diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index deb0080..06b2f1e 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -50,6 +50,8 @@ docker run --rm squarebox:test bash -c '
 | `setup.sh` | First-run interactive setup (AI tools, editors, SDKs) |
 | `install.sh` | Host-side install script for Linux/macOS (clone, build, create container) |
 | `install.ps1` | Host-side install script for Windows/PowerShell 7+ |
+| `uninstall.sh` | Host-side uninstall script for Linux/macOS/Git Bash |
+| `uninstall.ps1` | Host-side uninstall script for Windows/PowerShell 7+ |
 | `scripts/squarebox-update.sh` | In-container tool updater (`sqrbx-update`) |
 | `scripts/update-versions.sh` | Fetches latest Dockerfile-tier releases and updates checksums |
 | `checksums.txt` | SHA256 checksums for Dockerfile binary tools |
diff --git a/README.md b/README.md
index 707b683..d426cb8 100644
--- a/README.md
+++ b/README.md
@@ -377,13 +377,32 @@ using `gh codespace ssh`.
 Uninstall
 ---------
 
-    docker stop squarebox 2>/dev/null; docker rm squarebox
-    docker rmi squarebox
-    rm -rf ~/squarebox
+    sqrbx-uninstall
 
-Then remove the `sqrbx` and `sqrbx-rebuild` aliases from your shell config
-(`~/.bashrc`, `~/.zshrc`, or `~/Documents/PowerShell/Microsoft.PowerShell_profile.ps1`).
-Back up `~/squarebox/workspace` first if you need your code.
+Removes the container, image, and shell integration but **keeps**
+`~/squarebox` (including `workspace/`) so your code is safe by default.
+Pass `--purge` to also remove `~/squarebox`:
+
+    sqrbx-uninstall --purge
+
+A second confirmation is required if `~/squarebox/workspace` is non-empty.
+Pass `-y` (or `-Yes` on PowerShell) to skip all prompts for scripting.
+Idempotent: safe to re-run once uninstalled.
+
+**Windows (PowerShell 7+):**
+
+    sqrbx-uninstall                # keep ~/squarebox
+    sqrbx-uninstall -Purge         # also remove ~/squarebox
+    sqrbx-uninstall -Yes           # skip confirmations
+
+**Broken-state recovery** (e.g. shell functions are missing, or after partial
+install): run the script directly from the install directory:
+
+    ~/squarebox/uninstall.sh              # Linux / macOS / Git Bash
+    ~/squarebox/uninstall.ps1             # Windows PowerShell
+
+Start a new shell afterwards (or `exec bash` / `exec zsh`) so the `sqrbx` and
+`squarebox` functions are dropped from the current session.
 
 Make it your own
 -----------------
diff --git a/install.ps1 b/install.ps1
index a4f96ed..aaf679b 100644
--- a/install.ps1
+++ b/install.ps1
@@ -216,7 +216,7 @@ if (Test-Path $PROFILE) {
         if ($line -match '^# >>> squarebox >>>') { $skip = $true; continue }
         if ($line -match '^# <<< squarebox <<<') { $skip = $false; continue }
         if ($skip) { continue }
-        if ($line -match '^\s*function\s+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild)\s*(\{|$)') { continue }
+        if ($line -match '^\s*function\s+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)\s*(\{|$)') { continue }
         $filtered.Add($line)
     }
     Set-Content -Path $PROFILE -Value ($filtered -join "`n")
@@ -227,8 +227,15 @@ if (Test-Path $PROFILE) {
 $profileBlock = @'
 # >>> squarebox >>>
 # squarebox shell integration - managed by install.ps1.
-Remove-Item Alias:sqrbx, Alias:squarebox, Alias:sqrbx-rebuild, Alias:squarebox-rebuild -ErrorAction SilentlyContinue
+Remove-Item Alias:sqrbx, Alias:squarebox, Alias:sqrbx-rebuild, Alias:squarebox-rebuild, Alias:sqrbx-uninstall, Alias:squarebox-uninstall -ErrorAction SilentlyContinue
 function sqrbx {
+    # Dispatch subcommands (currently: uninstall) so 'sqrbx uninstall' is
+    # symmetric with the standalone sqrbx-uninstall function below.
