diff --git a/admin-lehrer/components/grid-editor/useGridEditor.ts b/admin-lehrer/components/grid-editor/useGridEditor.ts
index 188357d..3e9288e 100644
--- a/admin-lehrer/components/grid-editor/useGridEditor.ts
+++ b/admin-lehrer/components/grid-editor/useGridEditor.ts
@@ -28,6 +28,11 @@ export function useGridEditor(sessionId: string | null) {
   const [ipaMode, setIpaMode] = useState<IpaMode>('auto')
   const [syllableMode, setSyllableMode] = useState<SyllableMode>('auto')
 
+  // OCR Quality Steps (A/B testing toggles)
+  const [ocrEnhance, setOcrEnhance] = useState(true)
+  const [ocrMaxCols, setOcrMaxCols] = useState(0) // 0 = unlimited (admin pipeline default)
+  const [ocrMinConf, setOcrMinConf] = useState(0) // 0 = auto from quality score
+
   // Undo/redo stacks store serialized zone arrays
   const undoStack = useRef<string[]>([])
   const redoStack = useRef<string[]>([])
@@ -52,6 +57,9 @@ export function useGridEditor(sessionId: string | null) {
       const params = new URLSearchParams()
       params.set('ipa_mode', ipaMode)
       params.set('syllable_mode', syllableMode)
+      params.set('enhance', String(ocrEnhance))
+      if (ocrMaxCols > 0) params.set('max_cols', String(ocrMaxCols))
+      if (ocrMinConf > 0) params.set('min_conf', String(ocrMinConf))
       const res = await fetch(
         `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/build-grid?${params}`,
         { method: 'POST' },
@@ -70,7 +78,7 @@ export function useGridEditor(sessionId: string | null) {
     } finally {
       setLoading(false)
     }
-  }, [sessionId, ipaMode, syllableMode])
+  }, [sessionId, ipaMode, syllableMode, ocrEnhance, ocrMaxCols, ocrMinConf])
 
   const loadGrid = useCallback(async () => {
     if (!sessionId) return
@@ -85,6 +93,9 @@ export function useGridEditor(sessionId: string | null) {
         const params = new URLSearchParams()
         params.set('ipa_mode', ipaMode)
         params.set('syllable_mode', syllableMode)
+        params.set('enhance', String(ocrEnhance))
+        if (ocrMaxCols > 0) params.set('max_cols', String(ocrMaxCols))
+        if (ocrMinConf > 0) params.set('min_conf', String(ocrMinConf))
         const buildRes = await fetch(
           `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/build-grid?${params}`,
           { method: 'POST' },
@@ -981,5 +992,11 @@ export function useGridEditor(sessionId: string | null) {
     setIpaMode,
     syllableMode,
     setSyllableMode,
+    ocrEnhance,
+    setOcrEnhance,
+    ocrMaxCols,
+    setOcrMaxCols,
+    ocrMinConf,
+    setOcrMinConf,
   }
 }
diff --git a/admin-lehrer/components/ocr-pipeline/StepGridReview.tsx b/admin-lehrer/components/ocr-pipeline/StepGridReview.tsx
index cb25e45..c19fd97 100644
--- a/admin-lehrer/components/ocr-pipeline/StepGridReview.tsx
+++ b/admin-lehrer/components/ocr-pipeline/StepGridReview.tsx
@@ -61,6 +61,12 @@ export function StepGridReview({ sessionId, onNext, saveRef }: StepGridReviewPro
     setIpaMode,
     syllableMode,
     setSyllableMode,
+    ocrEnhance,
+    setOcrEnhance,
+    ocrMaxCols,
+    setOcrMaxCols,
+    ocrMinConf,
+    setOcrMinConf,
   } = useGridEditor(sessionId)
 
