionKeySchema = z.url({ protocol: /^https$/ });
+
 export const DeepLinkingSettingsSchema = z
-  .strictObject({
-    deep_link_return_url: z.string(),
-    accept_types: z.array(z.string()),
-    accept_presentation_document_targets: z.array(z.string()),
-    accept_media_types: z.string().optional(),
-    accept_multiple: z.boolean().optional(),
-    accept_lineitem: z.boolean().optional(),
-    auto_create: z.boolean().optional(),
-    title: z.string().optional(),
-    text: z.string().optional(),
-    data: z.string().optional(),
+  .object(DeepLinkingSettingsShape)
+  .catchall(z.unknown())
+  .superRefine((settings, context) => {
+    const unrecognizedKeys = Object.keys(settings).filter(
+      (key) =>
+        !DeepLinkingSettingsKnownKeys.has(key) &&
+        !DeepLinkingSettingsExtensionKeySchema.safeParse(key).success,
+    );
+
+    if (unrecognizedKeys.length > 0) {
+      context.addIssue({
+        code: 'unrecognized_keys',
+        keys: unrecognizedKeys,
+      });
+    }
   })
   .optional();
diff --git a/packages/core/test/schemas.test.ts b/packages/core/test/schemas.test.ts
index 0f88afd..f732e4a 100644
--- a/packages/core/test/schemas.test.ts
+++ b/packages/core/test/schemas.test.ts
@@ -472,6 +472,81 @@ describe('Schema Validation Tests', () => {
       expect(() => LTI13JwtPayloadSchema.parse(validPayload)).not.toThrow();
     });
 
+    it('preserves Sakai HTTPS URI extensions in Deep Linking settings', () => {
+      const sakaiPlacementKey = 'https://www.sakailms.org/spec/lti-dl/placement';
+      const sakaiAcceptLineItemKey =
+        'https://www.sakailms.org/spec/lti-dl/accept_lineitem';
+      const sakaiAcceptAvailableKey =
+        'https://www.sakailms.org/spec/lti-dl/accept_available';
+      const sakaiAcceptSubmissionKey =
+        'https://www.sakailms.org/spec/lti-dl/accept_submission';
+      const parsed = LTI13JwtPayloadSchema.parse({
+        iss: 'https://platform.example.com',
+        aud: 'client123',
+        exp: Math.floor(Date.now() / 1000) + 300,
+        iat: Math.floor(Date.now() / 1000),
+        nonce: 'test-nonce',
+        [LTI_CLAIM_MESSAGE_TYPE]: LTI_MESSAGE_TYPE_DEEP_LINKING_REQUEST,
+        [LTI_CLAIM_VERSION]: LTI_VERSION_1P3P0,
+        [LTI_CLAIM_DEPLOYMENT_ID]: 'deployment1',
+        [LTI_CLAIM_TARGET_LINK_URI]: 'https://tool.example.com/content',
+        [LTI_CLAIM_DEEP_LINKING_SETTINGS]: {
+          deep_link_return_url: 'https://platform.example.com/deep_links',
+          accept_types: ['ltiResourceLink'],
+          accept_presentation_document_targets: ['iframe'],
+          [sakaiPlacementKey]: 'lessons',
+          [sakaiAcceptLineItemKey]: true,
+          [sakaiAcceptAvailableKey]: false,
+          [sakaiAcceptSubmissionKey]: false,
+        },
+      });
+
+      const settings = parsed[LTI_CLAIM_DEEP_LINKING_SETTINGS];
+      expect(settings).toMatchObject({
+        [sakaiPlacementKey]: 'lessons',
+        [sakaiAcceptLineItemKey]: true,
+        [sakaiAcceptAvailableKey]: false,
+        [sakaiAcceptSubmissionKey]: false,
+      });
+    });
+
+    it.each([
+      ['ordinary unknown key', 'accept_mulitple'],
+      ['HTTP URL key', 'http://www.sakailms.org/spec/lti-dl/placement'],
+      ['malformed URL-like key', 'https//www.sakailms.org/spec/lti-dl/placement'],
+    ])('rejects a Deep Linking settings %s', (_description, unknownKey) => {
+      const invalidPayload = {
+        iss: 'https://platform.example.com',
+        aud: 'client123',
+        exp: Math.floor(Date.now() / 1000) + 300,
+        iat: Math.floor(Date.now() / 1000),
+        nonce: 'test-nonce',
+        [LTI_CLAIM_MESSAGE_TYPE]: LTI_MESSAGE_TYPE_DEEP_LINKING_REQUEST,
+        [LTI_CLAIM_VERSION]: LTI_VERSION_1P3P0,
+        [LTI_CLAIM_DEPLOYMENT_ID]: 'deployment1',
+        [LTI_CLAIM_TARGET_LINK_URI]: 'https://tool.example.com/content',
+        [LTI_CLAIM_DEEP_LINKING_SETTINGS]: {
+          deep_link_return_url: 'https://platform.example.com/deep_links',
+          accept_types: ['ltiResourceLink'],
+          accept_presentation_document_targets: ['iframe'],
+          [unknownKey]: true,
+        },
+      };
+
+      const result = LTI13JwtPayloadSchema.safeParse(invalidPayload);
+
+      expect(result.success).toBe(false);
+      if (!result.success) {
+        expect(result.error.issues).toContainEqual(
+          expect.objectContaining({
+            code: 'unrecognized_keys',
+            keys: [unknownKey],
+            path: [LTI_CLAIM_DEEP_LINKING_SETTINGS],
+          }),
+        );
+      }
+    });
+
     it('rejects payload with invalid message type', () => {
       const invalidPayload = {
         iss: 'https://platform.example.com',