diff --git a/scripts/avastha_calculator.py b/scripts/avastha_calculator.py
index 574b3bed..0956a4f8 100644
--- a/scripts/avastha_calculator.py
+++ b/scripts/avastha_calculator.py
@@ -227,7 +227,16 @@ class AvasthaCalculator:
         result["avasthas"]["Shayanadi"] = self._calculate_shayanadi_avastha(planet, sign)
         for name in ('Deeptadi', 'Lajjitadi', 'Shayanadi'):
             result['avasthas'][name]['method_status'] = 'simplified_heuristic'
-        if activity_context is not None:
+        if activity_context is not None and activity_context.get('unavailable_reason'):
+            # 极昼极夜等算不出日出时，PVR 公式缺一项。不退回元素启发式冒充，标成无法计算（BUG-1390）。
+            result['avasthas']['Shayanadi'] = {
+                'state': None,
+                'sign': sign,
+                'meaning': '当天没有可用的日出（极昼或极夜），姿态无法按 PVR 公式计算。',
+                'method_status': 'blocked',
+                'blocked_reason': activity_context['unavailable_reason'],
+            }
+        elif activity_context is not None:
             result['avasthas']['Shayanadi'] = calculate_pvr_shayanadi(
                 planet,
                 SIGNS.index(sign) * 30 + degree,
@@ -540,7 +549,7 @@ class AvasthaCalculator:
         
         # Shayanadi Avastha
         shayanadi = avasthas["Shayanadi"]
-        interpretation += f"5. 行为模式：{shayanadi['state']}（{shayanadi['sign']}）\n"
+        interpretation += f"5. 行为模式：{shayanadi['state'] or '无法计算'}（{shayanadi['sign']}）\n"
         interpretation += f"   {shayanadi['meaning']}\n"
         
         return interpretation
diff --git a/scripts/jyotish_engine.py b/scripts/jyotish_engine.py
index a7be4b8e..9f9917c0 100644
--- a/scripts/jyotish_engine.py
+++ b/scripts/jyotish_engine.py
@@ -16369,15 +16369,20 @@ def cmd_full_reading(args):
     # ── Step 10.5: Avasthas 行星状态 (v4.4.0) ──
     try:
         from avastha_calculator import AvasthaCalculator
-        from saham_daynight import determine_daytime
-        avastha_solar_day = determine_daytime(
-            _birth_datetime_from_args(args), lat=args.lat, lon=args.lon, tz=args.tz, rising='hindu')
-        hours_since_sunrise = (avastha_solar_day['julian_day_ut'] - avastha_solar_day['sunrise_jd_ut']) * 24
-        avastha_activity_context = {
-            'moon_longitude': planet_lons['Moon'],
-            'asc_longitude': asc_deg,
-            'hours_since_sunrise': hours_since_sunrise,
-        }
+        from saham_daynight import SahamDayNightError, determine_daytime
+        try:
+            avastha_solar_day = determine_daytime(
+                _birth_datetime_from_args(args), lat=args.lat, lon=args.lon, tz=args.tz, rising='hindu')
+        except SahamDayNightError as exc:
+            # 极昼极夜没有日出：只让姿态一项标无法计算，其余四类照常（BUG-1390）。
+            avastha_activity_context = {'unavailable_reason': str(exc)}
+        else:
+            hours_since_sunrise = (avastha_solar_day['julian_day_ut'] - avastha_solar_day['sunrise_jd_ut']) * 24
+            avastha_activity_context = {
+                'moon_longitude': planet_lons['Moon'],
+                'asc_longitude': asc_deg,
+                'hours_since_sunrise': hours_since_sunrise,
+            }
         avast_calc = AvasthaCalculator()
         avast_result = {}
         for pn, pd in planets.items():
diff --git a/tests/test_avastha_full_reading_wiring.py b/tests/test_avastha_full_reading_wiring.py
index 54419eb9..31e09cb2 100644
--- a/tests/test_avastha_full_reading_wiring.py
+++ b/tests/test_avastha_full_reading_wiring.py
@@ -37,3 +37,29 @@ def test_full_reading_wires_hindu_sunrise_into_activity_formula(monkeypatch):
     assert actual['method_status'] == 'pvr_15_4_4_running_ghati'
     assert actual['components']['running_ghati'] == 43
     assert actual['state_index'] == 10
+
+
+def test_polar_birth_without_sunrise_keeps_other_avasthas(monkeypatch):
+    # BUG-1390：北极圈夏至没有日出。原来整个 avasthas 模块报错消失；现在只有姿态一项标无法计算。
+    repo = Path(__file__).resolve().parents[1]
+    monkeypatch.syspath_prepend(str(repo / 'scripts'))
+    tree = ast.parse((repo / 'scripts/jyotish_engine.py').read_text(encoding='utf-8'))
+    blocks = [node for node in ast.walk(tree) if isinstance(node, ast.Try)
+              and any(isinstance(item, ast.ImportFrom) and item.module == 'avastha_calculator'
+                      for item in node.body)]
+    report = {'modules': {}, 'errors': []}
+    env = dict(
+        report=report,
+        args=SimpleNamespace(lat=69.65, lon=18.96, tz=2),
+        asc_deg=0,
+        planet_lons={'Sun': 90, 'Moon': 0},
+        planets={'Sun': {'degree': 90, 'degree_raw': 90, 'sign': 'Cancer', 'house': 4}},
+        _birth_datetime_from_args=lambda args: datetime(1990, 6, 21, 12, 0),
+    )
+    exec(compile(ast.Module(body=blocks, type_ignores=[]), '<avastha-polar>', 'exec'), env)
+    assert report['errors'] == []
+    sun = report['modules']['avasthas']['Sun']
+    assert sun['avasthas']['Shayanadi']['state'] is None
+    assert sun['avasthas']['Shayanadi']['method_status'] == 'blocked'
+    assert sun['avasthas']['Deeptadi']['state']
+    assert '无法计算' in sun['interpretation']