From e38e6d16896f025a369aa5a8cb2d581d4c02d7e1 Mon Sep 17 00:00:00 2001
From: Yaojia Wang <yaojia.wang@billo.life>
Date: Tue, 7 Jul 2026 09:42:12 +0200
Subject: [PATCH] =?UTF-8?q?feat(ios):=20device=20client-cert=20mTLS=20?=
 =?UTF-8?q?=E2=80=94=20ClientTLS=20package,=20transport=20wiring,=20instal?=
 =?UTF-8?q?l=20UX=20(C-iOS)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- ios/Packages/ClientTLS: SecIdentity wrapper, PKCS12 importer (typed errors), keychain store
  (AfterFirstUnlockThisDeviceOnly), pure MutualTLSChallengeResponder truth table, cross-platform
  X.509 DER summary. 14/14 tests.
- Both transports (SessionCore URLSessionTermTransport, App URLSessionHTTPTransport) + SessionThumbnail
  take a lazy @Sendable ()->ClientIdentity? provider: WS resolves per-connect, HTTP per client-cert
  challenge, so a freshly-imported cert applies without an app relaunch. AppEnvironment injects
  { store.loadedIdentityOrNil() }.
- ClientCertScreen (.fileImporter([.pkcs12]) + passphrase -> import -> keychain), reachable via a
  设备证书 entry in SessionListScreen.hostMenu. PairingViewModel gates tunnel-host probes on cert
  presence and re-maps mTLS-reject to a clientCertRejected message.
Verified: ClientTLS 14/14, SessionCore 93/93, xcodegen + xcodebuild BUILD SUCCEEDED.
---
 .../WebTerm/Components/SessionThumbnail.swift |  18 +-
 .../WebTerm/Screens/ClientCertScreen.swift    | 243 ++++++++++++++++++
 .../WebTerm/Screens/SessionListScreen.swift   |  13 +
 .../WebTerm/ViewModels/PairingViewModel.swift |  63 ++++-
 ios/App/WebTerm/Wiring/AdaptiveRootView.swift |  19 ++
 ios/App/WebTerm/Wiring/AppCoordinator.swift   |  12 +
 ios/App/WebTerm/Wiring/AppEnvironment.swift   |  17 +-
 ios/App/WebTerm/Wiring/RootView.swift         |   4 +-
 ios/App/WebTerm/Wiring/SplitRootView.swift    |   3 +-
 .../Wiring/URLSessionHTTPTransport.swift      |  77 +++++-
 ios/Packages/ClientTLS/Package.swift          |  22 ++
 .../ClientTLS/CertificateSummary.swift        | 188 ++++++++++++++
 .../Sources/ClientTLS/ClientIdentity.swift    |  55 ++++
 .../ClientTLS/ClientTLSSessionDelegate.swift  |  36 +++
 .../KeychainClientIdentityStore.swift         | 200 ++++++++++++++
 .../MutualTLSChallengeResponder.swift         |  73 ++++++
 .../Sources/ClientTLS/PKCS12Importer.swift    |  89 +++++++
 .../ClientIdentityStoreTests.swift            |  62 +++++
 .../Tests/ClientTLSTests/Fixtures.swift       |  33 +++
 .../MutualTLSChallengeResponderTests.swift    | 114 ++++++++
 .../ClientTLSTests/PKCS12ImporterTests.swift  |  69 +++++
 ios/Packages/SessionCore/Package.swift        |  10 +-
 .../SessionCore/URLSessionTermTransport.swift |  84 +++++-
 .../URLSessionTermTransportTests.swift        |  32 +++
 ios/project.yml                               |   4 +
 25 files changed, 1510 insertions(+), 30 deletions(-)
 create mode 100644 ios/App/WebTerm/Screens/ClientCertScreen.swift
 create mode 100644 ios/Packages/ClientTLS/Package.swift
 create mode 100644 ios/Packages/ClientTLS/Sources/ClientTLS/CertificateSummary.swift
 create mode 100644 ios/Packages/ClientTLS/Sources/ClientTLS/ClientIdentity.swift
 create mode 100644 ios/Packages/ClientTLS/Sources/ClientTLS/ClientTLSSessionDelegate.swift
 create mode 100644 ios/Packages/ClientTLS/Sources/ClientTLS/KeychainClientIdentityStore.swift
 create mode 100644 ios/Packages/ClientTLS/Sources/ClientTLS/MutualTLSChallengeResponder.swift
 create mode 100644 ios/Packages/ClientTLS/Sources/ClientTLS/PKCS12Importer.swift
 create mode 100644 ios/Packages/ClientTLS/Tests/ClientTLSTests/ClientIdentityStoreTests.swift
 create mode 100644 ios/Packages/ClientTLS/Tests/ClientTLSTests/Fixtures.swift
 create mode 100644 ios/Packages/ClientTLS/Tests/ClientTLSTests/MutualTLSChallengeResponderTests.swift
 create mode 100644 ios/Packages/ClientTLS/Tests/ClientTLSTests/PKCS12ImporterTests.swift

diff --git a/ios/App/WebTerm/Components/SessionThumbnail.swift b/ios/App/WebTerm/Components/SessionThumbnail.swift
index 4619f5d..4b05e45 100644
--- a/ios/App/WebTerm/Components/SessionThumbnail.swift
+++ b/ios/App/WebTerm/Components/SessionThumbnail.swift
@@ -1,4 +1,5 @@
 import APIClient
+import ClientTLS
 import Foundation
 import os
 import SwiftUI
@@ -225,12 +226,19 @@ final class SessionThumbnailPipeline {
         cache = SessionThumbnailCache(maxEntries: maxCacheEntries)
     }
 
-    /// 生产装配：共享一个 ephemeral URLSession（preview 字节可能含屏上密钥，
-    /// 内存缓存 only——同 T-iOS-19 对 RO GET 的裁定）。
+    /// 生产装配：ephemeral URLSession（preview 字节可能含屏上密钥，内存缓存
+    /// only——同 T-iOS-19 对 RO GET 的裁定），并携带 C-iOS-2 的设备证书身份，
+    /// 这样对隧道主机的预览取数也能通过 mTLS（否则缩略图会被 nginx 拒握手）。
+    /// 身份经 provider 每次握手时按需从 keychain 载入（MEDIUM 无需重启修复：
+    /// 中途导入的证书下次取数即生效；缺证=nil，对本地主机无副作用）。
     static func live() -> SessionThumbnailPipeline {
-        SessionThumbnailPipeline(
+        let identityStore = KeychainClientIdentityStore()
+        let transport = URLSessionHTTPTransport(identityProvider: {
+            identityStore.loadedIdentityOrNil()
+        })
+        return SessionThumbnailPipeline(
             loader: { request in
-                try await APIClient(endpoint: request.endpoint, http: liveTransport)
+                try await APIClient(endpoint: request.endpoint, http: transport)
                     .preview(id: request.sessionId)
             },
             renderer: { data, cols, rows in
@@ -239,8 +247,6 @@ final class SessionThumbnailPipeline {
         )
     }
 
