diff --git a/apps/edr-freight-web/backoffice/src/components/fleet/FleetFormDialog.tsx b/apps/edr-freight-web/backoffice/src/components/fleet/FleetFormDialog.tsx
index 7262e7927..dfb27ed36 100644
--- a/apps/edr-freight-web/backoffice/src/components/fleet/FleetFormDialog.tsx
+++ b/apps/edr-freight-web/backoffice/src/components/fleet/FleetFormDialog.tsx
@@ -271,8 +271,14 @@ const FleetFormDialog = ({
       return;
     }
     if (!validate()) return;
+    // Derived fields are never edited, so form state for them can be stale (or
+    // seeded from the record) — recompute before building the payload.
+    const submitted: Record<string, unknown> = { ...values };
+    fields.forEach((field) => {
+      if (field.derivedValue) submitted[field.name] = field.derivedValue(values);
+    });
     const payload = Object.fromEntries(
-      Object.entries(values)
+      Object.entries(submitted)
         .map(([key, value]) => {
           if (value === FLEET_SELECT_NONE || value === "")
             return [key, undefined];
@@ -294,6 +300,23 @@ const FleetFormDialog = ({
     // only by verification and never hand-edited.
     const isDisabled = Boolean(field.disabled || field.faydaLocked);
 
+    // Computed from other fields (e.g. the import run implied by the export
+    // run) — read-only, and recomputed here rather than read from form state.
+    if (field.derivedValue) {
+      return (
+        <TextInput
+          key={field.name}
+          label={field.label}
+          description={field.description}
+          placeholder={field.placeholder}
+          value={field.derivedValue(values)}
+          readOnly
+          variant="filled"
+          error={error}
+        />
+      );
+    }
+
     if (field.type === "radio") {
       return (
         <Radio.Group
@@ -319,6 +342,8 @@ const FleetFormDialog = ({
         <Select
           key={field.name}
           label={field.label}
+          description={field.description}
+          placeholder={field.placeholder}
           data={field.options ?? []}
           value={
             value == null || value === ""
diff --git a/apps/edr-freight-web/backoffice/src/pages/fleet/config/resources.ts b/apps/edr-freight-web/backoffice/src/pages/fleet/config/resources.ts
index b5bc5d415..baeaa99a5 100644
--- a/apps/edr-freight-web/backoffice/src/pages/fleet/config/resources.ts
+++ b/apps/edr-freight-web/backoffice/src/pages/fleet/config/resources.ts
@@ -40,6 +40,13 @@ export interface FleetResourceColumn {
 export interface FleetFormFieldDef extends FormFieldDef {
   dynamicOptions?: FleetDynamicOptions;
   noneOption?: boolean;
+  /**
+   * Read-only field whose value is computed from the other fields rather than
+   * typed. Rendered non-editable and recomputed on every change, so the stored
+   * form value for this field is never trusted — the function is the source of
+   * truth at both render and submit.
+   */
+  derivedValue?: (values: Record<string, unknown>) => string;
   /**
    * Field is owned by the Fayda identity — populated only by verification and
    * never hand-edited. Rendered disabled in the form.
@@ -116,6 +123,32 @@ const WAGON_STATUS_OPTIONS = [
   { label: "Detained", value: Freight.WagonStatus.Detained },
 ];
 
+/**
+ * EDR run-number pairs, keyed by the odd EXPORT run (Ethiopia → Djibouti). The
+ * even IMPORT run (Djibouti → Ethiopia) is fixed by the export run, so choosing
+ * an export number fully determines the import one. Listed explicitly rather
+ * than computed as export+1, so a pair that ever breaks that convention stays
+ * correct here.
+ */
+const TRAIN_RUN_PAIRS: Record<string, string> = {
+  "8001": "8002",
+  "81001": "81002",
+  "82001": "82002",
+  "83001": "83002",
+  "84001": "84002",
+  "85001": "85002",
+  "86001": "86002",
+  "87001": "87002",
+  "88001": "88002",
+  "8901": "8902",
+  "9001": "9002",
+};
+
+const EXPORT_TRAIN_OPTIONS = Object.keys(TRAIN_RUN_PAIRS).map((run) => ({
+  label: run,
+  value: run,
+}));
+
 
 
 export const FLEET_RESOURCES: FleetResourceConfig[] = [
@@ -272,13 +305,15 @@ export const FLEET_RESOURCES: FleetResourceConfig[] = [
     ],
     formFields: [
       // Run numbers are optional — a wagon sits in the fleet unassigned to any
-      // run until an operator fills these in.
+      // run until an operator picks an export run. The import run is fixed by
+      // that choice, so it is derived rather than typed.
       {
         name: "exportTrainNumber",
         label: "Export train number",
-        type: "text",
+        type: "select",
         description: "Odd — Ethiopia → Djibouti runs",
         placeholder: "e.g. 8001",
+        options: EXPORT_TRAIN_OPTIONS,
       },
       {
         name: "importTrainNumber",
@@ -286,6 +321,8 @@ export const FLEET_RESOURCES: FleetResourceConfig[] = [
         type: "text",
         description: "Even — Djibouti → Ethiopia runs",
         placeholder: "e.g. 8002",
+        derivedValue: (values) =>
+          TRAIN_RUN_PAIRS[String(values.exportTrainNumber ?? "")] ?? "",
       },
       { name: "wagonNumber", label: "Wagon number", type: "text", required: true },
       { name: "wagonTypeId", label: "Wagon type", type: "select", required: true, dynamicOptions: "wagonTypes" },