Tessera network help

WSL2 and Tailscale MTU warning

Tessera detected a WSL2 network shape that can allow SSH to connect while silently dropping larger terminal replies. This is a host networking issue, not damage to your tmux session.

Why “attaching pane” can stall

Small replies pass

Authentication and short tmux control messages fit below the broken packet-size boundary.

A pane capture is larger

Tessera requests the visible pane and scrollback so the restored terminal can paint immediately.

The path drops it

The SSH connection stays open, but the larger encrypted response never reaches the device.

What the probe reads

The probe is read-only, runs over the SSH connection you already authorized, and does not use sudo or change the host.

WSL version signal	`/proc/sys/kernel/osrelease`
Connection route	The server address from `SSH_CONNECTION`, matched against addresses on `tailscale0`
Outer MTU	The MTU of WSL’s default-route interface
Inner MTU	`/sys/class/net/tailscale0/mtu`

Verify the host

Run these commands inside the affected WSL distribution. They only display state.

uname -a
ip -br link
ip route show default

default_dev="$(ip route show default | awk 'NR == 1 { print $5 }')"
printf 'default interface: %s\n' "$default_dev"
cat "/sys/class/net/$default_dev/mtu"
cat /sys/class/net/tailscale0/mtu 2>/dev/null || true

tailscale version 2>/dev/null || true
tailscale status 2>/dev/null || true

For Tailscale running inside WSL2, the common healthy relationship is an outer/default interface of at least 1340 carrying the 1280-byte Tailscale interface.

Choose the remediation that matches your topology

Tailscale recommendation

Run Tailscale on Windows only

Tailscale advises against running it simultaneously on Windows and inside WSL2. First confirm which Tailscale IP Tessera targets so you do not cut off your own access.

Keep Tailscale inside WSL2

Update Tailscale and confirm its WSL workaround raises the outer/default interface to 1340. Test a temporary MTU adjustment before making startup configuration persistent.

Important safety notes

Do not lower tailscale0 blindly, reset the Windows network stack, shut down WSL, or disable either Tailscale installation from a remote session. Those actions can end the connection you need for recovery.

A configured MTU is not proof of the end-to-end path. If the warning persists after correction, compare ordinary OS traffic with Tailscale’s layered pings and perform a bounded packet-size test from another device.

Authoritative references

Tailscale: Install on Windows with WSL2
Tailscale: Troubleshoot TCP connection issues

Tessera reports this as a possible cause because other routing, VPN, firewall, and packet-loss problems can produce similar symptoms.