diff --git a/gecko-patches/anti-fingerprint/anti-fp-audio.patch b/gecko-patches/anti-fingerprint/anti-fp-audio.patch
index ea81561..e047c5e 100644
--- a/gecko-patches/anti-fingerprint/anti-fp-audio.patch
+++ b/gecko-patches/anti-fingerprint/anti-fp-audio.patch
@@ -66,7 +66,7 @@
 +  // fingerprint cannot be linked between sessions — RFP randomizes canvas but
 +  // not audio, and this closes that residual).
 +  static const double sFarbleFactor = []() {
-+    uint64_t r = mozilla::RandomUint64OrZero();
++    uint64_t r = mozilla::RandomUint64().valueOr(0);
 +    double frac = (double)(r % 2000001) / 1000000.0 - 1.0;  // [-1, 1]
 +    return 1.0 + frac * 1e-7;
 +  }();
diff --git a/scripts/apply-sourceos-overlays.sh b/scripts/apply-sourceos-overlays.sh
index dd44bb1..dcfc287 100755
--- a/scripts/apply-sourceos-overlays.sh
+++ b/scripts/apply-sourceos-overlays.sh
@@ -249,6 +249,14 @@ afp_dir="$repo_root/gecko-patches/anti-fingerprint"
 patches_txt="$workspace/source/assets/patches.txt"
 if [ "$profile" = "tor-mode" ]; then
   echo "feature-layer: tor-mode omits the canvas/audio anti-fp patches (disabled to match cohort; see docs/tor-mode.md)"
+  # Drop msix.patch (Windows Store packaging) from the tor-mode stack: it's
+  # irrelevant to a Linux/macOS Tor browser AND it fails to apply on the 140 ESR
+  # tree (hunk drift), which aborts the whole `make` build. The CI patch-apply
+  # gate already excludes it; do the same for the real build.
+  if [ -f "$patches_txt" ]; then
+    grep -v 'patches/msix\.patch' "$patches_txt" > "$patches_txt.tmp" && mv "$patches_txt.tmp" "$patches_txt"
+    echo "feature-layer: tor-mode dropped msix.patch (Windows-only; drifts on ESR)"
+  fi
   # ...but tor-mode DOES need the OS-spoof patch: Tor forces the Windows identity
   # on all desktop platforms, which is a cohort REQUIREMENT (not one of our extra
   # protections). It's gated on -DBEARBROWSER_FORCE_WIN_SPOOF, set below.
diff --git a/scripts/gcp-build-linux.sh b/scripts/gcp-build-linux.sh
new file mode 100755
index 0000000..dc09143
--- /dev/null
+++ b/scripts/gcp-build-linux.sh
@@ -0,0 +1,122 @@
+#!/usr/bin/env bash
+# Builds BearBrowser from source on a GCP VM and pulls back binaries + fingerprint
+# scorecards. NO SSH is used — this org blocks port 22 and OS Login key
+# registration, so the VM is driven entirely through GCS + a startup script:
+# upload repo -> VM builds autonomously -> VM pushes artifacts + DONE to GCS ->
+# we poll GCS, download, and tear the VM down. (Linux binaries: proves the engine
+# patches + gives the scorecard; a runnable macOS app needs Apple hardware.)
