feat(train-scheduling): load returned empties onto an export train

Empties had no way onto a departure: the return record could name a train but nothing seated it on a wagon. Export schedules now expose a loading action that packs selected returns onto free wagons at one 40ft or two 20ft each, enforced both in the picker and in the API (existing empties on the schedule count against their wagon). Adds container_size, train_schedule_id and wagon_sequence_no to freight.empty_container_returns.
2026-08-26 18:42:49 +00:00 · 2026-08-14 09:57:20 +00:00
parent 30c3567048
commit b4f2ec1c75
15 changed files with 630 additions and 2 deletions
--- a/apps/edr-freight-api/src/migrations/3540000000000-EmptyReturnTrainLoad.ts
+++ b/apps/edr-freight-api/src/migrations/3540000000000-EmptyReturnTrainLoad.ts
@@ -0,0 +1,35 @@
+import { MigrationInterface, QueryRunner } from "typeorm";
+
+/**
+ * Empty containers ride an export departure back to Djibouti, so a return now
+ * records which train schedule carries it and on which wagon slot. Size is
+ * captured too: the wagon rule is one 40ft OR two 20ft per wagon, which cannot
+ * be enforced without knowing the box size.
+ */
+export class EmptyReturnTrainLoad3540000000000 implements MigrationInterface {
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      ALTER TABLE freight.empty_container_returns
+        ADD COLUMN IF NOT EXISTS container_size character varying(10),
+        ADD COLUMN IF NOT EXISTS train_schedule_id uuid,
+        ADD COLUMN IF NOT EXISTS wagon_sequence_no integer
+    `);
+    await queryRunner.query(`
+      CREATE INDEX IF NOT EXISTS idx_empty_container_returns_train_schedule_id
+        ON freight.empty_container_returns (train_schedule_id)
+        WHERE train_schedule_id IS NOT NULL
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      DROP INDEX IF EXISTS freight.idx_empty_container_returns_train_schedule_id
+    `);
+    await queryRunner.query(`
+      ALTER TABLE freight.empty_container_returns
+        DROP COLUMN IF EXISTS container_size,
+        DROP COLUMN IF EXISTS train_schedule_id,
+        DROP COLUMN IF EXISTS wagon_sequence_no
+    `);
+  }
+}
--- a/apps/edr-freight-api/src/modules/import-operations/dto/import-operations.dto.ts
+++ b/apps/edr-freight-api/src/modules/import-operations/dto/import-operations.dto.ts
@@ -1,5 +1,17 @@
 import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
-import { IsArray, IsDateString, IsIn, IsOptional, IsString, IsUUID } from 'class-validator';
+import { Type } from 'class-transformer';
+import {
+  ArrayNotEmpty,
+  IsArray,
+  IsDateString,
+  IsIn,
+  IsInt,
+  IsOptional,
+  IsString,
+  IsUUID,
+  Min,
+  ValidateNested,
+} from 'class-validator';

 import { DJIBOUTI_INCIDENT_TYPES, type DjiboutiIncidentType } from '../entities/djibouti-incident.entity';
 import {
@@ -120,6 +132,9 @@ export class ImportOperationActionDto {
  notes?: string;
 }

+export const EMPTY_CONTAINER_SIZES = ['20', '40'] as const;
+export type EmptyContainerSize = (typeof EMPTY_CONTAINER_SIZES)[number];
+
 export class CreateEmptyContainerReturnDto {
  @ApiProperty()
  @IsString()
@@ -140,6 +155,11 @@ export class CreateEmptyContainerReturnDto {
  @IsDateString()
  returnDate?: string;

+  @ApiPropertyOptional({ enum: EMPTY_CONTAINER_SIZES })
+  @IsOptional()
+  @IsIn(EMPTY_CONTAINER_SIZES)
+  containerSize?: EmptyContainerSize;
+
  @ApiPropertyOptional()
  @IsOptional()
  @IsString()
@@ -176,6 +196,39 @@ export class CreateEmptyContainerReturnDto {
  returnedBy?: 'EDR' | 'CUSTOMER';
 }

