diff --git a/changes.d/6772.fix.md b/changes.d/6772.fix.md
new file mode 100644
index 00000000000..38bcf33347a
--- /dev/null
+++ b/changes.d/6772.fix.md
@@ -0,0 +1 @@
+Xtriggers with an OR operator (`|`) between them now correctly fail validation as Cylc does not support this.
diff --git a/cylc/flow/config.py b/cylc/flow/config.py
index fbd996350fc..e9cc09c6d8f 100644
--- a/cylc/flow/config.py
+++ b/cylc/flow/config.py
@@ -1841,6 +1841,7 @@ def generate_edges(self, lexpr, orig_lexpr, left_nodes, right, seq,
             # Right is a lone node.
             self.edges[seq].add((right, None, suicide, conditional))
 
+        conditional_xtriggers = []
         for left in left_nodes:
             # if left is None:
             #    continue
@@ -1856,7 +1857,16 @@ def generate_edges(self, lexpr, orig_lexpr, left_nodes, right, seq,
                     LOG.error(f"{orig_lexpr} => {right}")
                 raise WorkflowConfigError(
                     f"self-edge detected: {left} => {right}")
-            self.edges[seq].add((left, right, suicide, conditional))
+            if left.startswith('@') and conditional:
+                conditional_xtriggers.append(f'{lexpr} => {right}')
+            else:
+                self.edges[seq].add((left, right, suicide, conditional))
+        if conditional_xtriggers:
+            raise WorkflowConfigError(
+                'Xtriggers cannot be used in conditional graph'
+                ' expressions:\n' +
+                '\n * '.join(conditional_xtriggers)
+            )
 
     def generate_taskdef(self, orig_expr, node):
         """Generate task definition for node."""
diff --git a/cylc/flow/prerequisite.py b/cylc/flow/prerequisite.py
index 1462f9e9666..d0c70767fe2 100644
--- a/cylc/flow/prerequisite.py
+++ b/cylc/flow/prerequisite.py
@@ -253,12 +253,8 @@ def _eval_satisfied(self) -> bool:
             # * the expression is constructed internally
             # * https://github.com/cylc/cylc-flow/issues/4403
         except (SyntaxError, ValueError) as exc:
-            err_msg = str(exc)
-            if str(exc).find("unexpected EOF") != -1:
-                err_msg += (
-                    " (could be unmatched parentheses in the graph string?)")
             raise TriggerExpressionError(
-                '"%s":\n%s' % (self.get_raw_conditional_expression(), err_msg)
+                f'"{self.get_raw_conditional_expression}":\n{str(exc)}'
             ) from None
         return res
 
diff --git a/cylc/flow/scripts/validate.py b/cylc/flow/scripts/validate.py
index edabd6bdab2..aae4238760a 100755
--- a/cylc/flow/scripts/validate.py
+++ b/cylc/flow/scripts/validate.py
@@ -196,18 +196,7 @@ async def run(
         # force trigger evaluation now
         try:
             itask.state.prerequisites_eval_all()
-        except TriggerExpressionError as exc:
-            err = str(exc)
-            if '@' in err:
-                print(
-                    f"ERROR, {name}: xtriggers can't be in conditional"
-                    f" expressions: {err}",
-                    file=sys.stderr,
-                )
-            else:
-                print(
-                    'ERROR, %s: bad trigger: %s' % (name, err), file=sys.stderr
-                )
+        except TriggerExpressionError:
             raise WorkflowConfigError("ERROR: bad trigger") from None
         except Exception as exc:
             print(str(exc), file=sys.stderr)
diff --git a/tests/integration/test_config.py b/tests/integration/test_config.py
index 1a2023a93f4..a29927df2b9 100644
--- a/tests/integration/test_config.py
+++ b/tests/integration/test_config.py
@@ -34,6 +34,7 @@
 from cylc.flow.pathutil import get_workflow_run_pub_db_path
 
 Fixture = Any
+param = pytest.param
 
 
 @pytest.mark.parametrize(
@@ -488,6 +489,44 @@ def test_xtrig_signature_validation(
         validate(id_)
 
 
+@pytest.mark.parametrize(
+    'left',
+    (
+        param('@xrandom | @echo', id='xtrig-or-xtrig'),
+        param('@xrandom | task', id='xtrig-or-task'),
+        param('task | @echo', id='task-or-xtrig'),
+        param('@xrandom | foo & bar', id='xtrig-or-complex'),
+        param('@xrandom & bar | foo', id='complex-or-xtrig'),
+    )
+)
+def test_xtrig_or_fails_validation(
+    flow: "Fixture",
+    validate: "Fixture",
+    left: str
+):
+    """Xtriggers cannot be chained with the 'or'
+
+    https://github.com/cylc/cylc-flow/issues/6771
+    https://github.com/cylc/cylc-flow/issues/2712
+    """
+    id_ = flow(
+        {
+            "scheduling": {
+                "initial cycle point": "2024",
+                "xtriggers": {
+                    "xrandom": "xrandom(100)",
+                    "echo": "echo(succeed=True)"
+                },
+                "graph": {"R1": f"{left} => fin"},
+            }
+        }
+    )
+    expected_msg = (
+        "Xtriggers cannot be used in conditional graph expressions:\n")
+    with pytest.raises(WorkflowConfigError, match=expected_msg):
+        validate(id_)
+
+
 def test_special_task_non_word_names(flow: Fixture, validate: Fixture):
     """Test validation of special tasks names with non-word characters"""
     wid = flow({
diff --git a/tests/unit/test_prerequisite.py b/tests/unit/test_prerequisite.py
index 0f28150a105..2a0509b2cfb 100644
--- a/tests/unit/test_prerequisite.py
+++ b/tests/unit/test_prerequisite.py
@@ -21,6 +21,7 @@
 
 from cylc.flow.cycling.integer import IntegerPoint
 from cylc.flow.cycling.loader import ISO8601_CYCLING_TYPE, get_point
+from cylc.flow.exceptions import TriggerExpressionError
 from cylc.flow.id import Tokens, detokenise
 from cylc.flow.prerequisite import Prerequisite, SatisfiedState
 from cylc.flow.run_modes import RunMode
@@ -259,3 +260,19 @@ def test_satisfy_me__override_truthy(
 
     prereq.satisfy_me([Tokens('//1/a:x')], forced=forced, mode=mode)
     assert prereq[('1', 'a', 'x')] == existing
+
+
+@pytest.mark.parametrize(
+    'expr, err', (
+        ('int("df")', 'invalid literal'),
+        ('7 +', 'invalid syntax'),
+    ))
+def test__eval_satisfied_raises(expr, err, monkeypatch):
+    monkeypatch.setattr(
+        'cylc.flow.prerequisite.Prerequisite.get_raw_conditional_expression',
+        lambda _: expr
+    )
+    prereq = Prerequisite(IntegerPoint('1'))
+    prereq.conditional_expression = expr
+    with pytest.raises(TriggerExpressionError, match=err):
+        prereq._eval_satisfied()