diff --git a/scripts/install.ps1 b/scripts/install.ps1
index 3469a70..ac8b616 100644
--- a/scripts/install.ps1
+++ b/scripts/install.ps1
@@ -7,6 +7,7 @@
         irm https://agentkey.app/install.ps1 | iex
         & ([scriptblock]::Create((irm https://agentkey.app/install.ps1))) -Yes
         & ([scriptblock]::Create((irm https://agentkey.app/install.ps1))) -Only "claude-code,cursor"
+        & ([scriptblock]::Create((irm https://agentkey.app/install.ps1))) -NoTelemetry
 
     Behavior mirrors install.sh: checks Node >= 18 (installs via winget/scoop/choco),
     auto-detects which AI agents are installed and runs `npx skills add` for them,
@@ -28,6 +29,7 @@ param(
     [switch]$ForceMcp,
     [switch]$SkipSkill,
     [switch]$SkipMcp,
+    [switch]$NoTelemetry,
     [switch]$Help
 )
 
@@ -159,6 +161,9 @@ Parameters:
   -ForceMcp         Re-run MCP auth even if AgentKey is already configured
   -SkipSkill        Skip the skill install step (only run MCP auth)
   -SkipMcp          Skip the MCP auth step (only install the skill)
+  -NoTelemetry      Disable anonymous usage telemetry (writes
+                    %USERPROFILE%\.config\agentkey\telemetry-disabled so
+                    the skill stays opted-out across runs)
   -Help             Show this help
 
 Behavior:
@@ -213,6 +218,19 @@ else {
 }
 Write-Ok "Mode: $Mode"
 
+# Resolve telemetry intent: -NoTelemetry overrides everything; existing
+# %USERPROFILE%\.config\agentkey\telemetry-disabled file means already-opted-out.
+$TelemetryOptOutFile = Join-Path $env:USERPROFILE '.config\agentkey\telemetry-disabled'
+if ($NoTelemetry) {
+    New-Item -ItemType Directory -Path (Split-Path $TelemetryOptOutFile) -Force | Out-Null
+    New-Item -ItemType File -Path $TelemetryOptOutFile -Force | Out-Null
+    Write-Ok 'Telemetry: disabled (-NoTelemetry)'
+} elseif (Test-Path -LiteralPath $TelemetryOptOutFile) {
+    Write-Ok "Telemetry: disabled ($TelemetryOptOutFile exists)"
+} else {
+    Write-Info 'Telemetry: anonymous usage stats enabled (re-run with -NoTelemetry to opt out)'
+}
+
 # Node check
 function Get-NodeMajor {
     try {
@@ -357,6 +375,34 @@ if ($SkipMcp) {
     }
     Write-Host ''
 
+    # Telemetry context for install_completed. Opt-out is honored at the
+    # SOURCE: when AGENTKEY_TELEMETRY=0, no other context env vars are
+    # exported — hostname-derived fingerprint, agent lists, and installer
+    # flags are never computed nor passed to the child `npx @agentkey/mcp`
+    # process. The server treats AGENTKEY_TELEMETRY=0 as a hard skip.
+    if ($NoTelemetry -or (Test-Path -LiteralPath $TelemetryOptOutFile)) {
+        $env:AGENTKEY_TELEMETRY = '0'
+    } else {
+        $env:AGENTKEY_TELEMETRY = '1'
+
+        $_hn    = [System.Net.Dns]::GetHostName()
+        $_user  = $env:USERNAME
+        $_input = "$_hn|windows|$_user"
+        $_bytes = [System.Text.Encoding]::UTF8.GetBytes($_input)
+        $_sha   = [System.Security.Cryptography.SHA256]::Create()
+        $_hash  = ($_sha.ComputeHash($_bytes) | ForEach-Object { $_.ToString('x2') }) -join ''
+        $DeviceFingerprint = $_hash.Substring(0, 16)
+
+        $DetectedAgents = Get-DetectedAgents
+        if (-not (Get-Variable -Name targets -Scope Script -ErrorAction SilentlyContinue)) { $targets = @() }
+
+        $env:AGENTKEY_INSTALL_SOURCE     = 'one_liner'
+        $env:AGENTKEY_DETECTED_AGENTS    = ($DetectedAgents -join ',')
+        $env:AGENTKEY_SELECTED_AGENTS    = ($targets -join ',')
+        $env:AGENTKEY_INSTALLER_FLAGS    = ($PSBoundParameters.Keys | ForEach-Object { "-$_" }) -join ','
+        $env:AGENTKEY_DEVICE_FINGERPRINT = $DeviceFingerprint
+    }
+
     & npx -y $McpPackage @authArgs
     if ($LASTEXITCODE -ne 0) {
         Write-Err 'MCP auth failed.'
diff --git a/scripts/install.sh b/scripts/install.sh
index 30009dc..4c1e8c3 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -111,6 +111,9 @@ Options:
   --force-mcp         Re-run MCP auth even if AgentKey is already configured
   --skip-skill        Skip the skill install step (only run MCP auth)
   --skip-mcp          Skip the MCP auth step (only install the skill)
+  --no-telemetry      Disable anonymous usage telemetry (writes
+                      ~/.config/agentkey/telemetry-disabled so the skill
+                      stays opted-out across runs)
   -h, --help          Show this help
 
