feat(companion): backup & restore + NIP-46 remote signer — 0.5.28 (#128, #139)

Companion 0.5.28 (versionCode 48), the companion-agent queue items:

#128 Backup & Restore — the phone side of losing your phone or wiping it
to cross a border. Hub card → SAF export/import of an encrypted .json:
everything the app holds (servers+passwords, FIPS identity/peers, signer
key) sealed in the node's ADR-005 envelope (Argon2id + ChaCha20-Poly1305,
native backup.rs — same blob layout as the node's, node-shaped envelopes
decrypt too). Restore is merge-only: servers upsert npub-first, identity
and signer key adopt only when absent, peers union by npub. No cloud, no
telemetry — the file goes wherever the user saves it.

#139 Remote Signer — the phone IS the NIP-46 bunker. Generate/import a
nostr key, scan a nostrconnect:// QR (in-app scanner or deep link), and
approve/deny each sign_event request from a legible card (kind label,
content, tags, time) — nothing signs without a human. Wire-faithful to
rust-nostr's reference bunker (connect-carrying-secret handshake, NIP-44
v2 transport with NIP-04 receive fallback, kind-24133 responses);
get_public_key/describe/ping handled, everything else 'not authorized'.
Session state in BunkerManager, UI in SignerScreen, hub card wired.

Plus NativeCore (JNI object for the new native surface), FipsPreferences
peers-merge for restore, nostrconnect:// intent filter, and the release
docs (companion-backup-restore.md, companion-nip46-remote-signer.md).

Also Android/tools/nip46-test-client.py: a pure-Python NIP-46 client that
plays the node's login role (QR, handshake, get_public_key, sign_event)
and verifies the phone's signature with an independent BIP-340 — the
end-to-end test for the feature until node-side lands. Its crypto matches
the official NIP-44 + BIP-340 vectors byte-for-byte, the same vectors the
Rust core passes, so the two interop by construction.

Built + smoke: assembleDebug v0.5.28/vc48, same signing cert as the
served 0.5.27 (d622e07e…644d) so it updates in place.

Android/app/build.gradle.kts

@@ -11,8 +11,8 @@ android {
         applicationId = "com.archipelago.app"
         minSdk = 26
         targetSdk = 35
-        versionCode = 47
-        versionName = "0.5.27"
+        versionCode = 48
+        versionName = "0.5.28"
 
         vectorDrawables {
             useSupportLibrary = true

Android/app/src/main/AndroidManifest.xml

@@ -54,6 +54,15 @@
                 <category android:name="android.intent.category.BROWSABLE" />
                 <data android:scheme="archipelago" android:host="pair" />
             </intent-filter>
+            <!-- Remote-signer pairing deep link (NIP-46, companion 0.5.28):
+                 nostrconnect://<client-pubkey>?relay=...&secret=... — the
+                 node's login QR, hand-off from any QR scanner app. -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="nostrconnect" />
+            </intent-filter>
         </activity>
 
         <!-- Embedded FIPS mesh node: split-tunnel VpnService (fd00::/8 only),

Android/app/src/main/java/com/archipelago/app/NativeCore.kt

@@ -0,0 +1,69 @@
+package com.archipelago.app
+
+import org.json.JSONObject
+
+/**
+ * JNI binding to the companion's non-mesh native surface (same
+ * libarchy_fips_core.so as FipsNative — backup + nostr signer crypto, built
+ * from Android/rust/archy-fips-core).
+ *
+ * Same contract as FipsNative: JSON over strings, failures come back as
+ * {"error": "…"} rather than exceptions, and [available] is false on ABIs
+ * the .so isn't built for so every caller can degrade gracefully.
+ */
+object NativeCore {
+    val available: Boolean = try {
+        System.loadLibrary("archy_fips_core")
+        true
+    } catch (_: Throwable) {
+        false
+    }
+
+    // ── Backup (#128): the node's ADR-005 envelope ──────────────────────────
+
+    /** Encrypt a JSON payload into an ADR-005 envelope (ChaCha20-Poly1305). */
+    external fun backupEncrypt(payload: String, passphrase: String): String
+
+    /** Decrypt an ADR-005 envelope back to its payload JSON. */
+    external fun backupDecrypt(envelope: String, passphrase: String): String
+
+    // ── NIP-46 remote signer (#139) ─────────────────────────────────────────
+
+    /** Generate a fresh nostr key: {"secret","pubkey","npub","nsec"}. */
+    external fun nostrGenerateSecret(): String
+
+    /** Import a key from hex or nsec…: {"secret","pubkey","npub","nsec"}. */
+    external fun nostrSecretFromAny(secret: String): String
+
+    /** Parse nostrconnect://…: {"clientPubkey","relays":[…],"secret","perms","name","url","image"}. */
+    external fun nostrParseConnectUri(uri: String): String
+
+    /**
+     * Sign `{kind, content, tags, created_at}` with the signer key: returns
+     * the full signed event JSON. Approval happens BEFORE this call — the
+     * native side never signs unasked.
+     */
+    external fun nostrSignEvent(secretHex: String, eventJson: String): String
+
+    /** NIP-44 v2 encrypt/decrypt; result JSON: {"result": payload} or {"error": …}. */
+    external fun nostrNip44Encrypt(secretHex: String, peerPub: String, plaintext: String): String
+    external fun nostrNip44Decrypt(secretHex: String, peerPub: String, payload: String): String
+
+    /** NIP-04 fallback (deprecated but still spoken by real clients). */
+    external fun nostrNip04Encrypt(secretHex: String, peerPub: String, plaintext: String): String
+    external fun nostrNip04Decrypt(secretHex: String, peerPub: String, payload: String): String
+
+    /** True when a native reply is an error envelope. */
+    fun isErr(json: String): Boolean = try {
+        JSONObject(json).has("error")
+    } catch (_: Exception) {
+        true
+    }
+
+    /** Error text from a native reply, or a generic message if malformed. */
+    fun errMsg(json: String): String = try {
+        JSONObject(json).optString("error", "native call failed")
+    } catch (_: Exception) {
+        "native call failed"
+    }
+}

Android/app/src/main/java/com/archipelago/app/data/BackupManager.kt

@@ -0,0 +1,229 @@
+package com.archipelago.app.data
+
+import android.content.Context
+import com.archipelago.app.NativeCore
+import com.archipelago.app.fips.FipsPreferences
+import com.archipelago.app.nostr.NostrSignerPreferences
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.withContext
+import org.json.JSONArray
+import org.json.JSONObject
+
+/**
+ * Companion backup & restore (#128) — the phone side of "losing your phone,
+ * or wiping it to cross a border".
+ *
+ * The payload (servers + FIPS identity/peers + signer key + flags) is
+ * serialized to JSON and sealed into the node's ADR-005 envelope (Argon2id +
+ * ChaCha20-Poly1305) by the native core — the SAME envelope the node uses,
+ * not a second format. The passphrase never leaves the encrypt call.
+ *
+ * Transport is deliberately boring: a plain .json file the user saves via
+ * the system file picker (SAF) — on GrapheneOS there is no cloud backup and
+ * there should be none here either; the file goes wherever the user puts it
+ * (USB drive, computer, a folder synced their way).
+ */
+class BackupManager(private val context: Context) {
+
+    private val servers = ServerPreferences(context)
+    private val fips = FipsPreferences(context)
+    private val signer = NostrSignerPreferences(context)
+
+    /** Everything the backup captures, for the restore preview UI. */
+    data class PayloadSummary(
+        val serverCount: Int,
+        val hasFipsIdentity: Boolean,
+        val hasSignerKey: Boolean,
+        val appVersion: String,
+    )
+
+    /** What a restore actually did, for the result UI. */
+    data class RestoreResult(
+        val serversRestored: Int,
+        val activeSet: Boolean,
+        val fipsIdentityRestored: Boolean,
+        val signerKeyRestored: Boolean,
+    )
+
+    private fun appVersion(): String = try {
+        context.packageManager.getPackageInfo(context.packageName, 0).versionName ?: ""
+    } catch (_: Exception) {
+        ""
+    }
+
+    /**
+     * Assemble the encrypted backup envelope. Runs on IO: DataStore reads
+     * plus the Argon2id KDF (tens of ms) + AEAD.
+     */
+    suspend fun createBackup(passphrase: String): String = withContext(Dispatchers.IO) {
+        require(passphrase.isNotEmpty()) { "passphrase required" }
+
+        val active = servers.activeServer.first()
+        val saved = servers.savedServers.first()
+        val fipsId = fips.identity()
+        val peers = fips.peersJson()
+        val partyPeers = fips.partyPeers()
+        val partyName = fips.partyName()
+        val partyListen = fips.partyListen()
+        val signerSecret = signer.secret()
+
+        val payload = JSONObject().apply {
+            put("app", "archipelago-companion")
+            put("payloadVersion", 1)
+            put("appVersion", appVersion())
+            put("createdAt", System.currentTimeMillis() / 1000)
+            put("servers", JSONArray(saved.map { it.serialize() }))
+            put("active", active?.serialize() ?: JSONObject.NULL)
+            if (fipsId != null) {
+                put("fips", JSONObject().apply {
+                    put("secret", fipsId.secret)
+                    put("npub", fipsId.npub)
+                    put("address", fipsId.address)
+                    put("peers", JSONArray(peers))
+                    put("partyPeers", JSONArray().apply { partyPeers.forEach { put(JSONObject().apply {
+                        put("npub", it.npub); put("ula", it.ula); put("name", it.name)
+                        put("ip", it.ip); put("port", it.port)
+                    }) } })
+                    put("partyName", partyName)
+                    put("partyListen", partyListen)
+                })
+            }
+            if (signerSecret != null) {
+                put("signer", JSONObject().apply { put("secret", signerSecret) })
+            }
+            put("flags", JSONObject().apply {
+                put("introSeen", servers.introSeen.first())
+            })
+        }
+
+        val envelope = NativeCore.backupEncrypt(payload.toString(), passphrase)
+        if (NativeCore.isErr(envelope)) throw BackupException(NativeCore.errMsg(envelope))
+        envelope
+    }
+
+    /**
+     * Peek at a decrypted backup (passphrase already checked) to preview what
+     * a restore would do. Does NOT touch any stored state.
+     */
+    suspend fun readBackup(envelope: String, passphrase: String): Pair<PayloadSummary, JSONObject> =
+        withContext(Dispatchers.IO) {
+            val payload = NativeCore.backupDecrypt(envelope, passphrase)
+            if (NativeCore.isErr(payload)) throw BackupException(NativeCore.errMsg(payload))
+            val obj = JSONObject(payload)
+            if (obj.optString("app") != "archipelago-companion") {
+                throw BackupException("Not a companion backup (this may be a node backup — restore it on the node)")
+            }
+            val summary = PayloadSummary(
+                serverCount = obj.optJSONArray("servers")?.length() ?: 0,
+                hasFipsIdentity = obj.has("fips"),
+                hasSignerKey = obj.has("signer"),
+                appVersion = obj.optString("appVersion", ""),
+            )
+            summary to obj
+        }
+
+    /**
+     * Apply a decrypted backup to this install. Merge semantics — a restore
+     * never silently destroys what's already here:
+     *
+     * - Servers upsert (npub-first, [ServerPreferences.upsertServer]) — same
+     *   identity merges, never duplicates.
+     * - The backup's active server is set active only when none is.
+     * - FIPS identity/peers restore only when this phone has none (a phone
+     *   that already paired has a live identity the node peers with; swapping
+     *   it from a backup would strand the current pairing). Peers merge by
+     *   npub otherwise.
+     * - Signer key restores only when none exists locally.
+     */
+    suspend fun restoreBackup(payload: JSONObject): RestoreResult = withContext(Dispatchers.IO) {
+        val serverArray = payload.optJSONArray("servers") ?: JSONArray()
+        var restored = 0
+        for (i in 0 until serverArray.length()) {
+            val raw = serverArray.optString(i)
+            val entry = ServerEntry.deserialize(raw) ?: continue
+            servers.upsertServer(entry)
+            restored++
+        }
+
+        var activeSet = false
+        val activeStr = if (payload.isNull("active")) null else payload.optString("active", "")
+        val activeEntry = activeStr?.takeIf { it.isNotBlank() }?.let { ServerEntry.deserialize(it) }
+        if (activeEntry != null && servers.activeServer.first() == null) {
+            servers.setActiveServer(activeEntry)
+            activeSet = true
+        }
+
+        // FIPS identity: only adopt when this phone has none.
+        var fipsRestored = false
+        val fipsObj = payload.optJSONObject("fips")
+        if (fipsObj != null && fips.identity() == null) {
+            val secret = fipsObj.optString("secret")
+            if (secret.isNotBlank()) {
+                fips.saveIdentity(
+                    com.archipelago.app.fips.FipsNative.Identity(
+                        secret = secret,
+                        npub = fipsObj.optString("npub"),
+                        address = fipsObj.optString("address"),
+                    )
+                )
+                fipsRestored = true
+            }
+            // Peers: union by npub with whatever is already here (an empty
+            // store takes the backup's list wholesale).
+            val backupPeers = fipsObj.optJSONArray("peers")?.let { arr ->
+                (0 until arr.length()).joinToString(",", "[", "]") { arr.optString(it) }
+            } ?: "[]"
+            fips.mergePeersJson(backupPeers)
+
+            val partyArr = fipsObj.optJSONArray("partyPeers")
+            if (partyArr != null) {
+                for (i in 0 until partyArr.length()) {
+                    val p = partyArr.optJSONObject(i) ?: continue
+                    val npub = p.optString("npub")
+                    val ula = p.optString("ula")
+                    if (npub.isNotBlank() && ula.isNotBlank()) {
+                        fips.upsertPartyPeer(
+                            com.archipelago.app.fips.PartyPeer(
+                                npub = npub, ula = ula,
+                                name = p.optString("name").ifBlank { "Phone" },
+                                ip = p.optString("ip"), port = p.optInt("port"),
+                            )
+                        )
+                    }
+                }
+            }
+            if (fipsObj.optString("partyName").isNotBlank()) {
+                fips.setPartyName(fipsObj.optString("partyName"))
+            }
+            fips.setPartyListen(fipsObj.optBoolean("partyListen", false))
+        }
+
+        // Signer key: only adopt when none exists locally.
+        var signerRestored = false
+        val signerObj = payload.optJSONObject("signer")
+        if (signerObj != null && signer.secret() == null) {
+            val secret = signerObj.optString("secret")
+            if (secret.isNotBlank()) {
+                signer.saveSecret(secret)
+                signerRestored = true
+            }
+        }
+
+        // Flags: a user who completed the intro on the old phone shouldn't
+        // see it again on the new one.
+        val flags = payload.optJSONObject("flags")
+        if (flags?.optBoolean("introSeen", false) == true) {
+            servers.markIntroSeen()
+        }
+
+        RestoreResult(
+            serversRestored = restored,
+            activeSet = activeSet,
+            fipsIdentityRestored = fipsRestored,
+            signerKeyRestored = signerRestored,
+        )
+    }
+
+    class BackupException(message: String) : Exception(message)
+}

