vncfix

#!/bin/bash
# vncfix — diagnose & fix the macOS Screen Sharing "black screen + cursor" symptom.
#
# Two known causes:
#   (A) Clamshell / daemon glitch on Apple Silicon.
#       Fix: restart screensharingd + the per-user ScreensharingAgent (this script
#       does it automatically). Screens refreshes within a couple seconds.
#   (B) ScreensharingAgent denied Screen Recording (TCC: kTCCServiceScreenCapture).
#       macOS 14+ captures the screen via ScreenCaptureKit, which needs the grant.
#       Without it the agent logs "Cannot get shareable content" and Screens shows
#       the cursor (drawn by the daemon) over a black frame (no framebuffer).
#       This CANNOT be fixed from a shell: SIP blocks all writes to TCC.db, and the
#       grant requires interactive admin auth. The only fix is to toggle Screen
#       Sharing OFF then ON in System Settings (TouchID/password), which re-seeds it.
#
# Run from SSH while Screens is black. Restarts the daemon+agent (cause A), then
# scans the agent log; if it sees the Screen-Recording denial (cause B) it explains
# the manual step and opens System Settings > Sharing for you.

set -u
UID_N=$(id -u)
AGENT_UNIT="gui/${UID_N}/com.apple.screensharing.agent"
DAEMON_UNIT="system/com.apple.screensharing"
DAEMON_PLIST="/System/Library/LaunchDaemons/com.apple.screensharing.plist"

echo "==> Restarting screensharingd (daemon)..."
if ! sudo launchctl kickstart -k "$DAEMON_UNIT" 2>/dev/null; then
  echo "    kickstart failed; trying bootout/bootstrap cycle..."
  sudo launchctl bootout "$DAEMON_UNIT" 2>/dev/null || true
  sudo launchctl bootstrap system "$DAEMON_PLIST" 2>/dev/null || true
fi

echo "==> Kicking the per-user ScreensharingAgent..."
launchctl kickstart -k "$AGENT_UNIT" 2>/dev/null || true

echo "==> Scanning recent agent log for a Screen-Recording (TCC) denial..."
DENIED=$(log show --last 10m --style compact \
  --predicate 'process == "ScreensharingAgent"' 2>/dev/null \
  | grep -c "Cannot get shareable content")

if [ "${DENIED:-0}" -gt 0 ]; then
  cat <<'DIAG'

   *** DIAGNOSIS: Screen Recording permission is DENIED for the screen-sharing agent. ***
   ScreenCaptureKit can't grab the framebuffer, so Screens shows cursor + black.
   Restarting the daemon does NOT fix this, and SIP blocks any CLI write to TCC.db.

   FIX (~10s at the Mac or via the JetKVM; needs TouchID/password):
     1. System Settings > General > Sharing
     2. Toggle "Screen Sharing" OFF, wait 2s, toggle it back ON (authenticate when asked)
     3. Reconnect Screens.

   Opening System Settings > Sharing now...
DIAG
  open "x-apple.systempreferences:com.apple.Sharing-Settings.extension" 2>/dev/null || true
  echo "   (If you're fully remote and can't authenticate: power on the JetKVM, or wait"
  echo "    until you have physical access — there is no shell-only fix for this one.)"
else
  echo
  echo "   No Screen-Recording denial found in the last 10m. If Screens was black, the"
  echo "   daemon+agent restart above (clamshell glitch) should have cleared it."
  echo "   Reconnect Screens now (or wait ~2s for it to refresh)."
fi