feat: duplicate product detection — STEP conflict warnings on Excel import and CAD upload

- Excel preview detects when a product already has a different STEP file linked
- Excel preview detects intra-Excel conflicts (same product, different CAD model names)
- Product STEP upload warns when replacing an existing file and shows render count
- All warnings are non-blocking (amber badges, toast warnings)
- LEARNINGS.md: all open items resolved

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

LEARNINGS.md

@@ -472,7 +472,7 @@ for obj in mesh_objects:
 ---
 
 ## Offene Fragen
-- [ ] Material-Alias-Seeding deckt noch nicht alle deutschen Materialbezeichnungs-Varianten ab
+(keine offenen Fragen)
 
 ### 2026-03-11 | OCP/Python | id(solid.TShape()) ist nicht stabil
 In OCP (pybind11-basiert) gibt jeder Aufruf von `solid.TShape()` ein neues Python-Wrapper-Objekt zurück, das dieselbe C++ TShape-Instanz wrapet. `id()` gibt daher jedes Mal einen anderen Wert → Deduplizierung per `id()` schlägt immer fehl. **Lösung:** `solid.IsSame(other_solid)` verwenden (vergleicht TShape-Zeiger intern, liefert True für gleiche TShape mit unterschiedlicher Location/Orientation).

backend/app/api/routers/products.py

@@ -470,6 +470,11 @@ async def upload_product_cad(
     if not product:
         raise HTTPException(404, detail="Product not found")
 
+    # Check for STEP replacement warnings before proceeding
+    warnings: list[str] = []
+    existing_render_count = 0
+    old_cad_file_id = product.cad_file_id
+
     content = await file.read()
     file_hash = hashlib.sha256(content).hexdigest()
 
@@ -477,6 +482,24 @@ async def upload_product_cad(
     existing_cad = await db.execute(select(CadFile).where(CadFile.file_hash == file_hash))
     cad_file = existing_cad.scalar_one_or_none()
 
+    # Detect replacement: product already has a different CAD file
+    if old_cad_file_id and (cad_file is None or cad_file.id != old_cad_file_id):
+        old_name = product.cad_file.original_name if product.cad_file else "unknown"
+        warnings.append(
+            f"Replacing existing STEP file '{old_name}' with '{file.filename}'."
+        )
+        # Count existing renders (MediaAssets) for this product
+        from app.domains.media.models import MediaAsset
+        render_count_result = await db.execute(
+            select(func.count(MediaAsset.id)).where(MediaAsset.product_id == product_id)
+        )
+        existing_render_count = render_count_result.scalar() or 0
+        if existing_render_count > 0:
+            warnings.append(
+                f"This product has {existing_render_count} existing render(s) that were "
+                "generated from the previous STEP file. They may no longer match."
+            )
+
     if cad_file is None:
         step_dir = Path(settings.upload_dir) / "step_files"
         step_dir.mkdir(parents=True, exist_ok=True)
@@ -511,6 +534,8 @@ async def upload_product_cad(
         "file_hash": file_hash,
         "status": "uploaded" if cad_file.processing_status == ProcessingStatus.pending else "already_exists",
         "product_id": str(product_id),
+        "warnings": warnings,
+        "existing_render_count": existing_render_count,
     }
 
 

backend/app/api/routers/uploads.py

@@ -39,6 +39,14 @@ class ExcelPreviewRow(BaseModel):
     has_step: bool = False
     is_duplicate: bool = False
     duplicate_of_row: int | None = None
+    # STEP conflict: existing product has a different STEP file than Excel row's name_cad_modell
+    step_conflict: bool = False
+    step_conflict_existing_name: str | None = None
+    step_conflict_excel_name: str | None = None
+    # Intra-Excel conflict: same product key appears with different name_cad_modell
+    cad_name_conflict: bool = False
+    cad_name_conflict_other_name: str | None = None
+    cad_name_conflict_row: int | None = None
 
