Upload alpha_factory/deterministic/theme_sampler.py

alpha_factory/deterministic/theme_sampler.py

@@ -175,12 +175,21 @@ def pick_theme(
     dead_themes: Optional[list[str]] = None,
     top_k: int = 3,
 ) -> str:
-    """Pick the best theme to explore next."""
+    """Pick the best theme to explore next.
+    
+    Never returns a dead theme. Falls back to a random non-dead theme.
+    """
+    dead_set = set(dead_themes or [])
     scores = compute_gap_scores(existing_themes, existing_anomaly_tags, dead_themes)
     top = scores[:top_k]
-    if not top:
-        return random.choice(list(THEME_FIELDS.keys()))
-    return random.choice(top)[0]
+    if top:
+        return random.choice(top)[0]
+    # All themes dead — return a random non-dead theme, or highest-gap dead as last resort
+    alive_themes = [t for t in THEME_FIELDS.keys() if t not in dead_set]
+    if alive_themes:
+        return random.choice(alive_themes)
+    # Absolute last resort: return first theme (all are dead)
+    return list(THEME_FIELDS.keys())[0]
 
 
 def get_theme_fields(theme: str) -> list[str]: