# ADR 0013 — Distributing the desktop client, and letting it replace itself

- Status: accepted
- Date: 2026-08-04
- Builds on: [ADR 0001](0001-e2ee-trust-model.md), [ADR 0011](0011-android-distribution.md)
- Settles: the desktop half of M4 packaging, which [ADR 0011](0011-android-distribution.md#consequences)
  left open

## Context

[ADR 0011](0011-android-distribution.md) settled the phone and said explicitly what it was not settling:
"M4's desktop packaging inherits rule 2 and not the rest." This is that inheritance, plus the thing the
phone deliberately does not have.

The desktop head was not packaged at all. There were no tags, no `Version` property anywhere in the
repository, and therefore no version: every assembly reported the SDK's default `1.0.0`, and the API had
been serving that string to every client that asked it for `serverVersion`. There was no installer and no
way for anybody holding a copy to learn that a newer one existed.

That is tolerable while nobody has it. It stops being tolerable at the first release, and it stops in a
particular direction: this client holds the plaintext of a team's infrastructure credentials, by
construction (ADR 0001). For software like that, "the fix shipped and the user never got it" is a security
outcome. ADR 0011 named the cost of shipping outside a store — "no discovery, no automatic update" — and
accepted it for Android because the platform left no better option. The desktop leaves a better option, and
this ADR takes it.

The new thing an updater introduces is a capability that did not exist before: **something that can replace
the binary on a user's machine, without the user choosing each build.** ADR 0001 models the party who wants
the secrets as attacking the client rather than the crypto, and ADR 0011 turns that into a question of
custody — *which parties can ship one person a build?* An updater is a second answer to that question, so
it needs the same treatment as the signing key, and it is easy to get wrong because the dangerous part does
not look like a key.

## Decision

### 1. Velopack, per-user, under `%LOCALAPPDATA%`, with no administrator prompt

`docs/platform-flags.md` had already ruled out the platform-native option, and it is worth restating
because it is the kind of decision that gets reopened: **MSIX is not deprioritised, it is impossible
here.** A packaged application runs WebView2 in an AppContainer where loopback connections are blocked
without a `CheckNetIsolation` exemption, and the terminal data plane *is* a loopback WebSocket. MSIX would
not degrade the product, it would remove the terminal.

Velopack's path was checked against that and reintroduces nothing: `Setup.exe` is an ordinary Win32
executable that unpacks a directory and creates shortcuts, there is no package manifest and no package
identity, and the process therefore stays an ordinary desktop process. Manual check 16.4 is what would
notice if that ever changed, because it connects a real shell from the installed build.

### 2. The pack id is `DodoSSH.Desktop`, and it is irreversible

Velopack installs to `%LOCALAPPDATA%\<packId>` and **removes that entire directory on uninstall**.
`ClientPaths.DataDirectory` is `%LOCALAPPDATA%\DodoSSH`, and it holds `cache.db` with its `-wal` and `-shm`
companions, `settings.json`, and `device.key`.

So the obvious pack id would have installed the application on top of the user's encrypted cache, and
uninstalling would have deleted the device key and the outbox — the changes this machine has made and not
yet pushed, which `MainWindowViewModel.SignOutWarning` already describes to users as existing "nowhere else
in the world". The application refuses to delete that without a counted confirmation; an uninstaller would
have done it silently.

Velopack's own guidance is to keep persistent files in roaming `%APPDATA%`. **That guidance is declined**,
and `ClientPaths` already explains why: two machines writing one SQLite file through a file-sync client
corrupts it, and the outbox is per-machine by design. The install moves; the profile does not.

Like the Android package id, this is a one-way door — it is the identity an installed client matches an
update against, so changing it later orphans every existing install: still running, never updated, and
invisible to the new one.

### 3. The release is cut by a person, and the forge token never goes near CI

This is the paragraph that will be argued with, so it is the one written most carefully.

The tempting argument is that a Gitea write token is not a signing key, and so — unlike the Android
keystore ADR 0011 rule 1 keeps off runners — it could live in a CI secret and let a tag cut a release.

**It does not survive contact with what the token can do.** Velopack clients fetch from the configured
source over TLS and do not verify a package signature when they apply it. So anyone who can write a release
on this repository can publish an update that every installed client downloads and runs. That is precisely
the capability ADR 0011 rule 1 places on a machine which is not a runner, reached through a different door —
and a workflow secret is held by everyone who can change a workflow file, which for a repository with any
contributors is a wider set than it looks.