+export class LoadEmptyContainerItemDto {
+  @ApiProperty({ format: 'uuid' })
+  @IsUUID()
+  id!: string;
+
+  @ApiProperty({ enum: EMPTY_CONTAINER_SIZES })
+  @IsIn(EMPTY_CONTAINER_SIZES)
+  containerSize!: EmptyContainerSize;
+
+  @ApiProperty()
+  @IsInt()
+  @Min(1)
+  wagonSequenceNo!: number;
+}
+
+export class LoadEmptyContainersOnTrainDto extends ImportOperationActionDto {
+  @ApiProperty({ format: 'uuid' })
+  @IsUUID()
+  trainScheduleId!: string;
+
+  @ApiPropertyOptional({ description: 'Run number shown on the return record.' })
+  @IsOptional()
+  @IsString()
+  trainNumber?: string;
+
+  @ApiProperty({ type: [LoadEmptyContainerItemDto] })
+  @IsArray()
+  @ArrayNotEmpty()
+  @ValidateNested({ each: true })
+  @Type(() => LoadEmptyContainerItemDto)
+  items!: LoadEmptyContainerItemDto[];
+}
+
 export class UpdateEmptyContainerReturnStatusDto extends ImportOperationActionDto {
  @ApiProperty({ enum: EMPTY_CONTAINER_RETURN_STATUSES })
  @IsIn(EMPTY_CONTAINER_RETURN_STATUSES)
--- a/apps/edr-freight-api/src/modules/import-operations/empty-container-wagon.util.spec.ts
+++ b/apps/edr-freight-api/src/modules/import-operations/empty-container-wagon.util.spec.ts
@@ -0,0 +1,23 @@
+import { assertWagonLoad } from './empty-container-wagon.util';
+
+describe('assertWagonLoad', () => {
+  it('accepts one 40ft or two 20ft per wagon', () => {
+    expect(() =>
+      assertWagonLoad(
+        new Map([
+          [1, ['40']],
+          [2, ['20', '20']],
+          [3, ['20']],
+        ]),
+      ),
+    ).not.toThrow();
+  });
+
+  it('rejects a 40ft sharing a wagon', () => {
+    expect(() => assertWagonLoad(new Map([[4, ['40', '20']]]))).toThrow(/Wagon 4/);
+  });
+
+  it('rejects three containers on a wagon', () => {
+    expect(() => assertWagonLoad(new Map([[5, ['20', '20', '20']]]))).toThrow(/Wagon 5/);
+  });
+});
--- a/apps/edr-freight-api/src/modules/import-operations/empty-container-wagon.util.ts
+++ b/apps/edr-freight-api/src/modules/import-operations/empty-container-wagon.util.ts
@@ -0,0 +1,16 @@
+import { BadRequestException } from '@nestjs/common';
+
+/**
+ * A wagon carries ONE 40ft OR TWO 20ft empties — never a mix, never three.
+ * Throws on the first wagon that breaks the rule.
+ */
+export function assertWagonLoad(sizesByWagon: Map<number, string[]>): void {
+  for (const [wagon, sizes] of sizesByWagon) {
+    const has40 = sizes.some((size) => size === '40');
+    if ((has40 && sizes.length > 1) || sizes.length > 2) {
+      throw new BadRequestException(
+        `Wagon ${wagon} takes one 40ft or two 20ft containers — got ${sizes.join('ft + ')}ft`,
+      );
+    }
+  }
+}
--- a/apps/edr-freight-api/src/modules/import-operations/entities/empty-container-return.entity.ts
+++ b/apps/edr-freight-api/src/modules/import-operations/entities/empty-container-return.entity.ts
@@ -51,6 +51,17 @@ export class EmptyContainerReturn extends BaseEntity {
  @Column({ name: 'wagon_allocation_reference', type: 'varchar', length: 120, nullable: true })
  wagonAllocationReference?: string | null;

+  /** '20' or '40' — drives the one-40ft-or-two-20ft-per-wagon loading rule. */
+  @Column({ name: 'container_size', type: 'varchar', length: 10, nullable: true })
+  containerSize?: string | null;
+
+  /** Export departure carrying this empty back to Djibouti. */
+  @Column({ name: 'train_schedule_id', type: 'uuid', nullable: true })
+  trainScheduleId?: string | null;
+
+  @Column({ name: 'wagon_sequence_no', type: 'int', nullable: true })
+  wagonSequenceNo?: number | null;
+
  @Column({ name: 'performed_by', type: 'varchar', length: 120, nullable: true })
  performedBy?: string | null;

--- a/apps/edr-freight-api/src/modules/import-operations/import-operations.controller.ts
+++ b/apps/edr-freight-api/src/modules/import-operations/import-operations.controller.ts
@@ -8,6 +8,7 @@ import {
  CreateDjiboutiIncidentDto,
  CreateEmptyContainerReturnDto,
  ImportOperationActionDto,
+  LoadEmptyContainersOnTrainDto,
  RecordDeclarationDto,
  UpdateEmptyContainerReturnStatusDto,
  UploadImportCustomsDocumentDto,
@@ -104,6 +105,14 @@ export class ImportOperationsController {
    return this.service.createEmptyReturn(dto);
  }

