adding complete db migrations from posgres

Backend/ERPCore/Controllers/ProductionRunsController.cs

@@ -56,6 +56,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(typeof(RunGraphDto), StatusCodes.Status201Created)]
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<RunGraphDto>> Create([FromBody] CreateRunRequest request, CancellationToken ct)
     {
         var result = await _runs.CreateAsync(request, ct);
@@ -69,6 +70,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<RunStageDto>> UpdateQuantities(
         int runId, int runStageId, [FromBody] UpdateStageQuantitiesRequest request, CancellationToken ct)
         => Ok(await _runs.UpdateStageQuantitiesAsync(runId, runStageId, request, ct));
@@ -86,6 +88,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<StartStageResultDto>> Start(
         int runId, int runStageId,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -98,6 +101,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<RunStageDto>> Complete(
         int runId, int runStageId, [FromBody] CompleteStageRequest request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -109,6 +113,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<ApproveStageResultDto>> Approve(
         int runId, int runStageId, [FromBody] ApproveStageRequest? request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -120,6 +125,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<TransferResultDto>> Transfer(
         int runId, int runStageId, [FromBody] TransferRemainderRequest request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -132,6 +138,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<ReturnLeftoverResultDto>> ReturnLeftover(
         int runId, int runInputId, [FromBody] ReturnLeftoverRequest request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -142,6 +149,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(typeof(RejectIntakeResultDto), StatusCodes.Status200OK)]
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<RejectIntakeResultDto>> RejectIntake(
         int runId, int runStageId, [FromBody] RejectRequest? request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -153,6 +161,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(typeof(TerminalRejectResultDto), StatusCodes.Status200OK)]
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<TerminalRejectResultDto>> Reject(
         int runId, int runStageId, [FromBody] RejectRequest? request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,
@@ -165,6 +174,7 @@ public sealed class ProductionRunsController : ApiControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     [ProducesResponseType(StatusCodes.Status409Conflict)]
     [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
     public async Task<ActionResult<CancelRunResultDto>> Cancel(
         int runId, [FromBody] CancelRunRequest request,
         [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey,

Backend/ERPCore/Domain/Entities/Branch.cs

@@ -9,6 +9,18 @@ namespace ERPCore.Domain.Entities;
 /// </summary>
 public class Branch
 {
+    /// <summary>
+    /// Code of the deployment's default branch. Every branch-scoped entity has a
+    /// non-nullable <c>BranchId</c> with a Restrict FK, so this row must exist before any
+    /// of them can be written — see <c>DataSeeder.EnsureDefaultBranchAsync</c>, which
+    /// creates it at startup, and <c>BranchConfigService.ResolveDefaultBranchIdAsync</c>,
+    /// which is the lazy runtime fallback.
+    /// </summary>
+    public const string DefaultCode = "BR-000";
+
+    /// <summary>Display name paired with <see cref="DefaultCode"/>.</summary>
+    public const string DefaultName = "Main Branch";
+
     public int BranchId { get; set; }
 
     /// <summary>Server-generated on create ("BR-001", "BR-002", ...) — never accepted from the client.</summary>

Backend/ERPCore/Domain/Entities/BundleSale.cs

@@ -27,7 +27,7 @@ public class BundleSale
     public decimal GrandTotal { get; set; }
     public DateTime CreatedAt { get; set; }
     public DateTime? UpdatedAt { get; set; }
-    public int ConcurrencyStamp { get; set; }
+    public uint RowVersion { get; set; }
 
     /// <summary>Set once this bundle's business date is closed by <see cref="SalesDayEnd"/> — a
     /// closed bundle sale is frozen (no further edits). Same role as <see cref="SalesSlip.DayEndId"/>;

Backend/ERPCore/Domain/Entities/BundleSaleTemplate.cs

@@ -11,7 +11,7 @@ public class BundleSaleTemplate
     public EntityStatus Status { get; set; } = EntityStatus.Active;
     public DateTime CreatedAt { get; set; }
     public DateTime? UpdatedAt { get; set; }
-    public int ConcurrencyStamp { get; set; }
+    public uint RowVersion { get; set; }
 
     public ICollection<BundleSaleTemplateLine> Lines { get; set; } = new List<BundleSaleTemplateLine>();
 }

Backend/ERPCore/ERPCore.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
     <TargetFramework>net10.0</TargetFramework>
@@ -10,18 +10,18 @@
   <ItemGroup>
     <PackageReference Include="ClosedXML" Version="0.105.0" />
     <PackageReference Include="CsvHelper" Version="33.1.0" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.9" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="10.0.9">
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.20" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.20">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="10.0.9">
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="9.0.20">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.2" />
+    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="9.0.0" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.9" />
-    <PackageReference Include="Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore" Version="10.0.9" />
+    <PackageReference Include="Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore" Version="9.0.20" />
     <PackageReference Include="Serilog.AspNetCore" Version="9.0.0" />
     <PackageReference Include="Serilog.Sinks.File" Version="6.0.0" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="10.2.3" />

Backend/ERPCore/Infra/Persistence/Auditing/AuditScribe.cs

@@ -78,7 +78,11 @@ public static class AuditScribe
         foreach (var p in entry.Properties)
         {
             if (p.Metadata.IsPrimaryKey()) continue;
-            if (p.Metadata.Name == nameof(Item.RowVersion)) continue;
+            // Semantic rather than name-matched: covers every concurrency token automatically
+            // and survives a rename. (This used to be `Name == nameof(Item.RowVersion)`, which
+            // silently missed BundleSale/BundleSaleTemplate's differently-named token and so
+            // leaked it into every bundle-sale change set.)
+            if (p.Metadata.IsConcurrencyToken) continue;
 
             switch (action)
             {

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

@@ -22,8 +22,6 @@ public sealed class AttendanceRecordConfiguration : IEntityTypeConfiguration<Att
         builder.HasOne(r => r.WorkShift).WithMany()
             .HasForeignKey(r => r.WorkShiftId).OnDelete(DeleteBehavior.Restrict);
 
-        builder.Property(r => r.RowVersion).IsRowVersion();
-
         builder.HasIndex(r => new { r.EmployeeId, r.AttendanceDate });
         builder.HasIndex(r => r.AttendanceUploadBatchId);
     }

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

@@ -19,7 +19,6 @@ public sealed class AttendanceUploadBatchConfiguration : IEntityTypeConfiguratio
         builder.Property(b => b.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
 
         builder.Property(b => b.UploadedAt).IsRequired();
-        builder.Property(b => b.RowVersion).IsRowVersion();
 
         builder.HasIndex(b => b.Status);
         builder.HasIndex(b => new { b.PeriodStart, b.PeriodEnd });

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

@@ -13,7 +13,7 @@ public sealed class AuditLogConfiguration : IEntityTypeConfiguration<AuditLog>
 
         builder.Property(a => a.EntityType).IsRequired().HasMaxLength(80);
         builder.Property(a => a.Action).HasConversion<string>().HasMaxLength(10).IsRequired();
-        builder.Property(a => a.ChangeSet).IsRequired().HasColumnType("jsonb");
+        builder.Property(a => a.ChangeSet).IsRequired().HasColumnType("longtext");
         builder.Property(a => a.CreatedAt).IsRequired();
 
         builder.HasOne<User>().WithMany().HasForeignKey(a => a.UserId).OnDelete(DeleteBehavior.Restrict);

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

@@ -13,7 +13,7 @@ public sealed class BranchConfigConfiguration : IEntityTypeConfiguration<BranchC
     public void Configure(EntityTypeBuilder<BranchConfig> builder)
     {
         builder.ToTable("branch_config", t =>
-            t.HasCheckConstraint("ck_branch_config_singleton", $"\"ConfigId\" = {BranchConfig.SingletonId}"));
+            t.HasCheckConstraint("ck_branch_config_singleton", $"`ConfigId` = {BranchConfig.SingletonId}"));
 
         builder.HasKey(c => c.ConfigId);
 
@@ -22,9 +22,6 @@ public sealed class BranchConfigConfiguration : IEntityTypeConfiguration<BranchC
 
         builder.Property(c => c.BranchingEnabled).IsRequired().HasDefaultValue(true);
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(c => c.RowVersion).IsRowVersion();
-
         builder.HasOne(c => c.UpdatedByUser)
             .WithMany()
             .HasForeignKey(c => c.UpdatedBy)

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

@@ -23,7 +23,6 @@ public sealed class BranchConfiguration : IEntityTypeConfiguration<Branch>
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(b => b.CreatedAt).IsRequired();
-        builder.Property(b => b.RowVersion).IsRowVersion();
 
         builder.HasIndex(b => b.Status);
     }

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

@@ -21,9 +21,6 @@ public sealed class BrandConfiguration : IEntityTypeConfiguration<Brand>
 
         builder.Property(b => b.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(b => b.RowVersion).IsRowVersion();
-
         builder.HasIndex(b => b.Status);
     }
 }

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

@@ -27,11 +27,6 @@ public sealed class BundleSaleConfiguration : IEntityTypeConfiguration<BundleSal
         builder.Property(x => x.TaxTotal).HasPrecision(18, 4);
         builder.Property(x => x.GrandTotal).HasPrecision(18, 4);
         builder.Property(x => x.CreatedAt).IsRequired();
-        builder.Property(x => x.ConcurrencyStamp)
-            .IsRequired()
-            .HasColumnType("integer")
-            .HasDefaultValue(0)
-            .IsConcurrencyToken();
 
         builder.HasOne(x => x.Customer).WithMany().HasForeignKey(x => x.CustomerId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(x => x.Warehouse).WithMany().HasForeignKey(x => x.WarehouseId).OnDelete(DeleteBehavior.Restrict);

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

@@ -20,11 +20,6 @@ public sealed class BundleSaleTemplateConfiguration : IEntityTypeConfiguration<B
             .HasConversion<string>().HasMaxLength(20).IsRequired()
             .HasDefaultValue(EntityStatus.Active);
         builder.Property(x => x.CreatedAt).IsRequired();
-        builder.Property(x => x.ConcurrencyStamp)
-            .IsRequired()
-            .HasColumnType("integer")
-            .HasDefaultValue(0)
-            .IsConcurrencyToken();
 
         builder.HasMany(x => x.Lines)
             .WithOne(x => x.BundleSaleTemplate)

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

@@ -21,9 +21,6 @@ public sealed class CategoryConfiguration : IEntityTypeConfiguration<Category>
 
         builder.Property(c => c.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(c => c.RowVersion).IsRowVersion();
-
         builder.HasIndex(c => c.Status);
     }
 }

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

@@ -42,7 +42,6 @@ public sealed class CustomerConfiguration : IEntityTypeConfiguration<Customer>
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(c => c.CreatedAt).IsRequired();
-        builder.Property(c => c.RowVersion).IsRowVersion();
 
         builder.HasIndex(c => c.Status);
         builder.HasIndex(c => c.CustomerType);

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

@@ -32,7 +32,6 @@ public sealed class DepartmentConfiguration : IEntityTypeConfiguration<Departmen
             .HasForeignKey(d => d.BranchId).OnDelete(DeleteBehavior.Restrict);
 
         builder.Property(d => d.CreatedAt).IsRequired();
-        builder.Property(d => d.RowVersion).IsRowVersion();
 
         builder.HasIndex(d => d.Status);
         builder.HasIndex(d => d.ParentDepartmentId);

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

@@ -21,7 +21,6 @@ public sealed class DesignationConfiguration : IEntityTypeConfiguration<Designat
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(d => d.CreatedAt).IsRequired();
-        builder.Property(d => d.RowVersion).IsRowVersion();
 
         builder.HasIndex(d => d.Status);
     }

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

@@ -26,7 +26,6 @@ public sealed class EmployeeBankDetailConfiguration : IEntityTypeConfiguration<E
             .HasForeignKey(b => b.EmployeeId).OnDelete(DeleteBehavior.Cascade);
 
         builder.Property(b => b.CreatedAt).IsRequired();
-        builder.Property(b => b.RowVersion).IsRowVersion();
 
         builder.HasIndex(b => b.EmployeeId);
     }

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

@@ -63,7 +63,6 @@ public sealed class EmployeeConfiguration : IEntityTypeConfiguration<Employee>
             .HasDefaultValue(EmployeeStatus.Active);
 
         builder.Property(e => e.CreatedAt).IsRequired();
-        builder.Property(e => e.RowVersion).IsRowVersion();
 
         builder.HasIndex(e => e.Status);
         builder.HasIndex(e => e.DepartmentId);

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

@@ -28,7 +28,6 @@ public sealed class EmployeeDocumentConfiguration : IEntityTypeConfiguration<Emp
             .HasForeignKey(d => d.HrDocumentTypeId).OnDelete(DeleteBehavior.Restrict);
 
         builder.Property(d => d.UploadedAt).IsRequired();
-        builder.Property(d => d.RowVersion).IsRowVersion();
 
         builder.HasIndex(d => d.EmployeeId);
         builder.HasIndex(d => d.ExpiryDate);

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

@@ -28,7 +28,6 @@ public sealed class EmployeeLoanConfiguration : IEntityTypeConfiguration<Employe
             .HasForeignKey(i => i.EmployeeLoanId).OnDelete(DeleteBehavior.Cascade);
 
         builder.Property(l => l.CreatedAt).IsRequired();
-        builder.Property(l => l.RowVersion).IsRowVersion();
 
         builder.HasIndex(l => l.EmployeeId);
         builder.HasIndex(l => l.Status);
@@ -49,8 +48,6 @@ public sealed class LoanInstallmentConfiguration : IEntityTypeConfiguration<Loan
         builder.HasOne(i => i.PayrollRun).WithMany()
             .HasForeignKey(i => i.PayrollRunId).OnDelete(DeleteBehavior.Restrict);
 
-        builder.Property(i => i.RowVersion).IsRowVersion();
-
         builder.HasIndex(i => new { i.DueYear, i.DueMonth });
     }
 }

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

@@ -22,7 +22,6 @@ public sealed class EmployeeSalaryStructureConfiguration : IEntityTypeConfigurat
             .HasForeignKey(l => l.EmployeeSalaryStructureId).OnDelete(DeleteBehavior.Cascade);
 
         builder.Property(s => s.CreatedAt).IsRequired();
-        builder.Property(s => s.RowVersion).IsRowVersion();
 
         builder.HasIndex(s => new { s.EmployeeId, s.EffectiveTo });
     }

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

@@ -21,7 +21,6 @@ public sealed class EmploymentTypeConfiguration : IEntityTypeConfiguration<Emplo
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(e => e.CreatedAt).IsRequired();
-        builder.Property(e => e.RowVersion).IsRowVersion();
 
         builder.HasIndex(e => e.Status);
     }

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

@@ -17,7 +17,6 @@ public sealed class GrnConfiguration : IEntityTypeConfiguration<Grn>
         builder.Property(g => g.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(g => g.CreatedAt).IsRequired();
         builder.Property(g => g.GlJournalNo).HasMaxLength(30);
-        builder.Property(g => g.RowVersion).IsRowVersion();
 
         builder.HasOne(g => g.PurchaseOrder).WithMany().HasForeignKey(g => g.PoId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(g => g.Vendor).WithMany().HasForeignKey(g => g.VendorId).OnDelete(DeleteBehavior.Restrict);