-    private static let liveTransport = URLSessionHTTPTransport()
-
     /// 取（或渲染）一张缩略图。永不抛错：任何失败显式降级为 `.placeholder`
     /// （占位图就是缩略图的错误 UI；细节进内部日志，绝不静默无痕）。
     func thumbnail(for request: SessionThumbnailRequest) async -> SessionThumbnailImage {
diff --git a/ios/App/WebTerm/Screens/ClientCertScreen.swift b/ios/App/WebTerm/Screens/ClientCertScreen.swift
new file mode 100644
index 0000000..679dd47
--- /dev/null
+++ b/ios/App/WebTerm/Screens/ClientCertScreen.swift
@@ -0,0 +1,243 @@
+import ClientTLS
+import Foundation
+import Observation
+import SwiftUI
+import UniformTypeIdentifiers
+
+/// C-iOS-3 · Device-certificate install / rotation screen.
+///
+/// Flow: `.fileImporter([.pkcs12])` → secure passphrase → import (validates via
+/// `SecPKCS12Import`) → persist in the keychain → show issuer CN + expiry, with
+/// replace/rotate + remove. This is the in-app, app-sandboxed install path (a
+/// `.p12` delivered via AirDrop/Files), NOT a configuration profile.
+///
+/// INTEGRATION NOTE: presenting this screen needs a one-line nav/Settings entry
+/// ("Device certificate") in the app chrome (RootView / PairingScreen), which
+/// live outside this task's ownership. The screen is fully self-contained so
+/// that wiring is a single `NavigationLink { ClientCertScreen() }`.
+struct ClientCertScreen: View {
+    @State private var model: ClientCertViewModel
+
+    init(model: ClientCertViewModel = ClientCertViewModel()) {
+        _model = State(initialValue: model)
+    }
+
+    var body: some View {
+        Form {
+            installedSection
+            importSection
+            if model.summary != nil {
+                removeSection
+            }
+        }
+        .navigationTitle(ClientCertCopy.title)
+        .fileImporter(
+            isPresented: $model.isPickingFile,
+            allowedContentTypes: [.pkcs12],
+            allowsMultipleSelection: false
+        ) { result in
+            model.handleFileSelection(result)
+        }
+        .task { model.refresh() }
+    }
+
+    // MARK: - Sections
+
+    @ViewBuilder private var installedSection: some View {
+        Section(ClientCertCopy.installedHeader) {
+            if let summary = model.summary {
+                LabeledContent(ClientCertCopy.subject, value: summary.subjectCommonName ?? "—")
+                LabeledContent(ClientCertCopy.issuer, value: summary.issuerCommonName ?? "—")
+                LabeledContent(ClientCertCopy.expiry, value: model.expiryText(summary))
+                if summary.isExpired() {
+                    Label(ClientCertCopy.expiredWarning, systemImage: "exclamationmark.triangle")
+                        .foregroundStyle(.orange)
+                }
+            } else {
+                Text(ClientCertCopy.noneInstalled).foregroundStyle(.secondary)
+            }
+        }
+    }
+
+    @ViewBuilder private var importSection: some View {
+        Section {
+            if let name = model.pendingFileName {
+                LabeledContent(ClientCertCopy.selectedFile, value: name)
+                SecureField(ClientCertCopy.passphrase, text: $model.passphrase)
+                    .textContentType(.password)
+                    .autocorrectionDisabled()
+                Button(ClientCertCopy.importAction) { model.importPending() }
+                    .disabled(!model.canImport)
+                Button(ClientCertCopy.cancelAction, role: .cancel) { model.clearPending() }
+            } else {
+                Button {
+                    model.beginPicking()
+                } label: {
+                    Label(
+                        model.summary == nil
+                            ? ClientCertCopy.chooseFile
+                            : ClientCertCopy.replaceFile,
+                        systemImage: "doc.badge.plus"
+                    )
+                }
+            }
+            if let error = model.errorMessage {
+                Text(error).foregroundStyle(.red).font(.footnote)
+            }
+        } header: {
+            Text(model.summary == nil ? ClientCertCopy.importHeader : ClientCertCopy.rotateHeader)
+        } footer: {
+            Text(ClientCertCopy.importFooter)
+        }
+    }
+
+    @ViewBuilder private var removeSection: some View {
+        Section {
+            Button(ClientCertCopy.removeAction, role: .destructive) { model.remove() }
+        }
+    }
+}
+
+/// State machine for the install screen. Errors are mapped to actionable copy
+/// and never swallowed; a failed import leaves any prior identity intact.
+@MainActor
+@Observable
+final class ClientCertViewModel {
+    private(set) var summary: ClientCertificateSummary?
+    var isPickingFile = false
+    var passphrase = ""
+    private(set) var pendingData: Data?
+    private(set) var pendingFileName: String?
+    private(set) var errorMessage: String?
+
+    @ObservationIgnored private let store: any ClientIdentityStore
+
+    init(store: any ClientIdentityStore = KeychainClientIdentityStore()) {
+        self.store = store
+    }
+
+    var canImport: Bool { pendingData != nil && !passphrase.isEmpty }
+
+    func refresh() {
+        do {
+            summary = try store.loadSummary()
+        } catch {
+            summary = nil
+            errorMessage = ClientCertCopy.loadFailed
+        }
+    }
+
+    func beginPicking() {
+        errorMessage = nil
+        isPickingFile = true
+    }
+
+    func handleFileSelection(_ result: Result<[URL], Error>) {
+        switch result {
+        case .failure:
+            errorMessage = ClientCertCopy.fileReadFailed
+        case .success(let urls):
+            guard let url = urls.first else { return }
+            readFile(at: url)
+        }
+    }
+
+    private func readFile(at url: URL) {
+        let didAccess = url.startAccessingSecurityScopedResource()
+        defer { if didAccess { url.stopAccessingSecurityScopedResource() } }
+        do {
+            pendingData = try Data(contentsOf: url)
+            pendingFileName = url.lastPathComponent
+            passphrase = ""
+            errorMessage = nil
+        } catch {
+            pendingData = nil
+            pendingFileName = nil
+            errorMessage = ClientCertCopy.fileReadFailed
+        }
+    }
+
+    func importPending() {
+        guard let data = pendingData else { return }
+        do {
+            try store.save(p12Data: data, passphrase: passphrase)
+            clearPending()
+            refresh()
+        } catch {
+            errorMessage = Self.copy(for: error)
+        }
+    }
+
+    func clearPending() {
+        pendingData = nil
+        pendingFileName = nil
+        passphrase = ""
+        errorMessage = nil
+    }
+
+    func remove() {
+        do {
+            try store.remove()
+            summary = nil
+            errorMessage = nil
+        } catch {
+            errorMessage = ClientCertCopy.removeFailed
+        }
+    }
+
+    func expiryText(_ summary: ClientCertificateSummary) -> String {
+        guard let notAfter = summary.notAfter else { return "—" }
+        return notAfter.formatted(date: .abbreviated, time: .omitted)
+    }
+
+    /// Map an import/storage error to install-UX copy (never swallowed).
+    private static func copy(for error: any Error) -> String {
+        switch error {
+        case PKCS12ImportError.wrongPassphrase:
+            return ClientCertCopy.errWrongPassphrase
+        case PKCS12ImportError.corruptFile:
+            return ClientCertCopy.errCorruptFile
+        case PKCS12ImportError.unsupported:
+            return ClientCertCopy.errUnsupported
+        case PKCS12ImportError.noIdentity:
+            return ClientCertCopy.errNoIdentity
+        case ClientIdentityStoreError.keychain, ClientIdentityStoreError.corruptStoredBlob:
+            return ClientCertCopy.errKeychain
+        default:
+            return ClientCertCopy.errUnknown
+        }
+    }
+}
+
+/// User-facing copy (Chinese, matching the rest of the app).
+enum ClientCertCopy {
+    static let title = "设备证书"
+    static let installedHeader = "已安装证书"
+    static let subject = "设备 (CN)"
+    static let issuer = "签发 CA"
+    static let expiry = "有效期至"
+    static let expiredWarning = "证书已过期，请重新导入。"
+    static let noneInstalled = "尚未安装设备证书。"
+
+    static let importHeader = "导入证书"
+    static let rotateHeader = "替换证书"
+    static let chooseFile = "选择 .p12 文件"
+    static let replaceFile = "选择新的 .p12 文件"
+    static let selectedFile = "已选文件"
+    static let passphrase = "证书密码"
+    static let importAction = "导入"
+    static let cancelAction = "取消"
+    static let removeAction = "移除证书"
+    static let importFooter =
+        "证书用于连接你自己的隧道主机 (mTLS)。通过 AirDrop / 文件 把 .p12 传到本机后在此导入；证书与密码只保存在本设备钥匙串。"
+
+    static let errWrongPassphrase = "密码错误，请重试。"
+    static let errCorruptFile = "文件无法识别，请确认是有效的 .p12 证书。"
+    static let errUnsupported = "证书格式不受支持（请用 openssl pkcs12 -export -legacy 生成）。"
+    static let errNoIdentity = "该 .p12 不含身份（缺少私钥），无法用于客户端认证。"
+    static let errKeychain = "保存到钥匙串失败，请重试。"
+    static let errUnknown = "导入失败，请重试。"
+    static let loadFailed = "读取已安装证书失败。"
+    static let fileReadFailed = "无法读取所选文件。"
+    static let removeFailed = "移除证书失败，请重试。"
+}
diff --git a/ios/App/WebTerm/Screens/SessionListScreen.swift b/ios/App/WebTerm/Screens/SessionListScreen.swift
index 39a3a3f..7113323 100644
--- a/ios/App/WebTerm/Screens/SessionListScreen.swift
+++ b/ios/App/WebTerm/Screens/SessionListScreen.swift
@@ -23,6 +23,12 @@ struct SessionListScreen: View {
     var onOpen: (SessionListViewModel.OpenRequest) -> Void = { _ in }
     /// Host-switch header hook: "添加主机" entry (pairing sheet, T-iOS-15).
     var onAddHost: () -> Void = {}
+    /// C-iOS-3 (HIGH reachability fix) · "设备证书" entry — presents
+    /// `ClientCertScreen` (import / rotate the mTLS device cert). The device
+    /// cert is a global concern, but the toolbar host-menu is the app's only
+    /// settings-like surface and is present in every empty state, so this is the
+    /// nav idiom that makes the orphaned screen reachable.
+    var onDeviceCert: () -> Void = {}
     /// T-iOS-28 (additive slot) · shared thumbnail pipeline: one cache + one
     /// render-concurrency gate across ALL rows (scrolling must never spawn
     /// unbounded offscreen terminals). `@State` keeps it stable across body
@@ -213,6 +219,12 @@ struct SessionListScreen: View {
                 } label: {
                     Label(ScreenCopy.addHost, systemImage: "plus")
                 }
+                Button {
+                    onDeviceCert()
+                } label: {
+                    Label(ScreenCopy.deviceCert, systemImage: "lock.shield")
+                }
+                .accessibilityIdentifier("sessions.deviceCert")
             } label: {
                 Label(
                     viewModel.activeHost?.name ?? ScreenCopy.hostMenuFallback,
@@ -342,6 +354,7 @@ private enum ScreenCopy {
     static let newSession = "新建会话"
     static let kill = "结束"
     static let addHost = "配对新主机"
+    static let deviceCert = "设备证书"
     static let hostMenuFallback = "主机"
     static let notPairedTitle = "还没有配对的主机"
     static let notPairedHint = "先配对你电脑上的 web-terminal（扫码或手输地址），会话会出现在这里。"
diff --git a/ios/App/WebTerm/ViewModels/PairingViewModel.swift b/ios/App/WebTerm/ViewModels/PairingViewModel.swift
index a96dacd..7db901f 100644
--- a/ios/App/WebTerm/ViewModels/PairingViewModel.swift
+++ b/ios/App/WebTerm/ViewModels/PairingViewModel.swift
@@ -1,4 +1,5 @@
 import APIClient
+import ClientTLS
 import Foundation
 import HostRegistry
 import Observation
@@ -116,10 +117,21 @@ final class PairingViewModel {
 
     @ObservationIgnored private let store: any HostStore
     @ObservationIgnored private let probe: Probe
+    /// C-iOS-3 · Whether a device client certificate is installed. Used to gate
+    /// the probe for tunnel hosts (mTLS-only). Injected so tests control it;
+    /// production reads the keychain. Defaulted so existing call sites compile.
+    @ObservationIgnored private let isDeviceCertInstalled: @Sendable () -> Bool
 
-    init(store: any HostStore, probe: @escaping Probe) {
+    init(
+        store: any HostStore,
+        probe: @escaping Probe,
+        isDeviceCertInstalled: @escaping @Sendable () -> Bool = {
+            KeychainClientIdentityStore().hasInstalledIdentity()
+        }
+    ) {
         self.store = store
         self.probe = probe
+        self.isDeviceCertInstalled = isDeviceCertInstalled
     }
 
     // MARK: - Input boundaries (untrusted, validated via HostEndpoint)
@@ -205,10 +217,20 @@ final class PairingViewModel {
 
     private func runProbe(for pending: PendingHost) async {
         needsPublicRiskAcknowledgement = false
+        // C-iOS-3 · Tunnel hosts are mTLS-only: refuse to probe (which would
+        // fail at the TLS handshake) until a device certificate is installed.
+        // This is the single choke point both confirmConnect and retry funnel
+        // through, so the gate can't be bypassed via retry().
+        if Self.isTunnelHost(pending.endpoint), !isDeviceCertInstalled() {
+            phase = .failed(pending, FailureDisplay(
+                message: PairingCopy.deviceCertRequired, action: .retry
+            ))
+            return
+        }
         phase = .probing(pending)
         switch await probe(pending.endpoint) {
         case .failure(let error):
-            phase = .failed(pending, Self.display(for: error))
+            phase = .failed(pending, Self.display(for: error, endpoint: pending.endpoint))
         case .success(let endpoint):
             await storePairedHost(endpoint: endpoint, pending: pending)
         }
@@ -239,6 +261,19 @@ final class PairingViewModel {
 
     // MARK: - PairingError → copy + action (task RED list, one case each)
 
+    /// C-iOS-3 · Host-aware display. nginx rejects an invalid/absent/revoked
+    /// client cert at the TLS layer; URLSession surfaces that as
+    /// secureConnectionFailed / connection-reset → `PairingError.classify` maps
+    /// it to `.tlsFailure` ("server cert invalid"), which is the WRONG diagnosis
+    /// for an mTLS tunnel host. Re-map that one case to the device-cert copy;
+    /// everything else falls through to the per-case mapping.
+    static func display(for error: PairingError, endpoint: HostEndpoint) -> FailureDisplay {
+        if case .tlsFailure = error, isTunnelHost(endpoint) {
+            return FailureDisplay(message: PairingCopy.clientCertRejected, action: .retry)
+        }
+        return display(for: error)
+    }
+
     static func display(for error: PairingError) -> FailureDisplay {
         switch error {
         case .localNetworkDenied:
@@ -270,6 +305,14 @@ final class PairingViewModel {
     /// block regardless of scheme (§5.4 table: https is included in the
     /// public-host confirm warning); otherwise https clears every notice.
     static func warning(for endpoint: HostEndpoint) -> SecurityWarning {
+        // C-iOS-3 · A *.terminal.yaojia.wang tunnel host is gated by the device
+        // client certificate (mTLS), so the "anyone who can reach the port gets
+        // a shell" blocking warning is FALSE here and would only deter the
+        // intended flow. The real gate is the cert-install check in runProbe.
+        // Genuinely public NON-tunnel hosts still hit .publicHostBlocking below.
+        if isTunnelHost(endpoint) {
+            return .none
+        }
         let hostClass = classifyHost(endpoint.baseURL.host ?? "")
         if hostClass == .publicHost {
             return .publicHostBlocking
@@ -353,8 +396,17 @@ final class PairingViewModel {
         return octets
     }
 
+    /// C-iOS-3 · A native mTLS reverse-tunnel host (`<name>.terminal.yaojia.wang`).
+    /// These reach a loopback base app through the VPS and are protected ONLY by
+    /// the device client certificate — hence the softened warning + the
+    /// cert-install gate + the client-cert-rejected re-classification.
+    static func isTunnelHost(_ endpoint: HostEndpoint) -> Bool {
+        (endpoint.baseURL.host ?? "").lowercased().hasSuffix(tunnelZoneSuffix)
+    }
+
     // MARK: - Named constants (no magic values, plan §4)
 
+    private static let tunnelZoneSuffix = ".terminal.yaojia.wang"
     private static let schemeSeparator = "://"
     private static let defaultManualScheme = "http://"
     private static let httpsScheme = "https"
@@ -385,6 +437,13 @@ enum PairingCopy {
         "TLS 连接失败：证书无效或不受信任。"
     static let timeout =
         "连接超时。请确认主机在线、与手机在同一网络后重试。"
+    /// C-iOS-3 · Tunnel host reached without a device certificate installed.
+    static let deviceCertRequired =
+        "请先安装本设备证书：到 设置 →「设备证书」导入 .p12 后，再连接该隧道主机。"
+    /// C-iOS-3 · nginx rejected the presented client certificate (invalid /
+    /// revoked). Surfaced in place of the mis-classified "server cert invalid".
+    static let clientCertRejected =
+        "本设备证书无效或已吊销，请重新导入。"
 
     static func hostUnreachable(_ underlying: String) -> String {
         "无法连接主机：\(underlying)"
diff --git a/ios/App/WebTerm/Wiring/AdaptiveRootView.swift b/ios/App/WebTerm/Wiring/AdaptiveRootView.swift
index fb25f0b..716e380 100644
--- a/ios/App/WebTerm/Wiring/AdaptiveRootView.swift
+++ b/ios/App/WebTerm/Wiring/AdaptiveRootView.swift
@@ -51,6 +51,9 @@ struct AdaptiveRootView: View {
         ) {
             projectsSheet
         }
+        .sheet(isPresented: $coordinator.isDeviceCertPresented) {
+            deviceCertSheet
+        }
     }
 
     // MARK: - Layout branch (the SOLE size-class consumer)
@@ -107,4 +110,20 @@ struct AdaptiveRootView: View {
             }
         }
     }
+
+    // MARK: - Device certificate sheet (C-iOS-3, HIGH reachability fix)
+
+    /// 自带 NavigationStack（`ClientCertScreen` 用 `.navigationTitle`）+ 右上「完成」
+    /// 关闭按钮，保证导入 .p12 后能明确返回。`ClientCertScreen` 自持
+    /// `ClientCertViewModel`（keychain store），此处零依赖注入。
+    @ViewBuilder private var deviceCertSheet: some View {
+        NavigationStack {
+            ClientCertScreen()
+                .toolbar {
+                    ToolbarItem(placement: .topBarTrailing) {
+                        Button(RootCopy.done) { coordinator.isDeviceCertPresented = false }
+                    }
+                }
+        }
+    }
 }
diff --git a/ios/App/WebTerm/Wiring/AppCoordinator.swift b/ios/App/WebTerm/Wiring/AppCoordinator.swift
index 4ba86bc..0f1b30e 100644
--- a/ios/App/WebTerm/Wiring/AppCoordinator.swift
+++ b/ios/App/WebTerm/Wiring/AppCoordinator.swift
@@ -31,6 +31,11 @@ final class AppCoordinator {
     /// prefs 每次进入都重新拉取。
     private(set) var projectsViewModel: ProjectsViewModel?
     var isProjectsPresented = false
+    /// C-iOS-3 (HIGH reachability fix) · "设备证书" sheet (import / rotate the
+    /// mTLS device cert via `ClientCertScreen`). No VM state — the screen owns
+    /// its own `ClientCertViewModel` over the keychain store; dismissal needs no
+    /// refresh because the transports resolve the identity lazily per connection.
+    var isDeviceCertPresented = false
 
     let sessionList: SessionListViewModel
     @ObservationIgnored let environment: AppEnvironment
@@ -108,6 +113,13 @@ final class AppCoordinator {
         projectsViewModel = nil
     }
 
+    // MARK: - Device certificate (C-iOS-3)
+
+    /// Toolbar host-menu 入口：呈现设备证书导入/轮换 sheet。
+    func presentDeviceCert() {
+        isDeviceCertPresented = true
+    }
+
     /// "在此仓库开新会话"：关 sheet → fresh spawn（`attach(null, cwd)`）+
     /// attach 后注入 `claude\r`（帧序由 engine 的 attach-first 队列保证）。
     func openProject(_ request: ProjectOpenRequest) {
diff --git a/ios/App/WebTerm/Wiring/AppEnvironment.swift b/ios/App/WebTerm/Wiring/AppEnvironment.swift
index db6fe0a..f7a5b35 100644
--- a/ios/App/WebTerm/Wiring/AppEnvironment.swift
+++ b/ios/App/WebTerm/Wiring/AppEnvironment.swift
@@ -1,4 +1,5 @@
 import APIClient
+import ClientTLS
 import Foundation
 import HostRegistry
 import SessionCore
@@ -37,8 +38,20 @@ struct AppEnvironment: Sendable {
     var unreadStore: any UnreadWatermarkStore = UserDefaultsUnreadWatermarkStore()
 
     static func production() -> AppEnvironment {
-        let http = URLSessionHTTPTransport()
-        let termTransport = URLSessionTermTransport()
+        // C-iOS-2 (MEDIUM no-relaunch fix) · Resolve the installed device client
+        // identity LAZILY from the keychain on each connect/challenge, injected
+        // into BOTH transports + the probe as a provider. This way a certificate
+        // imported from the "设备证书" screen takes effect on the NEXT connection
+        // without relaunching — a snapshot captured here would stay stale. A
+        // missing cert is the normal pre-install state (→ nil); genuine faults
+        // are logged, not fatal (`loadedIdentityOrNil`). mTLS challenges only
+        // fire for tunnel hosts, so a `nil` result is inert for local hosts.
+        let identityStore = KeychainClientIdentityStore()
+        let identityProvider: @Sendable () -> ClientIdentity? = {
+            identityStore.loadedIdentityOrNil()
+        }
+        let http = URLSessionHTTPTransport(identityProvider: identityProvider)
+        let termTransport = URLSessionTermTransport(identityProvider: identityProvider)
         return AppEnvironment(
             hostStore: KeychainHostStore(),
             lastSessionStore: UserDefaultsLastSessionStore(),
diff --git a/ios/App/WebTerm/Wiring/RootView.swift b/ios/App/WebTerm/Wiring/RootView.swift
index eaa32eb..cd22681 100644
--- a/ios/App/WebTerm/Wiring/RootView.swift
+++ b/ios/App/WebTerm/Wiring/RootView.swift
@@ -74,7 +74,8 @@ struct StackRootView: View {
         SessionListScreen(
             viewModel: coordinator.sessionList,
             onOpen: { coordinator.open($0) },
-            onAddHost: { coordinator.presentAddHost() }
+            onAddHost: { coordinator.presentAddHost() },
+            onDeviceCert: { coordinator.presentDeviceCert() }
         )
         .safeAreaInset(edge: .bottom) { continueLastBanner }
         // 横幅出现/消失走 DS 动效（reduceMotion 时塌成瞬切，无位移）。
@@ -178,4 +179,5 @@ struct ProjectsToolbarItem: ToolbarContent {
 enum RootCopy {
     static let continueLast = "继续上次会话"
     static let projects = "项目"
+    static let done = "完成"
 }
diff --git a/ios/App/WebTerm/Wiring/SplitRootView.swift b/ios/App/WebTerm/Wiring/SplitRootView.swift
index 6a9a678..97bb24d 100644
--- a/ios/App/WebTerm/Wiring/SplitRootView.swift
+++ b/ios/App/WebTerm/Wiring/SplitRootView.swift
@@ -39,7 +39,8 @@ struct SplitRootView: View {
                 // 分栏只是又一个触发面：映射到同一 selectSidebarItem 路由。
                 coordinator.selectSidebarItem(sidebarItem(for: request))
             },
-            onAddHost: { coordinator.presentAddHost() }
+            onAddHost: { coordinator.presentAddHost() },
+            onDeviceCert: { coordinator.presentDeviceCert() }
         )
         .safeAreaInset(edge: .bottom) { continueLastBanner }
         .animation(
diff --git a/ios/App/WebTerm/Wiring/URLSessionHTTPTransport.swift b/ios/App/WebTerm/Wiring/URLSessionHTTPTransport.swift
index 4b7f1cc..0bdab89 100644
--- a/ios/App/WebTerm/Wiring/URLSessionHTTPTransport.swift
+++ b/ios/App/WebTerm/Wiring/URLSessionHTTPTransport.swift
@@ -1,3 +1,4 @@
+import ClientTLS
 import Foundation
 import WireProtocol
 
@@ -9,14 +10,39 @@ import WireProtocol
 /// bypass that single audited point (review CRITICAL).
 struct URLSessionHTTPTransport: HTTPTransport {
     private let session: URLSession
+    /// Strong reference to the mTLS delegate. URLSession retains its delegate
+    /// until invalidated, but this ephemeral session is never explicitly
+    /// invalidated, so holding it here documents the ownership and keeps the
+    /// transport a self-contained value.
+    private let tlsDelegate: LazyClientTLSSessionDelegate
 
-    /// Default is EPHEMERAL, not `.shared` (T-iOS-19 finding): RO GET bodies
-    /// include `/live-sessions/:id/preview` — raw terminal ring-buffer bytes
-    /// that may contain printed secrets — and `.shared`'s default URLCache
-    /// writes responses to disk. Ephemeral keeps them memory-only, matching
-    /// the WS transport and the privacy-shade posture.
-    init(session: URLSession = URLSession(configuration: .ephemeral)) {
-        self.session = session
+    /// Fixed-identity convenience (snapshot callers / tests): wraps a constant
+    /// provider, so behaviour is identical to capturing the identity directly.
+    init(identity: ClientIdentity? = nil) {
+        self.init(identityProvider: { identity })
+    }
+
+    /// C-iOS-2 (MEDIUM no-relaunch fix) · The session's mTLS delegate resolves
+    /// the device identity LAZILY, per client-certificate challenge, from
+    /// `identityProvider`. A `ClientCertificate` challenge from a tunneled host
+    /// is thus answered with whatever cert is installed AT CHALLENGE TIME — so a
+    /// certificate imported mid-run is presented on the NEXT TLS handshake
+    /// without an app relaunch (a snapshot captured here would stay stale). The
+    /// session itself stays a single long-lived value (no per-request churn).
+    /// Local http/https hosts never issue that challenge, so the provider is
+    /// never even consulted for them (and a `nil` result is inert regardless).
+    ///
+    /// EPHEMERAL, not `.shared` (T-iOS-19 finding): RO GET bodies include
+    /// `/live-sessions/:id/preview` — raw terminal ring-buffer bytes that may
+    /// contain printed secrets — and `.shared`'s default URLCache writes
+    /// responses to disk. Ephemeral keeps them memory-only, matching the WS
+    /// transport and the privacy-shade posture.
+    init(identityProvider: @escaping @Sendable () -> ClientIdentity?) {
+        let delegate = LazyClientTLSSessionDelegate(identityProvider: identityProvider)
+        self.tlsDelegate = delegate
+        self.session = URLSession(
+            configuration: .ephemeral, delegate: delegate, delegateQueue: nil
+        )
     }
 
