feat: initial public release

Stealthfox — a patched Firefox 150.0.1 for browser-fingerprint stealth,
shipped as a Playwright-compatible Python wrapper.

  * Sync + async Stealthfox launcher (firefox_user_prefs, virtual desktop
    on Windows, SOCKS5 auth via patched nsProtocolProxyService)
  * fpforge: Bayesian fingerprint sampler over GPU / audio / fonts /
    screen / TCP options / ~400 other navigator fields
  * WebRTC stealth: srflx address swap, synthetic srflx fallback,
    private-LAN host candidates — no real public IP leak via STUN
  * GPU sandbox fix for FF150 alt-desktop regression
  * Bezier-curve mouse motion baked into Juggler

Targets Windows x86_64 + Linux x86_64. Binary fetched on first run from
GitHub Release "firefox-1".

src/stealthfox/__init__.py

@@ -0,0 +1,22 @@
+"""stealthfox — Playwright wrapper for a patched Firefox with stealth profile.
+
+Quickstart:
+
+    from stealthfox import Stealthfox
+
+    with Stealthfox() as browser:        # random seed
+        page = browser.new_page()
+        page.goto("https://example.com")
+
+    with Stealthfox(seed=42) as browser: # deterministic
+        ...
+
+    with Stealthfox(humanize=True) as browser:  # human-like cursor motion
+        page = browser.new_page()
+        page.click("#submit")   # expanded into a Bezier trajectory
+"""
+from .launcher import Stealthfox
+from .constants import BINARY_VERSION, FIREFOX_UPSTREAM_VERSION
+
+__version__ = "0.1.0"
+__all__ = ["Stealthfox", "BINARY_VERSION", "FIREFOX_UPSTREAM_VERSION", "__version__"]

src/stealthfox/__main__.py

@@ -0,0 +1,4 @@
+from .cli import main
+import sys
+
+sys.exit(main())

src/stealthfox/_fpforge/__init__.py

@@ -0,0 +1,26 @@
+"""Internal Bayesian fingerprint generator used by stealthfox.
+
+Private module — do not import from user code. Use
+stealthfox.Stealthfox(seed=..., pin=...) instead.
+"""
+from .profile import (
+    AudioProfile,
+    CodecProfile,
+    GPUProfile,
+    HardwareProfile,
+    Profile,
+    ScreenProfile,
+    WebGLProfile,
+    generate_profile,
+)
+
+__all__ = [
+    "generate_profile",
+    "Profile",
+    "GPUProfile",
+    "ScreenProfile",
+    "HardwareProfile",
+    "AudioProfile",
+    "CodecProfile",
+    "WebGLProfile",
+]

src/stealthfox/_fpforge/_network.py

@@ -0,0 +1,131 @@
+# -*- coding: utf-8 -*-
+"""Generic Bayesian network for fingerprint sampling.
+
+A Node has:
+  - name
+  - parents (list of parent node names)
+  - CPT: either
+      * marginal (no parents): flat [{value, prob}, ...]
+      * conditional: {parent_tuple: [{value, prob}, ...]}
+  - OR deterministic: a classifier function `(context) -> value` (no CPT)
+
+Sampling:
+  - Nodes are topologically sorted
+  - For each node, look up the conditional distribution given parent values
+    already sampled in `context`, then weighted-pick
+  - Deterministic nodes apply their classifier directly
+
+Values can be ANY JSON-serializable type (int, str, dict, list, bool).
+Complex values (e.g. screen joint {w, h, dpr}) are stored as dicts in the
+CPT and returned as-is in the context.
+"""
+import json
+import random
+from typing import Any, Callable, Dict, List, Optional, Tuple
+
+
+class Node:
+    """Single Bayesian node."""
+
+    __slots__ = ("name", "parents", "cpt", "classifier", "_marginal")
+
+    def __init__(
+        self,
+        name: str,
+        parents: Optional[List[str]] = None,
+        cpt: Optional[Any] = None,
+        classifier: Optional[Callable[[Dict[str, Any]], Any]] = None,
+    ):
+        self.name = name
+        self.parents = list(parents or [])
+        self.cpt = cpt
+        self.classifier = classifier
+        # Precompute: for no-parent nodes, cpt is the marginal list
+        self._marginal = cpt if not self.parents and classifier is None else None
+
+    def sample(self, context: Dict[str, Any], rng: random.Random) -> Any:
+        # Deterministic nodes don't sample
+        if self.classifier is not None:
+            return self.classifier(context)
+
+        if not self.parents:
+            # Marginal root
+            return _weighted_pick(self._marginal, rng)
+
+        # Conditional node: build the key from parent values
+        key = _parent_key(self.parents, context)
+        if key not in self.cpt:
+            # Fallback: concatenate all parents' tables (uniform over union)
+            # Keeps sampler from crashing if data doesn't cover some combo.
+            pool = []
+            for v in self.cpt.values():
+                pool.extend(v)
+            if not pool:
+                raise ValueError(
+                    f"Node {self.name!r}: no CPT entries for {self.parents}={key}"
+                )
+            return _weighted_pick(pool, rng)
+        return _weighted_pick(self.cpt[key], rng)
+
+
+class Network:
+    """Collection of nodes with topological sampling."""
+
+    def __init__(self, nodes: List[Node]):
+        self.nodes = _topsort(nodes)
+        self.by_name = {n.name: n for n in self.nodes}
+
+    def sample(self, rng: random.Random) -> Dict[str, Any]:
+        context: Dict[str, Any] = {}
+        for node in self.nodes:
+            context[node.name] = node.sample(context, rng)
+        return context
+
+
+# ── Helpers ─────────────────────────────────────────────────────────────
+
+def _weighted_pick(table: List[Dict[str, Any]], rng: random.Random) -> Any:
+    """`table` is a list of {value, prob} dicts. Returns one value."""
+    values = [e["value"] for e in table]
+    probs = [float(e["prob"]) for e in table]
+    if not values:
+        raise ValueError("Empty CPT entry")
+    total = sum(probs)
+    if total <= 0:
+        return rng.choice(values)
+    # Normalize to be safe (CPTs can be unnormalized)
+    probs = [p / total for p in probs]
+    return rng.choices(values, weights=probs, k=1)[0]
+
+
+def _parent_key(parents: List[str], context: Dict[str, Any]) -> str:
+    """Build a JSON-stable key from parent values in declared order."""
+    if len(parents) == 1:
+        v = context[parents[0]]
+        return v if isinstance(v, str) else json.dumps(v, sort_keys=True)
+    return json.dumps([context[p] for p in parents], sort_keys=True)
+
+
+def _topsort(nodes: List[Node]) -> List[Node]:
+    """Topological sort by parent-before-child."""
+    by_name = {n.name: n for n in nodes}
+    visited: set = set()
+    order: List[Node] = []
+
+    def visit(n: Node, path: set):
+        if n.name in visited:
+            return
+        if n.name in path:
+            raise ValueError(f"Cycle at {n.name}")
+        path.add(n.name)
+        for p in n.parents:
+            if p not in by_name:
+                raise ValueError(f"Node {n.name} has unknown parent {p}")
+            visit(by_name[p], path)
+        path.discard(n.name)
+        visited.add(n.name)
+        order.append(n)
+
+    for n in nodes:
+        visit(n, set())
+    return order

src/stealthfox/_fpforge/_sampler.py

@@ -0,0 +1,358 @@
+# -*- coding: utf-8 -*-
+"""stealth_forge — Bayesian fingerprint generator for Firefox 150 Windows.
+
+Everything the Firefox build exposes to JS (screen, hardwareConcurrency,
+WebGL, audio, MSAA, theme, media codecs) is sampled from a Bayesian network
+with coherent cross-field dependencies. Identity (userAgent, platform,
+oscpu, webdriver=false, maxTouchPoints=0) is locked by the compiled build.
+
+Graph:
+
+    gpu (root, 444 real Windows ANGLE renderers)
+     │
+     └─> gpu_class (deterministic classifier, 6 classes)
+          ├─> hw_concurrency       (CPT per class)
+          ├─> screen (w/h/dpr/av)  (CPT per class)
+          └─> msaa_samples         (CPT per class)
+
+    audio (root, joint rate+latency+channels — marginal)
+    dark_theme                     (marginal)
+    av1_enabled                    (marginal)
+    webm_encoder_enabled           (marginal)
+
+    font_exclude  ← deterministic hash of stealth_seed (seed-derived)
+
+CPTs live in `data/*.json` (easy to tune without code changes).
+Sampling is deterministic per stealth_seed via a private random.Random.
+"""
+import json
+import os
+import re
+from typing import Any, Dict
+
+from ._network import Network, Node
+
+_HERE = os.path.dirname(os.path.abspath(__file__))
+
+
+def _load(filename: str) -> Any:
+    with open(os.path.join(_HERE, "data", filename), "r", encoding="utf-8") as f:
+        return json.load(f)
+
+
+# ═══════════════════════════════════════════════════════════════════════
+#  LOCKED IDENTITY (compiled into our Firefox 150 build — never varies)
+# ═══════════════════════════════════════════════════════════════════════
+_LOCKED: Dict[str, Any] = {
+    "user_agent": (
+        "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:150.0) "
+        "Gecko/20100101 Firefox/150.0.1"
+    ),
+    "platform": "Win32",
+    "oscpu": "Windows NT 10.0; Win64; x64",
+    "app_code_name": "Mozilla",
+    "app_version": "5.0 (Windows)",
+    "product_sub": "20100101",
+    "webdriver": False,
+    "max_touch_points": 0,
+}
+
+
+# ═══════════════════════════════════════════════════════════════════════
+#  DATA
+# ═══════════════════════════════════════════════════════════════════════
+_GPU_POOL = _load("webgl_renderer_pool.json")["entries"]
+# hwc/screen/storage now keyed on (gpu_class, intra_tier) for triangulation
+_CPT_HWC = _load("cpt_hwc_given_class_tier.json")["table"]
+_CPT_SCREEN = _load("cpt_screen_given_class_tier.json")["table"]
+_CPT_STORAGE = _load("cpt_storage_given_class_tier.json")["table"]
+# Hidden tier variable that makes hwc/screen/storage jointly coherent
+_CPT_INTRA_TIER = _load("cpt_intra_tier_given_class.json")["table"]
+# MSAA depends on (gpu_class, screen_tier) — 4K gaming → MSAA=0, 1080p+GPU → MSAA=4
+_CPT_MSAA = _load("cpt_msaa_given_class_screen.json")["table"]
+# Codec unchanged
+_CPT_CODEC = _load("cpt_codec_given_class.json")["table"]
+# Audio now conditional on gpu_class (workstation → pro audio, old → 44.1kHz onboard)
+_CPT_AUDIO = _load("cpt_audio_given_class.json")["table"]
+_INDEP = _load("priors_independent.json")
+_FONT_POOL = _load("font_pool.json")
+# Each entry is a dict {"name": "<lowercase family>", "factor": float}.
+# - name: the font family advertised to the page.
+# - factor: per-family width scale used by the consumer to make the family
+#   detectable by width-diff probes.
+# Core = always-included; Optional = sampled with P(font | gpu_class).
+_FONT_CORE: list = _FONT_POOL["core"]
+_FONT_OPTIONAL: list = _FONT_POOL["optional"]
+_CPT_FONTS_OPT = _load("cpt_fonts_optional_given_class.json")["table"]
+
+
+# ═══════════════════════════════════════════════════════════════════════
+#  GPU CLASSIFIER (deterministic function of gpu → gpu_class)
+# ═══════════════════════════════════════════════════════════════════════
+_GPU_CLASSES = (
+    "integrated_old", "integrated_modern", "low_end",
+    "mid_range", "high_end", "workstation",
+)
+
+
+def classify_gpu(gpu_value: Dict[str, str]) -> str:
+    """Deterministic: maps (renderer, vendor) dict to one of 6 classes.
+
+    See data/cpt_*.json — each CPT table has an entry for every class.
+    """
+    r = gpu_value.get("renderer", "")
+
+    if re.search(r"Intel.*HD Graphics (3000|4000|2500)", r):
+        return "integrated_old"
+    if re.search(
+        r"Intel.*(HD Graphics (4[56]|5\d\d|6\d\d)|UHD Graphics|Graphics Family|Iris|Arc)",
+        r,
+    ):
+        return "integrated_modern"
+    if re.search(
+        r"AMD.*(Radeon(\(TM\))? (Graphics|6\d\dM|7\d\dM|8\d\dM)|Vega [0-9]|"
+        r"Renoir|Rembrandt|TM Graphics)",
+        r, re.IGNORECASE,
+    ):
+        return "integrated_modern"
+
+    # NVIDIA: Firefox SanitizeRenderer.cpp collapses every GeForce into one of
+    # 3 vintage buckets (8800 GTX / GTX 480 / GTX 980). The renderer string
+    # exposed to JS is therefore vintage; pairing it with modern cores/screen
+    # creates an internal mismatch that FP Pro's tampering_ml flags. We pick
+    # `low_end` for all 3 buckets so cores stay 4-12 and screen 1080-1440p,
+    # consistent with what a real user with each of those (vintage) cards
+    # would have. Workstation overrides keep their high-tier classification.
+    if re.search(
+        r"(GeForce (8\d\d\d?|9\d\d\d?|GTX 980|GTX 480|GT 1030|GT 710|GT 730|"
+        r"GT 220|GT 240|210|310)|Quadro K\d|Radeon HD [1234]\d\d\d)", r,
+    ):
+        return "low_end"
+
+    # NVIDIA discrete (any other GeForce — should be rare after the pool was
+    # collapsed to the 3 sanitize buckets, but kept as a safety net).
+    m = re.search(r"GeForce\s+(?:GTX\s+|RTX\s+)?(\d{3,4})", r)
+    if m:
+        if "Quadro" in r or "Workstation" in r:
+            return "workstation"
+        # Anything that survives the sanitize collapse stays low_end to avoid
+        # the modern-cores/vintage-renderer pairing.
+        return "low_end"
+
+    # AMD discrete
+    m = re.search(r"Radeon[^0-9]*(\d{3,4})", r)
+    if m:
+        n = int(m.group(1))
+        if "FirePro" in r or "Radeon Pro" in r:
+            return "workstation"
+        if n >= 5700:
+            return "high_end"
+        if 5500 <= n <= 5600 or 580 <= n <= 590:
+            return "mid_range"
+        return "low_end"
+
+    # Fallback
+    return "mid_range"
+
+
+# ═══════════════════════════════════════════════════════════════════════
+#  NETWORK CONSTRUCTION
+# ═══════════════════════════════════════════════════════════════════════
+# Build once at import — the network is stateless, only the RNG varies.
+
+def _gpu_marginal():
+    """Build marginal distribution over GPU pool (uniform for now)."""
+    n = len(_GPU_POOL)
+    p = 1.0 / n
+    return [{"value": g, "prob": p} for g in _GPU_POOL]
+
+
+def _cpt_from_table(table: Dict[str, Any]) -> Dict[str, list]:
+    """CPT for conditional nodes: `{class_name: [{value, prob}, ...]}`."""
+    return dict(table)
+
+
+def _screen_tier(ctx):
+    """Classify screen width into tier for (gpu_class, screen_tier) CPTs."""
+    s = ctx.get("screen", {}) or {}
+    w = int(s.get("w", 1920))
+    h = int(s.get("h", 1080))
+    # Ultrawide: aspect ratio > 2.1 (e.g. 3440x1440, 5120x1440)
+    if h > 0 and (w / h) > 2.1:
+        return "ultrawide"
+    if w <= 1920:
+        return "1080p"
+    if w <= 2560:
+        return "1440p"
+    if w <= 3840:
+        return "2160p"
+    return "ultrawide"
+
+
+_NETWORK = Network([
+    Node("gpu", parents=[], cpt=_gpu_marginal()),
+    Node("gpu_class", parents=["gpu"], classifier=lambda ctx: classify_gpu(ctx["gpu"])),
+    # Hidden variable: within a gpu_class, user's OTHER components (RAM, SSD,
+    # cores, screen) correlate — a 'premium' mid_range user has more cores,
+    # larger SSD, higher-res screen than a 'budget' mid_range user. Without
+    # this, hwc/screen/storage would be independent given gpu_class (noisy).
+    Node("intra_tier", parents=["gpu_class"], cpt=_cpt_from_table(_CPT_INTRA_TIER)),
+    # hwc/screen/storage now jointly coherent via (gpu_class, intra_tier).
+    Node("hw_concurrency", parents=["gpu_class", "intra_tier"],
+         cpt=_cpt_from_table(_CPT_HWC)),
+    Node("screen", parents=["gpu_class", "intra_tier"],
+         cpt=_cpt_from_table(_CPT_SCREEN)),
+    # Derive screen_tier from screen for msaa parent lookup.
+    Node("screen_tier", parents=["screen"], classifier=_screen_tier),
+    # MSAA: realistic combo (4K + high_end GPU → MSAA=0 due to perf cost;
+    # 1080p + high_end → MSAA=4 common; 1080p + integrated → MSAA=0).
+    Node("msaa_samples", parents=["gpu_class", "screen_tier"],
+         cpt=_cpt_from_table(_CPT_MSAA)),
+    # Joint codec distribution (gpu_class only).
+    Node("codec", parents=["gpu_class"], cpt=_cpt_from_table(_CPT_CODEC)),
+    # Storage quota: coherent within gpu_class × intra_tier (premium workstation
+    # user → 2-3TB SSD; budget workstation user → 512GB; budget integrated_old
+    # → 128GB).
+    Node("storage_quota_mb", parents=["gpu_class", "intra_tier"],
+         cpt=_cpt_from_table(_CPT_STORAGE)),
+    # Audio: pro users (workstation) → 48/96kHz 6-8ch; old onboard → 44.1kHz
+    # 2ch high latency. Workstation GPU + 44.1kHz mono was previously
+    # implausible; now blocked by the CPT.
+    Node("audio", parents=["gpu_class"], cpt=_cpt_from_table(_CPT_AUDIO)),
+    Node("dark_theme", parents=[], cpt=_INDEP["dark_theme"]["table"]),
+])
+
+
+# ═══════════════════════════════════════════════════════════════════════
+#  FONT WHITELIST (Bayesian: core ∪ sampled_optional | gpu_class)
+# ═══════════════════════════════════════════════════════════════════════
+# Semantic flip: previously exclude-list (block N probed fonts per seed).
+# Now whitelist (browser sees ONLY these fonts, everything else hidden).
+# Core (~112): always included — fresh Win11 + Office 2021 English.
+# Optional (~40): sampled per-session with P(present | gpu_class). Gives
+# small realistic variance (~3-8 optional fonts differ per session) while
+# keeping the profile strongly centered on 'typical Windows user'.
+
+
+def derive_font_prefs(gpu_class: str, rng) -> Dict[str, str]:
+    """Build COHERENT whitelist + metrics strings for the session.
+
+    Sampling:
+      - Core fonts always included.
+      - Optional fonts sampled with P(font | gpu_class) from the CPT table.
+
+    Returns:
+      {
+        "whitelist": "arial,calibri,marlett,...",
+        "metrics":   "arial|0.978,calibri|0.934,marlett|0.855,..."
+      }
+
+    The whitelist is the list of font families to advertise. The metrics
+    string encodes per-family width scale factors that the consumer can
+    use to make each family detectable by width-diff font probes.
+
+    Each entry in font_pool.json carries its own {name, factor} pair so the
+    two pref strings are GUARANTEED coherent — no chance of a fabricated
+    font with factor 1.0 (undetectable) or a metrics entry for a font not
+    in the whitelist (useless).
+
+    Markers & add-new-font: simply add an entry to font_pool.json:core (with
+    a factor at least 4% away from 1.0) — no special-case code needed.
+    """
+    cpt = _CPT_FONTS_OPT.get(gpu_class)
+    if cpt is None:
+        cpt = _CPT_FONTS_OPT["integrated_modern"]
+    included: list = list(_FONT_CORE)  # always present
+    for entry in _FONT_OPTIONAL:
+        name = entry["name"]
+        p = cpt.get(name, 0.7)  # default 0.7 if CPT has no row for this font
+        if rng.random() < p:
+            included.append(entry)
+    # Deterministic ordering: sort by name
+    included.sort(key=lambda e: e["name"])
+    whitelist = ",".join(e["name"] for e in included)
+    metrics = ",".join(
+        f'{e["name"]}|{e["factor"]:.3f}' for e in included
+    )
+    return {"whitelist": whitelist, "metrics": metrics}
+
+
+# Back-compat shim: legacy callers still import derive_font_whitelist.
+def derive_font_whitelist(gpu_class: str, rng) -> str:
+    return derive_font_prefs(gpu_class, rng)["whitelist"]
+
+
+# ═══════════════════════════════════════════════════════════════════════
+#  PUBLIC API: Forge
+# ═══════════════════════════════════════════════════════════════════════
+import random
+
+
+class Forge:
+    """Fingerprint forge — single seed → coherent bundle."""
+
+    def __init__(self, seed: int):
+        self.seed = int(seed)
+        self._rng = random.Random(self.seed)
+
+    def sample(self) -> Dict[str, Any]:
+        bundle = _NETWORK.sample(self._rng)
+        gpu = bundle["gpu"]
+        screen = bundle["screen"]
+        audio = bundle["audio"]
+        codec = bundle["codec"]
+        return {
+            # Seed tracking
+            "stealth_seed": self.seed,
+            # Locked identity
+            **_LOCKED,
+            # GPU (coherent pair from 444 pool)
+            "webgl_renderer": gpu["renderer"],
+            "webgl_vendor": gpu["vendor"],
+            "gpu_class": bundle["gpu_class"],
+            # Hidden-variable debug metadata (not a Firefox pref, just for
+            # analysis / test result correlation tracking)
+            "intra_tier": bundle["intra_tier"],
+            "screen_tier": bundle["screen_tier"],
+            # Screen (coherent with GPU class)
+            "screen_w": int(screen["w"]),
+            "screen_h": int(screen["h"]),
+            "screen_avail_w": int(screen.get("aw", screen["w"])),
+            "screen_avail_h": int(screen.get("ah", screen["h"] - 40)),
+            "dpr": float(screen["dpr"]),
+            # Hardware (coherent with GPU class)
+            "hw_concurrency": int(bundle["hw_concurrency"]),
+            # WebGL MSAA (coherent with GPU class)
+            "msaa_samples": int(bundle["msaa_samples"]),
+            # Audio (independent joint)
+            "audio_sample_rate": int(audio["rate"]),
+            "audio_output_latency_ms": int(audio["latency"]),
+            "audio_max_channel_count": int(audio["channels"]),
+            # Codec prefs (joint, coherent with GPU class). All 5 are
+            # JS-visible: av1/webm_encoder via canPlayType/MediaRecorder,
+            # mediasource_* via MediaSource.isTypeSupported, webspeech_synth
+            # via 'speechSynthesis' in window (CreepJS voices probe).
+            "av1_enabled": bool(codec["av1_enabled"]),
+            "webm_encoder_enabled": bool(codec["webm_encoder_enabled"]),
+            "mediasource_webm": bool(codec["mediasource_webm"]),
+            "mediasource_mp4": bool(codec["mediasource_mp4"]),
+            "webspeech_synth": bool(codec["webspeech_synth"]),
+            # Storage quota MB (coherent with GPU class — workstation larger SSDs).
+            "storage_quota_mb": int(bundle["storage_quota_mb"]),
+            # Independent marginals
+            "dark_theme": int(bundle["dark_theme"]),
+            # Bayesian font prefs (coherent pair: whitelist + per-family
+            # width scale metrics, both sampled from the same font_pool.json
+            # and conditioned on gpu_class).
+            **{
+                f"font_{k}": v
+                for k, v in derive_font_prefs(
+                    bundle["gpu_class"], self._rng
+                ).items()
+            },
+        }
+
+
+def sample(seed: int) -> Dict[str, Any]:
+    """Convenience: `Forge(seed).sample()`."""
+    return Forge(seed).sample()