+  @Post('empty-container-returns/load-on-train')
+  @ApiOperation({
+    summary: 'Load returned empties onto an export train (1×40ft or 2×20ft per wagon)',
+  })
+  loadEmptyReturnsOnTrain(@Body() dto: LoadEmptyContainersOnTrainDto) {
+    return this.service.loadEmptyReturnsOnTrain(dto);
+  }
+
  @Post('empty-container-returns/:id/status')
  @ApiOperation({ summary: 'Batch 16: advance empty container return workflow' })
  updateEmptyReturnStatus(
--- a/apps/edr-freight-api/src/modules/import-operations/import-operations.service.ts
+++ b/apps/edr-freight-api/src/modules/import-operations/import-operations.service.ts
@@ -1,11 +1,12 @@
 import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
-import { Repository } from 'typeorm';
+import { In, Repository } from 'typeorm';

 import {
  CreateDjiboutiIncidentDto,
  CreateEmptyContainerReturnDto,
  ImportOperationActionDto,
+  LoadEmptyContainersOnTrainDto,
  RecordDeclarationDto,
  AssignCustomsRiskDto,
  UpdateEmptyContainerReturnStatusDto,
@@ -15,6 +16,7 @@ import {
  DjiboutiIncident,
  type DjiboutiIncidentType,
 } from './entities/djibouti-incident.entity';
+import { assertWagonLoad } from './empty-container-wagon.util';
 import { EmptyContainerReturn } from './entities/empty-container-return.entity';
 import {
  ImportCustomsFinalization,
@@ -156,6 +158,7 @@ export class ImportOperationsService {
        bookingId: dto.bookingId ?? null,
        customerId: dto.customerId ?? null,
        returnDate,
+        containerSize: dto.containerSize ?? null,
        facility: dto.facility ?? null,
        yard: dto.yard ?? null,
        zone: dto.zone ?? null,
@@ -170,6 +173,63 @@ export class ImportOperationsService {
    );
  }