 Behavior:
@@ -237,6 +240,26 @@ install_node() {
     ui_ok "Node.js installed"
 }
 
+# Compute a stable per-device fingerprint for install_completed dedup.
+# spec §6.3: sha256(hostname+platform+username)[:16]. Falls back to a random
+# value if neither sha256sum nor shasum is available (extremely rare).
+compute_device_fingerprint() {
+    local platform="$1"
+    local hn user input hash
+    hn="$(hostname 2>/dev/null || echo "")"
+    user="${USER:-$(id -un 2>/dev/null || echo "")}"
+    input="$hn|$platform|$user"
+    if command -v sha256sum >/dev/null 2>&1; then
+        hash="$(printf '%s' "$input" | sha256sum | cut -c1-16)"
+    elif command -v shasum >/dev/null 2>&1; then
+        hash="$(printf '%s' "$input" | shasum -a 256 | cut -c1-16)"
+    else
+        # Last resort: use $RANDOM. Won't dedup across runs but won't crash.
+        hash="rnd$(printf '%04x%04x%04x' "$RANDOM" "$RANDOM" "$RANDOM")"
+    fi
+    printf '%s' "$hash"
+}
+
 # ──────────────────────────────────────────────────────────────────────────
 # main — wraps the entire procedural body so that under `curl | bash`
 # bash finishes reading the script before any fd-rebinding happens.
@@ -256,6 +279,11 @@ main() {
     # `set -u` happy.
     FORCE_REMOTE=false
     FORCE_LOCAL=false
+    local NO_TELEMETRY=false
+
+    # Snapshot original args before the parse loop shifts them away — needed
+    # later for AGENTKEY_INSTALLER_FLAGS env passthrough.
+    local _orig_args=("$@")
 
     while [ $# -gt 0 ]; do
         case "$1" in
@@ -270,6 +298,7 @@ main() {
             --force-mcp)       FORCE_MCP=true; shift ;;
             --skip-skill)      SKIP_SKILL=true; shift ;;
             --skip-mcp)        SKIP_MCP=true; shift ;;
+            --no-telemetry)    NO_TELEMETRY=true; shift ;;
             -h|--help)         PRINT_HELP=true; shift ;;
             *)                 ui_warn "Unknown argument: $1"; shift ;;
         esac
@@ -332,6 +361,19 @@ main() {
     fi
     ui_ok "Mode: $MODE"
 
+    # Resolve telemetry intent: --no-telemetry overrides everything; existing
+    # ~/.config/agentkey/telemetry-disabled file means already-opted-out.
+    local TELEMETRY_OPT_OUT_FILE="$HOME/.config/agentkey/telemetry-disabled"
+    if $NO_TELEMETRY; then
+        mkdir -p "$(dirname "$TELEMETRY_OPT_OUT_FILE")" 2>/dev/null || true
+        touch "$TELEMETRY_OPT_OUT_FILE" 2>/dev/null || true
+        ui_ok "Telemetry: disabled (--no-telemetry)"
+    elif [ -f "$TELEMETRY_OPT_OUT_FILE" ]; then
+        ui_ok "Telemetry: disabled (~/.config/agentkey/telemetry-disabled exists)"
+    else
+        ui_info "Telemetry: anonymous usage stats enabled (re-run with --no-telemetry to opt out)"
+    fi
+
     # Node check
     local NODE_OK=false NODE_VERSION NODE_MAJOR
     if command -v node >/dev/null 2>&1; then
@@ -471,6 +513,27 @@ main() {
         fi
         echo
 
+        # Telemetry context for `install_completed`. Opt-out is honored at
+        # the SOURCE: when AGENTKEY_TELEMETRY=0, no other context env vars
+        # are exported — hostname-derived fingerprint, agent lists, and
+        # installer flags are never computed nor passed to the child
+        # `npx @agentkey/mcp` process. The server treats AGENTKEY_TELEMETRY=0
+        # as a hard skip.
+        if $NO_TELEMETRY || [ -f "$TELEMETRY_OPT_OUT_FILE" ]; then
+            export AGENTKEY_TELEMETRY=0
+        else
+            export AGENTKEY_TELEMETRY=1
+            local _flags=""
+            for _f in "${_orig_args[@]:-}"; do
+                _flags="${_flags:+$_flags,}$_f"
+            done
+            export AGENTKEY_INSTALL_SOURCE="one_liner"
+            export AGENTKEY_DETECTED_AGENTS="$(detect_agents)"
+            export AGENTKEY_SELECTED_AGENTS="${TARGETS:-}"
+            export AGENTKEY_INSTALLER_FLAGS="$_flags"
+            export AGENTKEY_DEVICE_FINGERPRINT="$(compute_device_fingerprint "$PLATFORM")"
+        fi
+
         if ! npx -y "$MCP_PACKAGE" "${AUTH_ARGS[@]}"; then
             ui_error "MCP auth failed."
             ui_muted "Retry manually:  npx -y $MCP_PACKAGE ${AUTH_ARGS[*]}"