diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e64c854620f..e4399ad40d3 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -1,3 +1,5 @@
+# TODO(a.garipov):  Use client_v2 for the frontend tests once Windows build is
+# fixed.
 'name': 'build'
 # Permissions are disabled for all the jobs by default, and then overridden for
 # specific jobs if needed.  This is a recommended practice for security reasons,
@@ -64,7 +66,7 @@
           'restore-keys': '${{ runner.os }}-node-'
       - 'name': 'Run tests'
         'shell': 'bash'
-        'run': 'make VERBOSE=1 deps test go-bench go-fuzz'
+        'run': 'make CLIENT_DIR=client VERBOSE=1 deps test go-bench go-fuzz'
       - 'name': 'Upload coverage'
         'uses': 'codecov/codecov-action@v1'
         'if': "success() && matrix.os == 'ubuntu-latest'"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 531b9c674f1..0ce0805ee21 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,22 @@ See also the [v0.107.79 GitHub milestone][ms-v0.107.79].
 NOTE: Add new changes BELOW THIS COMMENT.
 -->
 
+### Added
+
+- New property `"language"` in `POST /control/install/check_config` and `POST /control/install/configure` HTTP APIs.
+
+- The user is able to remove the static lease's hostname via the HTTP API.
+
+### Changed
+
+- The `edge` channel has been switched to the new UI and versioning scheme.
+
+### Fixed
+
+- Blocked requests without an EDNS(0) OPT record ([#8183]).
+
+[#8183]: https://github.com/AdguardTeam/AdGuardHome/issues/8183
+
 <!--
 NOTE: Add new changes ABOVE THIS COMMENT.
 -->
@@ -62,8 +78,6 @@ See also the [v0.107.78 GitHub milestone][ms-v0.107.78].
 
 - The `filtering` object of the YAML configuration now includes a new property, `max_http_size`, which defines the maximum size of the HTTP request for rulelists. To disable the limitation, set a large size, such as `1 TB`.
 
-### Fixed
-
 - Invalid AA flag in DNS responses ([#7955]).
 
 - The parsing of the `ech` parameter in DNS rewrite rules for the HTTPS record type ([#8276]).
diff --git a/Makefile b/Makefile
index 935932ecf14..e947fcefa0a 100644
--- a/Makefile
+++ b/Makefile
@@ -19,8 +19,7 @@ GO.MACRO = $${GO:-go}
 VERBOSE.MACRO = $${VERBOSE:-0}
 
 CHANNEL = development
-# TODO(ik): Update CLIENT_DIR to client_v2 for new frontend migration
-CLIENT_DIR = client
+CLIENT_DIR = client_v2
 DEPLOY_SCRIPT_PATH = not/a/real/path
 DIST_DIR = dist
 GOAMD64 = v1
diff --git a/bamboo-specs/release.yaml b/bamboo-specs/release.yaml
index 82b2dcd6934..cbb3fc9f5fc 100644
--- a/bamboo-specs/release.yaml
+++ b/bamboo-specs/release.yaml
@@ -10,6 +10,7 @@
     # flaky test suite.
     'cacheBuster': '0'
     'channel': 'edge'
+    'clientDir': 'client_v2'
     'dockerFrontend': 'adguard/home-js-builder:4.0'
     'dockerGo': 'adguard/go-builder:1.26.5--1'
 
@@ -67,8 +68,9 @@
                   docker info
 
                   docker build \
-                      --build-arg "BASE_IMAGE=${bamboo.dockerFrontend}" \
+                      --build-arg "BASE_IMAGE=${bamboo_dockerFrontend}" \
                       --build-arg "CACHE_BUSTER=${bamboo_cacheBuster}" \
+                      --build-arg "CLIENT_DIR=${bamboo_clientDir}" \
                       --output '.' \
                       --progress 'plain' \
                       --target 'builder-exporter' \
@@ -104,7 +106,7 @@
                 set -e -f -u -x
 
                 # Explicitly checkout the revision that we need.
-                git checkout "${bamboo.repository.revision.number}"
+                git checkout "${bamboo_repository_revision_number}"
 
                 version="$(env CHANNEL=${bamboo_channel} sh ./scripts/make/version.sh)"
                 readonly version
@@ -160,8 +162,8 @@
 
                 # Login to DockerHub.
                 docker login \
-                    -u="${bamboo.dockerHubUsername}" \
-                    -p="${bamboo.dockerHubPassword}"
+                    -u="${bamboo_dockerHubUsername}" \
+                    -p="${bamboo_dockerHubPassword}"
 
                 # Boot the builder.
                 docker buildx inspect --bootstrap
@@ -172,8 +174,8 @@
 
                 # Prepare and push the build.
                 env \
-                    CHANNEL="${bamboo.channel}" \
-                    REVISION="${bamboo.repository.revision.number}" \
+                    CHANNEL="${bamboo_channel}" \
+                    REVISION="${bamboo_repository_revision_number}" \
                     DIST_DIR='dist' \
                     DOCKER_IMAGE_NAME='adguard/adguardhome' \
                     DOCKER_PUSH='1' \
@@ -202,7 +204,7 @@
 
                 cd ./dist/
 
-                CHANNEL="${bamboo.channel}"
+                CHANNEL="${bamboo_channel}"
                 export CHANNEL
 
                 ../bamboo-deploy-publisher/deploy.sh adguard-home-"$CHANNEL"
@@ -227,7 +229,7 @@
 
                 set -e -f -u -x
 
-                channel="${bamboo.channel}"
+                channel="${bamboo_channel}"
                 readonly channel
 
                 if [ "$channel" != 'release' ] && [ "${channel}" != 'beta' ]
@@ -240,7 +242,7 @@
                 cd ./dist/
 
                 env\
-                        GITHUB_TOKEN="${bamboo.githubPublicRepoPassword}"\
+                        GITHUB_TOKEN="${bamboo_githubPublicRepoPassword}"\
                         ../bamboo-deploy-publisher/deploy.sh adguard-home-github
 
 'triggers':
@@ -279,6 +281,7 @@
         # need to build a few of these.
         'variables':
             'channel': 'beta'
+            'clientDir': 'client'
             'dockerFrontend': 'adguard/home-js-builder:4.0'
             'dockerGo': 'adguard/go-builder:1.26.5--1'
     # release-vX.Y.Z branches are the branches from which the actual final
@@ -295,5 +298,6 @@
         # are the ones that actually get released.
         'variables':
             'channel': 'release'
+            'clientDir': 'client'
             'dockerFrontend': 'adguard/home-js-builder:4.0'
             'dockerGo': 'adguard/go-builder:1.26.5--1'
diff --git a/bamboo-specs/test.yaml b/bamboo-specs/test.yaml
index faedf10e39c..f78992e0a15 100644
--- a/bamboo-specs/test.yaml
+++ b/bamboo-specs/test.yaml
@@ -9,6 +9,7 @@
     # flaky test suite.
     'cacheBuster': '0'
     'channel': 'development'
+    'clientDir': 'client_v2'
     'dockerFrontend': 'adguard/home-js-builder:4.0'
     'dockerGo': 'adguard/go-builder:1.26.5--1'
 
@@ -58,8 +59,9 @@
                 docker info
 
                 docker build \
-                    --build-arg "BASE_IMAGE=${bamboo.dockerFrontend}" \
+                    --build-arg "BASE_IMAGE=${bamboo_dockerFrontend}" \
                     --build-arg "CACHE_BUSTER=${bamboo_cacheBuster}" \
+                    --build-arg "CLIENT_DIR=${bamboo_clientDir}" \
                     --output '.' \
                     --progress 'plain' \
                     --target 'tester' \
@@ -127,8 +129,9 @@
                 docker info
 
                 docker build \
-                    --build-arg "BASE_IMAGE=${bamboo.dockerFrontend}" \
+                    --build-arg "BASE_IMAGE=${bamboo_dockerFrontend}" \
                     --build-arg "CACHE_BUSTER=${bamboo_cacheBuster}" \
+                    --build-arg "CLIENT_DIR=${bamboo_clientDir}" \
                     --output '.' \
                     --progress 'plain' \
                     --target 'builder-exporter' \
@@ -216,8 +219,9 @@
                 docker info
 
