diff --git a/src/av1.c b/src/av1.c
index 5b2970c..964c035 100644
--- a/src/av1.c
+++ b/src/av1.c
@@ -53,11 +53,14 @@
 #include "av1.h"
 
 #include "context.h"
+#include "object_heap.h"
 #include "request.h"
 #include "surface.h"
 #include "utils.h"
 #include "v4l2.h"
 
+#include <va/va.h>
+
 #include <linux/videodev2.h>
 #include <linux/v4l2-controls.h>
 
@@ -359,11 +362,13 @@ static void av1_fill_frame(VADecPictureParameterBufferAV1 *picture,
 	}
 
 	/* ---- reference frames + order hints ---- */
-	for (i = 0; i < BACKEND_AV1_TOTAL_REFS_PER_FRAME; i++) {
-		/* VAAPI doesn't expose order_hints[]; leave zero. */
+	/* reference_frame_ts[] is filled by the orchestrator (av1_set_controls)
+	 * which has driver_data for the SURFACE() lookup. order_hints[] not
+	 * exposed per-ref by VAAPI — leave zero. ref_frame_idx[7] is the
+	 * index map from spec-defined ref slots (LAST..ALTREF) into
+	 * ref_frame_map[8] (the surface IDs). */
+	for (i = 0; i < BACKEND_AV1_TOTAL_REFS_PER_FRAME; i++)
 		ctrl->order_hints[i] = 0;
-		ctrl->reference_frame_ts[i] = 0;
-	}
 	for (i = 0; i < BACKEND_AV1_REFS_PER_FRAME; i++)
 		ctrl->ref_frame_idx[i] = picture->ref_frame_idx[i];
 
@@ -534,6 +539,29 @@ int av1_set_controls(struct request_data *driver_data,
 
 	av1_fill_sequence(picture, &sequence);
 	av1_fill_frame(picture, &frame);
+
+	/*
+	 * Phase 2.1 + frame-2 divergence fix: wire reference_frame_ts[].
+	 * VAAPI exposes ref_frame_map[8] as VASurfaceIDs; the kernel needs
+	 * v4l2-style timestamps to cross-reference the corresponding
+	 * CAPTURE buffers (set on the OUTPUT buffer at QBUF time per
+	 * picture.c::EndPicture, via surface_object->timestamp). Mirrors
+	 * the vp9.c:614-628 pattern, scaled to AV1's 8 ref slots.
+	 *
+	 * VA_INVALID_SURFACE entries stay at the calloc'd zero timestamp
+	 * (kernel reads zero, doesn't try to dereference).
+	 */
+	for (i = 0; i < BACKEND_AV1_TOTAL_REFS_PER_FRAME; i++) {
+		VASurfaceID ref_id = picture->ref_frame_map[i];
+		struct object_surface *ref_surface;
+		if (ref_id == VA_INVALID_SURFACE)
+			continue;
+		ref_surface = SURFACE(driver_data, ref_id);
+		if (ref_surface)
+			frame.reference_frame_ts[i] =
+				v4l2_timeval_to_ns(&ref_surface->timestamp);
+	}
+
 	if (driver_data->has_av1_film_grain)
 		av1_fill_film_grain(picture, &film_grain);