+#
+#   scripts/gcp-build-linux.sh --dry-run     # free: validate auth/machine/image/bucket
+#   scripts/gcp-build-linux.sh               # build human-secure + tor-mode
+set -uo pipefail
+
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+repo_root="${BEARBROWSER_HOME:-$(cd "$script_dir/.." && pwd)}"
+
+INSTANCE="${BB_GCP_INSTANCE:-bearbrowser-build-$(date +%Y%m%d-%H%M%S)}"
+ZONE="${BB_GCP_ZONE:-us-central1-a}"
+MACHINE="${BB_GCP_MACHINE:-c2d-standard-32}"
+IMAGE_FAMILY="${BB_GCP_IMAGE_FAMILY:-ubuntu-2404-lts-amd64}"
+IMAGE_PROJECT="${BB_GCP_IMAGE_PROJECT:-ubuntu-os-cloud}"
+DISK_GB="${BB_GCP_DISK_GB:-150}"
+MAX_HOURS="${BB_GCP_MAX_HOURS:-5}"
+SERVICE_ACCOUNT="${BB_GCP_SA:-synapseiq-build@socioprophet-platform.iam.gserviceaccount.com}"
+BUCKET="${BB_GCP_BUCKET:-sourceos-artifacts-socioprophet}"
+PROFILES="${BB_PROFILES:-human-secure tor-mode}"
+art_out="$repo_root/build/gcp-artifacts"
+keep=""; dry_run=""
+
+while [ "$#" -gt 0 ]; do
+  case "$1" in
+    --profiles) PROFILES="${2:?}"; shift 2 ;;
+    --machine)  MACHINE="${2:?}"; shift 2 ;;
+    --zone)     ZONE="${2:?}"; shift 2 ;;
+    --bucket)   BUCKET="${2:?}"; shift 2 ;;
+    --instance) INSTANCE="${2:?}"; shift 2 ;;
+    --keep)     keep="1"; shift ;;
+    --dry-run)  dry_run="1"; shift ;;
+    -h|--help)  grep '^#' "$0" | sed 's/^# \{0,1\}//'; exit 0 ;;
+    *) echo "ERROR: unknown arg: $1" >&2; exit 1 ;;
+  esac
+done
+
+PREFIX="gs://$BUCKET/bearbrowser-builds/$INSTANCE"
+created=""
+cleanup() {
+  local rc=$?
+  if [ -n "$created" ] && [ -z "$keep" ]; then
+    echo ">> Tearing down $INSTANCE ..."
+    gcloud compute instances delete "$INSTANCE" --zone="$ZONE" --quiet 2>/dev/null \
+      && echo ">> $INSTANCE deleted." \
+      || { echo "!! WARNING: delete failed — $INSTANCE MAY STILL BE BILLING."; \
+           echo "!! Run: gcloud compute instances delete $INSTANCE --zone=$ZONE --quiet"; }
+  elif [ -n "$created" ]; then
+    echo ">> --keep set: $INSTANCE left running (remember to delete it)."
+  fi
+  exit "$rc"
+}
+trap cleanup EXIT INT TERM
+
+# ── Preflight (all free) ────────────────────────────────────────────────────
+echo ">> Preflight..."
+gcloud auth print-access-token >/dev/null 2>&1 \
+  || { echo "ERROR: gcloud not authenticated. Run: gcloud auth login"; exit 1; }
+echo "   account: $(gcloud config get-value account 2>/dev/null)   project: $(gcloud config get-value project 2>/dev/null)"
+gcloud compute machine-types describe "$MACHINE" --zone="$ZONE" --format='value(name)' >/dev/null 2>&1 \
+  || { echo "ERROR: machine type '$MACHINE' not available in '$ZONE'."; exit 1; }
+img="$(gcloud compute images describe-from-family "$IMAGE_FAMILY" --project="$IMAGE_PROJECT" --format='value(name)' 2>/dev/null)"
+[ -n "$img" ] || { echo "ERROR: image family '$IMAGE_FAMILY' not found."; exit 1; }
+gcloud storage ls "gs://$BUCKET" >/dev/null 2>&1 \
+  || { echo "ERROR: cannot access bucket gs://$BUCKET"; exit 1; }
+echo "   machine: $MACHINE   image: $img   bucket: gs://$BUCKET   profiles: [$PROFILES]"
+[ -f "$script_dir/gcp-vm-startup.sh" ] || { echo "ERROR: missing gcp-vm-startup.sh"; exit 1; }
+if [ -n "$dry_run" ]; then echo ">> DRY RUN OK — auth + machine + image + bucket all valid. No VM, no cost."; exit 0; fi
+
+# ── Package + upload repo to GCS ────────────────────────────────────────────
+echo ">> Packaging + uploading repo to $PREFIX/bb-repo.tgz ..."
+tarball="/tmp/bb-repo-$$.tgz"
+tar --exclude='./build' --exclude='./node_modules' --exclude='./.git' \
+    --exclude='*.tar.gz' --exclude='*.tar.xz' -czf "$tarball" -C "$repo_root" . \
+  || { echo "ERROR: repo tar failed"; exit 1; }
+gcloud storage cp "$tarball" "$PREFIX/bb-repo.tgz" >/dev/null 2>&1 \
+  || { echo "ERROR: repo upload failed"; exit 1; }
+rm -f "$tarball"
+echo "   uploaded."