                 docker build \
-                    --build-arg "BASE_IMAGE=${bamboo.dockerFrontend}" \
+                    --build-arg "BASE_IMAGE=${bamboo_dockerFrontend}" \
                     --build-arg "CACHE_BUSTER=${bamboo_cacheBuster}" \
+                    --build-arg "CLIENT_DIR=${bamboo_clientDir}" \
                     --output '.' \
                     --progress 'plain' \
                     --target 'e2etester' \
@@ -254,6 +258,7 @@
         # Set the default release channel on the release branch to beta, as we
         # may need to build a few of these.
         'variables':
+            'channel': 'candidate'
+            'clientDir': 'client'
             'dockerFrontend': 'adguard/home-js-builder:4.0'
             'dockerGo': 'adguard/go-builder:1.26.5--1'
-            'channel': 'candidate'
diff --git a/docker/frontend.Dockerfile b/docker/frontend.Dockerfile
index 0f4d3a9f38e..d37bdab7def 100644
--- a/docker/frontend.Dockerfile
+++ b/docker/frontend.Dockerfile
@@ -29,6 +29,7 @@
 
 # NOTE:  Keep in sync with bamboo-specs/bamboo.yaml.
 ARG BASE_IMAGE=adguard/home-js-builder:4.0
+ARG CLIENT_DIR=client
 
 # The dependencies stage is needed to install packages and tool dependencies.
 # This is also where binaries like osslsigncode, which may be required for tests
@@ -38,13 +39,15 @@ ARG BASE_IMAGE=adguard/home-js-builder:4.0
 FROM "$BASE_IMAGE" AS dependencies
 ADD Makefile /app/
 ADD scripts /app/scripts
-ADD client /app/client
+ARG CLIENT_DIR
+ADD "${CLIENT_DIR}" "/app/${CLIENT_DIR}"
 WORKDIR /app
 RUN \
     --mount=type=cache,id=npm-root-cache,target=/root/.npm \
 <<-'EOF'
 set -e -f -u -x
 make \
+	CLIENT_DIR="${CLIENT_DIR}" \
 	VERBOSE=1 \
 	js-deps \
 	;
@@ -53,14 +56,16 @@ EOF
 # The linter stage is separated from the tester stage to make catching test
 # failures easier.
 FROM dependencies AS linter
-ARG CACHE_BUSTER=0
 ADD . /app
+ARG CACHE_BUSTER=0
+ARG CLIENT_DIR
 WORKDIR /app
 RUN \
     --mount=type=cache,id=npm-root-cache,target=/root/.npm \
 <<-'EOF'
 set -e -f -u -x
 make \
+	CLIENT_DIR="${CLIENT_DIR}" \
 	VERBOSE=1 \
 	js-typecheck \
 	js-lint \
@@ -70,11 +75,13 @@ EOF
 # The test stage.
 FROM linter AS tester
 ARG CACHE_BUSTER=0
+ARG CLIENT_DIR
 RUN \
     --mount=type=cache,id=npm-root-cache,target=/root/.npm \
 <<-'EOF'
 set -e -f -u -x
 make \
+	CLIENT_DIR="${CLIENT_DIR}" \
 	VERBOSE=1 \
 	js-test \
 	;
@@ -83,6 +90,7 @@ EOF
 # The e2e test stage.
 FROM dependencies AS e2etester
 ARG CACHE_BUSTER=0
+ARG CLIENT_DIR
 ADD . /app
 WORKDIR /app
 RUN \
@@ -90,6 +98,7 @@ RUN \
 <<-'EOF'
 set -e -f -u -x
 make \
+	CLIENT_DIR="${CLIENT_DIR}" \
 	CI='true' \
 	VERBOSE=1 \
 	js-test-e2e \
@@ -99,6 +108,7 @@ EOF
 # The builder stage.
 FROM dependencies AS builder
 ARG CACHE_BUSTER=0
+ARG CLIENT_DIR
 ADD . /app
 WORKDIR /app
 RUN \
@@ -106,6 +116,7 @@ RUN \
 <<-'EOF'
 set -e -f -u -x
 make \
+	CLIENT_DIR="${CLIENT_DIR}" \
 	VERBOSE=1 \
 	js-build \
 	;
@@ -115,4 +126,5 @@ EOF
 # could be published.  This stage should only be used in a CI.
 FROM scratch AS builder-exporter
 ARG CACHE_BUSTER=0
+ARG CLIENT_DIR
 COPY --from=builder /app/build /build
diff --git a/internal/dhcpd/http_unix_internal_test.go b/internal/dhcpd/http_unix_internal_test.go
index 059e40ac994..ed5fe2401da 100644
--- a/internal/dhcpd/http_unix_internal_test.go
+++ b/internal/dhcpd/http_unix_internal_test.go
@@ -209,6 +209,14 @@ func TestServer_HandleUpdateStaticLease(t *testing.T) {
 			IP:       leaseV4IP,
 			Hostname: "updated-client-v4",
 		},
+	}, {
+		name: "update_v4_empty_hostname",
+		pos:  leaseV4Pos,
+		lease: &leaseStatic{
+			HWAddr:   leaseV4MAC,
+			IP:       leaseV4IP,
+			Hostname: "",
+		},
 	}, {
 		name: "update_v4_ip",
 		pos:  leaseV4Pos,
@@ -306,7 +314,7 @@ func TestServer_HandleUpdateStaticLease_validation(t *testing.T) {
 			IP:       anotherV4IP,
 			Hostname: leaseV4Name,
 		},
-		want: "dhcpv4: updating static lease: ip address is not unique\n",
+		want: "dhcpv4: updating static lease: ip address: duplicated value\n",
 	}, {
 		name: "update_v4_same_name",
 		lease: &leaseStatic{
@@ -314,7 +322,7 @@ func TestServer_HandleUpdateStaticLease_validation(t *testing.T) {
 			IP:       leaseV4IP,
 			Hostname: anotherV4Name,
 		},
-		want: "dhcpv4: updating static lease: hostname is not unique\n",
+		want: "dhcpv4: updating static lease: hostname: duplicated value\n",
 	}}
 
