diff --git a/src/interfaze/_chat.py b/src/interfaze/_chat.py
index de9ce15..82aa4b2 100644
--- a/src/interfaze/_chat.py
+++ b/src/interfaze/_chat.py
@@ -48,7 +48,19 @@ def prepare(
     tags = " ".join(
         t for t in (f"<task>{task}</task>" if task else None, guard_tag(guard) if guard else None) if t
     )
-    msgs = [{"role": "system", "content": tags}, *messages] if tags else list(messages)
+    msgs = list(messages)
+    if tags:
+        idx = next(
+            (i for i, m in enumerate(msgs) if isinstance(m, dict) and m.get("role") == "system"),
+            None,
+        )
+        if idx is not None and isinstance(msgs[idx].get("content"), str):
+            merged = dict(msgs[idx])
+            existing = merged["content"]
+            merged["content"] = f"{tags}\n{existing}" if existing else tags
+            msgs[idx] = merged
+        else:
+            msgs = [{"role": "system", "content": tags}, *msgs]
     strip = isinstance(rf, dict) and rf.get("type") == "json_object"
     return msgs, (model or INTERFAZE_MODEL), rf, strip
 
diff --git a/src/interfaze/_constants.py b/src/interfaze/_constants.py
index 044b6cc..14e36e1 100644
--- a/src/interfaze/_constants.py
+++ b/src/interfaze/_constants.py
@@ -12,13 +12,28 @@
     "scraper",
     "translate",
     "speech_to_text",
+    "forecast",
 )
 
 # Guardrail categories (ALL enables everything).
 GUARD_CODES = (
-    "S1", "S2", "S3", "S4", "S5", "S6", "S7",
-    "S8", "S9", "S10", "S11", "S12", "S13", "S14",
-    "S1_IMAGE", "S12_IMAGE", "S15_IMAGE",
+    "S1",
+    "S2",
+    "S3",
+    "S4",
+    "S5",
+    "S6",
+    "S7",
+    "S8",
+    "S9",
+    "S10",
+    "S11",
+    "S12",
+    "S13",
+    "S14",
+    "S1_IMAGE",
+    "S12_IMAGE",
+    "S15_IMAGE",
     "ALL",
 )
 
diff --git a/src/interfaze/_types.py b/src/interfaze/_types.py
index 9292424..2ceae98 100644
--- a/src/interfaze/_types.py
+++ b/src/interfaze/_types.py
@@ -13,12 +13,27 @@
     "scraper",
     "translate",
     "speech_to_text",
+    "forecast",
 ]
 
 GuardCode = Literal[
-    "S1", "S2", "S3", "S4", "S5", "S6", "S7",
-    "S8", "S9", "S10", "S11", "S12", "S13", "S14",
-    "S1_IMAGE", "S12_IMAGE", "S15_IMAGE",
+    "S1",
+    "S2",
+    "S3",
+    "S4",
+    "S5",
+    "S6",
+    "S7",
+    "S8",
+    "S9",
+    "S10",
+    "S11",
+    "S12",
+    "S13",
+    "S14",
+    "S1_IMAGE",
+    "S12_IMAGE",
+    "S15_IMAGE",
     "ALL",
 ]
 
diff --git a/tests/test_chat.py b/tests/test_chat.py
index 892caa7..abef288 100644
--- a/tests/test_chat.py
+++ b/tests/test_chat.py
@@ -61,6 +61,33 @@ def test_guard_serialization():
     assert "<guard>S1, S12_IMAGE</guard>" in last_body(route)["messages"][0]["content"]
 
 
+@respx.mock
+def test_forecast_is_a_valid_task():
+    route = mock_json(BASIC)
+    Interfaze(api_key="t").chat.completions.create(
+        task="forecast", messages=[{"role": "user", "content": "x"}]
+    )
+    assert "<task>forecast</task>" in last_body(route)["messages"][0]["content"]
+
+
+@respx.mock
+def test_tags_merge_into_existing_system_message():
+    route = mock_json(TASK_OCR)
+    Interfaze(api_key="t").chat.completions.create(
+        task="ocr",
+        guard=["S1"],
+        messages=[
+            {"role": "system", "content": "You are helpful."},
+            {"role": "user", "content": "x"},
+        ],
+    )
+    systems = [m for m in last_body(route)["messages"] if m["role"] == "system"]
+    assert len(systems) == 1
+    assert "<task>ocr</task>" in systems[0]["content"]
+    assert "<guard>S1</guard>" in systems[0]["content"]
+    assert "You are helpful." in systems[0]["content"]
+
+
 def test_task_plus_nonempty_schema_raises():
     with pytest.raises(InterfazeError, match="non-empty"):
         Interfaze(api_key="t").chat.completions.create(