diff --git a/src/webwright/models/base.py b/src/webwright/models/base.py
index 7728bb8..99d4708 100644
--- a/src/webwright/models/base.py
+++ b/src/webwright/models/base.py
@@ -296,11 +296,11 @@ def get_template_vars(self, **kwargs) -> dict[str, Any]:
         for k, v in self._last_request_metrics.items():
             vars[f"last_request_{k}"] = v
         for k, v in self._last_usage_metrics.items():
-            vars[f"last_request_{k}"] = v
+            vars[f"last_usage_{k}"] = v
         for k, v in self._cumulative_request_metrics.items():
             vars[f"cumulative_request_{k}"] = v
         for k, v in self._cumulative_usage_metrics.items():
-            vars[f"cumulative_{k}"] = v
+            vars[f"cumulative_usage_{k}"] = v
         vars.update(kwargs)
         return vars
 
diff --git a/tests/unit/test_get_template_vars.py b/tests/unit/test_get_template_vars.py
new file mode 100644
index 0000000..6a285c5
--- /dev/null
+++ b/tests/unit/test_get_template_vars.py
@@ -0,0 +1,54 @@
+"""Tests for get_template_vars metric key naming."""
+
+from webwright.models.base import BaseModel
+
+
+class _ConcreteModel(BaseModel):
+    """Minimal concrete subclass — no API key required."""
+
+    _API_KEY_FIELD = ""
+
+
+def test_last_usage_keys_do_not_overwrite_last_request_keys() -> None:
+    model = _ConcreteModel(action_field="bash_command")
+
+    # Inject distinct values so we can tell them apart.
+    model._last_request_metrics["message_count"] = 3
+    model._last_usage_metrics["input_tokens"] = 100
+
+    result = model.get_template_vars()
+
+    assert "last_request_message_count" in result, (
+        "last_request_message_count missing from get_template_vars output"
+    )
+    assert "last_usage_input_tokens" in result, (
+        "last_usage_input_tokens missing from get_template_vars output"
+    )
+    assert result["last_request_message_count"] == 3
+    assert result["last_usage_input_tokens"] == 100
+
+    # The old bug: usage keys were written as last_request_*, which would
+    # clobber real request keys.  Verify the buggy key is absent.
+    assert "last_request_input_tokens" not in result, (
+        "last_request_input_tokens should not exist; usage metrics must use last_usage_ prefix"
+    )
+
+
+def test_cumulative_usage_keys_use_cumulative_usage_prefix() -> None:
+    model = _ConcreteModel(action_field="bash_command")
+
+    model._cumulative_usage_metrics["input_tokens"] = 500
+    model._cumulative_request_metrics["message_count"] = 7
+
+    result = model.get_template_vars()
+
+    assert "cumulative_usage_input_tokens" in result
+    assert result["cumulative_usage_input_tokens"] == 500
+
+    assert "cumulative_request_message_count" in result
+    assert result["cumulative_request_message_count"] == 7
+
+    # Old bug: cumulative usage used "cumulative_" prefix, which is inconsistent.
+    assert "cumulative_input_tokens" not in result, (
+        "cumulative_input_tokens should not exist; cumulative usage must use cumulative_usage_ prefix"
+    )