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

@@ -22,7 +22,6 @@ public sealed class HrDocumentTypeConfiguration : IEntityTypeConfiguration<HrDoc
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(t => t.CreatedAt).IsRequired();
-        builder.Property(t => t.RowVersion).IsRowVersion();
 
         builder.HasIndex(t => t.Status);
     }

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

@@ -51,9 +51,6 @@ public sealed class ItemConfiguration : IEntityTypeConfiguration<Item>
 
         builder.Property(i => i.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(i => i.RowVersion).IsRowVersion();
-
         builder.HasOne(i => i.Category)
             .WithMany()
             .HasForeignKey(i => i.CategoryId)

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

@@ -30,9 +30,6 @@ public sealed class ItemTypeConfiguration : IEntityTypeConfiguration<ItemType>
 
         builder.Property(t => t.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(t => t.RowVersion).IsRowVersion();
-
         builder.HasIndex(t => t.Status);
     }
 }

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

@@ -21,8 +21,6 @@ public sealed class LeaveBalanceConfiguration : IEntityTypeConfiguration<LeaveBa
         builder.HasOne(b => b.LeaveType).WithMany()
             .HasForeignKey(b => b.LeaveTypeId).OnDelete(DeleteBehavior.Restrict);
 
-        builder.Property(b => b.RowVersion).IsRowVersion();
-
         builder.HasIndex(b => new { b.EmployeeId, b.LeaveTypeId, b.Year }).IsUnique();
     }
 }

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

@@ -26,7 +26,6 @@ public sealed class LeaveRequestConfiguration : IEntityTypeConfiguration<LeaveRe
             .HasForeignKey(r => r.LeaveTypeId).OnDelete(DeleteBehavior.Restrict);
 
         builder.Property(r => r.CreatedAt).IsRequired();
-        builder.Property(r => r.RowVersion).IsRowVersion();
 
         builder.HasIndex(r => r.EmployeeId);
         builder.HasIndex(r => r.Status);

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

@@ -22,7 +22,6 @@ public sealed class LeaveTypeConfiguration : IEntityTypeConfiguration<LeaveType>
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(t => t.CreatedAt).IsRequired();
-        builder.Property(t => t.RowVersion).IsRowVersion();
 
         builder.HasIndex(t => t.Status);
     }

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

@@ -9,13 +9,11 @@ public sealed class NotificationConfigConfiguration : IEntityTypeConfiguration<N
     public void Configure(EntityTypeBuilder<NotificationConfig> builder)
     {
         builder.ToTable("notification_config", t =>
-            t.HasCheckConstraint("ck_notification_config_singleton", $"\"NotificationConfigId\" = {NotificationConfig.SingletonId}"));
+            t.HasCheckConstraint("ck_notification_config_singleton", $"`NotificationConfigId` = {NotificationConfig.SingletonId}"));
 
         builder.HasKey(c => c.NotificationConfigId);
         builder.Property(c => c.NotificationConfigId).ValueGeneratedNever();
 
-        builder.Property(c => c.RowVersion).IsRowVersion();
-
         builder.HasMany(c => c.Modules)
             .WithOne(m => m.NotificationConfig)
             .HasForeignKey(m => m.NotificationConfigId)

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

@@ -20,7 +20,7 @@ public sealed class PayrollLineConfiguration : IEntityTypeConfiguration<PayrollL
             nameof(PayrollLine.NetSalary)
         })
         {
-            builder.Property(money).HasColumnType("numeric(18,2)");
+            builder.Property(money).HasPrecision(18, 2);
         }
 
         builder.HasOne(l => l.Employee).WithMany()
@@ -29,8 +29,6 @@ public sealed class PayrollLineConfiguration : IEntityTypeConfiguration<PayrollL
         builder.HasMany(l => l.Components).WithOne(c => c.PayrollLine!)
             .HasForeignKey(c => c.PayrollLineId).OnDelete(DeleteBehavior.Cascade);
 
-        builder.Property(l => l.RowVersion).IsRowVersion();
-
         builder.HasIndex(l => new { l.PayrollRunId, l.EmployeeId }).IsUnique();
     }
 }

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

@@ -23,7 +23,6 @@ public sealed class PayrollRunConfiguration : IEntityTypeConfiguration<PayrollRu
             .HasForeignKey(l => l.PayrollRunId).OnDelete(DeleteBehavior.Cascade);
 
         builder.Property(r => r.GeneratedAt).IsRequired();
-        builder.Property(r => r.RowVersion).IsRowVersion();
 
         builder.HasIndex(r => new { r.PeriodYear, r.PeriodMonth, r.BranchId });
         builder.HasIndex(r => r.Status);

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

@@ -17,7 +17,6 @@ public sealed class PayrollStatutorySettingConfiguration : IEntityTypeConfigurat
         builder.Property(s => s.OtMultiplierDefault).HasPrecision(6, 2);
 
         builder.Property(s => s.CreatedAt).IsRequired();
-        builder.Property(s => s.RowVersion).IsRowVersion();
 
         builder.HasIndex(s => s.EffectiveFrom);
     }
@@ -35,7 +34,6 @@ public sealed class TaxSlabConfiguration : IEntityTypeConfiguration<TaxSlab>
         builder.Property(s => s.Rate).HasPrecision(6, 4);
 
         builder.Property(s => s.CreatedAt).IsRequired();
-        builder.Property(s => s.RowVersion).IsRowVersion();
 
         builder.HasIndex(s => s.EffectiveFrom);
     }

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

@@ -15,7 +15,7 @@ public sealed class ProductConfigConfiguration : IEntityTypeConfiguration<Produc
         // The column is created as quoted PascalCase ("ConfigId"), so the constraint must
         // quote it too — an unquoted config_id would fold to a column that does not exist.
         builder.ToTable("product_config", t =>
-            t.HasCheckConstraint("ck_product_config_singleton", $"\"ConfigId\" = {ProductConfig.SingletonId}"));
+            t.HasCheckConstraint("ck_product_config_singleton", $"`ConfigId` = {ProductConfig.SingletonId}"));
 
         builder.HasKey(c => c.ConfigId);
 
@@ -29,9 +29,7 @@ public sealed class ProductConfigConfiguration : IEntityTypeConfiguration<Produc
         builder.Property(c => c.SerialNumbersEnabled).IsRequired().HasDefaultValue(true);
         builder.Property(c => c.BatchListsEnabled).IsRequired().HasDefaultValue(true);
         builder.Property(c => c.WarrantyPeriodsEnabled).IsRequired().HasDefaultValue(true);
-        builder.Property(c => c.CustomVariantsEnabled).IsRequired().HasDefaultValue(false);
-        builder.Property(c => c.ItemImagesEnabled).IsRequired().HasDefaultValue(false);
-        builder.Property(c => c.CustomWarrantyPeriodsEnabled).IsRequired().HasDefaultValue(false);
+
         // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
         builder.Property(c => c.RowVersion).IsRowVersion();
 

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

@@ -32,13 +32,10 @@ public sealed class ProductionTemplateConfiguration : IEntityTypeConfiguration<P
 
         // Same jsonb-as-string mapping as TemplateStage.FieldDefs and AuditLog.ChangeSet: a
         // typed/owned mapping would make AuditScribe emit audit rows for the nested entries.
-        builder.Property(t => t.Annotations).HasColumnType("jsonb");
+        builder.Property(t => t.Annotations).HasColumnType("longtext");
 
         builder.Property(t => t.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(t => t.RowVersion).IsRowVersion();
-
         builder.HasOne(t => t.Creator).WithMany().HasForeignKey(t => t.CreatedBy).OnDelete(DeleteBehavior.Restrict);
 
         builder.HasIndex(t => t.Status);
@@ -56,7 +53,7 @@ public sealed class TemplateStageConfiguration : IEntityTypeConfiguration<Templa
         builder.Property(s => s.RoleLabel).HasMaxLength(60);
         builder.Property(s => s.PosX).HasPrecision(18, 4);
         builder.Property(s => s.PosY).HasPrecision(18, 4);
-        builder.Property(s => s.FieldDefs).IsRequired().HasColumnType("jsonb");
+        builder.Property(s => s.FieldDefs).IsRequired().HasColumnType("longtext");
 
         builder.HasOne(s => s.Template).WithMany(t => t.Stages)
             .HasForeignKey(s => s.TemplateId).OnDelete(DeleteBehavior.Cascade);
@@ -135,7 +132,6 @@ public sealed class ProductionRunConfiguration : IEntityTypeConfiguration<Produc
         builder.Property(r => r.ScaleFactor).HasPrecision(18, 6);
         builder.Property(r => r.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(r => r.CreatedAt).IsRequired();
-        builder.Property(r => r.RowVersion).IsRowVersion();
 
         builder.HasOne(r => r.Template).WithMany(t => t.Runs)
             .HasForeignKey(r => r.TemplateId).OnDelete(DeleteBehavior.Restrict);
@@ -162,9 +158,8 @@ public sealed class RunStageConfiguration : IEntityTypeConfiguration<RunStage>
         builder.Property(s => s.PosX).HasPrecision(18, 4);
         builder.Property(s => s.PosY).HasPrecision(18, 4);
         builder.Property(s => s.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
-        builder.Property(s => s.FieldDefs).IsRequired().HasColumnType("jsonb");
-        builder.Property(s => s.FieldValues).HasColumnType("jsonb");
-        builder.Property(s => s.RowVersion).IsRowVersion();
+        builder.Property(s => s.FieldDefs).IsRequired().HasColumnType("longtext");
+        builder.Property(s => s.FieldValues).HasColumnType("longtext");
 
         builder.HasOne(s => s.Run).WithMany(r => r.Stages)
             .HasForeignKey(s => s.RunId).OnDelete(DeleteBehavior.Cascade);
@@ -258,7 +253,7 @@ public sealed class RunStageEventConfiguration : IEntityTypeConfiguration<RunSta
 
         builder.Property(e => e.EventType).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(e => e.Note).HasMaxLength(500);
-        builder.Property(e => e.Payload).HasColumnType("jsonb");
+        builder.Property(e => e.Payload).HasColumnType("longtext");
         builder.Property(e => e.CreatedAt).IsRequired();
 
         builder.HasOne(e => e.Run).WithMany(r => r.Events)

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

@@ -40,7 +40,6 @@ public sealed class PurchaseInvoiceConfiguration : IEntityTypeConfiguration<Purc
 
         builder.HasOne(x => x.Creator).WithMany().HasForeignKey(x => x.CreatedBy).OnDelete(DeleteBehavior.Restrict);
         builder.Property(x => x.CreatedAt).IsRequired();
-        builder.Property(x => x.RowVersion).IsRowVersion();
 
         builder.HasIndex(x => x.Status);
         builder.HasIndex(x => x.VendorId);

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

@@ -18,9 +18,6 @@ public sealed class PurchaseOrderConfiguration : IEntityTypeConfiguration<Purcha
             .HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(p => p.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(p => p.RowVersion).IsRowVersion();
-
         builder.HasOne(p => p.Vendor)
             .WithMany()
             .HasForeignKey(p => p.VendorId)

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

@@ -27,7 +27,5 @@ public sealed class RoleConfiguration : IEntityTypeConfiguration<Role>
 
         builder.Property(r => r.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(r => r.RowVersion).IsRowVersion();
     }
 }

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

@@ -22,7 +22,6 @@ public sealed class SalaryComponentConfiguration : IEntityTypeConfiguration<Sala
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(c => c.CreatedAt).IsRequired();
-        builder.Property(c => c.RowVersion).IsRowVersion();
 
         builder.HasIndex(c => c.Status);
     }

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

@@ -25,7 +25,6 @@ public sealed class SalesDayEndConfiguration : IEntityTypeConfiguration<SalesDay
 
         builder.Property(x => x.GlJournalNo).HasMaxLength(30);
         builder.Property(x => x.ClosedAt).IsRequired();
-        builder.Property(x => x.RowVersion).IsRowVersion();
 
         builder.HasOne(x => x.CashierUser).WithMany().HasForeignKey(x => x.CashierUserId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(x => x.ClosedByUser).WithMany().HasForeignKey(x => x.ClosedBy).OnDelete(DeleteBehavior.Restrict);

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

@@ -48,7 +48,6 @@ public sealed class SalesInvoiceConfiguration : IEntityTypeConfiguration<SalesIn
         builder.Property(x => x.GlJournalNo).HasMaxLength(30);
 
         builder.Property(x => x.CreatedAt).IsRequired();
-        builder.Property(x => x.RowVersion).IsRowVersion();
 
         builder.HasIndex(x => x.Status);
         builder.HasIndex(x => x.InvoiceDate);
@@ -113,6 +112,5 @@ public sealed class SalesInvoiceLineConfiguration : IEntityTypeConfiguration<Sal
             .OnDelete(DeleteBehavior.Restrict);
 
         builder.Property(x => x.PriceSource).HasMaxLength(50);
-        builder.Property(x => x.RowVersion).IsRowVersion();
     }
 }

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

@@ -42,7 +42,6 @@ public sealed class SalesSlipConfiguration : IEntityTypeConfiguration<SalesSlip>
             builder.Property<decimal>(p).HasPrecision(18, 4);
 
         builder.Property(x => x.CreatedAt).IsRequired();
-        builder.Property(x => x.RowVersion).IsRowVersion();
 
         builder.HasIndex(x => x.Status);
         builder.HasIndex(x => x.SlipDate);
@@ -95,6 +94,5 @@ public sealed class SalesSlipLineConfiguration : IEntityTypeConfiguration<SalesS
             .OnDelete(DeleteBehavior.Restrict);
 
         builder.Property(x => x.PriceSource).HasMaxLength(50);
-        builder.Property(x => x.RowVersion).IsRowVersion();
     }
 }

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

@@ -17,7 +17,6 @@ public sealed class StockAdjustmentConfiguration : IEntityTypeConfiguration<Stoc
         builder.Property(a => a.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(a => a.CreatedAt).IsRequired();
         builder.Property(a => a.GlJournalNo).HasMaxLength(30);
-        builder.Property(a => a.RowVersion).IsRowVersion();
 
         builder.HasOne(a => a.Warehouse).WithMany().HasForeignKey(a => a.WarehouseId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(a => a.ReasonCode).WithMany().HasForeignKey(a => a.ReasonCodeId).OnDelete(DeleteBehavior.Restrict);

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

@@ -17,7 +17,6 @@ public sealed class StockCountConfiguration : IEntityTypeConfiguration<StockCoun
         builder.Property(c => c.CountType).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(c => c.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(c => c.CreatedAt).IsRequired();
-        builder.Property(c => c.RowVersion).IsRowVersion();
 
         builder.HasOne(c => c.Warehouse).WithMany().HasForeignKey(c => c.WarehouseId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(c => c.Branch).WithMany().HasForeignKey(c => c.BranchId).OnDelete(DeleteBehavior.Restrict);

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

@@ -16,7 +16,6 @@ public sealed class StockTransferConfiguration : IEntityTypeConfiguration<StockT
 
         builder.Property(t => t.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(t => t.CreatedAt).IsRequired();
-        builder.Property(t => t.RowVersion).IsRowVersion();
 
         builder.HasOne(t => t.SrcWarehouse).WithMany().HasForeignKey(t => t.SrcWarehouseId).OnDelete(DeleteBehavior.Restrict);
         builder.HasOne(t => t.DestWarehouse).WithMany().HasForeignKey(t => t.DestWarehouseId).OnDelete(DeleteBehavior.Restrict);

