Tim-1e · Tim-1e · Jul 24, 2026 · Jul 24, 2026
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -91,6 +91,8 @@ jobs:
           test ! -e "$HOME/.local/share/cxcc"
 
       - name: Install pinned cxcc and verify repeat apply
+        env:
+          INSTALL_CXCC: "1"
         run: |
           profiles_before="$(sha256sum "$HOME/.ai-env/profiles.json" | awk '{print $1}')"
           chezmoi apply --source "$GITHUB_WORKSPACE"
@@ -104,6 +106,7 @@ jobs:
       - name: Run full smoke check
         env:
           DOTFILES_SOURCE_DIR: ${{ github.workspace }}
+          INSTALL_CXCC: "1"
         run: bash ./test/smoke.sh
 
   macos:
@@ -205,6 +208,8 @@ jobs:
           }
 
       - name: Install pinned cxcc and verify repeat apply
+        env:
+          INSTALL_CXCC: "1"
         run: |
           $profilesPath = Join-Path $HOME ".ai-env\profiles.json"
           $currentPath = Join-Path $HOME ".local\share\cxcc\current.json"
@@ -218,4 +223,6 @@ jobs:
           if ($currentBefore -cne $currentAfter) { throw "Repeated cxcc apply changed current.json." }
 
       - name: Run full Windows smoke check
+        env:
+          INSTALL_CXCC: "1"
         run: ./test/windows-full-smoke.ps1 -SourceDir "$PWD"
diff --git a/README.ja.md b/README.ja.md
@@ -70,7 +70,7 @@ INSTALL_CLAUDE=1 bash ./bootstrap.sh
 INSTALL_NODE=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FASTFETCH=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_MODERN_CLI=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
-INSTALL_CXCC=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
+INSTALL_CXCC=1 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FONTS=0 bash ./bootstrap.sh
 INSTALL_WINDOWS_FONTS_FROM_WSL=0 bash ./bootstrap.sh
 DOTFILES_USE_SUDO=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
@@ -92,7 +92,8 @@ sudo にパスワードが必要な場合は確認し、デフォルトでは使
 - 互換性のある fastfetch を `~/.local/bin` へ
 - システムパッケージが有効な場合は Node.js と npm
 - 現在ユーザーの font directory へ 0xProto Nerd Font
-- 固定バージョンの cxcc と、`cx`、`cc`、`mcp` を読み込む PowerShell/Zsh hook
+- 選択した場合、固定バージョンの cxcc と `cx`、`cc`、`mcp` を読み込む
+  PowerShell/Zsh hook
 
 zsh がなく build tools がある場合は、zsh を `~/.local` にビルドします。
 古い Linux では fastfetch の polyfilled binary を優先し、適合するものがなければ
@@ -121,7 +122,7 @@ flag が互換ではない `rg`、`fd`、`sd`、`jq`、`yq`、`xh`、`delta` は
 
