SSH immediately disconnects after logging in

I'm trying to log in my SSH administration console on my 
laptop-turned-server.
I can connect fine from other devices, whether locally or from remote.
Here on iPhone with iSH, an Alpine Linux emulator, I get this strange 
behavior
where it will display the log in prompt (see below) as if the logging in 
were
successful but immediately disconnect. This happens both locally and 
from
remote, the log in this case is from remote.

I believe the instructive lines are
debug2: fd 3 setting O_NONBLOCK
...
debug3: fd 1 is not O_NONBLOCK
...
debug2: fd 3 setting TCP_NODELAY
...
debug1: Exit status 129

localhost:~# more .ssh/ssh_config
IdentityFile ~/.ssh/id_rsa
Host site
	Hostname saboua.xyz
	Port 4444
	User sylvain
Host lap
	Hostname 10.0.0.11
	Port 22
	User sylvain

localhost:~# ssh -vvv site
OpenSSH_8.6p1, OpenSSL 1.1.1l  24 Aug 2021
debug1: Reading configuration data /root/.ssh/ssh_config
debug1: /root/.ssh/ssh_config line 2: Applying options for site
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> 
'/root/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> 
'/root/.ssh/known_hosts2'
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; 
disabling
debug2: resolving "saboua.xyz" port 4444
debug3: ssh_connect_direct: entering
debug1: Connecting to saboua.xyz [176.129.104.68] port 4444.
debug3: set_sock_tos: set socket 3 IP_TOS 0x48
debug1: Connection established.
debug1: identity file /root/.ssh/id_rsa type 0
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.6
debug1: Remote protocol version 2.0, remote software version 
OpenSSH_10.3
debug1: compat_banner: match: OpenSSH_10.3 pat OpenSSH* compat 
0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to saboua.xyz:4444 as 'sylvain'
debug3: put_host_port: [saboua.xyz]:4444
debug3: record_hostkey: found key type ED25519 in file 
/root/.ssh/known_hosts:6
debug3: load_hostkeys_file: loaded 1 keys from [saboua.xyz]:4444
debug1: load_hostkeys: fopen /root/.ssh/known_hosts2: No such file or 
directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or 
directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or 
directory
debug3: order_hostkeyalgs: have matching best-preference key type 
[email protected], using HostkeyAlgorithms verbatim
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: 
curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: 
[email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: 
[email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: 
mlkem768x25519-sha256,sntrup761x25519-sha512,[email protected],curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,ext-info-s,[email protected]
debug2: host key algorithms: 
rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: 
[email protected],[email protected],[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: ciphers stoc: 
[email protected],[email protected],[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: MACs ctos: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: [email protected] MAC: 
<implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: 
<implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 
SHA256:KISxYDnYhDdE5furF1w2UZ15rU/LAIGtU0onOGm0HW0
debug3: put_host_port: [176.129.104.68]:4444
debug3: put_host_port: [saboua.xyz]:4444
debug3: record_hostkey: found key type ED25519 in file 
/root/.ssh/known_hosts:6
debug3: load_hostkeys_file: loaded 1 keys from [saboua.xyz]:4444
debug1: load_hostkeys: fopen /root/.ssh/known_hosts2: No such file or 
directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or 
directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or 
directory
debug1: Host '[saboua.xyz]:4444' is known and matches the ED25519 host 
key.
debug1: Found key in /root/.ssh/known_hosts:6
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /root/.ssh/id_rsa RSA 
SHA256:xayq3IM1R3LxBwGAyCVe8Pplfhb/sKvuQHx2Drt1k6U explicit
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: 
server-sig-algs=<ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],rsa-sha2-512,rsa-sha2-256,[email protected]>
debug1: kex_input_ext_info: [email protected] 
(unrecognised)
debug1: kex_input_ext_info: [email protected] (unrecognised)
debug1: kex_input_ext_info: agent-forward (unrecognised)
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /root/.ssh/id_rsa RSA 
SHA256:xayq3IM1R3LxBwGAyCVe8Pplfhb/sKvuQHx2Drt1k6U explicit
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: /root/.ssh/id_rsa RSA 
SHA256:xayq3IM1R3LxBwGAyCVe8Pplfhb/sKvuQHx2Drt1k6U explicit
debug3: sign_and_send_pubkey: RSA 
SHA256:xayq3IM1R3LxBwGAyCVe8Pplfhb/sKvuQHx2Drt1k6U
debug3: sign_and_send_pubkey: signing using rsa-sha2-512 
SHA256:xayq3IM1R3LxBwGAyCVe8Pplfhb/sKvuQHx2Drt1k6U
debug3: send packet: type 50
debug3: receive packet: type 52
debug1: Authentication succeeded (publickey).
Authenticated to saboua.xyz ([176.129.104.68]:4444).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: filesystem full
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] 
want_reply 0
debug3: client_input_hostkeys: received RSA key 
SHA256:ws9DPRKcHdgHzRpmTfiX2Ypn60o7PJyueHp6CDtnvSY
debug3: client_input_hostkeys: received ECDSA key 
SHA256:cqlmDQIIY4Fo2s5zULqc85NC5wU3k2C+v+xUabM8TLM
debug3: client_input_hostkeys: received ED25519 key 
SHA256:KISxYDnYhDdE5furF1w2UZ15rU/LAIGtU0onOGm0HW0
debug3: put_host_port: [saboua.xyz]:4444
debug1: client_input_hostkeys: searching /root/.ssh/known_hosts for 
[saboua.xyz]:4444 / (none)
debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts"
debug3: hostkeys_find: found ssh-ed25519 key under different name/addr 
at /root/.ssh/known_hosts:1
debug3: hostkeys_find: found ssh-rsa key under different name/addr at 
/root/.ssh/known_hosts:2
debug3: hostkeys_find: found ecdsa-sha2-nistp256 key under different 
name/addr at /root/.ssh/known_hosts:3
debug3: hostkeys_find: found ssh-ed25519 key under different name/addr 
at /root/.ssh/known_hosts:4
debug3: hostkeys_find: found ssh-ed25519 key under different name/addr 
at /root/.ssh/known_hosts:5
debug3: hostkeys_find: found ssh-ed25519 key at /root/.ssh/known_hosts:6
debug1: client_input_hostkeys: searching /root/.ssh/known_hosts2 for 
[saboua.xyz]:4444 / (none)
debug1: client_input_hostkeys: hostkeys file /root/.ssh/known_hosts2 
does not exist
debug3: client_input_hostkeys: 3 server keys: 2 new, 4294967295 
retained, 2 incomplete match. 0 to remove
debug1: client_input_hostkeys: host key found matching a different 
name/address, skipping UserKnownHostsFile update
debug3: receive packet: type 4
debug1: Remote: /home/sylvain/.ssh/authorized_keys:11: key options: 
agent-forwarding port-forwarding pty user-rc x11-forwarding
debug3: receive packet: type 4
debug1: Remote: /home/sylvain/.ssh/authorized_keys:11: key options: 
agent-forwarding port-forwarding pty user-rc x11-forwarding
debug3: receive packet: type 91
debug2: channel_input_open_confirmation: channel 0: callback start
debug2: fd 3 setting TCP_NODELAY
debug3: set_sock_tos: set socket 3 IP_TOS 0x48
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug3: send packet: type 98
debug2: channel 0: request shell confirm 1
debug3: send packet: type 98
debug2: channel_input_open_confirmation: channel 0: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Last login: Wed Jul 29 06:49:14 2026 from 37.66.89.136
OpenBSD 7.9 (GENERIC.MP) #449: Wed May  6 13:17:25 MDT 2026

