diff --git a/src/h264.c b/src/h264.c
index 353cfa0..0ae5724 100644
--- a/src/h264.c
+++ b/src/h264.c
@@ -531,6 +531,21 @@ int h264_set_controls(struct request_data *driver_data,
 
 	sps.profile_idc = h264_profile_to_idc(profile);
 
+	/*
+	 * Per-request control batch, ordered so the controls REQUIRED in
+	 * V4L2_STATELESS_H264_DECODE_MODE_FRAME_BASED come first
+	 * (indices 0..3) and the SLICE_BASED-only controls come last
+	 * (indices 4..5).
+	 *
+	 * Cross-reference: GStreamer gst-plugins-bad
+	 * sys/v4l2codecs/gstv4l2codech264dec.c (commit 9e3e775,
+	 * lines 1263-1304) gates SLICE_PARAMS and PRED_WEIGHTS on
+	 * is_slice_based(self); under FRAME_BASED only SPS/PPS/
+	 * SCALING_MATRIX/DECODE_PARAMS are submitted. The kernel
+	 * parses the bitstream itself in FRAME_BASED mode; submitting
+	 * per-slice controls in that mode triggers cluster-validation
+	 * EINVAL at error_idx=count.
+	 */
 	struct v4l2_ext_control controls[6] = {
 		{
 			.id = V4L2_CID_STATELESS_H264_SPS,
@@ -544,14 +559,14 @@ int h264_set_controls(struct request_data *driver_data,
 			.id = V4L2_CID_STATELESS_H264_SCALING_MATRIX,
 			.p_h264_scaling_matrix = &matrix,
 			.size = sizeof(matrix),
-		}, {
-			.id = V4L2_CID_STATELESS_H264_SLICE_PARAMS,
-			.p_h264_slice_params = &slice,
-			.size = sizeof(slice),
 		}, {
 			.id = V4L2_CID_STATELESS_H264_DECODE_PARAMS,
 			.p_h264_decode_params = &decode,
 			.size = sizeof(decode),
+		}, {
+			.id = V4L2_CID_STATELESS_H264_SLICE_PARAMS,
+			.p_h264_slice_params = &slice,
+			.size = sizeof(slice),
 		}, {
 			.id = V4L2_CID_STATELESS_H264_PRED_WEIGHTS,
 			.ptr = &weights,
@@ -560,20 +575,24 @@ int h264_set_controls(struct request_data *driver_data,
 	};
 
 	/*
-	 * PRED_WEIGHTS is conditionally required per kernel UAPI:
-	 * V4L2_H264_CTRL_PRED_WEIGHTS_REQUIRED(pps, slice) is only
-	 * true when explicit weighted prediction applies (P/SP slice
-	 * with WEIGHTED_PRED flag, or B slice with weighted_bipred_idc
-	 * == 1). Submitting it unconditionally on a frame that does
-	 * not need it triggers EINVAL at error_idx=5 on hantro and
-	 * other drivers that strictly enforce the spec.
+	 * Decode-mode dispatch. Patch 0002 unconditionally sets the
+	 * device to FRAME_BASED, so we hardcode that here. When the
+	 * planned probe-then-set commit lands, slice_based becomes
+	 *     context->decode_mode == V4L2_STATELESS_H264_DECODE_MODE_SLICE_BASED
+	 * with context->decode_mode populated at CreateContext via
+	 * VIDIOC_QUERYCTRL/G_EXT_CTRLS.
 	 *
-	 * controls[5] is PRED_WEIGHTS (last in array); narrow the
-	 * submission count to exclude it when not required.
+	 * FRAME_BASED:    4 controls (SPS, PPS, SCALING_MATRIX, DECODE_PARAMS).
+	 * SLICE_BASED:   +SLICE_PARAMS (always), +PRED_WEIGHTS (when
+	 *                V4L2_H264_CTRL_PRED_WEIGHTS_REQUIRED).
 	 */
-	unsigned int num_controls = 6;
-	if (!V4L2_H264_CTRL_PRED_WEIGHTS_REQUIRED(&pps, &slice))
+	const bool slice_based = false; /* TODO: probe via context->decode_mode */
+	unsigned int num_controls = 4;
+	if (slice_based) {
 		num_controls = 5;
+		if (V4L2_H264_CTRL_PRED_WEIGHTS_REQUIRED(&pps, &slice))
+			num_controls = 6;
+	}
 
 	rc = v4l2_set_controls(driver_data->video_fd, surface->request_fd,
 			       controls, num_controls);