src/stealthfox/_fpforge/data/cpt_audio_given_class.json

@@ -0,0 +1,193 @@
+{
+  "_meta": "audio (rate/latency/channels) given gpu_class",
+  "table": {
+    "integrated_old": [
+      {
+        "value": {
+          "rate": 44100,
+          "latency": 50,
+          "channels": 2
+        },
+        "prob": 0.7
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 50,
+          "channels": 2
+        },
+        "prob": 0.3
+      }
+    ],
+    "integrated_modern": [
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 30,
+          "channels": 2
+        },
+        "prob": 0.6
+      },
+      {
+        "value": {
+          "rate": 44100,
+          "latency": 40,
+          "channels": 2
+        },
+        "prob": 0.25
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 25,
+          "channels": 6
+        },
+        "prob": 0.15
+      }
+    ],
+    "low_end": [
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 40,
+          "channels": 2
+        },
+        "prob": 0.55
+      },
+      {
+        "value": {
+          "rate": 44100,
+          "latency": 50,
+          "channels": 2
+        },
+        "prob": 0.3
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 30,
+          "channels": 6
+        },
+        "prob": 0.15
+      }
+    ],
+    "mid_range": [
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 25,
+          "channels": 2
+        },
+        "prob": 0.45
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 20,
+          "channels": 6
+        },
+        "prob": 0.3
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 20,
+          "channels": 8
+        },
+        "prob": 0.15
+      },
+      {
+        "value": {
+          "rate": 44100,
+          "latency": 30,
+          "channels": 2
+        },
+        "prob": 0.1
+      }
+    ],
+    "high_end": [
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 15,
+          "channels": 6
+        },
+        "prob": 0.3
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 15,
+          "channels": 8
+        },
+        "prob": 0.3
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 15,
+          "channels": 2
+        },
+        "prob": 0.2
+      },
+      {
+        "value": {
+          "rate": 96000,
+          "latency": 15,
+          "channels": 6
+        },
+        "prob": 0.1
+      },
+      {
+        "value": {
+          "rate": 96000,
+          "latency": 15,
+          "channels": 8
+        },
+        "prob": 0.1
+      }
+    ],
+    "workstation": [
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 10,
+          "channels": 8
+        },
+        "prob": 0.25
+      },
+      {
+        "value": {
+          "rate": 96000,
+          "latency": 10,
+          "channels": 8
+        },
+        "prob": 0.3
+      },
+      {
+        "value": {
+          "rate": 96000,
+          "latency": 10,
+          "channels": 6
+        },
+        "prob": 0.2
+      },
+      {
+        "value": {
+          "rate": 192000,
+          "latency": 10,
+          "channels": 8
+        },
+        "prob": 0.15
+      },
+      {
+        "value": {
+          "rate": 48000,
+          "latency": 15,
+          "channels": 6
+        },
+        "prob": 0.1
+      }
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_codec_given_class.json

@@ -0,0 +1,147 @@
+{
+  "_meta": "codec given gpu_class",
+  "table": {
+    "integrated_old": [
+      {
+        "value": {
+          "av1_enabled": false,
+          "webm_encoder_enabled": false,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 1.0
+      }
+    ],
+    "integrated_modern": [
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.55
+      },
+      {
+        "value": {
+          "av1_enabled": false,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.35
+      },
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": false
+        },
+        "prob": 0.1
+      }
+    ],
+    "low_end": [
+      {
+        "value": {
+          "av1_enabled": false,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.85
+      },
+      {
+        "value": {
+          "av1_enabled": false,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": false
+        },
+        "prob": 0.15
+      }
+    ],
+    "mid_range": [
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.55
+      },
+      {
+        "value": {
+          "av1_enabled": false,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.35
+      },
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": false
+        },
+        "prob": 0.1
+      }
+    ],
+    "high_end": [
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.85
+      },
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": false
+        },
+        "prob": 0.15
+      }
+    ],
+    "workstation": [
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": true
+        },
+        "prob": 0.7
+      },
+      {
+        "value": {
+          "av1_enabled": true,
+          "webm_encoder_enabled": true,
+          "mediasource_webm": true,
+          "mediasource_mp4": true,
+          "webspeech_synth": false
+        },
+        "prob": 0.3
+      }
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_fonts_optional_given_class.json

@@ -0,0 +1,295 @@
+{
+  "_meta": {
+    "name": "optional_font presence | gpu_class",
+    "parents": [
+      "gpu_class"
+    ],
+    "child": "optional_fonts_subset",
+    "description": "Per-optional-font presence probabilities given gpu_class. Each optional font in font_pool.json sampled INDEPENDENTLY with P(present | gpu_class) given here. Integrated_old: fewer language packs (older/cheaper machines). Workstation: more regional/language packs (international users, enterprise deployments).",
+    "rationale": "Near-invariant by design: most optional fonts have baseline P ~ 0.60-0.85 across classes. Per-session variance is small (~3-6 fonts toggling on/off out of 40 optional). Result: fingerprint always looks like 'typical Windows 11 + Office', with small realistic per-user variance in regional support."
+  },
+  "table": {
+    "integrated_old": {
+      "aparajita": 0.45,
+      "calibri": 0.9,
+      "dengxian": 0.3,
+      "dfkai-sb": 0.25,
+      "dokchampa": 0.2,
+      "estrangelo edessa": 0.55,
+      "euphemia": 0.6,
+      "fangsong": 0.35,
+      "gadugi": 0.88,
+      "gautami": 0.55,
+      "helv": 0.7,
+      "iskoola pota": 0.5,
+      "javanese text": 0.85,
+      "kaiti": 0.3,
+      "kalinga": 0.5,
+      "kartika": 0.5,
+      "khmer ui": 0.35,
+      "kokila": 0.55,
+      "lao ui": 0.35,
+      "latha": 0.65,
+      "leelawadee ui": 0.87,
+      "mangal": 0.65,
+      "meiryo": 0.6,
+      "microsoft uighur": 0.4,
+      "ms pmincho": 0.65,
+      "ms reference sans serif": 0.55,
+      "ms reference specialty": 0.5,
+      "ms ui gothic": 0.82,
+      "myanmar text": 0.84,
+      "nyala": 0.55,
+      "plantagenet cherokee": 0.6,
+      "raavi": 0.55,
+      "segoe fluent icons": 0.5,
+      "segoe ui light": 0.75,
+      "shonar bangla": 0.55,
+      "shruti": 0.55,
+      "simkai": 0.25,
+      "small fonts": 0.75,
+      "traditional arabic": 0.55,
+      "tunga": 0.55,
+      "urdu typesetting": 0.45,
+      "utsaah": 0.55,
+      "vani": 0.55,
+      "vijaya": 0.55,
+      "yu mincho": 0.55
+    },
+    "integrated_modern": {
+      "aparajita": 0.65,
+      "calibri": 0.78,
+      "dengxian": 0.5,
+      "dfkai-sb": 0.4,
+      "dokchampa": 0.4,
+      "estrangelo edessa": 0.7,
+      "euphemia": 0.78,
+      "fangsong": 0.55,
+      "gadugi": 0.96,
+      "gautami": 0.75,
+      "helv": 0.6,
+      "iskoola pota": 0.7,
+      "javanese text": 0.94,
+      "kaiti": 0.45,
+      "kalinga": 0.7,
+      "kartika": 0.7,
+      "khmer ui": 0.55,
+      "kokila": 0.75,
+      "lao ui": 0.55,
+      "latha": 0.82,
+      "leelawadee ui": 0.95,
+      "mangal": 0.82,
+      "meiryo": 0.8,
+      "microsoft uighur": 0.55,
+      "ms pmincho": 0.85,
+      "ms reference sans serif": 0.72,
+      "ms reference specialty": 0.68,
+      "ms ui gothic": 0.75,
+      "myanmar text": 0.94,
+      "nyala": 0.72,
+      "plantagenet cherokee": 0.78,
+      "raavi": 0.72,
+      "segoe fluent icons": 0.92,
+      "segoe ui light": 0.72,
+      "shonar bangla": 0.72,
+      "shruti": 0.72,
+      "simkai": 0.4,
+      "small fonts": 0.65,
+      "traditional arabic": 0.72,
+      "tunga": 0.72,
+      "urdu typesetting": 0.65,
+      "utsaah": 0.72,
+      "vani": 0.72,
+      "vijaya": 0.72,
+      "yu mincho": 0.75
+    },
+    "low_end": {
+      "aparajita": 0.55,
+      "calibri": 0.94,
+      "dengxian": 0.4,
+      "dfkai-sb": 0.3,
+      "dokchampa": 0.3,
+      "estrangelo edessa": 0.62,
+      "euphemia": 0.68,
+      "fangsong": 0.45,
+      "gadugi": 0.93,
+      "gautami": 0.65,
+      "helv": 0.78,
+      "iskoola pota": 0.6,
+      "javanese text": 0.91,
+      "kaiti": 0.35,
+      "kalinga": 0.6,
+      "kartika": 0.6,
+      "khmer ui": 0.45,
+      "kokila": 0.65,
+      "lao ui": 0.45,
+      "latha": 0.72,
+      "leelawadee ui": 0.92,
+      "mangal": 0.72,
+      "meiryo": 0.7,
+      "microsoft uighur": 0.48,
+      "ms pmincho": 0.75,
+      "ms reference sans serif": 0.62,
+      "ms reference specialty": 0.58,
+      "ms ui gothic": 0.9,
+      "myanmar text": 0.9,
+      "nyala": 0.62,
+      "plantagenet cherokee": 0.68,
+      "raavi": 0.62,
+      "segoe fluent icons": 0.8,
+      "segoe ui light": 0.88,
+      "shonar bangla": 0.62,
+      "shruti": 0.62,
+      "simkai": 0.3,
+      "small fonts": 0.83,
+      "traditional arabic": 0.62,
+      "tunga": 0.62,
+      "urdu typesetting": 0.55,
+      "utsaah": 0.62,
+      "vani": 0.62,
+      "vijaya": 0.62,
+      "yu mincho": 0.65
+    },
+    "mid_range": {
+      "aparajita": 0.72,
+      "calibri": 0.98,
+      "dengxian": 0.6,
+      "dfkai-sb": 0.5,
+      "dokchampa": 0.5,
+      "estrangelo edessa": 0.78,
+      "euphemia": 0.82,
+      "fangsong": 0.65,
+      "gadugi": 0.97,
+      "gautami": 0.8,
+      "helv": 0.85,
+      "iskoola pota": 0.78,
+      "javanese text": 0.96,
+      "kaiti": 0.55,
+      "kalinga": 0.78,
+      "kartika": 0.78,
+      "khmer ui": 0.65,
+      "kokila": 0.8,
+      "lao ui": 0.65,
+      "latha": 0.85,
+      "leelawadee ui": 0.97,
+      "mangal": 0.85,
+      "meiryo": 0.85,
+      "microsoft uighur": 0.65,
+      "ms pmincho": 0.88,
+      "ms reference sans serif": 0.78,
+      "ms reference specialty": 0.75,
+      "ms ui gothic": 0.96,
+      "myanmar text": 0.96,
+      "nyala": 0.78,
+      "plantagenet cherokee": 0.82,
+      "raavi": 0.78,
+      "segoe fluent icons": 0.94,
+      "segoe ui light": 0.94,
+      "shonar bangla": 0.78,
+      "shruti": 0.78,
+      "simkai": 0.5,
+      "small fonts": 0.9,
+      "traditional arabic": 0.78,
+      "tunga": 0.78,
+      "urdu typesetting": 0.72,
+      "utsaah": 0.78,
+      "vani": 0.78,
+      "vijaya": 0.78,
+      "yu mincho": 0.8
+    },
+    "high_end": {
+      "aparajita": 0.8,
+      "calibri": 0.99,
+      "dengxian": 0.7,
+      "dfkai-sb": 0.6,
+      "dokchampa": 0.6,
+      "estrangelo edessa": 0.85,
+      "euphemia": 0.88,
+      "fangsong": 0.72,
+      "gadugi": 0.98,
+      "gautami": 0.85,
+      "helv": 0.88,
+      "iskoola pota": 0.82,
+      "javanese text": 0.97,
+      "kaiti": 0.65,
+      "kalinga": 0.82,
+      "kartika": 0.82,
+      "khmer ui": 0.72,
+      "kokila": 0.85,
+      "lao ui": 0.72,
+      "latha": 0.9,
+      "leelawadee ui": 0.98,
+      "mangal": 0.9,
+      "meiryo": 0.9,
+      "microsoft uighur": 0.72,
+      "ms pmincho": 0.92,
+      "ms reference sans serif": 0.85,
+      "ms reference specialty": 0.82,
+      "ms ui gothic": 0.98,
+      "myanmar text": 0.97,
+      "nyala": 0.85,
+      "plantagenet cherokee": 0.88,
+      "raavi": 0.85,
+      "segoe fluent icons": 0.97,
+      "segoe ui light": 0.96,
+      "shonar bangla": 0.85,
+      "shruti": 0.85,
+      "simkai": 0.6,
+      "small fonts": 0.92,
+      "traditional arabic": 0.85,
+      "tunga": 0.85,
+      "urdu typesetting": 0.8,
+      "utsaah": 0.85,
+      "vani": 0.85,
+      "vijaya": 0.85,
+      "yu mincho": 0.88
+    },
+    "workstation": {
+      "aparajita": 0.88,
+      "calibri": 0.99,
+      "dengxian": 0.8,
+      "dfkai-sb": 0.75,
+      "dokchampa": 0.72,
+      "estrangelo edessa": 0.9,
+      "euphemia": 0.92,
+      "fangsong": 0.82,
+      "gadugi": 0.99,
+      "gautami": 0.92,
+      "helv": 0.9,
+      "iskoola pota": 0.9,
+      "javanese text": 0.98,
+      "kaiti": 0.78,
+      "kalinga": 0.9,
+      "kartika": 0.9,
+      "khmer ui": 0.8,
+      "kokila": 0.92,
+      "lao ui": 0.8,
+      "latha": 0.95,
+      "leelawadee ui": 0.99,
+      "mangal": 0.95,
+      "meiryo": 0.95,
+      "microsoft uighur": 0.82,
+      "ms pmincho": 0.95,
+      "ms reference sans serif": 0.92,
+      "ms reference specialty": 0.9,
+      "ms ui gothic": 0.98,
+      "myanmar text": 0.98,
+      "nyala": 0.92,
+      "plantagenet cherokee": 0.92,
+      "raavi": 0.92,
+      "segoe fluent icons": 0.98,
+      "segoe ui light": 0.97,
+      "shonar bangla": 0.92,
+      "shruti": 0.92,
+      "simkai": 0.72,
+      "small fonts": 0.94,
+      "traditional arabic": 0.92,
+      "tunga": 0.92,
+      "urdu typesetting": 0.88,
+      "utsaah": 0.92,
+      "vani": 0.92,
+      "vijaya": 0.92,
+      "yu mincho": 0.92
+    }
+  }
+}

src/stealthfox/_fpforge/data/cpt_hwc_given_class.json

@@ -0,0 +1,50 @@
+{
+  "_meta": {
+    "name": "hw_concurrency | gpu_class",
+    "parents": ["gpu_class"],
+    "child": "hw_concurrency",
+    "source": "Curated from realistic CPU/GPU pairings (Steam HW Survey + DIY build norms + laptop SKU patterns)"
+  },
+  "table": {
+    "integrated_old": [
+      {"value": 2, "prob": 0.20},
+      {"value": 4, "prob": 0.60},
+      {"value": 8, "prob": 0.20}
+    ],
+    "integrated_modern": [
+      {"value": 4, "prob": 0.20},
+      {"value": 6, "prob": 0.15},
+      {"value": 8, "prob": 0.35},
+      {"value": 12, "prob": 0.20},
+      {"value": 16, "prob": 0.10}
+    ],
+    "low_end": [
+      {"value": 4, "prob": 0.25},
+      {"value": 6, "prob": 0.25},
+      {"value": 8, "prob": 0.35},
+      {"value": 12, "prob": 0.15}
+    ],
+    "mid_range": [
+      {"value": 6, "prob": 0.15},
+      {"value": 8, "prob": 0.30},
+      {"value": 12, "prob": 0.30},
+      {"value": 16, "prob": 0.20},
+      {"value": 24, "prob": 0.05}
+    ],
+    "high_end": [
+      {"value": 8, "prob": 0.10},
+      {"value": 12, "prob": 0.25},
+      {"value": 16, "prob": 0.35},
+      {"value": 20, "prob": 0.05},
+      {"value": 24, "prob": 0.20},
+      {"value": 32, "prob": 0.05}
+    ],
+    "workstation": [
+      {"value": 8, "prob": 0.15},
+      {"value": 12, "prob": 0.20},
+      {"value": 16, "prob": 0.30},
+      {"value": 24, "prob": 0.20},
+      {"value": 32, "prob": 0.15}
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_hwc_given_class_tier.json

@@ -0,0 +1,349 @@
+{
+  "_meta": "hardware_concurrency given (gpu_class, intra_tier)",
+  "table": {
+    "[\"integrated_old\", \"budget\"]": [
+      {
+        "value": 2,
+        "prob": 0.65
+      },
+      {
+        "value": 4,
+        "prob": 0.3
+      },
+      {
+        "value": 8,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_old\", \"standard\"]": [
+      {
+        "value": 2,
+        "prob": 0.3
+      },
+      {
+        "value": 4,
+        "prob": 0.55
+      },
+      {
+        "value": 8,
+        "prob": 0.15
+      }
+    ],
+    "[\"integrated_old\", \"premium\"]": [
+      {
+        "value": 4,
+        "prob": 0.65
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 12,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_modern\", \"budget\"]": [
+      {
+        "value": 4,
+        "prob": 0.55
+      },
+      {
+        "value": 6,
+        "prob": 0.2
+      },
+      {
+        "value": 8,
+        "prob": 0.2
+      },
+      {
+        "value": 12,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_modern\", \"standard\"]": [
+      {
+        "value": 6,
+        "prob": 0.2
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 10,
+        "prob": 0.2
+      },
+      {
+        "value": 12,
+        "prob": 0.2
+      },
+      {
+        "value": 16,
+        "prob": 0.1
+      }
+    ],
+    "[\"integrated_modern\", \"premium\"]": [
+      {
+        "value": 8,
+        "prob": 0.2
+      },
+      {
+        "value": 10,
+        "prob": 0.2
+      },
+      {
+        "value": 12,
+        "prob": 0.3
+      },
+      {
+        "value": 14,
+        "prob": 0.15
+      },
+      {
+        "value": 16,
+        "prob": 0.15
+      }
+    ],
+    "[\"low_end\", \"budget\"]": [
+      {
+        "value": 4,
+        "prob": 0.5
+      },
+      {
+        "value": 6,
+        "prob": 0.25
+      },
+      {
+        "value": 8,
+        "prob": 0.2
+      },
+      {
+        "value": 12,
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"standard\"]": [
+      {
+        "value": 4,
+        "prob": 0.1
+      },
+      {
+        "value": 6,
+        "prob": 0.35
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 12,
+        "prob": 0.18
+      },
+      {
+        "value": 16,
+        "prob": 0.07
+      }
+    ],
+    "[\"low_end\", \"premium\"]": [
+      {
+        "value": 6,
+        "prob": 0.1
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 12,
+        "prob": 0.3
+      },
+      {
+        "value": 16,
+        "prob": 0.22
+      },
+      {
+        "value": 24,
+        "prob": 0.08
+      }
+    ],
+    "[\"mid_range\", \"budget\"]": [
+      {
+        "value": 6,
+        "prob": 0.55
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 12,
+        "prob": 0.1
+      },
+      {
+        "value": 16,
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"standard\"]": [
+      {
+        "value": 6,
+        "prob": 0.4
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 12,
+        "prob": 0.18
+      },
+      {
+        "value": 16,
+        "prob": 0.1
+      },
+      {
+        "value": 24,
+        "prob": 0.02
+      }
+    ],
+    "[\"mid_range\", \"premium\"]": [
+      {
+        "value": 6,
+        "prob": 0.15
+      },
+      {
+        "value": 8,
+        "prob": 0.45
+      },
+      {
+        "value": 12,
+        "prob": 0.2
+      },
+      {
+        "value": 16,
+        "prob": 0.15
+      },
+      {
+        "value": 24,
+        "prob": 0.05
+      }
+    ],
+    "[\"high_end\", \"budget\"]": [
+      {
+        "value": 6,
+        "prob": 0.1
+      },
+      {
+        "value": 8,
+        "prob": 0.55
+      },
+      {
+        "value": 12,
+        "prob": 0.2
+      },
+      {
+        "value": 16,
+        "prob": 0.15
+      }
+    ],
+    "[\"high_end\", \"standard\"]": [
+      {
+        "value": 8,
+        "prob": 0.3
+      },
+      {
+        "value": 12,
+        "prob": 0.18
+      },
+      {
+        "value": 14,
+        "prob": 0.15
+      },
+      {
+        "value": 16,
+        "prob": 0.27
+      },
+      {
+        "value": 24,
+        "prob": 0.1
+      }
+    ],
+    "[\"high_end\", \"premium\"]": [
+      {
+        "value": 12,
+        "prob": 0.1
+      },
+      {
+        "value": 14,
+        "prob": 0.15
+      },
+      {
+        "value": 16,
+        "prob": 0.3
+      },
+      {
+        "value": 24,
+        "prob": 0.35
+      },
+      {
+        "value": 32,
+        "prob": 0.1
+      }
+    ],
+    "[\"workstation\", \"budget\"]": [
+      {
+        "value": 8,
+        "prob": 0.4
+      },
+      {
+        "value": 12,
+        "prob": 0.3
+      },
+      {
+        "value": 16,
+        "prob": 0.2
+      },
+      {
+        "value": 24,
+        "prob": 0.1
+      }
+    ],
+    "[\"workstation\", \"standard\"]": [
+      {
+        "value": 12,
+        "prob": 0.1
+      },
+      {
+        "value": 16,
+        "prob": 0.4
+      },
+      {
+        "value": 24,
+        "prob": 0.3
+      },
+      {
+        "value": 32,
+        "prob": 0.2
+      }
+    ],
+    "[\"workstation\", \"premium\"]": [
+      {
+        "value": 24,
+        "prob": 0.3
+      },
+      {
+        "value": 32,
+        "prob": 0.45
+      },
+      {
+        "value": 48,
+        "prob": 0.15
+      },
+      {
+        "value": 64,
+        "prob": 0.1
+      }
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_intra_tier_given_class.json

