diff --git a/skillscope/cli.py b/skillscope/cli.py
index f9d93b4..03b3ebb 100644
--- a/skillscope/cli.py
+++ b/skillscope/cli.py
@@ -148,12 +148,16 @@ def _structural_or_exit(skills: list[str] | None = None) -> list[references.Refe
     return found
 
 
-def routing_gate(totals: dict, min_accuracy: float) -> str | None:
+def routing_gate(
+    totals: dict, min_accuracy: float, missing_skills: list[str] | None = None
+) -> str | None:
     """Why this routing run should fail, or ``None`` if it should not.
 
-    The first two answers are infrastructure, not score, and hold whatever the
-    bar is: a run where nothing was graded, or where no skill ever activated,
-    has not measured routing at all.
+    The first three answers are infrastructure, not score, and hold whatever
+    the bar is: a run where nothing was graded, where no skill ever activated,
+    or where a staged skill never reached the agent has not measured routing at
+    all. The last of those is the quietest, because the cases still run and
+    still produce a number.
     """
     if totals["graded"] == 0:
         return "every case errored; treating the run as a failure."
@@ -163,6 +167,15 @@ def routing_gate(totals: dict, min_accuracy: float) -> str | None:
             "or activation detection is broken. Failing rather than reporting "
             "a 0% routing rate as if it were real."
         )
+    if missing_skills:
+        return (
+            "the CLI did not report these installed skills at session init: "
+            f"{', '.join(sorted(missing_skills))}. A skill the agent was never "
+            "offered cannot be routed to, so every case for it reads as a "
+            "missed trigger and the author is told a description that was never "
+            "listed does not trigger. Failing rather than scoring a room that "
+            "was not the one asked for."
+        )
     if min_accuracy <= 0:
         return None
     # Compared against the exact ratio rather than the reported accuracy,
@@ -415,7 +428,11 @@ def cmd_routing(args: argparse.Namespace) -> int:
 
     if (code := _fail_if_expired()) is not None:
         return code
-    reason = routing_gate(summary["totals"], args.min_accuracy)
+    reason = routing_gate(
+        summary["totals"],
+        args.min_accuracy,
+        summary["skills_missing_from_session"],
+    )
     if reason:
         print(f"[routing] {reason}", file=sys.stderr)
         return 1
diff --git a/tests/test_skillscope.py b/tests/test_skillscope.py
index 11cdee6..0b1d7df 100644
--- a/tests/test_skillscope.py
+++ b/tests/test_skillscope.py
@@ -2032,6 +2032,28 @@ def totals(self, passed: int, graded: int, **extra) -> dict:
     def gate(self, passed: int, graded: int, bar: float = 1.0, **extra) -> str | None:
         return cli.routing_gate(self.totals(passed, graded, **extra), bar)
 
+    def test_a_skill_the_agent_never_saw_fails_the_run(self) -> None:
+        """The quiet one. A staged skill that never reached the agent still has
+        cases, and every one of them reads as a missed trigger, so the run
+        produces a plausible number for a room that was not the one asked for."""
+        reason = cli.routing_gate(self.totals(11, 12), 1.0, ["absent-skill"])
+        self.assertIn("absent-skill", reason)
+        self.assertIn("session init", reason)
+
+    def test_a_missing_skill_outranks_the_accuracy_bar(self) -> None:
+        """Infrastructure before score: a perfect sweep of a wrong room is not a
+        pass, and `--min-accuracy 0` does not license one either."""
+        for bar in (1.0, 0.0):
+            with self.subTest(bar=bar):
+                reason = cli.routing_gate(self.totals(12, 12), bar, ["absent-skill"])
+                self.assertIsNotNone(reason)
+                self.assertNotIn("--min-accuracy", reason)
+
+    def test_nothing_missing_leaves_the_gate_alone(self) -> None:
+        for missing in (None, []):
+            with self.subTest(missing=missing):
+                self.assertIsNone(cli.routing_gate(self.totals(12, 12), 1.0, missing))
+
     def test_the_default_bar_is_every_graded_case(self) -> None:
         self.assertEqual(cli.build_parser().parse_args(["routing"]).min_accuracy, 1.0)