refactor(browser): native CDP fingerprinting, drop patch.js + localized profiles. Update docker chrome

2026-08-05 16:53:54 +08:00 · 2026-07-13 06:07:37 +03:00
parent cf21bf5150
commit e7827cc03d
25 changed files with 531 additions and 1022 deletions
--- a/2
+++ b/2
@@ -12,7 +12,7 @@ ARG TARGETARCH
 RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH:-amd64} go build -trimpath -ldflags="-s -w" -o /app/openserp .

 # `chromedp/headless-shell:stable` also works here
-FROM chromedp/headless-shell:stable@sha256:aac539266027f91cf47610da1129dce360d23f45f8f150683cca94223fa2f1e2
+FROM chromedp/headless-shell:stable@sha256:f7e7ac721b023cb8717f8108aef8b3e49995fb1e5a912f41e570c29e45d24961

 WORKDIR /usr/src/app

--- a/baidu/search.go
+++ b/baidu/search.go
@@ -72,7 +72,7 @@ func (baid *Baidu) classifyBlockPage(page *rod.Page, url string) error {
 // Search executes a Baidu web search and returns normalized search results.
 // It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (baid *Baidu) Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, baid.Name(), true)
+	ctx = core.PrepareEngineContext(ctx, query, baid.Name())
 	scoped := *baid
 	scoped.logger = baid.logger.WithRequest(ctx)
 	if scoped.Browser.WaitLoadTime == 0 || scoped.Browser.WaitLoadTime > 250*time.Millisecond {
@@ -170,7 +170,7 @@ func (baid *Baidu) waitForParsedSearchResults(ctx context.Context, page *rod.Pag
 // SearchImage executes a Baidu image search and returns normalized image
 // results. It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (baid *Baidu) SearchImage(ctx context.Context, query core.Query) ([]core.SearchResult, error) {
-	ctx = core.PrepareEngineContext(ctx, query, baid.Name(), true)
+	ctx = core.PrepareEngineContext(ctx, query, baid.Name())
 	scoped := *baid
 	scoped.logger = baid.logger.WithRequest(ctx)
 	baid = &scoped
--- a/baidu/search_raw.go
+++ b/baidu/search_raw.go
@@ -19,7 +19,7 @@ func classifyBaiduRawHTML(body []byte) error {
 }

 func Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, "baidu", false)
+	ctx = core.PrepareEngineContext(ctx, query, "baidu")

 	searchURL, err := BuildURL(query)
 	if err != nil {
--- a/bing/search.go
+++ b/bing/search.go
@@ -155,7 +155,7 @@ func (bing *Bing) parseResultElement(el *rod.Element, isAd bool, rank *core.Rank
 // Search executes a Bing web search and returns normalized search results.
 // It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (bing *Bing) Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, bing.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, bing.Name())
 	scoped := *bing
 	scoped.logger = bing.logger.WithRequest(ctx)
 	bing = &scoped
@@ -256,7 +256,7 @@ func resolveImageLinkElement(container *rod.Element) (*rod.Element, error) {
 // SearchImage executes a Bing image search and returns normalized image
 // results. It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (bing *Bing) SearchImage(ctx context.Context, query core.Query) ([]core.SearchResult, error) {
-	ctx = core.PrepareEngineContext(ctx, query, bing.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, bing.Name())
 	scoped := *bing
 	scoped.logger = bing.logger.WithRequest(ctx)
 	bing = &scoped
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -17,7 +17,7 @@ import (
 )

 const (
-	version               = "0.8.9"
+	version               = "0.8.10"
 	defaultConfigFilename = "config"
 	envPrefix             = "OPENSERP"
 )
--- a/core/browser.go
+++ b/core/browser.go
@@ -2,13 +2,13 @@ package core

 import (
 	"context"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
 	"os"
 	"regexp"
+	"runtime"
 	"runtime/debug"
 	"strings"
 	"sync"
@@ -30,7 +30,7 @@ type BrowserOpts struct {
 	IsLeakless bool
 	// Timeout is applied to browser connect and page navigation operations.
 	Timeout time.Duration
-	// LanguageCode sets Accept-Language for emulated requests.
+	// LanguageCode selects the regional browser lane and search locale.
 	LanguageCode string
 	// WaitRequests waits for request-idle state after navigation.
 	WaitRequests bool
@@ -279,20 +279,17 @@ func NewBrowser(opts BrowserOpts) (*Browser, error) {
 		return nil, err
 	}

-	// Create launcher.
-	// headless=new uses the full Chrome renderer; legacy --headless disables the
-	// GPU process entirely, making WebGL context creation fail even with SwiftShader.
-	// use-angle=swiftshader-webgl (Chrome ≥112) enables a software WebGL renderer.
-	// Rod enables leakless by default, so always pass the configured value
-	// through. OpenSERP defaults it to false because the helper binary is
-	// commonly flagged by antivirus on Windows.
+	// headless=new keeps the full renderer, so WebGL falls back to SwiftShader
+	// when there's no GPU - which is what the swiftshader profiles describe.
+	// Legacy --headless kills the GPU process and breaks WebGL entirely.
+	// Leakless defaults to false: the helper binary trips antivirus on Windows.
 	l := launcher.New().Leakless(opts.IsLeakless).
+		Set("lang", browserLaunchLanguage(opts)).
 		Set("disable-blink-features", "AutomationControlled").
-		Delete("enable-automation").
-		Set("use-angle", "swiftshader-webgl").
-		Set("ignore-gpu-blocklist")
+		Delete("enable-automation")
 	if opts.IsHeadless {
-		l = l.HeadlessNew(true)
+		// Initial window only; per-page setDeviceMetricsOverride is what pages see. Sized for the 1920x1080 swiftshader profiles that run on Docker.
+		l = l.HeadlessNew(true).Set("window-size", "1920,1040")
 	} else {
 		l = l.Headless(false)
 	}
@@ -365,6 +362,12 @@ func browserOptsLogFields(opts BrowserOpts) logrus.Fields {
 	}
 }

+func browserLaunchLanguage(_ BrowserOpts) string {
+	// Speech voices are per-process and CDP can't change them, so pin the
+	// launch locale to the catalog rather than the request hint.
+	return "en-US"
+}
+
 func maskedProxyLogValue(proxyURL string) string {
 	if strings.TrimSpace(proxyURL) == "" {
 		return ""
@@ -653,7 +656,6 @@ func (b *Browser) laneProfile(ctx context.Context, browser *rod.Browser) (browse
 		profile, ok := browserprofile.ProfileByID(forcedID)
 		if ok {
 			profile = applyRuntimeBrowserVersion(profile, browser)
-			profile = applyProfileLanguageHint(profile, region)
 			if overrideUA := strings.TrimSpace(b.UserAgent); overrideUA != "" {
 				profile.UserAgent = overrideUA
 			}
@@ -663,9 +665,8 @@ func (b *Browser) laneProfile(ctx context.Context, browser *rod.Browser) (browse

 	if laneKey := proxyLaneKeyFromContext(ctx); !laneKey.Empty() && b.ProxyLaneStore != nil {
 		profile := b.ProxyLaneStore.Profile(laneKey, func() browserprofile.Profile {
-			selected := browserprofile.SelectProfileForSession(engine, region, laneKey.SessionID)
+			selected := browserprofile.SelectProfileForSessionHeadless(engine, region, laneKey.SessionID, b.IsHeadless)
 			selected = applyRuntimeBrowserVersion(selected, browser)
-			selected = applyProfileLanguageHint(selected, region)
 			if overrideUA := strings.TrimSpace(b.UserAgent); overrideUA != "" {
 				selected.UserAgent = overrideUA
 			}
@@ -691,9 +692,8 @@ func (b *Browser) laneProfile(ctx context.Context, browser *rod.Browser) (browse
 	// RWMutex-guarded catalog, and applyRuntimeBrowserVersion makes a CDP
 	// round-trip (browser.Version). Holding state.mu over network I/O would
 	// serialize all concurrent Navigate calls.
-	profile := browserprofile.SelectProfileForSession(engine, region, laneKey)
+	profile := browserprofile.SelectProfileForSessionHeadless(engine, region, laneKey, b.IsHeadless)
 	profile = applyRuntimeBrowserVersion(profile, browser)
-	profile = applyProfileLanguageHint(profile, region)
 	if overrideUA := strings.TrimSpace(b.UserAgent); overrideUA != "" {
 		profile.UserAgent = overrideUA
 	}
@@ -712,17 +712,46 @@ func (b *Browser) laneProfile(ctx context.Context, browser *rod.Browser) (browse
 	return profile, laneKey
 }

+// removeChromeBrand drops the "Google Chrome" client-hint brand from a profile,
+// used when the launched binary is Chromium rather than Google Chrome.
+func removeChromeBrand(profile browserprofile.Profile) browserprofile.Profile {
+	profile.UACHBrands = removeBrand(profile.UACHBrands, "google chrome")
+	profile.UACHFullVerList = removeBrand(profile.UACHFullVerList, "google chrome")
+	return profile
+}
+
+func removeBrand(values []browserprofile.BrandVersion, unwanted string) []browserprofile.BrandVersion {
+	out := make([]browserprofile.BrandVersion, 0, len(values))
+	for _, value := range values {
+		if strings.EqualFold(strings.TrimSpace(value.Brand), unwanted) {
+			continue
+		}
+		out = append(out, value)
+	}
+	return out
+}
+
 func applyRuntimeBrowserVersion(profile browserprofile.Profile, browser *rod.Browser) browserprofile.Profile {
 	fullVersion := ""
+	product := ""
 	if browser != nil {
 		version, err := browser.Version()
 		if err == nil && version != nil {
+			product = strings.TrimSpace(version.Product)
 			fullVersion = extractChromeVersion(version.UserAgent)
 			if fullVersion == "" {
-				fullVersion = extractChromeVersion(version.Product)
+				fullVersion = extractChromeVersion(product)
 			}
 		}
 	}
+
+	// version.Product tells us the real binary: "Chrome/..." for genuine Chrome,
+	// "Chromium/..." or "HeadlessChrome/..." otherwise. On non-Chrome builds we
+	// drop the "Google Chrome" UA-CH brand so the hints match the binary.
+	return applyRuntimeBrowserVersionValues(profile, product, fullVersion)
+}
+
+func applyRuntimeBrowserVersionValues(profile browserprofile.Profile, product, fullVersion string) browserprofile.Profile {
 	if fullVersion == "" {
 		fullVersion = extractChromeVersion(profile.UserAgent)
 	}
@@ -735,12 +764,39 @@ func applyRuntimeBrowserVersion(profile browserprofile.Profile, browser *rod.Bro
 		return profile
 	}

-	profile.UserAgent = replaceChromeUserAgentVersion(profile.UserAgent, major+".0.0.0")
-	profile.UACHBrands = patchBrandVersions(profile.UACHBrands, major, false)
-	profile.UACHFullVerList = patchBrandVersions(profile.UACHFullVerList, fullVersion, true)
+	if template := strings.TrimSpace(profile.UserAgentTemplate); template != "" {
+		profile.UserAgent = strings.ReplaceAll(template, "{chrome_major}", major)
+	} else {
+		profile.UserAgent = replaceChromeUserAgentVersion(profile.UserAgent, major+".0.0.0")
+	}
+	if len(profile.UACHBrands) == 0 {
+		profile.UACHBrands = runtimeUACHBrands(major, false)
+	} else {
+		profile.UACHBrands = patchBrandVersions(profile.UACHBrands, major, false)
+	}
+	if len(profile.UACHFullVerList) == 0 {
+		profile.UACHFullVerList = runtimeUACHBrands(fullVersion, true)
+	} else {
+		profile.UACHFullVerList = patchBrandVersions(profile.UACHFullVerList, fullVersion, true)
+	}
+	if product != "" && !strings.HasPrefix(product, "Chrome/") {
+		profile = removeChromeBrand(profile)
+	}
 	return profile
 }

