diff --git a/src/__tests__/x-glean.test.ts b/src/__tests__/x-glean.test.ts
index 342e1c6a..ad9927ca 100644
--- a/src/__tests__/x-glean.test.ts
+++ b/src/__tests__/x-glean.test.ts
@@ -2,12 +2,19 @@ import { afterEach, beforeEach, describe, expect, it } from "vitest";
 import { XGlean } from "../hooks/x-glean.js";
 import { BeforeRequestContext } from "../hooks/types.js";
 import { SDKOptions } from "../lib/config.js";
+import { XGleanOptions } from "../hooks/x-glean-options.js";
 
 function createMockRequest(): Request {
   return new Request("https://example.com/api/test");
 }
 
-function createMockContext(options: SDKOptions = {}): BeforeRequestContext {
+/**
+ * Creates a mock BeforeRequestContext for testing.
+ * Uses intersection type to support both base SDKOptions and X-Glean custom options.
+ */
+function createMockContext(
+  options: SDKOptions & XGleanOptions = {},
+): BeforeRequestContext {
   return {
     baseURL: "https://example.com",
     operationID: "test-operation",
diff --git a/src/hooks/x-glean-options.ts b/src/hooks/x-glean-options.ts
new file mode 100644
index 00000000..f4a20d39
--- /dev/null
+++ b/src/hooks/x-glean-options.ts
@@ -0,0 +1,29 @@
+/**
+ * X-Glean custom options for configuring deprecation and experimental headers.
+ *
+ * These properties allow configuring X-Glean headers through the SDK constructor.
+ * Since SDKOptions in lib/config.ts is generated by Speakeasy and gets overwritten
+ * during regeneration, we define these as a separate type that can be used with
+ * intersection types.
+ */
+
+/**
+ * Custom SDK options for X-Glean header configuration.
+ * Use these options when constructing the SDK client to configure
+ * experimental features and deprecation testing.
+ */
+export interface XGleanOptions {
+  /**
+   * Exclude API endpoints that will be deprecated after this date.
+   * Use this to test your integration against upcoming deprecations.
+   * Format: YYYY-MM-DD (e.g., '2026-10-15')
+   *
+   * More information: https://developers.glean.com/deprecations/overview
+   */
+  excludeDeprecatedAfter?: string | undefined;
+  /**
+   * When true, enables experimental API features that are not yet generally available.
+   * Use this to preview and test new functionality.
+   */
+  includeExperimental?: boolean | undefined;
+}
diff --git a/src/hooks/x-glean.ts b/src/hooks/x-glean.ts
index 491ecf84..01a0fc5f 100644
--- a/src/hooks/x-glean.ts
+++ b/src/hooks/x-glean.ts
@@ -1,4 +1,5 @@
 import { BeforeRequestContext, BeforeRequestHook } from "./types.js";
+import { XGleanOptions } from "./x-glean-options.js";
 
 /**
  * Get the first non-empty value from the provided arguments.
@@ -14,14 +15,18 @@ function getFirstValue(
 
 export class XGlean implements BeforeRequestHook {
   beforeRequest(hookCtx: BeforeRequestContext, request: Request): Request {
+    // Cast options to include X-Glean custom properties
+    // These properties may be passed by users but aren't in the generated SDKOptions type
+    const options = hookCtx.options as XGleanOptions;
+
     const deprecatedValue = getFirstValue(
       process.env["X_GLEAN_EXCLUDE_DEPRECATED_AFTER"],
-      hookCtx.options.excludeDeprecatedAfter,
+      options.excludeDeprecatedAfter,
     );
 
     const experimentalValue = getFirstValue(
       process.env["X_GLEAN_INCLUDE_EXPERIMENTAL"],
-      hookCtx.options.includeExperimental === true ? "true" : undefined,
+      options.includeExperimental === true ? "true" : undefined,
     );
 
     if (deprecatedValue) {
diff --git a/src/lib/config.ts b/src/lib/config.ts
index 259cb401..20bc3868 100644
--- a/src/lib/config.ts
+++ b/src/lib/config.ts
@@ -40,19 +40,6 @@ export type SDKOptions = {
   retryConfig?: RetryConfig;
   timeoutMs?: number;
   debugLogger?: Logger;
-  /**
-   * Exclude API endpoints that will be deprecated after this date.
-   * Use this to test your integration against upcoming deprecations.
-   * Format: YYYY-MM-DD (e.g., '2026-10-15')
-   *
-   * More information: https://developers.glean.com/deprecations/overview
-   */
-  excludeDeprecatedAfter?: string | undefined;
-  /**
-   * When true, enables experimental API features that are not yet generally available.
-   * Use this to preview and test new functionality.
-   */
-  includeExperimental?: boolean | undefined;
 };
 
 export function serverURLFromOptions(options: SDKOptions): URL | null {