@@ -0,0 +1,17 @@
+{
+  "_meta": {
+    "name": "intra_tier | gpu_class",
+    "parents": ["gpu_class"],
+    "child": "intra_tier",
+    "value_type": "str (budget|standard|premium)",
+    "rationale": "Hidden variable catching 'intra-class premium-ness'. Within a gpu_class, users vary in how premium their OTHER components are (RAM, SSD, cores). A mid_range GPU paired with 32 cores + 2TB SSD is a 'premium' mid_range user. Without this var, hwc/screen/storage would be statistically independent given gpu_class — unrealistic (real users pick coherent bundles). Tier distribution biased: integrated_old mostly budget/standard, workstation mostly premium."
+  },
+  "table": {
+    "integrated_old":    [{"value": "budget", "prob": 0.65}, {"value": "standard", "prob": 0.30}, {"value": "premium", "prob": 0.05}],
+    "integrated_modern": [{"value": "budget", "prob": 0.30}, {"value": "standard", "prob": 0.55}, {"value": "premium", "prob": 0.15}],
+    "low_end":           [{"value": "budget", "prob": 0.50}, {"value": "standard", "prob": 0.40}, {"value": "premium", "prob": 0.10}],
+    "mid_range":         [{"value": "budget", "prob": 0.25}, {"value": "standard", "prob": 0.50}, {"value": "premium", "prob": 0.25}],
+    "high_end":          [{"value": "budget", "prob": 0.15}, {"value": "standard", "prob": 0.50}, {"value": "premium", "prob": 0.35}],
+    "workstation":       [{"value": "budget", "prob": 0.10}, {"value": "standard", "prob": 0.40}, {"value": "premium", "prob": 0.50}]
+  }
+}

src/stealthfox/_fpforge/data/cpt_msaa_given_class.json

@@ -0,0 +1,16 @@
+{
+  "_meta": {
+    "name": "webgl.msaa-samples | gpu_class",
+    "parents": ["gpu_class"],
+    "child": "msaa_samples",
+    "source": "High-end GPUs more likely to have MSAA enabled in games; integrated usually off"
+  },
+  "table": {
+    "integrated_old":    [{"value": 0, "prob": 0.85}, {"value": 2, "prob": 0.15}],
+    "integrated_modern": [{"value": 0, "prob": 0.70}, {"value": 2, "prob": 0.25}, {"value": 4, "prob": 0.05}],
+    "low_end":           [{"value": 0, "prob": 0.55}, {"value": 2, "prob": 0.35}, {"value": 4, "prob": 0.10}],
+    "mid_range":         [{"value": 0, "prob": 0.35}, {"value": 2, "prob": 0.35}, {"value": 4, "prob": 0.30}],
+    "high_end":          [{"value": 0, "prob": 0.20}, {"value": 2, "prob": 0.25}, {"value": 4, "prob": 0.55}],
+    "workstation":       [{"value": 0, "prob": 0.50}, {"value": 2, "prob": 0.25}, {"value": 4, "prob": 0.25}]
+  }
+}

src/stealthfox/_fpforge/data/cpt_msaa_given_class_screen.json

@@ -0,0 +1,305 @@
+{
+  "_meta": "msaa_samples given (gpu_class, screen_tier)",
+  "table": {
+    "[\"integrated_old\", \"1080p\"]": [
+      {
+        "value": 2,
+        "prob": 0.75
+      },
+      {
+        "value": 4,
+        "prob": 0.2
+      },
+      {
+        "value": 8,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_old\", \"1440p\"]": [
+      {
+        "value": 2,
+        "prob": 0.85
+      },
+      {
+        "value": 4,
+        "prob": 0.15
+      }
+    ],
+    "[\"integrated_old\", \"2160p\"]": [
+      {
+        "value": 2,
+        "prob": 1.0
+      }
+    ],
+    "[\"integrated_old\", \"ultrawide\"]": [
+      {
+        "value": 2,
+        "prob": 1.0
+      }
+    ],
+    "[\"integrated_modern\", \"1080p\"]": [
+      {
+        "value": 2,
+        "prob": 0.5
+      },
+      {
+        "value": 4,
+        "prob": 0.4
+      },
+      {
+        "value": 8,
+        "prob": 0.1
+      }
+    ],
+    "[\"integrated_modern\", \"1440p\"]": [
+      {
+        "value": 2,
+        "prob": 0.6
+      },
+      {
+        "value": 4,
+        "prob": 0.35
+      },
+      {
+        "value": 8,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_modern\", \"2160p\"]": [
+      {
+        "value": 2,
+        "prob": 0.85
+      },
+      {
+        "value": 4,
+        "prob": 0.15
+      }
+    ],
+    "[\"integrated_modern\", \"ultrawide\"]": [
+      {
+        "value": 2,
+        "prob": 0.8
+      },
+      {
+        "value": 4,
+        "prob": 0.2
+      }
+    ],
+    "[\"low_end\", \"1080p\"]": [
+      {
+        "value": 2,
+        "prob": 0.4
+      },
+      {
+        "value": 4,
+        "prob": 0.45
+      },
+      {
+        "value": 8,
+        "prob": 0.15
+      }
+    ],
+    "[\"low_end\", \"1440p\"]": [
+      {
+        "value": 2,
+        "prob": 0.55
+      },
+      {
+        "value": 4,
+        "prob": 0.4
+      },
+      {
+        "value": 8,
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"2160p\"]": [
+      {
+        "value": 2,
+        "prob": 0.85
+      },
+      {
+        "value": 4,
+        "prob": 0.15
+      }
+    ],
+    "[\"low_end\", \"ultrawide\"]": [
+      {
+        "value": 2,
+        "prob": 0.7
+      },
+      {
+        "value": 4,
+        "prob": 0.3
+      }
+    ],
+    "[\"mid_range\", \"1080p\"]": [
+      {
+        "value": 2,
+        "prob": 0.3
+      },
+      {
+        "value": 4,
+        "prob": 0.5
+      },
+      {
+        "value": 8,
+        "prob": 0.2
+      }
+    ],
+    "[\"mid_range\", \"1440p\"]": [
+      {
+        "value": 2,
+        "prob": 0.4
+      },
+      {
+        "value": 4,
+        "prob": 0.45
+      },
+      {
+        "value": 8,
+        "prob": 0.15
+      }
+    ],
+    "[\"mid_range\", \"2160p\"]": [
+      {
+        "value": 2,
+        "prob": 0.65
+      },
+      {
+        "value": 4,
+        "prob": 0.3
+      },
+      {
+        "value": 8,
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"ultrawide\"]": [
+      {
+        "value": 2,
+        "prob": 0.55
+      },
+      {
+        "value": 4,
+        "prob": 0.4
+      },
+      {
+        "value": 8,
+        "prob": 0.05
+      }
+    ],
+    "[\"high_end\", \"1080p\"]": [
+      {
+        "value": 2,
+        "prob": 0.2
+      },
+      {
+        "value": 4,
+        "prob": 0.45
+      },
+      {
+        "value": 8,
+        "prob": 0.35
+      }
+    ],
+    "[\"high_end\", \"1440p\"]": [
+      {
+        "value": 2,
+        "prob": 0.25
+      },
+      {
+        "value": 4,
+        "prob": 0.5
+      },
+      {
+        "value": 8,
+        "prob": 0.25
+      }
+    ],
+    "[\"high_end\", \"2160p\"]": [
+      {
+        "value": 2,
+        "prob": 0.4
+      },
+      {
+        "value": 4,
+        "prob": 0.45
+      },
+      {
+        "value": 8,
+        "prob": 0.15
+      }
+    ],
+    "[\"high_end\", \"ultrawide\"]": [
+      {
+        "value": 2,
+        "prob": 0.3
+      },
+      {
+        "value": 4,
+        "prob": 0.5
+      },
+      {
+        "value": 8,
+        "prob": 0.2
+      }
+    ],
+    "[\"workstation\", \"1080p\"]": [
+      {
+        "value": 2,
+        "prob": 0.15
+      },
+      {
+        "value": 4,
+        "prob": 0.5
+      },
+      {
+        "value": 8,
+        "prob": 0.35
+      }
+    ],
+    "[\"workstation\", \"1440p\"]": [
+      {
+        "value": 2,
+        "prob": 0.15
+      },
+      {
+        "value": 4,
+        "prob": 0.55
+      },
+      {
+        "value": 8,
+        "prob": 0.3
+      }
+    ],
+    "[\"workstation\", \"2160p\"]": [
+      {
+        "value": 2,
+        "prob": 0.25
+      },
+      {
+        "value": 4,
+        "prob": 0.55
+      },
+      {
+        "value": 8,
+        "prob": 0.2
+      }
+    ],
+    "[\"workstation\", \"ultrawide\"]": [
+      {
+        "value": 2,
+        "prob": 0.2
+      },
+      {
+        "value": 4,
+        "prob": 0.55
+      },
+      {
+        "value": 8,
+        "prob": 0.25
+      }
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_screen_given_class.json

@@ -0,0 +1,54 @@
+{
+  "_meta": {
+    "name": "screen | gpu_class",
+    "parents": ["gpu_class"],
+    "child": "screen",
+    "value_shape": {"w": "int css px", "h": "int css px", "dpr": "float", "aw": "availWidth", "ah": "availHeight"},
+    "source": "Curated Windows desktop/laptop resolutions. Restricted to width >= 1920 to avoid FP Pro's server-side screen_resolution normalization (FP Pro sorts non-standard landscape resolutions like 1536x864 into [smaller, larger] order in raw_device_attributes.screen_resolution, appearing flipped vs our spoof). All retained resolutions are common and NOT normalized by FP Pro."
+  },
+  "table": {
+    "integrated_old": [
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.0, "aw": 1920, "ah": 1040}, "prob": 0.90},
+      {"value": {"w": 1920, "h": 1200, "dpr": 1.0, "aw": 1920, "ah": 1160}, "prob": 0.10}
+    ],
+    "integrated_modern": [
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.0, "aw": 1920, "ah": 1040}, "prob": 0.60},
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.25, "aw": 1920, "ah": 1040}, "prob": 0.18},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.0, "aw": 2560, "ah": 1400}, "prob": 0.10},
+      {"value": {"w": 1920, "h": 1200, "dpr": 1.0, "aw": 1920, "ah": 1160}, "prob": 0.08},
+      {"value": {"w": 2560, "h": 1600, "dpr": 1.25, "aw": 2560, "ah": 1560}, "prob": 0.04}
+    ],
+    "low_end": [
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.0, "aw": 1920, "ah": 1040}, "prob": 0.70},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.0, "aw": 2560, "ah": 1400}, "prob": 0.20},
+      {"value": {"w": 1920, "h": 1200, "dpr": 1.0, "aw": 1920, "ah": 1160}, "prob": 0.10}
+    ],
+    "mid_range": [
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.0, "aw": 1920, "ah": 1040}, "prob": 0.50},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.0, "aw": 2560, "ah": 1400}, "prob": 0.25},
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.25, "aw": 1920, "ah": 1040}, "prob": 0.08},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.25, "aw": 2560, "ah": 1400}, "prob": 0.05},
+      {"value": {"w": 3840, "h": 2160, "dpr": 1.0, "aw": 3840, "ah": 2120}, "prob": 0.04},
+      {"value": {"w": 3840, "h": 2160, "dpr": 1.5, "aw": 3840, "ah": 2120}, "prob": 0.04},
+      {"value": {"w": 2560, "h": 1080, "dpr": 1.0, "aw": 2560, "ah": 1040}, "prob": 0.04}
+    ],
+    "high_end": [
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.0, "aw": 1920, "ah": 1040}, "prob": 0.25},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.0, "aw": 2560, "ah": 1400}, "prob": 0.30},
+      {"value": {"w": 3840, "h": 2160, "dpr": 1.0, "aw": 3840, "ah": 2120}, "prob": 0.15},
+      {"value": {"w": 3840, "h": 2160, "dpr": 1.5, "aw": 3840, "ah": 2120}, "prob": 0.10},
+      {"value": {"w": 3440, "h": 1440, "dpr": 1.0, "aw": 3440, "ah": 1400}, "prob": 0.08},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.25, "aw": 2560, "ah": 1400}, "prob": 0.05},
+      {"value": {"w": 5120, "h": 1440, "dpr": 1.0, "aw": 5120, "ah": 1400}, "prob": 0.04},
+      {"value": {"w": 3840, "h": 2160, "dpr": 2.0, "aw": 3840, "ah": 2120}, "prob": 0.03}
+    ],
+    "workstation": [
+      {"value": {"w": 1920, "h": 1080, "dpr": 1.0, "aw": 1920, "ah": 1040}, "prob": 0.25},
+      {"value": {"w": 2560, "h": 1440, "dpr": 1.0, "aw": 2560, "ah": 1400}, "prob": 0.25},
+      {"value": {"w": 3840, "h": 2160, "dpr": 1.0, "aw": 3840, "ah": 2120}, "prob": 0.25},
+      {"value": {"w": 3840, "h": 2160, "dpr": 1.5, "aw": 3840, "ah": 2120}, "prob": 0.15},
+      {"value": {"w": 5120, "h": 2880, "dpr": 1.0, "aw": 5120, "ah": 2840}, "prob": 0.05},
+      {"value": {"w": 3840, "h": 2400, "dpr": 1.5, "aw": 3840, "ah": 2360}, "prob": 0.05}
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_screen_given_class_tier.json

@@ -0,0 +1,761 @@
+{
+  "_meta": "screen given (gpu_class, intra_tier)",
+  "table": {
+    "[\"integrated_old\", \"budget\"]": [
+      {
+        "value": {
+          "w": 1366,
+          "h": 768,
+          "aw": 1366,
+          "ah": 728,
+          "dpr": 1.0
+        },
+        "prob": 0.78
+      },
+      {
+        "value": {
+          "w": 1280,
+          "h": 800,
+          "aw": 1280,
+          "ah": 760,
+          "dpr": 1.0
+        },
+        "prob": 0.15
+      },
+      {
+        "value": {
+          "w": 1024,
+          "h": 768,
+          "aw": 1024,
+          "ah": 728,
+          "dpr": 1.0
+        },
+        "prob": 0.07
+      }
+    ],
+    "[\"integrated_old\", \"standard\"]": [
+      {
+        "value": {
+          "w": 1366,
+          "h": 768,
+          "aw": 1366,
+          "ah": 728,
+          "dpr": 1.0
+        },
+        "prob": 0.55
+      },
+      {
+        "value": {
+          "w": 1600,
+          "h": 900,
+          "aw": 1600,
+          "ah": 860,
+          "dpr": 1.0
+        },
+        "prob": 0.25
+      },
+      {
+        "value": {
+          "w": 1280,
+          "h": 800,
+          "aw": 1280,
+          "ah": 760,
+          "dpr": 1.0
+        },
+        "prob": 0.1
+      },
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.1
+      }
+    ],
+    "[\"integrated_old\", \"premium\"]": [
+      {
+        "value": {
+          "w": 1600,
+          "h": 900,
+          "aw": 1600,
+          "ah": 860,
+          "dpr": 1.0
+        },
+        "prob": 0.45
+      },
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.4
+      },
+      {
+        "value": {
+          "w": 1366,
+          "h": 768,
+          "aw": 1366,
+          "ah": 728,
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+    ],
+    "[\"integrated_modern\", \"budget\"]": [
+      {
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+          "h": 768,
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+          "dpr": 1.0
+        },
+        "prob": 0.3
+      },
+      {
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+          "dpr": 1.0
+        },
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+      },
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+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_modern\", \"standard\"]": [
+      {
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+          "h": 1080,
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+          "dpr": 1.0
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+        },
+        "prob": 0.08
+      }
+    ],
+    "[\"integrated_modern\", \"premium\"]": [
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+          "h": 1080,
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+        },
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+        },
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+      {
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+          "dpr": 1.0
+        },
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+      {
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+          "dpr": 1.0
+        },
+        "prob": 0.2
+      }
+    ],
+    "[\"low_end\", \"budget\"]": [
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.85
+      },
+      {
+        "value": {
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+          "h": 1200,
+          "aw": 1920,
+          "ah": 1160,
+          "dpr": 1.0
+        },
+        "prob": 0.1
+      },
+      {
+        "value": {
+          "w": 2560,
+          "h": 1440,
+          "aw": 2560,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"standard\"]": [
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.6
+      },
+      {
+        "value": {
+          "w": 1920,
+          "h": 1200,
+          "aw": 1920,
+          "ah": 1160,
+          "dpr": 1.0
+        },
+        "prob": 0.1
+      },
+      {
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+          "dpr": 1.0
+        },
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+      },
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+          "ah": 2120,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"premium\"]": [
+      {
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+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.25
+      },
+      {
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+          "aw": 2560,
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+          "dpr": 1.0
+        },
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+      },
+      {
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+        },
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+      },
+      {
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+          "dpr": 1.0
+        },
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+      },
+      {
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+          "h": 1200,
+          "aw": 1920,
+          "ah": 1160,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"budget\"]": [
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.75
+      },
+      {
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+          "dpr": 1.0
+        },
+        "prob": 0.2
+      },
+      {
+        "value": {
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+          "h": 1200,
+          "aw": 1920,
+          "ah": 1160,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"standard\"]": [
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.45
+      },
+      {
+        "value": {
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+          "h": 1440,
+          "aw": 2560,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.4
+      },
+      {
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+          "h": 2160,
+          "aw": 3840,
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+          "dpr": 1.0
+        },
+        "prob": 0.1
+      },
+      {
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+          "h": 1440,
+          "aw": 3440,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"premium\"]": [
+      {
+        "value": {
+          "w": 1920,
+          "h": 1080,
+          "aw": 1920,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.15
+      },
+      {
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+          "aw": 2560,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.5
+      },
+      {
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+        },
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+      },
+      {
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+        },
+        "prob": 0.1
+      },
+      {
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+          "aw": 2560,
+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"high_end\", \"budget\"]": [
+      {
+        "value": {
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+          "h": 1080,
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+          "ah": 1040,
+          "dpr": 1.0
+        },
+        "prob": 0.2
+      },
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+          "dpr": 1.0
+        },
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+      },
+      {
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+          "h": 2160,
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+          "ah": 2120,
+          "dpr": 1.0
+        },
+        "prob": 0.2
+      },
+      {
+        "value": {
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+          "h": 1440,
+          "aw": 3440,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"high_end\", \"standard\"]": [
+      {
+        "value": {
+          "w": 2560,
+          "h": 1440,
+          "aw": 2560,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.4
+      },
+      {
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+          "h": 2160,
+          "aw": 3840,
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+          "dpr": 1.0
+        },
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+      {
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+          "dpr": 1.0
+        },
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+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"high_end\", \"premium\"]": [
+      {
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+          "h": 2160,
+          "aw": 3840,
+          "ah": 2120,
+          "dpr": 1.0
+        },
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+      {
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+          "aw": 2560,
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+        },
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+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"workstation\", \"budget\"]": [
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+          "h": 1440,
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+          "dpr": 1.0
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+          "dpr": 1.0
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+      {
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+          "h": 1200,
+          "aw": 1920,
+          "ah": 1160,
+          "dpr": 1.0
+        },
+        "prob": 0.1
+      },
+      {
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+          "h": 1600,
+          "aw": 2560,
+          "ah": 1560,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ],
+    "[\"workstation\", \"standard\"]": [
+      {
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+          "h": 1440,
+          "aw": 2560,
+          "ah": 1400,
+          "dpr": 1.0
+        },
+        "prob": 0.3
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+          "dpr": 1.0
+        },
+        "prob": 0.45
+      },
+      {
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+          "h": 1600,
+          "aw": 2560,
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+          "dpr": 1.0
+        },
+        "prob": 0.1
+      }
+    ],
+    "[\"workstation\", \"premium\"]": [
+      {
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+          "h": 2160,
+          "aw": 3840,
+          "ah": 2120,
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+        },
+        "prob": 0.55
+      },
+      {
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+          "w": 2560,
+          "h": 1600,
+          "aw": 2560,
+          "ah": 1560,
+          "dpr": 1.0
+        },
+        "prob": 0.15
+      },
+      {
+        "value": {
+          "w": 5120,
+          "h": 2160,
+          "aw": 5120,
+          "ah": 2120,
+          "dpr": 1.0
+        },
+        "prob": 0.15
+      },
+      {
+        "value": {
+          "w": 3840,
+          "h": 2400,
+          "aw": 3840,
+          "ah": 2360,
+          "dpr": 1.0
+        },
+        "prob": 0.1
+      },
+      {
+        "value": {
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+          "h": 2160,
+          "aw": 7680,
+          "ah": 2120,
+          "dpr": 1.0
+        },
+        "prob": 0.05
+      }
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_storage_given_class.json