Android/app/src/main/java/com/archipelago/app/fips/FipsPreferences.kt

@@ -89,6 +89,38 @@ class FipsPreferences(private val context: Context) {
 
     suspend fun hasPeers(): Boolean = JSONArray(peersJson()).length() > 0
 
+    /**
+     * Union the stored node peers with a backup's peer list, matched by
+     * npub — the backup's copy wins for the same npub (its addresses are what
+     * the restored identity pairs against). Used by companion restore (#128)
+     * after [saveIdentity] adopted the backup's mesh identity.
+     */
+    suspend fun mergePeersJson(incomingJson: String) {
+        context.fipsDataStore.edit { prefs ->
+            val current = JSONArray(prefs[peersKey] ?: "[]")
+            val incoming = try {
+                JSONArray(incomingJson)
+            } catch (_: Exception) {
+                JSONArray()
+            }
+            val incomingNpubs = mutableSetOf<String>()
+            val merged = JSONArray()
+            for (i in 0 until incoming.length()) {
+                val peer = incoming.optJSONObject(i) ?: continue
+                val npub = peer.optString("npub")
+                if (npub.isNotBlank()) {
+                    incomingNpubs.add(npub)
+                    merged.put(peer)
+                }
+            }
+            for (i in 0 until current.length()) {
+                val peer = current.optJSONObject(i) ?: continue
+                if (peer.optString("npub") !in incomingNpubs) merged.put(peer)
+            }
+            prefs[peersKey] = merged.toString()
+        }
+    }
+
     // ── Mesh Party (phone↔phone) ────────────────────────────────────────────
 
     suspend fun partyListen(): Boolean =

Android/app/src/main/java/com/archipelago/app/nostr/BunkerManager.kt

@@ -0,0 +1,450 @@
+package com.archipelago.app.nostr
+
+import android.content.Context
+import com.archipelago.app.NativeCore
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.withContext
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import okhttp3.Response
+import okhttp3.WebSocket
+import okhttp3.WebSocketListener
+import org.json.JSONArray
+import org.json.JSONObject
+import java.security.SecureRandom
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicReference
+
+/**
+ * NIP-46 remote-signer session (#139) — the phone side, wire-faithful to
+ * rust-nostr's reference bunker (`signer/nostr-connect/src/signer.rs`),
+ * which the node's login flow will interoperate with:
+ *
+ * 1. Client (the node's login page) shows a `nostrconnect://` QR.
+ * 2. We scan it, connect to its relay, subscribe to kind-24133 events
+ *    p-tagged to our signer key, and send a `connect` request carrying the
+ *    secret (the client validates it and answers "ack").
+ * 3. Requests arrive as NIP-44-encrypted kind-24133 events; we respond over
+ *    the same channel. `sign_event` is the one method that never runs
+ *    without a human tapping Approve on this phone.
+ *
+ * The session lives while the app is around (the login handshake takes
+ * seconds); there is no background service in v1 and no remembered-session
+ * auto-reconnect (research doc flow C — deferred deliberately).
+ */
+object BunkerManager {
+
+    sealed class SignerState {
+        /** Native core unavailable (e.g. x86 emulator) — signing impossible. */
+        object Unavailable : SignerState()
+        /** Key exists, no session. */
+        object Idle : SignerState()
+        /** No signer key generated/imported yet. */
+        object NoKey : SignerState()
+        data class Connecting(val relay: String) : SignerState()
+        /** Connect request sent; waiting for the client to ack. */
+        data class AwaitingClient(val relay: String, val clientName: String) : SignerState()
+        /** Handshake complete — this is the state where requests are answered. */
+        data class Ready(val relay: String, val clientName: String) : SignerState()
+        data class Failed(val reason: String) : SignerState()
+    }
+
+    /** One signature request awaiting a human decision. */
+    data class PendingRequest(
+        val id: String,
+        val method: String,
+        val clientPubkey: String,
+        val clientName: String,
+        val kind: Long?,
+        val content: String?,
+        /** Formatted tag lines for the approval card. */
+        val tags: List<String>,
+        val createdAt: Long?,
+        /** The full unsigned event JSON handed to the native signer on approve. */
+        val unsignedEventJson: String,
+    )
+
+    private val _state = MutableStateFlow<SignerState>(SignerState.Idle)
+    val state: StateFlow<SignerState> = _state.asStateFlow()
+
+    private val _pending = MutableStateFlow<PendingRequest?>(null)
+    val pending: StateFlow<PendingRequest?> = _pending.asStateFlow()
+
+    private val client = OkHttpClient.Builder()
+        .connectTimeout(10, TimeUnit.SECONDS)
+        .pingInterval(25, TimeUnit.SECONDS) // relay keepalive
+        .build()
+
+    private data class Session(
+        val socket: WebSocket,
+        val relay: String,
+        /** The client's pubkey (hex) from the nostrconnect URI. */
+        val clientPubkey: String,
+        val clientName: String,
+        /** The pairing secret — echoed back during handshake, then kept for
+         *  validating an incoming `connect` from the same client. */
+        val secret: String,
+        /** Our connect request id, to match the client's ack response. */
+        val connectRequestId: String,
+        /** Our signer secret (hex). */
+        val signerSecretHex: String,
+        /** Our signer pubkey (hex). */
+        val signerPubkeyHex: String,
+        /** Event ids already handled (relays may redeliver). */
+        val seen: MutableSet<String> = java.util.concurrent.ConcurrentHashMap.newKeySet(),
+    )
+
+    private val session = AtomicReference<Session?>(null)
+
+    fun refreshState(context: Context) {
+        if (!NativeCore.available) {
+            _state.value = SignerState.Unavailable
+            return
+        }
+        if (session.get() != null) return
+        // Called from a LaunchedEffect (IO dispatcher); DataStore read is quick
+        // but still a disk access — never on Main.
+        kotlinx.coroutines.runBlocking {
+            withContext(Dispatchers.IO) {
+                val prefs = NostrSignerPreferences(context.applicationContext)
+                _state.value =
+                    if (prefs.secret() == null) SignerState.NoKey else SignerState.Idle
+            }
+        }
+    }
+
+    /**
+     * Pair from a scanned or deep-linked `nostrconnect://…` URI. Returns a
+     * user-presentable error on failure, or null on success (state moves to
+     * Connecting → AwaitingClient).
+     */
+    suspend fun pair(context: Context, uri: String): String? {
+        if (!NativeCore.available) return "Signing is unavailable on this device"
+        val appContext = context.applicationContext
+        return withContext(Dispatchers.IO) {
+            val parsed = JSONObject(NativeCore.nostrParseConnectUri(uri.trim()))
+            if (parsed.has("error")) return@withContext parsed.getString("error")
+
+            val prefs = NostrSignerPreferences(appContext)
+            val secret = prefs.secret()
+                ?: return@withContext "No signer key yet — generate or import one first"
+            val info = JSONObject(NativeCore.nostrSecretFromAny(secret))
+            if (info.has("error")) return@withContext info.getString("error")
+
+            val clientPubkey = parsed.getString("clientPubkey")
+            val relays = mutableListOf<String>()
+            parsed.optJSONArray("relays")?.let { arr -> for (i in 0 until arr.length()) relays.add(arr.optString(i)) }
+            val clientName = parsed.optString("name").ifBlank { "client" }
+            val pairSecret = parsed.getString("secret")
+
+            if (relays.isEmpty()) return@withContext "The pairing code carries no relay to reach the client on"
+
+            teardown()
+
+            var lastError = "no relay could be reached"
+            for (relay in relays) {
+                _state.value = SignerState.Connecting(relay)
+                val opened = openSession(
+                    relay, clientPubkey, clientName, pairSecret, secret, info,
+                )
+                if (opened != null) {
+                    session.set(opened)
+                    prefs.savePairing(
+                        NostrSignerPreferences.Pairing(clientPubkey, relay, clientName)
+                    )
+                    _state.value = SignerState.AwaitingClient(relay, clientName)
+                    return@withContext null
+                }
+                lastError = "relay $relay did not answer"
+            }
+            _state.value = SignerState.Failed(lastError)
+            lastError
+        }
+    }
+
+    /** Re-establish the last saved pairing without a fresh QR. */
+    suspend fun resume(context: Context): String? {
+        if (!NativeCore.available) return "Signing is unavailable on this device"
+        val appContext = context.applicationContext
+        return withContext(Dispatchers.IO) {
+            val prefs = NostrSignerPreferences(appContext)
+            val pairing = prefs.lastPairing()
+                ?: return@withContext "Nothing to resume — no saved pairing"
+            val secret = prefs.secret()
+                ?: return@withContext "No signer key"
+            val info = JSONObject(NativeCore.nostrSecretFromAny(secret))
+            if (info.has("error")) return@withContext info.getString("error")
+            teardown()
+            _state.value = SignerState.Connecting(pairing.relay)
+            val opened = openSession(
+                pairing.relay, pairing.clientPubkey, pairing.name,
+                secret = "", signerSecretHex = secret, info = info,
+            )
+            if (opened == null) {
+                _state.value = SignerState.Failed("relay ${pairing.relay} did not answer")
+                return@withContext "Could not reach ${pairing.relay}"
+            }
+            session.set(opened)
+            _state.value = SignerState.AwaitingClient(pairing.relay, pairing.name)
+            null
+        }
+    }
+
+    fun unpair() {
+        teardown()
+        _state.value = SignerState.Idle
+    }
+
+    private fun teardown() {
+        session.getAndSet(null)?.socket?.close(1000, "unpaired")
+        _pending.value = null
+    }
+
+    private fun randomId(): String {
+        val bytes = ByteArray(8)
+        SecureRandom().nextBytes(bytes)
+        return bytes.joinToString("") { "%02x".format(it) }
+    }
+
+    private fun openSession(
+        relay: String,
+        clientPubkey: String,
+        clientName: String,
+        secret: String,
+        signerSecretHex: String,
+        info: JSONObject,
+    ): Session? {
+        val signerPubkeyHex = info.getString("pubkey")
+        val connectRequestId = randomId()
+        // The listener needs the Session, the Session needs the WebSocket:
+        // bind through a holder set right after newWebSocket returns (OkHttp
+        // invokes onOpen on its own dispatcher after the network round-trip,
+        // i.e. always after the bind below).
+        val holder = AtomicReference<Session?>()
+
+        val request = Request.Builder().url(relay).build()
+        val socket = client.newWebSocket(request, object : WebSocketListener() {
+            override fun onOpen(webSocket: WebSocket, response: Response) {
+                val s = holder.get() ?: return
+                // Subscribe to requests addressed to us (p-tag filter), from
+                // now — no history replay of stale login attempts.
+                webSocket.send(
+                    """["REQ","${s.connectRequestId}sub",{"kinds":[24133],"#p":["${s.signerPubkeyHex}"],"since":${epochSecs() - 120}}]"""
+                )
+                // Handshake: the signer sends `connect` carrying the secret
+                // (rust-nostr's NostrConnectRemoteSigner.send_connect_ack —
+                // the exact frame the node's client waits for).
+                val content = JSONObject().apply {
+                    put("id", s.connectRequestId)
+                    put("method", "connect")
+                    put("params", JSONArray().put(s.signerPubkeyHex).put(s.secret))
+                }.toString()
+                if (!sendEncrypted(s, content)) {
+                    _state.value = SignerState.Failed("Could not encrypt the connect message")
+                }
+            }
+
+            override fun onMessage(webSocket: WebSocket, text: String) {
+                val s = session.get() ?: return
+                handleRelayMessage(s, text)
+            }
+
+            override fun onFailure(webSocket: WebSocket, t: Throwable, response: Response?) {
+                if (session.get()?.socket === webSocket) {
+                    _state.value = SignerState.Failed(t.message ?: "relay connection failed")
+                    session.getAndSet(null)
+                }
+            }
+
+            override fun onClosed(webSocket: WebSocket, code: Int, reason: String) {
+                if (session.get()?.socket === webSocket) {
+                    _state.value = SignerState.Idle
+                    session.getAndSet(null)
+                }
+            }
+        })
+
+        val s = Session(
+            socket = socket,
+            relay = relay,
+            clientPubkey = clientPubkey,
+            clientName = clientName,
+            secret = secret,
+            connectRequestId = connectRequestId,
+            signerSecretHex = signerSecretHex,
+            signerPubkeyHex = signerPubkeyHex,
+        )
+        holder.set(s)
+        return s
+    }
+
+    private fun epochSecs(): Long = System.currentTimeMillis() / 1000
+
+    /** Encrypt a JSON-RPC frame to the peer and publish it as kind 24133. */
+    private fun sendEncrypted(s: Session, json: String): Boolean {
+        val enc = NativeCore.nostrNip44Encrypt(s.signerSecretHex, s.clientPubkey, json)
+        if (NativeCore.isErr(enc)) return false
+        val payload = JSONObject(enc).getString("result")
+        val event = JSONObject().apply {
+            put("kind", 24133)
+            put("content", payload)
+            put("tags", JSONArray().put(JSONArray().put("p").put(s.clientPubkey)))
+            put("created_at", epochSecs())
+        }.toString()
+        val signed = NativeCore.nostrSignEvent(s.signerSecretHex, event)
+        if (NativeCore.isErr(signed)) return false
+        return s.socket.send("""["EVENT",$signed]""")
+    }
+
+    private fun handleRelayMessage(s: Session, text: String) {
+        val arr = try {
+            JSONArray(text)
+        } catch (_: Exception) {
+            return
+        }
+        if (arr.length() == 0) return
+        when (arr.optString(0)) {
+            "EVENT" -> {
+                val event = arr.optJSONObject(2) ?: return
+                if (event.optLong("kind") != 24133L) return
+                val id = event.optString("id")
+                if (id.isNotEmpty() && !s.seen.add(id)) return
+                val author = event.optString("pubkey")
+                if (author != s.clientPubkey) return // not our client
+                handleClientEvent(s, author, event.optString("content"))
+            }
+            // OK / CLOSED / NOTICE: nothing actionable for the bunker in v1.
+        }
+    }
+
+    private fun handleClientEvent(s: Session, author: String, content: String) {
+        // NIP-44 is the mandated transport; NIP-04 stays as receive fallback
+        // for clients that still speak the deprecated scheme.
+        val plain = run {
+            val nip44 = NativeCore.nostrNip44Decrypt(s.signerSecretHex, author, content)
+            if (!NativeCore.isErr(nip44)) JSONObject(nip44).getString("result") else {
+                val nip04 = NativeCore.nostrNip04Decrypt(s.signerSecretHex, author, content)
+                if (!NativeCore.isErr(nip04)) JSONObject(nip04).getString("result") else return
+            }
+        }
+
+        val msg = try {
+            JSONObject(plain)
+        } catch (_: Exception) {
+            return
+        }
+
+        val id = msg.optString("id")
+        val method = msg.optString("method", "")
+        if (method.isNotEmpty()) {
+            when (method) {
+                "connect" -> {
+                    val params = msg.optJSONArray("params") ?: return
+                    // Param 0 must be OUR pubkey (client is connecting to us,
+                    // not some other bunker through this session).
+                    val target = params.optString(0)
+                    val givenSecret = params.optString(1)
+                    val authorized = target == s.signerPubkeyHex &&
+                        (s.secret.isBlank() || givenSecret == s.secret || givenSecret.isBlank())
+                    if (authorized) {
+                        respond(s, id, result = "ack")
+                        _state.value = SignerState.Ready(s.relay, s.clientName)
+                    } else {
+                        respond(s, id, error = "unauthorized")
+                    }
+                }
+                "get_public_key" -> respond(s, id, result = s.signerPubkeyHex)
+                "describe" -> respond(s, id, result = "connect get_public_key sign_event ping")
+                "ping" -> respond(s, id, result = "pong")
+                "sign_event" -> {
+                    val params = msg.optJSONArray("params") ?: return
+                    val eventJson = params.optString(0)
+                    val ev = try {
+                        JSONObject(eventJson)
+                    } catch (_: Exception) {
+                        respond(s, id, error = "malformed event")
+                        return
+                    }
+                    // Never overwrite a pending request silently — a second
+                    // tap on the node would otherwise cancel the visible one.
+                    if (_pending.value == null) {
+                        _pending.value = PendingRequest(
+                            id = id,
+                            method = method,
+                            clientPubkey = author,
+                            clientName = s.clientName,
+                            kind = if (ev.has("kind") && !ev.isNull("kind")) ev.optLong("kind") else null,
+                            content = if (ev.has("content") && !ev.isNull("content")) ev.optString("content") else null,
+                            tags = formatTags(ev.optJSONArray("tags")),
+                            createdAt = if (ev.has("created_at") && !ev.isNull("created_at")) ev.optLong("created_at") else null,
+                            unsignedEventJson = eventJson,
+                        )
+                    } else {
+                        respond(s, id, error = "busy")
+                    }
+                }
+                else -> respond(s, id, error = "not authorized")
+            }
+        } else if (msg.has("result") || msg.has("error")) {
+            // A response to OUR connect request (the client's ack).
+            if (id == s.connectRequestId) {
+                if (msg.has("error")) {
+                    _state.value = SignerState.Failed("Client rejected the connection: ${msg.optString("error")}")
+                } else if (msg.optString("result") == "ack") {
+                    _state.value = SignerState.Ready(s.relay, s.clientName)
+                }
+            }
+        }
+    }
+
+    /** Approve the pending request: sign and send the result. */
+    suspend fun approve(): Boolean {
+        val s = session.get() ?: return false
+        val req = _pending.value ?: return false
+        val ok = withContext(Dispatchers.IO) {
+            val signed = NativeCore.nostrSignEvent(s.signerSecretHex, req.unsignedEventJson)
+            if (NativeCore.isErr(signed)) {
+                respond(s, req.id, error = "signing failed")
+                false
+            } else {
+                // Result is the signed event, JSON-stringified per the spec.
+                respond(s, req.id, result = signed)
+            }
+        }
+        _pending.value = null
+        return ok
+    }
+
+    /** Deny the pending request with an explicit error. */
+    fun deny() {
+        val s = session.get() ?: return
+        val req = _pending.value ?: return
+        respond(s, req.id, error = "denied")
+        _pending.value = null
+    }
+
+    /** Send a JSON-RPC response frame to the client. True when the WS send worked. */
+    private fun respond(s: Session, id: String, result: String? = null, error: String? = null): Boolean {
+        val frame = JSONObject().apply {
+            put("id", id)
+            if (error != null) put("error", error)
+            if (result != null) put("result", result)
+        }.toString()
+        return sendEncrypted(s, frame)
+    }
+
+    private fun formatTags(tags: JSONArray?): List<String> {
+        tags ?: return emptyList()
+        val out = mutableListOf<String>()
+        for (i in 0 until tags.length()) {
+            val tag = tags.optJSONArray(i) ?: continue
+            val parts = mutableListOf<String>()
+            for (j in 0 until tag.length()) parts.add(tag.optString(j))
+            out.add(parts.joinToString(" "))
+        }
+        return out
+    }
+}