+func runtimeUACHBrands(version string, full bool) []browserprofile.BrandVersion {
+	notABrandVersion := "24"
+	if full {
+		notABrandVersion = "24.0.0.0"
+	}
+	return []browserprofile.BrandVersion{
+		{Brand: "Not_A Brand", Version: notABrandVersion},
+		{Brand: "Chromium", Version: version},
+		{Brand: "Google Chrome", Version: version},
+	}
+}
+
 func extractChromeVersion(value string) string {
 	matches := chromeVersionPattern.FindStringSubmatch(strings.TrimSpace(value))
 	if len(matches) < 2 {
@@ -808,9 +864,6 @@ type profileDisplayMetrics struct {
 	ViewportHeight int
 	ScreenWidth    int
 	ScreenHeight   int
-	AvailWidth     int
-	AvailHeight    int
-	AvailTop       int
 	OuterWidth     int
 	OuterHeight    int
 	PositionX      int
@@ -849,9 +902,6 @@ func profileDisplayMetricsFor(profile browserprofile.Profile) profileDisplayMetr
 		ViewportHeight: viewportHeight,
 		ScreenWidth:    screenWidth,
 		ScreenHeight:   screenHeight,
-		AvailWidth:     screenWidth,
-		AvailHeight:    availHeight,
-		AvailTop:       availTop,
 		OuterWidth:     screenWidth,
 		OuterHeight:    availHeight,
 		PositionX:      0,
@@ -897,12 +947,12 @@ func applyProfileLanguageHint(profile browserprofile.Profile, langCode string) b
 	return profile
 }

-func applyProfile(page *rod.Page, profile browserprofile.Profile, minimal bool) error {
+func applyProfile(page *rod.Page, profile browserprofile.Profile, headless bool) error {
 	if page == nil {
 		return fmt.Errorf("page is nil")
 	}

-	navigatorLangs := profileNavigatorLanguages(profile)
+	navigatorLangs := profileNavigatorLanguagesForRuntime(profile, runtime.GOOS, headless)
 	acceptLanguage := strings.TrimSpace(profile.AcceptLanguage)
 	if acceptLanguage == "" {
 		acceptLanguage = navigatorLangs[0]
@@ -913,6 +963,18 @@ func applyProfile(page *rod.Page, profile browserprofile.Profile, minimal bool)
 	}

 	metrics := profileDisplayMetricsFor(profile)
+	// setWindowBounds can close the target under headless, and there's no real
+	// window anyway - setDeviceMetricsOverride below covers those dimensions.
+	if !headless {
+		if err := page.SetWindow(&proto.BrowserBounds{
+			Left:   &metrics.PositionX,
+			Top:    &metrics.PositionY,
+			Width:  &metrics.OuterWidth,
+			Height: &metrics.OuterHeight,
+		}); err != nil {
+			logrus.WithError(err).Debug("set browser window unsupported")
+		}
+	}

 	metadata := &proto.EmulationUserAgentMetadata{
 		Brands:          toProtoBrandVersions(profile.UACHBrands),
@@ -924,9 +986,11 @@ func applyProfile(page *rod.Page, profile browserprofile.Profile, minimal bool)
 		Mobile:          profile.Mobile,
 	}

+	// This only seeds navigator.languages (Chrome strips q-values), so it's the
+	// plain tag list. The wire header with q-weights is set below.
 	if err := (proto.NetworkSetUserAgentOverride{
 		UserAgent:         strings.TrimSpace(profile.UserAgent),
-		AcceptLanguage:    acceptLanguage,
+		AcceptLanguage:    strings.Join(navigatorLangs, ","),
 		Platform:          navigatorPlatformForProfile(profile),
 		UserAgentMetadata: metadata,
 	}).Call(page); err != nil {
@@ -958,6 +1022,14 @@ func applyProfile(page *rod.Page, profile browserprofile.Profile, minimal bool)
 		return fmt.Errorf("set device metrics failed: %w", err)
 	}

+	if err := (proto.EmulationSetEmulatedMedia{Features: []*proto.EmulationMediaFeature{
+		{Name: "prefers-reduced-motion", Value: "no-preference"},
+		{Name: "prefers-color-scheme", Value: "light"},
+		{Name: "forced-colors", Value: "none"},
+	}}).Call(page); err != nil {
+		return fmt.Errorf("set emulated media failed: %w", err)
+	}
+
 	if err := (proto.NetworkSetExtraHTTPHeaders{
 		Headers: proto.NetworkHeaders{
 			"Accept-Language": gson.New(acceptLanguage),
@@ -966,14 +1038,6 @@ func applyProfile(page *rod.Page, profile browserprofile.Profile, minimal bool)
 		return fmt.Errorf("set extra headers failed: %w", err)
 	}

-	if minimal {
-		return nil
-	}
-
-	if err := evalPatchScript(page, profile, navigatorLangs, metrics); err != nil {
-		return err
-	}
-
 	return nil
 }

@@ -1023,14 +1087,7 @@ type networkUsageWatcher struct {
 	done   chan struct{}
 }

-type workerPatchWatcher struct {
-	cancel context.CancelFunc
-	done   chan struct{}
-	page   *rod.Page
-}
-
 var pageNetworkUsageWatchers sync.Map
-var pageWorkerPatchWatchers sync.Map

 func startMainDocumentStatusWatcher(ctx context.Context, page *rod.Page) *mainDocumentStatusWatcher {
 	watchCtx, cancel := context.WithCancel(EnsureContext(ctx))
@@ -1098,95 +1155,6 @@ func startNetworkUsageWatcher(ctx context.Context, page *rod.Page) *networkUsage
 	return watcher
 }

-func startWorkerPatchWatcher(ctx context.Context, page *rod.Page, script string) (*workerPatchWatcher, error) {
-	if page == nil || strings.TrimSpace(script) == "" {
-		return nil, nil
-	}
-
-	watchCtx, cancel := context.WithCancel(EnsureContext(ctx))
-	watcher := &workerPatchWatcher{
-		cancel: cancel,
-		done:   make(chan struct{}),
-		page:   page,
-	}
-
-	scopedPage := page.Context(watchCtx)
-	started := make(chan struct{})
-	go func() {
-		defer close(watcher.done)
-		wait := scopedPage.EachEvent(func(e *proto.TargetAttachedToTarget) bool {
-			if e == nil || e.SessionID == "" {
-				return false
-			}
-			go injectWorkerPatch(watchCtx, scopedPage.Browser(), e, script)
-			return false
-		})
-		close(started)
-		wait()
-	}()
-
-	<-started
-	if err := (proto.TargetSetAutoAttach{
-		AutoAttach:             true,
-		WaitForDebuggerOnStart: true,
-		Flatten:                true,
-		Filter:                 workerTargetFilter(),
-	}).Call(scopedPage); err != nil {
-		cancel()
-		<-watcher.done
-		return nil, fmt.Errorf("enable worker auto-attach: %w", err)
-	}
-
-	return watcher, nil
-}
-
-func workerTargetFilter() proto.TargetTargetFilter {
-	return proto.TargetTargetFilter{
-		{Type: "worker"},
-		{Type: string(proto.TargetTargetInfoTypeSharedWorker)},
-		{Type: string(proto.TargetTargetInfoTypeServiceWorker)},
-	}
-}
-
-func injectWorkerPatch(ctx context.Context, browser *rod.Browser, e *proto.TargetAttachedToTarget, script string) {
-	if browser == nil || e == nil || e.SessionID == "" {
-		return
-	}
-
-	injectCtx, cancel := context.WithTimeout(EnsureContext(ctx), 3*time.Second)
-	defer cancel()
-
-	if isPatchableWorkerTarget(e.TargetInfo) {
-		eval := proto.RuntimeEvaluate{
-			Expression:                  script,
-			Silent:                      true,
-			AllowUnsafeEvalBlockedByCSP: true,
-		}
-		if _, err := browser.Call(injectCtx, string(e.SessionID), eval.ProtoReq(), eval); err != nil && !errors.Is(err, context.Canceled) {
-			logrus.WithError(err).Debug("Worker profile patch failed")
-		}
-	}
-
-	if e.WaitingForDebugger {
-		run := proto.RuntimeRunIfWaitingForDebugger{}
-		if _, err := browser.Call(injectCtx, string(e.SessionID), run.ProtoReq(), run); err != nil && !errors.Is(err, context.Canceled) {
-			logrus.WithError(err).Debug("Resume worker after profile patch failed")
-		}
-	}
-}
-
-func isPatchableWorkerTarget(info *proto.TargetTargetInfo) bool {
-	if info == nil {
-		return true
-	}
-	switch string(info.Type) {
-	case "worker", string(proto.TargetTargetInfoTypeSharedWorker), string(proto.TargetTargetInfoTypeServiceWorker):
-		return true
-	default:
-		return false
-	}
-}
-
 func rememberNetworkUsageWatcher(page *rod.Page, watcher *networkUsageWatcher) {
 	if page == nil || watcher == nil {
 		return
@@ -1194,13 +1162,6 @@ func rememberNetworkUsageWatcher(page *rod.Page, watcher *networkUsageWatcher) {
 	pageNetworkUsageWatchers.Store(page, watcher)
 }

-func rememberWorkerPatchWatcher(page *rod.Page, watcher *workerPatchWatcher) {
-	if page == nil || watcher == nil {
-		return
-	}
-	pageWorkerPatchWatchers.Store(page, watcher)
-}
-
 func stopNetworkUsageWatcher(page *rod.Page) {
 	if page == nil {
 		return
@@ -1214,19 +1175,6 @@ func stopNetworkUsageWatcher(page *rod.Page) {
 	}
 }

-func stopWorkerPatchWatcher(page *rod.Page) {
-	if page == nil {
-		return
-	}
-	raw, ok := pageWorkerPatchWatchers.LoadAndDelete(page)
-	if !ok {
-		return
-	}
-	if watcher, ok := raw.(*workerPatchWatcher); ok {
-		watcher.Stop()
-	}
-}
-
 func (w *networkUsageWatcher) Stop() {
 	if w == nil {
 		return
@@ -1238,27 +1186,6 @@ func (w *networkUsageWatcher) Stop() {
 	}
 }

-func (w *workerPatchWatcher) Stop() {
-	if w == nil {
-		return
-	}
-	if w.page != nil {
-		disableCtx, cancel := context.WithTimeout(context.Background(), time.Second)
-		_ = (proto.TargetSetAutoAttach{
-			AutoAttach:             false,
-			WaitForDebuggerOnStart: false,
-			Flatten:                true,
-			Filter:                 workerTargetFilter(),
-		}).Call(w.page.Context(disableCtx))
-		cancel()
-	}
-	w.cancel()
-	select {
-	case <-w.done:
-	case <-time.After(100 * time.Millisecond):
-	}
-}
-
 func (w *mainDocumentStatusWatcher) Status() int {
 	if w == nil {
 		return 0
@@ -1281,21 +1208,22 @@ func classifyMainDocumentStatus(status int) error {

 func profileNavigatorLanguages(profile browserprofile.Profile) []string {
 	langs := make([]string, 0, len(profile.NavigatorLangs))
+	seen := make(map[string]struct{}, len(profile.NavigatorLangs))
 	for _, language := range profile.NavigatorLangs {
 		trimmed := strings.TrimSpace(language)
 		if trimmed == "" {
 			continue
 		}
+		if _, ok := seen[trimmed]; ok {
+			continue
+		}
+		seen[trimmed] = struct{}{}
 		langs = append(langs, trimmed)
 	}
-	if len(langs) > 0 {
-		return langs
-	}

 	acceptLanguage := strings.TrimSpace(profile.AcceptLanguage)
 	if acceptLanguage != "" {
 		parts := strings.Split(acceptLanguage, ",")
-		langs = make([]string, 0, len(parts))
 		for _, part := range parts {
 			part = strings.TrimSpace(part)
 			if part == "" {
@@ -1305,12 +1233,16 @@ func profileNavigatorLanguages(profile browserprofile.Profile) []string {
 				part = strings.TrimSpace(part[:idx])
 			}
 			if part != "" {
+				if _, ok := seen[part]; ok {
+					continue
+				}
+				seen[part] = struct{}{}
 				langs = append(langs, part)
 			}
 		}
-		if len(langs) > 0 {
-			return langs
-		}
+	}
+	if len(langs) > 0 {
+		return langs
 	}

 	if locale := strings.TrimSpace(profile.Locale); locale != "" {
@@ -1319,6 +1251,15 @@ func profileNavigatorLanguages(profile browserprofile.Profile) []string {
 	return []string{"en-US"}
 }

+func profileNavigatorLanguagesForRuntime(profile browserprofile.Profile, goos string, headless bool) []string {
+	langs := profileNavigatorLanguages(profile)
+	// Linux headless-shell keeps workers at the process locale only.
+	if headless && goos == "linux" {
+		return langs[:1]
+	}
+	return langs
+}
+
 func toProtoBrandVersions(values []browserprofile.BrandVersion) []*proto.EmulationUserAgentBrandVersion {
 	out := make([]*proto.EmulationUserAgentBrandVersion, 0, len(values))
 	for _, value := range values {
@@ -1335,60 +1276,6 @@ func toProtoBrandVersions(values []browserprofile.BrandVersion) []*proto.Emulati
 	return out
 }

-func buildProfilePatchScript(profile browserprofile.Profile, langs []string, metrics profileDisplayMetrics) (string, error) {
-	langsJSON, err := json.Marshal(langs)
-	if err != nil {
-		return "", fmt.Errorf("marshal navigator languages: %w", err)
-	}
-
-	webGLVendor := strings.TrimSpace(profile.WebGLVendor)
-	if webGLVendor == "" {
-		webGLVendor = "Intel Inc."
-	}
-	webGLRenderer := strings.TrimSpace(profile.WebGLRenderer)
-	if webGLRenderer == "" {
-		webGLRenderer = "Intel Iris OpenGL Engine"
-	}
-
-	webGLVendorJSON, err := json.Marshal(webGLVendor)
-	if err != nil {
-		return "", fmt.Errorf("marshal webgl vendor: %w", err)
-	}
-	webGLRendererJSON, err := json.Marshal(webGLRenderer)
-	if err != nil {
-		return "", fmt.Errorf("marshal webgl renderer: %w", err)
-	}
-
-	return fmt.Sprintf("(() => {\nconst __langs = %s;\nconst __w = %d;\nconst __h = %d;\nconst __screenW = %d;\nconst __screenH = %d;\nconst __availW = %d;\nconst __availH = %d;\nconst __availTop = %d;\nconst __outerW = %d;\nconst __outerH = %d;\nconst __webglVendor = %s;\nconst __webglRenderer = %s;\n%s\n})();",
-		string(langsJSON),
-		metrics.ViewportWidth,
-		metrics.ViewportHeight,
-		metrics.ScreenWidth,
-		metrics.ScreenHeight,
-		metrics.AvailWidth,
-		metrics.AvailHeight,
-		metrics.AvailTop,
-		metrics.OuterWidth,
-		metrics.OuterHeight,
-		string(webGLVendorJSON),
-		string(webGLRendererJSON),
-		string(browserprofile.PatchJS),
-	), nil
-}
-
-func evalPatchScript(page *rod.Page, profile browserprofile.Profile, langs []string, metrics profileDisplayMetrics) error {
-	script, err := buildProfilePatchScript(profile, langs, metrics)
-	if err != nil {
-		return err
-	}
-
-	_, err = page.EvalOnNewDocument(script)
-	if err != nil {
-		return fmt.Errorf("eval patch script: %w", err)
-	}
-	return nil
-}
-
 // Navigate connects to Chromium, creates a page, applies a coherent profile and
 // proxy auth, then navigates to URL. It returns an initialized page ready for
 // selector queries, or an error when browser setup/navigation fails.
@@ -1437,7 +1324,6 @@ func (b *Browser) Navigate(ctx context.Context, URL string) (*rod.Page, error) {
 	// context first causes Chrome to kill the page target before our Close call,
 	// producing a spurious "target closed" error on the page.Close() that follows.
 	closeOnErr := func() {
-		stopWorkerPatchWatcher(page)
 		stopNetworkUsageWatcher(page)
 		if cerr := page.Close(); cerr != nil && !isBrowserClosedError(cerr) {
 			WithRequest(ctx).WithError(cerr).Debug("Close page after navigate error failed")
@@ -1450,7 +1336,6 @@ func (b *Browser) Navigate(ctx context.Context, URL string) (*rod.Page, error) {
 	// background watchers attached to it must still stop or they leak goroutines.
 	stopWatchersOnErr := func() {
 		if b.LeavePageOpen {
-			stopWorkerPatchWatcher(page)
 			stopNetworkUsageWatcher(page)
 		} else {
 			closeOnErr()
@@ -1459,12 +1344,10 @@ func (b *Browser) Navigate(ctx context.Context, URL string) (*rod.Page, error) {

 	profile, laneKey := b.laneProfile(ctx, browser)
 	SetBrowserProfileID(ctx, profile.ID)
-	minimalProfile := minimalBrowserProfileFromContext(ctx)
 	WithRequest(ctx).WithFields(logrus.Fields{
-		"lane_id":         laneKey,
-		"minimal_profile": minimalProfile,
+		"lane_id": laneKey,
 	}).Info("Browser profile selected")
-	if err := applyProfile(page, profile, minimalProfile); err != nil {
+	if err := applyProfile(page, profile, b.IsHeadless); err != nil {
 		closeOnErr()
 		return nil, fmt.Errorf("apply profile %s (%s) failed: %w", profile.ID, laneKey, err)
 	}
@@ -1474,20 +1357,6 @@ func (b *Browser) Navigate(ctx context.Context, URL string) (*rod.Page, error) {
 	}

