Add inventory duplicate detection on add and label scan

Introduce a shared InventoryDuplicateMatcher (SKU, manufacturer part number,
manufacturer color) used by both manual inventory creation and powder-label
scanning, so the two paths flag duplicates consistently. Surfaces a duplicate
warning in the Create/Edit forms via inventory-duplicate-check.js and the
catalog-lookup / label-scan flows. Callers pass tenant-restricted inventory;
the matcher re-checks CompanyId as defense in depth.

Adds InventoryDuplicateMatcherTests covering the match precedence.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Application/DTOs/Inventory/InventoryDtos.cs

@@ -225,6 +225,12 @@ public class CreateInventoryItemDto
     [Display(Name = "Incoming / On Order")]
     public bool IsIncoming { get; set; }
 
+    /// <summary>
+    /// Existing inventory record the user explicitly chose to bypass when creating a separate
+    /// powder lot or location. SKU duplicates can never be bypassed.
+    /// </summary>
+    public int? DuplicateOverrideInventoryItemId { get; set; }
+
 }
 
 public class UpdateInventoryItemDto : CreateInventoryItemDto

src/PowderCoating.Application/Services/InventoryDuplicateMatcher.cs

@@ -0,0 +1,91 @@
+using PowderCoating.Core.Entities;
+
+namespace PowderCoating.Application.Services;
+
+public enum InventoryDuplicateMatchType
+{
+    Sku,
+    ManufacturerPartNumber,
+    ManufacturerColor
+}
+
+public sealed record InventoryDuplicateMatch(
+    InventoryItem Item,
+    InventoryDuplicateMatchType MatchType);
+
+/// <summary>
+/// Shared inventory duplicate rules used by manual creation and powder-label scanning.
+/// Callers are responsible for supplying inventory already restricted to the current tenant.
+/// </summary>
+public static class InventoryDuplicateMatcher
+{
+    public static InventoryDuplicateMatch? Find(
+        IEnumerable<InventoryItem> inventoryItems,
+        int companyId,
+        string? sku,
+        string? manufacturer,
+        string? manufacturerPartNumber,
+        string? colorName,
+        bool isCoating,
+        int? excludeId = null)
+    {
+        var candidates = inventoryItems
+            .Where(i => i.CompanyId == companyId && i.Id != excludeId)
+            .ToList();
+
+        var normalizedSku = Normalize(sku);
+        if (normalizedSku.Length > 0)
+        {
+            var skuMatch = candidates.FirstOrDefault(i => Normalize(i.SKU) == normalizedSku);
+            if (skuMatch != null)
+                return new InventoryDuplicateMatch(skuMatch, InventoryDuplicateMatchType.Sku);
+        }
+
+        if (!isCoating)
+            return null;
+
+        var coatingCandidates = candidates
+            .Where(i => i.InventoryCategory?.IsCoating == true)
+            .ToList();
+
+        var normalizedManufacturer = Normalize(manufacturer);
+        var normalizedPartNumber = Normalize(manufacturerPartNumber);
+        if (normalizedPartNumber.Length > 0)
+        {
+            var partNumberMatch = coatingCandidates.FirstOrDefault(i =>
+                Normalize(i.ManufacturerPartNumber) == normalizedPartNumber &&
+                (normalizedManufacturer.Length == 0 ||
+                 Normalize(i.Manufacturer) == normalizedManufacturer));
+
+            if (partNumberMatch != null)
+                return new InventoryDuplicateMatch(
+                    partNumberMatch,
+                    InventoryDuplicateMatchType.ManufacturerPartNumber);
+        }
+
+        var normalizedColorName = Normalize(colorName);
+        if (normalizedManufacturer.Length == 0 || normalizedColorName.Length == 0)
+            return null;
+
+        var manufacturerColorMatch = coatingCandidates.FirstOrDefault(i =>
+            Normalize(i.Manufacturer) == normalizedManufacturer &&
+            Normalize(i.ColorName ?? i.Name) == normalizedColorName);
+
+        return manufacturerColorMatch == null
+            ? null
+            : new InventoryDuplicateMatch(
+                manufacturerColorMatch,
+                InventoryDuplicateMatchType.ManufacturerColor);
+    }
+
+    private static string Normalize(string? value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+            return string.Empty;
+
+        return string.Join(
+                ' ',
+                value.Split((char[]?)null, StringSplitOptions.RemoveEmptyEntries))
+            .ToUpperInvariant();
+    }
+}

src/PowderCoating.Web/Controllers/InventoryController.cs

@@ -298,6 +298,27 @@ public class InventoryController : Controller
             return View(dto);
         }
 