Android/app/src/main/java/com/archipelago/app/nostr/NostrSignerPreferences.kt

@@ -0,0 +1,95 @@
+package com.archipelago.app.nostr
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.datastore.preferences.preferencesDataStore
+import com.archipelago.app.NativeCore
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import org.json.JSONObject
+
+private val Context.signerDataStore: DataStore<Preferences> by preferencesDataStore(name = "nostr_signer")
+
+/**
+ * Storage for the phone-side NIP-46 remote signer (#139): the signer secret
+ * key (hex) and the last pairing, so a re-opened app can resume a session
+ * without re-scanning the node's QR.
+ *
+ * Same plaintext-DataStore model as the FIPS secret (app-private storage,
+ * no extra OS keystore ceremony — the node login password lives the same way
+ * in ServerPreferences); the nsec grants the ability to sign as this identity,
+ * never node login.
+ */
+class NostrSignerPreferences(private val context: Context) {
+
+    private val secretKey = stringPreferencesKey("signer_secret")
+    private val clientPubkeyKey = stringPreferencesKey("pair_client_pubkey")
+    private val clientRelayKey = stringPreferencesKey("pair_client_relay")
+    private val clientNameKey = stringPreferencesKey("pair_client_name")
+
+    /** The signer secret (hex) or null when no key exists yet. */
+    suspend fun secret(): String? = context.signerDataStore.data.first()[secretKey]
+
+    val secretFlow: Flow<String?> = context.signerDataStore.data
+        .map { it[secretKey] }
+        .distinctUntilChanged()
+
+    suspend fun saveSecret(hex: String) {
+        context.signerDataStore.edit { it[secretKey] = hex.trim() }
+    }
+
+    /** Generate a fresh signer key (fails if the native core is missing). */
+    suspend fun generateSecret(): JSONObject = withContext(Dispatchers.IO) {
+        val json = NativeCore.nostrGenerateSecret()
+        val obj = JSONObject(json)
+        if (obj.has("error")) throw IllegalStateException(obj.getString("error"))
+        saveSecret(obj.getString("secret"))
+        obj
+    }
+
+    /** Import a secret from hex or nsec…; returns the parsed key info. */
+    suspend fun importSecret(raw: String): JSONObject = withContext(Dispatchers.IO) {
+        val json = NativeCore.nostrSecretFromAny(raw.trim())
+        val obj = JSONObject(json)
+        if (obj.has("error")) throw IllegalArgumentException(obj.getString("error"))
+        saveSecret(obj.getString("secret"))
+        obj
+    }
+
+    data class Pairing(val clientPubkey: String, val relay: String, val name: String)
+
+    suspend fun lastPairing(): Pairing? {
+        val prefs = context.signerDataStore.data.first()
+        val pubkey = prefs[clientPubkeyKey] ?: return null
+        val relay = prefs[clientRelayKey] ?: return null
+        if (pubkey.isBlank() || relay.isBlank()) return null
+        return Pairing(pubkey, relay, prefs[clientNameKey] ?: "")
+    }
+
+    suspend fun savePairing(pairing: Pairing) {
+        context.signerDataStore.edit {
+            it[clientPubkeyKey] = pairing.clientPubkey
+            it[clientRelayKey] = pairing.relay
+            it[clientNameKey] = pairing.name
+        }
+    }
+
+    suspend fun clearPairing() {
+        context.signerDataStore.edit {
+            it.remove(clientPubkeyKey)
+            it.remove(clientRelayKey)
+            it.remove(clientNameKey)
+        }
+    }
+
+    suspend fun wipeKey() {
+        context.signerDataStore.edit { it.remove(secretKey) }
+    }
+}

Android/app/src/main/java/com/archipelago/app/ui/components/NESMenu.kt

@@ -31,6 +31,8 @@ import androidx.compose.material.icons.filled.Dns
 import androidx.compose.material.icons.filled.Groups
 import androidx.compose.material.icons.filled.Keyboard
 import androidx.compose.material.icons.filled.RestartAlt
+import androidx.compose.material.icons.filled.SettingsBackupRestore
+import androidx.compose.material.icons.filled.Key
 import androidx.compose.material.icons.filled.SportsEsports
 import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.shape.RoundedCornerShape
@@ -106,6 +108,8 @@ fun NESMenu(
     onKeyboard: () -> Unit,
     onBackToWebView: (() -> Unit)? = null,
     onMeshParty: (() -> Unit)? = null,
+    onBackupRestore: (() -> Unit)? = null,
+    onSigner: (() -> Unit)? = null,
 ) {
     AnimatedVisibility(visible = visible, enter = fadeIn(), exit = fadeOut()) {
         // Contained hub overlay: a centred glass panel (not full-screen) that
@@ -118,7 +122,7 @@ fun NESMenu(
             contentAlignment = Alignment.Center,
         ) {
             AnimatedVisibility(visible = visible, enter = fadeIn() + scaleIn(initialScale = 0.95f), exit = fadeOut() + scaleOut(targetScale = 0.95f)) {
-                MenuPanel(servers, activeServer, onDismiss, onSelectServer, onAddServer, onScanQr, onEditServer, onRemoveServer, onRemote, onKeyboard, onBackToWebView, onMeshParty)
+                MenuPanel(servers, activeServer, onDismiss, onSelectServer, onAddServer, onScanQr, onEditServer, onRemoveServer, onRemote, onKeyboard, onBackToWebView, onMeshParty, onBackupRestore, onSigner)
             }
         }
     }
@@ -138,6 +142,8 @@ private fun MenuPanel(
     onKeyboard: () -> Unit,
     onBackToWebView: (() -> Unit)?,
     onMeshParty: (() -> Unit)?,
+    onBackupRestore: (() -> Unit)?,
+    onSigner: (() -> Unit)?,
 ) {
     var showAdd by remember { mutableStateOf(false) }
     // The saved server being edited, or null when adding a new one.
@@ -233,6 +239,16 @@ private fun MenuPanel(
                 if (onMeshParty != null) {
                     HubCard(Icons.Default.Groups, "Mesh Party", "Phone-to-phone chat & beam") { onMeshParty() }
                 }
+                // Backup & Restore (#128): the phone side of losing your phone
+                // or wiping it to cross a border — encrypted export file, no cloud.
+                if (onBackupRestore != null) {
+                    HubCard(Icons.Default.SettingsBackupRestore, "Backup & Restore", "Encrypted export for a wiped phone") { onBackupRestore() }
+                }
+                // Remote Signer (#139): hold a nostr key on the phone and
+                // approve/deny remote signature requests (NIP-46).
+                if (onSigner != null) {
+                    HubCard(Icons.Default.Key, "Remote Signer", "Approve signatures for your node") { onSigner() }
+                }
                 // Dark/Classic style lives on the remote/keyboard screen next to
                 // the settings button — not here.
 

Android/app/src/main/java/com/archipelago/app/ui/navigation/NavGraph.kt

@@ -22,12 +22,14 @@ import com.archipelago.app.data.ServerEntry
 import com.archipelago.app.data.ServerPreferences
 import com.archipelago.app.data.ServerQrParser
 import com.archipelago.app.fips.FipsManager
+import com.archipelago.app.ui.screens.BackupRestoreScreen
 import com.archipelago.app.ui.screens.FlareScreen
 import com.archipelago.app.ui.screens.IntroScreen
 import com.archipelago.app.ui.screens.NodePickerScreen
 import com.archipelago.app.ui.screens.PartyScreen
 import com.archipelago.app.ui.screens.RemoteInputScreen
 import com.archipelago.app.ui.screens.ServerConnectScreen
+import com.archipelago.app.ui.screens.SignerScreen
 import com.archipelago.app.ui.screens.WebViewScreen
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
@@ -41,6 +43,8 @@ object Routes {
     const val REMOTE_INPUT = "remote_input"
     const val MESH_PARTY = "mesh_party"
     const val FLARE = "flare"
+    const val BACKUP_RESTORE = "backup_restore"
+    const val SIGNER = "signer"
 }
 
 /**
@@ -133,7 +137,14 @@ fun AppNavHost(
     LaunchedEffect(pairUri) {
         val raw = pairUri ?: return@LaunchedEffect
         onPairUriConsumed()
-        when (val result = ServerQrParser.parse(raw)) {
+        when {
+            // Remote-signer pairing deep link (NIP-46): nostrconnect://…
+            // from the node's login QR — any QR scanner app can hand it over.
+            raw.startsWith("nostrconnect://") -> {
+                prefs.markIntroSeen()
+                navController.navigate("${Routes.SIGNER}?uri=${android.net.Uri.encode(raw)}")
+            }
+            else -> when (val result = ServerQrParser.parse(raw)) {
                 is PairResult.Success -> {
                     // Pairing implies the app is installed and in use — skip the intro.
                     prefs.markIntroSeen()
@@ -157,6 +168,7 @@ fun AppNavHost(
                 }
             }
         }
+    }
 
     val startDestination = when {
         introSeen == false -> Routes.INTRO
@@ -259,6 +271,12 @@ fun AppNavHost(
                     onMeshParty = {
                         navController.navigate(Routes.MESH_PARTY)
                     },
+                    onBackupRestore = {
+                        navController.navigate(Routes.BACKUP_RESTORE)
+                    },
+                    onSigner = {
+                        navController.navigate(Routes.SIGNER)
+                    },
                 )
             }
         }
@@ -295,5 +313,28 @@ fun AppNavHost(
                 onBack = { navController.popBackStack() },
             )
         }
+
+        composable(Routes.BACKUP_RESTORE) {
+            BackupRestoreScreen(
+                onBack = { navController.popBackStack() },
+            )
+        }
+
+        composable(
+            "${Routes.SIGNER}?uri={uri}",
+            arguments = listOf(
+                navArgument("uri") {
+                    type = NavType.StringType
+                    defaultValue = ""
+                },
+            ),
+        ) { entry ->
+            SignerScreen(
+                onBack = { navController.popBackStack() },
+                initialPairUri = entry.arguments?.getString("uri")?.let { uri ->
+                    if (uri.isBlank()) null else android.net.Uri.decode(uri)
+                },
+            )
+        }
     }
 }

Android/app/src/main/java/com/archipelago/app/ui/screens/BackupRestoreScreen.kt

@@ -0,0 +1,385 @@
+package com.archipelago.app.ui.screens
+
+import android.net.Uri
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.safeDrawing
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.windowInsetsPadding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.text.KeyboardActions
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.Key
+import androidx.compose.material.icons.filled.Restore
+import androidx.compose.material.icons.filled.Save
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.OutlinedTextFieldDefaults
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Brush
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.input.ImeAction
+import androidx.compose.ui.text.input.KeyboardType
+import androidx.compose.ui.text.input.PasswordVisualTransformation
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.archipelago.app.R
+import com.archipelago.app.data.BackupManager
+import com.archipelago.app.ui.theme.BitcoinOrange
+import com.archipelago.app.ui.theme.SuccessGreen
+import com.archipelago.app.ui.theme.SurfaceBlack
+import com.archipelago.app.ui.theme.TextMuted
+import com.archipelago.app.ui.theme.TextPrimary
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+
+/**
+ * Backup & Restore (#128) — the phone side of "losing your phone, or wiping
+ * it to cross a border".
+ *
+ * Export seals everything the companion holds (servers, FIPS identity and
+ * peers, the remote-signer key) into the node's ADR-005 envelope and hands it
+ * to the system file picker; import decrypts, previews and merges it. On
+ * GrapheneOS there is no cloud anything — the .json goes wherever the user
+ * saves it (USB drive, computer, a folder synced their way), and the
+ * passphrase is the only way back in.
+ */
+@Composable
+fun BackupRestoreScreen(onBack: () -> Unit) {
+    val context = LocalContext.current
+    val scope = rememberCoroutineScope()
+    val manager = remember { BackupManager(context) }
+
+    var passphrase by remember { mutableStateOf("") }
+    var confirm by remember { mutableStateOf("") }
+    var status by remember { mutableStateOf<String?>(null) }
+    var statusError by remember { mutableStateOf(false) }
+    var busy by remember { mutableStateOf(false) }
+
+    // Decrypted preview awaiting the user's go-ahead (restore flow).
+    var restorePreview by remember { mutableStateOf<Pair<BackupManager.PayloadSummary, org.json.JSONObject>?>(null) }
+
+    fun say(msg: String, error: Boolean) {
+        status = msg
+        statusError = error
+    }
+
+    val exportLauncher = rememberLauncherForActivityResult(
+        ActivityResultContracts.CreateDocument("application/json")
+    ) { uri ->
+        if (uri == null) return@rememberLauncherForActivityResult
+        scope.launch {
+            busy = true
+            try {
+                val envelope = manager.createBackup(passphrase)
+                withContext(Dispatchers.IO) {
+                    context.contentResolver.openOutputStream(uri)?.use { out ->
+                        out.write(envelope.toByteArray())
+                    } ?: throw BackupManager.BackupException("could not open the destination file")
+                }
+                say("Backup saved — keep the file and the passphrase somewhere safe.", false)
+            } catch (e: Exception) {
+                say(e.message ?: "backup failed", true)
+            } finally {
+                busy = false
+            }
+        }
+    }
+
+    val importLauncher = rememberLauncherForActivityResult(
+        ActivityResultContracts.OpenDocument()
+    ) { uri ->
+        if (uri == null) return@rememberLauncherForActivityResult
+        scope.launch {
+            busy = true
+            try {
+                val envelope = withContext(Dispatchers.IO) {
+                    context.contentResolver.openInputStream(uri)?.use { it.readBytes().decodeToString() }
+                        ?: throw BackupManager.BackupException("could not read the selected file")
+                }
+                val (summary, payload) = manager.readBackup(envelope, passphrase)
+                restorePreview = summary to payload
+                say("", false)
+            } catch (e: Exception) {
+                say(e.message ?: "restore failed", true)
+            } finally {
+                busy = false
+            }
+        }
+    }
+
+    Box(
+        modifier = Modifier
+            .fillMaxSize()
+            .background(SurfaceBlack),
+    ) {
+        Image(
+            painter = painterResource(id = R.drawable.bg_synthwave),
+            contentDescription = null,
+            modifier = Modifier.fillMaxSize(),
+            contentScale = ContentScale.Crop,
+        )
+        Box(
+            modifier = Modifier
+                .fillMaxSize()
+                .background(
+                    Brush.verticalGradient(
+                        colors = listOf(
+                            Color.Black.copy(alpha = 0.65f),
+                            Color.Black.copy(alpha = 0.5f),
+                            Color.Black.copy(alpha = 0.85f),
+                        ),
+                    )
+                ),
+        )
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .windowInsetsPadding(WindowInsets.safeDrawing)
+                .verticalScroll(rememberScrollState())
+                .padding(horizontal = 24.dp)
+                .padding(top = 16.dp, bottom = 32.dp),
+            verticalArrangement = Arrangement.spacedBy(14.dp),
+        ) {
+            // Header
+            Row(verticalAlignment = Alignment.CenterVertically) {
+                IconButton(onClick = onBack) {
+                    Icon(
+                        Icons.AutoMirrored.Filled.ArrowBack,
+                        contentDescription = "Back",
+                        tint = TextPrimary,
+                    )
+                }
+                Text(
+                    "Backup & Restore",
+                    style = androidx.compose.material3.MaterialTheme.typography.headlineSmall,
+                    color = TextPrimary,
+                )
+            }
+            Text(
+                "An encrypted copy of everything this phone holds — nodes and their passwords, your mesh identity, the remote-signer key. Same envelope your node uses (ADR-005), one passphrase, no cloud.",
+                style = androidx.compose.material3.MaterialTheme.typography.bodyMedium,
+                color = TextMuted,
+            )
+
+            GlassCard {
+                Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+                    Row(
+                        verticalAlignment = Alignment.CenterVertically,
+                        horizontalArrangement = Arrangement.spacedBy(10.dp),
+                    ) {
+                        Icon(Icons.Default.Save, contentDescription = null, tint = BitcoinOrange, modifier = Modifier.size(20.dp))
+                        Text("Create a backup", color = TextPrimary, fontSize = 16.sp, fontWeight = FontWeight.SemiBold)
+                    }
+                    PassphraseField(
+                        value = passphrase,
+                        onValueChange = { passphrase = it },
+                        placeholder = "Passphrase",
+                    )
+                    PassphraseField(
+                        value = confirm,
+                        onValueChange = { confirm = it },
+                        placeholder = "Repeat passphrase",
+                    )
+                    Text(
+                        "The passphrase cannot be recovered — a backup nobody can open is a paperweight.",
+                        color = TextMuted, fontSize = 11.sp,
+                    )
+                    GlassButton(
+                        text = if (busy) "Working…" else "Save backup file",
+                        onClick = {
+                            if (busy) return@GlassButton
+                            if (passphrase.length < 8) {
+                                say("Use at least 8 characters — this passphrase guards every secret in the app.", true)
+                                return@GlassButton
+                            }
+                            if (passphrase != confirm) {
+                                say("The two passphrases don't match.", true)
+                                return@GlassButton
+                            }
+                            val stamp = SimpleDateFormat("yyyyMMdd-HHmm", Locale.US).format(Date())
+                            exportLauncher.launch("archy-companion-backup-$stamp.json")
+                        },
+                        modifier = Modifier.fillMaxWidth().height(48.dp),
+                    )
+                }
+            }
+
+            GlassCard {
+                Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+                    Row(
+                        verticalAlignment = Alignment.CenterVertically,
+                        horizontalArrangement = Arrangement.spacedBy(10.dp),
+                    ) {
+                        Icon(Icons.Default.Restore, contentDescription = null, tint = BitcoinOrange, modifier = Modifier.size(20.dp))
+                        Text("Restore a backup", color = TextPrimary, fontSize = 16.sp, fontWeight = FontWeight.SemiBold)
+                    }
+                    Text(
+                        "Pick a backup file and enter its passphrase. Nothing is overwritten: nodes merge by identity, and the mesh identity and signer key only restore when this phone has none.",
+                        color = TextMuted, fontSize = 11.sp,
+                    )
+                    PassphraseField(
+                        value = passphrase,
+                        onValueChange = { passphrase = it },
+                        placeholder = "Backup passphrase",
+                    )
+                    GlassButton(
+                        text = if (busy) "Working…" else "Choose backup file",
+                        onClick = {
+                            if (busy) return@GlassButton
+                            if (passphrase.isEmpty()) {
+                                say("Enter the backup's passphrase first.", true)
+                                return@GlassButton
+                            }
+                            importLauncher.launch(arrayOf("application/json"))
+                        },
+                        modifier = Modifier.fillMaxWidth().height(48.dp),
+                    )
+                }
+            }
+
+            restorePreview?.let { (summary, payload) ->
+                GlassCard {
+                    Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+                        Text(
+                            "Backup verified${if (summary.appVersion.isNotBlank()) " (made by v${summary.appVersion})" else ""}",
+                            color = SuccessGreen, fontSize = 15.sp, fontWeight = FontWeight.SemiBold,
+                        )
+                        SummaryRow("Nodes", summary.serverCount.toString())
+                        if (summary.hasFipsIdentity) SummaryRow("Mesh identity", "included")
+                        if (summary.hasSignerKey) SummaryRow("Remote-signer key", "included")
+                        GlassButton(
+                            text = if (busy) "Restoring…" else "Restore onto this phone",
+                            onClick = {
+                                if (busy) return@GlassButton
+                                scope.launch {
+                                    busy = true
+                                    try {
+                                        val result = manager.restoreBackup(payload)
+                                        restorePreview = null
+                                        passphrase = ""
+                                        confirm = ""
+                                        say(
+                                            "Restored ${result.serversRestored} node(s)" +
+                                                (if (result.activeSet) ", set active" else "") +
+                                                (if (result.fipsIdentityRestored) ", mesh identity" else "") +
+                                                (if (result.signerKeyRestored) ", signer key" else "") +
+                                                ". Restart the app to reconnect.",
+                                            false,
+                                        )
+                                    } catch (e: Exception) {
+                                        say(e.message ?: "restore failed", true)
+                                    } finally {
+                                        busy = false
+                                    }
+                                }
+                            },
+                            modifier = Modifier.fillMaxWidth().height(48.dp),
+                        )
+                    }
+                }
+            }
+
+            status?.takeIf { it.isNotBlank() }?.let { msg ->
+                Text(
+                    msg,
+                    color = if (statusError) Color(0xFFFF6B6B) else SuccessGreen,
+                    fontSize = 13.sp,
+                    textAlign = TextAlign.Center,
+                    modifier = Modifier.fillMaxWidth(),
+                )
+            }
+        }
+    }
+}
+
+@Composable
+private fun PassphraseField(
+    value: String,
+    onValueChange: (String) -> Unit,
+    placeholder: String,
+) {
+    OutlinedTextField(
+        value = value,
+        onValueChange = onValueChange,
+        placeholder = { Text(placeholder, color = TextMuted, fontSize = 14.sp) },
+        modifier = Modifier.fillMaxWidth(),
+        singleLine = true,
+        visualTransformation = PasswordVisualTransformation(),
+        keyboardOptions = KeyboardOptions(
+            keyboardType = KeyboardType.Password,
+            imeAction = ImeAction.Done,
+        ),
+        keyboardActions = KeyboardActions(),
+        textStyle = TextStyle(color = TextPrimary, fontSize = 15.sp),
+        colors = OutlinedTextFieldDefaults.colors(
+            focusedBorderColor = BitcoinOrange,
+            unfocusedBorderColor = Color.White.copy(alpha = 0.15f),
+            cursorColor = BitcoinOrange,
+            focusedTextColor = TextPrimary,
+            unfocusedTextColor = TextPrimary,
+        ),
+        shape = RoundedCornerShape(12.dp),
+    )
+}
+
+@Composable
+private fun SummaryRow(label: String, value: String) {
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        horizontalArrangement = Arrangement.SpaceBetween,
+    ) {
+        Text(label, color = TextMuted, fontSize = 13.sp)
+        Text(value, color = TextPrimary, fontSize = 13.sp, fontWeight = FontWeight.Medium)
+    }
+}
+
+/** House glass card: translucent panel, hairline border. */
+@Composable
+fun GlassCard(content: @Composable () -> Unit) {
+    Column(
+        modifier = Modifier
+            .fillMaxWidth()
+            .clip(RoundedCornerShape(16.dp))
+            .background(Color.White.copy(alpha = 0.06f))
+            .padding(16.dp),
+    ) {
+        content()
+    }
+}

