DodoSSH/docs/android-port.md

# An Android client: what it would take

**Status: started. Steps 3, 4 and 6 are done; the interface is next.** `src/DodoSSH.Client.Android` is a
real head that builds and packages. The four decisions that shape the work are recorded in
[Decisions](#decisions-taken); everything below them is the audit they were taken against, and it has held
up — with three corrections and one addition, all marked **✅ settled** or **⚠️ corrected** where they
belong.

**What the spike came back with**, since everything downstream was gated on it:

- **The cryptography works.** `libsodium.so` and `libe_sqlite3.so` are both in the arm64 APK. NSec
  resolving its native half despite shipping no Android-specific build was the one dependency this
  document said was worth proving with a build, and it proves out.
- **`Avalonia.Controls.WebView` forces `targetSdk` 36**, which settles the open question about Android
  versions — see [Still open](#still-open). This head is minSdk 28 / targetSdk 36.
- **Cleartext to loopback has to be allowed explicitly.** Not in the original audit and easy to lose a day
  to: Android has blocked plaintext HTTP by default since API 28, so the terminal renderer needs a network
  security config scoped to `127.0.0.1` or the WebView loads nothing and the failure looks like a renderer
  that never attached. See `Resources/xml/network_security_config.xml`.

**Still unverified, and it is the honest limit of all this:** nothing has run on a device or an emulator.
No system image is installed here, so every statement below about *runtime* behaviour — Argon2id actually
completing at the 256 MiB profile on a phone, the WebView actually loading the renderer, the biometric
prompt actually releasing the key — remains reasoning from the code and the platform's rules. What is
verified is that it compiles, links, packages, and carries the right natives.

**The shape agreed:** a **phone-first** client that is the keychain plus a **terminal**, with sessions and
transfers protected by a **foreground service**. File transfer is not in the first scope; when it arrives it
is **one remote pane** with Android's document picker for moving files in and out.

**What was actually checked**, so the rest can be read with the right amount of trust:

- Every project's target framework, read from `Directory.Build.props` and the `.csproj` files.
- The target frameworks each pinned package ships, read out of the local NuGet cache — so these are the
  assemblies this solution would actually resolve, not what a package's README claims.
- Every site in `src/` that names a Windows API, a Windows path convention, or a desktop lifetime.

**What was not**: nothing was compiled for Android, nothing was run on a device or emulator, and no Android
SDK is installed here. Every statement below about *runtime* behaviour is reasoning from the code and the
platform's documented rules, and is marked where it matters.

---

## The headline

The port is smaller than it looks in one dimension and much larger in another.

**The core is already portable.** Every project targets plain `net10.0`, with no `net10.0-windows` anywhere
and no conditional compilation. All the Windows-specific code now sits in one project — `DodoSSH.Client.App`,
the desktop head. The cryptography, the sync engine, the local cache, the SSH layer, the item kinds and every
view model are platform-neutral today, and that is not luck: it is what the project structure has been
enforcing all along.

(One file was out of place when this was written — `WindowsDeviceKeyStore`, in `DodoSSH.Client.Session`. It
has since been moved, which is the only code change this audit produced; see §4.)

**The product is not.** DodoSSH is a two-pane file browser, a tab strip, a nav rail and a terminal, laid out
at a minimum of 880×560, driven by hover, right-click, middle-click and drag-and-drop. A phone is about
360dp wide and has none of those inputs. Roughly none of the *interface* ports; the question an Android
client really asks is not "will this compile" but "what is the Android product".

Two platform rules make that sharper, and they are the things most likely to be underestimated:

- **Scoped storage.** Android has no arbitrary local filesystem for an app to browse. The left-hand pane of
  the Files screen — this machine's drives and directories — has no Android equivalent at all.
- **Background execution.** Android stops a backgrounded process. A terminal client whose whole premise is
  that a shell survives locking the vault, and a transfer queue that runs for minutes, both assume a process
  that keeps running. On Android that needs a foreground service with a persistent notification, or the
  feature changes shape.

Neither is a porting problem; both were product decisions, and both have now been taken — a foreground
service, and a single remote pane. See [Decisions](#decisions-taken).

