Merge pull request 'Refactor production and stock tests to remove UOM dependency' (#38) from fix/uom-overall into Dev

Reviewed-on: #38

Backend/ERPCore/Controllers/ItemsController.cs

@@ -81,11 +81,4 @@ public sealed class ItemsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     public async Task<ActionResult<ItemReorderSettingsDto>> UpdateReorder(int itemId, [FromBody] UpdateReorderRequest request, CancellationToken ct)
         => Ok(await _items.UpdateReorderAsync(itemId, request, ct));
-
-    /// <summary>Replace the item's UOM conversions (FR-MD-02).</summary>
-    [HttpPut("{itemId:int}/uom-conversions")]
-    [ProducesResponseType(typeof(ItemUomConversionsDto), StatusCodes.Status200OK)]
-    [ProducesResponseType(StatusCodes.Status404NotFound)]
-    public async Task<ActionResult<ItemUomConversionsDto>> UpdateUomConversions(int itemId, [FromBody] UpdateUomConversionsRequest request, CancellationToken ct)
-        => Ok(await _items.UpdateUomConversionsAsync(itemId, request, ct));
 }

Backend/ERPCore/Domain/Entities/BundleSaleLine.cs

@@ -12,8 +12,6 @@ public class BundleSaleLine
     public Item? Item { get; set; }
     public string Description { get; set; } = string.Empty;
     public decimal Qty { get; set; }
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
     public int WarehouseId { get; set; }
     public Warehouse? Warehouse { get; set; }
     public decimal UnitPrice { get; set; }

Backend/ERPCore/Domain/Entities/BundleSaleTemplateLine.cs

@@ -8,8 +8,6 @@ public class BundleSaleTemplateLine
 
     public int ItemId { get; set; }
     public Item? Item { get; set; }
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
     public int WarehouseId { get; set; }
     public Warehouse? Warehouse { get; set; }
 

Backend/ERPCore/Domain/Entities/GrnLine.cs

@@ -25,9 +25,6 @@ public class GrnLine
     public int ItemId { get; set; }
     public Item? Item { get; set; }
 
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
-
     public int? BinId { get; set; }
     public Bin? Bin { get; set; }
 

Backend/ERPCore/Domain/Entities/Item.cs

@@ -24,6 +24,12 @@ public class Item
     public int? BrandId { get; set; }
     public Brand? Brand { get; set; }
 
+    /// <summary>
+    /// The stocking unit — the pack the item is counted in (BOTTLE, PACKET, BOX, PCS).
+    /// <b>Every</b> quantity in the system is a count of these: stock layers, the ledger,
+    /// and every document line. Nothing converts, so this is the sole meaning of a
+    /// quantity and cannot be changed once the item has stock history.
+    /// </summary>
     public int BaseUomId { get; set; }
     public Uom? BaseUom { get; set; }
 
@@ -41,6 +47,34 @@ public class Item
     /// </summary>
     public decimal? SalePrice { get; set; }
 
+    /// <summary>
+    /// How much one pack holds, as the user entered it — <c>500</c> with
+    /// <see cref="ContentUnit"/> <c>Ml</c> for a 500 ml bottle, <c>1.5</c> with <c>L</c>
+    /// for a 1.5 L one. Null (together with the other three) when the item has no
+    /// measurable content: a screw, a label, a service.
+    /// <para>
+    /// Content never affects stock — that is always a pack count. It exists so production
+    /// can express a formula in millilitres or grams and resolve it to packs
+    /// (see <c>IItemMeasure</c>).
+    /// </para>
+    /// <para>
+    /// A loose bulk item bought by weight is modelled the same way:
+    /// <c>BaseUom = KG, ContentQty = 1, ContentUnit = Kg</c> ⇒ 1000 g per stocked unit.
+    /// </para>
+    /// </summary>
+    public decimal? ContentQty { get; set; }
+    public MeasureUnit? ContentUnit { get; set; }
+
+    /// <summary>
+    /// <see cref="ContentQty"/>/<see cref="ContentUnit"/> normalised to a base unit
+    /// (L→Ml, Kg→G, both ×1000) at write time by <c>ItemContent.Normalize</c>. Server-derived
+    /// and never accepted from a client. <see cref="ContentBaseUnit"/> is therefore only ever
+    /// <see cref="MeasureUnit.Ml"/> or <see cref="MeasureUnit.G"/>.
+    /// <para>Stored rather than recomputed so every consumer reads one settled number.</para>
+    /// </summary>
+    public decimal? ContentBaseQty { get; set; }
+    public MeasureUnit? ContentBaseUnit { get; set; }
+
     public EntityStatus Status { get; set; } = EntityStatus.Active;
 
     public DateTime CreatedAt { get; set; }
@@ -50,5 +84,4 @@ public class Item
     public uint RowVersion { get; set; }
 
     public ICollection<ItemReorder> ReorderSettings { get; set; } = new List<ItemReorder>();
-    public ICollection<UomConversion> UomConversions { get; set; } = new List<UomConversion>();
 }

Backend/ERPCore/Domain/Entities/PoLine.cs

@@ -15,9 +15,6 @@ public class PoLine
     public int ItemId { get; set; }
     public Item? Item { get; set; }
 
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
-
     public int WarehouseId { get; set; }
     public Warehouse? Warehouse { get; set; }
 

Backend/ERPCore/Domain/Entities/RunStageInput.cs

@@ -31,10 +31,14 @@ public class RunStageInput
     public int? FromRunOutputId { get; set; }
     public RunStageOutput? FromRunOutput { get; set; }
 
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
+    /// <summary>Copied from the template input: what <see cref="PlannedQty"/> is expressed in.</summary>
+    public StageQtyUnit QtyUnit { get; set; } = StageQtyUnit.Pack;
 
-    /// <summary>Scaled at creation; per-run editable until the stage starts (FR-MFG-08, <c>409 STAGE_NOT_EDITABLE</c>).</summary>
+    /// <summary>
+    /// Scaled at creation; per-run editable until the stage starts (FR-MFG-08,
+    /// <c>409 STAGE_NOT_EDITABLE</c>). Expressed in <see cref="QtyUnit"/> — so unlike the
+    /// consumption figures below it is <b>not</b> necessarily a pack count.
+    /// </summary>
     public decimal PlannedQty { get; set; }
 
     /// <summary>

Backend/ERPCore/Domain/Entities/RunStageOutput.cs

@@ -23,10 +23,17 @@ public class RunStageOutput
 
     public string Name { get; set; } = string.Empty;
 
-    public int UomId { get; set; }
+    /// <summary>
+    /// Display label for intermediate WIP; null on the terminal output, whose unit is the
+    /// finished item's base UOM. Never converted — see <see cref="StageOutput.UomId"/>.
+    /// </summary>
+    public int? UomId { get; set; }
     public Uom? Uom { get; set; }
 
-    /// <summary>Scaled at creation; per-run editable until the stage starts.</summary>
+    /// <summary>
+    /// Scaled at creation; per-run editable until the stage starts. Every quantity on an
+    /// output is a pack count, so scrap is recorded in whole broken bottles rather than ml.
+    /// </summary>
     public decimal PlannedQty { get; set; }
 
     /// <summary>Recorded at complete. A re-complete after a rework <b>overwrites</b> this, never adds to it.</summary>

Backend/ERPCore/Domain/Entities/SalesInvoiceLine.cs

@@ -16,8 +16,6 @@ public class SalesInvoiceLine
 
     public decimal Qty { get; set; }
     public decimal FreeQty { get; set; }
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
     public int WarehouseId { get; set; }
     public Warehouse? Warehouse { get; set; }
 

Backend/ERPCore/Domain/Entities/SalesSlipLine.cs

@@ -16,8 +16,6 @@ public class SalesSlipLine
 
     public decimal Qty { get; set; }
     public decimal FreeQty { get; set; }
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
     public int WarehouseId { get; set; }
     public Warehouse? Warehouse { get; set; }
 

Backend/ERPCore/Domain/Entities/StageInput.cs

@@ -32,8 +32,13 @@ public class StageInput
     public int? FromOutputId { get; set; }
     public StageOutput? FromOutput { get; set; }
 
-    public int UomId { get; set; }
-    public Uom? Uom { get; set; }
+    /// <summary>
+    /// What <see cref="QtyPerBatch"/> is expressed in. Stock inputs may use
+    /// <see cref="StageQtyUnit.Content"/> (ml/g) when the item has a content size; Upstream
+    /// inputs are always <see cref="StageQtyUnit.Pack"/> — WIP is counted in the unit its
+    /// source output declares.
+    /// </summary>
+    public StageQtyUnit QtyUnit { get; set; } = StageQtyUnit.Pack;
 
     public decimal QtyPerBatch { get; set; }
 }

Backend/ERPCore/Domain/Entities/StageOutput.cs

@@ -20,8 +20,14 @@ public class StageOutput
 
     public string Name { get; set; } = string.Empty;
 
-    public int UomId { get; set; }
+    /// <summary>
+    /// Display label for intermediate work-in-progress. Required when <see cref="ItemId"/>
+    /// is null and must be null when it is set — a real item's unit is its own base UOM.
+    /// WIP never touches stock or the ledger, so this is never converted, only shown.
+    /// </summary>
+    public int? UomId { get; set; }
     public Uom? Uom { get; set; }
 
+    /// <summary>Always a pack count: of the WIP unit above, or of the item's base UOM.</summary>
     public decimal QtyPerBatch { get; set; }
 }

Backend/ERPCore/Domain/Entities/Uom.cs

@@ -1,8 +1,10 @@
 namespace ERPCore.Domain.Entities;
 
 /// <summary>
-/// Unit of Measure (FR-MD-02). Referenced as an item's base UOM and as the
-/// endpoints of a <see cref="UomConversion"/>. Model: docs/10-BACKEND-PHASE1.md Part C.1.
+/// Unit of Measure (FR-MD-02). A flat lookup, used as an item's base UOM — the pack every
+/// quantity in the system counts — and as the display label on an intermediate production
+/// output. There are no conversions between UOMs: an item is stocked in exactly one, and a
+/// differently sized pack is a different item. Model: docs/10-BACKEND-PHASE1.md Part C.1.
 /// </summary>
 public class Uom
 {

Backend/ERPCore/Domain/Entities/UomConversion.cs

@@ -1,22 +0,0 @@
-namespace ERPCore.Domain.Entities;
-
-/// <summary>
-/// Per-item conversion factor between two UOMs (FR-MD-02/03): quantity in
-/// <see cref="FromUomId"/> × <see cref="Factor"/> = quantity in <see cref="ToUomId"/>.
-/// Model: docs/10-BACKEND-PHASE1.md Part C.1.
-/// </summary>
-public class UomConversion
-{
-    public int ConversionId { get; set; }
-
-    public int ItemId { get; set; }
-    public Item? Item { get; set; }
-
-    public int FromUomId { get; set; }
-    public Uom? FromUom { get; set; }
-
-    public int ToUomId { get; set; }
-    public Uom? ToUom { get; set; }
-
-    public decimal Factor { get; set; }
-}

Backend/ERPCore/Domain/Enums/MeasureUnit.cs

@@ -0,0 +1,23 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>
+/// Unit of an item's <b>content size</b> — how much a single stocked pack holds
+/// (a 500 ml bottle, a 50 kg sack). Stored as a string in the database.
+/// <para>
+/// This is <b>not</b> a stocking unit. Stock is always counted in packs
+/// (<c>Item.BaseUomId</c>); content is a separate, optional attribute used by
+/// production to turn "2000 ml of syrup" into a pack count.
+/// </para>
+/// <para>
+/// Only <see cref="Ml"/> and <see cref="G"/> are ever stored as a <i>base</i> content
+/// unit. <see cref="L"/> and <see cref="Kg"/> are entry conveniences normalised ×1000
+/// on write by <c>ItemContent.Normalize</c>, so nothing downstream has to convert.
+/// </para>
+/// </summary>
+public enum MeasureUnit
+{
+    Ml,
+    L,
+    G,
+    Kg
+}

Backend/ERPCore/Domain/Enums/StageQtyUnit.cs

@@ -0,0 +1,22 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>
+/// What a stage input's quantity is expressed in (FR-MFG-04). Stored as a string.
+/// <para>
+/// Deliberately explicit rather than inferred from whether the item happens to have a
+/// content size: templates outlive item edits, so an inferred unit would let adding a
+/// content size to an existing item silently reinterpret every saved formula — "300"
+/// meaning 300 packs would become 300 ml.
+/// </para>
+/// </summary>
+public enum StageQtyUnit
+{
+    /// <summary>A count of the item's base UOM — bottles, packets, pieces.</summary>
+    Pack,
+
+    /// <summary>
+    /// An amount of the item's content in its base content unit (ml or g), resolved to
+    /// packs by <c>IItemMeasure</c> at stage start. Requires the item to have a content size.
+    /// </summary>
+    Content
+}

Backend/ERPCore/Dtos/Grn/GrnDtos.cs

@@ -6,7 +6,7 @@ namespace ERPCore.Dtos.Grn;
 // Responses (docs/11 §4) --------------------------------------------------------
 
 public sealed record GrnLineDto(
-    int GrnLineId, int? PoLineId, int ItemId, int UomId, int? BinId,
+    int GrnLineId, int? PoLineId, int ItemId, int? BinId,
     decimal Qty, decimal UnitCost, decimal? PoUnitPrice,
     decimal DiscountPct, decimal NetUnitCost, decimal VatPct, decimal VatAmount,
     decimal ReceivedValue, decimal LineTotal, decimal PriceVariance,
@@ -44,7 +44,6 @@ public sealed class CreateGrnLineInput
     /// <summary>Set for a PO-based receipt; cost is then derived from the PO line (02-SECURITY C.3).</summary>
     public int? PoLineId { get; set; }
     [Required] public int ItemId { get; set; }
-    [Required] public int UomId { get; set; }
     public int? BinId { get; set; }
     [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
     /// <summary>

Backend/ERPCore/Dtos/Items/ItemDtos.cs

@@ -9,7 +9,10 @@ namespace ERPCore.Dtos.Items;
 public sealed record ItemListItemDto(
     int ItemId, string Sku, string Name, int CategoryId, int? SubCategoryId, int? BrandId,
     int BaseUomId, int? DefaultVendorId, StockNature StockNature, TrackingMode TrackingMode,
-    string? TaxClass, decimal? SalePrice, EntityStatus Status);
+    string? TaxClass, decimal? SalePrice,
+    decimal? ContentQty, MeasureUnit? ContentUnit,
+    decimal? ContentBaseQty, MeasureUnit? ContentBaseUnit,
+    EntityStatus Status);
 
 /// <summary>A single per-warehouse reorder policy row.</summary>
 public sealed record ItemReorderDto(int WarehouseId, decimal ReorderPoint, decimal ReorderQty);
@@ -17,26 +20,21 @@ public sealed record ItemReorderDto(int WarehouseId, decimal ReorderPoint, decim
 /// <summary>
 /// Full item resource for <c>GET /items/{id}</c> and create/update responses.
 /// <para>
-/// <see cref="Conversions"/> is embedded because they are otherwise unreadable: they can
-/// only be written via <c>PUT /items/{id}/uom-conversions</c>, which returns them, but no
-/// endpoint reads them back — so a detail screen could never show current state before
-/// editing. Mirrors how <see cref="Reorder"/> is already inlined.
+/// <c>ContentBaseQty</c>/<c>ContentBaseUnit</c> are echoed back so a detail screen can show
+/// what the entered size normalised to (1.5 L ⇒ 1500 ml) — they are server-derived and are
+/// not accepted on write.
 /// </para>
 /// </summary>
 public sealed record ItemDetailDto(
     int ItemId, string Sku, string Name, string? Description, int CategoryId,
     int? SubCategoryId, int? BrandId, int BaseUomId, int? DefaultVendorId,
     StockNature StockNature, TrackingMode TrackingMode,
-    string? TaxClass, decimal? SalePrice, EntityStatus Status, IReadOnlyList<ItemReorderDto> Reorder,
-    IReadOnlyList<UomConversionDto> Conversions,
+    string? TaxClass, decimal? SalePrice,
+    decimal? ContentQty, MeasureUnit? ContentUnit,
+    decimal? ContentBaseQty, MeasureUnit? ContentBaseUnit,
+    EntityStatus Status, IReadOnlyList<ItemReorderDto> Reorder,
     DateTime CreatedAt, DateTime? UpdatedAt);
 
-/// <summary>UOM conversion row (docs/11 §2.2).</summary>
-public sealed record UomConversionDto(int ConversionId, int FromUom, int ToUom, decimal Factor);
-
-/// <summary>Response body for <c>PUT /items/{id}/uom-conversions</c>.</summary>
-public sealed record ItemUomConversionsDto(int ItemId, int BaseUomId, IReadOnlyList<UomConversionDto> Conversions);
-
 /// <summary>Response body for <c>PUT /items/{id}/reorder</c>.</summary>
 public sealed record ItemReorderSettingsDto(IReadOnlyList<ItemReorderDto> Settings);
 
@@ -64,6 +62,14 @@ public sealed class CreateItemRequest
     [StringLength(20)] public string? TaxClass { get; set; }
     /// <summary>Optional fixed sale price (Sales only). Null ⇒ sell at stock/FIFO value.</summary>
     [Range(0, double.MaxValue)] public decimal? SalePrice { get; set; }
+
+    /// <summary>
+    /// How much one pack holds. Supply with <see cref="ContentUnit"/> or leave both null
+    /// for items with no measurable content. The normalised base pair is derived by the
+    /// server and is deliberately not accepted here.
+    /// </summary>
+    [Range(0.0001, double.MaxValue)] public decimal? ContentQty { get; set; }
+    [EnumDataType(typeof(MeasureUnit))] public MeasureUnit? ContentUnit { get; set; }
 }
 
 public sealed class UpdateItemRequest
@@ -83,6 +89,14 @@ public sealed class UpdateItemRequest
     [StringLength(20)] public string? TaxClass { get; set; }
     /// <summary>Optional fixed sale price (Sales only). Null ⇒ sell at stock/FIFO value.</summary>
     [Range(0, double.MaxValue)] public decimal? SalePrice { get; set; }
+
+    /// <summary>
+    /// How much one pack holds. Supply with <see cref="ContentUnit"/> or leave both null
+    /// for items with no measurable content. The normalised base pair is derived by the
+    /// server and is deliberately not accepted here.
+    /// </summary>
+    [Range(0.0001, double.MaxValue)] public decimal? ContentQty { get; set; }
+    [EnumDataType(typeof(MeasureUnit))] public MeasureUnit? ContentUnit { get; set; }
 }
 
 public sealed class UpdateItemStatusRequest
@@ -101,15 +115,3 @@ public sealed class UpdateReorderRequest
 {
     [Required, MinLength(1)] public List<ReorderSettingInput> Settings { get; set; } = new();
 }
-
-public sealed class UomConversionInput
-{
-    [Required] public int FromUom { get; set; }
-    [Required] public int ToUom { get; set; }
-    [Range(0.000001, double.MaxValue)] public decimal Factor { get; set; }
-}
-
-public sealed class UpdateUomConversionsRequest
-{
-    [Required, MinLength(1)] public List<UomConversionInput> Conversions { get; set; } = new();
-}

Backend/ERPCore/Dtos/Procurement/PurchaseOrderDtos.cs

@@ -6,7 +6,7 @@ namespace ERPCore.Dtos.Procurement;
 // Responses (docs/11 §3.3) ------------------------------------------------------
 
 public sealed record PoLineDto(
-    int PoLineId, int ItemId, int UomId, int WarehouseId,
+    int PoLineId, int ItemId, int WarehouseId,
     decimal Qty, decimal UnitPrice, decimal Tax, decimal QtyReceived);
 
 public sealed record PoTotalsDto(decimal SubTotal, decimal Tax, decimal GrandTotal, string Currency);
@@ -25,7 +25,6 @@ public sealed record PurchaseOrderSummaryDto(
 public sealed class CreatePoLineInput
 {
     [Required] public int ItemId { get; set; }
-    [Required] public int UomId { get; set; }
     [Required] public int WarehouseId { get; set; }
     [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
     [Range(0, double.MaxValue)] public decimal UnitPrice { get; set; }

Backend/ERPCore/Dtos/Production/RunDtos.cs

@@ -29,17 +29,23 @@ public sealed record RunSummaryDto(
 /// </summary>
 public sealed record CostPoolDto(decimal Consumed, decimal Returned, decimal Net);
 
+/// <summary>
+/// One input of a run stage. <c>PlannedQty</c> is expressed in <c>QtyUnit</c> — content
+/// (ml/g) or packs — while every consumption figure is always a pack count, so the two are
+/// not directly comparable for a Content input.
+/// </summary>
 public sealed record RunStageInputDto(
-    int RunInputId, StageInputSource Source, int? ItemId, int? FromRunOutputId, int UomId,
+    int RunInputId, StageInputSource Source, int? ItemId, int? FromRunOutputId, StageQtyUnit QtyUnit,
     decimal PlannedQty, decimal ConsumedQty, decimal ConsumedValue,
     decimal DeliveredQty, decimal ReturnedQty, decimal ReturnedValue);
 
 /// <summary>
 /// One output of a run stage. <c>AvailableToTransfer</c> is derived — produced − scrapped −
-/// transferred (FR-MFG-12) — and never stored.
+/// transferred (FR-MFG-12) — and never stored. <c>UomId</c> is the WIP label and is null on
+/// the terminal output, whose unit is the finished item's base UOM.
 /// </summary>
 public sealed record RunStageOutputDto(
-    int RunOutputId, int? ItemId, string Name, int UomId,
+    int RunOutputId, int? ItemId, string Name, int? UomId,
     decimal PlannedQty, decimal ProducedQty, decimal ScrappedQty, int? ScrapReasonCodeId,
     decimal TransferredQty, decimal AvailableToTransfer);
 

Backend/ERPCore/Dtos/Production/TemplateDtos.cs

@@ -35,10 +35,11 @@ public sealed record FieldDefDto(
 
 public sealed record StageInputDto(
     int InputId, StageInputSource Source, int? ItemId,
-    int? FromOutputId, string? FromOutputKey, int UomId, decimal QtyPerBatch);
+    int? FromOutputId, string? FromOutputKey, StageQtyUnit QtyUnit, decimal QtyPerBatch);
 
+/// <summary><c>UomId</c> is the WIP label and is null exactly when <c>ItemId</c> is set.</summary>
 public sealed record StageOutputDto(
-    int OutputId, string Key, int? ItemId, string Name, int UomId, decimal QtyPerBatch);
+    int OutputId, string Key, int? ItemId, string Name, int? UomId, decimal QtyPerBatch);
 
 public sealed record TemplateStageDto(
     int StageId, string Key, string Name, string? RoleLabel, int EstimatedMinutes,
@@ -134,8 +135,12 @@ public sealed class SaveInputRequest
     [StringLength(60)]
     public string? FromOutputKey { get; set; }
 
-    [Range(1, int.MaxValue)]
-    public int UomId { get; set; }
+    /// <summary>
+    /// What <see cref="QtyPerBatch"/> means. <c>Content</c> (ml/g) is allowed only on a Stock
+    /// input whose item has a content size; Upstream inputs must be <c>Pack</c>.
+    /// </summary>
+    [EnumDataType(typeof(StageQtyUnit))]
+    public StageQtyUnit QtyUnit { get; set; } = StageQtyUnit.Pack;
 
     [Range(0.0001, double.MaxValue)]
     public decimal QtyPerBatch { get; set; }
@@ -153,8 +158,12 @@ public sealed class SaveOutputRequest
     [Required, StringLength(150, MinimumLength = 1)]
     public string Name { get; set; } = string.Empty;
 
+    /// <summary>
+    /// The WIP display unit. Required when <see cref="ItemId"/> is null; must be null when it
+    /// is set, because a real item's unit is its own base UOM.
+    /// </summary>
     [Range(1, int.MaxValue)]
-    public int UomId { get; set; }
+    public int? UomId { get; set; }
 
     [Range(0.0001, double.MaxValue)]
     public decimal QtyPerBatch { get; set; }

Backend/ERPCore/Dtos/Sales/BundleSaleDtos.cs

@@ -4,7 +4,7 @@ using ERPCore.Domain.Enums;
 namespace ERPCore.Dtos.Sales;
 
 public sealed record BundleSaleLineDto(
-    int BundleSaleLineId, int ItemId, string Description, decimal Qty, int UomId, int WarehouseId,
+    int BundleSaleLineId, int ItemId, string Description, decimal Qty, int WarehouseId,
     decimal UnitPrice, decimal LineTotal, bool IncludeInBundle, bool IsComponent, int? ParentLineId);
 
 public sealed record BundleSaleDto(
@@ -20,7 +20,7 @@ public sealed record BundleSaleSummaryDto(
     decimal ComponentSubtotal, decimal BundlePrice, decimal GrandTotal, DateTime CreatedAt);
 
 public sealed record BundleSaleTemplateLineDto(
-    int BundleSaleTemplateLineId, int ItemId, int UomId, int WarehouseId, decimal Qty,
+    int BundleSaleTemplateLineId, int ItemId, int WarehouseId, decimal Qty,
     decimal UnitPrice, bool IncludeInBundle, int SortOrder);
 
 public sealed record BundleSaleTemplateDto(
@@ -42,7 +42,6 @@ public sealed record BundleSalePostingCheckDto(
 public sealed class CreateBundleSaleTemplateLineRequest
 {
     [Required] public int ItemId { get; set; }
-    [Required] public int UomId { get; set; }
     [Required] public int WarehouseId { get; set; }
     [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
     [Range(0, double.MaxValue)] public decimal UnitPrice { get; set; }

Backend/ERPCore/Dtos/Sales/SalesInvoiceDtos.cs

@@ -4,7 +4,7 @@ using ERPCore.Domain.Enums;
 namespace ERPCore.Dtos.Sales;
 
 public sealed record SalesInvoiceLineDto(
-    int SalesInvoiceLineId, int ItemId, string Description, decimal Qty, decimal FreeQty, int UomId,
+    int SalesInvoiceLineId, int ItemId, string Description, decimal Qty, decimal FreeQty,
     int WarehouseId, decimal UnitPrice, decimal BaseCost, string PriceSource, decimal DiscountPct,
     decimal DiscountAmount, SalesDiscountMode DiscountMode, decimal NetUnitPrice, decimal LineTotal,
     decimal TaxPct, decimal TaxAmount, bool IsFreeIssue, int? ParentLineId);
@@ -35,7 +35,6 @@ public sealed record SalesInvoicePostingCheckDto(
 public sealed class CreateSalesInvoiceLineRequest
 {
     [Required] public int ItemId { get; set; }
-    [Required] public int UomId { get; set; }
     [Required] public int WarehouseId { get; set; }
     [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
     [Range(0, double.MaxValue)] public decimal FreeQty { get; set; }

Backend/ERPCore/Dtos/Sales/SalesSlipDtos.cs

@@ -4,7 +4,7 @@ using ERPCore.Domain.Enums;
 namespace ERPCore.Dtos.Sales;
 
 public sealed record SalesSlipLineDto(
-    int SalesSlipLineId, int ItemId, string Description, decimal Qty, decimal FreeQty, int UomId,
+    int SalesSlipLineId, int ItemId, string Description, decimal Qty, decimal FreeQty,
     int WarehouseId, decimal UnitPrice, decimal BaseCost, string PriceSource, decimal DiscountPct,
     decimal DiscountAmount, SalesDiscountMode DiscountMode, decimal NetUnitPrice, decimal LineTotal,
     decimal TaxPct, decimal TaxAmount, bool IsFreeIssue, int? ParentLineId);
@@ -34,7 +34,7 @@ public sealed record SalesSlipPostingCheckDto(
 public sealed record FreeIssueSummaryDto(
     int SalesSlipId, string SlipNo, SalesSlipStatus Status, DateTime CreatedAt,
     int WarehouseId, string WarehouseName, int ItemId, string ItemSku, string ItemName,
-    int UomId, string UomName, decimal Qty, decimal FreeQty, string SchemeLabel);
+    string UomName, decimal Qty, decimal FreeQty, string SchemeLabel);
 
 public sealed record FreeIssueDto(
     int SalesSlipId, string SlipNo, DateTime SlipDate, SalesSlipStatus Status,
@@ -45,7 +45,6 @@ public sealed record FreeIssueDto(
 public sealed class CreateSalesSlipLineRequest
 {
     [Required] public int ItemId { get; set; }
-    [Required] public int UomId { get; set; }
     [Required] public int WarehouseId { get; set; }
     [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
     [Range(0, double.MaxValue)] public decimal FreeQty { get; set; }

