diff --git a/backend/packages/harness/deerflow/config/scheduler_config.py b/backend/packages/harness/deerflow/config/scheduler_config.py
index 3f860c8c5d..b3541ced1b 100644
--- a/backend/packages/harness/deerflow/config/scheduler_config.py
+++ b/backend/packages/harness/deerflow/config/scheduler_config.py
@@ -1,4 +1,6 @@
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, ValidationInfo, field_validator
+
+from deerflow.config._boolean_guards import reject_boolean
 
 
 class SchedulerConfig(BaseModel):
@@ -21,3 +23,16 @@ class SchedulerConfig(BaseModel):
             "AppConfig.max_recursion_limit are clamped."
         ),
     )
+
+    @field_validator(
+        "poll_interval_seconds",
+        "lease_seconds",
+        "max_concurrent_runs",
+        "queue_timeout_seconds",
+        "min_once_delay_seconds",
+        "recursion_limit",
+        mode="before",
+    )
+    @classmethod
+    def _reject_boolean_scheduler_integers(cls, value: object, info: ValidationInfo) -> object:
+        return reject_boolean(value, info, kind="an integer")
diff --git a/backend/tests/test_scheduler_config_boolean_integers.py b/backend/tests/test_scheduler_config_boolean_integers.py
new file mode 100644
index 0000000000..829c37b43d
--- /dev/null
+++ b/backend/tests/test_scheduler_config_boolean_integers.py
@@ -0,0 +1,42 @@
+"""YAML booleans must not coerce into the scheduler's integer knobs.
+
+`config.yaml` legitimately mixes booleans (`enabled: true`) with integer knobs on
+neighbouring lines, so a typo like `scheduler.recursion_limit: true` loads
+cleanly — and Pydantic coerces it to `1`, which makes every scheduler-launched
+run hit the LangGraph recursion ceiling at its first super-step (the same hole
+the app-config guard already closes for Gateway runs). `max_concurrent_runs: true`
+serializes the scheduler and `poll_interval_seconds: true` polls five times a
+second. Mirrors the app-config boolean guard.
+"""
+
+import pytest
+from pydantic import ValidationError
+
+from deerflow.config.scheduler_config import SchedulerConfig
+
+SCHEDULER_INT_FIELDS = (
+    "poll_interval_seconds",
+    "lease_seconds",
+    "max_concurrent_runs",
+    "queue_timeout_seconds",
+    "min_once_delay_seconds",
+    "recursion_limit",
+)
+
+
+@pytest.mark.parametrize("value", [True, False])
+@pytest.mark.parametrize("field", SCHEDULER_INT_FIELDS)
+def test_scheduler_config_rejects_boolean_integers(field: str, value: bool) -> None:
+    with pytest.raises(ValidationError, match="must be an integer, not a boolean"):
+        SchedulerConfig(**{field: value})
+
+
+def test_scheduler_config_keeps_numeric_inputs() -> None:
+    config = SchedulerConfig(
+        poll_interval_seconds="30",
+        max_concurrent_runs=5,
+        recursion_limit=500,
+    )
+    assert config.poll_interval_seconds == 30
+    assert config.max_concurrent_runs == 5
+    assert config.recursion_limit == 500