fix: AV_MISMATCH hard override always sets verdict to FAKE

- AV_MISMATCH now bypasses visual threshold entirely
- Confidence boosted to min 72% when AV_MISMATCH fires
- Lowered mismatch trigger: visual >= 0.45 AND audio < 0.55
- Cleaned up broken if/elif syntax in verdict block

backend/audio_detector.py

@@ -340,11 +340,10 @@ class AudioReportAgent:
         # If visual says FAKE (high prob) but audio says HUMAN → mismatch
         av_mismatch = False
         av_mismatch_score = 0.0
-        if visual_fake_prob >= 0.55 and model_prob < 0.50:
-            # Visual strongly fake, audio sounds human → classic face-swap
+        if visual_fake_prob >= 0.45 and model_prob < 0.55:
+            # Visual shows manipulation signs, audio sounds human → face-swap
             av_mismatch = True
             av_mismatch_score = visual_fake_prob * 0.6
-            # Boost audio fake probability to reflect the mismatch
             combined = max(combined, av_mismatch_score)
             logger.info(
                 f"Audio-visual mismatch detected: visual_fake={visual_fake_prob:.2f} "

backend/detector.py

@@ -446,29 +446,28 @@ class ReportGeneratorAgent:
         audio_prob = 0.0
         if audio and audio.get("available"):
             audio_prob = audio.get("fake_probability", 0.0)
-            # AV_MISMATCH counts as fake — face-swap with dubbed audio
             audio_fake = audio.get("result") in ("AI_VOICE", "AV_MISMATCH")
 
-        # Final verdict: visual is primary, audio can upgrade OR downgrade
-        if audio and audio.get("available"):
+        # ── Determine final verdict ───────────────────────────────────
+        # AV_MISMATCH is a hard override — face-swap confirmed
+        if audio and audio.get("result") == "AV_MISMATCH":
+            is_fake    = True
+            calibrated = self._calibrate(max(prob, 0.72))
+            logger.info("AV_MISMATCH hard override → FAKE")
+        elif audio and audio.get("available"):
             if visual_fake and audio_fake:
                 is_fake = True
             elif not visual_fake and not audio_fake:
                 is_fake = False
             elif visual_fake and not audio_fake:
-                # Audio says real — only keep FAKE if visual is strong
                 is_fake = prob >= (threshold + 0.05)
             else:
-                # Visual says real but audio says AI/mismatch
-                # AV_MISMATCH is a very strong signal — override visual
-                if audio.get("result") == "AV_MISMATCH":
-                    is_fake = True   # face-swap confirmed by mismatch
-                else:
-                    is_fake = audio_prob >= 0.75
+                is_fake = audio_prob >= 0.75
+            calibrated = self._calibrate(prob)
         else:
-            is_fake = visual_fake
+            is_fake    = visual_fake
+            calibrated = self._calibrate(prob)
 
-        calibrated = self._calibrate(prob)
         confidence = round(calibrated * 100, 1)
         result     = "FAKE" if is_fake else "REAL"