 	page = page.Context(ctx)
-	if !minimalProfile {
-		metrics := profileDisplayMetricsFor(profile)
-		patchScript, err := buildProfilePatchScript(profile, profileNavigatorLanguages(profile), metrics)
-		if err != nil {
-			closeOnErr()
-			return nil, err
-		}
-		workerPatchWatcher, err := startWorkerPatchWatcher(ctx, page, patchScript)
-		if err != nil {
-			closeOnErr()
-			return nil, err
-		}
-		rememberWorkerPatchWatcher(page, workerPatchWatcher)
-	}
 	if err := b.configureRequestBlocking(ctx, page); err != nil {
 		closeOnErr()
 		return nil, fmt.Errorf("configure request blocking failed: %w", err)
@@ -1603,7 +1472,6 @@ func ClosePageWithTimeout(ctx context.Context, page *rod.Page, timeout time.Dura
 	if page == nil {
 		return nil
 	}
-	stopWorkerPatchWatcher(page)
 	stopNetworkUsageWatcher(page)
 	if timeout <= 0 {
 		timeout = time.Second
--- a/core/browser/patch.js
+++ b/core/browser/patch.js
@@ -1,273 +0,0 @@
-// Stealth patches injected via EvalOnNewDocument.
-// Arguments are injected as a leading const block by the Go caller:
-//   const __langs = [...];          // navigator_langs from profile
-//   const __w = 1920;               // viewport/content width
-//   const __h = 955;                // viewport/content height
-//   const __screenW = 1920;         // screen.width
-//   const __screenH = 1080;         // screen.height
-//   const __availW = 1920;          // screen.availWidth
-//   const __availH = 1040;          // screen.availHeight
-//   const __availTop = 0;           // screen.availTop
-//   const __outerW = 1920;          // window.outerWidth
-//   const __outerH = 1040;          // window.outerHeight
-//   const __webglVendor = "...";    // UNMASKED_VENDOR_WEBGL spoof
-//   const __webglRenderer = "...";  // UNMASKED_RENDERER_WEBGL spoof
-//
-// Scope: only patches that fix detectors with high ROI and low introspection
-// surface. Notably absent: Function.prototype.toString proxy, custom Worker
-// constructor, mass plugin/mimeType arrays, iframe contentWindow patching.
-// Those triggered server-side detection on Google in commit 612e0dc.
-(() => {
-  'use strict';
-
-  const sealGetter = (target, prop, fn) => {
-    try {
-      Object.defineProperty(target, prop, {
-        get: fn,
-        set: undefined,
-        enumerable: true,
-        configurable: true,
-      });
-      Object.defineProperty(target, prop, { configurable: false });
-    } catch (_) {}
-  };
-
-  // --- navigator.webdriver ---
-  // headless Chrome sets this to true. Delete it so getter returns undefined.
-  // (We rely on `disable-blink-features=AutomationControlled` already turning
-  // this off via the launcher; this is belt-and-braces in case it leaks.)
-  try {
-    if (typeof navigator.webdriver !== 'undefined') {
-      delete Object.getPrototypeOf(navigator).webdriver;
-    }
-  } catch (_) {}
-
-  // --- navigator.language / navigator.languages ---
-  // CDP setUserAgentOverride sets the HTTP header but not these JS props.
-  const primary = __langs.length ? __langs[0] : 'en-US';
-  const patchLangs = (target) => {
-    if (!target) return;
-    sealGetter(target, 'language', () => primary);
-    sealGetter(target, 'languages', () => Object.freeze(__langs.slice()));
-  };
-  patchLangs(Object.getPrototypeOf(navigator));
-  if (typeof WorkerNavigator !== 'undefined') {
-    patchLangs(WorkerNavigator.prototype);
-  }
-
-  // --- screen dimensions ---
-  // EmulationSetDeviceMetricsOverride sets the CSS viewport but leaves
-  // window.screen.* at headless defaults.
-  const screenProto = typeof Screen !== 'undefined' ? Screen.prototype : null;
-  if (screenProto) {
-    sealGetter(screenProto, 'width', () => __screenW);
-    sealGetter(screenProto, 'height', () => __screenH);
-    sealGetter(screenProto, 'availWidth', () => __availW);
-    sealGetter(screenProto, 'availHeight', () => __availH);
-    sealGetter(screenProto, 'availLeft', () => 0);
-    sealGetter(screenProto, 'availTop', () => __availTop);
-    // Headless reports colorDepth/pixelDepth=24 already in most builds, but
-    // some checks see 0 in WSL/Docker. Lock to 24 which matches real Chrome.
-    sealGetter(screenProto, 'colorDepth', () => 24);
-    sealGetter(screenProto, 'pixelDepth', () => 24);
-  }
-  if (typeof window !== 'undefined') {
-    sealGetter(window, 'outerWidth', () => __outerW);
-    sealGetter(window, 'outerHeight', () => __outerH);
-  }
-
-  // --- WebGL vendor/renderer spoof ---
-  // Patches getParameter(37445=UNMASKED_VENDOR_WEBGL, 37446=UNMASKED_RENDERER_WEBGL)
-  // on WebGLRenderingContext.prototype and WebGL2RenderingContext.prototype.
-  // Only delegates to the original for all other params, so behavioral
-  // signals (extension list, real pixel rendering) still pass through.
-  const patchWebGLProto = (proto) => {
-    if (!proto) return;
-    const original = proto.getParameter;
-    if (typeof original !== 'function') return;
-    const replacement = function getParameter(parameter) {
-      if (parameter === 37445) return __webglVendor;
-      if (parameter === 37446) return __webglRenderer;
-      return original.apply(this, arguments);
-    };
-    try {
-      Object.defineProperty(proto, 'getParameter', {
-        value: replacement,
-        writable: true,
-        enumerable: false,
-        configurable: true,
-      });
-    } catch (_) {}
-  };
-  if (typeof WebGLRenderingContext !== 'undefined') {
-    patchWebGLProto(WebGLRenderingContext.prototype);
-  }
-  if (typeof WebGL2RenderingContext !== 'undefined') {
-    patchWebGLProto(WebGL2RenderingContext.prototype);
-  }
-
-  // --- navigator.plugins / mimeTypes ---
-  // Match real Chrome 136 exactly: 5 plugins (all "internal-pdf-viewer"), each
-  // exposing application/pdf + text/pdf. navigator.mimeTypes dedupes to 2.
-  // Each MimeType.enabledPlugin must back-reference the FIRST plugin that owns
-  // that type (Chrome's invariant). Plugin order is fixed.
-  try {
-    const PluginArrayProto = typeof PluginArray !== 'undefined' ? PluginArray.prototype : null;
-    const PluginProto = typeof Plugin !== 'undefined' ? Plugin.prototype : null;
-    const MimeTypeArrayProto = typeof MimeTypeArray !== 'undefined' ? MimeTypeArray.prototype : null;
-    const MimeTypeProto = typeof MimeType !== 'undefined' ? MimeType.prototype : null;
-
-    if (PluginArrayProto && PluginProto && MimeTypeArrayProto && MimeTypeProto) {
-      const pluginNames = [
-        'PDF Viewer',
-        'Chrome PDF Viewer',
-        'Chromium PDF Viewer',
-        'Microsoft Edge PDF Viewer',
-        'WebKit built-in PDF',
-      ];
-      const mimeSpecs = [
-        { type: 'application/pdf', suffixes: 'pdf', description: 'Portable Document Format' },
-        { type: 'text/pdf', suffixes: 'pdf', description: 'Portable Document Format' },
-      ];
-
-      // Two MimeType instances, each enabledPlugin points to the first plugin
-      // (PDF Viewer) per Chrome's invariant: navigator.mimeTypes[i].enabledPlugin
-      // === navigator.plugins[0] for every PDF mime.
-      const sharedMimes = mimeSpecs.map((spec) => {
-        const m = Object.create(MimeTypeProto);
-        Object.defineProperty(m, 'type', { value: spec.type, enumerable: true });
-        Object.defineProperty(m, 'suffixes', { value: spec.suffixes, enumerable: true });
-        Object.defineProperty(m, 'description', { value: spec.description, enumerable: true });
-        return m;
-      });
-
-      const plugins = pluginNames.map((name) => {
-        const p = Object.create(PluginProto);
-        Object.defineProperty(p, 'name', { value: name, enumerable: true });
-        Object.defineProperty(p, 'filename', { value: 'internal-pdf-viewer', enumerable: true });
-        Object.defineProperty(p, 'description', { value: 'Portable Document Format', enumerable: true });
-        Object.defineProperty(p, 'length', { value: sharedMimes.length, enumerable: true });
-        sharedMimes.forEach((m, i) => {
-          Object.defineProperty(p, String(i), { value: m, enumerable: true });
-          Object.defineProperty(p, m.type, { value: m });
-        });
-        return p;
-      });
-
-      // Set enabledPlugin AFTER plugins are constructed, pointing to plugins[0].
-      sharedMimes.forEach((m) => {
-        Object.defineProperty(m, 'enabledPlugin', { value: plugins[0], enumerable: true });
-      });
-
-      const pluginArr = Object.create(PluginArrayProto);
-      Object.defineProperty(pluginArr, 'length', { value: plugins.length, enumerable: true });
-      plugins.forEach((p, i) => {
-        Object.defineProperty(pluginArr, String(i), { value: p, enumerable: true });
-        Object.defineProperty(pluginArr, p.name, { value: p });
-      });
-
-      const mimeArr = Object.create(MimeTypeArrayProto);
-      Object.defineProperty(mimeArr, 'length', { value: sharedMimes.length, enumerable: true });
-      sharedMimes.forEach((m, i) => {
-        Object.defineProperty(mimeArr, String(i), { value: m, enumerable: true });
-        Object.defineProperty(mimeArr, m.type, { value: m });
-      });
-
-      sealGetter(Object.getPrototypeOf(navigator), 'plugins', () => pluginArr);
-      sealGetter(Object.getPrototypeOf(navigator), 'mimeTypes', () => mimeArr);
-    }
-  } catch (_) {}
-
-  // --- navigator.permissions.query notifications fix ---
-  // headless returns 'denied' for notifications when Notification.permission is
-  // 'default'. Real Chrome returns 'prompt' in that case. Sannysoft checks this
-  // mismatch (permissions_new / headchr_permissions).
-  try {
-    if (navigator.permissions && typeof navigator.permissions.query === 'function') {
-      const proto = Object.getPrototypeOf(navigator.permissions);
-      const desc = Object.getOwnPropertyDescriptor(proto, 'query');
-      if (desc && typeof desc.value === 'function') {
-        const original = desc.value;
-        const replacement = function query(parameters) {
-          if (parameters && parameters.name === 'notifications' &&
-              typeof Notification !== 'undefined' && Notification.permission === 'default') {
-            return Promise.resolve({ state: 'prompt', onchange: null });
-          }
-          return original.apply(this, arguments);
-        };
-        Object.defineProperty(proto, 'query', {
-          value: replacement,
-          writable: desc.writable,
-          enumerable: desc.enumerable,
-          configurable: desc.configurable,
-        });
-      }
-    }
-  } catch (_) {}
-
-  // --- getBoundingClientRect / getClientRects subpixel jitter ---
-  // Headless Chrome returns integer-valued rects; real Chrome returns subpixel
-  // floats due to CSS layout fractions. Fingerprinters hash rect tuples; even
-  // a sub-pixel offset breaks the canonical "headless rect" hash.
-  // Jitter is deterministic per-element (based on element identity) so the
-  // same element returns the same value across calls within the page lifetime.
-  try {
-    const rectProto = typeof DOMRect !== 'undefined' ? DOMRect.prototype : null;
-    const elProto = typeof Element !== 'undefined' ? Element.prototype : null;
-    if (rectProto && elProto) {
-      const wmJitter = new WeakMap();
-      const jitterFor = (el) => {
-        let j = wmJitter.get(el);
-        if (!j) {
-          // Tiny noise in [-0.05, +0.05) — well below visual threshold but
-          // changes hash output. Generated once per element.
-          j = {
-            x: (Math.random() - 0.5) * 0.1,
-            y: (Math.random() - 0.5) * 0.1,
-          };
-          wmJitter.set(el, j);
-        }
-        return j;
-      };
-      const origGBCR = elProto.getBoundingClientRect;
-      Object.defineProperty(elProto, 'getBoundingClientRect', {
-        value: function getBoundingClientRect() {
-          const r = origGBCR.apply(this, arguments);
-          const j = jitterFor(this);
-          // DOMRect is mutable; nudge x/y. width/height left intact so layout
-          // calculations don't drift.
-          try { r.x = r.x + j.x; r.y = r.y + j.y; } catch (_) {}
-          return r;
-        },
-        writable: true,
-        enumerable: false,
-        configurable: true,
-      });
-    }
-  } catch (_) {}
-
-  // --- window.chrome.runtime stub ---
-  // Real Chrome exposes window.chrome with a .runtime sub-object.
-  // headless leaves window.chrome empty, which sannysoft (chrome_new,
-  // headchr_chrome_obj) flags. A minimal runtime stub satisfies the check
-  // without touching method behavior.
-  try {
-    if (typeof window !== 'undefined') {
-      if (!window.chrome) {
-        Object.defineProperty(window, 'chrome', { value: {}, writable: true, configurable: true });
-      }
-      if (window.chrome && !window.chrome.runtime) {
-        Object.defineProperty(window.chrome, 'runtime', {
-          value: {
-            OnInstalledReason: { CHROME_UPDATE: 'chrome_update', INSTALL: 'install', UPDATE: 'update' },
-            OnRestartRequiredReason: { APP_UPDATE: 'app_update', OS_UPDATE: 'os_update', PERIODIC: 'periodic' },
-            PlatformOs: { ANDROID: 'android', CROS: 'cros', LINUX: 'linux', MAC: 'mac', WIN: 'win' },
-          },
-          writable: true,
-          enumerable: true,
-          configurable: true,
-        });
-      }
-    }
-  } catch (_) {}
-})();
--- a/core/browser/profile.go
+++ b/core/browser/profile.go
@@ -23,24 +23,23 @@ type Viewport struct {
 }

 type Profile struct {
-	ID              string         `json:"id"`
-	UserAgent       string         `json:"user_agent"`
-	UACHBrands      []BrandVersion `json:"uach_brands"`
-	UACHFullVerList []BrandVersion `json:"uach_full_version_list"`
-	Platform        string         `json:"platform"`
-	PlatformVersion string         `json:"platform_version"`
-	Architecture    string         `json:"architecture"`
-	Bitness         string         `json:"bitness"`
-	Mobile          bool           `json:"mobile"`
-	AcceptLanguage  string         `json:"accept_language"`
-	NavigatorLangs  []string       `json:"navigator_langs"`
-	Locale          string         `json:"locale"`
-	Timezone        string         `json:"timezone"`
-	Viewport        Viewport       `json:"viewport"`
-	WebGLVendor     string         `json:"webgl_vendor"`
-	WebGLRenderer   string         `json:"webgl_renderer"`
-	Tags            []string       `json:"tags"`
-	Weight          int            `json:"weight"`
+	ID                string         `json:"id"`
+	UserAgentTemplate string         `json:"user_agent_template"`
+	UserAgent         string         `json:"user_agent,omitempty"`
+	UACHBrands        []BrandVersion `json:"uach_brands,omitempty"`
+	UACHFullVerList   []BrandVersion `json:"uach_full_version_list,omitempty"`
+	Platform          string         `json:"platform"`
+	PlatformVersion   string         `json:"platform_version"`
+	Architecture      string         `json:"architecture"`
+	Bitness           string         `json:"bitness"`
+	Mobile            bool           `json:"mobile"`
+	AcceptLanguage    string         `json:"accept_language"`
+	NavigatorLangs    []string       `json:"navigator_langs"`
+	Locale            string         `json:"locale"`
+	Timezone          string         `json:"timezone"`
+	Viewport          Viewport       `json:"viewport"`
+	Tags              []string       `json:"tags"`
+	Weight            int            `json:"weight"`
 }

 type catalogConfig struct {
@@ -51,18 +50,13 @@ type catalogConfig struct {

 const (
 	ProfileChromeWinUS   = "chrome-win-uhd620"
-	ProfileChromeWinRU   = "chrome-win-ru"
 	ProfileChromeMacUS   = "chrome-macos-intel-iris"
 	ProfileChromeLinuxUS = "chrome-linux-mesa-uhd620"
-	ProfileChromeLinuxRU = "chrome-linux-ru"
 )

