diff --git a/tests/test_scan_terminal_modules.py b/tests/test_scan_terminal_modules.py
index 72a1dd2e..b273033f 100644
--- a/tests/test_scan_terminal_modules.py
+++ b/tests/test_scan_terminal_modules.py
@@ -5,6 +5,9 @@ from web.scan_terminal_payloads import (
     build_failed_scan_terminal_payload,
     build_scan_terminal_snapshot_id,
     build_stale_scan_terminal_payload,
+    compact_ranked_scan_rows_for_payload,
+    SCAN_PAYLOAD_DEFERRED_RUNWAY_POINTS,
+    SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS,
 )
 from web.scan_terminal_ranker import build_ranked_scan_terminal_result
 from web.scan_terminal_city_row import _build_quick_row
@@ -206,6 +209,43 @@ def test_scan_terminal_snapshot_id_is_stable_for_same_ranked_inputs():
     assert first.startswith("scan-")
 
 
+def test_scan_terminal_payload_slims_deferred_runway_history_rows():
+    runway_points = [
+        {"time": f"2026-05-31T{hour:02d}:00:00+00:00", "temp": 20 + hour}
+        for hour in range(24)
+    ]
+    rows = [
+        {
+            "id": f"row-{index}",
+            "runway_plate_history": {"35R": list(runway_points)},
+        }
+        for index in range(SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS + 2)
+    ]
+
+    compacted = compact_ranked_scan_rows_for_payload(rows)
+
+    assert len(compacted[0]["runway_plate_history"]["35R"]) == len(runway_points)
+    assert (
+        len(
+            compacted[SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS - 1][
+                "runway_plate_history"
+            ]["35R"]
+        )
+        == len(runway_points)
+    )
+    assert (
+        len(
+            compacted[SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS][
+                "runway_plate_history"
+            ]["35R"]
+        )
+        == SCAN_PAYLOAD_DEFERRED_RUNWAY_POINTS
+    )
+    assert len(rows[SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS]["runway_plate_history"]["35R"]) == len(
+        runway_points
+    )
+
+
 def test_scan_terminal_quick_row_compacts_runway_history_for_list_payload():
     raw_history = {
         "35R": [
diff --git a/web/scan_terminal_payloads.py b/web/scan_terminal_payloads.py
index bcb16278..c07f6364 100644
--- a/web/scan_terminal_payloads.py
+++ b/web/scan_terminal_payloads.py
@@ -5,6 +5,48 @@ import json
 from datetime import datetime
 from typing import Any, Dict, List, Optional
 
+SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS = 9
+SCAN_PAYLOAD_DEFERRED_RUNWAY_POINTS = 12
+
+
+def _compact_runway_history_points(
+    history: Any,
+    *,
+    max_points: int,
+) -> Dict[str, List[Dict[str, Any]]]:
+    if not isinstance(history, dict) or max_points <= 0:
+        return {}
+    compacted: Dict[str, List[Dict[str, Any]]] = {}
+    for runway, points in history.items():
+        if not isinstance(points, list) or not points:
+            continue
+        compacted[str(runway)] = points[-max_points:]
+    return compacted
+
+
+def compact_ranked_scan_rows_for_payload(
+    rows: List[Dict[str, Any]],
+    *,
+    full_history_rows: int = SCAN_PAYLOAD_FULL_RUNWAY_HISTORY_ROWS,
+    deferred_runway_points: int = SCAN_PAYLOAD_DEFERRED_RUNWAY_POINTS,
+) -> List[Dict[str, Any]]:
+    compacted_rows: List[Dict[str, Any]] = []
+    for index, row in enumerate(rows):
+        if index < full_history_rows:
+            compacted_rows.append(row)
+            continue
+        history = row.get("runway_plate_history")
+        if not isinstance(history, dict) or not history:
+            compacted_rows.append(row)
+            continue
+        next_row = dict(row)
+        next_row["runway_plate_history"] = _compact_runway_history_points(
+            history,
+            max_points=deferred_runway_points,
+        )
+        compacted_rows.append(next_row)
+    return compacted_rows
+
 
 def build_scan_terminal_snapshot_id(
     filters: Dict[str, Any],
diff --git a/web/scan_terminal_service.py b/web/scan_terminal_service.py
index 6134fe11..0f32b535 100644
--- a/web/scan_terminal_service.py
+++ b/web/scan_terminal_service.py
@@ -35,6 +35,7 @@ from web.scan_terminal_payloads import (
     build_failed_scan_terminal_payload,
     build_scan_terminal_snapshot_id,
     build_stale_scan_terminal_payload,
+    compact_ranked_scan_rows_for_payload,
 )
 from web.scan_terminal_ranker import build_ranked_scan_terminal_result
 def _normalize_locale(value: Any) -> str:
@@ -210,7 +211,9 @@ def _build_scan_terminal_payload_uncached(
             total_city_count=len(city_names),
             failed_city_count=len(failed_cities),
         )
-        ranked_rows = ranked_result["ranked_rows"]
+        ranked_rows = compact_ranked_scan_rows_for_payload(
+            ranked_result["ranked_rows"]
+        )
 
         if timed_out and not ranked_rows:
             success_payload = cached_entry.get("success_payload")