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

@@ -20,9 +20,6 @@ public sealed class SubCategoryConfiguration : IEntityTypeConfiguration<SubCateg
 
         builder.Property(s => s.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(s => s.RowVersion).IsRowVersion();
-
         builder.HasOne(s => s.Category)
             .WithMany(c => c.SubCategories)
             .HasForeignKey(s => s.CategoryId)

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

@@ -13,7 +13,6 @@ public sealed class SupportTicketConfiguration : IEntityTypeConfiguration<Suppor
 
         builder.Property(t => t.Subject).IsRequired().HasMaxLength(200);
         builder.Property(t => t.Status).IsRequired().HasConversion<string>().HasMaxLength(20);
-        builder.Property(t => t.RowVersion).IsRowVersion();
 
         builder.HasIndex(t => t.CreatedBy);
         builder.HasIndex(t => t.Status);

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

@@ -24,9 +24,6 @@ public sealed class TaxRateConfiguration : IEntityTypeConfiguration<TaxRate>
 
         builder.Property(t => t.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(t => t.RowVersion).IsRowVersion();
-
         builder.HasIndex(t => t.Status);
 
         // Seeded so Item.TaxRateId has something real to point at immediately — codes
@@ -34,9 +31,9 @@ public sealed class TaxRateConfiguration : IEntityTypeConfiguration<TaxRate>
         // afterward (percentages are typically jurisdiction-specific).
         var seededAt = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc);
         builder.HasData(
-            new TaxRate { TaxRateId = 1, Code = "STANDARD", Name = "Standard", Percentage = 15m, CreatedAt = seededAt },
-            new TaxRate { TaxRateId = 2, Code = "ZERO", Name = "Zero-Rated", Percentage = 0m, CreatedAt = seededAt },
-            new TaxRate { TaxRateId = 3, Code = "EXEMPT", Name = "Exempt", Percentage = 0m, CreatedAt = seededAt }
+            new TaxRate { TaxRateId = 1, Code = "STANDARD", Name = "Standard", Percentage = 15m, CreatedAt = seededAt, RowVersion = 1 },
+            new TaxRate { TaxRateId = 2, Code = "ZERO", Name = "Zero-Rated", Percentage = 0m, CreatedAt = seededAt, RowVersion = 1 },
+            new TaxRate { TaxRateId = 3, Code = "EXEMPT", Name = "Exempt", Percentage = 0m, CreatedAt = seededAt, RowVersion = 1 }
         );
     }
 }

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

@@ -26,9 +26,6 @@ public sealed class VendorConfiguration : IEntityTypeConfiguration<Vendor>
 
         builder.Property(v => v.CreatedAt).IsRequired();
 
-        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
-        builder.Property(v => v.RowVersion).IsRowVersion();
-
         builder.HasIndex(v => v.Status);
 
         builder.HasOne(v => v.Branch).WithMany()

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

@@ -22,7 +22,6 @@ public sealed class WorkShiftConfiguration : IEntityTypeConfiguration<WorkShift>
             .HasDefaultValue(EntityStatus.Active);
 
         builder.Property(w => w.CreatedAt).IsRequired();
-        builder.Property(w => w.RowVersion).IsRowVersion();
 
         builder.HasIndex(w => w.Status);
     }

Backend/ERPCore/Infra/Persistence/DataSeeder.cs

@@ -1,15 +1,23 @@
 using ERPCore.Domain.Entities;
-using ERPCore.Domain;
 using ERPCore.Domain.Enums;
 using Microsoft.EntityFrameworkCore;
 
 namespace ERPCore.Infra.Persistence;
 
 /// <summary>
-/// Idempotent startup seeding of configurable reference data (docs/10 §B.8.3).
-/// Reason codes are seeded at runtime (not via <c>HasData</c>) so the identity
-/// sequence advances normally and later admin <c>POST /reason-codes</c> calls
-/// cannot collide with seeded ids.
+/// Idempotent startup seeding of the reference data the application cannot run without
+/// (docs/10 §B.8.3): the default branch, reason codes, item types, and the three singleton
+/// config rows. Navigation items, sub-nav items, permissions, tax rates and the `system`
+/// user come from <c>HasData</c> in Infra/Persistence/Configurations instead, so the
+/// baseline migration emits them as InsertData.
+///
+/// Reason codes are seeded at runtime (not via <c>HasData</c>) so the identity sequence
+/// advances normally and later admin <c>POST /reason-codes</c> calls cannot collide with
+/// seeded ids.
+///
+/// Demo/sample data (warehouses MAIN/SHOP, UOMs, categories, demo items, fabricated stock
+/// layers, sample invoices/slips, bundle sales) was removed with the MySQL port: a fresh
+/// database is now production-shaped. The e2e suite creates whatever fixtures it needs.
 /// </summary>
 public static class DataSeeder
 {
@@ -41,21 +49,57 @@ public static class DataSeeder
 
     public static async Task SeedAsync(ErpDbContext db, CancellationToken ct = default)
     {
+        // Must come first, and must save on its own: every branch-scoped entity has a
+        // non-nullable BranchId with a Restrict FK, so nothing branch-scoped can be written
+        // until this row has a real generated id.
+        await EnsureDefaultBranchAsync(db, ct);
+
         var dirty = await SeedReasonCodesAsync(db, ct);
         dirty |= await SeedItemTypesAsync(db, ct);
-        // dirty |= await SeedCompanyProfileAsync(db, ct);
         dirty |= await SeedProductConfigAsync(db, ct);
         dirty |= await SeedBranchConfigAsync(db, ct);
         dirty |= await SeedSalesConfigAsync(db, ct);
         dirty |= await SeedGrnConfigAsync(db, ct);
         dirty |= await SeedNotificationConfigAsync(db, ct);
-        dirty |= await SeedSalesMastersAsync(db, ct);
-        dirty |= await SeedSalesStockAsync(db, ct);
-        dirty |= await SeedSalesAsync(db, ct);
 