+    if ($args.Count -gt 0 -and $args[0] -eq 'uninstall') {
+        $rest = if ($args.Count -gt 1) { $args[1..($args.Count - 1)] } else { @() }
+        & "__INSTALL_DIR__\uninstall.ps1" @rest
+        return
+    }
     # If the container was left running after an ungraceful exit (closed
     # terminal instead of 'exit'), attaching to PID1 bash drops you onto a
     # prompt it already printed to the dead TTY - blinking cursor, no output.
@@ -242,6 +249,8 @@ function sqrbx {
 function squarebox { sqrbx @args }
 function sqrbx-rebuild { & "__INSTALL_DIR__\install.ps1" @args }
 function squarebox-rebuild { sqrbx-rebuild @args }
+function sqrbx-uninstall { & "__INSTALL_DIR__\uninstall.ps1" @args }
+function squarebox-uninstall { sqrbx-uninstall @args }
 # <<< squarebox <<<
 '@
 $profileBlock = $profileBlock -replace '__INSTALL_DIR__', $InstallDir
diff --git a/install.sh b/install.sh
index e675bf5..61cc365 100755
--- a/install.sh
+++ b/install.sh
@@ -200,8 +200,15 @@ SQRBX_INIT="${HOME}/.squarebox-shell-init"
 cat > "$SQRBX_INIT" <<SQRBXEOF
 # Managed by squarebox install.sh — overwritten on every install.
 # Drop any stale aliases with these names so they don't shadow the functions.
-unalias sqrbx squarebox sqrbx-rebuild squarebox-rebuild 2>/dev/null || true
+unalias sqrbx squarebox sqrbx-rebuild squarebox-rebuild sqrbx-uninstall squarebox-uninstall 2>/dev/null || true
 sqrbx() {
+	# Dispatch subcommands (currently: uninstall) so \`sqrbx uninstall\` is
+	# symmetric with the standalone \`sqrbx-uninstall\` function below.
+	if [ "\${1:-}" = "uninstall" ]; then
+		shift
+		"${INSTALL_DIR}/uninstall.sh" "\$@"
+		return
+	fi
 	# If the container was left running after an ungraceful exit (closed
 	# terminal instead of \`exit\`), attaching to PID1 bash drops you onto a
 	# prompt it already printed to the dead TTY — blinking cursor, no
@@ -219,6 +226,8 @@ sqrbx() {
 squarebox() { sqrbx "\$@"; }
 sqrbx-rebuild() { "${INSTALL_DIR}/install.sh" "\$@"; }
 squarebox-rebuild() { sqrbx-rebuild "\$@"; }
+sqrbx-uninstall() { "${INSTALL_DIR}/uninstall.sh" "\$@"; }
+squarebox-uninstall() { sqrbx-uninstall "\$@"; }
 SQRBXEOF
 
 # Scrub legacy content from $SHELL_RC and append a fresh sentinel block that
@@ -229,8 +238,8 @@ if [ -f "$SHELL_RC" ]; then
 		/^# >>> squarebox >>>/ { skip=1; next }
 		/^# <<< squarebox <<</ { skip=0; next }
 		skip { next }
-		/^[[:space:]]*alias[[:space:]]+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild)=/ { next }
-		/^(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild)\(\)[[:space:]]*\{/ { next }
+		/^[[:space:]]*alias[[:space:]]+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)=/ { next }
+		/^(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)\(\)[[:space:]]*\{/ { next }
 		{ print }
 	' "$SHELL_RC" > "$_rc_tmp" && mv "$_rc_tmp" "$SHELL_RC"
 	_rc_tmp=""
diff --git a/uninstall.ps1 b/uninstall.ps1
new file mode 100644
index 0000000..19a1338
--- /dev/null
+++ b/uninstall.ps1
@@ -0,0 +1,255 @@
+#!/usr/bin/env pwsh
+<#
+.SYNOPSIS
+    Windows uninstaller for squarebox.
+.DESCRIPTION
+    Removes the squarebox container, image, PowerShell profile sentinel block,
+    and (optionally, via -Purge) the install directory.
+
+    Usage:
+      .\uninstall.ps1                       # remove container, image, profile block; keep ~/squarebox
+      .\uninstall.ps1 -Purge                # additionally rm -rf ~/squarebox
+      .\uninstall.ps1 -Yes                  # skip all confirmations
+      .\uninstall.ps1 -Runtime podman       # force podman
+
+    Broken-state recovery: run "%USERPROFILE%\squarebox\uninstall.ps1" directly
+    if the sqrbx-uninstall function is not available.
+
+    Idempotent: safe to run when nothing is installed.
