diff --git a/core/domain/src/main/java/com/rtbishop/look4sat/core/domain/model/GridQso.kt b/core/domain/src/main/java/com/rtbishop/look4sat/core/domain/model/GridQso.kt
index cdd83275..4f5bc310 100644
--- a/core/domain/src/main/java/com/rtbishop/look4sat/core/domain/model/GridQso.kt
+++ b/core/domain/src/main/java/com/rtbishop/look4sat/core/domain/model/GridQso.kt
@@ -131,3 +131,13 @@ fun GridQso.stationGridSetKey(): String? =
  */
 fun List<GridQso>.scopedToStation(stationId: String?): List<GridQso> =
     if (stationId == null) this else filter { it.stationGridSetKey() == stationId }
+
+/**
+ * For every grid in the store, the callsign of the earliest QSO — scoped to the
+ * operated-grid selector's choice first, so a specific 台址 labels each worked
+ * cell with ITS first contact; null ("All") keeps the global first call.
+ */
+fun Map<String, List<GridQso>>.firstCallsByGrid(stationId: String?): Map<String, String> =
+    mapNotNull { (grid, qsos) ->
+        qsos.scopedToStation(stationId).minByOrNull { it.epochMs }?.let { grid to it.call }
+    }.toMap()
diff --git a/core/domain/src/test/java/com/rtbishop/look4sat/core/domain/model/GridQsoStationScopeTest.kt b/core/domain/src/test/java/com/rtbishop/look4sat/core/domain/model/GridQsoStationScopeTest.kt
index fe372938..433e1ec2 100644
--- a/core/domain/src/test/java/com/rtbishop/look4sat/core/domain/model/GridQsoStationScopeTest.kt
+++ b/core/domain/src/test/java/com/rtbishop/look4sat/core/domain/model/GridQsoStationScopeTest.kt
@@ -94,4 +94,35 @@ class GridQsoStationScopeTest {
         val list = listOf(qso("A", myGrid = "OL62"))
         assertEquals(emptyList<GridQso>(), list.scopedToStation("PM01"))
     }
+
+    // --- firstCallsByGrid ---
+
+    @Test
+    fun `first call per grid picks the earliest of the scoped records`() {
+        val store = mapOf(
+            "OL62" to listOf(
+                qso("OTHER", myGrid = "PM01").copy(epochMs = 10),
+                qso("MINE", myGrid = "OL62").copy(epochMs = 20)
+            ),
+            "PM95" to listOf(qso("MINE2", myGrid = "OL62").copy(epochMs = 30))
+        )
+        assertEquals(mapOf("OL62" to "MINE", "PM95" to "MINE2"), store.firstCallsByGrid("OL62"))
+    }
+
+    @Test
+    fun `first call per grid with All uses every record`() {
+        val store = mapOf(
+            "OL62" to listOf(
+                qso("OTHER", myGrid = "PM01").copy(epochMs = 10),
+                qso("MINE", myGrid = "OL62").copy(epochMs = 20)
+            )
+        )
+        assertEquals(mapOf("OL62" to "OTHER"), store.firstCallsByGrid(null))
+    }
+
+    @Test
+    fun `grids without scoped records get no first call`() {
+        val store = mapOf("OL62" to listOf(qso("A", myGrid = "PM01")))
+        assertEquals(emptyMap<String, String>(), store.firstCallsByGrid("OL62"))
+    }
 }
diff --git a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt
index 8ec681c7..5eac2468 100644
--- a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt
+++ b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt
@@ -85,6 +85,7 @@ import androidx.lifecycle.viewmodel.compose.viewModel
 import com.rtbishop.look4sat.core.domain.model.AwardCalculator
 import com.rtbishop.look4sat.core.domain.model.AwardProgress
 import com.rtbishop.look4sat.core.domain.model.AwardType
+import com.rtbishop.look4sat.core.domain.model.firstCallsByGrid
 import com.rtbishop.look4sat.core.domain.model.MapSource
 import com.rtbishop.look4sat.core.domain.model.myStationGrids
 import com.rtbishop.look4sat.core.domain.model.scopedToStation
@@ -306,13 +307,6 @@ private fun MapScreen(
     // Selected award filter. Lives in an Activity-scoped ViewModel so it
     // survives page switches; defaults to VUCC only once per process (cold start).
     var selectedAward by mapFilterViewModel.selectedAward
-    // First callsign worked in each grid (earliest QSO by time), used by the
-    // "首通呼号" label mode — derived from the same QSO store as the worked fills.
-    val firstCallsByGrid: Map<String, String> = remember(uiState.workedGridQsos) {
-        uiState.workedGridQsos.mapNotNull { (grid, qsos) ->
-            qsos.minByOrNull { it.epochMs }?.let { grid to it.call }
-        }.toMap()
-    }
     // 台址名单: QSOs grouped by the 台址's GRID SET. A station location (台址)
     // can span several grids (MY_GRIDSQUARE + MY_VUCC_GRIDS), and QSOs whose
     // location covers the same grid set belong to the same 台址; groups with an
@@ -353,6 +347,13 @@ private fun MapScreen(
         if (selectedStationId == null) uiState.workedGrids
         else stationGroups.firstOrNull { it.id == selectedStationId }?.worked ?: emptySet()
     }
+    // First callsign worked in each grid (earliest QSO by time), used by the
+    // "首通呼号" label mode. Scoped to the selected 台址 like the fills: with a
+    // specific operated grid chosen, the label must show ITS first contact, not
+    // another 台址's (user decision 2026-10-05); "All" = global first call.
+    val firstCallsByGrid: Map<String, String> = remember(uiState.workedGridQsos, selectedStationId) {
+        uiState.workedGridQsos.firstCallsByGrid(selectedStationId)
+    }
     val isGridMode = uiState.isGridMode
     // True when this composition restored a saved viewport. Only grid mode
     // restores the viewport the user left (satellite mode keeps its original