     func send(_ request: URLRequest) async throws -> (Data, HTTPURLResponse) {
@@ -29,3 +55,40 @@ struct URLSessionHTTPTransport: HTTPTransport {
         return (data, httpResponse)
     }
 }
+
+/// C-iOS-2 (MEDIUM no-relaunch fix) · Session-level mTLS delegate that resolves
+/// the device identity FRESH per client-certificate challenge — the App-layer
+/// twin of ClientTLS's fixed-identity `ClientTLSSessionDelegate` (which captures
+/// the identity once). The provider is only consulted for a `ClientCertificate`
+/// challenge, so a `ServerTrust` challenge never triggers a keychain read; the
+/// pure decision itself is delegated to the shared `MutualTLSChallengeResponder`
+/// (single truth table, unit-tested in ClientTLS).
+///
+/// `@unchecked Sendable`: URLSession retains its delegate and invokes it from
+/// arbitrary queues; every stored field is an immutable `let` over a `@Sendable`
+/// value (the provider is `@Sendable`, the responder is stateless).
+private final class LazyClientTLSSessionDelegate:
+    NSObject, URLSessionDelegate, @unchecked Sendable {
+    private let identityProvider: @Sendable () -> ClientIdentity?
+    private let responder = MutualTLSChallengeResponder()
+
+    init(identityProvider: @escaping @Sendable () -> ClientIdentity?) {
+        self.identityProvider = identityProvider
+        super.init()
+    }
+
+    func urlSession(
+        _ session: URLSession,
+        didReceive challenge: URLAuthenticationChallenge,
+        completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void
+    ) {
+        // Only a client-certificate challenge needs the identity; resolving it
+        // for a server-trust challenge would do a needless keychain read/import
+        // on every HTTPS handshake.
+        let isClientCert = challenge.protectionSpace.authenticationMethod
+            == NSURLAuthenticationMethodClientCertificate
+        let identity = isClientCert ? identityProvider() : nil
+        let resolution = responder.resolve(challenge, identity: identity)
+        completionHandler(resolution.disposition, resolution.credential)
+    }
+}
diff --git a/ios/Packages/ClientTLS/Package.swift b/ios/Packages/ClientTLS/Package.swift
new file mode 100644
index 0000000..6b5f2c2
--- /dev/null
+++ b/ios/Packages/ClientTLS/Package.swift
@@ -0,0 +1,22 @@
+// swift-tools-version: 6.0
+// C-iOS-1 · Device client-certificate (mutual-TLS) leaf package.
+//
+// Standalone, no local-package dependencies — imports ONLY Security/Foundation.
+// It is a downward leaf: SessionCore and the App target may depend on it, it
+// depends on nothing in this workspace. This keeps the pure, unit-testable
+// mTLS logic (identity wrapper, PKCS#12 import, challenge responder) isolated
+// from the WS/HTTP transport plumbing that consumes it.
+import PackageDescription
+
+let package = Package(
+    name: "ClientTLS",
+    platforms: [.iOS(.v17), .macOS(.v14)],
+    products: [
+        .library(name: "ClientTLS", targets: ["ClientTLS"]),
+    ],
+    targets: [
+        .target(name: "ClientTLS"),
+        .testTarget(name: "ClientTLSTests", dependencies: ["ClientTLS"]),
+    ],
+    swiftLanguageModes: [.v6]
+)
diff --git a/ios/Packages/ClientTLS/Sources/ClientTLS/CertificateSummary.swift b/ios/Packages/ClientTLS/Sources/ClientTLS/CertificateSummary.swift
new file mode 100644
index 0000000..190ab87
--- /dev/null
+++ b/ios/Packages/ClientTLS/Sources/ClientTLS/CertificateSummary.swift
@@ -0,0 +1,188 @@
+import Foundation
+import Security
+
+/// C-iOS-3 · Display summary of a device certificate, shown on the install /
+/// rotation screen so the user can confirm *which* cert is active and *when*
+/// it expires before relying on it.
+public struct ClientCertificateSummary: Equatable, Sendable {
+    /// Subject common name — the device/leaf CN (e.g. `t1-iphone`).
+    public let subjectCommonName: String?
+    /// Issuer common name — the device-CA CN (e.g. `webterm-device-ca`).
+    public let issuerCommonName: String?
+    /// Not-after date; `nil` if it could not be parsed.
+    public let notAfter: Date?
+
+    public init(subjectCommonName: String?, issuerCommonName: String?, notAfter: Date?) {
+        self.subjectCommonName = subjectCommonName
+        self.issuerCommonName = issuerCommonName
+        self.notAfter = notAfter
+    }
+
+    /// Expired relative to `now` (defaults to the current instant). Unknown
+    /// expiry is treated as NOT expired (fail-open for display only — the TLS
+    /// stack, not this label, is the real gate).
+    public func isExpired(asOf now: Date = Date()) -> Bool {
+        guard let notAfter else { return false }
+        return notAfter < now
+    }
+}
+
+/// Reads the display fields off a `SecCertificate`.
+///
+/// Implemented as a minimal X.509 DER walk over `SecCertificateCopyData` rather
+/// than `SecCertificateCopyValues`, because that API and its `kSecOID*` /
+/// `kSecPropertyKey*` constants are **macOS-only** — unavailable on iOS, which
+/// is the real deployment target. The DER walk is identical on both platforms
+/// and unit-testable against the fixture. Any parse miss degrades to `nil`
+/// fields (the summary is display-only; the TLS stack is the gate).
+enum CertificateInspector {
+    static func summary(of certificate: SecCertificate) -> ClientCertificateSummary {
+        let der = [UInt8](SecCertificateCopyData(certificate) as Data)
+        let fields = X509Fields.parse(der: der)
+        return ClientCertificateSummary(
+            subjectCommonName: fields?.subjectCommonName,
+            issuerCommonName: fields?.issuerCommonName,
+            notAfter: fields?.notAfter
+        )
+    }
+}
+
+// MARK: - Minimal ASN.1 DER reader
+
+/// One tag-length-value element, as byte ranges into the source buffer.
+private struct DERElement {
+    let tag: UInt8
+    let valueStart: Int
+    let valueEnd: Int
+}
+
+private enum DER {
+    /// DER tags used here.
+    static let sequence: UInt8 = 0x30
+    static let set: UInt8 = 0x31
+    static let oid: UInt8 = 0x06
+    static let contextTag0: UInt8 = 0xA0 // [0] EXPLICIT (X.509 version)
+    static let utcTime: UInt8 = 0x17
+    static let generalizedTime: UInt8 = 0x18
+
+    /// Read a single TLV at `start`. Returns the element and the index just
+    /// past it, or `nil` on any malformed length/overrun (defensive: the cert
+    /// bytes come from the system but are still parsed as untrusted input).
+    static func read(_ bytes: [UInt8], at start: Int) -> DERElement? {
+        guard start >= 0, start + 1 < bytes.count else { return nil }
+        let tag = bytes[start]
+        var index = start + 1
+        let firstLengthByte = bytes[index]
+        index += 1
+        var length = 0
+        if firstLengthByte & 0x80 == 0 {
+            length = Int(firstLengthByte)
+        } else {
+            let byteCount = Int(firstLengthByte & 0x7F)
+            guard byteCount > 0, byteCount <= 4, index + byteCount <= bytes.count else {
+                return nil
+            }
+            for _ in 0..<byteCount {
+                length = (length << 8) | Int(bytes[index])
+                index += 1
+            }
+        }
+        let valueEnd = index + length
+        guard length >= 0, valueEnd <= bytes.count else { return nil }
+        return DERElement(tag: tag, valueStart: index, valueEnd: valueEnd)
+    }
+
+    /// Split a constructed value `[start, end)` into its immediate children.
+    static func children(_ bytes: [UInt8], from start: Int, to end: Int) -> [DERElement] {
+        var elements: [DERElement] = []
+        var index = start
+        while index < end, let element = read(bytes, at: index) {
+            elements.append(element)
+            index = element.valueEnd
+        }
+        return elements
+    }
+}
+
+// MARK: - X.509 field extraction
+
+private struct X509Fields {
+    let subjectCommonName: String?
+    let issuerCommonName: String?
+    let notAfter: Date?
+
+    /// CommonName attribute OID `2.5.4.3` → DER content bytes `55 04 03`.
+    private static let commonNameOID: [UInt8] = [0x55, 0x04, 0x03]
+
+    /// Certificate ::= SEQUENCE { tbsCertificate, signatureAlgorithm, signature }
+    /// tbsCertificate ::= SEQUENCE { [0] version?, serialNumber, signature,
+    ///   issuer Name, validity, subject Name, subjectPublicKeyInfo, ... }
+    static func parse(der bytes: [UInt8]) -> X509Fields? {
+        guard let certificate = DER.read(bytes, at: 0), certificate.tag == DER.sequence else {
+            return nil
+        }
+        let certChildren = DER.children(
+            bytes, from: certificate.valueStart, to: certificate.valueEnd
+        )
+        guard let tbs = certChildren.first, tbs.tag == DER.sequence else { return nil }
+
+        var tbsChildren = DER.children(bytes, from: tbs.valueStart, to: tbs.valueEnd)
+        // Optional EXPLICIT [0] version — drop it so the fixed fields align.
+        if let first = tbsChildren.first, first.tag == DER.contextTag0 {
+            tbsChildren.removeFirst()
+        }
+        // Fixed order after (optional) version: serialNumber, signature,
+        // issuer, validity, subject, ...
+        guard tbsChildren.count >= 5 else { return nil }
+        let issuer = tbsChildren[2]
+        let validity = tbsChildren[3]
+        let subject = tbsChildren[4]
+
+        return X509Fields(
+            subjectCommonName: commonName(bytes, in: subject),
+            issuerCommonName: commonName(bytes, in: issuer),
+            notAfter: notAfterDate(bytes, in: validity)
+        )
+    }
+
+    /// Name ::= SEQUENCE OF RDN(SET) OF AttributeTypeAndValue(SEQ{OID, value}).
+    /// Returns the first CN value found.
+    private static func commonName(_ bytes: [UInt8], in name: DERElement) -> String? {
+        for rdn in DER.children(bytes, from: name.valueStart, to: name.valueEnd)
+        where rdn.tag == DER.set {
+            for atv in DER.children(bytes, from: rdn.valueStart, to: rdn.valueEnd)
+            where atv.tag == DER.sequence {
+                let parts = DER.children(bytes, from: atv.valueStart, to: atv.valueEnd)
+                guard parts.count >= 2, parts[0].tag == DER.oid else { continue }
+                let oid = Array(bytes[parts[0].valueStart..<parts[0].valueEnd])
+                if oid == commonNameOID {
+                    let value = Array(bytes[parts[1].valueStart..<parts[1].valueEnd])
+                    // PrintableString / UTF8String both decode as UTF-8.
+                    return String(bytes: value, encoding: .utf8)
+                }
+            }
+        }
+        return nil
+    }
+
+    /// Validity ::= SEQUENCE { notBefore Time, notAfter Time } — the 2nd child.
+    private static func notAfterDate(_ bytes: [UInt8], in validity: DERElement) -> Date? {
+        let times = DER.children(bytes, from: validity.valueStart, to: validity.valueEnd)
+        guard times.count >= 2 else { return nil }
+        let notAfter = times[1]
+        let value = Array(bytes[notAfter.valueStart..<notAfter.valueEnd])
+        guard let text = String(bytes: value, encoding: .ascii) else { return nil }
+        return parseTime(text, tag: notAfter.tag)
+    }
+
+    private static func parseTime(_ text: String, tag: UInt8) -> Date? {
+        let formatter = DateFormatter()
+        formatter.locale = Locale(identifier: "en_US_POSIX")
+        formatter.timeZone = TimeZone(identifier: "UTC")
+        // UTCTime: YYMMDDHHMMSSZ (used for years < 2050); GeneralizedTime:
+        // YYYYMMDDHHMMSSZ. The 2-digit-year window covers the relevant range
+        // (device certs live in the 2020s-2040s).
+        formatter.dateFormat = tag == DER.utcTime ? "yyMMddHHmmss'Z'" : "yyyyMMddHHmmss'Z'"
+        return formatter.date(from: text)
+    }
+}
diff --git a/ios/Packages/ClientTLS/Sources/ClientTLS/ClientIdentity.swift b/ios/Packages/ClientTLS/Sources/ClientTLS/ClientIdentity.swift
new file mode 100644
index 0000000..faaab84
--- /dev/null
+++ b/ios/Packages/ClientTLS/Sources/ClientTLS/ClientIdentity.swift
@@ -0,0 +1,55 @@
+import Foundation
+import Security
+
+/// C-iOS-1 · An imported device client identity: the `SecIdentity` (leaf
+/// certificate + its private key) plus the issuer chain that accompanies it in
+/// the TLS handshake.
+///
+/// `@unchecked Sendable`: `SecIdentity` / `SecCertificate` are CoreFoundation
+/// handles that are immutable once imported and thread-safe to read; this value
+/// only ever holds finished imports and never mutates them. Marking it lets the
+/// identity flow into the `@unchecked Sendable` WS connection and the URLSession
+/// delegates that answer client-certificate challenges.
+public struct ClientIdentity: @unchecked Sendable {
+    /// The leaf certificate + private key used to authenticate to the server.
+    public let secIdentity: SecIdentity
+    /// Issuer certificates to present alongside the leaf (the CA chain, leaf
+    /// excluded). May be empty when the trust anchor is already pinned server
+    /// side (nginx `ssl_client_certificate` = the device-CA) — the leaf alone
+    /// then verifies at `ssl_verify_depth 1`.
+    public let issuerCertificates: [SecCertificate]
+
+    public init(secIdentity: SecIdentity, issuerCertificates: [SecCertificate] = []) {
+        self.secIdentity = secIdentity
+        self.issuerCertificates = issuerCertificates
+    }
+
+    /// The `URLCredential` handed back to a `ClientCertificate` auth challenge.
+    ///
+    /// `.forSession` (not `.permanent`) per plan §C-iOS-1: the identity already
+    /// lives in the app's keychain item — persisting the credential in the
+    /// shared URL credential store would be a second, unmanaged copy.
+    public func urlCredential(
+        persistence: URLCredential.Persistence = .forSession
+    ) -> URLCredential {
+        URLCredential(
+            identity: secIdentity,
+            certificates: issuerCertificates.isEmpty ? nil : issuerCertificates,
+            persistence: persistence
+        )
+    }
+
+    /// The leaf `SecCertificate` backing this identity (for display / summary).
+    public func leafCertificate() -> SecCertificate? {
+        var certificate: SecCertificate?
+        let status = SecIdentityCopyCertificate(secIdentity, &certificate)
+        return status == errSecSuccess ? certificate : nil
+    }
+
+    /// Human-readable summary of the leaf certificate (subject CN, issuer CN,
+    /// expiry) for the install/rotation UI. `nil` only if the leaf can't be
+    /// read (should never happen for a valid import).
+    public func summary() -> ClientCertificateSummary? {
+        leafCertificate().map(CertificateInspector.summary(of:))
+    }
+}
diff --git a/ios/Packages/ClientTLS/Sources/ClientTLS/ClientTLSSessionDelegate.swift b/ios/Packages/ClientTLS/Sources/ClientTLS/ClientTLSSessionDelegate.swift
new file mode 100644
index 0000000..e84a7ae
--- /dev/null
+++ b/ios/Packages/ClientTLS/Sources/ClientTLS/ClientTLSSessionDelegate.swift
@@ -0,0 +1,36 @@
+import Foundation
+
+/// C-iOS-2 · Reusable `NSObject` URLSession delegate that answers
+/// **session-level** auth challenges by delegating to `MutualTLSChallengeResponder`.
+///
+/// This is the seam for the HTTP transport (`session.data(for:)` surfaces
+/// challenges through `urlSession(_:didReceive:completionHandler:)`). The WS
+/// transport can't reuse it — its connection object is already the session's
+/// delegate and needs the **task-level** callback — so that one implements the
+/// task-level method itself against the same responder.
+///
+/// `@unchecked Sendable`: URLSession retains its delegate and invokes it from
+/// arbitrary queues; every stored field is an immutable `let` over thread-safe
+/// values (`ClientIdentity` is `@unchecked Sendable`, the responder is stateless).
+public final class ClientTLSSessionDelegate: NSObject, URLSessionDelegate, @unchecked Sendable {
+    private let identity: ClientIdentity?
+    private let responder: MutualTLSChallengeResponder
+
+    public init(
+        identity: ClientIdentity?,
+        responder: MutualTLSChallengeResponder = MutualTLSChallengeResponder()
+    ) {
+        self.identity = identity
+        self.responder = responder
+        super.init()
+    }
+
+    public func urlSession(
+        _ session: URLSession,
+        didReceive challenge: URLAuthenticationChallenge,
+        completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void
+    ) {
+        let resolution = responder.resolve(challenge, identity: identity)
+        completionHandler(resolution.disposition, resolution.credential)
+    }
+}
diff --git a/ios/Packages/ClientTLS/Sources/ClientTLS/KeychainClientIdentityStore.swift b/ios/Packages/ClientTLS/Sources/ClientTLS/KeychainClientIdentityStore.swift
new file mode 100644
index 0000000..7fe081c
--- /dev/null
+++ b/ios/Packages/ClientTLS/Sources/ClientTLS/KeychainClientIdentityStore.swift
@@ -0,0 +1,200 @@
+import Foundation
+import os
+import Security
+
+/// Persists the device identity so it survives relaunch. The raw `.p12` bytes
+/// **and** its passphrase are stored together (the passphrase is required to
+/// re-import via `SecPKCS12Import` at every launch), then re-imported on load.
+public protocol ClientIdentityStore: Sendable {
+    /// Validate (`SecPKCS12Import`) then persist the `.p12` + passphrase.
+    /// Throws `PKCS12ImportError` on a bad passphrase / corrupt file (nothing is
+    /// persisted in that case) and `ClientIdentityStoreError` on a storage fault.
+    func save(p12Data: Data, passphrase: String) throws
+    /// Re-import and return the stored identity; `nil` if none is installed.
+    func loadIdentity() throws -> ClientIdentity?
+    /// Display summary of the stored certificate; `nil` if none is installed.
+    func loadSummary() throws -> ClientCertificateSummary?
+    /// Delete the stored identity (rotation / removal). Idempotent.
+    func remove() throws
+    /// Cheap existence check for gating (does NOT re-import).
+    func hasInstalledIdentity() -> Bool
+}
+
+public enum ClientIdentityStoreError: Error, Equatable, Sendable {
+    /// A Keychain `SecItem*` call failed with this `OSStatus`.
+    case keychain(OSStatus)
+    /// The stored blob was present but could not be decoded.
+    case corruptStoredBlob
+}
+
+public extension ClientIdentityStore {
+    /// Convenience for composition roots: load the identity, logging and
+    /// swallowing errors into `nil`. A missing cert is the normal pre-install
+    /// state; a genuine fault must not crash launch, but is logged (never
+    /// silently dropped).
+    func loadedIdentityOrNil() -> ClientIdentity? {
+        do {
+            return try loadIdentity()
+        } catch {
+            ClientTLSLog.identity.error(
+                "loadIdentity failed: \(String(describing: error), privacy: .public)"
+            )
+            return nil
+        }
+    }
+}
+
+/// The stored payload — `.p12` bytes plus the passphrase needed to re-import.
+private struct StoredP12Blob: Codable {
+    let p12: Data
+    let passphrase: String
+}
+
+/// Keychain-backed store: one `kSecClassGenericPassword` item holding the
+/// JSON-encoded `StoredP12Blob` in `kSecValueData`, protected with
+/// `kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly` (available after the first
+/// unlock post-boot, never migrates off this device).
+public struct KeychainClientIdentityStore: ClientIdentityStore {
+    public static let defaultService = "com.yaojia.webterm.clienttls"
+    public static let defaultAccount = "device-identity"
+
+    private let service: String
+    private let account: String
+
+    public init(
+        service: String = defaultService, account: String = defaultAccount
+    ) {
+        self.service = service
+        self.account = account
+    }
+
+    public func save(p12Data: Data, passphrase: String) throws {
+        // Validate BEFORE persisting — a wrong passphrase / corrupt file must
+        // surface to the install UI and leave any prior identity untouched.
+        _ = try PKCS12Importer.importIdentity(data: p12Data, passphrase: passphrase)
+        let blob = try encode(StoredP12Blob(p12: p12Data, passphrase: passphrase))
+        try writeItem(blob)
+    }
+
+    public func loadIdentity() throws -> ClientIdentity? {
+        guard let blob = try readBlob() else { return nil }
+        return try PKCS12Importer.importIdentity(
+            data: blob.p12, passphrase: blob.passphrase
+        )
+    }
+
+    public func loadSummary() throws -> ClientCertificateSummary? {
+        try loadIdentity()?.summary()
+    }
+
+    public func remove() throws {
+        let status = SecItemDelete(baseQuery() as CFDictionary)
+        guard status == errSecSuccess || status == errSecItemNotFound else {
+            throw ClientIdentityStoreError.keychain(status)
+        }
+    }
+
+    public func hasInstalledIdentity() -> Bool {
+        var query = baseQuery()
+        query[kSecReturnData as String] = false
+        query[kSecMatchLimit as String] = kSecMatchLimitOne
+        return SecItemCopyMatching(query as CFDictionary, nil) == errSecSuccess
+    }
+
+    // MARK: - Keychain plumbing
+
+    private func baseQuery() -> [String: Any] {
+        [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: account,
+        ]
+    }
+
+    private func writeItem(_ data: Data) throws {
+        // Delete-then-add keeps the item's protection class deterministic
+        // (SecItemUpdate can't change kSecAttrAccessible in place).
+        let deleteStatus = SecItemDelete(baseQuery() as CFDictionary)
+        guard deleteStatus == errSecSuccess || deleteStatus == errSecItemNotFound else {
+            throw ClientIdentityStoreError.keychain(deleteStatus)
+        }
+        var attributes = baseQuery()
+        attributes[kSecValueData as String] = data
+        attributes[kSecAttrAccessible as String] =
+            kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly
+        let addStatus = SecItemAdd(attributes as CFDictionary, nil)
+        guard addStatus == errSecSuccess else {
+            throw ClientIdentityStoreError.keychain(addStatus)
+        }
+    }
+
+    private func readBlob() throws -> StoredP12Blob? {
+        var query = baseQuery()
+        query[kSecReturnData as String] = true
+        query[kSecMatchLimit as String] = kSecMatchLimitOne
+        var result: CFTypeRef?
+        let status = SecItemCopyMatching(query as CFDictionary, &result)
+        if status == errSecItemNotFound { return nil }
+        guard status == errSecSuccess, let data = result as? Data else {