So: `scripts/release-windows.ps1`, run by a person on a Windows machine, in two phases. Phase one builds and
packs and stops. Phase two, a separate invocation, asks for the token and uploads. The split exists so that
what reaches users has been installed and started by a human first, and so that the credential is in memory
only for the minutes that need it.

A second, smaller reason was recorded here — that `vpk` stamps and embeds the `Setup.exe` and
`Update.exe` stubs with Windows tooling, and every job in `ci.yml` is `runs-on: [linux]` — on the
reasoning that somebody will fix one reason and believe they are done.

◆ **That second reason was not true, and the correction is worth more than the claim was.** `vpk`
cross-compiles when it is told to: the bracketed OS directive, `vpk [win] pack`, builds the setup stub,
the portable bundle and the `.nupkg` on Linux, and reports `Directive enabled for cross-compiling from
Linux (current os) to Windows` while doing it. Only signing needs Windows tooling, and rule 8 above is
why nothing is signed yet. Plain `vpk pack` on Linux targets Linux and rejects a Windows RID, which is
the shape of the mistake: the tool does not fail because it cannot, it fails because it was not asked.

The correction does not move this rule at all, and that is the point of separating the two. The reason
that stands was never mechanical, so a Linux runner that *can* pack changes nothing: what may not be on
a runner is the token, not the build.

What CI gains is the same thing the `android` job already does — it proves the artefact still builds and
still packages. On main and on tags the build job publishes `win-x64` and then packs it, so a restore
graph that resolves for `net10.0` and not for `net10.0/win-x64` fails there rather than under a person
midway through a release. Packaging is the more valuable half and adds a few seconds to a publish that
has already happened — measured at two to seven, against the minutes the publish itself takes: `vpk` verifies
that the main executable actually calls `VelopackApp.Build().Run()`, so the change that quietly produces
an application which never updates itself — compiling, tested, and invisible until a release goes
unreceived — fails in CI. The packages are written to `RUNNER_TEMP` and discarded, and are deliberately
not offered as workflow artefacts: an installer nobody has run should not sit somewhere that invites
passing it on.

CI does not call `scripts/release-windows.ps1` to do any of this, and should not. That script is the
person's procedure — it refuses a dirty tree, requires a tagged `HEAD`, fetches the previous release for
deltas, and prompts for the token — so running it on a runner would mean either weakening it with CI
switches or having CI satisfy conditions that only make sense at a desk. The workflow writes the same
`vpk` arguments out in shell, and the constants they share (pack id, title, authors, channel, icon) are
noted in both places as a contract with `VelopackUpdateChannel` and with every installed client.

### 4. The update check points at the project's forge, and the address is a constant

ADR 0011 rule 2 carries over unchanged, and its update clause carries with it: "If an update check is ever
added it points at the project's domain." Here that is `git.dodotech.cloud`, and it is a `const` in
`VelopackUpdateChannel` rather than a setting.

**The constant is the mechanism, not a convention.** A configurable feed address is exactly the knob that
would let an operator — or an edit to a plaintext `settings.json` — point the update path at the
deployment, and an operator who can answer "is there a newer version" can answer "no" forever, pinning a
chosen user to a build with a known hole while holding no key at all. Making it unsettable is that rule
expressed in a way nobody has to remember.

`ClientSettings` therefore stores whether to check, and nothing else: no address, no channel, no token. A
private release repository is incompatible with this design and that is worth knowing rather than
discovering, because the token would have to be readable before the vault is unlocked, and this file is the
one place that can be read then — which is the one place a token may not go.