+        var category = dto.InventoryCategoryId.HasValue
+            ? await _unitOfWork.InventoryCategoryLookups.GetByIdAsync(dto.InventoryCategoryId.Value)
+            : null;
+        var duplicate = await FindInventoryDuplicateAsync(
+            dto.SKU,
+            dto.Manufacturer,
+            dto.ManufacturerPartNumber,
+            dto.ColorName,
+            category?.IsCoating == true);
+
+        if (duplicate != null &&
+            (duplicate.MatchType == InventoryDuplicateMatchType.Sku ||
+             dto.DuplicateOverrideInventoryItemId != duplicate.Item.Id))
+        {
+            ModelState.AddModelError(
+                duplicate.MatchType == InventoryDuplicateMatchType.Sku ? nameof(dto.SKU) : string.Empty,
+                BuildDuplicateMessage(duplicate));
+            await PopulateDropdowns();
+            return View(dto);
+        }
+
         try
         {
             var item = _mapper.Map<InventoryItem>(dto);
@@ -306,12 +327,8 @@ public class InventoryController : Controller
             item.Name = ToTitleCase(item.Name);
 
             // Populate legacy Category field from lookup table
-            if (item.InventoryCategoryId.HasValue)
+            if (category != null)
-            {
+                item.Category = category.DisplayName;
-                var category = await _unitOfWork.InventoryCategoryLookups.GetByIdAsync(item.InventoryCategoryId.Value);
-                if (category != null)
-                    item.Category = category.DisplayName;
-            }
 
             // Link to the platform catalog row when this item's identity matches one, so the detail
             // screen can show manufacturer-level status (discontinued / cannot reorder) and quotes
@@ -1042,45 +1059,12 @@ public class InventoryController : Controller
         // TDS cure fallback — same logic as AiLookup button
         await ApplyTdsCureFallbackAsync(aiResult, colorName);
 
-        // Check if this product already exists in the tenant's inventory.
+        var duplicate = await FindInventoryDuplicateAsync(
-        // Match by ManufacturerPartNumber first (most precise); fall back to color name + manufacturer.
+            null,
-        // Returns the first active match so the UI can prompt to add stock inline.
+            manufacturer,
-        int?     existingInventoryId       = null;
+            sku,
-        string?  existingInventoryName     = null;
+            colorName,
-        decimal? existingQuantityOnHand    = null;
+            isCoating: true);
-        string?  existingUnitOfMeasure     = null;
-
-        InventoryItem? existingHit = null;
-
-        if (!string.IsNullOrEmpty(sku))
-        {
-            var skuLower = sku.ToLower();
-            var byPart = await _unitOfWork.InventoryItems.FindAsync(i =>
-                i.ManufacturerPartNumber != null &&
-                i.ManufacturerPartNumber.ToLower() == skuLower);
-            existingHit = byPart.FirstOrDefault();
-        }
-
-        if (existingHit == null && !string.IsNullOrEmpty(colorName))
-        {
-            var nameLower = colorName.ToLower();
-            var mfrLower  = manufacturer?.ToLower() ?? "";
-            var byName = await _unitOfWork.InventoryItems.FindAsync(i =>
-                (i.ColorName != null && i.ColorName.ToLower() == nameLower) ||
-                i.Name.ToLower() == nameLower);
-            existingHit = byName.FirstOrDefault(i =>
-                string.IsNullOrEmpty(mfrLower) ||
-                (i.Manufacturer ?? "").ToLower().Contains(mfrLower) ||
-                mfrLower.Contains((i.Manufacturer ?? "").ToLower().Trim()));
-        }
-
-        if (existingHit != null)
-        {
-            existingInventoryId    = existingHit.Id;
-            existingInventoryName  = existingHit.Name;
-            existingQuantityOnHand = existingHit.QuantityOnHand;
-            existingUnitOfMeasure  = existingHit.UnitOfMeasure;
-        }
 
         return Json(new
         {
@@ -1105,16 +1089,61 @@ public class InventoryController : Controller
             vendorName             = manufacturer,
             wasInCatalog           = wasInCatalog,
             addedToCatalog         = addedToCatalog,
-            existingInventoryId    = existingInventoryId,
+            existingInventoryId    = duplicate?.Item.Id,
-            existingInventoryName  = existingInventoryName,
+            existingInventoryName  = duplicate?.Item.Name,
-            existingQuantityOnHand = existingQuantityOnHand,
+            existingQuantityOnHand = duplicate?.Item.QuantityOnHand,
-            existingUnitOfMeasure  = existingUnitOfMeasure,
+            existingUnitOfMeasure  = duplicate?.Item.UnitOfMeasure,
+            duplicateMatchType     = duplicate?.MatchType.ToString(),
             reasoning              = aiResult.Reasoning,
         });
     }
 