@@ -0,0 +1,60 @@
+{
+  "_meta": {
+    "name": "storage_quota_mb | gpu_class",
+    "parents": ["gpu_class"],
+    "child": "storage_quota_mb",
+    "value_shape": "int megabytes (reported as navigator.storage.estimate().quota / (1024*1024))",
+    "description": "Storage quota override returned by navigator.storage.estimate(). Real Firefox computes quota from disk space, which is a fingerprinting signal (stable per host). We replace it with a realistic per-session value conditioned on gpu_class — modern/high-end users tend to have larger SSDs, integrated_old older/smaller disks.",
+    "source": "Typical Windows 11 disk sizes 2024-2026 per segment: budget laptops 256-512GB SSD, mainstream 512GB-1TB SSD, gaming/workstation 1-4TB SSD. Firefox default storage quota is ~50% of available disk (capped). We simulate that computation per-tier.",
+    "rationale": "Values are pre-quota-limit MB as Firefox would return to navigator.storage.estimate().quota. Probabilities cover realistic ranges centered on the segment median. A single session returns one value; fingerprinters that hash the exact quota get per-session variance, matching cross-user diversity."
+  },
+  "table": {
+    "integrated_old": [
+      {"value": 61440,   "prob": 0.30},
+      {"value": 102400,  "prob": 0.25},
+      {"value": 122880,  "prob": 0.20},
+      {"value": 204800,  "prob": 0.15},
+      {"value": 40960,   "prob": 0.10}
+    ],
+    "integrated_modern": [
+      {"value": 204800,  "prob": 0.30},
+      {"value": 307200,  "prob": 0.25},
+      {"value": 122880,  "prob": 0.15},
+      {"value": 409600,  "prob": 0.15},
+      {"value": 102400,  "prob": 0.10},
+      {"value": 512000,  "prob": 0.05}
+    ],
+    "low_end": [
+      {"value": 122880,  "prob": 0.30},
+      {"value": 204800,  "prob": 0.25},
+      {"value": 102400,  "prob": 0.20},
+      {"value": 61440,   "prob": 0.15},
+      {"value": 307200,  "prob": 0.10}
+    ],
+    "mid_range": [
+      {"value": 307200,  "prob": 0.30},
+      {"value": 409600,  "prob": 0.25},
+      {"value": 204800,  "prob": 0.20},
+      {"value": 512000,  "prob": 0.15},
+      {"value": 716800,  "prob": 0.05},
+      {"value": 122880,  "prob": 0.05}
+    ],
+    "high_end": [
+      {"value": 512000,  "prob": 0.25},
+      {"value": 716800,  "prob": 0.25},
+      {"value": 409600,  "prob": 0.20},
+      {"value": 1024000, "prob": 0.15},
+      {"value": 307200,  "prob": 0.10},
+      {"value": 1536000, "prob": 0.05}
+    ],
+    "workstation": [
+      {"value": 1024000, "prob": 0.25},
+      {"value": 1536000, "prob": 0.20},
+      {"value": 716800,  "prob": 0.20},
+      {"value": 2048000, "prob": 0.15},
+      {"value": 512000,  "prob": 0.10},
+      {"value": 3072000, "prob": 0.05},
+      {"value": 409600,  "prob": 0.05}
+    ]
+  }
+}

src/stealthfox/_fpforge/data/cpt_storage_given_class_tier.json

@@ -0,0 +1,305 @@
+{
+  "_meta": "storage_quota_mb given (gpu_class, intra_tier)",
+  "table": {
+    "[\"integrated_old\", \"budget\"]": [
+      {
+        "value": 32000,
+        "prob": 0.3
+      },
+      {
+        "value": 64000,
+        "prob": 0.4
+      },
+      {
+        "value": 128000,
+        "prob": 0.25
+      },
+      {
+        "value": 256000,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_old\", \"standard\"]": [
+      {
+        "value": 64000,
+        "prob": 0.2
+      },
+      {
+        "value": 128000,
+        "prob": 0.45
+      },
+      {
+        "value": 256000,
+        "prob": 0.25
+      },
+      {
+        "value": 500000,
+        "prob": 0.1
+      }
+    ],
+    "[\"integrated_old\", \"premium\"]": [
+      {
+        "value": 128000,
+        "prob": 0.2
+      },
+      {
+        "value": 256000,
+        "prob": 0.45
+      },
+      {
+        "value": 500000,
+        "prob": 0.3
+      },
+      {
+        "value": 1000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_modern\", \"budget\"]": [
+      {
+        "value": 64000,
+        "prob": 0.2
+      },
+      {
+        "value": 128000,
+        "prob": 0.3
+      },
+      {
+        "value": 256000,
+        "prob": 0.3
+      },
+      {
+        "value": 500000,
+        "prob": 0.2
+      }
+    ],
+    "[\"integrated_modern\", \"standard\"]": [
+      {
+        "value": 256000,
+        "prob": 0.25
+      },
+      {
+        "value": 500000,
+        "prob": 0.45
+      },
+      {
+        "value": 1000000,
+        "prob": 0.25
+      },
+      {
+        "value": 2000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"integrated_modern\", \"premium\"]": [
+      {
+        "value": 500000,
+        "prob": 0.25
+      },
+      {
+        "value": 1000000,
+        "prob": 0.5
+      },
+      {
+        "value": 2000000,
+        "prob": 0.2
+      },
+      {
+        "value": 4000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"budget\"]": [
+      {
+        "value": 128000,
+        "prob": 0.2
+      },
+      {
+        "value": 256000,
+        "prob": 0.5
+      },
+      {
+        "value": 500000,
+        "prob": 0.25
+      },
+      {
+        "value": 1000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"standard\"]": [
+      {
+        "value": 256000,
+        "prob": 0.2
+      },
+      {
+        "value": 500000,
+        "prob": 0.5
+      },
+      {
+        "value": 1000000,
+        "prob": 0.25
+      },
+      {
+        "value": 2000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"low_end\", \"premium\"]": [
+      {
+        "value": 500000,
+        "prob": 0.2
+      },
+      {
+        "value": 1000000,
+        "prob": 0.5
+      },
+      {
+        "value": 2000000,
+        "prob": 0.25
+      },
+      {
+        "value": 4000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"budget\"]": [
+      {
+        "value": 256000,
+        "prob": 0.15
+      },
+      {
+        "value": 500000,
+        "prob": 0.5
+      },
+      {
+        "value": 1000000,
+        "prob": 0.3
+      },
+      {
+        "value": 2000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"standard\"]": [
+      {
+        "value": 500000,
+        "prob": 0.2
+      },
+      {
+        "value": 1000000,
+        "prob": 0.55
+      },
+      {
+        "value": 2000000,
+        "prob": 0.2
+      },
+      {
+        "value": 4000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"mid_range\", \"premium\"]": [
+      {
+        "value": 1000000,
+        "prob": 0.4
+      },
+      {
+        "value": 2000000,
+        "prob": 0.45
+      },
+      {
+        "value": 4000000,
+        "prob": 0.15
+      }
+    ],
+    "[\"high_end\", \"budget\"]": [
+      {
+        "value": 500000,
+        "prob": 0.15
+      },
+      {
+        "value": 1000000,
+        "prob": 0.5
+      },
+      {
+        "value": 2000000,
+        "prob": 0.3
+      },
+      {
+        "value": 4000000,
+        "prob": 0.05
+      }
+    ],
+    "[\"high_end\", \"standard\"]": [
+      {
+        "value": 1000000,
+        "prob": 0.3
+      },
+      {
+        "value": 2000000,
+        "prob": 0.5
+      },
+      {
+        "value": 4000000,
+        "prob": 0.2
+      }
+    ],
+    "[\"high_end\", \"premium\"]": [
+      {
+        "value": 2000000,
+        "prob": 0.4
+      },
+      {
+        "value": 4000000,
+        "prob": 0.45
+      },
+      {
+        "value": 8000000,
+        "prob": 0.15
+      }
+    ],
+    "[\"workstation\", \"budget\"]": [
+      {
+        "value": 1000000,
+        "prob": 0.3
+      },
+      {
+        "value": 2000000,
+        "prob": 0.5
+      },
+      {
+        "value": 4000000,
+        "prob": 0.2
+      }
+    ],
+    "[\"workstation\", \"standard\"]": [
+      {
+        "value": 2000000,
+        "prob": 0.3
+      },
+      {
+        "value": 4000000,
+        "prob": 0.5
+      },
+      {
+        "value": 8000000,
+        "prob": 0.2
+      }
+    ],
+    "[\"workstation\", \"premium\"]": [
+      {
+        "value": 4000000,
+        "prob": 0.35
+      },
+      {
+        "value": 8000000,
+        "prob": 0.45
+      },
+      {
+        "value": 16000000,
+        "prob": 0.2
+      }
+    ]
+  }
+}

src/stealthfox/_fpforge/data/ff_win_distributions.json

@@ -0,0 +1,650 @@
+{
+  "_source": "browserforge fingerprint-network.zip, FF/Windows slice, 3 userAgent leaves merged",
+  "_ff_win_uas": [
+    "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:145.0) Gecko/20100101 Firefox/145.0",
+    "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:135.0) Gecko/20100101 Firefox/135.0",
+    "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:147.0) Gecko/20100101 Firefox/147.0"
+  ],
+  "_note": "Per-node weighted distributions. Marginal over the 3 Firefox/Windows UAs present in browserforge data.",
+  "distributions": {
+    "appCodeName": [
+      [
+        "Mozilla",
+        1.0
+      ]
+    ],
+    "appVersion": [
+      [
+        "5.0 (Windows)",
+        1.0
+      ]
+    ],
+    "doNotTrack": [
+      [
+        "1",
+        1.0
+      ]
+    ],
+    "extraProperties": [
+      [
+        {
+          "vendorFlavors": [],
+          "globalPrivacyControl": true,
+          "pdfViewerEnabled": true,
+          "installedApps": []
+        },
+        0.6111111111111112
+      ],
+      [
+        {
+          "vendorFlavors": [],
+          "globalPrivacyControl": null,
+          "pdfViewerEnabled": null,
+          "installedApps": []
+        },
+        0.3888888888888889
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+    ],
+    "maxTouchPoints": [
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+      ],
+      [
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+        0.05555555555555555
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+    ],
+    "oscpu": [
+      [
+        "Windows NT 10.0; Win64; x64",
+        1.0
+      ]
+    ],
+    "webdriver": [
+      [
+        false,
+        1.0
+      ]
+    ],
+    "productSub": [
+      [
+        "20100101",
+        1.0
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+    ],
+    "hardwareConcurrency": [
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+        0.06666666666666667
+      ],
+      [
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+        0.05555555555555555
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+      [
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+          "colorDepth": 24,
+          "pixelDepth": 24,
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+        0.05555555555555555
+      ],
+      [
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+          "colorDepth": 24,
+          "pixelDepth": 24,
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+        0.05555555555555555
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+      [
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+          "height": 768,
+          "availWidth": 1366,
+          "availHeight": 768,
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+          "outerHeight": 1280,
+          "colorDepth": 24,
+          "pixelDepth": 24,
+          "devicePixelRatio": 1
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+        0.03333333333333333
+      ],
+      [
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+        0.03333333333333333
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+        {
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+              "name": "PDF Viewer",
+              "description": "Portable Document Format",
+              "filename": "internal-pdf-viewer",
+              "mimeTypes": [
+                {
+                  "type": "application/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                },
+                {
+                  "type": "text/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                }
+              ]
+            },
+            {
+              "name": "Chrome PDF Viewer",
+              "description": "Portable Document Format",
+              "filename": "internal-pdf-viewer",
+              "mimeTypes": [
+                {
+                  "type": "application/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                },
+                {
+                  "type": "text/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                }
+              ]
+            },
+            {
+              "name": "Chromium PDF Viewer",
+              "description": "Portable Document Format",
+              "filename": "internal-pdf-viewer",
+              "mimeTypes": [
+                {
+                  "type": "application/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                },
+                {
+                  "type": "text/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                }
+              ]
+            },
+            {
+              "name": "Microsoft Edge PDF Viewer",
+              "description": "Portable Document Format",
+              "filename": "internal-pdf-viewer",
+              "mimeTypes": [
+                {
+                  "type": "application/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                },
+                {
+                  "type": "text/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                }
+              ]
+            },
+            {
+              "name": "WebKit built-in PDF",
+              "description": "Portable Document Format",
+              "filename": "internal-pdf-viewer",
+              "mimeTypes": [
+                {
+                  "type": "application/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                },
+                {
+                  "type": "text/pdf",
+                  "suffixes": "pdf",
+                  "description": "Portable Document Format",
+                  "enabledPlugin": "PDF Viewer"
+                }
+              ]
+            }
+          ],
+          "mimeTypes": [
+            "Portable Document Format~~application/pdf~~pdf",
+            "Portable Document Format~~text/pdf~~pdf"
+          ]
+        },
+        0.6111111111111112
+      ],
+      [
+        {
+          "plugins": [],
+          "mimeTypes": []
+        },
+        0.3888888888888889
+      ]
+    ],
+    "audioCodecs": [
+      [
+        {
+          "ogg": "probably",
+          "mp3": "maybe",
+          "wav": "probably",
+          "m4a": "maybe",
+          "aac": "maybe"
+        },
+        1.0
+      ]
+    ],
+    "videoCodecs": [
+      [
+        {
+          "ogg": "",
+          "h264": "probably",
+          "webm": "probably"
+        },
+        1.0
+      ]
+    ],
+    "videoCard": [
+      [
+        {
+          "renderer": "ANGLE (NVIDIA, NVIDIA GeForce GTX 980 Direct3D11 vs_5_0 ps_5_0), or similar",
+          "vendor": "Google Inc. (NVIDIA)"
+        },
+        0.8444444444444444
+      ],
+      [
+        {
+          "renderer": "ANGLE (AMD, Radeon R9 200 Series Direct3D11 vs_5_0 ps_5_0), or similar",
+          "vendor": "Google Inc. (AMD)"
+        },
+        0.08888888888888889
+      ],
+      [
+        {
+          "renderer": "ANGLE (Intel, Intel(R) HD Graphics 400 Direct3D11 vs_5_0 ps_5_0), or similar",
+          "vendor": "Google Inc. (Intel)"
+        },
+        0.06666666666666667
+      ]
+    ],
+    "multimediaDevices": [
+      [
+        {
+          "speakers": [],
+          "micros": [],
+          "webcams": []
+        },
+        1.0
+      ]
+    ],
+    "fonts": [
+      [
+        [],
+        0.3888888888888889
+      ],
+      [
+        [
+          "Calibri",
+          "HELV",
+          "MS UI Gothic",
+          "Marlett",
+          "Segoe UI Light",
+          "Small Fonts"
+        ],
+        0.3222222222222222
+      ],
+      [
+        [
+          "Agency FB",
+          "Calibri",
+          "Century",
+          "Century Gothic",
+          "Franklin Gothic",
+          "HELV",
+          "Haettenschweiler",
+          "Leelawadee",
+          "Lucida Bright",
+          "Lucida Sans",
+          "MS Outlook",
+          "MS Reference Specialty",
+          "MS UI Gothic",
+          "MT Extra",
+          "Marlett",
+          "Microsoft Uighur",
+          "Monotype Corsiva",
+          "Pristina",
+          "Segoe UI Light",
+          "Small Fonts"
+        ],
+        0.13333333333333333
+      ],
+      [
+        [
+          "AvantGarde Bk BT",
+          "Calibri",
+          "Clarendon",
+          "Franklin Gothic",
+          "Futura Bk BT",
+          "Futura Md BT",
+          "GOTHAM",
+          "HELV",
+          "Humanst521 BT",
+          "MS UI Gothic",
+          "MYRIAD PRO",
+          "Marlett",
+          "Minion Pro",
+          "Segoe UI Light",
+          "Small Fonts",
+          "TRAJAN PRO"
+        ],
+        0.06666666666666667
+      ],
+      [
+        [
+          "Calibri",
+          "MS UI Gothic",
+          "Marlett",
+          "Segoe UI Light"
+        ],
+        0.05555555555555555
+      ],
+      [
+        [
+          "Agency FB",
+          "Calibri",
+          "Century",
+          "Century Gothic",
+          "Franklin Gothic",
+          "Futura Bk BT",
+          "Futura Md BT",
+          "GOTHAM",
+          "HELV",
+          "Haettenschweiler",
+          "Humanst521 BT",
+          "Lucida Bright",
+          "Lucida Sans",
+          "MS Outlook",
+          "MS Reference Specialty",
+          "MS UI Gothic",
+          "MT Extra",
+          "MYRIAD PRO",
+          "Marlett",
+          "Minion Pro",
+          "Monotype Corsiva",
+          "Pristina",
+          "Segoe UI Light",
+          "Small Fonts"
+        ],
+        0.03333333333333333
+      ]
+    ]
+  }
+}