Backend/ERPCore/Infra/Persistence/Configurations/BundleSaleLineConfiguration.cs

@@ -18,7 +18,6 @@ public sealed class BundleSaleLineConfiguration : IEntityTypeConfiguration<Bundl
         builder.Property(x => x.IsComponent).HasDefaultValue(true);
 
         builder.HasOne(x => x.Item).WithMany().HasForeignKey(x => x.ItemId).OnDelete(DeleteBehavior.Restrict);
-        builder.HasOne(x => x.Uom).WithMany().HasForeignKey(x => x.UomId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(x => x.Warehouse).WithMany().HasForeignKey(x => x.WarehouseId).OnDelete(DeleteBehavior.Restrict);
     }
 }

Backend/ERPCore/Infra/Persistence/Configurations/BundleSaleTemplateLineConfiguration.cs

@@ -15,7 +15,6 @@ public sealed class BundleSaleTemplateLineConfiguration : IEntityTypeConfigurati
         builder.Property(x => x.SortOrder).HasDefaultValue(0);
 
         builder.HasOne(x => x.Item).WithMany().HasForeignKey(x => x.ItemId).OnDelete(DeleteBehavior.Restrict);
-        builder.HasOne(x => x.Uom).WithMany().HasForeignKey(x => x.UomId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(x => x.Warehouse).WithMany().HasForeignKey(x => x.WarehouseId).OnDelete(DeleteBehavior.Restrict);
     }
 }

Backend/ERPCore/Infra/Persistence/Configurations/GrnConfiguration.cs

@@ -49,7 +49,6 @@ public sealed class GrnLineConfiguration : IEntityTypeConfiguration<GrnLine>
         builder.HasOne(l => l.Grn).WithMany(g => g.Lines).HasForeignKey(l => l.GrnId).OnDelete(DeleteBehavior.Cascade);
         builder.HasOne(l => l.PoLine).WithMany().HasForeignKey(l => l.PoLineId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
-        builder.HasOne(l => l.Uom).WithMany().HasForeignKey(l => l.UomId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(l => l.Bin).WithMany().HasForeignKey(l => l.BinId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(l => l.Batch).WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
     }

Backend/ERPCore/Infra/Persistence/Configurations/ItemConfiguration.cs

@@ -22,6 +22,16 @@ public sealed class ItemConfiguration : IEntityTypeConfiguration<Item>
         // Sales-only fixed selling price; nullable (null ⇒ sell at stock/FIFO value).
         builder.Property(i => i.SalePrice).HasPrecision(18, 4);
 
+        // Optional content size (how much one stocked pack holds). All four are nullable
+        // together: null ⇒ the item has no measurable content. The base pair is derived
+        // server-side by ItemContent.Normalize and is only ever Ml or G.
+        builder.Property(i => i.ContentQty).HasPrecision(18, 4);
+        builder.Property(i => i.ContentBaseQty).HasPrecision(18, 4);
+        builder.Property(i => i.ContentUnit)
+            .HasConversion<string>().HasMaxLength(20);
+        builder.Property(i => i.ContentBaseUnit)
+            .HasConversion<string>().HasMaxLength(20);
+
         builder.Property(i => i.StockNature)
             .HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(i => i.TrackingMode)

Backend/ERPCore/Infra/Persistence/Configurations/ProductionConfiguration.cs

@@ -91,13 +91,13 @@ public sealed class StageInputConfiguration : IEntityTypeConfiguration<StageInpu
         builder.HasKey(i => i.InputId);
 
         builder.Property(i => i.Source).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(i => i.QtyUnit).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(i => i.QtyPerBatch).HasPrecision(18, 4);
 
         builder.HasOne(i => i.Stage).WithMany(s => s.Inputs)
             .HasForeignKey(i => i.StageId).OnDelete(DeleteBehavior.Cascade);
 
         builder.HasOne(i => i.Item).WithMany().HasForeignKey(i => i.ItemId).OnDelete(DeleteBehavior.Restrict);
-        builder.HasOne(i => i.Uom).WithMany().HasForeignKey(i => i.UomId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(i => i.FromOutput).WithMany()
             .HasForeignKey(i => i.FromOutputId).OnDelete(DeleteBehavior.Restrict);
     }
@@ -206,6 +206,7 @@ public sealed class RunStageInputConfiguration : IEntityTypeConfiguration<RunSta
         builder.HasKey(i => i.RunInputId);
 
         builder.Property(i => i.Source).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(i => i.QtyUnit).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(i => i.PlannedQty).HasPrecision(18, 4);
         builder.Property(i => i.ConsumedQty).HasPrecision(18, 4);
         builder.Property(i => i.ConsumedValue).HasPrecision(18, 4);
@@ -217,7 +218,6 @@ public sealed class RunStageInputConfiguration : IEntityTypeConfiguration<RunSta
             .HasForeignKey(i => i.RunStageId).OnDelete(DeleteBehavior.Cascade);
 
         builder.HasOne(i => i.Item).WithMany().HasForeignKey(i => i.ItemId).OnDelete(DeleteBehavior.Restrict);
-        builder.HasOne(i => i.Uom).WithMany().HasForeignKey(i => i.UomId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(i => i.FromRunOutput).WithMany()
             .HasForeignKey(i => i.FromRunOutputId).OnDelete(DeleteBehavior.Restrict);
 

Backend/ERPCore/Infra/Persistence/Configurations/PurchaseOrderConfiguration.cs

@@ -63,11 +63,6 @@ public sealed class PoLineConfiguration : IEntityTypeConfiguration<PoLine>
             .HasForeignKey(l => l.ItemId)
             .OnDelete(DeleteBehavior.Restrict);
 
-        builder.HasOne(l => l.Uom)
-            .WithMany()
-            .HasForeignKey(l => l.UomId)
-            .OnDelete(DeleteBehavior.Restrict);
-
         builder.HasOne(l => l.Warehouse)
             .WithMany()
             .HasForeignKey(l => l.WarehouseId)

Backend/ERPCore/Infra/Persistence/Configurations/SalesInvoiceConfiguration.cs

@@ -79,11 +79,6 @@ public sealed class SalesInvoiceLineConfiguration : IEntityTypeConfiguration<Sal
         builder.Property(x => x.TaxPct).HasPrecision(9, 4);
         builder.Property(x => x.TaxAmount).HasPrecision(18, 4);
 
-        builder.HasOne(x => x.Uom)
-            .WithMany()
-            .HasForeignKey(x => x.UomId)
-            .OnDelete(DeleteBehavior.Restrict);
-
         builder.HasOne(x => x.Warehouse)
             .WithMany()
             .HasForeignKey(x => x.WarehouseId)

Backend/ERPCore/Infra/Persistence/Configurations/SalesSlipConfiguration.cs

@@ -79,11 +79,6 @@ public sealed class SalesSlipLineConfiguration : IEntityTypeConfiguration<SalesS
         builder.Property(x => x.TaxPct).HasPrecision(9, 4);
         builder.Property(x => x.TaxAmount).HasPrecision(18, 4);
 
-        builder.HasOne(x => x.Uom)
-            .WithMany()
-            .HasForeignKey(x => x.UomId)
-            .OnDelete(DeleteBehavior.Restrict);
-
         builder.HasOne(x => x.Warehouse)
             .WithMany()
             .HasForeignKey(x => x.WarehouseId)

Backend/ERPCore/Infra/Persistence/Configurations/UomConversionConfiguration.cs

@@ -1,34 +0,0 @@
-using ERPCore.Domain.Entities;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.EntityFrameworkCore.Metadata.Builders;
-
-namespace ERPCore.Infra.Persistence.Configurations;
-
-public sealed class UomConversionConfiguration : IEntityTypeConfiguration<UomConversion>
-{
-    public void Configure(EntityTypeBuilder<UomConversion> builder)
-    {
-        builder.ToTable("uom_conversions");
-        builder.HasKey(c => c.ConversionId);
-
-        builder.Property(c => c.Factor).HasPrecision(18, 6);
-
-        builder.HasOne(c => c.Item)
-            .WithMany(i => i.UomConversions)
-            .HasForeignKey(c => c.ItemId)
-            .OnDelete(DeleteBehavior.Cascade);
-
-        builder.HasOne(c => c.FromUom)
-            .WithMany()
-            .HasForeignKey(c => c.FromUomId)
-            .OnDelete(DeleteBehavior.Restrict);
-
-        builder.HasOne(c => c.ToUom)
-            .WithMany()
-            .HasForeignKey(c => c.ToUomId)
-            .OnDelete(DeleteBehavior.Restrict);
-
-        // One conversion per (item, from, to) triple.
-        builder.HasIndex(c => new { c.ItemId, c.FromUomId, c.ToUomId }).IsUnique();
-    }
-}

Backend/ERPCore/Infra/Persistence/DataSeeder.cs

@@ -285,13 +285,18 @@ public static class DataSeeder
             new Item
             {
                 Sku = "SKU-DEMO-002",
-                Name = "Demo Item 2",
-                Description = "Secondary seeded sample item for sales documents",
+                Name = "Demo Item 2 (500 ml)",
+                Description = "Secondary seeded sample item; carries a content size so the "
+                    + "production content-unit path has a fixture",
                 CategoryId = category.CategoryId,
                 BaseUomId = uom.UomId,
                 StockNature = StockNature.Stocked,
                 TrackingMode = TrackingMode.None,
                 SalePrice = 50m,
+                ContentQty = 500m,
+                ContentUnit = MeasureUnit.Ml,
+                ContentBaseQty = 500m,
+                ContentBaseUnit = MeasureUnit.Ml,
                 Status = EntityStatus.Active,
                 CreatedAt = now
             }
@@ -438,7 +443,6 @@ public static class DataSeeder
                 new BundleSaleTemplateLine
                 {
                     ItemId = items[0].ItemId,
-                    UomId = uom.UomId,
                     WarehouseId = warehouse.WarehouseId,
                     Qty = 1m,
                     UnitPrice = items[0].SalePrice.GetValueOrDefault(),
@@ -448,7 +452,6 @@ public static class DataSeeder
                 new BundleSaleTemplateLine
                 {
                     ItemId = items[1].ItemId,
-                    UomId = uom.UomId,
                     WarehouseId = warehouse.WarehouseId,
                     Qty = 1m,
                     UnitPrice = items[1].SalePrice.GetValueOrDefault(),
@@ -489,7 +492,6 @@ public static class DataSeeder
                         ItemId = items[0].ItemId,
                         Description = items[0].Name,
                         Qty = 1m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = items[0].SalePrice.GetValueOrDefault(),
                         LineTotal = items[0].SalePrice.GetValueOrDefault(),
@@ -501,7 +503,6 @@ public static class DataSeeder
                         ItemId = items[1].ItemId,
                         Description = items[1].Name,
                         Qty = 1m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = items[1].SalePrice.GetValueOrDefault(),
                         LineTotal = items[1].SalePrice.GetValueOrDefault(),
@@ -537,7 +538,6 @@ public static class DataSeeder
                         ItemId = items[0].ItemId,
                         Description = items[0].Name,
                         Qty = 1m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = items[0].SalePrice.GetValueOrDefault(),
                         LineTotal = items[0].SalePrice.GetValueOrDefault(),
@@ -549,7 +549,6 @@ public static class DataSeeder
                         ItemId = items[1].ItemId,
                         Description = items[1].Name,
                         Qty = 1m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = items[1].SalePrice.GetValueOrDefault(),
                         LineTotal = items[1].SalePrice.GetValueOrDefault(),
@@ -585,7 +584,6 @@ public static class DataSeeder
                         ItemId = items[0].ItemId,
                         Description = items[0].Name,
                         Qty = 1m,
-                        UomId = uom.UomId,
                         WarehouseId = secondaryWarehouse.WarehouseId,
                         UnitPrice = items[0].SalePrice.GetValueOrDefault(),
                         LineTotal = items[0].SalePrice.GetValueOrDefault(),
@@ -662,7 +660,6 @@ public static class DataSeeder
                         Description = postableItem.Name,
                         Qty = 2m,
                         FreeQty = 0m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = 100m,
                         BaseCost = 0m,
@@ -706,7 +703,6 @@ public static class DataSeeder
                         Description = shortageItem.Name,
                         Qty = 6m,
                         FreeQty = 0m,
-                        UomId = uom.UomId,
                         WarehouseId = secondaryWarehouse.WarehouseId,
                         UnitPrice = 50m,
                         BaseCost = 0m,
@@ -751,7 +747,6 @@ public static class DataSeeder
                         Description = postableItem.Name,
                         Qty = 1m,
                         FreeQty = 0m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = 100m,
                         BaseCost = 0m,
@@ -794,7 +789,6 @@ public static class DataSeeder
                         Description = postableItem.Name,
                         Qty = 1m,
                         FreeQty = 0m,
-                        UomId = uom.UomId,
                         WarehouseId = warehouse.WarehouseId,
                         UnitPrice = 50m,
                         BaseCost = 0m,
@@ -834,7 +828,6 @@ public static class DataSeeder
                         Description = shortageItem.Name,
                         Qty = 3m,
                         FreeQty = 0m,
-                        UomId = uom.UomId,
                         WarehouseId = secondaryWarehouse.WarehouseId,
                         UnitPrice = 50m,
                         BaseCost = 0m,

Backend/ERPCore/Infra/Persistence/ErpDbContext.cs

@@ -30,7 +30,6 @@ public class ErpDbContext : DbContext
     /// <summary>Color/Size/Material dimension names. Unlinked to Item by design (docs/10 C.9).</summary>
     public DbSet<ItemType> ItemTypes => Set<ItemType>();
     public DbSet<Uom> Uoms => Set<Uom>();
-    public DbSet<UomConversion> UomConversions => Set<UomConversion>();
     public DbSet<Item> Items => Set<Item>();
     public DbSet<ItemReorder> ItemReorders => Set<ItemReorder>();
     public DbSet<Vendor> Vendors => Set<Vendor>();

Backend/ERPCore/Program.cs

@@ -99,7 +99,7 @@ builder.Services.AddScoped<IRfqService, RfqService>();
 builder.Services.AddScoped<IPurchaseOrderService, PurchaseOrderService>();
 
 // Stock core + goods receipt (docs/11 §4–5)
-builder.Services.AddScoped<IUomConverter, UomConverter>();
+builder.Services.AddScoped<IItemMeasure, ItemMeasure>();
 builder.Services.AddScoped<IFifoCostingService, FifoCostingService>();
 builder.Services.AddScoped<IStockService, StockService>();
 builder.Services.AddScoped<IGrnService, GrnService>();

Backend/ERPCore/Services/BundleSaleService.cs

@@ -19,11 +19,9 @@ public sealed class BundleSaleService : IBundleSaleService
     private readonly IRepository<BundleSale> _bundles;
     private readonly IRepository<Customer> _customers;
     private readonly IRepository<Item> _items;
-    private readonly IRepository<Uom> _uoms;
     private readonly IRepository<Warehouse> _warehouses;
     private readonly IRepository<User> _users;
     private readonly ISalesDomainService _sales;
-    private readonly IUomConverter _uomConverter;
     private readonly ISalesPostingService _posting;
     private readonly ICurrentUser _currentUser;
     private readonly INumberSequenceService _numbers;
@@ -34,11 +32,9 @@ public sealed class BundleSaleService : IBundleSaleService
         IRepository<BundleSaleTemplate> templates,
         IRepository<Customer> customers,
         IRepository<Item> items,
-        IRepository<Uom> uoms,
         IRepository<Warehouse> warehouses,
         IRepository<User> users,
         ISalesDomainService sales,
-        IUomConverter uomConverter,
         ISalesPostingService posting,
         ICurrentUser currentUser,
         INumberSequenceService numbers,
@@ -48,11 +44,9 @@ public sealed class BundleSaleService : IBundleSaleService
         _bundles = bundles;
         _customers = customers;
         _items = items;
-        _uoms = uoms;
         _warehouses = warehouses;
         _users = users;
         _sales = sales;
-        _uomConverter = uomConverter;
         _posting = posting;
         _currentUser = currentUser;
         _numbers = numbers;
@@ -85,7 +79,7 @@ public sealed class BundleSaleService : IBundleSaleService
             template.CreatedAt,
             template.UpdatedAt,
             template.Lines.OrderBy(x => x.SortOrder).Select(x => new BundleSaleTemplateLineDto(
-                x.BundleSaleTemplateLineId, x.ItemId, x.UomId, x.WarehouseId, x.Qty, x.UnitPrice, x.IncludeInBundle, x.SortOrder)).ToList());
+                x.BundleSaleTemplateLineId, x.ItemId, x.WarehouseId, x.Qty, x.UnitPrice, x.IncludeInBundle, x.SortOrder)).ToList());
     }
 
     public async Task<PagedResponse<BundleSaleSummaryDto>> ListAsync(PageQuery query, BundleSaleStatus? status, int? customerId, int? warehouseId, CancellationToken ct = default)
@@ -196,7 +190,6 @@ public sealed class BundleSaleService : IBundleSaleService
             : template.Lines.OrderBy(x => x.SortOrder).Select(x => new CreateBundleSaleTemplateLineRequest
             {
                 ItemId = x.ItemId,
-                UomId = x.UomId,
                 WarehouseId = x.WarehouseId,
                 Qty = x.Qty,
                 UnitPrice = x.UnitPrice,
@@ -214,17 +207,15 @@ public sealed class BundleSaleService : IBundleSaleService
             var lineWarehouseId = warehouseId;
 
             var item = await _items.Query().AsNoTracking().FirstAsync(x => x.ItemId == r.ItemId, ct);
-            await _sales.ValidateSalesLineAsync(warehouseId, r.ItemId, r.UomId, lineWarehouseId, r.Qty, 0m, null, ct);
-            var (qtyBase, unitCostBase) = await _uomConverter.ToBaseAsync(item, r.UomId, r.Qty, r.UnitPrice, ct);
-            var calc = _sales.ComputeLine(qtyBase, 0m, unitCostBase, SalesDiscountMode.Amount, 0m, 0m, 0m, 0m, false);
+            await _sales.ValidateSalesLineAsync(warehouseId, r.ItemId, lineWarehouseId, r.Qty, 0m, null, ct);
+            var calc = _sales.ComputeLine(r.Qty, 0m, r.UnitPrice, SalesDiscountMode.Amount, 0m, 0m, 0m, 0m, false);
             lines.Add(new BundleSaleLine
             {
                 ItemId = r.ItemId,
                 Description = item.Name,
-                Qty = qtyBase,
-                UomId = item.BaseUomId,
+                Qty = r.Qty,
                 WarehouseId = lineWarehouseId,
-                UnitPrice = unitCostBase,
+                UnitPrice = r.UnitPrice,
                 LineTotal = calc.LineTotal,
                 IncludeInBundle = r.IncludeInBundle,
                 IsComponent = true,
@@ -251,6 +242,6 @@ public sealed class BundleSaleService : IBundleSaleService
         x.BundleSaleId, x.BundleNo, x.BundleDate, x.CustomerId, x.CustomerSnapshotName, x.WarehouseId, x.CashierUserId, x.BundleSaleTemplateId,
         x.BundleName, x.BundleCode, x.Status, x.ComponentSubtotal, x.BundlePrice, x.MarginAmount, x.DiscountTotal, x.TaxTotal, x.GrandTotal,
         x.CreatedAt, x.UpdatedAt,
-        x.Lines.Select(l => new BundleSaleLineDto(l.BundleSaleLineId, l.ItemId, l.Description, l.Qty, l.UomId, l.WarehouseId, l.UnitPrice, l.LineTotal, l.IncludeInBundle, l.IsComponent, l.ParentLineId)).ToList());
+        x.Lines.Select(l => new BundleSaleLineDto(l.BundleSaleLineId, l.ItemId, l.Description, l.Qty, l.WarehouseId, l.UnitPrice, l.LineTotal, l.IncludeInBundle, l.IsComponent, l.ParentLineId)).ToList());
 
 }

Backend/ERPCore/Services/GrnService.cs

@@ -28,14 +28,12 @@ public sealed class GrnService : IGrnService
     private readonly IRepository<PurchaseOrder> _pos;
     private readonly IRepository<PoLine> _poLines;
     private readonly IRepository<Item> _items;
-    private readonly IRepository<Uom> _uoms;
     private readonly IRepository<Warehouse> _warehouses;
     private readonly IRepository<Bin> _bins;
     private readonly IRepository<Vendor> _vendors;
     private readonly IRepository<Batch> _batches;
     private readonly IRepository<StockLayer> _layers;
     private readonly IRepository<StockLedger> _ledger;
-    private readonly IUomConverter _uomConverter;
     private readonly IFifoCostingService _fifo;
     private readonly INumberSequenceService _numbers;
     private readonly ICurrentUser _currentUser;
@@ -43,23 +41,21 @@ public sealed class GrnService : IGrnService
 
     public GrnService(
         IRepository<Grn> grns, IRepository<PurchaseOrder> pos, IRepository<PoLine> poLines,
-        IRepository<Item> items, IRepository<Uom> uoms, IRepository<Warehouse> warehouses,
+        IRepository<Item> items, IRepository<Warehouse> warehouses,
         IRepository<Bin> bins, IRepository<Vendor> vendors, IRepository<Batch> batches,
-        IRepository<StockLayer> layers, IRepository<StockLedger> ledger, IUomConverter uomConverter,
+        IRepository<StockLayer> layers, IRepository<StockLedger> ledger,
         IFifoCostingService fifo, INumberSequenceService numbers, ICurrentUser currentUser, IUnitOfWork uow)
     {
         _grns = grns;
         _pos = pos;
         _poLines = poLines;
         _items = items;
-        _uoms = uoms;
         _warehouses = warehouses;
         _bins = bins;
         _vendors = vendors;
         _batches = batches;
         _layers = layers;
         _ledger = ledger;
-        _uomConverter = uomConverter;
         _fifo = fifo;
         _numbers = numbers;
         _currentUser = currentUser;
@@ -133,8 +129,6 @@ public sealed class GrnService : IGrnService
         {
             var item = await _items.Query().AsNoTracking().FirstOrDefaultAsync(i => i.ItemId == input.ItemId, ct)
                 ?? throw new DomainException(ErrorCodes.Validation, $"Item {input.ItemId} does not exist.", 422);
-            if (!await _uoms.Query().AnyAsync(u => u.UomId == input.UomId, ct))
-                throw new DomainException(ErrorCodes.Validation, $"UOM {input.UomId} does not exist.", 422);
             if (input.BinId is not null && !await _bins.Query().AnyAsync(b => b.BinId == input.BinId && b.WarehouseId == request.WarehouseId, ct))
                 throw new DomainException(ErrorCodes.Validation, $"Bin {input.BinId} is not in warehouse {request.WarehouseId}.", 422);
 
@@ -150,6 +144,8 @@ public sealed class GrnService : IGrnService
                 if (poLine.ItemId != input.ItemId)
                     throw new DomainException(ErrorCodes.Validation, $"PO line {input.PoLineId} is for a different item.", 422);
 
+                // Both sides are counts of the item's base UOM — the GRN line no longer carries
+                // a unit of its own — so this comparison and the accrual below are like-for-like.
                 var openQty = poLine.Qty - poLine.QtyReceived;
                 if (input.Qty > openQty * (1 + OverReceiptTolerance))
                     throw new DomainException(ErrorCodes.OverReceiptTolerance,
@@ -174,7 +170,6 @@ public sealed class GrnService : IGrnService
             {
                 PoLineId = input.PoLineId,
                 ItemId = input.ItemId,
-                UomId = input.UomId,
                 BinId = input.BinId,
                 Batch = batch, // navigation so EF fixes up BatchId once the batch is inserted
                 Qty = input.Qty,
@@ -234,10 +229,11 @@ public sealed class GrnService : IGrnService
         {
             foreach (var line in grn.Lines.OrderBy(l => l.GrnLineId))
             {
-                var item = await _items.Query().AsNoTracking().FirstAsync(i => i.ItemId == line.ItemId, token);
                 // FIFO layer costs at the after-discount net price; VAT is recoverable and never
-                // enters stock value (docs/10 FR-GRN-06, revised).
-                var (qtyBase, unitCostBase) = await ToBaseAsync(item, line.UomId, line.Qty, line.NetUnitCost, token);
+                // enters stock value (docs/10 FR-GRN-06, revised). The line quantity is already
+                // a count of the item's base UOM, so it layers exactly as entered.
+                var qtyBase = line.Qty;
+                var unitCostBase = line.NetUnitCost;
 
                 var layer = await _fifo.CreateInboundLayerAsync(
                     line.ItemId, grn.WarehouseId, line.BatchId, null, line.GrnLineId,
@@ -345,15 +341,6 @@ public sealed class GrnService : IGrnService
         return created; // linked via GrnLine.Batch navigation; FK fixed up on SaveChanges
     }
 
-    /// <summary>
-    /// Delegates to the shared <see cref="IUomConverter"/>. This was a private method here
-    /// until manufacturing needed the same conversion for stage stock inputs; behaviour is
-    /// identical, so receive costing is unchanged.
-    /// </summary>
-    private Task<(decimal QtyBase, decimal UnitCostBase)> ToBaseAsync(
-        Item item, int uomId, decimal qty, decimal unitCostPerUom, CancellationToken ct)
-        => _uomConverter.ToBaseAsync(item, uomId, qty, unitCostPerUom, ct);
-
     private async Task UpdatePoStatusAsync(int? poId, CancellationToken ct)
     {
         if (poId is null) return;
@@ -392,7 +379,7 @@ public sealed class GrnService : IGrnService
     private static GrnDto Map(Grn g) => new(
         g.GrnId, g.DocNo, g.PoId, g.VendorId, g.WarehouseId, g.Status, g.CreatedBy, g.CreatedAt, g.PostedAt,
         g.Lines.OrderBy(l => l.GrnLineId).Select(l => new GrnLineDto(
-            l.GrnLineId, l.PoLineId, l.ItemId, l.UomId, l.BinId, l.Qty, l.UnitCost, l.PoUnitPrice,
+            l.GrnLineId, l.PoLineId, l.ItemId, l.BinId, l.Qty, l.UnitCost, l.PoUnitPrice,
             l.DiscountPct, l.NetUnitCost, l.VatPct, l.VatAmount, l.ReceivedValue, l.LineTotal,
             l.PoUnitPrice is null ? 0m : Math.Round((l.UnitCost - l.PoUnitPrice.Value) * l.Qty, 4, MidpointRounding.AwayFromZero),
             l.HoldStatus, l.BatchId)).ToList());

Backend/ERPCore/Services/Interfaces/IItemMeasure.cs

@@ -0,0 +1,25 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>
+/// Resolves a production formula quantity to the only unit stock speaks: a count of the
+/// item's base UOM. Replaces the old per-item UOM conversion table — everything needed is
+/// on the item row, so this does no I/O.
+/// </summary>
+public interface IItemMeasure
+{
+    /// <summary>
+    /// Formula quantity → packs. <see cref="StageQtyUnit.Pack"/> passes straight through;
+    /// <see cref="StageQtyUnit.Content"/> divides by the item's content size, so 2000 ml of
+    /// a 500 ml bottle is 4 bottles and 300 ml is 0.6 of one.
+    /// </summary>
+    decimal ToPacks(Item item, decimal formulaQty, StageQtyUnit unit);
+
+    /// <summary>Packs → formula quantity. The exact inverse of <see cref="ToPacks"/>, for display.</summary>
+    decimal FromPacks(Item item, decimal packs, StageQtyUnit unit);
+
+    /// <summary>Whether the item carries a usable content size.</summary>
+    bool HasContent(Item item);
+}

Backend/ERPCore/Services/Interfaces/IItemService.cs

@@ -24,6 +24,4 @@ public interface IItemService
     Task SetStatusAsync(int itemId, EntityStatus status, CancellationToken ct = default);
 
     Task<ItemReorderSettingsDto> UpdateReorderAsync(int itemId, UpdateReorderRequest request, CancellationToken ct = default);
-
-    Task<ItemUomConversionsDto> UpdateUomConversionsAsync(int itemId, UpdateUomConversionsRequest request, CancellationToken ct = default);
 }

Backend/ERPCore/Services/Interfaces/ISalesDomainService.cs

@@ -15,7 +15,6 @@ public interface ISalesDomainService
     Task ValidateSalesLineAsync(
         int headerWarehouseId,
         int lineItemId,
-        int lineUomId,
         int lineWarehouseId,
         decimal qty,
         decimal freeQty,