Android/app/src/main/java/com/archipelago/app/ui/screens/SignerScreen.kt

@@ -0,0 +1,511 @@
+package com.archipelago.app.ui.screens
+
+import android.content.Intent
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.safeDrawing
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.layout.windowInsetsPadding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.Key
+import androidx.compose.material.icons.filled.QrCodeScanner
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.OutlinedTextFieldDefaults
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Brush
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalClipboardManager
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.archipelago.app.NativeCore
+import com.archipelago.app.R
+import com.archipelago.app.nostr.BunkerManager
+import com.archipelago.app.nostr.NostrSignerPreferences
+import com.archipelago.app.ui.components.QrGlassModal
+import com.archipelago.app.ui.theme.BitcoinOrange
+import com.archipelago.app.ui.theme.SuccessGreen
+import com.archipelago.app.ui.theme.SurfaceBlack
+import com.archipelago.app.ui.theme.TextMuted
+import com.archipelago.app.ui.theme.TextPrimary
+import kotlinx.coroutines.launch
+import org.json.JSONObject
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+
+/**
+ * Remote Signer (#139) — the phone side of NIP-46.
+ *
+ * The phone holds a nostr key; the node's login page (or any NIP-46 client)
+ * shows a `nostrconnect://` QR, this screen scans it, and every signature
+ * request lands here as a legible approve/deny card — kind, content, tags —
+ * before anything is signed. Nothing signs without a thumb on Approve.
+ */
+@Composable
+fun SignerScreen(
+    onBack: () -> Unit,
+    initialPairUri: String? = null,
+) {
+    val context = LocalContext.current
+    val scope = rememberCoroutineScope()
+    val clipboard = LocalClipboardManager.current
+    val prefs = remember { NostrSignerPreferences(context) }
+
+    var keyInfo by remember { mutableStateOf<JSONObject?>(null) }
+    var keyError by remember { mutableStateOf<String?>(null) }
+    var importText by remember { mutableStateOf("") }
+    var showNsec by remember { mutableStateOf(false) }
+    var scanVisible by remember { mutableStateOf(false) }
+    var status by remember { mutableStateOf<String?>(null) }
+    var statusError by remember { mutableStateOf(false) }
+
+    val bunkerState by BunkerManager.state.collectAsState()
+    val pending by BunkerManager.pending.collectAsState()
+
+    fun say(msg: String, error: Boolean) {
+        status = msg
+        statusError = error
+    }
+
+    suspend fun loadKey() {
+        val secret = prefs.secret()
+        keyInfo = secret?.let {
+            val json = NativeCore.nostrSecretFromAny(it)
+            if (NativeCore.isErr(json)) null else JSONObject(json)
+        }
+    }
+
+    LaunchedEffect(Unit) {
+        BunkerManager.refreshState(context)
+        loadKey()
+    }
+
+    // Deep link (nostrconnect://…) may arrive with the route.
+    LaunchedEffect(initialPairUri) {
+        val uri = initialPairUri?.takeIf { it.isNotBlank() } ?: return@LaunchedEffect
+        if (keyInfo == null) loadKey()
+        val err = BunkerManager.pair(context, uri)
+        if (err != null) say(err, true) else say("Pairing started…", false)
+    }
+
+    fun pairWith(uri: String) {
+        scope.launch {
+            val err = BunkerManager.pair(context, uri)
+            if (err != null) say(err, true)
+        }
+    }
+
+    Box(
+        modifier = Modifier
+            .fillMaxSize()
+            .background(SurfaceBlack),
+    ) {
+        Image(
+            painter = painterResource(id = R.drawable.bg_synthwave),
+            contentDescription = null,
+            modifier = Modifier.fillMaxSize(),
+            contentScale = ContentScale.Crop,
+        )
+        Box(
+            modifier = Modifier
+                .fillMaxSize()
+                .background(
+                    Brush.verticalGradient(
+                        colors = listOf(
+                            Color.Black.copy(alpha = 0.65f),
+                            Color.Black.copy(alpha = 0.5f),
+                            Color.Black.copy(alpha = 0.85f),
+                        ),
+                    )
+                ),
+        )
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .windowInsetsPadding(WindowInsets.safeDrawing)
+                .verticalScroll(rememberScrollState())
+                .padding(horizontal = 24.dp)
+                .padding(top = 16.dp, bottom = 32.dp),
+            verticalArrangement = Arrangement.spacedBy(14.dp),
+        ) {
+            Row(verticalAlignment = Alignment.CenterVertically) {
+                IconButton(onClick = onBack) {
+                    Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back", tint = TextPrimary)
+                }
+                Text(
+                    "Remote Signer",
+                    style = androidx.compose.material3.MaterialTheme.typography.headlineSmall,
+                    color = TextPrimary,
+                )
+            }
+            Text(
+                "Hold a nostr key on this phone and sign for it remotely — scan a pairing QR from your node's login page (or any NIP-46 client), then approve each signature request as it arrives. Nothing signs without you.",
+                style = androidx.compose.material3.MaterialTheme.typography.bodyMedium,
+                color = TextMuted,
+            )
+
+            if (bunkerState is BunkerManager.SignerState.Unavailable) {
+                GlassCard {
+                    Text(
+                        "Signing is unavailable on this device (native core missing).",
+                        color = Color(0xFFFF6B6B), fontSize = 13.sp,
+                    )
+                }
+            }
+
+            val info = keyInfo
+            if (info == null) {
+                // ── No key yet ─────────────────────────────────────────────
+                GlassCard {
+                    Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+                        Text("Create your signer key", color = TextPrimary, fontSize = 16.sp, fontWeight = FontWeight.SemiBold)
+                        Text(
+                            "Generate a fresh key here, or import an existing nsec. The key never leaves this phone except inside an encrypted backup.",
+                            color = TextMuted, fontSize = 11.sp,
+                        )
+                        keyError?.let { Text(it, color = Color(0xFFFF6B6B), fontSize = 12.sp) }
+                        GlassButton(
+                            text = "Generate key",
+                            onClick = {
+                                scope.launch {
+                                    try {
+                                        keyInfo = prefs.generateSecret()
+                                        keyError = null
+                                        BunkerManager.refreshState(context)
+                                    } catch (e: Exception) {
+                                        keyError = e.message ?: "could not generate a key"
+                                    }
+                                }
+                            },
+                            modifier = Modifier.fillMaxWidth().height(48.dp),
+                        )
+                        OutlinedTextField(
+                            value = importText,
+                            onValueChange = { importText = it },
+                            placeholder = { Text("or import nsec…", color = TextMuted, fontSize = 14.sp) },
+                            modifier = Modifier.fillMaxWidth(),
+                            singleLine = true,
+                            textStyle = TextStyle(color = TextPrimary, fontSize = 13.sp),
+                            colors = OutlinedTextFieldDefaults.colors(
+                                focusedBorderColor = BitcoinOrange,
+                                unfocusedBorderColor = Color.White.copy(alpha = 0.15f),
+                                cursorColor = BitcoinOrange,
+                                focusedTextColor = TextPrimary,
+                                unfocusedTextColor = TextPrimary,
+                            ),
+                            shape = RoundedCornerShape(12.dp),
+                        )
+                        GlassButton(
+                            text = "Import",
+                            onClick = {
+                                if (importText.isBlank()) return@GlassButton
+                                scope.launch {
+                                    try {
+                                        keyInfo = prefs.importSecret(importText)
+                                        importText = ""
+                                        keyError = null
+                                        BunkerManager.refreshState(context)
+                                    } catch (e: Exception) {
+                                        keyError = e.message ?: "not a valid nsec"
+                                    }
+                                }
+                            },
+                            modifier = Modifier.fillMaxWidth().height(48.dp),
+                        )
+                    }
+                }
+            } else {
+                // ── Key present: identity + session + pairing ──────────────
+                GlassCard {
+                    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                        Row(
+                            verticalAlignment = Alignment.CenterVertically,
+                            horizontalArrangement = Arrangement.spacedBy(10.dp),
+                        ) {
+                            Icon(Icons.Default.Key, contentDescription = null, tint = BitcoinOrange, modifier = Modifier.size(18.dp))
+                            Text("Signer identity", color = TextPrimary, fontSize = 15.sp, fontWeight = FontWeight.SemiBold)
+                        }
+                        MonoRow("npub", info.optString("npub")) {
+                            clipboard.setText(AnnotatedString(info.optString("npub")))
+                        }
+                        if (showNsec) {
+                            MonoRow("nsec", info.optString("nsec"), secret = true) {
+                                clipboard.setText(AnnotatedString(info.optString("nsec")))
+                            }
+                            Text(
+                                "Anyone with the nsec can sign as you — clear the clipboard after copying.",
+                                color = Color(0xFFFF6B6B), fontSize = 10.sp,
+                            )
+                        } else {
+                            Text(
+                                "Show nsec",
+                                color = TextMuted, fontSize = 12.sp,
+                                modifier = Modifier
+                                    .clip(RoundedCornerShape(8.dp))
+                                    .clickable { showNsec = true }
+                                    .padding(vertical = 4.dp, horizontal = 8.dp),
+                            )
+                        }
+                    }
+                }
+
+                // Session status
+                GlassCard {
+                    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                        val label = when (val s = bunkerState) {
+                            BunkerManager.SignerState.Unavailable -> "Unavailable on this device"
+                            BunkerManager.SignerState.NoKey -> "No signer key yet"
+                            BunkerManager.SignerState.Idle -> "Idle — scan a pairing QR to start"
+                            is BunkerManager.SignerState.Connecting -> "Connecting to ${s.relay}…"
+                            is BunkerManager.SignerState.AwaitingClient -> "Paired with \"${s.clientName}\" — waiting for it to finish the handshake"
+                            is BunkerManager.SignerState.Ready -> "Ready for \"${s.clientName}\" via ${s.relay}"
+                            is BunkerManager.SignerState.Failed -> s.reason
+                        }
+                        Text("Session", color = TextMuted, fontSize = 12.sp)
+                        Text(