 	for _, tc := range testCases {
diff --git a/internal/dhcpd/v4_unix.go b/internal/dhcpd/v4_unix.go
index 0350d7f3b51..e5814012e1a 100644
--- a/internal/dhcpd/v4_unix.go
+++ b/internal/dhcpd/v4_unix.go
@@ -313,16 +313,6 @@ func (s *v4Server) rmDynamicLease(lease *dhcpsvc.Lease) (err error) {
 	return nil
 }
 
-const (
-	// ErrDupHostname is returned by addLease, validateStaticLease when the
-	// modified lease has a not empty non-unique hostname.
-	ErrDupHostname = errors.Error("hostname is not unique")
-
-	// ErrDupIP is returned by addLease, validateStaticLease when the modified
-	// lease has a non-unique IP address.
-	ErrDupIP = errors.Error("ip address is not unique")
-)
-
 // addLease adds a dynamic or static lease.
 func (s *v4Server) addLease(l *dhcpsvc.Lease) (err error) {
 	r := s.conf.ipRange
@@ -342,7 +332,7 @@ func (s *v4Server) addLease(l *dhcpsvc.Lease) (err error) {
 	// TODO(e.burkov):  l must have a valid hostname here, investigate.
 	if l.Hostname != "" {
 		if _, ok := s.hostsIndex[l.Hostname]; ok {
-			return ErrDupHostname
+			return fmt.Errorf("hostname: %w", errors.ErrDuplicated)
 		}
 
 		s.hostsIndex[l.Hostname] = l
@@ -485,23 +475,25 @@ func (s *v4Server) validateStaticLease(l *dhcpsvc.Lease) (err error) {
 		return err
 	}
 
-	err = netutil.ValidateHostname(hostname)
-	if err != nil {
-		return fmt.Errorf("validating hostname: %w", err)
-	}
+	if hostname != "" {
+		err = netutil.ValidateHostname(hostname)
+		if err != nil {
+			return fmt.Errorf("hostname: %w", err)
+		}
 
-	dup, ok := s.hostsIndex[hostname]
-	if ok && !bytes.Equal(dup.HWAddr, l.HWAddr) {
-		return ErrDupHostname
+		dup, ok := s.hostsIndex[hostname]
+		if ok && !bytes.Equal(dup.HWAddr, l.HWAddr) {
+			return fmt.Errorf("hostname: %w", errors.ErrDuplicated)
+		}
 	}
 
-	dup, ok = s.ipIndex[l.IP]
+	l.Hostname = hostname
+
+	dup, ok := s.ipIndex[l.IP]
 	if ok && !bytes.Equal(dup.HWAddr, l.HWAddr) {
-		return ErrDupIP
+		return fmt.Errorf("ip address: %w", errors.ErrDuplicated)
 	}
 