◆ **It was discovered.** The paragraph above was written and the repository was private anyway, so every
check on every client asked an address that answers `404` — Gitea does not distinguish "not there" from
"not yours" — and both heads reported the running build as current. It had never once worked, on either
platform, and nothing anywhere said so. Two things came out of that and both are now written down rather
than assumed:

- **The feed repository must be readable with no credentials, and that is a deployment precondition** rather
  than a property of the code. It is checkable in one line, which is the only reason it is worth stating:
  `curl -so /dev/null -w '%{http_code}' https://git.dodotech.cloud/api/v1/repos/DodoTech-Public/DodoSSH` answers
  `200` when the design holds and `404` when it does not. `/api/v1/version` answering `200` proves only that
  the forge is reachable, which is what made this look like nothing was wrong.
- **An unreachable channel must be distinguishable from a current build.** `IUpdateChannel.CheckAsync` used
  to document null as the honest answer for both, on the reasoning that the caller does the same thing
  either way. That is true of the six-hourly pass and false of CHECK NOW, and it is what turned a total
  outage into a reassuring sentence. It throws now, and `UpdateViewModel` keeps the distinction it always
  had: silent on the timer, the exception's own message on the button.

### 5. `MinClientVersion` stays unread, and if it is ever read it may not fetch

`MetaResponse.MinClientVersion` has existed since M1, is served, is fetched on every sign-in, and is read
by nothing. Hanging the updater off it would have been natural and would have been wrong — and note the
shape of the error, because it is not "inherits an existing risk". Today the field controls nothing at all.
The moment an update check is conditioned on it, rule 2's sentence applies verbatim and the risk is
*created*.

The split to preserve:

- A deployment may say **"I will not serve a client this old"** and draw a remediation screen. That is the
  deployment describing itself, which is legitimate and is what the field's own documentation asks for.
  That screen may carry a sentence and a link to the project's release page.
- It may **not** carry a button that triggers a check or a download. A link is the user going somewhere; a
  fetch is the operator's answer steering this process.

Under the design as built, an operator withholding or deflating the value achieves nothing — the check runs
on its own timer and never consults the deployment. Inflating it denies service to their own users, which
they can already do by turning the server off.

### 6. Self-contained, and not single-file

Self-contained because .NET 10 is recent enough that almost no machine has the runtime, and because the
usual objection — that runtime security patches then require an application update — is answered by the
feature this ADR is about. Velopack's deltas are per-file and the runtime files do not change between our
releases, so the runtime costs almost nothing per update; it is paid on first install.

Not single-file, for four independent reasons: `platform-flags.md` records that libsodium ships native
binaries per RID and complicates single-file publishing, and `libe_sqlite3`, `libSkiaSharp` and
`libHarfBuzzSharp` do the same; a bundle changes wholly on every build, so deltas stop working; Velopack is
a directory-based updater by design; and a self-extracting bundle puts the executable under a temp path
deep enough to hit the WebView2 long-path failure that same document records. Not trimmed — EF Core is not
trim-safe and `TreatWarningsAsErrors` turns every `IL2xxx` into a build break, so trimming is a project
rather than a flag.

**Native symbol files are excluded and ours are kept**, which is worth recording as a decision because the
numbers are so lopsided: `libSkiaSharp.pdb` and `libHarfBuzzSharp.pdb` are 100 MB of debug symbols for
third-party native code nobody here will step through, and all fifteen of our own managed PDBs together are
0.93 MB. Dropping the two took a publish from 227 MB to 127 MB. Keeping ours means an
`Exception.ToString()` carries file names and line numbers, which for a self-hosted product is the whole
diagnostic channel — the way a fault gets reported is a user pasting a stack into an issue.

### 7. One version, derived from the tag

MinVer, with `MinVerTagPrefix` of `v`, matching the tags CI already triggers on. The tag was already the
version of record for the API's container image; this makes it the version of record for everything,
including the client's own `AssemblyInformationalVersion`, which is what the preferences screen prints and
what Velopack compares.

MinVer's one sharp edge is that it answers plausibly rather than failing: a shallow clone with no tags
yields `0.0.0-alpha.0.N`. Here a wrong version is a client that never updates, so it is guarded twice —
`fetch-depth: 0` on every checkout, and a step that fails a tag build when the computed version and the tag
disagree.

The Windows application manifest's `assemblyIdentity` version is **deliberately** left at `1.0.0.0`. It is a
side-by-side activation field this application does not use and nothing reads; what a person sees comes from
the PE version resource, which MSBuild fills from `FileVersion`.