+
+# ── Provision with startup script (no SSH) ──────────────────────────────────
+echo ">> Creating VM $INSTANCE ($MACHINE, $ZONE, ${DISK_GB}GB)..."
+gcloud compute instances create "$INSTANCE" \
+  --zone="$ZONE" --machine-type="$MACHINE" \
+  --image-family="$IMAGE_FAMILY" --image-project="$IMAGE_PROJECT" \
+  --boot-disk-size="${DISK_GB}GB" --boot-disk-type=pd-ssd \
+  --max-run-duration="$(( MAX_HOURS*3600 ))s" --instance-termination-action=DELETE \
+  --service-account="$SERVICE_ACCOUNT" --scopes=cloud-platform \
+  --metadata="bb-prefix=$PREFIX,bb-profiles=$PROFILES" \
+  --metadata-from-file="startup-script=$script_dir/gcp-vm-startup.sh" \
+  --quiet || { echo "ERROR: instance create failed"; exit 1; }
+created="1"
+
+# ── Poll GCS for the DONE marker (no SSH) ───────────────────────────────────
+echo ">> Building on VM (polling GCS every 60s; safety cap ${MAX_HOURS}h)..."
+deadline=$(( $(date +%s) + MAX_HOURS*3600 ))
+build_rc="1"
+while :; do
+  if gcloud storage cat "$PREFIX/DONE" >/tmp/bb-done 2>/dev/null; then
+    build_rc="$(tr -dc 0-9 </tmp/bb-done)"; build_rc="${build_rc:-0}"
+    echo "   build finished (rc=$build_rc)."; break
+  fi
+  if [ "$(date +%s)" -gt "$deadline" ]; then echo "!! build exceeded ${MAX_HOURS}h cap — tearing down."; break; fi
+  # progress from serial console (no SSH needed)
+  line="$(gcloud compute instances get-serial-port-output "$INSTANCE" --zone="$ZONE" 2>/dev/null | grep -aE '===|profile|make build|BUILT|FAIL|OS-spoof' | tail -1)"
+  echo "   [$(date -u +%H:%M:%S)] ${line:-(booting / installing toolchain…)}"
+  sleep 60
+done
+
+# ── Collect artifacts from GCS ──────────────────────────────────────────────
+mkdir -p "$art_out"
+echo ">> Downloading artifacts from $PREFIX/ ..."
+gcloud storage cp -r "$PREFIX/artifacts/*" "$art_out/" >/dev/null 2>&1 || echo "   (no artifacts — see build.log)"
+gcloud storage cp "$PREFIX/build.log" "$art_out/build.log" >/dev/null 2>&1 || true
+echo ">> Build finished (rc=$build_rc). Artifacts in $art_out:"
+ls -lh "$art_out" 2>/dev/null | sed 's/^/   /'
+exit "$build_rc"   # teardown in trap
diff --git a/scripts/gcp-remote-build.sh b/scripts/gcp-remote-build.sh
new file mode 100755
index 0000000..619607f
--- /dev/null
+++ b/scripts/gcp-remote-build.sh
@@ -0,0 +1,95 @@
+#!/usr/bin/env bash
+# Runs ON the GCP build VM (Ubuntu). Builds one or more BearBrowser profiles from
+# source (full Gecko compile with our engine patches), measures the real binary,
+# and stages artifacts in ~/artifacts. Driven by scripts/gcp-build-linux.sh.
+#
+# Not set -e: one profile failing must not abort the others. Each profile is
+# isolated and its failures are logged + collected.
+set -uo pipefail
+
+profiles="${1:-human-secure tor-mode}"
+repo="${BB_REPO:-$HOME/BearBrowser}"
+art="$HOME/artifacts"
+mkdir -p "$art"
+log() { echo "[$(date -u +%H:%M:%S)] $*"; }
+fail=0
+
+log "BearBrowser GCP build — profiles: [$profiles]"
+log "cores=$(nproc) mem=$(free -g | awk '/Mem:/{print $2}')GB disk_free=$(df -h "$HOME" | awk 'NR==2{print $4}')"
+
+# ── Base OS dependencies (Mozilla's own toolchain comes from `mach bootstrap`) ──
+log "Installing base apt dependencies..."