+  /**
+   * Load returned empties onto an export departure. A wagon takes ONE 40ft or
+   * TWO 20ft — never a mix, never three. Empties already sitting on a wagon of
+   * the same schedule count against that wagon, so incremental loads cannot
+   * quietly double-book a slot.
+   *
+   * ponytail: does not check the wagon is free of cargo bookings — the loading
+   * UI picks only unallocated wagons from the schedule's plan. Cross-check here
+   * if empties ever get loaded from another client.
+   */
+  async loadEmptyReturnsOnTrain(dto: LoadEmptyContainersOnTrainDto) {
+    const ids = dto.items.map((item) => item.id);
+    const rows = await this.emptyReturns.find({ where: { id: In(ids) } });
+    const missing = ids.filter((id) => !rows.some((row) => row.id === id));
+    if (missing.length) {
+      throw new NotFoundException(`Empty container return(s) not found: ${missing.join(', ')}`);
+    }
+
+    const alreadyOnTrain = await this.emptyReturns.find({
+      where: { trainScheduleId: dto.trainScheduleId },
+    });
+    const byWagon = new Map<number, string[]>();
+    for (const row of alreadyOnTrain) {
+      if (row.wagonSequenceNo == null || ids.includes(row.id)) continue;
+      byWagon.set(row.wagonSequenceNo, [
+        ...(byWagon.get(row.wagonSequenceNo) ?? []),
+        row.containerSize ?? '40',
+      ]);
+    }
+    for (const item of dto.items) {
+      byWagon.set(item.wagonSequenceNo, [
+        ...(byWagon.get(item.wagonSequenceNo) ?? []),
+        item.containerSize,
+      ]);
+    }
+    assertWagonLoad(byWagon);
+
+    const changedAt = new Date().toISOString();
+    for (const item of dto.items) {
+      const row = rows.find((candidate) => candidate.id === item.id)!;
+      await this.emptyReturns.update(item.id, {
+        status: 'WAGON_ALLOCATED',
+        containerSize: item.containerSize,
+        trainScheduleId: dto.trainScheduleId,
+        wagonSequenceNo: item.wagonSequenceNo,
+        wagonAllocationReference: dto.trainNumber ?? dto.trainScheduleId,
+        performedBy: dto.performedBy ?? row.performedBy ?? null,
+        statusHistory: [
+          ...(row.statusHistory ?? []),
+          { status: 'WAGON_ALLOCATED' as const, changedAt, performedBy: dto.performedBy ?? null },
+        ],
+      });
+    }
+
+    return this.emptyReturns.find({ where: { trainScheduleId: dto.trainScheduleId } });
+  }
+
  async updateEmptyReturnStatus(id: string, dto: UpdateEmptyContainerReturnStatusDto) {
    const row = await this.emptyReturns.findOne({ where: { id } });
    if (!row) {
--- a/apps/edr-freight-web/backoffice/src/components/trainScheduling/LoadEmptyContainersModal.tsx
+++ b/apps/edr-freight-web/backoffice/src/components/trainScheduling/LoadEmptyContainersModal.tsx
@@ -0,0 +1,249 @@
+import { useMemo, useState } from "react";
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import {
+  Alert,
+  Badge,
+  Button,
+  Checkbox,
+  Group,
+  Loader,
+  Modal,
+  SegmentedControl,
+  Stack,
+  Table,
+  Text,
+} from "@mantine/core";
+
+import { useToast } from "@/hooks/use-toast";
+import { importOperationsService } from "@/services/importOperations.service";
+import type {
+  EmptyContainerReturn,
+  EmptyContainerSize,
+} from "@/types/importOperations";
+import type { TrainScheduleDetail } from "@/types/trainScheduling";
+import { packEmptiesOntoWagons, wagonsNeeded } from "./emptyContainerLoad.util";
+
+/** Empties still on the ground — past these the box has already left the yard. */
+const LOADABLE_STATUSES = ["RETURNED", "ASSIGNED_STORAGE", "DOCUMENTATION_CLEARED"];
+
+interface LoadEmptyContainersModalProps {
+  opened: boolean;
+  onClose: () => void;
+  schedule: TrainScheduleDetail;
+}
+
+/**
+ * Loads returned empty containers onto an export departure. Wagons are filled
+ * one 40ft OR two 20ft each (see `packEmptiesOntoWagons`), drawing only on
+ * wagons of this train that carry no cargo booking and no empty already.
+ */
+export function LoadEmptyContainersModal({
+  opened,
+  onClose,
+  schedule,
+}: LoadEmptyContainersModalProps) {
+  const { toast } = useToast();
+  const qc = useQueryClient();
+  const [selected, setSelected] = useState<string[]>([]);
+  const [sizeOverrides, setSizeOverrides] = useState<Record<string, EmptyContainerSize>>({});
+
+  const returnsQuery = useQuery({
+    queryKey: ["empty-container-returns"],
+    queryFn: () => importOperationsService.listEmptyReturns(),
+    enabled: opened,
+  });
+
+  const returns = returnsQuery.data ?? [];
+  const loaded = useMemo(
+    () => returns.filter((ret) => ret.trainScheduleId === schedule.id),
+    [returns, schedule.id],
+  );
+  const available = useMemo(
+    () =>
+      returns.filter(
+        (ret) => !ret.trainScheduleId && LOADABLE_STATUSES.includes(ret.status),
+      ),
+    [returns],
+  );
+
+  const sizeOf = (ret: EmptyContainerReturn): EmptyContainerSize =>
+    sizeOverrides[ret.id] ?? (ret.containerSize === "20" ? "20" : "40");
+
+  // A wagon is up for grabs when no booking rides it and no empty sits on it.
+  const freeWagons = useMemo(() => {
+    const takenByEmpties = new Set(
+      loaded.map((ret) => ret.wagonSequenceNo).filter((no): no is number => no != null),
+    );
+    return (schedule.trainSet?.wagons ?? [])
+      .filter((wagon) => !wagon.allocations?.length && !takenByEmpties.has(wagon.sequenceNo))
+      .map((wagon) => wagon.sequenceNo)
+      .sort((a, b) => a - b);
+  }, [schedule.trainSet?.wagons, loaded]);
+
+  const picks = useMemo(
+    () =>
+      available
+        .filter((ret) => selected.includes(ret.id))
+        .map((ret) => ({ id: ret.id, containerSize: sizeOf(ret) })),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    [available, selected, sizeOverrides],
+  );
+  const needed = wagonsNeeded(picks);
+  const { assignments, unplaced } = packEmptiesOntoWagons(picks, freeWagons);
+
+  const load = useMutation({
+    mutationFn: () =>
+      importOperationsService.loadEmptyContainersOnTrain({
+        trainScheduleId: schedule.id,
+        trainNumber: schedule.trainNumber ?? undefined,
+        items: assignments,
+      }),
+    onSuccess: () => {
+      toast({ title: `${assignments.length} empty container(s) loaded` });
+      qc.invalidateQueries({ queryKey: ["empty-container-returns"] });
+      qc.invalidateQueries({ queryKey: ["train-scheduling"] });
+      setSelected([]);
+      onClose();
+    },
+    onError: (error: any) => {
+      toast({
+        variant: "destructive",
+        title: "Failed to load empty containers",
+        description: error?.response?.data?.message || error?.message,
+      });
+    },
+  });
+
+  return (
+    <Modal
+      opened={opened}
+      onClose={onClose}
+      title="Load Empty Containers"
+      size="xl"
+    >
+      <Stack gap="md">
+        <Text size="sm" c="dimmed">
+          One 40ft or two 20ft containers per wagon. {freeWagons.length} free wagon
+          {freeWagons.length === 1 ? "" : "s"} on this train.
+        </Text>
+
+        {loaded.length > 0 ? (
+          <Alert color="gray" title={`${loaded.length} empty container(s) already loaded`}>
+            <Group gap="xs">
+              {loaded.map((ret) => (
+                <Badge key={ret.id} size="sm" variant="light">
+                  {ret.containerNumber} · wagon {ret.wagonSequenceNo ?? "—"}
+                </Badge>
+              ))}
+            </Group>
+          </Alert>
+        ) : null}
+
+        {returnsQuery.isLoading ? (
+          <Group justify="center" py="md">
+            <Loader size="sm" />
+          </Group>
+        ) : available.length === 0 ? (
+          <Alert color="gray">
+            No returned empty containers are waiting — record returns in Container Returns.
+          </Alert>
+        ) : (
+          <Table.ScrollContainer minWidth={700}>
+            <Table highlightOnHover>
+              <Table.Thead>
+                <Table.Tr>
+                  <Table.Th w={40} />
+                  <Table.Th>Container</Table.Th>
+                  <Table.Th>Size</Table.Th>
+                  <Table.Th>Facility</Table.Th>
+                  <Table.Th>Returned</Table.Th>
+                  <Table.Th>Status</Table.Th>
+                </Table.Tr>
+              </Table.Thead>
+              <Table.Tbody>
+                {available.map((ret) => {
