diff --git a/rlix/scheduler/scheduler.py b/rlix/scheduler/scheduler.py
index 99602c4..00c2eb9 100644
--- a/rlix/scheduler/scheduler.py
+++ b/rlix/scheduler/scheduler.py
@@ -585,6 +585,32 @@ async def clear_progress(self, *, pipeline_id: str) -> None:
     def _clear_rollout_intent_locked(self, pipeline_id: str) -> None:
         self._state.rollout_open_pipelines.pop(pipeline_id, None)
 
+    def _warn_gen_request_without_demand_locked(
+        self, *, cluster_id: str, pipeline_id: str, step_target_estimate: Optional[int]
+    ) -> None:
+        """Warn when a GENERATION request carries no usable demand signal.
+
+        The gap-ratio planner skips pipelines whose registry entry has no
+        positive ``step_target_estimate`` AND no stored progress (see the
+        bootstrap-estimate branch in ``planner.plan_generation_gap_ratio``).
+        Such a request is never signaled and the caller blocks indefinitely.
+        Warn-only: progress may still arrive later on some backends, so
+        rejecting outright could break legitimate request-then-report flows.
+        """
+        if step_target_estimate is not None and int(step_target_estimate) > 0:
+            return
+        _, step_target = self._pipeline_progress_totals_locked(pipeline_id=pipeline_id)
+        if step_target > 0.0:
+            return
+        logger.warning(
+            "request_gpus(GENERATION) for cluster_id=%r has no step_target_estimate "
+            "(got %r) and no stored progress; the gap-ratio planner will skip this "
+            "pipeline and the request may block indefinitely until progress or a "
+            "positive estimate arrives",
+            cluster_id,
+            step_target_estimate,
+        )
+
     async def request_gpus(
         self,
         *,
@@ -636,6 +662,9 @@ async def request_gpus(
             self._state.pending_bucket(priority).append(pending)
             if priority == Priority.GENERATION:
                 self._state.rollout_open_pipelines[pipeline_id] = step_target_estimate
+                self._warn_gen_request_without_demand_locked(
+                    cluster_id=cluster_id, pipeline_id=pipeline_id, step_target_estimate=step_target_estimate
+                )
             # Queue Tracing: Track enqueue AFTER append (depth is correct)
             self._tracer.trace_queue_enqueue(
                 cluster_id, priority, lora_name, bucket_depth=len(self._state.pending_bucket(priority))
@@ -737,6 +766,11 @@ async def notify_release_then_request_gpus(
             if request_priority == Priority.GENERATION:
                 pipeline_id_gen, _ = parse_cluster_id(request_cluster_id)
                 self._state.rollout_open_pipelines[pipeline_id_gen] = request_step_target_estimate
+                self._warn_gen_request_without_demand_locked(
+                    cluster_id=request_cluster_id,
+                    pipeline_id=pipeline_id_gen,
+                    step_target_estimate=request_step_target_estimate,
+                )
             # Queue Tracing: Track enqueue AFTER append (depth is correct)
             self._tracer.trace_queue_enqueue(
                 request_cluster_id,
diff --git a/tests/test_scheduler_gen_request_warning.py b/tests/test_scheduler_gen_request_warning.py
new file mode 100644
index 0000000..d05b3a5
--- /dev/null
+++ b/tests/test_scheduler_gen_request_warning.py
@@ -0,0 +1,113 @@
+"""PR ingress-validation test for the scheduler.
+
+A GENERATION request with neither a positive ``step_target_estimate`` nor any
+stored progress is skipped by the gap-ratio planner (bootstrap-estimate
+branch) and blocks its caller indefinitely. The scheduler now warns at
+enqueue time; these tests pin the warn / no-warn matrix.
+"""
+
+from __future__ import annotations
+
+import importlib
+import logging
+import sys
+import types
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+RLIX_ROOT = REPO_ROOT / "rlix"
+
+
+def _install_import_stubs(monkeypatch: pytest.MonkeyPatch) -> None:
+    for module_name in list(sys.modules):
+        if module_name == "ray" or module_name.startswith("rlix"):
+            monkeypatch.delitem(sys.modules, module_name, raising=False)
+
+    ray_stub = types.ModuleType("ray")
+
+    def _remote(*args, **kwargs):
+        def _decorate(obj):
+            return obj
+
+        return _decorate
+
+    ray_stub.remote = _remote
+    ray_stub.get_actor = lambda *args, **kwargs: None
+    ray_stub.get = lambda value: value
+    monkeypatch.setitem(sys.modules, "ray", ray_stub)
+
+    package_roots = {
+        "rlix": RLIX_ROOT,
+        "rlix.protocol": RLIX_ROOT / "protocol",
+        "rlix.scheduler": RLIX_ROOT / "scheduler",
+        "rlix.utils": RLIX_ROOT / "utils",
+    }
+    for module_name, module_path in package_roots.items():
+        package_module = types.ModuleType(module_name)
+        package_module.__path__ = [str(module_path)]  # type: ignore[attr-defined]
+        monkeypatch.setitem(sys.modules, module_name, package_module)
+
+
+def _make_scheduler(monkeypatch: pytest.MonkeyPatch):
+    _install_import_stubs(monkeypatch)
+    scheduler_module = importlib.import_module("rlix.scheduler.scheduler")
+    protocol_types = importlib.import_module("rlix.protocol.types")
+    return scheduler_module, protocol_types, scheduler_module.SchedulerImpl()
+
+
+_PIPELINE_ID = "miles_test"
+_CLUSTER_ID = f"{_PIPELINE_ID}_actor_infer"
+
+
+def test_warns_when_no_estimate_and_no_progress(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    _, _, scheduler = _make_scheduler(monkeypatch)
+    with caplog.at_level(logging.WARNING):
+        scheduler._warn_gen_request_without_demand_locked(
+            cluster_id=_CLUSTER_ID, pipeline_id=_PIPELINE_ID, step_target_estimate=None
+        )
+    assert "may block indefinitely" in caplog.text
+
+
+def test_warns_on_non_positive_estimate(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    _, _, scheduler = _make_scheduler(monkeypatch)
+    with caplog.at_level(logging.WARNING):
+        scheduler._warn_gen_request_without_demand_locked(
+            cluster_id=_CLUSTER_ID, pipeline_id=_PIPELINE_ID, step_target_estimate=0
+        )
+    assert "may block indefinitely" in caplog.text
+
+
+def test_silent_with_positive_estimate(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    _, _, scheduler = _make_scheduler(monkeypatch)
+    with caplog.at_level(logging.WARNING):
+        scheduler._warn_gen_request_without_demand_locked(
+            cluster_id=_CLUSTER_ID, pipeline_id=_PIPELINE_ID, step_target_estimate=8
+        )
+    assert caplog.text == ""
+
+
+def test_silent_when_progress_already_stored(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    scheduler_module, protocol_types, scheduler = _make_scheduler(monkeypatch)
+    report = protocol_types.ProgressReport(
+        pipeline_id=_PIPELINE_ID,
+        step_target_trajectories=8,
+        metrics={"completed": 2},
+    )
+    scheduler._state.latest_progress_by_pipeline[_PIPELINE_ID] = {
+        "train": {"__full_finetune__": report}
+    }
+    with caplog.at_level(logging.WARNING):
+        scheduler._warn_gen_request_without_demand_locked(
+            cluster_id=_CLUSTER_ID, pipeline_id=_PIPELINE_ID, step_target_estimate=None
+        )
+    assert caplog.text == ""