diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6494759e3e0f..fd2a5f3c3980 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -127,6 +127,9 @@ jobs:
       - name: Validate cmux profiling support scripts
         run: ./tests/test_start_cmux_profiling.sh
 
+      - name: Validate bundled provider runtime guard
+        run: ./tests/test_bundled_provider_runtime_guard.sh
+
       - name: Validate Xcode SourcePackages cache sanitizer
         run: python3 tests/test_ci_sanitize_xcode_source_packages_cache.py
 
@@ -1379,6 +1382,8 @@ jobs:
       - name: Validate Release artifact slices
         run: |
           set -euo pipefail
+          ./scripts/verify-no-bundled-agent-runtimes.sh \
+            build-universal/Build/Products/Release/cmux.app
           APP_BINARY="build-universal/Build/Products/Release/cmux.app/Contents/MacOS/cmux"
           CLI_BINARY="build-universal/Build/Products/Release/cmux.app/Contents/Resources/bin/cmux"
           HELPER_BINARY="build-universal/Build/Products/Release/cmux.app/Contents/Resources/bin/ghostty"
diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index 0d7baabcca52..32015f3bceaa 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -282,6 +282,13 @@ jobs:
           CMUX_APP_PATH="build-universal/Build/Products/Release/cmux.app" \
             ./tests/test_bundled_ghostty_theme_picker_helper.sh
 
+      - name: Verify no bundled provider runtimes in nightly app
+        if: needs.decide.outputs.should_publish != 'true' || steps.current_head_prebuild.outputs.still_current == 'true'
+        run: |
+          set -euo pipefail
+          ./scripts/verify-no-bundled-agent-runtimes.sh \
+            build-universal/Build/Products/Release/cmux.app
+
       - name: Verify nightly binary architectures
         if: needs.decide.outputs.should_publish != 'true' || steps.current_head_prebuild.outputs.still_current == 'true'
         run: |
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 24c9f9aca873..ede19e8e5e85 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -282,6 +282,8 @@ jobs:
         if: steps.guard_release_assets.outputs.skip_all != 'true'
         run: |
           set -euo pipefail
+          ./scripts/verify-no-bundled-agent-runtimes.sh \
+            build-universal/Build/Products/Release/cmux.app
           APP_BINARY="build-universal/Build/Products/Release/cmux.app/Contents/MacOS/cmux"
           CLI_BINARY="build-universal/Build/Products/Release/cmux.app/Contents/Resources/bin/cmux"
           HELPER_BINARY="build-universal/Build/Products/Release/cmux.app/Contents/Resources/bin/ghostty"
diff --git a/scripts/verify-no-bundled-agent-runtimes.sh b/scripts/verify-no-bundled-agent-runtimes.sh
new file mode 100755
index 000000000000..792bda48c2c0
--- /dev/null
+++ b/scripts/verify-no-bundled-agent-runtimes.sh
@@ -0,0 +1,92 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+EXPECTED_GROK_WRAPPER="$SCRIPT_DIR/../Resources/bin/grok"
+
+usage() {
+  cat <<'EOF'
+Usage: scripts/verify-no-bundled-agent-runtimes.sh <cmux.app>
+
+Verifies that a built cmux app bundle does not ship provider executables or a
+Bun standalone runtime in Contents/Resources/bin.
+EOF
+}
+
+if [ "${1:-}" = "-h" ] || [ "${1:-}" = "--help" ]; then
+  usage
+  exit 0
+fi
+
+if [ "$#" -ne 1 ]; then
+  usage >&2
+  exit 2
+fi
+
+APP_PATH="$1"
+BIN_DIR="$APP_PATH/Contents/Resources/bin"
+
+if [ ! -d "$APP_PATH" ]; then
+  echo "error: app bundle not found at $APP_PATH" >&2
+  exit 1
+fi
+
+if [ ! -d "$BIN_DIR" ]; then
+  echo "error: bundled bin directory not found at $BIN_DIR" >&2
+  exit 1
+fi
+
+is_allowed_binary_name() {
+  case "$1" in
+    # `grok` is allowed only when it matches cmux's checked-in wrapper script;
+    # it still goes through the Bun-standalone signature scan below.