     /// <summary>
-    /// Adds stock to an existing inventory item from the label scanner inline prompt.
+    /// Checks the current tenant's active inventory for an existing SKU or powder identity.
+    /// Uses the same matcher as label scanning and repeats the tenant boundary explicitly.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> CheckDuplicate(
+        string? sku,
+        int? categoryId,
+        string? manufacturer,
+        string? manufacturerPartNumber,
+        string? colorName,
+        int? currentId = null)
+    {
+        var category = categoryId.HasValue
+            ? await _unitOfWork.InventoryCategoryLookups.GetByIdAsync(categoryId.Value)
+            : null;
+
+        var duplicate = await FindInventoryDuplicateAsync(
+            sku,
+            manufacturer,
+            manufacturerPartNumber,
+            colorName,
+            category?.IsCoating == true,
+            currentId);
+
+        if (duplicate == null)
+            return Json(new { hasDuplicate = false });
+
+        return Json(new
+        {
+            hasDuplicate = true,
+            isBlocking = duplicate.MatchType == InventoryDuplicateMatchType.Sku,
+            matchType = duplicate.MatchType.ToString(),
+            message = BuildDuplicateMessage(duplicate),
+            existingInventoryId = duplicate.Item.Id,
+            existingInventoryName = duplicate.Item.Name,
+            existingSku = duplicate.Item.SKU,
+            existingManufacturer = duplicate.Item.Manufacturer,
+            existingColorName = duplicate.Item.ColorName,
+            existingQuantityOnHand = duplicate.Item.QuantityOnHand,
+            existingUnitOfMeasure = duplicate.Item.UnitOfMeasure,
+        });
+    }
+
+    /// <summary>
+    /// Adds stock to an existing inventory item from the shared duplicate prompt.
     /// Creates a Purchase transaction and updates QuantityOnHand without navigating away.
     /// </summary>
     [HttpPost]
@@ -1360,6 +1389,48 @@ public class InventoryController : Controller
         }
     }
 
+    private async Task<InventoryDuplicateMatch?> FindInventoryDuplicateAsync(
+        string? sku,
+        string? manufacturer,
+        string? manufacturerPartNumber,
+        string? colorName,
+        bool isCoating,
+        int? excludeId = null)
+    {
+        var companyId = _tenantContext.GetCurrentCompanyId();
+        if (!companyId.HasValue || companyId.Value <= 0)
+            return null;
+
+        // Explicit CompanyId predicate is intentional defense-in-depth on top of the global filter.
+        var tenantInventory = await _unitOfWork.InventoryItems.FindAsync(
+            i => i.CompanyId == companyId.Value,
+            false,
+            i => i.InventoryCategory!);
+
+        return InventoryDuplicateMatcher.Find(
+            tenantInventory,
+            companyId.Value,
+            sku,
+            manufacturer,
+            manufacturerPartNumber,
+            colorName,
+            isCoating,
+            excludeId);
+    }
+
+    private static string BuildDuplicateMessage(InventoryDuplicateMatch duplicate)
+    {
+        return duplicate.MatchType switch
+        {
+            InventoryDuplicateMatchType.Sku =>
+                $"SKU '{duplicate.Item.SKU}' is already used by '{duplicate.Item.Name}'.",
+            InventoryDuplicateMatchType.ManufacturerPartNumber =>
+                $"This manufacturer's part number is already recorded as '{duplicate.Item.Name}' ({duplicate.Item.SKU}).",
+            _ =>
+                $"{duplicate.Item.Manufacturer} {duplicate.Item.ColorName ?? duplicate.Item.Name} is already in inventory as '{duplicate.Item.Name}' ({duplicate.Item.SKU})."
+        };
+    }
+
     private static decimal GetEffectiveTransferEfficiency(decimal? transferEfficiency)
     {
         return transferEfficiency ?? DefaultTransferEfficiency;

src/PowderCoating.Web/Views/Inventory/Create.cshtml

@@ -17,8 +17,10 @@
 
         <div class="card border-0 shadow-sm">
             <div class="card-body p-4">
-                <form asp-action="Create" method="post">
+                <form asp-action="Create" method="post" id="inventory-create-form">
+                    <input type="hidden" asp-for="DuplicateOverrideInventoryItemId" id="duplicate-override-id" />
                     <partial name="_ValidationSummary" />
+                    <div id="inventory-duplicate-status" class="d-none mb-3" role="alert"></div>
 
                     <!-- Basic Information -->
                     <div class="mb-4">
@@ -428,16 +430,14 @@
     </div>
 </div>
 
-@if ((bool)(ViewBag.AiInventoryAssistEnabled ?? false))
+<partial name="_LabelScanModal" />
-{
-    <partial name="_LabelScanModal" />
-}
 
