diff --git a/composeApp/src/commonMain/kotlin/press/mantra/compose/ui/composable/AddArtifactScreen.kt b/composeApp/src/commonMain/kotlin/press/mantra/compose/ui/composable/AddArtifactScreen.kt
index 34e7932f..5d451f8d 100644
--- a/composeApp/src/commonMain/kotlin/press/mantra/compose/ui/composable/AddArtifactScreen.kt
+++ b/composeApp/src/commonMain/kotlin/press/mantra/compose/ui/composable/AddArtifactScreen.kt
@@ -20,10 +20,12 @@ import androidx.compose.material.icons.filled.LocalOffer
 import androidx.compose.material.icons.filled.MoreVert
 import androidx.compose.material3.BottomAppBar
 import androidx.compose.material3.BottomAppBarDefaults
+import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.ExperimentalMaterial3ExpressiveApi
 import androidx.compose.material3.ExtendedFloatingActionButton
 import androidx.compose.material3.FilterChip
+import androidx.compose.material3.FloatingActionButtonDefaults
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
@@ -33,6 +35,7 @@ import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
 import androidx.compose.material3.TopAppBar
+import androidx.compose.material3.contentColorFor
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
@@ -42,6 +45,8 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.semantics.disabled
+import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
@@ -110,6 +115,16 @@ fun AddArtifactScreen(
             // one is picked; dialects are defined from the group detail screen.
             var selectedDialectId: String? by remember { mutableStateOf(null) }
 
+            // Of the required fields this is the only one the screen cannot ask
+            // for again: a dialect has to already exist, and nothing here can
+            // create one. So an unpicked dialect is a dead end rather than
+            // something to submit and be told about, and the button says so.
+            val canAddArtifact = selectedDialectId != null
+
+            // M3 gives a FAB no `enabled`, so borrow the disabled colours every
+            // other button in the app uses rather than inventing a shade here.
+            val buttonColors = ButtonDefaults.buttonColors()
+
             Scaffold(
                 topBar = {
                     TopAppBar(
@@ -126,7 +141,27 @@ fun AddArtifactScreen(
                         actions = {},
                         floatingActionButton = {
                             ExtendedFloatingActionButton(
+                                modifier = if (canAddArtifact) {
+                                    Modifier
+                                } else {
+                                    // Looking unavailable is not being unavailable:
+                                    // without this a screen reader still announces
+                                    // a button it is happy to press.
+                                    Modifier.semantics { disabled() }
+                                },
+                                containerColor = if (canAddArtifact) {
+                                    FloatingActionButtonDefaults.containerColor
+                                } else {
+                                    buttonColors.disabledContainerColor
+                                },
+                                contentColor = if (canAddArtifact) {
+                                    contentColorFor(FloatingActionButtonDefaults.containerColor)
+                                } else {
+                                    buttonColors.disabledContentColor
+                                },
                                 onClick = {
+                                    if (!canAddArtifact) return@ExtendedFloatingActionButton
+
                                     addArtifactViewModel.addArtifact(
                                         localChatRoom = addArtifactUIState.localChatRoom,
                                         nameField = nameFieldState,