---

## What ports as it stands

Verified from the resolved package assemblies.

| Dependency | Ships for Android | Note |
| --- | --- | --- |
| `libsodium` 1.0.22 | ✅ `android-arm64`, `android-arm`, `android-x64`, `android-x86` | The native half of all the cryptography |
| `NSec.Cryptography` 26.4.0 | ⚠️ no Android-specific build | Ships `net9.0` plus iOS/tvOS/MacCatalyst. The plain `net9.0` assembly should load, since the platform-specific part is libsodium — but this is the one dependency worth proving with a build before anything else |
| `SSH.NET` 2025.1.0 | ✅ `netstandard2.0`, `net8.0` | Sockets only; needs the `INTERNET` permission |
| `SQLitePCLRaw.bundle_e_sqlite3` 2.1.12 | ✅ `net6.0-android31.0` | The local cache |
| `AWSSDK.S3` 4.0 | ✅ `netstandard2.0`, `net8.0` | |
| `CommunityToolkit.Mvvm` 8.4.2 | ✅ `netstandard2.0` | Every view model |
| `Avalonia.Controls.WebView` 12.0.1 | ✅ `net10.0-android36.0` | The surprise — see below |
| `Avalonia.Desktop` 12.1.1 | ❌ `net10.0` only | Replaced by `Avalonia.Android`, not ported |

So: **`DodoSSH.Client.Domain`, `.Storage`, `.Sync`, `.Api`, `.Auth`, `.Ssh`, `.Terminal`, `.Transfer`,
`.ObjectStore`, `.Import` and `.Crypto` should all target `net10.0-android` unchanged.** That is the great
majority of the code, including all of the cryptography and all of the sync protocol.

`DodoSSH.Client.Session` needed one file moved and no longer does — see §4. `DodoSSH.Client.App` is the
desktop head and does not port; an Android head would be a sibling project sharing its view models.

---

## What does not port, in order of how much it costs

### 1. The interface — the largest item by far, and it is not a port

880×560 minimum, a 54-pixel nav rail, a 268-pixel host sidebar, a two-pane file browser with six columns per
pane, a tab strip, and a layout suite (`DodoSSH.Client.App.Layout.Tests`, 64 tests) whose entire premise is
that everything fits at that minimum.

None of it survives a phone. What an Android client would be is a different product with the same core:
probably a host list, a terminal, and a single-pane file browser, with the keychain, snippets, logs and pins
as screens rather than as a rail. The desktop screens are not a starting point for that — they are a
different answer to a different question.

**This is where the real effort is**, and it is design effort before it is engineering effort. Everything
else on this list is a week or two of work; this is the product.

**Decided: phone first.** See [Decisions](#phone-first) — which means a redesign rather than a reflow, and
rules out the cheaper tablet route deliberately.

### 2. The Files screen's left pane has no Android equivalent

Scoped storage means an app sees its own directory and whatever the user hands it through the system
picker. There is no browsable `C:\` or `/home`. So the two-pane layout — the thing the whole screen is built
around — does not exist on Android.

The honest shapes are: a one-pane remote browser with **download to** and **upload from** going through the
system document picker, or a remote-to-remote transfer tool with no local side at all. Both are fine; both
mean the transfer queue's local half (`LocalDirectory`, the drive list, the breadcrumb trail) is desktop-only
code.

Note what *does* carry: `FileTransferQueue` itself, and `IRemoteFileStore` — Phase 6 already proved that
seam holds two very different remotes, and a `Uri`-backed Android document would be a third.

**Decided: one remote pane and the document picker**, and out of the first scope. See
[Decisions](#file-transfer-when-it-comes-one-pane-and-the-document-picker).

### 3. Background execution

`TerminalWorkspace` keeps shells running across a vault lock, deliberately and documented. `FileTransferQueue`
runs one transfer at a time for as long as it takes. `VaultViewModel` runs an auto-sync pass every minute.
All three assume a process Android will stop.

