diff --git a/src/backend_win/asb_core.c b/src/backend_win/asb_core.c
index dc7e0f5..d69fc86 100644
--- a/src/backend_win/asb_core.c
+++ b/src/backend_win/asb_core.c
@@ -2119,11 +2119,19 @@ static HRESULT run_iso_patch_ubuntu(const wchar_t *iso_path,
                             if (g_progress_cb && pvm)
                                 g_progress_cb(vm_handle(pvm), pct, is_staging, g_progress_ud);
                         } else if (strncmp(line, "ERROR:", 6) == 0) {
+                            asb_log(L"iso-patch: ERROR: %S", line + 6);
                             if (error_msg && error_msg[0] == L'\0')
                                 MultiByteToWideChar(CP_ACP, 0, line + 6, -1, error_msg, (int)error_msg_cap);
                             result = E_FAIL;
                         } else if (strncmp(line, "DONE:", 5) == 0) {
                             result = S_OK;
+                        } else if (strncmp(line, "STATUS:", 7) == 0) {
+                            /* Unlike the Windows --to-vhdx path there is no
+                               in-guest installer log to fall back on, so the
+                               iso-patch status lines (source squashfs, detected
+                               kernel, ingest totals, ...) are the only host-side
+                               record of how the Linux disk was built. */
+                            asb_log(L"iso-patch: %S", line + 7);
                         }
                     }
                     start = ci + 1;
diff --git a/tools/iso-patch/ubuntu_vhdx.c b/tools/iso-patch/ubuntu_vhdx.c
index 696650f..929e66d 100644
--- a/tools/iso-patch/ubuntu_vhdx.c
+++ b/tools/iso-patch/ubuntu_vhdx.c
@@ -2081,6 +2081,22 @@ int do_ubuntu_to_vhdx(const wchar_t *iso_path_arg,
             goto cleanup;
         }
         strncpy(kernel_ver, pl.kernel_version, sizeof(kernel_ver) - 1);
+        if (kernel_ver[0] == 0) {
+            /* No /boot/vmlinuz-* was seen during the walk.  minimal.squashfs
+               carries the kernel on the 26.04 desktop ISO, but on 24.04 it
+               lives only in the minimal.standard.live overlay, so the rootfs
+               built here has nothing to boot.  Writing the bootstrap
+               grub.cfg with an empty version produces a disk that hangs at
+               the GRUB prompt while the UI shows "Installing Linux" forever
+               (jamesstringer90/appsandbox#66).  Fail loudly instead;
+               exit_code stays 1 so cleanup deletes the VHDX. */
+            log_err(L"no kernel (/boot/vmlinuz-*) found in %s - the disk would not boot. "
+                    L"Only Ubuntu Desktop 26.04 LTS ISOs are supported.", sqfs_path);
+            sqfs_close(sq);
+            ext4_writer_close(ew);
+            goto cleanup;
+        }
+        log_msg(L"kernel: %hs", kernel_ver);
         sqfs_close(sq);
     }