+#>
+#Requires -Version 7.0
+
+param(
+    [switch]$Purge,
+    [Alias('y')][switch]$Yes,
+    [ValidateSet('docker', 'podman')]
+    [string]$Runtime
+)
+
+$ErrorActionPreference = 'Stop'
+
+$ImageName     = 'squarebox'
+$ContainerName = 'squarebox'
+$InstallDir    = Join-Path $env:USERPROFILE 'squarebox'
+
+function Abort([string]$msg) {
+    Write-Host "Error: $msg" -ForegroundColor Red
+    exit 1
+}
+
+function Test-RuntimeHasState([string]$rt) {
+    $names = & $rt ps -a --format '{{.Names}}' 2>$null
+    if ($LASTEXITCODE -eq 0 -and $names -and ($names -split "`n" | Where-Object { $_.Trim() -eq $ContainerName })) {
+        return $true
+    }
+    $images = & $rt images --format '{{.Repository}}' 2>$null
+    if ($LASTEXITCODE -eq 0 -and $images -and ($images -split "`n" | Where-Object { $_.Trim() -eq $ImageName })) {
+        return $true
+    }
+    return $false
+}
+
+# Runtime detection: -Runtime > $env:SQUAREBOX_RUNTIME > auto-detect. Auto-detect
+# prefers the runtime that has squarebox state; if both do, prefer docker and
+# warn about podman (matches install.ps1's preference).
+$hasDocker = [bool](Get-Command docker -ErrorAction SilentlyContinue)
+$hasPodman = [bool](Get-Command podman -ErrorAction SilentlyContinue)
+
+$SelectedRuntime  = $null
+$SecondaryRuntime = $null
+
+if ($Runtime) {
+    $SelectedRuntime = $Runtime
+    if (-not (Get-Command $SelectedRuntime -ErrorAction SilentlyContinue)) {
+        Abort "-Runtime $SelectedRuntime but '$SelectedRuntime' is not installed."
+    }
+} elseif ($env:SQUAREBOX_RUNTIME) {
+    if ($env:SQUAREBOX_RUNTIME -notin @('docker', 'podman')) {
+        Abort "SQUAREBOX_RUNTIME must be 'docker' or 'podman' (got '$($env:SQUAREBOX_RUNTIME)')."
+    }
+    $SelectedRuntime = $env:SQUAREBOX_RUNTIME
+    if (-not (Get-Command $SelectedRuntime -ErrorAction SilentlyContinue)) {
+        Abort "SQUAREBOX_RUNTIME=$SelectedRuntime but '$SelectedRuntime' is not installed."
+    }
+} else {
+    $dockerState = $hasDocker -and (Test-RuntimeHasState 'docker')
+    $podmanState = $hasPodman -and (Test-RuntimeHasState 'podman')
+
+    if ($dockerState -and $podmanState) {
+        $SelectedRuntime  = 'docker'
+        $SecondaryRuntime = 'podman'
+    } elseif ($dockerState) {
+        $SelectedRuntime = 'docker'
+    } elseif ($podmanState) {
+        $SelectedRuntime = 'podman'
+    } elseif ($hasDocker) {
+        $SelectedRuntime = 'docker'
+    } elseif ($hasPodman) {
+        $SelectedRuntime = 'podman'
+    }
+}
+
+# Probe state.
+$hasContainer = $false
+$hasImage     = $false
+if ($SelectedRuntime) {
+    $names = & $SelectedRuntime ps -a --format '{{.Names}}' 2>$null
+    if ($LASTEXITCODE -eq 0 -and $names) {
+        $hasContainer = [bool]($names -split "`n" | Where-Object { $_.Trim() -eq $ContainerName })
+    }
+    $images = & $SelectedRuntime images --format '{{.Repository}}' 2>$null
+    if ($LASTEXITCODE -eq 0 -and $images) {
+        $hasImage = [bool]($images -split "`n" | Where-Object { $_.Trim() -eq $ImageName })
+    }
+}
+
+$hasProfileBlock = $false
+if (Test-Path $PROFILE) {
+    $hasProfileBlock = [bool](Select-String -Path $PROFILE -Pattern '^# >>> squarebox >>>' -Quiet)
+    if (-not $hasProfileBlock) {
+        # Also scrub orphan function defs from a legacy install with no sentinel.
+        $hasProfileBlock = [bool](Select-String -Path $PROFILE -Pattern '^\s*function\s+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)\s*(\{|$)' -Quiet)
+    }
+}
+
+$hasInstallDir = Test-Path $InstallDir
+
+# Summary.
+Write-Host "squarebox uninstall"
+Write-Host "==================="
+Write-Host ""
+
+if ($SelectedRuntime) {
+    Write-Host "Container runtime: $SelectedRuntime"
+} else {
+    Write-Host "Container runtime: none detected (skipping container/image cleanup)"
+}
+
+if ($SecondaryRuntime) {
+    Write-Host ""
+    Write-Host "Note: squarebox state also detected in $SecondaryRuntime."