 ## CX/CC AI Profile ツール
 
-dotfiles は固定バージョンの cxcc をインストールし、その軽量 shell function で
+dotfiles は固定バージョンの cxcc を選択してインストールでき、その軽量 shell function で
 Codex と Claude Code のローカル状態を切り替えます。CLI 自体は起動しません。
 コマンド実装と cross-platform test は cxcc が、version pin、install hook、loader
 接続、default user config はこの repo が管理します。
@@ -160,9 +161,10 @@ Payload:   ~/.local/share/cxcc/versions/v0.1.0/
 ```
 
 release tag、immutable commit、installer digest、platform artifact digest は
-`.chezmoidata.toml` にまとめてあります。対応する pin をすべて更新して
-`chezmoi apply` を実行すると upgrade できます。`INSTALL_CXCC=0` で install を
-skip でき、変数を外した次回 apply で通常動作に戻ります。
+`.chezmoidata.toml` にまとめてあります。cxcc はデフォルトではインストールされません。
+interactive apply は `Install the cx/cc environment? [y/N]` と確認し、Enter では
+skip します。non-interactive install には `INSTALL_CXCC=1`、確認なしで skip する
+場合は `INSTALL_CXCC=0` を設定します。
 
 状態ファイル:
 

diff --git a/README.ko.md b/README.ko.md
@@ -70,7 +70,7 @@ INSTALL_CLAUDE=1 bash ./bootstrap.sh
 INSTALL_NODE=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FASTFETCH=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_MODERN_CLI=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
-INSTALL_CXCC=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
+INSTALL_CXCC=1 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FONTS=0 bash ./bootstrap.sh
 INSTALL_WINDOWS_FONTS_FROM_WSL=0 bash ./bootstrap.sh
 DOTFILES_USE_SUDO=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
@@ -92,7 +92,7 @@ DOTFILES_USE_SUDO=1 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/
 - 호환 가능한 fastfetch를 `~/.local/bin`에 설치
 - 시스템 패키지 설치가 켜져 있으면 Node.js와 npm 설치
 - 현재 사용자 font 디렉터리에 0xProto Nerd Font 설치
-- 고정 버전 cxcc와 `cx`, `cc`, `mcp`를 로드하는 PowerShell/Zsh hook
+- 선택 시 고정 버전 cxcc와 `cx`, `cc`, `mcp`를 로드하는 PowerShell/Zsh hook
 
 zsh가 없고 build tool이 있으면 zsh를 `~/.local`에 빌드합니다. 오래된 Linux에서는
 fastfetch polyfilled binary를 우선 사용하고, 맞는 binary가 없으면 전체 apply를
@@ -121,7 +121,7 @@ interactive alias는 보수적으로만 켭니다. `du` -> `dust`, `df` -> `duf`
 
 ## CX/CC AI Profile 도구
 
-dotfiles는 고정 버전 cxcc를 설치하고 가벼운 shell function으로 Codex와 Claude Code의
+dotfiles는 고정 버전 cxcc를 선택하여 설치하고 가벼운 shell function으로 Codex와 Claude Code의
 로컬 상태를 전환합니다. CLI를 직접 실행하지는 않습니다. 명령 구현과 cross-platform
 test는 cxcc가, version pin, install hook, loader 연결, default user config는 이 repo가
 관리합니다.
@@ -160,9 +160,10 @@ Payload:   ~/.local/share/cxcc/versions/v0.1.0/
 ```
 
 release tag, immutable commit, installer digest, platform artifact digest는
-`.chezmoidata.toml`에 함께 있습니다. 대응하는 pin을 모두 갱신하고 `chezmoi apply`를
-실행하면 upgrade할 수 있습니다. `INSTALL_CXCC=0`은 설치를 건너뛰며, 변수를 제거한
-다음 apply부터 정상 설치가 다시 시작됩니다.
+`.chezmoidata.toml`에 함께 있습니다. cxcc는 기본적으로 설치하지 않습니다.
+interactive apply는 `Install the cx/cc environment? [y/N]`라고 묻고 Enter를 누르면
+건너뜁니다. non-interactive 설치에는 `INSTALL_CXCC=1`, 질문 없이 건너뛰려면
+`INSTALL_CXCC=0`을 설정합니다.
 
 상태 파일:
 

diff --git a/README.md b/README.md
@@ -71,7 +71,7 @@ INSTALL_CLAUDE=1 bash ./bootstrap.sh
 INSTALL_NODE=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FASTFETCH=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_MODERN_CLI=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
-INSTALL_CXCC=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
+INSTALL_CXCC=1 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FONTS=0 bash ./bootstrap.sh
 INSTALL_WINDOWS_FONTS_FROM_WSL=0 bash ./bootstrap.sh
 DOTFILES_USE_SUDO=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
@@ -94,8 +94,8 @@ The base layer installs or configures:
 - latest compatible fastfetch in `~/.local/bin`
 - Node.js and npm by default when system package installation is enabled
 - 0xProto Nerd Fonts in the current user's font directory
-- a pinned cxcc release plus PowerShell/Zsh loader hooks for `cx`, `cc`, and
-  `mcp`
+- when selected, a pinned cxcc release plus PowerShell/Zsh loader hooks for
+  `cx`, `cc`, and `mcp`
 
 If `zsh` is unavailable but build tools are present, zsh is built into
 `~/.local`. On older Linux systems, fastfetch falls back to its polyfilled
@@ -124,7 +124,7 @@ over standard commands.
 