Backend/ERPCore/Services/Interfaces/IUomConverter.cs

@@ -1,35 +0,0 @@
-using ERPCore.Domain.Entities;
-
-namespace ERPCore.Services.Interfaces;
-
-/// <summary>
-/// Converts a quantity and its per-UOM cost into the item's <b>base</b> UOM.
-/// </summary>
-/// <remarks>
-/// <para>Everything in the FIFO engine — <c>StockLayer</c>, <c>StockLedger</c>,
-/// <c>IFifoCostingService.ConsumeAsync</c> — works exclusively in base UOM, while
-/// documents let a user enter a line in any UOM the item has a conversion for. This is the
-/// one place that bridges the two.</para>
-/// <para>Extracted from <c>GrnService</c>'s private <c>ToBaseAsync</c> when manufacturing
-/// needed the same conversion for stage stock inputs (docs/30 never mentions UOM
-/// conversion, but <c>STAGE_INPUT.uom_id</c> is a free FK — without this, an input
-/// specified in "Box of 12" would consume 1 base unit instead of 12 and silently
-/// mis-cost the run).</para>
-/// </remarks>
-public interface IUomConverter
-{
-    /// <summary>
-    /// Returns the quantity and unit cost restated in <paramref name="item"/>'s base UOM.
-    /// A no-op when <paramref name="uomId"/> already is the base UOM. Throws 422 when no
-    /// conversion is defined for the item from that UOM to its base.
-    /// </summary>
-    Task<(decimal QtyBase, decimal UnitCostBase)> ToBaseAsync(
-        Item item, int uomId, decimal qty, decimal unitCostPerUom, CancellationToken ct = default);
-
-    /// <summary>
-    /// Quantity-only conversion, for callers that have no per-UOM cost to restate (a
-    /// production stage input declares a quantity; its cost comes from the FIFO layers it
-    /// consumes, not from the document).
-    /// </summary>
-    Task<decimal> ToBaseQtyAsync(Item item, int uomId, decimal qty, CancellationToken ct = default);
-}

Backend/ERPCore/Services/ItemContent.cs

@@ -0,0 +1,61 @@
+using ERPCore.Domain.Enums;
+using ERPCore.System.Errors;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Item content-size rules: validate the (qty, unit) pair and normalise it to a base
+/// unit. Pure — no DI, no database — because everything it needs is on the item row.
+/// <para>
+/// Litres and kilograms exist only at the point of entry. Everything stored and every
+/// downstream calculation works in millilitres or grams, so no consumer ever has to ask
+/// which unit it is holding.
+/// </para>
+/// </summary>
+public static class ItemContent
+{
+    /// <summary>
+    /// Rejects a half-filled pair. Both null is valid and means "this item has no
+    /// measurable content" — a screw, a label, a service.
+    /// </summary>
+    public static void ValidatePair(decimal? contentQty, MeasureUnit? contentUnit)
+    {
+        if (contentQty is null && contentUnit is null) return;
+
+        if (contentQty is null || contentUnit is null)
+            throw new DomainException(
+                ErrorCodes.Validation,
+                "contentQty and contentUnit must be supplied together, or both left null.", 422);
+
+        if (contentQty <= 0)
+            throw new DomainException(
+                ErrorCodes.Validation, "contentQty must be greater than zero.", 422);
+    }
+
+    /// <summary>
+    /// Converts an entered content size to its base unit: L → Ml and Kg → G, both ×1000;
+    /// Ml and G pass through. Both-null in, both-null out.
+    /// <para>
+    /// Rounded to 4dp AwayFromZero to match the quantity columns' <c>(18,4)</c> scale and
+    /// <c>ProductionRunService.Scale</c>, so a content size can never carry precision the
+    /// database would silently drop.
+    /// </para>
+    /// </summary>
+    public static (decimal? BaseQty, MeasureUnit? BaseUnit) Normalize(
+        decimal? contentQty, MeasureUnit? contentUnit)
+    {
+        if (contentQty is null || contentUnit is null) return (null, null);
+
+        var (factor, baseUnit) = contentUnit.Value switch
+        {
+            MeasureUnit.Ml => (1m, MeasureUnit.Ml),
+            MeasureUnit.L => (1000m, MeasureUnit.Ml),
+            MeasureUnit.G => (1m, MeasureUnit.G),
+            MeasureUnit.Kg => (1000m, MeasureUnit.G),
+            _ => throw new DomainException(
+                ErrorCodes.Validation, $"Unsupported content unit '{contentUnit}'.", 422)
+        };
+
+        return (Math.Round(contentQty.Value * factor, 4, MidpointRounding.AwayFromZero), baseUnit);
+    }
+}

Backend/ERPCore/Services/ItemService.cs

@@ -31,6 +31,8 @@ public sealed class ItemService : IItemService
     private readonly IRepository<Uom> _uoms;
     private readonly IRepository<Vendor> _vendors;
     private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<StockLayer> _stockLayers;
+    private readonly IRepository<StockLedger> _stockLedger;
     private readonly IProductConfigService _config;
     private readonly IUnitOfWork _uow;
 
@@ -42,6 +44,8 @@ public sealed class ItemService : IItemService
         IRepository<Uom> uoms,
         IRepository<Vendor> vendors,
         IRepository<Warehouse> warehouses,
+        IRepository<StockLayer> stockLayers,
+        IRepository<StockLedger> stockLedger,
         IProductConfigService config,
         IUnitOfWork uow)
     {
@@ -52,6 +56,8 @@ public sealed class ItemService : IItemService
         _uoms = uoms;
         _vendors = vendors;
         _warehouses = warehouses;
+        _stockLayers = stockLayers;
+        _stockLedger = stockLedger;
         _config = config;
         _uow = uow;
     }
@@ -79,7 +85,9 @@ public sealed class ItemService : IItemService
             .Select(i => new ItemListItemDto(
                 i.ItemId, i.Sku, i.Name, i.CategoryId, i.SubCategoryId, i.BrandId,
                 i.BaseUomId, i.DefaultVendorId,
-                i.StockNature, i.TrackingMode, i.TaxClass, i.SalePrice, i.Status))
+                i.StockNature, i.TrackingMode, i.TaxClass, i.SalePrice,
+                i.ContentQty, i.ContentUnit, i.ContentBaseQty, i.ContentBaseUnit,
+                i.Status))
             .ToListAsync(ct);
 
         return PagedResponse<ItemListItemDto>.Create(rows, query.Page, query.PageSize, total);
@@ -89,7 +97,6 @@ public sealed class ItemService : IItemService
     {
         var item = await _items.Query().AsNoTracking()
             .Include(i => i.ReorderSettings)
-            .Include(i => i.UomConversions)
             .FirstOrDefaultAsync(i => i.ItemId == itemId, ct);
 
         return item is null ? null : new ETagged<ItemDetailDto>(ToDetail(item), item.RowVersion);
@@ -104,6 +111,9 @@ public sealed class ItemService : IItemService
             request.CategoryId, request.SubCategoryId, request.BrandId,
             request.BaseUomId, request.DefaultVendorId, ct);
 
+        ItemContent.ValidatePair(request.ContentQty, request.ContentUnit);
+        var (contentBaseQty, contentBaseUnit) = ItemContent.Normalize(request.ContentQty, request.ContentUnit);
+
         var item = new Item
         {
             Sku = request.Sku.Trim(),
@@ -118,6 +128,10 @@ public sealed class ItemService : IItemService
             TrackingMode = request.TrackingMode,
             TaxClass = request.TaxClass,
             SalePrice = request.SalePrice,
+            ContentQty = request.ContentQty,
+            ContentUnit = request.ContentUnit,
+            ContentBaseQty = contentBaseQty,
+            ContentBaseUnit = contentBaseUnit,
             Status = EntityStatus.Active,
             CreatedAt = DateTime.UtcNow
         };
@@ -133,7 +147,6 @@ public sealed class ItemService : IItemService
     {
         var item = await _items.Query()
             .Include(i => i.ReorderSettings)
-            .Include(i => i.UomConversions)
             .FirstOrDefaultAsync(i => i.ItemId == itemId, ct)
             ?? throw new NotFoundException($"Item {itemId} was not found.");
 
@@ -148,6 +161,18 @@ public sealed class ItemService : IItemService
             request.CategoryId, request.SubCategoryId, request.BrandId,
             request.BaseUomId, request.DefaultVendorId, ct);
 
+        // The base UOM is the sole meaning of every quantity recorded against this item —
+        // stock layers, ledger rows and document lines are all plain counts of it. Once any
+        // of that history exists, changing it would silently reinterpret every one of those
+        // numbers (240 bottles becoming 240 cases), so it is frozen instead.
+        if (item.BaseUomId != request.BaseUomId && await HasStockHistoryAsync(itemId, ct))
+            throw new DomainException(
+                ErrorCodes.MasterInUse,
+                $"Item {itemId} has stock history; its base UOM can no longer be changed.", 409);
+
+        ItemContent.ValidatePair(request.ContentQty, request.ContentUnit);
+        var (contentBaseQty, contentBaseUnit) = ItemContent.Normalize(request.ContentQty, request.ContentUnit);
+
         item.Sku = request.Sku.Trim();
         item.Name = request.Name.Trim();
         item.Description = request.Description;
@@ -160,6 +185,10 @@ public sealed class ItemService : IItemService
         item.TrackingMode = request.TrackingMode;
         item.TaxClass = request.TaxClass;
         item.SalePrice = request.SalePrice;
+        item.ContentQty = request.ContentQty;
+        item.ContentUnit = request.ContentUnit;
+        item.ContentBaseQty = contentBaseQty;
+        item.ContentBaseUnit = contentBaseUnit;
         item.UpdatedAt = DateTime.UtcNow;
 
         await SaveGuardingConcurrencyAsync(ct);
@@ -224,52 +253,14 @@ public sealed class ItemService : IItemService
         return new ItemReorderSettingsDto(settings);
     }
 
-    public async Task<ItemUomConversionsDto> UpdateUomConversionsAsync(
-        int itemId, UpdateUomConversionsRequest request, CancellationToken ct = default)
-    {
-        var pairs = request.Conversions.Select(c => (c.FromUom, c.ToUom)).ToList();
-        if (pairs.Distinct().Count() != pairs.Count)
-            throw new DomainException(ErrorCodes.Validation, "Duplicate (fromUom, toUom) in conversions.", 400);
-
-        var item = await _items.Query()
-            .Include(i => i.UomConversions)
-            .FirstOrDefaultAsync(i => i.ItemId == itemId, ct)
-            ?? throw new NotFoundException($"Item {itemId} was not found.");
-
-        foreach (var uomId in request.Conversions.SelectMany(c => new[] { c.FromUom, c.ToUom }).Distinct())
-            if (!await _uoms.Query().AnyAsync(u => u.UomId == uomId, ct))
-                throw new DomainException(ErrorCodes.Validation, $"UOM {uomId} does not exist.", 422);
-
-        foreach (var stale in item.UomConversions.Where(c => request.Conversions.All(r => r.FromUom != c.FromUomId || r.ToUom != c.ToUomId)).ToList())
-            item.UomConversions.Remove(stale);
-        foreach (var input in request.Conversions)
-        {
-            var existing = item.UomConversions.FirstOrDefault(c => c.FromUomId == input.FromUom && c.ToUomId == input.ToUom);
-            if (existing is null)
-            {
-                item.UomConversions.Add(new UomConversion
-                {
-                    ItemId = itemId,
-                    FromUomId = input.FromUom,
-                    ToUomId = input.ToUom,
-                    Factor = input.Factor
-                });
-            }
-            else
-            {
-                existing.Factor = input.Factor;
-            }
-        }
-
-        item.UpdatedAt = DateTime.UtcNow;
-        await _uow.SaveChangesAsync(ct);
-
-        var conversions = item.UomConversions
-            .OrderBy(c => c.ConversionId)
-            .Select(c => new UomConversionDto(c.ConversionId, c.FromUomId, c.ToUomId, c.Factor))
-            .ToList();
-        return new ItemUomConversionsDto(item.ItemId, item.BaseUomId, conversions);
-    }
+    /// <summary>
+    /// Whether anything has ever been recorded against this item's stock. Checks the ledger
+    /// as well as live layers, because a fully consumed item has no layer left but its
+    /// history still reads in the old unit.
+    /// </summary>
+    private async Task<bool> HasStockHistoryAsync(int itemId, CancellationToken ct)
+        => await _stockLayers.Query().AnyAsync(l => l.ItemId == itemId, ct)
+           || await _stockLedger.Query().AnyAsync(l => l.ItemId == itemId, ct);
 
     /// <summary>
     /// Validates every FK on an item write, and gates the optional ones on the product
@@ -350,14 +341,12 @@ public sealed class ItemService : IItemService
     private static ItemDetailDto ToDetail(Item i) => new(
         i.ItemId, i.Sku, i.Name, i.Description, i.CategoryId, i.SubCategoryId, i.BrandId,
         i.BaseUomId, i.DefaultVendorId,
-        i.StockNature, i.TrackingMode, i.TaxClass, i.SalePrice, i.Status,
+        i.StockNature, i.TrackingMode, i.TaxClass, i.SalePrice,
+        i.ContentQty, i.ContentUnit, i.ContentBaseQty, i.ContentBaseUnit,
+        i.Status,
         i.ReorderSettings
             .OrderBy(r => r.WarehouseId)
             .Select(r => new ItemReorderDto(r.WarehouseId, r.ReorderPoint, r.ReorderQty))
             .ToList(),
-        i.UomConversions
-            .OrderBy(c => c.ConversionId)
-            .Select(c => new UomConversionDto(c.ConversionId, c.FromUomId, c.ToUomId, c.Factor))
-            .ToList(),
         i.CreatedAt, i.UpdatedAt);
 }

Backend/ERPCore/Services/Production/ProductionGraphValidator.cs

@@ -21,9 +21,10 @@ namespace ERPCore.Services.Production;
 /// </remarks>
 public static class ProductionGraphValidator
 {
-    public sealed record InputDraft(int Index, StageInputSource Source, int? ItemId, string? FromOutputKey);
+    public sealed record InputDraft(
+        int Index, StageInputSource Source, int? ItemId, string? FromOutputKey, StageQtyUnit QtyUnit);
 
-    public sealed record OutputDraft(string Key, string Name, int? ItemId);
+    public sealed record OutputDraft(string Key, string Name, int? ItemId, int? UomId);
 
     public sealed record StageDraft(
         string Key, string Name, IReadOnlyList<InputDraft> Inputs, IReadOnlyList<OutputDraft> Outputs);
@@ -171,6 +172,12 @@ public static class ProductionGraphValidator
                         throw new DomainException(ErrorCodes.GraphInputSourceInvalid,
                             $"Input {input.Index + 1} of stage '{s.Name}' is a Stock input and cannot reference an upstream output.", 422);
                 }
+
+                // WIP has no content size — it is counted in whatever unit its source output
+                // declares — so only a Stock input may be expressed in ml/g.
+                if (input.Source == StageInputSource.Upstream && input.QtyUnit != StageQtyUnit.Pack)
+                    throw new DomainException(ErrorCodes.GraphInputSourceInvalid,
+                        $"Input {input.Index + 1} of stage '{s.Name}' is Upstream, so its quantity must be in whole units of its source output, not content units.", 422);
             }
         }
 
@@ -189,6 +196,20 @@ public static class ProductionGraphValidator
             foreach (var o in s.Outputs.Where(o => o.ItemId is not null))
                 throw Invalid(
                     $"Output '{o.Name}' of stage '{s.Name}' is intermediate work-in-progress and cannot reference an item — only the final stage produces a stocked item.");
+
+        // 7 — output units. An item-bearing output already has a unit (the item's base UOM),
+        // so carrying a second one could only contradict it. WIP has no item to ask, so it
+        // must name its own — the label the run board and any downstream input display.
+        foreach (var s in stages)
+            foreach (var o in s.Outputs)
+            {
+                if (o.ItemId is null && o.UomId is null)
+                    throw new DomainException(ErrorCodes.WipUnitRequired,
+                        $"Output '{o.Name}' of stage '{s.Name}' is work-in-progress and must declare a unit.", 422);
+                if (o.ItemId is not null && o.UomId is not null)
+                    throw Invalid(
+                        $"Output '{o.Name}' of stage '{s.Name}' references an item, so its unit comes from that item and must not be set.");
+            }
     }
 
     /// <summary>Set of keys reachable from <paramref name="roots"/> following <paramref name="next"/>.</summary>

Backend/ERPCore/Services/Production/ProductionRunService.cs

@@ -26,7 +26,7 @@ public sealed class ProductionRunService : IProductionRunService
     private readonly IRepository<Item> _items;
     private readonly IRepository<ReasonCode> _reasonCodes;
     private readonly IFifoCostingService _fifo;
-    private readonly IUomConverter _uomConverter;
+    private readonly IItemMeasure _measure;
     private readonly INumberSequenceService _numbers;
     private readonly IUnitOfWork _uow;
     private readonly ICurrentUser _currentUser;
@@ -35,7 +35,7 @@ public sealed class ProductionRunService : IProductionRunService
         IRepository<ProductionRun> runs, IRepository<ProductionTemplate> templates,
         IRepository<Warehouse> warehouses, IRepository<Bin> bins,
         IRepository<Item> items, IRepository<ReasonCode> reasonCodes,
-        IFifoCostingService fifo, IUomConverter uomConverter,
+        IFifoCostingService fifo, IItemMeasure measure,
         INumberSequenceService numbers, IUnitOfWork uow, ICurrentUser currentUser)
     {
         _runs = runs;
@@ -45,7 +45,7 @@ public sealed class ProductionRunService : IProductionRunService
         _items = items;
         _reasonCodes = reasonCodes;
         _fifo = fifo;
-        _uomConverter = uomConverter;
+        _measure = measure;
         _numbers = numbers;
         _uow = uow;
         _currentUser = currentUser;
@@ -245,7 +245,7 @@ public sealed class ProductionRunService : IProductionRunService
                     Source = i.Source,
                     ItemId = i.ItemId,
                     FromRunOutput = i.FromOutputId is null ? null : outputByTemplateOutputId[i.FromOutputId.Value],
-                    UomId = i.UomId,
+                    QtyUnit = i.QtyUnit,
                     PlannedQty = Scale(i.QtyPerBatch, ratio)
                 });
             }
@@ -367,9 +367,11 @@ public sealed class ProductionRunService : IProductionRunService
                     ?? throw new DomainException(ErrorCodes.Validation,
                         $"Item {input.ItemId} on stage '{stage.Name}' no longer exists.", 422);
 
-                // PlannedQty is in the input's declared UOM; ConsumedQty is in the item's
-                // base UOM (the only unit FIFO and the ledger speak). Compare in base.
-                var plannedBase = await _uomConverter.ToBaseQtyAsync(item, input.UomId, input.PlannedQty, token);
+                // PlannedQty is in the input's declared unit — content (ml/g) for an item with
+                // a content size, otherwise packs. ConsumedQty is always packs, the only unit
+                // FIFO and the ledger speak, so resolve before comparing. 2000 ml of a 500 ml
+                // bottle is 4 bottles; 300 ml is 0.6 of one, which (18,4) stores exactly.
+                var plannedBase = _measure.ToPacks(item, input.PlannedQty, input.QtyUnit);
                 var delta = plannedBase - input.ConsumedQty;
                 if (delta <= 0) continue; // rework restart with no increase — nothing to draw
 
@@ -1057,7 +1059,9 @@ public sealed class ProductionRunService : IProductionRunService
                 $"Item {item.Sku} is {item.TrackingMode}-tracked; batch/serial-tracked finished goods "
                 + "are not supported in this phase.", 422);
 
-        var qtyBase = await _uomConverter.ToBaseQtyAsync(item, output.UomId, good, ct);
+        // Output quantities are always a count of the finished item's base UOM — produced and
+        // scrapped are recorded in whole bottles, not millilitres — so nothing to resolve.
+        var qtyBase = good;
 
         var consumedValue = run.Stages.SelectMany(s => s.Inputs).Sum(i => i.ConsumedValue);
         var returnedValue = run.Stages.SelectMany(s => s.Inputs).Sum(i => i.ReturnedValue);
@@ -1223,7 +1227,7 @@ public sealed class ProductionRunService : IProductionRunService
                 ProductionJson.Deserialize<List<FieldDefDto>>(s.FieldDefs, []),
                 ParseJson(s.FieldValues),
                 s.Inputs.OrderBy(i => i.RunInputId).Select(i => new RunStageInputDto(
-                    i.RunInputId, i.Source, i.ItemId, i.FromRunOutputId, i.UomId,
+                    i.RunInputId, i.Source, i.ItemId, i.FromRunOutputId, i.QtyUnit,
                     i.PlannedQty, i.ConsumedQty, i.ConsumedValue,
                     i.DeliveredQty, i.ReturnedQty, i.ReturnedValue)).ToList(),
                 s.Outputs.OrderBy(o => o.RunOutputId).Select(o => new RunStageOutputDto(

Backend/ERPCore/Services/Production/ProductionTemplateService.cs

@@ -253,19 +253,20 @@ public sealed class ProductionTemplateService : IProductionTemplateService
         ProductionGraphValidator.Validate(
             request.Stages.Select(s => new ProductionGraphValidator.StageDraft(
                 s.Key, s.Name,
-                s.Inputs.Select((i, idx) => new ProductionGraphValidator.InputDraft(idx, i.Source, i.ItemId, i.FromOutputKey)).ToList(),
-                s.Outputs.Select(o => new ProductionGraphValidator.OutputDraft(o.Key, o.Name, o.ItemId)).ToList())).ToList(),
+                s.Inputs.Select((i, idx) => new ProductionGraphValidator.InputDraft(idx, i.Source, i.ItemId, i.FromOutputKey, i.QtyUnit)).ToList(),
+                s.Outputs.Select(o => new ProductionGraphValidator.OutputDraft(o.Key, o.Name, o.ItemId, o.UomId)).ToList())).ToList(),
             request.Edges.Select(e => new ProductionGraphValidator.EdgeDraft(e.ParentKey, e.ChildKey)).ToList());
 
         var itemIds = request.Stages
             .SelectMany(s => s.Inputs.Select(i => i.ItemId).Concat(s.Outputs.Select(o => o.ItemId)))
             .OfType<int>().Distinct().ToList();
 
+        var contentByItem = new Dictionary<int, decimal?>();
         if (itemIds.Count > 0)
         {
             var found = await _items.Query().AsNoTracking()
                 .Where(i => itemIds.Contains(i.ItemId))
-                .Select(i => new { i.ItemId, i.Status })
+                .Select(i => new { i.ItemId, i.Status, i.ContentBaseQty })
                 .ToListAsync(ct);
 
             var missing = itemIds.Except(found.Select(f => f.ItemId)).ToList();
@@ -277,12 +278,34 @@ public sealed class ProductionTemplateService : IProductionTemplateService
             if (inactive.Count > 0)
                 throw new DomainException(ErrorCodes.Validation,
                     $"Item(s) {string.Join(", ", inactive)} are inactive and cannot be used in a template.", 422);
+
+            contentByItem = found.ToDictionary(f => f.ItemId, f => f.ContentBaseQty);
         }
 
-        var uomIds = request.Stages
-            .SelectMany(s => s.Inputs.Select(i => i.UomId).Concat(s.Outputs.Select(o => o.UomId)))
-            .Distinct().ToList();
+        // A Content quantity is only meaningful against an item that declares a content size,
+        // and it must still land on a storable pack count: quantities persist at (18,4), so
+        // anything under 0.0001 packs would round to zero and consume nothing at stage start.
+        foreach (var s in request.Stages)
+            foreach (var i in s.Inputs.Where(i => i.QtyUnit == StageQtyUnit.Content))
+            {
+                var contentBaseQty = contentByItem.GetValueOrDefault(i.ItemId ?? 0);
+                if (contentBaseQty is not > 0m)
+                    throw new DomainException(ErrorCodes.Validation,
+                        $"Stage '{s.Name}' has an input in content units, but item {i.ItemId} has no content size.", 422);
 
+                if (i.QtyPerBatch / contentBaseQty.Value < 0.0001m)
+                    throw new DomainException(ErrorCodes.Validation,
+                        $"Stage '{s.Name}': {i.QtyPerBatch} is less than 0.0001 of item {i.ItemId}'s content size ({contentBaseQty}), which would round to no stock at all.", 422);
+            }
+
+        // Only WIP outputs carry a UOM now; the validator has already rejected one on an
+        // item-bearing output, so every non-null id here belongs to real work-in-progress.
+        var uomIds = request.Stages
+            .SelectMany(s => s.Outputs.Select(o => o.UomId))
+            .OfType<int>().Distinct().ToList();
+
+        if (uomIds.Count > 0)
+        {
             var knownUoms = await _uoms.Query().AsNoTracking()
                 .Where(u => uomIds.Contains(u.UomId)).Select(u => u.UomId).ToListAsync(ct);
 
@@ -290,6 +313,7 @@ public sealed class ProductionTemplateService : IProductionTemplateService
             if (missingUoms.Count > 0)
                 throw new DomainException(ErrorCodes.Validation,
                     $"UOM(s) {string.Join(", ", missingUoms)} do not exist.", 422);
+        }
 
         // Annotations go into jsonb unvalidated by anything else, so pin the one field the
         // client renders off. Unknown kinds would round-trip fine but draw nothing.
@@ -428,7 +452,7 @@ public sealed class ProductionTemplateService : IProductionTemplateService
                     Source = i.Source,
                     ItemId = i.Source == StageInputSource.Stock ? i.ItemId : null,
                     FromOutput = i.Source == StageInputSource.Upstream ? outputsByKey[i.FromOutputKey!] : null,
-                    UomId = i.UomId,
+                    QtyUnit = i.QtyUnit,
                     QtyPerBatch = i.QtyPerBatch
                 });
             }
@@ -476,7 +500,7 @@ public sealed class ProductionTemplateService : IProductionTemplateService
                 s.Inputs.OrderBy(i => i.InputId).Select(i => new StageInputDto(
                     i.InputId, i.Source, i.ItemId, i.FromOutputId,
                     i.FromOutputId is null ? null : outputKeyById.GetValueOrDefault(i.FromOutputId.Value),
-                    i.UomId, i.QtyPerBatch)).ToList(),
+                    i.QtyUnit, i.QtyPerBatch)).ToList(),
                 s.Outputs.OrderBy(o => o.OutputId).Select(o => new StageOutputDto(
                     o.OutputId, o.OutputId.ToString(), o.ItemId, o.Name, o.UomId, o.QtyPerBatch)).ToList()))
             .ToList();

Backend/ERPCore/Services/PurchaseOrderService.cs

@@ -222,7 +222,6 @@ public sealed class PurchaseOrderService : IPurchaseOrderService
     private static PoLine ToLine(CreatePoLineInput l) => new()
     {
         ItemId = l.ItemId,
-        UomId = l.UomId,
         WarehouseId = l.WarehouseId,
         Qty = l.Qty,
         UnitPrice = l.UnitPrice,
@@ -258,7 +257,6 @@ public sealed class PurchaseOrderService : IPurchaseOrderService
             throw new DomainException(ErrorCodes.Validation, $"Requisition {requisitionId} does not exist.", 422);
 
         await EnsureAllExistAsync(_items.Query().Select(i => i.ItemId), lines.Select(l => l.ItemId), "Item", ct);
-        await EnsureAllExistAsync(_uoms.Query().Select(u => u.UomId), lines.Select(l => l.UomId), "UOM", ct);
         await EnsureAllExistAsync(_warehouses.Query().Select(w => w.WarehouseId), lines.Select(l => l.WarehouseId), "Warehouse", ct);
     }
 
@@ -276,5 +274,5 @@ public sealed class PurchaseOrderService : IPurchaseOrderService
         p.PoId, p.DocNo, p.VendorId, p.RequisitionId, p.Status, p.ApprovalRequired,
         p.CreatedBy, p.CreatedAt, p.UpdatedAt, ComputeTotals(p.Lines),
         p.Lines.OrderBy(l => l.PoLineId).Select(l => new PoLineDto(
-            l.PoLineId, l.ItemId, l.UomId, l.WarehouseId, l.Qty, l.UnitPrice, l.Tax, l.QtyReceived)).ToList());
+            l.PoLineId, l.ItemId, l.WarehouseId, l.Qty, l.UnitPrice, l.Tax, l.QtyReceived)).ToList());
 }

Backend/ERPCore/Services/SalesDomainService.cs

@@ -13,7 +13,6 @@ public sealed class SalesDomainService : ISalesDomainService
     private readonly IRepository<Warehouse> _warehouses;
     private readonly IRepository<User> _users;
     private readonly IRepository<Item> _items;
-    private readonly IRepository<Uom> _uoms;
     private readonly ISalesPricingService _pricing;
 
     public SalesDomainService(
@@ -21,14 +20,12 @@ public sealed class SalesDomainService : ISalesDomainService
         IRepository<Warehouse> warehouses,
         IRepository<User> users,
         IRepository<Item> items,
-        IRepository<Uom> uoms,
         ISalesPricingService pricing)
     {
         _customers = customers;
         _warehouses = warehouses;
         _users = users;
         _items = items;
-        _uoms = uoms;
         _pricing = pricing;
     }
 