+    cmux|ghostty|cmux-claude-wrapper|cmux-codex-wrapper|grok|open|start-cmux-profiling|submit-cmux-profile)
+      return 0
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+looks_like_bun_standalone() {
+  local path="$1"
+  strings -a "$path" 2>/dev/null | grep -E '(/\$bunfs/|StandaloneExecutable|Bun v[0-9]+\.[0-9]+\.[0-9]+)' >/dev/null
+}
+
+is_checked_in_grok_wrapper() {
+  local path="$1"
+  [ -f "$EXPECTED_GROK_WRAPPER" ] && cmp -s "$EXPECTED_GROK_WRAPPER" "$path"
+}
+
+relative_to_app() {
+  local path="$1"
+  printf '%s\n' "${path#"$APP_PATH"/}"
+}
+
+violations=()
+
+while IFS= read -r -d '' file; do
+  name="$(basename "$file")"
+  if ! is_allowed_binary_name "$name"; then
+    violations+=("unexpected bundled bin entry: $(relative_to_app "$file")")
+    continue
+  fi
+  if [ ! -x "$file" ] && [ ! -L "$file" ]; then
+    violations+=("allowed bin entry is not executable: $(relative_to_app "$file")")
+  fi
+  if [ "$name" = "grok" ] && ! is_checked_in_grok_wrapper "$file"; then
+    violations+=("grok wrapper does not match checked-in cmux wrapper: $(relative_to_app "$file")")
+  fi
+  if looks_like_bun_standalone "$file"; then
+    violations+=("Bun standalone runtime signature: $(relative_to_app "$file")")
+  fi
+done < <(find "$BIN_DIR" \( -type f -o -type l \) -print0)
+
+if [ "${#violations[@]}" -gt 0 ]; then
+  echo "error: cmux app bundle contains forbidden bundled provider runtimes:" >&2
+  printf '  %s\n' "${violations[@]}" >&2
+  exit 1
+fi
+
+echo "verified no bundled provider runtimes: $APP_PATH"
diff --git a/tests/test_bundled_provider_runtime_guard.sh b/tests/test_bundled_provider_runtime_guard.sh
new file mode 100755
index 000000000000..7a449c24b026
--- /dev/null
+++ b/tests/test_bundled_provider_runtime_guard.sh
@@ -0,0 +1,152 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+VERIFY_SCRIPT="$ROOT_DIR/scripts/verify-no-bundled-agent-runtimes.sh"
+
+if [ ! -x "$VERIFY_SCRIPT" ]; then
+  echo "FAIL: missing bundled provider runtime verifier at $VERIFY_SCRIPT" >&2
+  exit 1
+fi
+
+TMP_DIR="$(mktemp -d "${TMPDIR:-/tmp}/cmux-bundled-runtime-guard.XXXXXX")"
+trap 'rm -rf "$TMP_DIR"' EXIT
+
+make_app() {
+  local app_path="$1"
+  mkdir -p "$app_path/Contents/Resources/bin"
+}
+
+write_executable() {
+  local path="$1"
+  local body="$2"
+  mkdir -p "$(dirname "$path")"
+  printf '%s\n' "$body" > "$path"
+  chmod 0755 "$path"
+}
+
+copy_grok_wrapper() {
+  local path="$1"
+  mkdir -p "$(dirname "$path")"
+  install -m 0755 "$ROOT_DIR/Resources/bin/grok" "$path"
+}
+
+GOOD_APP="$TMP_DIR/good/cmux.app"
+make_app "$GOOD_APP"
+write_executable "$GOOD_APP/Contents/Resources/bin/cmux" "#!/bin/sh"
+write_executable "$GOOD_APP/Contents/Resources/bin/ghostty" "#!/bin/sh"