-	l.Hostname = hostname
-
 	if gwIP := s.conf.GatewayIP; gwIP == l.IP {
 		return fmt.Errorf("can't assign the gateway IP %q to the lease", gwIP)
 	}
diff --git a/internal/dhcpd/v4_unix_internal_test.go b/internal/dhcpd/v4_unix_internal_test.go
index ae80b5bdcb4..9d09687f2ba 100644
--- a/internal/dhcpd/v4_unix_internal_test.go
+++ b/internal/dhcpd/v4_unix_internal_test.go
@@ -12,6 +12,7 @@ import (
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/AdGuardHome/internal/dhcpsvc"
+	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/AdguardTeam/golibs/stringutil"
 	"github.com/AdguardTeam/golibs/testutil"
@@ -83,7 +84,7 @@ func TestV4Server_leasing(t *testing.T) {
 				IP:       anotherIP,
 				IsStatic: true,
 			})
-			assert.ErrorIs(t, err, ErrDupHostname)
+			assert.ErrorIs(t, err, errors.ErrDuplicated)
 		})
 
 		t.Run("same_mac", func(t *testing.T) {
@@ -914,3 +915,71 @@ func TestV4Server_handleRelease(t *testing.T) {
 
 	require.Equal(t, wantResp, resp)
 }
+
+func TestV4Server_validateStaticLease_emptyHostname(t *testing.T) {
+	t.Parallel()
+
+	const (
+		existingHostname = "existing-client"
+	)
+
+	existingIP := netip.MustParseAddr("192.168.10.150")
+	nonExistingIP := existingIP.Next()
+	existingMAC := net.HardwareAddr{0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA}
+	otherMAC := net.HardwareAddr{0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB}
+
+	s := defaultSrv(t)
+
+	s4, ok := s.(*v4Server)
+	require.True(t, ok)
+
+	existingLease := &dhcpsvc.Lease{
+		Hostname: existingHostname,
+		HWAddr:   existingMAC,
+		IP:       existingIP,
+		IsStatic: true,
+	}
+	err := s4.addLease(existingLease)
+	require.NoError(t, err)
+
+	testCases := []struct {
+		name    string
+		wantErr string
+		lease   *dhcpsvc.Lease
+	}{{
+		name: "empty_hostname_allowed",
+		lease: &dhcpsvc.Lease{
+			Hostname: "",
+			HWAddr:   otherMAC,
+			IP:       nonExistingIP,
+			IsStatic: true,
+		},
+	}, {
+		name:    "non_empty_hostname_duplicate_hostname",
+		wantErr: "hostname: duplicated value",
+		lease: &dhcpsvc.Lease{
+			Hostname: existingHostname,
+			HWAddr:   otherMAC,
+			IP:       nonExistingIP,
+			IsStatic: true,
+		},
+	}, {
+		name:    "non_empty_hostname_duplicate_ip",
+		wantErr: "ip address: duplicated value",
+		lease: &dhcpsvc.Lease{
+			Hostname: "new-client",
+			HWAddr:   otherMAC,
+			IP:       existingIP,
+			IsStatic: true,
+		},
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Don't run subtests in parallel because they modify the server's
+			// leases.
+			err = s4.validateStaticLease(tc.lease)
+			testutil.AssertErrorMsg(t, tc.wantErr, err)
+		})
+	}
+}
diff --git a/internal/dnsforward/msg.go b/internal/dnsforward/msg.go
index 5dba5927aef..b361f22d7ee 100644
--- a/internal/dnsforward/msg.go
+++ b/internal/dnsforward/msg.go
@@ -17,10 +17,17 @@ import (
 // template.  Also extract all the methods to a separate entity.
 
