diff --git a/core/file_manager.py b/core/file_manager.py
index 3190314..d51a0ea 100644
--- a/core/file_manager.py
+++ b/core/file_manager.py
@@ -30,9 +30,9 @@ def _normalized_absolute_path(path_value: str) -> str:
 def normalize_file_manager_path(path_value: Any) -> str:
     """Normalize a local path and recover UI-style separators when necessary.
 
-    The frontend uses backslashes as its canonical subfolder separator. On
-    POSIX, a backslash is a valid filename character, so the literal path is
-    always checked first. It is interpreted as a separator only when the
+    Legacy frontend state may contain backslashes as subfolder separators. On
+    POSIX, a backslash is also a valid filename character, so the literal path
+    is always checked first. It is interpreted as a separator only when the
     literal path does not exist and the converted path does.
     """
     if not isinstance(path_value, (str, os.PathLike)):
diff --git a/tests/test_downloads_tab_workflow_route.mjs b/tests/test_downloads_tab_workflow_route.mjs
index 2b8ddf2..4a9e0cc 100644
--- a/tests/test_downloads_tab_workflow_route.mjs
+++ b/tests/test_downloads_tab_workflow_route.mjs
@@ -927,6 +927,22 @@ test('portable subfolder paths use forward slashes and join to the host path sty
     joinLocalPath.call(dialog, 'C:\\models\\loras', 'Pony/Styles'),
     'C:\\models\\loras\\Pony\\Styles'
   );
+  assert.equal(
+    joinLocalPath.call(dialog, '/', 'models\\Pony'),
+    '/models/Pony'
+  );
+  assert.equal(
+    joinLocalPath.call(dialog, '/models/literal\\name', 'Pony\\Styles'),
+    '/models/literal\\name/Pony/Styles'
+  );
+  assert.equal(
+    joinLocalPath.call(dialog, 'C:\\', 'Pony/Styles'),
+    'C:\\Pony\\Styles'
+  );
+  assert.equal(
+    joinLocalPath.call(dialog, '\\\\server\\share\\', 'Pony/Styles'),
+    '\\\\server\\share\\Pony\\Styles'
+  );
 });
 
 test('download subfolder tooltip identifies a folder taken from the workflow model path', () => {
diff --git a/web/resolver/search/download_target_methods.js b/web/resolver/search/download_target_methods.js
index dca388e..b8e78b7 100644
--- a/web/resolver/search/download_target_methods.js
+++ b/web/resolver/search/download_target_methods.js
@@ -1004,13 +1004,19 @@ export const downloadTargetMethods = {
     },
 
     joinLocalPath(basePath = '', relativePath = '') {
-        const base = String(basePath || '').replace(/[\/\\]+$/, '');
+        const rawBase = String(basePath || '');
         const relative = String(relativePath || '').replace(/^[\/\\]+/, '');
+        const usesBackslash = /^[A-Za-z]:\\/.test(rawBase)
+            || /^\\\\/.test(rawBase)
+            || (!rawBase.includes('/') && rawBase.includes('\\'));
+        const separator = usesBackslash ? '\\' : '/';
+        const base = rawBase.replace(usesBackslash ? /[\/\\]+$/ : /\/+$/, '')
+            || (usesBackslash ? (/^\\+$/.test(rawBase) ? '\\' : '') : (/^\/+$/.test(rawBase) ? '/' : ''));
         if (!base) return this.normalizePathToForward(relative);
         if (!relative) return base;
-        const separator = base.includes('\\') ? '\\' : '/';
         const normalizedRelative = relative.replace(/[\/\\]+/g, separator);
-        return `${base}${separator}${normalizedRelative}`;
+        const joiner = base.endsWith(separator) ? '' : separator;
+        return `${base}${joiner}${normalizedRelative}`;
     },
 
     getDownloadTargetFolderContext(category = '', subfolder = '', baseDirectory = '') {
diff --git a/web/resolver/views/missing_browser_methods.js b/web/resolver/views/missing_browser_methods.js
index 05f8b64..fef27d3 100644
--- a/web/resolver/views/missing_browser_methods.js
+++ b/web/resolver/views/missing_browser_methods.js
@@ -1533,12 +1533,18 @@ export const missingBrowserMethods = {
             if (typeof this.joinLocalPath === 'function') {
                 return this.joinLocalPath(basePath, relativePath);
             }
-            const base = String(basePath || '').replace(/[\/\\]+$/, '');
+            const rawBase = String(basePath || '');
             const relative = String(relativePath || '').replace(/^[\/\\]+/, '');
+            const usesBackslash = /^[A-Za-z]:\\/.test(rawBase)
+                || /^\\\\/.test(rawBase)
+                || (!rawBase.includes('/') && rawBase.includes('\\'));
+            const separator = usesBackslash ? '\\' : '/';
+            const base = rawBase.replace(usesBackslash ? /[\/\\]+$/ : /\/+$/, '')
+                || (usesBackslash ? (/^\\+$/.test(rawBase) ? '\\' : '') : (/^\/+$/.test(rawBase) ? '/' : ''));
             if (!base) return relative;
             if (!relative) return base;
-            const separator = base.includes('\\') ? '\\' : '/';
-            return `${base}${separator}${relative.replace(/[\/\\]+/g, separator)}`;
+            const joiner = base.endsWith(separator) ? '' : separator;
+            return `${base}${joiner}${relative.replace(/[\/\\]+/g, separator)}`;
         };
         const buildLocalFolderContext = (folderPath = '', name = 'Folder', category = '') => {
             const path = String(folderPath || '').trim();