diff --git a/apps/desktop/electron/git-worktree-ops.ts b/apps/desktop/electron/git-worktree-ops.ts
index dcde29b682c3..e84324a004b5 100644
--- a/apps/desktop/electron/git-worktree-ops.ts
+++ b/apps/desktop/electron/git-worktree-ops.ts
@@ -251,7 +251,25 @@ async function addWorktree(repoPath, options, gitBin) {
   const args = ['worktree', 'add', '-b', branch, dir]
 
   if (opts.base) {
-    args.push(String(opts.base))
+    // Remote-tracking branches may be stale or missing if the user hasn't
+    // fetched recently. When the base is an `origin/…` ref, fetch just that
+    // branch so `git worktree add -b new origin/main` works against the
+    // latest remote commit. Local branches are used as-is.
+    const base = String(opts.base)
+
+    if (base.startsWith('origin/')) {
+      const remoteBranch = base.slice('origin/'.length)
+
+      try {
+        await runGit(gitBin, ['fetch', 'origin', remoteBranch], root)
+      } catch {
+        // The fetch isn't mandatory, but it would be nice to do if possible.
+        // If it's not possible, just use the local ref of the remote branch.
+        // If it doesn't exist locally, we'll get an error anyways 
+      }
+    }
+
+    args.push(base)
   }
 
   try {
diff --git a/hermes_cli/web_git.py b/hermes_cli/web_git.py
index 6f0dcfd885ab..0af12106745a 100644
--- a/hermes_cli/web_git.py
+++ b/hermes_cli/web_git.py
@@ -597,7 +597,15 @@ def worktree_add(cwd: str, options: dict) -> dict:
     target = _unique_dir(os.path.join(root, ".worktrees", slug))
     args = ["worktree", "add", "-b", branch, target]
     if options.get("base"):
-        args.append(str(options["base"]))
+        base = str(options["base"])
+        # Remote-tracking branches may be stale or missing; fetch just that
+        # branch so the local ref is up to date before branching. Ignore fetch
+        # failures (offline / no remote) — git will use whatever local ref
+        # exists, or raise a clear error below if the ref is entirely missing.
+        if base.startswith("origin/"):
+            remote_branch = base[len("origin/"):]
+            _git(root, ["fetch", "origin", remote_branch])
+        args.append(base)
     code, _, err = _git(root, args)
     if code != 0:
         if "already exists" in (err or "").lower():