+sudo apt-get update -qq
+sudo DEBIAN_FRONTEND=noninteractive apt-get install -y -qq \
+  git python3 python3-dev python3-pip python3-venv curl wget mercurial zstd \
+  build-essential pkg-config libssl-dev libxml2-dev nodejs npm xz-utils \
+  >/dev/null 2>&1 || log "WARN: some apt deps failed (continuing — mach bootstrap covers most)"
+
+# Node deps for the fingerprint scorecard (geckodriver + selenium are in package.json).
+cd "$repo" || { log "FATAL: repo not found at $repo"; exit 1; }
+log "Installing node measurement deps..."
+npm ci >/dev/null 2>&1 || npm install >/dev/null 2>&1 || log "WARN: npm deps failed (scorecard may be skipped)"
+
+for p in $profiles; do
+  log "=================== PROFILE: $p ==================="
+  pfail=0
+
+  log "[$p] overlay prep (apply-sourceos-overlays --profile $p)..."
+  if ! bash scripts/apply-sourceos-overlays.sh --profile "$p" --ref latest > "$art/$p-overlay.log" 2>&1; then
+    log "[$p] FAIL: overlay prep — see $p-overlay.log"; fail=1; continue
+  fi
+  ws="$(find build/workspaces -maxdepth 2 -type d -name source 2>/dev/null | sort | tail -1)"
+  if [ -z "$ws" ] || [ ! -f "$ws/Makefile" ]; then
+    log "[$p] FAIL: no workspace/Makefile produced"; fail=1; continue
+  fi
+  log "[$p] workspace: $ws (firefox version: $(cat "$ws/version" 2>/dev/null))"
+
+  (
+    cd "$ws" || exit 1
+    echo "=== make bootstrap (Mozilla toolchain + fetch/extract/patch source) ==="
+    MOZBUILD_STATE_PATH="$HOME/.mozbuild" make bootstrap || exit 11
+    echo "=== make build (compile — the long step) ==="
+    make build || exit 12
+  ) > "$art/$p-build.log" 2>&1
+  rc=$?
+  if [ "$rc" -ne 0 ]; then
+    log "[$p] FAIL: build rc=$rc — see $p-build.log (tail below)"; tail -25 "$art/$p-build.log"; fail=1; continue
+  fi
+
+  # The branded build names the binary bearbrowser/librewolf, not firefox.
+  bin="$(find "$ws" -type f \( -name bearbrowser -o -name librewolf -o -name firefox \) -path '*dist/bin*' 2>/dev/null | head -1)"
+  if [ -z "$bin" ]; then
+    log "[$p] FAIL: build succeeded but no dist/bin binary found (looked for bearbrowser/librewolf/firefox)"
+    find "$ws" -type f -path '*dist/bin*' 2>/dev/null | grep -viE '\.(so|js|json|txt|xpi|ini)$' | head -20
+    fail=1; continue
+  fi
+  log "[$p] BUILT: $bin"
+  "$bin" --version > "$art/$p-version.txt" 2>&1 || true
+
+  # ── Scorecard: drive the REAL binary (authoritative) ──
+  log "[$p] measuring fingerprint scorecard..."
+  PATH="$repo/node_modules/.bin:$PATH" \
+    node scripts/measure-fingerprint.mjs --profile "$p" --bin "$bin" --json \
+    > "$art/$p-scorecard.json" 2> "$art/$p-measure.log" || log "[$p] WARN: measurement failed — see $p-measure.log"
+
+  # tor-mode: assert the OS-spoof actually compiled in (Windows identity on this Linux host)
+  if [ "$p" = "tor-mode" ] && [ -s "$art/$p-scorecard.json" ]; then
+    if grep -q "Windows NT 10.0" "$art/$p-scorecard.json" && grep -q "Win32" "$art/$p-scorecard.json"; then
+      log "[$p] ✓ OS-spoof VERIFIED: binary reports Windows identity"
+    else
+      log "[$p] ✗ OS-spoof NOT present: binary did not report Windows — the mozconfig flag did not take effect"; fail=1
+    fi
+  fi
+
+  # ── Package the runnable dist for download ──
+  distbin="$(dirname "$bin")"          # .../obj-*/dist/bin
+  log "[$p] packaging dist..."
