diff --git a/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow+Connectivity.swift b/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow+Connectivity.swift
new file mode 100644
index 00000000..b14ad8d1
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow+Connectivity.swift
@@ -0,0 +1,56 @@
+import Foundation
+
+extension CatalogTreeNode {
+  var connectivityServerIDs: [NodeID] {
+    isGroup ? childNodes.flatMap(\.connectivityServerIDs) : [id]
+  }
+}
+
+extension CatalogWorkflow {
+  /// Hash connection facts only; display-name and directory edits preserve observations.
+  func connectivityRevision(for id: NodeID) -> String {
+    guard let entry = dependencies.coordinator.committedCatalog.entry(for: id),
+      case .server(var fields) = entry.kind
+    else { return "missing" }
+    fields.remark = ""
+    let plugin = fields.pluginProgram.flatMap {
+      dependencies.plugins.catalogSnapshot().entry(for: $0)
+    }
+    let secrets = [fields.passwordRef, fields.pluginOptionsRef].compactMap { $0 }.map {
+      (try? dependencies.credentials.secret(for: $0)) ?? "unreadable"
+    }
+    let encoder = JSONEncoder()
+    encoder.outputFormatting = [.sortedKeys]
+    let facts =
+      [
+        String(data: (try? encoder.encode(fields)) ?? Data(), encoding: .utf8) ?? "",
+        String(describing: plugin),
+      ] + secrets
+    return ProxyACLDocument.digest((try? JSONEncoder().encode(facts)) ?? Data())
+  }
+
+  /// Captures all descendants in catalog order, independently of UI collapse or sort.
+  func connectivityTargets(source: NodeSource?) -> [NodeID] {
+    let nodes = source == nil ? favorites : tree.roots.filter { $0.source == source }
+    var seen = Set<NodeID>()
+    return nodes.flatMap(\.connectivityServerIDs).filter { seen.insert($0).inserted }
+  }
+
+  /// This local state machine derives a single leaf without publishing activation.
+  func connectivityConfiguration(for id: NodeID) throws -> SslocalServerDocument {
+    let catalog = dependencies.coordinator.committedCatalog
+    guard case .server? = catalog.entry(for: id)?.kind else { throw ServerFormLoadError.notFound }
+    var derivation = ActivationStateMachine()
+    if case .server(let fields)? = catalog.entry(for: id)?.kind,
+      !EncryptionMethodCatalog.isSupported(fields.encryptionMethod)
+    {
+      throw ServerConnectivity.ConfigurationFailure.unsupported
+    }
+    let config = try derivation.activate(
+      id, in: catalog, credentials: dependencies.credentials,
+      plugins: dependencies.plugins,
+      options: RuntimeDocumentOptions(listen: SslocalListenSettings()))
+    guard let server = config.document.servers.first else { throw ServerFormLoadError.notFound }
+    return server
+  }
+}
diff --git a/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow.swift b/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow.swift
index 11715608..11399942 100644
--- a/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow.swift
+++ b/ShadowsocksX-NG2/App/Application/CatalogWorkflow/CatalogWorkflow.swift
@@ -46,6 +46,8 @@ final class CatalogWorkflow: ObservableObject {
   /// 插件、订阅获取、Legacy 导入服务、导入后回调与激活缝只经此束持有，
   /// 不再作为 workflow 属性暴露。仅供组合根与测试构造；视图不得访问——
   /// 独立 target 拆分前由 architecture deletion check 守护残余可见性。
+  var connectivity: ServerConnectivity?
+
   let dependencies: CatalogWorkflowDependencies
   /// 启动时发现的 Legacy 快照（导入编排用；秘密值不进 projection）。
   var discoveredLegacySnapshot: LegacySnapshot?