+    Write-Host "      This run will clean $SelectedRuntime only. To also clean ${SecondaryRuntime}:"
+    Write-Host "        `$env:SQUAREBOX_RUNTIME = '$SecondaryRuntime'; .\uninstall.ps1"
+}
+
+$anythingToDo = $false
+
+Write-Host ""
+Write-Host "Will remove:"
+if ($hasContainer)    { Write-Host "  - Container:      $ContainerName ($SelectedRuntime)"; $anythingToDo = $true }
+if ($hasImage)        { Write-Host "  - Image:          $ImageName ($SelectedRuntime)";     $anythingToDo = $true }
+if ($hasProfileBlock) { Write-Host "  - Profile block:  $PROFILE";                          $anythingToDo = $true }
+if ($Purge -and $hasInstallDir) {
+    Write-Host "  - Install dir:    $InstallDir"
+    $anythingToDo = $true
+}
+if (-not $anythingToDo) {
+    Write-Host "  (nothing)"
+}
+
+if (-not $Purge -and $hasInstallDir) {
+    Write-Host ""
+    Write-Host "Will KEEP:"
+    Write-Host "  - $InstallDir (re-run with -Purge to remove, including workspace)"
+}
+
+Write-Host ""
+
+if (-not $anythingToDo) {
+    Write-Host "Nothing to do - squarebox appears to be already uninstalled."
+    exit 0
+}
+
+# Confirmation.
+if (-not $Yes -and [System.Console]::IsInputRedirected) {
+    Abort "stdin is not a terminal; pass -Yes to run non-interactively."
+}
+
+if (-not $Yes) {
+    $answer = Read-Host "Proceed? [y/N]"
+    if ($answer -notmatch '^[yY]([eE][sS])?$') {
+        Write-Host "Aborted." -ForegroundColor Yellow
+        exit 1
+    }
+}
+
+if ($Purge -and $hasInstallDir -and -not $Yes) {
+    $workspaceDir = Join-Path $InstallDir 'workspace'
+    if (Test-Path $workspaceDir) {
+        $items = @(Get-ChildItem -Force -LiteralPath $workspaceDir -ErrorAction SilentlyContinue)
+        if ($items.Count -gt 0) {
+            Write-Host ""
+            Write-Host "Warning: $workspaceDir contains $($items.Count) item(s)." -ForegroundColor Yellow
+            Write-Host "         Purging will permanently delete them."
+            $answer = Read-Host "Really purge workspace? [y/N]"
+            if ($answer -notmatch '^[yY]([eE][sS])?$') {
+                Write-Host "Aborted." -ForegroundColor Yellow
+                exit 1
+            }
+        }
+    }
+}
+
+# Perform the work. Set-Location away from the install dir so a later remove
+# doesn't fail on "directory in use" (or succeed and leave the process in a
+# deleted cwd).
+Set-Location $env:USERPROFILE
+
+$removedContainer    = $false
+$removedImage        = $false
+$removedProfileBlock = $false
+$removedInstallDir   = $false
+
+if ($hasContainer) {
+    Write-Host "Stopping container..."
+    & $SelectedRuntime stop $ContainerName 2>$null | Out-Null
+    Write-Host "Removing container..."
+    & $SelectedRuntime rm -f $ContainerName 2>$null | Out-Null
+    if ($LASTEXITCODE -eq 0) { $removedContainer = $true }
+}
+
+if ($hasImage) {
+    Write-Host "Removing image..."
+    & $SelectedRuntime rmi -f $ImageName 2>$null | Out-Null
+    if ($LASTEXITCODE -eq 0) { $removedImage = $true }
+}
+
+# Scrub profile. Mirrors install.ps1's strip logic at install.ps1:211-223,
+# extended to match -uninstall function names.
+if ($hasProfileBlock -and (Test-Path $PROFILE)) {
+    $lines    = Get-Content $PROFILE
+    $filtered = [System.Collections.Generic.List[string]]::new()
+    $skip     = $false
+    foreach ($line in $lines) {
+        if ($line -match '^# >>> squarebox >>>') { $skip = $true; continue }
+        if ($line -match '^# <<< squarebox <<<') { $skip = $false; continue }
+        if ($skip) { continue }
+        if ($line -match '^\s*function\s+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)\s*(\{|$)') { continue }
+        $filtered.Add($line)
+    }
+    Set-Content -Path $PROFILE -Value ($filtered -join "`n")
+    $removedProfileBlock = $true
+}
+
+if ($Purge -and $hasInstallDir) {
+    Write-Host "Removing install directory..."
+    Remove-Item -Recurse -Force -LiteralPath $InstallDir
+    $removedInstallDir = $true
+}
+
+Write-Host ""
+Write-Host "Done."