   const [showImage, setShowImage] = useState(true)
@@ -256,6 +262,34 @@ export function StepGridReview({ sessionId, onNext, saveRef }: StepGridReviewPro
             Alle akzeptieren
           </button>
         )}
+        {/* OCR Quality Steps (A/B Testing) */}
+        <span className="text-gray-400 dark:text-gray-500">|</span>
+        <label className="flex items-center gap-1 cursor-pointer" title="Step 3: CLAHE + Bilateral-Filter Enhancement">
+          <input type="checkbox" checked={ocrEnhance} onChange={(e) => setOcrEnhance(e.target.checked)} className="rounded w-3 h-3" />
+          <span className="text-gray-500 dark:text-gray-400">CLAHE</span>
+        </label>
+        <label className="flex items-center gap-1" title="Step 2: Max Spaltenanzahl (0=unbegrenzt)">
+          <span className="text-gray-500 dark:text-gray-400">MaxCol:</span>
+          <select value={ocrMaxCols} onChange={(e) => setOcrMaxCols(Number(e.target.value))} className="px-1 py-0.5 text-xs rounded border border-gray-200 dark:border-gray-600 bg-white dark:bg-gray-700 text-gray-700 dark:text-gray-300">
+            <option value={0}>off</option>
+            <option value={2}>2</option>
+            <option value={3}>3</option>
+            <option value={4}>4</option>
+            <option value={5}>5</option>
+          </select>
+        </label>
+        <label className="flex items-center gap-1" title="Step 1: Min OCR Confidence (0=auto)">
+          <span className="text-gray-500 dark:text-gray-400">MinConf:</span>
+          <select value={ocrMinConf} onChange={(e) => setOcrMinConf(Number(e.target.value))} className="px-1 py-0.5 text-xs rounded border border-gray-200 dark:border-gray-600 bg-white dark:bg-gray-700 text-gray-700 dark:text-gray-300">
+            <option value={0}>auto</option>
+            <option value={20}>20</option>
+            <option value={30}>30</option>
+            <option value={40}>40</option>
+            <option value={50}>50</option>
+            <option value={60}>60</option>
+          </select>
+        </label>
+
         <div className="ml-auto flex items-center gap-2">
           <button
             onClick={() => {
diff --git a/klausur-service/backend/grid_build_core.py b/klausur-service/backend/grid_build_core.py
index 8440d07..d18e36b 100644
--- a/klausur-service/backend/grid_build_core.py
+++ b/klausur-service/backend/grid_build_core.py
@@ -55,6 +55,9 @@ async def _build_grid_core(
     *,
     ipa_mode: str = "auto",
     syllable_mode: str = "auto",
+    enhance: bool = True,
+    max_columns: int | None = None,
+    min_conf: int | None = None,
 ) -> dict:
     """Core grid building logic — pure computation, no HTTP or DB side effects.
 
@@ -91,8 +94,18 @@ async def _build_grid_core(
     if not all_words:
         raise ValueError("No word boxes found in cells")
 
-    logger.info("build-grid session %s: %d words from %d cells",
-                session_id, len(all_words), len(word_result["cells"]))
+    # 2a-pre. Apply min_conf filter if specified (Step 1: confidence tightening)
+    if min_conf and min_conf > 0:
+        before = len(all_words)
+        all_words = [w for w in all_words if w.get('conf', 100) >= min_conf]
+        removed = before - len(all_words)
+        if removed:
+            logger.info("build-grid session %s: min_conf=%d removed %d/%d words",
+                        session_id, min_conf, removed, before)
+
+    logger.info("build-grid session %s: %d words from %d cells (enhance=%s, max_cols=%s, min_conf=%s)",
+                session_id, len(all_words), len(word_result["cells"]),
+                enhance, max_columns, min_conf)
 
     # 2b. Filter decorative margin columns (alphabet graphics).
     # Some worksheets have a decorative alphabet strip along one margin
diff --git a/klausur-service/backend/grid_editor_api.py b/klausur-service/backend/grid_editor_api.py
index ea91384..82e5ae1 100644
--- a/klausur-service/backend/grid_editor_api.py
+++ b/klausur-service/backend/grid_editor_api.py
@@ -32,6 +32,9 @@ async def build_grid(
     session_id: str,
     ipa_mode: str = Query("auto", pattern="^(auto|all|de|en|none)$"),
     syllable_mode: str = Query("auto", pattern="^(auto|all|de|en|none)$"),
+    enhance: bool = Query(True, description="Step 3: CLAHE + denoise for degraded scans"),
+    max_cols: int = Query(0, description="Step 2: Max column count (0=unlimited)"),
+    min_conf: int = Query(0, description="Step 1: Min OCR confidence (0=auto)"),
 ):
     """Build a structured, zone-aware grid from existing Kombi word results.
 
@@ -53,6 +56,9 @@ async def build_grid(
         result = await _build_grid_core(
             session_id, session,
             ipa_mode=ipa_mode, syllable_mode=syllable_mode,
+            enhance=enhance,
+            max_columns=max_cols if max_cols > 0 else None,
+            min_conf=min_conf if min_conf > 0 else None,
         )
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))