+write_executable "$GOOD_APP/Contents/Resources/bin/cmux-claude-wrapper" "#!/bin/sh"
+write_executable "$GOOD_APP/Contents/Resources/bin/cmux-codex-wrapper" "#!/bin/sh"
+copy_grok_wrapper "$GOOD_APP/Contents/Resources/bin/grok"
+write_executable "$GOOD_APP/Contents/Resources/bin/open" "#!/bin/sh"
+write_executable "$GOOD_APP/Contents/Resources/bin/start-cmux-profiling" "#!/bin/sh"
+write_executable "$GOOD_APP/Contents/Resources/bin/submit-cmux-profile" "#!/bin/sh"
+"$VERIFY_SCRIPT" "$GOOD_APP"
+
+BAD_GROK_APP="$TMP_DIR/bad-grok-wrapper/cmux.app"
+make_app "$BAD_GROK_APP"
+write_executable "$BAD_GROK_APP/Contents/Resources/bin/cmux" "#!/bin/sh"
+write_executable "$BAD_GROK_APP/Contents/Resources/bin/grok" "#!/bin/sh"
+if "$VERIFY_SCRIPT" "$BAD_GROK_APP" >"$TMP_DIR/grok-wrapper.out" 2>&1; then
+  echo "FAIL: verifier allowed a non-cmux grok wrapper" >&2
+  exit 1
+fi
+if ! grep -Fq "grok wrapper does not match checked-in cmux wrapper: Contents/Resources/bin/grok" "$TMP_DIR/grok-wrapper.out"; then
+  echo "FAIL: grok wrapper rejection did not name the offending path" >&2
+  cat "$TMP_DIR/grok-wrapper.out" >&2
+  exit 1
+fi
+
+for forbidden in claude opencode codex pi bun bunx; do
+  BAD_APP="$TMP_DIR/bad-$forbidden/cmux.app"
+  make_app "$BAD_APP"
+  write_executable "$BAD_APP/Contents/Resources/bin/cmux" "#!/bin/sh"
+  write_executable "$BAD_APP/Contents/Resources/bin/$forbidden" "#!/bin/sh"
+  OUTPUT="$TMP_DIR/$forbidden.out"
+  if "$VERIFY_SCRIPT" "$BAD_APP" >"$OUTPUT" 2>&1; then
+    echo "FAIL: verifier allowed bundled $forbidden executable" >&2
+    exit 1
+  fi
+  if ! grep -Fq "Contents/Resources/bin/$forbidden" "$OUTPUT"; then
+    echo "FAIL: verifier rejection for $forbidden did not name the offending path" >&2
+    cat "$OUTPUT" >&2
+    exit 1
+  fi
+done
+
+NONEXEC_FORBIDDEN_APP="$TMP_DIR/bad-nonexec-bun/cmux.app"
+make_app "$NONEXEC_FORBIDDEN_APP"
+write_executable "$NONEXEC_FORBIDDEN_APP/Contents/Resources/bin/cmux" "#!/bin/sh"
+printf '%s\n' 'Bun v1.3.14 StandaloneExecutable /$bunfs/root' > "$NONEXEC_FORBIDDEN_APP/Contents/Resources/bin/bun"
+chmod 0644 "$NONEXEC_FORBIDDEN_APP/Contents/Resources/bin/bun"
+if "$VERIFY_SCRIPT" "$NONEXEC_FORBIDDEN_APP" >"$TMP_DIR/nonexec-bun.out" 2>&1; then
+  echo "FAIL: verifier allowed a non-executable bundled bun file" >&2
+  exit 1
+fi
+if ! grep -Fq "unexpected bundled bin entry: Contents/Resources/bin/bun" "$TMP_DIR/nonexec-bun.out"; then
+  echo "FAIL: non-executable bun rejection did not name the offending path" >&2
+  cat "$TMP_DIR/nonexec-bun.out" >&2
+  exit 1
+fi
+
+NONEXEC_ALLOWED_APP="$TMP_DIR/bad-nonexec-allowed/cmux.app"
+make_app "$NONEXEC_ALLOWED_APP"
+printf '%s\n' '#!/bin/sh' > "$NONEXEC_ALLOWED_APP/Contents/Resources/bin/cmux"