         if (dirty) await db.SaveChangesAsync(ct);
     }
 
+    /// <summary>
+    /// Creates the deployment's default branch (<see cref="Branch.DefaultCode"/>) if absent.
+    /// </summary>
+    /// <remarks>
+    /// Before the MySQL port this row was inserted by raw SQL inside the BranchIsolationPhase1
+    /// migration, which the squash to a single baseline deleted — so on a genuinely fresh
+    /// database there would be no branch at all and the first branch-scoped insert would fail
+    /// on the FK. It is deliberately NOT <c>HasData</c>: branches are user-editable business
+    /// data, and an admin renaming this one through the UI would become permanent model drift
+    /// that EF tries to "correct" on the next migration.
+    ///
+    /// <see cref="Services.BranchConfigService.ResolveDefaultBranchIdAsync"/> keeps its lazy
+    /// create as the runtime fallback, but seeding here means it never has to fire mid-request
+    /// (where it would do a nested SaveChanges inside a caller's UoW transaction).
+    /// </remarks>
+    private static async Task<int> EnsureDefaultBranchAsync(ErpDbContext db, CancellationToken ct)
+    {
+        var existingId = await db.Branches.AsNoTracking()
+            .Where(b => b.Code == Branch.DefaultCode)
+            .Select(b => b.BranchId)
+            .FirstOrDefaultAsync(ct);
+        if (existingId != 0) return existingId;
+
+        var branch = new Branch
+        {
+            Code = Branch.DefaultCode,
+            Name = Branch.DefaultName,
+            Status = EntityStatus.Active,
+            CreatedAt = DateTime.UtcNow
+        };
+        db.Branches.Add(branch);
+        await db.SaveChangesAsync(ct);
+        return branch.BranchId;
+    }
+
     private static async Task<bool> SeedReasonCodesAsync(ErpDbContext db, CancellationToken ct)
     {
         var existing = await db.ReasonCodes
@@ -165,747 +209,4 @@ public static class DataSeeder
         });
         return true;
     }
-
-    /// <summary>
-    /// Seeds a printable company profile with reasonable defaults for invoice headers.
-    /// These values are intentionally editable later through the API.
-    /// </summary>
-    //private static async Task<bool> SeedCompanyProfileAsync(ErpDbContext db, CancellationToken ct)
-    //{
-    //    if (await db.CompanyProfiles.AnyAsync(c => c.CompanyProfileId == CompanyProfile.SingletonId, ct)) return false;
-
-    //    db.CompanyProfiles.Add(new CompanyProfile
-    //    {
-    //        CompanyProfileId = CompanyProfile.SingletonId,
-    //        LegalName = "ERP Core Trading (Pvt) Ltd",
-    //        TradeName = "ERP Core Trading",
-    //        TaxRegistrationNo = "TAX-DEFAULT-001",
-    //        VatRegistrationNo = "VAT-DEFAULT-001",
-    //        AddressLine1 = "1 Demo Street",
-    //        City = "Colombo",
-    //        Country = "Sri Lanka",
-    //        Phone = "+94 11 000 0000",
-    //        Email = "accounts@example.com",
-    //        BankName = "Demo Bank",
-    //        BankBranch = "Colombo Main",
-    //        AccountName = "ERP Core Trading (Pvt) Ltd",
-    //        AccountNumber = "000123456789",
-    //        SwiftCode = "DEMO1234",
-    //        FooterNote = "Thank you for your business."
-    //    });
-    //    return true;
-    //}
-
-    /// <summary>
-    /// Seeds the minimum catalog data required for the sales demo rows to exist.
-    /// These are safe additive rows and do not alter any existing data.
-    /// </summary>
-    private static async Task<bool> SeedSalesMastersAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var dirty = false;
-
-        dirty |= await SeedWarehousesAsync(db, ct);
-        dirty |= await SeedUomsAsync(db, ct);
-        dirty |= await SeedCategoriesAsync(db, ct);
-        dirty |= await SeedItemsAsync(db, ct);
-
-        return dirty;
-    }
-
-    /// <summary>
-    /// Seeds a simple on-hand FIFO layer for the demo sales item so the sample
-    /// invoices can be posted without immediately failing stock validation.
-    /// This keeps the stock-check and posting flows testable on a fresh database.
-    /// </summary>
-    private static async Task<bool> SeedSalesStockAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var warehouse = await db.Warehouses.AsNoTracking()
-            .OrderBy(w => w.WarehouseId)
-            .FirstOrDefaultAsync(ct);
-        var item = await db.Items.AsNoTracking()
-            .OrderBy(i => i.ItemId)
-            .FirstOrDefaultAsync(ct);
-        var secondItem = await db.Items.AsNoTracking()
-            .OrderByDescending(i => i.ItemId)
-            .FirstOrDefaultAsync(ct);
-
-        if (warehouse is null || item is null || secondItem is null)
-            return false;
-
-        var existing = await db.StockLayers.AnyAsync(
-            l => (l.ItemId == item.ItemId || l.ItemId == secondItem.ItemId) && l.WarehouseId == warehouse.WarehouseId && l.QtyRemaining > 0m,
-            ct);
-        if (existing) return false;
-
-        db.StockLayers.Add(new StockLayer
-        {
-            ItemId = item.ItemId,
-            WarehouseId = warehouse.WarehouseId,
-            QtyReceived = 100m,
-            QtyRemaining = 100m,
-            UnitCost = item.SellingFlatPrice.GetValueOrDefault() > 0m ? item.SellingFlatPrice.GetValueOrDefault() / 2m : 25m,
-            ReceiptDate = DateTime.UtcNow.AddDays(-7)
-        });
-        db.StockLayers.Add(new StockLayer
-        {
-            ItemId = secondItem.ItemId,
-            WarehouseId = warehouse.WarehouseId,
-            QtyReceived = 5m,
-            QtyRemaining = 5m,
-            UnitCost = secondItem.SellingFlatPrice.GetValueOrDefault() > 0m ? secondItem.SellingFlatPrice.GetValueOrDefault() / 2m : 15m,
-            ReceiptDate = DateTime.UtcNow.AddDays(-6)
-        });
-        return true;
-    }
-
-    private static async Task<bool> SeedWarehousesAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var existingCodes = await db.Warehouses.Select(w => w.Code).ToListAsync(ct);
-        var have = existingCodes.ToHashSet(StringComparer.OrdinalIgnoreCase);
-
-        var seeds = new[]
-        {
-            new Warehouse { Code = "MAIN", Name = "Main Warehouse" },
-            new Warehouse { Code = "SHOP", Name = "Sales Counter" }
-        };
-
-        var toAdd = seeds.Where(w => !have.Contains(w.Code)).ToList();
-        if (toAdd.Count == 0) return false;
-
-        db.Warehouses.AddRange(toAdd);
-        return true;
-    }
-
-    private static async Task<bool> SeedUomsAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var existingNames = await db.Uoms.Select(u => u.Name).ToListAsync(ct);
-        var have = existingNames.ToHashSet(StringComparer.OrdinalIgnoreCase);
-
-        var seeds = new[]
-        {
-            new Uom { Name = "PCS" },
-            new Uom { Name = "BOX" }
-        };
-
-        var toAdd = seeds.Where(u => !have.Contains(u.Name)).ToList();
-        if (toAdd.Count == 0) return false;
-
-        db.Uoms.AddRange(toAdd);
-        return true;
-    }
-
-    private static async Task<bool> SeedCategoriesAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var existingNames = await db.Categories.Select(c => c.Name).ToListAsync(ct);
-        var have = existingNames.ToHashSet(StringComparer.OrdinalIgnoreCase);
-
-        var seeds = new[]
-        {
-            new Category { Name = "General Goods", Status = EntityStatus.Active, CreatedAt = DateTime.UtcNow },
-            new Category { Name = "Accessories", Status = EntityStatus.Active, CreatedAt = DateTime.UtcNow }
-        };
-
-        var toAdd = seeds.Where(c => !have.Contains(c.Name)).ToList();
-        if (toAdd.Count == 0) return false;
-
-        db.Categories.AddRange(toAdd);
-        return true;
-    }
-
-    private static async Task<bool> SeedItemsAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var existingSkus = await db.Items.Select(i => i.Sku).ToListAsync(ct);
-        var have = existingSkus.ToHashSet(StringComparer.OrdinalIgnoreCase);
-
-        var category = await db.Categories.AsNoTracking()
-            .OrderBy(c => c.CategoryId)
-            .FirstOrDefaultAsync(ct);
-        var uom = await db.Uoms.AsNoTracking()
-            .OrderBy(u => u.UomId)
-            .FirstOrDefaultAsync(ct);
-
-        if (category is null || uom is null)
-            return false;
-
-        var now = DateTime.UtcNow;
-        var seeds = new[]
-        {
-            new Item
-            {
-                Sku = "SKU-DEMO-001",
-                Name = "Demo Item 1",
-                Description = "Seeded sample item for sales documents",
-                CategoryId = category.CategoryId,
-                BaseUomId = uom.UomId,
-                StockNature = StockNature.Stocked,
-                TrackingMode = TrackingMode.None,
-                SellingFlatPrice = 100m,
-                Status = EntityStatus.Active,
-                CreatedAt = now
-            },
-            new Item
-            {
-                Sku = "SKU-DEMO-002",
-                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,
-                SellingFlatPrice = 50m,
-                ContentQty = 500m,
-                ContentUnit = MeasureUnit.Ml,
-                ContentBaseQty = 500m,
-                ContentBaseUnit = MeasureUnit.Ml,
-                Status = EntityStatus.Active,
-                CreatedAt = now
-            }
-        };
-
-        var toAdd = seeds.Where(i => !have.Contains(i.Sku)).ToList();
-        if (toAdd.Count == 0) return false;
-
-        db.Items.AddRange(toAdd);
-        return true;
-    }
-
-    /// <summary>
-    /// Seeds the minimum sales bootstrap data needed for UI/backend development:
-    /// a couple of customer rows, current-year document counters, and a few draft
-    /// invoice/slip samples when the required master data already exists.
-    /// This intentionally never clears or rewrites any existing rows.
-    /// </summary>
-    private static async Task<bool> SeedSalesAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var dirty = false;
-
-        dirty |= await SeedSalesCustomersAsync(db, ct);
-        dirty |= await SeedSalesSequencesAsync(db, ct);
-        dirty |= await SeedSampleSalesDocsAsync(db, ct);
-
-        try
-        {
-            dirty |= await SeedBundleSalesAsync(db, ct);
-        }
-        catch
-        {
-            // Bundle demo data is best-effort only; never block startup because of seed drift.
-        }
-
-        return dirty;
-    }
-
-    private static async Task<bool> SeedSalesCustomersAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var existingCodes = await db.Customers.Select(c => c.CustomerCode).ToListAsync(ct);
-        var have = existingCodes.ToHashSet(StringComparer.OrdinalIgnoreCase);
-
-        var seeds = new[]
-        {
-            new Customer
-            {
-                CustomerCode = "CUST-WALKIN",
-                CustomerType = CustomerType.B2C,
-                Name = "Walk-in Customer",
-                DisplayName = "Walk-in Customer",
-                CreditLimit = 0m,
-                CreditDays = 0,
-                Status = EntityStatus.Active,
-                CreatedAt = DateTime.UtcNow
-            },
-            new Customer
-            {
-                CustomerCode = "CUST-DEMO",
-                CustomerType = CustomerType.B2B,
-                Name = "Demo Retail Ltd",
-                DisplayName = "Demo Retail Ltd",
-                Phone = "+94 11 000 0000",
-                Email = "sales@example.com",
-                AddressLine1 = "1 Demo Street",
-                City = "Colombo",
-                Country = "Sri Lanka",
-                TaxRegistrationNo = "VAT-DEMO-001",
-                CreditLimit = 250000m,
-                CreditDays = 30,
-                Status = EntityStatus.Active,
-                CreatedAt = DateTime.UtcNow
-            }
-        };
-
-        var toAdd = seeds.Where(c => !have.Contains(c.CustomerCode)).ToList();
-        if (toAdd.Count == 0) return false;
-
-        db.Customers.AddRange(toAdd);
-        return true;
-    }
-
-    private static async Task<bool> SeedSalesSequencesAsync(ErpDbContext db, CancellationToken ct)
-    {
-        var year = DateTime.UtcNow.Year;
-        var existing = await db.NumberSequences
-            .Where(s => s.Year == year && (s.DocType == DocumentTypes.SalesInvoice || s.DocType == DocumentTypes.SalesSlip || s.DocType == DocumentTypes.BundleSale))
-            .Select(s => s.DocType)
-            .ToListAsync(ct);
-        var have = existing.ToHashSet(StringComparer.OrdinalIgnoreCase);
-
-        var seeds = new[]
-        {
-            new NumberSequence { DocType = DocumentTypes.SalesInvoice, Year = year, LastNumber = 0 },
-            new NumberSequence { DocType = DocumentTypes.SalesSlip, Year = year, LastNumber = 0 },
-            new NumberSequence { DocType = DocumentTypes.BundleSale, Year = year, LastNumber = 0 }
-        };
-
-        var toAdd = seeds.Where(s => !have.Contains(s.DocType)).ToList();
-        if (toAdd.Count == 0) return false;
-
-        db.NumberSequences.AddRange(toAdd);
-        return true;
-    }
-
-    private static async Task<bool> SeedBundleSalesAsync(ErpDbContext db, CancellationToken ct)
-    {
-        if (await db.BundleSaleTemplates.AnyAsync(ct) || await db.BundleSales.AnyAsync(ct))
-            return false;
-
-        var customer = await db.Customers.AsNoTracking()
-            .OrderBy(c => c.CustomerId)
-            .FirstOrDefaultAsync(ct);
-        var warehouse = await db.Warehouses.AsNoTracking()
-            .OrderBy(w => w.WarehouseId)
-            .FirstOrDefaultAsync(ct);
-        var secondaryWarehouse = await db.Warehouses.AsNoTracking()
-            .OrderByDescending(w => w.WarehouseId)
-            .FirstOrDefaultAsync(ct);
-        var items = await db.Items.AsNoTracking()
-            .OrderBy(i => i.ItemId)
-            .Take(2)
-            .ToListAsync(ct);
-        var uom = await db.Uoms.AsNoTracking()
-            .OrderBy(u => u.UomId)
-            .FirstOrDefaultAsync(ct);
-        var user = await db.Users.AsNoTracking()
-            .OrderBy(u => u.UserId)
-            .FirstOrDefaultAsync(ct);
-
-        if (customer is null || warehouse is null || secondaryWarehouse is null || items.Count < 2 || uom is null || user is null)
-            return false;
-
-        var now = DateTime.UtcNow;
-        var template = new BundleSaleTemplate
-        {
-            TemplateCode = "BND-DEMO-001",
-            TemplateName = "Demo Bundle Pack",
-            Description = "Seeded fixed bundle template for integration testing",
-            Status = EntityStatus.Active,
-            CreatedAt = now,
-            Lines =
-            [
-                new BundleSaleTemplateLine
-                {
-                    ItemId = items[0].ItemId,
-                    WarehouseId = warehouse.WarehouseId,
-                    Qty = 1m,
-                    UnitPrice = items[0].SellingFlatPrice.GetValueOrDefault(),
-                    IncludeInBundle = true,
-                    SortOrder = 1
-                },
-                new BundleSaleTemplateLine
-                {
-                    ItemId = items[1].ItemId,
-                    WarehouseId = warehouse.WarehouseId,
-                    Qty = 1m,
-                    UnitPrice = items[1].SellingFlatPrice.GetValueOrDefault(),
-                    IncludeInBundle = true,
-                    SortOrder = 2
-                }
-            ]
-        };
-
-        db.BundleSaleTemplates.Add(template);
-        await db.SaveChangesAsync(ct);
-
-        var bundleSales = new[]
-        {
-            new BundleSale
-            {
-                BundleNo = $"BND-{now:yyyy}-00001",
-                BundleDate = now.Date.AddDays(-2),
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.DisplayName ?? customer.Name,
-                WarehouseId = warehouse.WarehouseId,
-                CashierUserId = user.UserId,
-                BundleSaleTemplateId = template.BundleSaleTemplateId,
-                BundleName = "Demo Bundle Draft",
-                BundleCode = "BND-DEMO-001",
-                Status = BundleSaleStatus.Draft,
-                ComponentSubtotal = items[0].SellingFlatPrice.GetValueOrDefault() + items[1].SellingFlatPrice.GetValueOrDefault(),
-                BundlePrice = 0m,
-                MarginAmount = -(items[0].SellingFlatPrice.GetValueOrDefault() + items[1].SellingFlatPrice.GetValueOrDefault()),
-                DiscountTotal = items[0].SellingFlatPrice.GetValueOrDefault() + items[1].SellingFlatPrice.GetValueOrDefault(),
-                TaxTotal = 0m,
-                GrandTotal = 0m,
-                CreatedAt = now.AddDays(-2),
-                Lines =
-                [
-                    new BundleSaleLine
-                    {
-                        ItemId = items[0].ItemId,
-                        Description = items[0].Name,
-                        Qty = 1m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = items[0].SellingFlatPrice.GetValueOrDefault(),
-                        LineTotal = items[0].SellingFlatPrice.GetValueOrDefault(),
-                        IncludeInBundle = true,
-                        IsComponent = true
-                    },
-                    new BundleSaleLine
-                    {
-                        ItemId = items[1].ItemId,
-                        Description = items[1].Name,
-                        Qty = 1m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = items[1].SellingFlatPrice.GetValueOrDefault(),
-                        LineTotal = items[1].SellingFlatPrice.GetValueOrDefault(),
-                        IncludeInBundle = true,
-                        IsComponent = true
-                    }
-                ]
-            },
-            new BundleSale
-            {
-                BundleNo = $"BND-{now:yyyy}-00002",
-                BundleDate = now.Date.AddDays(-1),
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.DisplayName ?? customer.Name,
-                WarehouseId = warehouse.WarehouseId,
-                CashierUserId = user.UserId,
-                BundleSaleTemplateId = template.BundleSaleTemplateId,
-                BundleName = "Demo Bundle Posted",
-                BundleCode = "BND-DEMO-001",
-                Status = BundleSaleStatus.Posted,
-                ComponentSubtotal = items[0].SellingFlatPrice.GetValueOrDefault() + items[1].SellingFlatPrice.GetValueOrDefault(),
-                BundlePrice = (items[0].SellingFlatPrice.GetValueOrDefault() + items[1].SellingFlatPrice.GetValueOrDefault()) - 10m,
-                MarginAmount = -10m,
-                DiscountTotal = 10m,
-                TaxTotal = 0m,
-                GrandTotal = (items[0].SellingFlatPrice.GetValueOrDefault() + items[1].SellingFlatPrice.GetValueOrDefault()) - 10m,
-                CreatedAt = now.AddDays(-1),
-                UpdatedAt = now.AddHours(-2),
-                Lines =
-                [
-                    new BundleSaleLine
-                    {
-                        ItemId = items[0].ItemId,
-                        Description = items[0].Name,
-                        Qty = 1m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = items[0].SellingFlatPrice.GetValueOrDefault(),
-                        LineTotal = items[0].SellingFlatPrice.GetValueOrDefault(),
-                        IncludeInBundle = true,
-                        IsComponent = true
-                    },
-                    new BundleSaleLine
-                    {
-                        ItemId = items[1].ItemId,
-                        Description = items[1].Name,
-                        Qty = 1m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = items[1].SellingFlatPrice.GetValueOrDefault(),
-                        LineTotal = items[1].SellingFlatPrice.GetValueOrDefault(),
-                        IncludeInBundle = true,
-                        IsComponent = true
-                    }
-                ]
-            },
-            new BundleSale
-            {
-                BundleNo = $"BND-{now:yyyy}-00003",
-                BundleDate = now.Date,
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.DisplayName ?? customer.Name,
-                WarehouseId = secondaryWarehouse.WarehouseId,
-                CashierUserId = user.UserId,
-                BundleSaleTemplateId = template.BundleSaleTemplateId,
-                BundleName = "Demo Bundle Cancelled",
-                BundleCode = "BND-DEMO-001",
-                Status = BundleSaleStatus.Cancelled,
-                ComponentSubtotal = items[0].SellingFlatPrice.GetValueOrDefault(),
-                BundlePrice = items[0].SellingFlatPrice.GetValueOrDefault(),
-                MarginAmount = 0m,
-                DiscountTotal = 0m,
-                TaxTotal = 0m,
-                GrandTotal = items[0].SellingFlatPrice.GetValueOrDefault(),
-                CreatedAt = now,
-                UpdatedAt = now,
-                Lines =
-                [
-                    new BundleSaleLine
-                    {
-                        ItemId = items[0].ItemId,
-                        Description = items[0].Name,
-                        Qty = 1m,
-                        WarehouseId = secondaryWarehouse.WarehouseId,
-                        UnitPrice = items[0].SellingFlatPrice.GetValueOrDefault(),
-                        LineTotal = items[0].SellingFlatPrice.GetValueOrDefault(),
-                        IncludeInBundle = true,
-                        IsComponent = true
-                    }
-                ]
-            }
-        };
-
-        db.BundleSales.AddRange(bundleSales);
-        return true;
-    }
-
-    private static async Task<bool> SeedSampleSalesDocsAsync(ErpDbContext db, CancellationToken ct)
-    {
-        if (await db.SalesInvoices.AnyAsync(ct) || await db.SalesSlips.AnyAsync(ct))
-            return false;
-
-        var customer = await db.Customers.AsNoTracking()
-            .OrderBy(c => c.CustomerId)
-            .FirstOrDefaultAsync(ct);
-        var warehouse = await db.Warehouses.AsNoTracking()
-            .OrderBy(w => w.WarehouseId)
-            .FirstOrDefaultAsync(ct);
-        var secondaryWarehouse = await db.Warehouses.AsNoTracking()
-            .OrderByDescending(w => w.WarehouseId)
-            .FirstOrDefaultAsync(ct);
-        var items = await db.Items.AsNoTracking()
-            .OrderBy(i => i.ItemId)
-            .Take(2)
-            .ToListAsync(ct);
-        var uom = await db.Uoms.AsNoTracking()
-            .OrderBy(u => u.UomId)
-            .FirstOrDefaultAsync(ct);
-        var user = await db.Users.AsNoTracking()
-            .OrderBy(u => u.UserId)
-            .FirstOrDefaultAsync(ct);
-
-        if (customer is null || warehouse is null || secondaryWarehouse is null || items.Count < 2 || uom is null || user is null)
-            return false;
-
-        var postableItem = items[0];
-        var shortageItem = items[1];
-        var today = DateTime.UtcNow.Date;
-        var createdAt = DateTime.UtcNow.AddDays(-1);
-
-        db.SalesInvoices.AddRange(
-            new SalesInvoice
-            {
-                InvoiceNo = $"SI-{today:yyyy}-00001",
-                InvoiceDate = today.AddDays(-2),
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.Name,
-                CustomerSnapshotTaxNo = customer.TaxRegistrationNo,
-                WarehouseId = warehouse.WarehouseId,
-                InvoiceType = SalesInvoiceType.B2C,
-                Status = SalesInvoiceStatus.Draft,
-                Subtotal = 200m,
-                DiscountTotal = 0m,
-                TaxTotal = 0m,
-                GrandTotal = 200m,
-                RoundOff = 0m,
-                NetPayable = 200m,
-                PaidAmount = 0m,
-                BalanceAmount = 200m,
-                CreatedBy = user.UserId,
-                CreatedAt = createdAt,
-                Lines =
-                [
-                    new SalesInvoiceLine
-                    {
-                        ItemId = postableItem.ItemId,
-                        Description = postableItem.Name,
-                        Qty = 2m,
-                        FreeQty = 0m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = 100m,
-                        BaseCost = 0m,
-                        PriceSource = "seed",
-                        DiscountMode = SalesDiscountMode.Percentage,
-                        DiscountPct = 0m,
-                        DiscountAmount = 0m,
-                        NetUnitPrice = 100m,
-                        LineTotal = 200m,
-                        TaxPct = 0m,
-                        TaxAmount = 0m,
-                        IsFreeIssue = false
-                    }
-                ]
-            },
-            new SalesInvoice
-            {
-                InvoiceNo = $"SI-{today:yyyy}-00002",
-                InvoiceDate = today.AddDays(-1),
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.Name,
-                CustomerSnapshotTaxNo = customer.TaxRegistrationNo,
-                WarehouseId = secondaryWarehouse.WarehouseId,
-                InvoiceType = SalesInvoiceType.B2B,
-                Status = SalesInvoiceStatus.Draft,
-                Subtotal = 300m,
-                DiscountTotal = 0m,
-                TaxTotal = 0m,
-                GrandTotal = 300m,
-                RoundOff = 0m,
-                NetPayable = 300m,
-                PaidAmount = 0m,
-                BalanceAmount = 300m,
-                CreatedBy = user.UserId,
-                CreatedAt = createdAt,
-                Lines =
-                [
-                    new SalesInvoiceLine
-                    {
-                        ItemId = shortageItem.ItemId,
-                        Description = shortageItem.Name,
-                        Qty = 6m,
-                        FreeQty = 0m,
-                        WarehouseId = secondaryWarehouse.WarehouseId,
-                        UnitPrice = 50m,
-                        BaseCost = 0m,
-                        PriceSource = "seed",
-                        DiscountMode = SalesDiscountMode.Percentage,
-                        DiscountPct = 0m,
-                        DiscountAmount = 0m,
-                        NetUnitPrice = 50m,
-                        LineTotal = 300m,
-                        TaxPct = 0m,
-                        TaxAmount = 0m,
-                        IsFreeIssue = false
-                    }
-                ]
-            },
-            new SalesInvoice
-            {
-                InvoiceNo = $"SI-{today:yyyy}-00003",
-                InvoiceDate = today,
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.Name,
-                CustomerSnapshotTaxNo = customer.TaxRegistrationNo,
-                WarehouseId = warehouse.WarehouseId,
-                InvoiceType = SalesInvoiceType.B2C,
-                Status = SalesInvoiceStatus.Posted,
-                Subtotal = 100m,
-                DiscountTotal = 0m,
-                TaxTotal = 0m,
-                GrandTotal = 100m,
-                RoundOff = 0m,
-                NetPayable = 100m,
-                PaidAmount = 100m,
-                BalanceAmount = 0m,
-                CreatedBy = user.UserId,
-                CreatedAt = createdAt,
-                UpdatedAt = DateTime.UtcNow,
-                Lines =
-                [
-                    new SalesInvoiceLine
-                    {
-                        ItemId = postableItem.ItemId,
-                        Description = postableItem.Name,
-                        Qty = 1m,
-                        FreeQty = 0m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = 100m,
-                        BaseCost = 0m,
-                        PriceSource = "seed",
-                        DiscountMode = SalesDiscountMode.Percentage,
-                        DiscountPct = 0m,
-                        DiscountAmount = 0m,
-                        NetUnitPrice = 100m,
-                        LineTotal = 100m,
-                        TaxPct = 0m,
-                        TaxAmount = 0m,
-                        IsFreeIssue = false
-                    }
-                ]
-            }
-        );
-
-        db.SalesSlips.AddRange(
-            new SalesSlip
-            {
-                SlipNo = $"SSL-{today:yyyy}-00001",
-                SlipDate = today.AddDays(-2),
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.Name,
-                WarehouseId = warehouse.WarehouseId,
-                CashierUserId = user.UserId,
-                Status = SalesSlipStatus.Draft,
-                Subtotal = 50m,
-                DiscountTotal = 0m,
-                TaxTotal = 0m,
-                GrandTotal = 50m,
-                PaidAmount = 0m,
-                BalanceAmount = 50m,
-                CreatedAt = createdAt,
-                Lines =
-                [
-                    new SalesSlipLine
-                    {
-                        ItemId = postableItem.ItemId,
-                        Description = postableItem.Name,
-                        Qty = 1m,
-                        FreeQty = 0m,
-                        WarehouseId = warehouse.WarehouseId,
-                        UnitPrice = 50m,
-                        BaseCost = 0m,
-                        PriceSource = "seed",
-                        DiscountMode = SalesDiscountMode.Percentage,
-                        DiscountPct = 0m,
-                        DiscountAmount = 0m,
-                        NetUnitPrice = 50m,
-                        LineTotal = 50m,
-                        TaxPct = 0m,
-                        TaxAmount = 0m,
-                        IsFreeIssue = false
-                    }
-                ]
-            },
-            new SalesSlip
-            {
-                SlipNo = $"SSL-{today:yyyy}-00002",
-                SlipDate = today.AddDays(-1),
-                CustomerId = customer.CustomerId,
-                CustomerSnapshotName = customer.Name,
-                WarehouseId = secondaryWarehouse.WarehouseId,
-                CashierUserId = user.UserId,
-                Status = SalesSlipStatus.Draft,
-                Subtotal = 150m,
-                DiscountTotal = 15m,
-                TaxTotal = 0m,
-                GrandTotal = 135m,
-                PaidAmount = 0m,
-                BalanceAmount = 135m,
-                CreatedAt = createdAt,
-                Lines =
-                [
-                    new SalesSlipLine
-                    {
-                        ItemId = shortageItem.ItemId,
-                        Description = shortageItem.Name,
-                        Qty = 3m,
-                        FreeQty = 0m,
-                        WarehouseId = secondaryWarehouse.WarehouseId,
-                        UnitPrice = 50m,
-                        BaseCost = 0m,
-                        PriceSource = "seed",
-                        DiscountMode = SalesDiscountMode.Percentage,
-                        DiscountPct = 10m,
-                        DiscountAmount = 15m,
-                        NetUnitPrice = 45m,
-                        LineTotal = 135m,
-                        TaxPct = 0m,
-                        TaxAmount = 0m,
-                        IsFreeIssue = false
-                    }
-                ]
-            }
-        );
-
-        return true;
-    }
 }

