diff --git a/admin-lehrer/app/(admin)/ai/ocr-pipeline/types.ts b/admin-lehrer/app/(admin)/ai/ocr-pipeline/types.ts
index ce4de3a..a0feca1 100644
--- a/admin-lehrer/app/(admin)/ai/ocr-pipeline/types.ts
+++ b/admin-lehrer/app/(admin)/ai/ocr-pipeline/types.ts
@@ -81,6 +81,7 @@ export interface ColumnResult {
 
 export interface ColumnGroundTruth {
   is_correct: boolean
+  corrected_columns?: PageRegion[]
   notes?: string
 }
 
diff --git a/admin-lehrer/components/ocr-pipeline/ColumnControls.tsx b/admin-lehrer/components/ocr-pipeline/ColumnControls.tsx
index df2d2ad..d6c44c8 100644
--- a/admin-lehrer/components/ocr-pipeline/ColumnControls.tsx
+++ b/admin-lehrer/components/ocr-pipeline/ColumnControls.tsx
@@ -1,15 +1,17 @@
 'use client'
 
-import { useState } from 'react'
+import { useState, useMemo } from 'react'
 import type { ColumnResult, ColumnGroundTruth, PageRegion } from '@/app/(admin)/ai/ocr-pipeline/types'
 
 interface ColumnControlsProps {
   columnResult: ColumnResult | null
   onRerun: () => void
   onManualMode: () => void
+  onGtMode: () => void
   onGroundTruth: (gt: ColumnGroundTruth) => void
   onNext: () => void
   isDetecting: boolean
+  savedGtColumns: PageRegion[] | null
 }
 
 const TYPE_COLORS: Record<string, string> = {
@@ -42,9 +44,95 @@ const METHOD_LABELS: Record<string, string> = {
   position_fallback: 'Fallback',
 }
 
-export function ColumnControls({ columnResult, onRerun, onManualMode, onGroundTruth, onNext, isDetecting }: ColumnControlsProps) {
+interface DiffRow {
+  index: number
+  autoCol: PageRegion | null
+  gtCol: PageRegion | null
+  diffX: number | null
+  diffW: number | null
+  typeMismatch: boolean
+}
+
+/** Match auto columns to GT columns by overlap on X-axis (IoU > 50%) */
+function computeDiff(autoCols: PageRegion[], gtCols: PageRegion[]): DiffRow[] {
+  const rows: DiffRow[] = []
+  const usedGt = new Set<number>()
+  const usedAuto = new Set<number>()
+
+  // Match auto → GT by best X-axis overlap
+  for (let ai = 0; ai < autoCols.length; ai++) {
+    const a = autoCols[ai]
+    let bestIdx = -1
+    let bestIoU = 0
+
+    for (let gi = 0; gi < gtCols.length; gi++) {
+      if (usedGt.has(gi)) continue
+      const g = gtCols[gi]
+      const overlapStart = Math.max(a.x, g.x)
+      const overlapEnd = Math.min(a.x + a.width, g.x + g.width)
+      const overlap = Math.max(0, overlapEnd - overlapStart)
+      const union = (a.width + g.width) - overlap
+      const iou = union > 0 ? overlap / union : 0
+      if (iou > bestIoU) {
+        bestIoU = iou
+        bestIdx = gi
+      }
+    }
+
+    if (bestIdx >= 0 && bestIoU > 0.3) {
+      usedGt.add(bestIdx)
+      usedAuto.add(ai)
+      const g = gtCols[bestIdx]
+      rows.push({
+        index: rows.length + 1,
+        autoCol: a,
+        gtCol: g,
+        diffX: g.x - a.x,
+        diffW: g.width - a.width,
+        typeMismatch: a.type !== g.type,
+      })
+    }
+  }
+
+  // Unmatched auto columns
+  for (let ai = 0; ai < autoCols.length; ai++) {
+    if (usedAuto.has(ai)) continue
+    rows.push({
+      index: rows.length + 1,
+      autoCol: autoCols[ai],
+      gtCol: null,
+      diffX: null,
+      diffW: null,
+      typeMismatch: false,
+    })
+  }
+
+  // Unmatched GT columns
+  for (let gi = 0; gi < gtCols.length; gi++) {
+    if (usedGt.has(gi)) continue
+    rows.push({
+      index: rows.length + 1,
+      autoCol: null,
+      gtCol: gtCols[gi],
+      diffX: null,
+      diffW: null,
+      typeMismatch: false,
+    })
+  }
+
+  return rows
+}
+
+export function ColumnControls({ columnResult, onRerun, onManualMode, onGtMode, onGroundTruth, onNext, isDetecting, savedGtColumns }: ColumnControlsProps) {
   const [gtSaved, setGtSaved] = useState(false)
 