The options are a foreground service with a notification for as long as a session or a transfer is live
(which is what every serious SSH client on Android does), or accepting that backgrounding the app drops the
connection. The first is not hard; it is a decision about what the app is allowed to do to the user's
battery and notification shade, and it wants taking deliberately.

**Decided: a foreground service** while a shell or a transfer is live. See
[Decisions](#sessions-survive-backgrounding-via-a-foreground-service).

### 4. The device key store — the cheap one, because the seam exists

`WindowsDeviceKeyStore` is DPAPI over a TPM-held key. `IDeviceKeyStore` is already the interface everything
else uses, with three methods and an `IsAvailableAsync` that exists precisely so a platform without a
keystore can say no.

Android's equivalent is the Android Keystore, with StrongBox where the hardware has it, and it is a closer
match than the Windows one: it can require biometric or device-credential authentication to release the key,
which is what the unlock screen would want anyway. **This is a straightforward implementation of an existing
interface**, and it is the piece of Android integration most clearly worth doing well.

**Done, ahead of any decision:** `WindowsDeviceKeyStore` used to sit in `DodoSSH.Client.Session`, which was
the one thing keeping that project from being portable. It now lives in `DodoSSH.Client.App/Platform/`, and
its factory is `DesktopDeviceKeyStores` — named for the head it belongs to. `IDeviceKeyStore` and
`UnavailableDeviceKeyStore` stayed behind, because they are the seam rather than an implementation.

The move cost nothing but a namespace, which is the useful part of the finding: the session layer takes a
store and has never known which one, so an Android implementation drops into the same hole. Verified by the
build and the suite, with the two Windows-only tests moving to `DodoSSH.Client.App.Tests` alongside it.

### 5. Sign-in

`BrowserLauncher` uses `Process.Start(UseShellExecute: true)`; `LoopbackCallbackListener` implements RFC 8252
§7.3 loopback redirect with a raw `TcpListener`.

Neither is right on Android. `Process.Start` does not exist; the platform way is an `Intent`, and the
platform way to receive the redirect is a Custom Tab plus an app link or a custom scheme. Loopback redirect
*might* work, and should not be used: on a shared device any other app can bind a loopback port, which is
exactly the attack RFC 8252 §8.3 warns about and the reason app links exist.

So this is a second implementation of an existing shape rather than a port. The PKCE flow, the discovery, the
key binding and the token handling above it are all unchanged.

### 6. `ClientPaths`

Branches Windows / macOS / XDG, with an explicit comment about wanting a *local, non-roaming* directory
because two machines sharing one cache file corrupts the outbox. On Android the right answer is the app's own
`filesDir`, which is per-app, non-roaming and not user-visible — it satisfies the requirement more cleanly
than any desktop platform does. One more branch, or better, the value injected by the head. `ClientPaths`
already takes an explicit directory for exactly this reason.

### 7. `Environment.MachineName`

Used as the device name on connection and activity log entries, and when registering a device. On Android it
returns something like `localhost`, which would make every log entry from a phone indistinguishable. Needs a
real device name from the head.

### 8. The Windows-only bits of the desktop head

Listed for completeness; none of these is ported, they are simply absent from an Android head.

- `NativeKeyboardFocus` — `user32.dll SetFocus`, and the whole documented asymmetry about focus not
  returning from the WebView. Android's focus model is different and this problem may simply not exist there.
- `Program.Main` — `[STAThread]` (required by WebView2 specifically) and `StartWithClassicDesktopLifetime`.
  An Android head is an `AvaloniaMainActivity` instead.
- Middle-click tab close, right-click, hover states, drag-and-drop between panes.

### 9. The terminal — better news than expected, with one unknown

`Avalonia.Controls.WebView` ships a `net10.0-android36.0` target, which was the single fact most likely to
sink this. And the transport underneath is more portable than it looks: `TerminalDataPlane` serves the page
and the binary protocol over a **loopback WebSocket**, and an Android WebView can load `http://127.0.0.1:port`
just as WebView2 does. The xterm.js bundles are embedded resources and are platform-neutral.