 // reply creates a DNS response for req.
+//
+// NOTE: If req uses EDNS(0), the response copies its UDP size and DO flag.
 func (*Server) reply(req *dns.Msg, code int) (resp *dns.Msg) {
 	resp = (&dns.Msg{}).SetRcode(req, code)
 	resp.RecursionAvailable = true
 
+	opt := req.IsEdns0()
+	if opt != nil {
+		resp.SetEdns0(opt.UDPSize(), opt.Do())
+	}
+
 	return resp
 }
 
@@ -404,7 +411,11 @@ func (s *Server) NewMsgSERVFAIL(req *dns.Msg) (resp *dns.Msg) {
 // NewMsgNOTIMPLEMENTED implements the [proxy.MessageConstructor] interface for
 // *Server.
 func (s *Server) NewMsgNOTIMPLEMENTED(req *dns.Msg) (resp *dns.Msg) {
-	resp = s.reply(req, dns.RcodeNotImplemented)
+	// NOTE: [Server.reply] must not be used there, because it unconditionally
+	// copies UDP size and DO bit from the request, when in this case we want to
+	// use constant values.
+	resp = (&dns.Msg{}).SetRcode(req, dns.RcodeNotImplemented)
+	resp.RecursionAvailable = true
 
 	// Most of the Internet and especially the inner core has an MTU of at least
 	// 1500 octets.  Maximum DNS/UDP payload size for IPv6 on MTU 1500 ethernet
@@ -415,7 +426,10 @@ func (s *Server) NewMsgNOTIMPLEMENTED(req *dns.Msg) (resp *dns.Msg) {
 
 	// NOTIMPLEMENTED without EDNS is treated as 'we don't support EDNS', so
 	// explicitly set it.
-	resp.SetEdns0(maxUDPPayload, false)
+	opt := req.IsEdns0()
+	if opt != nil {
+		resp.SetEdns0(maxUDPPayload, false)
+	}
 
 	return resp
 }
diff --git a/internal/home/controlinstall.go b/internal/home/controlinstall.go
index 4e26c4bcf29..c217ea3f9ae 100644
--- a/internal/home/controlinstall.go
+++ b/internal/home/controlinstall.go
@@ -84,9 +84,12 @@ type checkConfReqEnt struct {
 }
 
 type checkConfReq struct {
-	Web         checkConfReqEnt `json:"web"`
-	DNS         checkConfReqEnt `json:"dns"`
-	SetStaticIP bool            `json:"set_static_ip"`
+	Web checkConfReqEnt `json:"web"`
+	DNS checkConfReqEnt `json:"dns"`
+
+	Language string `json:"language"`
+
+	SetStaticIP bool `json:"set_static_ip"`
 }
 
 type checkConfRespEnt struct {
@@ -102,8 +105,9 @@ type staticIPJSON struct {
 
 type checkConfResp struct {
 	StaticIP staticIPJSON     `json:"static_ip"`
-	Web      checkConfRespEnt `json:"web"`
 	DNS      checkConfRespEnt `json:"dns"`
+	Language checkConfRespEnt `json:"language"`
+	Web      checkConfRespEnt `json:"web"`
 }
 
 // validateWeb returns error is the web part if the initial configuration can't
@@ -200,6 +204,12 @@ func (web *webAPI) handleInstallCheckConfig(w http.ResponseWriter, r *http.Reque
 	}
 
 	resp := &checkConfResp{}
+
+	err = validateLang(req.Language, true)
+	if err != nil {
+		resp.Language.Status = err.Error()
+	}
+
 	tcpPorts := aghalg.UniqChecker[tcpPort]{}
 	if err = req.validateWeb(tcpPorts); err != nil {
 		resp.Web.Status = err.Error()
@@ -362,19 +372,21 @@ type applyConfigReqEnt struct {
 }
 
 type applyConfigReq struct {
-	Username string `json:"username"`
+	Language string `json:"language"`
 	Password string `json:"password"`
+	Username string `json:"username"`
 
 	Web applyConfigReqEnt `json:"web"`
 	DNS applyConfigReqEnt `json:"dns"`
 }
 
 // copyInstallSettings copies the installation parameters between two
-// configuration structures.
+// configuration structures.  All arguments must not be nil.
 func copyInstallSettings(dst, src *configuration) {
-	dst.HTTPConfig = src.HTTPConfig
 	dst.DNS.BindHosts = src.DNS.BindHosts
 	dst.DNS.Port = src.DNS.Port
+	dst.HTTPConfig = src.HTTPConfig
+	dst.Language = src.Language
 }
 
 // shutdownTimeout is the timeout for shutting HTTP server down operation.
@@ -491,6 +503,10 @@ func (web *webAPI) finalizeInstall(
 		}
 	}()
 
