DodoSSH/docs/adr/0014-android-updates.md

# ADR 0014 — Updating the Android client, and the two channels that makes necessary

- Status: accepted
- Date: 2026-08-04
- Builds on: [ADR 0011](0011-android-distribution.md), [ADR 0013](0013-desktop-distribution-and-updates.md)
- Amends: ADR 0011's consequence that there is "no automatic update"

## Context

[ADR 0011](0011-android-distribution.md) settled who holds the Android release key and listed the price
of shipping outside a store: *"There is no discovery, no automatic update, and no Play channel."* It
also left the door open in rule 2 — *"If an update check is ever added it points at the project's
domain"* — and named the missing update path as **the sharpest edge of the decision** for a product sold
to teams.

[ADR 0013](0013-desktop-distribution-and-updates.md) then built exactly that for Windows, and the
argument it turns on applies here word for word: an SSH client holding a team's infrastructure
credentials is precisely the software where *"the fix shipped and the user never got it"* is a security
outcome rather than an inconvenience.

So the question is not whether the phone should update itself. It is how, given one Android fact that
decides everything else:

**An installed app can only be updated by a package signed with the same key.** Not "should not" —
Android refuses, with `INSTALL_FAILED_UPDATE_INCOMPATIBLE`. A key is an app's identity for its whole
life.

That collides with ADR 0011 rule 1, which puts the release key on a machine that is not a runner. CI can
build an APK; what it cannot do is sign one that any installed copy will accept, because the debug key it
falls back to is generated fresh in every container. An APK released from CI today could be installed
once and never updated again — and each "update" would require an uninstall, which on this product means
losing the local cache, the outbox and the device key.

## Decision

**Two channels, which are two applications, because Android has no third option.**

1. **`release` — `dev.dodotech.dodossh`, signed by the key ADR 0011 rule 1 describes.** Cut from a `v*`
   tag by a person running `scripts/release-android.ps1` on a machine that is not a runner. No workflow
   touches it, no secret exists for it, and CI has no job that could. ADR 0011 rule 1 is unchanged, and
   its "Rejected" entry — *a release key held by CI so tagging cuts a release* — still stands.

2. **`nightly` — `dev.dodotech.dodossh.nightly`, signed by a keystore committed to this repository in the
   open.** Cut from `main` by CI on every push, published as a pre-release on the project's own forge.

   **The key is public on purpose, and that is what makes it safe to put in CI.** ADR 0011 rule 1 exists
   because a key a workflow can reach is a key held by everyone who can change a workflow file. A key
   everybody already has cannot be stolen, needs no secret to configure, and grants nothing by being
   held — so the rule has nothing to protect. It also means this channel works on a fresh runner with no
   setup, which is the practical reason it was reachable at all.

3. **Neither channel can update the other, by construction rather than by care.** Different package ids
   and different keys, so a mistake is an install Android refuses rather than a nightly quietly replacing
   somebody's real client. Both can be installed at once, which is the useful half: testing a nightly
   costs nobody the build they rely on.

4. **The update check reads the project's forge and never the deployment**, which is ADR 0011 rule 2
   applied unchanged. The feed address is a `const` in `AndroidUpdateChannel` and there is deliberately
   no setting for it — a configurable update URL is exactly the knob that would let an operator, or a
   stray edit to a plaintext file, point the update path at the party ADR 0001 models as the adversary.

   ◆ **Which means the repository has to be public, and it was not.** A constant address with no token is
   an anonymous read; the repository was private, so every check answered `404` and every phone reported
   itself current. See ADR 0013 §4, which had written the incompatibility down as a fact about where a
   token could live and not as something to check on the deployment. The check is one `curl` and it is
   there.

   The Android channel made it invisible rather than merely broken: it caught every network and parse
   failure and answered null, which `IUpdateChannel` then documented as meaning "this build is current". So
   a pressed CHECK NOW reported the latest build for an outage that had lasted since the feature shipped.
   It throws now. The timer still swallows — a phone on a train is not news, and a half-published release
   still fixes itself in six hours without anybody being told — and the button reports what happened,
   which is the distinction `UpdateViewModel` was written to make and was never given anything to make it
   with.

5. **The comparison is Android's `versionCode` and not the version name.** That integer is what the
   platform itself uses to accept or refuse an install, so comparing anything else would let the client
   offer an update the platform then rejects. The feed publishes it in a small JSON manifest beside the
   APK — the counterpart of `releases.win.json` — so a check costs a few hundred bytes rather than a
   download.