src/stealthfox/_fpforge/data/font_pool.json

@@ -0,0 +1,670 @@
+{
+  "core": [
+    {
+      "name": "arial",
+      "factor": 0.978
+    },
+    {
+      "name": "arial black",
+      "factor": 1.168
+    },
+    {
+      "name": "arial narrow",
+      "factor": 0.854
+    },
+    {
+      "name": "bahnschrift",
+      "factor": 0.951
+    },
+    {
+      "name": "bahnschrift condensed",
+      "factor": 1.179
+    },
+    {
+      "name": "bahnschrift light",
+      "factor": 0.908
+    },
+    {
+      "name": "bahnschrift light condensed",
+      "factor": 1.053
+    },
+    {
+      "name": "bahnschrift light semicondensed",
+      "factor": 1.063
+    },
+    {
+      "name": "bahnschrift semibold",
+      "factor": 0.926
+    },
+    {
+      "name": "bahnschrift semibold condensed",
+      "factor": 1.131
+    },
+    {
+      "name": "bahnschrift semibold semicondensed",
+      "factor": 1.043
+    },
+    {
+      "name": "bahnschrift semicondensed",
+      "factor": 1.098
+    },
+    {
+      "name": "bahnschrift semilight",
+      "factor": 0.873
+    },
+    {
+      "name": "bahnschrift semilight condensed",
+      "factor": 0.905
+    },
+    {
+      "name": "bahnschrift semilight semicondensed",
+      "factor": 1.135
+    },
+    {
+      "name": "calibri light",
+      "factor": 0.901
+    },
+    {
+      "name": "cambria",
+      "factor": 1.063
+    },
+    {
+      "name": "cambria math",
+      "factor": 1.041
+    },
+    {
+      "name": "candara",
+      "factor": 0.927
+    },
+    {
+      "name": "candara light",
+      "factor": 0.892
+    },
+    {
+      "name": "cascadia code",
+      "factor": 1.139
+    },
+    {
+      "name": "cascadia mono",
+      "factor": 0.95
+    },
+    {
+      "name": "comic sans ms",
+      "factor": 1.087
+    },
+    {
+      "name": "consolas",
+      "factor": 1.158
+    },
+    {
+      "name": "constantia",
+      "factor": 1.052
+    },
+    {
+      "name": "corbel",
+      "factor": 0.895
+    },
+    {
+      "name": "corbel light",
+      "factor": 0.876
+    },
+    {
+      "name": "courier new",
+      "factor": 1.187
+    },
+    {
+      "name": "ebrima",
+      "factor": 0.962
+    },
+    {
+      "name": "franklin gothic medium",
+      "factor": 1.031
+    },
+    {
+      "name": "gabriola",
+      "factor": 1.077
+    },
+    {
+      "name": "georgia",
+      "factor": 1.094
+    },
+    {
+      "name": "hololens mdl2 assets",
+      "factor": 1.145
+    },
+    {
+      "name": "impact",
+      "factor": 0.862
+    },
+    {
+      "name": "ink free",
+      "factor": 1.048
+    },
+    {
+      "name": "leelawadee ui semilight",
+      "factor": 1.061
+    },
+    {
+      "name": "lucida console",
+      "factor": 1.131
+    },
+    {
+      "name": "lucida sans unicode",
+      "factor": 1.014
+    },
+    {
+      "name": "malgun gothic",
+      "factor": 1.128
+    },
+    {
+      "name": "malgun gothic semilight",
+      "factor": 1.051
+    },
+    {
+      "name": "marlett",
+      "factor": 0.855
+    },
+    {
+      "name": "microsoft himalaya",
+      "factor": 1.022
+    },
+    {
+      "name": "microsoft jhenghei",
+      "factor": 1.061
+    },
+    {
+      "name": "microsoft jhenghei light",
+      "factor": 0.94
+    },
+    {
+      "name": "microsoft jhenghei ui",
+      "factor": 1.136
+    },
+    {
+      "name": "microsoft jhenghei ui light",
+      "factor": 0.826
+    },
+    {
+      "name": "microsoft new tai lue",
+      "factor": 0.953
+    },
+    {
+      "name": "microsoft phagspa",
+      "factor": 0.988
+    },
+    {
+      "name": "microsoft sans serif",
+      "factor": 0.941
+    },
+    {
+      "name": "microsoft tai le",
+      "factor": 0.957
+    },
+    {
+      "name": "microsoft yahei",
+      "factor": 1.076
+    },
+    {
+      "name": "microsoft yahei light",
+      "factor": 1.043
+    },
+    {
+      "name": "microsoft yahei ui",
+      "factor": 1.076
+    },
+    {
+      "name": "microsoft yahei ui light",
+      "factor": 1.094
+    },
+    {
+      "name": "microsoft yi baiti",
+      "factor": 1.008
+    },
+    {
+      "name": "mingliu-extb",
+      "factor": 1.173
+    },
+    {
+      "name": "mingliu_hkscs-extb",
+      "factor": 1.101
+    },
+    {
+      "name": "mongolian baiti",
+      "factor": 1.056
+    },
+    {
+      "name": "ms gothic",
+      "factor": 1.119
+    },
+    {
+      "name": "ms pgothic",
+      "factor": 1.074
+    },
+    {
+      "name": "mv boli",
+      "factor": 0.932
+    },
+    {
+      "name": "nirmala ui",
+      "factor": 0.916
+    },
+    {
+      "name": "nirmala ui semilight",
+      "factor": 1.15
+    },
+    {
+      "name": "nsimsun",
+      "factor": 1.119
+    },
+    {
+      "name": "palatino linotype",
+      "factor": 1.067
+    },
+    {
+      "name": "pmingliu-extb",
+      "factor": 1.16
+    },
+    {
+      "name": "sans serif collection",
+      "factor": 0.854
+    },
+    {
+      "name": "segoe mdl2 assets",
+      "factor": 0.858
+    },
+    {
+      "name": "segoe print",
+      "factor": 1.033
+    },
+    {
+      "name": "segoe script",
+      "factor": 1.058
+    },
+    {
+      "name": "segoe ui",
+      "factor": 0.948
+    },
+    {
+      "name": "segoe ui black",
+      "factor": 1.148
+    },
+    {
+      "name": "segoe ui emoji",
+      "factor": 0.924
+    },
+    {
+      "name": "segoe ui historic",
+      "factor": 0.969
+    },
+    {
+      "name": "segoe ui semibold",
+      "factor": 0.965
+    },
+    {
+      "name": "segoe ui semilight",
+      "factor": 1.055
+    },
+    {
+      "name": "segoe ui symbol",
+      "factor": 0.972
+    },
+    {
+      "name": "segoe ui variable",
+      "factor": 0.907
+    },
+    {
+      "name": "simsun",
+      "factor": 1.113
+    },
+    {
+      "name": "simsun-extb",
+      "factor": 1.095
+    },
+    {
+      "name": "sitka banner",
+      "factor": 1.078
+    },
+    {
+      "name": "sitka display",
+      "factor": 0.838
+    },
+    {
+      "name": "sitka heading",
+      "factor": 0.843
+    },
+    {
+      "name": "sitka small",
+      "factor": 1.131
+    },
+    {
+      "name": "sitka subheading",
+      "factor": 0.942
+    },
+    {
+      "name": "sitka text",
+      "factor": 1.044
+    },
+    {
+      "name": "sylfaen",
+      "factor": 0.971
+    },
+    {
+      "name": "symbol",
+      "factor": 0.866
+    },
+    {
+      "name": "tahoma",
+      "factor": 0.962
+    },
+    {
+      "name": "times new roman",
+      "factor": 0.926
+    },
+    {
+      "name": "trebuchet ms",
+      "factor": 0.912
+    },
+    {
+      "name": "verdana",
+      "factor": 1.128
+    },
+    {
+      "name": "webdings",
+      "factor": 0.849
+    },
+    {
+      "name": "wingdings",
+      "factor": 0.864
+    },
+    {
+      "name": "wingdings 2",
+      "factor": 1.093
+    },
+    {
+      "name": "wingdings 3",
+      "factor": 0.861
+    },
+    {
+      "name": "yu gothic",
+      "factor": 1.069
+    },
+    {
+      "name": "yu gothic light",
+      "factor": 1.038
+    },
+    {
+      "name": "yu gothic medium",
+      "factor": 1.161
+    },
+    {
+      "name": "yu gothic ui",
+      "factor": 0.886
+    },
+    {
+      "name": "yu gothic ui light",
+      "factor": 1.093
+    },
+    {
+      "name": "yu gothic ui semibold",
+      "factor": 0.942
+    },
+    {
+      "name": "yu gothic ui semilight",
+      "factor": 0.923
+    }
+  ],
+  "optional": [
+    {
+      "name": "aparajita",
+      "factor": 0.94
+    },
+    {
+      "name": "arabic typesetting",
+      "factor": 1.093
+    },
+    {
+      "name": "arial unicode ms",
+      "factor": 1.047
+    },
+    {
+      "name": "batang",
+      "factor": 0.911
+    },
+    {
+      "name": "calibri",
+      "factor": 0.934
+    },
+    {
+      "name": "century",
+      "factor": 1.078
+    },
+    {
+      "name": "century gothic",
+      "factor": 0.886
+    },
+    {
+      "name": "dengxian",
+      "factor": 0.846
+    },
+    {
+      "name": "dfkai-sb",
+      "factor": 0.946
+    },
+    {
+      "name": "dokchampa",
+      "factor": 1.162
+    },
+    {
+      "name": "estrangelo edessa",
+      "factor": 1.095
+    },
+    {
+      "name": "euphemia",
+      "factor": 1.117
+    },
+    {
+      "name": "fangsong",
+      "factor": 0.942
+    },
+    {
+      "name": "franklin gothic",
+      "factor": 0.942
+    },
+    {
+      "name": "gadugi",
+      "factor": 0.945
+    },
+    {
+      "name": "gautami",
+      "factor": 1.134
+    },
+    {
+      "name": "haettenschweiler",
+      "factor": 0.874
+    },
+    {
+      "name": "helv",
+      "factor": 0.923
+    },
+    {
+      "name": "iskoola pota",
+      "factor": 0.857
+    },
+    {
+      "name": "javanese text",
+      "factor": 1.083
+    },
+    {
+      "name": "kaiti",
+      "factor": 1.145
+    },
+    {
+      "name": "kalinga",
+      "factor": 0.953
+    },
+    {
+      "name": "kartika",
+      "factor": 0.882
+    },
+    {
+      "name": "khmer ui",
+      "factor": 1.137
+    },
+    {
+      "name": "kokila",
+      "factor": 0.919
+    },
+    {
+      "name": "lao ui",
+      "factor": 0.904
+    },
+    {
+      "name": "latha",
+      "factor": 0.839
+    },
+    {
+      "name": "leelawadee",
+      "factor": 0.982
+    },
+    {
+      "name": "leelawadee ui",
+      "factor": 0.992
+    },
+    {
+      "name": "levenim mt",
+      "factor": 1.054
+    },
+    {
+      "name": "mangal",
+      "factor": 1.154
+    },
+    {
+      "name": "meiryo",
+      "factor": 1.165
+    },
+    {
+      "name": "meiryo ui",
+      "factor": 1.081
+    },
+    {
+      "name": "microsoft uighur",
+      "factor": 0.969
+    },
+    {
+      "name": "monotype corsiva",
+      "factor": 0.939
+    },
+    {
+      "name": "ms mincho",
+      "factor": 1.112
+    },
+    {
+      "name": "ms outlook",
+      "factor": 0.921
+    },
+    {
+      "name": "ms pmincho",
+      "factor": 0.925
+    },
+    {
+      "name": "ms reference sans serif",
+      "factor": 0.858
+    },
+    {
+      "name": "ms reference specialty",
+      "factor": 0.958
+    },
+    {
+      "name": "ms ui gothic",
+      "factor": 1.097
+    },
+    {
+      "name": "mt extra",
+      "factor": 0.905
+    },
+    {
+      "name": "myanmar text",
+      "factor": 0.961
+    },
+    {
+      "name": "nyala",
+      "factor": 1.108
+    },
+    {
+      "name": "plantagenet cherokee",
+      "factor": 1.115
+    },
+    {
+      "name": "pmingliu",
+      "factor": 1.125
+    },
+    {
+      "name": "pristina",
+      "factor": 1.023
+    },
+    {
+      "name": "raavi",
+      "factor": 0.826
+    },
+    {
+      "name": "segoe fluent icons",
+      "factor": 1.049
+    },
+    {
+      "name": "segoe ui light",
+      "factor": 0.918
+    },
+    {
+      "name": "shonar bangla",
+      "factor": 1.141
+    },
+    {
+      "name": "shruti",
+      "factor": 1.172
+    },
+    {
+      "name": "simhei",
+      "factor": 1.141
+    },
+    {
+      "name": "simkai",
+      "factor": 1.1
+    },
+    {
+      "name": "small fonts",
+      "factor": 0.849
+    },
+    {
+      "name": "traditional arabic",
+      "factor": 0.893
+    },
+    {
+      "name": "tunga",
+      "factor": 0.825
+    },
+    {
+      "name": "urdu typesetting",
+      "factor": 0.869
+    },
+    {
+      "name": "utsaah",
+      "factor": 1.144
+    },
+    {
+      "name": "vani",
+      "factor": 1.078
+    },
+    {
+      "name": "vijaya",
+      "factor": 0.917
+    },
+    {
+      "name": "vrinda",
+      "factor": 0.985
+    },
+    {
+      "name": "yu mincho",
+      "factor": 0.867
+    }
+  ]
+}

src/stealthfox/_fpforge/data/prior_audio.json

@@ -0,0 +1,17 @@
+{
+  "_meta": {
+    "name": "audio (joint: sample_rate, output_latency_ms, max_channel_count)",
+    "parents": [],
+    "child": "audio",
+    "source": "Curated from common Windows WASAPI/DirectSound configs on FF desktop"
+  },
+  "table": [
+    {"value": {"rate": 44100, "latency": 40, "channels": 2}, "prob": 0.20},
+    {"value": {"rate": 48000, "latency": 30, "channels": 2}, "prob": 0.25},
+    {"value": {"rate": 48000, "latency": 20, "channels": 2}, "prob": 0.15},
+    {"value": {"rate": 48000, "latency": 40, "channels": 6}, "prob": 0.08},
+    {"value": {"rate": 48000, "latency": 60, "channels": 2}, "prob": 0.12},
+    {"value": {"rate": 44100, "latency": 50, "channels": 2}, "prob": 0.10},
+    {"value": {"rate": 48000, "latency": 25, "channels": 2}, "prob": 0.10}
+  ]
+}

src/stealthfox/_fpforge/data/priors_independent.json

@@ -0,0 +1,14 @@
+{
+  "_meta": {
+    "name": "Independent marginal priors (no parents)",
+    "source": "StatCounter GlobalStats + Firefox defaults + community data 2025-2026",
+    "note": "Codec prefs (av1_enabled, webm_encoder_enabled, hw_video_decoding, wmf_enabled, ffvpx_enabled) moved to cpt_codec_given_class.json — they correlate with GPU class via Firefox version / user-tier distribution."
+  },
+  "dark_theme": {
+    "_note": "0=light, 1=dark. StatCounter ~40% users report dark theme preference on desktop.",
+    "table": [
+      {"value": 0, "prob": 0.60},
+      {"value": 1, "prob": 0.40}
+    ]
+  }
+}

src/stealthfox/_fpforge/profile.py

@@ -0,0 +1,259 @@
+"""Public dataclass surface for fpforge."""
+from __future__ import annotations
+
+from dataclasses import dataclass, field, replace as _dc_replace
+from typing import Any, Dict, List, Optional
+
+from ._sampler import sample as _sample_raw
+
+
+@dataclass(frozen=True)
+class GPUProfile:
+    vendor: str
+    renderer: str
+    class_tier: str        # "low_end" | "mid_range" | "high_end" | "integrated_old" | "integrated_modern"
+
+
+@dataclass(frozen=True)
+class ScreenProfile:
+    width: int
+    height: int
+    avail_width: int
+    avail_height: int
+    dpr: float
+    tier: str
+
+
+@dataclass(frozen=True)
+class HardwareProfile:
+    concurrency: int
+    storage_quota_mb: int
+
+
+@dataclass(frozen=True)
+class AudioProfile:
+    sample_rate: int
+    output_latency_ms: int
+    max_channel_count: int
+
+
+@dataclass(frozen=True)
+class CodecProfile:
+    av1_enabled: bool
+    webm_encoder_enabled: bool
+    mediasource_webm: bool
+    mediasource_mp4: bool
+    webspeech_synth: bool
+
+
+@dataclass(frozen=True)
+class WebGLProfile:
+    msaa_samples: int
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Pin map: flat dotted-path -> value. Set via `pin=` on generate_profile.
+#
+#  Supported keys:
+#      "gpu.vendor", "gpu.renderer", "gpu.class_tier"
+#      "screen.width", "screen.height", "screen.avail_width",
+#      "screen.avail_height", "screen.dpr", "screen.tier"
+#      "hardware.concurrency", "hardware.storage_quota_mb"
+#      "audio.sample_rate", "audio.output_latency_ms",
+#      "audio.max_channel_count"
+#      "codec.av1_enabled", "codec.webm_encoder_enabled",
+#      "codec.mediasource_webm", "codec.mediasource_mp4",
+#      "codec.webspeech_synth"
+#      "webgl.msaa_samples"
+#      "fonts"            (replaces the whole list)
+#      "dark_theme"
+# ──────────────────────────────────────────────────────────────────────
+
+_PIN_GROUPS = {
+    "gpu": {"vendor", "renderer", "class_tier"},
+    "screen": {"width", "height", "avail_width", "avail_height", "dpr", "tier"},
+    "hardware": {"concurrency", "storage_quota_mb"},
+    "audio": {"sample_rate", "output_latency_ms", "max_channel_count"},
+    "codec": {
+        "av1_enabled", "webm_encoder_enabled",
+        "mediasource_webm", "mediasource_mp4", "webspeech_synth",
+    },
+    "webgl": {"msaa_samples"},
+}
+_PIN_TOP = {"fonts", "dark_theme"}
+
+
+def _validate_pin_key(key: str) -> None:
+    if key in _PIN_TOP:
+        return
+    if "." not in key:
+        raise ValueError(
+            f"pin key {key!r} is not valid. "
+            f"Use 'group.field' (e.g. 'screen.width') or one of {sorted(_PIN_TOP)}."
+        )
+    group, field_name = key.split(".", 1)
+    if group not in _PIN_GROUPS:
+        raise ValueError(
+            f"pin key {key!r}: unknown group {group!r}. "
+            f"Known groups: {sorted(_PIN_GROUPS)}."
+        )
+    if field_name not in _PIN_GROUPS[group]:
+        raise ValueError(
+            f"pin key {key!r}: unknown field {field_name!r} in group {group!r}. "
+            f"Known fields: {sorted(_PIN_GROUPS[group])}."
+        )
+
+
+@dataclass(frozen=True)
+class Profile:
+    """Coherent browser fingerprint profile sampled from a single integer seed.
+
+    Use `generate_profile(seed)` to build one. Pin specific values at build
+    time with `generate_profile(seed, pin={"screen.width": 2560, ...})`.
+    """
+    seed: int
+    gpu: GPUProfile
+    screen: ScreenProfile
+    hardware: HardwareProfile
+    audio: AudioProfile
+    codec: CodecProfile
+    webgl: WebGLProfile
+    fonts: List[str]
+    dark_theme: bool
+    _raw: Dict[str, Any] = field(default_factory=dict, repr=False, compare=False)
+
+    def to_prefs_dict(self) -> Dict[str, Any]:
+        """Return the flat dict of raw sampler fields, as produced by the
+        underlying Bayesian sampler. Stable across releases for a given seed."""
+        return dict(self._raw)
+
+
+# Mapping from flat pin key -> raw sampler dict key, so `to_prefs_dict()`
+# and `stealthfox.prefs.translate_profile_to_prefs` observe the pinned value.
+_PIN_TO_RAW = {
+    "gpu.vendor": "webgl_vendor",
+    "gpu.renderer": "webgl_renderer",
+    "gpu.class_tier": "gpu_class",
+    "screen.width": "screen_w",
+    "screen.height": "screen_h",
+    "screen.avail_width": "screen_avail_w",
+    "screen.avail_height": "screen_avail_h",
+    "screen.dpr": "dpr",
+    "screen.tier": "screen_tier",
+    "hardware.concurrency": "hw_concurrency",
+    "hardware.storage_quota_mb": "storage_quota_mb",
+    "audio.sample_rate": "audio_sample_rate",
+    "audio.output_latency_ms": "audio_output_latency_ms",
+    "audio.max_channel_count": "audio_max_channel_count",
+    "codec.av1_enabled": "av1_enabled",
+    "codec.webm_encoder_enabled": "webm_encoder_enabled",
+    "codec.mediasource_webm": "mediasource_webm",
+    "codec.mediasource_mp4": "mediasource_mp4",
+    "codec.webspeech_synth": "webspeech_synth",
+    "webgl.msaa_samples": "msaa_samples",
+    "dark_theme": "dark_theme",
+    # "fonts" is a list — handled specially (joined into font_whitelist).
+}
+
+
+def _apply_pins_to_raw(raw: Dict[str, Any], pin: Dict[str, Any]) -> Dict[str, Any]:
+    """Return a copy of `raw` with the pinned sampler-level fields updated."""
+    out = dict(raw)
+    for key, value in pin.items():
+        if key == "fonts":
+            if not isinstance(value, (list, tuple)):
+                raise TypeError("pin 'fonts' must be a list/tuple of strings")
+            out["font_whitelist"] = ",".join(value)
+            continue
+        raw_key = _PIN_TO_RAW.get(key)
+        if raw_key is None:
+            # Shouldn't happen after validation, but guard anyway.
+            continue
+        out[raw_key] = value
+    return out
+
+
+def generate_profile(seed: int, pin: Optional[Dict[str, Any]] = None) -> Profile:
+    """Return a deterministic Profile for the given integer seed.
+
+    pin: optional dict of dotted-path keys (e.g. "screen.width", "gpu.renderer")
+        to values that are FORCED in the resulting profile. All other fields
+        are still sampled from the Bayesian network based on `seed`, so the
+        same seed + same pin map always yields the same profile.
+
+        Example — force a specific GPU and screen while letting everything
+        else vary with the seed (via the public stealthfox API):
+
+            from stealthfox import Stealthfox
+
+            with Stealthfox(
+                seed=42,
+                pin={
+                    "gpu.renderer": "ANGLE (NVIDIA, NVIDIA GeForce RTX 4090 Direct3D11)",
+                    "gpu.vendor":   "Google Inc. (NVIDIA)",
+                    "gpu.class_tier": "high_end",
+                    "screen.width":  2560,
+                    "screen.height": 1440,
+                },
+            ) as browser:
+                ...
+
+        Warning: pinning breaks Bayesian coherence across the pinned fields
+        (if you pin a high-end GPU but leave screen unpinned, you may get a
+        1080p screen that would be unusual for that GPU class). Pin related
+        fields together when coherence matters.
+
+        Supported keys: see the module-level _PIN_GROUPS / _PIN_TOP tables
+        or run `help(generate_profile)` after import.
+    """
+    if pin:
+        for key in pin:
+            _validate_pin_key(key)
+
+    raw = _sample_raw(int(seed))
+    if pin:
+        raw = _apply_pins_to_raw(raw, pin)
+
+    # Font whitelist is stored as a comma-separated string in raw; split it.
+    font_wl = raw.get("font_whitelist", "")
+    if isinstance(font_wl, str):
+        fonts = [f.strip() for f in font_wl.split(",") if f.strip()]
+    else:
+        fonts = list(font_wl) if font_wl else []
+
+    return Profile(
+        seed=int(raw["stealth_seed"]),
+        gpu=GPUProfile(
+            vendor=raw["webgl_vendor"],
+            renderer=raw["webgl_renderer"],
+            class_tier=raw["gpu_class"],
+        ),
+        screen=ScreenProfile(
+            width=int(raw["screen_w"]),
+            height=int(raw["screen_h"]),
+            avail_width=int(raw["screen_avail_w"]),
+            avail_height=int(raw["screen_avail_h"]),
+            dpr=float(raw["dpr"]),
+            tier=str(raw.get("screen_tier", "")),
+        ),
+        hardware=HardwareProfile(
+            concurrency=int(raw["hw_concurrency"]),
+            storage_quota_mb=int(raw["storage_quota_mb"]),
+        ),
+        audio=AudioProfile(
+            sample_rate=int(raw["audio_sample_rate"]),
+            output_latency_ms=int(raw["audio_output_latency_ms"]),
+            max_channel_count=int(raw["audio_max_channel_count"]),
+        ),
+        codec=CodecProfile(
+            av1_enabled=bool(raw["av1_enabled"]),
+            webm_encoder_enabled=bool(raw["webm_encoder_enabled"]),
+            mediasource_webm=bool(raw["mediasource_webm"]),
+            mediasource_mp4=bool(raw["mediasource_mp4"]),
+            webspeech_synth=bool(raw["webspeech_synth"]),
+        ),
+        webgl=WebGLProfile(msaa_samples=int(raw["msaa_samples"])),
+        fonts=fonts,
+        dark_theme=bool(raw["dark_theme"]),
+        _raw=raw,
+    )

