fix: align channel QR share contract

core/model/src/commonMain/kotlin/org/meshtastic/core/model/util/ChannelSet.kt

@@ -184,7 +184,7 @@ private fun ChannelSettings.withoutPositionSharing(): ChannelSettings =
  * @param upperCasePrefix portions of the URL can be upper case to make for more efficient QR codes
  */
 fun ChannelSet.getChannelUrl(upperCasePrefix: Boolean = false, shouldAdd: Boolean = false): CommonUri {
-    val channelBytes = ChannelSet.ADAPTER.encode(this)
+    val channelBytes = ChannelSet.ADAPTER.encode(if (shouldAdd) copy(lora_config = null) else this)
     val enc = channelBytes.toByteString().base64Url().replace("=", "")
     val p = if (upperCasePrefix) CHANNEL_URL_PREFIX.uppercase() else CHANNEL_URL_PREFIX
     val query = if (shouldAdd) "?add=true" else ""

core/model/src/commonTest/kotlin/org/meshtastic/core/model/util/ChannelSetUrlTest.kt

@@ -16,6 +16,7 @@
  */
 package org.meshtastic.core.model.util
 
+import okio.ByteString.Companion.decodeBase64
 import okio.ByteString.Companion.toByteString
 import org.meshtastic.core.common.util.CommonUri
 import org.meshtastic.proto.ChannelSet
@@ -43,16 +44,34 @@ class ChannelSetUrlTest {
     fun `all supported channel counts preserve settings for replace and add`() {
         for (channelCount in 1..8) {
             val original = channelSet(channelCount)
-            val replace = original.getChannelUrl().toChannelSet()
-            val add = original.getChannelUrl(shouldAdd = true).toChannelSet()
+            val replaceUrl = original.getChannelUrl()
+            val addUrl = original.getChannelUrl(shouldAdd = true)
+            val replace = replaceUrl.toChannelSet()
+            val add = addUrl.toChannelSet()
+            val replacePayload = replaceUrl.encodedChannelSet()
+            val addPayload = addUrl.encodedChannelSet()
 
+            assertEquals(original.settings, replacePayload.settings, "$channelCount-channel replace payload settings")
+            assertEquals(
+                original.lora_config,
+                replacePayload.lora_config,
+                "$channelCount-channel replace payload LoRa config",
+            )
             assertEquals(original.settings, replace.settings, "$channelCount-channel replace settings")
             assertEquals(original.lora_config, replace.lora_config, "$channelCount-channel replace LoRa config")
+            assertEquals(original.settings, addPayload.settings, "$channelCount-channel add payload settings")
+            assertNull(addPayload.lora_config, "$channelCount-channel add payload must omit LoRa config")
             assertEquals(original.settings, add.settings, "$channelCount-channel add settings")
             assertNull(add.lora_config, "$channelCount-channel add must not retune")
         }
     }
 
+    private fun CommonUri.encodedChannelSet(): ChannelSet {
+        val base64 = requireNotNull(fragment).substringBefore('?').replace('-', '+').replace('_', '/')
+        val bytes = requireNotNull(base64.decodeBase64())
+        return ChannelSet.ADAPTER.decode(bytes)
+    }
+
     private fun channelSet(channelCount: Int): ChannelSet = ChannelSet(
         settings =
         (0 until channelCount).map { index ->

feature/settings/src/commonMain/kotlin/org/meshtastic/feature/settings/radio/channel/ChannelScreen.kt

@@ -64,7 +64,6 @@ import org.koin.compose.viewmodel.koinViewModel
 import org.meshtastic.core.model.Channel
 import org.meshtastic.core.model.ConnectionState
 import org.meshtastic.core.model.defaultPresetFor
-import org.meshtastic.core.model.util.getChannelUrl
 import org.meshtastic.core.navigation.Route
 import org.meshtastic.core.resources.Res
 import org.meshtastic.core.resources.add
@@ -126,7 +125,7 @@ fun ChannelScreen(
 
     var showResetDialog by rememberSaveable { mutableStateOf(false) }
 
-    var shouldAddChannelsState by remember { mutableStateOf(true) }
+    val channelShareState = rememberChannelShareState()
 
     val requestChannelSet by viewModel.requestChannelSet.collectAsStateWithLifecycle()
 
@@ -222,8 +221,7 @@ fun ChannelScreen(
 
     if (showShareDialog) {
         ChannelShareDialog(
-            channelSet = selectedChannelSet,
-            shouldAddChannel = shouldAddChannelsState,
+            uriString = channelShareState.uriString(selectedChannelSet),
             onDismiss = { showShareDialog = false },
         )
     }
@@ -264,14 +262,14 @@ fun ChannelScreen(
                 SingleChoiceSegmentedButtonRow(modifier = Modifier.fillMaxWidth().padding(8.dp)) {
                     SegmentedButton(
                         label = { Text(text = stringResource(Res.string.replace)) },
-                        onClick = { shouldAddChannelsState = false },
-                        selected = !shouldAddChannelsState,
+                        onClick = { channelShareState.shouldAdd = false },
+                        selected = !channelShareState.shouldAdd,
                         shape = SegmentedButtonDefaults.itemShape(0, 2),
                     )
                     SegmentedButton(
                         label = { Text(text = stringResource(Res.string.add)) },
-                        onClick = { shouldAddChannelsState = true },
-                        selected = shouldAddChannelsState,
+                        onClick = { channelShareState.shouldAdd = true },
+                        selected = channelShareState.shouldAdd,
                         shape = SegmentedButtonDefaults.itemShape(1, 2),
                     )
                 }
@@ -303,8 +301,7 @@ fun ChannelScreen(
 }
 
 @Composable
-private fun ChannelShareDialog(channelSet: ChannelSet, shouldAddChannel: Boolean, onDismiss: () -> Unit) {
-    val uriString = channelSet.getChannelUrl(false, shouldAddChannel).toString()
+private fun ChannelShareDialog(uriString: String, onDismiss: () -> Unit) {
     QrDialog(title = stringResource(Res.string.share_channels_qr), uriString = uriString, onDismiss = onDismiss)
 }
 

feature/settings/src/commonMain/kotlin/org/meshtastic/feature/settings/radio/channel/ChannelShareState.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.feature.settings.radio.channel
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import org.meshtastic.core.model.util.getChannelUrl
+import org.meshtastic.proto.ChannelSet
+
+internal class ChannelShareState {
+    var shouldAdd by mutableStateOf(false)
+
+    fun uriString(channelSet: ChannelSet): String = channelSet.getChannelUrl(shouldAdd = shouldAdd).toString()
+}
+
+@Composable internal fun rememberChannelShareState(): ChannelShareState = remember { ChannelShareState() }

feature/settings/src/commonTest/kotlin/org/meshtastic/feature/settings/radio/channel/ChannelScreenTest.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.feature.settings.radio.channel
+
+import org.meshtastic.core.common.util.CommonUri
+import org.meshtastic.core.model.util.toChannelSet
+import org.meshtastic.proto.ChannelSet
+import org.meshtastic.proto.Config.LoRaConfig
+import org.meshtastic.proto.Config.LoRaConfig.RegionCode
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+
+class ChannelScreenTest {
+    @Test
+    fun `channel share state defaults to a replace URL`() {
+        val channelSet = ChannelSet(lora_config = LoRaConfig(region = RegionCode.US))
+
+        val url = ChannelShareState().uriString(channelSet)
+
+        assertFalse(url.contains("?add=true"))
+        assertEquals(channelSet.lora_config, CommonUri.parse(url).toChannelSet().lora_config)
+    }
+}