diff --git a/pyproject.toml b/pyproject.toml
index 682fef1..1072b4f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,12 +36,17 @@ dependencies = [
     # not evidence that an API is present, which is the whole reason that test exists.
     #
     # RAISED TO 0.5.0 for crucible.validation.monitor (EdgeBaseline / edge_monitor),
-    # which orchestrate.decay and EdgeDecayTrigger are built on. Unlike the 0.3.0 note
-    # above, this constraint is NOT yet true: at the time of writing the monitor sits in
-    # crucible's [Unreleased] and the newest published crucible is 0.4.0. This must not
-    # merge before crucible 0.5.0 is on PyPI, or `pip install crucible-stack` resolves
-    # to a crucible without the monitor and `import crucible_stack.orchestrate` raises.
-    "crucible>=0.5.0",
+    # which orchestrate.decay and EdgeDecayTrigger are built on. That note used to warn
+    # the constraint was not yet true; crucible 0.5.0 published 2026-08-02, so it is.
+    #
+    # RAISED TO 0.6.0 for Thresholds.monitor_arl0_years, which --arl0-years constructs.
+    # This one was briefly WRONG rather than aspirational: the flag merged while the
+    # floor still said 0.5.0, whose Thresholds has no such field, so a fresh
+    # `pip install crucible-stack` could resolve a crucible that raises TypeError the
+    # first time anyone passed it. Nothing caught it, because every local checkout
+    # already had 0.6.0 installed and a floor is only exercised by the version you do
+    # NOT have. Raise the floor in the same change as the API, never afterwards.
+    "crucible>=0.6.0",
 ]
 
 [project.optional-dependencies]
diff --git a/tests/test_crucible_compat.py b/tests/test_crucible_compat.py
index 870a77f..4aa4ef6 100644
--- a/tests/test_crucible_compat.py
+++ b/tests/test_crucible_compat.py
@@ -72,3 +72,42 @@ def test_edge_monitor_still_refuses_to_rebuild_its_own_baseline():
         "trades", "baseline", "design", "thresholds"}, (
         "edge_monitor's signature changed. The decay trigger depends on there being no "
         "parameter from which a baseline could be rebuilt; re-check before relaxing this.")
+
+
+def test_the_false_alarm_budget_can_be_set_in_years():
+    """`--arl0-years` builds `Thresholds(monitor_arl0_years=...)`, added in crucible
+    0.6.0. On 0.5.0 that field does not exist and the dataclass raises TypeError the
+    first time anyone passes the flag, which is a long way from the version constraint
+    that allowed it."""
+    from crucible.validation import Thresholds
+    try:
+        t = Thresholds(monitor_arl0_years=10.0)
+    except TypeError as exc:                                       # pragma: no cover
+        pytest.fail(
+            f"the installed crucible predates the calendar-time budget ({exc}). "
+            "--arl0-years requires Thresholds.monitor_arl0_years; install crucible "
+            ">= 0.6.0.")
+    assert t.monitor_arl0_years == 10.0
+    # and the trades fallback is still there for a baseline with no known firing rate
+    assert getattr(t, "monitor_arl0_trades", None) is not None
+
+
+def test_the_floor_is_not_lower_than_the_apis_this_package_uses():
+    """The floor is a claim about the OLDEST crucible that works, and the tests above
+    only ever run against whatever is installed, which is normally the newest. So check
+    the declared floor itself, and fail when someone adds an API without raising it.
+
+    Keep `MIN` in step with the `crucible>=` pin in pyproject.toml and with the newest
+    crucible feature this package touches.
+    """
+    import pathlib
+    import re
+
+    MIN = "0.6.0"                       # bump with the pin when a newer API is adopted
+    text = (pathlib.Path(__file__).resolve().parents[1] / "pyproject.toml").read_text()
+    m = re.search(r'"crucible>=([0-9.]+)"', text)
+    assert m, "no crucible floor found in pyproject.toml"
+    assert m.group(1) == MIN, (
+        f"pyproject pins crucible>={m.group(1)} but this package uses APIs added in "
+        f"{MIN}. A floor satisfied by a crucible that cannot run the code is worse than "
+        "no floor: it resolves, installs, and fails at the call site.")