 //go:embed profiles.json
 var defaultProfilesJSON []byte

-//go:embed patch.js
-var PatchJS []byte
-
 var profileCatalogMu sync.RWMutex

 var catalog = map[string]Profile{}
@@ -110,8 +104,8 @@ func loadProfilesFromJSONBytes(data []byte) error {
 		if profile.ID == "" {
 			return fmt.Errorf("profiles[%d].id is empty", i)
 		}
-		if strings.TrimSpace(profile.UserAgent) == "" {
-			return fmt.Errorf("profiles[%d].user_agent is empty", i)
+		if strings.TrimSpace(profile.UserAgentTemplate) == "" && strings.TrimSpace(profile.UserAgent) == "" {
+			return fmt.Errorf("profiles[%d] has no user_agent_template or user_agent", i)
 		}
 		if _, exists := nextCatalog[profile.ID]; exists {
 			return fmt.Errorf("duplicate profile id %q", profile.ID)
@@ -201,6 +195,13 @@ func SelectProfile(engine string, region string) Profile {
 // Non-empty salt uses weighted selection seeded by FNV-1a hash of salt,
 // giving each session a stable but varied profile.
 func SelectProfileForSession(engine, region, salt string) Profile {
+	return SelectProfileForSessionHeadless(engine, region, salt, false)
+}
+
+// SelectProfileForSessionHeadless is SelectProfileForSession, but headless Linux
+// (the Docker deployment) renders WebGL via SwiftShader, so it only picks
+// swiftshader-tagged profiles. Runtimes with a real GPU exclude them.
+func SelectProfileForSessionHeadless(engine, region, salt string, headless bool) Profile {
 	engine = NormalizeEngine(engine)
 	region = NormalizeRegion(region)
 	if region == "" {
@@ -215,7 +216,7 @@ func SelectProfileForSession(engine, region, salt string) Profile {
 		return profileByID(profileID)
 	}

-	pool := eligibleProfiles(engine, region)
+	pool := eligibleProfiles(runtime.GOOS, headless)
 	return pickWeighted(pool, salt)
 }

@@ -224,10 +225,11 @@ type weightedProfile struct {
 	weight  int
 }

-// eligibleProfiles builds the weighted pool for (engine, region).
-// Linux profiles are preferred 4x on linux runtime; Windows 4x on windows; macOS 4x on darwin.
-// Profiles tagged "ru" are included only when region == "ru"; "ru"-tagged profiles are excluded otherwise.
-func eligibleProfiles(engine, region string) []weightedProfile {
+// eligibleProfiles builds the pool for the runtime platform. Headless Linux
+// keeps only swiftshader-tagged profiles (SwiftShader WebGL); a real GPU
+// excludes them. We no longer spoof WebGL, so the GPU sub-tag (nvidia/amd/mesa)
+// only steers selection - it matches reality on Docker, cosmetic on a headful box.
+func eligibleProfiles(goos string, headless bool) []weightedProfile {
 	profileCatalogMu.RLock()
 	snap := make([]Profile, 0, len(catalog))
 	for _, p := range catalog {
@@ -240,50 +242,52 @@ func eligibleProfiles(engine, region string) []weightedProfile {
 		return strings.Compare(a.ID, b.ID)
 	})

-	goos := runtime.GOOS
+	platformTag := runtimePlatformTag(goos)
+	wantSwiftShader := headless && goos == "linux"

 	var pool []weightedProfile
 	for _, p := range snap {
-		isRu := slices.Contains(p.Tags, "ru")
-		if region == "ru" && !isRu {
+		if platformTag != "" && !slices.Contains(p.Tags, platformTag) {
 			continue
 		}
-		if region != "ru" && isRu {
+		if slices.Contains(p.Tags, "swiftshader") != wantSwiftShader {
 			continue
 		}
-
 		w := p.Weight
 		if w <= 0 {
 			w = 1
 		}

-		platformLower := strings.ToLower(p.Platform)
-		switch goos {
-		case "linux":
-			if platformLower == "linux" {
-				w *= 4
-			}
-		case "windows":
-			if platformLower == "windows" {
-				w *= 4
-			}
-		case "darwin":
-			if platformLower == "macos" {
-				w *= 4
-			}
-		}
-
 		pool = append(pool, weightedProfile{profile: p, weight: w})
 	}

+	// Fall back to the platform pool if no swiftshader profile exists yet, so
+	// selection never returns empty.
+	if len(pool) == 0 && wantSwiftShader {
+		return eligibleProfiles(goos, false)
+	}
+
 	return pool
 }

+func runtimePlatformTag(goos string) string {
+	switch strings.ToLower(strings.TrimSpace(goos)) {
+	case "windows":
+		return "windows"
+	case "darwin":
+		return "macos"
+	case "linux":
+		return "linux"
+	default:
+		return ""
+	}
+}
+
 // pickWeighted selects a profile from pool using FNV-1a hash of salt modulo total weight.
 // Empty salt returns the first profile in the pool (deterministic for tests).
 func pickWeighted(pool []weightedProfile, salt string) Profile {
 	if len(pool) == 0 {
-		return profileByID(defaultProfileID("us"))
+		return profileByID(defaultProfileID())
 	}
 	if salt == "" {
 		return pool[0].profile
@@ -384,7 +388,7 @@ func profileByID(profileID string) Profile {
 	if profile, ok := catalog[profileID]; ok {
 		return profile
 	}
-	if fallback, ok := catalog[defaultProfileID("us")]; ok {
+	if fallback, ok := catalog[defaultProfileID()]; ok {
 		return fallback
 	}
 	for _, profile := range catalog {
@@ -393,24 +397,13 @@ func profileByID(profileID string) Profile {
 	return Profile{}
 }

-func defaultProfileID(region string) string {
-	region = NormalizeRegion(region)
-	if region == "" {
-		region = "us"
-	}
-
+func defaultProfileID() string {
 	switch runtime.GOOS {
 	case "windows":
-		if region == "ru" {
-			return ProfileChromeWinRU
-		}
 		return ProfileChromeWinUS
 	case "darwin":
 		return ProfileChromeMacUS
 	default:
-		if region == "ru" {
-			return ProfileChromeLinuxRU
-		}
 		return ProfileChromeLinuxUS
 	}
 }
--- a/core/browser/profile_coherence_test.go
+++ b/core/browser/profile_coherence_test.go
@@ -51,12 +51,12 @@ func TestProfileCoherence(t *testing.T) {
 		region string
 	}{
 		{
-			name:   "windows lane",
+			name:   "ru lane",
 			engine: "google",
 			region: "ru",
 		},
 		{
-			name:   "mac lane",
+			name:   "us lane",
 			engine: "bing",
 			region: "en-US",
 		},
@@ -84,7 +84,7 @@ func TestProfileCoherence(t *testing.T) {
 			}

 			expected := selectedProfileFromContext(t, ctx)
-			expected.UserAgent = expectedUserAgentForRuntime(expected.UserAgent, got.UserAgent)
+			expected.UserAgent = expectedUserAgentForRuntime(expectedProfileUserAgent(expected, got.UserAgent), got.UserAgent)
 			if got.UserAgent != expected.UserAgent {
 				t.Fatalf("navigator.userAgent mismatch:\nexpected: %s\nactual:   %s", expected.UserAgent, got.UserAgent)
 			}
@@ -106,11 +106,26 @@ func TestProfileCoherence(t *testing.T) {
 			if got.NavigatorLanguages[0] != expected.NavigatorLangs[0] {
 				t.Fatalf("navigator.languages[0] mismatch: expected %q got %q", expected.NavigatorLangs[0], got.NavigatorLanguages[0])
 			}
-			if got.WebdriverType != "undefined" {
-				t.Fatalf("navigator.webdriver expected undefined, got %q", got.WebdriverType)
+			// Real Chrome exposes navigator.webdriver as an inherited boolean
+			// that reads false; --disable-blink-features=AutomationControlled
+			// gives us that. Deleting the property (typeof undefined) is itself a
+			// bot tell, so we assert the genuine-browser shape instead.
+			if got.WebdriverType != "boolean" {
+				t.Fatalf("navigator.webdriver expected boolean, got %q", got.WebdriverType)
+			}
+			if got.WebdriverValue {
+				t.Fatal("navigator.webdriver should read false")
 			}
 			if got.WebdriverOwnPropPresent {
-				t.Fatal("navigator own property 'webdriver' should not be present")
+				t.Fatal("navigator.webdriver should be inherited, not an own property")
+			}
+			// hardwareConcurrency is left native (no override), so main and
+			// worker must simply agree on the machine's real core count.
+			if got.HardwareConcurrency <= 0 {
+				t.Fatal("navigator.hardwareConcurrency should be reported")
+			}
+			if got.WorkerHardwareConcurrency != got.HardwareConcurrency {
+				t.Fatalf("worker hardwareConcurrency mismatch: main %d worker %d", got.HardwareConcurrency, got.WorkerHardwareConcurrency)
 			}
 			if got.WorkerUserAgent != got.UserAgent {
 				t.Fatalf("worker userAgent mismatch: main %q worker %q", got.UserAgent, got.WorkerUserAgent)
@@ -127,11 +142,11 @@ func TestProfileCoherence(t *testing.T) {
 			if got.WorkerTimezone != got.Timezone {
 				t.Fatalf("worker timezone mismatch: main %q worker %q", got.Timezone, got.WorkerTimezone)
 			}
-			if got.WorkerWebGLVendor != expected.WebGLVendor {
-				t.Fatalf("worker WebGL vendor mismatch: expected %q got %q", expected.WebGLVendor, got.WorkerWebGLVendor)
+			if got.WorkerWebGLVendor != got.WebGLVendor {
+				t.Fatalf("worker WebGL vendor mismatch: main %q worker %q", got.WebGLVendor, got.WorkerWebGLVendor)
 			}
-			if got.WorkerWebGLRenderer != expected.WebGLRenderer {
-				t.Fatalf("worker WebGL renderer mismatch: expected %q got %q", expected.WebGLRenderer, got.WorkerWebGLRenderer)
+			if got.WorkerWebGLRenderer != got.WebGLRenderer {
+				t.Fatalf("worker WebGL renderer mismatch: main %q worker %q", got.WebGLRenderer, got.WorkerWebGLRenderer)
 			}
 			if got.InnerHeight >= got.OuterHeight {
 				t.Fatalf("innerHeight should be smaller than outerHeight, got inner=%d outer=%d", got.InnerHeight, got.OuterHeight)
@@ -139,32 +154,37 @@ func TestProfileCoherence(t *testing.T) {
 			if got.OuterHeight > got.ScreenAvailHeight {
 				t.Fatalf("outerHeight should fit in screen.availHeight, got outer=%d avail=%d", got.OuterHeight, got.ScreenAvailHeight)
 			}
-			if got.ScreenAvailHeight >= got.ScreenHeight {
-				t.Fatalf("screen.availHeight should be smaller than screen.height, got avail=%d screen=%d", got.ScreenAvailHeight, got.ScreenHeight)
+			if got.ScreenAvailHeight > got.ScreenHeight {
+				t.Fatalf("screen.availHeight should fit in screen.height, got avail=%d screen=%d", got.ScreenAvailHeight, got.ScreenHeight)
 			}
 		})
 	}
 }