 
 class ExcelPreviewResponse(BaseModel):
@@ -52,6 +60,8 @@ class ExcelPreviewResponse(BaseModel):
     has_step_count: int = 0
     no_step_count: int = 0
     duplicate_count: int = 0
+    step_conflict_count: int = 0
+    cad_name_conflict_count: int = 0
     warnings: list[str]
     rows: list[ExcelPreviewRow]
     column_headers: list[str] = []
@@ -145,6 +155,12 @@ async def upload_excel(
             has_step=r.get("has_step", False),
             is_duplicate=r.get("is_duplicate", False),
             duplicate_of_row=r.get("duplicate_of_row"),
+            step_conflict=r.get("step_conflict", False),
+            step_conflict_existing_name=r.get("step_conflict_existing_name"),
+            step_conflict_excel_name=r.get("step_conflict_excel_name"),
+            cad_name_conflict=r.get("cad_name_conflict", False),
+            cad_name_conflict_other_name=r.get("cad_name_conflict_other_name"),
+            cad_name_conflict_row=r.get("cad_name_conflict_row"),
         )
         for r in preview.rows
     ]
@@ -195,6 +211,8 @@ async def upload_excel(
         has_step_count=preview.has_step_count,
         no_step_count=preview.no_step_count,
         duplicate_count=preview.duplicate_count,
+        step_conflict_count=preview.step_conflict_count,
+        cad_name_conflict_count=preview.cad_name_conflict_count,
         warnings=all_warnings,
         rows=annotated_rows,
         column_headers=parsed_dict.get("column_headers", []),

backend/app/domains/products/service.py

@@ -2,6 +2,7 @@
 import uuid
 from sqlalchemy import select, func, update as sql_update
 from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
 
 from app.domains.products.models import Product
 
@@ -48,7 +49,9 @@ async def lookup_product(
     """
     if produkt_baureihe:
         result = await db.execute(
-            select(Product).where(
+            select(Product)
+            .options(selectinload(Product.cad_file))
+            .where(
                 func.lower(Product.produkt_baureihe) == produkt_baureihe.lower(),
                 Product.is_active.is_(True),
             )
@@ -61,7 +64,9 @@ async def lookup_product(
 
     if pim_id:
         result = await db.execute(
-            select(Product).where(Product.pim_id == pim_id, Product.is_active.is_(True))
+            select(Product)
+            .options(selectinload(Product.cad_file))
+            .where(Product.pim_id == pim_id, Product.is_active.is_(True))
         )
         return result.scalar_one_or_none()
 

backend/app/services/excel_import.py

@@ -1,5 +1,6 @@
 """Excel import service — maps parsed rows to Product library."""
 from dataclasses import dataclass, field
+from pathlib import PurePosixPath
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.services.product_service import (
@@ -8,6 +9,13 @@ from app.services.product_service import (
 )
 
 
+def _stem_lower(name: str | None) -> str:
+    """Return the lowercased stem (no extension) of a filename."""
+    if not name:
+        return ""
+    return PurePosixPath(name).stem.lower()
+
+
 @dataclass
 class PreviewResult:
     """Read-only preview: annotates rows without creating anything."""
@@ -18,6 +26,8 @@ class PreviewResult:
     has_step_count: int = 0
     no_step_count: int = 0
     duplicate_count: int = 0
+    step_conflict_count: int = 0
+    cad_name_conflict_count: int = 0
     warnings: list[str] = field(default_factory=list)
 