 @section Scripts {
     <partial name="_ValidationScriptsPartial" />
     <script>const inventoryFormIsCreate = true;</script>
     <partial name="_InventoryColorFamilyScripts" />
     <script src="~/js/inventory-catalog-lookup.js"></script>
+    <script src="~/js/inventory-duplicate-check.js"></script>
     @if ((bool)(ViewBag.AiInventoryAssistEnabled ?? false))
     {
         <script src="~/js/inventory-label-scan.js"></script>

src/PowderCoating.Web/Views/Inventory/Edit.cshtml

@@ -448,15 +448,13 @@
     </div>
 </div>
 
-@if ((bool)(ViewBag.AiInventoryAssistEnabled ?? false))
+<partial name="_LabelScanModal" />
-{
-    <partial name="_LabelScanModal" />
-}
 
 @section Scripts {
     <partial name="_ValidationScriptsPartial" />
     <partial name="_InventoryColorFamilyScripts" />
     <script src="~/js/inventory-catalog-lookup.js"></script>
+    <script src="~/js/inventory-duplicate-check.js"></script>
     @if ((bool)(ViewBag.AiInventoryAssistEnabled ?? false))
     {
         <script src="~/js/inventory-label-scan.js"></script>

src/PowderCoating.Web/wwwroot/js/inventory-catalog-lookup.js

@@ -208,6 +208,8 @@
             if (match) { vendorSel.value = match.value; filled.push('Vendor'); }
         }
 
+        document.dispatchEvent(new CustomEvent('inventory:identity-changed'));
+
         const discontinuedNote = item.isDiscontinued
             ? ' <span class="badge bg-warning text-dark ms-1">Discontinued</span>' : '';
 