 type profileSurface struct {
-	UserAgent               string   `json:"userAgent"`
-	Platform                string   `json:"platform"`
-	NavigatorPlatform       string   `json:"navigatorPlatform"`
-	NavigatorLanguages      []string `json:"navigatorLanguages"`
-	Timezone                string   `json:"timezone"`
-	Locale                  string   `json:"locale"`
-	WebdriverType           string   `json:"webdriverType"`
-	WebdriverOwnPropPresent bool     `json:"webdriverOwnPropPresent"`
-	WorkerUserAgent         string   `json:"workerUserAgent"`
-	WorkerPlatform          string   `json:"workerPlatform"`
-	WorkerNavigatorLangs    []string `json:"workerNavigatorLangs"`
-	WorkerTimezone          string   `json:"workerTimezone"`
-	WorkerWebGLVendor       string   `json:"workerWebGLVendor"`
-	WorkerWebGLRenderer     string   `json:"workerWebGLRenderer"`
-	InnerHeight             int      `json:"innerHeight"`
-	OuterHeight             int      `json:"outerHeight"`
-	ScreenHeight            int      `json:"screenHeight"`
-	ScreenAvailHeight       int      `json:"screenAvailHeight"`
+	UserAgent                 string   `json:"userAgent"`
+	Platform                  string   `json:"platform"`
+	NavigatorPlatform         string   `json:"navigatorPlatform"`
+	NavigatorLanguages        []string `json:"navigatorLanguages"`
+	Timezone                  string   `json:"timezone"`
+	Locale                    string   `json:"locale"`
+	WebdriverType             string   `json:"webdriverType"`
+	WebdriverValue            bool     `json:"webdriverValue"`
+	WebdriverOwnPropPresent   bool     `json:"webdriverOwnPropPresent"`
+	HardwareConcurrency       int      `json:"hardwareConcurrency"`
+	WorkerHardwareConcurrency int      `json:"workerHardwareConcurrency"`
+	WorkerUserAgent           string   `json:"workerUserAgent"`
+	WorkerPlatform            string   `json:"workerPlatform"`
+	WorkerNavigatorLangs      []string `json:"workerNavigatorLangs"`
+	WorkerTimezone            string   `json:"workerTimezone"`
+	WebGLVendor               string   `json:"webGLVendor"`
+	WebGLRenderer             string   `json:"webGLRenderer"`
+	WorkerWebGLVendor         string   `json:"workerWebGLVendor"`
+	WorkerWebGLRenderer       string   `json:"workerWebGLRenderer"`
+	InnerHeight               int      `json:"innerHeight"`
+	OuterHeight               int      `json:"outerHeight"`
+	ScreenHeight              int      `json:"screenHeight"`
+	ScreenAvailHeight         int      `json:"screenAvailHeight"`
 }

 func browserProfileSurface(page *rod.Page) (profileSurface, error) {
@@ -205,6 +225,25 @@ func selectedProfileFromContext(t *testing.T, ctx context.Context) browserprofil
 	return profile
 }

+// expectedProfileUserAgent resolves the profile's user agent, expanding the
+// {chrome_major} template with the runtime's major when the profile carries a
+// template rather than a literal UA.
+func expectedProfileUserAgent(profile browserprofile.Profile, runtimeUserAgent string) string {
+	if ua := strings.TrimSpace(profile.UserAgent); ua != "" {
+		return ua
+	}
+	template := strings.TrimSpace(profile.UserAgentTemplate)
+	if template == "" {
+		return ""
+	}
+	major := chromeToken(runtimeUserAgent)
+	major = strings.TrimPrefix(major, "Chrome/")
+	if idx := strings.IndexByte(major, '.'); idx >= 0 {
+		major = major[:idx]
+	}
+	return strings.ReplaceAll(template, "{chrome_major}", major)
+}
+
 func expectedUserAgentForRuntime(profileUserAgent, runtimeUserAgent string) string {
 	runtimeChrome := chromeToken(runtimeUserAgent)
 	if runtimeChrome == "" {
--- a/core/browser/profile_surface_test.js
+++ b/core/browser/profile_surface_test.js
@@ -1,4 +1,17 @@
 async () => {
+  const readWebGL = (canvas) => {
+    try {
+      const gl = canvas ? (canvas.getContext('webgl') || canvas.getContext('experimental-webgl') || canvas.getContext('webgl2')) : null;
+      const debugInfo = gl && gl.getExtension('WEBGL_debug_renderer_info');
+      return {
+        vendor: gl && debugInfo ? (gl.getParameter(debugInfo.UNMASKED_VENDOR_WEBGL) || '') : '',
+        renderer: gl && debugInfo ? (gl.getParameter(debugInfo.UNMASKED_RENDERER_WEBGL) || '') : '',
+      };
+    } catch (_) {
+      return { vendor: '', renderer: '' };
+    }
+  };
+  const webGL = readWebGL(document.createElement('canvas'));
  const workerData = await new Promise((resolve) => {
    try {
      const source = [
@@ -19,6 +32,7 @@ async () => {
        "platform: self.navigator.platform || '',",
        "navigatorLanguages: Array.from(self.navigator.languages || []),",
        "timezone: Intl.DateTimeFormat().resolvedOptions().timeZone || '',",
+        "hardwareConcurrency: self.navigator.hardwareConcurrency || 0,",
        "webGLVendor,",
        "webGLRenderer,",
        "});",
@@ -51,11 +65,16 @@ async () => {
    timezone: Intl.DateTimeFormat().resolvedOptions().timeZone || "",
    locale: Intl.DateTimeFormat().resolvedOptions().locale || "",
    webdriverType: typeof navigator.webdriver,
+    webdriverValue: navigator.webdriver === true,
    webdriverOwnPropPresent: Object.getOwnPropertyNames(navigator).includes("webdriver"),
+    hardwareConcurrency: navigator.hardwareConcurrency || 0,
+    workerHardwareConcurrency: workerData.hardwareConcurrency || 0,
    workerUserAgent: workerData.userAgent || "",
    workerPlatform: workerData.platform || "",
    workerNavigatorLangs: Array.from(workerData.navigatorLanguages || []),
    workerTimezone: workerData.timezone || "",
+    webGLVendor: webGL.vendor,
+    webGLRenderer: webGL.renderer,
    workerWebGLVendor: workerData.webGLVendor || "",
    workerWebGLRenderer: workerData.webGLRenderer || "",
    innerHeight: window.innerHeight || 0,
--- a/core/browser/profile_test.go
+++ b/core/browser/profile_test.go
@@ -69,14 +69,73 @@ func TestSelectProfileForSession(t *testing.T) {
 		}
 	})

-	t.Run("ru region returns ru-tagged profile", func(t *testing.T) {
+	t.Run("locale does not change hardware profile pool", func(t *testing.T) {
 		p := SelectProfileForSession("yandex", "ru", "some-session")
-		if !slices.Contains(p.Tags, "ru") {
-			t.Fatalf("expected ru-tagged profile, got ID=%q tags=%v", p.ID, p.Tags)
+		if slices.Contains(p.Tags, "ru") {
+			t.Fatalf("expected locale-neutral profile, got ID=%q tags=%v", p.ID, p.Tags)
 		}
 	})
 }