+            throw ClientIdentityStoreError.keychain(status)
+        }
+        do {
+            return try JSONDecoder().decode(StoredP12Blob.self, from: data)
+        } catch {
+            throw ClientIdentityStoreError.corruptStoredBlob
+        }
+    }
+
+    private func encode(_ blob: StoredP12Blob) throws -> Data {
+        do {
+            return try JSONEncoder().encode(blob)
+        } catch {
+            throw ClientIdentityStoreError.corruptStoredBlob
+        }
+    }
+}
+
+/// In-memory store for previews and unit tests: same import/summary code path as
+/// the keychain store (so the roundtrip is exercised) without any keychain
+/// entitlement. `@unchecked Sendable` — mutable blob guarded by a lock.
+public final class InMemoryClientIdentityStore: ClientIdentityStore, @unchecked Sendable {
+    private let lock = NSLock()
+    private var blob: StoredP12BlobBox?
+
+    /// Boxed so the private `StoredP12Blob` type stays file-private above; this
+    /// mirror keeps the two bytes+passphrase without exposing the Codable type.
+    private struct StoredP12BlobBox {
+        let p12: Data
+        let passphrase: String
+    }
+
+    public init() {}
+
+    public func save(p12Data: Data, passphrase: String) throws {
+        _ = try PKCS12Importer.importIdentity(data: p12Data, passphrase: passphrase)
+        lock.withLock { blob = StoredP12BlobBox(p12: p12Data, passphrase: passphrase) }
+    }
+
+    public func loadIdentity() throws -> ClientIdentity? {
+        guard let stored = lock.withLock({ blob }) else { return nil }
+        return try PKCS12Importer.importIdentity(
+            data: stored.p12, passphrase: stored.passphrase
+        )
+    }
+
+    public func loadSummary() throws -> ClientCertificateSummary? {
+        try loadIdentity()?.summary()
+    }
+
+    public func remove() throws {
+        lock.withLock { blob = nil }
+    }
+
+    public func hasInstalledIdentity() -> Bool {
+        lock.withLock { blob != nil }
+    }
+}
+
+enum ClientTLSLog {
+    static let identity = Logger(subsystem: "com.yaojia.webterm", category: "client-tls")
+}
diff --git a/ios/Packages/ClientTLS/Sources/ClientTLS/MutualTLSChallengeResponder.swift b/ios/Packages/ClientTLS/Sources/ClientTLS/MutualTLSChallengeResponder.swift
new file mode 100644
index 0000000..441ad27
--- /dev/null
+++ b/ios/Packages/ClientTLS/Sources/ClientTLS/MutualTLSChallengeResponder.swift
@@ -0,0 +1,73 @@
+import Foundation
+
+/// C-iOS-1 · The pure, synchronous decision at the heart of mutual TLS.
+///
+/// It maps a URLSession auth challenge (+ the optionally-installed device
+/// identity) to a disposition and credential. Deliberately free of any
+/// URLSession / socket state so the full truth table is unit-testable without a
+/// live connection — the transports (WS task delegate, HTTP session delegate)
+/// are thin adapters that call `resolve` and forward its result to the
+/// completion handler.
+///
+/// Truth table (plan §C-iOS-1):
+///  a. `ClientCertificate` + identity present → `.useCredential` with the
+///     identity's `URLCredential`.
+///  b. `ClientCertificate` + no identity      → `.cancelAuthenticationChallenge`
+///     (a clean, classifiable failure — never a silent no-cert continue).
+///  c. `ServerTrust`                          → `.performDefaultHandling`
+///     (the LE wildcard is validated by the system trust store).
+///  d. anything else                          → `.performDefaultHandling`.
+public struct MutualTLSChallengeResponder: Sendable {
+    /// The responder's decision. Not `Sendable` (it may carry a `URLCredential`,
+    /// which isn't) — it is produced and consumed synchronously on the delegate
+    /// queue, never sent across isolation domains.
+    public struct Resolution {
+        public let disposition: URLSession.AuthChallengeDisposition
+        public let credential: URLCredential?
+
+        public init(
+            disposition: URLSession.AuthChallengeDisposition,
+            credential: URLCredential? = nil
+        ) {
+            self.disposition = disposition
+            self.credential = credential
+        }
+    }
+
+    public init() {}
+
+    /// Resolve a full `URLAuthenticationChallenge` by dispatching on its
+    /// authentication method.
+    public func resolve(
+        _ challenge: URLAuthenticationChallenge, identity: ClientIdentity?
+    ) -> Resolution {
+        resolve(
+            authenticationMethod: challenge.protectionSpace.authenticationMethod,
+            identity: identity
+        )
+    }
+
+    /// Method-keyed core (challenge-free) — the directly-tested pure function.
+    public func resolve(
+        authenticationMethod: String, identity: ClientIdentity?
+    ) -> Resolution {
+        switch authenticationMethod {
+        case NSURLAuthenticationMethodClientCertificate:
+            guard let identity else {
+                // (b) No installed identity: cancel so the failure surfaces as a
+                // classifiable client-cert error rather than a bare TLS reset.
+                return Resolution(disposition: .cancelAuthenticationChallenge)
+            }
+            // (a) Present the device certificate for this session.
+            return Resolution(
+                disposition: .useCredential, credential: identity.urlCredential()
+            )
+        case NSURLAuthenticationMethodServerTrust:
+            // (c) System-trusted LE wildcard — default evaluation.
+            return Resolution(disposition: .performDefaultHandling)
+        default:
+            // (d) Basic/Digest/NTLM/etc. — not used by this app; default.
+            return Resolution(disposition: .performDefaultHandling)
+        }
+    }
+}
diff --git a/ios/Packages/ClientTLS/Sources/ClientTLS/PKCS12Importer.swift b/ios/Packages/ClientTLS/Sources/ClientTLS/PKCS12Importer.swift
new file mode 100644
index 0000000..82872ab
--- /dev/null
+++ b/ios/Packages/ClientTLS/Sources/ClientTLS/PKCS12Importer.swift
@@ -0,0 +1,89 @@
+import Foundation
+import Security
+
+/// Failure modes of a PKCS#12 import, each mapped to actionable install-UX copy
+/// (C-iOS-3). The three plan-named `OSStatus` mappings are honored:
+/// `errSecAuthFailed → .wrongPassphrase`, `errSecDecode → .corruptFile`, and any
+/// other non-success status (unsupported/unknown format — the plan's "errSecPkg"
+/// bucket) → `.unsupported`.
+public enum PKCS12ImportError: Error, Equatable, Sendable {
+    /// Wrong passphrase (`errSecAuthFailed`).
+    case wrongPassphrase
+    /// Not a decodable PKCS#12 blob (`errSecDecode`) — truncated / not a `.p12`.
+    case corruptFile
+    /// Decoded, but the format/algorithms aren't importable on this OS
+    /// (any other non-success `OSStatus`). Retains the raw status for logs.
+    case unsupported(OSStatus)
+    /// Import succeeded but carried no `SecIdentity` (e.g. a certs-only `.p12`).
+    case noIdentity
+
+    public static func == (lhs: PKCS12ImportError, rhs: PKCS12ImportError) -> Bool {
+        switch (lhs, rhs) {
+        case (.wrongPassphrase, .wrongPassphrase),
+             (.corruptFile, .corruptFile),
+             (.noIdentity, .noIdentity):
+            return true
+        case let (.unsupported(a), .unsupported(b)):
+            return a == b
+        default:
+            return false
+        }
+    }
+}
+
+/// Imports a `.p12` into a `ClientIdentity` via `SecPKCS12Import`.
+///
+/// Memory-only: `SecPKCS12Import` returns the identity/chain as CoreFoundation
+/// handles without writing to the keychain, so callers control persistence
+/// (see `KeychainClientIdentityStore`).
+public enum PKCS12Importer {
+    public static func importIdentity(
+        data: Data, passphrase: String
+    ) throws -> ClientIdentity {
+        let options = [kSecImportExportPassphrase as String: passphrase] as CFDictionary
+        var rawItems: CFArray?
+        let status = SecPKCS12Import(data as CFData, options, &rawItems)
+
+        switch status {
+        case errSecSuccess:
+            break
+        case errSecAuthFailed:
+            throw PKCS12ImportError.wrongPassphrase
+        case errSecDecode:
+            throw PKCS12ImportError.corruptFile
+        default:
+            // Covers unsupported formats/algorithms and any other failure —
+            // the plan's `errSecPkg → .unsupported` mapping (that symbol does
+            // not exist in the SDK; the status is preserved for diagnostics).
+            throw PKCS12ImportError.unsupported(status)
+        }
+
+        guard let items = rawItems as? [[String: Any]], let first = items.first,
+              let identityValue = first[kSecImportItemIdentity as String]
+        else {
+            throw PKCS12ImportError.noIdentity
+        }
+        // Force-cast is safe: `kSecImportItemIdentity` is always a SecIdentity.
+        let secIdentity = identityValue as! SecIdentity
+        let chain = (first[kSecImportItemCertChain as String] as? [SecCertificate]) ?? []
+        return ClientIdentity(
+            secIdentity: secIdentity,
+            issuerCertificates: issuerChain(from: chain, identity: secIdentity)
+        )
+    }
+
+    /// The chain from `SecPKCS12Import` includes the leaf at index 0; the
+    /// `URLCredential` must carry only the *issuer* certs (Apple: do not repeat
+    /// the identity's own cert). Drops whichever chain entry DER-matches the
+    /// identity's leaf.
+    private static func issuerChain(
+        from chain: [SecCertificate], identity: SecIdentity
+    ) -> [SecCertificate] {
+        var leaf: SecCertificate?
+        SecIdentityCopyCertificate(identity, &leaf)
+        guard let leafData = leaf.map({ SecCertificateCopyData($0) as Data }) else {
+            return chain
+        }
+        return chain.filter { SecCertificateCopyData($0) as Data != leafData }
+    }
+}
diff --git a/ios/Packages/ClientTLS/Tests/ClientTLSTests/ClientIdentityStoreTests.swift b/ios/Packages/ClientTLS/Tests/ClientTLSTests/ClientIdentityStoreTests.swift
new file mode 100644
index 0000000..78de7b4
--- /dev/null
+++ b/ios/Packages/ClientTLS/Tests/ClientTLSTests/ClientIdentityStoreTests.swift
@@ -0,0 +1,62 @@
+import Foundation
+import Testing
+@testable import ClientTLS
+
+// C-iOS-1 · Store roundtrip via the InMemory store (same import/summary code
+// path as the keychain store, minus the entitlement — the keychain variant is
+// covered by on-device/simulator tests, mirroring KeychainHostStoreLiveTests).
+
+@Test("save → loadIdentity roundtrips and hasInstalledIdentity flips")
+func storeRoundtrip() throws {
+    // Arrange
+    let store = InMemoryClientIdentityStore()
+    #expect(store.hasInstalledIdentity() == false)
+    #expect(try store.loadIdentity() == nil)
+
+    // Act
+    try store.save(
+        p12Data: ClientTLSFixtures.deviceP12Data, passphrase: ClientTLSFixtures.passphrase
+    )
+
+    // Assert
+    #expect(store.hasInstalledIdentity() == true)
+    let identity = try #require(try store.loadIdentity())
+    #expect(identity.summary()?.subjectCommonName == ClientTLSFixtures.leafCommonName)
+    let summary = try #require(try store.loadSummary())
+    #expect(summary.issuerCommonName == ClientTLSFixtures.issuerCommonName)
+}
+
+@Test("save validates the passphrase and leaves prior state untouched on failure")
+func storeSaveValidatesBeforePersisting() {
+    // Arrange
+    let store = InMemoryClientIdentityStore()
+
+    // Act / Assert — a wrong passphrase must surface, not persist.
+    #expect(throws: PKCS12ImportError.wrongPassphrase) {
+        try store.save(p12Data: ClientTLSFixtures.deviceP12Data, passphrase: "wrong")
+    }
+    #expect(store.hasInstalledIdentity() == false)
+}
+
+@Test("remove clears the stored identity")
+func storeRemove() throws {
+    // Arrange
+    let store = InMemoryClientIdentityStore()
+    try store.save(
+        p12Data: ClientTLSFixtures.deviceP12Data, passphrase: ClientTLSFixtures.passphrase
+    )
+    #expect(store.hasInstalledIdentity() == true)
+
+    // Act
+    try store.remove()
+
+    // Assert
+    #expect(store.hasInstalledIdentity() == false)
+    #expect(try store.loadIdentity() == nil)
+}
+
+@Test("loadedIdentityOrNil returns nil (not a throw) when nothing is installed")
+func loadedIdentityOrNilEmpty() {
+    let store = InMemoryClientIdentityStore()
+    #expect(store.loadedIdentityOrNil() == nil)
+}
diff --git a/ios/Packages/ClientTLS/Tests/ClientTLSTests/Fixtures.swift b/ios/Packages/ClientTLS/Tests/ClientTLSTests/Fixtures.swift
new file mode 100644
index 0000000..1706397
--- /dev/null
+++ b/ios/Packages/ClientTLS/Tests/ClientTLSTests/Fixtures.swift
@@ -0,0 +1,33 @@
+import Foundation
+
+/// Embedded test fixture: a real PKCS#12 generated at authoring time with
+/// OpenSSL (EC P-256 self-signed device-CA → EC P-256 leaf, `EKU=clientAuth`,
+/// exported `-legacy` for iOS/Android import parity — mirrors
+/// `deploy/scripts/gen-device-ca.sh` / `issue-device-cert.sh`).
+///
+/// Embedded as base64 rather than an SPM resource so the MUST-PASS package test
+/// runs headless with no `Bundle.module` resource wiring. Regenerate with:
+///   openssl ecparam -name prime256v1 -genkey -noout -out ca.key.pem
+///   openssl req -x509 -new -key ca.key.pem -sha256 -days 3650 \
+///     -subj "/CN=webterm-device-ca-fixture" \
+///     -addext "basicConstraints=critical,CA:TRUE" \
+///     -addext "keyUsage=critical,keyCertSign,cRLSign" -out ca.cert.pem
+///   openssl ecparam -name prime256v1 -genkey -noout -out leaf.key.pem
+///   openssl req -new -key leaf.key.pem -subj "/CN=device-fixture" -out leaf.csr.pem
+///   openssl x509 -req -in leaf.csr.pem -CA ca.cert.pem -CAkey ca.key.pem \
+///     -CAcreateserial -days 825 -sha256 -extfile leaf.ext -out leaf.cert.pem
+///   openssl pkcs12 -export -legacy -inkey leaf.key.pem -in leaf.cert.pem \
+///     -certfile ca.cert.pem -passout pass:clienttls-test-pass \
+///     -name device-fixture -out device.p12 ; base64 device.p12
+enum ClientTLSFixtures {
+    static let passphrase = "clienttls-test-pass"
+    static let leafCommonName = "device-fixture"
+    static let issuerCommonName = "webterm-device-ca-fixture"
+
+    static var deviceP12Data: Data {
+        Data(base64Encoded: deviceP12Base64)!
+    }
+
+    // swiftlint:disable:next line_length
+    static let deviceP12Base64 = "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"
+}
diff --git a/ios/Packages/ClientTLS/Tests/ClientTLSTests/MutualTLSChallengeResponderTests.swift b/ios/Packages/ClientTLS/Tests/ClientTLSTests/MutualTLSChallengeResponderTests.swift
new file mode 100644
index 0000000..5523acf
--- /dev/null
+++ b/ios/Packages/ClientTLS/Tests/ClientTLSTests/MutualTLSChallengeResponderTests.swift
@@ -0,0 +1,114 @@
+import Foundation
+import Testing
+@testable import ClientTLS
+
+// C-iOS-1 · The responder truth table: 3 challenge types × identity present /
+// absent. Exercised through the pure method-keyed core AND through a real
+// `URLAuthenticationChallenge` (proving the method is extracted correctly),
+// with no live socket.
+
+private let responder = MutualTLSChallengeResponder()
+
+private func makeIdentity() throws -> ClientIdentity {
+    try PKCS12Importer.importIdentity(
+        data: ClientTLSFixtures.deviceP12Data, passphrase: ClientTLSFixtures.passphrase
+    )
+}
+
+// MARK: - ClientCertificate
+
+@Test("ClientCertificate + identity → .useCredential with a credential")
+func clientCertWithIdentityUsesCredential() throws {
+    // Arrange
+    let identity = try makeIdentity()
+
+    // Act
+    let resolution = responder.resolve(
+        authenticationMethod: NSURLAuthenticationMethodClientCertificate, identity: identity
+    )
+
+    // Assert
+    #expect(resolution.disposition == .useCredential)
+    #expect(resolution.credential != nil)
+    #expect(resolution.credential?.identity != nil)
+}
+
+@Test("ClientCertificate + no identity → .cancelAuthenticationChallenge, no credential")
+func clientCertWithoutIdentityCancels() {
+    // Act
+    let resolution = responder.resolve(
+        authenticationMethod: NSURLAuthenticationMethodClientCertificate, identity: nil
+    )
+
+    // Assert
+    #expect(resolution.disposition == .cancelAuthenticationChallenge)
+    #expect(resolution.credential == nil)
+}
+
+// MARK: - ServerTrust
+
+@Test("ServerTrust → .performDefaultHandling regardless of identity")
+func serverTrustDefaultHandling() throws {
+    let identity = try makeIdentity()
+    for id in [identity, nil] as [ClientIdentity?] {
+        let resolution = responder.resolve(
+            authenticationMethod: NSURLAuthenticationMethodServerTrust, identity: id
+        )
+        #expect(resolution.disposition == .performDefaultHandling)
+        #expect(resolution.credential == nil)
+    }
+}
+
+// MARK: - Other method (e.g. Basic)
+
+@Test("an unrelated method → .performDefaultHandling regardless of identity")
+func otherMethodDefaultHandling() throws {
+    let identity = try makeIdentity()
+    for id in [identity, nil] as [ClientIdentity?] {
+        let resolution = responder.resolve(
+            authenticationMethod: NSURLAuthenticationMethodHTTPBasic, identity: id
+        )
+        #expect(resolution.disposition == .performDefaultHandling)
+        #expect(resolution.credential == nil)
+    }
+}
+
+// MARK: - Full URLAuthenticationChallenge extraction
+
+@Test("resolve(challenge:) extracts the method from the protection space")
+func resolveFromRealChallenge() throws {
+    // Arrange — a real challenge for the ClientCertificate method.
+    let identity = try makeIdentity()
+    let challenge = makeChallenge(method: NSURLAuthenticationMethodClientCertificate)
+
+    // Act
+    let withIdentity = responder.resolve(challenge, identity: identity)
+    let withoutIdentity = responder.resolve(challenge, identity: nil)
+
+    // Assert
+    #expect(withIdentity.disposition == .useCredential)
+    #expect(withIdentity.credential != nil)
+    #expect(withoutIdentity.disposition == .cancelAuthenticationChallenge)
+}
+
+// MARK: - Helpers
+
+/// Minimal sender so `URLAuthenticationChallenge` can be constructed in-process
+/// (its designated init requires a non-optional sender). The responder never
+/// calls back into the sender — it only reads `protectionSpace`.
+private final class NoopChallengeSender: NSObject, URLAuthenticationChallengeSender {
+    func use(_ credential: URLCredential, for challenge: URLAuthenticationChallenge) {}
+    func continueWithoutCredential(for challenge: URLAuthenticationChallenge) {}
+    func cancel(_ challenge: URLAuthenticationChallenge) {}
+}
+
+private func makeChallenge(method: String) -> URLAuthenticationChallenge {
+    let space = URLProtectionSpace(
+        host: "t1.terminal.yaojia.wang", port: 443, protocol: "https",
+        realm: nil, authenticationMethod: method
+    )
+    return URLAuthenticationChallenge(
+        protectionSpace: space, proposedCredential: nil, previousFailureCount: 0,
+        failureResponse: nil, error: nil, sender: NoopChallengeSender()
+    )
+}
diff --git a/ios/Packages/ClientTLS/Tests/ClientTLSTests/PKCS12ImporterTests.swift b/ios/Packages/ClientTLS/Tests/ClientTLSTests/PKCS12ImporterTests.swift
new file mode 100644
index 0000000..cfeabf0
--- /dev/null
+++ b/ios/Packages/ClientTLS/Tests/ClientTLSTests/PKCS12ImporterTests.swift
@@ -0,0 +1,69 @@
+import Foundation
+import Security
+import Testing
+@testable import ClientTLS
+
+// C-iOS-1 · PKCS#12 import against a real OpenSSL-generated fixture `.p12`,
+// including the wrong-passphrase and corrupt-file error mappings.
+
+@Test("import with the correct passphrase yields an identity whose leaf CN matches")
+func importSucceedsAndExposesLeaf() throws {
+    // Arrange
+    let data = ClientTLSFixtures.deviceP12Data
+
+    // Act
+    let identity = try PKCS12Importer.importIdentity(
+        data: data, passphrase: ClientTLSFixtures.passphrase
+    )
+
+    // Assert
+    let summary = try #require(identity.summary())
+    #expect(summary.subjectCommonName == ClientTLSFixtures.leafCommonName)
+    #expect(summary.issuerCommonName == ClientTLSFixtures.issuerCommonName)
+    // 825-day leaf minted at authoring time → not yet expired.
+    #expect(summary.isExpired() == false)
+}
+
+@Test("import drops the leaf from the issuer chain (credential must not repeat it)")
+func importIssuerChainExcludesLeaf() throws {
+    // Arrange / Act
+    let identity = try PKCS12Importer.importIdentity(
+        data: ClientTLSFixtures.deviceP12Data, passphrase: ClientTLSFixtures.passphrase
+    )
+
+    // Assert — fixture chain is [leaf, CA]; issuerCertificates keeps only the CA.
+    let leaf = try #require(identity.leafCertificate())
+    let leafData = SecCertificateCopyData(leaf) as Data
+    #expect(identity.issuerCertificates.count == 1)
+    for issuer in identity.issuerCertificates {
+        #expect((SecCertificateCopyData(issuer) as Data) != leafData)
+    }
+}
+
+@Test("wrong passphrase maps errSecAuthFailed → .wrongPassphrase")
+func importWrongPassphrase() {
+    // Arrange / Act / Assert
+    #expect(throws: PKCS12ImportError.wrongPassphrase) {
+        _ = try PKCS12Importer.importIdentity(
+            data: ClientTLSFixtures.deviceP12Data, passphrase: "not-the-passphrase"
+        )
+    }
+}
+
+@Test("garbage bytes map errSecDecode → .corruptFile")
+func importCorruptFile() {
+    // Arrange
+    let garbage = Data([0x00, 0x01, 0x02, 0x03, 0x99, 0xAB, 0xCD, 0xEF])
+
+    // Act / Assert
+    #expect(throws: PKCS12ImportError.corruptFile) {
+        _ = try PKCS12Importer.importIdentity(data: garbage, passphrase: "x")
+    }
+}
+
+@Test("empty data is treated as a corrupt file, not a crash")
+func importEmptyData() {
+    #expect(throws: PKCS12ImportError.corruptFile) {
+        _ = try PKCS12Importer.importIdentity(data: Data(), passphrase: "x")
+    }
+}
diff --git a/ios/Packages/SessionCore/Package.swift b/ios/Packages/SessionCore/Package.swift
index 5ff7ddf..b472f38 100644
--- a/ios/Packages/SessionCore/Package.swift
+++ b/ios/Packages/SessionCore/Package.swift
@@ -1,7 +1,9 @@
 // swift-tools-version: 6.0
 // T-iOS-1 scaffold shell. SessionEngine / ReconnectMachine / PingScheduler /
 // GateState / AwayDigest / URLSessionTermTransport land in W1–W2 tasks.
-// Dependency direction is strictly downward: SessionCore → WireProtocol only.
+// Dependency direction is strictly downward: SessionCore → WireProtocol, plus
+// ClientTLS (C-iOS-2) for the device client-cert mTLS responder the WS transport
+// answers connection-level challenges with. Both are downward leaves.
 import PackageDescription
 
