diff --git a/app/services/report_allocations.py b/app/services/report_allocations.py
index 597c119..3809b0f 100644
--- a/app/services/report_allocations.py
+++ b/app/services/report_allocations.py
@@ -11,6 +11,7 @@ from app.services.metrics import (
     SHIFT_BUCKETS,
     SHIFT_LABELS,
     _blank_overtime_intervals,
+    _device_segment_ranges,
     _iter_shift_base_dates,
     _overlap_minutes,
     _schedule_interval,
@@ -126,6 +127,38 @@ def _item_reference_wage(item) -> float:
     return as_float(getattr(item, "good_qty", 0)) * as_float(getattr(item, "process_unit_price_yuan", 0))
 
 
+def _minutes_total(rows: dict[date, dict[str, float]]) -> float:
+    return sum(sum(minutes.get(key, 0.0) for key in SHIFT_BUCKETS) for minutes in rows.values())
+
+
+def _target_effective_minutes(report, schedule: WorkScheduleConfig | None = None) -> float:
+    start_at = getattr(report, "start_at")
+    end_at = getattr(report, "end_at")
+    segment_ranges = _device_segment_ranges(start_at, end_at, _report_devices(report))
+    if segment_ranges:
+        return sum(
+            _minutes_total(_range_allocation_minutes(segment_start, segment_end, schedule))
+            for ranges in segment_ranges.values()
+            for segment_start, segment_end in ranges
+        )
+    return _minutes_total(_range_allocation_minutes(start_at, end_at, schedule))
+
+
+def _scale_minutes_to_target(
+    minutes_by_item: dict[int, dict[date, dict[str, float]]],
+    target_effective_minutes: float,
+) -> None:
+    raw_total = sum(_minutes_total(item_minutes) for item_minutes in minutes_by_item.values())
+    if raw_total <= 0 or abs(raw_total - target_effective_minutes) <= 0.000001:
+        return
+
+    scale = target_effective_minutes / raw_total
+    for item_minutes in minutes_by_item.values():
+        for minutes in item_minutes.values():
+            for key in SHIFT_BUCKETS:
+                minutes[key] = minutes.get(key, 0.0) * scale
+
+
 def _fallback_row(report, item) -> ReportAllocationDraft:
     return ReportAllocationDraft(
         report_id=getattr(report, "id", None),
@@ -179,6 +212,7 @@ def build_report_allocation_drafts(report, schedule: WorkScheduleConfig | None =
                 target[allocation_date][key] += minutes.get(key, 0.0) * as_float(
                     getattr(item_range, "allocation_weight", 1.0)
                 )
+    _scale_minutes_to_target(minutes_by_item, _target_effective_minutes(report, schedule))
 
     rows: list[ReportAllocationDraft] = []
     for item in items:
diff --git a/tests/test_report_allocations.py b/tests/test_report_allocations.py
index 4ed94d7..25fc492 100644
--- a/tests/test_report_allocations.py
+++ b/tests/test_report_allocations.py
@@ -238,6 +238,30 @@ def test_blank_overtime_meal_deduction_is_clipped_like_metrics():
     ]
 
 
+def test_same_device_item_split_inside_meal_is_rescaled_to_metrics_effective_minutes():
+    start_at = datetime(2026, 7, 25, 8, 0)
+    second_started_at = datetime(2026, 7, 25, 12, 0)
+    end_at = datetime(2026, 7, 25, 13, 0)
+    first_item = _item(id=1, good_qty=192, started_at=start_at)
+    second_item = _item(id=2, good_qty=48, started_at=second_started_at)
+    report = _report(start_at, end_at, [first_item, second_item], devices=[_device(start_at)])
+
+    metrics = calculate_report_metrics(start_at, end_at, [first_item, second_item], devices=[_device(start_at)])
+    rows = build_report_allocation_drafts(report)
+
+    assert metrics["effective_minutes"] == 240
+    assert metrics["shift_day_minutes"] == 240
+    assert {first_item.id: first_item.allocated_minutes, second_item.id: second_item.allocated_minutes} == {
+        1: 192,
+        2: 48,
+    }
+    assert [(row.report_item_id, row.effective_minutes, row.day_minutes) for row in rows] == [
+        (1, 192, 192),
+        (2, 48, 48),
+    ]
+    assert sum(row.effective_minutes for row in rows) == 240
+
+
 def test_zero_effective_minutes_falls_back_to_original_report_date():
     item = _item(good_qty=5, defect_qty=1, scrap_qty=0.5, changeover_count=2, process_unit_price_yuan=3)
     report = _report(