+func TestEligibleProfilesMatchRuntimePlatform(t *testing.T) {
+	tests := []struct {
+		goos string
+		tag  string
+	}{
+		{goos: "linux", tag: "linux"},
+		{goos: "windows", tag: "windows"},
+		{goos: "darwin", tag: "macos"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.goos, func(t *testing.T) {
+			pool := eligibleProfiles(tt.goos, false)
+			if len(pool) == 0 {
+				t.Fatal("expected eligible profiles")
+			}
+			for _, candidate := range pool {
+				if !slices.Contains(candidate.profile.Tags, tt.tag) {
+					t.Fatalf("profile %q does not match %s", candidate.profile.ID, tt.goos)
+				}
+			}
+		})
+	}
+}
+
+// Headless Linux (the Docker deployment) has no real GPU, so only
+// swiftshader-tagged profiles are eligible; headful Linux excludes them.
+func TestEligibleProfilesHeadlessLinuxUsesSwiftShader(t *testing.T) {
+	headless := eligibleProfiles("linux", true)
+	if len(headless) == 0 {
+		t.Fatal("expected a Linux SwiftShader profile")
+	}
+	for _, candidate := range headless {
+		if !slices.Contains(candidate.profile.Tags, "swiftshader") {
+			t.Fatalf("headless profile %q is not a SwiftShader profile", candidate.profile.ID)
+		}
+	}
+	if len(headless) < 2 {
+		t.Fatalf("expected multiple SwiftShader profiles so Docker is not a single fingerprint, got %d", len(headless))
+	}
+	timezones := make(map[string]struct{}, len(headless))
+	for _, candidate := range headless {
+		timezones[candidate.profile.Timezone] = struct{}{}
+	}
+	if len(timezones) < 2 {
+		t.Fatalf("expected distinct CDP-visible SwiftShader profiles, got timezones %v", timezones)
+	}
+
+	headful := eligibleProfiles("linux", false)
+	if len(headful) == 0 {
+		t.Fatal("expected headful Linux profiles")
+	}
+	for _, candidate := range headful {
+		if slices.Contains(candidate.profile.Tags, "swiftshader") {
+			t.Fatalf("headful profile %q should not be a SwiftShader profile", candidate.profile.ID)
+		}
+	}
+}
+
 func TestNormalizeRegion(t *testing.T) {
 	tests := []struct {
 		input string
--- a/core/browser/profiles.json
+++ b/core/browser/profiles.json
@@ -2,399 +2,96 @@
  "profiles": [
    {
      "id": "chrome-linux-mesa-uhd620",
-      "user_agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Linux",
-      "platform_version": "6.1.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Intel Inc.",
-      "webgl_renderer": "Mesa Intel(R) UHD Graphics 620 (KBL GT2)",
-      "tags": ["linux", "mesa", "integrated"],
-      "weight": 3
+      "user_agent_template": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Linux", "platform_version": "6.1.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["linux", "mesa", "integrated"], "weight": 3
    },
    {
      "id": "chrome-linux-mesa-iris-xe",
-      "user_agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Linux",
-      "platform_version": "6.1.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Intel Inc.",
-      "webgl_renderer": "Mesa Intel(R) Graphics (RPL-S)",
-      "tags": ["linux", "mesa", "integrated"],
-      "weight": 2
+      "user_agent_template": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Linux", "platform_version": "6.1.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["linux", "mesa", "integrated"], "weight": 2
    },
    {
      "id": "chrome-linux-nvidia",
-      "user_agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Linux",
-      "platform_version": "6.1.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Google Inc. (NVIDIA Corporation)",
-      "webgl_renderer": "ANGLE (NVIDIA Corporation, NVIDIA GeForce GTX 1660 SUPER/PCIe/SSE2, OpenGL 4.5.0 NVIDIA 535.86.05)",
-      "tags": ["linux", "nvidia"],
-      "weight": 2
+      "user_agent_template": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Linux", "platform_version": "6.1.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["linux", "nvidia"], "weight": 2
    },
    {
      "id": "chrome-linux-amd",
-      "user_agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Linux",
-      "platform_version": "6.1.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Google Inc. (AMD)",
-      "webgl_renderer": "ANGLE (AMD, AMD Radeon RX 6600 (radeonsi, navi23, ACO, DRM 3.42.0, 5.15.0-91-generic), OpenGL 4.6 (Core Profile))",
-      "tags": ["linux", "amd"],
-      "weight": 1
+      "user_agent_template": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Linux", "platform_version": "6.1.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["linux", "amd"], "weight": 1
    },
    {
      "id": "chrome-linux-swiftshader",
-      "user_agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Linux",
-      "platform_version": "6.1.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1366, "height": 768},
-      "webgl_vendor": "Google Inc. (Google)",
-      "webgl_renderer": "ANGLE (Google, Vulkan 1.3.0 (SwiftShader Device (Subzero) (0x0000C0DE)), SwiftShader driver)",
-      "tags": ["linux", "swiftshader", "headless"],
-      "weight": 1
+      "user_agent_template": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Linux", "platform_version": "6.1.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["linux", "swiftshader", "headless"], "weight": 1
    },
    {
-      "id": "chrome-linux-ru",
-      "user_agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Linux",
-      "platform_version": "6.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7",
-      "navigator_langs": ["ru-RU"],
-      "locale": "ru-RU",
-      "timezone": "Europe/Moscow",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Intel Inc.",
-      "webgl_renderer": "Mesa Intel(R) UHD Graphics 620 (KBL GT2)",
-      "tags": ["linux", "ru"],
-      "weight": 1
+      "id": "chrome-linux-swiftshader-fhd",
+      "user_agent_template": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Linux", "platform_version": "6.1.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/Chicago",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["linux", "swiftshader", "headless"], "weight": 1
    },
    {
      "id": "chrome-win-uhd620",
-      "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Windows",
-      "platform_version": "15.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Intel Inc.",
-      "webgl_renderer": "ANGLE (Intel, Intel(R) UHD Graphics 620 Direct3D11 vs_5_0 ps_5_0, D3D11)",
-      "tags": ["windows"],
-      "weight": 2
+      "user_agent_template": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Windows", "platform_version": "15.0.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["windows"], "weight": 2
    },
    {
      "id": "chrome-win-nvidia",
-      "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Windows",
-      "platform_version": "15.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Google Inc. (NVIDIA)",
-      "webgl_renderer": "ANGLE (NVIDIA, NVIDIA GeForce RTX 3060 Direct3D11 vs_5_0 ps_5_0, D3D11)",
-      "tags": ["windows", "nvidia"],
-      "weight": 2
+      "user_agent_template": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Windows", "platform_version": "15.0.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["windows", "nvidia"], "weight": 2
    },
    {
      "id": "chrome-win-iris-xe",
-      "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Windows",
-      "platform_version": "15.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1536, "height": 864},
-      "webgl_vendor": "Google Inc. (Intel)",
-      "webgl_renderer": "ANGLE (Intel, Intel(R) Iris(R) Xe Graphics Direct3D11 vs_5_0 ps_5_0, D3D11)",
-      "tags": ["windows", "integrated"],
-      "weight": 1
+      "user_agent_template": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Windows", "platform_version": "15.0.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["windows", "integrated"], "weight": 1
    },
    {
      "id": "chrome-win-amd",
-      "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Windows",
-      "platform_version": "15.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Google Inc. (AMD)",
-      "webgl_renderer": "ANGLE (AMD, AMD Radeon RX 6600 Direct3D11 vs_5_0 ps_5_0, D3D11)",
-      "tags": ["windows", "amd"],
-      "weight": 1
-    },
-    {
-      "id": "chrome-win-ru",
-      "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "Windows",
-      "platform_version": "15.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7",
-      "navigator_langs": ["ru-RU"],
-      "locale": "ru-RU",
-      "timezone": "Europe/Moscow",
-      "viewport": {"width": 1920, "height": 1080},
-      "webgl_vendor": "Intel Inc.",
-      "webgl_renderer": "ANGLE (Intel, Intel(R) UHD Graphics 620 Direct3D11 vs_5_0 ps_5_0, D3D11)",
-      "tags": ["windows", "ru"],
-      "weight": 1
+      "user_agent_template": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "Windows", "platform_version": "15.0.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1920, "height": 1080}, "tags": ["windows", "amd"], "weight": 1
    },
    {
      "id": "chrome-macos-m1",
-      "user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "macOS",
-      "platform_version": "13.0.0",
-      "architecture": "arm",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1440, "height": 900},
-      "webgl_vendor": "Google Inc. (Apple)",
-      "webgl_renderer": "ANGLE (Apple, ANGLE Metal Renderer: Apple M1, Unspecified Version)",
-      "tags": ["macos", "apple-silicon"],
-      "weight": 2
+      "user_agent_template": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "macOS", "platform_version": "13.0.0", "architecture": "arm", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1440, "height": 900}, "tags": ["macos", "apple-silicon"], "weight": 2
    },
    {
      "id": "chrome-macos-m2",
-      "user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "macOS",
-      "platform_version": "14.0.0",
-      "architecture": "arm",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1512, "height": 982},
-      "webgl_vendor": "Google Inc. (Apple)",
-      "webgl_renderer": "ANGLE (Apple, ANGLE Metal Renderer: Apple M2, Unspecified Version)",
-      "tags": ["macos", "apple-silicon"],
-      "weight": 2
+      "user_agent_template": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "macOS", "platform_version": "14.0.0", "architecture": "arm", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1512, "height": 982}, "tags": ["macos", "apple-silicon"], "weight": 2
    },
    {
      "id": "chrome-macos-intel-iris",
-      "user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      "uach_brands": [
-        {"brand": "Not_A Brand", "version": "24"},
-        {"brand": "Chromium", "version": "136"},
-        {"brand": "Google Chrome", "version": "136"}
-      ],
-      "uach_full_version_list": [
-        {"brand": "Not_A Brand", "version": "24.0.0.0"},
-        {"brand": "Chromium", "version": "136.0.0.0"},
-        {"brand": "Google Chrome", "version": "136.0.0.0"}
-      ],
-      "platform": "macOS",
-      "platform_version": "14.0.0",
-      "architecture": "x86",
-      "bitness": "64",
-      "mobile": false,
-      "accept_language": "en-US,en;q=0.9",
-      "navigator_langs": ["en-US"],
-      "locale": "en-US",
-      "timezone": "America/New_York",
-      "viewport": {"width": 1680, "height": 1050},
-      "webgl_vendor": "Intel Inc.",
-      "webgl_renderer": "Intel Iris OpenGL Engine",
-      "tags": ["macos", "integrated"],
-      "weight": 1
+      "user_agent_template": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/{chrome_major}.0.0.0 Safari/537.36",
+      "platform": "macOS", "platform_version": "14.0.0", "architecture": "x86", "bitness": "64", "mobile": false,
+      "accept_language": "en-US,en;q=0.9", "navigator_langs": ["en-US"], "locale": "en-US", "timezone": "America/New_York",
+      "viewport": {"width": 1680, "height": 1050}, "tags": ["macos", "integrated"], "weight": 1
    }
  ],
  "lane_profile_ids": {},
-  "default_region_by_engine": {
-    "yandex": "ru"
-  }
+  "default_region_by_engine": {"yandex": "ru"}
 }
--- a/core/browser_unit_test.go
+++ b/core/browser_unit_test.go
@@ -61,6 +61,61 @@ func TestResolveBrowserBinaryPathRejectsInvalidExplicit(t *testing.T) {
 	}
 }

+func TestBrowserLaunchLanguageIsProcessStable(t *testing.T) {
+	tests := []struct {
+		name string
+		opts BrowserOpts
+		want string
+	}{
+		{name: "default locale", opts: BrowserOpts{}, want: "en-US"},
+		{name: "request hint does not change process locale", opts: BrowserOpts{LanguageCode: "de"}, want: "en-US"},
+		{name: "regional hint does not change process locale", opts: BrowserOpts{LanguageCode: "en-GB"}, want: "en-US"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := browserLaunchLanguage(tt.opts); got != tt.want {
+				t.Fatalf("browserLaunchLanguage() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestProfileNavigatorLanguagesStripsHeaderWeights(t *testing.T) {
+	profile := browserprofile.Profile{
+		AcceptLanguage: "en-US,en;q=0.9",
+		NavigatorLangs: []string{"en-US"},
+	}
+
+	got := profileNavigatorLanguages(profile)
+	want := []string{"en-US", "en"}
+	if len(got) != len(want) {
+		t.Fatalf("profileNavigatorLanguages() = %v, want %v", got, want)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("profileNavigatorLanguages() = %v, want %v", got, want)
+		}
+	}
+}
+
+func TestProfileNavigatorLanguagesForRuntime(t *testing.T) {
+	profile := browserprofile.Profile{
+		AcceptLanguage: "en-US,en;q=0.9",
+		NavigatorLangs: []string{"en-US"},
+	}
+
+	linuxHeadless := profileNavigatorLanguagesForRuntime(profile, "linux", true)
+	if len(linuxHeadless) != 1 || linuxHeadless[0] != "en-US" {
+		t.Fatalf("linux headless languages = %v, want [en-US]", linuxHeadless)
+	}
+
+	windowsHeadless := profileNavigatorLanguagesForRuntime(profile, "windows", true)
+	if len(windowsHeadless) != 2 || windowsHeadless[0] != "en-US" || windowsHeadless[1] != "en" {
+		t.Fatalf("windows headless languages = %v, want [en-US en]", windowsHeadless)
+	}
+}
+
 func TestMinPositiveDuration(t *testing.T) {
 	tests := []struct {
 		name string
@@ -95,6 +150,35 @@ func TestApplyProfileLanguageHintRewritesTimezone(t *testing.T) {
 	}
 }