+	if req.Language != "" {
+		config.Language = req.Language
+	}
+
 	config.DNS.BindHosts = []netip.Addr{req.DNS.IP}
 	config.DNS.Port = req.DNS.Port
 	config.Filtering.Logger = web.baseLogger.With(slogutil.KeyPrefix, "filtering")
@@ -589,6 +605,12 @@ func decodeApplyConfigReq(r io.Reader) (req *applyConfigReq, restartHTTP bool, e
 		return nil, false, fmt.Errorf("parsing request: %w", err)
 	}
 
+	err = validateLang(req.Language, true)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return nil, false, err
+	}
+
 	if req.Web.Port == 0 || req.DNS.Port == 0 {
 		return nil, false, errors.Error("ports cannot be 0")
 	}
diff --git a/internal/home/i18n.go b/internal/home/i18n.go
index b784f006575..4d733cead4c 100644
--- a/internal/home/i18n.go
+++ b/internal/home/i18n.go
@@ -2,6 +2,7 @@ package home
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/http"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
@@ -48,6 +49,20 @@ var allowedLanguages = container.NewMapSet(
 	"zh-tw",
 )
 
+// validateLang returns a standard error about if lang is an unknown language.
+// If allowEmpty is true, the language can also be empty.
+func validateLang(lang string, allowEmpty bool) (err error) {
+	if allowEmpty && lang == "" {
+		return nil
+	}
+
+	if !allowedLanguages.Has(lang) {
+		return fmt.Errorf("unknown language: %q", lang)
+	}
+
+	return nil
+}
+
 // languageJSON is the JSON structure for language requests and responses.
 type languageJSON struct {
 	Language string `json:"language"`
@@ -89,8 +104,9 @@ func (web *webAPI) handleI18nChangeLanguage(w http.ResponseWriter, r *http.Reque
 	}
 
 	lang := langReq.Language
-	if !allowedLanguages.Has(lang) {
-		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "unknown language: %q", lang)
+	err = validateLang(lang, false)
+	if err != nil {
+		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
diff --git a/internal/home/profilehttp.go b/internal/home/profilehttp.go
index 73c24e223ac..1b27f5ce834 100644
--- a/internal/home/profilehttp.go
+++ b/internal/home/profilehttp.go
@@ -94,8 +94,9 @@ func (web *webAPI) handlePutProfile(w http.ResponseWriter, r *http.Request) {
 	}
 
 	lang := profileReq.Language
-	if !allowedLanguages.Has(lang) {
-		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "unknown language: %q", lang)
+	err = validateLang(lang, false)
+	if err != nil {
+		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
diff --git a/openapi/CHANGELOG.md b/openapi/CHANGELOG.md
index 1009cba05d7..e33f21ccc61 100644
--- a/openapi/CHANGELOG.md
+++ b/openapi/CHANGELOG.md
@@ -2,9 +2,13 @@
 
 <!-- TODO(a.garipov): Reformat in accordance with the KeepAChangelog spec. -->
 
-## v0.107.78: API changes
+## v0.107.79: API changes
+
+### Setting the UI language through the install API
 
-### New `interval` values in `GET /control/filtering/status` and `POST /control/filtering/config` APIs
+- New property `"language"` in `POST /control/install/check_config` and `POST /control/install/configure` HTTP APIs defines the language to use once AdGuard Home is installed.
+
+## v0.107.78: API changes
 
 The property `interval` of the objects returned from and accepted by the aforementioned APIs can now be any integer between 0 and 8760 (365 days).
 
