diff --git a/src/rlm/tools/ipython.py b/src/rlm/tools/ipython.py
index 230506e..0eccf8f 100644
--- a/src/rlm/tools/ipython.py
+++ b/src/rlm/tools/ipython.py
@@ -74,6 +74,19 @@ def schema(self) -> dict[str, Any]:
         return schema
 
     def execute(self, args: dict[str, Any], context: ToolContext) -> ToolOutcome:
+        # A missing "code" key used to fall through to "" and execute nothing
+        # silently — the model would then hit NameErrors on state it thought it
+        # created. Laguna in particular emits the arg under "cmd". Turn any such
+        # call into a loud, learnable error instead of a no-op.
+        if "code" not in args or args.get("code") in (None, ""):
+            wrong = ", ".join(repr(k) for k in args if k != "timeout") or "none"
+            return ToolOutcome(
+                content=(
+                    "Error: the ipython tool requires a non-empty 'code' argument; "
+                    f"got keys: {wrong}. Pass your Python under the 'code' key."
+                ),
+                metric_events=[IpythonExecuted(input_chars=0, input_loc=0)],
+            )
         code = args.get("code", "")
         if not isinstance(code, str):
             code = str(code)
diff --git a/tests/test_tools.py b/tests/test_tools.py
index 3cd6ce6..58e8244 100644
--- a/tests/test_tools.py
+++ b/tests/test_tools.py
@@ -92,3 +92,33 @@ def test_ipython_kernel_does_not_inherit_parent_stdio(session, capfd):
     assert captured.out == ""
     assert captured.err == ""
     assert result.strip() == "4 14"
+
+
+def _ipython_ctx():
+    from rlm.tools.base import ToolContext
+    from rlm.types import RLMMetrics, TokenUsage
+
+    return ToolContext(
+        messages=[],
+        metrics=RLMMetrics(),
+        total_usage=TokenUsage(),
+        last_prompt_tokens=0,
+        exec_timeout=30,
+        repl=None,  # error paths return before touching the REPL
+    )
+
+
+def test_ipython_missing_code_key_errors_not_noop():
+    """A tool call under the wrong key (e.g. Laguna's 'cmd') must error loudly."""
+    from rlm.tools.ipython import IpythonTool
+
+    out = IpythonTool().execute({"cmd": "print(1)"}, _ipython_ctx())
+    assert "Error" in out.content and "code" in out.content
+    assert "'cmd'" in out.content
+
+
+def test_ipython_empty_code_errors():
+    from rlm.tools.ipython import IpythonTool
+
+    out = IpythonTool().execute({"code": ""}, _ipython_ctx())
+    assert "Error" in out.content and "code" in out.content