6. **Nothing is installed by the application.** It fetches, then asks Android to ask. The platform draws
   its own confirmation naming the package, and from API 26 will not draw even that until the user has
   turned this application on in the unknown-sources screen. Two deliberate answers, neither to a screen
   DodoSSH controls.

   ◆ "Asks Android to ask" is one step longer than it sounds, and reading it as one step is why this
   installed nothing at all from the day it shipped until 2026-08-05. An application holding only
   `REQUEST_INSTALL_PACKAGES` gets no verdict back from committing a session: what the platform returns
   first is `STATUS_PENDING_USER_ACTION`, carrying the confirmation activity in `Intent.EXTRA_INTENT` for
   the application to start. **Android does not draw the dialogue on its own.** The commit succeeded, the
   session staged, and nobody was ever asked anything. The receiver that starts it is
   `InstallSessionReceiver`; the intent naming it has to be explicit, since a mutable pending intent
   wrapping an implicit one is refused outright from API 34. Check 17.5 asks for exactly the right thing
   — "Android's own installer appears naming the package" — so nothing needed rewording; it wants an
   older build installed and a newer one published to run at all, and on the evidence it was never run
   against a real pair.

7. **Applying does not end the process, and the shell had to learn that.** On Windows, applying replaces
   the files and restarts, so the shell disposes the vault first — that is what zeroes the identity keys,
   the vault keys and the cache key. On Android the install is a *request* and the answer may be no, so
   disposing first would answer "not now" with a locked keychain and every shell closed. `IUpdateChannel`
   gained `ApplyingEndsTheProcess`; where it is false the session is left alone, and the keys go when
   Android kills the process on the install it agreed to.

## Consequences

**The nightly channel is a real attack surface and should be described as one.** Anyone can build an APK
a nightly phone will accept, because the key is public. Reaching one still means being what it fetches
from — a release on `git.dodotech.cloud` over TLS — so the practical set is *whoever can write a release
on this repository*, which is the same set ADR 0013 names for the desktop. That is acceptable for a
channel whose users are testing it and is not acceptable for the one holding people's credentials, which
is the entire reason there are two.

**A nightly is not a beta of the release channel; it is a different application.** Moving from one to the
other is an uninstall and a fresh enrolment. There is no migration and there will not be one — the two
caches are encrypted under keys held by two package identities the platform keeps apart.

◆ **The desktop has since taken this arrangement, and it had to build what Android is given.**
[ADR 0013](0013-desktop-distribution-and-updates.md) decision 9 is this ADR applied to Windows: a nightly
CI publishes from main, installing beside the release build rather than over it. The difference worth
carrying back here is that every separation this ADR gets from the platform — different package identity,
signature-checked updates, a per-app data directory — is on Windows a thing somebody had to choose and can
therefore undo. The paragraph above about the attack surface applies there word for word, with one line
removed: on the desktop the packages are not signed at all, so the feed is the only thing standing between
a nightly install and an arbitrary build.

**ADR 0011's "no automatic update" consequence is now wrong for the release channel and remains true for
reach.** Discovery, MDM deployment and the sideloading permission are all unchanged. What changed is only
that an installed copy can now learn a newer one exists.

**The release channel's `versionCode` stays a hand-bumped literal**, and forgetting to bump it is caught
rather than shipped: the release script reads what is already published and refuses to build a package
that does not beat it.

**Two identical launcher icons.** A nightly installed beside a release shows the same name under both.
Four ways to vary it per channel were tried and none reached the launcher label; the findings are in
`docs/platform-flags.md`. What tells them apart today is the package name in Android's app info, the
version, and the channel the application names on its own preferences screen.

## Rejected

- **A release keystore in CI so tagging cuts the real release.** The convenience is the point of CI and
  the key is the point of ADR 0011; where they collide the key wins. This ADR is what makes that refusal
  survivable rather than merely principled — the nightly channel is where the convenience went.
- **One channel, released from CI, signed with a stable key held as a secret.** This is the arrangement
  most projects land on and it is ADR 0011's rejected entry with an extra step: the secret is reachable
  by whoever can change a workflow file, and what it signs is the client holding the credentials.
- **Opening the release page in a browser instead of installing.** It would work, and it moves the same
  APK through the same unknown-sources gate with one more step and no less trust. What it gives up is any
  way of knowing a fix has been fetched, which is the property this ADR exists to buy.
- **A version-name comparison, so the feed could be a directory listing.** SemVer with prerelease heights
  needs a parser, and the parser would disagree with the platform sooner or later. The number Android
  uses is the number to compare.