diff --git a/app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt b/app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt
index 893f801..78ed30d 100644
--- a/app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt
+++ b/app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt
@@ -93,6 +93,17 @@ sealed class TranscriptItem {
     data class ToolRun(
         override val seq: Long,
         val id: String,
+        /**
+         * The run of adjacent calls this one belongs to, named once when the call is folded in and
+         * never recomputed.
+         *
+         * Carried rather than derived because a run can gain members at *either* end -- a new call
+         * arriving beside it, or a page of history arriving in front of it -- so no function of its
+         * current members is stable. It is the first call's id at the moment the run started, which
+         * is a name rather than a description: [joinPages] hands it to older calls that turn out to
+         * belong to the same run, instead of renaming the run they joined.
+         */
+        val runId: String,
         val tool: String,
         val input: String,
         val output: String,
@@ -177,6 +188,16 @@ sealed class TranscriptItem {
     ) : TranscriptItem()
 }
 
+/**
+ * The run a call joins: the one it lands next to, or a new one named after itself.
+ *
+ * Only ever consulted when the call is first folded in. That is what makes the name stable -- a run
+ * keeps whatever it was called when it started, however many calls arrive at either end of it
+ * afterwards.
+ */
+private fun runIdFor(items: List<TranscriptItem>, id: String): String =
+    (items.lastOrNull() as? TranscriptItem.ToolRun)?.runId ?: id
+
 /**
  * Puts a page of older items in front of the ones already loaded, healing any tool call the page
  * boundary cut in two.
@@ -220,7 +241,28 @@ fun joinPages(earlier: List<TranscriptItem>, later: List<TranscriptItem>): List<
             row
         }
     }
-    return healed + later.filterNot { it is TranscriptItem.ToolRun && it.id in endedLater }
+    val kept = later.filterNot { it is TranscriptItem.ToolRun && it.id in endedLater }
+    return adoptRun(healed, kept) + kept
+}
+
+/**
+ * Hands the older calls at the join the name of the run they are joining.
+ *
+ * The two pages were folded separately, so a run split by the boundary came back as two runs with
+ * two names. Naming the joined run after the *older* half would be the obvious way round and is the
+ * wrong one: the newer half is the part already on screen, and renaming it is renaming the row the
+ * reader is looking at, which is how a list loses its anchor and steps under them. So the arriving
+ * calls take the name of the ones already there, and nothing visible changes identity.
+ */
+private fun adoptRun(
+    earlier: List<TranscriptItem>,
+    later: List<TranscriptItem>,
+): List<TranscriptItem> {
+    val joining = (later.firstOrNull() as? TranscriptItem.ToolRun)?.runId ?: return earlier
+    val tail = earlier.takeLastWhile { it is TranscriptItem.ToolRun }
+    if (tail.isEmpty()) return earlier
+    return earlier.dropLast(tail.size) +
+        tail.map { (it as TranscriptItem.ToolRun).copy(runId = joining) }
 }
 
 fun foldEvent(items: List<TranscriptItem>, entry: SeqEvent): List<TranscriptItem> =
@@ -242,6 +284,7 @@ fun foldEvent(items: List<TranscriptItem>, entry: SeqEvent): List<TranscriptItem
                 TranscriptItem.ToolRun(
                     entry.seq,
                     event.id,
+                    runIdFor(items, event.id),
                     event.tool,
                     event.input,
                     "",
@@ -262,6 +305,7 @@ fun foldEvent(items: List<TranscriptItem>, entry: SeqEvent): List<TranscriptItem
                     TranscriptItem.ToolRun(
                         entry.seq,
                         event.id,
+                        runIdFor(items, event.id),
                         "tool",
                         "",
                         event.output,
@@ -908,7 +952,7 @@ fun SessionScreen(
                 // reason: the working indicator appearing and disappearing is another insertion
                 // at the same end. Paging older history is the opposite insertion and was
                 // already fine, and stays fine, because a key survives both.
-                items(rows.asReversed(), key = { it.seq }) { row ->
+                items(rows.asReversed(), key = { it.key }) { row ->
                     when (row) {
                         is TranscriptRow.Tools ->
                             ToolGroup(
diff --git a/app/androidApp/src/main/kotlin/com/example/aiapp/ToolRows.kt b/app/androidApp/src/main/kotlin/com/example/aiapp/ToolRows.kt
index 66d3af6..d2c3570 100644
--- a/app/androidApp/src/main/kotlin/com/example/aiapp/ToolRows.kt
+++ b/app/androidApp/src/main/kotlin/com/example/aiapp/ToolRows.kt
@@ -32,26 +32,34 @@ import androidx.compose.ui.unit.dp
  */
 sealed class TranscriptRow {
     /**
-     * This row's identity in the list, taken from the first transcript event behind it.
+     * This row's identity in the list, which must survive everything that can happen to the row.
      *
-     * See [TranscriptItem.seq]: the list is keyed by this so that inserting a new message at one
-     * end, or a page of history at the other, moves the rows and not the reader.
+     * The list is keyed by this so that inserting a new message at one end, or a page of history at
+     * the other, moves the rows and not the reader. That makes it the load-bearing value on this
+     * screen: when a key changes, the list loses its anchor and the transcript steps under whoever
+     * is reading it.
+     *
+     * A tool row therefore keys on [TranscriptItem.ToolRun.runId] rather than on a sequence number,
+     * and it is the *same* value whether the run is drawn as one card or as a group. A lone call
+     * that gains a neighbour becomes a group without changing identity, which is the case a
+     * seq-based key got wrong: the row the reader was looking at was replaced rather than updated.
+     * Everything else keys on the seq of the event behind it, which never moves.
      */
-    abstract val seq: Long
+    abstract val key: Any
 
     data class Single(val item: TranscriptItem) : TranscriptRow() {
-        override val seq: Long
-            get() = item.seq
+        override val key: Any
+            get() = (item as? TranscriptItem.ToolRun)?.runId ?: item.seq
     }
 
     /** Two or more calls with nothing between them; drawn as one collapsed card. */
     data class Tools(val calls: List<TranscriptItem.ToolRun>) : TranscriptRow() {
-        /** Stable across reloads because it is the first call's own id. */
+        /** The run's own name, which every call in it already carries. */
         val id: String
-            get() = calls.first().id
+            get() = calls.first().runId
 
-        override val seq: Long
-            get() = calls.first().seq
+        override val key: Any
+            get() = id
     }
 }
 
@@ -75,10 +83,16 @@ fun groupToolRuns(items: List<TranscriptItem>): List<TranscriptRow> {
     }
 
     items.forEach { item ->
-        if (item is TranscriptItem.ToolRun) run += item
-        else {
+        // Grouped by the run each call says it belongs to, not by adjacency worked out here.
+        // Adjacency is the same answer most of the time and a worse one at the edges: a call
+        // arriving next to an existing run, or a page of history arriving in front of one, both
+        // change which call is *first*, and a group named after its first member is a different
+        // group every time that happens.
+        if (item is TranscriptItem.ToolRun && (run.isEmpty() || run.first().runId == item.runId)) {
+            run += item
+        } else {
             flush()
-            rows += TranscriptRow.Single(item)
+            if (item is TranscriptItem.ToolRun) run += item else rows += TranscriptRow.Single(item)
         }
     }
     flush()