+  const diffRows = useMemo(() => {
+    if (!columnResult || !savedGtColumns) return null
+    const autoCols = columnResult.columns.filter(c => c.type.startsWith('column') || c.type === 'page_ref')
+    const gtCols = savedGtColumns.filter(c => c.type.startsWith('column') || c.type === 'page_ref')
+    return computeDiff(autoCols, gtCols)
+  }, [columnResult, savedGtColumns])
+
   if (!columnResult) return null
 
   const columns = columnResult.columns.filter((c: PageRegion) => c.type.startsWith('column') || c.type === 'page_ref')
@@ -58,7 +146,7 @@ export function ColumnControls({ columnResult, onRerun, onManualMode, onGroundTr
   return (
     <div className="bg-white dark:bg-gray-800 rounded-xl border border-gray-200 dark:border-gray-700 p-4 space-y-4">
       {/* Summary */}
-      <div className="flex items-center gap-3">
+      <div className="flex items-center gap-3 flex-wrap">
         <div className="text-sm text-gray-600 dark:text-gray-400">
           <span className="font-medium text-gray-800 dark:text-gray-200">{columns.length} Spalten</span> erkannt
           {columnResult.duration_seconds > 0 && (
@@ -78,6 +166,12 @@ export function ColumnControls({ columnResult, onRerun, onManualMode, onGroundTr
         >
           Manuell markieren
         </button>
+        <button
+          onClick={onGtMode}
+          className="text-xs px-2 py-1 bg-amber-100 text-amber-700 dark:bg-amber-900/30 dark:text-amber-400 rounded hover:bg-amber-200 dark:hover:bg-amber-900/50 transition-colors"
+        >
+          {savedGtColumns ? 'Ground Truth bearbeiten' : 'Ground Truth eintragen'}
+        </button>
       </div>
 
       {/* Column list */}
@@ -114,6 +208,82 @@ export function ColumnControls({ columnResult, onRerun, onManualMode, onGroundTr
         ))}
       </div>
 
