diff --git a/.antigravity-plugin/scripts/monk-launcher-telemetry.sh b/.antigravity-plugin/scripts/monk-launcher-telemetry.sh
index 1ae5279..fed7d03 100755
--- a/.antigravity-plugin/scripts/monk-launcher-telemetry.sh
+++ b/.antigravity-plugin/scripts/monk-launcher-telemetry.sh
@@ -92,16 +92,35 @@ monk_emit_launcher_event() {
   _osa="$(uname -m 2>/dev/null || printf unknown)"
   _plat="$(printf '%s' "$_osn" | tr '[:upper:]' '[:lower:]')"
 
-  # Strip characters that would break the hand-built JSON.
-  _msan() { printf '%s' "$1" | tr -d '"\\' | tr -d '\n\r'; }
+  # Encode a shell string as JSON string content. LC_ALL=C makes awk's %c
+  # byte-preserving, so UTF-8 survives while every U+0000-U+001F byte that JSON
+  # forbids is escaped. POSIX od/awk keep this usable before the agent exists.
+  _mjson() {
+    printf '%s' "$1" |
+      LC_ALL=C od -An -v -t u1 2>/dev/null |
+      LC_ALL=C awk '{
+        for (i = 1; i <= NF; i++) {
+          b = $i + 0
+          if (b == 34)       printf "\\\""
+          else if (b == 92)  printf "\\\\"
+          else if (b == 8)   printf "\\b"
+          else if (b == 9)   printf "\\t"
+          else if (b == 10)  printf "\\n"
+          else if (b == 12)  printf "\\f"
+          else if (b == 13)  printf "\\r"
+          else if (b < 32)   printf "\\u%04x", b
+          else               printf "%c", b
+        }
+      }'
+  }
 
   _payload="$(
     printf '{"api_key":"%s","event":"plugin_launcher_started","distinct_id":"%s","properties":{"launch_client":"%s","host_client":"%s","client":"%s","first_start":%s,"agent_installed":%s,"client_id_source":"%s","plugin_version":"%s","ide_version":"%s","platform":"%s","os_arch":"%s","source":"monk-plugin-launcher"}}' \
-      "$(_msan "$_ph_key")" "$(_msan "$_cid")" \
-      "$(_msan "$_mlc")" "$(_msan "$_mlc")" "$(_msan "$_mlc")" \
+      "$(_mjson "$_ph_key")" "$(_mjson "$_cid")" \
+      "$(_mjson "$_mlc")" "$(_mjson "$_mlc")" "$(_mjson "$_mlc")" \
       "$_first_start" "$_agent_installed" "$_cid_src" \
-      "$(_msan "$_pv")" "$(_msan "$_mlc_ide")" \
-      "$(_msan "$_plat")" "$(_msan "$_osa")"
+      "$(_mjson "$_pv")" "$(_mjson "$_mlc_ide")" \
+      "$(_mjson "$_plat")" "$(_mjson "$_osa")"
   )"
 
   if command -v curl >/dev/null 2>&1; then
diff --git a/.github/workflows/install-e2e.yml b/.github/workflows/install-e2e.yml
index 52ce071..913ec87 100644
--- a/.github/workflows/install-e2e.yml
+++ b/.github/workflows/install-e2e.yml
@@ -62,6 +62,10 @@ jobs:
         shell: bash
         run: ./tests/start-monk-agent-readiness-timeout.sh
 
+      - name: Check launcher telemetry JSON escaping
+        shell: bash
+        run: ./tests/monk-launcher-telemetry-json.sh
+
   windows:
     name: windows-latest
     runs-on: windows-latest
diff --git a/plugins/monk/scripts/monk-launcher-telemetry.sh b/plugins/monk/scripts/monk-launcher-telemetry.sh
index 1ae5279..fed7d03 100755
--- a/plugins/monk/scripts/monk-launcher-telemetry.sh
+++ b/plugins/monk/scripts/monk-launcher-telemetry.sh
@@ -92,16 +92,35 @@ monk_emit_launcher_event() {
   _osa="$(uname -m 2>/dev/null || printf unknown)"
   _plat="$(printf '%s' "$_osn" | tr '[:upper:]' '[:lower:]')"
 