 let package = Package(
@@ -12,12 +14,16 @@ let package = Package(
     ],
     dependencies: [
         .package(path: "../WireProtocol"),
+        .package(path: "../ClientTLS"),
         .package(path: "../TestSupport"),
     ],
     targets: [
         .target(
             name: "SessionCore",
-            dependencies: [.product(name: "WireProtocol", package: "WireProtocol")]
+            dependencies: [
+                .product(name: "WireProtocol", package: "WireProtocol"),
+                .product(name: "ClientTLS", package: "ClientTLS"),
+            ]
         ),
         .testTarget(
             name: "SessionCoreTests",
diff --git a/ios/Packages/SessionCore/Sources/SessionCore/URLSessionTermTransport.swift b/ios/Packages/SessionCore/Sources/SessionCore/URLSessionTermTransport.swift
index bc2e164..638b1ff 100644
--- a/ios/Packages/SessionCore/Sources/SessionCore/URLSessionTermTransport.swift
+++ b/ios/Packages/SessionCore/Sources/SessionCore/URLSessionTermTransport.swift
@@ -1,3 +1,4 @@
+import ClientTLS
 import Darwin
 import Foundation
 import WireProtocol
@@ -76,16 +77,45 @@ protocol ConnectionPinger: Sendable {
 public struct URLSessionTermTransport: TermTransport {
     /// `URLSessionWebSocketTask.maximumMessageSize` applied to every task.
     private let maxMessageBytes: Int
+    /// C-iOS-2 (MEDIUM no-relaunch fix) · Resolve the optional device client
+    /// identity LAZILY, once per `connect`, so a certificate imported mid-run
+    /// takes effect on the NEXT connection without an app relaunch (a snapshot
+    /// captured at composition would stay stale). When the resolved identity is
+    /// present, the connection answers a `ClientCertificate` challenge (mTLS to a
+    /// tunneled host) with its credential; when `nil`, the challenge is cancelled
+    /// cleanly. Local (non-mTLS) hosts never issue the challenge, so a `nil`
+    /// result is inert there.
+    private let identityProvider: @Sendable () -> ClientIdentity?
 