src/PowderCoating.Web/wwwroot/js/inventory-duplicate-check.js

@@ -0,0 +1,263 @@
+/**
+ * Shared inventory duplicate UI.
+ *
+ * Owns the "already in inventory" modal and the manual Create-form preflight check.
+ * Label scanning calls window.inventoryDuplicateUi.show(...) so both entry paths use
+ * the same prompt and add-stock implementation.
+ */
+(function () {
+    'use strict';
+
+    const modalEl = document.getElementById('addStockModal');
+    const modal = modalEl ? bootstrap.Modal.getOrCreateInstance(modalEl) : null;
+    const itemNameEl = document.getElementById('add-stock-item-name');
+    const currentQtyEl = document.getElementById('add-stock-current-qty');
+    const uomEl = document.getElementById('add-stock-uom-label');
+    const qtyEl = document.getElementById('add-stock-qty');
+    const costEl = document.getElementById('add-stock-cost');
+    const notesEl = document.getElementById('add-stock-notes');
+    const modalStatusEl = document.getElementById('add-stock-status');
+    const addButton = document.getElementById('add-stock-confirm-btn');
+    const createSeparateButton = document.getElementById('add-stock-new-btn');
+
+    let activeData = null;
+    let activeOptions = {};
+
+    function show(data, options) {
+        if (!modal || !data?.existingInventoryId) return;
+
+        activeData = data;
+        activeOptions = options || {};
+        const uom = data.existingUnitOfMeasure || 'lbs';
+
+        itemNameEl.textContent = data.existingInventoryName || data.colorName || 'This product';
+        currentQtyEl.textContent = `${Number(data.existingQuantityOnHand || 0).toFixed(2)} ${uom}`;
+        uomEl.textContent = uom;
+        qtyEl.value = '';
+        costEl.value = Number(data.unitPrice || 0) > 0 ? data.unitPrice : '';
+        notesEl.value = '';
+        modalStatusEl.className = 'd-none';
+        modalStatusEl.textContent = '';
+        addButton.disabled = false;
+        addButton.innerHTML = '<i class="bi bi-plus-circle me-1"></i>Add Stock';
+        createSeparateButton.classList.toggle('d-none', data.isBlocking === true);
+        modal.show();
+    }
+
+    async function addStock() {
+        const quantity = Number(qtyEl.value);
+        if (!quantity || quantity <= 0) {
+            showModalStatus('danger', 'Enter a quantity greater than zero.');
+            return;
+        }
+
+        addButton.disabled = true;
+        addButton.innerHTML = '<span class="spinner-border spinner-border-sm me-1"></span>Saving…';
+
+        try {
+            const params = new URLSearchParams({
+                inventoryItemId: activeData.existingInventoryId,
+                quantity: quantity.toString()
+            });
+            const unitCost = Number(costEl.value);
+            if (unitCost > 0) params.set('unitCost', unitCost.toString());
+            if (notesEl.value.trim()) params.set('notes', notesEl.value.trim());
+
+            const response = await fetch(`/Inventory/AddStock?${params}`, { method: 'POST' });
+            if (!response.ok) throw new Error(`Server error ${response.status}`);
+            const result = await response.json();
+            if (!result.success) {
+                showModalStatus('danger', result.errorMessage || 'Failed to add stock.');
+                return;
+            }
+
+            modal.hide();
+            if (typeof activeOptions.onAdded === 'function') {
+                activeOptions.onAdded(result, quantity, activeData);
+            } else {
+                showFormMessage(
+                    'success',
+                    `Added <strong>${quantity.toFixed(2)} ${escapeHtml(result.unitOfMeasure)}</strong> to ` +
+                    `<strong>${escapeHtml(result.itemName)}</strong>. New stock: ` +
+                    `${Number(result.newQuantityOnHand || 0).toFixed(2)} ${escapeHtml(result.unitOfMeasure)}.`
+                );
+            }
+        } catch (error) {
+            showModalStatus('danger', error.message);
+        } finally {
+            addButton.disabled = false;
+            addButton.innerHTML = '<i class="bi bi-plus-circle me-1"></i>Add Stock';
+        }
+    }
+
+    addButton?.addEventListener('click', addStock);
+    createSeparateButton?.addEventListener('click', function () {
+        modal?.hide();
+        if (typeof activeOptions.onCreateSeparate === 'function') {
+            activeOptions.onCreateSeparate(activeData);
+        }
+    });
+
+    window.inventoryDuplicateUi = { show };
+
+    const form = document.getElementById('inventory-create-form');
+    const statusEl = document.getElementById('inventory-duplicate-status');
+    const overrideEl = document.getElementById('duplicate-override-id');
+    if (!form || !statusEl || !overrideEl) return;
+
+    const fields = {
+        sku: document.getElementById('field-sku'),
+        categoryId: document.getElementById('field-category'),
+        manufacturer: document.getElementById('field-manufacturer'),
+        manufacturerPartNumber: document.getElementById('field-partnumber'),
+        colorName: document.getElementById('field-colorname')
+    };
+
+    let timer = null;
+    let requestVersion = 0;
+    let latestDuplicate = null;
+    let acknowledgedSignature = null;
+
+    function signature() {
+        return Object.values(fields)
+            .map(field => field?.value?.trim().toUpperCase() || '')
+            .join('|');
+    }
+
+    function scheduleCheck() {
+        overrideEl.value = '';
+        acknowledgedSignature = null;
+        clearTimeout(timer);
+        timer = setTimeout(() => checkDuplicate(false), 400);
+    }
+
+    Object.values(fields).forEach(field => {
+        field?.addEventListener('input', scheduleCheck);
+        field?.addEventListener('change', scheduleCheck);
+        field?.addEventListener('blur', () => checkDuplicate(false));
+    });
+    document.addEventListener('inventory:identity-changed', scheduleCheck);
+
+    async function checkDuplicate(showChecking) {
+        const version = ++requestVersion;
+        const params = new URLSearchParams();
+        Object.entries(fields).forEach(([key, field]) => {
+            if (field?.value?.trim()) params.set(key, field.value.trim());
+        });
+
+        if (!params.has('sku') &&
+            !(params.has('manufacturer') &&
+              (params.has('manufacturerPartNumber') || params.has('colorName')))) {
+            latestDuplicate = null;
+            hideStatus();
+            return null;
+        }
+
+        if (showChecking) showFormMessage('info', 'Checking existing inventory…');
+
+        try {
+            const response = await fetch(`/Inventory/CheckDuplicate?${params}`);
+            if (!response.ok) throw new Error(`Server error ${response.status}`);
+            const data = await response.json();
+            if (version !== requestVersion) return latestDuplicate;
+
+            latestDuplicate = data.hasDuplicate ? data : null;
+            if (!latestDuplicate) {
+                hideStatus();
+                return null;
+            }
+
+            renderDuplicate(latestDuplicate);
+            return latestDuplicate;
+        } catch {
+            if (showChecking) {
+                showFormMessage(
+                    'warning',
+                    'Inventory could not be checked right now. The item will be checked again when saved.'
+                );
+            }
+            return latestDuplicate;
+        }
+    }
+
+    function renderDuplicate(data) {
+        const quantity = Number(data.existingQuantityOnHand || 0).toFixed(2);
+        const uom = escapeHtml(data.existingUnitOfMeasure || 'lbs');
+        const viewLink = `/Inventory/Details/${data.existingInventoryId}`;
+        const overrideButton = data.isBlocking
+            ? ''
+            : '<button type="button" class="btn btn-sm btn-outline-secondary duplicate-create-separate">Create separate entry</button>';
+
+        statusEl.className = 'alert alert-warning mb-3';
+        statusEl.innerHTML = `
+            <div class="d-flex gap-2 align-items-start">
+                <i class="bi bi-exclamation-triangle-fill mt-1"></i>
+                <div class="flex-grow-1">
+                    <div class="fw-semibold">Already in inventory</div>
+                    <div class="small">${escapeHtml(data.message)}</div>
+                    <div class="small text-muted mt-1">Current stock: ${quantity} ${uom}</div>
+                    <div class="d-flex flex-wrap gap-2 mt-2">
+                        <a class="btn btn-sm btn-outline-secondary" href="${viewLink}">View existing item</a>
+                        <button type="button" class="btn btn-sm btn-primary duplicate-add-stock">Add stock</button>
+                        ${overrideButton}
+                    </div>
+                </div>
+            </div>`;
+
+        statusEl.querySelector('.duplicate-add-stock')?.addEventListener('click', () => show(data));
+        statusEl.querySelector('.duplicate-create-separate')?.addEventListener('click', () => {
+            overrideEl.value = data.existingInventoryId;
+            acknowledgedSignature = signature();
+            statusEl.className = 'alert alert-warning mb-3';
+            statusEl.innerHTML =
+                `<strong>Separate entry confirmed.</strong> ${escapeHtml(data.message)} ` +
+                `<a class="alert-link" href="${viewLink}">View existing item</a>`;
+        });
+    }
+
+    form.addEventListener('submit', async function (event) {
+        if (form.dataset.duplicateValidated === 'true') {
+            form.dataset.duplicateValidated = '';
+            return;
+        }
+
+        event.preventDefault();
+        const duplicate = await checkDuplicate(true);
+        const isAcknowledged = duplicate &&
+            !duplicate.isBlocking &&
+            Number(overrideEl.value) === Number(duplicate.existingInventoryId) &&
+            acknowledgedSignature === signature();
+
+        if (!duplicate || isAcknowledged) {
+            form.dataset.duplicateValidated = 'true';
+            form.requestSubmit(event.submitter);
+            return;
+        }
+
+        statusEl.scrollIntoView({ behavior: 'smooth', block: 'center' });
+        statusEl.querySelector('button, a')?.focus({ preventScroll: true });
+    });
+
+    function showModalStatus(type, message) {
+        modalStatusEl.className = `alert alert-${type} py-2 small`;
+        modalStatusEl.textContent = message;
+    }
+
+    function showFormMessage(type, message) {
+        statusEl.className = `alert alert-${type} mb-3`;
+        statusEl.innerHTML = message;
+    }
+
+    function hideStatus() {
+        statusEl.className = 'd-none mb-3';
+        statusEl.innerHTML = '';
+    }
+
+    function escapeHtml(value) {
+        return String(value ?? '')
+            .replace(/&/g, '&amp;')
+            .replace(/</g, '&lt;')
+            .replace(/>/g, '&gt;')
+            .replace(/"/g, '&quot;');
+    }
+})();

