Verified against the fips crate source: the mesh ULA is a pure function
of the PUBLIC key — fd || sha256(x-only pubkey)[0..15] — so the npub is
the durable address and needs no resolver. Android/tools/fipssh wraps
ssh for Termux: 'fipssh user@npub1…' derives the ULA (pure-python
bech32 + sha256, checksum-validated, typo protection) and execs ssh
over the companion's split tunnel; --resolve prints the ULA alone.
The derivation is pinned by a new Rust test
(npub_derives_the_same_mesh_ula_as_the_fips_identity, 3 seeds against
fips::Identity) and the helper's output was verified byte-identical
against a live fips identity pair. SSH-over-mesh handover updated with
an addendum: node docs/UI can advertise npub-based addressing, no
node-side DNS needed for this case.
Today's field test: Termux over the companion's split tunnel reaches the
node's fips0 ULA and gets RST — the mesh path works end to end, port 22
is refused by the node (fips0 default-deny, no 22 in the fips.d drop-ins;
sshd IPv6 listening unverified). The interim manual unblock (a
source-restricted 90-ssh.nft drop-in) is documented, but the real ask is
a first-class 'SSH over mesh' settings toggle in the node UI, with the
drop-in lifecycle owned by the daemon, a source-scope decision (paired
phones vs any mesh peer), sshd preflights, and an acceptance checklist.
Companion side is done (device-wide split tunnel + the node ULA now
displayed/copyable in the hub Nodes page) — the node agent is downstream.
Dorian