Backend/ERPCore/Infra/Persistence/ErpDbContext.cs

@@ -2,6 +2,7 @@ using ERPCore.Domain.Entities;
 using ERPCore.Infra.Auth;
 using ERPCore.Infra.Persistence.Auditing;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata;
 
 namespace ERPCore.Infra.Persistence;
 
@@ -189,6 +190,15 @@ public class ErpDbContext : DbContext
         // (Infra/Persistence/Configurations/*).
         modelBuilder.ApplyConfigurationsFromAssembly(typeof(ErpDbContext).Assembly);
 
+        // Pin the collation on the model. Pomelo emits `CharSet utf8mb4` per table/column but
+        // no collation, so without this every column silently takes the charset's server
+        // default — utf8mb4_general_ci on MariaDB — regardless of what the database is set to.
+        // utf8mb4_unicode_ci is case-insensitive (which is the decided semantics: it keeps the
+        // 48 EF.Functions.Like searches behaving like the old ILIKE, and makes the uniqueness
+        // guards consistent with their backing indexes) but uses proper UCA ordering rather
+        // than general_ci's simplified table. MariaDB has no utf8mb4_0900_ai_ci.
+        modelBuilder.UseCollation("utf8mb4_unicode_ci");
+
         // Global read-side branch scoping (docs/BRANCH_ISOLATION_PLAN.md). Only for entities
         // that carry an explicit BranchId directly — warehouse-inherited entities (Grn,
         // StockLayer, StockTransfer, ...) are NOT covered here (would need an extra join in
@@ -202,10 +212,35 @@ public class ErpDbContext : DbContext
         modelBuilder.Entity<PurchaseOrder>().HasQueryFilter(e => !_currentBranch.IsActive || e.BranchId == _currentBranch.BranchId);
         modelBuilder.Entity<PurchaseInvoice>().HasQueryFilter(e => !_currentBranch.IsActive || e.BranchId == _currentBranch.BranchId);
 
-        // Npgsql requires DateTime values written to `timestamp with time zone` columns
-        // to have Kind=Utc; dates deserialized from a JSON request body (hire date,
-        // salary-structure effective date, etc.) come in as Kind=Unspecified and would
-        // otherwise throw at SaveChanges time. Force Utc kind globally for every
+        // Optimistic concurrency token. On PostgreSQL this was the virtual `xmin` system
+        // column via .IsRowVersion(), which the engine maintained for free. MariaDB has no
+        // equivalent: Pomelo maps .IsRowVersion() on a uint to a plain `int unsigned` column
+        // marked ValueGeneratedOnAddOrUpdate, so EF expects the *database* to bump it and the
+        // database never does — every row would sit at 0 and the concurrency check would
+        // silently always pass. So the column is real, generated by nothing, and incremented
+        // by BumpRowVersions() in the SaveChanges overrides below.
+        //
+        // Applied as a convention rather than 49 hand edits: a loop cannot miss an entity,
+        // and a missed one is invisible (a non-token column, no error, no protection).
+        foreach (var entityType in modelBuilder.Model.GetEntityTypes())
+        {
+            var rowVersion = entityType.FindProperty(RowVersionProperty);
+            if (rowVersion is null || rowVersion.ClrType != typeof(uint)) continue;
+
+            rowVersion.IsConcurrencyToken = true;
+            // ValueGenerated.Never is load-bearing: anything else and EF refuses to write the
+            // value we compute. Deliberately no HasDefaultValue(0) either — a store default
+            // makes EF omit the column from INSERTs and treat it as store-generated.
+            rowVersion.ValueGenerated = ValueGenerated.Never;
+            rowVersion.IsNullable = false;
+        }
+
+        // MariaDB does not have `timestamp with time zone`; values are stored as datetime(6)
+        // in UTC. This converter is still load-bearing (do NOT delete it as a Postgres-only
+        // artifact): dates deserialized from a JSON request body (hire date, salary-structure
+        // effective date, etc.) arrive as Kind=Unspecified, and MySqlConnector hands values
+        // back as Kind=Unspecified too, so both directions need pinning. Force Utc kind
+        // globally for every
         // DateTime/DateTime? property rather than remembering to convert at each HRM
         // service call site (docs/12-BACKEND-HRM.md — new in Phase 2; Phase 1 never hit
         // this because it only ever persisted server-generated DateTime.UtcNow values).
@@ -226,14 +261,60 @@ public class ErpDbContext : DbContext
         }
     }
 
+    /// <summary>
+    /// Name of the optimistic-concurrency token property. Must stay <c>"RowVersion"</c>:
+    /// the CLR type <c>uint</c> is what lets <see cref="Common.Http.ETag"/> and every
+    /// <c>If-Match</c> call site stay unchanged.
+    /// </summary>
+    internal const string RowVersionProperty = "RowVersion";
+
+    /// <summary>
+    /// Increments the concurrency token for every inserted or modified entity that carries
+    /// one. Replaces what PostgreSQL's <c>xmin</c> did automatically.
+    /// </summary>
+    private void BumpRowVersions()
+    {
+        foreach (var entry in ChangeTracker.Entries())
+        {
+            if (entry.State is not (EntityState.Added or EntityState.Modified)) continue;
+
+            var meta = entry.Metadata.FindProperty(RowVersionProperty);
+            if (meta is null || meta.ClrType != typeof(uint)) continue;
+
+            var p = entry.Property(RowVersionProperty);
+
+            // New rows start at 1, never 0: ETag.TryParse("AAAAAA==") succeeds and yields 0,
+            // so a client sending the all-zero token (exactly what a default-initialised uint
+            // produces) would otherwise pass the pre-check on every never-updated row.
+            // Starting at 1 keeps 0 permanently non-live.
+            //
+            // Updates increment OriginalValue, NOT CurrentValue. EF emits
+            //   SET RowVersion = @new WHERE pk = @pk AND RowVersion = @orig
+            // taking WHERE from OriginalValue and SET from CurrentValue. Basing the new value
+            // on CurrentValue would break the moment anything else touches the property (a DTO
+            // mapper, a detached graph attach), producing a value unrelated to the row and an
+            // intermittent spurious 412 on the happy path.
+            p.CurrentValue = entry.State == EntityState.Added
+                ? 1u
+                : (uint)(p.OriginalValue ?? 0u) + 1u;
+        }
+    }
+
     // Audit trail (FR-X-02): capture mutations before save (accurate old→new), then
     // write the log rows once inserts have their generated keys. A second base save
     // persists the logs without re-auditing them.
+    //
+    // BumpRowVersions runs AFTER AuditScribe.Capture (which has already serialised each
+    // change set into an immutable string, so the token bump physically cannot leak into an
+    // audit payload) and BEFORE the first base save. It is called here rather than from a
+    // SaveChangesInterceptor precisely because base.Save… is invoked twice below — an
+    // interceptor would fire on both and double-bump.
     public override async Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken ct = default)
     {
         IReadOnlyList<PendingAudit> pending = _writingAuditLogs
             ? Array.Empty<PendingAudit>()
             : AuditScribe.Capture(ChangeTracker);
+        BumpRowVersions();
         var result = await base.SaveChangesAsync(acceptAllChangesOnSuccess, ct);
         if (pending.Count > 0)
         {
@@ -256,6 +337,7 @@ public class ErpDbContext : DbContext
         IReadOnlyList<PendingAudit> pending = _writingAuditLogs
             ? Array.Empty<PendingAudit>()
             : AuditScribe.Capture(ChangeTracker);
+        BumpRowVersions();
         var result = base.SaveChanges(acceptAllChangesOnSuccess);
         if (pending.Count > 0)
         {

Backend/ERPCore/Infra/UoW/UnitOfWork.cs

@@ -1,12 +1,22 @@
+using System.Data;
 using ERPCore.Infra.Persistence;
 using Microsoft.EntityFrameworkCore;
 
 namespace ERPCore.Infra.UoW;
 
 /// <summary>
-/// EF Core-backed unit of work. Uses the provider execution strategy so the
-/// transactional path is safe under connection resiliency / retries.
+/// EF Core-backed unit of work. Opens every transaction at READ COMMITTED to match the
+/// semantics the code was written against (MariaDB defaults to REPEATABLE READ, where a
+/// plain read inside a transaction returns a pinned snapshot while a locking read does not).
 /// </summary>
+/// <remarks>
+/// Do NOT enable <c>EnableRetryOnFailure</c> to "harden" this. The execution strategy is
+/// currently non-retrying, so the lambda runs exactly once. With retries on, EF re-runs the
+/// lambda without resetting the ChangeTracker, and callers such as
+/// <c>ProductionRunService.ApproveStageAsync</c> capture mutable state outside it — a retry
+/// would re-insert already-Added entities and duplicate ledger/layer rows, which is precisely
+/// the corruption the concurrency token exists to prevent.
+/// </remarks>
 public sealed class UnitOfWork : IUnitOfWork
 {
     private readonly ErpDbContext _db;
@@ -29,7 +39,7 @@ public sealed class UnitOfWork : IUnitOfWork
         var strategy = _db.Database.CreateExecutionStrategy();
         return await strategy.ExecuteAsync(async () =>
         {
-            await using var tx = await _db.Database.BeginTransactionAsync(ct);
+            await using var tx = await _db.Database.BeginTransactionAsync(IsolationLevel.ReadCommitted, ct);
             try
             {
                 var result = await action(ct);

Backend/ERPCore/Program.cs

@@ -17,9 +17,7 @@ using ERPCore.System.Errors;
 using Microsoft.AspNetCore.Authentication;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.EntityFrameworkCore;
-using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.OpenApi;
-using Npgsql;
 using Serilog;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -33,11 +31,17 @@ builder.Host.UseSerilog((ctx, cfg) => cfg
 builder.Services.AddControllers()
     .AddJsonOptions(o => o.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter()));
 