@@ -48,7 +45,7 @@ public sealed class SalesDomainService : ISalesDomainService
     }
 
     public async Task ValidateSalesLineAsync(
-        int headerWarehouseId, int lineItemId, int lineUomId, int lineWarehouseId, decimal qty, decimal freeQty, int? parentLineId, CancellationToken ct = default)
+        int headerWarehouseId, int lineItemId, int lineWarehouseId, decimal qty, decimal freeQty, int? parentLineId, CancellationToken ct = default)
     {
         if (qty <= 0)
             throw new DomainException(ErrorCodes.Validation, "Sales line quantity must be greater than zero.", 422);
@@ -60,8 +57,6 @@ public sealed class SalesDomainService : ISalesDomainService
             throw new DomainException(ErrorCodes.Validation, $"Sales line warehouse {lineWarehouseId} must match header warehouse {headerWarehouseId}.", 422);
         if (!await _items.Query().AnyAsync(x => x.ItemId == lineItemId, ct))
             throw new NotFoundException($"Item {lineItemId} was not found.");
-        if (!await _uoms.Query().AnyAsync(x => x.UomId == lineUomId, ct))
-            throw new NotFoundException($"UOM {lineUomId} was not found.");
         if (!await _warehouses.Query().AnyAsync(x => x.WarehouseId == lineWarehouseId, ct))
             throw new NotFoundException($"Warehouse {lineWarehouseId} was not found.");
     }

Backend/ERPCore/Services/SalesInvoiceService.cs

@@ -145,7 +145,7 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
         foreach (var r in requests)
         {
             var item = await _items.Query().AsNoTracking().FirstAsync(x => x.ItemId == r.ItemId, ct);
-            await _sales.ValidateSalesLineAsync(headerWarehouseId, r.ItemId, r.UomId, r.WarehouseId, r.Qty, r.FreeQty, r.ParentLineId, ct);
+            await _sales.ValidateSalesLineAsync(headerWarehouseId, r.ItemId, r.WarehouseId, r.Qty, r.FreeQty, r.ParentLineId, ct);
             var resolved = await _sales.ResolveLinePriceAsync(r.ItemId, r.WarehouseId, r.UnitPrice, r.AllowManualPriceOverride, ct);
             var unitPrice = resolved.UnitPrice;
             var priceSource = resolved.PriceSource;
@@ -158,7 +158,6 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
                 Description = item.Name,
                 Qty = r.Qty,
                 FreeQty = r.FreeQty,
-                UomId = r.UomId,
                 WarehouseId = r.WarehouseId,
                 UnitPrice = unitPrice,
                 BaseCost = unitPrice,

Backend/ERPCore/Services/SalesMappingService.cs

@@ -35,7 +35,7 @@ public sealed class SalesMappingService : ISalesMappingService
             invoice.InvoiceType, invoice.Status, invoice.CreatedBy, invoice.CreatedAt, invoice.UpdatedAt,
             MapInvoiceTotals(invoice),
             invoice.Lines.Select(l => new SalesInvoiceLineDto(
-                l.SalesInvoiceLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.UomId, l.WarehouseId,
+                l.SalesInvoiceLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.WarehouseId,
                 l.UnitPrice, l.BaseCost, l.PriceSource, l.DiscountPct, l.DiscountAmount, l.DiscountMode,
                 l.NetUnitPrice, l.LineTotal, l.TaxPct, l.TaxAmount, l.IsFreeIssue, l.ParentLineId)).ToList());
 
@@ -45,7 +45,7 @@ public sealed class SalesMappingService : ISalesMappingService
             slip.WarehouseId, slip.CashierUserId, slip.Status, slip.CreatedAt, slip.UpdatedAt,
             MapSlipTotals(slip),
             slip.Lines.Select(l => new SalesSlipLineDto(
-                l.SalesSlipLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.UomId, l.WarehouseId,
+                l.SalesSlipLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.WarehouseId,
                 l.UnitPrice, l.BaseCost, l.PriceSource, l.DiscountPct, l.DiscountAmount, l.DiscountMode,
                 l.NetUnitPrice, l.LineTotal, l.TaxPct, l.TaxAmount, l.IsFreeIssue, l.ParentLineId)).ToList());
 }

Backend/ERPCore/Services/SalesPostingService.cs

@@ -20,7 +20,6 @@ public sealed class SalesPostingService : ISalesPostingService
     private readonly IRepository<Item> _items;
     private readonly IFifoCostingService _fifo;
     private readonly ISalesDomainService _sales;
-    private readonly IUomConverter _uomConverter;
     private readonly ICurrentUser _currentUser;
     private readonly IUnitOfWork _uow;
 
@@ -31,7 +30,6 @@ public sealed class SalesPostingService : ISalesPostingService
         IRepository<Item> items,
         IFifoCostingService fifo,
         ISalesDomainService sales,
-        IUomConverter uomConverter,
         ICurrentUser currentUser,
         IUnitOfWork uow)
     {
@@ -41,7 +39,6 @@ public sealed class SalesPostingService : ISalesPostingService
         _items = items;
         _fifo = fifo;
         _sales = sales;
-        _uomConverter = uomConverter;
         _currentUser = currentUser;
         _uow = uow;
     }
@@ -141,7 +138,7 @@ public sealed class SalesPostingService : ISalesPostingService
             notFoundMessage: $"Sales invoice {salesInvoiceId} was not found.",
             statusSelector: x => x.Status,
             ensureDraftMessage: x => $"Sales invoice {x.SalesInvoiceId} is {x.Status} and cannot be posted.",
-            getLines: x => x.Lines.Select(l => new PostingLine(l.ItemId, l.WarehouseId, l.UomId, l.Qty + l.FreeQty, l.Qty, l.FreeQty)),
+            getLines: x => x.Lines.Select(l => new PostingLine(l.ItemId, l.WarehouseId, l.Qty + l.FreeQty, l.Qty, l.FreeQty)),
             setPosted: x => x.Status = SalesInvoiceStatus.Posted,
             setUpdated: x => x.UpdatedAt = DateTime.UtcNow,
             sourceDocType: DocumentTypes.SalesInvoice,
@@ -154,7 +151,7 @@ public sealed class SalesPostingService : ISalesPostingService
             notFoundMessage: $"Sales slip {salesSlipId} was not found.",
             statusSelector: x => x.Status,
             ensureDraftMessage: x => $"Sales slip {x.SalesSlipId} is {x.Status} and cannot be posted.",
-            getLines: x => x.Lines.Select(l => new PostingLine(l.ItemId, l.WarehouseId, l.UomId, l.Qty + l.FreeQty, l.Qty, l.FreeQty)),
+            getLines: x => x.Lines.Select(l => new PostingLine(l.ItemId, l.WarehouseId, l.Qty + l.FreeQty, l.Qty, l.FreeQty)),
             setPosted: x => x.Status = SalesSlipStatus.Posted,
             setUpdated: x => x.UpdatedAt = DateTime.UtcNow,
             sourceDocType: DocumentTypes.SalesSlip,
@@ -167,9 +164,7 @@ public sealed class SalesPostingService : ISalesPostingService
             notFoundMessage: $"Bundle sale {bundleSaleId} was not found.",
             statusSelector: x => x.Status,
             ensureDraftMessage: x => $"Bundle sale {x.BundleSaleId} is {x.Status} and cannot be posted.",
-            // Bundle lines are normalized to base UOM on save, so posting should consume the
-            // stored base quantity directly instead of converting again.
-            getLines: x => x.Lines.Where(l => l.IncludeInBundle).Select(l => new PostingLine(l.ItemId, l.WarehouseId, l.UomId, l.Qty, l.Qty, 0m)),
+            getLines: x => x.Lines.Where(l => l.IncludeInBundle).Select(l => new PostingLine(l.ItemId, l.WarehouseId, l.Qty, l.Qty, 0m)),
             setPosted: x => x.Status = BundleSaleStatus.Posted,
             setUpdated: x => x.UpdatedAt = DateTime.UtcNow,
             sourceDocType: DocumentTypes.BundleSale,
@@ -203,6 +198,8 @@ public sealed class SalesPostingService : ISalesPostingService
                 if (!await _sales.IsStockedItemAsync(line.ItemId, token))
                     continue;
 
+                // Line quantities are already a count of the item's base UOM — sales documents
+                // carry no unit of their own — so this is the quantity FIFO consumes verbatim.
                 var consumed = await _fifo.ConsumeAsync(line.ItemId, line.WarehouseId, null, line.Qty, token);
                 var cost = consumed.Count == 0 ? 0m : consumed.Sum(x => x.Qty * x.UnitCost) / consumed.Sum(x => x.Qty);
                 await _fifo.PostLedgerAsync(line.ItemId, line.WarehouseId, null, null, null, _currentUser.AuditUserId,
@@ -214,5 +211,5 @@ public sealed class SalesPostingService : ISalesPostingService
         }, ct);
     }
 
-    private sealed record PostingLine(int ItemId, int WarehouseId, int UomId, decimal Qty, decimal PaidQty, decimal FreeQty);
+    private sealed record PostingLine(int ItemId, int WarehouseId, decimal Qty, decimal PaidQty, decimal FreeQty);
 }

Backend/ERPCore/Services/SalesSlipService.cs

@@ -169,7 +169,7 @@ public sealed class SalesSlipService : ISalesSlipService
         foreach (var r in requests)
         {
             var item = await _items.Query().AsNoTracking().FirstAsync(x => x.ItemId == r.ItemId, ct);
-            await _sales.ValidateSalesLineAsync(headerWarehouseId, r.ItemId, r.UomId, r.WarehouseId, r.Qty, r.FreeQty, r.ParentLineId, ct);
+            await _sales.ValidateSalesLineAsync(headerWarehouseId, r.ItemId, r.WarehouseId, r.Qty, r.FreeQty, r.ParentLineId, ct);
             var resolved = await _sales.ResolveLinePriceAsync(r.ItemId, r.WarehouseId, r.UnitPrice, r.AllowManualPriceOverride, ct);
             var unitPrice = resolved.UnitPrice;
             var priceSource = resolved.PriceSource;
@@ -182,7 +182,6 @@ public sealed class SalesSlipService : ISalesSlipService
                 Description = item.Name,
                 Qty = r.Qty,
                 FreeQty = r.FreeQty,
-                UomId = r.UomId,
                 WarehouseId = r.WarehouseId,
                 UnitPrice = unitPrice,
                 BaseCost = unitPrice,
@@ -222,8 +221,10 @@ public sealed class SalesSlipService : ISalesSlipService
             .Where(i => i.ItemId == line.ItemId)
             .Select(i => new { i.ItemId, i.Sku, i.Name, i.BaseUomId })
             .FirstOrDefault();
-        var uom = line is null ? null : _uoms.Query().AsNoTracking()
-            .Where(u => u.UomId == line.UomId)
+        // The line carries no unit of its own — its quantity is a count of the item's base
+        // UOM — so the display name comes from there.
+        var uom = item is null ? null : _uoms.Query().AsNoTracking()
+            .Where(u => u.UomId == item.BaseUomId)
             .Select(u => new { u.UomId, u.Name })
             .FirstOrDefault();
         var warehouse = _warehouses.Query().AsNoTracking()
@@ -240,8 +241,7 @@ public sealed class SalesSlipService : ISalesSlipService
             line?.ItemId ?? 0,
             item?.Sku ?? $"SKU-{line?.ItemId ?? 0}",
             item?.Name ?? line?.Description ?? "—",
-            line?.UomId ?? 0,
-            uom?.Name ?? $"UOM {line?.UomId ?? 0}",
+            uom?.Name ?? $"UOM {item?.BaseUomId ?? 0}",
             line?.Qty ?? 0m,
             line?.FreeQty ?? 0m,
             line is null ? "No line" : $"Buy {line.Qty} Get {line.FreeQty}");
@@ -263,7 +263,7 @@ public sealed class SalesSlipService : ISalesSlipService
             x.CreatedAt,
             x.UpdatedAt,
             summary,
-            x.Lines.Select(l => new SalesSlipLineDto(l.SalesSlipLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.UomId, l.WarehouseId, l.UnitPrice, l.BaseCost, l.PriceSource, l.DiscountPct, l.DiscountAmount, l.DiscountMode, l.NetUnitPrice, l.LineTotal, l.TaxPct, l.TaxAmount, l.IsFreeIssue, l.ParentLineId)).ToList());
+            x.Lines.Select(l => new SalesSlipLineDto(l.SalesSlipLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.WarehouseId, l.UnitPrice, l.BaseCost, l.PriceSource, l.DiscountPct, l.DiscountAmount, l.DiscountMode, l.NetUnitPrice, l.LineTotal, l.TaxPct, l.TaxAmount, l.IsFreeIssue, l.ParentLineId)).ToList());
     }
 
     private SalesSlipDto Map(SalesSlip x) => _mapping.MapSlip(x);

Backend/ERPCore/Services/Stock/ItemMeasure.cs

@@ -0,0 +1,39 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+
+namespace ERPCore.Services.Stock;
+
+/// <summary>
+/// Content ↔ pack arithmetic (see <see cref="IItemMeasure"/>). Stateless and I/O-free:
+/// the content size is already on the <see cref="Item"/> every caller has loaded.
+/// </summary>
+public sealed class ItemMeasure : IItemMeasure
+{
+    public bool HasContent(Item item) => item.ContentBaseQty is > 0m;
+
+    public decimal ToPacks(Item item, decimal formulaQty, StageQtyUnit unit)
+    {
+        if (unit == StageQtyUnit.Pack) return formulaQty;
+
+        // Rounded to the quantity columns' (18,4) scale with the same mode as
+        // ProductionRunService.Scale, so what FIFO consumes and what the cost pool divides
+        // by are the same number to the last stored digit.
+        return Math.Round(formulaQty / RequireContent(item), 4, MidpointRounding.AwayFromZero);
+    }
+
+    public decimal FromPacks(Item item, decimal packs, StageQtyUnit unit)
+    {
+        if (unit == StageQtyUnit.Pack) return packs;
+
+        return Math.Round(packs * RequireContent(item), 4, MidpointRounding.AwayFromZero);
+    }
+
+    private static decimal RequireContent(Item item)
+        => item.ContentBaseQty is > 0m
+            ? item.ContentBaseQty.Value
+            : throw new DomainException(
+                ErrorCodes.Validation,
+                $"Item {item.ItemId} has no content size, so its quantity cannot be expressed in content units.", 422);
+}

Backend/ERPCore/Services/Stock/UomConverter.cs

@@ -1,38 +0,0 @@
-using ERPCore.Domain.Entities;
-using ERPCore.Repositories.Interfaces;
-using ERPCore.Services.Interfaces;
-using ERPCore.System.Errors;
-using Microsoft.EntityFrameworkCore;
-
-namespace ERPCore.Services.Stock;
-
-/// <summary>
-/// Shared UOM → base-UOM conversion (see <see cref="IUomConverter"/>). Behaviour is
-/// unchanged from the <c>GrnService.ToBaseAsync</c> it was extracted from, so the GRN
-/// receive path keeps costing exactly as before.
-/// </summary>
-public sealed class UomConverter : IUomConverter
-{
-    private readonly IRepository<UomConversion> _conversions;
-
-    public UomConverter(IRepository<UomConversion> conversions) => _conversions = conversions;
-
-    public async Task<(decimal QtyBase, decimal UnitCostBase)> ToBaseAsync(
-        Item item, int uomId, decimal qty, decimal unitCostPerUom, CancellationToken ct = default)
-    {
-        if (uomId == item.BaseUomId)
-            return (qty, unitCostPerUom);
-
-        var conv = await _conversions.Query().AsNoTracking()
-            .FirstOrDefaultAsync(c => c.ItemId == item.ItemId && c.FromUomId == uomId && c.ToUomId == item.BaseUomId, ct)
-            ?? throw new DomainException(ErrorCodes.Validation,
-                $"No UOM conversion from {uomId} to base UOM {item.BaseUomId} for item {item.ItemId}.", 422);
-
-        // Quantity scales up by the factor, so the per-unit cost scales down by it —
-        // total value is preserved.
-        return (qty * conv.Factor, unitCostPerUom / conv.Factor);
-    }
-
-    public async Task<decimal> ToBaseQtyAsync(Item item, int uomId, decimal qty, CancellationToken ct = default)
-        => (await ToBaseAsync(item, uomId, qty, 0m, ct)).QtyBase;
-}

Backend/ERPCore/System/Errors/ErrorCodes.cs

@@ -56,6 +56,7 @@ public static class ErrorCodes
     public const string GraphDisconnected = "GRAPH_DISCONNECTED";
     public const string GraphInputSourceInvalid = "GRAPH_INPUT_SOURCE_INVALID";
     public const string TerminalOutputItemRequired = "TERMINAL_OUTPUT_ITEM_REQUIRED";
+    public const string WipUnitRequired = "WIP_UNIT_REQUIRED";
     public const string StageNotReady = "STAGE_NOT_READY";
     public const string StageNotInProgress = "STAGE_NOT_IN_PROGRESS";
     public const string StageNotDone = "STAGE_NOT_DONE";

Backend/PROGRESS.md

@@ -4,6 +4,37 @@ Legend: `[ ]` not started · `[~]` in progress · `[x]` done
 Spec: `docs/10-BACKEND-PHASE1.md` (model + rules) · `docs/11-BACKEND-PHASE1.md` (API)
 Convention: `docs/01-DOC-GUIDE.md §6`. Update this file in the **same commit** as the code. When ticking `[x]`, append a short note + any deviation.
 
+## UOM re-model (2026-08-11) — supersedes every "UOM conversion" note below
+
+Per-item UOM conversion is **gone**. Entries further down this file that describe
+`IUomConverter`, `PUT /items/{id}/uom-conversions`, `uom_conversions`, or a line-level
+`uomId` are historical and no longer describe the code.
+
+What replaced it:
+
+- **One unit per item.** `Item.BaseUomId` is the pack an item is stocked and counted in, and
+  every quantity in the system — stock layers, ledger rows, GRN/PO/sales/bundle/transfer lines
+  — is a plain count of it. A differently sized pack is a different item. `UomId` was dropped
+  from all six document-line entities; `Uom` itself survives as the lookup.
+- **Optional content size on `Item`**: `ContentQty` + `ContentUnit` as entered (`Ml|L|G|Kg`),
+  normalised on write into `ContentBaseQty` + `ContentBaseUnit` (only ever `Ml` or `G`, L/Kg
+  ×1000). All four null ⇒ nothing measurable to hold. `ItemContent` is the pure normaliser.
+- **Production is the only content consumer.** `StageInput.QtyUnit` (`Pack|Content`) says what
+  `QtyPerBatch` means; `IItemMeasure` divides a `Content` quantity by the item's content size
+  to get packs. **Fractional packs are legal** — 300 ml of a 500 ml bottle consumes 0.6000.
+  Outputs are always pack counts, so scrap stays in whole broken bottles.
+- **WIP keeps a label.** `StageOutput.UomId`/`RunStageOutput.UomId` are now nullable and
+  required *only* when `ItemId` is null (`422 WIP_UNIT_REQUIRED`), since an item-bearing output
+  takes its unit from the item. WIP never touches stock, so the label is never converted.
+- **Two live defects fixed as a consequence.** `SalesPostingService` injected `IUomConverter`
+  and never called it, so a sales line in a non-base UOM consumed the wrong quantity outright;
+  `GrnService` accrued `poLine.QtyReceived += line.Qty` and range-checked over-receipt across
+  the same unit boundary. Both are now like-for-like by construction.
+- **`BaseUomId` is frozen once an item has stock history** (`409 MASTER_IN_USE`) — it is the
+  sole meaning of every recorded quantity, so changing it would silently reinterpret all of it.
+- Smoke: `m4b_uom_conversion.py` deleted; `m4c_content_units.py` added (whole packs, fractional
+  packs, and the contentless-item guard).
+
 ## 8. Sales
 - [x] Sales bootstrap data seeded locally for development: warehouses, UOMs, categories, items, customers, current-year `SI`/`SSL` sequences, plus sample invoice/slip headers and lines. Existing data is preserved.
 - [x] Sales report API consolidated into `GET /api/v1/reports/sales` (catalog), `GET /api/v1/reports/sales/{reportId}` (report metadata), and `POST /api/v1/reports/sales/query` (filtered data). Legacy per-report GET routes removed; invalid report/filter combinations now fail validation.

Backend/smoke/m2_templates.py

@@ -44,25 +44,26 @@ def diamond(raw_item, finished_item, uom):
                 "estimatedMinutes": 60, "posX": 80, "posY": 120,
                 "fieldDefs": [{"key": "moisture_ok", "label": "Moisture check",
                                "type": "Checkbox", "required": True}],
-                "inputs": [{"source": "Stock", "itemId": raw_item, "uomId": uom, "qtyPerBatch": 8}],
+                "inputs": [{"source": "Stock", "itemId": raw_item, "qtyPerBatch": 8}],
                 "outputs": [{"key": "tmp-frame", "name": "Frame set", "uomId": uom, "qtyPerBatch": 1}],
             },
             {
                 "key": "tmp-prep", "name": "Prep cushions", "roleLabel": "Upholstery",
                 "estimatedMinutes": 30, "posX": 80, "posY": 320, "fieldDefs": [],
-                "inputs": [{"source": "Stock", "itemId": raw_item, "uomId": uom, "qtyPerBatch": 2}],
+                "inputs": [{"source": "Stock", "itemId": raw_item, "qtyPerBatch": 2}],
                 "outputs": [{"key": "tmp-cushion", "name": "Cushion set", "uomId": uom, "qtyPerBatch": 1}],
             },
             {
                 "key": "tmp-asm", "name": "Assemble & QA", "roleLabel": "QA",
                 "estimatedMinutes": 45, "posX": 560, "posY": 200, "fieldDefs": [],
                 "inputs": [
-                    {"source": "Upstream", "fromOutputKey": "tmp-frame", "uomId": uom, "qtyPerBatch": 1},
-                    {"source": "Upstream", "fromOutputKey": "tmp-cushion", "uomId": uom, "qtyPerBatch": 1},
+                    {"source": "Upstream", "fromOutputKey": "tmp-frame", "qtyPerBatch": 1},
+                    {"source": "Upstream", "fromOutputKey": "tmp-cushion", "qtyPerBatch": 1},
                 ],
-                # Terminal output must name the finished item (FR-MFG-05).
+                # Terminal output must name the finished item (FR-MFG-05), and takes its unit
+                # from that item — sending a uomId as well is rejected.
                 "outputs": [{"key": "tmp-chair", "name": "Chair", "itemId": finished_item,
-                             "uomId": uom, "qtyPerBatch": 1}],
+                             "qtyPerBatch": 1}],
             },
         ],
         "edges": [
@@ -243,7 +244,7 @@ def main():
     grandparent["stages"].append({
         "key": "tmp-mid", "name": "Middle", "estimatedMinutes": 5, "posX": 320, "posY": 120,
         "fieldDefs": [],
-        "inputs": [{"source": "Upstream", "fromOutputKey": cut_output_key, "uomId": uom, "qtyPerBatch": 1}],
+        "inputs": [{"source": "Upstream", "fromOutputKey": cut_output_key, "qtyPerBatch": 1}],
         "outputs": [{"key": "tmp-mid-out", "name": "Mid part", "uomId": uom, "qtyPerBatch": 1}],
     })
     grandparent["edges"] = [e for e in grandparent["edges"] if e["parentKey"] != cut_key]
@@ -320,9 +321,11 @@ def rebuild_from_get(g: dict) -> dict:
                 "inputs": [
                     {"source": i["source"], "itemId": i.get("itemId"),
                      "fromOutputKey": i.get("fromOutputKey"),
-                     "uomId": i["uomId"], "qtyPerBatch": i["qtyPerBatch"]}
+                     "qtyUnit": i["qtyUnit"], "qtyPerBatch": i["qtyPerBatch"]}
                     for i in s["inputs"]
                 ],
+                # uomId round-trips as null on an item-bearing output and as the WIP label
+                # otherwise, so echoing it back verbatim is correct either way.
                 "outputs": [
                     {"key": o["key"], "itemId": o.get("itemId"), "name": o["name"],
                      "uomId": o["uomId"], "qtyPerBatch": o["qtyPerBatch"]}

Backend/smoke/m3_runs.py

@@ -147,7 +147,7 @@ def main():
              "estimatedMinutes": s["estimatedMinutes"], "posX": s["posX"], "posY": s["posY"],
              "fieldDefs": s["fieldDefs"],
              "inputs": [{"source": i["source"], "itemId": i.get("itemId"),
-                         "fromOutputKey": i.get("fromOutputKey"), "uomId": i["uomId"],
+                         "fromOutputKey": i.get("fromOutputKey"), "qtyUnit": i["qtyUnit"],
                          "qtyPerBatch": i["qtyPerBatch"]} for i in s["inputs"]],
              "outputs": [{"key": o["key"], "itemId": o.get("itemId"), "name": o["name"],
                           "uomId": o["uomId"], "qtyPerBatch": o["qtyPerBatch"]} for o in s["outputs"]]}

Backend/smoke/m4_stage_actions.py

@@ -65,16 +65,16 @@ def ledger_rows(c, run_id, source):
     return rows
 
 
-def seed_stock(c, wh, raw, pack, uom):
+def seed_stock(c, wh, raw, pack):
     """
     Seed on-hand at explicit unit costs. Two raw layers at different costs mean the FIFO
     consumption at start has to weight them, so `consumedValue` is a real number the
     assertions can check rather than the 0.00 a positive adjustment would produce.
     """
     seed_costed_stock(c, wh, [
-        (raw, uom, SEED_RAW * 0.4, RAW_COST_1),
-        (raw, uom, SEED_RAW * 0.6, RAW_COST_2),
-        (pack, uom, SEED_PACK, PACK_COST),
+        (raw, SEED_RAW * 0.4, RAW_COST_1),
+        (raw, SEED_RAW * 0.6, RAW_COST_2),
+        (pack, SEED_PACK, PACK_COST),
     ])
 
 
@@ -90,7 +90,7 @@ def build_template(c, raw, pack, finished, uom):
                 "estimatedMinutes": 60, "posX": 80, "posY": 100,
                 "fieldDefs": [{"key": "moisture_ok", "label": "Moisture check",
                                "type": "Checkbox", "required": True}],
-                "inputs": [{"source": "Stock", "itemId": raw, "uomId": uom, "qtyPerBatch": 8}],
+                "inputs": [{"source": "Stock", "itemId": raw, "qtyPerBatch": 8}],
                 "outputs": [{"key": "tmp-frame", "name": "Frame", "uomId": uom, "qtyPerBatch": 1}],
             },
             {
@@ -99,11 +99,11 @@ def build_template(c, raw, pack, finished, uom):
                 "key": "tmp-asm", "name": "Assemble", "roleLabel": "QA",
                 "estimatedMinutes": 45, "posX": 520, "posY": 100, "fieldDefs": [],
                 "inputs": [
-                    {"source": "Upstream", "fromOutputKey": "tmp-frame", "uomId": uom, "qtyPerBatch": 1},
-                    {"source": "Stock", "itemId": pack, "uomId": uom, "qtyPerBatch": 2},
+                    {"source": "Upstream", "fromOutputKey": "tmp-frame", "qtyPerBatch": 1},
+                    {"source": "Stock", "itemId": pack, "qtyPerBatch": 2},
                 ],
                 "outputs": [{"key": "tmp-chair", "name": "Chair", "itemId": finished,
-                             "uomId": uom, "qtyPerBatch": 1}],
+                             "qtyPerBatch": 1}],
             },
         ],
         "edges": [{"parentKey": "tmp-cut", "childKey": "tmp-asm"}],
@@ -141,7 +141,7 @@ def main():
     drained = drain_stock(c, wh)
     if drained:
         print(f"drained {len(drained)} leftover item(s) from a previous execution")
-    seed_stock(c, wh, raw, pack, uom)
+    seed_stock(c, wh, raw, pack)
     raw_before = on_hand(c, raw, wh)
     pack_before = on_hand(c, pack, wh)
     print(f"warehouse={wh} raw={raw}(on-hand {raw_before}) pack={pack}(on-hand {pack_before}) finished={finished}")

