**Outbound tailnet access for the claudebox and pibox-zai agent containers.
When `TAILSCALE=1` runs alongside `CLAUDEBOX=1` or `PIBOX_ZAI=1`, those
containers can reach machines on your tailnet over any protocol, on top of the
existing inbound `tailscale serve` proxy.**
- Tailnet egress overlay (`docker-compose.tailscale.yml`), loaded by the
Makefile only when `TAILSCALE=1`. It routes the `100.64.0.0/10` Tailscale
CGNAT range out through the existing tailscale node and configures split DNS,
so claudebox and pibox-zai resolve tailnet names and connect to tailnet peers
while public and sibling-container names keep resolving. Both containers stay
on the bridge, so nginx and LiteLLM still reach them.
- The tailscale container becomes a NAT gateway (`MASQUERADE` on `tailscale0`,
kept present by a sidecar). Each agent container gets the tailnet route
installed in its network namespace by a per-container sidecar that re-adds it
after a restart. All egress sidecars run with `no-new-privileges:true` and
`cap_drop: [ALL]`, adding back only `NET_ADMIN` (plus `NET_RAW` on the
gateway sidecar for the NAT rule).
- DNS: Tailscale MagicDNS (`100.100.100.100`) answers tailnet names and
SERVFAILs everything else; Docker's embedded resolver falls through to a
public resolver for public names.
- `TS_MAGICDNS_SUFFIX` (optional): your tailnet's MagicDNS suffix, so the agent
containers resolve bare tailnet names in addition to FQDNs. Leave unset to
require fully-qualified names.
- `TS_FALLBACK_DNS` (optional, default `1.1.1.1`): resolver the agent containers
use for non-tailnet names. Set your own to keep public DNS on your
infrastructure.
Scope: IPv4 tailnet peers by their `100.64.0.0/10` address or MagicDNS name. A
LAN behind a subnet router and tailnet IPv6 are not routed. See
[docs/services/tailscale.md](docs/services/tailscale.md).