-  # Strip characters that would break the hand-built JSON.
-  _msan() { printf '%s' "$1" | tr -d '"\\' | tr -d '\n\r'; }
+  # Encode a shell string as JSON string content. LC_ALL=C makes awk's %c
+  # byte-preserving, so UTF-8 survives while every U+0000-U+001F byte that JSON
+  # forbids is escaped. POSIX od/awk keep this usable before the agent exists.
+  _mjson() {
+    printf '%s' "$1" |
+      LC_ALL=C od -An -v -t u1 2>/dev/null |
+      LC_ALL=C awk '{
+        for (i = 1; i <= NF; i++) {
+          b = $i + 0
+          if (b == 34)       printf "\\\""
+          else if (b == 92)  printf "\\\\"
+          else if (b == 8)   printf "\\b"
+          else if (b == 9)   printf "\\t"
+          else if (b == 10)  printf "\\n"
+          else if (b == 12)  printf "\\f"
+          else if (b == 13)  printf "\\r"
+          else if (b < 32)   printf "\\u%04x", b
+          else               printf "%c", b
+        }
+      }'
+  }
 
   _payload="$(
     printf '{"api_key":"%s","event":"plugin_launcher_started","distinct_id":"%s","properties":{"launch_client":"%s","host_client":"%s","client":"%s","first_start":%s,"agent_installed":%s,"client_id_source":"%s","plugin_version":"%s","ide_version":"%s","platform":"%s","os_arch":"%s","source":"monk-plugin-launcher"}}' \
-      "$(_msan "$_ph_key")" "$(_msan "$_cid")" \
-      "$(_msan "$_mlc")" "$(_msan "$_mlc")" "$(_msan "$_mlc")" \
+      "$(_mjson "$_ph_key")" "$(_mjson "$_cid")" \
+      "$(_mjson "$_mlc")" "$(_mjson "$_mlc")" "$(_mjson "$_mlc")" \
       "$_first_start" "$_agent_installed" "$_cid_src" \
-      "$(_msan "$_pv")" "$(_msan "$_mlc_ide")" \
-      "$(_msan "$_plat")" "$(_msan "$_osa")"
+      "$(_mjson "$_pv")" "$(_mjson "$_mlc_ide")" \
+      "$(_mjson "$_plat")" "$(_mjson "$_osa")"
   )"
 
   if command -v curl >/dev/null 2>&1; then
diff --git a/scripts/monk-launcher-telemetry.sh b/scripts/monk-launcher-telemetry.sh
index 1ae5279..fed7d03 100755
--- a/scripts/monk-launcher-telemetry.sh
+++ b/scripts/monk-launcher-telemetry.sh
@@ -92,16 +92,35 @@ monk_emit_launcher_event() {
   _osa="$(uname -m 2>/dev/null || printf unknown)"
   _plat="$(printf '%s' "$_osn" | tr '[:upper:]' '[:lower:]')"
 
-  # Strip characters that would break the hand-built JSON.
-  _msan() { printf '%s' "$1" | tr -d '"\\' | tr -d '\n\r'; }
+  # Encode a shell string as JSON string content. LC_ALL=C makes awk's %c
+  # byte-preserving, so UTF-8 survives while every U+0000-U+001F byte that JSON
+  # forbids is escaped. POSIX od/awk keep this usable before the agent exists.
+  _mjson() {
+    printf '%s' "$1" |
+      LC_ALL=C od -An -v -t u1 2>/dev/null |
+      LC_ALL=C awk '{
+        for (i = 1; i <= NF; i++) {
+          b = $i + 0
+          if (b == 34)       printf "\\\""
+          else if (b == 92)  printf "\\\\"
+          else if (b == 8)   printf "\\b"
+          else if (b == 9)   printf "\\t"
+          else if (b == 10)  printf "\\n"
+          else if (b == 12)  printf "\\f"
+          else if (b == 13)  printf "\\r"
+          else if (b < 32)   printf "\\u%04x", b
+          else               printf "%c", b
+        }
+      }'
+  }
 