Welcome to OpenBSD: The proactively secure Unix-like operating system.

Please use the sendbug(1) utility to report bugs in the system.
Before reporting a bug, please try to reproduce it with the latest
version of the code.  With bug reports, please try to ensure that
enough information to reproduce the problem is enclosed, and if a
known fix for it exists, include that as well.

debug3: receive packet: type 96
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: chan_shutdown_write: channel 0: (i0 o1 sock -1 wfd 5 efd 6 
[write])
debug2: channel 0: output drain -> closed
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype [email protected] reply 
0
debug2: channel 0: rcvd eow
debug2: chan_shutdown_read: channel 0: (i0 o3 sock -1 wfd 4 efd 6 
[write])
debug2: channel 0: input open -> closed
debug3: receive packet: type 97
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: almost dead
debug2: channel 0: gc: notify user
debug2: channel 0: gc: user detached
debug2: channel 0: send close
debug3: send packet: type 97
debug2: channel 0: is dead
debug2: channel 0: garbage collecting
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
   #0 client-session (t4 r0 i3/0 o3/0 e[write]/0 fd -1/-1/6 sock -1 cc 
-1)

debug3: send packet: type 1
debug3: fd 1 is not O_NONBLOCK
Connection to saboua.xyz closed.
Transferred: sent 3536, received 3788 bytes, in 0.2 seconds
Bytes per second: sent 20780.4, received 22261.4
debug1: Exit status 129

--
Sylvain Saboua
looking for a PDP-11