diff --git a/openapi/openapi.yaml b/openapi/openapi.yaml
index c214be1cdd9..c190efbd099 100644
--- a/openapi/openapi.yaml
+++ b/openapi/openapi.yaml
@@ -1,4 +1,4 @@
-'openapi': '3.0.3'
+'openapi': '3.2.0'
 'info':
   'title': 'AdGuard Home'
   'description': >
@@ -1543,8 +1543,7 @@
           'type': 'string'
           'example': 'v0.123.4'
         'language':
-          'type': 'string'
-          'example': 'en'
+          '$ref': '#/components/schemas/Lang'
         'start_time':
           'type': 'number'
           'format': 'double'
@@ -2685,7 +2684,7 @@
         'name':
           'type': 'string'
         'language':
-          'type': 'string'
+          '$ref': '#/components/schemas/Lang'
         'theme':
           'type': 'string'
           'description': 'Interface theme'
@@ -3159,11 +3158,13 @@
       'properties':
         'dns':
           '$ref': '#/components/schemas/CheckConfigRequestInfo'
-        'web':
-          '$ref': '#/components/schemas/CheckConfigRequestInfo'
+        'language':
+          '$ref': '#/components/schemas/Lang'
         'set_static_ip':
           'type': 'boolean'
           'example': false
+        'web':
+          '$ref': '#/components/schemas/CheckConfigRequestInfo'
     'CheckConfigRequestInfo':
       'type': 'object'
       'properties':
@@ -3181,15 +3182,18 @@
       'type': 'object'
       'required':
       - 'dns'
-      - 'web'
+      - 'language'
       - 'static_ip'
+      - 'web'
       'properties':
         'dns':
           '$ref': '#/components/schemas/CheckConfigResponseInfo'
-        'web':
+        'language':
           '$ref': '#/components/schemas/CheckConfigResponseInfo'
         'static_ip':
           '$ref': '#/components/schemas/CheckConfigStaticIpInfo'
+        'web':
+          '$ref': '#/components/schemas/CheckConfigResponseInfo'
     'CheckConfigResponseInfo':
       'type': 'object'
       'required':
@@ -3231,21 +3235,23 @@
       'required':
       - 'dns'
       - 'web'
-      - 'username'
       - 'password'
+      - 'username'
       'properties':
         'dns':
           '$ref': '#/components/schemas/AddressInfo'
         'web':
           '$ref': '#/components/schemas/AddressInfo'
-        'username':
+        'language':
+          '$ref': '#/components/schemas/Lang'
+        'password':
+          'description': 'Basic auth password'
+          'example': 'password'
           'type': 'string'
+        'username':
           'description': 'Basic auth username'
           'example': 'admin'
-        'password':
           'type': 'string'
-          'description': 'Basic auth password'
-          'example': 'password'
     'Login':
       'type': 'object'
       'description': 'Login request data'
@@ -3267,11 +3273,52 @@
       'description': 'Language settings object.'
       'properties':
         'language':
-          'description': 'The current language or the language to set.'
-          'type': 'string'
+          '$ref': '#/components/schemas/Lang'
       'required':
       - 'language'
       'type': 'object'
+    'Lang':
+      'description': >
+        Language code.
+      # Hold the enum in sync with .twosky.json.
+      'enum':
+      - 'ar'
+      - 'be'
+      - 'bg'
+      - 'cs'
+      - 'da'
+      - 'de'
+      - 'en'
+      - 'es'
+      - 'fa'
+      - 'fi'
+      - 'fr'
+      - 'hr'
+      - 'hu'
+      - 'id'
+      - 'it'
+      - 'ja'
+      - 'ko'
+      - 'nl'
+      - 'no'
+      - 'pl'
+      - 'pt-br'
+      - 'pt-pt'
+      - 'ro'
+      - 'ru'
+      - 'si-lk'
+      - 'sk'
+      - 'sl'
+      - 'sr-cs'
+      - 'sv'
+      - 'th'
+      - 'tr'
+      - 'uk'
+      - 'vi'
+      - 'zh-cn'
+      - 'zh-hk'
+      - 'zh-tw'
+      'type': 'string'
   'securitySchemes':
     'basicAuth':
       'type': 'http'
diff --git a/scripts/make/version.sh b/scripts/make/version.sh
index 46382740fd6..32e38170d17 100644
--- a/scripts/make/version.sh
+++ b/scripts/make/version.sh
@@ -85,6 +85,19 @@ case "$channel" in
 	version="v0.0.0-dev.${commit_number}+$(git rev-parse --short HEAD)"
 	;;
 'edge')
+	# TODO(a.garipov):  Remove this and use edge_todo below instead once v1.0.0
+	# is out.
+
+	# Temporarily, use the last v0.108.0 beta as the starting point for the
+	# v1.0.0 alpha (edge, nightly) releases.
+	num_commits="$(git rev-list --count "v0.108.0-b.89..HEAD")"
+	readonly num_commits
+
+	version="v1.0.0-a.${num_commits}+$(git rev-parse --short HEAD)"
+	;;
+'edge_todo')
+	# TODO(a.garipov):  Use this again once v1.0.0 is out.
+
 	# last_minor_zero is the last new minor release.
 	last_minor_zero="$(get_last_minor_zero)"
 	readonly last_minor_zero