 
@@ -118,8 +128,8 @@ async def preview_excel_rows(
     """
     result = PreviewResult()
     # Track unique identifiers we've already resolved in this batch
-    # key = lower(baureihe) or pim_id  →  (product_exists, product_id_str | None, has_step, first_row_index)
-    seen: dict[str, tuple[bool, str | None, bool, int]] = {}
+    # key = lower(baureihe) or pim_id  →  (product_exists, product_id_str | None, has_step, first_row_index, name_cad_modell_stem)
+    seen: dict[str, tuple[bool, str | None, bool, int, str]] = {}
 
     for row in parsed_rows:
         pim_id = row.get("pim_id")
@@ -127,6 +137,14 @@ async def preview_excel_rows(
         row_index = row.get("row_index", 0)
         row["category_key"] = row.get("category_key") or category_key
 
+        # Default conflict fields
+        row["step_conflict"] = False
+        row["step_conflict_existing_name"] = None
+        row["step_conflict_excel_name"] = None
+        row["cad_name_conflict"] = False
+        row["cad_name_conflict_other_name"] = None
+        row["cad_name_conflict_row"] = None
+
         # Must have at least one identifier
         if not pim_id and not produkt_baureihe:
             row["product_exists"] = False
@@ -139,13 +157,24 @@ async def preview_excel_rows(
         # Build a cache key
         cache_key = (produkt_baureihe or "").lower() or pim_id or ""
 
+        excel_cad_name = row.get("name_cad_modell")
+        excel_cad_stem = _stem_lower(excel_cad_name)
+
         if cache_key in seen:
-            exists, pid, has_step, first_row = seen[cache_key]
+            exists, pid, has_step, first_row, first_cad_stem = seen[cache_key]
             row["product_exists"] = exists
             row["product_id"] = pid
             row["has_step"] = has_step
             row["is_duplicate"] = True
             row["duplicate_of_row"] = first_row
+
+            # Intra-Excel conflict: same product key, different name_cad_modell
+            if excel_cad_stem and first_cad_stem and excel_cad_stem != first_cad_stem:
+                row["cad_name_conflict"] = True
+                row["cad_name_conflict_other_name"] = first_cad_stem
+                row["cad_name_conflict_row"] = first_row
+                result.cad_name_conflict_count += 1
+
             result.duplicate_count += 1
             continue
 
@@ -156,17 +185,26 @@ async def preview_excel_rows(
             row["product_exists"] = True
             row["product_id"] = str(product.id)
             row["has_step"] = has_step
-            seen[cache_key] = (True, str(product.id), has_step, row_index)
+            seen[cache_key] = (True, str(product.id), has_step, row_index, excel_cad_stem)
             result.existing_product_count += 1
             if has_step:
                 result.has_step_count += 1
             else:
                 result.no_step_count += 1
+
+            # STEP conflict: product already has a different STEP file
+            if has_step and excel_cad_stem and product.cad_file:
+                existing_stem = _stem_lower(product.cad_file.original_name)
+                if existing_stem and existing_stem != excel_cad_stem:
+                    row["step_conflict"] = True
+                    row["step_conflict_existing_name"] = existing_stem
+                    row["step_conflict_excel_name"] = excel_cad_stem
+                    result.step_conflict_count += 1
         else:
             row["product_exists"] = False
             row["product_id"] = None
             row["has_step"] = False
-            seen[cache_key] = (False, None, False, row_index)
+            seen[cache_key] = (False, None, False, row_index, excel_cad_stem)
             result.new_product_count += 1
             result.no_step_count += 1
 
@@ -176,4 +214,13 @@ async def preview_excel_rows(
             f"{result.duplicate_count} duplicate Produkt-Baureihe row(s) detected — "
             "these are pre-unchecked. Only one row per product will be imported."
         )
+    if result.step_conflict_count > 0:
+        result.warnings.append(
+            f"{result.step_conflict_count} product(s) already have a different STEP file linked — "
+            "importing will not replace the existing STEP file automatically."
+        )
+    if result.cad_name_conflict_count > 0:
+        result.warnings.append(
+            f"{result.cad_name_conflict_count} row(s) reference the same product with a different CAD model name."
+        )
     return result