+                  const checked = selected.includes(ret.id);
+                  return (
+                    <Table.Tr key={ret.id}>
+                      <Table.Td>
+                        <Checkbox
+                          checked={checked}
+                          onChange={(event) =>
+                            setSelected(
+                              event.currentTarget.checked
+                                ? [...selected, ret.id]
+                                : selected.filter((id) => id !== ret.id),
+                            )
+                          }
+                        />
+                      </Table.Td>
+                      <Table.Td>
+                        <Text fw={600} size="sm">
+                          {ret.containerNumber}
+                        </Text>
+                      </Table.Td>
+                      <Table.Td>
+                        {/* Legacy returns carry no size — the operator sets it here
+                            because the wagon rule cannot be applied without it. */}
+                        <SegmentedControl
+                          size="xs"
+                          value={sizeOf(ret)}
+                          onChange={(value) =>
+                            setSizeOverrides({
+                              ...sizeOverrides,
+                              [ret.id]: value as EmptyContainerSize,
+                            })
+                          }
+                          data={[
+                            { label: "20ft", value: "20" },
+                            { label: "40ft", value: "40" },
+                          ]}
+                        />
+                      </Table.Td>
+                      <Table.Td>{ret.facility ?? "—"}</Table.Td>
+                      <Table.Td>
+                        {ret.returnDate ? new Date(ret.returnDate).toLocaleDateString() : "—"}
+                      </Table.Td>
+                      <Table.Td>
+                        <Badge size="sm" variant="light">
+                          {ret.status}
+                        </Badge>
+                      </Table.Td>
+                    </Table.Tr>
+                  );
+                })}
+              </Table.Tbody>
+            </Table>
+          </Table.ScrollContainer>
+        )}
+
+        {unplaced.length > 0 ? (
+          <Alert color="red">
+            {needed} wagon(s) needed but only {freeWagons.length} free — unselect{" "}
+            {unplaced.length} container(s) or add wagons to the consist.
+          </Alert>
+        ) : picks.length > 0 ? (
+          <Text size="sm">
+            {picks.length} container(s) → wagons{" "}
+            {[...new Set(assignments.map((a) => a.wagonSequenceNo))].join(", ")}
+          </Text>
+        ) : null}
+
+        <Group justify="flex-end" gap="sm">
+          <Button variant="default" onClick={onClose} disabled={load.isPending}>
+            Cancel
+          </Button>
+          <Button
+            disabled={!picks.length || unplaced.length > 0}
+            loading={load.isPending}
+            onClick={() => load.mutate()}
+          >
+            Load {picks.length || ""} on train
+          </Button>
+        </Group>
+      </Stack>
+    </Modal>
+  );
+}
+
+export default LoadEmptyContainersModal;
--- a/apps/edr-freight-web/backoffice/src/components/trainScheduling/emptyContainerLoad.util.spec.ts
+++ b/apps/edr-freight-web/backoffice/src/components/trainScheduling/emptyContainerLoad.util.spec.ts
@@ -0,0 +1,60 @@
+import { describe, it, expect } from 'vitest';
+import { packEmptiesOntoWagons, wagonsNeeded, type EmptyLoadPick } from './emptyContainerLoad.util';
+
+const pick = (id: string, containerSize: '20' | '40'): EmptyLoadPick => ({ id, containerSize });
+
+describe('emptyContainerLoad.util', () => {
+  it('gives each 40ft its own wagon', () => {
+    const { assignments, unplaced } = packEmptiesOntoWagons(
+      [pick('a', '40'), pick('b', '40')],
+      [1, 2, 3],
+    );
+    expect(unplaced).toEqual([]);
+    expect(assignments.map((a) => a.wagonSequenceNo)).toEqual([1, 2]);
+  });
+
+  it('pairs 20ft two to a wagon, last odd one alone', () => {
+    const { assignments } = packEmptiesOntoWagons(
+      [pick('a', '20'), pick('b', '20'), pick('c', '20')],
+      [4, 5],
+    );
+    expect(assignments.map((a) => [a.id, a.wagonSequenceNo])).toEqual([
+      ['a', 4],
+      ['b', 4],
+      ['c', 5],
+    ]);
+  });
+
+  it('never mixes a 40ft and a 20ft on one wagon', () => {
+    const { assignments } = packEmptiesOntoWagons(
+      [pick('a', '20'), pick('b', '40'), pick('c', '20')],
+      [1, 2],
+    );
+    const bySizeOnWagon = new Map<number, string[]>();
+    for (const a of assignments) {
+      bySizeOnWagon.set(a.wagonSequenceNo, [
+        ...(bySizeOnWagon.get(a.wagonSequenceNo) ?? []),
+        a.containerSize,
+      ]);
+    }
+    for (const sizes of bySizeOnWagon.values()) {
+      expect(sizes.includes('40') ? sizes.length : 0).toBeLessThan(2);
+      expect(sizes.length).toBeLessThanOrEqual(2);
+    }
+  });
+
+  it('reports picks that ran out of wagons instead of dropping them', () => {
+    const { assignments, unplaced } = packEmptiesOntoWagons(
+      [pick('a', '40'), pick('b', '40'), pick('c', '20'), pick('d', '20')],
+      [7],
+    );
+    expect(assignments).toHaveLength(1);
+    expect(unplaced.map((p) => p.id)).toEqual(['b', 'c', 'd']);
+  });
+
+  it('counts wagons needed', () => {
+    expect(wagonsNeeded([])).toBe(0);
+    expect(wagonsNeeded([pick('a', '40'), pick('b', '20'), pick('c', '20')])).toBe(2);
+    expect(wagonsNeeded([pick('a', '20')])).toBe(1);
+  });
+});
--- a/apps/edr-freight-web/backoffice/src/components/trainScheduling/emptyContainerLoad.util.ts
+++ b/apps/edr-freight-web/backoffice/src/components/trainScheduling/emptyContainerLoad.util.ts
@@ -0,0 +1,54 @@
+import type { EmptyContainerSize } from "@/types/importOperations";
+
+export interface EmptyLoadPick {
+  id: string;
+  containerSize: EmptyContainerSize;
+}
+
+export interface EmptyLoadAssignment extends EmptyLoadPick {
+  wagonSequenceNo: number;
+}
+
+/**
+ * Fill wagons with the picked empties: a wagon takes ONE 40ft or TWO 20ft,
+ * never a mix. 40ft boxes are seated first so a half-filled 20ft wagon can
+ * never block them, and the 20s pair up behind them.
+ *
+ * `freeWagons` is the caller's ordered list of wagon sequence numbers with no
+ * cargo allocation. Returns the assignments that fit plus the picks that had
+ * no wagon left — the caller surfaces the shortfall instead of silently
+ * dropping boxes.
+ */
+export function packEmptiesOntoWagons(
+  picks: EmptyLoadPick[],
+  freeWagons: number[],
+): { assignments: EmptyLoadAssignment[]; unplaced: EmptyLoadPick[] } {
+  const forty = picks.filter((pick) => pick.containerSize === "40");
+  const twenty = picks.filter((pick) => pick.containerSize === "20");
+
+  const assignments: EmptyLoadAssignment[] = [];
+  const unplaced: EmptyLoadPick[] = [];
+  const wagons = [...freeWagons];
+
+  for (const pick of forty) {
+    const wagon = wagons.shift();
+    if (wagon == null) unplaced.push(pick);
+    else assignments.push({ ...pick, wagonSequenceNo: wagon });
+  }
+
+  for (let index = 0; index < twenty.length; index += 2) {
+    const pair = twenty.slice(index, index + 2);
+    const wagon = wagons.shift();
+    if (wagon == null) unplaced.push(...pair);
+    else assignments.push(...pair.map((pick) => ({ ...pick, wagonSequenceNo: wagon })));
+  }
+
+  return { assignments, unplaced };
+}
+
+/** Wagons the picks consume, whether or not enough are free. */
+export function wagonsNeeded(picks: EmptyLoadPick[]): number {
+  const forty = picks.filter((pick) => pick.containerSize === "40").length;
+  const twenty = picks.length - forty;
+  return forty + Math.ceil(twenty / 2);
+}
--- a/apps/edr-freight-web/backoffice/src/constants/URLS.ts
+++ b/apps/edr-freight-web/backoffice/src/constants/URLS.ts
@@ -733,6 +733,8 @@ export const URL_CONSTANTS = {
    EMPTY_CONTAINER_RETURNS: "/import-operations/empty-container-returns",
    EMPTY_CONTAINER_RETURN_STATUS: (id: string) =>
      `/import-operations/empty-container-returns/${id}/status`,
+    EMPTY_CONTAINER_RETURNS_LOAD_ON_TRAIN:
+      "/import-operations/empty-container-returns/load-on-train",
  },