src/PowderCoating.Web/wwwroot/js/inventory-label-scan.js

@@ -46,33 +46,14 @@
     const processingEl   = document.getElementById('scan-processing');
     const processingMsgEl= document.getElementById('scan-processing-msg');
 
-    // Add-stock modal elements
+    let _lastScanData = null;
-    const addStockModalEl   = document.getElementById('addStockModal');
-    const bsAddStockModal   = addStockModalEl ? new bootstrap.Modal(addStockModalEl) : null;
-    const addStockItemName  = document.getElementById('add-stock-item-name');
-    const addStockCurrentQty= document.getElementById('add-stock-current-qty');
-    const addStockUomLabel  = document.getElementById('add-stock-uom-label');
-    const addStockQtyInput  = document.getElementById('add-stock-qty');
-    const addStockCostInput = document.getElementById('add-stock-cost');
-    const addStockNotesInput= document.getElementById('add-stock-notes');
-    const addStockStatusEl  = document.getElementById('add-stock-status');
-    const addStockConfirmBtn= document.getElementById('add-stock-confirm-btn');
-
-    let _addStockItemId  = null;
-    let _lastScanData    = null;
 
     if (!modalEl || !videoEl || !canvasEl) return;
 
     scanBtn.addEventListener('click', openScanner);
     modalEl.addEventListener('hide.bs.modal', onModalClose);
     if (shutterBtn) shutterBtn.addEventListener('click', captureFrame);
-    if (addStockConfirmBtn) addStockConfirmBtn.addEventListener('click', submitAddStock);
+
-    // "Create new entry instead" hides the add-stock modal and pre-fills the create form
-    const addStockNewBtn = document.getElementById('add-stock-new-btn');
-    if (addStockNewBtn) addStockNewBtn.addEventListener('click', () => {
-        bsAddStockModal?.hide();
-        if (_lastScanData) fillFromScan(_lastScanData, /* skipDuplicatePrompt */ true);
-    });
     window.addEventListener('beforeunload', releaseCamera);
 
