fix(sync): fail loud when tethys lacks gadget

scripts/manual/run_upstream_av_sync.sh

@@ -43,6 +43,7 @@ FETCH_CAPTURE=${FETCH_CAPTURE:-0}
 REMOTE_SERVER_PREFLIGHT=${REMOTE_SERVER_PREFLIGHT:-1}
 REMOTE_EXPECT_CAM_OUTPUT=${REMOTE_EXPECT_CAM_OUTPUT:-uvc}
 REMOTE_EXPECT_UVC_CODEC=${REMOTE_EXPECT_UVC_CODEC:-mjpeg}
+CAPTURE_READY_MARKER="__LESAVKA_CAPTURE_READY__"
 
 mkdir -p "${LOCAL_OUTPUT_DIR}"
 STAMP="$(date +%Y%m%d-%H%M%S)"
@@ -286,7 +287,8 @@ resolve_video_device() {
     fi
   fi
 
-  printf '/dev/video0\n'
+  printf 'Lesavka UVC video device not found on Tethys; refusing to fall back to an unrelated webcam/capture card.\n' >&2
+  exit 64
 }
 
 resolve_pulse_source() {
@@ -305,6 +307,31 @@ resolve_pulse_source() {
     '
 }
 
+resolve_alsa_audio_device() {
+  if ! command -v arecord >/dev/null 2>&1; then
+    return 1
+  fi
+
+  arecord -l 2>/dev/null | awk '
+    /^card [0-9]+:/ && ($0 ~ /Lesavka|UAC2_Gadget|UAC2Gadget|Composite/) {
+      card=$2
+      sub(":", "", card)
+      for (i = 1; i <= NF; i++) {
+        if ($i == "device") {
+          dev=$(i + 1)
+          sub(":", "", dev)
+          printf "hw:%s,%s\n", card, dev
+          found=1
+          exit 0
+        }
+      }
+    }
+    END {
+      if (!found) exit 1
+    }
+  '
+}
+
 gst_video_source_caps() {
   case "${video_format}" in
     ""|mjpeg|MJPG)
@@ -478,12 +505,16 @@ case "${remote_capture_stack}" in
     if [[ "${remote_audio_source}" == "auto" ]]; then
       if pulse_source="$(resolve_pulse_source)"; then
         capture_mode="pulse"
+      elif alsa_audio_dev="$(resolve_alsa_audio_device)"; then
+        capture_mode="alsa"
+        printf 'PipeWire Lesavka source not found; falling back to ALSA device %s\n' "${alsa_audio_dev}" >&2
       elif command -v pw-record >/dev/null 2>&1 \
         && command -v pw-v4l2 >/dev/null 2>&1 \
         && pw_audio_target="$(resolve_pw_audio_target)"; then
         capture_mode="pwpipe"
       else
-        printf 'PipeWire Lesavka source not found; falling back to hw:3,0\n' >&2
+        printf 'Lesavka audio source not found in PipeWire or ALSA; capture host does not currently expose the gadget microphone.\n' >&2
+        exit 64
       fi
     elif [[ "${remote_audio_source}" == pulse:* ]]; then
       capture_mode="pulse"
@@ -538,6 +569,7 @@ resolved_video_size="$(resolve_video_size "${video_size}")"
 resolved_video_fps="$(resolve_video_fps "${video_fps}")"
 printf 'using video device: %s\n' "${resolved_video_device}" >&2
 printf 'using video mode: %s @ %s fps (%s)\n' "${resolved_video_size}" "${resolved_video_fps}" "${video_format:-driver-default}" >&2
+printf '%s\n' "__LESAVKA_CAPTURE_READY__"
 video_args=(-f video4linux2 -framerate "${resolved_video_fps}" -video_size "${resolved_video_size}")
 if [[ -n "${video_format}" ]]; then
   video_args+=(-input_format "${video_format}")
@@ -699,13 +731,28 @@ fi
 REMOTE_CAPTURE_SCRIPT
 capture_pid=$!
 
-sleep 1
-if ! kill -0 "${capture_pid}" >/dev/null 2>&1; then
-  capture_status=0
-  wait "${capture_pid}" || capture_status=$?
-  echo "Tethys capture failed before the sync probe could start; see ${LOCAL_CAPTURE_LOG} for details." >&2
-  exit "${capture_status}"
-fi
+wait_for_capture_ready() {
+  local tries=100
+  local i=0
+  while (( i < tries )); do
+    if [[ -f "${LOCAL_CAPTURE_LOG}" ]] && grep -q "${CAPTURE_READY_MARKER}" "${LOCAL_CAPTURE_LOG}"; then
+      return 0
+    fi
+    if ! kill -0 "${capture_pid}" >/dev/null 2>&1; then
+      capture_status=0
+      wait "${capture_pid}" || capture_status=$?
+      echo "Tethys capture failed before the sync probe could start; see ${LOCAL_CAPTURE_LOG} for details." >&2
+      exit "${capture_status}"
+    fi
+    sleep 0.1
+    ((i += 1))
+  done
+
+  echo "Timed out waiting for Tethys capture to become ready; see ${LOCAL_CAPTURE_LOG} for details." >&2
+  exit 90
+}
+
+wait_for_capture_ready
 
 sleep "${LEAD_IN_SECONDS}"
 

testing/tests/client_manual_sync_script_contract.rs

@@ -18,8 +18,15 @@ fn upstream_sync_script_tunnels_auto_server_addr_through_ssh() {
         "127.0.0.1:${local_port}:127.0.0.1:${remote_port}",
         "RESOLVED_LESAVKA_SERVER_ADDR=\"http://127.0.0.1:${SERVER_TUNNEL_LOCAL_PORT}\"",
         "tunneled to ${LESAVKA_SERVER_HOST}:127.0.0.1:${SERVER_TUNNEL_REMOTE_PORT}",
+        "CAPTURE_READY_MARKER=\"__LESAVKA_CAPTURE_READY__\"",
         "Tethys capture failed before the sync probe could start",
-        "kill -0 \"${capture_pid}\"",
+        "wait_for_capture_ready",
+        "Timed out waiting for Tethys capture to become ready",
+        "grep -q \"${CAPTURE_READY_MARKER}\"",
+        "Lesavka UVC video device not found on Tethys; refusing to fall back to an unrelated webcam/capture card.",
+        "resolve_alsa_audio_device",
+        "PipeWire Lesavka source not found; falling back to ALSA device",
+        "Lesavka audio source not found in PipeWire or ALSA; capture host does not currently expose the gadget microphone.",
     ] {
         assert!(
             SYNC_SCRIPT.contains(expected),