+  tar -C "$(dirname "$distbin")" -czf "$art/bearbrowser-$p-linux-x86_64.tar.gz" bin 2>/dev/null \
+    || log "[$p] WARN: packaging failed"
+  log "=================== DONE: $p (size: $(du -h "$art/bearbrowser-$p-linux-x86_64.tar.gz" 2>/dev/null | cut -f1)) ==================="
+done
+
+log "Artifacts staged in $art:"
+ls -lh "$art" 2>/dev/null | sed 's/^/  /'
+[ "$fail" -eq 0 ] && log "ALL PROFILES OK" || log "ONE OR MORE PROFILES FAILED (rc collected; see per-profile logs)"
+exit "$fail"
diff --git a/scripts/gcp-vm-startup.sh b/scripts/gcp-vm-startup.sh
new file mode 100644
index 0000000..3d7d242
--- /dev/null
+++ b/scripts/gcp-vm-startup.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# VM startup script (runs as root at boot via instance metadata). No SSH is used —
+# this org blocks port 22 + OS Login key registration, so the VM is fully
+# autonomous: pull the repo from GCS, build (as a non-root user), push artifacts +
+# a DONE marker back to GCS. The orchestrator polls GCS and tears the VM down.
+set -uo pipefail
+exec > >(tee /var/log/bb-build.log) 2>&1   # also visible via serial console
+md() { curl -s -H 'Metadata-Flavor: Google' "http://metadata.google.internal/computeMetadata/v1/instance/attributes/$1"; }
+
+BUCKET_PREFIX="$(md bb-prefix)"   # gs://bucket/path/<ts>
+PROFILES="$(md bb-profiles)"
+echo "=== BearBrowser VM build start $(date -u) — prefix=$BUCKET_PREFIX profiles=[$PROFILES] ==="
+
+# gsutil/gcloud: Ubuntu GCP images don't ship the CLI — install via snap.
+if ! command -v gsutil >/dev/null 2>&1; then
+  echo "=== installing google-cloud-cli ==="
+  snap install google-cloud-cli --classic || { echo "FATAL: cannot install gcloud cli"; exit 1; }
+fi
+
+mark_done() { echo "$1" | gsutil cp - "$BUCKET_PREFIX/DONE" 2>/dev/null; }
+push_log()  { gsutil cp /var/log/bb-build.log "$BUCKET_PREFIX/build.log" 2>/dev/null || true; }
+trap 'push_log' EXIT
+
+# Non-root build user (mach refuses to build as root); passwordless sudo for apt + mach bootstrap.
+id builder >/dev/null 2>&1 || useradd -m -s /bin/bash builder
+echo 'builder ALL=(ALL) NOPASSWD:ALL' > /etc/sudoers.d/builder
+
+echo "=== fetching repo from $BUCKET_PREFIX/bb-repo.tgz ==="
+if ! gsutil cp "$BUCKET_PREFIX/bb-repo.tgz" /tmp/bb-repo.tgz; then echo "FATAL: repo fetch failed"; mark_done 90; exit 1; fi
+sudo -u builder mkdir -p /home/builder/BearBrowser
+tar xzf /tmp/bb-repo.tgz -C /home/builder/BearBrowser
+chown -R builder:builder /home/builder/BearBrowser
+
+echo "=== building (as builder): profiles [$PROFILES] ==="
+su - builder -c "cd ~/BearBrowser && bash scripts/gcp-remote-build.sh '$PROFILES'"
+rc=$?
+echo "=== build finished rc=$rc ==="
+
+echo "=== uploading artifacts to $BUCKET_PREFIX/artifacts/ ==="
+gsutil -m cp -r /home/builder/artifacts/'*' "$BUCKET_PREFIX/artifacts/" 2>/dev/null || echo "WARN: artifact upload partial"
+push_log
+mark_done "$rc"
+echo "=== DONE (rc=$rc) — orchestrator will collect + tear down ==="