+      {/* Diff table (Auto vs GT) */}
+      {diffRows && diffRows.length > 0 && (
+        <div className="border-t border-gray-100 dark:border-gray-700 pt-3">
+          <div className="text-xs font-medium text-gray-500 dark:text-gray-400 mb-2">
+            Vergleich: Auto vs Ground Truth
+          </div>
+          <div className="overflow-x-auto">
+            <table className="w-full text-xs">
+              <thead>
+                <tr className="text-gray-500 dark:text-gray-400 border-b border-gray-100 dark:border-gray-700">
+                  <th className="text-left py-1 pr-2">#</th>
+                  <th className="text-left py-1 pr-2">Auto (Typ, x, w)</th>
+                  <th className="text-left py-1 pr-2">GT (Typ, x, w)</th>
+                  <th className="text-right py-1 pr-2">Diff X</th>
+                  <th className="text-right py-1">Diff W</th>
+                </tr>
+              </thead>
+              <tbody>
+                {diffRows.map((row) => (
+                  <tr
+                    key={row.index}
+                    className={
+                      !row.autoCol || !row.gtCol || row.typeMismatch
+                        ? 'bg-red-50 dark:bg-red-900/10'
+                        : (row.diffX !== null && Math.abs(row.diffX) > 20) || (row.diffW !== null && Math.abs(row.diffW) > 20)
+                          ? 'bg-amber-50 dark:bg-amber-900/10'
+                          : ''
+                    }
+                  >
+                    <td className="py-1 pr-2 font-mono text-gray-400">{row.index}</td>
+                    <td className="py-1 pr-2 font-mono">
+                      {row.autoCol ? (
+                        <span>
+                          <span className={`inline-block px-1 rounded ${TYPE_COLORS[row.autoCol.type] || ''}`}>
+                            {TYPE_LABELS[row.autoCol.type] || row.autoCol.type}
+                          </span>
+                          {' '}{row.autoCol.x}, {row.autoCol.width}
+                        </span>
+                      ) : (
+                        <span className="text-red-400">fehlt</span>
+                      )}
+                    </td>
+                    <td className="py-1 pr-2 font-mono">
+                      {row.gtCol ? (
+                        <span>
+                          <span className={`inline-block px-1 rounded ${TYPE_COLORS[row.gtCol.type] || ''}`}>
+                            {TYPE_LABELS[row.gtCol.type] || row.gtCol.type}
+                          </span>
+                          {' '}{row.gtCol.x}, {row.gtCol.width}
+                        </span>
+                      ) : (
+                        <span className="text-red-400">fehlt</span>
+                      )}
+                    </td>
+                    <td className="py-1 pr-2 text-right font-mono">
+                      {row.diffX !== null ? (
+                        <span className={Math.abs(row.diffX) > 20 ? 'text-amber-600 dark:text-amber-400' : 'text-gray-500'}>
+                          {row.diffX > 0 ? '+' : ''}{row.diffX}
+                        </span>
+                      ) : '—'}
+                    </td>
+                    <td className="py-1 text-right font-mono">
+                      {row.diffW !== null ? (
+                        <span className={Math.abs(row.diffW) > 20 ? 'text-amber-600 dark:text-amber-400' : 'text-gray-500'}>
+                          {row.diffW > 0 ? '+' : ''}{row.diffW}
+                        </span>
+                      ) : '—'}
+                    </td>
+                  </tr>
+                ))}
+              </tbody>
+            </table>
+          </div>
+        </div>
+      )}
+
       {/* Ground Truth + Navigation */}
       <div className="flex items-center justify-between pt-2 border-t border-gray-100 dark:border-gray-700">
         <div className="flex items-center gap-2">
diff --git a/admin-lehrer/components/ocr-pipeline/ManualColumnEditor.tsx b/admin-lehrer/components/ocr-pipeline/ManualColumnEditor.tsx
index 4994410..a490120 100644
--- a/admin-lehrer/components/ocr-pipeline/ManualColumnEditor.tsx
+++ b/admin-lehrer/components/ocr-pipeline/ManualColumnEditor.tsx
@@ -47,6 +47,10 @@ interface ManualColumnEditorProps {
   onApply: (columns: PageRegion[]) => void
   onCancel: () => void
   applying: boolean
+  mode?: 'manual' | 'ground-truth'
+  layout?: 'two-column' | 'stacked'
+  initialDividers?: number[]
+  initialColumnTypes?: ColumnTypeKey[]
 }
 
 export function ManualColumnEditor({
@@ -56,13 +60,19 @@ export function ManualColumnEditor({
   onApply,
   onCancel,
   applying,
+  mode = 'manual',
+  layout = 'two-column',
+  initialDividers,
+  initialColumnTypes,
 }: ManualColumnEditorProps) {
   const containerRef = useRef<HTMLDivElement>(null)
-  const [dividers, setDividers] = useState<number[]>([]) // xPercent values
-  const [columnTypes, setColumnTypes] = useState<ColumnTypeKey[]>([])
+  const [dividers, setDividers] = useState<number[]>(initialDividers ?? [])
+  const [columnTypes, setColumnTypes] = useState<ColumnTypeKey[]>(initialColumnTypes ?? [])
   const [dragging, setDragging] = useState<number | null>(null)
   const [imageLoaded, setImageLoaded] = useState(false)
 
