Fix realtime initial greeting handling (#481)

api/tests/test_template_renderer.py

@@ -0,0 +1,38 @@
+from api.utils.template_renderer import render_template
+
+
+def test_initial_context_prefix_resolves_against_flat_context():
+    context = {
+        "first_name": "Abhishek",
+        "runtime_configuration": {
+            "realtime_model": "gpt-realtime-2",
+        },
+    }
+
+    assert (
+        render_template("Hi {{initial_context.first_name | there}}", context)
+        == "Hi Abhishek"
+    )
+    assert (
+        render_template(
+            "Model {{initial_context.runtime_configuration.realtime_model}}", context
+        )
+        == "Model gpt-realtime-2"
+    )
+
+
+def test_initial_context_prefix_prefers_explicit_initial_context():
+    context = {
+        "first_name": "Flat",
+        "initial_context": {
+            "first_name": "Nested",
+        },
+    }
+
+    assert render_template("Hi {{initial_context.first_name}}", context) == "Hi Nested"
+
+
+def test_initial_context_prefix_uses_fallback_when_missing_from_both_contexts():
+    assert (
+        render_template("Hi {{initial_context.first_name | there}}", {}) == "Hi there"
+    )