Backend/smoke/m4b_uom_conversion.py

@@ -1,170 +0,0 @@
-"""M4b smoke test — UOM conversion on production stock inputs.
-
-This covers the single highest-risk correctness gap in the manufacturing phase.
-`IFifoCostingService.ConsumeAsync` works exclusively in an item's BASE UOM, while
-`STAGE_INPUT.uom_id` is a free FK — docs/30 never mentions conversion at all. Without the
-shared `IUomConverter` (extracted from `GrnService.ToBaseAsync`), a stage input declared in
-"box of 12" would consume 1 base unit instead of 12 and silently mis-cost the whole run.
-
-The dev database has no `uom_conversions` rows at all, so the non-base path was previously
-unexercised by any data. This script creates a real conversion and proves:
-
-  * a stage input in a non-base UOM consumes qtyPerBatch x scaleFactor x factor base units
-  * the ledger records the BASE quantity, not the declared one
-  * an input in a UOM with no conversion defined is refused with 422 rather than mis-consumed
-
-    python Backend/smoke/m4b_uom_conversion.py
-"""
-
-from __future__ import annotations
-
-import sys
-
-from smoke_common import bootstrap
-
-WAREHOUSE_CODE = "SMOKE-PRD"
-TEMPLATE_CODE = "SMOKE-PT-M4B"
-FACTOR = 12          # 1 case = 12 base units
-QTY_PER_BATCH = 3    # cases per batch
-TARGET_QTY = 10      # -> scale 10 -> 30 cases -> 360 base units
-SEED = 5000
-
-
-def main():
-    c, chk, args = bootstrap(__doc__)
-    print(f"API {args.api}")
-
-    # --- fixtures ---------------------------------------------------------
-    wh = next((w["warehouseId"] for w in c.get(f"/warehouses?q={WAREHOUSE_CODE}&pageSize=50").body["items"]
-               if w["code"] == WAREHOUSE_CODE), None)
-    if wh is None:
-        sys.exit("FATAL: run m4_stage_actions.py first (it creates the SMOKE-PRD warehouse).")
-
-    items = c.get("/items?pageSize=5&status=Active").body["items"]
-    raw, finished = items[0], items[1]
-    base_uom = raw["baseUomId"]
-
-    uoms = c.get("/uoms?pageSize=50").body["items"]
-    case_uom = next((u["uomId"] for u in uoms if u["uomId"] != base_uom), None)
-    if case_uom is None:
-        sys.exit("FATAL: need at least 2 UOMs to test conversion.")
-    print(f"item={raw['itemId']} baseUom={base_uom} caseUom={case_uom} factor={FACTOR}")
-
-    # --- define the conversion -------------------------------------------
-    chk.section("1. Define a non-base UOM conversion for the item")
-    conv = c.put(f"/items/{raw['itemId']}/uom-conversions",
-                 {"conversions": [{"fromUom": case_uom, "toUom": base_uom, "factor": FACTOR}]})
-    chk.status("PUT /items/{id}/uom-conversions", conv, 200)
-    if conv.status != 200:
-        return chk.finish("M4b")
-    chk.check("conversion stored", any(float(x["factor"]) == FACTOR for x in conv.body["conversions"]), True)
-
-    reason = c.get("/reason-codes?context=Adjustment&pageSize=5").body["items"][0]["reasonCodeId"]
-    c.post("/stock-adjustments", {"warehouseId": wh, "reasonCodeId": reason,
-                                  "lines": [{"itemId": raw["itemId"], "qtyDelta": SEED}]})
-    before = float(c.get(f"/stock/on-hand?itemId={raw['itemId']}&warehouseId={wh}").body["onHand"])
-    print(f"on-hand before: {before}")
-
-    # --- template whose stock input is declared in CASES ------------------
-    chk.section("2. A stage input declared in the non-base UOM")
-    payload = {
-        "code": TEMPLATE_CODE, "name": "Smoke M4b conversion line",
-        "stages": [{
-            "key": "tmp-only", "name": "Pack", "estimatedMinutes": 10,
-            "posX": 0, "posY": 0, "fieldDefs": [],
-            # Declared in cases, not base units.
-            "inputs": [{"source": "Stock", "itemId": raw["itemId"],
-                        "uomId": case_uom, "qtyPerBatch": QTY_PER_BATCH}],
-            "outputs": [{"key": "tmp-out", "name": "Packed", "itemId": finished["itemId"],
-                         "uomId": base_uom, "qtyPerBatch": 1}],
-        }],
-        "edges": [],
-    }
-
-    existing = next((t for t in c.get(f"/production-templates?q={TEMPLATE_CODE}").body["items"]
-                     if t["code"] == TEMPLATE_CODE), None)
-    if existing:
-        head = c.get(f"/production-templates/{existing['templateId']}")
-        res = c.put(f"/production-templates/{existing['templateId']}", payload, if_match=head.etag)
-        tid = existing["templateId"] if res.status in (200, 409) else None
-        chk.check("template ready", tid is not None, True)
-    else:
-        res = c.post("/production-templates", payload)
-        chk.status("create single-stage template", res, 201)
-        tid = res.body["templateId"] if res.status == 201 else None
-
-    if tid is None:
-        return chk.finish("M4b")
-
-    # A lone stage is both the entry and the terminal — worth asserting explicitly.
-    run = c.post("/production-runs", {"templateId": tid, "targetQty": TARGET_QTY, "warehouseId": wh})
-    chk.status("create the run", run, 201)
-    if run.status != 201:
-        return chk.finish("M4b")
-
-    stage = run.body["stages"][0]
-    chk.check("single stage is both entry and terminal",
-              (stage["isEntry"], stage["isTerminal"]), (True, True))
-    chk.check("single stage starts Ready", stage["status"], "Ready")
-    chk.check("plannedQty stays in the DECLARED uom (3 x 10 cases)",
-              float(stage["inputs"][0]["plannedQty"]), float(QTY_PER_BATCH * TARGET_QTY))
-
-    # --- the actual conversion assertion ---------------------------------
-    chk.section("3. Consumption converts cases to base units")
-    expected_base = QTY_PER_BATCH * TARGET_QTY * FACTOR   # 3 x 10 x 12 = 360
-    started = c.post(f"/production-runs/{run.body['runId']}/stages/{stage['runStageId']}/start")
-    chk.status("start the stage", started, 200)
-    if started.status != 200:
-        return chk.finish("M4b")
-
-    con = started.body["consumed"][0]
-    chk.check(f"consumed {expected_base} BASE units, not {QTY_PER_BATCH * TARGET_QTY}",
-              float(con["qty"]), float(expected_base))
-    chk.check("on-hand fell by the base quantity",
-              float(c.get(f"/stock/on-hand?itemId={raw['itemId']}&warehouseId={wh}").body["onHand"]),
-              before - expected_base)
-
-    rows = c.get(f"/stock/ledger?sourceDocType=PRDI&sourceDocId={run.body['runId']}&pageSize=50").body["items"]
-    chk.check("one PRDI row", len(rows), 1)
-    if rows:
-        chk.check("ledger qtyBase is the converted quantity", float(rows[0]["qtyBase"]), float(expected_base))
-
-    detail = c.get(f"/production-runs/{run.body['runId']}").body
-    chk.check("consumedQty stored in base units",
-              float(detail["stages"][0]["inputs"][0]["consumedQty"]), float(expected_base))
-
-    # --- missing conversion is refused, not silently mis-consumed --------
-    chk.section("4. An undefined conversion is refused (422), never assumed 1:1")
-    third_uom = next((u["uomId"] for u in c.get("/uoms?pageSize=50").body["items"]
-                      if u["uomId"] not in (base_uom, case_uom)), None)
-    if third_uom is None:
-        chk.check("skipped: need a third UOM", True, True)
-    else:
-        bad = dict(payload)
-        bad["code"] = TEMPLATE_CODE + "-BAD"
-        bad["stages"] = [dict(payload["stages"][0])]
-        bad["stages"][0] = {**payload["stages"][0],
-                            "inputs": [{"source": "Stock", "itemId": raw["itemId"],
-                                        "uomId": third_uom, "qtyPerBatch": 1}]}
-        made = c.post("/production-templates", bad)
-        if made.status != 201:
-            head = c.get(f"/production-templates?q={TEMPLATE_CODE}-BAD")
-            tid2 = next((t["templateId"] for t in head.body["items"]
-                         if t["code"] == TEMPLATE_CODE + "-BAD"), None)
-        else:
-            tid2 = made.body["templateId"]
-
-        if tid2:
-            run2 = c.post("/production-runs", {"templateId": tid2, "targetQty": 1, "warehouseId": wh})
-            if run2.status == 201:
-                s2 = run2.body["stages"][0]["runStageId"]
-                chk.status("start a stage whose input UOM has no conversion",
-                           c.post(f"/production-runs/{run2.body['runId']}/stages/{s2}/start"), 422)
-            else:
-                chk.check("could create the second run", run2.status, 201)
-
-    return chk.finish("M4b")
-
-
-if __name__ == "__main__":
-    sys.exit(main())

Backend/smoke/m4c_content_units.py

@@ -0,0 +1,182 @@
+"""M4c smoke test — production stage inputs expressed in content units (FR-MFG-04).
+
+Replaces m4b_uom_conversion.py, which tested the per-item UOM conversion table that no longer
+exists. Stock is now always a count of the item's base UOM (a bottle, a packet), and the only
+place another unit appears is a production formula: a stage input may be written as an amount
+of the item's *content* (ml or g), which the server divides by the item's content size to get
+the pack count FIFO actually consumes.
+
+What this pins down, none of which any other script covers:
+
+  * 2000 ml against a 500 ml bottle consumes exactly 4.0000 bottles, and the ledger agrees;
+  * 300 ml against the same item consumes 0.6000 — **fractional packs are legal**, which is
+    the whole reason the quantity columns are (18,4);
+  * a Content input on an item with no content size is refused at template save (422), not
+    silently treated as packs at stage start.
+
+Self-contained: creates its own item, warehouse, template and runs.
+
+    python Backend/smoke/m4c_content_units.py
+"""
+
+from __future__ import annotations
+
+import sys
+
+from smoke_common import bootstrap, drain_stock, seed_costed_stock
+
+WAREHOUSE_CODE = "SMOKE-CONTENT"
+TEMPLATE_CODE = "SMOKE-PT-M4C"
+SKU = "SMOKE-BOTTLE-500ML"
+PLAIN_SKU = "SMOKE-NO-CONTENT"
+
+CONTENT_QTY = 500          # ml held by one bottle
+SEED_BOTTLES = 100
+UNIT_COST = 3.0
+
+
+def ensure_warehouse(c):
+    for w in c.get(f"/warehouses?q={WAREHOUSE_CODE}&pageSize=50").body["items"]:
+        if w["code"] == WAREHOUSE_CODE:
+            return w["warehouseId"]
+    created = c.post("/warehouses", {"code": WAREHOUSE_CODE, "name": "Content-unit smoke warehouse"})
+    if created.status != 201:
+        sys.exit(f"FATAL: could not create the smoke warehouse: {created.status} {created.body}")
+    return created.body["warehouseId"]
+
+
+def ensure_item(c, sku, name, content_qty, content_unit):
+    """Find-or-create; content fields are only sent when the item is meant to have them."""
+    for i in c.get(f"/items?q={sku}&pageSize=50").body["items"]:
+        if i["sku"] == sku:
+            return i
+
+    category = c.get("/categories?pageSize=1").body["items"]
+    uoms = c.get("/uoms?pageSize=1").body["items"]
+    if not category or not uoms:
+        sys.exit("FATAL: need at least one category and one UOM seeded.")
+
+    body = {
+        "sku": sku, "name": name,
+        "categoryId": category[0]["categoryId"],
+        "baseUomId": uoms[0]["uomId"],
+        "stockNature": "Stocked", "trackingMode": "None",
+    }
+    if content_qty is not None:
+        body["contentQty"] = content_qty
+        body["contentUnit"] = content_unit
+
+    created = c.post("/items", body)
+    if created.status != 201:
+        sys.exit(f"FATAL: could not create item {sku}: {created.status} {created.body}")
+    return created.body
+
+
+def save_template(c, raw_item, finished_item, qty_per_batch, qty_unit):
+    payload = {
+        "code": TEMPLATE_CODE, "name": "Content-unit smoke line",
+        "stages": [{
+            "key": "tmp-mix", "name": "Mix", "estimatedMinutes": 5, "posX": 0, "posY": 0,
+            "fieldDefs": [],
+            "inputs": [{"source": "Stock", "itemId": raw_item,
+                        "qtyUnit": qty_unit, "qtyPerBatch": qty_per_batch}],
+            "outputs": [{"key": "tmp-out", "name": "Mixed", "itemId": finished_item,
+                         "qtyPerBatch": 1}],
+        }],
+        "edges": [],
+    }
+    existing = next((t for t in c.get(f"/production-templates?q={TEMPLATE_CODE}").body["items"]
+                     if t["code"] == TEMPLATE_CODE), None)
+    if existing:
+        head = c.get(f"/production-templates/{existing['templateId']}")
+        return c.put(f"/production-templates/{existing['templateId']}", payload, if_match=head.etag)
+    return c.post("/production-templates", payload)
+
+
+def saved_ok(chk, label, response):
+    """Template save is find-or-create, so a POST gives 201 and a PUT gives 200."""
+    ok = chk.check(f"{label} -> 200/201", response.status in (200, 201), True)
+    if not ok:
+        print(f"          server said: {response.body}")
+    return ok
+
+
+def consume_once(c, chk, tid, wh, target_qty, label, expected_packs):
+    """
+    Create a run, start its only stage, and assert what FIFO actually took.
+
+    `expected_packs` is compared against the RAW formula quantity resolved to packs, which is
+    only valid while the run scale factor is 1. Run creation computes
+    `ratio = targetQty / terminalOutput.qtyPerBatch` and pre-scales every planned quantity, so
+    this holds because `save_template` pins the terminal output to `qtyPerBatch: 1` and every
+    caller here passes `target_qty=1`. Change either and these numbers move by that ratio.
+    """
+    created = c.post("/production-runs", {"templateId": tid, "targetQty": target_qty, "warehouseId": wh})
+    if not chk.status(f"{label}: create the run", created, 201):
+        return
+    run = created.body
+    stage_id = run["stages"][0]["runStageId"]
+
+    started = c.post(f"/production-runs/{run['runId']}/stages/{stage_id}/start",
+                     idempotency_key=f"m4c-{run['runId']}")
+    if not chk.status(f"{label}: POST .../start", started, 200):
+        return
+
+    consumed = started.body["consumed"]
+    if not chk.check(f"{label}: exactly one input consumed", len(consumed), 1):
+        return
+    chk.check(f"{label}: consumed {expected_packs} base units",
+              round(float(consumed[0]["qty"]), 4), expected_packs)
+
+    rows = c.get(f"/stock/ledger?sourceDocType=PRDI&sourceDocId={run['runId']}&pageSize=50").body["items"]
+    chk.check(f"{label}: one PRDI ledger row", len(rows), 1)
+    if rows:
+        chk.check(f"{label}: ledger qtyBase matches the consumption",
+                  round(abs(float(rows[0]["qtyBase"])), 4), expected_packs)
+
+
+def main():
+    c, chk, args = bootstrap(__doc__)
+    print(f"API {args.api}")
+
+    bottle = ensure_item(c, SKU, "Smoke syrup 500ml bottle", CONTENT_QTY, "Ml")
+    plain = ensure_item(c, PLAIN_SKU, "Smoke item with no content", None, None)
+    finished = c.get("/items?pageSize=5&status=Active").body["items"][0]
+    print(f"bottle={bottle['itemId']} contentBaseQty={bottle.get('contentBaseQty')} "
+          f"plain={plain['itemId']} finished={finished['itemId']}")
+
+    chk.section("0. Content size normalises to a base unit on the item")
+    chk.check("contentBaseQty is the entered ml", float(bottle["contentBaseQty"]), float(CONTENT_QTY))
+    chk.check("contentBaseUnit is Ml", bottle["contentBaseUnit"], "Ml")
+
+    wh = ensure_warehouse(c)
+    drain_stock(c, wh)
+    seed_costed_stock(c, wh, [(bottle["itemId"], SEED_BOTTLES, UNIT_COST)])
+
+    # ------------------------------------------------- whole packs out of content units
+    chk.section("1. A content quantity resolves to whole packs (2000 ml / 500 ml = 4)")
+    saved = save_template(c, bottle["itemId"], finished["itemId"], 2000, "Content")
+    if saved_ok(chk, "save the Content template", saved):
+        consume_once(c, chk, saved.body["templateId"], wh, 1, "2000 ml", 4.0)
+
+    # --------------------------------------------------------------- fractional packs
+    chk.section("2. A content quantity below one pack consumes a FRACTION of one (300 ml = 0.6)")
+    saved = save_template(c, bottle["itemId"], finished["itemId"], 300, "Content")
+    if saved_ok(chk, "save the fractional Content template", saved):
+        consume_once(c, chk, saved.body["templateId"], wh, 1, "300 ml", 0.6)
+
+    # ------------------------------------------------------------------ the guard rail
+    chk.section("3. Content units are refused on an item that has no content size")
+    refused = save_template(c, plain["itemId"], finished["itemId"], 100, "Content")
+    chk.status("Content input on a contentless item", refused, 422)
+
+    chk.section("4. The same item still works when the formula is written in packs")
+    saved = save_template(c, bottle["itemId"], finished["itemId"], 3, "Pack")
+    if saved_ok(chk, "save the Pack template", saved):
+        consume_once(c, chk, saved.body["templateId"], wh, 1, "3 bottles", 3.0)
+
+    return chk.finish("M4c")
+
+
+if __name__ == "__main__":
+    sys.exit(main())

Backend/smoke/m5_receipt.py

@@ -157,18 +157,18 @@ def main():
                    if i["itemId"] == raw)
     finished_b = state["finishedItemId"]
 
-    # A fresh single-stage template: base-UOM input so no conversion muddies the arithmetic,
-    # qtyPerBatch 3.5 so the consumed quantity is NOT a multiple of the target (which is what
+    # A fresh single-stage template: a pack-counted input, so no content division muddies
+    # the arithmetic; qtyPerBatch 3.5 so consumed is NOT a multiple of the target (which is what
     # forces pool / goodQty to repeat).
     payload_b = {
         "code": BIG_TEMPLATE_CODE, "name": "Smoke M5 rounding line",
         "stages": [{
             "key": "tmp-b", "name": "Mix", "estimatedMinutes": 5, "posX": 0, "posY": 0,
             "fieldDefs": [],
-            "inputs": [{"source": "Stock", "itemId": raw, "uomId": raw_uom,
+            "inputs": [{"source": "Stock", "itemId": raw,
                         "qtyPerBatch": BIG_QTY_PER_BATCH}],
             "outputs": [{"key": "tmp-bo", "name": "Mixed", "itemId": finished_b,
-                         "uomId": raw_uom, "qtyPerBatch": 1}],
+                         "qtyPerBatch": 1}],
         }],
         "edges": [],
     }
@@ -190,7 +190,7 @@ def main():
         # and the pool would not match the figures this section reasons about — the assertions
         # would still "pass" while testing something else entirely.
         drain_stock(c, wh)
-        seed_costed_stock(c, wh, [(raw, raw_uom, 5000, BIG_UNIT_COST)])
+        seed_costed_stock(c, wh, [(raw, 5000, BIG_UNIT_COST)])
 
         big = c.post("/production-runs", {"templateId": tid, "targetQty": BIG_TARGET, "warehouseId": wh})
         if big.status != 201:
@@ -243,7 +243,7 @@ def main():
                 "key": "tmp-one", "name": "Make", "estimatedMinutes": 1, "posX": 0, "posY": 0,
                 "fieldDefs": [], "inputs": [],
                 "outputs": [{"key": "tmp-o", "name": "Tracked", "itemId": tracked["itemId"],
-                             "uomId": tracked["baseUomId"], "qtyPerBatch": 1}],
+                             "qtyPerBatch": 1}],
             }],
             "edges": [],
         }

Backend/smoke/m6_m7_leftover_rework_cancel.py

@@ -54,13 +54,13 @@ def ensure_template(c, raw, finished, uom):
         "stages": [
             {"key": "tmp-cut", "name": "Cut", "estimatedMinutes": 10, "posX": 0, "posY": 0,
              "fieldDefs": [],
-             "inputs": [{"source": "Stock", "itemId": raw, "uomId": uom, "qtyPerBatch": RAW_QPB}],
+             "inputs": [{"source": "Stock", "itemId": raw, "qtyPerBatch": RAW_QPB}],
              "outputs": [{"key": "tmp-f", "name": "Frame", "uomId": uom, "qtyPerBatch": 1}]},
             {"key": "tmp-asm", "name": "Assemble", "estimatedMinutes": 10, "posX": 400, "posY": 0,
              "fieldDefs": [],
-             "inputs": [{"source": "Upstream", "fromOutputKey": "tmp-f", "uomId": uom, "qtyPerBatch": 1}],
+             "inputs": [{"source": "Upstream", "fromOutputKey": "tmp-f", "qtyPerBatch": 1}],
              "outputs": [{"key": "tmp-c", "name": "Chair", "itemId": finished,
-                          "uomId": uom, "qtyPerBatch": 1}]},
+                          "qtyPerBatch": 1}]},
         ],
         "edges": [{"parentKey": "tmp-cut", "childKey": "tmp-asm"}],
     }
@@ -101,7 +101,7 @@ def main():
     uom = items[0]["baseUomId"]
 
     drain_stock(c, wh)
-    seed_costed_stock(c, wh, [(raw, uom, SEED, UNIT_COST)])
+    seed_costed_stock(c, wh, [(raw, SEED, UNIT_COST)])
     tid = ensure_template(c, raw, finished, uom)
     consumed_units = RAW_QPB * TARGET      # 50
     consumed_value = consumed_units * UNIT_COST   # 150.00

Backend/smoke/run_all.py

@@ -22,7 +22,7 @@ SCRIPTS = [
     ("M2  templates + graph validation", "m2_templates.py"),
     ("M3  run creation / board / quantities", "m3_runs.py"),
     ("M4  stage start / complete / approve / transfer", "m4_stage_actions.py"),
-    ("M4b UOM conversion on stock inputs", "m4b_uom_conversion.py"),
+    ("M4c content-unit stage inputs + fractional packs", "m4c_content_units.py"),
     ("M5  terminal receipt + cost pool", "m5_receipt.py"),
     ("M6+M7 leftover / rework / cancel", "m6_m7_leftover_rework_cancel.py"),
 ]

Backend/smoke/smoke_common.py

@@ -240,15 +240,16 @@ def seed_costed_stock(c, warehouse_id: int, lines, vendor_id: int | None = None)
     """
     Create on-hand at explicit unit costs via a direct GRN + confirm.
 
-    `lines` is an iterable of (item_id, uom_id, qty, unit_cost).
+    `lines` is an iterable of (item_id, qty, unit_cost). Quantities are counts of the item's
+    base UOM — document lines carry no unit of their own.
     """
     vendor_id = vendor_id or ensure_vendor(c)
     grn = c.post("/grns", {
         "vendorId": vendor_id,
         "warehouseId": warehouse_id,
         "lines": [
-            {"itemId": i, "uomId": u, "qty": q, "unitCost": cost, "discountPct": 0, "vatPct": 0}
-            for (i, u, q, cost) in lines
+            {"itemId": i, "qty": q, "unitCost": cost, "discountPct": 0, "vatPct": 0}
+            for (i, q, cost) in lines
         ],
     })
     if grn.status != 201:

Frontend/erp-system/app/dashboard/procurement/purchase-orders/[id]/page.tsx

@@ -8,6 +8,7 @@ import { isPoEditable, purchaseOrdersApi } from "@/lib/api/purchase-orders"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { vendorsApi } from "@/lib/api/vendors"
 import { errorMessage } from "@/lib/error-map"
 import { validatePoLine } from "@/lib/validations/procurement"
@@ -28,7 +29,6 @@ interface DraftLine {
   key: string
   poLineId: number | null
   itemId: number | null
-  uomId: number | null
   warehouseId: number | null
   qty: string
   unitPrice: string
@@ -72,7 +72,6 @@ export default function PurchaseOrderDetailPage() {
       key: newKey(),
       poLineId: l.poLineId,
       itemId: l.itemId,
-      uomId: l.uomId,
       warehouseId: l.warehouseId,
       qty: String(l.qty),
       unitPrice: String(l.unitPrice),
@@ -111,9 +110,6 @@ export default function PurchaseOrderDetailPage() {
   function itemFor(itemId: number | null) {
     return items.find((i) => i.itemId === itemId) ?? null
   }
-  function uomName(uomId: number) {
-    return uoms.find((u) => u.uomId === uomId)?.name ?? `#${uomId}`
-  }
   function warehouseCode(warehouseId: number) {
     return warehouses.find((w) => w.warehouseId === warehouseId)?.code ?? `#${warehouseId}`
   }
@@ -141,7 +137,6 @@ export default function PurchaseOrderDetailPage() {
     for (const line of lines) {
       const errors = validatePoLine({
         itemId: line.itemId,
-        uomId: line.uomId,
         warehouseId: line.warehouseId,
         qty: line.qty,
         unitPrice: line.unitPrice,
@@ -157,7 +152,6 @@ export default function PurchaseOrderDetailPage() {
 
     const payloadLines: CreatePoLineInput[] = lines.map((l) => ({
       itemId: l.itemId as number,
-      uomId: l.uomId as number,
       warehouseId: l.warehouseId as number,
       qty: Number(l.qty),
       unitPrice: Number(l.unitPrice),
@@ -347,7 +341,7 @@ export default function PurchaseOrderDetailPage() {
         <div className="flex items-center justify-between">
           <h2 className="text-base font-semibold text-foreground">Lines</h2>
           {editable && (
-            <Button type="button" variant="outline" onClick={() => setLines((prev) => [...prev, { key: newKey(), poLineId: null, itemId: null, uomId: null, warehouseId: null, qty: "", unitPrice: "", tax: "0.18", qtyReceived: 0 }])}>
+            <Button type="button" variant="outline" onClick={() => setLines((prev) => [...prev, { key: newKey(), poLineId: null, itemId: null, warehouseId: null, qty: "", unitPrice: "", tax: "0.18", qtyReceived: 0 }])}>
               <Plus className="size-5" />
               Add line
             </Button>
@@ -376,7 +370,7 @@ export default function PurchaseOrderDetailPage() {
                   return (
                     <TableRow key={line.key}>
                       <TableCell className="px-3 py-3.5">{item ? `${item.sku} — ${item.name}` : `Item #${line.itemId}`}</TableCell>
-                      <TableCell className="px-3 py-3.5">{line.uomId ? uomName(line.uomId) : "—"}</TableCell>
+                      <TableCell className="px-3 py-3.5">{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                       <TableCell className="px-3 py-3.5">{line.warehouseId ? warehouseCode(line.warehouseId) : "—"}</TableCell>
                       <TableCell className="px-3 py-3.5">{line.qty}</TableCell>
                       <TableCell className="px-3 py-3.5">{line.qtyReceived}</TableCell>
@@ -403,19 +397,9 @@ export default function PurchaseOrderDetailPage() {
                       <FieldError errors={[errors.itemId ? { message: errors.itemId } : undefined]} />
                     </TableCell>
                     <TableCell className="px-3 py-3 align-top">
-                      <Select<number | null> value={line.uomId} onValueChange={(v) => updateLine(line.key, { uomId: v })}>
-                        <SelectTrigger className="h-11! w-full text-base" aria-invalid={!!errors.uomId}>
-                          <SelectValue placeholder="UOM" />
-                        </SelectTrigger>
-                        <SelectContent>
-                          {uoms.map((u) => (
-                            <SelectItem key={u.uomId} value={u.uomId} className="text-base">
-                              {u.name}
-                            </SelectItem>
-                          ))}
-                        </SelectContent>
-                      </Select>
-                      <FieldError errors={[errors.uomId ? { message: errors.uomId } : undefined]} />
+                      <div className="flex h-11 items-center text-base text-muted-foreground">
+                        {baseUomLabel(items, uoms, line.itemId)}
+                      </div>
                     </TableCell>
                     <TableCell className="px-3 py-3 align-top">
                       <Select<number | null> value={line.warehouseId} onValueChange={(v) => updateLine(line.key, { warehouseId: v })}>

Frontend/erp-system/app/dashboard/procurement/purchase-orders/new/page.tsx

@@ -12,6 +12,7 @@ import { vendorsApi } from "@/lib/api/vendors"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { errorMessage } from "@/lib/error-map"
 import { validatePoLine } from "@/lib/validations/procurement"
 import { cn } from "@/lib/utils"
@@ -39,7 +40,6 @@ import { toast } from "@/components/ui/toast"
 interface DraftLine {
   key: string
   itemId: number | null
-  uomId: number | null
   warehouseId: number | null
   qty: string
   unitPrice: string
@@ -57,7 +57,7 @@ function newKey() {
 // DTO still requires it. Unit price *is* entered here; a PO prefilled from an RFQ starts
 // from its negotiated price (below) but stays editable.
 function emptyLine(): DraftLine {
-  return { key: newKey(), itemId: null, uomId: null, warehouseId: null, qty: "", unitPrice: "0", tax: "0" }
+  return { key: newKey(), itemId: null, warehouseId: null, qty: "", unitPrice: "0", tax: "0" }
 }
 
 function NewPurchaseOrderContent() {
@@ -169,7 +169,6 @@ function NewPurchaseOrderContent() {
               (l): DraftLine => ({
                 key: newKey(),
                 itemId: l.itemId,
-                uomId: null,
                 warehouseId: null,
                 qty: String(l.qty),
                 unitPrice: "0",
@@ -195,7 +194,6 @@ function NewPurchaseOrderContent() {
               return {
                 key: newKey(),
                 itemId: l.itemId,
-                uomId: null,
                 warehouseId: null,
                 qty: String(l.qty),
                 unitPrice: cell ? String(cell.unitPrice) : "0",
@@ -242,7 +240,6 @@ function NewPurchaseOrderContent() {
     for (const line of lines) {
       const errors = validatePoLine({
         itemId: line.itemId,
-        uomId: line.uomId,
         warehouseId: line.warehouseId,
         qty: line.qty,
         unitPrice: line.unitPrice,
@@ -258,7 +255,6 @@ function NewPurchaseOrderContent() {
 
     const payloadLines: CreatePoLineInput[] = lines.map((l) => ({
       itemId: l.itemId as number,
-      uomId: l.uomId as number,
       warehouseId: l.warehouseId as number,
       qty: Number(l.qty),
       unitPrice: Number(l.unitPrice),
@@ -449,19 +445,9 @@ function NewPurchaseOrderContent() {
                             )}
                           </TableCell>
                           <TableCell className="px-3 py-3 align-top">
-                            <Select<number | null> value={line.uomId} onValueChange={(v) => updateLine(line.key, { uomId: v })}>
-                              <SelectTrigger className="h-11! w-full text-base" aria-invalid={!!errors.uomId}>
-                                <SelectValue placeholder="UOM" />
-                              </SelectTrigger>
-                              <SelectContent>
-                                {(uoms ?? []).map((u) => (
-                                  <SelectItem key={u.uomId} value={u.uomId} className="text-base">
-                                    {u.name}
-                                  </SelectItem>
-                                ))}
-                              </SelectContent>
-                            </Select>
-                            <FieldError errors={[errors.uomId ? { message: errors.uomId } : undefined]} />
+                            <div className="flex h-11 items-center text-base text-muted-foreground">
+                              {baseUomLabel(items ?? [], uoms ?? [], line.itemId)}
+                            </div>
                           </TableCell>
                           <TableCell className="px-3 py-3 align-top">
                             <Select<number | null> value={line.warehouseId} onValueChange={(v) => updateLine(line.key, { warehouseId: v })}>

Frontend/erp-system/app/dashboard/production/runs/[id]/StageDrawer.tsx

@@ -18,6 +18,7 @@ import {
   TransferLine,
 } from "@/types/production"
 import { ItemListItem, Uom } from "@/types/master-data"
+import { baseUomLabel, contentUnitLabel, uomLabel } from "@/lib/uom-label"
 import { ReasonCode } from "@/types/stock"
 
 import { AlertDialog, AlertDialogContent } from "@/components/ui/alert-dialog"
@@ -154,10 +155,24 @@ export function StageDrawer({
     return (id: number | null) => (id === null ? "—" : byId.get(id) ?? `Item #${id}`)
   }, [items])
 
-  const uomName = useMemo(() => {
-    const byId = new Map(uoms.map((u) => [u.uomId, u.name]))
-    return (id: number) => byId.get(id) ?? `#${id}`
-  }, [uoms])
+  // Nothing on a run line carries a unit of its own any more. An output that references a
+  // real item shows that item's base UOM; only intermediate WIP falls back to its own label.
+  const outputUnit = useMemo(
+    () => (output: RunStageOutput) =>
+      output.itemId !== null ? baseUomLabel(items, uoms, output.itemId) : uomLabel(uoms, output.uomId),
+    [items, uoms],
+  )
+
+  // An input's unit follows how its quantity was expressed: ml/g for a content formula,
+  // otherwise a count of the item's packs. Upstream inputs are WIP from a parent stage.
+  const inputUnit = useMemo(
+    () => (input: RunStageInput) => {
+      if (input.source === "Upstream") return "WIP"
+      if (input.qtyUnit === "Content") return contentUnitLabel(items, input.itemId) ?? "—"
+      return baseUomLabel(items, uoms, input.itemId)
+    },
+    [items, uoms],
+  )
 
   const stageName = useMemo(() => {
     const byId = new Map(run.stages.map((s) => [s.runStageId, s.name]))
@@ -323,7 +338,7 @@ export function StageDrawer({
                   value={plannedInputs[input.runInputId] ?? String(input.plannedQty)}
                   onValueChange={(v) => setPlannedInputs((prev) => ({ ...prev, [input.runInputId]: v }))}
                   itemName={itemName}
-                  uomName={uomName}
+                  unitLabel={inputUnit}
                 />
               ))}
             </section>
@@ -337,7 +352,7 @@ export function StageDrawer({
                 <div key={output.runOutputId} className="rounded-lg border border-border p-3">
                   <div className="flex items-baseline justify-between gap-2">
                     <p className="min-w-0 truncate text-sm font-medium text-foreground">{output.name}</p>
-                    <span className="shrink-0 text-xs text-muted-foreground">{uomName(output.uomId)}</span>
+                    <span className="shrink-0 text-xs text-muted-foreground">{outputUnit(output)}</span>
                   </div>
                   {output.itemId !== null && (
                     <p className="text-xs text-muted-foreground">Finished good: {itemName(output.itemId)}</p>
@@ -522,7 +537,7 @@ export function StageDrawer({
               <section className="flex flex-col gap-3">
                 <h3 className="text-sm font-bold text-foreground">Finish the run</h3>
                 <div className="flex flex-col gap-1 rounded-lg border border-info/30 bg-info/5 p-3">
-                  <Row label="Good quantity">{fmt(goodQty)} {uomName(terminalOutput.uomId)}</Row>
+                  <Row label="Good quantity">{fmt(goodQty)} {outputUnit(terminalOutput)}</Row>
                   <Row label="Materials consumed">{money(run.costPool.consumed)}</Row>
                   <Row label="Leftovers returned">−{money(run.costPool.returned)}</Row>
                   <Separator className="my-1" />
@@ -653,14 +668,14 @@ function InputCard({
   value,
   onValueChange,
   itemName,
-  uomName,
+  unitLabel,
 }: {
   input: RunStageInput
   editable: boolean
   value: string
   onValueChange: (value: string) => void
   itemName: (id: number | null) => string
-  uomName: (id: number) => string
+  unitLabel: (input: RunStageInput) => string
 }) {
   const isUpstream = input.source === "Upstream"
   const short = isUpstream && input.deliveredQty < input.plannedQty
@@ -671,7 +686,7 @@ function InputCard({
         <p className="min-w-0 truncate text-sm font-medium text-foreground">
           {isUpstream ? "Upstream work in progress" : itemName(input.itemId)}
         </p>
-        <span className="shrink-0 text-xs text-muted-foreground">{uomName(input.uomId)}</span>
+        <span className="shrink-0 text-xs text-muted-foreground">{unitLabel(input)}</span>
       </div>
 
       <div className="mt-2 flex flex-col gap-1">
@@ -698,9 +713,10 @@ function InputCard({
         )}
 
         {/*
-          Consumed/returned figures are in the item's BASE uom, while `plannedQty` above is in the
-          input's declared uom — an input declared in "box of 12" shows planned 3 and consumed 36.
-          Labelled explicitly so the two are never read as the same unit.
+          Consumed/returned figures are always a count of the item's packs, while `plannedQty`
+          above is in the input's declared unit — a formula written as 2000 ml against a 500 ml
+          bottle shows planned 2000 and consumed 4. Labelled explicitly so the two are never
+          read as the same unit.
         */}
         {input.consumedQty > 0 && (
           <>

Frontend/erp-system/app/dashboard/production/templates/[id]/StageEditorPanel.tsx

@@ -1,9 +1,11 @@
 "use client"
 
+import type { ReactNode } from "react"
 import { Plus, Trash2 } from "lucide-react"
 
 import { cn } from "@/lib/utils"
-import { CustomFieldType, StageInputSource } from "@/types/production"
+import { baseUomLabel, contentUnitLabel } from "@/lib/uom-label"
+import { CustomFieldType, StageInputSource, StageQtyUnit } from "@/types/production"
 import { ItemListItem, Uom } from "@/types/master-data"
 import {
   BuilderFieldDef,
@@ -35,21 +37,24 @@ export interface UpstreamOutputOption {
   outputName: string
 }
 
-/** One row per input/output quantity — UOM select plus qty, used three times below. */
+/**
+ * One quantity row: the number, plus whatever names its unit.
+ *
+ * The unit is no longer a free choice. An input's is decided by its item (and, when that item
+ * has a content size, by the Pack/Content toggle); an output's comes from its item, or from a
+ * WIP label when it has none. So each caller supplies its own `unit` control and this row only
+ * owns the number.
+ */
 function QtyRow({
   qty,
-  uomId,
-  uoms,
   readOnly,
   onQtyChange,
-  onUomChange,
+  unit,
 }: {
   qty: number
-  uomId: number | null
-  uoms: Uom[]
   readOnly: boolean
   onQtyChange: (qty: number) => void
-  onUomChange: (uomId: number) => void
+  unit: ReactNode
 }) {
   return (
     <div className="flex items-center gap-2">
@@ -64,19 +69,56 @@ function QtyRow({
         placeholder="Qty per batch"
         aria-label="Quantity per batch"
       />
-      <Select<number> value={uomId} onValueChange={(v) => v && onUomChange(v)}>
-        <SelectTrigger className="h-8! w-24 shrink-0 text-sm" disabled={readOnly} aria-label="UOM">
-          <SelectValue placeholder="UOM" />
+      {unit}
+    </div>
+  )
+}
+
+/** Static unit name, for the rows whose unit is derived and therefore not editable. */
+function UnitLabel({ children }: { children: ReactNode }) {
+  return (
+    <span className="flex h-8 w-24 shrink-0 items-center text-sm text-muted-foreground">{children}</span>
+  )
+}
+
+/**
+ * Names the unit of a stage input's quantity.
+ *
+ * Only one case is a choice: a Stock input whose item declares a content size can be written
+ * either as an amount of that content (2000 ml) or as a pack count (4 bottles). Everything
+ * else has exactly one possible unit, so it renders as a label rather than a control.
+ */
+function InputUnitControl({
+  input,
+  items,
+  uoms,
+  readOnly,
+  onChange,
+}: {
+  input: BuilderInput
+  items: ItemListItem[]
+  uoms: Uom[]
+  readOnly: boolean
+  onChange: (unit: StageQtyUnit) => void
+}) {
+  if (input.source === "Upstream") return <UnitLabel>WIP</UnitLabel>
+
+  const item = items.find((candidate) => candidate.itemId === input.itemId)
+  const packName = baseUomLabel(items, uoms, input.itemId)
+  const contentName = contentUnitLabel(items, input.itemId)
+
+  if (!item?.contentBaseQty || !contentName) return <UnitLabel>{packName}</UnitLabel>
+
+  return (
+    <Select<string> value={input.qtyUnit} onValueChange={(v) => v && onChange(v as StageQtyUnit)}>
+      <SelectTrigger className="h-8! w-24 shrink-0 text-sm" disabled={readOnly} aria-label="Quantity unit">
+        <SelectValue />
       </SelectTrigger>
       <SelectContent>
-          {uoms.map((u) => (
-            <SelectItem key={u.uomId} value={u.uomId} className="text-sm">
-              {u.name}
-            </SelectItem>
-          ))}
+        <SelectItem value="Content" className="text-sm">{contentName}</SelectItem>
+        <SelectItem value="Pack" className="text-sm">{packName}</SelectItem>
       </SelectContent>
     </Select>
-    </div>
   )
 }
 
@@ -108,7 +150,7 @@ export function StageEditorPanel({
     onChange({
       inputs: [
         ...data.inputs,
-        { localId: newLocalId(), source: "Stock", itemId: null, fromOutputKey: null, uomId: null, qtyPerBatch: 1 },
+        { localId: newLocalId(), source: "Stock", itemId: null, fromOutputKey: null, qtyUnit: "Pack", qtyPerBatch: 1 },
       ],
     })
   }
@@ -122,13 +164,20 @@ export function StageEditorPanel({
    * the validator rejects an input that carries both.
    */
   function changeInputSource(localId: string, source: StageInputSource) {
-    updateInput(localId, source === "Stock" ? { source, fromOutputKey: null } : { source, itemId: null })
+    updateInput(
+      localId,
+      // WIP has no content size, so an Upstream input can only ever be counted in whole units.
+      source === "Stock" ? { source, fromOutputKey: null } : { source, itemId: null, qtyUnit: "Pack" },
+    )
   }
 
-  /** Default the UOM to the item's base unit — right most of the time, still overridable. */
+  /**
+   * Default to content units when the item has a content size — a recipe is far more often
+   * written as "2000 ml of syrup" than "4 bottles" — and to packs otherwise. Still switchable.
+   */
   function pickInputItem(input: BuilderInput, itemId: number) {
     const item = items.find((i) => i.itemId === itemId)
-    updateInput(input.localId, { itemId, uomId: input.uomId ?? item?.baseUomId ?? null })
+    updateInput(input.localId, { itemId, qtyUnit: item?.contentBaseQty ? "Content" : "Pack" })
   }
 
   function updateOutput(key: string, patch: Partial<BuilderOutput>) {
@@ -287,11 +336,15 @@ export function StageEditorPanel({
 
                     <QtyRow
                       qty={input.qtyPerBatch}
-                      uomId={input.uomId}
-                      uoms={uoms}
                       readOnly={readOnly}
                       onQtyChange={(qtyPerBatch) => updateInput(input.localId, { qtyPerBatch })}
-                      onUomChange={(uomId) => updateInput(input.localId, { uomId })}
+                      unit={<InputUnitControl
+                        input={input}
+                        items={items}
+                        uoms={uoms}
+                        readOnly={readOnly}
+                        onChange={(qtyUnit) => updateInput(input.localId, { qtyUnit })}
+                      />}
                     />
                   </div>
                 </div>
@@ -347,11 +400,27 @@ export function StageEditorPanel({
                   </div>
                   <QtyRow
                     qty={output.qtyPerBatch}
-                    uomId={output.uomId}
-                    uoms={uoms}
                     readOnly={readOnly}
                     onQtyChange={(qtyPerBatch) => updateOutput(output.key, { qtyPerBatch })}
-                    onUomChange={(uomId) => updateOutput(output.key, { uomId })}
+                    unit={
+                      // A finished good is counted in its item's own unit; only WIP names one.
+                      output.itemId !== null ? (
+                        <UnitLabel>{baseUomLabel(items, uoms, output.itemId)}</UnitLabel>
+                      ) : (
+                        <Select<number> value={output.uomId} onValueChange={(v) => v && updateOutput(output.key, { uomId: v })}>
+                          <SelectTrigger className="h-8! w-24 shrink-0 text-sm" disabled={readOnly} aria-label="WIP unit">
+                            <SelectValue placeholder="Unit" />
+                          </SelectTrigger>
+                          <SelectContent>
+                            {uoms.map((u) => (
+                              <SelectItem key={u.uomId} value={u.uomId} className="text-sm">
+                                {u.name}
+                              </SelectItem>
+                            ))}
+                          </SelectContent>
+                        </Select>
+                      )
+                    }
                   />
                 </div>
               ))}

Frontend/erp-system/app/dashboard/production/templates/[id]/page.tsx

@@ -77,7 +77,7 @@ function graphToFlow(graph: ProductionTemplateGraph): { nodes: Node[]; edges: Ed
         source: i.source,
         itemId: i.itemId,
         fromOutputKey: i.fromOutputKey,
-        uomId: i.uomId,
+        qtyUnit: i.qtyUnit,
         qtyPerBatch: i.qtyPerBatch,
       })),
       outputs: s.outputs.map((o) => ({
@@ -414,14 +414,21 @@ function TemplateBuilderContent() {
         const where = `Input ${i + 1} of "${label}"`
         if (input.source === "Stock" && input.itemId === null) list.push(`${where} needs an item.`)
         if (input.source === "Upstream" && !input.fromOutputKey) list.push(`${where} needs an upstream output.`)
-        if (input.uomId === null) list.push(`${where} needs a UOM.`)
+        // Content quantities divide by the item's content size, so the item must declare one.
+        if (input.qtyUnit === "Content") {
+          const item = items.find((candidate) => candidate.itemId === input.itemId)
+          if (item && !item.contentBaseQty) {
+            list.push(`${where} is in content units, but ${item.sku} has no content size.`)
+          }
+        }
         if (input.qtyPerBatch <= 0) list.push(`${where} needs a quantity greater than zero.`)
       })
 
       data.outputs.forEach((output, i) => {
         const where = `Output ${i + 1} of "${label}"`
         if (!isTerminal && !output.name.trim()) list.push(`${where} needs a name.`)
-        if (output.uomId === null) list.push(`${where} needs a UOM.`)
+        // Only work-in-progress declares its own unit; a finished good takes its item's.
+        if (!isTerminal && output.uomId === null) list.push(`${where} needs a UOM.`)
         if (output.qtyPerBatch <= 0) list.push(`${where} needs a quantity greater than zero.`)
       })
 
@@ -502,7 +509,7 @@ function TemplateBuilderContent() {
           source: i.source,
           itemId: i.source === "Stock" ? i.itemId : null,
           fromOutputKey: i.source === "Upstream" ? i.fromOutputKey : null,
-          uomId: i.uomId!,
+          qtyUnit: i.source === "Upstream" ? "Pack" : i.qtyUnit,
           qtyPerBatch: i.qtyPerBatch,
         })),
         // Only the terminal stage's output may name an item (FR-MFG-05). A stage that *was*
@@ -513,7 +520,8 @@ function TemplateBuilderContent() {
           key: o.key,
           itemId: isTerminal ? o.itemId : null,
           name: o.name.trim(),
-          uomId: o.uomId!,
+          // An item-bearing output takes its unit from the item, so it must send none.
+          uomId: isTerminal ? null : o.uomId,
           qtyPerBatch: o.qtyPerBatch,
         })),
       }

Frontend/erp-system/app/dashboard/production/templates/[id]/types.ts

@@ -7,15 +7,15 @@
 //     the contract (only outputs do, because Upstream inputs reference them by key). Rendering
 //     them by array index would make React reuse the wrong <input> when a row is removed, so
 //     every editable row carries a throwaway `localId` that is stripped on save.
-//   * **Half-filled rows.** `uomId` is `number | null` here but `number` on the wire: a row the
-//     user just added has nothing picked yet. `page.tsx` blocks the save until every one is set,
-//     which is what makes the non-null assertions in its payload builder sound.
+//   * **Half-filled rows.** A row the user just added has nothing picked yet, so `itemId` and a
+//     WIP output's `uomId` are nullable here. `page.tsx` blocks the save until the required ones
+//     are set, which is what makes the non-null assertions in its payload builder sound.
 //
 // A stage's identity IS its React Flow node id, which is its server key — the stringified
 // stage id, or `tmp-<uuid>` for a stage drawn in this session. That is why edges need no
 // translation on save: `edge.source`/`edge.target` are already `parentKey`/`childKey`.
 
-import { CustomFieldType, StageInputSource } from "@/types/production"
+import { CustomFieldType, StageInputSource, StageQtyUnit } from "@/types/production"
 
 /** `tmp-` prefixed so the server can tell a newly drawn stage/output from one it already has. */
 export function newKey(): string {
@@ -34,7 +34,11 @@ export interface BuilderInput {
   itemId: number | null
   /** Upstream inputs only — an output key belonging to a *direct* parent stage. */
   fromOutputKey: string | null
-  uomId: number | null
+  /**
+   * Whether `qtyPerBatch` is a pack count or an amount of the item's content (ml/g).
+   * `Content` is only offered for a Stock input whose item declares a content size.
+   */
+  qtyUnit: StageQtyUnit
   qtyPerBatch: number
 }
 
@@ -44,6 +48,7 @@ export interface BuilderOutput {
   /** Terminal stage only — the finished good. Must stay null on WIP outputs (FR-MFG-05). */
   itemId: number | null
   name: string
+  /** WIP label — required when `itemId` is null, and must stay null when it is set. */
   uomId: number | null
   qtyPerBatch: number
 }

Frontend/erp-system/app/dashboard/products/[id]/page.tsx

@@ -12,7 +12,10 @@ import { warehousesApi } from "@/lib/api/warehouses"
 import { errorMessage, fieldErrors } from "@/lib/error-map"
 import { validateItemForm } from "@/lib/validations/master-data"
 import { cn } from "@/lib/utils"
-import { Item, StockNature, TrackingMode } from "@/types/master-data"
+import { Item, MeasureUnit, StockNature, TrackingMode } from "@/types/master-data"
+
+/** Entry units. Only ml/g are stored — the server normalises L and Kg ×1000 on write. */
+const CONTENT_UNITS: MeasureUnit[] = ["Ml", "L", "G", "Kg"]
 
 import { Badge } from "@/components/ui/badge"
 import { Button, buttonVariants } from "@/components/ui/button"
@@ -52,6 +55,9 @@ export default function ItemDetailPage() {
   const [defaultVendorId, setDefaultVendorId] = useState<number | null>(null)
   const [trackingMode, setTrackingMode] = useState<TrackingMode>("None")
   const [taxClass, setTaxClass] = useState("")
+  // Raw string: an empty box means "no content size", which is not the same as 0.
+  const [contentQty, setContentQty] = useState("")
+  const [contentUnit, setContentUnit] = useState<MeasureUnit | null>(null)
   // Frontend-only: there's no warehouse field anywhere on the Item contract, so this
   // isn't sent on save — nothing to wire it to server-side.
   const [warehouseId, setWarehouseId] = useState<number | null>(null)
@@ -75,6 +81,8 @@ export default function ItemDetailPage() {
     setStockNature(data.stockNature)
     setTrackingMode(data.trackingMode)
     setTaxClass(data.taxClass ?? "")
+    setContentQty(data.contentQty === null ? "" : String(data.contentQty))
+    setContentUnit(data.contentUnit)
   }
 
   function load() {
@@ -105,7 +113,7 @@ export default function ItemDetailPage() {
   async function handleSave() {
     if (!item || !etag) return
     setSaveError(null)
-    const nextErrors = validateItemForm({ sku, name, categoryId, baseUomId })
+    const nextErrors = validateItemForm({ sku, name, categoryId, baseUomId, contentQty, contentUnit })
     setErrors(nextErrors)
     if (Object.keys(nextErrors).length > 0) return
 
@@ -117,6 +125,8 @@ export default function ItemDetailPage() {
           sku, name, description: description || null, categoryId: categoryId as number, subCategoryId, brandId,
           baseUomId: baseUomId as number, defaultVendorId, stockNature, trackingMode,
           taxClass: taxClass || null,
+          contentQty: contentQty.trim() ? Number(contentQty) : null,
+          contentUnit: contentQty.trim() ? contentUnit : null,
         },
         etag
       )
@@ -273,6 +283,53 @@ export default function ItemDetailPage() {
             </Select>
             <FieldError errors={[errors.baseUomId ? { message: errors.baseUomId } : undefined]} />
           </div>
+          {/* Content size (FR-MD-02): how much one pack holds. Optional, and independent of the
+              base UOM above — stock is counted in packs either way. */}
+          <div className="flex flex-col gap-2">
+            <Label className="text-base">Content size</Label>
+            <div className="flex gap-2">
+              <Input
+                type="number"
+                min="0"
+                step="any"
+                value={contentQty}
+                disabled={conflict}
+                onChange={(e) => setContentQty(e.target.value)}
+                placeholder="e.g. 500"
+                aria-invalid={!!errors.contentQty}
+                className="h-12! text-base"
+              />
+              <Select<MeasureUnit | null>
+                value={contentUnit}
+                onValueChange={setContentUnit}
+                disabled={conflict}
+                items={CONTENT_UNITS.map((u) => ({ label: u, value: u }))}
+              >
+                <SelectTrigger className="h-12! w-28 shrink-0 text-base" aria-invalid={!!errors.contentUnit}>
+                  <SelectValue placeholder="Unit" />
+                </SelectTrigger>
+                <SelectContent>
+                  {CONTENT_UNITS.map((u) => (
+                    <SelectItem key={u} value={u} className="text-base">
+                      {u.toLowerCase()}
+                    </SelectItem>
+                  ))}
+                </SelectContent>
+              </Select>
+            </div>
+            <FieldError
+              errors={[
+                errors.contentQty ? { message: errors.contentQty } : undefined,
+                errors.contentUnit ? { message: errors.contentUnit } : undefined,
+              ]}
+            />
+            {/* The stored value, so the ×1000 normalisation is never a surprise. */}
+            <p className="text-sm text-muted-foreground">
+              {item.contentBaseQty !== null && item.contentBaseUnit
+                ? `Stored as ${item.contentBaseQty} ${item.contentBaseUnit.toLowerCase()} per ${uomName(item.baseUomId)}.`
+                : "No content size — leave blank for items with nothing measurable to hold."}
+            </p>
+          </div>
           <div className="flex flex-col gap-2">
             {/* "Item type" now means a Color/Size dimension master — this field is the
                 stock-nature one it used to be confused with (docs/11 §8). */}
@@ -321,7 +378,8 @@ export default function ItemDetailPage() {
       </div>
 
       <p className="text-sm text-muted-foreground">
-        {uomName(item.baseUomId)} is the base UOM — every transaction converts to and stores quantities in base UOM (FR-MD-03).
+        {uomName(item.baseUomId)} is the base UOM — every transaction records quantities as a count of it (FR-MD-03).
+        There are no conversions: a differently sized pack is a different item.
       </p>
     </div>
   )

Frontend/erp-system/app/dashboard/products/new/page.tsx

@@ -13,9 +13,12 @@ import { productConfig } from "@/lib/api/product-config"
 import { uomsApi } from "@/lib/api/uoms"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { errorMessage } from "@/lib/error-map"
-import { validateVariantItemForm, validateVariantPrices } from "@/lib/validations/master-data"
+import { contentPairErrors, validateVariantItemForm, validateVariantPrices } from "@/lib/validations/master-data"
 import { cn } from "@/lib/utils"
-import { Brand, Category, ItemType, ProductConfig, StockNature, SubCategory } from "@/types/master-data"
+import { Brand, Category, ItemType, MeasureUnit, ProductConfig, StockNature, SubCategory } from "@/types/master-data"
+
+/** Entry units. Only ml/g are stored — the server normalises L and Kg ×1000 on write. */
+const CONTENT_UNITS: MeasureUnit[] = ["Ml", "L", "G", "Kg"]
 
 import { Badge } from "@/components/ui/badge"
 import { Button, buttonVariants } from "@/components/ui/button"
@@ -54,6 +57,9 @@ export default function NewItemPage() {
   const [uoms, setUoms] = useState<{ uomId: number; name: string }[]>([])
   /** Defaults to the first UOM once loaded; null only means none exist yet. */
   const [baseUomId, setBaseUomId] = useState<number | null>(null)
+  // Kept as a raw string: an empty box means "no content size", which is different from 0.
+  const [contentQty, setContentQty] = useState("")
+  const [contentUnit, setContentUnit] = useState<MeasureUnit | null>(null)
   const [stockNature, setStockNature] = useState<StockNature>("Stocked")
   const [loadError, setLoadError] = useState<string | null>(null)
 
@@ -199,7 +205,10 @@ export default function NewItemPage() {
 
   async function handleSubmit() {
     setSubmitError(null)
-    const nextErrors = validateVariantItemForm({ categoryId, hasVariants: variants.length > 0 })
+    const nextErrors = {
+      ...validateVariantItemForm({ categoryId, hasVariants: variants.length > 0 }),
+      ...contentPairErrors(contentQty, contentUnit),
+    }
     setErrors(nextErrors)
     // In fixed mode, block the whole submit until every variant has a price > 0.
     const nextPriceErrors =
@@ -228,6 +237,8 @@ export default function NewItemPage() {
           stockNature,
           trackingMode: "None",
           salePrice: priceMode === "fixed" ? Number(priceFor(variant.key)) : null,
+          contentQty: contentQty.trim() ? Number(contentQty) : null,
+          contentUnit: contentQty.trim() ? contentUnit : null,
         })
         created += 1
       }
@@ -382,6 +393,48 @@ export default function NewItemPage() {
                 </SelectContent>
               </Select>
             </div>
+            {/* Content size (FR-MD-02): how much one stocked pack holds. Optional — a screw
+                or a label has none. Litres/kilograms are normalised to ml/g by the server. */}
+            <div className="flex flex-col gap-2">
+              <Label className="text-base">Content size</Label>
+              <div className="flex gap-2">
+                <Input
+                  type="number"
+                  min="0"
+                  step="any"
+                  value={contentQty}
+                  onChange={(e) => setContentQty(e.target.value)}
+                  placeholder="e.g. 500"
+                  aria-invalid={!!errors.contentQty}
+                  className="h-12! text-base"
+                />
+                <Select<MeasureUnit | null>
+                  value={contentUnit}
+                  onValueChange={setContentUnit}
+                  items={CONTENT_UNITS.map((u) => ({ label: u, value: u }))}
+                >
+                  <SelectTrigger className="h-12! w-28 shrink-0 text-base" aria-invalid={!!errors.contentUnit}>
+                    <SelectValue placeholder="Unit" />
+                  </SelectTrigger>
+                  <SelectContent>
+                    {CONTENT_UNITS.map((u) => (
+                      <SelectItem key={u} value={u} className="text-base">
+                        {u.toLowerCase()}
+                      </SelectItem>
+                    ))}
+                  </SelectContent>
+                </Select>
+              </div>
+              <FieldError
+                errors={[
+                  errors.contentQty ? { message: errors.contentQty } : undefined,
+                  errors.contentUnit ? { message: errors.contentUnit } : undefined,
+                ]}
+              />
+              <p className="text-sm text-muted-foreground">
+                Leave blank for items with no measurable content. Stock is still counted in the base UOM.
+              </p>
+            </div>
             <div className="flex flex-col gap-2">
               <Label className="text-base">Stock nature</Label>
               <Select<StockNature> value={stockNature} onValueChange={(v) => v && setStockNature(v)}>

Frontend/erp-system/app/dashboard/products/uoms/page.tsx

@@ -59,7 +59,7 @@ export default function UomsPage() {
         <div className="flex items-center gap-3">
           <div>
             <h1 className="text-2xl font-bold text-foreground">Units of Measure</h1>
-            <p className="text-base text-muted-foreground">Flat UOM master, used as item base UOMs and in per-item conversions (FR-MD-02).</p>
+            <p className="text-base text-muted-foreground">Flat UOM master, used as item base UOMs and as work-in-progress labels in production (FR-MD-02).</p>
           </div>
         </div>
 

Frontend/erp-system/app/dashboard/receiving/grn/[id]/page.tsx

@@ -9,6 +9,7 @@ import { grnsApi } from "@/lib/api/grns"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { errorMessage } from "@/lib/error-map"
 import { cn } from "@/lib/utils"
 import { ConfirmGrnResponse, Grn } from "@/types/grn"
@@ -56,9 +57,6 @@ export default function GrnDetailPage() {
   function itemFor(itemId: number) {
     return items.find((i) => i.itemId === itemId)
   }
-  function uomFor(uomId: number) {
-    return uoms.find((u) => u.uomId === uomId)?.name ?? `#${uomId}`
-  }
   function binFor(binId: number | null) {
     if (!binId) return "—"
     return bins.find((b) => b.binId === binId)?.code ?? `#${binId}`
@@ -179,7 +177,7 @@ export default function GrnDetailPage() {
             return (
               <TableRow key={line.grnLineId}>
                 <TableCell className="px-3 py-3.5">{item ? `${item.sku} — ${item.name}` : `Item #${line.itemId}`}</TableCell>
-                <TableCell className="px-3 py-3.5">{uomFor(line.uomId)}</TableCell>
+                <TableCell className="px-3 py-3.5">{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                 <TableCell className="px-3 py-3.5">{binFor(line.binId)}</TableCell>
                 <TableCell className="px-3 py-3.5">{line.qty}</TableCell>
                 <TableCell className="px-3 py-3.5 text-right tabular-nums">

Frontend/erp-system/app/dashboard/receiving/grn/new/page.tsx

@@ -11,6 +11,7 @@ import { vendorsApi } from "@/lib/api/vendors"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { errorMessage } from "@/lib/error-map"
 import { validateLine, splitSerials, grnHeaderSchema } from "@/lib/validations/grn"
 import { cn } from "@/lib/utils"
@@ -33,7 +34,6 @@ interface DraftLine {
   key: string
   poLineId: number | null
   itemId: number | null
-  uomId: number | null
   binId: number | null
   qty: string
   unitCost: string
@@ -70,7 +70,6 @@ function emptyLine(): DraftLine {
     key: newKey(),
     poLineId: null,
     itemId: null,
-    uomId: null,
     binId: null,
     qty: "",
     unitCost: "",
@@ -168,7 +167,6 @@ export default function NewGrnPage() {
             key: newKey(),
             poLineId: l.poLineId,
             itemId: l.itemId,
-            uomId: l.uomId,
             binId: null,
             qty: String(l.qty - l.qtyReceived),
             unitCost: String(l.unitPrice),
@@ -246,7 +244,6 @@ export default function NewGrnPage() {
     for (const line of lines) {
       const errors = validateLine({
         itemId: line.itemId,
-        uomId: line.uomId,
         qty: line.qty,
         unitCost: line.unitCost,
         discountPct: line.discountPct,
@@ -268,7 +265,6 @@ export default function NewGrnPage() {
       return {
         poLineId: l.poLineId,
         itemId: l.itemId as number,
-        uomId: l.uomId as number,
         binId: l.binId,
         qty: Number(l.qty),
         unitCost: Number(l.unitCost),
@@ -486,27 +482,9 @@ export default function NewGrnPage() {
                             )}
                           </TableCell>
                           <TableCell className="px-3 py-3 align-top">
-                            {line.poLineId ? (
-                              <div className="flex h-11 items-center text-base">
-                                {uoms?.find((u) => u.uomId === line.uomId)?.name ?? `#${line.uomId}`}
+                            <div className="flex h-11 items-center text-base text-muted-foreground">
+                              {baseUomLabel(items ?? [], uoms ?? [], line.itemId)}
                             </div>
-                            ) : (
-                              <>
-                                <Select<number | null> value={line.uomId} onValueChange={(v) => updateLine(line.key, { uomId: v })}>
-                                  <SelectTrigger className="h-11! w-full text-base" aria-invalid={!!errors.uomId}>
-                                    <SelectValue placeholder="UOM" />
-                                  </SelectTrigger>
-                                  <SelectContent>
-                                    {(uoms ?? []).map((u) => (
-                                      <SelectItem key={u.uomId} value={u.uomId} className="text-base">
-                                        {u.name}
-                                      </SelectItem>
-                                    ))}
-                                  </SelectContent>
-                                </Select>
-                                <FieldError errors={[errors.uomId ? { message: errors.uomId } : undefined]} />
-                              </>
-                            )}
                           </TableCell>
                           <TableCell className="px-3 py-3 align-top">
                             <Select<number | null> value={line.binId} onValueChange={(v) => updateLine(line.key, { binId: v })}>

Frontend/erp-system/app/dashboard/sales/bundles/[id]/page.tsx

@@ -8,6 +8,7 @@ import { ArrowLeft, CheckCircle2, Edit, ExternalLink, Minus, Plus, Printer, Save
 import { bundleApi } from "@/lib/api/bundles"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { errorMessage } from "@/lib/error-map"
 import { Button, buttonVariants } from "@/components/ui/button"
 import { Badge } from "@/components/ui/badge"
@@ -30,7 +31,6 @@ const createBlankLine = (templateLine?: BundleSaleTemplateLine): EditableLine =>
   key: crypto.randomUUID(),
   bundleSaleTemplateLineId: templateLine?.bundleSaleTemplateLineId ?? 0,
   itemId: templateLine?.itemId ?? 0,
-  uomId: templateLine?.uomId ?? 0,
   warehouseId: templateLine?.warehouseId ?? 0,
   qty: templateLine?.qty ?? 1,
   unitPrice: templateLine?.unitPrice ?? 0,
@@ -107,7 +107,6 @@ export default function BundleSaleDetailPage() {
             key: `${line.bundleSaleLineId}`,
             bundleSaleTemplateLineId: line.bundleSaleLineId,
             itemId: line.itemId,
-            uomId: items.find((candidate) => candidate.itemId === line.itemId)?.baseUomId ?? line.uomId,
             warehouseId: line.warehouseId,
             qty: line.qty,
             unitPrice: line.unitPrice,
@@ -377,7 +376,7 @@ export default function BundleSaleDetailPage() {
                       <Select value={line.itemId ? String(line.itemId) : "all"} onValueChange={(v) => {
                         const itemId = Number(v)
                         const item = items.find((candidate) => candidate.itemId === itemId)
-                        updateLine(line.key, { itemId, uomId: item?.baseUomId ?? line.uomId, unitPrice: item?.salePrice ?? line.unitPrice })
+                        updateLine(line.key, { itemId, unitPrice: item?.salePrice ?? line.unitPrice })
                       }} disabled={!editing || !isDraft}>
                         <SelectTrigger className="h-9 text-sm">
                           <SelectValue placeholder="Select item" />
@@ -391,19 +390,8 @@ export default function BundleSaleDetailPage() {
                         </SelectContent>
                       </Select>
                     </TableCell>
-                    <TableCell className="min-w-40">
-                      <Select value={line.uomId ? String(line.uomId) : "all"} onValueChange={(v) => updateLine(line.key, { uomId: v === "all" ? 0 : Number(v) })} disabled>
-                        <SelectTrigger className="h-9 text-sm">
-                          <SelectValue placeholder="Select UOM" />
-                        </SelectTrigger>
-                        <SelectContent>
-                          {uoms.map((uom) => (
-                            <SelectItem key={uom.uomId} value={String(uom.uomId)}>
-                              {uom.name}
-                            </SelectItem>
-                          ))}
-                        </SelectContent>
-                      </Select>
+                    <TableCell className="min-w-40 text-sm text-muted-foreground">
+                      {baseUomLabel(items, uoms, line.itemId)}
                     </TableCell>
                     <TableCell className="text-right w-28"><Input type="number" min="0" step="0.01" value={line.qty} onChange={(e) => updateLine(line.key, { qty: Number(e.target.value) })} disabled={!editing || !isDraft} className="text-right" /></TableCell>
                     <TableCell className="text-right w-32"><Input type="number" min="0" step="0.01" value={line.unitPrice} onChange={(e) => updateLine(line.key, { unitPrice: Number(e.target.value) })} disabled={!editing || !isDraft} className="text-right" /></TableCell>

Frontend/erp-system/app/dashboard/sales/bundles/new/page.tsx

@@ -9,6 +9,7 @@ import { bundleApi } from "@/lib/api/bundles"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { usersApi } from "@/lib/api/users"
 import { errorMessage } from "@/lib/error-map"
@@ -31,7 +32,6 @@ const createBlankLine = (templateLine?: BundleSaleTemplateLine): EditableLine =>
   key: crypto.randomUUID(),
   bundleSaleTemplateLineId: templateLine?.bundleSaleTemplateLineId ?? 0,
   itemId: templateLine?.itemId ?? 0,
-  uomId: templateLine?.uomId ?? 0,
   warehouseId: templateLine?.warehouseId ?? 0,
   qty: templateLine?.qty ?? 1,
   unitPrice: templateLine?.unitPrice ?? 0,
@@ -97,7 +97,6 @@ function NewBundleSaleContent() {
               const item = items.find((candidate) => candidate.itemId === line.itemId)
               return createBlankLine({
                 ...line,
-                uomId: item?.baseUomId ?? line.uomId,
               })
             })
           : [createBlankLine()]
@@ -261,7 +260,6 @@ function NewBundleSaleContent() {
                         const item = items.find((candidate) => candidate.itemId === itemId)
                         updateLine(line.key, {
                           itemId,
-                          uomId: item?.baseUomId ?? line.uomId,
                           unitPrice: item?.salePrice ?? line.unitPrice,
                         })
                     }}>
@@ -277,19 +275,8 @@ function NewBundleSaleContent() {
                       </SelectContent>
                     </Select>
                   </TableCell>
-                  <TableCell className="min-w-40">
-                      <Select value={line.uomId ? String(line.uomId) : "all"} onValueChange={(v) => updateLine(line.key, { uomId: v === "all" ? 0 : Number(v) })} disabled>
-                      <SelectTrigger className="h-9 text-sm">
-                        <SelectValue placeholder="Select UOM" />
-                      </SelectTrigger>
-                      <SelectContent>
-                        {uoms.map((uom) => (
-                          <SelectItem key={uom.uomId} value={String(uom.uomId)}>
-                            {uom.name}
-                          </SelectItem>
-                        ))}
-                      </SelectContent>
-                    </Select>
+                  <TableCell className="min-w-40 text-sm text-muted-foreground">
+                    {baseUomLabel(items, uoms, line.itemId)}
                   </TableCell>
                   <TableCell className="text-right w-28"><Input type="number" min="0" step="0.01" value={line.qty} onChange={(e) => updateLine(line.key, { qty: Number(e.target.value) })} className="text-right" /></TableCell>
                   <TableCell className="text-right w-32"><Input type="number" min="0" step="0.01" value={line.unitPrice} onChange={(e) => updateLine(line.key, { unitPrice: Number(e.target.value) })} className="text-right" /></TableCell>

Frontend/erp-system/app/dashboard/sales/free-issues/new/page.tsx

@@ -14,6 +14,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { usersApi } from "@/lib/api/users"
 import { toast } from "@/components/ui/toast"
@@ -40,7 +41,6 @@ type FreeIssueRow = {
 const blankLine = (key: string): Line => ({
   key,
   itemId: 0,
-  uomId: 0,
   warehouseId: 0,
   qty: 1,
   freeQty: 0,
@@ -78,7 +78,6 @@ export default function NewFreeIssuePage() {
         const detail = await salesApi.getFreeIssue(summary.salesSlipId)
         const firstLine = detail.data.lines[0]
         const item = items.find((x) => x.itemId === firstLine?.itemId)
-        const uom = uoms.find((x) => x.uomId === firstLine?.uomId)
         const warehouse = warehouses.find((x) => x.warehouseId === detail.data.warehouseId)
         return {
           salesSlipId: detail.data.salesSlipId,
@@ -88,7 +87,7 @@ export default function NewFreeIssuePage() {
           warehouseName: warehouse?.name ?? `Warehouse ${detail.data.warehouseId}`,
           itemName: item?.name ?? firstLine?.description ?? "—",
           itemSku: item?.sku ?? `SKU-${firstLine?.itemId ?? 0}`,
-          uomName: uom?.name ?? `UOM ${firstLine?.uomId ?? 0}`,
+          uomName: baseUomLabel(items, uoms, firstLine?.itemId),
           qty: firstLine?.qty ?? 0,
           freeQty: firstLine?.freeQty ?? 0,
         } satisfies FreeIssueRow
@@ -118,7 +117,6 @@ export default function NewFreeIssuePage() {
           {
             ...blankLine("line-1"),
             itemId: itemRes.items[0]?.itemId ?? 0,
-            uomId: itemRes.items[0]?.baseUomId ?? uomRes.items[0]?.uomId ?? 0,
             warehouseId: whRes.items[0]?.warehouseId ?? 0,
           },
         ])
@@ -145,20 +143,17 @@ export default function NewFreeIssuePage() {
   }
 
   function selectItem(key: string, itemId: number) {
-    const item = items.find((candidate) => candidate.itemId === itemId)
-    updateLine(key, { itemId, uomId: item?.baseUomId ?? 0 })
+    updateLine(key, { itemId })
   }
 
   function selectEditingItem(key: string, itemId: number) {
-    const item = items.find((candidate) => candidate.itemId === itemId)
-    updateEditingLine(key, { itemId, uomId: item?.baseUomId ?? 0 })
+    updateEditingLine(key, { itemId })
   }
 
   async function submit() {
     const activeLines = editingRowId ? editingLines : lines
     if (!customerId || !warehouseId || !cashierUserId) return setError("Select customer, warehouse, and cashier.")
     if (activeLines.some((line) => !line.itemId)) return setError("Select an item for every line.")
-    if (activeLines.some((line) => !line.uomId)) return setError("Select a valid UOM for every line.")
     if (activeLines.some((line) => !line.warehouseId)) return setError("Select a warehouse for every line.")
 
     setSaving(true)
@@ -170,7 +165,6 @@ export default function NewFreeIssuePage() {
         cashierUserId,
         lines: activeLines.map((line) => ({
           itemId: Number(line.itemId),
-          uomId: Number(line.uomId),
           warehouseId: Number(line.warehouseId),
           qty: Number(line.qty),
           freeQty: Number(line.freeQty),
@@ -219,7 +213,6 @@ export default function NewFreeIssuePage() {
         {
           key: "edit-line-1",
           itemId: detailLine?.itemId ?? 0,
-          uomId: detailLine?.uomId ?? 0,
           warehouseId: detailLine?.warehouseId ?? detail.data.warehouseId,
           qty: detailLine?.qty ?? 1,
           freeQty: detailLine?.freeQty ?? 0,
@@ -319,19 +312,8 @@ export default function NewFreeIssuePage() {
                         </SelectContent>
                       </Select>
                     </TableCell>
-                    <TableCell className="px-4 py-2 min-w-44">
-                      <Select value={line.uomId ? String(line.uomId) : ""} onValueChange={(v) => updateEditingLine(line.key, { uomId: Number(v) })}>
-                        <SelectTrigger className="h-9 text-sm">
-                          <SelectValue placeholder="UOM" />
-                        </SelectTrigger>
-                        <SelectContent>
-                          {uoms.map((u) => (
-                            <SelectItem key={u.uomId} value={String(u.uomId)}>
-                              {u.name}
-                            </SelectItem>
-                          ))}
-                        </SelectContent>
-                      </Select>
+                    <TableCell className="px-4 py-2 min-w-44 text-sm text-muted-foreground">
+                      {baseUomLabel(items, uoms, line.itemId)}
                     </TableCell>
                     <TableCell className="px-4 py-2">
                       <Input type="number" min="0" step="1" value={line.qty} onChange={(e) => updateEditingLine(line.key, { qty: Number(e.target.value) })} className="h-9 w-24 text-right font-mono text-sm tabular-nums" />
@@ -385,18 +367,7 @@ export default function NewFreeIssuePage() {
                       </Select>
                     </TableCell>
                     <TableCell className="px-4 py-2 min-w-44">
-                      <Select value={line.uomId ? String(line.uomId) : ""} onValueChange={(v) => updateLine(line.key, { uomId: Number(v) })}>
-                        <SelectTrigger className="h-9 text-sm">
-                          <SelectValue placeholder="UOM" />
-                        </SelectTrigger>
-                        <SelectContent>
-                          {uoms.map((u) => (
-                            <SelectItem key={u.uomId} value={String(u.uomId)}>
-                              {u.name}
-                            </SelectItem>
-                          ))}
-                        </SelectContent>
-                      </Select>
+                      {baseUomLabel(items, uoms, line.itemId)}
                     </TableCell>
                     <TableCell className="px-4 py-2">
                       <Input type="number" min="0" step="1" value={line.qty} onChange={(e) => updateLine(line.key, { qty: Number(e.target.value) })} className="h-9 w-24 text-right font-mono text-sm tabular-nums" />

Frontend/erp-system/app/dashboard/sales/invoices/[id]/page.tsx

@@ -9,6 +9,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { errorMessage } from "@/lib/error-map"
 import { cn } from "@/lib/utils"
@@ -30,7 +31,6 @@ const money = new Intl.NumberFormat("en-LK", {
 const blankLine = (key: string): Line => ({
   key,
   itemId: 0,
-  uomId: 0,
   warehouseId: 0,
   qty: 1,
   freeQty: 0,
@@ -103,7 +103,6 @@ export default function SalesInvoiceDetailPage({ params }: { params: Promise<{ i
           doc.data.lines.map((line) => ({
             key: String(line.salesInvoiceLineId),
             itemId: line.itemId,
-            uomId: line.uomId,
             warehouseId: line.warehouseId,
             qty: line.qty,
             freeQty: line.freeQty,
@@ -152,7 +151,6 @@ export default function SalesInvoiceDetailPage({ params }: { params: Promise<{ i
     const item = items.find((candidate) => candidate.itemId === itemId)
     updateLine(key, {
       itemId,
-      uomId: item?.baseUomId ?? 0,
       unitPrice: getSuggestedUnitPrice(items, itemId),
     })
   }
@@ -172,7 +170,7 @@ export default function SalesInvoiceDetailPage({ params }: { params: Promise<{ i
 
   async function save() {
     if (!customerId || !warehouseId || !etag) return
-    if (lines.some((line) => !line.itemId || !line.uomId || !line.warehouseId)) {
+    if (lines.some((line) => !line.itemId || !line.warehouseId)) {
       setError("Select item, UOM and warehouse for every line.")
       return
     }
@@ -188,7 +186,6 @@ export default function SalesInvoiceDetailPage({ params }: { params: Promise<{ i
           invoiceType,
             lines: lines.map((line) => ({
               itemId: Number(line.itemId),
-              uomId: Number(line.uomId),
               warehouseId: Number(line.warehouseId),
               qty: Number(line.qty),
               freeQty: Number(line.freeQty),
@@ -353,7 +350,7 @@ export default function SalesInvoiceDetailPage({ params }: { params: Promise<{ i
                     <div className="font-medium text-foreground">{line.description}</div>
                     <div className="text-xs text-muted-foreground">SKU {items.find((i) => i.itemId === line.itemId)?.sku ?? `#${line.itemId}`}</div>
                   </td>
-                  <td className="px-4 py-3">{uoms.find((u) => u.uomId === line.uomId)?.name ?? `#${line.uomId}`}</td>
+                  <td className="px-4 py-3">{baseUomLabel(items, uoms, line.itemId)}</td>
                   <td className="px-4 py-3 text-right">{line.qty.toFixed(0)}</td>
                   <td className="px-4 py-3 text-right">{line.freeQty > 0 ? line.freeQty.toFixed(0) : "—"}</td>
                   <td className="px-4 py-3 text-right">{money.format(line.unitPrice)}</td>
@@ -496,19 +493,8 @@ export default function SalesInvoiceDetailPage({ params }: { params: Promise<{ i
                             ))}
                           </select>
                         </td>
-                        <td className="px-4 py-3 min-w-40">
-                          <select
-                            value={line.uomId ? String(line.uomId) : ""}
-                            onChange={(e) => updateLine(line.key, { uomId: Number(e.target.value) })}
-                            className="h-10 w-full rounded-lg border border-input bg-background px-3 text-sm"
-                          >
-                            <option value="">UOM</option>
-                            {uoms.map((u) => (
-                              <option key={u.uomId} value={String(u.uomId)}>
-                                {u.name}
-                              </option>
-                            ))}
-                          </select>
+                        <td className="px-4 py-3 min-w-40 text-sm text-muted-foreground">
+                          {baseUomLabel(items, uoms, line.itemId)}
                         </td>
                         <td className="px-4 py-3 w-28">
                           <input

Frontend/erp-system/app/dashboard/sales/invoices/[id]/print/page.tsx

@@ -8,6 +8,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { errorMessage } from "@/lib/error-map"
 import { Button, buttonVariants } from "@/components/ui/button"
@@ -143,7 +144,7 @@ export default function SalesInvoicePrintPage({ params }: { params: { id: string
                     <div className="font-medium text-foreground">{line.description}</div>
                     <div className="text-xs text-muted-foreground">SKU {items.find((i) => i.itemId === line.itemId)?.sku ?? `#${line.itemId}`}</div>
                   </TableCell>
-                  <TableCell>{uoms.find((u) => u.uomId === line.uomId)?.name ?? `#${line.uomId}`}</TableCell>
+                  <TableCell>{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                   <TableCell className="text-right">{line.qty.toFixed(2)}</TableCell>
                   <TableCell className="text-right">{line.freeQty > 0 ? line.freeQty.toFixed(2) : "—"}</TableCell>
                   <TableCell className="text-right">{line.unitPrice.toFixed(2)}</TableCell>

Frontend/erp-system/app/dashboard/sales/invoices/new/page.tsx

@@ -13,6 +13,7 @@ import { Badge } from "@/components/ui/badge"
 import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/components/ui/table"
 import { cn } from "@/lib/utils"
 import { getSuggestedUnitPrice } from "@/lib/sales-line-utils"
+import { baseUomLabel } from "@/lib/uom-label"
 import { errorMessage } from "@/lib/error-map"
 import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
@@ -36,7 +37,6 @@ type ActiveFocScheme = {
 const blankLine = (key: string): Line => ({
   key,
   itemId: 0,
-  uomId: 0,
   warehouseId: 0,
   qty: 1,
   freeQty: 0,
@@ -92,7 +92,6 @@ export default function NewSalesInvoicePage() {
           {
             ...blankLine("line-1"),
             itemId: itemRes.items[0]?.itemId ?? 0,
-            uomId: itemRes.items[0]?.baseUomId ?? uomRes.items[0]?.uomId ?? 0,
             warehouseId: defaultWarehouseId ?? 0,
             unitPrice: getSuggestedUnitPrice(itemRes.items, itemRes.items[0]?.itemId),
           },
@@ -131,7 +130,6 @@ export default function NewSalesInvoicePage() {
     const item = items.find((candidate) => candidate.itemId === itemId)
     updateLine(key, {
       itemId,
-      uomId: item?.baseUomId ?? 0,
       unitPrice: getSuggestedUnitPrice(items, itemId),
     })
   }
@@ -181,7 +179,6 @@ export default function NewSalesInvoicePage() {
     if (!customerId || !warehouseId) return setSubmitError("Select a customer and warehouse.")
     if (lines.some((line) => !line.itemId)) return setSubmitError("Select an item for every line.")
     if (lines.some((line) => !line.warehouseId)) return setSubmitError("Select a warehouse for every line.")
-    if (lines.some((line) => !line.uomId)) return setSubmitError("Select a valid UOM for every line.")
 
     const payload: CreateSalesInvoiceRequest = {
       customerId,
@@ -189,7 +186,6 @@ export default function NewSalesInvoicePage() {
       invoiceType,
       lines: lines.map((line) => ({
         itemId: Number(line.itemId),
-        uomId: Number(line.uomId),
         warehouseId: Number(line.warehouseId),
         qty: Number(line.qty),
         freeQty: Number(line.freeQty),
@@ -357,19 +353,8 @@ export default function NewSalesInvoicePage() {
                         </SelectContent>
                       </Select>
                     </TableCell>
-                    <TableCell className="px-4 py-2 min-w-36">
-                      <Select value={line.uomId ? String(line.uomId) : ""} onValueChange={(v) => updateLine(line.key, { uomId: Number(v) })}>
-                        <SelectTrigger className="h-9 text-sm">
-                          <SelectValue placeholder="UOM" />
-                        </SelectTrigger>
-                        <SelectContent>
-                          {uoms.map((u) => (
-                            <SelectItem key={u.uomId} value={String(u.uomId)}>
-                              {u.name}
-                            </SelectItem>
-                          ))}
-                        </SelectContent>
-                      </Select>
+                    <TableCell className="px-4 py-2 min-w-36 text-sm text-muted-foreground">
+                      {baseUomLabel(items, uoms, line.itemId)}
                     </TableCell>
                     <TableCell className="px-4 py-2">
                       <Input

