diff --git a/src/rtichoke/calibration/__init__.py b/src/rtichoke/calibration/__init__.py
index b04d51eb..6e89c060 100644
--- a/src/rtichoke/calibration/__init__.py
+++ b/src/rtichoke/calibration/__init__.py
@@ -8,6 +8,13 @@
 _original_create_calibration_curve = _calibration.create_calibration_curve
 _original_create_calibration_curve_times = _calibration.create_calibration_curve_times
 
+_DEFAULT_TIME_CALIBRATION_HEURISTICS = [
+    {
+        "censoring_heuristic": "adjusted",
+        "competing_heuristic": "adjusted_as_negative",
+    }
+]
+
 
 def create_calibration_curve(*args, **kwargs):
     """Create an interactive calibration plot with a square main panel."""
@@ -18,6 +25,18 @@ def create_calibration_curve(*args, **kwargs):
 
 def create_calibration_curve_times(*args, **kwargs):
     """Create an interactive time-dependent calibration plot with a square main panel."""
+    heuristics_sets = kwargs.get("heuristics_sets")
+    if heuristics_sets is None:
+        heuristics_sets = [dict(_DEFAULT_TIME_CALIBRATION_HEURISTICS[0])]
+        kwargs["heuristics_sets"] = heuristics_sets
+
+    if len(heuristics_sets) != 1:
+        raise ValueError(
+            "create_calibration_curve_times() currently supports exactly one "
+            "heuristic set. Multiple heuristic sets would be combined in the "
+            "same calibration trace because the plot has no heuristic selector."
+        )
+
     return enforce_square_calibration_panel(
         _original_create_calibration_curve_times(*args, **kwargs)
     )
diff --git a/tests/test_calibration_times_heuristics_contract.py b/tests/test_calibration_times_heuristics_contract.py
new file mode 100644
index 00000000..b81d9c9a
--- /dev/null
+++ b/tests/test_calibration_times_heuristics_contract.py
@@ -0,0 +1,74 @@
+import numpy as np
+import pytest
+
+from rtichoke import (
+    create_calibration_curve_times as create_calibration_curve_times_top_level,
+)
+from rtichoke.calibration import create_calibration_curve_times
+from rtichoke.calibration.calibration import (
+    create_calibration_curve_times as create_calibration_curve_times_direct,
+)
+
+
+ENTRY_POINTS = [
+    create_calibration_curve_times_top_level,
+    create_calibration_curve_times,
+    create_calibration_curve_times_direct,
+]
+
+
+def _inputs():
+    probs = {"model_1": np.array([0.1, 0.2, 0.3, 0.4])}
+    reals = np.array([0, 1, 1, 1])
+    times = np.array([1.0, 2.0, 3.0, 4.0])
+    return probs, reals, times
+
+
+@pytest.mark.parametrize("entry_point", ENTRY_POINTS)
+def test_time_calibration_defaults_to_adjusted_heuristics(entry_point):
+    probs, reals, times = _inputs()
+
+    default_fig = entry_point(
+        probs,
+        reals,
+        times,
+        fixed_time_horizons=[2.0],
+    )
+    explicit_fig = entry_point(
+        probs,
+        reals,
+        times,
+        fixed_time_horizons=[2.0],
+        heuristics_sets=[
+            {
+                "censoring_heuristic": "adjusted",
+                "competing_heuristic": "adjusted_as_negative",
+            }
+        ],
+    )
+
+    np.testing.assert_allclose(default_fig.data[1].x, explicit_fig.data[1].x)
+    np.testing.assert_allclose(default_fig.data[1].y, explicit_fig.data[1].y)
+
+
+@pytest.mark.parametrize("entry_point", ENTRY_POINTS)
+def test_time_calibration_rejects_multiple_heuristic_sets(entry_point):
+    probs, reals, times = _inputs()
+
+    with pytest.raises(ValueError, match="exactly one heuristic set"):
+        entry_point(
+            probs,
+            reals,
+            times,
+            fixed_time_horizons=[2.0],
+            heuristics_sets=[
+                {
+                    "censoring_heuristic": "adjusted",
+                    "competing_heuristic": "adjusted_as_negative",
+                },
+                {
+                    "censoring_heuristic": "excluded",
+                    "competing_heuristic": "excluded",
+                },
+            ],
+        )
diff --git a/user_guide/02-curve-api-compatibility.qmd b/user_guide/02-curve-api-compatibility.qmd
index e603b3fd..1a0b3905 100644
--- a/user_guide/02-curve-api-compatibility.qmd
+++ b/user_guide/02-curve-api-compatibility.qmd
@@ -48,12 +48,7 @@ These statements describe the effect of the heuristics on the estimates. Functio
 
 ## Time-dependent calibration heuristics
 
-`create_calibration_curve_times()` differs from its ROC, precision-recall, Gains, Lift, and decision-curve siblings in two important ways:
-
-1. `heuristics_sets` is currently required rather than defaulted.
-2. Calibration explicitly rejects unsupported heuristic combinations (specifically `competing_heuristic="adjusted_as_censored"`) with an `Unsupported calibration heuristics` error instead of silently skipping requested horizons.
-
-Pass the calibration heuristic explicitly. For adjusted or exclusion-based paths:
+`create_calibration_curve_times()` defaults to one adjusted heuristic set:
 
 ```python
 heuristics_sets = [
@@ -64,12 +59,14 @@ heuristics_sets = [
 ]
 ```
 
+You can still provide a different single heuristic set explicitly. Calibration currently accepts exactly one heuristic set per call because the plot has no heuristic selector; passing several sets raises a clear `ValueError` instead of combining them into one calibration trace. Calibration also rejects unsupported combinations such as `competing_heuristic="adjusted_as_censored"`.
+
 When `calibration_type="smooth"`, you can also specify the `smooth_method`:
 - `"local_aj"` (default): Gerds' local Aalen-Johansen/KM neighborhood estimation.
 - `"secondary_cox"`: Secondary Cox regression method (Austin, Harrell & McLernon 2020).
 - `"pseudo_values"`: Leave-one-out Aalen-Johansen pseudo-observations lowess.
 
-Then call:
+The default call is therefore simply:
 
 ```python
 fig = rk.create_calibration_curve_times(
@@ -77,7 +74,6 @@ fig = rk.create_calibration_curve_times(
     reals=reals,
     times=times,
     fixed_time_horizons=[3.0, 6.0, 9.0],
-    heuristics_sets=heuristics_sets,
 )
 ```