 ## CX/CC AI Profile Tools
 
-The dotfiles install a pinned cxcc release, then load its lightweight shell
+The dotfiles can install a pinned cxcc release, then load its lightweight shell
 functions for switching local Codex and Claude Code state without launching
 either CLI. cxcc owns the command implementation and its cross-platform tests;
 this repo owns the version pin, installation hook, loader wiring, and default
@@ -164,9 +164,10 @@ Payload:   ~/.local/share/cxcc/versions/v0.1.0/
 ```
 
 The release tag, immutable commit, installer digest, and platform artifact
-digests are stored together in `.chezmoidata.toml`. Update all matching pins
-and run `chezmoi apply` to upgrade. Set `INSTALL_CXCC=0` to skip the install
-hook; a later apply without the variable resumes normal installation.
+digests are stored together in `.chezmoidata.toml`. cxcc is not installed by
+default. An interactive apply asks `Install the cx/cc environment? [y/N]`;
+pressing Enter skips it. Set `INSTALL_CXCC=1` to install non-interactively or
+`INSTALL_CXCC=0` to skip without prompting.
 
 Runtime state:
 

diff --git a/README.zh-CN.md b/README.zh-CN.md
@@ -68,7 +68,7 @@ INSTALL_CLAUDE=1 bash ./bootstrap.sh
 INSTALL_NODE=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FASTFETCH=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_MODERN_CLI=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
-INSTALL_CXCC=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
+INSTALL_CXCC=1 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
 INSTALL_FONTS=0 bash ./bootstrap.sh
 INSTALL_WINDOWS_FONTS_FROM_WSL=0 bash ./bootstrap.sh
 DOTFILES_USE_SUDO=0 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/dotfiles
@@ -89,7 +89,7 @@ DOTFILES_USE_SUDO=1 sh -c "$(curl -fsLS get.chezmoi.io)" -- init --apply Tim-1e/
 - 兼容的 fastfetch 到 `~/.local/bin`
 - Node.js 和 npm，默认随系统包安装
 - 0xProto Nerd Font 到当前用户字体目录
-- 固定版本的 cxcc，以及加载 `cx`、`cc`、`mcp` 的 PowerShell/Zsh hook
+- 选择安装时提供固定版本的 cxcc，以及加载 `cx`、`cc`、`mcp` 的 PowerShell/Zsh hook
 
 如果系统没有 zsh，但有编译工具，脚本会把 zsh 编译到 `~/.local`。老 Linux
 系统上，fastfetch 会优先尝试 polyfilled binary；没有合适版本时跳过，不让整个
@@ -116,7 +116,7 @@ apply 失败。
 
 ## CX/CC AI Profile 工具
 
-dotfiles 安装固定版本的 cxcc，再加载其轻量 shell function，用于切换 Codex 和
+dotfiles 可安装固定版本的 cxcc，再加载其轻量 shell function，用于切换 Codex 和
 Claude Code 的本地状态，但不会直接启动 CLI。命令实现和跨平台测试归 cxcc 仓库
 维护；本仓库只负责版本钉住、安装 hook、loader 接线和默认用户配置：
 
@@ -154,8 +154,9 @@ Payload:   ~/.local/share/cxcc/versions/v0.1.0/
 ```
 
 release tag、不可变 commit、installer digest 和平台 artifact digest 统一位于
-`.chezmoidata.toml`；同步更新这些 pin 后运行 `chezmoi apply` 即可升级。设置
-`INSTALL_CXCC=0` 会跳过安装，之后取消变量再 apply 即可恢复。
+`.chezmoidata.toml`。cxcc 默认不安装；交互 apply 会询问
+`Install the cx/cc environment? [y/N]`，直接回车即跳过。非交互安装设置
+`INSTALL_CXCC=1`，需要无提示跳过时设置 `INSTALL_CXCC=0`。
 