**Unverified, and it is the thing to check first if this goes ahead:** whether Avalonia's Android WebView
composites the same way — a native view above everything Avalonia draws. If it does, the occlusion rule in
`docs/platform-flags.md` applies unchanged and `IsTerminalShowing` keeps doing its job. If it does not, the
rule is unnecessary rather than wrong, which is the harmless direction.

The parts that are definitely different are the on-screen keyboard, and the fact that a terminal on a phone
needs Ctrl, Esc, Tab and arrows that the software keyboard does not offer — every Android SSH client ships an
accessory key row for this. That is UI work, not porting.

---

## Decisions taken

Four, each recorded with the reasoning that was actually weighed rather than only the outcome.

### Scope: the keychain and a terminal

Not a companion, and not the file browser. Everything that is already a list or a form — hosts, groups,
keys, passwords, snippets, pins, logs — plus opening a shell.

The terminal is the expensive half and it is the half that makes it an SSH client rather than a viewer. It
depends on the WebView spike coming back clean; if it does not, the companion subset is what is left and is
still worth shipping, so the work is ordered to find that out early.

### File transfer, when it comes: one pane and the document picker

Out of the first scope, decided now so the seams are not built the wrong way. A single remote pane, with
Android's document picker for moving files in and out.

This is the shape scoped storage allows, and the interesting part is how little it costs: `FileTransferQueue`
and `IRemoteFileStore` both carry over unchanged. Phase 6 already put a bucket behind that interface beside
an SFTP host, so a picker-granted document is a third implementation of a seam that has been exercised twice.
What is desktop-only is the *left* pane — `LocalDirectory`, the drive list, the breadcrumb trail.

### Sessions survive backgrounding, via a foreground service

A persistent notification for as long as a shell or a transfer is live.

It costs the user a notification and some battery. It buys the behaviour the desktop client already promises
and documents — that a shell outlives a vault lock, and that a transfer finishes — and the alternative was
to make `TerminalWorkspace`'s guarantee desktop-only, which is a worse thing to have to write down than a
notification is to look at.

### Phone first

About 360dp wide. The tablet route was cheaper — a landscape tablet is close to the existing 880×560 minimum
and much of the current layout could have been reused — and the phone is the device people have with them,
which for an SSH client is most of the point.

So the interface is a redesign rather than a reflow, and that is the largest single item of work here. The
nav rail, the 268-pixel sidebar and the two-pane browser do not survive. What does survive is everything
behind them: every view model, every command, every piece of state.

---

## What the interface actually has to carry

Written for designing the phone client. It is an inventory of what exists today and what each part is
*for* — not a layout, and not a claim that any of it should look the same.

**Read it as a checklist of things that need somewhere to go.** The desktop has room to put a warning, a
confirmation and a form on screen at once; a phone does not, and the states most easily lost are the ones
that appear rarely and matter most. Those are marked **◆**.

### Getting in: six states before the app is usable

`ShellState`, and every one of them is a screen.

1. **Starting** — reading the local cache to find out whether this machine is enrolled.
2. **Needs a server** — nothing cached: name a server, sign in through the browser. The only state that
   requires a network.
3. **Needs enrollment** — signed in, but the account has no vault key yet. Choose a passphrase.
4. **◆ Showing the recovery code** — *the user must not be able to click past this.* It is the only moment
   the code exists; losing it along with the passphrase means the vault is unrecoverable, and there is no
   server-side reset by design. On desktop it is a whole screen with a confirmation. It needs to stay one.
5. **Locked** — the unlock screen. Passphrase box, optional device unlock (biometric on Android), a status
   line, and the line saying this works with no network. **◆** Also carries two disclosures: how many shells
   are still connected behind the lock screen, and the paragraph explaining that *locked* describes the
   keychain and not this machine's access to the hosts. Plus **reset this machine** for a forgotten
   passphrase.
6. **Unlocked** — everything below.

