Add A/B testing toggles for OCR quality steps

Each quality improvement step can now be toggled independently:
- CLAHE checkbox (Step 3: image enhancement on/off)
- MaxCols dropdown (Step 2: 0=unlimited, 2-5)
- MinConf dropdown (Step 1: auto/20/30/40/50/60)

Backend: Query params enhance, max_cols, min_conf on process-single-page.
Response includes active_steps dict showing which steps are enabled.
Frontend: Toggle controls in VocabularyTab above the table.

This allows empirical A/B testing of each step on the same scan.

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

klausur-service/backend/vocab_worksheet_api.py

@@ -1290,6 +1290,9 @@ async def process_single_page(
     page_number: int,
     ipa_mode: str = Query("none", pattern="^(auto|all|de|en|none)$"),
     syllable_mode: str = Query("none", pattern="^(auto|all|de|en|none)$"),
+    enhance: bool = Query(True, description="Step 3: CLAHE + Denoise for degraded scans"),
+    max_cols: int = Query(3, description="Step 2: Max column count (0=unlimited)"),
+    min_conf: int = Query(0, description="Step 1: Min OCR confidence (0=auto from quality score)"),
 ):
     """
     Process a SINGLE page of an uploaded PDF using the Kombi OCR pipeline.
@@ -1300,6 +1303,9 @@ async def process_single_page(
     Query params:
         ipa_mode: "none" (default), "auto", "all", "en", "de"
         syllable_mode: "none" (default), "auto", "all", "en", "de"
+        enhance: true (default) — apply CLAHE/denoise for degraded scans
+        max_cols: 3 (default) — max column count (0=unlimited)
+        min_conf: 0 (default=auto) — min OCR confidence (0=from quality score)
 
     The frontend should call this sequentially for each page.
     Returns the vocabulary for just this one page.
@@ -1332,6 +1338,9 @@ async def process_single_page(
             page_vocabulary, rotation_deg, quality_report = await _run_ocr_pipeline_for_page(
                 img_bgr, page_number, session_id,
                 ipa_mode=ipa_mode, syllable_mode=syllable_mode,
+                enable_enhance=enhance,
+                max_columns=max_cols if max_cols > 0 else None,
+                override_min_conf=min_conf if min_conf > 0 else None,
             )
         except Exception as e:
             logger.error(f"OCR pipeline failed for page {page_number + 1}: {e}", exc_info=True)
@@ -1395,11 +1404,17 @@ async def process_single_page(
         "rotation": rotation_deg,
     }
 
-    # Add scan quality report if available
+    # Add scan quality report + active steps info
     if quality_report:
-        result["scan_quality"] = quality_report.to_dict()
+        sq = quality_report.to_dict()
+        sq["active_steps"] = {
+            "step1_confidence": f"min_conf={min_ocr_conf}" if not override_min_conf else f"min_conf={override_min_conf} (override)",
+            "step2_max_columns": f"max_cols={max_columns}" if max_columns else "unlimited",
+            "step3_enhance": "on" if enable_enhance and quality_report.is_degraded else "off",
+        }
+        result["scan_quality"] = sq
     else:
-        quality_report = None  # ensure variable exists for non-pipeline path
+        quality_report = None
 
     return result
 
@@ -1411,6 +1426,9 @@ async def _run_ocr_pipeline_for_page(
     *,
     ipa_mode: str = "none",
     syllable_mode: str = "none",
+    enable_enhance: bool = True,
+    max_columns: Optional[int] = 3,
+    override_min_conf: Optional[int] = None,
 ) -> tuple:
     """Run the full Kombi OCR pipeline on a single page and return vocab entries.
 
@@ -1488,11 +1506,14 @@ async def _run_ocr_pipeline_for_page(
     except Exception as e:
         logger.warning(f"  scan quality: failed ({e})")
 
-    min_ocr_conf = scan_quality_report.recommended_min_conf if scan_quality_report else 40
+    if override_min_conf:
+        min_ocr_conf = override_min_conf
+    else:
+        min_ocr_conf = scan_quality_report.recommended_min_conf if scan_quality_report else 40
 
     # 5c. Image enhancement for degraded scans
     is_degraded = scan_quality_report.is_degraded if scan_quality_report else False
-    if is_degraded:
+    if is_degraded and enable_enhance:
         try:
             from ocr_image_enhance import enhance_for_ocr
             dewarped_bgr = enhance_for_ocr(dewarped_bgr, is_degraded=True)
@@ -1547,8 +1568,8 @@ async def _run_ocr_pipeline_for_page(
     else:
         merged_words = tess_words  # fallback to Tesseract only
 
-    # Build initial grid from merged words (limit to 3 columns for vocab tables)
-    cells, columns_meta = build_grid_from_words(merged_words, img_w, img_h, max_columns=3)
+    # Build initial grid from merged words
+    cells, columns_meta = build_grid_from_words(merged_words, img_w, img_h, max_columns=max_columns)
     for cell in cells:
         cell["ocr_engine"] = "rapid_kombi"
 

studio-v2/app/vocab-worksheet/components/VocabularyTab.tsx

@@ -120,6 +120,36 @@ export function VocabularyTab({ h }: { h: VocabWorksheetHook }) {
           </div>
         </div>
 
+        {/* OCR Quality Steps (A/B Testing) */}
+        <div className={`flex items-center gap-3 mb-3 flex-shrink-0 flex-wrap ${isDark ? 'text-white/60' : 'text-slate-500'}`}>
+          <span className="text-xs font-medium">Steps:</span>
+          <label className="flex items-center gap-1 text-xs cursor-pointer">
+            <input type="checkbox" checked={h.ocrEnhance} onChange={(e) => h.setOcrEnhance(e.target.checked)} className="rounded" />
+            CLAHE
+          </label>
+          <label className="flex items-center gap-1 text-xs">
+            <span>MaxCols:</span>
+            <select value={h.ocrMaxCols} onChange={(e) => h.setOcrMaxCols(Number(e.target.value))} className={`px-1 py-0.5 text-xs rounded border ${isDark ? 'border-white/20 bg-white/10 text-white' : 'border-gray-200 bg-white text-gray-600'}`}>
+              <option value={0}>unbegrenzt</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 text-xs">
+            <span>MinConf:</span>
+            <select value={h.ocrMinConf} onChange={(e) => h.setOcrMinConf(Number(e.target.value))} className={`px-1 py-0.5 text-xs rounded border ${isDark ? 'border-white/20 bg-white/10 text-white' : 'border-gray-200 bg-white text-gray-600'}`}>
+              <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>
+
         {/* Error messages for failed pages */}
         {h.processingErrors.length > 0 && (
           <div className={`rounded-xl p-3 mb-3 flex-shrink-0 ${isDark ? 'bg-orange-500/20 text-orange-200 border border-orange-500/30' : 'bg-orange-100 text-orange-700 border border-orange-200'}`}>

studio-v2/app/vocab-worksheet/types.ts

@@ -140,6 +140,14 @@ export interface VocabWorksheetHook {
   showSettings: boolean
   setShowSettings: (show: boolean) => void
 
+  // OCR Quality Steps (A/B testing)
+  ocrEnhance: boolean
+  setOcrEnhance: (v: boolean) => void
+  ocrMaxCols: number
+  setOcrMaxCols: (v: number) => void
+  ocrMinConf: number
+  setOcrMinConf: (v: number) => void
+
   // QR
   showQRModal: boolean
   setShowQRModal: (show: boolean) => void

studio-v2/app/vocab-worksheet/useVocabWorksheet.ts

@@ -90,6 +90,11 @@ export function useVocabWorksheet(): VocabWorksheetHook {
   const [ocrPrompts, setOcrPrompts] = useState<OcrPrompts>(defaultOcrPrompts)
   const [showSettings, setShowSettings] = useState(false)
 
+  // OCR Quality Steps (toggle individually for A/B testing)
+  const [ocrEnhance, setOcrEnhance] = useState(true)     // Step 3: CLAHE + denoise
+  const [ocrMaxCols, setOcrMaxCols] = useState(3)         // Step 2: max columns (0=unlimited)
+  const [ocrMinConf, setOcrMinConf] = useState(0)          // Step 1: 0=auto from quality score
+
   // QR Code Upload
   const [showQRModal, setShowQRModal] = useState(false)
   const [uploadSessionId, setUploadSessionId] = useState('')
@@ -359,7 +364,14 @@ export function useVocabWorksheet(): VocabWorksheetHook {
     const API_BASE = getApiBase()
 
     try {
-      const res = await fetch(`${API_BASE}/api/v1/vocab/sessions/${session!.id}/process-single-page/${pageIndex}?ipa_mode=${ipa}&syllable_mode=${syllable}`, {
+      const params = new URLSearchParams({
+        ipa_mode: ipa,
+        syllable_mode: syllable,
+        enhance: String(ocrEnhance),
+        max_cols: String(ocrMaxCols),
+        min_conf: String(ocrMinConf),
+      })
+      const res = await fetch(`${API_BASE}/api/v1/vocab/sessions/${session!.id}/process-single-page/${pageIndex}?${params}`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({ ocr_prompts: ocrPrompts }),
@@ -793,7 +805,14 @@ export function useVocabWorksheet(): VocabWorksheetHook {
       for (const pageIndex of pagesToReprocess) {
         setExtractionStatus(`Verarbeite Seite ${pageIndex + 1}...`)
         try {
-          const res = await fetch(`${API_BASE}/api/v1/vocab/sessions/${session.id}/process-single-page/${pageIndex}?ipa_mode=${ipa}&syllable_mode=${syllable}`, {
+          const params = new URLSearchParams({
+            ipa_mode: ipa,
+            syllable_mode: syllable,
+            enhance: String(ocrEnhance),
+            max_cols: String(ocrMaxCols),
+            min_conf: String(ocrMinConf),
+          })
+          const res = await fetch(`${API_BASE}/api/v1/vocab/sessions/${session.id}/process-single-page/${pageIndex}?${params}`, {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },
             body: JSON.stringify({ ocr_prompts: ocrPrompts }),
@@ -849,6 +868,7 @@ export function useVocabWorksheet(): VocabWorksheetHook {
     processingErrors, successfulPages, failedPages, currentlyProcessingPage,
     // OCR settings
     ocrPrompts, showSettings, setShowSettings,
+    ocrEnhance, setOcrEnhance, ocrMaxCols, setOcrMaxCols, ocrMinConf, setOcrMinConf,
     // QR
     showQRModal, setShowQRModal, uploadSessionId,
     mobileUploadedFiles, selectedMobileFile, setSelectedMobileFile, setMobileUploadedFiles,