Very high GPU usage when Codex is active window. REPORT.md and reproduction scripts included

Codex
1

Codex Desktop macOS GPU spike when focused

Summary

On macOS, the Codex Desktop app appears to trigger heavy sustained GPU/compositor activity whenever the Codex window is focused/frontmost. Switching focus to Chrome drops the GPU monitor to near idle immediately.

The effect reproduces with a small A/B script that focuses Chrome, samples powermetrics, then focuses Codex and samples again.

Environment

  • App: Codex Desktop
  • Bundle ID: com.openai.codex
  • Codex version: 26.623.61825 (CFBundleVersion 4548)
  • Chromium base: 149.0.7827.197
  • Machine: Mac15,10, Apple Silicon / arm64
  • macOS: 27.0 build 26A5368g
  • Kernel: Darwin 27.0.0

Quick reproduction

  1. Open Chrome and Codex Desktop.
  2. Run a focus A/B capture:
sudo powermetrics \
  --sample-rate 1000 \
  --sample-count 8 \
  --samplers tasks,gpu_power,cpu_power,thermal \
  --show-process-gpu \
  --show-process-energy \
  --output-file <output.txt>
  1. Capture once with Chrome focused and once with Codex focused. In my local script, focus switching is done with osascript using bundle IDs com.google.Chrome and com.openai.codex.

Portable repro and logging script

The following script should run on any macOS machine with Codex installed in /Applications/Codex.app. It creates a timestamped folder containing:

  • metadata.txt: macOS, hardware, Codex version, current Codex process flags, thermal status, swap status.
  • Chrome-powermetrics.txt: raw baseline capture.
  • Codex-powermetrics.txt: raw target capture.
  • summary.txt: compact GPU active/power comparison to paste into an issue.

Usage:

chmod +x repro-codex-gpu-focus.sh
./repro-codex-gpu-focus.sh

If Chrome is not the desired baseline app, override the bundle ID:

BASELINE_APP_ID=com.apple.Safari BASELINE_LABEL=Safari ./repro-codex-gpu-focus.sh
repro-codex-gpu-focus.sh 
#!/usr/bin/env bash
set -euo pipefail

SAMPLE_COUNT="${SAMPLE_COUNT:-8}"
SAMPLE_RATE_MS="${SAMPLE_RATE_MS:-1000}"
SETTLE_SECONDS="${SETTLE_SECONDS:-3}"
BASELINE_APP_ID="${BASELINE_APP_ID:-com.google.Chrome}"
TARGET_APP_ID="${TARGET_APP_ID:-com.openai.codex}"
BASELINE_LABEL="${BASELINE_LABEL:-Chrome}"
TARGET_LABEL="${TARGET_LABEL:-Codex}"
OUT_DIR="${1:-./codex-gpu-repro-$(date +%Y%m%d-%H%M%S)}"

mkdir -p "$OUT_DIR"

{
  echo "# System"
  sw_vers 2>/dev/null || true
  echo "hw.model: $(sysctl -n hw.model 2>/dev/null || true)"
  echo "kernel: $(uname -a 2>/dev/null || true)"
  echo
  echo "# Codex app"
  defaults read /Applications/Codex.app/Contents/Info CFBundleShortVersionString 2>/dev/null | sed 's/^/CFBundleShortVersionString: /' || true
  defaults read /Applications/Codex.app/Contents/Info CFBundleVersion 2>/dev/null | sed 's/^/CFBundleVersion: /' || true
  defaults read /Applications/Codex.app/Contents/Info ChromiumBaseVersion 2>/dev/null | sed 's/^/ChromiumBaseVersion: /' || true
  echo
  echo "# Codex processes"
  ps -axo pid,ppid,stat,etime,%cpu,%mem,rss,command | grep -E '/Applications/Codex.app|Codex \\(|codex app-server' | grep -v grep || true
  echo
  echo "# Thermal and swap"
  pmset -g therm 2>/dev/null || true
  sysctl -n vm.swapusage 2>/dev/null | sed 's/^/swap: /' || true
} >"$OUT_DIR/metadata.txt"