### Chrome that is present on every screen

- **Titlebar** — vault name, account name, a search affordance (Ctrl+K on desktop), and a sync dot with a
  label: synced, pending count, offline, unreachable.
- **Status bar** — the selected terminal's live dot and address, the vault's last status sentence, the sync
  label again, and the search hint.
- **Nav rail** — eight destinations: `HOSTS FILES KEYS PINS SNIPS LOGS TEAM PREFS`. Five characters is a
  desktop constraint, not a product one; the phone can use words.
- **Terminal strip** — always visible, above every screen. Tabs with a close cross *inside* each tab, a `+`,
  and a sentence when there are none. This is what makes a terminal a surface the window switches to rather
  than a screen you navigate away from, and it is the single most desktop-shaped idea in the product.
- **Quick connect** — a search palette over hosts that connects on Enter.

### The nine destinations

**1. Hosts** — the list of machines, and what is known about the selected one.

- *Sidebar:* filter box; group headings with a chevron and a count, **shown only when groups exist**; host
  rows carrying a connected dot, name, sync badge, address and one word for how it authenticates.
- *Editor* (doubles as "add"): name, hostname, port, username, notes, one authentication picker covering
  typed password / key / stored credential, a group picker, a relay checkbox with the sentence explaining
  that relay puts the address on the server in plain text, and **◆ forget host key** — the only way back from
  a legitimately rebuilt server.
- *Actions:* new / edit / delete, **replaced in place** by the delete confirmation rather than stacked under
  it.
- *Right column:* the connect banner — a password box only for a host that asks for one, a sentence in its
  place when it does not, and CONNECT.
- **◆ Unknown host key prompt** — fingerprint shown in full, TRUST AND CONNECT / CANCEL. Appears on first
  contact with any host.
- **◆ Changed host key refusal** — deliberately has *no* continue button. Presenting this as dismissible is
  the one design mistake that matters here.
- **◆ Conflict log** — what a merge overrode and what it discarded, scrollable, with DISMISS ALL. The merge
  is only allowed to pick a winner because this exists.
- *Groups panel:* the groups as chips with host counts, a name box that both adds and renames, delete with
  its own confirmation counting the affected hosts.

**2. Files** — two panes and a queue.

- *Bar:* a HOST / BUCKET toggle, the matching picker, a password box for hosts that need one, CONNECT
  (or OPEN for a bucket), DISCONNECT, a connected chip, a status line.
- *Panes:* breadcrumb trail, drive roots on the local side, and a listing with name, size, modified and —
  remote only — POSIX permissions. Each pane has an empty state and a drop highlight in two flavours,
  accepting and refusing.
- *Queue:* direction arrow, name, the remote path, progress with bytes and rate, state, and RESUME / RETRY /
  stop per row.
- **◆ The host key prompts appear here too.** File transfer is a second, separate connection that makes its
  own trust decision.
- On Android this becomes one remote pane plus the document picker — see the decision above — but the queue,
  its states and the prompts are unchanged.

**3. Keychain** — everything that is not a host.

- *Categories:* ALL / SSH KEYS / PASSWORDS / BUCKETS, each with a count.
- *Table:* name, type, one line of detail, sync badge. The detail is what is *known about* an item and never
  the secret.
- *Four editors,* which are four different shapes: an SSH key (label, private key armour shown unmasked so a
  truncated paste is visible, passphrase, public key, notes); **generate a key** (algorithm choice, comment,
  and it fills the editor rather than saving); a password (label, username, password masked, notes); a bucket
  (label, bucket, access key id, secret access key masked, region, endpoint, **◆ a path-style checkbox with
  the sentence explaining why**, notes).
- **◆ Delete confirmations that count** — "three hosts authenticate with this key and will refuse to connect".
  The number is the difference between a sentence somebody reads and one they click past.

**4. Pins** — the host keys this keychain has approved.

- Filter that matches **fingerprints as well as names**, because the workflow is "the operator published
  SHA256:… — do I have that one?".
- Table: host, port, algorithm, **◆ fingerprint never truncated**, approved date.
- Detail pane with the fingerprint in full again, a "no host uses this" chip, the note that the date is
  derived from the item id and means first approval rather than last use, and FORGET THIS HOST KEY.