-// EF Core + PostgreSQL
+// EF Core + MariaDB (Pomelo). The server version is pinned explicitly rather than using
+// ServerVersion.AutoDetect: AutoDetect opens a connection, which would make design-time
+// commands (`dotnet ef migrations add`) and startup depend on the database being reachable.
+// MariaDbServerVersion — not MySqlServerVersion — because the target is MariaDB 10.11, and
+// Pomelo changes its SQL translation based on which it is given.
+var connectionString = builder.Configuration.GetConnectionString("DefaultConnection")
+    ?? throw new InvalidOperationException("ConnectionStrings:DefaultConnection is not configured.");
+
 builder.Services.AddDbContext<ErpDbContext>(o =>
 {
-    o.UseNpgsql(builder.Configuration.GetConnectionString("DefaultConnection"));
-    o.ConfigureWarnings(w => w.Ignore(RelationalEventId.PendingModelChangesWarning));
+    o.UseMySql(connectionString, new MariaDbServerVersion(new Version(10, 11, 15)));
 });
 
 // ProblemDetails (RFC 7807) + domain-exception mapping

Backend/ERPCore/Repositories/Interfaces/IRepository.cs

@@ -14,6 +14,5 @@ public interface IRepository<T> where T : class
     IQueryable<T> Query();
 
     Task AddAsync(T entity, CancellationToken ct = default);
-    void Update(T entity);
     void Remove(T entity);
 }

Backend/ERPCore/Repositories/Repository.cs

@@ -31,7 +31,5 @@ public class Repository<T> : IRepository<T> where T : class
     public virtual async Task AddAsync(T entity, CancellationToken ct = default)
         => await Set.AddAsync(entity, ct);
 
-    public virtual void Update(T entity) => Set.Update(entity);
-
     public virtual void Remove(T entity) => Set.Remove(entity);
 }

Backend/ERPCore/Services/AdjustmentService.cs

@@ -106,7 +106,7 @@ public sealed class AdjustmentService : IAdjustmentService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(a => EF.Functions.ILike(a.DocNo, $"%{term}%"));
+            q = q.Where(a => EF.Functions.Like(a.DocNo, $"%{term}%"));
         }
         if (warehouseId is not null) q = q.Where(a => a.WarehouseId == warehouseId);
         // Warehouses are shared across branches — the adjustment carries its own owning BranchId.

Backend/ERPCore/Services/BranchConfigService.cs

@@ -18,8 +18,6 @@ namespace ERPCore.Services;
 /// </summary>
 public sealed class BranchConfigService : IBranchConfigService
 {
-    private const string DefaultBranchCode = "BR-000";
-    private const string DefaultBranchName = "Main Branch";
 
     private readonly IRepository<BranchConfig> _config;
     private readonly IRepository<Branch> _branches;
@@ -116,10 +114,10 @@ public sealed class BranchConfigService : IBranchConfigService
     public async Task<int> ResolveDefaultBranchIdAsync(CancellationToken ct = default)
     {
         var existingId = await _branches.Query().AsNoTracking()
-            .Where(b => b.Code == DefaultBranchCode).Select(b => b.BranchId).FirstOrDefaultAsync(ct);
+            .Where(b => b.Code == Branch.DefaultCode).Select(b => b.BranchId).FirstOrDefaultAsync(ct);
         if (existingId != 0) return existingId;
 
-        var branch = new Branch { Code = DefaultBranchCode, Name = DefaultBranchName, Status = EntityStatus.Active, CreatedAt = DateTime.UtcNow };
+        var branch = new Branch { Code = Branch.DefaultCode, Name = Branch.DefaultName, Status = EntityStatus.Active, CreatedAt = DateTime.UtcNow };
         await _branches.AddAsync(branch, ct);
         await _uow.SaveChangesAsync(ct);
         return branch.BranchId;

Backend/ERPCore/Services/BrandService.cs

@@ -32,7 +32,7 @@ public sealed class BrandService : IBrandService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(b => EF.Functions.ILike(b.Name, $"%{term}%"));
+            q = q.Where(b => EF.Functions.Like(b.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(b => b.Status == status);
 

Backend/ERPCore/Services/BundleSaleService.cs

@@ -62,7 +62,7 @@ public sealed class BundleSaleService : IBundleSaleService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(x => EF.Functions.ILike(x.TemplateCode, $"%{term}%") || EF.Functions.ILike(x.TemplateName, $"%{term}%") || EF.Functions.ILike(x.Description ?? "", $"%{term}%"));
+            q = q.Where(x => EF.Functions.Like(x.TemplateCode, $"%{term}%") || EF.Functions.Like(x.TemplateName, $"%{term}%") || EF.Functions.Like(x.Description ?? "", $"%{term}%"));
         }
         var total = await q.CountAsync(ct);
         var rows = await q.OrderByDescending(x => x.BundleSaleTemplateId).Skip(query.Skip).Take(query.PageSize).ToListAsync(ct);
@@ -130,7 +130,7 @@ public sealed class BundleSaleService : IBundleSaleService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(x => EF.Functions.ILike(x.BundleNo, $"%{term}%") || EF.Functions.ILike(x.BundleName, $"%{term}%") || EF.Functions.ILike(x.BundleCode, $"%{term}%"));
+            q = q.Where(x => EF.Functions.Like(x.BundleNo, $"%{term}%") || EF.Functions.Like(x.BundleName, $"%{term}%") || EF.Functions.Like(x.BundleCode, $"%{term}%"));
         }
         if (status is not null) q = q.Where(x => x.Status == status);
         if (customerId is not null) q = q.Where(x => x.CustomerId == customerId);
@@ -181,7 +181,6 @@ public sealed class BundleSaleService : IBundleSaleService
         Recalculate(bundle, request.BundlePrice);
         bundle.BundleCode = $"{bundle.BundleNo}-B";
         await _bundles.AddAsync(bundle, ct);
-        bundle.ConcurrencyStamp = 1;
         await _uow.SaveChangesAsync(ct);
         return Map(bundle);
     }
@@ -206,7 +205,6 @@ public sealed class BundleSaleService : IBundleSaleService
         foreach (var line in await BuildLinesAsync(template, request.WarehouseId, request.Lines, ct)) bundle.Lines.Add(line);
         Recalculate(bundle, request.BundlePrice);
         bundle.UpdatedAt = DateTime.UtcNow;
-        bundle.ConcurrencyStamp++;
         await _uow.SaveChangesAsync(ct);
         return Map(bundle);
     }
@@ -227,7 +225,6 @@ public sealed class BundleSaleService : IBundleSaleService
             throw new ConflictException($"Bundle sale {bundleSaleId} is {bundle.Status} and cannot be cancelled.");
         bundle.Status = BundleSaleStatus.Cancelled;
         bundle.UpdatedAt = DateTime.UtcNow;
-        bundle.ConcurrencyStamp++;
         await _uow.SaveChangesAsync(ct);
         return Map(bundle);
     }

Backend/ERPCore/Services/CategoryService.cs

@@ -41,7 +41,7 @@ public sealed class CategoryService : ICategoryService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(c => EF.Functions.ILike(c.Name, $"%{term}%"));
+            q = q.Where(c => EF.Functions.Like(c.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(c => c.Status == status);
 
@@ -123,7 +123,7 @@ public sealed class CategoryService : ICategoryService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(s => EF.Functions.ILike(s.Name, $"%{term}%"));
+            q = q.Where(s => EF.Functions.Like(s.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(s => s.Status == status);
 

Backend/ERPCore/Services/CountService.cs

@@ -113,7 +113,7 @@ public sealed class CountService : ICountService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(c => EF.Functions.ILike(c.DocNo, $"%{term}%"));
+            q = q.Where(c => EF.Functions.Like(c.DocNo, $"%{term}%"));
         }
         if (status is not null) q = q.Where(c => c.Status == status);
         if (warehouseId is not null) q = q.Where(c => c.WarehouseId == warehouseId);

Backend/ERPCore/Services/CustomerService.cs

@@ -54,9 +54,9 @@ public sealed class CustomerService : ICustomerService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(c => EF.Functions.ILike(c.Name, $"%{term}%")
-                             || EF.Functions.ILike(c.CustomerCode, $"%{term}%")
-                             || (c.DisplayName != null && EF.Functions.ILike(c.DisplayName, $"%{term}%")));
+            q = q.Where(c => EF.Functions.Like(c.Name, $"%{term}%")
+                             || EF.Functions.Like(c.CustomerCode, $"%{term}%")
+                             || (c.DisplayName != null && EF.Functions.Like(c.DisplayName, $"%{term}%")));
         }
         if (status is not null) q = q.Where(c => c.Status == status);
         if (customerType is not null) q = q.Where(c => c.CustomerType == customerType);
@@ -172,7 +172,15 @@ public sealed class CustomerService : ICustomerService
         customer.BranchId = await _branchConfig.ResolveBranchIdAsync(request.BranchId, ct);
         customer.UpdatedAt = DateTime.UtcNow;
 
-        await _uow.SaveChangesAsync(ct);
+        try
+        {
+            await _uow.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The customer was modified by another request.", 412);
+        }
+
         return new ETagged<CustomerDto>(Map(customer), customer.RowVersion);
     }
 

Backend/ERPCore/Services/GlobalSearchService.cs

@@ -40,28 +40,28 @@ public sealed class GlobalSearchService : IGlobalSearchService
         // Sequential, not parallel: these share one scoped DbContext, which EF Core
         // does not allow concurrent operations against.
         var items = await _items.Query().AsNoTracking()
-            .Where(i => EF.Functions.ILike(i.Sku, pattern) || EF.Functions.ILike(i.Name, pattern))
+            .Where(i => EF.Functions.Like(i.Sku, pattern) || EF.Functions.Like(i.Name, pattern))
             .OrderBy(i => i.Name)
             .Take(takePerType)
             .Select(i => new GlobalSearchResultDto(GlobalSearchResultType.Item, i.ItemId, i.Sku, i.Name, i.Sku))
             .ToListAsync(ct);
 
         var pos = await _purchaseOrders.Query().AsNoTracking()
-            .Where(p => EF.Functions.ILike(p.DocNo, pattern))
+            .Where(p => EF.Functions.Like(p.DocNo, pattern))
             .OrderByDescending(p => p.PoId)
             .Take(takePerType)
             .Select(p => new GlobalSearchResultDto(GlobalSearchResultType.PurchaseOrder, p.PoId, p.DocNo, p.DocNo, p.Status.ToString()))
             .ToListAsync(ct);
 
         var invoices = await _salesSlips.Query().AsNoTracking()
-            .Where(s => EF.Functions.ILike(s.SlipNo, pattern) || EF.Functions.ILike(s.CustomerSnapshotName, pattern))
+            .Where(s => EF.Functions.Like(s.SlipNo, pattern) || EF.Functions.Like(s.CustomerSnapshotName, pattern))
             .OrderByDescending(s => s.SalesSlipId)
             .Take(takePerType)
             .Select(s => new GlobalSearchResultDto(GlobalSearchResultType.Invoice, s.SalesSlipId, s.SlipNo, s.SlipNo, s.CustomerSnapshotName))
             .ToListAsync(ct);
 
         var employees = await _employees.Query().AsNoTracking()
-            .Where(e => EF.Functions.ILike(e.FullName, pattern) || EF.Functions.ILike(e.EmployeeCode, pattern))
+            .Where(e => EF.Functions.Like(e.FullName, pattern) || EF.Functions.Like(e.EmployeeCode, pattern))
             .OrderBy(e => e.FullName)
             .Take(takePerType)
             .Select(e => new GlobalSearchResultDto(GlobalSearchResultType.Employee, e.EmployeeId, e.EmployeeCode, e.FullName, e.EmployeeCode))

Backend/ERPCore/Services/GrnService.cs

@@ -88,7 +88,7 @@ public sealed class GrnService : IGrnService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(g => EF.Functions.ILike(g.DocNo, $"%{term}%"));
+            q = q.Where(g => EF.Functions.Like(g.DocNo, $"%{term}%"));
         }
         if (status is not null) q = q.Where(g => g.Status == status);
         if (poId is not null) q = q.Where(g => g.PoId == poId);

Backend/ERPCore/Services/Hrm/BranchService.cs

@@ -29,7 +29,7 @@ public sealed class BranchService : IBranchService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(b => EF.Functions.ILike(b.Name, $"%{term}%") || EF.Functions.ILike(b.Code, $"%{term}%"));
+            q = q.Where(b => EF.Functions.Like(b.Name, $"%{term}%") || EF.Functions.Like(b.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(b => b.Status == status);
 

Backend/ERPCore/Services/Hrm/DepartmentService.cs

@@ -34,7 +34,7 @@ public sealed class DepartmentService : IDepartmentService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(d => EF.Functions.ILike(d.Name, $"%{term}%") || EF.Functions.ILike(d.Code, $"%{term}%"));
+            q = q.Where(d => EF.Functions.Like(d.Name, $"%{term}%") || EF.Functions.Like(d.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(d => d.Status == status);
 

Backend/ERPCore/Services/Hrm/DesignationService.cs

@@ -29,7 +29,7 @@ public sealed class DesignationService : IDesignationService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(d => EF.Functions.ILike(d.Name, $"%{term}%") || EF.Functions.ILike(d.Code, $"%{term}%"));
+            q = q.Where(d => EF.Functions.Like(d.Name, $"%{term}%") || EF.Functions.Like(d.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(d => d.Status == status);
 

Backend/ERPCore/Services/Hrm/EmployeeService.cs

@@ -70,7 +70,7 @@ public sealed class EmployeeService : IEmployeeService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(e => EF.Functions.ILike(e.FullName, $"%{term}%") || EF.Functions.ILike(e.EmployeeCode, $"%{term}%"));
+            q = q.Where(e => EF.Functions.Like(e.FullName, $"%{term}%") || EF.Functions.Like(e.EmployeeCode, $"%{term}%"));
         }
         if (status is not null) q = q.Where(e => e.Status == status);
         if (departmentId is not null) q = q.Where(e => e.DepartmentId == departmentId);

Backend/ERPCore/Services/Hrm/EmployeeUserLinkService.cs

@@ -34,7 +34,7 @@ public sealed class EmployeeUserLinkService : IEmployeeUserLinkService
     {
         var term = email.Trim();
         var employee = await _employees.Query().AsNoTracking()
-            .Where(e => e.UserId == null && e.Email != null && EF.Functions.ILike(e.Email, term))
+            .Where(e => e.UserId == null && e.Email != null && e.Email == term)
             .Select(e => new EmployeeMatchDto(e.EmployeeId, e.EmployeeCode, e.FullName, e.Email!))
             .FirstOrDefaultAsync(ct);
         return employee;
@@ -46,7 +46,7 @@ public sealed class EmployeeUserLinkService : IEmployeeUserLinkService
         var linkedUserIds = _employees.Query().Where(e => e.UserId != null).Select(e => e.UserId!.Value);
 
         var user = await _users.Query().AsNoTracking()
-            .Where(u => u.Email != null && EF.Functions.ILike(u.Email, term) && !linkedUserIds.Contains(u.UserId))
+            .Where(u => u.Email != null && u.Email == term && !linkedUserIds.Contains(u.UserId))
             .Select(u => new UserMatchDto(u.UserId, u.Username, u.DisplayName, u.Email!))
             .FirstOrDefaultAsync(ct);
         return user;

