diff --git a/python/rafter_cli/__main__.py b/python/rafter_cli/__main__.py
index fc1ae807..ed79863c 100644
--- a/python/rafter_cli/__main__.py
+++ b/python/rafter_cli/__main__.py
@@ -25,6 +25,8 @@
     help="Rafter CLI — the default security agent for AI workflows. Free for individuals and open source. No account required.",
     add_completion=True,
     no_args_is_help=True,
+    # Never render frame locals in tracebacks: they hold the API key.
+    pretty_exceptions_show_locals=False,
 )
 
 
diff --git a/python/tests/test_traceback_no_locals.py b/python/tests/test_traceback_no_locals.py
new file mode 100644
index 00000000..43255845
--- /dev/null
+++ b/python/tests/test_traceback_no_locals.py
@@ -0,0 +1,45 @@
+"""An unhandled exception must not print the API key.
+
+Typer's pretty tracebacks render every frame's local variables by default,
+and the request helpers hold the key in ``api_key`` / ``headers`` locals.
+A plain transport failure (here: an unreachable proxy) is enough to raise
+out of a command, so the key would land on stderr, which in CI is the
+build log.
+"""
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+
+SENTINEL = "RAFTER_TEST_SENTINEL_KEY_9f3c1a"
+
+
+def test_unhandled_exception_does_not_print_api_key(tmp_path):
+    env = os.environ.copy()
+    env.pop("_TYPER_STANDARD_TRACEBACK", None)
+    env.update(
+        {
+            "HOME": str(tmp_path),
+            "RAFTER_API_KEY": SENTINEL,
+            "HTTPS_PROXY": "http://127.0.0.1:1",
+            "https_proxy": "http://127.0.0.1:1",
+            "NO_PROXY": "",
+            "no_proxy": "",
+        }
+    )
+    result = subprocess.run(
+        [sys.executable, "-m", "rafter_cli", "usage"],
+        capture_output=True,
+        text=True,
+        cwd=tmp_path,
+        env=env,
+        timeout=60,
+    )
+
+    assert result.returncode != 0
+    # Positive control: the command did fail with a traceback, so the
+    # assertion below is about its content rather than its absence.
+    assert "Traceback" in result.stderr or "Error" in result.stderr
+    assert SENTINEL not in result.stderr
+    assert SENTINEL not in result.stdout