diff --git a/templates/pages/generate.html b/templates/pages/generate.html
index a2f9bba..54f463a 100644
--- a/templates/pages/generate.html
+++ b/templates/pages/generate.html
@@ -113,12 +113,25 @@
                     headSelect.appendChild(opt2);
                 });
 
-                // Auto-select main/master as base, HEAD as head
+                // Auto-select from URL params, or fall back to main/master and HEAD
+                const params = new URLSearchParams(window.location.search);
+                const urlBase = params.get('base');
+                const urlHead = params.get('head');
+
                 const mainBranch = branches.find(b => b.name === 'main' || b.name === 'master');
                 const headBranch = branches.find(r => r.is_head);
 
-                if (mainBranch) baseSelect.value = mainBranch.name;
-                if (headBranch) headSelect.value = headBranch.name;
+                if (urlBase && branches.some(b => b.name === urlBase)) {
+                    baseSelect.value = urlBase;
+                } else if (mainBranch) {
+                    baseSelect.value = mainBranch.name;
+                }
+
+                if (urlHead && branches.some(b => b.name === urlHead)) {
+                    headSelect.value = urlHead;
+                } else if (headBranch) {
+                    headSelect.value = headBranch.name;
+                }
             } catch (err) {
                 console.error('Load refs error:', err);
                 const errDiv = document.getElementById('load-error');