diff --git a/crates/wzp-video/src/decoder.rs b/crates/wzp-video/src/decoder.rs
index a0cf6fc..b6d5e2d 100644
--- a/crates/wzp-video/src/decoder.rs
+++ b/crates/wzp-video/src/decoder.rs
@@ -12,4 +12,9 @@ pub trait VideoDecoder: Send {
     /// Returns `Ok(Some(frame))` when a frame is ready, `Ok(None)` if more
     /// data is needed (e.g., for reordering), or an error.
     fn decode(&mut self, access_unit: &[u8]) -> Result<Option<VideoFrame>, VideoError>;
+
+    /// Compact implementation-specific state useful for field diagnostics.
+    fn debug_snapshot(&self) -> Option<String> {
+        None
+    }
 }
diff --git a/crates/wzp-video/src/mediacodec.rs b/crates/wzp-video/src/mediacodec.rs
index f60f64d..b6e22a5 100644
--- a/crates/wzp-video/src/mediacodec.rs
+++ b/crates/wzp-video/src/mediacodec.rs
@@ -359,6 +359,17 @@ impl VideoDecoder for MediaCodecDecoder {
             Err(VideoError::NotInitialized)
         }
     }
+
+    fn debug_snapshot(&self) -> Option<String> {
+        #[cfg(target_os = "android")]
+        {
+            media_codec_debug_snapshot(self.codec.as_ref())
+        }
+        #[cfg(not(target_os = "android"))]
+        {
+            None
+        }
+    }
 }
 
 // ============================================================================
@@ -847,6 +858,17 @@ impl VideoDecoder for MediaCodecHevcDecoder {
             Err(VideoError::NotInitialized)
         }
     }
+
+    fn debug_snapshot(&self) -> Option<String> {
+        #[cfg(target_os = "android")]
+        {
+            media_codec_debug_snapshot(self.codec.as_ref())
+        }
+        #[cfg(not(target_os = "android"))]
+        {
+            None
+        }
+    }
 }
 
 /// Android MediaCodec AV1 decoder.
@@ -987,6 +1009,35 @@ impl VideoDecoder for MediaCodecAv1Decoder {
             Err(VideoError::NotInitialized)
         }
     }
+
+    fn debug_snapshot(&self) -> Option<String> {
+        #[cfg(target_os = "android")]
+        {
+            media_codec_debug_snapshot(self.codec.as_ref())
+        }
+        #[cfg(not(target_os = "android"))]
+        {
+            None
+        }
+    }
+}
+
+#[cfg(target_os = "android")]
+fn media_codec_debug_snapshot(codec: Option<&MediaCodec>) -> Option<String> {
+    let codec = codec?;
+    let format = codec.output_format();
+    Some(format!(
+        "color_format={:?} width={:?} height={:?} stride={:?} slice_height={:?} crop=({:?},{:?},{:?},{:?})",
+        format.i32("color-format"),
+        format.i32("width"),
+        format.i32("height"),
+        format.i32("stride"),
+        format.i32("slice-height"),
+        format.i32("crop-left"),
+        format.i32("crop-top"),
+        format.i32("crop-right"),
+        format.i32("crop-bottom"),
+    ))
 }
 
 #[cfg(target_os = "android")]
diff --git a/desktop/src-tauri/src/engine.rs b/desktop/src-tauri/src/engine.rs
index a77dbde..4c220c3 100644
--- a/desktop/src-tauri/src/engine.rs
+++ b/desktop/src-tauri/src/engine.rs
@@ -177,6 +177,10 @@ fn i420_sample(data: &[u8], width: u32, height: u32) -> serde_json::Value {
     })
 }
 
+fn should_log_video_sample(frame_no: u64, is_keyframe: bool) -> bool {
+    frame_no <= 5 || is_keyframe || frame_no % 30 == 0
+}
+
 /// Resolve a quality string from the UI to a QualityProfile.
 /// Returns None for "auto" (use default adaptive behavior).
 fn resolve_quality(quality: &str) -> Option<QualityProfile> {
@@ -1321,7 +1325,7 @@ impl CallEngine {
                                         }),
                                     );
                                 }
-                                if video_reassembled_samples <= 5 {
+                                if should_log_video_sample(video_reassembled_samples, is_kf) {
                                     crate::emit_call_debug(
                                         &recv_app,
                                         "video:reassembled_frame",
@@ -1401,6 +1405,8 @@ impl CallEngine {
                                                         "yuv_bytes": yuv_frame.data.len(),
                                                         "jpeg_ok": jpeg_ok,
                                                         "platform": "android",
+                                                        "source_is_keyframe": is_kf,
+                                                        "decoder_debug": dec.debug_snapshot(),
                                                         "i420_sample": i420_sample(
                                                             &yuv_frame.data,
                                                             yuv_frame.width,
@@ -1409,7 +1415,7 @@ impl CallEngine {
                                                     }),
                                                 );
                                             }
-                                            if video_decoded_samples <= 5 {
+                                            if should_log_video_sample(video_decoded_samples, is_kf) {
                                                 crate::emit_call_debug(
                                                     &recv_app,
                                                     "video:decoded_frame_sample",
@@ -1422,6 +1428,8 @@ impl CallEngine {
                                                         "yuv_bytes": yuv_frame.data.len(),
                                                         "jpeg_ok": jpeg_ok,
                                                         "platform": "android",
+                                                        "source_is_keyframe": is_kf,
+                                                        "decoder_debug": dec.debug_snapshot(),
                                                         "i420_sample": i420_sample(
                                                             &yuv_frame.data,
                                                             yuv_frame.width,
@@ -2608,7 +2616,7 @@ impl CallEngine {
                                         }),
                                     );
                                 }
-                                if video_reassembled_samples <= 5 {
+                                if should_log_video_sample(video_reassembled_samples, is_kf) {
                                     crate::emit_call_debug(
                                         &recv_app,
                                         "video:reassembled_frame",
@@ -2692,6 +2700,8 @@ impl CallEngine {
                                                         "yuv_bytes": yuv_frame.data.len(),
                                                         "jpeg_ok": jpeg_ok,
                                                         "platform": "desktop",
+                                                        "source_is_keyframe": is_kf,
+                                                        "decoder_debug": dec.debug_snapshot(),
                                                         "i420_sample": i420_sample(
                                                             &yuv_frame.data,
                                                             yuv_frame.width,
@@ -2700,7 +2710,7 @@ impl CallEngine {
                                                     }),
                                                 );
                                             }
-                                            if video_decoded_samples <= 5 {
+                                            if should_log_video_sample(video_decoded_samples, is_kf) {
                                                 crate::emit_call_debug(
                                                     &recv_app,
                                                     "video:decoded_frame_sample",
@@ -2713,6 +2723,8 @@ impl CallEngine {
                                                         "yuv_bytes": yuv_frame.data.len(),
                                                         "jpeg_ok": jpeg_ok,
                                                         "platform": "desktop",
+                                                        "source_is_keyframe": is_kf,
+                                                        "decoder_debug": dec.debug_snapshot(),
                                                         "i420_sample": i420_sample(
                                                             &yuv_frame.data,
                                                             yuv_frame.width,