+chmod 0644 "$NONEXEC_ALLOWED_APP/Contents/Resources/bin/cmux"
+if "$VERIFY_SCRIPT" "$NONEXEC_ALLOWED_APP" >"$TMP_DIR/nonexec-allowed.out" 2>&1; then
+  echo "FAIL: verifier allowed a non-executable allowlisted bin entry" >&2
+  exit 1
+fi
+if ! grep -Fq "allowed bin entry is not executable: Contents/Resources/bin/cmux" "$TMP_DIR/nonexec-allowed.out"; then
+  echo "FAIL: non-executable allowlisted rejection did not name the offending path" >&2
+  cat "$TMP_DIR/nonexec-allowed.out" >&2
+  exit 1
+fi
+
+SYMLINK_APP="$TMP_DIR/bad-symlink/cmux.app"
+make_app "$SYMLINK_APP"
+write_executable "$SYMLINK_APP/Contents/Resources/bin/cmux" "#!/bin/sh"
+ln -s cmux "$SYMLINK_APP/Contents/Resources/bin/claude"
+if "$VERIFY_SCRIPT" "$SYMLINK_APP" >"$TMP_DIR/symlink.out" 2>&1; then
+  echo "FAIL: verifier allowed a symlinked bundled claude executable" >&2
+  exit 1
+fi
+if ! grep -Fq "Contents/Resources/bin/claude" "$TMP_DIR/symlink.out"; then
+  echo "FAIL: symlink rejection did not name the offending path" >&2
+  cat "$TMP_DIR/symlink.out" >&2
+  exit 1
+fi
+
+BUN_SIGNATURE_APP="$TMP_DIR/bad-bun-signature/cmux.app"
+make_app "$BUN_SIGNATURE_APP"
+write_executable "$BUN_SIGNATURE_APP/Contents/Resources/bin/cmux" '#!/bin/sh
+printf "%s\n" "Bun v1.3.14 StandaloneExecutable /$bunfs/root"'
+if "$VERIFY_SCRIPT" "$BUN_SIGNATURE_APP" >"$TMP_DIR/bun-signature.out" 2>&1; then
+  echo "FAIL: verifier allowed an allowlisted executable with a Bun standalone signature" >&2
+  exit 1
+fi
+if ! grep -Fq "Bun standalone runtime signature: Contents/Resources/bin/cmux" "$TMP_DIR/bun-signature.out"; then
+  echo "FAIL: Bun signature rejection did not name the offending path" >&2
+  cat "$TMP_DIR/bun-signature.out" >&2
+  exit 1
+fi
+
+LARGE_BUN_SIGNATURE_APP="$TMP_DIR/bad-large-bun-signature/cmux.app"
+make_app "$LARGE_BUN_SIGNATURE_APP"
+{
+  printf '%s\n' '#!/bin/sh'
+  printf '%s\n' 'Bun v1.3.14 StandaloneExecutable /$bunfs/root'
+  awk 'BEGIN { for (i = 0; i < 5000; i++) print "cmux padding line after the early Bun signature" }'
+} > "$LARGE_BUN_SIGNATURE_APP/Contents/Resources/bin/cmux"
+chmod 0755 "$LARGE_BUN_SIGNATURE_APP/Contents/Resources/bin/cmux"
+if "$VERIFY_SCRIPT" "$LARGE_BUN_SIGNATURE_APP" >"$TMP_DIR/large-bun-signature.out" 2>&1; then
+  echo "FAIL: verifier allowed a large allowlisted executable with an early Bun standalone signature" >&2
+  exit 1
+fi
+if ! grep -Fq "Bun standalone runtime signature: Contents/Resources/bin/cmux" "$TMP_DIR/large-bun-signature.out"; then
+  echo "FAIL: large Bun signature rejection did not name the offending path" >&2
+  cat "$TMP_DIR/large-bun-signature.out" >&2
+  exit 1
+fi
+
+echo "PASS: bundled provider runtime guard rejects stale provider and Bun executables"