src/stealthfox/_headless.py

@@ -0,0 +1,228 @@
+"""Invisible-but-headed browser windows.
+
+Playwright's ``headless=True`` flips Firefox onto a different code path —
+no widget tree, software-only rendering, distinct timing — and anti-bot
+systems can spot the divergence. Running the browser *headed* on a
+virtual display gives us the real rendering pipeline while keeping the
+windows off the user's screen.
+
+Linux: spawns its own ``Xvfb`` instance, points ``DISPLAY`` at it.
+Windows: creates a hidden desktop via ``CreateDesktop`` and binds the
+calling thread to it, so Playwright's child processes inherit it.
+"""
+from __future__ import annotations
+
+import os
+import secrets
+import subprocess
+import sys
+import time
+from typing import Optional
+
+
+# Inherited from WSLg / GNOME / etc. these env vars make Firefox prefer a
+# Wayland compositor over the X11 DISPLAY we set, so the window leaks onto
+# the real desktop. Strip them all before starting.
+_WAYLAND_LEAK_VARS = (
+    "WAYLAND_DISPLAY",
+    "XDG_RUNTIME_DIR",
+    "XDG_SESSION_TYPE",
+    "PULSE_SERVER",
+    "WSL2_GUI_APPS_ENABLED",
+)
+
+
+class _LinuxVirtualDisplay:
+    """Standalone Xvfb instance owned by this Stealthfox session."""
+
+    def __init__(self, width: int = 1920, height: int = 1080) -> None:
+        self._geometry = f"{width}x{height}x24"
+        self._proc: Optional[subprocess.Popen] = None
+        self._display: Optional[str] = None
+        self._saved_env: dict[str, Optional[str]] = {}
+
+    def start(self) -> None:
+        if not _binary_on_path("Xvfb"):
+            raise RuntimeError(
+                "stealthfox headless=True requires Xvfb. "
+                "Install it: sudo apt install xvfb"
+            )
+        # Retry: when many workers start in parallel they can pick the same
+        # display number before any has created its lockfile. Xvfb on the
+        # losing side exits immediately — try again with a fresh number.
+        last_err: Optional[Exception] = None
+        for _ in range(10):
+            display = self._pick_display()
+            try:
+                self._spawn(display)
+                self._wait_until_ready(display)
+                self._display = display
+                self._apply_env(display)
+                return
+            except RuntimeError as e:
+                last_err = e
+                if self._proc is not None and self._proc.poll() is None:
+                    self._proc.kill()
+                self._proc = None
+        raise RuntimeError(f"Xvfb failed to start after 10 attempts: {last_err}")
+
+    def _spawn(self, display: str) -> None:
+        self._proc = subprocess.Popen(
+            [
+                "Xvfb", display,
+                "-screen", "0", self._geometry,
+                "+extension", "GLX",
+                "+extension", "RENDER",
+                "-nolisten", "unix",
+                "-listen", "tcp",
+                "-ac",
+            ],
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+            start_new_session=True,
+        )
+
+    def _pick_display(self) -> str:
+        for n in range(99, 400):
+            if not os.path.exists(f"/tmp/.X{n}-lock"):
+                return f":{n}"
+        raise RuntimeError("no free X display number in :99–:399")
+
+    def _wait_until_ready(self, display: str) -> None:
+        # We start Xvfb with -nolisten unix → no /tmp/.X11-unix socket appears.
+        # Xvfb creates /tmp/.X{n}-lock immediately though — wait for that.
+        lockfile = f"/tmp/.X{display[1:]}-lock"
+        deadline = time.monotonic() + 3.0
+        assert self._proc is not None
+        while time.monotonic() < deadline:
+            if self._proc.poll() is not None:
+                raise RuntimeError(f"Xvfb {display} exited immediately")
+            if os.path.exists(lockfile):
+                return
+            time.sleep(0.02)
+        raise RuntimeError(f"Xvfb {display} did not become ready in 3s")
+
+    def _apply_env(self, display: str) -> None:
+        keys = ("DISPLAY", "MOZ_ENABLE_WAYLAND", "GDK_BACKEND") + _WAYLAND_LEAK_VARS
+        for k in keys:
+            self._saved_env[k] = os.environ.get(k)
+        for k in _WAYLAND_LEAK_VARS:
+            os.environ.pop(k, None)
+        os.environ["DISPLAY"] = display
+        os.environ["MOZ_ENABLE_WAYLAND"] = "0"
+        os.environ["GDK_BACKEND"] = "x11"
+
+    def stop(self) -> None:
+        for k, v in self._saved_env.items():
+            if v is None:
+                os.environ.pop(k, None)
+            else:
+                os.environ[k] = v
+        self._saved_env.clear()
+
+        if self._proc is not None and self._proc.poll() is None:
+            self._proc.terminate()
+            try:
+                self._proc.wait(timeout=3)
+            except subprocess.TimeoutExpired:
+                self._proc.kill()
+                self._proc.wait(timeout=2)
+        self._proc = None
+        self._display = None
+
+
+class _WindowsVirtualDesktop:
+    """A hidden Windows desktop the calling thread is bound to.
+
+    Playwright's child processes (node driver → firefox.exe) inherit the
+    desktop because their ``STARTUPINFO.lpDesktop`` is NULL — Windows uses
+    the calling thread's desktop in that case.
+
+    pywin32 ships ``CreateDesktop`` in ``win32service`` but doesn't expose
+    ``SetThreadDesktop`` / ``GetThreadDesktop`` as module functions. We
+    call them directly via ctypes against ``user32.dll``.
+    """
+
+    def __init__(self) -> None:
+        self._desktop = None      # PyHDESK from win32service.CreateDesktop
+        self._original_handle = 0  # raw HDESK int of the previous desktop
+
+    def start(self) -> None:
+        try:
+            import win32con  # type: ignore
+            import win32service  # type: ignore
+        except ImportError as e:
+            raise RuntimeError(
+                "stealthfox headless=True on Windows requires pywin32. "
+                "Install it: pip install pywin32"
+            ) from e
+
+        import ctypes
+        from ctypes import wintypes
+        user32 = ctypes.windll.user32
+        kernel32 = ctypes.windll.kernel32
+
+        # Save the current desktop handle so we can restore it on stop().
+        get_thread_desktop = user32.GetThreadDesktop
+        get_thread_desktop.argtypes = [wintypes.DWORD]
+        get_thread_desktop.restype  = wintypes.HANDLE
+        self._original_handle = get_thread_desktop(kernel32.GetCurrentThreadId())
+
+        name = f"sf_{secrets.token_hex(4)}"
+        self._desktop = win32service.CreateDesktop(
+            name, 0, win32con.GENERIC_ALL, None
+        )
+
+        # Bind the calling thread to the new desktop. Children spawned
+        # afterwards (Playwright driver → firefox.exe) inherit it because
+        # their STARTUPINFO.lpDesktop is NULL.
+        set_thread_desktop = user32.SetThreadDesktop
+        set_thread_desktop.argtypes = [wintypes.HANDLE]
+        set_thread_desktop.restype  = wintypes.BOOL
+        if not set_thread_desktop(int(self._desktop)):
+            err = ctypes.get_last_error()
+            raise RuntimeError(
+                f"SetThreadDesktop failed (GetLastError={err}). "
+                "The thread cannot have any windows or hooks; close them first."
+            )
+
+    def stop(self) -> None:
+        import ctypes
+        from ctypes import wintypes
+        user32 = ctypes.windll.user32
+
+        if self._original_handle:
+            try:
+                set_thread_desktop = user32.SetThreadDesktop
+                set_thread_desktop.argtypes = [wintypes.HANDLE]
+                set_thread_desktop.restype  = wintypes.BOOL
+                set_thread_desktop(self._original_handle)
+            except Exception:
+                pass
+            self._original_handle = 0
+
+        if self._desktop is not None:
+            try:
+                self._desktop.CloseDesktop()
+            except Exception:
+                pass
+            self._desktop = None
+
+
+def make_virtual_display():
+    """Return a started/stoppable virtual-display object for this platform.
+
+    Stealthfox supports Windows x86_64 and Linux x86_64 only.
+    """
+    if sys.platform == "win32":
+        return _WindowsVirtualDesktop()
+    if sys.platform.startswith("linux"):
+        return _LinuxVirtualDisplay()
+    raise RuntimeError(
+        f"stealthfox supports Windows and Linux only (got {sys.platform!r})"
+    )
+
+
+def _binary_on_path(name: str) -> bool:
+    import shutil
+    return shutil.which(name) is not None

src/stealthfox/_proxy.py

@@ -0,0 +1,56 @@
+"""Proxy translation shared by sync and async launchers.
+
+SOCKS proxies are driven entirely by the patched Firefox prefs (the
+``nsProtocolProxyService`` patch reads ``network.proxy.socks_username``
+and ``socks_password``). HTTP/HTTPS proxies go through Playwright's own
+``proxy=`` kwarg so it can negotiate Basic auth.
+"""
+from __future__ import annotations
+
+from typing import Any, Dict, Optional
+
+
+_SOCKS_SCHEMES = ("socks5://", "socks4://", "socks://")
+
+
+def configure_proxy(
+    proxy: Optional[Dict[str, str]],
+    prefs: Dict[str, Any],
+) -> Optional[Dict[str, str]]:
+    """Mutate ``prefs`` for SOCKS auth; return what to pass to Playwright.
+
+    * ``None`` proxy → returns ``None``.
+    * SOCKS proxy → writes the auth prefs and returns ``None`` (Playwright
+      gets nothing; Firefox does the rest).
+    * HTTP / HTTPS proxy → returns the dict unchanged for Playwright.
+    """
+    if not proxy:
+        return None
+
+    server = (proxy.get("server") or "").strip()
+    if not server or server.lower() == "direct://":
+        return None
+    if not _is_socks_scheme(server):
+        return proxy
+
+    host_port = _strip_scheme(server)
+    if ":" not in host_port:
+        return None  # malformed, drop silently
+
+    host, port_str = host_port.rsplit(":", 1)
+    prefs["network.proxy.type"]            = 1
+    prefs["network.proxy.socks"]           = host
+    prefs["network.proxy.socks_port"]      = int(port_str)
+    prefs["network.proxy.socks_version"]   = 4 if server.lower().startswith("socks4://") else 5
+    prefs["network.proxy.socks_username"]  = proxy.get("username") or ""
+    prefs["network.proxy.socks_password"]  = proxy.get("password") or ""
+    prefs["network.proxy.socks_remote_dns"] = True
+    return None
+
+
+def _is_socks_scheme(server: str) -> bool:
+    return server.lower().startswith(_SOCKS_SCHEMES)
+
+
+def _strip_scheme(server: str) -> str:
+    return server.split("://", 1)[1] if "://" in server else server

src/stealthfox/async_api.py

@@ -0,0 +1,178 @@
+"""Async Playwright façade — mirrors sync_api but with async/await."""
+from __future__ import annotations
+
+import asyncio
+import secrets
+from typing import Any, Dict, Optional, Union
+
+from playwright.async_api import Browser, Playwright, async_playwright
+
+from ._fpforge import Profile, generate_profile
+from ._headless import make_virtual_display
+from ._proxy import configure_proxy as _configure_proxy_shared
+from .download import ensure_binary
+from .launcher import _CHROME_H, _CHROME_W, _TASKBAR_H, _tz_env
+from .prefs import translate_profile_to_prefs
+
+
+def _patch_new_page_sleep(ctx: Any) -> None:
+    """Wrap ctx.new_page() to add a brief settle after tab creation.
+
+    FF150 with Fission emits an about:newtab navigation ~100ms after a tab
+    is created.  If goto() is called immediately, it races with that internal
+    navigation and raises "Navigation interrupted by about:newtab".  A short
+    sleep breaks the race without requiring every call-site to know about it.
+    """
+    original_new_page = ctx.new_page
+
+    async def patched_new_page(**kw):
+        page = await original_new_page(**kw)
+        await asyncio.sleep(0.4)
+        return page
+
+    ctx.new_page = patched_new_page  # type: ignore[assignment]
+
+
+class Stealthfox:
+    """Async context manager — see stealthfox.Stealthfox for the sync variant."""
+
+    def __init__(
+        self,
+        seed: Optional[int] = None,
+        *,
+        pin: Optional[Dict[str, Any]] = None,
+        headless: bool = False,
+        proxy: Optional[Dict[str, str]] = None,
+        extra_args: Optional[list[str]] = None,
+        humanize: Union[bool, float] = True,
+        locale: str = "en-US",
+        timezone: str = "",
+        extra_prefs: Optional[Dict[str, Any]] = None,
+        binary_path: Optional[str] = None,
+    ) -> None:
+        # See sync launcher: `zoom.stealth.fpp.hw_seed` is int32_t — clamp.
+        self.seed: int = int(seed) if seed is not None else secrets.randbits(31)
+        self._pin = pin
+        self._headless = headless
+        self._proxy = proxy
+        self._extra_args = list(extra_args or [])
+        self._humanize = humanize
+        self._locale = locale
+        self._timezone = timezone
+        self._extra_prefs = extra_prefs
+        self._binary_path = binary_path
+        self._profile: Profile = generate_profile(self.seed, pin=self._pin)
+        self._pw: Optional[Playwright] = None
+        self._browser: Optional[Browser] = None
+        self._virtual_display: Any = None
+
+    async def __aenter__(self) -> Browser:
+        import sys as _sys
+        executable = self._binary_path or ensure_binary()
+        prefs = translate_profile_to_prefs(
+            self._profile,
+            locale=self._locale,
+            timezone=self._timezone,
+            extra_prefs=self._extra_prefs,
+            virtual_display=bool(self._headless and _sys.platform == "win32"),
+        )
+        prefs["stealthfox.humanize"] = bool(self._humanize)
+        if self._humanize:
+            cap = 1.5 if self._humanize is True else float(self._humanize)
+            prefs["stealthfox.humanize.maxTime"] = str(cap)
+        playwright_proxy = _configure_proxy_shared(self._proxy, prefs)
+        pw_headless = self._resolve_headless()
+        env = self._build_env()
+        try:
+            self._pw = await async_playwright().start()
+            self._browser = await self._pw.firefox.launch(
+                executable_path=str(executable),
+                headless=pw_headless,
+                firefox_user_prefs=prefs,
+                proxy=playwright_proxy,
+                args=self._extra_args,
+                env=env,
+            )
+        except BaseException:
+            await self._teardown()
+            raise
+        self._patch_new_context_defaults(self._browser)
+        return self._browser
+
+    def _patch_new_context_defaults(self, browser: Browser) -> None:
+        original = browser.new_context
+        defaults = self._default_context_kwargs()
+
+        async def patched(**kw):
+            merged = dict(defaults)
+            merged.update(kw)
+            ctx = await original(**merged)
+            _patch_new_page_sleep(ctx)
+            return ctx
+
+        browser.new_context = patched  # type: ignore[assignment]
+
+    def _default_context_kwargs(self) -> Dict[str, Any]:
+        p = self._profile
+        kwargs: Dict[str, Any] = {
+            "viewport":            {"width":  p.screen.width  - _CHROME_W,
+                                     "height": p.screen.height - _TASKBAR_H - _CHROME_H},
+            "screen":              {"width": p.screen.width, "height": p.screen.height},
+            "device_scale_factor": p.screen.dpr,
+            "color_scheme":        "dark" if p.dark_theme else "light",
+        }
+        # Pass timezone via Playwright per-realm override (works for every
+        # IANA name, including no-DST zones that Windows ICU silently drops
+        # on the global pref path).
+        if self._timezone:
+            kwargs["timezone_id"] = self._timezone
+        if self._locale:
+            kwargs["locale"] = self._locale
+        return kwargs
+
+    async def __aexit__(self, *exc: Any) -> None:
+        await self._teardown()
+
+    async def _teardown(self) -> None:
+        if self._browser is not None:
+            try:
+                await self._browser.close()
+            except Exception:
+                pass
+            self._browser = None
+        if self._pw is not None:
+            try:
+                await self._pw.stop()
+            except Exception:
+                pass
+            self._pw = None
+        if self._virtual_display is not None:
+            try:
+                self._virtual_display.stop()
+            except Exception:
+                pass
+            self._virtual_display = None
+
+    def _build_env(self) -> Dict[str, str]:
+        import os as _os
+        env = _os.environ.copy()
+        if self._timezone:
+            env["TZ"] = _tz_env(self._timezone)
+        # Propagate STEALTHFOX_WEBRTC_PUBLIC_IP if the process set it — read
+        # by nICEr's nr_stealth_bridge to inject a synthetic srflx candidate
+        # matching the proxy egress IP. This avoids the StaticPref IPC
+        # propagation timing issue between parent and socket processes.
+        if _os.environ.get("STEALTHFOX_WEBRTC_PUBLIC_IP"):
+            env["STEALTHFOX_WEBRTC_PUBLIC_IP"] = _os.environ["STEALTHFOX_WEBRTC_PUBLIC_IP"]
+        return env
+
+    def _resolve_headless(self) -> bool:
+        if not self._headless:
+            return False
+        vd = make_virtual_display()
+        vd.start()
+        self._virtual_display = vd
+        return False
+
+
+__all__ = ["Stealthfox"]

src/stealthfox/cli.py

@@ -0,0 +1,68 @@
+"""Command-line interface for stealthfox."""
+from __future__ import annotations
+
+import argparse
+import shutil
+import sys
+
+from . import __version__
+from .constants import BINARY_VERSION, FIREFOX_UPSTREAM_VERSION
+from .download import cache_root, ensure_binary
+
+
+def _cmd_fetch(_args: argparse.Namespace) -> int:
+    path = ensure_binary()
+    print(path)
+    return 0
+
+
+def _cmd_path(_args: argparse.Namespace) -> int:
+    try:
+        path = ensure_binary()
+    except Exception as e:
+        print(f"error: {e}", file=sys.stderr)
+        return 1
+    print(path)
+    return 0
+
+
+def _cmd_version(_args: argparse.Namespace) -> int:
+    print(f"stealthfox {__version__}")
+    print(f"BINARY_VERSION={BINARY_VERSION} (Firefox {FIREFOX_UPSTREAM_VERSION})")
+    return 0
+
+
+def _cmd_clear_cache(_args: argparse.Namespace) -> int:
+    root = cache_root()
+    if root.exists():
+        shutil.rmtree(root)
+        print(f"removed: {root}")
+    else:
+        print(f"nothing to remove: {root}")
+    return 0
+
+
+def build_parser() -> argparse.ArgumentParser:
+    p = argparse.ArgumentParser(prog="stealthfox", description="stealthfox CLI")
+    sub = p.add_subparsers(dest="cmd", required=True)
+
+    sub.add_parser("fetch", help="download the patched Firefox binary")
+    sub.add_parser("path", help="print the absolute path to the cached binary")
+    sub.add_parser("version", help="print wrapper and binary versions")
+    sub.add_parser("clear-cache", help="remove all cached binaries")
+    return p
+
+
+def main(argv: list[str] | None = None) -> int:
+    args = build_parser().parse_args(argv)
+    dispatch = {
+        "fetch": _cmd_fetch,
+        "path": _cmd_path,
+        "version": _cmd_version,
+        "clear-cache": _cmd_clear_cache,
+    }
+    return dispatch[args.cmd](args)
+
+
+if __name__ == "__main__":
+    sys.exit(main())

src/stealthfox/constants.py

@@ -0,0 +1,48 @@
+"""Compile-time constants that pin the wrapper to a specific Firefox build.
+
+BINARY_VERSION is bumped every time new Firefox patches are released. It is
+deliberately decoupled from the Python package version so that pure-Python
+bugfixes don't force a multi-hour Firefox rebuild.
+"""
+from __future__ import annotations
+
+# Bump this when a new patched Firefox build is released on GitHub.
+BINARY_VERSION: str = "firefox-1"
+
+# Underlying Firefox version (for display only; does not drive downloads).
+FIREFOX_UPSTREAM_VERSION: str = "150.0.1"
+
+# The base filename prefix used inside archives.
+BINARY_BASENAME: str = f"firefox-{FIREFOX_UPSTREAM_VERSION}-stealth"
+
+
+def ARCHIVE_NAME(platform_key: str, machine: str) -> str:
+    """Return the platform-specific archive filename.
+
+    platform_key: sys.platform ("win32", "linux")
+    machine:      platform.machine() ("AMD64", "x86_64", ...)
+    """
+    pk = platform_key.lower()
+    m = machine.lower()
+    if m in {"amd64", "x86_64"}:
+        arch = "x86_64"
+    else:
+        raise NotImplementedError(f"unsupported arch: {machine}")
+
+    if pk == "win32":
+        return f"{BINARY_BASENAME}-win-{arch}.zip"
+    if pk == "linux":
+        return f"{BINARY_BASENAME}-linux-{arch}.tar.gz"
+    raise NotImplementedError(f"unsupported platform: {platform_key}")
+
+
+# Binary entry point relative path inside the extracted archive root.
+BINARY_ENTRY_REL = {
+    "win32": "firefox.exe",
+    "linux": "firefox",
+}
+
+# GitHub release URL template. The "TODO" owner is resolved at publication time.
+RELEASE_URL_TEMPLATE = (
+    "https://github.com/feder-cr/stealthfox/releases/download/{tag}/{asset}"
+)

