diff --git a/backend/src/app/config.clj b/backend/src/app/config.clj
index 6f69047382..3a332bffb5 100644
--- a/backend/src/app/config.clj
+++ b/backend/src/app/config.clj
@@ -377,6 +377,20 @@
   (or (c/get config :file-clean-delay)
       (ct/duration {:days 2})))
 
+(defn join-uri
+  "Join path segments onto a base URI, preserving a potential subpath
+  (same semantics as the frontend config). The base is normalized with
+  a trailing slash; segments must not start with `/` (a leading slash
+  would resolve against the host root and drop the subpath)."
+  [base & segments]
+  (str (apply u/join (u/ensure-path-slash base) segments)))
+
+(defn get-public-uri
+  "Canonical public URI builder: `join-uri` over the configured
+  :public-uri. With no segments, returns the normalized base."
+  [& segments]
+  (apply join-uri (c/get config :public-uri) segments))
+
 (defn get
   "A configuration getter. Helps code be more testable."
   ([key]
diff --git a/backend/src/app/http/link_preview.clj b/backend/src/app/http/link_preview.clj
index c415b2a99b..c024f6d651 100644
--- a/backend/src/app/http/link_preview.clj
+++ b/backend/src/app/http/link_preview.clj
@@ -35,14 +35,6 @@
     ORDER BY ft.revn DESC NULLS LAST
     LIMIT 1")
 
-(defn- resolve-image-uri
-  [media-id]
-  (str (cf/get :public-uri) "/assets/by-id/" media-id))
-
-(defn- resolve-default-image-uri
-  []
-  (str (cf/get :public-uri) "/images/penpot-link-preview.png"))
-
 (defn- get-file-context
   "Return the link preview context for a file link: the file name as title
   and, when available, the last dashboard thumbnail as image."
@@ -50,7 +42,7 @@
   (when-let [{:keys [name media-id]} (db/exec-one! pool [sql:get-file file-id])]
     (cond-> (assoc default-context :title (str name " | Penpot"))
       (some? media-id)
-      (assoc :image (resolve-image-uri media-id)))))
+      (assoc :image (cf/get-public-uri (str "assets/by-id/" media-id))))))
 
 (defn- get-context
   [pool params]
@@ -71,7 +63,7 @@
   (let [context (when (contains? cf/flags :link-preview)
                   (get-context pool (:query-params request)))
         context (-> (or context default-context)
-                    (update :image #(or % (resolve-default-image-uri))))]
+                    (update :image #(or % (cf/get-public-uri "images/penpot-link-preview.png"))))]
     {::yres/status 200
      ::yres/headers {"content-type" "text/html; charset=utf-8"
                      "cache-control" "no-store, no-cache, max-age=0"}
diff --git a/backend/test/backend_tests/config_test.clj b/backend/test/backend_tests/config_test.clj
new file mode 100644
index 0000000000..ce070ec20b
--- /dev/null
+++ b/backend/test/backend_tests/config_test.clj
@@ -0,0 +1,35 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC Sucursal en España SL
+
+(ns backend-tests.config-test
+  (:require
+   [app.config :as cf]
+   [clojure.test :as t]))
+
+(t/deftest get-public-uri-normalizes-base
+  (t/testing "trailing slash is ensured with and without subpath"
+    (doseq [[base expected] [["http://localhost:3449" "http://localhost:3449/"]
+                             ["http://localhost:3449/" "http://localhost:3449/"]
+                             ["https://example.com/penpot" "https://example.com/penpot/"]
+                             ["https://example.com/penpot/" "https://example.com/penpot/"]]]
+      (t/testing (str "base " base)
+        (with-redefs [cf/config (assoc cf/config :public-uri base)]
+          (t/is (= expected (cf/get-public-uri))))))))
+
+(t/deftest get-public-uri-preserves-subpath
+  (t/testing "joined segments keep the subpath"
+    (with-redefs [cf/config (assoc cf/config :public-uri "https://example.com/penpot")]
+      (t/is (= "https://example.com/penpot/assets/by-id/123"
+               (cf/get-public-uri "assets/by-id/123")))
+      (t/is (= "https://example.com/penpot/api/main/doc"
+               (cf/get-public-uri "api/main/doc"))))))
+
+(t/deftest join-uri-joins-arbitrary-base
+  (t/testing "segments join onto any base with trailing slash normalization"
+    (t/is (= "https://nitrate.example.com/api/teams/123"
+             (cf/join-uri "https://nitrate.example.com" "api/teams/123")))
+    (t/is (= "https://nitrate.example.com/api/teams/123"
+             (cf/join-uri "https://nitrate.example.com/" "api/teams/123")))))