**5. Snippets** — saved commands.

- Filter matching the command text as well as the name.
- Rows: name, **◆ a "runs immediately" chip**, sync badge, and a one-line preview with newlines shown as `⏎`.
- Editor: name, a multi-line command box, notes, and **◆ a "press Enter after inserting this" checkbox with
  the paragraph explaining that leaving it off is the whole safety property**.
- Detail pane with the command in full and two buttons that **name the terminal they will type into** —
  `TYPE INTO prod-db` and, only for a snippet marked as running, `RUN IN prod-db`. Plus the "no terminal
  open" state, and the sentence saying whatever is in the terminal receives this.

**6. Logs** — two logs behind one screen.

- A CONNECTIONS / KEYCHAIN toggle and a refresh.
- *Connections:* live dot, host, address, **◆ "still open" rather than a dash for a session in progress**,
  kind (terminal or files), started, device, and a chip for a refused host key.
- *Keychain:* item, type, what happened, **the names of the fields that changed**, when.

**7. Preferences** — import `~/.ssh/config`, register or forget this device, sign out.

**8. Team** — nothing behind it, and the screen says so rather than being hidden from the rail.

**9. Import** — a preview before anything is written: tick per row, alias, resolved address, how it
authenticates, a warnings chip, an "already in the keychain" badge, TICK ALL / NONE, and IMPORT N HOSTS.
Nothing is stored until the button.

### States that cut across every screen

- **Empty states**, with copy written per screen — each says what the thing is *for*, not "no items".
- **A read-only item**, written by a newer client: shown, refused for editing, with a message saying to
  update. Re-encoding would silently drop a colleague's field.
- **Sync badges** per row: not synced yet, refused and waiting on a person, read-only.
- **Unreadable items** — a count of things that would not decrypt, which is the signal that new key grants
  are needed after a rekey.
- **Busy**, and **offline / unreachable**, which are different from each other and both different from
  "everything is synced".

### The five most likely to be lost on a phone

In the order I would worry about them, and all of them are full-width blocks today with nowhere obvious to
go at 360dp:

1. The changed-host-key refusal, which must not become dismissible.
2. The recovery code screen, which must not become skippable.
3. The counted delete confirmations, which are the difference between a decision and a reflex.
4. The unknown-host-key prompt, which is the one interruption that is genuinely load-bearing.
5. The conflict log, which is what makes the merge honest rather than last-writer-wins.

---

## The order of work

1. ~~Decide the product questions.~~ **Done** — see [Decisions](#decisions-taken).
2. ~~Move `WindowsDeviceKeyStore` into the desktop head.~~ **Done** — `DodoSSH.Client.Session` is now free
   of Windows APIs entirely.
3. ~~**The spike.**~~ **Done.** It came back clean — see the summary at the top. The throwaway screen has
   been deleted; what it proved is now load-bearing in the head itself.

   It also produced the one structural change the audit did not anticipate. The interface is a redesign, but
   *what survives it* — every view model, command and piece of state — had to be reachable from two heads,
   and it was sitting inside the desktop one. So **`DodoSSH.Client.Shell` is new**: the view models, the
   terminal renderer's files and the palette moved there, and both heads reference it. It is the one place
   the "everything except `App` is free of Avalonia" rule bends, and it bends narrowly — what it uses is
   `Dispatcher`, the asset loader and a resource dictionary, none of which imply a window.
4. ~~**Android device key store.**~~ **Done** — `AndroidDeviceKeyStore` plus `BiometricGate`. A StrongBox-backed
   AES-GCM key, generated with `setUserAuthenticationRequired`, wraps the X25519 scalar into a file beside
   the cache; the keystore will not perform the unwrap unless the prompt actually happened, because the
   cipher is bound to the prompt rather than merely following it.

   Two things worth knowing. StrongBox is asked for and fell back from, because refusing a TEE-backed key
   would cost a mid-range phone the whole feature to buy a distinction the threat model does not draw. And
   `setInvalidatedByBiometricEnrollment` is on, which is what stops somebody who can add a fingerprint to an
   unlocked phone from inheriting the vault — the cost being that re-enrolment permanently destroys the key,
   which the load path treats as ordinary rather than exceptional.
5. **Android sign-in**: Custom Tabs plus an app link, behind the existing seams. Not the loopback listener —
   on a shared device any app can bind a loopback port, which is the attack RFC 8252 §8.3 names.

   **Not started, and it is now the gap that matters most.** The head composes a sign-in delegate that
   throws, and `NeedsServer` draws a screen saying so in the user's words. A phone enrolled from the desktop
   client unlocks here perfectly well, because unlocking needs no network — so this blocks first-run, not
   the product. It is the next piece of work.
6. ~~**The foreground service.**~~ **Done** — `SessionForegroundService`, with `SessionKeepAlive` starting and
   stopping it from a count rather than a lifecycle. `TerminalWorkspace.LiveSessionCount` is the source of
   truth deliberately: it already knows that a session whose shell exited is not live, which a counter
   incremented on open would not, and a phone showing "1 shell connected" over nothing would be exactly the
   dishonesty the unlock screen's count exists to prevent.
7. **The interface**, phone-first. The actual project, and the one that dominates the estimate. **Started:**
   the shell switches on `ShellState` and the unlock screen is built from the design — including both of its
   ◆ disclosures, the shell count and the paragraph saying *locked* describes the keychain and not this
   phone's access to the hosts. Every other state draws a `PendingScreen` naming what is missing, in the
   desktop head's `NotBuiltScreen` tradition and for the same reason.
8. **The terminal**, last — the highest-value screen, and the one whose remaining unknowns are cheapest to
   resolve once the shell around it exists. Plus an accessory key row: a software keyboard has no Ctrl, Esc,
   Tab or arrows, and every Android SSH client ships one for exactly this reason.

Steps 1–4 and 6 are done. Step 5 is ordinary work behind seams that already exist, and is what first-run
waits on. Step 7 still dominates everything else put together — the unlock screen is one of nine
destinations and the least structural of them — and step 8 is small only because step 7 comes first.

---

## Still open

Neither of these blocks the spike, and both want answering before there is anything to release.

- ~~**Which Android versions.**~~ **✅ Settled: minSdk 28, targetSdk 36**, and the reasoning divided in two.

  The ceiling is not a choice at all, which the audit had slightly wrong. `Avalonia.Controls.WebView` ships
  **only** a `net10.0-android36.0` assembly — there is no lower Android target in the package — so a project
  below `targetSdk` 36 cannot resolve it and therefore cannot have a terminal. That is a hard constraint
  rather than a preference, and it also means the API 36 platform must be installed to build this head at
  all.

  The floor *was* a real choice, and 28 is where the three platform APIs the device key store depends on all
  exist in the framework rather than behind an AndroidX shim: `BiometricPrompt`, StrongBox-backed keys, and
  `setInvalidatedByBiometricEnrollment`. Going lower would mean carrying `androidx.biometric` to reach
  devices that mostly cannot hold a hardware-backed key anyway — which is the one thing the store is for.
  API 28 and 29 still cost one branch each in `BiometricGate`, because allowed-authenticator lists arrived
  in 30.
- **How it is distributed, and what that does to the supply-chain story.** ADR 0001 says plainly that an
  operator who wants the secrets attacks the client rather than the crypto, and that release signing with a
  key **not held by the server** is what that costs. Play App Signing means Google holds the release key.
  That is not necessarily wrong — it is a different, and in some ways better-audited, trust arrangement —
  but it is a change to a documented security property of this product, and it should be reasoned about in
  an ADR rather than discovered at upload time. Sideloading a self-signed APK preserves the current story and
  costs reach.

## Smaller things, decided by default

Recorded so they are choices rather than accidents. Any of them is cheap to revisit.

- **`ClientPaths`** gets the app's own `filesDir`, injected by the head rather than branched for inside the
  record — which already takes an explicit directory for exactly this reason. It satisfies the
  local-and-non-roaming requirement more cleanly than any desktop platform does.
- **The device name** on log entries comes from the head, not `Environment.MachineName`, which returns
  something like `localhost` on Android and would make every entry from a phone indistinguishable.
- **`NativeKeyboardFocus` is not ported.** It exists for a documented Win32 asymmetry — focus crosses into
  WebView2 but does not come back — and Android's focus model is different enough that the problem should be
  confirmed to exist before anything is written to solve it.