+func TestRemoveChromeBrand(t *testing.T) {
+	profile := browserprofile.Profile{
+		UACHBrands: []browserprofile.BrandVersion{
+			{Brand: "Not_A Brand", Version: "24"},
+			{Brand: "Chromium", Version: "136"},
+			{Brand: "Google Chrome", Version: "136"},
+		},
+		UACHFullVerList: []browserprofile.BrandVersion{
+			{Brand: "Chromium", Version: "136.0.0.0"},
+			{Brand: "Google Chrome", Version: "136.0.0.0"},
+		},
+	}
+
+	got := removeChromeBrand(profile)
+	for _, brand := range got.UACHBrands {
+		if brand.Brand == "Google Chrome" {
+			t.Fatal("expected Google Chrome brand to be removed from UACHBrands")
+		}
+	}
+	for _, brand := range got.UACHFullVerList {
+		if brand.Brand == "Google Chrome" {
+			t.Fatal("expected Google Chrome brand to be removed from UACHFullVerList")
+		}
+	}
+	if len(got.UACHBrands) != 2 || len(got.UACHFullVerList) != 1 {
+		t.Fatalf("unexpected brand counts: brands=%d fullList=%d", len(got.UACHBrands), len(got.UACHFullVerList))
+	}
+}
+
 func TestApplyProfileLanguageHint(t *testing.T) {
 	base := browserprofile.Profile{
 		AcceptLanguage: "en-US,en;q=0.9",
--- a/core/context.go
+++ b/core/context.go
@@ -39,12 +39,9 @@ func IsContextDone(err error) bool {

 // PrepareEngineContext applies request-scoped metadata expected by all engine
 // search implementations.
-func PrepareEngineContext(ctx context.Context, query Query, engineName string, minimalBrowserProfile bool) context.Context {
+func PrepareEngineContext(ctx context.Context, query Query, engineName string) context.Context {
 	ctx = WithEngine(EnsureContext(ctx), engineName)
 	ctx = WithProfileRegion(ctx, profileRegionHint(query))
-	if minimalBrowserProfile {
-		ctx = WithMinimalBrowserProfile(ctx)
-	}
 	return WithQueryHash(ctx, QueryHashFromQuery(query))
 }

--- a/core/http_client.go
+++ b/core/http_client.go
@@ -419,15 +419,38 @@ func rawRequestProfileFor(ctx context.Context, query Query) rawRequestProfile {

 func applyRawChromeMajor(profile browserprofile.Profile, major int) browserprofile.Profile {
 	version := strconv.Itoa(major)
-	if extractChromeVersion(profile.UserAgent) == "" {
+	if template := strings.TrimSpace(profile.UserAgentTemplate); template != "" {
+		profile.UserAgent = strings.ReplaceAll(template, "{chrome_major}", version)
+	} else if extractChromeVersion(profile.UserAgent) == "" {
 		profile.UserAgent = fallbackRawUserAgent
+	} else {
+		profile.UserAgent = replaceChromeUserAgentVersion(profile.UserAgent, version+".0.0.0")
+	}
+	if len(profile.UACHBrands) == 0 {
+		profile.UACHBrands = rawUACHBrands(version, false)
+	} else {
+		profile.UACHBrands = patchBrandVersions(profile.UACHBrands, version, false)
+	}
+	if len(profile.UACHFullVerList) == 0 {
+		profile.UACHFullVerList = rawUACHBrands(version+".0.0.0", true)
+	} else {
+		profile.UACHFullVerList = patchBrandVersions(profile.UACHFullVerList, version+".0.0.0", true)
 	}
-	profile.UserAgent = replaceChromeUserAgentVersion(profile.UserAgent, version+".0.0.0")
-	profile.UACHBrands = patchBrandVersions(profile.UACHBrands, version, false)
-	profile.UACHFullVerList = patchBrandVersions(profile.UACHFullVerList, version+".0.0.0", true)
 	return profile
 }

+func rawUACHBrands(version string, full bool) []browserprofile.BrandVersion {
+	notABrandVersion := "24"
+	if full {
+		notABrandVersion = "24.0.0.0"
+	}
+	return []browserprofile.BrandVersion{
+		{Brand: "Not_A Brand", Version: notABrandVersion},
+		{Brand: "Chromium", Version: version},
+		{Brand: "Google Chrome", Version: version},
+	}
+}
+
 func rawProfileRegion(ctx context.Context, query Query) string {
 	if region := profileRegionFromContext(ctx); region != "" {
 		return region
--- a/core/profile_context.go
+++ b/core/profile_context.go
@@ -9,7 +9,6 @@ type profileContextKey string

 const profileRegionContextKey profileContextKey = "profile_region"
 const forcedProfileIDContextKey profileContextKey = "forced_profile_id"
-const minimalProfileContextKey profileContextKey = "minimal_profile"

 func WithProfileRegion(ctx context.Context, region string) context.Context {
 	region = strings.TrimSpace(region)
@@ -41,12 +40,3 @@ func forcedProfileIDFromContext(ctx context.Context) string {
 	value, _ := EnsureContext(ctx).Value(forcedProfileIDContextKey).(string)
 	return strings.TrimSpace(value)
 }
-
-func WithMinimalBrowserProfile(ctx context.Context) context.Context {
-	return context.WithValue(EnsureContext(ctx), minimalProfileContextKey, true)
-}
-
-func minimalBrowserProfileFromContext(ctx context.Context) bool {
-	value, _ := EnsureContext(ctx).Value(minimalProfileContextKey).(bool)
-	return value
-}
--- a/core/proxy_lane.go
+++ b/core/proxy_lane.go
@@ -224,6 +224,9 @@ func ProxyLaneKeyForTenant(engine string, tenant string, q Query, proxyURL strin
 	if sessionID == "" {
 		sessionID = proxyLaneIDFromProxyURL(proxyURL)
 	}
+	if sessionID == "" {
+		sessionID = "direct"
+	}
 	return NormalizeProxyLaneKey(ProxyLaneKey{Tenant: tenant, Engine: engine, SessionID: sessionID})
 }

--- a/core/proxy_lane_test.go
+++ b/core/proxy_lane_test.go
@@ -103,3 +103,13 @@ func TestProxyLaneKeyIncludesTenant(t *testing.T) {
 		t.Fatalf("unexpected tenant lane id: %q", got)
 	}
 }
+
+func TestProxyLaneKeyUsesStableDirectSession(t *testing.T) {
+	key := ProxyLaneKeyForTenant("google", "tenant-a", Query{}, "")
+	if key.Empty() {
+		t.Fatal("expected a direct lane")
+	}
+	if key.SessionID != "direct" {
+		t.Fatalf("SessionID = %q, want direct", key.SessionID)
+	}
+}
--- a/duckduckgo/search.go
+++ b/duckduckgo/search.go
@@ -149,7 +149,7 @@ func ddgElementHasAdMarker(el *rod.Element) bool {
 // Search executes a DuckDuckGo web search and returns normalized search
 // results. It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (ddg *DuckDuckGo) Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, ddg.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, ddg.Name())
 	scoped := *ddg
 	scoped.logger = ddg.logger.WithRequest(ctx)
 	ddg = &scoped
@@ -229,7 +229,7 @@ func (ddg *DuckDuckGo) Search(ctx context.Context, query core.Query) (results []
 // SearchImage executes a DuckDuckGo image search and returns normalized image
 // results. It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (ddg *DuckDuckGo) SearchImage(ctx context.Context, query core.Query) ([]core.SearchResult, error) {
-	ctx = core.PrepareEngineContext(ctx, query, ddg.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, ddg.Name())
 	scoped := *ddg
 	scoped.logger = ddg.logger.WithRequest(ctx)
 	ddg = &scoped
--- a/ecosia/search.go
+++ b/ecosia/search.go
@@ -105,7 +105,7 @@ func (e *Ecosia) parseResult(elem *rod.Element, rank int, ad bool) (core.SearchR
 // Search executes an Ecosia web search and returns normalized search results.
 // It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (e *Ecosia) Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, e.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, e.Name())
 	scoped := *e
 	scoped.logger = e.logger.WithRequest(ctx)
 	e = &scoped
@@ -237,7 +237,7 @@ func elementText(el *rod.Element, selector string) string {
 // query.Start is ignored: per-page card count varies, so callers should
 // drive depth through query.Limit alone.
 func (e *Ecosia) SearchImage(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, e.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, e.Name())
 	scoped := *e
 	scoped.logger = e.logger.WithRequest(ctx)
 	e = &scoped
--- a/ecosia/search_raw.go
+++ b/ecosia/search_raw.go
@@ -57,7 +57,7 @@ func imageResultParser(response *http.Response) ([]core.SearchResult, error) {
 }

 func Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, "ecosia", false)
+	ctx = core.PrepareEngineContext(ctx, query, "ecosia")

 	pageNum, startRank, err := startPage(query.Start)
 	if err != nil {
--- a/google/search.go
+++ b/google/search.go
@@ -228,7 +228,7 @@ func googleElementHasAdMarker(el *rod.Element) bool {
 // Search executes a Google web search and returns normalized search results.
 // It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (gogl *Google) Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, gogl.Name(), true)
+	ctx = core.PrepareEngineContext(ctx, query, gogl.Name())
 	scoped := *gogl
 	scoped.logger = gogl.logger.WithRequest(ctx)
 	gogl = &scoped
@@ -494,7 +494,7 @@ func (gogl *Google) Search(ctx context.Context, query core.Query) (results []cor
 // SearchImage executes a Google image search and returns normalized image
 // results. It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (gogl *Google) SearchImage(ctx context.Context, query core.Query) ([]core.SearchResult, error) {
-	ctx = core.PrepareEngineContext(ctx, query, gogl.Name(), true)
+	ctx = core.PrepareEngineContext(ctx, query, gogl.Name())
 	scoped := *gogl
 	scoped.logger = gogl.logger.WithRequest(ctx)
 	gogl = &scoped
--- a/google/search_raw.go
+++ b/google/search_raw.go
@@ -173,7 +173,7 @@ func isZeroResultStats(s string) bool {
 }

 func Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, "google", false)
+	ctx = core.PrepareEngineContext(ctx, query, "google")

 	googleURL, err := BuildURL(query)
 	if err != nil {
--- a/yandex/search.go
+++ b/yandex/search.go
@@ -191,7 +191,7 @@ func (yand *Yandex) parseImageEntities(items rod.Elements) map[string]ImageEntit
 // Search executes a Yandex web search and returns normalized search results.
 // It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (yand *Yandex) Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, yand.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, yand.Name())
 	scoped := *yand
 	scoped.logger = yand.logger.WithRequest(ctx)
 	yand = &scoped
@@ -286,7 +286,7 @@ func (yand *Yandex) Search(ctx context.Context, query core.Query) (results []cor
 // SearchImage executes a Yandex image search and returns normalized image
 // results. It may return core.ErrCaptcha or core.ErrSearchTimeout.
 func (yand *Yandex) SearchImage(ctx context.Context, query core.Query) ([]core.SearchResult, error) {
-	ctx = core.PrepareEngineContext(ctx, query, yand.Name(), false)
+	ctx = core.PrepareEngineContext(ctx, query, yand.Name())
 	scoped := *yand
 	scoped.logger = yand.logger.WithRequest(ctx)
 	yand = &scoped
--- a/yandex/search_raw.go
+++ b/yandex/search_raw.go
@@ -19,7 +19,7 @@ func classifyYandexRawHTML(body []byte) error {
 }

 func Search(ctx context.Context, query core.Query) (results []core.SearchResult, err error) {
-	ctx = core.PrepareEngineContext(ctx, query, "yandex", false)
+	ctx = core.PrepareEngineContext(ctx, query, "yandex")

 	startPage, skipOnFirstPage, err := core.ComputePagination(query.Start, 10)
 	if err != nil {