Review finding: `--http` parsed whatever address it was given and bound
it. The door is the plaintext MCP service with a static bearer token;
plan 3.9 and the P9a model put a TLS proxy or tunnel in front of a
loopback listener, and no decision authorises exposing the books
unencrypted. `--http 0.0.0.0:7411` would have done exactly that.
`local::tunnel_address` now accepts only a loopback address
(127.0.0.0/8 or ::1; `127.0.0.1:7411` stays the default) and refuses
anything else with a message naming loopback and why. `server` refuses
while parsing, before it takes the lock or binds a socket; `serve`
refuses before it starts a host, so nothing is left half-open. The
bind-failure behaviour for a loopback address is unchanged (said, not
fatal, 3.9), as is the unit's hardening.
The test `the_tunnel_door_binds_loopback_only` refuses 0.0.0.0, a public
sample address and [::] through `server`, checks no socket or host was
left behind, refuses through `serve`, then starts a loopback listener and
reaches `books.start` with the bearer.
No accounting code, report or figure changes.
The books can live on a machine of the owner's own (plan 3.8, 8.2 P9a,
D-51). Three things make that honest instead of nominal:
- `--isolation same_user|enforced` sets `server::Isolation`, carried
through `Served` and `BooksServer` to `books.start`. Locally the books
stay `same_user (advisory)`; under the self-host unit the server is told
`enforced` and reports `service_user (enforced)`. The server never
guesses, and the literal it used to report is gone.
- `--http [ADDR]` binds the same MCP router on loopback (default
127.0.0.1:7411) beside the Unix sockets, before the ready line, for the
TLS proxy or tunnel in front of the server. It is the same bearer door
and the same graceful close; a failed bind is reported and is not fatal
(3.9). `serve` carries both flags through the host, so the system unit
can ask for them once.
`deploy/wanderbooks-server.service` is the unit: a dedicated account, a
0700 data root, `ProtectSystem=strict`, no seccomp or Landlock (D-32), and
loopback-only networking. `deploy/README.md` is the recipe: install, setup,
move the books by `books adopt` with its head check (D-31: a copied book
is the transport), mint a bearer token, put Caddy or Tailscale Funnel in
front of the loopback door, and point Claude Code and Codex at it.
The two-account CI job (`.github/workflows/two-user.yml`) makes the
deployment and runs `crates/ledger-cli/tests/two_user.rs` as another
account: `agent_uid_cannot_read_tenant` proves the tenant root and its
journal are refused, then reads, writes, uploads, files, exports and
verifies over HTTP with the bearer (in a second book, so the moved books'
head is not advanced); `self_host_adopt_same_head` compares the moved
books' head and event count with the source clone's.
`isolation_label_is_enforced_under_the_unit` runs everywhere, including
the unit-file read that keeps the recipe from drifting.
Accounting reason for the shape: nothing here changes an entry, a report
or a figure. It changes who can reach them: the move is lossless and
verifiable at the head, and the boundary is the operating system's, not a
promise in our text. No journal code, kernel function, Kani harness or
Lean step is touched, so `just prove` is not required.
No go-ahead needed: no new journal feature or event; the live books are
unaffected.
swaits