diff --git a/app/main.py b/app/main.py
index b700c55..3439aac 100644
--- a/app/main.py
+++ b/app/main.py
@@ -146,8 +146,14 @@ app.mount("/static", StaticFiles(directory=static_dir), name="static")
 templates = Jinja2Templates(directory=str(templates_dir))
 
 # Detail-Marker im Jinja-Environment registrieren (siehe ADR 0010)
-from .marker import heuchelei_score, decisive_outcome, consistency_state  # noqa: E402
+from .marker import (  # noqa: E402
+    heuchelei_score,
+    opportunismus_score,
+    decisive_outcome,
+    consistency_state,
+)
 templates.env.globals["heuchelei_score"] = heuchelei_score
+templates.env.globals["opportunismus_score"] = opportunismus_score
 templates.env.globals["decisive_outcome"] = decisive_outcome
 templates.env.globals["consistency_state"] = consistency_state
 
diff --git a/app/marker.py b/app/marker.py
index a47b7dc..440da39 100644
--- a/app/marker.py
+++ b/app/marker.py
@@ -70,6 +70,36 @@ def decisive_outcome(plenum_votes: Optional[Iterable[dict]]) -> Optional[str]:
     return None
 
 
+def opportunismus_score(
+    fraktion: str,
+    fraktions_scores: Optional[Iterable[dict]],
+    threshold: float = 3.0,
+) -> Optional[float]:
+    """Wahlprogramm-Score einer Fraktion, falls < threshold; sonst None.
+
+    Symmetrisch zu ``heuchelei_score``, aber für den Fall, dass eine
+    Fraktion mit JA stimmt, obwohl der Antrag inhaltlich nicht zu
+    ihrem Wahlprogramm passt (`wahlprogramm.score < 3`).
+
+    Wenn die Fraktion nicht gefunden wird, der Score fehlt oder
+    ≥ threshold ist, wird ``None`` zurückgegeben.
+    """
+    if not fraktions_scores:
+        return None
+    for fs in fraktions_scores:
+        if fs.get("fraktion") == fraktion:
+            wp = fs.get("wahlprogramm") or {}
+            score = wp.get("score")
+            if score is None:
+                return None
+            try:
+                score_f = float(score)
+            except (TypeError, ValueError):
+                return None
+            return score_f if score_f < threshold else None
+    return None
+
+
 def consistency_state(
     verdict_title: Optional[str],
     plenum_votes: Optional[Iterable[dict]],
diff --git a/app/templates/v2/screens/antrag_detail.html b/app/templates/v2/screens/antrag_detail.html
index a94e799..8965ecc 100644
--- a/app/templates/v2/screens/antrag_detail.html
+++ b/app/templates/v2/screens/antrag_detail.html
@@ -301,7 +301,10 @@
       <div style="display:flex;flex-wrap:wrap;gap:12px;font-family:var(--font-mono);font-size:11px;">
         {% if v.fraktionen_ja %}
         <div><span style="color:#2da44e;font-weight:700;">Ja:</span>
-          {% for f in v.fraktionen_ja %}<span style="display:inline-block;padding:1px 6px;background:color-mix(in srgb,#2da44e 15%,transparent);color:#1a7f37;border-radius:3px;margin-right:3px;">{{ f }}</span>{% endfor %}
+          {% for f in v.fraktionen_ja %}
+            {% set _opp_match = opportunismus_score(f, antrag.fraktions_scores) %}
+            <span style="display:inline-block;padding:1px 6px;background:color-mix(in srgb,#2da44e 15%,transparent);color:#1a7f37;border-radius:3px;margin-right:3px;">{{ f }}{% if _opp_match is not none %}<span style="margin-left:4px;cursor:help;font-style:italic;color:#bf8700;" title="Diese Fraktion stimmte mit Ja, obwohl der Antrag nicht zum eigenen Wahlprogramm passt (WP-Score {{ '%.0f' | format(_opp_match) }}/10).">!</span>{% endif %}</span>
+          {% endfor %}
         </div>
         {% endif %}
         {% if v.fraktionen_nein %}
diff --git a/tests/test_marker.py b/tests/test_marker.py
index 5210521..659b01d 100644
--- a/tests/test_marker.py
+++ b/tests/test_marker.py
@@ -4,6 +4,7 @@ import pytest
 try:
     from app.marker import (
         heuchelei_score,
+        opportunismus_score,
         decisive_outcome,
         consistency_state,
         DECISIVE_OUTCOMES,
@@ -75,6 +76,50 @@ class TestHeucheleiScore:
         assert heuchelei_score("CDU", fs) == 8.0
 
 
+# ─── opportunismus_score ────────────────────────────────────────────────────
+
+class TestOpportunismusScore:
+    """opportunismus_score liefert WP-Score wenn Fraktion JA-stimmt aber WP<3."""
+
+    def test_score_low_returns_score(self):
+        fs = [{"fraktion": "AfD", "wahlprogramm": {"score": 1.0}}]
+        assert opportunismus_score("AfD", fs) == 1.0
+
+    def test_score_zero_returns_score(self):
+        fs = [{"fraktion": "GRÜNE", "wahlprogramm": {"score": 0.0}}]
+        assert opportunismus_score("GRÜNE", fs) == 0.0
+
+    def test_score_at_threshold_returns_none(self):
+        # 3.0 ist genau Schwelle, sollte NICHT greifen (wir wollen < 3)
+        fs = [{"fraktion": "CDU", "wahlprogramm": {"score": 3.0}}]
+        assert opportunismus_score("CDU", fs) is None
+
+    def test_score_above_returns_none(self):
+        fs = [{"fraktion": "CDU", "wahlprogramm": {"score": 5.0}}]
+        assert opportunismus_score("CDU", fs) is None
+
+    def test_unknown_fraktion_returns_none(self):
+        fs = [{"fraktion": "CDU", "wahlprogramm": {"score": 1.0}}]
+        assert opportunismus_score("AfD", fs) is None
+
+    def test_empty_list_returns_none(self):
+        assert opportunismus_score("CDU", []) is None
+
+    def test_none_input_returns_none(self):
+        assert opportunismus_score("CDU", None) is None
+
+    def test_missing_score_returns_none(self):
+        fs = [{"fraktion": "CDU", "wahlprogramm": {}}]
+        assert opportunismus_score("CDU", fs) is None
+
+    def test_custom_threshold(self):
+        fs = [{"fraktion": "CDU", "wahlprogramm": {"score": 4.0}}]
+        # threshold=5 → 4 < 5 → opportunism greift
+        assert opportunismus_score("CDU", fs, threshold=5.0) == 4.0
+        # threshold=3 → 4 ≥ 3 → kein opportunism
+        assert opportunismus_score("CDU", fs, threshold=3.0) is None
+
+
 # ─── decisive_outcome ───────────────────────────────────────────────────────
 
 class TestDecisiveOutcome: