diff --git a/grubby-bls b/grubby-bls
index fd76f63..f09156b 100755
--- a/grubby-bls
+++ b/grubby-bls
@@ -827,13 +827,14 @@ fi
 remove_var_prefix "$(get_prefix)"
 
 if [[ -n $kernel ]]; then
-    opts="${bls_options[$default_index]}"
-    if [[ $copy_default != "true" ]]; then
-        opts=$(echo $opts | sed -e 's/ .*//')
+    if [[ $copy_default = "true" ]]; then
+       opts="${bls_options[$default_index]}"
+       if [[ -n $args ]]; then
+           opts="${opts} ${args}"
+       fi
+    else
+       opts="${args}"
     fi
-    if [[ -n $args ]]; then
-        opts="${opts} ${args}"
-    fi    
 
     add_bls_fragment "${kernel}" "${title}" "${opts}" "${initrd}" \
                      "${extra_initrd}"

Thanks, applied fix to Fedora.

Reproduced on RHEL-9.2 with grubby 8.40-61:
# rpm -qa grubby\*
grubby-8.40-61.el9.x86_64
[root@kvm-08-guest31 ~]# cd /boot/
[root@kvm-08-guest31 boot]# touch my_kernel my_initrd
[root@kvm-08-guest31 boot]# grubby --add-kernel=/boot/my_kernel --initrd=/boot/my_initrd --title=no_args
[root@kvm-08-guest31 boot]# grubby --add-kernel=/boot/my_kernel --initrd=/boot/my_initrd --args=bla --title=some_args
An entry for kernel my_kernel already exists, adding /boot/loader/entries/5c9135a4657146f3bcd4a2844700f9bd-my_kernel.0~custom.conf

[root@kvm-08-guest31 boot]# grubby --info=/boot/my_kernel
index=2
kernel="/boot/my_kernel"
args="bla"
initrd="/boot/my_initrd"
title="some_args"
id="5c9135a4657146f3bcd4a2844700f9bd-my_kernel.0~custom"

index=3
kernel="/boot/my_kernel"
args="$kernelopts"
initrd="/boot/my_initrd"
title="no_args"
id="5c9135a4657146f3bcd4a2844700f9bd-my_kernel"

Verified on RHEL-9.2 with grubby 8.40-62:
# rpm -qa grubby\*
grubby-8.40-62.el9.aarch64
[root@hpe-apollo-cn99xx-15-vm-20 ~]# cd /boot
[root@hpe-apollo-cn99xx-15-vm-20 boot]# touch my_kernel my_initrd
[root@hpe-apollo-cn99xx-15-vm-20 boot]# grubby --add-kernel=/boot/my_kernel --initrd=/boot/my_initrd --title=no_args
[root@hpe-apollo-cn99xx-15-vm-20 boot]# grubby --add-kernel=/boot/my_kernel --initrd=/boot/my_initrd --args=bla --title=some_args
An entry for kernel my_kernel already exists, adding /boot/loader/entries/c08f08492d714fc087dcb5accc2746fc-my_kernel.0~custom.conf

[root@hpe-apollo-cn99xx-15-vm-20 boot]# grubby --info=/boot/my_kernel
index=2
kernel="/boot/my_kernel"
args="bla"
root="/dev/mapper/rhel_hpe--apollo--cn99xx--15--vm--20-root"
initrd="/boot/my_initrd"
title="some_args"
id="c08f08492d714fc087dcb5accc2746fc-my_kernel.0~custom"

index=3
kernel="/boot/my_kernel"
args=""
root="/dev/mapper/rhel_hpe--apollo--cn99xx--15--vm--20-root"
initrd="/boot/my_initrd"
title="no_args"
id="c08f08492d714fc087dcb5accc2746fc-my_kernel"

root is set, default arguments are not copied.

grubby-8.40-62.el9 adds an unexpected root=... boot argument when the user specifies --args=... See:

[root@localhost boot]# grubby --add-kernel=/boot/vmlinuz --initrd=/boot/initrd.img --args="my_arg" --title="Test"
[root@localhost boot]# cat /boot/loader/entries/dc227bca83644c7aad89fa7e31bb3e4e-vmlinuz.conf 
title Test
version vmlinuz
linux /vmlinuz
initrd /initrd.img
options root=/dev/mapper/rhel-root my_arg
id rhel-0-vmlinuz
grub_users $grub_users
grub_arg --unrestricted
grub_class kernel
[root@localhost boot]#

The expected behavior is that only "my_arg" would be present on the kernel command line, root=/dev/mapper/rhel-root should not be there.

I'm moving this bug back to ASSIGNED. This is a change of behavior and has an impact on our automated testing.

I thought the root= was desired! But since it is not, here it is again with grubby-8.40-63.el9:

[root@ibm-p9z-23-lp3 boot]# grubby --add-kernel my_kernel --initrd my_initrd --title no_args

[root@ibm-p9z-23-lp3 boot]# grubby --add-kernel my_kernel --initrd my_initrd --args args --title some_args
args
An entry for kernel my_kernel already exists, adding /boot/loader/entries/a7c94d39d09c4db1a076bdfc5ca994e7-my_kernel.0~custom.conf

[root@ibm-p9z-23-lp3 boot]# grubby --info my_kernel
index=2
kernel="/boot/my_kernel"
args="args"
initrd="/boot/my_initrd"
title="some_args"
id="a7c94d39d09c4db1a076bdfc5ca994e7-my_kernel.0~custom"

index=3
kernel="/boot/my_kernel"
args=""
initrd="/boot/my_initrd"
title="no_args"
id="a7c94d39d09c4db1a076bdfc5ca994e7-my_kernel"

The results from comment 17 look good, thank you Marta.

You're welcome, Honzo. :)
Setting back to Verified: Tested based on c#17 & 18

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (grubby bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2023:2584