diff --git a/src/unilab/tasks/motion_tracking/common/motion_loader.py b/src/unilab/tasks/motion_tracking/common/motion_loader.py
index 663f94dca..653bd319d 100644
--- a/src/unilab/tasks/motion_tracking/common/motion_loader.py
+++ b/src/unilab/tasks/motion_tracking/common/motion_loader.py
@@ -510,8 +510,13 @@ def _sample_adaptive(self, env_ids: np.ndarray) -> np.ndarray:
             padded = np.pad(sampling_probs, (0, self.adaptive_kernel_size - 1), mode="edge")
             sampling_probs = np.convolve(padded, self.kernel, mode="valid")
 
-        # Normalize to probabilities
-        sampling_probs = sampling_probs / sampling_probs.sum()
+        # With no failure statistics yet, a zero uniform floor leaves every bin
+        # at weight zero. Initialize that cold-start state as uniform.
+        sampling_weight_sum = float(sampling_probs.sum())
+        if sampling_weight_sum <= 0.0:
+            sampling_probs = np.full(self.bin_count, 1.0 / self.bin_count, dtype=np.float64)
+        else:
+            sampling_probs = sampling_probs / sampling_weight_sum
 
         # Sample bins
         sampled_bins = (
diff --git a/tests/envs/test_motion_loader.py b/tests/envs/test_motion_loader.py
index 1139b8ba0..ceb9c56d8 100644
--- a/tests/envs/test_motion_loader.py
+++ b/tests/envs/test_motion_loader.py
@@ -208,6 +208,26 @@ def test_motion_sampler_uses_env_owned_rng_and_steps_only_selected_rows(tmp_path
     assert sampler.current_frames[2] == frames[1] + 1
 
 
+def test_motion_sampler_adaptive_zero_floor_cold_starts_uniform(tmp_path):
+    motion = tmp_path / "motion.npz"
+    _write_motion_npz(motion, base_value=0.0, num_frames=70)
+    loader = MotionLoader(str(motion))
+    sampler = MotionSampler(
+        loader,
+        mode="adaptive",
+        num_envs=64,
+        adaptive_uniform_ratio=0.0,
+        rng=np.random.default_rng(7),
+    )
+
+    frames = sampler.sample_frames(np.arange(64, dtype=np.int32))
+
+    assert frames.min() >= 0
+    assert frames.max() < loader.num_frames
+    np.testing.assert_allclose(sampler.sampling_entropy, 1.0)
+    np.testing.assert_allclose(sampler.sampling_top1_prob, 1.0 / sampler.bin_count)
+
+
 def test_box_motion_loader_reads_object_state_and_trims_robot_joints(tmp_path):
     from unilab.tasks.motion_tracking.g1.motion_box_loader import BoxMotionLoader