### 8. Unsigned for now, with a named trigger

Every installer will raise SmartScreen's "Windows protected your PC" until reputation accrues. The cost is
smaller and more precisely bounded than the reflex suggests, and the bound is worth knowing: Mark-of-the-Web
is applied by the *browser* that downloads `Setup.exe`, so the warning lands at first install only. In-app
updates are fetched by the application's own HTTP client and applied by `Update.exe` from a local file, and
never trip it. **One dialog per user per lifetime, not one per update.**

The trigger for buying an OV certificate on a hardware token is the first release the README invites a
stranger to install. ADR 0011 already describes Authenticode as the easy custody case — the key stays with
the developer — and the post-2023 requirement that it live on FIPS 140-2 Level 2 hardware enforces "offline,
never in CI" physically rather than by policy. `--signParams` is the single line in the release script that
changes.

**Azure Trusted Signing is not the quiet default and needs its own ADR.** It is cheaper and has no hardware
token, and it puts a compellable third party in the signing path — which is ADR 0011 rule 3's shape one
layer down, declined there for reasons that do not stop applying because the vendor changed.

## Consequences

**The desktop gets what ADR 0011 had to refuse the phone.** Discovery is still manual — somebody has to be
told where the release page is — but from the first install onward the client keeps itself current without
anybody deciding to go and look. That is the sharpest edge of the Android decision, blunted on the platform
where it could be.

**Nothing is ever installed while the application is running.** A fetched update waits for a restart the
user presses, or for the next launch they were going to do anyway. This is not caution for its own sake:
this application deliberately keeps shells running across a lock, and argues in `LockAsync` that a lock
which destroyed work would simply stop being used. A restart does end every shell, so it is a decision that
belongs to the person whose job is running in one — and the interface says so, in the same words the close
button already uses.

**The release is a manual step, and that will feel slow.** It is roughly ten minutes of a person's attention
per release, and the convenience being refused is the entire point of CI. Where the two collide the custody
argument wins, exactly as it does for the Android keystore.

**The forge grows by about 125 MB per release, forever.** Measured on the first real pack rather than
estimated: a 127 MB publish directory compresses to a 60 MB full `.nupkg` and a 64 MB `Setup.exe`, and both
are uploaded. Velopack needs the previous full package present to build a delta against, so pruning old
releases has a real cost — a client several versions behind falls back to a full download. A 64 MB asset is
also large enough to meet whatever body-size limit fronts `git.dodotech.cloud` (nginx's
`client_max_body_size` defaults to 1 MB), which is worth checking before the first upload rather than
discovering after ten minutes of transfer.

**Uninstalling leaves the vault cache behind, on purpose.** `%LOCALAPPDATA%\DodoSSH` survives, so a
reinstall finds an enrolled machine and asks for the passphrase — which is what somebody reinstalling wants.
The honest cost is that `device.key` is left too, and the account goes on listing a device that is no longer
installed. That is a wart rather than a hole: the blob is decryptable only by this machine's TPM, and Sign
Out is the button that withdraws the registration. An uninstall is not a sign-out and must not pretend to
be one.

**Contracts and client now share a version number.** `DodoSSH.Contracts` is packable, so a contracts-only
change ships as a client version bump. One number is the point; this is the price of it.

**The Android head's `versionName` now follows the same tag**, while its integer `versionCode` stays
hand-bumped, because Android needs a monotonic integer and SemVer does not provide one. Nothing else about
ADR 0011 changes.

## Rejected

- **MSIX.** Not a preference. It would break the terminal outright; see decision 1.
- **A CI job that cuts the release on a tag.** The convenience is the point of CI and the custody is the
  point of ADR 0011; where they collide the custody wins. See decision 3, and note that a Windows runner
  answers the mechanical objection while leaving the real one untouched.
- **A configurable update feed.** Named here because it is the change somebody will propose in good faith,
  for a self-hosted product where making things configurable is usually right. It is the one setting that
  would hand the operator the capability the whole trust model is about.
- **The deployment serving the installer.** Refused again, for the third ADR running, because it is
  genuinely the nicest onboarding available and will be proposed again.
- **Conditioning updates on `MinClientVersion`.** See decision 5. It would create the attack rather than
  inherit it.
- **Azure Trusted Signing**, for now, on custody grounds rather than on mechanics. See decision 8.
- **A hand-edited version property.** Considered seriously against MinVer, and it loses on the thing that
  matters here: the tag is already the version of record for the container image, and two places to write
  one number is a pair that can disagree. MinVer's silent-wrong-answer failure mode is real and is what the
  two CI guards in decision 7 exist for.