fix: mark tracer disabled when tracing is disabled via env var

packages/traceloop-sdk/tests/test_sdk_initialization.py

@@ -358,3 +358,25 @@ def probe():
             del TracerWrapper.instance
         if saved_instance is not None:
             TracerWrapper.instance = saved_instance
+
+
+def test_tracing_disabled_via_env_var_is_silent_noop(
+    isolated_tracer_wrapper, monkeypatch, capsys
+):
+    """When tracing is disabled via TRACELOOP_TRACING_ENABLED=false, init() must
+    mark the tracer disabled so @workflow becomes a silent no-op rather than
+    warning that Traceloop was never initialized (issue #4191)."""
+    monkeypatch.setenv("TRACELOOP_TRACING_ENABLED", "false")
+    try:
+        Traceloop.init(app_name="test")
+        assert TracerWrapper.verify_initialized() is False
+
+        @workflow(name="w")
+        def f():
+            return 42
+
+        capsys.readouterr()  # discard init() output
+        assert f() == 42
+        assert "Traceloop not initialized" not in capsys.readouterr().out
+    finally:
+        TracerWrapper.set_disabled(False)

packages/traceloop-sdk/traceloop/sdk/__init__.py

@@ -122,6 +122,10 @@ def init(
         Traceloop.__app_name = app_name
 
         if not is_tracing_enabled():
+            # Mirror the `enabled=False` path: mark the tracer disabled so the
+            # @workflow/@task decorators become silent no-ops instead of warning
+            # that Traceloop was never initialized.
+            TracerWrapper.set_disabled(True)
             print(Fore.YELLOW + "Tracing is disabled" + Fore.RESET)
             return