   _payload="$(
     printf '{"api_key":"%s","event":"plugin_launcher_started","distinct_id":"%s","properties":{"launch_client":"%s","host_client":"%s","client":"%s","first_start":%s,"agent_installed":%s,"client_id_source":"%s","plugin_version":"%s","ide_version":"%s","platform":"%s","os_arch":"%s","source":"monk-plugin-launcher"}}' \
-      "$(_msan "$_ph_key")" "$(_msan "$_cid")" \
-      "$(_msan "$_mlc")" "$(_msan "$_mlc")" "$(_msan "$_mlc")" \
+      "$(_mjson "$_ph_key")" "$(_mjson "$_cid")" \
+      "$(_mjson "$_mlc")" "$(_mjson "$_mlc")" "$(_mjson "$_mlc")" \
       "$_first_start" "$_agent_installed" "$_cid_src" \
-      "$(_msan "$_pv")" "$(_msan "$_mlc_ide")" \
-      "$(_msan "$_plat")" "$(_msan "$_osa")"
+      "$(_mjson "$_pv")" "$(_mjson "$_mlc_ide")" \
+      "$(_mjson "$_plat")" "$(_mjson "$_osa")"
   )"
 
   if command -v curl >/dev/null 2>&1; then
diff --git a/tests/monk-launcher-telemetry-json.sh b/tests/monk-launcher-telemetry-json.sh
new file mode 100755
index 0000000..532b8ab
--- /dev/null
+++ b/tests/monk-launcher-telemetry-json.sh
@@ -0,0 +1,79 @@
+#!/usr/bin/env sh
+# Regression coverage for #179: launcher telemetry must emit valid JSON without
+# losing quotes, slashes, controls, or UTF-8 bytes from dynamic properties.
+set -eu
+
+repo_root="$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)"
+work_dir="$(mktemp -d)"
+trap 'rm -rf "$work_dir"' EXIT HUP INT TERM
+capture_path="$work_dir/payload.json"
+
+curl() {
+  _test_payload=""
+  while [ "$#" -gt 0 ]; do
+    if [ "$1" = "-d" ]; then
+      shift
+      _test_payload="$1"
+    fi
+    shift
+  done
+  printf '%s' "$_test_payload" >"$capture_path"
+}
+
+# shellcheck source=../scripts/monk-launcher-telemetry.sh
+. "$repo_root/scripts/monk-launcher-telemetry.sh"
+
+client="$(printf 'codex"\\\tline\nctrl\001<caf\303\251>&end')"
+ide_version="$(printf 'v1\r\f\b\002done')"
+plugin_version="$(printf 'plugin"\\\t\n\003<caf\303\251>')"
+posthog_key="$(printf 'key"\\\t\004end')"
+
+HOME="$work_dir/home"
+MONK_AGENT_HOME="$work_dir/monk"
+MONK_AGENT_INSTALL_DIR="$work_dir/bin"
+MONK_POSTHOG_HOST="https://capture.invalid"
+MONK_POSTHOG_KEY="$posthog_key"
+MONK_PLUGIN_VERSION="$plugin_version"
+export HOME MONK_AGENT_HOME MONK_AGENT_INSTALL_DIR
+export MONK_POSTHOG_HOST MONK_POSTHOG_KEY MONK_PLUGIN_VERSION
+export client ide_version plugin_version posthog_key capture_path
+
+monk_emit_launcher_event "$client" "$ide_version"
+wait
+test -s "$capture_path"
+
+if [ -z "${PYTHON:-}" ]; then
+  if command -v python3 >/dev/null 2>&1; then
+    PYTHON=python3
+  elif command -v python >/dev/null 2>&1; then
+    PYTHON=python
+  else
+    echo "python is required to validate the captured JSON" >&2
+    exit 1
+  fi
+fi
+
+"$PYTHON" - <<'PY'
+import json
+import os
+
+with open(os.environ["capture_path"], encoding="utf-8") as stream:
+    payload = json.load(stream)
+
+properties = payload["properties"]
+assert payload["api_key"] == os.environ["posthog_key"]
+assert properties["launch_client"] == os.environ["client"]
+assert properties["host_client"] == os.environ["client"]
+assert properties["client"] == os.environ["client"]
+assert properties["plugin_version"] == os.environ["plugin_version"]
+assert properties["ide_version"] == os.environ["ide_version"]
+assert properties["first_start"] is True
+assert properties["agent_installed"] is False
+PY
+
+cmp "$repo_root/scripts/monk-launcher-telemetry.sh" \
+  "$repo_root/plugins/monk/scripts/monk-launcher-telemetry.sh"
+cmp "$repo_root/scripts/monk-launcher-telemetry.sh" \
+  "$repo_root/.antigravity-plugin/scripts/monk-launcher-telemetry.sh"
+
+printf 'launcher_telemetry_json_status=pass\n'