fix: Default to a relative path for the admin backend URL (#9947)

packages/core/framework/src/config/types.ts

@@ -72,7 +72,7 @@ export type AdminOptions = {
    */
   outDir?: string
   /**
-   * The URL of your Medusa application. This is useful to set when you deploy the Medusa application.
+   * The URL of your Medusa application. Defaults to the browser origin. This is useful to set when running the admin on a separate domain.
    *
    * @example
    * ```ts title="medusa-config.ts"

packages/core/types/src/common/config-module.ts

@@ -50,7 +50,7 @@ export interface AdminOptions {
    */
   path: `/${string}`
   /**
-   * The URL of your Medusa application. This is useful to set when you deploy the Medusa application.
+   * The URL of your Medusa application. Defaults to the browser origin. This is useful to set when running the admin on a separate domain.
    *
    * @example
    * ```js title="medusa-config.js"

packages/core/utils/src/common/__tests__/define-config.spec.ts

@@ -6,7 +6,7 @@ describe("defineConfig", function () {
     expect(defineConfig()).toMatchInlineSnapshot(`
       {
         "admin": {
-          "backendUrl": "http://localhost:9000",
+          "backendUrl": "/",
           "path": "/app",
         },
         "featureFlags": {},
@@ -159,7 +159,7 @@ describe("defineConfig", function () {
     ).toMatchInlineSnapshot(`
       {
         "admin": {
-          "backendUrl": "http://localhost:9000",
+          "backendUrl": "/",
           "path": "/app",
         },
         "featureFlags": {},
@@ -318,7 +318,7 @@ describe("defineConfig", function () {
     ).toMatchInlineSnapshot(`
       {
         "admin": {
-          "backendUrl": "http://localhost:9000",
+          "backendUrl": "/",
           "path": "/app",
         },
         "featureFlags": {},
@@ -483,7 +483,7 @@ describe("defineConfig", function () {
     ).toMatchInlineSnapshot(`
       {
         "admin": {
-          "backendUrl": "http://localhost:9000",
+          "backendUrl": "/",
           "path": "/app",
         },
         "featureFlags": {},
@@ -644,7 +644,7 @@ describe("defineConfig", function () {
     ).toMatchInlineSnapshot(`
       {
         "admin": {
-          "backendUrl": "http://localhost:9000",
+          "backendUrl": "/",
           "path": "/app",
         },
         "featureFlags": {},
@@ -800,7 +800,7 @@ describe("defineConfig", function () {
     ).toMatchInlineSnapshot(`
       {
         "admin": {
-          "backendUrl": "http://localhost:9000",
+          "backendUrl": "/",
           "path": "/app",
         },
         "featureFlags": {},

packages/core/utils/src/common/define-config.ts

@@ -14,7 +14,7 @@ import { normalizeImportPathWithSource } from "./normalize-import-path-with-sour
 import { resolveExports } from "./resolve-exports"
 
 const DEFAULT_SECRET = "supersecret"
-const DEFAULT_ADMIN_URL = "http://localhost:9000"
+const DEFAULT_ADMIN_URL = "/"
 const DEFAULT_STORE_CORS = "http://localhost:8000"
 const DEFAULT_DATABASE_URL = "postgres://localhost/medusa-starter-default"
 const DEFAULT_ADMIN_CORS =