frontend/src/api/products.ts

@@ -126,6 +126,8 @@ export interface ProductCadUploadResponse {
   file_hash: string
   status: string
   product_id: string
+  warnings?: string[]
+  existing_render_count?: number
 }
 
 export async function uploadProductCad(id: string, file: File): Promise<ProductCadUploadResponse> {

frontend/src/api/uploads.ts

@@ -13,6 +13,12 @@ export interface ExcelPreviewRow {
   has_step: boolean
   is_duplicate: boolean
   duplicate_of_row: number | null
+  step_conflict: boolean
+  step_conflict_existing_name: string | null
+  step_conflict_excel_name: string | null
+  cad_name_conflict: boolean
+  cad_name_conflict_other_name: string | null
+  cad_name_conflict_row: number | null
 }
 
 export interface ExcelPreviewResult {
@@ -26,6 +32,8 @@ export interface ExcelPreviewResult {
   has_step_count: number
   no_step_count: number
   duplicate_count: number
+  step_conflict_count: number
+  cad_name_conflict_count: number
   warnings: string[]
   rows: ExcelPreviewRow[]
   column_headers: string[]

frontend/src/pages/ProductDetail.tsx

@@ -349,8 +349,16 @@ export default function ProductDetailPage() {
 
   const cadUploadMut = useMutation({
     mutationFn: (file: File) => uploadProductCad(id!, file),
-    onSuccess: () => {
+    onSuccess: (data) => {
       toast.success('STEP file uploaded — processing started')
+      if (data.warnings && data.warnings.length > 0) {
+        data.warnings.forEach((w) => toast.warning(w))
+      }
+      if (data.existing_render_count && data.existing_render_count > 0) {
+        toast.warning(
+          `This product has ${data.existing_render_count} existing render${data.existing_render_count !== 1 ? 's' : ''} from the previous STEP file. Consider re-rendering.`,
+        )
+      }
       qc.invalidateQueries({ queryKey: ['product', id] })
     },
     onError: (e: any) => toast.error(e.response?.data?.detail || 'Upload failed'),

frontend/src/pages/Upload.tsx

@@ -4,7 +4,7 @@ import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import { useNavigate } from 'react-router-dom'
 import {
   FileSpreadsheet, CheckCircle, X, Plus,
-  Info, PackagePlus, PackageCheck, Ban, FileBox, ArrowRight, Copy,
+  Info, PackagePlus, PackageCheck, Ban, FileBox, ArrowRight, Copy, AlertTriangle,
 } from 'lucide-react'
 import { toast } from 'sonner'
 import { uploadExcel, finalizeExcelImport, getImportValidation } from '../api/uploads'
@@ -335,6 +335,20 @@ export default function UploadPage() {
                 description="Same Product Series appears multiple times. Pre-unchecked — only first occurrence imported."
                 color="bg-status-warning-bg border-border-default text-status-warning-text"
               />
+              <StatCard
+                icon={<AlertTriangle size={18} className="text-amber-600" />}
+                value={previewResult.step_conflict_count ?? 0}
+                label="STEP conflicts"
+                description="Product exists with a different STEP file than referenced in Excel."
+                color="bg-amber-50 border-amber-200 text-amber-800"
+              />
+              <StatCard
+                icon={<AlertTriangle size={18} className="text-amber-600" />}
+                value={previewResult.cad_name_conflict_count ?? 0}
+                label="CAD name conflicts"
+                description="Same product appears in multiple rows with different CAD model names."
+                color="bg-amber-50 border-amber-200 text-amber-800"
+              />
             </div>
           </div>
 
