diff --git a/tests/gateway/test_env_flag_truthy.py b/tests/gateway/test_env_flag_truthy.py
new file mode 100644
index 000000000..9095dd703
--- /dev/null
+++ b/tests/gateway/test_env_flag_truthy.py
@@ -0,0 +1,49 @@
+"""Env flags accept 'on' as truthy consistently (salvage of #2863).
+
+Behavior contract: every env-driven enable flag in gateway config coerces
+through the shared TRUTHY_STRINGS set, so "on" behaves like "1"/"true"/"yes".
+"""
+
+import os
+from unittest.mock import patch
+
+from utils import TRUTHY_STRINGS, env_var_enabled
+
+
+def test_truthy_strings_include_on():
+    assert "on" in TRUTHY_STRINGS
+
+
+def test_env_var_enabled_accepts_on():
+    with patch.dict(os.environ, {"WHATSAPP_ENABLED": "on"}):
+        assert env_var_enabled("WHATSAPP_ENABLED") is True
+
+
+def test_env_var_enabled_default_respected():
+    with patch.dict(os.environ, {}, clear=False):
+        os.environ.pop("SIGNAL_IGNORE_STORIES", None)
+        assert env_var_enabled("SIGNAL_IGNORE_STORIES", "true") is True
+        assert env_var_enabled("SIGNAL_IGNORE_STORIES") is False
+
+
+def test_gateway_config_flags_use_shared_helper():
+    """Invariant: no env-flag site in gateway/config.py hand-rolls a truthy
+    set that omits 'on'."""
+    import inspect
+
+    import gateway.config as gc
+
+    src = inspect.getsource(gc)
+    for pattern in ('in {"true", "1", "yes"}', 'in ("true", "1", "yes")'):
+        assert pattern not in src, f"hand-rolled truthy set without 'on': {pattern}"
+
+
+def test_desktop_gate_accepts_on():
+    from tools.close_terminal_tool import check_close_terminal_requirements
+    from tools.read_terminal_tool import check_read_terminal_requirements
+
+    with patch.dict(os.environ, {"HERMES_DESKTOP": "on"}):
+        assert check_read_terminal_requirements() is True
+        assert check_close_terminal_requirements() is True
+    with patch.dict(os.environ, {"HERMES_DESKTOP": "off"}):
+        assert check_read_terminal_requirements() is False