+if ($removedContainer)    { Write-Host "  Removed container $ContainerName from $SelectedRuntime." }
+if ($removedImage)        { Write-Host "  Removed image $ImageName from $SelectedRuntime." }
+if ($removedProfileBlock) { Write-Host "  Scrubbed squarebox block from $PROFILE." }
+if ($removedInstallDir)   { Write-Host "  Removed $InstallDir." }
+
+if (-not $Purge -and $hasInstallDir) {
+    Write-Host ""
+    Write-Host "Kept $InstallDir (including workspace). Remove manually with:"
+    Write-Host "  Remove-Item -Recurse -Force $InstallDir"
+}
+
+Write-Host ""
+Write-Host "Note: sqrbx, squarebox, and related functions may still be defined in"
+Write-Host "      your current shell. Start a new PowerShell session to drop them."
diff --git a/uninstall.sh b/uninstall.sh
new file mode 100755
index 0000000..8516586
--- /dev/null
+++ b/uninstall.sh
@@ -0,0 +1,392 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+IMAGE_NAME="squarebox"
+CONTAINER_NAME="squarebox"
+
+# On MSYS2/Git Bash, HOME points to the MSYS home (/home/user) while the
+# install dir was placed under $USERPROFILE (C:/Users/user/squarebox). Mirror
+# install.sh's USER_HOME handling so --purge targets the right directory; the
+# shell init file and rc files still live under $HOME (where bash reads from).
+if [ -n "${USERPROFILE:-}" ]; then
+	USER_HOME="$(cygpath -m "$USERPROFILE" 2>/dev/null || true)"
+	if [ -z "$USER_HOME" ]; then
+		USER_HOME="${USERPROFILE//\\//}"
+		if [[ "$USER_HOME" =~ ^/([a-zA-Z])(/.*)$ ]]; then
+			USER_HOME="$(printf '%s' "${BASH_REMATCH[1]}" | tr '[:lower:]' '[:upper:]'):${BASH_REMATCH[2]}"
+		fi
+	fi
+else
+	USER_HOME="${HOME}"
+fi
+INSTALL_DIR="${USER_HOME}/squarebox"
+SHELL_INIT_FILE="${HOME}/.squarebox-shell-init"
+
+usage() {
+	cat <<'EOF'
+Usage: uninstall.sh [OPTIONS]
+
+Remove the squarebox container, image, and shell integration.
+
+Options:
+  --purge              Also remove the install directory (~/squarebox),
+                       including workspace/ and any host-side config under it.
+  -y, --yes            Skip all confirmation prompts (for scripting).
+  --runtime RUNTIME    Use docker or podman explicitly (default: auto-detect by
+                       looking for the squarebox container/image).
+  -h, --help           Show this help and exit.
+
+Environment:
+  SQUAREBOX_RUNTIME    Same as --runtime (the flag takes priority).
+
+By default, ~/squarebox is preserved so your workspace is not lost. Use --purge
+to remove it; a second confirmation is required if workspace/ is non-empty.
+EOF
+}
+
+PURGE=0
+YES=0
+RUNTIME_OVERRIDE=""
+
+while [ $# -gt 0 ]; do
+	case "$1" in
+		--purge) PURGE=1; shift ;;
+		-y|--yes) YES=1; shift ;;
+		--runtime=*) RUNTIME_OVERRIDE="${1#*=}"; shift ;;
+		--runtime)
+			if [ $# -lt 2 ]; then
+				echo "Error: --runtime requires a value (docker or podman)." >&2
+				exit 1
+			fi
+			RUNTIME_OVERRIDE="$2"
+			shift 2
+			;;
+		-h|--help) usage; exit 0 ;;
+		*) echo "Error: unknown option '$1'" >&2; usage >&2; exit 1 ;;
+	esac
+done
+
+# On MSYS2/Git Bash, disable automatic path conversion for container runtime
+# args (same rationale as install.sh's rt_cmd).
+rt_cmd() {
+	if [[ -n "${MSYSTEM:-}" ]]; then
+		MSYS_NO_PATHCONV=1 MSYS2_ARG_CONV_EXCL='*' "$RUNTIME" "$@"
+	else
+		"$RUNTIME" "$@"
+	fi
+}
+
+# Returns 0 if the given runtime has a squarebox container or image.
+_rt_has_state() {
+	local rt="$1" out
+	local msys_env=()
+	[[ -n "${MSYSTEM:-}" ]] && msys_env=(env MSYS_NO_PATHCONV=1 MSYS2_ARG_CONV_EXCL='*')
+	out="$("${msys_env[@]}" "$rt" ps -a --format '{{.Names}}' 2>/dev/null || true)"
+	printf '%s\n' "$out" | grep -qx "$CONTAINER_NAME" && return 0
+	out="$("${msys_env[@]}" "$rt" images --format '{{.Repository}}' 2>/dev/null || true)"
+	printf '%s\n' "$out" | grep -qx "$IMAGE_NAME" && return 0
+	return 1
+}
+
+# Detect runtime. Priority: --runtime > SQUAREBOX_RUNTIME > auto-detect by
+# looking for squarebox container/image. If both runtimes have state (unusual),
+# prefer docker (matching install.sh's preference) and warn about podman.
+_has_docker=0; command -v docker &>/dev/null && _has_docker=1
+_has_podman=0; command -v podman &>/dev/null && _has_podman=1
+
+RUNTIME=""
+SECONDARY_RUNTIME=""
+
+if [ -n "$RUNTIME_OVERRIDE" ]; then
+	case "$RUNTIME_OVERRIDE" in
+		docker|podman) RUNTIME="$RUNTIME_OVERRIDE" ;;
+		*) echo "Error: --runtime must be 'docker' or 'podman' (got '$RUNTIME_OVERRIDE')." >&2; exit 1 ;;
+	esac
+	if ! command -v "$RUNTIME" &>/dev/null; then
+		echo "Error: --runtime=$RUNTIME but '$RUNTIME' is not installed." >&2
+		exit 1
+	fi
+elif [ -n "${SQUAREBOX_RUNTIME:-}" ]; then
+	case "$SQUAREBOX_RUNTIME" in
+		docker|podman) RUNTIME="$SQUAREBOX_RUNTIME" ;;
+		*) echo "Error: SQUAREBOX_RUNTIME must be 'docker' or 'podman' (got '$SQUAREBOX_RUNTIME')." >&2; exit 1 ;;
+	esac
+	if ! command -v "$RUNTIME" &>/dev/null; then
+		echo "Error: SQUAREBOX_RUNTIME=$RUNTIME but '$RUNTIME' is not installed." >&2
+		exit 1
+	fi
+else
+	_docker_state=0
+	_podman_state=0
+	[ "$_has_docker" = 1 ] && _rt_has_state docker && _docker_state=1
+	[ "$_has_podman" = 1 ] && _rt_has_state podman && _podman_state=1
+
+	if [ "$_docker_state" = 1 ] && [ "$_podman_state" = 1 ]; then
+		RUNTIME="docker"
+		SECONDARY_RUNTIME="podman"
+	elif [ "$_docker_state" = 1 ]; then
+		RUNTIME="docker"
+	elif [ "$_podman_state" = 1 ]; then
+		RUNTIME="podman"
+	elif [ "$_has_docker" = 1 ]; then
+		RUNTIME="docker"
+	elif [ "$_has_podman" = 1 ]; then
+		RUNTIME="podman"
+	fi
+fi
+
+# Probe state for the summary.
+has_container=0
+has_image=0
+if [ -n "$RUNTIME" ]; then
+	if rt_cmd ps -a --format '{{.Names}}' 2>/dev/null | grep -qx "$CONTAINER_NAME"; then
+		has_container=1
+	fi
+	if rt_cmd images --format '{{.Repository}}' 2>/dev/null | grep -qx "$IMAGE_NAME"; then
+		has_image=1
+	fi
+fi
+
+has_shell_init=0
+[ -f "$SHELL_INIT_FILE" ] && has_shell_init=1
+
+# An rc file needs scrubbing if it has a squarebox sentinel block OR orphan
+# alias/function defs from a legacy install. Same patterns install.sh uses to
+# decide whether its scrub will change anything.
+_rc_scrub_pattern='^# >>> squarebox >>>|^[[:space:]]*alias[[:space:]]+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)=|^(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)\(\)[[:space:]]*\{'
+
+_rc_files_to_scrub=()
+for f in "${HOME}/.bashrc" "${HOME}/.zshrc" "${HOME}/.bash_profile"; do
+	if [ -f "$f" ] && grep -qE "$_rc_scrub_pattern" "$f" 2>/dev/null; then
+		_rc_files_to_scrub+=("$f")
+	fi
+done
+
+# install.sh appends this exact 2-line snippet to ~/.bash_profile on Git Bash
+# so a login shell picks up the sentinel in ~/.bashrc. Remove it on match.