 运行状态：
 

diff --git a/scripts/install/cxcc.ps1 b/scripts/install/cxcc.ps1
@@ -22,8 +22,26 @@ foreach ($digest in @($InstallerSha256, $ArtifactSha256)) {
   if ($digest -notmatch '^[0-9a-f]{64}$') { throw "cxcc SHA-256 pins must contain 64 lowercase hexadecimal characters." }
 }
 
-if ($env:INSTALL_CXCC -ceq "0") {
-  Write-Host "Skipping cxcc installation because INSTALL_CXCC=0."
+if ([string]::IsNullOrEmpty($env:INSTALL_CXCC)) {
+  $shouldInstall = $false
+  if ([Environment]::UserInteractive -and -not [Console]::IsInputRedirected -and -not [Console]::IsOutputRedirected) {
+    try {
+      $answer = Read-Host "Install the cx/cc environment? [y/N]"
+      $shouldInstall = ([string]$answer).Trim() -match '^(?i:y|yes)$'
+    } catch {
+      $shouldInstall = $false
+    }
+  }
+} elseif ($env:INSTALL_CXCC -ceq "1") {
+  $shouldInstall = $true
+} elseif ($env:INSTALL_CXCC -ceq "0") {
+  $shouldInstall = $false
+} else {
+  throw "INSTALL_CXCC must be 0 or 1."
+}
+
+if (-not $shouldInstall) {
+  Write-Host "Skipping cxcc installation. Set INSTALL_CXCC=1 to install it."
   return
 }
 

diff --git a/scripts/install/cxcc.sh b/scripts/install/cxcc.sh
@@ -29,8 +29,30 @@ sha256_file() {
 [[ "$installer_sha256" =~ ^[0-9a-f]{64}$ ]] || fail "cxcc installer SHA-256 pin must contain 64 lowercase hexadecimal characters."
 [[ "$artifact_sha256" =~ ^[0-9a-f]{64}$ ]] || fail "cxcc artifact SHA-256 pin must contain 64 lowercase hexadecimal characters."
 
-if [ "${INSTALL_CXCC:-1}" = "0" ]; then
-  echo "Skipping cxcc installation because INSTALL_CXCC=0."
+case "${INSTALL_CXCC-}" in
+  1)
+    should_install=1
+    ;;
+  0)
+    should_install=0
+    ;;
+  "")
+    should_install=0
+    if [ -t 0 ] && [ -t 1 ]; then
+      printf 'Install the cx/cc environment? [y/N] '
+      IFS= read -r answer || answer=""
+      case "$answer" in
+        [Yy] | [Yy][Ee][Ss]) should_install=1 ;;
+      esac
+    fi
+    ;;
+  *)
+    fail "INSTALL_CXCC must be 0 or 1."
+    ;;
+esac
+
+if [ "$should_install" != "1" ]; then
+  echo "Skipping cxcc installation. Set INSTALL_CXCC=1 to install it."
   exit 0
 fi
 

diff --git a/test/cxcc-consumer-smoke.ps1 b/test/cxcc-consumer-smoke.ps1
@@ -22,6 +22,7 @@ foreach ($required in @($installer, $hook, $dataFile, $profileSource)) {
 $dataText = Get-Content -LiteralPath $dataFile -Raw
 $hookText = Get-Content -LiteralPath $hook -Raw
 $profileText = Get-Content -LiteralPath $profileSource -Raw
+$installerText = Get-Content -LiteralPath $installer -Raw
 Assert-True ($dataText -match '(?m)^version = "v0\.1\.0"$') "dotfiles does not pin cxcc v0.1.0."
 Assert-True $dataText.Contains($expectedCommit) "dotfiles does not pin an immutable cxcc commit."
 Assert-True $dataText.Contains($expectedInstallerSha256) "dotfiles does not pin the PowerShell installer digest."
@@ -34,6 +35,8 @@ Assert-True $hookText.Contains(".cxcc.windowsArtifactSha256") "PowerShell hook d
 Assert-True ($profileText -match 'CXCC_HOME') "PowerShell profile does not honor CXCC_HOME."
 Assert-True ($profileText -match 'load\.ps1') "PowerShell profile does not load the stable cxcc loader."
 Assert-True ($profileText -notmatch 'Scripts\\ai-env\.ps1') "PowerShell profile still loads the legacy ai-env implementation."
+Assert-True $installerText.Contains("Install the cx/cc environment? [y/N]") "PowerShell installer does not offer the default-No cx/cc prompt."
+Assert-True ($installerText -match 'INSTALL_CXCC.+1') "PowerShell installer does not support INSTALL_CXCC=1."
 