+  const isGT = mode === 'ground-truth'
+
   // Sync columnTypes length when dividers change
   useEffect(() => {
     const numColumns = dividers.length + 1
@@ -187,8 +197,8 @@ export function ManualColumnEditor({
 
   return (
     <div className="space-y-4">
-      {/* Two-column layout: image (left) + controls (right) */}
-      <div className="grid grid-cols-2 gap-4">
+      {/* Layout: image + controls */}
+      <div className={layout === 'stacked' ? 'space-y-4' : 'grid grid-cols-2 gap-4'}>
         {/* Left: Interactive image */}
         <div>
           <div className="flex items-center justify-between mb-1">
@@ -328,7 +338,11 @@ export function ManualColumnEditor({
               disabled={dividers.length === 0 || applying}
               className="w-full px-4 py-2 bg-teal-600 text-white rounded-lg hover:bg-teal-700 transition-colors text-sm font-medium disabled:opacity-50 disabled:cursor-not-allowed"
             >
-              {applying ? 'Wird gespeichert...' : `${dividers.length + 1} Spalten uebernehmen`}
+              {applying
+                ? 'Wird gespeichert...'
+                : isGT
+                  ? `${dividers.length + 1} Spalten als Ground Truth speichern`
+                  : `${dividers.length + 1} Spalten uebernehmen`}
             </button>
             <button
               onClick={() => setDividers([])}
diff --git a/admin-lehrer/components/ocr-pipeline/StepColumnDetection.tsx b/admin-lehrer/components/ocr-pipeline/StepColumnDetection.tsx
index fe31287..30bad55 100644
--- a/admin-lehrer/components/ocr-pipeline/StepColumnDetection.tsx
+++ b/admin-lehrer/components/ocr-pipeline/StepColumnDetection.tsx
@@ -4,21 +4,44 @@ import { useCallback, useEffect, useState } from 'react'
 import type { ColumnResult, ColumnGroundTruth, PageRegion } from '@/app/(admin)/ai/ocr-pipeline/types'
 import { ColumnControls } from './ColumnControls'
 import { ManualColumnEditor } from './ManualColumnEditor'
+import type { ColumnTypeKey } from '@/app/(admin)/ai/ocr-pipeline/types'
 
 const KLAUSUR_API = '/klausur-api'
 
+type ViewMode = 'normal' | 'ground-truth' | 'manual'
+
 interface StepColumnDetectionProps {
   sessionId: string | null
   onNext: () => void
 }
 
+/** Convert PageRegion[] to divider percentages + column types for ManualColumnEditor */
+function columnsToEditorState(
+  columns: PageRegion[],
+  imageWidth: number
+): { dividers: number[]; columnTypes: ColumnTypeKey[] } {
+  if (!columns.length || !imageWidth) return { dividers: [], columnTypes: [] }
+
+  const sorted = [...columns].sort((a, b) => a.x - b.x)
+  const dividers: number[] = []
+  const columnTypes: ColumnTypeKey[] = sorted.map(c => c.type)
+
+  for (let i = 1; i < sorted.length; i++) {
+    const xPct = (sorted[i].x / imageWidth) * 100
+    dividers.push(xPct)
+  }
+
+  return { dividers, columnTypes }
+}
+
 export function StepColumnDetection({ sessionId, onNext }: StepColumnDetectionProps) {
   const [columnResult, setColumnResult] = useState<ColumnResult | null>(null)
   const [detecting, setDetecting] = useState(false)
   const [error, setError] = useState<string | null>(null)
-  const [manualMode, setManualMode] = useState(false)
+  const [viewMode, setViewMode] = useState<ViewMode>('normal')
   const [applying, setApplying] = useState(false)
   const [imageDimensions, setImageDimensions] = useState<{ width: number; height: number } | null>(null)
+  const [savedGtColumns, setSavedGtColumns] = useState<PageRegion[] | null>(null)
 
   // Fetch session info (image dimensions) + check for cached column result
   useEffect(() => {
@@ -49,6 +72,24 @@ export function StepColumnDetection({ sessionId, onNext }: StepColumnDetectionPr
   // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [sessionId])
 