+_bash_profile="${HOME}/.bash_profile"
+has_bash_profile_source_line=0
+if [ -f "$_bash_profile" ] \
+	&& grep -qxF '# Source .bashrc for aliases and functions' "$_bash_profile" 2>/dev/null \
+	&& grep -qxF '[ -f "$HOME/.bashrc" ] && . "$HOME/.bashrc"' "$_bash_profile" 2>/dev/null; then
+	has_bash_profile_source_line=1
+fi
+
+has_install_dir=0
+[ -d "$INSTALL_DIR" ] && has_install_dir=1
+
+# Summary.
+echo "squarebox uninstall"
+echo "==================="
+echo ""
+
+if [ -n "$RUNTIME" ]; then
+	echo "Container runtime: $RUNTIME"
+else
+	echo "Container runtime: none detected (skipping container/image cleanup)"
+fi
+
+if [ -n "$SECONDARY_RUNTIME" ]; then
+	echo ""
+	echo "Note: squarebox state also detected in $SECONDARY_RUNTIME."
+	echo "      This run will clean $RUNTIME only. To also clean $SECONDARY_RUNTIME, run again with:"
+	echo "        SQUAREBOX_RUNTIME=$SECONDARY_RUNTIME $0"
+fi
+
+anything_to_do=0
+
+echo ""
+echo "Will remove:"
+if [ "$has_container" = 1 ]; then
+	echo "  - Container:      $CONTAINER_NAME ($RUNTIME)"
+	anything_to_do=1
+fi
+if [ "$has_image" = 1 ]; then
+	echo "  - Image:          $IMAGE_NAME ($RUNTIME)"
+	anything_to_do=1
+fi
+if [ "$has_shell_init" = 1 ]; then
+	echo "  - Shell init:     $SHELL_INIT_FILE"
+	anything_to_do=1
+fi
+for f in "${_rc_files_to_scrub[@]}"; do
+	echo "  - Sentinel block: $f"
+	anything_to_do=1
+done
+if [ "$has_bash_profile_source_line" = 1 ]; then
+	echo "  - Source snippet: $_bash_profile"
+	anything_to_do=1
+fi
+if [ "$PURGE" = 1 ] && [ "$has_install_dir" = 1 ]; then
+	echo "  - Install dir:    $INSTALL_DIR"
+	anything_to_do=1
+fi
+if [ "$anything_to_do" = 0 ]; then
+	echo "  (nothing)"
+fi
+
+if [ "$PURGE" = 0 ] && [ "$has_install_dir" = 1 ]; then
+	echo ""
+	echo "Will KEEP:"
+	echo "  - $INSTALL_DIR (re-run with --purge to remove, including workspace)"
+fi
+
+echo ""
+
+if [ "$anything_to_do" = 0 ]; then
+	echo "Nothing to do - squarebox appears to be already uninstalled."
+	exit 0
+fi
+
+# Confirmation. Non-interactive stdin without -y is an error, otherwise the
+# read would hang or consume a subsequent line the caller didn't intend.
+if [ "$YES" = 0 ] && [ ! -t 0 ]; then
+	echo "Error: stdin is not a terminal; pass -y to run non-interactively." >&2
+	exit 1
+fi
+
+if [ "$YES" = 0 ]; then
+	printf "Proceed? [y/N]: "
+	read -r _answer
+	case "$_answer" in
+		[yY]|[yY][eE][sS]) ;;
+		*) echo "Aborted." >&2; exit 1 ;;
+	esac
+fi
+
+if [ "$PURGE" = 1 ] && [ "$has_install_dir" = 1 ] && [ "$YES" = 0 ]; then
+	_workspace_dir="${INSTALL_DIR}/workspace"
+	if [ -d "$_workspace_dir" ]; then
+		_count=$(find "$_workspace_dir" -mindepth 1 -maxdepth 1 2>/dev/null | wc -l | tr -d ' ')
+		if [ "$_count" -gt 0 ]; then
+			echo ""
+			echo "Warning: $_workspace_dir contains $_count item(s)."
+			echo "         Purging will permanently delete them."
+			printf "Really purge workspace? [y/N]: "
+			read -r _answer
+			case "$_answer" in
+				[yY]|[yY][eE][sS]) ;;
+				*) echo "Aborted." >&2; exit 1 ;;
+			esac
+		fi
+	fi
+fi
+
+# Perform the work. cd away first so we can safely rm INSTALL_DIR if --purge
+# and so we don't trip over a deleted cwd on return.
+cd /
+
+removed_container=0
+removed_image=0
+removed_shell_init=0
+removed_rc_entries=()
+removed_bash_profile_source=0
+removed_install_dir=0
+
+if [ "$has_container" = 1 ]; then
+	echo "Stopping container..."
+	rt_cmd stop "$CONTAINER_NAME" >/dev/null 2>&1 || true
+	echo "Removing container..."