 $legacyPaths = @(
   "Documents/PowerShell/Scripts/ai-env.ps1",
@@ -150,6 +153,12 @@ $loader = @(
   $env:CXCC_TEST_INSTALL_LOG = $installLog
   Remove-Item -LiteralPath Env:\INSTALL_CXCC -ErrorAction SilentlyContinue
 
+  & $installer @installerArguments
+  Assert-True (-not (Test-Path -LiteralPath $installRoot)) "Unset INSTALL_CXCC installed cxcc in a non-interactive session."
+  Assert-True (-not (Test-Path -LiteralPath $downloadLog)) "Unset INSTALL_CXCC accessed the network in a non-interactive session."
+  Assert-StatePreserved
+
+  $env:INSTALL_CXCC = "1"
   & $installer @installerArguments
   $downloadLines = @(Get-Content -LiteralPath $downloadLog)
   Assert-True ($downloadLines.Count -eq 2) "PowerShell consumer did not download the installer and artifact exactly once."
@@ -185,11 +194,17 @@ $loader = @(
   Assert-True (@(Get-Content -LiteralPath $downloadLog).Count -eq 4) "INSTALL_CXCC=0 accessed the network."
   Assert-StatePreserved
 
+  $env:INSTALL_CXCC = "yes"
+  $invalidInstallChoiceFailed = $false
+  try { & $installer @installerArguments } catch { $invalidInstallChoiceFailed = $true }
+  Assert-True $invalidInstallChoiceFailed "PowerShell consumer accepted INSTALL_CXCC other than 0 or 1."
+  Assert-True (@(Get-Content -LiteralPath $downloadLog).Count -eq 4) "Invalid INSTALL_CXCC accessed the network."
+
   $invalidVersionFailed = $false
   try { & $installer -Version "main" -Commit $testCommit -InstallerSha256 $testInstallerSha256 -ArtifactSha256 $testArtifactSha256 } catch { $invalidVersionFailed = $true }
   Assert-True $invalidVersionFailed "PowerShell consumer accepted an unpinned version."
 
-  Remove-Item -LiteralPath Env:\INSTALL_CXCC -ErrorAction SilentlyContinue
+  $env:INSTALL_CXCC = "1"
   $env:CXCC_HOME = Join-Path $testHome "bad\cxcc"
   $checksumFailed = $false
   try { & $installer -Version $expectedVersion -Commit $testCommit -InstallerSha256 ("0" * 64) -ArtifactSha256 $testArtifactSha256 } catch { $checksumFailed = $true }

diff --git a/test/cxcc-consumer-smoke.sh b/test/cxcc-consumer-smoke.sh
@@ -44,7 +44,9 @@ grep -Fq '.cxcc.posixArtifactSha256' "$HOOK" || fail "Shell hook does not use th
 grep -Fq -- '--connect-timeout' "$INSTALLER" || fail "Shell consumer download has no connection timeout."
 grep -Fq -- '--max-time' "$INSTALLER" || fail "Shell consumer download has no total timeout."
 grep -Fq -- '--ipv4' "$INSTALLER" || fail "Shell consumer download has no IPv4 fallback."
-grep -Fq 'INSTALL_CXCC' "$FULL_SMOKE" || fail "Full smoke does not honor INSTALL_CXCC=0."
+grep -Fq 'Install the cx/cc environment? [y/N]' "$INSTALLER" || fail "Shell installer does not offer the default-No cx/cc prompt."
+grep -Fq 'INSTALL_CXCC=1' "$INSTALLER" || fail "Shell installer does not support INSTALL_CXCC=1."
+grep -Fq '${INSTALL_CXCC:-0}' "$FULL_SMOKE" || fail "Full smoke does not default cxcc checks to disabled."
 grep -Fq 'CXCC_HOME' "$ZSHRC" || fail "Zsh profile does not honor CXCC_HOME."
 grep -Fq '/load.sh' "$ZSHRC" || fail "Zsh profile does not load the stable cxcc loader."
 ! grep -Fq '.local/share/ai-env/ai-env.sh' "$ZSHRC" || fail "Zsh profile still loads the legacy ai-env implementation."
@@ -180,7 +182,13 @@ run_installer() {
   bash "$INSTALLER" "$EXPECTED_VERSION" "$test_commit" "$test_installer_sha256" "$test_artifact_sha256"
 }
 
