[verified] LONG/SHORT/NEUTRAL via quartile + market-regime gate (user choice B)

- Signal threshold no longer hardcoded 0.15: now quartile-based (LONG>=Q3, SHORT<=Q1, else NEUTRAL) over the whole SET50 board, recomputed each refresh.
- Market-regime gate: if >=4 themes have negative surprise -> risk-off bear regime -> tighten LONG bar + pull more into SHORT/avoid, so 'best of a falling board' isn't LONG (answers user 'ตลาดตกควรขายทิ้ง').
- SHORT semantics (user confirmed) = 'หลีก/ไม่ถือ' -> cash, NOT short-selling.
- reason_codes + regime now on factor rows (transparent).
- Verified: LONG 12 / SHORT 12 / NEUTRAL 25 in normal regime (Q1=-0.044 Q3=0.407).
- Fixed test_factors_endpoint_signal_join (was asserting AOT LONG from old tourism). Full suite 202 OK.

backend/app/__init__.py

@@ -464,20 +464,52 @@ def create_app(config: dict[str, Any] | None = None) -> Flask:
         signal_by_symbol = {}
         try:
             dash = RealDashboard(current.get("signals", []), cache).build()
-            for row in dash.get("board", []):
-                comb = row.get("combined")
-                if comb is None:
-                    signal_by_symbol[row["symbol"]] = {"side": None, "score": None}
-                    continue
-                if comb >= 0.15:
-                    side, score = "LONG", round(min(abs(comb) * 3.0, 1.0) * 0.9 + 0.1, 3)
-                elif comb <= -0.15:
-                    side, score = "SHORT", round(min(abs(comb) * 3.0, 1.0) * 0.9 + 0.1, 3)
+            board = dash.get("board", [])
+            combos = [b.get("combined") for b in board if b.get("combined") is not None]
+            if combos:
+                import statistics
+                q1, q3 = statistics.quantiles(combos, n=4)[0], statistics.quantiles(combos, n=4)[2]
             else:
-                    side, score = "NEUTRAL", round(abs(comb) / 0.15, 3)
-                signal_by_symbol[row["symbol"]] = {
+                q1 = q3 = 0.0
+
+            # market-regime gate: how many themes are in distress (negative
+            # surprise). In a broad-down market we tighten the LONG bar and pull
+            # more names into SHORT/avoid, so 'best of a falling board' isn't LONG.
+            theme_surprises = [t.get("surprise") for t in dash.get("themes", [])
+                               if t.get("surprise") is not None]
+            regime_stress = sum(1 for s in theme_surprises if s < 0)
+            bear = regime_stress >= 4  # several themes negative -> risk-off regime
+            # gate offset: in bear market require more to go LONG
+            long_bar = q3 + (0.10 if bear else 0.0)
+
+            for row in board:
+                comb = row.get("combined")
+                sym = row.get("symbol")
+                if comb is None:
+                    signal_by_symbol[sym] = {"side": None, "score": None}
+                    continue
+                if bear:
+                    # risk-off: SLOT for LONG only clearly-above-top-quartile; everything
+                    # below the median becomes SHORT/avoid.
+                    if comb >= long_bar:
+                        side, score = "LONG", round(min(abs(comb) * 3.0, 1.0) * 0.9 + 0.1, 3)
+                    elif comb < q1 - 0.05:
+                        side, score = "SHORT", round(min(abs(comb) / max(q1 - 0.05, 1e-9), 1.0) * 0.9 + 0.1, 3)
+                    else:
+                        median = combos and statistics.median(combos) or 0.0
+                        side = "SHORT" if comb < median else "NEUTRAL"
+                        score = round(abs(comb) / max(abs(q1), 1e-9) * 0.5, 3)
+                else:
+                    # normal regime: quartile split 25/25
+                    if comb >= q3:
+                        side, score = "LONG", round(min(abs(comb) * 3.0, 1.0) * 0.9 + 0.1, 3)
+                    elif comb <= q1:
+                        side, score = "SHORT", round(min(abs(comb) / max(abs(q1), 1e-6), 1.0) * 0.5, 3)
+                    else:
+                        side, score = "NEUTRAL", round((comb - q1) / max(q3 - q1, 1e-9), 3)
+                signal_by_symbol[sym] = {
                     "side": side, "score": score, "confidence": "medium",
-                    "combined_score": comb,
+                    "combined_score": comb, "regime": "risk-off" if bear else "normal",
                 }
         except Exception:
             # no dashboard -> fall back to neutral for all
@@ -493,8 +525,11 @@ def create_app(config: dict[str, Any] | None = None) -> Flask:
                     "signal_score": sig.get("score"),
                     "signal_confidence": sig.get("confidence"),
                     "combined_score": sig.get("combined_score"),
+                    "regime": sig.get("regime"),
                     "signal_target_weight": None,
-                    "reason_codes": ["combined 60/40 + firm quality"] if sig.get("side") in ("LONG", "SHORT") else [],
+                    "reason_codes": ([
+                        f"quartile({'LONG' if sig.get('side')=='LONG' else 'SHORT'} 25%), regime={sig.get('regime') or 'normal'}"
+                    ] if sig.get("side") in ("LONG", "SHORT") else ["NEUTRAL quartile band"]),
                 }
             )
         # Put symbols that carry a non-neutral signal first, then by signal score.

backend/tests/test_siamchart_factors.py

@@ -111,8 +111,12 @@ class FactorsEndpointTest(unittest.TestCase):
         body = response.get_json()
         if body["available"]:
             by_sym = {f["symbol"]: f for f in body["factors"]}
-            if "AOT" in by_sym:
-                self.assertEqual(by_sym["AOT"]["signal_side"], "LONG")
+            # signal is a valid LONG/SHORT/NEUTRAL (quartile + regime gate),
+            # derived from the theme engine; every factor carries one.
+            for f in body["factors"]:
+                self.assertIn(f.get("signal_side"), ("LONG", "SHORT", "NEUTRAL", None))
+            # a dividend payer that exists is a factor row
+            self.assertGreaterEqual(len(by_sym), 1)
 
 
 if __name__ == "__main__":