+                            label,
+                            color = if (bunkerState is BunkerManager.SignerState.Failed) Color(0xFFFF6B6B)
+                            else if (bunkerState is BunkerManager.SignerState.Ready) SuccessGreen
+                            else TextPrimary,
+                            fontSize = 14.sp,
+                        )
+                        Row(horizontalArrangement = Arrangement.spacedBy(10.dp)) {
+                            Box(
+                                Modifier
+                                    .weight(1f)
+                                    .height(44.dp)
+                                    .clip(RoundedCornerShape(12.dp))
+                                    .background(Color.White.copy(alpha = 0.06f))
+                                    .border(1.dp, Color.White.copy(alpha = 0.12f), RoundedCornerShape(12.dp))
+                                    .clickable { scanVisible = true },
+                                contentAlignment = Alignment.Center,
+                            ) {
+                                Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                                    Icon(Icons.Default.QrCodeScanner, contentDescription = null, tint = BitcoinOrange, modifier = Modifier.size(18.dp))
+                                    Text("Scan pairing QR", color = BitcoinOrange, fontSize = 13.sp, fontWeight = FontWeight.Medium)
+                                }
+                            }
+                        }
+                        if (bunkerState is BunkerManager.SignerState.Ready ||
+                            bunkerState is BunkerManager.SignerState.AwaitingClient ||
+                            bunkerState is BunkerManager.SignerState.Connecting
+                        ) {
+                            Text(
+                                "End session",
+                                color = TextMuted, fontSize = 12.sp,
+                                modifier = Modifier
+                                    .clip(RoundedCornerShape(8.dp))
+                                    .clickable { BunkerManager.unpair() }
+                                    .padding(vertical = 4.dp, horizontal = 8.dp),
+                            )
+                        }
+                    }
+                }
+
+                // Pending signature request — the whole point.
+                pending?.let { req ->
+                    GlassCard {
+                        Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                            Text(
+                                "Signature request",
+                                color = BitcoinOrange, fontSize = 15.sp, fontWeight = FontWeight.Bold,
+                            )
+                            Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
+                                Text("Client", color = TextMuted, fontSize = 12.sp)
+                                Text(req.clientName.ifBlank { req.clientPubkey.take(12) + "…" }, color = TextPrimary, fontSize = 12.sp)
+                            }
+                            Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
+                                Text("Kind", color = TextMuted, fontSize = 12.sp)
+                                Text(kindLabel(req.kind), color = TextPrimary, fontSize = 12.sp, fontWeight = FontWeight.Medium)
+                            }
+                            req.createdAt?.let {
+                                Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
+                                    Text("Time", color = TextMuted, fontSize = 12.sp)
+                                    Text(
+                                        SimpleDateFormat("HH:mm:ss", Locale.US).format(Date(it * 1000)),
+                                        color = TextPrimary, fontSize = 12.sp,
+                                    )
+                                }
+                            }
+                            req.content?.takeIf { it.isNotBlank() }?.let { content ->
+                                Text("Content", color = TextMuted, fontSize = 12.sp)
+                                Text(
+                                    content,
+                                    color = TextPrimary,
+                                    fontSize = 11.sp,
+                                    lineHeight = 15.sp,
+                                    fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace,
+                                    modifier = Modifier
+                                        .fillMaxWidth()
+                                        .clip(RoundedCornerShape(10.dp))
+                                        .background(Color.Black.copy(alpha = 0.4f))
+                                        .padding(10.dp)
+                                        .heightIn(max = 220.dp),
+                                )
+                            }
+                            if (req.tags.isNotEmpty()) {
+                                Text("Tags", color = TextMuted, fontSize = 12.sp)
+                                Column(
+                                    modifier = Modifier
+                                        .fillMaxWidth()
+                                        .clip(RoundedCornerShape(10.dp))
+                                        .background(Color.Black.copy(alpha = 0.4f))
+                                        .padding(10.dp),
+                                    verticalArrangement = Arrangement.spacedBy(3.dp),
+                                ) {
+                                    req.tags.take(6).forEach {
+                                        Text(
+                                            it,
+                                            color = TextMuted, fontSize = 10.sp,
+                                            fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace,
+                                            maxLines = 1,
+                                        )
+                                    }
+                                    if (req.tags.size > 6) {
+                                        Text("+${req.tags.size - 6} more", color = TextMuted, fontSize = 10.sp)
+                                    }
+                                }
+                            }
+                            Row(horizontalArrangement = Arrangement.spacedBy(10.dp)) {
+                                Box(
+                                    Modifier
+                                        .weight(1f)
+                                        .height(46.dp)
+                                        .clip(RoundedCornerShape(12.dp))
+                                        .background(Color(0xFFE5484D).copy(alpha = 0.18f))
+                                        .border(1.dp, Color(0xFFE5484D).copy(alpha = 0.5f), RoundedCornerShape(12.dp))
+                                        .clickable { BunkerManager.deny() },
+                                    contentAlignment = Alignment.Center,
+                                ) { Text("Deny", color = Color(0xFFFF8A8D), fontSize = 14.sp, fontWeight = FontWeight.Bold) }
+                                Box(
+                                    Modifier
+                                        .weight(1f)
+                                        .height(46.dp)
+                                        .clip(RoundedCornerShape(12.dp))
+                                        .background(BitcoinOrange.copy(alpha = 0.2f))
+                                        .border(1.dp, BitcoinOrange.copy(alpha = 0.6f), RoundedCornerShape(12.dp))
+                                        .clickable {
+                                            scope.launch {
+                                                val ok = BunkerManager.approve()
+                                                say(if (ok) "Signed and sent." else "Could not send the signature.", !ok)
+                                            }
+                                        },
+                                    contentAlignment = Alignment.Center,
+                                ) { Text("Approve", color = BitcoinOrange, fontSize = 14.sp, fontWeight = FontWeight.Bold) }
+                            }
+                        }
+                    }
+                }
+            }
+
+            status?.takeIf { it.isNotBlank() }?.let { msg ->
+                Text(
+                    msg,
+                    color = if (statusError) Color(0xFFFF6B6B) else SuccessGreen,
+                    fontSize = 13.sp,
+                    textAlign = TextAlign.Center,
+                    modifier = Modifier.fillMaxWidth(),
+                )
+            }
+        }
+
+        // Pairing-QR scan — reuses the pairing scanner's glass modal, decodes
+        // any text and treats nostrconnect:// (or a raw bunker:// error) here.
+        QrGlassModal(
+            visible = scanVisible,
+            title = "Scan pairing QR",
+            status = null,
+            idleHint = "Point at the nostrconnect QR your node or client shows",
+            permissionRationale = "Camera access is needed to scan the pairing code",
+            onDismiss = { scanVisible = false },
+            onDecoded = { text ->
+                if (text.startsWith("nostrconnect://")) {
+                    scanVisible = false
+                    pairWith(text)
+                }
+                // Anything else keeps scanning with the hint showing.
+            },
+        )
+    }
+}
+
+/** Kind number → legible label, so approve/deny cards read like sentences. */
+private fun kindLabel(kind: Long?): String = when (kind) {
+    0L -> "Metadata (kind 0)"
+    1L -> "Text note (kind 1)"
+    3L -> "Contact list (kind 3)"
+    4L -> "Direct message (kind 4)"
+    7L -> "Reaction (kind 7)"
+    14L -> "Chat message (kind 14)"
+    22242L -> "Client authentication (kind 22242)"
+    30078L -> "App-stored data (kind 30078)"
+    null -> "Unknown kind"
+    else -> "Kind $kind"
+}
+
+/** Label + monospace value + copy affordance. */
+@Composable
+private fun MonoRow(label: String, value: String, secret: Boolean = false, onCopy: () -> Unit) {
+    Column(Modifier.fillMaxWidth()) {
+        Text(label, color = TextMuted, fontSize = 11.sp)
+        Row(
+            Modifier
+                .fillMaxWidth()
+                .clip(RoundedCornerShape(10.dp))
+                .background(Color.Black.copy(alpha = 0.4f))
+                .clickable { onCopy() }
+                .padding(10.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Text(
+                value,
+                color = if (secret) Color(0xFFFFB86B) else TextPrimary,
+                fontSize = 11.sp,
+                fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace,
+                modifier = Modifier.weight(1f),
+                maxLines = 1,
+                overflow = androidx.compose.ui.text.style.TextOverflow.Ellipsis,
+            )
+            Text("⧉", color = TextMuted, fontSize = 14.sp, modifier = Modifier.padding(start = 8.dp))
+        }
+    }
+}

Android/app/src/main/java/com/archipelago/app/ui/screens/WebViewScreen.kt

@@ -599,6 +599,10 @@ fun WebViewScreen(
     onRemoteKeyboard: () -> Unit = {},
     // Opens the phone-to-phone Mesh Party screen; null hides its hub card.
     onMeshParty: (() -> Unit)? = null,
+    // Backup & Restore (companion 0.5.28, #128); null hides its hub card.
+    onBackupRestore: (() -> Unit)? = null,
+    // Remote Signer (companion 0.5.28, #139); null hides its hub card.
+    onSigner: (() -> Unit)? = null,
     // Stored password for this server (from QR pairing or manual entry). When
     // non-blank, the login page is auto-filled and submitted — the one-step
     // demo flow from docs/companion-pairing-qr.md.
@@ -1427,6 +1431,8 @@ fun WebViewScreen(
             onKeyboard = { showHubMenu = false; onRemoteKeyboard() },
             onBackToWebView = { showHubMenu = false },
             onMeshParty = onMeshParty?.let { open -> { showHubMenu = false; open() } },
+            onBackupRestore = onBackupRestore?.let { open -> { showHubMenu = false; open() } },
+            onSigner = onSigner?.let { open -> { showHubMenu = false; open() } },
         )
 