     // Pre-warm camera if browser has already granted permission (no prompt risk)
@@ -326,9 +307,10 @@
 
             if (data.existingInventoryId) {
                 // Product already in inventory — show inline add-stock prompt
-                _lastScanData   = data;
+                _lastScanData = data;
-                _addStockItemId = data.existingInventoryId;
+                window.inventoryDuplicateUi?.show(data, {
-                openAddStockModal(data);
+                    onCreateSeparate: () => fillFromScan(_lastScanData, true)
+                });
             } else {
                 fillFromScan(data);
             }
@@ -339,79 +321,6 @@
         }
     }
 
-    // ── Add-stock modal ───────────────────────────────────────────────────
-
-    function openAddStockModal(data) {
-        if (!bsAddStockModal) { fillFromScan(data); return; }
-
-        const uom = data.existingUnitOfMeasure || 'lbs';
-        if (addStockItemName)   addStockItemName.textContent   = data.existingInventoryName || data.colorName || 'This product';
-        if (addStockCurrentQty) addStockCurrentQty.textContent = `${(data.existingQuantityOnHand ?? 0).toFixed(2)} ${uom}`;
-        if (addStockUomLabel)   addStockUomLabel.textContent   = uom;
-        if (addStockQtyInput)   addStockQtyInput.value         = '';
-        if (addStockCostInput)  addStockCostInput.value        = data.unitPrice > 0 ? data.unitPrice : '';
-        if (addStockNotesInput) addStockNotesInput.value       = '';
-        if (addStockStatusEl)   { addStockStatusEl.className = 'd-none'; addStockStatusEl.textContent = ''; }
-        if (addStockConfirmBtn) addStockConfirmBtn.disabled    = false;
-
-        bsAddStockModal.show();
-    }
-
-    async function submitAddStock() {
-        const qty = parseFloat(addStockQtyInput?.value);
-        if (!qty || qty <= 0) {
-            showAddStockStatus('danger', 'Please enter a quantity greater than zero.');
-            return;
-        }
-
-        addStockConfirmBtn.disabled = true;
-        addStockConfirmBtn.innerHTML = '<span class="spinner-border spinner-border-sm me-1"></span>Saving…';
-
-        try {
-            const params = new URLSearchParams({
-                inventoryItemId: _addStockItemId,
-                quantity:        qty,
-            });
-            const cost = parseFloat(addStockCostInput?.value);
-            if (cost > 0) params.append('unitCost', cost);
-            const notes = addStockNotesInput?.value?.trim();
-            if (notes) params.append('notes', notes);
-
-            const resp = await fetch('/Inventory/AddStock?' + params.toString(), { method: 'POST' });
-            if (!resp.ok) throw new Error(`Server error ${resp.status}`);
-            const data = await resp.json();
-
-            if (!data.success) {
-                showAddStockStatus('danger', data.errorMessage || 'Failed to add stock.');
-                addStockConfirmBtn.disabled = false;
-                addStockConfirmBtn.innerHTML = '<i class="bi bi-plus-circle me-1"></i>Add Stock';
-                return;
-            }
-
-            // Success — close modal and show confirmation on the form
-            bsAddStockModal.hide();
-            showFormStatus('success',
-                `<i class="bi bi-check-circle-fill me-1"></i>` +
-                `Added <strong>${qty.toFixed(2)} ${data.unitOfMeasure}</strong> to <strong>${data.itemName}</strong>. ` +
-                `New stock: ${(data.newQuantityOnHand ?? 0).toFixed(2)} ${data.unitOfMeasure}. ` +
-                `<a href="/Inventory/Details/${_addStockItemId}" class="alert-link">View item</a>`
-            );
-
-        } catch (err) {
-            showAddStockStatus('danger', 'Error: ' + err.message);
-            addStockConfirmBtn.disabled = false;
-            addStockConfirmBtn.innerHTML = '<i class="bi bi-plus-circle me-1"></i>Add Stock';
-        }
-    }
-
-    function showAddStockStatus(type, msg) {
-        if (!addStockStatusEl) return;
-        addStockStatusEl.className = `alert alert-${type} py-2 small`;
-        addStockStatusEl.textContent = msg;
-    }
-
-    // ── Fill the inventory form from scan result ───────────────────────────
-
     function fillFromScan(data, skipDuplicatePrompt = false) {
         const filled = [];
 
@@ -506,6 +415,8 @@
                 ? ' <span class="badge bg-success ms-1">Added to platform catalog</span>'
                 : '';
 