capture() {
  label="$1"
  app_id="$2"
  echo "Activating $label..."
  osascript -e "tell application id \"$app_id\" to activate"
  sleep "$SETTLE_SECONDS"
  sudo powermetrics \
    --sample-rate "$SAMPLE_RATE_MS" \
    --sample-count "$SAMPLE_COUNT" \
    --samplers tasks,gpu_power,cpu_power,thermal \
    --show-process-gpu \
    --show-process-energy \
    --output-file "$OUT_DIR/${label}-powermetrics.txt" \
    2>"$OUT_DIR/${label}-powermetrics.stderr.log"
}

summarize() {
  label="$1"
  file="$2"
  perl -MList::Util=sum,min,max -e '
    my ($label, $file) = @ARGV;
    open my $fh, "<", $file or die "Unable to read $file: $!\n";
    my (@gpu_power, @gpu_active);
    while (<$fh>) {
      push @gpu_power, $1 if /GPU Power:\s*(\d+)\s*mW/;
      push @gpu_active, $1 if /GPU HW active residency:\s*([0-9.]+)%/;
    }
    printf "%-10s active avg=%6.2f%% max=%6.2f%% | power avg=%5.0f mW max=%5d mW | %s\n",
      $label, sum(@gpu_active) / @gpu_active, max(@gpu_active),
      sum(@gpu_power) / @gpu_power, max(@gpu_power), $file;
  ' "$label" "$file"
}

echo "Output folder: $OUT_DIR"
sudo -v
capture "$BASELINE_LABEL" "$BASELINE_APP_ID"
capture "$TARGET_LABEL" "$TARGET_APP_ID"

{
  echo "# GPU focus comparison"
  summarize "$BASELINE_LABEL" "$OUT_DIR/${BASELINE_LABEL}-powermetrics.txt"
  summarize "$TARGET_LABEL" "$OUT_DIR/${TARGET_LABEL}-powermetrics.txt"
  echo
  echo "# Attach"
  echo "$OUT_DIR/summary.txt"
  echo "$OUT_DIR/metadata.txt"
  echo "$OUT_DIR/${BASELINE_LABEL}-powermetrics.txt"
  echo "$OUT_DIR/${TARGET_LABEL}-powermetrics.txt"
} | tee "$OUT_DIR/summary.txt"

Results

Launch mode Focused app GPU active avg GPU active max GPU power avg GPU power max
Normal Codex launch Chrome 1.94% 2.92% 19 mW 26 mW
Normal Codex launch Codex 70.16% 76.86% 2324 mW 3214 mW
Reduced-GPU flags Chrome 1.70% 2.11% 15 mW 19 mW
Reduced-GPU flags Codex 70.84% 78.59% 2644 mW 3404 mW

Reduced-GPU test flags:

open -a "Codex" --args \
  --disable-zero-copy \
  --disable-gpu-memory-buffer-compositor-resources \
  --disable-accelerated-2d-canvas \
  --disable-accelerated-video-decode \
  --disable-features=CanvasOopRasterization

The reduced flags were visible in the Codex process command line, but did not reduce the GPU load. A harder launch using --disable-gpu --disable-gpu-compositing caused Codex to start without a visible window and required force quit, so that path was not usable.

Additional observations

  • pmset -g therm reported no thermal or performance warnings.
  • sysctl -n vm.swapusage reported 0.00M swap used.
  • powermetrics often attributes the sustained work to WindowServer rather than directly to Codex per-process GPU columns, but the focus A/B isolates the trigger to Codex being frontmost.
  • Other background CPU noise was present during some captures (fileproviderd, bird, cloudd), but it did not explain the GPU delta: Chrome focus stayed around 2% GPU active while Codex focus stayed around 70%.

Expected

An idle/focused Codex Desktop window should not sustain roughly 70% GPU active residency and 2.3-2.6 W GPU power when another Chromium/Electron-style app focus state is near idle.

Request

Please investigate whether the focused Codex Desktop window has a rendering/compositor loop or macOS WindowServer interaction that keeps the GPU active. I can provide the raw powermetrics captures if useful.

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