Backend/ERPCore/Services/Hrm/EmploymentTypeService.cs

@@ -29,7 +29,7 @@ public sealed class EmploymentTypeService : IEmploymentTypeService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(e => EF.Functions.ILike(e.Name, $"%{term}%") || EF.Functions.ILike(e.Code, $"%{term}%"));
+            q = q.Where(e => EF.Functions.Like(e.Name, $"%{term}%") || EF.Functions.Like(e.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(e => e.Status == status);
 

Backend/ERPCore/Services/Hrm/HrDocumentTypeService.cs

@@ -29,7 +29,7 @@ public sealed class HrDocumentTypeService : IHrDocumentTypeService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(t => EF.Functions.ILike(t.Name, $"%{term}%") || EF.Functions.ILike(t.Code, $"%{term}%"));
+            q = q.Where(t => EF.Functions.Like(t.Name, $"%{term}%") || EF.Functions.Like(t.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(t => t.Status == status);
 

Backend/ERPCore/Services/Hrm/LeaveRequestService.cs

@@ -46,7 +46,7 @@ public sealed class LeaveRequestService : ILeaveRequestService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.DocNo, $"%{term}%") || EF.Functions.ILike(r.Employee!.FullName, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.DocNo, $"%{term}%") || EF.Functions.Like(r.Employee!.FullName, $"%{term}%"));
         }
 
         var total = await q.CountAsync(ct);

Backend/ERPCore/Services/Hrm/LeaveTypeService.cs

@@ -29,7 +29,7 @@ public sealed class LeaveTypeService : ILeaveTypeService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(t => EF.Functions.ILike(t.Name, $"%{term}%") || EF.Functions.ILike(t.Code, $"%{term}%"));
+            q = q.Where(t => EF.Functions.Like(t.Name, $"%{term}%") || EF.Functions.Like(t.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(t => t.Status == status);
 

Backend/ERPCore/Services/Hrm/SalaryComponentService.cs

@@ -29,7 +29,7 @@ public sealed class SalaryComponentService : ISalaryComponentService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(c => EF.Functions.ILike(c.Name, $"%{term}%") || EF.Functions.ILike(c.Code, $"%{term}%"));
+            q = q.Where(c => EF.Functions.Like(c.Name, $"%{term}%") || EF.Functions.Like(c.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(c => c.Status == status);
 

Backend/ERPCore/Services/Hrm/WorkShiftService.cs

@@ -32,7 +32,7 @@ public sealed class WorkShiftService : IWorkShiftService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(w => EF.Functions.ILike(w.Name, $"%{term}%") || EF.Functions.ILike(w.Code, $"%{term}%"));
+            q = q.Where(w => EF.Functions.Like(w.Name, $"%{term}%") || EF.Functions.Like(w.Code, $"%{term}%"));
         }
         if (status is not null) q = q.Where(w => w.Status == status);
 

Backend/ERPCore/Services/ItemService.cs

@@ -88,7 +88,7 @@ public sealed class ItemService : IItemService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(i => EF.Functions.ILike(i.Sku, $"%{term}%") || EF.Functions.ILike(i.Name, $"%{term}%"));
+            q = q.Where(i => EF.Functions.Like(i.Sku, $"%{term}%") || EF.Functions.Like(i.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(i => i.Status == status);
         if (categoryId is not null) q = q.Where(i => i.CategoryId == categoryId);
@@ -122,7 +122,7 @@ public sealed class ItemService : IItemService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(i => EF.Functions.ILike(i.Sku, $"%{term}%") || EF.Functions.ILike(i.Name, $"%{term}%"));
+            q = q.Where(i => EF.Functions.Like(i.Sku, $"%{term}%") || EF.Functions.Like(i.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(i => i.Status == status);
         if (categoryId is not null) q = q.Where(i => i.CategoryId == categoryId);

Backend/ERPCore/Services/ItemTypeService.cs

@@ -34,7 +34,7 @@ public sealed class ItemTypeService : IItemTypeService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(t => EF.Functions.ILike(t.Name, $"%{term}%"));
+            q = q.Where(t => EF.Functions.Like(t.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(t => t.Status == status);
 

Backend/ERPCore/Services/NumberSequenceService.cs

@@ -9,16 +9,30 @@ using Microsoft.EntityFrameworkCore.Storage;
 namespace ERPCore.Services;
 
 /// <summary>
-/// Atomic document-number issuer. Uses a single <c>INSERT … ON CONFLICT … DO UPDATE
-/// … RETURNING</c> so concurrent issues for the same (docType, branchId, year) cannot get
-/// the same number (the row is locked for the duration of the upsert). Runs as a direct
-/// ADO.NET command enlisted in the DbContext's current transaction so it commits or
-/// rolls back with the document (FR-X-03). EF's <c>SqlQuery</c> is avoided here
-/// because it wraps the statement in a subquery, which PostgreSQL disallows for a
-/// data-modifying statement. Numbering is per-branch (docs/BRANCH_ISOLATION_PLAN.md §5):
-/// the sequence key is (doc_type, branch_id, year) and the format includes the branch code,
-/// e.g. <c>PO-BR-001-2026-00042</c>.
+/// Atomic document-number issuer. Uses a single <c>INSERT … ON DUPLICATE KEY UPDATE …
+/// RETURNING</c> so concurrent issues for the same (docType, branchId, year) cannot get
+/// the same number (the upsert holds an exclusive lock on the row until commit). Runs as a
+/// direct ADO.NET command enlisted in the DbContext's current transaction so it commits or
+/// rolls back with the document (FR-X-03). EF's <c>SqlQuery</c> is avoided here because it
+/// wraps the statement in a subquery, which is not valid for a data-modifying statement.
+/// Numbering is per-branch (docs/BRANCH_ISOLATION_PLAN.md §5): the sequence key is
+/// (doc_type, branch_id, year) and the format includes the branch code, e.g.
+/// <c>PO-BR-001-2026-00042</c>.
 /// </summary>
+/// <remarks>
+/// MariaDB 10.5+ supports <c>RETURNING</c> on an upsert, so this stays a single atomic
+/// statement exactly as the PostgreSQL version was — which is what keeps the callers that
+/// run outside a UoW transaction safe. Do NOT "optimise" this into the one-statement
+/// <c>LAST_INSERT_ID()</c> trick: this table has an AUTO_INCREMENT surrogate key, so on the
+/// insert branch the engine's own auto-increment value clobbers the explicit one and the
+/// first document of a (docType, branch, year) would be numbered with the sequence table's
+/// PK. Splitting it into INSERT-then-SELECT is also wrong here, because the non-transacted
+/// callers would then race. Side note: the surrogate AUTO_INCREMENT burns a value on the
+/// duplicate path, so <c>sequence_id</c> has gaps — harmless, do not "fix" it.
+/// <c>ON DUPLICATE KEY UPDATE</c> fires on any unique-key collision; today the only unique
+/// keys are the never-supplied PK and IX(doc_type, branch_id, year), so it is unambiguous.
+/// Adding another unique index to this table would silently change which row gets updated.
+/// </remarks>
 public sealed class NumberSequenceService : INumberSequenceService
 {
     private readonly ErpDbContext _db;
@@ -53,11 +67,10 @@ public sealed class NumberSequenceService : INumberSequenceService
         await using var cmd = conn.CreateCommand();
         cmd.Transaction = _db.Database.CurrentTransaction?.GetDbTransaction();
         cmd.CommandText = """
-            INSERT INTO number_sequences (doc_type, branch_id, year, last_number)
+            INSERT INTO `number_sequences` (`doc_type`, `branch_id`, `year`, `last_number`)
             VALUES (@docType, @branchId, @year, 1)
-            ON CONFLICT (doc_type, branch_id, year)
-            DO UPDATE SET last_number = number_sequences.last_number + 1
-            RETURNING last_number;
+            ON DUPLICATE KEY UPDATE `last_number` = `last_number` + 1
+            RETURNING `last_number`;
             """;
         AddParam(cmd, "docType", docType);
         AddParam(cmd, "branchId", branchId);

Backend/ERPCore/Services/Production/ProductionRunService.cs

@@ -73,7 +73,7 @@ public sealed class ProductionRunService : IProductionRunService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.DocNo, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.DocNo, $"%{term}%"));
         }
 
         if (status is not null) q = q.Where(r => r.Status == status);
@@ -342,7 +342,7 @@ public sealed class ProductionRunService : IProductionRunService
             });
         }
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             // Must be inside the transaction — NumberSequenceService enlists in it.
             run.DocNo = await _numbers.NextAsync(DocumentTypes.Production, token);
@@ -363,7 +363,7 @@ public sealed class ProductionRunService : IProductionRunService
     {
         RunStage? stage = null;
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var run = await LoadGraphQuery().FirstOrDefaultAsync(r => r.RunId == runId, token)
                 ?? throw new NotFoundException($"Production run {runId} was not found.");
@@ -546,7 +546,7 @@ public sealed class ProductionRunService : IProductionRunService
         var consumed = new List<ConsumedInputDto>();
         var ledgerRefs = new List<StockLedger>();
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var (run, stage) = await LoadForActionAsync(runId, runStageId, token);
 
@@ -607,7 +607,7 @@ public sealed class ProductionRunService : IProductionRunService
     public async Task<RunStageDto> CompleteStageAsync(
         int runId, int runStageId, CompleteStageRequest request, CancellationToken ct = default)
     {
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var (run, stage) = await LoadForActionAsync(runId, runStageId, token);
 
@@ -677,7 +677,7 @@ public sealed class ProductionRunService : IProductionRunService
         CostPoolDto? costPool = null;
         var runStatus = ProductionRunStatus.InProgress;
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var (run, stage) = await LoadForActionAsync(runId, runStageId, token);
 
@@ -756,7 +756,7 @@ public sealed class ProductionRunService : IProductionRunService
     {
         var transfers = new List<TransferDto>();
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var (run, stage) = await LoadForActionAsync(runId, runStageId, token);
 
@@ -785,7 +785,7 @@ public sealed class ProductionRunService : IProductionRunService
         decimal unitCost = 0, returnValue = 0, returnedQty = 0;
         CostPoolDto pool = new(0, 0, 0);
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var run = await LoadGraphQuery().FirstOrDefaultAsync(r => r.RunId == runId, token)
                 ?? throw new NotFoundException($"Production run {runId} was not found.");
@@ -856,7 +856,7 @@ public sealed class ProductionRunService : IProductionRunService
     {
         var pulled = new List<PulledBackDto>();
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var (run, stage) = await LoadForActionAsync(runId, runStageId, token);
 
@@ -930,7 +930,7 @@ public sealed class ProductionRunService : IProductionRunService
     {
         var reworkNumber = 0;
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var (run, stage) = await LoadForActionAsync(runId, runStageId, token);
 
@@ -1026,7 +1026,7 @@ public sealed class ProductionRunService : IProductionRunService
         var writeOffs = new List<ScrapWriteOffDto>();
         var ledgerRefs = new List<StockLedger>();
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var run = await LoadGraphQuery().FirstOrDefaultAsync(r => r.RunId == runId, token)
                 ?? throw new NotFoundException($"Production run {runId} was not found.");
@@ -1297,6 +1297,26 @@ public sealed class ProductionRunService : IProductionRunService
                 $"Required field(s) not provided for stage '{stage.Name}': {string.Join(", ", missing)}.", 400);
     }
 
+    /// <summary>
+    /// Runs <paramref name="work"/> in a transaction, translating a lost optimistic-concurrency
+    /// race (two users acting on the same run or stage) into a 412 rather than a bare 500.
+    /// The catch has to sit outside the lambda: <see cref="IUnitOfWork.ExecuteInTransactionAsync{T}"/>
+    /// issues its own <c>SaveChangesAsync</c> after the lambda returns, so a try inside it would
+    /// miss the save that actually writes the <c>RowVersion</c> check.
+    /// </summary>
+    private async Task SaveGuardingConcurrencyAsync(Func<CancellationToken, Task> work, CancellationToken ct)
+    {
+        try
+        {
+            await _uow.ExecuteInTransactionAsync(work, ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict,
+                "The production run or the stock it uses was modified by another request.", 412);
+        }
+    }
+
     private async Task EnsureProductionReasonAsync(int reasonCodeId, CancellationToken ct)
     {
         var reason = await _reasonCodes.Query().AsNoTracking()

Backend/ERPCore/Services/Production/ProductionTemplateService.cs

@@ -56,7 +56,7 @@ public sealed class ProductionTemplateService : IProductionTemplateService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(t => EF.Functions.ILike(t.Code, $"%{term}%") || EF.Functions.ILike(t.Name, $"%{term}%"));
+            q = q.Where(t => EF.Functions.Like(t.Code, $"%{term}%") || EF.Functions.Like(t.Name, $"%{term}%"));
         }
 
         if (status is not null) q = q.Where(t => t.Status == status);
@@ -192,7 +192,7 @@ public sealed class ProductionTemplateService : IProductionTemplateService
         if (await _templates.Query().AnyAsync(t => t.Code == code && t.TemplateId != templateId, ct))
             throw new ConflictException($"A production template with code '{code}' already exists.");
 
-        await _uow.ExecuteInTransactionAsync(async token =>
+        await SaveGuardingConcurrencyAsync(async token =>
         {
             var template = await LoadGraphQuery().FirstOrDefaultAsync(t => t.TemplateId == templateId, token)
                 ?? throw new NotFoundException($"Production template {templateId} was not found.");
@@ -478,6 +478,26 @@ public sealed class ProductionTemplateService : IProductionTemplateService
         }
     }
 
+    /// <summary>
+    /// Runs <paramref name="work"/> in a transaction, translating a lost optimistic-concurrency
+    /// race into the same 412 the <c>RowVersion</c> pre-check returns. The catch has to sit
+    /// outside the lambda: <see cref="IUnitOfWork.ExecuteInTransactionAsync{T}"/> issues its own
+    /// <c>SaveChangesAsync</c> after the lambda returns, so a try inside it would miss the save
+    /// that actually writes the token check.
+    /// </summary>
+    private async Task SaveGuardingConcurrencyAsync(Func<CancellationToken, Task> work, CancellationToken ct)
+    {
+        try
+        {
+            await _uow.ExecuteInTransactionAsync(work, ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict,
+                "The template was modified by another request.", 412);
+        }
+    }
+
     // --- mapping -------------------------------------------------------------
 
     private async Task<ETagged<TemplateGraphDto>> RequireGraphAsync(int templateId, CancellationToken ct)