+        document.dispatchEvent(new CustomEvent('inventory:identity-changed'));
+
         if (data.existingInventoryId && !skipDuplicatePrompt) {
             // Duplicate handled by add-stock modal — don't show a banner here
         } else if (data.existingInventoryId && skipDuplicatePrompt) {

tests/PowderCoating.UnitTests/InventoryDuplicateMatcherTests.cs

@@ -0,0 +1,167 @@
+using PowderCoating.Application.Services;
+using PowderCoating.Core.Entities;
+
+namespace PowderCoating.UnitTests;
+
+public class InventoryDuplicateMatcherTests
+{
+    [Fact]
+    public void Find_SkuMatch_IsRestrictedToRequestedCompany()
+    {
+        var otherTenantItem = Item(
+            id: 1,
+            companyId: 22,
+            sku: "POW-001",
+            manufacturer: "Prismatic Powders",
+            colorName: "Illusion Malbec");
+
+        var result = InventoryDuplicateMatcher.Find(
+            new[] { otherTenantItem },
+            companyId: 11,
+            sku: "POW-001",
+            manufacturer: null,
+            manufacturerPartNumber: null,
+            colorName: null,
+            isCoating: false);
+
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void Find_SkuMatch_IsCaseAndWhitespaceInsensitive()
+    {
+        var item = Item(1, 11, "POW-001", null, null);
+
+        var result = InventoryDuplicateMatcher.Find(
+            new[] { item },
+            companyId: 11,
+            sku: "  pow-001 ",
+            manufacturer: null,
+            manufacturerPartNumber: null,
+            colorName: null,
+            isCoating: false);
+
+        Assert.NotNull(result);
+        Assert.Equal(InventoryDuplicateMatchType.Sku, result!.MatchType);
+        Assert.Same(item, result.Item);
+    }
+
+    [Fact]
+    public void Find_PowderManufacturerAndColor_NormalizesSpacingAndCase()
+    {
+        var item = Item(
+            id: 1,
+            companyId: 11,
+            sku: "POW-001",
+            manufacturer: "Prismatic   Powders",
+            colorName: "Illusion Malbec");
+
+        var result = InventoryDuplicateMatcher.Find(
+            new[] { item },
+            companyId: 11,
+            sku: null,
+            manufacturer: " prismatic powders ",
+            manufacturerPartNumber: null,
+            colorName: "illusion   malbec",
+            isCoating: true);
+
+        Assert.NotNull(result);
+        Assert.Equal(InventoryDuplicateMatchType.ManufacturerColor, result!.MatchType);
+    }
+
+    [Fact]
+    public void Find_SameColorFromDifferentManufacturer_IsNotDuplicate()
+    {
+        var item = Item(
+            id: 1,
+            companyId: 11,
+            sku: "POW-001",
+            manufacturer: "Prismatic Powders",
+            colorName: "Gloss Black");
+
+        var result = InventoryDuplicateMatcher.Find(
+            new[] { item },
+            companyId: 11,
+            sku: null,
+            manufacturer: "Columbia Coatings",
+            manufacturerPartNumber: null,
+            colorName: "Gloss Black",
+            isCoating: true);
+
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void Find_ManufacturerPartNumber_UsesSharedPowderRule()
+    {
+        var item = Item(
+            id: 1,
+            companyId: 11,
+            sku: "POW-001",
+            manufacturer: "Columbia Coatings",
+            colorName: "Smokey Blue",
+            manufacturerPartNumber: "S5704126");
+
+        var result = InventoryDuplicateMatcher.Find(
+            new[] { item },
+            companyId: 11,
+            sku: null,
+            manufacturer: "columbia coatings",
+            manufacturerPartNumber: " s5704126 ",
+            colorName: null,
+            isCoating: true);
+
+        Assert.NotNull(result);
+        Assert.Equal(InventoryDuplicateMatchType.ManufacturerPartNumber, result!.MatchType);
+    }
+
+    [Fact]
+    public void Find_NonCoating_DoesNotUsePowderIdentityRules()
+    {
+        var item = Item(
+            id: 1,
+            companyId: 11,
+            sku: "SUP-001",
+            manufacturer: "Acme",
+            colorName: "Blue");
+
+        var result = InventoryDuplicateMatcher.Find(
+            new[] { item },
+            companyId: 11,
+            sku: null,
+            manufacturer: "Acme",
+            manufacturerPartNumber: null,
+            colorName: "Blue",
+            isCoating: false);
+
+        Assert.Null(result);
+    }
+
+    private static InventoryItem Item(
+        int id,
+        int companyId,
+        string sku,
+        string? manufacturer,
+        string? colorName,
+        string? manufacturerPartNumber = null)
+    {
+        return new InventoryItem
+        {
+            Id = id,
+            CompanyId = companyId,
+            SKU = sku,
+            Name = colorName ?? sku,
+            Manufacturer = manufacturer,
+            ManufacturerPartNumber = manufacturerPartNumber,
+            ColorName = colorName,
+            InventoryCategory = new InventoryCategoryLookup
+            {
+                Id = id,
+                CompanyId = companyId,
+                DisplayName = "Powder",
+                CategoryCode = "POWDER",
+                IsCoating = true
+            }
+        };
+    }
+}