  VEHICLES: {
--- a/apps/edr-freight-web/backoffice/src/pages/trainScheduling/TrainScheduleV2DetailPage.tsx
+++ b/apps/edr-freight-web/backoffice/src/pages/trainScheduling/TrainScheduleV2DetailPage.tsx
@@ -57,6 +57,7 @@ import { ContainerPlacementGrid } from "@/components/trainScheduling/ContainerPl
 import { FleetAvailabilitySummary } from "@/components/trainScheduling/FleetAvailabilitySummary";
 import { IntercityRideAlongPanel } from "@/components/trainScheduling/IntercityRideAlongPanel";
 import { LegCapacityPanel } from "@/components/trainScheduling/LegCapacityPanel";
+import { LoadEmptyContainersModal } from "@/components/trainScheduling/LoadEmptyContainersModal";
 import MergeScheduleTrainModal from "@/components/trainScheduling/MergeScheduleTrainModal";
 import ScheduleHistoryPanel from "@/components/trainScheduling/ScheduleHistoryPanel";
 // import { ImportLoadingConfirmationPanel } from "@/components/trainScheduling/ImportLoadingConfirmationPanel";
@@ -126,6 +127,7 @@ export default function TrainScheduleV2DetailPage() {
  const [dispatchConfirmOpen, setDispatchConfirmOpen] = useState(false);
  const [switchTarget, setSwitchTarget] = useState<EligibleContainerBooking | null>(null);
  const [visualization3DOpen, setVisualization3DOpen] = useState(false);
+  const [loadEmptiesOpen, setLoadEmptiesOpen] = useState(false);
  const autoPreviewedRef = useRef(false);