src/stealthfox/download.py

@@ -0,0 +1,151 @@
+"""Download and cache the patched Firefox binary from GitHub Releases."""
+from __future__ import annotations
+
+import hashlib
+import os
+import platform
+import re
+import sys
+import tarfile
+import tempfile
+import zipfile
+from pathlib import Path
+
+import platformdirs
+import requests
+
+from .constants import (
+    ARCHIVE_NAME,
+    BINARY_ENTRY_REL,
+    BINARY_VERSION,
+    RELEASE_URL_TEMPLATE,
+)
+
+
+def _github_token() -> str | None:
+    return os.environ.get("STEALTHFOX_GITHUB_TOKEN") or os.environ.get("GITHUB_TOKEN")
+
+
+def _parse_owner_repo(template: str) -> tuple[str, str]:
+    """Extract (owner, repo) from RELEASE_URL_TEMPLATE."""
+    m = re.match(r"https://github\.com/([^/]+)/([^/]+)/releases/", template)
+    if not m:
+        raise RuntimeError(f"cannot parse owner/repo from {template!r}")
+    return m.group(1), m.group(2)
+
+
+def cache_root() -> Path:
+    """Directory where all cached binaries live."""
+    return Path(platformdirs.user_cache_dir("stealthfox"))
+
+
+def cache_dir_for_version(version: str = BINARY_VERSION) -> Path:
+    return cache_root() / version
+
+
+def _resolve_asset_url(tag: str, asset_name: str) -> str:
+    """Return a downloadable URL for the asset.
+
+    For private repos the direct `releases/download/<tag>/<asset>` URL returns
+    404 even with a token, so we resolve via the API: list assets for the
+    release tag, find the one matching `asset_name`, and use its API URL with
+    `Accept: application/octet-stream` (which 302-redirects to a signed URL).
+    For public repos the direct URL still works without a token.
+    """
+    token = _github_token()
+    if not token:
+        return RELEASE_URL_TEMPLATE.format(tag=tag, asset=asset_name)
+    owner, repo = _parse_owner_repo(RELEASE_URL_TEMPLATE)
+    api = f"https://api.github.com/repos/{owner}/{repo}/releases/tags/{tag}"
+    r = requests.get(api, headers={"Authorization": f"token {token}"}, timeout=30)
+    r.raise_for_status()
+    for a in r.json().get("assets", []):
+        if a.get("name") == asset_name:
+            return a["url"]
+    raise RuntimeError(f"asset {asset_name!r} not found in release {tag!r}")
+
+
+def _download_file(url: str, dst: Path, chunk_size: int = 1 << 16) -> None:
+    dst.parent.mkdir(parents=True, exist_ok=True)
+    headers: dict[str, str] = {}
+    token = _github_token()
+    if token and url.startswith("https://api.github.com/"):
+        headers["Authorization"] = f"token {token}"
+        headers["Accept"] = "application/octet-stream"
+    with requests.get(url, stream=True, timeout=60, headers=headers) as r:
+        r.raise_for_status()
+        with open(dst, "wb") as f:
+            for chunk in r.iter_content(chunk_size):
+                if chunk:
+                    f.write(chunk)
+
+
+def _sha256_file(path: Path) -> str:
+    h = hashlib.sha256()
+    with open(path, "rb") as f:
+        for chunk in iter(lambda: f.read(1 << 16), b""):
+            h.update(chunk)
+    return h.hexdigest()
+
+
+def _parse_checksums(text: str) -> dict[str, str]:
+    out: dict[str, str] = {}
+    for line in text.splitlines():
+        line = line.strip()
+        if not line or line.startswith("#"):
+            continue
+        parts = line.split()
+        if len(parts) >= 2:
+            out[parts[-1]] = parts[0]
+    return out
+
+
+def _extract(archive: Path, dst: Path) -> None:
+    dst.mkdir(parents=True, exist_ok=True)
+    if archive.suffix == ".zip":
+        with zipfile.ZipFile(archive) as zf:
+            zf.extractall(dst)
+    elif archive.name.endswith(".tar.gz") or archive.suffix in {".tgz", ".gz"}:
+        with tarfile.open(archive, "r:gz") as tf:
+            tf.extractall(dst)
+    else:
+        raise RuntimeError(f"unknown archive format: {archive}")
+
+
+def ensure_binary(version: str = BINARY_VERSION) -> Path:
+    """Return a path to a runnable Firefox executable. Download if needed."""
+    plat = sys.platform
+    mach = platform.machine()
+    asset = ARCHIVE_NAME(plat, mach)
+    entry_rel = BINARY_ENTRY_REL.get(plat)
+    if entry_rel is None:
+        raise NotImplementedError(f"no binary entry for platform {plat}")
+
+    version_dir = cache_dir_for_version(version)
+    entry = version_dir / entry_rel
+    if entry.exists():
+        return entry
+
+    url_archive = _resolve_asset_url(version, asset)
+    url_sums = _resolve_asset_url(version, "checksums.txt")
+
+    with tempfile.TemporaryDirectory() as td:
+        tmp = Path(td)
+        archive_path = tmp / asset
+        _download_file(url_archive, archive_path)
+        sums_path = tmp / "checksums.txt"
+        _download_file(url_sums, sums_path)
+        sums = _parse_checksums(sums_path.read_text())
+        expected = sums.get(asset)
+        if expected is None:
+            raise RuntimeError(f"no SHA256 for {asset} in checksums.txt")
+        actual = _sha256_file(archive_path)
+        if actual.lower() != expected.lower():
+            raise RuntimeError(
+                f"SHA256 mismatch for {asset}: got {actual}, expected {expected}"
+            )
+        _extract(archive_path, version_dir)
+
+    if not entry.exists():
+        raise RuntimeError(f"binary not found after extraction: {entry}")
+    return entry

src/stealthfox/launcher.py

@@ -0,0 +1,307 @@
+"""Sync Playwright launcher for stealthfox."""
+from __future__ import annotations
+
+import secrets
+from typing import Any, Dict, Optional, Union
+
+from playwright.sync_api import Browser, Playwright, sync_playwright
+
+from ._fpforge import Profile, generate_profile
+from ._headless import make_virtual_display
+from ._proxy import configure_proxy as _configure_proxy_shared
+from .download import ensure_binary
+from .prefs import translate_profile_to_prefs
+
+
+def _patch_sync_new_page_sleep(ctx: Any) -> None:
+    """Wrap ctx.new_page() to add a brief settle after tab creation.
+
+    FF150 with Fission emits an about:newtab navigation ~100ms after a tab
+    is created.  If goto() is called immediately, it races with that internal
+    navigation and raises "Navigation interrupted by about:newtab".  A short
+    sleep breaks the race without requiring every call-site to know about it.
+    """
+    import time as _time
+    original_new_page = ctx.new_page
+
+    def patched_new_page(**kw):
+        page = original_new_page(**kw)
+        _time.sleep(0.4)
+        return page
+
+    ctx.new_page = patched_new_page  # type: ignore[assignment]
+
+
+# Window-chrome and taskbar offsets measured empirically on a headed
+# Firefox 150 (no compositor). Used to derive the default new_context
+# viewport so it fits inside the spoofed screen without out-of-bounds.
+_CHROME_W  = 14
+_CHROME_H  = 91
+_TASKBAR_H = 40
+
+# IANA → POSIX TZ mapping. Linux glibc accepts IANA names directly via
+# /usr/share/zoneinfo, but Windows MSVCRT only understands the POSIX form
+# ("EST5EDT") — convert here so ``TZ`` works on both platforms when the
+# binary runs on Windows. Common US zones cover the vast majority of
+# residential proxies; everything else falls through to its IANA name.
+_IANA_TO_POSIX_TZ = {
+    "America/New_York":            "EST5EDT",
+    "America/Detroit":              "EST5EDT",
+    "America/Indiana/Indianapolis": "EST5EDT",
+    "America/Kentucky/Louisville":  "EST5EDT",
+    "America/Chicago":              "CST6CDT",
+    "America/Denver":               "MST7MDT",
+    "America/Los_Angeles":          "PST8PDT",
+    # Arizona (except Navajo Nation) does NOT observe DST. Mapping it to
+    # MST7MDT made libc apply DST → Date.getTimezoneOffset() returned -360
+    # in summer (Denver-like) instead of -420 (true Phoenix), and FP Pro
+    # deduced vpn_origin_timezone="America/Denver" → timezone_mismatch.
+    "America/Phoenix":              "MST7",
+    "America/Anchorage":            "AKST9AKDT",
+    # Hawaii does not observe DST.
+    "Pacific/Honolulu":             "HST10",
+}
+
+
+def _tz_env(timezone: str) -> str:
+    """Return the value to set in ``TZ`` for the given IANA zone."""
+    return _IANA_TO_POSIX_TZ.get(timezone, timezone)
+
+
+class Stealthfox:
+    """Context manager launching a patched Firefox with a deterministic profile.
+
+    Usage:
+
+        from stealthfox import Stealthfox
+
+        # random seed (different fingerprint each call)
+        with Stealthfox() as browser:
+            page = browser.new_page()
+            page.goto("https://example.com")
+
+        # explicit seed → same profile every time
+        with Stealthfox(seed=42) as browser:
+            ...
+
+        # human-like cursor motion (Bezier trajectory on every mousemove)
+        with Stealthfox(humanize=True) as browser:
+            ...
+
+    Optional ``pin`` forces specific fingerprint fields while the rest still
+    varies with ``seed``::
+
+        with Stealthfox(seed=42, pin={"screen.width": 2560}) as browser:
+            ...
+
+    After construction, the chosen seed is available as ``self.seed`` — useful
+    to reproduce a random run later.
+    """
+
+    def __init__(
+        self,
+        seed: Optional[int] = None,
+        *,
+        pin: Optional[Dict[str, Any]] = None,
+        headless: bool = False,
+        proxy: Optional[Dict[str, str]] = None,
+        extra_args: Optional[list[str]] = None,
+        humanize: Union[bool, float] = True,
+        locale: str = "en-US",
+        timezone: str = "",
+        extra_prefs: Optional[Dict[str, Any]] = None,
+        binary_path: Optional[str] = None,
+    ) -> None:
+        """
+        Args:
+            seed: Integer seed driving the Bayesian fingerprint sampler.
+                Same seed → same fingerprint. ``None`` = fresh random.
+            pin: Force specific fingerprint fields (see docs/pinning.md).
+            headless: When ``True``, browser renders on a hidden virtual
+                display (Xvfb on Linux, ``CreateDesktop`` on Windows) so
+                Firefox stays in *headed* mode (real rendering pipeline,
+                coherent fingerprint) without showing windows.
+            proxy: ``{"server": "...", "username": "...", "password": "..."}``.
+                ``socks5://`` / ``socks4://`` go through the patched
+                ``nsProtocolProxyService``; ``http(s)://`` go through
+                Playwright's own ``proxy=`` kwarg.
+            extra_args: Extra command-line args forwarded to Firefox.
+            humanize: Every mouse move is expanded by the patched Juggler
+                into a Bezier trajectory with ~10 ms between waypoints.
+                Default ``True`` (~1.5 s max motion). ``False`` disables;
+                a float caps the motion in seconds.
+            locale: BCP-47 tag (e.g. ``"en-US"``). Drives the
+                ``Accept-Language`` header and ``navigator.language``.
+            timezone: IANA timezone (e.g. ``"America/New_York"``). Empty
+                means use the host TZ.
+            extra_prefs: Optional dict of Firefox prefs overlayed on top
+                of the generated profile — useful for niche tweaks
+                without monkey-patching the package.
+        """
+        # Constrain to int31 — Firefox's `zoom.stealth.fpp.hw_seed` and
+        # related stealth prefs are declared as ``int32_t`` in
+        # ``StaticPrefList.yaml``. A 32-bit seed risks the high bit being
+        # interpreted as negative on the C++ side, where the noise hooks
+        # bail out on ``seed <= 0`` — which produces bit-identical audio
+        # / canvas fingerprints across half the sessions.
+        self.seed: int = int(seed) if seed is not None else secrets.randbits(31)
+        self._pin = pin
+        self._headless = headless
+        self._proxy = proxy
+        self._extra_args = list(extra_args or [])
+        self._humanize = humanize
+        self._locale = locale
+        self._timezone = timezone
+        self._extra_prefs = extra_prefs
+        self._binary_path = binary_path
+        self._profile: Profile = generate_profile(self.seed, pin=self._pin)
+        self._pw: Optional[Playwright] = None
+        self._browser: Optional[Browser] = None
+        self._virtual_display: Any = None
+
+    def __enter__(self) -> Browser:
+        executable = self._binary_path or ensure_binary()
+        prefs = self._build_prefs()
+        playwright_proxy = _configure_proxy_shared(self._proxy, prefs)
+        pw_headless = self._resolve_headless()
+        env = self._build_env()
+
+        try:
+            self._pw = sync_playwright().start()
+            self._browser = self._pw.firefox.launch(
+                executable_path=str(executable),
+                headless=pw_headless,
+                firefox_user_prefs=prefs,
+                proxy=playwright_proxy,
+                args=self._extra_args,
+                env=env,
+            )
+        except BaseException:
+            # Python doesn't call __exit__ when __enter__ raises — clean up
+            # the virtual display + Playwright manually so we don't leak Xvfb
+            # / desktop handles into the user's process.
+            self._teardown()
+            raise
+        self._patch_new_context_defaults(self._browser)
+        return self._browser
+
+    def _patch_new_context_defaults(self, browser: Browser) -> None:
+        """Wrap ``browser.new_context`` so its defaults derive from the
+        profile (viewport, screen, DPR, color-scheme). Users get a
+        coherent context for free; explicit kwargs still override.
+        """
+        original = browser.new_context
+        defaults = self._default_context_kwargs()
+
+        def patched(**kw):
+            merged = dict(defaults)
+            merged.update(kw)  # user-supplied wins
+            ctx = original(**merged)
+            _patch_sync_new_page_sleep(ctx)
+            return ctx
+
+        browser.new_context = patched  # type: ignore[assignment]
+
+    def _default_context_kwargs(self) -> Dict[str, Any]:
+        p = self._profile
+        kwargs: Dict[str, Any] = {
+            "viewport":            {"width":  p.screen.width  - _CHROME_W,
+                                     "height": p.screen.height - _TASKBAR_H - _CHROME_H},
+            "screen":              {"width": p.screen.width, "height": p.screen.height},
+            "device_scale_factor": p.screen.dpr,
+            "color_scheme":        "dark" if p.dark_theme else "light",
+        }
+        # Pass timezone via Playwright's per-realm override (docShell.overrideTimezone
+        # → JS::SetRealmTimezoneOverride). The juggler.timezone.override pref path
+        # uses JS::SetTimeZoneOverride globally, which is broken on Windows ICU for
+        # no-DST IANA names (America/Phoenix, Pacific/Honolulu, ...) — those silently
+        # fall back to the host system TZ. The per-realm path works for every zone.
+        if self._timezone:
+            kwargs["timezone_id"] = self._timezone
+        if self._locale:
+            kwargs["locale"] = self._locale
+        return kwargs
+
+    def __exit__(self, *exc: Any) -> None:
+        self._teardown()
+
+    def _teardown(self) -> None:
+        if self._browser is not None:
+            try:
+                self._browser.close()
+            except Exception:
+                pass
+            self._browser = None
+        if self._pw is not None:
+            try:
+                self._pw.stop()
+            except Exception:
+                pass
+            self._pw = None
+        if self._virtual_display is not None:
+            try:
+                self._virtual_display.stop()
+            except Exception:
+                pass
+            self._virtual_display = None
+
+    # ── helpers ─────────────────────────────────────────────────────────
+
+    def _build_prefs(self) -> Dict[str, Any]:
+        """Fingerprint prefs plus humanize toggle (always set explicitly)."""
+        import sys as _sys
+        prefs = translate_profile_to_prefs(
+            self._profile,
+            locale=self._locale,
+            timezone=self._timezone,
+            extra_prefs=self._extra_prefs,
+            virtual_display=bool(self._headless and _sys.platform == "win32"),
+        )
+        prefs["stealthfox.humanize"] = bool(self._humanize)
+        if self._humanize:
+            prefs["stealthfox.humanize.maxTime"] = str(self._humanize_max_seconds())
+        return prefs
+
+    def _build_env(self) -> Dict[str, str]:
+        """Env vars passed to the Firefox subprocess.
+
+        ``TZ`` tunes the libc clock the content process reads for
+        ``Date`` / ``Intl.DateTimeFormat`` so the JS-visible timezone
+        matches ``self._timezone`` regardless of the host TZ.
+        ``STEALTHFOX_WEBRTC_PUBLIC_IP`` is propagated when the calling
+        process has set it — read by nICEr's nr_stealth_bridge to inject
+        a synthetic srflx candidate matching the proxy egress IP, avoiding
+        the StaticPref IPC propagation timing issue between parent and
+        socket processes.
+        """
+        import os as _os
+        env = _os.environ.copy()
+        if self._timezone:
+            env["TZ"] = _tz_env(self._timezone)
+        # Propagate STEALTHFOX_WEBRTC_PUBLIC_IP if the process set it — read
+        # by nICEr's nr_stealth_bridge to inject a synthetic srflx candidate
+        # matching the proxy egress IP. This avoids the StaticPref IPC
+        # propagation timing issue between parent and socket processes.
+        if _os.environ.get("STEALTHFOX_WEBRTC_PUBLIC_IP"):
+            env["STEALTHFOX_WEBRTC_PUBLIC_IP"] = _os.environ["STEALTHFOX_WEBRTC_PUBLIC_IP"]
+        return env
+
+    def _resolve_headless(self) -> bool:
+        """Translate the user's ``headless`` flag.
+
+        When ``True``, we keep Firefox in headed mode (real rendering
+        pipeline → coherent fingerprint) and hide the windows on a fresh
+        Xvfb (Linux) or hidden Windows desktop.
+        """
+        if not self._headless:
+            return False
+        vd = make_virtual_display()
+        vd.start()
+        self._virtual_display = vd
+        return False
+
+    def _humanize_max_seconds(self) -> float:
+        if self._humanize is True:
+            return 1.5
+        return float(self._humanize)
+