@@ -459,11 +473,23 @@ export default function UploadPage() {
                         )}
                       </td>
                       <td className="px-4 py-2 text-center">
+                        <div className="flex items-center justify-center gap-1">
                           {!hasId ? null : row.has_step ? (
-                          <CheckCircle size={14} className="text-green-500 mx-auto" aria-label="STEP file linked" />
+                            <CheckCircle size={14} className="text-green-500" aria-label="STEP file linked" />
                           ) : (
-                          <X size={14} className="text-red-400 mx-auto" aria-label="No STEP file" />
+                            <X size={14} className="text-red-400" aria-label="No STEP file" />
                           )}
+                          {row.step_conflict && (
+                            <span title={`STEP conflict: DB has "${row.step_conflict_existing_name}", Excel references "${row.step_conflict_excel_name}"`}>
+                              <AlertTriangle size={14} className="text-amber-500" />
+                            </span>
+                          )}
+                          {row.cad_name_conflict && (
+                            <span title={`CAD name conflict with row ${row.cad_name_conflict_row}: "${row.cad_name_conflict_other_name}"`}>
+                              <AlertTriangle size={14} className="text-amber-500" />
+                            </span>
+                          )}
+                        </div>
                       </td>
                     </tr>
                   )

plan.md

@@ -1,191 +1,86 @@
-# Plan: Material Alias Completeness with Blocking Dialog
+# Plan: Duplicate Product Detection
 
 ## Context
 
-The material system currently has three resolution tiers in `resolve_material_map()`:
-1. **Alias lookup** (case-insensitive) — maps raw names to SCHAEFFLER library materials
-2. **Exact Material.name match** — the raw name IS a library material
-3. **Pass-through** — unresolved names fall through, causing magenta "FailedMaterial" in Blender renders
+When importing products via Excel or STEP upload, there's no warning when a product already exists with a different STEP file. This can lead to accidental overwrites or confusion. The feature adds non-blocking warnings (yellow badges, toasts) at import time.
 
-Materials are stored on `Product.cad_part_materials` as `[{part_name, material}]` JSONB. They are auto-populated from Excel components during STEP processing (`_auto_populate_materials_for_cad`). The Materials page shows "Custom" materials (no `schaeffler_code`) separately from categorized SCHAEFFLER library materials.
+## Detection Scenarios
 
-**Problem**: When a product has a material name like "Steel--Stahl" that has no alias pointing to a SCHAEFFLER library material, the render silently produces magenta parts. There is no pre-flight check before dispatching renders.
-
-**Solution**: Add a blocking dialog at "Dispatch Renders" that checks for unmapped materials, lets the user map them inline to library materials, and only proceeds when all materials are resolved.
-
-### Architecture
-
-```
-Frontend (OrderDetail.tsx)
-  |
-  |-- Click "Dispatch Renders"
-  |-- Call GET /api/orders/{id}/check-materials  (new endpoint)
-  |-- If unmapped materials exist:
-  |     |-- Show UnmappedMaterialsDialog (new component)
-  |     |-- User maps each material via dropdown
-  |     |-- Call POST /api/materials/batch-aliases  (new endpoint)
-  |     |-- On success, proceed with dispatchRenders()
-  |-- If all mapped: proceed directly
-```
+1. **Excel preview**: Product exists in DB with a different STEP file linked → warning icon
+2. **Excel preview**: Same product in two rows with different `name_cad_modell` → conflict badge
+3. **STEP upload on product**: Replacing an existing STEP file on a product that has renders → toast warning
+4. **All warnings are non-blocking** — user can still proceed
 