  const detailQuery = useQuery(
@@ -967,6 +969,20 @@ export default function TrainScheduleV2DetailPage() {
                Merge
              </Button>
            ) : null}
+            {/* Empties ride an export departure back to Djibouti — offered only
+                while the train can still take load. */}
+            {schedule.direction === "EXPORT" &&
+            ["DRAFT", "SCHEDULED"].includes(schedule.status) ? (
+              <Button
+                variant="light"
+                color="edr-green"
+                size="compact-sm"
+                leftSection={<ContainerIcon size={14} />}
+                onClick={() => setLoadEmptiesOpen(true)}
+              >
+                Load Empty Container
+              </Button>
+            ) : null}
            {(schedule.trainSet?.wagons?.length ?? 0) > 0 ? (
              <Button
                variant="gradient"
@@ -1365,6 +1381,12 @@ export default function TrainScheduleV2DetailPage() {
        onSaved={() => void detailQuery.refetch()}
      />

+      <LoadEmptyContainersModal
+        opened={loadEmptiesOpen}
+        onClose={() => setLoadEmptiesOpen(false)}
+        schedule={schedule}
+      />
+
      <MergeScheduleTrainModal
        scheduleId={scheduleId ?? null}
        currentTrainId={schedule.trainSet?.trainId ?? null}
--- a/apps/edr-freight-web/backoffice/src/pages/warehouses/ContainerReturnsPage.tsx
+++ b/apps/edr-freight-web/backoffice/src/pages/warehouses/ContainerReturnsPage.tsx
@@ -36,6 +36,7 @@ import { importOperationsService } from "@/services/importOperations.service";
 import type {
  EmptyContainerReturn,
  EmptyContainerReturnStatus,
+  EmptyContainerSize,
 } from "@/types/importOperations";
 import type { TrainScheduleListItem } from "@/types/trainScheduling";
 import { formatDateTime } from "@/lib/format";
@@ -267,6 +268,7 @@ export default function ContainerReturnsPage() {
        returnType: "EDR" | "CUSTOMER";
        containers: Array<{
          containerNumber: string;
+          containerSize?: EmptyContainerSize;
          returnDate: string;
          warehouse: string;
          condition?: string;
@@ -279,6 +281,7 @@ export default function ContainerReturnsPage() {
        for (const container of truck.containers) {
          const result = await importOperationsService.createEmptyReturn({
            containerNumber: container.containerNumber,
+            containerSize: container.containerSize,
            returnDate: new Date(container.returnDate).toISOString(),
            bookingId: truck.bookingId,
            customerId: truck.customerId ?? undefined,
@@ -844,6 +847,8 @@ function ContainerReturnModal({ opened, onClose, group, onSubmit, loading }: Con
      .filter((c) => selectedContainers.includes(c.key))
      .map((c) => ({
        containerNumber: c.containerNumber,
+        // Inventory records "20ft"/"40ft"; the wagon rule only needs the number.
+        containerSize: c.size?.includes("40") ? ("40" as const) : c.size ? ("20" as const) : undefined,
        returnDate,
        warehouse: selectedWarehouse?.name || warehouse,
        condition: condition || undefined,
--- a/apps/edr-freight-web/backoffice/src/services/importOperations.service.ts
+++ b/apps/edr-freight-web/backoffice/src/services/importOperations.service.ts
@@ -5,6 +5,7 @@ import type {
  AssignCustomsRiskPayload,
  CreateDjiboutiIncidentPayload,
  CreateEmptyContainerReturnPayload,
+  LoadEmptyContainersOnTrainPayload,
  DjiboutiIncident,
  EmptyContainerReturn,
  ImportCustomsFinalization,
@@ -123,6 +124,16 @@ export const importOperationsService = {
    return unwrap(response.data);
  },

