diff --git a/home/bin/README.md b/home/bin/README.md
index 0c2a3c3..1f49d98 100644
--- a/home/bin/README.md
+++ b/home/bin/README.md
@@ -23,3 +23,9 @@ python frc-photo-checklist.py [Event Key]
 ## get-mouse-battery.sh
 
 Prints out the battery percentage of a mouse and if it is charging.
+
+## openai-usage.sh
+
+Shows the remaining 5-hour and weekly ChatGPT Codex allowances using the current
+OpenCode or Codex CLI login. Run `openai-usage --watch` to refresh every minute,
+or `openai-usage --json` for machine-readable output.
diff --git a/home/bin/executable_openai-usage.sh b/home/bin/executable_openai-usage.sh
new file mode 100644
index 0000000..f77cb01
--- /dev/null
+++ b/home/bin/executable_openai-usage.sh
@@ -0,0 +1,192 @@
+#!/bin/bash
+# Show the remaining ChatGPT Codex rate limits for the current OpenAI login.
+
+set -o pipefail
+
+usage_url="${OPENAI_USAGE_URL:-https://chatgpt.com/backend-api/wham/usage}"
+auth_file="${OPENAI_AUTH_FILE:-}"
+output_format="text"
+watch_interval=""
+
+function usage {
+  cat <<'EOF'
+Usage: openai-usage [--json] [--watch [SECONDS]]
+
+Show the remaining Codex allowance for the OpenAI account logged into OpenCode
+or the Codex CLI. The default watch interval is 60 seconds.
+
+Environment:
+  OPENAI_AUTH_FILE  Override the OAuth credential file
+  OPENAI_USAGE_URL  Override the ChatGPT usage endpoint
+EOF
+}
+
+function fail {
+  printf 'openai-usage: %s\n' "$1" >&2
+  exit 1
+}
+
+function require_command {
+  command -v "$1" &>/dev/null || fail "required command not found: $1"
+}
+
+function find_auth_file {
+  local opencode_auth
+  local codex_auth
+
+  if [[ -n "$auth_file" ]]; then
+    [[ -r "$auth_file" ]] || fail "cannot read auth file: $auth_file"
+    return
+  fi
+
+  opencode_auth="${XDG_DATA_HOME:-$HOME/.local/share}/opencode/auth.json"
+  codex_auth="${CODEX_HOME:-$HOME/.codex}/auth.json"
+
+  if [[ -r "$opencode_auth" ]]; then
+    auth_file="$opencode_auth"
+  elif [[ -r "$codex_auth" ]]; then
+    auth_file="$codex_auth"
+  else
+    fail "no OpenCode or Codex login found; run 'opencode auth login' first"
+  fi
+}
+
+function human_duration {
+  local total_seconds=$1
+  local days hours minutes
+
+  (( total_seconds < 0 )) && total_seconds=0
+  days=$((total_seconds / 86400))
+  hours=$(((total_seconds % 86400) / 3600))
+  minutes=$(((total_seconds % 3600) / 60))
+
+  if (( days > 0 )); then
+    printf '%dd %dh' "$days" "$hours"
+  elif (( hours > 0 )); then
+    printf '%dh %dm' "$hours" "$minutes"
+  else
+    printf '%dm' "$minutes"
+  fi
+}
+
+function format_reset_time {
+  local reset_at=$1
+
+  if date --date="@$reset_at" '+%a %b %-d, %-I:%M %p' 2>/dev/null; then
+    return
+  fi
+
+  # BSD date fallback.
+  date -r "$reset_at" '+%a %b %e, %l:%M %p' 2>/dev/null || printf '%s' "$reset_at"
+}
+
+function print_window {
+  local label=$1
+  local window=$2
+  local used_percent reset_after reset_at remaining
+
+  used_percent=$(jq -r '.used_percent // 0' <<<"$window")
+  reset_after=$(jq -r '.reset_after_seconds // 0 | floor' <<<"$window")
+  reset_at=$(jq -r '.reset_at // 0 | floor' <<<"$window")
+  remaining=$(jq -nr --argjson used "$used_percent" '100 - $used | if . < 0 then 0 else . end')
+
+  printf '%-8s %6g%% left  resets in %-8s  (%s)\n' \
+    "$label:" "$remaining" "$(human_duration "$reset_after")" "$(format_reset_time "$reset_at")"
+}
+
+function fetch_usage {
+  local access_token account_id raw_response status body
+
+  access_token=$(jq -r \
+    '.openai.access // .tokens.access_token // .access_token // empty' \
+    "$auth_file") || fail "invalid JSON in auth file: $auth_file"
+  account_id=$(jq -r \
+    '.openai.accountId // .tokens.account_id // .account_id // empty' \
+    "$auth_file") || fail "invalid JSON in auth file: $auth_file"
+
+  [[ -n "$access_token" ]] || fail "no OpenAI OAuth token found in $auth_file"
+
+  raw_response=$(curl --silent --show-error \
+    --header "Authorization: Bearer $access_token" \
+    --header "ChatGPT-Account-Id: $account_id" \
+    --header 'Accept: application/json' \
+    --write-out $'\n%{http_code}' \
+    "$usage_url") || fail "could not contact OpenAI"
+
+  status=${raw_response##*$'\n'}
+  body=${raw_response%$'\n'*}
+
+  case "$status" in
+    200) ;;
+    401|403) fail "OpenAI login expired; run 'opencode auth login' again" ;;
+    *) fail "OpenAI returned HTTP $status" ;;
+  esac
+
+  jq -e '.rate_limit' <<<"$body" >/dev/null || fail "unexpected response from OpenAI"
+  printf '%s\n' "$body"
+}
+
+function print_usage {
+  local response=$1
+  local plan primary secondary
+
+  if [[ "$output_format" == "json" ]]; then
+    jq '{
+      plan: .plan_type,
+      allowed: .rate_limit.allowed,
+      limit_reached: .rate_limit.limit_reached,
+      five_hour: (.rate_limit.primary_window | . + {
+        remaining_percent: ([100 - .used_percent, 0] | max)
+      }),
+      weekly: (.rate_limit.secondary_window | . + {
+        remaining_percent: ([100 - .used_percent, 0] | max)
+      })
+    }' <<<"$response"
+    return
+  fi
+
+  plan=$(jq -r '.plan_type // "unknown"' <<<"$response")
+  primary=$(jq -c '.rate_limit.primary_window' <<<"$response")
+  secondary=$(jq -c '.rate_limit.secondary_window' <<<"$response")
+
+  printf 'OpenAI Codex usage (%s)\n' "$plan"
+  print_window '5-hour' "$primary"
+  print_window 'Weekly' "$secondary"
+}
+
+while (( $# > 0 )); do
+  case "$1" in
+    --json)
+      output_format="json"
+      shift
+      ;;
+    --watch)
+      watch_interval=60
+      if [[ ${2:-} =~ ^[1-9][0-9]*$ ]]; then
+        watch_interval=$2
+        shift
+      fi
+      shift
+      ;;
+    -h|--help)
+      usage
+      exit 0
+      ;;
+    *)
+      usage >&2
+      fail "unknown argument: $1"
+      ;;
+  esac
+done
+
+require_command curl
+require_command jq
+find_auth_file
+
+while true; do
+  response=$(fetch_usage)
+  print_usage "$response"
+
+  [[ -n "$watch_interval" ]] || break
+  sleep "$watch_interval"
+done