-    public init() {
-        self.init(maxMessageBytes: Tunables.maxWSMessageBytes)
+    /// Fixed-identity convenience (snapshot callers / tests): wraps a constant
+    /// provider, so behaviour is identical to capturing the identity directly.
+    public init(identity: ClientIdentity? = nil) {
+        self.init(identityProvider: { identity })
+    }
+
+    /// C-iOS-2 (MEDIUM no-relaunch fix) · per-connect identity resolution: the
+    /// provider is re-consulted on every `connect`, so a nil→installed
+    /// transition is picked up without relaunch.
+    public init(identityProvider: @escaping @Sendable () -> ClientIdentity?) {
+        self.init(
+            maxMessageBytes: Tunables.maxWSMessageBytes, identityProvider: identityProvider
+        )
     }
 
     /// Internal TEST seam: a shrunken cap makes the oversize→EMSGSIZE path
     /// deterministic without 16 MiB fixtures. Production code paths always go
-    /// through `init()` and the frozen `Tunables.maxWSMessageBytes`.
-    init(maxMessageBytes: Int) {
+    /// through `init()` / `init(identityProvider:)` and the frozen
+    /// `Tunables.maxWSMessageBytes`.
+    init(maxMessageBytes: Int, identity: ClientIdentity? = nil) {
+        self.init(maxMessageBytes: maxMessageBytes, identityProvider: { identity })
+    }
+
+    init(
+        maxMessageBytes: Int,
+        identityProvider: @escaping @Sendable () -> ClientIdentity?
+    ) {
         self.maxMessageBytes = maxMessageBytes
+        self.identityProvider = identityProvider
     }
 