src/stealthfox/prefs.py

@@ -0,0 +1,568 @@
+"""Translate an internal Profile into the Firefox prefs dict that the
+patched Firefox binary expects.
+
+The output dict keys map 1:1 to ``user.js`` preferences. Playwright passes
+them via ``firefox_user_prefs=``. The patched binary propagates them to all
+content processes over IPC; C++ patches read the ``zoom.stealth.*``
+namespace.
+
+The translation is split into:
+
+  * ``_BASELINE`` — global stealth policy (RFP off, WebRTC leaks blocked,
+    safebrowsing disabled, debugger detach, …) plus Windows-canonical
+    constants that don't depend on the Profile (system colors palette,
+    WebGL extensions whitelist, speech voices, navigator identity).
+  * ``translate_profile_to_prefs`` — overlays the Profile fields plus the
+    user-supplied ``locale`` and ``timezone``.
+"""
+from __future__ import annotations
+
+import sys
+from typing import Any, Dict, Optional
+
+from ._fpforge import Profile
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Navigator identity — locked to Firefox 150 Windows so the binary
+#  reports the same UA / platform / oscpu regardless of the host OS.
+# ──────────────────────────────────────────────────────────────────────
+
+_NAVIGATOR_OVERRIDES: Dict[str, str] = {
+    "general.useragent.override":
+        "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:150.0) "
+        "Gecko/20100101 Firefox/150.0.1",
+    "general.platform.override":   "Win32",
+    "general.oscpu.override":      "Windows NT 10.0; Win64; x64",
+    # general.buildID.override removed 2026-04-28: the previous value
+    # "20181001000000" was a 2018 buildID stuck on a 2026-built Firefox 150
+    # binary (real BuildID=20260426192818 from application.ini). The 7.5-yr
+    # discrepancy is the kind of internal-consistency check Google reCAPTCHA
+    # can use to flag bot/spoofed browsers. Deleting the override lets
+    # Firefox emit its compiled-in buildID, which auto-tracks the binary.
+    # A/B knockout 2026-04-28 (n=30): F2 delete +0.083 RC vs BASE; n=100
+    # confirm: +0.021; overnight isolated: +0.155 single-variant. Variable
+    # signal, but the underlying data error is unambiguous.
+    "general.appversion.override": "5.0 (Windows)",
+}
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  System colors — FP Pro probes getComputedStyle(div) with CSS system
+#  keywords (ButtonFace, Menu, Highlight, …) and hashes the result into
+#  signal s142. On Linux, Firefox resolves these via GTK theme → GTK
+#  RGB values diverge from Windows Win32 palette → server-side anomaly
+#  even with Windows UA. Pinning the palette to Win10 default closes
+#  the gap (see project_css_system_colors.md memory).
+# ──────────────────────────────────────────────────────────────────────
+
+_WIN_LIGHT_COLORS: Dict[str, str] = {
+    "ui.activeborder":              "#B4B4B4",
+    "ui.activecaption":             "#99B4D1",
+    "ui.appworkspace":              "#ABABAB",
+    "ui.background":                "#000000",
+    "ui.buttonface":                "#F0F0F0",
+    "ui.buttonhighlight":           "#FFFFFF",
+    "ui.buttonshadow":              "#A0A0A0",
+    "ui.buttontext":                "#000000",
+    "ui.buttonborder":              "#000000",
+    "ui.captiontext":               "#000000",
+    "ui.graytext":                  "#6D6D6D",
+    "ui.highlight":                 "#0078D7",
+    "ui.highlighttext":             "#FFFFFF",
+    "ui.inactiveborder":            "#F4F7FC",
+    "ui.inactivecaption":           "#BFCDDB",
+    "ui.inactivecaptiontext":       "#434E54",
+    "ui.infobackground":            "#FFFFE1",
+    "ui.infotext":                  "#000000",
+    "ui.menu":                      "#F9F9FB",
+    "ui.menutext":                  "#000000",
+    "ui.scrollbar":                 "#C8C8C8",
+    "ui.threeddarkshadow":          "#696969",
+    "ui.threedface":                "#F0F0F0",
+    "ui.threedhighlight":           "#FFFFFF",
+    "ui.threedlightshadow":         "#E3E3E3",
+    "ui.threedshadow":              "#A0A0A0",
+    "ui.window":                    "#FFFFFF",
+    "ui.windowframe":               "#646464",
+    "ui.windowtext":                "#000000",
+    "ui.mark":                      "#FFFF00",
+    "ui.marktext":                  "#000000",
+    "ui.accentcolor":               "#0078D4",
+    "ui.accentcolortext":           "#FFFFFF",
+    "ui.selecteditem":              "#0078D7",
+    "ui.selecteditemtext":          "#FFFFFF",
+    "ui.-moz-hyperlinktext":        "#0066CC",
+    "ui.-moz-activehyperlinktext":  "#EE0000",
+    "ui.-moz-visitedhyperlinktext": "#551A8B",
+}
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  WebGL extensions — Windows ANGLE canonical lists. Empty string =
+#  fall back to native Mesa/ANGLE; non-empty = `getSupportedExtensions`
+#  returns this list verbatim and `IsSupported()` rejects anything else.
+# ──────────────────────────────────────────────────────────────────────
+
+_WEBGL1_EXTENSIONS = ",".join([
+    "ANGLE_instanced_arrays",
+    "EXT_blend_minmax",
+    "EXT_color_buffer_half_float",
+    "EXT_float_blend",
+    "EXT_frag_depth",
+    "EXT_sRGB",
+    "EXT_shader_texture_lod",
+    "EXT_texture_compression_bptc",
+    "EXT_texture_compression_rgtc",
+    "EXT_texture_filter_anisotropic",
+    "OES_element_index_uint",
+    "OES_fbo_render_mipmap",
+    "OES_standard_derivatives",
+    "OES_texture_float",
+    "OES_texture_float_linear",
+    "OES_texture_half_float",
+    "OES_texture_half_float_linear",
+    "OES_vertex_array_object",
+    "WEBGL_color_buffer_float",
+    "WEBGL_compressed_texture_s3tc",
+    "WEBGL_compressed_texture_s3tc_srgb",
+    "WEBGL_debug_renderer_info",
+    "WEBGL_debug_shaders",
+    "WEBGL_depth_texture",
+    "WEBGL_draw_buffers",
+    "WEBGL_lose_context",
+    "WEBGL_provoking_vertex",
+])
+
+_WEBGL2_EXTENSIONS = ",".join([
+    "EXT_color_buffer_float",
+    "EXT_color_buffer_half_float",
+    "EXT_float_blend",
+    "EXT_texture_compression_bptc",
+    "EXT_texture_compression_rgtc",
+    "EXT_texture_filter_anisotropic",
+    "OES_draw_buffers_indexed",
+    "OES_texture_float_linear",
+    "OES_texture_half_float_linear",
+    "OVR_multiview2",
+    "WEBGL_compressed_texture_s3tc",
+    "WEBGL_compressed_texture_s3tc_srgb",
+    "WEBGL_debug_renderer_info",
+    "WEBGL_debug_shaders",
+    "WEBGL_lose_context",
+    "WEBGL_provoking_vertex",
+])
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Speech voices — Windows canonical "Microsoft *" set. Format:
+#  "NAME|LANG|DEFAULT|LOCAL,...". Non-empty value drives the
+#  speechSynthesis.getVoices() patch; empty disables it.
+# ──────────────────────────────────────────────────────────────────────
+
+_WIN_VOICES = ",".join([
+    "Microsoft David - English (United States)|en-US|1|1",
+    "Microsoft Zira - English (United States)|en-US|0|1",
+    "Microsoft Mark - English (United States)|en-US|0|1",
+    "Microsoft David Desktop - English (United States)|en-US|0|1",
+    "Microsoft Zira Desktop - English (United States)|en-US|0|1",
+])
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Linux font compensation — Linux Firefox uses DejaVu / Liberation
+#  fonts which have wider/narrower glyphs than Windows Arial / Segoe.
+#  These per-generic factors are prepended to ``zoom.stealth.font.metrics``
+#  on Linux only; Windows-native rendering already matches the canonical
+#  widths so we pass an empty string (any factor !=1 would distort real
+#  metrics).
+# ──────────────────────────────────────────────────────────────────────
+
+_LINUX_GENERIC_FONT_FACTORS = (
+    # Calibrated to bring DejaVu/Liberation widths in line with what Windows
+    # FP Pro probes report for native Segoe/Times. Linux base measurements
+    # (font_preferences) and Windows targets:
+    #   serif:    162 → 149  factor 0.920
+    #   sans:     162 → 144  factor 0.889
+    #   monospace:121 → 121  factor 1.000
+    #   system:   162 → 147  factor 0.910
+    "serif|0.920,sans-serif|0.889,monospace|1.000,"
+    "system-ui|0.910,cursive|0.932,fantasy|0.812,"
+)
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Baseline — applied to every session regardless of Profile.
+# ──────────────────────────────────────────────────────────────────────
+
+_BASELINE: Dict[str, Any] = {
+    # Turn off Firefox's own resistFingerprinting; we do our own via patches.
+    "privacy.resistFingerprinting": False,
+    "privacy.resistFingerprinting.letterboxing": False,
+
+    # FF150 fingerprintingProtection — enabled by default (or remotely via
+    # Mozilla webcompat overrides). FP Pro detects the side-effects and
+    # flips `privacy_settings: true`. On FF146 these were all off → False.
+    # Force off so FP Pro reports privacy_settings:false (matches FF146).
+    "privacy.fingerprintingProtection":                              False,
+    "privacy.fingerprintingProtection.pbmode":                       False,
+    "privacy.fingerprintingProtection.remoteOverrides.enabled":      False,
+
+    # WebRTC: enabled, no public IP leak.
+    # obfuscate_host_addresses=false: our C++ injection handles candidate
+    # selection; mDNS causes mDNS-IPC to hang in sandboxed content processes.
+    # disableIPv6=true keeps IPv6 out of gathering (less entropy, no IPv6 leak).
+    "media.peerconnection.enabled":                       True,
+    "media.peerconnection.ice.no_host":                   False,
+    "media.peerconnection.ice.default_address_only":      False,
+    "media.peerconnection.ice.obfuscate_host_addresses":  False,
+    "media.peerconnection.ice.disableIPv6":               True,
+    "media.peerconnection.ice.proxy_only":                False,
+    "media.peerconnection.ice.relay_only":                False,
+    "media.peerconnection.use_document_iceservers":       True,
+
+    # Proxy — route DNS through SOCKS proxies to avoid local DNS leaks.
+    "network.proxy.socks_remote_dns":                     True,
+    "network.proxy.failover_direct":                      False,
+
+    # Safebrowsing — chatty and fingerprintable.
+    "browser.safebrowsing.malware.enabled":               False,
+    "browser.safebrowsing.phishing.enabled":              False,
+    "browser.safebrowsing.downloads.enabled":             False,
+    "browser.safebrowsing.downloads.remote.enabled":      False,
+
+    # First-run / welcome UI noise.
+    "browser.startup.page":                               0,
+    "browser.shell.checkDefaultBrowser":                  False,
+    "browser.aboutwelcome.enabled":                       False,
+    "browser.startup.upgradeDialog.enabled":              False,
+    "termsofuse.acceptedVersion":                         999,
+
+    # Disable about:newtab auto-load — TopSitesFeed.sys.mjs auto-fetches when
+    # a tab opens, triggering a cross-process BC swap that hijacks the first
+    # page.goto() (NS_BINDING_ABORTED on creepjs/peet/sannysoft/fppro).
+    "browser.newtabpage.enabled":                         False,
+    "browser.newtab.preload":                             False,
+    "browser.newtabpage.activity-stream.feeds.topsites":  False,
+    "browser.newtabpage.activity-stream.feeds.section.topstories": False,
+    "browser.newtabpage.activity-stream.enabled":         False,
+
+    # Disable Firefox internal services that hit the network on startup.
+    # Through a residential SOCKS5 proxy these compete with the test
+    # navigation and trigger NS_BINDING_FAILED (server-side rate-limit /
+    # connection drops). Domains observed in MOZ_LOG: push.services,
+    # firefox.settings.services, detectportal, ohttp-gateway, location.
+    "browser.aboutConfig.showWarning":                    False,
+    "network.captive-portal-service.enabled":             False,
+    "network.connectivity-service.enabled":               False,
+    "dom.push.enabled":                                   False,
+    "dom.push.connection.enabled":                        False,
+    "geo.enabled":                                        False,
+    "geo.provider.network.url":                           "",
+    "browser.region.network.url":                         "",
+    "browser.region.update.enabled":                      False,
+    "services.settings.server":                           "",
+    "browser.search.geoSpecificDefaults":                 False,
+    "browser.contentblocking.report.lockwise.enabled":    False,
+    "browser.contentblocking.report.monitor.enabled":     False,
+    "extensions.systemAddon.update.enabled":              False,
+    "extensions.update.enabled":                          False,
+    "extensions.getAddons.cache.enabled":                 False,
+    "browser.discovery.enabled":                          False,
+    "browser.ping-centre.telemetry":                      False,
+    "app.normandy.enabled":                               False,
+    "dom.private-attribution.submission.enabled":         False,
+    "browser.translations.enable":                        False,
+    "browser.search.update":                              False,
+
+    # HTTP/3 + speculative + Alt-Svc disabled. SOCKS5 proxy doesn't
+    # support UDP ASSOCIATE so HTTP/3 fails. Speculative connections
+    # under load cause early channel cancel (NS_BINDING_FAILED).
+    "network.http.http3.enable":                          False,
+    "network.http.http3.enabled":                         False,
+    "network.http.altsvc.enabled":                        False,
+    "network.http.altsvc.oe":                             False,
+    "network.http.speculative-parallel-limit":            0,
+    "network.predictor.enabled":                          False,
+    "network.dns.disablePrefetch":                        True,
+    "network.dns.disablePrefetchFromHTTPS":               True,
+    "network.dns.echconfig.enabled":                      False,
+    "network.dns.use_https_rr_as_altsvc":                 False,
+
+    # === A/B VARIANT B: Fission disabled ===
+    # Force single content-process model (e10s only, no BC outer/inner split).
+    # Diagnostic for the FF150 BC-swap theory: if peet_ws/fppro/sannysoft
+    # work with this off, the Juggler FF146 baseline breaks specifically on
+    # cross-process navigation tracking.
+    "fission.autostart":                                  False,
+    "fission.autostart.session":                          False,
+    "dom.ipc.processCount.webIsolated":                   1,
+
+
+    # Telemetry & data reporting.
+    "datareporting.healthreport.uploadEnabled":           False,
+    "datareporting.policy.dataSubmissionEnabled":         False,
+    "toolkit.telemetry.enabled":                          False,
+    "toolkit.telemetry.unified":                          False,
+    "app.shield.optoutstudies.enabled":                   False,
+
+    # Update channels.
+    "app.update.enabled":                                 False,
+    "app.update.auto":                                    False,
+
+    # Speech synth: enabled (the C++ patch fabricates voices from the
+    # comma list above) regardless of the host OS.
+    "media.webspeech.synth.enabled":                      True,
+    "zoom.stealth.voices.list":                           _WIN_VOICES,
+
+    # WebGL extensions whitelist — non-empty pre-empts native enumeration.
+    "zoom.stealth.webgl.extensions":                      _WEBGL1_EXTENSIONS,
+    "zoom.stealth.webgl2.extensions":                     _WEBGL2_EXTENSIONS,
+    # WebGL numeric param overrides — kept empty (A/B test 2026-04-22 showed
+    # mismatches between the values we shipped and ANGLE's real envelope
+    # raised FP Pro's ML tampering score). Slot kept for future experiments.
+    "zoom.stealth.webgl.int_params":                      "",
+    "zoom.stealth.webgl.int2_params":                     "",
+    "zoom.stealth.webgl.shader_precisions":               "",
+    "zoom.stealth.webgl.float_params":                    "",
+
+    # DevTools anti-detection.
+    "zoom.stealth.debugger.force_detach":                 True,
+
+    # Canvas substitution — additive ±1 noise over the OS base pattern;
+    # set to True to replace pixels with hash(seed, idx) instead.
+    "zoom.stealth.canvas.substitute_pixels":              False,
+
+    # Navigator identity (locked to Windows Firefox 150).
+    **_NAVIGATOR_OVERRIDES,
+}
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Linux-only Xvfb workarounds — the Linux Firefox build under Xvfb
+#  cannot run WebRender (`ConnectToCompositor` retries forever). We
+#  disable WebRender + force WebGL through the GL software path so
+#  webgl_basics / webgl_extensions still report.
+# ──────────────────────────────────────────────────────────────────────
+
+_LINUX_XVFB_WORKAROUNDS: Dict[str, Any] = {
+    "gfx.webrender.all":                       False,
+    "gfx.webrender.force-disabled":            True,
+    "webgl.force-enabled":                     True,
+    # webgl.software-rendering-enabled / webgl.force-layers-readback removed in FF150.
+}
+
+# ──────────────────────────────────────────────────────────────────────
+#  Windows virtual-desktop workarounds — when headless=True on Windows,
+#  Firefox runs on a CreateDesktop virtual desktop. The hardware GPU is
+#  inaccessible from the virtual desktop, so the GPU process crashes when
+#  it tries to initialize the D3D11 compositor with hardware acceleration.
+#
+#  Approach: force D3D11 WARP (CPU software renderer) for the GPU process.
+#  layers.d3d11.force-warp=True → compositor uses WARP → GPU process stable.
+#  webgl.angle.force-warp=True  → ANGLE uses WARP → WebGL context creates.
+#
+#  CRITICAL: do NOT set webgl.out-of-process=False. That moves WebGL from the
+#  GPU process to the sandboxed content process. The content process sandbox
+#  blocks D3D11 access entirely → ANGLE crashes the content process →
+#  canvas.getContext('webgl') throws instead of returning null.
+#
+#  gfx.canvas.accelerated=False: default is true, disabling avoids any
+#  hardware GPU dependency for 2D canvas in the content process.
+# ──────────────────────────────────────────────────────────────────────
+
+_WIN_VIRT_DESKTOP_WORKAROUNDS: Dict[str, Any] = {
+    # FF150 regression vs FF146 on CreateDesktop alt-desktop:
+    # The GPU process sandbox (level=1, default since FF110) tries to parent
+    # its compositor window to the parent process's window. Our worker spawns
+    # Firefox on a CreateDesktop-created alt desktop — parent and GPU process
+    # do not share the same desktop/HWND namespace, so window parenting fails
+    # silently. WebRender falls back to "Software D3D11" and OOP-WebGL never
+    # publishes a hardware ANGLE renderer → getContext('webgl') returns a
+    # context but extensions/parameters/$hash all come back null/empty (FF146
+    # had a more permissive sandbox, so the same setup worked there).
+    # Bugzilla refs: 1798091, 1524591, 1229829. Lowering the GPU sandbox to 0
+    # restores hardware compositor + functional WebGL on alt desktops.
+    "security.sandbox.gpu.level": 0,
+}
+
+
+# ──────────────────────────────────────────────────────────────────────
+#  Public helpers
+# ──────────────────────────────────────────────────────────────────────
+
+def _accept_language(locale: str) -> str:
+    lang = locale.replace("_", "-")
+    base = lang.split("-")[0]
+    return f"{lang}, {base}" if base != lang else lang
+
+
+def _font_metrics_for_platform(profile_metrics: str) -> str:
+    """Return ``zoom.stealth.font.metrics`` value.
+
+    Windows: empty string. The C++ width-scale hook is a no-op and
+    Firefox renders Arial/Segoe/Calibri/etc. at their native canonical
+    widths. Applying the Bayesian-sampled per-font factors on a Windows
+    build would *distort* real metrics and surface as a font_preferences
+    width anomaly to FP Pro / reCAPTCHA.
+
+    Linux: prepend generic-family compensation factors so DejaVu /
+    Liberation render at the widths Windows JS expects, then append the
+    per-font factors that make each fabricated family detectable by
+    width-diff probes.
+    """
+    if not profile_metrics:
+        return ""
+    if sys.platform.startswith("linux"):
+        return _LINUX_GENERIC_FONT_FACTORS + profile_metrics
+    return ""  # Windows: NEVER apply width-scale factors.
+
+
+def translate_profile_to_prefs(
+    profile: Profile,
+    *,
+    locale: str = "en-US",
+    timezone: str = "",
+    extra_prefs: Optional[Dict[str, Any]] = None,
+    virtual_display: bool = False,
+) -> Dict[str, Any]:
+    """Return a complete prefs dict ready for Playwright's firefox_user_prefs=.
+
+    Args:
+        profile:         Bayesian-sampled fingerprint (from ``generate_profile``).
+        locale:          BCP-47 tag, e.g. ``"en-US"``.
+        timezone:        IANA timezone name, e.g. ``"America/New_York"``.
+        extra_prefs:     Optional overlay applied LAST.
+        virtual_display: When True on Windows, apply GPU-disabling workarounds
+                         to prevent the GPU process from crashing on virtual
+                         desktops that have no D3D11 backend.
+    """
+    prefs: Dict[str, Any] = dict(_BASELINE)
+
+    # GPU / WebGL renderer/vendor.
+    # On Linux we spoof to a Windows ANGLE renderer string (profile.gpu.renderer)
+    # so cross-platform sessions report a consistent Windows GPU identity.
+    # On Windows, spoofing a different GPU creates a renderer/parameters hash
+    # mismatch: FP Pro hashes all 81 CN-set getParameter() values including
+    # enum 7937 (RENDERER). Setting GTX 980 while ANGLE returns Intel Arc A750
+    # parameters produces an OOD (hash 23d0a74b vs vanilla 66544db) that FP Pro
+    # ML scores at ~0.70 (confirmed: direct SF146 vs vanilla on same machine).
+    # Fix: leave renderer/vendor empty on Windows → ANGLE reports native hardware
+    # (SanitizeRenderer path at ClientWebGLContext.cpp:2592-2595) → consistent.
+    if sys.platform.startswith("linux"):
+        prefs["zoom.stealth.webgl.renderer"] = profile.gpu.renderer
+        prefs["zoom.stealth.webgl.vendor"]   = profile.gpu.vendor
+        _renderer_lo = (profile.gpu.renderer or "").lower()
+    else:
+        prefs["zoom.stealth.webgl.renderer"] = ""
+        prefs["zoom.stealth.webgl.vendor"]   = ""
+        _renderer_lo = "intel"  # test hardware is Intel Arc A750
+
+    # MSAA: on Windows, pin to 4 (Firefox default for ANGLE) so gl.SAMPLES is
+    # constant across all sessions. Different MSAA values cause different CN-set
+    # parameters hashes even with the same renderer → detectable variation.
+    # Vanilla Intel Arc A750 parameters hash (66544db8) verified at msaa=4.
+    _msaa = profile.webgl.msaa_samples if sys.platform.startswith("linux") else 4
+    prefs["zoom.stealth.webgl.msaa"]        = _msaa
+    prefs["webgl.msaa-samples"]             = _msaa
+    prefs["webgl.msaa-force"]               = _msaa > 0
+
+    # Canvas pixel-noise density per vendor. Intel has lower natural
+    # rendering variance than NVIDIA/AMD, so the default 1/8 noise rate
+    # over-amplifies the FP Pro tampering ML signal. Drop to 1/16 for Intel
+    # to keep tampering_ml below the detection threshold while still
+    # breaking the canvas geometry hash.
+    if "intel" in _renderer_lo:
+        prefs["zoom.stealth.canvas.noise_skip_mask"] = 15  # 1/16, ~6.25%
+    else:
+        prefs["zoom.stealth.canvas.noise_skip_mask"] = 7   # 1/8,  ~12.5%
+
+    # Screen
+    prefs["zoom.stealth.screen.width"]        = profile.screen.width
+    prefs["zoom.stealth.screen.height"]       = profile.screen.height
+    prefs["zoom.stealth.screen.avail_width"]  = profile.screen.avail_width
+    prefs["zoom.stealth.screen.avail_height"] = profile.screen.avail_height
+    prefs["zoom.stealth.screen.dpr"]          = profile.screen.dpr
+    prefs["layout.css.devPixelsPerPx"]        = str(profile.screen.dpr)
+
+    # Hardware
+    prefs["zoom.stealth.hw_concurrency"]      = profile.hardware.concurrency
+    prefs["zoom.stealth.storage.quota_mb"]    = profile.hardware.storage_quota_mb
+
+    # Audio
+    prefs["zoom.stealth.audio.sample_rate"]       = profile.audio.sample_rate
+    prefs["zoom.stealth.audio.output_latency_ms"] = profile.audio.output_latency_ms
+    prefs["zoom.stealth.audio.max_channel_count"] = profile.audio.max_channel_count
+
+    # Codec
+    prefs["media.av1.enabled"]                = profile.codec.av1_enabled
+    prefs["media.encoder.webm.enabled"]       = profile.codec.webm_encoder_enabled
+    prefs["media.mediasource.webm.enabled"]   = profile.codec.mediasource_webm
+    prefs["media.mediasource.mp4.enabled"]    = profile.codec.mediasource_mp4
+
+    # Fonts
+    prefs["zoom.stealth.font.whitelist"] = ",".join(profile.fonts)
+    prefs["zoom.stealth.font.metrics"]   = _font_metrics_for_platform(
+        profile._raw.get("font_metrics", "") or ""
+    )
+
+    # UI / dark mode + Windows colors palette (only when light theme).
+    prefs["ui.systemUsesDarkTheme"] = int(profile.dark_theme)
+    if not profile.dark_theme:
+        prefs.update(_WIN_LIGHT_COLORS)
+
+    # Locale prefs.
+    locale = locale or "en-US"
+    lang = locale.replace("_", "-")
+    prefs["intl.accept_languages"]     = _accept_language(locale)
+    prefs["general.useragent.locale"]  = lang
+    prefs["intl.locale.requested"]     = lang
+    prefs["privacy.spoof_english"]     = 0
+
+    if timezone:
+        prefs["zoom.stealth.timezone"] = timezone
+        prefs["juggler.timezone.override"] = timezone
+
+    # Cross-process seed (canvas noise + DWrite gamma share this).
+    prefs["zoom.stealth.fpp.hw_seed"] = profile.seed
+    prefs["zoom.stealth.seed"]        = profile.seed
+
+    # Synthetic host ICE candidate — injected by C++ when addr_ct==0 (SOCKS5
+    # proxy suppresses all local addresses so Firefox can't gather host cands).
+    # LAN IP is seed-derived so it's consistent per session and looks like a
+    # real home router assignment (192.168.x.x range).
+    _s = profile.seed
+    _lan_ip = f"192.168.{(_s >> 8) % 254 + 1}.{_s % 254 + 1}"
+    prefs["zoom.stealth.webrtc.host_ip"] = _lan_ip
+
+    # On Windows, native ANGLE extension list already matches real Windows users.
+    # The baseline hard-codes a curated _WEBGL1/2_EXTENSIONS list designed for
+    # Linux Mesa → clear it so Windows sessions report the native extension set
+    # (hash matches real Intel Arc A750 vanilla captures).
+    if not sys.platform.startswith("linux"):
+        prefs["zoom.stealth.webgl.extensions"]  = ""
+        prefs["zoom.stealth.webgl2.extensions"] = ""
+
+    # Linux Xvfb workarounds (no-op on Windows).
+    if sys.platform.startswith("linux"):
+        for k, v in _LINUX_XVFB_WORKAROUNDS.items():
+            prefs.setdefault(k, v)
+
+    # Windows virtual-desktop workarounds (headless=True on Windows).
+    if virtual_display and sys.platform == "win32":
+        for k, v in _WIN_VIRT_DESKTOP_WORKAROUNDS.items():
+            prefs.setdefault(k, v)
+
+    # Caller overlay LAST so users can override anything we set. A value of
+    # None is treated as a sentinel meaning "delete this pref entirely from
+    # the final dict" — useful for A/B harnesses that need to test what
+    # happens when an override is unset (vs set to empty string, which for
+    # some prefs like general.useragent.override means literally empty UA).
+    if extra_prefs:
+        for k, v in extra_prefs.items():
+            if v is None:
+                prefs.pop(k, None)
+            else:
+                prefs[k] = v
+
+    return prefs

src/stealthfox/sync_api.py

@@ -0,0 +1,4 @@
+"""Synchronous API — re-exports Stealthfox for parity with async_api."""
+from .launcher import Stealthfox
+
+__all__ = ["Stealthfox"]