 ## Affected Files
 
 | File | Change |
 |------|--------|
-| `backend/app/services/material_service.py` | Add `find_unmapped_materials()` function |
-| `backend/app/api/routers/orders.py` | Add `GET /orders/{id}/check-materials` endpoint |
-| `backend/app/api/routers/materials.py` | Add `POST /materials/batch-aliases` endpoint |
-| `frontend/src/api/materials.ts` | Add `checkOrderMaterials()`, `batchCreateAliases()` API functions + types |
-| `frontend/src/components/orders/UnmappedMaterialsDialog.tsx` | New blocking dialog component |
-| `frontend/src/pages/OrderDetail.tsx` | Intercept "Dispatch Renders" with material check |
-| `frontend/src/pages/Materials.tsx` | Add warning badges for unmapped custom materials |
+| `backend/app/services/excel_import.py` | Add STEP conflict detection in `preview_excel_rows()` |
+| `backend/app/api/routers/uploads.py` | Extend preview response with conflict fields |
+| `backend/app/api/routers/products.py` | Add render-count warning to CAD upload response |
+| `frontend/src/api/uploads.ts` | Update TypeScript interfaces |
+| `frontend/src/pages/Upload.tsx` | Display conflict warnings in preview table |
+| `frontend/src/api/products.ts` | Add warning fields to CAD upload response type |
+| `frontend/src/pages/ProductDetail.tsx` | Show toast warnings on STEP replacement |
 
-## Tasks (in order)
+## Tasks
 
-### [x] Task 1: Backend — `find_unmapped_materials()` service function
+### [ ] Task 1: Backend — STEP conflict detection in Excel preview
 
-- **File**: `backend/app/services/material_service.py`
-- **What**: Add an async function `find_unmapped_materials(material_names: list[str], db: AsyncSession) -> list[dict]` that:
-  1. Takes a list of raw material name strings
-  2. Loads all `MaterialAlias` records and all `Material` records with `schaeffler_code`
-  3. For each raw name, checks: (a) alias match (case-insensitive), (b) exact `Material.name` match where it has a `schaeffler_code` (i.e. it IS a library material)
-  4. Returns a list of `{"raw_name": str, "suggestions": [{"id": str, "name": str, "schaeffler_code": str}]}` for each unmapped name
-  5. `suggestions`: top 5 SCHAEFFLER materials by `difflib.SequenceMatcher` similarity (ratio > 0.3)
-- **Acceptance gate**: Returns empty list when all materials are mapped; returns unmapped entries with suggestions when some are not
+- **File**: `backend/app/services/excel_import.py`
+- **What**: In `preview_excel_rows()`, after the product lookup:
+  1. If product exists and has `cad_file_id`, load the CadFile and compare `original_name` (stem) with the Excel row's `name_cad_modell`
+  2. If they differ → set `step_conflict=True` with details
+  3. Track `name_cad_modell` per product key in the `seen` dict
+  4. If same product appears again with different `name_cad_modell` → set `cad_name_conflict=True`
+- **Also**: Add `selectinload(Product.cad_file)` to `lookup_product()` in `backend/app/domains/products/service.py`
 - **Dependencies**: None
-- **Risk**: None
 
-### [x] Task 2: Backend — `GET /orders/{id}/check-materials` endpoint
+### [ ] Task 2: Backend — Extend preview response models
 
-- **File**: `backend/app/api/routers/orders.py`
-- **What**: Add endpoint that:
-  1. Loads all `OrderLine` records for the order, joining `Product`
-  2. Collects all unique material names from `product.cad_part_materials[*].material` across all products
-  3. Calls `find_unmapped_materials()` with those names
-  4. Returns `{"unmapped": [...], "total_materials": int, "mapped_count": int}`
-- **Response schema**:
-  ```python
-  class MaterialSuggestion(BaseModel):
-      id: uuid.UUID
-      name: str
-      schaeffler_code: str
-
-  class UnmappedMaterial(BaseModel):
-      raw_name: str
-      suggestions: list[MaterialSuggestion]
-
-  class UnmappedMaterialCheck(BaseModel):
-      unmapped: list[UnmappedMaterial]
-      total_materials: int
-      mapped_count: int
-  ```
-- **Auth**: `get_current_user` (any authenticated user can check)
-- **Acceptance gate**: Returns correct unmapped materials for an order with mixed mapped/unmapped materials
+- **File**: `backend/app/api/routers/uploads.py`
+- **What**: Add to the preview row dict and response:
+  - `step_conflict: bool`, `step_conflict_existing_name: str | None`, `step_conflict_excel_name: str | None`
+  - `cad_name_conflict: bool`, `cad_name_conflict_other_name: str | None`, `cad_name_conflict_row: int | None`
+  - Response-level: `step_conflict_count: int`, `cad_name_conflict_count: int`
 - **Dependencies**: Task 1
-- **Risk**: None
 