Backend/ERPCore/Services/PurchaseInvoiceService.cs

@@ -59,9 +59,9 @@ public sealed class PurchaseInvoiceService : IPurchaseInvoiceService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(x => EF.Functions.ILike(x.DocNo, $"%{term}%")
-                || EF.Functions.ILike(x.VendorInvoiceNo, $"%{term}%")
-                || EF.Functions.ILike(x.VendorSnapshotName, $"%{term}%"));
+            q = q.Where(x => EF.Functions.Like(x.DocNo, $"%{term}%")
+                || EF.Functions.Like(x.VendorInvoiceNo, $"%{term}%")
+                || EF.Functions.Like(x.VendorSnapshotName, $"%{term}%"));
         }
         if (status is not null) q = q.Where(x => x.Status == status);
         if (vendorId is not null) q = q.Where(x => x.VendorId == vendorId);
@@ -156,7 +156,15 @@ public sealed class PurchaseInvoiceService : IPurchaseInvoiceService
         Recalculate(invoice);
         invoice.UpdatedAt = DateTime.UtcNow;
 
-        await _uow.SaveChangesAsync(ct);
+        try
+        {
+            await _uow.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The purchase invoice was modified by another request.", 412);
+        }
+
         return new ETagged<PurchaseInvoiceDto>(MapInvoice(invoice), invoice.RowVersion);
     }
 

Backend/ERPCore/Services/PurchaseOrderService.cs

@@ -61,7 +61,7 @@ public sealed class PurchaseOrderService : IPurchaseOrderService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(p => EF.Functions.ILike(p.DocNo, $"%{term}%"));
+            q = q.Where(p => EF.Functions.Like(p.DocNo, $"%{term}%"));
         }
         if (status is not null) q = q.Where(p => p.Status == status);
         if (vendorId is not null) q = q.Where(p => p.VendorId == vendorId);

Backend/ERPCore/Services/PurchaseReturnService.cs

@@ -79,7 +79,7 @@ public sealed class PurchaseReturnService : IPurchaseReturnService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.DocNo, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.DocNo, $"%{term}%"));
         }
         if (vendorId is not null) q = q.Where(r => r.VendorId == vendorId);
         if (warehouseId is not null) q = q.Where(r => r.WarehouseId == warehouseId);

Backend/ERPCore/Services/RequisitionService.cs

@@ -40,7 +40,7 @@ public sealed class RequisitionService : IRequisitionService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.DocNo, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.DocNo, $"%{term}%"));
         }
         if (status is not null) q = q.Where(r => r.Status == status);
 

Backend/ERPCore/Services/RfqService.cs

@@ -43,7 +43,7 @@ public sealed class RfqService : IRfqService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.DocNo, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.DocNo, $"%{term}%"));
         }
         if (status is not null) q = q.Where(r => r.Status == status);
 

Backend/ERPCore/Services/RoleService.cs

@@ -47,7 +47,7 @@ public sealed class RoleService : IRoleService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.Code, $"%{term}%") || EF.Functions.ILike(r.Name, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.Code, $"%{term}%") || EF.Functions.Like(r.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(r => r.Status == status);
 

Backend/ERPCore/Services/SalesInvoiceService.cs

@@ -57,7 +57,7 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(x => EF.Functions.ILike(x.InvoiceNo, $"%{term}%") || EF.Functions.ILike(x.CustomerSnapshotName, $"%{term}%"));
+            q = q.Where(x => EF.Functions.Like(x.InvoiceNo, $"%{term}%") || EF.Functions.Like(x.CustomerSnapshotName, $"%{term}%"));
         }
         if (status is not null) q = q.Where(x => x.Status == status);
         if (customerId is not null) q = q.Where(x => x.CustomerId == customerId);
@@ -140,7 +140,15 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
         foreach (var line in await BuildLinesAsync(request.WarehouseId, request.Lines, ct)) invoice.Lines.Add(line);
         Recalculate(invoice);
         invoice.UpdatedAt = DateTime.UtcNow;
-        await _uow.SaveChangesAsync(ct);
+        try
+        {
+            await _uow.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The sales invoice was modified by another request.", 412);
+        }
+
         return new ETagged<SalesInvoiceDto>(_mapping.MapInvoice(invoice), invoice.RowVersion);
     }
 

Backend/ERPCore/Services/SalesReturnService.cs

@@ -73,7 +73,7 @@ public sealed class SalesReturnService : ISalesReturnService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(r => EF.Functions.ILike(r.DocNo, $"%{term}%"));
+            q = q.Where(r => EF.Functions.Like(r.DocNo, $"%{term}%"));
         }
         if (customerId is not null) q = q.Where(r => r.CustomerId == customerId);
         if (warehouseId is not null) q = q.Where(r => r.WarehouseId == warehouseId);

Backend/ERPCore/Services/SalesSlipService.cs

@@ -66,7 +66,7 @@ public sealed class SalesSlipService : ISalesSlipService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(x => EF.Functions.ILike(x.SlipNo, $"%{term}%") || EF.Functions.ILike(x.CustomerSnapshotName, $"%{term}%"));
+            q = q.Where(x => EF.Functions.Like(x.SlipNo, $"%{term}%") || EF.Functions.Like(x.CustomerSnapshotName, $"%{term}%"));
         }
         if (status is not null) q = q.Where(x => x.Status == status);
         if (customerId is not null) q = q.Where(x => x.CustomerId == customerId);
@@ -91,7 +91,7 @@ public sealed class SalesSlipService : ISalesSlipService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(x => EF.Functions.ILike(x.SlipNo, $"%{term}%") || EF.Functions.ILike(x.CustomerSnapshotName, $"%{term}%"));
+            q = q.Where(x => EF.Functions.Like(x.SlipNo, $"%{term}%") || EF.Functions.Like(x.CustomerSnapshotName, $"%{term}%"));
         }
         if (status is not null) q = q.Where(x => x.Status == status);
         if (customerId is not null) q = q.Where(x => x.CustomerId == customerId);
@@ -165,7 +165,15 @@ public sealed class SalesSlipService : ISalesSlipService
         foreach (var line in await BuildLinesAsync(request.WarehouseId, request.Lines, ct)) slip.Lines.Add(line);
         Recalculate(slip, request.PaidAmount);
         slip.UpdatedAt = DateTime.UtcNow;
-        await _uow.SaveChangesAsync(ct);
+        try
+        {
+            await _uow.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The sales slip was modified by another request.", 412);
+        }
+
         return new ETagged<SalesSlipDto>(_mapping.MapSlip(slip), slip.RowVersion);
     }
 

Backend/ERPCore/Services/Stock/FifoCostingService.cs

@@ -78,41 +78,79 @@ public sealed class FifoCostingService : IFifoCostingService
                     $"Batch {batchId} expired on {expiry:yyyy-MM-dd} and cannot be issued.", 409);
         }
 
-        // Row-lock the issuable open layers oldest-first (SELECT … FOR UPDATE, NFR-02), plus any
-        // shortfall (negative) layers left by an over-stock sale. Excludes on-hold and rejected
-        // (grn line) and expired-batch stock — rejected stock sits quarantined until a Purchase
-        // Return consumes it directly (see PurchaseReturnService), never through this
-        // general-issue path. No LINQ is composed on top of the raw SQL so the FOR UPDATE
-        // reaches the database intact.
-        var locked = await _db.StockLayers
-            .FromSqlInterpolated($"""
-                SELECT * FROM stock_layers sl
-                WHERE sl."ItemId" = {itemId} AND sl."WarehouseId" = {warehouseId}
-                  AND (sl."QtyRemaining" < 0 OR (sl."QtyRemaining" > 0
-                    AND NOT EXISTS (SELECT 1 FROM grn_lines gl WHERE gl."GrnLineId" = sl."GrnLineId" AND gl."HoldStatus" IN ('OnHold', 'Rejected'))
-                    AND NOT EXISTS (SELECT 1 FROM batches b WHERE b."BatchId" = sl."BatchId" AND b."ExpiryDate" < {today})))
-                ORDER BY sl."ReceiptDate", sl."LayerId"
-                FOR UPDATE
+        // Row-lock the issuable open layers oldest-first (NFR-02), in two steps.
+        //
+        // Why two steps: InnoDB's locking clause applies to EVERY table a statement reads,
+        // including rows pulled in by the NOT EXISTS subqueries. A single-statement
+        // `... NOT EXISTS (grn_lines) ... FOR UPDATE` would therefore also X-lock grn_lines
+        // and batches rows, which creates a lock cycle against GrnService (it mutates
+        // HoldStatus). PostgreSQL locked only the outer FROM list, and MySQL 8.0.1+ can scope
+        // a lock with `FOR UPDATE OF sl` — but MariaDB has no `OF` clause at all (verified:
+        // syntax error). So step 1 evaluates the exclusions WITHOUT a locking clause, and
+        // step 2 locks exactly those ids against stock_layers alone.
+        //
+        // Excludes on-hold and rejected (grn line) and expired-batch stock — rejected stock
+        // sits quarantined until a Purchase Return consumes it directly (see
+        // PurchaseReturnService), never through this general-issue path.
+        var candidateIds = await _db.Database
+            .SqlQuery<int>($"""
+                SELECT sl.`LayerId` AS `Value` FROM `stock_layers` sl
+                WHERE sl.`ItemId` = {itemId} AND sl.`WarehouseId` = {warehouseId} AND sl.`QtyRemaining` > 0
+                  AND ({batchId} IS NULL OR sl.`BatchId` = {batchId})
+                  AND NOT EXISTS (SELECT 1 FROM `grn_lines` gl WHERE gl.`GrnLineId` = sl.`GrnLineId` AND gl.`HoldStatus` IN ('OnHold', 'Rejected'))
+                  AND NOT EXISTS (SELECT 1 FROM `batches` b WHERE b.`BatchId` = sl.`BatchId` AND b.`ExpiryDate` < {today})
+                ORDER BY sl.`ReceiptDate`, sl.`LayerId`
                 """)
             .ToListAsync(ct);
 
-        // Stock sold before it arrived is owed first: net shortfall layers off against issuable
-        // stock (oldest-first) before anything new is issued, so it can't be sold twice. The
-        // sale already posted its ledger Out, so settling writes no ledger entry of its own.
-        var owed = locked.Where(l => l.QtyRemaining < 0).ToList();
-        var open = locked.Where(l => l.QtyRemaining > 0).ToList();
-        foreach (var shortfall in owed)
+        // `IN ()` is a syntax error, so short-circuit to the normal insufficient-stock path.
+        List<StockLayer> layers;
+        if (candidateIds.Count == 0)
         {
-            foreach (var layer in open)
+            layers = new List<StockLayer>();
+        }
+        else
+        {
+            // SELECT sl.* (not *) and no LINQ composed on top: composition would wrap this in a
+            // derived table and the locking clause would be lost. Safe because StockLayer has no
+            // RowVersion and no shadow properties — note that if one is ever added, `*` WOULD
+            // return it here (a real column), unlike PostgreSQL's system-column xmin.
+            // Injection-safe by type, not by escaping: candidateIds is List<int> read straight
+            // back from the database, so it can only ever render as digits and commas.
+            var idList = string.Join(",", candidateIds);
+            // EF1002 is suppressed deliberately, not ignored: a parameterised IN list is not
+            // an option here because the parameter count varies per call, and FromSql would
+            // not let the `FOR UPDATE` survive. idList is built from List<int>, so it cannot
+            // contain anything but digits and commas.
+#pragma warning disable EF1002 // Possible SQL injection vulnerability — see above.
+            layers = await _db.StockLayers
+                .FromSqlRaw($"""
+                    SELECT sl.* FROM `stock_layers` sl
+                    WHERE sl.`LayerId` IN ({idList}) AND sl.`QtyRemaining` > 0
+                    ORDER BY sl.`ReceiptDate`, sl.`LayerId`
+                    FOR UPDATE
+                    """)
+                .ToListAsync(ct);
+#pragma warning restore EF1002
+
+            // Re-validate under the locks. Between step 1 and step 2 a layer could have gone
+            // on-hold or had its batch expire; now that the rows are locked nothing can change
+            // under us, so this restores the single-statement guarantee.
+            if (layers.Count > 0)
             {
-                if (shortfall.QtyRemaining >= 0) break;
-                var settle = Math.Min(-shortfall.QtyRemaining, layer.QtyRemaining);
-                layer.QtyRemaining -= settle;
-                shortfall.QtyRemaining += settle;
+                var stillIssuable = await _db.Database
+                    .SqlQuery<int>($"""
+                        SELECT sl.`LayerId` AS `Value` FROM `stock_layers` sl
+                        WHERE sl.`LayerId` IN ({idList})
+                          AND NOT EXISTS (SELECT 1 FROM `grn_lines` gl WHERE gl.`GrnLineId` = sl.`GrnLineId` AND gl.`HoldStatus` IN ('OnHold', 'Rejected'))
+                          AND NOT EXISTS (SELECT 1 FROM `batches` b WHERE b.`BatchId` = sl.`BatchId` AND b.`ExpiryDate` < {today})
+                        """)
+                    .ToListAsync(ct);
+                var issuable = stillIssuable.ToHashSet();
+                layers = layers.Where(l => issuable.Contains(l.LayerId)).ToList();
             }
         }
 
-        var layers = open.Where(l => l.QtyRemaining > 0 && (batchId == null || l.BatchId == batchId)).ToList();
         var available = layers.Sum(l => l.QtyRemaining);
         if (available < qtyBase && !allowShortfall)
         {

Backend/ERPCore/Services/TaxRateService.cs

@@ -29,7 +29,7 @@ public sealed class TaxRateService : ITaxRateService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(t => EF.Functions.ILike(t.Code, $"%{term}%") || EF.Functions.ILike(t.Name, $"%{term}%"));
+            q = q.Where(t => EF.Functions.Like(t.Code, $"%{term}%") || EF.Functions.Like(t.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(t => t.Status == status);
 

Backend/ERPCore/Services/TransferService.cs

@@ -62,7 +62,7 @@ public sealed class TransferService : ITransferService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(t => EF.Functions.ILike(t.DocNo, $"%{term}%"));
+            q = q.Where(t => EF.Functions.Like(t.DocNo, $"%{term}%"));
         }
         if (status is not null) q = q.Where(t => t.Status == status);
         if (srcWarehouseId is not null) q = q.Where(t => t.SrcWarehouseId == srcWarehouseId);

Backend/ERPCore/Services/UomService.cs

@@ -27,7 +27,7 @@ public sealed class UomService : IUomService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(u => EF.Functions.ILike(u.Name, $"%{term}%"));
+            q = q.Where(u => EF.Functions.Like(u.Name, $"%{term}%"));
         }
         if (status is not null) q = q.Where(u => u.Status == status);
 

Backend/ERPCore/Services/UserManagementService.cs

@@ -43,10 +43,10 @@ public sealed class UserManagementService : IUserManagementService
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();
-            q = q.Where(u => EF.Functions.ILike(u.Username, $"%{term}%") || EF.Functions.ILike(u.DisplayName, $"%{term}%"));
+            q = q.Where(u => EF.Functions.Like(u.Username, $"%{term}%") || EF.Functions.Like(u.DisplayName, $"%{term}%"));
         }
         if (status is not null) q = q.Where(u => u.Status == status);
-        if (!string.IsNullOrWhiteSpace(roleCode)) q = q.Where(u => u.Role != null && EF.Functions.ILike(u.Role.Code, roleCode));
+        if (!string.IsNullOrWhiteSpace(roleCode)) q = q.Where(u => u.Role != null && u.Role.Code == roleCode);
 
         var total = await q.CountAsync(ct);
         var rows = await q.OrderBy(u => u.Username)