diff --git a/tools/re-capture/launch_mission.sh b/tools/re-capture/launch_mission.sh
index cd9411c4..b69e99a1 100755
--- a/tools/re-capture/launch_mission.sh
+++ b/tools/re-capture/launch_mission.sh
@@ -58,10 +58,20 @@ XUID="${SYLPH_XUID:-$(ls "${XENIA_CONTENT:-$HOME/.local/share/Xenia/content}" 2>
 [ -n "$XUID" ] || { echo "NO PROFILE on disc"; exit 2; }
 LOG="${LAUNCH_MISSION_LOG:-$SHOTS/launch_mission-canary.stdout}"
 echo "signing in profile $XUID; emulator log: $LOG"
+# EXTRA_FLAGS is for one-off diagnostics that should not become defaults --
+# e.g. --log_high_frequency_kernel_calls=true, which is the only way to see
+# KeWaitForSingleObject at all (it is declared kHighFrequency and is therefore
+# silent even at LOG_LEVEL=3).
+# shellcheck disable=SC2086
 nohup run-canary --apu=sdl --log_mask="${LOG_MASK:-13}" --log_level="${LOG_LEVEL:-2}" \
-  --logged_profile_slot_0_xuid="$XUID" </dev/null >"$LOG" 2>&1 &
+  --logged_profile_slot_0_xuid="$XUID" ${EXTRA_FLAGS:-} </dev/null >"$LOG" 2>&1 &
 sleep 5
-"$SD/skip_intro.sh" 600 || { echo "BOOT FAILED (skip_intro exit $?)"; exit 1; }
+# The boot budget is a knob because one diagnostic blows straight through the
+# default: --log_high_frequency_kernel_calls=true writes ~157 MB in ten minutes
+# and the title had still not appeared, so skip_intro timed out and the run was
+# scored a BOOT FAILED when it was only slow.
+"$SD/skip_intro.sh" "${SKIP_INTRO_TIMEOUT:-600}" \
+  || { echo "BOOT FAILED (skip_intro exit $?)"; exit 1; }
 sleep 14                       # main menu is not input-ready before this
 
 step down                      # NEW GAME -> LOAD GAME