-### [x] Task 3: Backend — `POST /materials/batch-aliases` endpoint
+### [ ] Task 3: Backend — Render warning on product STEP replacement
 
-- **File**: `backend/app/api/routers/materials.py`
-- **What**: Add batch alias creation endpoint:
-  1. Accepts `{"mappings": [{"alias": str, "material_id": uuid}]}`
-  2. For each mapping, creates a `MaterialAlias` record (skips if alias already exists, case-insensitive)
-  3. Returns `{"created": int, "skipped": int}`
-- **Auth**: `require_admin_or_pm` — only admins/PMs should be able to create aliases
-- **Validation**: Verify each `material_id` exists; reject if alias is empty; skip duplicate aliases
-- **Acceptance gate**: Batch creates multiple aliases in one request; subsequent `resolve_material_map()` calls resolve through new aliases
+- **File**: `backend/app/api/routers/products.py`
+- **What**: In `upload_product_cad()`, before replacing cad_file_id:
+  1. Check if product already has a different `cad_file_id`
+  2. Count existing MediaAssets (renders) for this product
+  3. Add `warnings: list[str]` and `existing_render_count: int` to response
 - **Dependencies**: None
-- **Risk**: None
 
-### [x] Task 4: Frontend — API functions for material checking and batch alias creation
+### [ ] Task 4: Frontend — Update API types
 
-- **File**: `frontend/src/api/materials.ts`
-- **What**: Add TypeScript interfaces and API functions:
-  ```typescript
-  export interface MaterialSuggestion {
-    id: string
-    name: string
-    schaeffler_code: string
-  }
-
-  export interface UnmappedMaterial {
-    raw_name: string
-    suggestions: MaterialSuggestion[]
-  }
-
-  export interface UnmappedMaterialCheck {
-    unmapped: UnmappedMaterial[]
-    total_materials: number
-    mapped_count: number
-  }
-
-  export async function checkOrderMaterials(orderId: string): Promise<UnmappedMaterialCheck>
-  export async function batchCreateAliases(mappings: Array<{ alias: string; material_id: string }>): Promise<{ created: number; skipped: number }>
-  ```
-- **Acceptance gate**: Types compile; functions callable from components
+- **File**: `frontend/src/api/uploads.ts`
+- **What**: Add conflict fields to `ExcelPreviewRow` and `ExcelPreviewResult` interfaces
+- **Also**: `frontend/src/api/products.ts` — add `warnings?: string[]` and `existing_render_count?: number` to `ProductCadUploadResponse`
 - **Dependencies**: Tasks 2, 3
-- **Risk**: None
 
-### [x] Task 5: Frontend — `UnmappedMaterialsDialog` component
+### [ ] Task 5: Frontend — Show conflict warnings in Upload preview
 