+	if rt_cmd rm -f "$CONTAINER_NAME" >/dev/null 2>&1; then
+		removed_container=1
+	fi
+fi
+
+if [ "$has_image" = 1 ]; then
+	echo "Removing image..."
+	if rt_cmd rmi -f "$IMAGE_NAME" >/dev/null 2>&1; then
+		removed_image=1
+	fi
+fi
+
+if [ "$has_shell_init" = 1 ]; then
+	rm -f "$SHELL_INIT_FILE"
+	removed_shell_init=1
+fi
+
+# Same scrub as install.sh's awk at install.sh:228-235, extended to also match
+# sqrbx-uninstall / squarebox-uninstall legacy defs. Keeping this in sync with
+# install.sh is manual for now; consolidating into a shared helper is flagged
+# as future work.
+_scrub_rc() {
+	local rc="$1" tmp
+	[ -f "$rc" ] || return 0
+	tmp="$(mktemp "${rc}.sqrbx.XXXXXX")"
+	awk '
+		/^# >>> squarebox >>>/ { skip=1; next }
+		/^# <<< squarebox <<</ { skip=0; next }
+		skip { next }
+		/^[[:space:]]*alias[[:space:]]+(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)=/ { next }
+		/^(sqrbx|squarebox|sqrbx-rebuild|squarebox-rebuild|sqrbx-uninstall|squarebox-uninstall)\(\)[[:space:]]*\{/ { next }
+		{ print }
+	' "$rc" > "$tmp" && mv "$tmp" "$rc"
+}
+
+for f in "${_rc_files_to_scrub[@]}"; do
+	_scrub_rc "$f"
+	removed_rc_entries+=("$f")
+done
+
+# Scrub the Git Bash .bash_profile 2-line source snippet. Exact match only so
+# we don't touch user-authored .bashrc source lines.
+if [ "$has_bash_profile_source_line" = 1 ]; then
+	_tmp="$(mktemp "${_bash_profile}.sqrbx.XXXXXX")"
+	awk '
+		$0 == "# Source .bashrc for aliases and functions" {
+			if ((getline nextline) > 0) {
+				if (nextline == "[ -f \"$HOME/.bashrc\" ] && . \"$HOME/.bashrc\"") {
+					next
+				}
+				print
+				print nextline
+				next
+			}
+			print
+			next
+		}
+		{ print }
+	' "$_bash_profile" > "$_tmp" && mv "$_tmp" "$_bash_profile"
+	removed_bash_profile_source=1
+fi
+
+if [ "$PURGE" = 1 ] && [ "$has_install_dir" = 1 ]; then
+	echo "Removing install directory..."
+	# On Linux installs where host uid != 1000, files under workspace/ and
+	# .config/ may be owned by the container's dev user (uid 1000). Fall back
+	# to sudo if a plain rm fails for permission reasons.
+	if ! rm -rf "$INSTALL_DIR" 2>/dev/null; then
+		if [ "$(id -u)" -eq 0 ]; then
+			rm -rf "$INSTALL_DIR"
+		elif command -v sudo &>/dev/null; then
+			echo "Some files owned by uid 1000 (container's dev user); using sudo..."
+			sudo rm -rf "$INSTALL_DIR"
+		else
+			echo "Error: failed to remove $INSTALL_DIR - some files may be owned by uid 1000." >&2
+			echo "       Run: sudo rm -rf $INSTALL_DIR" >&2
+			exit 1
+		fi
+	fi
+	removed_install_dir=1
+fi
+
+echo ""
+echo "Done."
+[ "$removed_container" = 1 ] && echo "  Removed container $CONTAINER_NAME from $RUNTIME."
+[ "$removed_image" = 1 ]     && echo "  Removed image $IMAGE_NAME from $RUNTIME."
+[ "$removed_shell_init" = 1 ] && echo "  Removed $SHELL_INIT_FILE."
+for f in "${removed_rc_entries[@]}"; do
+	echo "  Scrubbed squarebox block from $f."
+done
+[ "$removed_bash_profile_source" = 1 ] && echo "  Scrubbed .bashrc source snippet from $_bash_profile."
+[ "$removed_install_dir" = 1 ]         && echo "  Removed $INSTALL_DIR."
+
+if [ "$PURGE" = 0 ] && [ "$has_install_dir" = 1 ]; then
+	echo ""
+	echo "Kept $INSTALL_DIR (including workspace). Remove manually with:"
+	echo "  rm -rf $INSTALL_DIR"
+fi
+
+echo ""
+echo "Note: sqrbx, squarebox, and related functions may still be defined in"
+echo "      your current shell. Start a new shell (or 'exec bash' / 'exec zsh')"
+echo "      to drop them."