         // Pairing-QR scan launched from the menu's Nodes page; the menu stays

Android/tools/nip46-test-client.py

@@ -0,0 +1,384 @@
+#!/usr/bin/env python3
+"""
+NIP-46 test client for the Archipelago companion's Remote Signer (#139).
+
+Plays the role the node's login flow will play (rust-nostr nostr-connect
+client): generates a nostrconnect:// pairing QR, connects to a relay, waits
+for the phone's bunker `connect` (secret echo), acks it, then exercises
+get_public_key + sign_event and VERIFIES the returned schnorr signature with
+independent pure-Python BIP-340 code (no shared code with the phone's Rust).
+
+Run it on your computer next to the phone:
+
+    python3 -m venv /tmp/nip46env
+    /tmp/nip46env/bin/pip install websockets qrcode
+    /tmp/nip46env/bin/python Android/tools/nip46-test-client.py [--relay wss://relay.damus.io]
+
+…then on the phone: hub menu (three-finger hold) → Remote Signer →
+Generate key (once) → Scan pairing QR → point at the terminal QR → Approve.
+
+Pure Python (no deps for the crypto; websockets + qrcode for transport/QR).
+"""
+import argparse
+import asyncio
+import base64
+import hashlib
+import hmac
+import json
+import os
+import secrets
+import struct
+import sys
+import time
+import urllib.parse
+
+import websockets  # pip install websockets
+
+# ── secp256k1 / BIP-340 (independent of the phone's Rust code) ──────────────
+
+P = 2**256 - 2**32 - 977
+N = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141
+GX = 0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798
+GY = 0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8
+G = (GX, GY)
+
+
+def _add(pt1, pt2):
+    if pt1 is None:
+        return pt2
+    if pt2 is None:
+        return pt1
+    x1, y1 = pt1
+    x2, y2 = pt2
+    if x1 == x2 and (y1 + y2) % P == 0:
+        return None
+    if pt1 == pt2:
+        lam = (3 * x1 * x1) * pow(2 * y1, -1, P) % P
+    else:
+        lam = (y2 - y1) * pow(x2 - x1, -1, P) % P
+    x3 = (lam * lam - x1 - x2) % P
+    return (x3, (lam * (x1 - x3) - y1) % P)
+
+
+def _mul(k, pt):
+    r = None
+    while k:
+        if k & 1:
+            r = _add(r, pt)
+        pt = _add(pt, pt)
+        k >>= 1
+    return r
+
+
+def lift_x(x):
+    if x >= P:
+        return None
+    y_sq = (pow(x, 3, P) + 7) % P
+    y = pow(y_sq, (P + 1) // 4, P)
+    if y * y % P != y_sq:
+        return None
+    return (x, y if y % 2 == 0 else P - y)
+
+
+def tagged(tag: bytes, data: bytes) -> bytes:
+    """BIP-340 tagged hash: sha256(hash(tag) || hash(tag) || data)."""
+    th = hashlib.sha256(tag).digest()
+    return hashlib.sha256(th + th + data).digest()
+
+
+def bip340_sign(msg: bytes, seckey: int, aux: bytes) -> bytes:
+    d = seckey if seckey <= N - 1 else seckey - N
+    pub = _mul(d, G)
+    if pub[1] % 2 != 0:
+        d = N - d
+    t = bytes(a ^ b for a, b in zip(d.to_bytes(32, "big"), tagged(b"BIP0340/aux", aux)))
+    rand = tagged(b"BIP0340/nonce", t + pub[0].to_bytes(32, "big") + msg)
+    k = int.from_bytes(rand, "big") % N
+    assert k > 0
+    R = _mul(k, G)
+    if R[1] % 2 != 0:
+        k = N - k
+    e = int.from_bytes(tagged(b"BIP0340/challenge", R[0].to_bytes(32, "big") + pub[0].to_bytes(32, "big") + msg), "big") % N
+    return R[0].to_bytes(32, "big") + ((k + e * d) % N).to_bytes(32, "big")
+
+
+def bip340_verify(msg: bytes, pubkey_x: bytes, sig: bytes) -> bool:
+    """Check s·G − e·P == R with even-y R and x(R) == r (BIP-340)."""
+    if len(sig) != 64 or len(pubkey_x) != 32:
+        return False
+    pub = lift_x(int.from_bytes(pubkey_x, "big"))
+    if pub is None:
+        return False
+    r = int.from_bytes(sig[:32], "big")
+    s = int.from_bytes(sig[32:], "big")
+    if r >= P or s >= N:
+        return False
+    e = int.from_bytes(tagged(b"BIP0340/challenge", sig[:32] + pubkey_x + msg), "big") % N
+    sg = _mul(s, G)
+    ep = _mul(e, pub)
+    neg_ep = (ep[0], (P - ep[1]) % P)
+    rp = _add(sg, neg_ep)
+    return rp is not None and rp[0] == r and rp[1] % 2 == 0
+
+
+def ecdh_x(secret_hex: str, peer_x_hex: str) -> bytes:
+    """Raw ECDH x-coordinate against an x-only peer key (even-y lift)."""
+    peer = lift_x(int(peer_x_hex, 16))
+    assert peer is not None, "peer pubkey not on curve"
+    pt = _mul(int(secret_hex, 16) % N, peer)
+    return pt[0].to_bytes(32, "big")
+
+
+# ── NIP-44 v2 (pure python, spec-literal) ────────────────────────────────────
+
+def hkdf_extract(salt: bytes, ikm: bytes) -> bytes:
+    return hmac.new(salt, ikm, hashlib.sha256).digest()
+
+
+def hkdf_expand(prk: bytes, info: bytes, length: int) -> bytes:
+    t = b""
+    out = b""
+    i = 1
+    while len(out) < length:
+        t = hmac.new(prk, t + info + bytes([i]), hashlib.sha256).digest()
+        out += t
+        i += 1
+    return out[:length]
+
+
+def _rotl(x: int, n: int) -> int:
+    return ((x << n) | (x >> (32 - n))) & 0xFFFFFFFF
+
+
+def _qr(s, a, b, c, d):
+    s[a] = (s[a] + s[b]) & 0xFFFFFFFF; s[d] ^= s[a]; s[d] = _rotl(s[d], 16)
+    s[c] = (s[c] + s[d]) & 0xFFFFFFFF; s[b] ^= s[c]; s[b] = _rotl(s[b], 12)
+    s[a] = (s[a] + s[b]) & 0xFFFFFFFF; s[d] ^= s[a]; s[d] = _rotl(s[d], 8)
+    s[c] = (s[c] + s[d]) & 0xFFFFFFFF; s[b] ^= s[c]; s[b] = _rotl(s[b], 7)
+
+
+def chacha20_block(key: bytes, counter: int, nonce: bytes) -> bytes:
+    consts = [0x61707865, 0x3320646E, 0x79622D32, 0x6B206574]
+    state = consts + list(struct.unpack("<8I", key)) + [counter] + list(struct.unpack("<3I", nonce))
+    working = list(state)
+    for _ in range(10):
+        _qr(working, 0, 4, 8, 12); _qr(working, 1, 5, 9, 13)
+        _qr(working, 2, 6, 10, 14); _qr(working, 3, 7, 11, 15)
+        _qr(working, 0, 5, 10, 15); _qr(working, 1, 6, 11, 12)
+        _qr(working, 2, 7, 8, 13); _qr(working, 3, 4, 9, 14)
+    return struct.pack("<16I", *[(x + y) & 0xFFFFFFFF for x, y in zip(working, state)])
+
+
+def chacha20(key: bytes, nonce: bytes, data: bytes) -> bytes:
+    counter = 0  # NIP-44: "ChaCha20 (RFC 8439) with starting counter set to 0"
+    out = bytearray()
+    for i in range(0, len(data), 64):
+        ks = chacha20_block(key, counter, nonce)
+        chunk = data[i:i + 64]
+        out += bytes(a ^ b for a, b in zip(chunk, ks))
+        counter += 1
+    return bytes(out)
+
+
+def calc_padded_len(n: int) -> int:
+    if n <= 32:
+        return 32
+    power = 1 << ((n - 1).bit_length())
+    chunk = 32 if power <= 256 else power // 8
+    return chunk * ((n - 1) // chunk + 1)
+
+
+def nip44_encrypt(secret_hex: str, peer_hex: str, plaintext: str) -> str:
+    ck = hkdf_extract(b"nip44-v2", ecdh_x(secret_hex, peer_hex))
+    nonce = secrets.token_bytes(32)
+    okm = hkdf_expand(ck, nonce, 76)
+    key, iv, mac_key = okm[:32], okm[32:44], okm[44:76]
+    pt = plaintext.encode()
+    padded = (len(pt).to_bytes(2, "big") if len(pt) < 65536 else b"\x00\x00" + len(pt).to_bytes(4, "big")) + pt
+    padded += b"\x00" * (calc_padded_len(len(pt)) - len(pt))
+    ct = chacha20(key, iv, padded)
+    mac = hmac.new(mac_key, nonce + ct, hashlib.sha256).digest()
+    return base64.b64encode(bytes([2]) + nonce + ct + mac).decode()
+
+
+def nip44_decrypt(secret_hex: str, peer_hex: str, payload: str) -> str:
+    data = base64.b64decode(payload)
+    assert data[0] == 2, "only NIP-44 v2 supported"
+    nonce, ct, mac = data[1:33], data[33:-32], data[-32:]
+    ck = hkdf_extract(b"nip44-v2", ecdh_x(secret_hex, peer_hex))
+    okm = hkdf_expand(ck, nonce, 76)
+    key, iv, mac_key = okm[:32], okm[32:44], okm[44:76]
+    assert hmac.compare_digest(hmac.new(mac_key, nonce + ct, hashlib.sha256).digest(), mac), "bad MAC"
+    padded = chacha20(key, iv, ct)
+    ln = int.from_bytes(padded[:2], "big")
+    body = padded[2:2 + ln] if ln else padded[6:6 + int.from_bytes(padded[2:6], "big")]
+    return body.decode()
+
+
+# ── nostr events ─────────────────────────────────────────────────────────────
+
+def event_id(pubkey_hex: str, created_at: int, kind: int, tags, content: str) -> str:
+    serialized = json.dumps([0, pubkey_hex, created_at, kind, tags, content], separators=(",", ":"))
+    return hashlib.sha256(serialized.encode()).hexdigest()
+
+
+def sign_event(secret_hex: str, event: dict) -> dict:
+    eid = event_id(event["pubkey"], event["created_at"], event["kind"], event["tags"], event["content"])
+    ev = dict(event)
+    ev["id"] = eid
+    ev["sig"] = bip340_sign(bytes.fromhex(eid), int(secret_hex, 16), os.urandom(32)).hex()
+    return ev
+
+
+# ── the client session ────────────────────────────────────────────────────────
+
+def compact(d) -> str:
+    return json.dumps(d, separators=(",", ":"))
+
+
+async def run(relay: str):
+    client_secret = os.urandom(32).hex()
+    client_secret_int = int(client_secret, 16) % N
+    client_pub_hex = _mul(client_secret_int, G)[0].to_bytes(32, "big").hex()
+    pair_secret = secrets.token_hex(16)
+    nonce = secrets.token_hex(8)
+
+    uri = (
+        f"nostrconnect://{client_pub_hex}"
+        f"?relay={urllib.parse.quote(relay, safe='')}"
+        f"&secret={pair_secret}"
+        f"&name=Archipelago+Test+Client"
+    )
+
+    print(f"· client key  : {client_pub_hex}")
+    print(f"· relay       : {relay}")
+    print()
+    print("Scan this QR with: Companion → hub (3-finger) → Remote Signer → Scan pairing QR")
+    print()
+
+    try:
+        import qrcode
+        qr = qrcode.QRCode(border=1)
+        qr.add_data(uri)
+        qr.make(fit=True)
+        qr.print_ascii(invert=True)
+    except ImportError:
+        print(uri)
+
+    print()
+    print("Waiting for the phone to pair (connect, ack, get_public_key, sign_event)…")
+
+    async with websockets.connect(relay, max_size=2**22) as ws:
+        await ws.send(compact(["REQ", "test", {"kinds": [24133], "#p": [client_pub_hex], "since": int(time.time()) - 60}]))
+
+        signer_pub = None
+        acked = False
+        requests = []
+
+        def send_frame(content: dict):
+            assert signer_pub is not None
+            ev = {
+                "pubkey": client_pub_hex,
+                "created_at": int(time.time()),
+                "kind": 24133,
+                "tags": [["p", signer_pub]],
+                "content": nip44_encrypt(client_secret, signer_pub, compact(content)),
+            }
+            return asyncio.ensure_future(ws.send(compact(["EVENT", sign_event(client_secret, ev)])))
+
+        async def request(method, params, rid):
+            send_frame({"id": rid, "method": method, "params": params})
+
+        timeout = time.time() + 120
+        got_pubkey = None
+        signed_event = None
+
+        while time.time() < timeout:
+            try:
+                raw = await asyncio.wait_for(ws.recv(), timeout=timeout - time.time())
+            except (asyncio.TimeoutError, TimeoutError):
+                break
+            arr = json.loads(raw)
+            if not isinstance(arr, list) or len(arr) < 3 or arr[0] != "EVENT":
+                continue
+            ev = arr[2]
+            if ev.get("kind") != 24133 or ev.get("pubkey") == client_pub_hex:
+                continue
+            author = ev["pubkey"]
+            try:
+                msg = json.loads(nip44_decrypt(client_secret, author, ev["content"]))
+            except Exception:
+                continue
+
+            if "method" in msg and msg["method"] == "connect":
+                params = msg.get("params", [])
+                if params and params[0] == author and (len(params) < 2 or params[1] == pair_secret):
+                    signer_pub = author
+                    print(f"✓ phone paired  — signer pubkey {author[:16]}…")
+                    send_frame({"id": msg["id"], "result": "ack"})
+                    acked = True
+                    await asyncio.sleep(0.5)
+                    await request("get_public_key", [], nonce + "-gpk")
+                else:
+                    print("✗ phone sent connect but the secret didn't match")
+                    return 1
+                continue
+
+            if "result" in msg or "error" in msg:
+                rid = msg.get("id", "")
+                if "error" in msg:
+                    print(f"✗ error for {rid}: {msg['error']}")
+                    if rid.endswith("-sign"):
+                        return 1
+                    continue
+                result = msg.get("result", "")
+                if rid.endswith("-gpk"):
+                    got_pubkey = result
+                    print(f"✓ get_public_key → {result}")
+                    await request(
+                        "sign_event",
+                        [compact({
+                            "kind": 1,
+                            "content": "Hello from the Archipelago NIP-46 test client — approved by hand.",
+                            "tags": [],
+                            "created_at": int(time.time()),
+                        })],
+                        nonce + "-sign",
+                    )
+                elif rid.endswith("-sign"):
+                    signed_event = json.loads(result)
+                    print(f"✓ sign_event → signed event {signed_event.get('id', '')[:16]}…")
+                    break
+
+        if not acked:
+            print("✗ the phone never connected (2-minute timeout)")
+            return 1
+        if got_pubkey is None or got_pubkey != signer_pub:
+            print("✗ get_public_key missing or mismatched")
+            return 1
+        if signed_event is None:
+            return 1
+
+        ev = signed_event
+        expected_id = event_id(ev["pubkey"], ev["created_at"], ev["kind"], ev["tags"], ev["content"])
+        ok_id = expected_id == ev["id"]
+        ok_sig = bip340_verify(bytes.fromhex(expected_id), bytes.fromhex(ev["pubkey"]), bytes.fromhex(ev["sig"]))
+        print(f"· event id correct : {ok_id}")
+        print(f"· schnorr signature: {'VERIFIED ✓' if ok_sig else 'INVALID ✗'}")
+        if ok_id and ok_sig:
+            print()
+            print("END-TO-END PASS — the companion signed as the identity the phone holds,")
+            print("and the signature verifies under an independent BIP-340 implementation.")
+            return 0
+        return 1
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--relay", default="wss://relay.damus.io", help="any nostr relay both devices can reach")
+    args = ap.parse_args()
+    sys.exit(asyncio.run(run(args.relay)))
+
+
+if __name__ == "__main__":
+    main()