Frontend/erp-system/app/dashboard/sales/slips/[id]/page.tsx

@@ -8,6 +8,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { usersApi } from "@/lib/api/users"
 import { errorMessage } from "@/lib/error-map"
@@ -37,7 +38,6 @@ const money = new Intl.NumberFormat("en-LK", {
 const blankLine = (key: string): Line => ({
   key,
   itemId: 0,
-  uomId: 0,
   warehouseId: 0,
   qty: 1,
   freeQty: 0,
@@ -101,7 +101,6 @@ export default function SalesSlipDetailPage({ params }: { params: Promise<{ id:
           doc.data.lines.map((line) => ({
             key: String(line.salesSlipLineId),
             itemId: line.itemId,
-            uomId: line.uomId,
             warehouseId: line.warehouseId,
             qty: line.qty,
             freeQty: line.freeQty,
@@ -179,7 +178,6 @@ export default function SalesSlipDetailPage({ params }: { params: Promise<{ id:
         cashierUserId,
           lines: lines.map((line) => ({
             itemId: Number(line.itemId),
-            uomId: Number(line.uomId),
             warehouseId: Number(line.warehouseId),
             qty: Number(line.qty),
             freeQty: Number(line.freeQty),
@@ -346,7 +344,7 @@ export default function SalesSlipDetailPage({ params }: { params: Promise<{ id:
                         : "No price suggestion available"}
                     </div>
                   </TableCell>
-                  <TableCell className="px-4 py-3">{uoms.find((u) => u.uomId === line.uomId)?.name ?? `#${line.uomId}`}</TableCell>
+                  <TableCell className="px-4 py-3">{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                   <TableCell className="px-4 py-3 text-right">{line.qty.toFixed(0)}</TableCell>
                   <TableCell className="px-4 py-3 text-right">{line.freeQty > 0 ? line.freeQty.toFixed(0) : "-"}</TableCell>
                   <TableCell className="px-4 py-3 text-right">{money.format(line.unitPrice)}</TableCell>
@@ -454,12 +452,7 @@ export default function SalesSlipDetailPage({ params }: { params: Promise<{ id:
                         <SelectContent>{items.map((i) => <SelectItem key={i.itemId} value={String(i.itemId)}>{i.sku} - {i.name}</SelectItem>)}</SelectContent>
                       </Select>
                     </TableCell>
-                    <TableCell>
-                      <Select value={line.uomId ? String(line.uomId) : ""} onValueChange={(v) => updateLine(line.key, { uomId: Number(v) })} disabled={locked}>
-                        <SelectTrigger className="h-11!"><SelectValue placeholder="UOM" /></SelectTrigger>
-                        <SelectContent>{uoms.map((u) => <SelectItem key={u.uomId} value={String(u.uomId)}>{u.name}</SelectItem>)}</SelectContent>
-                      </Select>
-                    </TableCell>
+                    <TableCell className="text-sm text-muted-foreground">{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                     <TableCell><Input type="number" min="0" step="0.01" value={line.qty} onChange={(e) => updateLine(line.key, { qty: Number(e.target.value) })} disabled={locked} /></TableCell>
                     <TableCell><Input type="number" min="0" step="0.01" value={line.freeQty} onChange={(e) => updateLine(line.key, { freeQty: Number(e.target.value) })} disabled={locked} /></TableCell>
                     <TableCell><Input type="number" min="0" step="0.01" value={line.unitPrice ?? ""} onChange={(e) => updateLine(line.key, { unitPrice: e.target.value === "" ? null : Number(e.target.value) })} disabled={locked} /></TableCell>

Frontend/erp-system/app/dashboard/sales/slips/new/page.tsx

@@ -18,6 +18,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { usersApi } from "@/lib/api/users"
 import { Customer } from "@/types/customers"
@@ -31,7 +32,6 @@ type Line = CreateSalesSlipLineRequest & { key: string }
 const blankLine = (key: string): Line => ({
   key,
   itemId: 0,
-  uomId: 0,
   warehouseId: 0,
   qty: 1,
   freeQty: 0,
@@ -88,7 +88,6 @@ export default function NewSalesSlipPage() {
           {
             ...blankLine("line-1"),
             itemId: itemRes.items[0]?.itemId ?? 0,
-            uomId: itemRes.items[0]?.baseUomId ?? uomRes.items[0]?.uomId ?? 0,
             warehouseId: whRes.items[0]?.warehouseId ?? 0,
             unitPrice: getSuggestedUnitPrice(itemRes.items, itemRes.items[0]?.itemId),
           },
@@ -106,7 +105,6 @@ export default function NewSalesSlipPage() {
     const item = items.find((candidate) => candidate.itemId === itemId)
     updateLine(key, {
       itemId,
-      uomId: item?.baseUomId ?? 0,
       unitPrice: getSuggestedUnitPrice(items, itemId),
     })
   }
@@ -155,7 +153,6 @@ export default function NewSalesSlipPage() {
     if (!customerId || !warehouseId || !cashierUserId) return setSubmitError("Select customer, warehouse, and cashier.")
     if (lines.some((line) => Number(line.itemId) === 0)) return setSubmitError("Select an item for every line.")
     if (lines.some((line) => Number(line.warehouseId) === 0)) return setSubmitError("Select a warehouse for every line.")
-    if (lines.some((line) => Number(line.uomId) === 0)) return setSubmitError("Select a valid UOM for every line.")
 
     const payload: CreateSalesSlipRequest = {
       customerId,
@@ -163,7 +160,6 @@ export default function NewSalesSlipPage() {
       cashierUserId,
       lines: lines.map((line) => ({
         itemId: Number(line.itemId),
-        uomId: Number(line.uomId),
         warehouseId: Number(line.warehouseId),
         qty: Number(line.qty),
         freeQty: Number(line.freeQty),
@@ -328,19 +324,8 @@ export default function NewSalesSlipPage() {
                         </SelectContent>
                       </Select>
                     </TableCell>
-                    <TableCell className="px-4 py-2 min-w-36">
-                      <Select value={line.uomId ? String(line.uomId) : ""} onValueChange={(v) => updateLine(line.key, { uomId: Number(v) })}>
-                        <SelectTrigger className="h-9 text-sm">
-                          <SelectValue placeholder="UOM" />
-                        </SelectTrigger>
-                        <SelectContent>
-                          {uoms.map((u) => (
-                            <SelectItem key={u.uomId} value={String(u.uomId)}>
-                              {u.name}
-                            </SelectItem>
-                          ))}
-                        </SelectContent>
-                      </Select>
+                    <TableCell className="px-4 py-2 min-w-36 text-sm text-muted-foreground">
+                      {baseUomLabel(items, uoms, line.itemId)}
                     </TableCell>
                     <TableCell className="px-4 py-2">
                       <Input

Frontend/erp-system/app/print/sales/invoices/[id]/page.tsx

@@ -7,6 +7,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { errorMessage } from "@/lib/error-map"
 import { Button } from "@/components/ui/button"
@@ -131,7 +132,7 @@ export default function SalesInvoicePrintPage({ params }: { params: Promise<{ id
                   <div className="font-medium text-foreground">{line.description}</div>
                   <div className="text-xs text-muted-foreground">SKU {items.find((i) => i.itemId === line.itemId)?.sku ?? `#${line.itemId}`}</div>
                 </TableCell>
-                <TableCell>{uoms.find((u) => u.uomId === line.uomId)?.name ?? `#${line.uomId}`}</TableCell>
+                <TableCell>{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                 <TableCell className="text-right">{line.qty.toFixed(2)}</TableCell>
                 <TableCell className="text-right">{line.freeQty > 0 ? line.freeQty.toFixed(2) : "—"}</TableCell>
                 <TableCell className="text-right">{line.unitPrice.toFixed(2)}</TableCell>

Frontend/erp-system/app/print/sales/slips/[id]/page.tsx

@@ -7,6 +7,7 @@ import { salesApi } from "@/lib/api/sales"
 import { customersApi } from "@/lib/api/customers"
 import { itemsApi } from "@/lib/api/items"
 import { uomsApi } from "@/lib/api/uoms"
+import { baseUomLabel } from "@/lib/uom-label"
 import { warehousesApi } from "@/lib/api/warehouses"
 import { usersApi } from "@/lib/api/users"
 import { errorMessage } from "@/lib/error-map"
@@ -123,7 +124,7 @@ export default function SalesSlipPrintPage({ params }: { params: Promise<{ id: s
                   <div className="font-medium text-foreground">{line.description}</div>
                   <div className="text-xs text-muted-foreground">SKU {items.find((i) => i.itemId === line.itemId)?.sku ?? `#${line.itemId}`}</div>
                 </TableCell>
-                <TableCell>{uoms.find((u) => u.uomId === line.uomId)?.name ?? `#${line.uomId}`}</TableCell>
+                <TableCell>{baseUomLabel(items, uoms, line.itemId)}</TableCell>
                 <TableCell className="text-right">{line.qty.toFixed(0)}</TableCell>
                 <TableCell className="text-right">{line.freeQty > 0 ? line.freeQty.toFixed(0) : "—"}</TableCell>
                 <TableCell className="text-right">{line.unitPrice.toFixed(2)}</TableCell>

Frontend/erp-system/lib/api/items.ts

@@ -10,8 +10,6 @@ import {
   TrackingMode,
   UpdateItemReorderRequest,
   UpdateItemRequest,
-  UpdateUomConversionsRequest,
-  UpdateUomConversionsResponse,
 } from "@/types/master-data"
 
 export interface ListItemsParams {
@@ -59,11 +57,4 @@ export const itemsApi = {
       body: request,
     })
   },
-
-  updateUomConversions(itemId: number, request: UpdateUomConversionsRequest): Promise<UpdateUomConversionsResponse> {
-    return apiRequest<UpdateUomConversionsResponse>(`/items/${itemId}/uom-conversions`, {
-      method: "PUT",
-      body: request,
-    })
-  },
 }

Frontend/erp-system/lib/uom-label.ts

@@ -0,0 +1,46 @@
+// Document lines carry no UOM of their own: every quantity in the system is a count of the
+// item's base UOM (FR-MD-02/03). Screens that used to render a per-line UOM picker now show
+// the unit as a derived, read-only label — the user still needs to know that "12" means
+// 12 bottles, they just cannot change it.
+
+import { ItemListItem, Uom } from "@/types/master-data"
+
+/** Minimal shapes so this works with both `Item` and `ItemListItem`. */
+type ItemLike = Pick<ItemListItem, "itemId" | "baseUomId">
+
+/**
+ * Display name of an item's base UOM, e.g. "BOTTLE". Returns an em dash when no item is
+ * selected yet, and falls back to the raw id if the UOM list has not loaded.
+ */
+export function baseUomLabel(
+  items: readonly ItemLike[],
+  uoms: readonly Uom[],
+  itemId: number | null | undefined,
+): string {
+  if (!itemId) return "—"
+  const item = items.find((candidate) => candidate.itemId === itemId)
+  if (!item) return "—"
+  return uoms.find((u) => u.uomId === item.baseUomId)?.name ?? `#${item.baseUomId}`
+}
+
+/**
+ * Display name for a UOM id that may be absent — an intermediate production output's WIP
+ * label, which is null on any output that references a real item.
+ */
+export function uomLabel(uoms: readonly Uom[], uomId: number | null | undefined): string {
+  if (!uomId) return "—"
+  return uoms.find((u) => u.uomId === uomId)?.name ?? `#${uomId}`
+}
+
+/**
+ * The unit an item's content is measured in — "ml" or "g" — or null when the item has no
+ * content size. Used to label a production input entered in content units.
+ */
+export function contentUnitLabel(
+  items: readonly Pick<ItemListItem, "itemId" | "contentBaseUnit">[],
+  itemId: number | null | undefined,
+): string | null {
+  if (!itemId) return null
+  const unit = items.find((candidate) => candidate.itemId === itemId)?.contentBaseUnit
+  return unit ? unit.toLowerCase() : null
+}

Frontend/erp-system/lib/validations/grn.ts

@@ -13,7 +13,6 @@ export const grnHeaderSchema = z.object({
 
 export function validateLine(input: {
   itemId: number | null
-  uomId: number | null
   qty: string
   unitCost: string
   discountPct: string
@@ -25,7 +24,6 @@ export function validateLine(input: {
   const errors: Record<string, string> = {}
 
   if (!input.itemId) errors.itemId = "Select an item"
-  if (!input.uomId) errors.uomId = "Select a UOM"
 
   const qty = Number(input.qty)
   if (!input.qty || Number.isNaN(qty) || qty <= 0) errors.qty = "Quantity must be greater than 0"

Frontend/erp-system/lib/validations/master-data.ts

@@ -10,12 +10,38 @@ export function validateItemForm(input: {
   name: string
   categoryId: number | null
   baseUomId: number | null
+  /** Raw field value; empty means "no measurable content", which is valid. */
+  contentQty?: string
+  contentUnit?: string | null
 }): Record<string, string> {
   const errors: Record<string, string> = {}
   if (!input.sku.trim()) errors.sku = "SKU is required"
   if (!input.name.trim()) errors.name = "Item name is required"
   if (!input.categoryId) errors.categoryId = "Select a category"
   if (!input.baseUomId) errors.baseUomId = "Select a base UOM"
+  Object.assign(errors, contentPairErrors(input.contentQty, input.contentUnit))
+  return errors
+}
+
+/**
+ * An item's content size is optional, but half of it is not: the server rejects a lone
+ * quantity or a lone unit with a 422. Shared because the variant builder validates its own
+ * shape and so cannot go through `validateItemForm`.
+ */
+export function contentPairErrors(
+  contentQty: string | undefined,
+  contentUnit: string | null | undefined,
+): Record<string, string> {
+  const errors: Record<string, string> = {}
+  const rawQty = (contentQty ?? "").trim()
+  const unit = contentUnit ?? null
+
+  if (rawQty && !unit) errors.contentUnit = "Select a unit for the content size"
+  if (!rawQty && unit) errors.contentQty = "Enter a content size, or clear the unit"
+  if (rawQty) {
+    const qty = Number(rawQty)
+    if (Number.isNaN(qty) || qty <= 0) errors.contentQty = "Content size must be greater than 0"
+  }
   return errors
 }
 
@@ -29,16 +55,6 @@ export function validateReorderLine(input: { warehouseId: number | null; reorder
   return errors
 }
 
-export function validateConversionLine(input: { fromUom: number | null; toUom: number | null; factor: string }): Record<string, string> {
-  const errors: Record<string, string> = {}
-  if (!input.fromUom) errors.fromUom = "Select a UOM"
-  if (!input.toUom) errors.toUom = "Select a UOM"
-  if (input.fromUom && input.toUom && input.fromUom === input.toUom) errors.toUom = "From and to UOM must differ"
-  const factor = Number(input.factor)
-  if (!input.factor || Number.isNaN(factor) || factor <= 0) errors.factor = "Factor must be greater than 0"
-  return errors
-}
-
 export function validateUomName(name: string): Record<string, string> {
   const errors: Record<string, string> = {}
   if (!name.trim()) errors.name = "UOM name is required"

Frontend/erp-system/lib/validations/procurement.ts

@@ -32,7 +32,6 @@ export function validateQuotationLine(input: { unitPrice: string; leadDays: stri
 
 export function validatePoLine(input: {
   itemId: number | null
-  uomId: number | null
   warehouseId: number | null
   qty: string
   unitPrice: string
@@ -40,7 +39,6 @@ export function validatePoLine(input: {
 }): Record<string, string> {
   const errors: Record<string, string> = {}
   if (!input.itemId) errors.itemId = "Select an item"
-  if (!input.uomId) errors.uomId = "Select a UOM"
   if (!input.warehouseId) errors.warehouseId = "Select a warehouse"
   const qty = Number(input.qty)
   if (!input.qty || Number.isNaN(qty) || qty <= 0) errors.qty = "Quantity must be greater than 0"

Frontend/erp-system/types/bundles.ts

@@ -5,7 +5,6 @@ export type BundleSaleStatus = "Draft" | "Posted" | "Cancelled"
 export interface BundleSaleTemplateLine {
   bundleSaleTemplateLineId: number
   itemId: number
-  uomId: number
   warehouseId: number
   qty: number
   unitPrice: number
@@ -40,7 +39,6 @@ export interface BundleSaleLine {
   itemId: number
   description: string
   qty: number
-  uomId: number
   warehouseId: number
   unitPrice: number
   lineTotal: number

Frontend/erp-system/types/grn.ts

@@ -26,7 +26,6 @@ export interface BatchInput {
 export interface CreateGrnLineInput {
   poLineId?: number | null
   itemId: number
-  uomId: number
   binId?: number | null
   qty: number
   /**
@@ -55,7 +54,6 @@ export interface GrnLine {
   grnLineId: number
   poLineId: number | null
   itemId: number
-  uomId: number
   binId: number | null
   qty: number
   /** Gross unit cost received at. */

Frontend/erp-system/types/master-data.ts

@@ -10,7 +10,26 @@ import { EntityStatus } from "@/types/common"
 export type StockNature = "Stocked" | "NonStocked" | "Service"
 export type TrackingMode = "None" | "Batch" | "Serial"
 
-export interface ItemListItem {
+/**
+ * Unit of an item's content size — how much one stocked pack holds.
+ *
+ * Not a stocking unit: stock is always counted in packs (`baseUomId`). Only `Ml` and `G`
+ * are ever returned as a *base* content unit; `L` and `Kg` are entry conveniences the
+ * server normalises ×1000 on write.
+ */
+export type MeasureUnit = "Ml" | "L" | "G" | "Kg"
+
+/** The four content fields, which are always all set or all null. */
+export interface ItemContent {
+  /** Content per pack as entered, e.g. 500 with `Ml`, or 1.5 with `L`. */
+  contentQty: number | null
+  contentUnit: MeasureUnit | null
+  /** Server-derived normalisation of the pair above; never sent on write. */
+  contentBaseQty: number | null
+  contentBaseUnit: MeasureUnit | null
+}
+
+export interface ItemListItem extends ItemContent {
   itemId: number
   sku: string
   name: string
@@ -33,13 +52,6 @@ export interface ItemReorderSetting {
   reorderQty: number
 }
 
-export interface UomConversion {
-  conversionId: number
-  fromUom: number
-  toUom: number
-  factor: number
-}
-
 /**
  * Full Item resource (docs/11 §2.1 `GET /items/{itemId}`).
  *
@@ -47,7 +59,7 @@ export interface UomConversion {
  * client-generated `sku` and never stored server-side (docs/10 Part C.9). The SKU is the
  * only record of which colour/size an item is.
  */
-export interface Item {
+export interface Item extends ItemContent {
   itemId: number
   sku: string
   name: string
@@ -65,7 +77,6 @@ export interface Item {
   salePrice: number | null
   status: EntityStatus
   reorder: ItemReorderSetting[]
-  conversions: UomConversion[]
   createdAt: string
   updatedAt: string | null
 }
@@ -87,6 +98,12 @@ export interface CreateItemRequest {
   taxClass?: string | null
   /** Optional fixed sale price (Sales only). Null/omitted ⇒ sell at stock/FIFO value. */
   salePrice?: number | null
+  /**
+   * Content per pack. Send both or neither — a half-filled pair is a 422. The base pair is
+   * derived server-side and is deliberately not accepted here.
+   */
+  contentQty?: number | null
+  contentUnit?: MeasureUnit | null
 }
 
 export type UpdateItemRequest = CreateItemRequest
@@ -95,16 +112,6 @@ export interface UpdateItemReorderRequest {
   settings: ItemReorderSetting[]
 }
 
-export interface UpdateUomConversionsRequest {
-  conversions: { fromUom: number; toUom: number; factor: number }[]
-}
-
-export interface UpdateUomConversionsResponse {
-  itemId: number
-  baseUomId: number
-  conversions: UomConversion[]
-}
-
 export interface Warehouse {
   warehouseId: number
   code: string

Frontend/erp-system/types/procurement.ts

@@ -136,7 +136,6 @@ export type PurchaseOrderStatus =
 export interface PoLine {
   poLineId: number
   itemId: number
-  uomId: number
   warehouseId: number
   qty: number
   unitPrice: number
@@ -178,7 +177,6 @@ export interface PurchaseOrderSummary {
 
 export interface CreatePoLineInput {
   itemId: number
-  uomId: number
   warehouseId: number
   qty: number
   unitPrice: number

Frontend/erp-system/types/production.ts

@@ -4,7 +4,9 @@
 // Three things changed when the real backend landed, and they are worth knowing if you are
 // reading old code or docs/21-FRONTEND-PHASE2.md:
 //   * a template is identified by `code`, not `docNo` (only runs carry a document number)
-//   * quantities reference `itemId`/`uomId` numeric FKs with `qtyPerBatch` — not free text
+//   * quantities reference an `itemId` numeric FK with `qtyPerBatch` — not free text. Lines
+//     carry no UOM: an input's unit is `qtyUnit` (packs or the item's content unit) and an
+//     output's is its item's base UOM, or `uomId` when it is intermediate WIP
 //   * stages carry `posX`/`posY`, so canvas layout round-trips through the server
 //
 // The `key` vocabulary (§D.1): every stage and output has a client-facing string key
@@ -17,6 +19,16 @@ export type TemplateStatus = "Active" | "Inactive"
 export type ProductionRunStatus = "InProgress" | "Completed" | "Cancelled"
 export type RunStageStatus = "Waiting" | "Ready" | "InProgress" | "Done" | "Approved"
 export type StageInputSource = "Stock" | "Upstream"
+
+/**
+ * What a stage input's quantity is expressed in.
+ *
+ * `Pack` is a count of the item's base UOM. `Content` is an amount of the item's content in
+ * its base content unit (ml or g), which the server divides by the item's content size to get
+ * packs — 2000 ml of a 500 ml bottle consumes 4, and 300 ml consumes 0.6. `Content` requires
+ * the item to have a content size, and Upstream inputs must always be `Pack`.
+ */
+export type StageQtyUnit = "Pack" | "Content"
 export type CustomFieldType = "Text" | "Number" | "Checkbox" | "Date" | "Select"
 
 export type RunStageEventType =
@@ -50,7 +62,7 @@ export interface StageInput {
   /** Set when `source` is `Upstream` — an output of a *direct* parent stage. */
   fromOutputId: number | null
   fromOutputKey: string | null
-  uomId: number
+  qtyUnit: StageQtyUnit
   qtyPerBatch: number
 }
 
@@ -60,7 +72,8 @@ export interface StageOutput {
   /** Null on intermediate (WIP) outputs; required on the terminal stage's single output. */
   itemId: number | null
   name: string
-  uomId: number
+  /** WIP display label — set exactly when `itemId` is null; the unit otherwise comes from the item. */
+  uomId: number | null
   qtyPerBatch: number
 }
 
@@ -137,7 +150,7 @@ export interface SaveStageInputInput {
   source: StageInputSource
   itemId?: number | null
   fromOutputKey?: string | null
-  uomId: number
+  qtyUnit: StageQtyUnit
   qtyPerBatch: number
 }
 
@@ -145,7 +158,8 @@ export interface SaveStageOutputInput {
   key: string
   itemId?: number | null
   name: string
-  uomId: number
+  /** Required when `itemId` is null (WIP); must be null when it is set. */
+  uomId?: number | null
   qtyPerBatch: number
 }
 
@@ -200,13 +214,14 @@ export interface RunStageInput {
   source: StageInputSource
   itemId: number | null
   fromRunOutputId: number | null
-  uomId: number
-  /** In the input's *declared* UOM. Editable until the stage starts. */
+  qtyUnit: StageQtyUnit
+  /** Expressed in `qtyUnit`. Editable until the stage starts. */
   plannedQty: number
   /**
-   * The four figures below are in the item's *base* UOM — the only unit the FIFO engine and
-   * the ledger speak. A stage input declared in "box of 12" therefore shows plannedQty 3 and
-   * consumedQty 36. Do not compare them to plannedQty without converting.
+   * The four figures below are always a count of the item's *base* UOM — the only unit the
+   * FIFO engine and the ledger speak. For a `Content` input they are therefore in different
+   * units from plannedQty: 2000 ml planned against a 500 ml bottle shows consumedQty 4. Do
+   * not compare them to plannedQty without dividing by the item's content size.
    */
   consumedQty: number
   consumedValue: number
@@ -220,7 +235,9 @@ export interface RunStageOutput {
   runOutputId: number
   itemId: number | null
   name: string
-  uomId: number
+  /** WIP display label; null on the terminal output, whose unit is the finished item's base UOM. */
+  uomId: number | null
+  /** Always a pack count — scrap is recorded in whole units, never in ml or g. */
   plannedQty: number
   producedQty: number
   scrappedQty: number

Frontend/erp-system/types/sales.ts

@@ -11,7 +11,6 @@ export interface SalesInvoiceLine {
   description: string
   qty: number
   freeQty: number
-  uomId: number
   warehouseId: number
   unitPrice: number
   baseCost: number
@@ -101,7 +100,6 @@ export interface SalesInvoice extends SalesInvoiceSummary {
 
 export interface CreateSalesInvoiceLineRequest {
   itemId: number
-  uomId: number
   warehouseId: number
   qty: number
   freeQty: number
@@ -131,7 +129,6 @@ export interface SalesSlipLine {
   description: string
   qty: number
   freeQty: number
-  uomId: number
   warehouseId: number
   unitPrice: number
   baseCost: number
@@ -186,7 +183,6 @@ export interface SalesSlip {
 
 export interface CreateSalesSlipLineRequest {
   itemId: number
-  uomId: number
   warehouseId: number
   qty: number
   freeQty: number
@@ -257,7 +253,6 @@ export interface FreeIssueSummary {
   itemId: number
   itemSku: string
   itemName: string
-  uomId: number
   uomName: string
   qty: number
   freeQty: number

Testing/e2e/pages/GrnPages.ts

@@ -54,15 +54,17 @@ export class GrnNewPage {
   }
 
   /**
-   * Item and UOM are each only a combobox when the row is NOT tied to a PO line
-   * (`line.poLineId` gates both cells identically in the source - a PO line renders them as
-   * plain text instead). Checked per-cell (td:nth(0) for Item, td:nth(1) for UOM) rather than
-   * "row has any combobox", since the Bin/Hold-status cells always have one regardless of PO
-   * mode - a row-wide check would false-positive on a PO line and select the wrong control.
-   * Selecting the app doesn't auto-fill UOM from the chosen item, so a direct-receipt/off-PO
-   * line needs it set explicitly or submit blocks with "Select a UOM".
+   * Item is only a combobox when the row is NOT tied to a PO line (`line.poLineId` gates the
+   * cell in the source - a PO line renders it as plain text instead). Checked per-cell
+   * (td:nth(0)) rather than "row has any combobox", since the Bin/Hold-status cells always
+   * have one regardless of PO mode - a row-wide check would false-positive on a PO line and
+   * select the wrong control.
+   *
+   * td:nth(1) is still the UOM column, but it is now a read-only label showing the chosen
+   * item's base UOM: lines carry no unit of their own, so there is nothing to pick. The
+   * column was kept rather than removed, which is why every index below is unchanged.
    */
-  async fillFirstLine(opts: { item?: string; uom?: string; qty: number; unitCost?: number }) {
+  async fillFirstLine(opts: { item?: string; qty: number; unitCost?: number }) {
     const row = this.firstRow()
     const cells = row.locator("td")
     if (opts.item) {
@@ -71,12 +73,6 @@ export class GrnNewPage {
         await selectOption(this.page, itemCombo, opts.item)
       }
     }
-    if (opts.uom) {
-      const uomCombo = cells.nth(1).getByRole("combobox")
-      if (await uomCombo.count()) {
-        await selectOption(this.page, uomCombo, opts.uom)
-      }
-    }
     const numberInputs = row.locator('input[type="number"]')
     await numberInputs.nth(0).fill(String(opts.qty)) // Qty
     if (opts.unitCost !== undefined) {

Testing/e2e/specs/chained-flow.spec.ts

@@ -1,5 +1,5 @@
 import { test, expect, APIRequestContext } from "@playwright/test"
-import { ApiSeeder, newApiContext, Warehouse, Item, Uom, Vendor } from "../support/api"
+import { ApiSeeder, newApiContext, Warehouse, Item, Vendor } from "../support/api"
 import { GrnNewPage, GrnDetailPage } from "../pages/GrnPages"
 import { ProductionRunListPage, ProductionRunDetailPage } from "../pages/ProductionRunPages"
 import { StockTransferNewPage, StockTransferDetailPage } from "../pages/StockPages"
@@ -16,7 +16,6 @@ test.describe("Chained flow: GRN -> Production -> Stock Transfer", () => {
   let sourceWarehouse: Warehouse
   let destWarehouse: Warehouse
   let vendor: Vendor
-  let uom: Uom
   let rawItem: Item
   let finishedItem: Item
   let templateName: string
@@ -26,7 +25,6 @@ test.describe("Chained flow: GRN -> Production -> Stock Transfer", () => {
     seeder = new ApiSeeder(api)
     sourceWarehouse = await seeder.firstWarehouse()
     destWarehouse = await seeder.secondWarehouse()
-    uom = await seeder.firstUom()
     vendor = await seeder.createVendor("Chained Flow Vendor")
     rawItem = await seeder.createItem({ namePrefix: "Chained Raw Material" })
     finishedItem = await seeder.createItem({ namePrefix: "Chained Finished Good" })
@@ -34,7 +32,7 @@ test.describe("Chained flow: GRN -> Production -> Stock Transfer", () => {
     const template = await seeder.createSingleStageTemplate({
       rawItemId: rawItem.itemId,
       finishedItemId: finishedItem.itemId,
-      uomId: uom.uomId,
+
     })
     templateName = template.name
   })
@@ -50,7 +48,7 @@ test.describe("Chained flow: GRN -> Production -> Stock Transfer", () => {
     await grnNew.useDirectReceipt()
     await grnNew.selectVendor(vendor.name)
     await grnNew.selectWarehouse(sourceWarehouse.name)
-    await grnNew.fillFirstLine({ item: rawItem.name, uom: uom.name, qty: 100, unitCost: 20 })
+    await grnNew.fillFirstLine({ item: rawItem.name, qty: 100, unitCost: 20 })
     await grnNew.submit()
 
     await expect(page).toHaveURL(/\/dashboard\/receiving\/grn\/\d+/)