+unset INSTALL_CXCC
 run_installer
+[ ! -e "$install_root" ] || fail "Unset INSTALL_CXCC installed cxcc in a non-interactive session."
+[ ! -e "$curl_log" ] || fail "Unset INSTALL_CXCC accessed the network in a non-interactive session."
+assert_state_preserved
+
+INSTALL_CXCC=1 run_installer
 [ "$(sed -n '1p' "$curl_log")" = "https://raw.githubusercontent.com/Tim-1e/cxcc/$test_commit/install.sh" ] || fail "Shell consumer used a mutable installer URL."
 [ "$(sed -n '2p' "$curl_log")" = "https://github.com/Tim-1e/cxcc/releases/download/$EXPECTED_VERSION/cxcc-$EXPECTED_VERSION-posix.tar.gz" ] || fail "Shell consumer used an unexpected artifact URL."
 grep -Eq "^--version $EXPECTED_VERSION --artifact .*/cxcc-$EXPECTED_VERSION-posix\.tar\.gz --sha256 $test_artifact_sha256$" "$install_log" || fail "Shell consumer passed unexpected installer arguments."
@@ -189,12 +197,12 @@ grep -Fq '"version":"v0.1.0"' "$install_root/current.json" || fail "Shell consum
 [ "$(cat "$install_root/versions/$EXPECTED_VERSION/VERSION")" = "$EXPECTED_VERSION" ] || fail "Shell consumer payload VERSION is invalid."
 assert_state_preserved
 
-run_installer
+INSTALL_CXCC=1 run_installer
 [ "$(wc -l <"$curl_log" | tr -d ' ')" = "2" ] || fail "Repeated Shell apply downloaded cxcc again."
 assert_state_preserved
 
 rm "$install_root/versions/$EXPECTED_VERSION/src/shell/cxcc.sh"
-run_installer
+INSTALL_CXCC=1 run_installer
 [ "$(wc -l <"$curl_log" | tr -d ' ')" = "4" ] || fail "Shell consumer ignored a damaged cxcc payload."
 assert_state_preserved
 
@@ -204,11 +212,16 @@ INSTALL_CXCC=0 run_installer
 [ "$(wc -l <"$curl_log" | tr -d ' ')" = "4" ] || fail "INSTALL_CXCC=0 accessed the network."
 assert_state_preserved
 
+if INSTALL_CXCC=yes run_installer >/dev/null 2>&1; then
+  fail "Shell consumer accepted INSTALL_CXCC other than 0 or 1."
+fi
+[ "$(wc -l <"$curl_log" | tr -d ' ')" = "4" ] || fail "Invalid INSTALL_CXCC accessed the network."
+
 if HOME="$test_home" CXCC_HOME="$install_root" PATH="$fake_bin:$PATH" bash "$INSTALLER" main "$test_commit" "$test_installer_sha256" "$test_artifact_sha256" >/dev/null 2>&1; then
   fail "Shell consumer accepted an unpinned version."
 fi
 
-if HOME="$test_home" \
+if INSTALL_CXCC=1 HOME="$test_home" \
   CXCC_HOME="$test_home/bad/cxcc" \
   CXCC_TEST_CURL_LOG="$curl_log" \
   CXCC_TEST_INSTALL_LOG="$install_log" \