+  loadEmptyContainersOnTrain: async (
+    payload: LoadEmptyContainersOnTrainPayload,
+  ): Promise<EmptyContainerReturn[]> => {
+    const response = await client.post<EmptyContainerReturn[]>(
+      URL_CONSTANTS.IMPORT_OPERATIONS.EMPTY_CONTAINER_RETURNS_LOAD_ON_TRAIN,
+      payload,
+    );
+    return unwrap(response.data);
+  },
+
  updateEmptyReturnStatus: async (
    id: string,
    payload: UpdateEmptyContainerReturnStatusPayload,
--- a/apps/edr-freight-web/backoffice/src/types/importOperations.ts
+++ b/apps/edr-freight-web/backoffice/src/types/importOperations.ts
@@ -101,6 +101,11 @@ export interface EmptyContainerReturn {
  handoverNote: string | null;
  status: EmptyContainerReturnStatus;
  wagonAllocationReference: string | null;
+  /** '20' or '40' — one 40ft OR two 20ft ride a wagon. */
+  containerSize: EmptyContainerSize | null;
+  /** Export departure this empty is loaded on, once allocated. */
+  trainScheduleId: string | null;
+  wagonSequenceNo: number | null;
  performedBy: string | null;
  returnedBy: 'EDR' | 'CUSTOMER' | null;
  statusHistory: Array<{
@@ -110,8 +115,11 @@ export interface EmptyContainerReturn {
  }>;
 }

+export type EmptyContainerSize = '20' | '40';
+
 export interface CreateEmptyContainerReturnPayload {
  containerNumber: string;
+  containerSize?: EmptyContainerSize;
  bookingId?: string;
  customerId?: string;
  returnDate?: string;
@@ -124,6 +132,16 @@ export interface CreateEmptyContainerReturnPayload {
  returnedBy?: 'EDR' | 'CUSTOMER';
 }

+export interface LoadEmptyContainersOnTrainPayload extends ImportOperationActionPayload {
+  trainScheduleId: string;
+  trainNumber?: string;
+  items: Array<{
+    id: string;
+    containerSize: EmptyContainerSize;
+    wagonSequenceNo: number;
+  }>;
+}
+
 export interface UpdateEmptyContainerReturnStatusPayload extends ImportOperationActionPayload {
  status: EmptyContainerReturnStatus;
  wagonAllocationReference?: string;