+  // Load saved GT if exists
+  useEffect(() => {
+    if (!sessionId) return
+    const fetchGt = async () => {
+      try {
+        const res = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/ground-truth/columns`)
+        if (res.ok) {
+          const data = await res.json()
+          const corrected = data.columns_gt?.corrected_columns
+          if (corrected) setSavedGtColumns(corrected)
+        }
+      } catch {
+        // No saved GT - that's fine
+      }
+    }
+    fetchGt()
+  }, [sessionId])
+
   const runAutoDetection = useCallback(async () => {
     if (!sessionId) return
     setDetecting(true)
@@ -106,7 +147,30 @@ export function StepColumnDetection({ sessionId, onNext }: StepColumnDetectionPr
         columns: data.columns,
         duration_seconds: data.duration_seconds ?? 0,
       })
-      setManualMode(false)
+      setViewMode('normal')
+    } catch (e) {
+      setError(e instanceof Error ? e.message : 'Fehler beim Speichern')
+    } finally {
+      setApplying(false)
+    }
+  }, [sessionId])
+
+  const handleGtApply = useCallback(async (columns: PageRegion[]) => {
+    if (!sessionId) return
+    setApplying(true)
+    setError(null)
+    try {
+      const gt: ColumnGroundTruth = {
+        is_correct: false,
+        corrected_columns: columns,
+      }
+      await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/ground-truth/columns`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(gt),
+      })
+      setSavedGtColumns(columns)
+      setViewMode('normal')
     } catch (e) {
       setError(e instanceof Error ? e.message : 'Fehler beim Speichern')
     } finally {
@@ -131,6 +195,11 @@ export function StepColumnDetection({ sessionId, onNext }: StepColumnDetectionPr
   const dewarpedUrl = `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/image/dewarped`
   const overlayUrl = `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/image/columns-overlay`
 
+  // Pre-compute editor state from saved GT or auto columns for GT mode
+  const gtInitial = savedGtColumns
+    ? columnsToEditorState(savedGtColumns, imageDimensions?.width ?? 1000)
+    : undefined
+
   return (
     <div className="space-y-4">
       {/* Loading indicator */}
@@ -141,18 +210,77 @@ export function StepColumnDetection({ sessionId, onNext }: StepColumnDetectionPr
         </div>
       )}
 
-      {manualMode ? (
-        /* Manual column editor */
+      {viewMode === 'manual' ? (
+        /* Manual column editor - overwrites column_result */
         <ManualColumnEditor
           imageUrl={dewarpedUrl}
           imageWidth={imageDimensions?.width ?? 1000}
           imageHeight={imageDimensions?.height ?? 1400}
           onApply={handleManualApply}
-          onCancel={() => setManualMode(false)}
+          onCancel={() => setViewMode('normal')}
           applying={applying}
+          mode="manual"
         />
+      ) : viewMode === 'ground-truth' ? (
+        /* GT mode: auto result (left, readonly) + GT editor (right) */
+        <div className="grid grid-cols-2 gap-4">
+          {/* Left: Auto result (readonly overlay) */}
+          <div>
+            <div className="text-xs font-medium text-gray-500 dark:text-gray-400 mb-1">
+              Auto-Ergebnis (readonly)
+            </div>
+            <div className="border rounded-lg overflow-hidden dark:border-gray-700 bg-gray-50 dark:bg-gray-900">
+              {columnResult ? (
+                // eslint-disable-next-line @next/next/no-img-element
+                <img
+                  src={`${overlayUrl}?t=${Date.now()}`}
+                  alt="Auto Spalten-Overlay"
+                  className="w-full h-auto"
+                />
+              ) : (
+                <div className="aspect-[3/4] flex items-center justify-center text-gray-400 text-sm">
+                  Keine Auto-Daten
+                </div>
+              )}
+            </div>
+            {/* Auto column list */}
+            {columnResult && (
+              <div className="mt-2 space-y-1">
+                <div className="text-xs font-medium text-gray-500 dark:text-gray-400">
+                  Auto: {columnResult.columns.length} Spalten
+                </div>
+                {columnResult.columns
+                  .filter(c => c.type.startsWith('column') || c.type === 'page_ref')
+                  .map((col, i) => (
+                    <div key={i} className="text-xs text-gray-500 dark:text-gray-400 font-mono">
+                      {i + 1}. {col.type} x={col.x} w={col.width}
+                    </div>
+                  ))}
+              </div>
+            )}
+          </div>
+
+          {/* Right: GT editor */}
+          <div>
+            <div className="text-xs font-medium text-gray-500 dark:text-gray-400 mb-1">
+              Ground Truth Editor
+            </div>
+            <ManualColumnEditor
+              imageUrl={dewarpedUrl}
+              imageWidth={imageDimensions?.width ?? 1000}
+              imageHeight={imageDimensions?.height ?? 1400}
+              onApply={handleGtApply}
+              onCancel={() => setViewMode('normal')}
+              applying={applying}
+              mode="ground-truth"
+              layout="stacked"
+              initialDividers={gtInitial?.dividers}
+              initialColumnTypes={gtInitial?.columnTypes}
+            />
+          </div>
+        </div>
       ) : (
-        /* Image comparison: overlay (left) vs clean (right) */
+        /* Normal mode: overlay (left) vs clean (right) */
         <div className="grid grid-cols-2 gap-4">
           <div>
             <div className="text-xs font-medium text-gray-500 dark:text-gray-400 mb-1">
@@ -190,14 +318,16 @@ export function StepColumnDetection({ sessionId, onNext }: StepColumnDetectionPr
       )}
 