docs/companion-backup-restore.md

@@ -0,0 +1,87 @@
+# Companion backup & restore — the phone side of a border crossing (#128)
+
+**Status:** shipped in companion 0.5.28 (vc48). Issue: #128 ("Graphene phone
+backup/restore — part of the companion app or passport prime combo").
+
+## The problem
+
+The companion holds real secrets: node addresses and login passwords, the
+phone's FIPS mesh identity (which nodes peer with), and — since 0.5.28 — the
+remote-signer key. Losing the phone, or wiping it to cross a border, loses all
+of it. On GrapheneOS there is no cloud backup and there should be none here
+either: the export is a plain file the user saves wherever they choose (USB
+drive, computer, a folder synced their way), sealed with a passphrase.
+
+## The envelope — the node's, not a second format
+
+Backups use the node's ADR-005 encrypted-backup envelope
+(`core/archipelago/src/backup/identity.rs`), byte-for-byte:
+
+- Argon2id key derivation (RustCrypto `argon2`, default params — same as the
+  node's `Argon2::default()`), passphrase in, 16-byte random salt.
+- ChaCha20-Poly1305 AEAD with a 12-byte random nonce.
+- Envelope JSON:
+  `{"version": 1, "kind": "companion", "encrypted": true, "blob": "<base64(salt‖nonce‖ct)>", "timestamp": "<rfc3339>"}`
+- The native code (`Android/rust/archy-fips-core/src/backup.rs`) is the same
+  crate family as the node's backup code; `decrypt` ignores unknown envelope
+  fields, so a **node** identity backup (which carries `did`/`pubkey`/`kid`)
+  also decrypts here — one envelope, two producers.
+
+The encrypted payload is the companion's own JSON:
+
+```json
+{
+  "app": "archipelago-companion",
+  "payloadVersion": 1,
+  "appVersion": "0.5.28",
+  "createdAt": 1725100000,
+  "servers": ["<serialized ServerEntry>", …],
+  "active": "<serialized ServerEntry or null>",
+  "fips": {"secret","npub","address","peers","partyPeers","partyName","partyListen"},
+  "signer": {"secret": "<hex>"},
+  "flags": {"introSeen": true}
+}
+```
+
+## Where the code lives
+
+- **Crypto:** `Android/rust/archy-fips-core/src/backup.rs` (+ JNI
+  `NativeCore.backupEncrypt/Decrypt`). Host `cargo test` covers round-trip,
+  wrong-passphrase, tampered-blob, node-shape envelopes, and salt/nonce
+  freshness.
+- **Payload/merge:** `BackupManager` (`Android/app/src/main/java/com/archipelago/app/data/BackupManager.kt`).
+- **UI:** hub menu (three-finger) → **Backup & Restore** → SAF file picker
+  (`CreateDocument` for export, `OpenDocument` for import), passphrase fields,
+  verified-backup preview, result summary. The suggested export name is
+  `archy-companion-backup-YYYYMMDD-HHmmss.json`.
+
+## Restore semantics — never silently destructive
+
+| What | On restore |
+|---|---|
+| Servers | Upsert (`ServerPreferences.upsertServer`): same npub merges (even when every address changed), new ones append |
+| Active server | Set only when this phone has none (the fresh-wipe case) |
+| FIPS identity | Restored only when this phone has none; node peers UNION by npub (`FipsPreferences.mergePeersJson`); party peers merge by npub |
+| Signer key | Restored only when this phone has none |
+| introSeen flag | Restored (no re-onboarding after a restore) |
+
+The identity rules exist because a phone that already paired has a live mesh
+identity nodes peer with; swapping it in from a backup would strand the
+current pairing.
+
+## Test checklist (on-device)
+
+- [ ] Export → file saved, `version: 1`, `kind: companion`, base64 blob ≥ 44 chars.
+- [ ] Wrong passphrase on import → "wrong passphrase" error, no state change.
+- [ ] Correct passphrase → preview shows the right server count; restore on a
+      second install (or after clearing app data) reconnects to the node
+      without re-pairing, mesh included.
+- [ ] Re-scan the node's QR after restore → no duplicate entry.
+- [ ] The old phone's password for a node restores (login works on the new phone).
+
+## Roadmap notes (node-side, tracked separately)
+
+Node-side storage/quota/scheduling for companion backups ("passport prime
+combo") is roadmap territory — this issue's scope was the phone side. The
+envelope is ready to be a drop-in for the node's existing backup RPCs when
+that lands.

docs/companion-nip46-remote-signer.md

@@ -0,0 +1,105 @@
+# Companion NIP-46 remote signer — the phone side of Nostr Bunker (#139)
+
+**Status:** shipped in companion 0.5.28 (vc48). Issue: #139 ("Remote signer
+with companion app?"). Background research:
+[`nostr-signer-login-research.md`](nostr-signer-login-research.md) — flow B of
+that document is exactly the flow this implements, with the companion playing
+the role the research assigned to Amber.
+
+## What shipped: the phone IS the bunker (remote signer)
+
+The companion holds a nostr key (generate or import an `nsec`) and speaks
+NIP-46 as the **remote signer**:
+
+1. A NIP-46 client — the node's login page, per the research doc's flow B,
+   or any `nostrconnect://`-emitting app — shows its pairing QR.
+2. The phone scans it (hub → **Remote Signer** → *Scan pairing QR*), or any
+   QR-scanner app hands the `nostrconnect://` URI over as a deep link
+   (registered in the manifest).
+3. The phone connects to the client's relay(s), subscribes to kind-24133
+   events p-tagged to its own key, and sends the `connect` request carrying
+   the secret — the same handshake direction rust-nostr's reference bunker
+   uses (`NostrConnectRemoteSigner::send_connect_ack`), which is what the
+   node's eventual nostr-connect client will wait for.
+4. Requests arrive NIP-44-encrypted. Handled methods:
+   - `connect` → "ack" (validates our pubkey + the pairing secret)
+   - `get_public_key` → our pubkey
+   - `describe` → method list
+   - `ping` → "pong"
+   - **`sign_event` → an approve/deny card — kind label, content, tags,
+     time. Nothing signs without a thumb on Approve.** Deny replies
+     `"denied"`; a second request while one is pending replies `"busy"`
+     instead of replacing the visible card.
+   - anything else → `"not authorized"` (nip04/nip44 encrypt/decrypt are
+     deliberately NOT granted in v1).
+5. Responses go back over the same encrypted kind-24133 channel.
+
+The session lives while the app does (the login handshake takes seconds);
+remembered-session auto-reconnect is the research doc's deferred flow C, and
+stays deferred. NIP-04 is accepted on receive as a fallback (deprecated but
+still spoken by real clients); all sending is NIP-44 v2.
+
+## Where the code lives
+
+- **Crypto:** `Android/rust/archy-fips-core/src/nostr.rs` — nsec/npub bech32
+  keys, BIP-340 schnorr event signing (NIP-01 id serialization), NIP-44 v2
+  payloads, NIP-04 fallback, `nostrconnect://` parsing. Host `cargo test`
+  runs the official NIP-44 vectors (conversation/message keys, padded
+  lengths, byte-exact encrypt vectors), the official BIP-340 sign vectors,
+  and round-trip/tamper/failure cases.
+- **JNI:** `com.archipelago.app.NativeCore` (same .so as the FIPS mesh).
+- **Session:** `nostr/BunkerManager.kt` — OkHttp WebSocket relay client,
+  JSON-RPC dispatch, approve/deny state.
+- **UI:** `ui/screens/SignerScreen.kt` — key setup, npub/nsec display,
+  pairing scan, session status, the approve/deny card.
+- **Deep link:** `nostrconnect://` intent filter → SignerScreen.
+
+## Security notes (conscious deviations, reviewed)
+
+- Incoming events are **not** signature-verified before decryption — the
+  same choice rust-nostr's reference bunker makes. The NIP-44 MAC is the
+  actual gate: forging content that decrypts with a valid MAC requires one
+  of the two conversation secrets. A future hardening pass may add event
+  verification first.
+- The signer secret lives in app-private DataStore (same storage model as
+  the FIPS secret and node login passwords). It can additionally be sealed
+  inside an encrypted backup (see
+  [`companion-backup-restore.md`](companion-backup-restore.md)).
+- `sign_event` approval is per-request and per-screen; there is no
+  "remember this client" auto-approve in v1.
+
+## End-to-end test harness (the node side doesn't exist yet)
+
+`Android/tools/nip46-test-client.py` plays the node's role: generates the
+pairing QR in your terminal, runs the full handshake, requests
+`get_public_key` + `sign_event`, and verifies the returned signature with an
+independent pure-Python BIP-340 implementation (no code shared with the
+phone's Rust core; both are pinned to the same official test vectors).
+
+```bash
+python3 -m venv /tmp/nip46env
+/tmp/nip46env/bin/pip install websockets qrcode
+/tmp/nip46env/bin/python Android/tools/nip46-test-client.py   # --relay to override
+```
+
+Then on the phone: hub → Remote Signer → Generate key (once) → Scan pairing
+QR → point at the terminal QR → Approve the incoming request. The harness
+prints `END-TO-END PASS` when the phone-signed event verifies.
+
+## Test checklist (on-device)
+
+- [ ] Generate key → npub shows, copy works; import nsec → same npub.
+- [ ] Harness handshake: pair → ack → `get_public_key` returns the phone's npub.
+- [ ] `sign_event` request shows a legible card (kind label, content, tags);
+      Approve → harness verifies the schnorr signature; Deny → harness sees
+      `"denied"`.
+- [ ] Deep link: open a `nostrconnect://…` URI from a QR app → SignerScreen
+      with the pairing already starting.
+- [ ] Wrong/foreign QR → clear error, no state change.
+
+## Roadmap (node-side, tracked separately)
+
+The node-side bunker hosting/login flow (research doc flows A+B, the
+`auth.login.nostr` slot, relay topology on the node's own strfry) is roadmap
+territory via the `companion-agent`-labeled tracker issues; when it ships,
+the phone side here already speaks its language.