     public func connect(to endpoint: HostEndpoint) async throws -> TransportConnection {
@@ -93,9 +123,13 @@ public struct URLSessionTermTransport: TermTransport {
     }
 
     /// Internal: concrete-typed connect (tests assert task configuration;
-    /// `connectPingable` builds on it).
+    /// `connectPingable` builds on it). The identity is resolved HERE, per
+    /// connect, from `identityProvider` (no-relaunch pickup).
     func openConnection(to endpoint: HostEndpoint) async throws -> WSConnection {
-        try await WSConnection.open(endpoint: endpoint, maxMessageBytes: maxMessageBytes)
+        try await WSConnection.open(
+            endpoint: endpoint, maxMessageBytes: maxMessageBytes,
+            identity: identityProvider()
+        )
     }
 }
 
@@ -135,6 +169,13 @@ final class WSConnection: NSObject, @unchecked Sendable {
     private let frames: AsyncThrowingStream<String, any Error>
     private let framesContinuation: AsyncThrowingStream<String, any Error>.Continuation
 
+    /// C-iOS-2 mTLS. Set once in `configure` BEFORE `task.resume()`, so the
+    /// connection-level challenge (which can only arrive after resume) always
+    /// reads a stable value without locking — same set-once discipline as
+    /// `task`/`session`.
+    private var identity: ClientIdentity?
+    private let challengeResponder = MutualTLSChallengeResponder()
+
     private override init() {
         (frames, framesContinuation) = AsyncThrowingStream<String, any Error>.makeStream()
         super.init()
@@ -143,9 +184,13 @@ final class WSConnection: NSObject, @unchecked Sendable {
     /// Connect: build session+task, resume, await the delegate-driven
     /// handshake (didOpen / didCompleteWithError — no receive-error guessing),
     /// then start the re-arming receive loop.
-    static func open(endpoint: HostEndpoint, maxMessageBytes: Int) async throws -> WSConnection {
+    static func open(
+        endpoint: HostEndpoint, maxMessageBytes: Int, identity: ClientIdentity? = nil
+    ) async throws -> WSConnection {
         let connection = WSConnection()
-        connection.configure(endpoint: endpoint, maxMessageBytes: maxMessageBytes)
+        connection.configure(
+            endpoint: endpoint, maxMessageBytes: maxMessageBytes, identity: identity
+        )
         try await connection.performHandshake()
         connection.startReceiveLoop()
         return connection
@@ -163,7 +208,12 @@ final class WSConnection: NSObject, @unchecked Sendable {
 
     // MARK: Setup
 
-    private func configure(endpoint: HostEndpoint, maxMessageBytes: Int) {
+    private func configure(
+        endpoint: HostEndpoint, maxMessageBytes: Int, identity: ClientIdentity?
+    ) {
+        // Set BEFORE building the task/resume: the mTLS challenge can only fire
+        // after `task.resume()`, so this write happens-before any read of it.
+        self.identity = identity
         // Origin: SINGLE source of truth = endpoint.originHeader (plan §5.1).
         var request = URLRequest(url: endpoint.wsURL)
         request.setValue(endpoint.originHeader, forHTTPHeaderField: "Origin")
@@ -311,6 +361,22 @@ extension WSConnection: URLSessionWebSocketDelegate {
         takeHandshakeContinuation()?.resume()
     }
 
+    /// C-iOS-2 · Connection-level auth challenge (server trust + client cert)
+    /// arrives task-level for a WS task. Delegate the decision to the pure
+    /// `MutualTLSChallengeResponder`: present the device identity for an mTLS
+    /// tunnel host, default-handle the LE server trust, cancel cleanly if a
+    /// client cert is demanded but none is installed. `identity` is set-once
+    /// before `resume()` (see `configure`), so this read needs no lock.
+    func urlSession(
+        _ session: URLSession,
+        task: URLSessionTask,
+        didReceive challenge: URLAuthenticationChallenge,
+        completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void
+    ) {
+        let resolution = challengeResponder.resolve(challenge, identity: identity)
+        completionHandler(resolution.disposition, resolution.credential)
+    }
+
     /// Server close frame processed → CLEAN close: the stream FINISHES
     /// (distinguishable from the transport-error THROW path).
     func urlSession(
diff --git a/ios/Packages/SessionCore/Tests/SessionCoreTests/URLSessionTermTransportTests.swift b/ios/Packages/SessionCore/Tests/SessionCoreTests/URLSessionTermTransportTests.swift
index 0acfbaf..df2ddf3 100644
--- a/ios/Packages/SessionCore/Tests/SessionCoreTests/URLSessionTermTransportTests.swift
+++ b/ios/Packages/SessionCore/Tests/SessionCoreTests/URLSessionTermTransportTests.swift
@@ -243,6 +243,29 @@ struct URLSessionTermTransportTests {
         await connection.close()
     }
 
+    @Test("identity provider is resolved PER CONNECT (no-relaunch pickup, not captured once)")
+    func identityProviderResolvedPerConnect() async throws {
+        // A cert imported mid-run must take effect on the NEXT connection. The
+        // transport therefore re-consults its provider on every `connect` rather
+        // than capturing a snapshot — proven here by a provider whose invocation
+        // count grows once per connect (nil identity: ScriptedWSServer is plain
+        // ws, so the connection succeeds regardless).
+        let (server, endpoint) = try await Self.startServer()
+        defer { server.stop() }
+        let calls = CallCounter()
+        let transport = URLSessionTermTransport(identityProvider: {
+            calls.increment()
+            return nil
+        })
+
+        let first = try await transport.connect(to: endpoint)
+        await first.close()
+        let second = try await transport.connect(to: endpoint)
+        await second.close()
+
+        #expect(calls.value == 2)
+    }
+
     @Test("connect to a dead port throws (handshake failure path, no hang)")
     func connectToDeadPortThrows() async throws {
         let server = ScriptedWSServer()
@@ -254,5 +277,14 @@ struct URLSessionTermTransportTests {
             _ = try await URLSessionTermTransport().connect(to: endpoint)
         }
     }
+
+    /// Thread-safe invocation counter for the `@Sendable` identity provider
+    /// (URLSession may consult it off the test's isolation domain).
+    private final class CallCounter: @unchecked Sendable {
+        private let lock = NSLock()
+        private var count = 0
+        func increment() { lock.withLock { count += 1 } }
+        var value: Int { lock.withLock { count } }
+    }
 }
 #endif
diff --git a/ios/project.yml b/ios/project.yml
index e0a5c53..0ec6c85 100644
--- a/ios/project.yml
+++ b/ios/project.yml
@@ -31,6 +31,8 @@ packages:
     path: Packages/HostRegistry
   APIClient:
     path: Packages/APIClient
+  ClientTLS:
+    path: Packages/ClientTLS      # C-iOS · device client-cert (mTLS) leaf package
   TestSupport:
     path: Packages/TestSupport   # test doubles — WebTermTests only, never the app target
   # SwiftTerm is the ONLY third-party dependency, attached to the App target
@@ -50,6 +52,7 @@ targets:
       - package: SessionCore
       - package: HostRegistry
       - package: APIClient
+      - package: ClientTLS
       - package: SwiftTerm
     settings:
       base:
@@ -119,6 +122,7 @@ targets:
       - package: SessionCore
       - package: HostRegistry
       - package: APIClient
+      - package: ClientTLS
       - package: TestSupport
     settings:
       base: