diff --git a/packages/core/src/lib/utils/providers.ts b/packages/core/src/lib/utils/providers.ts
index 2e1fd68492..84425f9a1d 100644
--- a/packages/core/src/lib/utils/providers.ts
+++ b/packages/core/src/lib/utils/providers.ts
@@ -32,7 +32,19 @@ export default function parseProviders(params: {
     const { options: userOptions, ...defaults } = provider
 
     const id = (userOptions?.id ?? defaults.id) as string
-    // TODO: Support if properties have different types, e.g. authorization: string or object
+    // `authorization`/`token`/`userinfo` accept a string shorthand for just
+    // the endpoint URL. If a user only overrides part of that config (e.g.
+    // `authorization: { params: { scope } }`, without a new `url`), `merge`
+    // would otherwise see a string next to an object, discard the string
+    // default entirely, and lose the base URL. Promoting the string default
+    // to `{ url }` first lets `merge` combine them instead.
+    const defaultsAsRecord = defaults as Record<string, unknown>
+    for (const key of ["authorization", "token", "userinfo"] as const) {
+      const value = defaultsAsRecord[key]
+      if (typeof value === "string") {
+        defaultsAsRecord[key] = { url: value }
+      }
+    }
     const merged = merge(defaults, userOptions, {
       signinUrl: `${url}/signin/${id}`,
       callbackUrl: `${url}/callback/${id}`,
diff --git a/packages/core/test/providers.test.ts b/packages/core/test/providers.test.ts
new file mode 100644
index 0000000000..2be5d2b778
--- /dev/null
+++ b/packages/core/test/providers.test.ts
@@ -0,0 +1,40 @@
+import { describe, expect, it } from "vitest"
+import parseProviders from "../src/lib/utils/providers"
+import Spotify from "../src/providers/spotify"
+import { testConfig } from "./utils"
+
+describe("parseProviders", () => {
+  it("merges a params-only authorization override into a string-shorthand default without losing the base URL", () => {
+    // Spotify's `authorization` default is a plain string
+    // ("https://accounts.spotify.com/authorize?scope=user-read-email").
+    // Overriding just the scope, as the docs recommend, must not discard
+    // that base URL.
+    const config = testConfig({
+      providers: [
+        Spotify({
+          clientId: "client-id",
+          clientSecret: "client-secret",
+          authorization: {
+            params: { scope: "user-read-email playlist-read-private" },
+          },
+        }),
+      ],
+    })
+
+    const { providers } = parseProviders({
+      url: new URL("http://localhost:3000/auth"),
+      config,
+    })
+
+    const spotify = providers[0] as any
+
+    expect(spotify.authorization.url).toBeInstanceOf(URL)
+    expect(spotify.authorization.url.origin).toBe(
+      "https://accounts.spotify.com"
+    )
+    expect(spotify.authorization.url.pathname).toBe("/authorize")
+    expect(spotify.authorization.url.searchParams.get("scope")).toBe(
+      "user-read-email playlist-read-private"
+    )
+  })
+})