       {/* Controls */}
-      {!manualMode && (
+      {viewMode === 'normal' && (
         <ColumnControls
           columnResult={columnResult}
           onRerun={handleRerun}
-          onManualMode={() => setManualMode(true)}
+          onManualMode={() => setViewMode('manual')}
+          onGtMode={() => setViewMode('ground-truth')}
           onGroundTruth={handleGroundTruth}
           onNext={onNext}
           isDetecting={detecting}
+          savedGtColumns={savedGtColumns}
         />
       )}
 
diff --git a/klausur-service/backend/ocr_pipeline_api.py b/klausur-service/backend/ocr_pipeline_api.py
index 7315f49..3a0e657 100644
--- a/klausur-service/backend/ocr_pipeline_api.py
+++ b/klausur-service/backend/ocr_pipeline_api.py
@@ -135,6 +135,7 @@ class ManualColumnsRequest(BaseModel):
 
 class ColumnGroundTruthRequest(BaseModel):
     is_correct: bool
+    corrected_columns: Optional[List[Dict[str, Any]]] = None
     notes: Optional[str] = None
 
 
@@ -711,6 +712,7 @@ async def save_column_ground_truth(session_id: str, req: ColumnGroundTruthReques
     ground_truth = session.get("ground_truth") or {}
     gt = {
         "is_correct": req.is_correct,
+        "corrected_columns": req.corrected_columns,
         "notes": req.notes,
         "saved_at": datetime.utcnow().isoformat(),
         "column_result": session.get("column_result"),
@@ -725,6 +727,25 @@ async def save_column_ground_truth(session_id: str, req: ColumnGroundTruthReques
     return {"session_id": session_id, "ground_truth": gt}
 
 
+@router.get("/sessions/{session_id}/ground-truth/columns")
+async def get_column_ground_truth(session_id: str):
+    """Retrieve saved ground truth for column detection, including auto vs GT diff."""
+    session = await get_session_db(session_id)
+    if not session:
+        raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
+
+    ground_truth = session.get("ground_truth") or {}
+    columns_gt = ground_truth.get("columns")
+    if not columns_gt:
+        raise HTTPException(status_code=404, detail="No column ground truth saved")
+
+    return {
+        "session_id": session_id,
+        "columns_gt": columns_gt,
+        "columns_auto": session.get("column_result"),
+    }
+
+
 async def _get_columns_overlay(session_id: str) -> Response:
     """Generate dewarped image with column borders drawn on it."""
     session = await get_session_db(session_id)