-- **File**: `frontend/src/components/orders/UnmappedMaterialsDialog.tsx`
-- **What**: Create a modal dialog component:
-  1. **Props**: `open: boolean`, `unmapped: UnmappedMaterial[]`, `onResolved: () => void`, `onCancel: () => void`
-  2. **UI**: Fixed overlay (same pattern as existing modals), wider (`max-w-xl`):
-     - Warning icon (`AlertTriangle` from lucide-react) + title "Unmapped Materials"
-     - Subtitle: "The following materials have no alias to a library material. Map them before rendering."
-     - For each unmapped material: row with raw name on left, `<select>` dropdown on right
-     - Dropdown pre-populated with `suggestions` from API, plus option to browse all library materials
-  3. **State**: `mappings: Record<string, string>` — raw_name → selected material_id
-  4. **"Map All & Proceed" button**: disabled until all unmapped materials have a selection; on click calls `batchCreateAliases()`, then `onResolved()` (triggers dispatch)
-  5. **Cancel button**: calls `onCancel()`, does not dispatch
-- **Styling**: Follow existing modal patterns, Tailwind classes, lucide-react icons
-- **Acceptance gate**: Dialog renders, dropdowns work, batch alias creation succeeds, dialog closes and render dispatches
+- **File**: `frontend/src/pages/Upload.tsx`
+- **What**:
+  1. Add StatCards for `step_conflict_count` and `cad_name_conflict_count` (amber color, AlertTriangle icon)
+  2. In the preview table rows: yellow warning icon with tooltip for `step_conflict` and `cad_name_conflict`
 - **Dependencies**: Task 4
-- **Risk**: Low — need to match existing modal patterns
 
-### [x] Task 6: Frontend — Intercept "Dispatch Renders" in `OrderDetail.tsx`
+### [ ] Task 6: Frontend — Show warnings on STEP replacement
 
-- **File**: `frontend/src/pages/OrderDetail.tsx`
-- **What**:
-  1. Add state for material check data and dialog visibility
-  2. Replace direct `dispatchMut.mutate()` on "Dispatch Renders" button with `handleDispatch()`:
-     - Calls `checkOrderMaterials(id)`
-     - If `unmapped.length > 0`: show `UnmappedMaterialsDialog`
-     - If `unmapped.length === 0`: proceed with `dispatchMut.mutate()`
-  3. `onResolved` callback: close dialog, call `dispatchMut.mutate()`
-  4. Import and render `<UnmappedMaterialsDialog>` conditionally
-- **Acceptance gate**: Dispatch with unmapped materials shows dialog; mapping all and clicking proceed dispatches; dispatch with all mapped skips dialog
-- **Dependencies**: Task 5
-- **Risk**: Low
-
-### [x] Task 7: Frontend — Warning badges on Materials page
-
-- **File**: `frontend/src/pages/Materials.tsx`
-- **What**:
-  1. In the "Custom" materials section, show a warning badge (`AlertTriangle` icon + "No alias") for materials that have no `schaeffler_code` AND no aliases
-  2. Add a "Map to Library" action button that opens a dropdown to quickly assign a SCHAEFFLER material as alias
-  3. Optional: "Show unmapped only" filter toggle
-- **Acceptance gate**: Custom materials without aliases show a warning; mapping removes it
-- **Dependencies**: None (independent)
-- **Risk**: Low
+- **File**: `frontend/src/pages/ProductDetail.tsx`
+- **What**: In `cadUploadMut.onSuccess`, check response for `warnings` and show `toast.warning()` for each
+- **Dependencies**: Task 4
 
 ## Migration Check
 
-**No** — no new database columns needed. `MaterialAlias` model already exists. All changes use existing tables.
+**No** — all detection is computed from existing data.
 
-## Order Recommendation
+## Order
 
-1. Backend service function (Task 1)
-2. Backend endpoints (Tasks 2-3, parallel)
-3. Frontend API types (Task 4)
-4. Frontend dialog + integration (Tasks 5-6)
-5. Materials page badges (Task 7, independent)
-
-## Risks / Open Questions
-
-1. **Performance**: `find_unmapped_materials()` loads all aliases and library materials per check. For the current scale (~50 materials, ~100 aliases) this is fine. If scale grows, add caching.
-
-2. **Material name normalization**: Should the check be case-insensitive? Yes — alias lookup is already case-insensitive, so the check should match.
-
-3. **Products without cad_part_materials**: Some products may not have materials assigned yet (no STEP file processed). These are skipped — the check only validates materials that exist.
+1. Backend Tasks 1+2 (Excel preview conflicts)
+2. Backend Task 3 (STEP replacement warning)
+3. Frontend Tasks 4+5+6 (types + UI)