@@ -393,6 +395,7 @@ final class CatalogWorkflow: ObservableObject {
 
   /// 提交成功后的 projection 重建（树 + 订阅卡片）。
   func republishCommittedState() {
+    connectivity?.configurationsChanged()
     let coordinator = dependencies.coordinator
     favoriteIDs = coordinator.committedFavoriteIDs
     tree = .build(
diff --git a/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPRequest.swift b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPRequest.swift
new file mode 100644
index 00000000..8d18516a
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPRequest.swift
@@ -0,0 +1,32 @@
+import Foundation
+
+/// System libcurl exposes complete headers without body sniffing. Each easy
+/// handle has isolated connection state and normal system certificate checks.
+struct ConnectivityHTTPRequest: Sendable {
+  func perform(url: URL, proxyPort: Int) async -> ServerConnectivity.Outcome {
+    let cancellation = Cancellation()
+    let started = ConnectivityHTTPNow()
+    return await withTaskCancellationHandler {
+      if Task.isCancelled { return .network }
+      return await Task.detached(priority: .utility) {
+        let result = url.absoluteString.withCString {
+          ConnectivityHTTPMeasure($0, Int32(proxyPort), started, cancellation.pointer)
+        }
+        if result.timed_out != 0 { return ServerConnectivity.Outcome.requestTimeout }
+        guard result.received_headers != 0 else { return .network }
+        return (200..<300).contains(result.status)
+          ? .success(milliseconds: Int(result.milliseconds)) : .http(Int(result.status))
+      }.value
+    } onCancel: {
+      cancellation.cancel()
+    }
+  }
+
+  /// Lifetime is shared by the worker and cancellation handler. The C token is
+  /// atomic; destruction happens only after both users release this object.
+  private final class Cancellation: @unchecked Sendable {
+    let pointer = ConnectivityHTTPCreateCancellation()
+    func cancel() { ConnectivityHTTPCancel(pointer) }
+    deinit { ConnectivityHTTPDestroyCancellation(pointer) }
+  }
+}
diff --git a/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPTransport.c b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPTransport.c
new file mode 100644
index 00000000..db8dcf5e
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPTransport.c
@@ -0,0 +1,109 @@
+#include "ConnectivityHTTPTransport.h"
+#include <curl/curl.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+struct ConnectivityHTTPCancellation { atomic_bool cancelled; };
+static pthread_once_t initialized = PTHREAD_ONCE_INIT;
+static void initialize_curl(void) { curl_global_init(CURL_GLOBAL_DEFAULT); }
+
+uint64_t ConnectivityHTTPNow(void) {
+  struct timespec time;
+  clock_gettime(CLOCK_MONOTONIC, &time);
+  return (uint64_t)time.tv_sec * 1000000000ULL + (uint64_t)time.tv_nsec;
+}
+ConnectivityHTTPCancellation *ConnectivityHTTPCreateCancellation(void) {
+  ConnectivityHTTPCancellation *token = malloc(sizeof(*token));
+  if (token) atomic_init(&token->cancelled, 0);
+  return token;
+}
+void ConnectivityHTTPCancel(ConnectivityHTTPCancellation *token) {
+  if (token) atomic_store(&token->cancelled, 1);
+}
+void ConnectivityHTTPDestroyCancellation(ConnectivityHTTPCancellation *token) { free(token); }
+
+typedef struct {
+  CURL *curl;
+  uint64_t started;
+  ConnectivityHTTPResult result;
+} Measurement;
+
+static size_t headers(char *bytes, size_t size, size_t count, void *opaque) {
+  Measurement *measurement = opaque;
+  size_t length = size * count;
+  if (length == 2 && bytes[0] == '\r' && bytes[1] == '\n') {
+    long status = 0;
+    curl_easy_getinfo(measurement->curl, CURLINFO_RESPONSE_CODE, &status);
+    if (status >= 200 || status == 101) {
+      uint64_t elapsed = ConnectivityHTTPNow() - measurement->started;
+      measurement->result.status = (int)status;
+      measurement->result.milliseconds = (int64_t)(elapsed / 1000000ULL);
+      measurement->result.received_headers = elapsed < 5000000000ULL;
+      measurement->result.timed_out = !measurement->result.received_headers;
+      // Aborting at the empty header line prevents all response-body delivery.
+      return 0;
+    }
+  }
+  return length;
+}
+static size_t discard_body(char *bytes, size_t size, size_t count, void *opaque) {
+  (void)bytes; (void)size; (void)count; (void)opaque;
+  return 0;
+}
+
+ConnectivityHTTPResult ConnectivityHTTPMeasure(const char *url, int proxy_port,
+  uint64_t started, ConnectivityHTTPCancellation *token) {
+  Measurement measurement = {0};
+  measurement.started = started;
+  pthread_once(&initialized, initialize_curl);
+  CURL *curl = curl_easy_init();
+  CURLM *multi = curl_multi_init();
+  if (!curl || !multi || !token) goto cleanup;
+  measurement.curl = curl;
+  char proxy[64];
+  snprintf(proxy, sizeof(proxy), "http://127.0.0.1:%d", proxy_port);
+  curl_easy_setopt(curl, CURLOPT_URL, url);
+  curl_easy_setopt(curl, CURLOPT_PROXY, proxy);
+  // Explicitly override environment bypasses, including loopback destinations.
+  curl_easy_setopt(curl, CURLOPT_NOPROXY, "");
+  curl_easy_setopt(curl, CURLOPT_PROTOCOLS_STR, "http,https");
+  curl_easy_setopt(curl, CURLOPT_HTTPGET, 1L);
+  curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 0L);
+  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);
+  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);
+  curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1L);
+  curl_easy_setopt(curl, CURLOPT_TIMEOUT_MS, 5000L);
+  curl_easy_setopt(curl, CURLOPT_SUPPRESS_CONNECT_HEADERS, 1L);
+  curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, headers);
+  curl_easy_setopt(curl, CURLOPT_HEADERDATA, &measurement);
+  curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, discard_body);
+  curl_easy_setopt(curl, CURLOPT_FRESH_CONNECT, 1L);
+  curl_easy_setopt(curl, CURLOPT_FORBID_REUSE, 1L);
+  if (curl_multi_add_handle(multi, curl) != CURLM_OK) goto cleanup;
+  int running = 1;
+  while (running && !atomic_load(&token->cancelled)) {
+    if (ConnectivityHTTPNow() - started >= 5000000000ULL) {
+      measurement.result.timed_out = 1;
+      break;
+    }
+    if (curl_multi_perform(multi, &running) != CURLM_OK) break;
+    if (!running) break;
+    int descriptors = 0;
+    if (curl_multi_poll(multi, NULL, 0, 50, &descriptors) != CURLM_OK) break;
+  }
+  int pending = 0;
+  CURLMsg *message;
+  while ((message = curl_multi_info_read(multi, &pending))) {
+    if (message->msg == CURLMSG_DONE && message->data.result == CURLE_OPERATION_TIMEDOUT)
+      measurement.result.timed_out = 1;
+  }
+  if (atomic_load(&token->cancelled)) measurement.result.received_headers = 0;
+  curl_multi_remove_handle(multi, curl);
+cleanup:
+  if (multi) curl_multi_cleanup(multi);
+  if (curl) curl_easy_cleanup(curl);
+  return measurement.result;
+}
diff --git a/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPTransport.h b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPTransport.h
new file mode 100644
index 00000000..2d0ff96b
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityHTTPTransport.h
@@ -0,0 +1,18 @@
+#ifndef ConnectivityHTTPTransport_h
+#define ConnectivityHTTPTransport_h
+#include <stdint.h>
+
+typedef struct ConnectivityHTTPCancellation ConnectivityHTTPCancellation;
+typedef struct {
+  int status;
+  int64_t milliseconds;
+  int timed_out;
+  int received_headers;
+} ConnectivityHTTPResult;
+ConnectivityHTTPCancellation *ConnectivityHTTPCreateCancellation(void);
+void ConnectivityHTTPCancel(ConnectivityHTTPCancellation *token);
+void ConnectivityHTTPDestroyCancellation(ConnectivityHTTPCancellation *token);
+uint64_t ConnectivityHTTPNow(void);
+ConnectivityHTTPResult ConnectivityHTTPMeasure(const char *url, int proxy_port,
+  uint64_t started, ConnectivityHTTPCancellation *token);
+#endif
diff --git a/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityRuntime.swift b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityRuntime.swift
new file mode 100644
index 00000000..3e163a31
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/Connectivity/ConnectivityRuntime.swift
@@ -0,0 +1,140 @@
+import Darwin
+import Foundation
+
+/// An isolated process group owns sslocal and every SIP003 child. No formal
+/// runtime file, ACL, activity selection, or system proxy is touched.
+@MainActor
+struct ConnectivityRuntime {
+  let executable: URL
+  var temporaryRoot: URL = FileManager.default.temporaryDirectory
+
+  func measure(
+    _ server: SslocalServerDocument, url: URL, preparationDeadline deadline: ContinuousClock.Instant
+  ) async -> ServerConnectivity.Outcome {
+    let directory = temporaryRoot.appendingPathComponent(UUID().uuidString)
+    var pid: pid_t = 0
+    var reaped = false
+    var result: ServerConnectivity.Outcome = .startup
+    do {
+      try FileManager.default.createDirectory(
+        at: directory, withIntermediateDirectories: true,
+        attributes: [.posixPermissions: 0o700])
+      try Task.checkCancellation()
+      guard ContinuousClock.now < deadline else {
+        try? FileManager.default.removeItem(at: directory)
+        return .preparationTimeout
+      }
+      let port = try freePort()
+      let config = directory.appendingPathComponent("test.json")
+      // A single TCP HTTP inbound, no ACL: every request must use this server.
+      let data = try JSONSerialization.data(withJSONObject: [
+        "servers": [try JSONSerialization.jsonObject(with: JSONEncoder().encode(server))],
+        "locals": [
+          [
+            "protocol": "http", "local_address": "127.0.0.1",
+            "local_port": port, "mode": "tcp_only",
+          ]
+        ],
+      ])
+      try AtomicFileWriter.write(data, to: config)
+      pid = try spawn(config)
+      while ContinuousClock.now < deadline {
+        try Task.checkCancellation()
+        var status: Int32 = 0
+        if waitpid(pid, &status, WNOHANG) == pid {
+          reaped = true
+          break
+        }
+        if RuntimeSocketOwnershipProbe.process(pid, ownsTCPListenerOn: port),
+          EndpointHealthProbe.probe(host: "127.0.0.1", port: port, timeout: 0.02) == .reachable
+        {
+          if ContinuousClock.now >= deadline { break }
+          result = await ConnectivityHTTPRequest().perform(url: url, proxyPort: port)
+          break
+        }
+        try await Task.sleep(for: .milliseconds(25))
+      }
+      if ContinuousClock.now >= deadline, result == .startup { result = .preparationTimeout }
+    } catch is CancellationError {
+      result = .network
+    } catch {
+      result = .startup
+    }
+    await cleanup(pid: pid, reaped: reaped, directory: directory)
+    return result
+  }
+
+  private func cleanup(pid child: pid_t, reaped alreadyReaped: Bool, directory: URL) async {
+    // Cleanup is not cancelled with the measurement. Slots remain occupied until
+    // the group has been terminated and its leader reaped.
+    await Task {
+      if child > 0 {
+        _ = kill(-child, SIGTERM)
+        let deadline = ContinuousClock.now.advanced(by: .seconds(2))
+        var reaped = alreadyReaped
+        while ContinuousClock.now < deadline {
+          if !reaped {
+            var status: Int32 = 0
+            reaped = waitpid(child, &status, WNOHANG) == child
+          }
+          if kill(-child, 0) != 0 { break }
+          try? await Task.sleep(for: .milliseconds(25))
+        }
+        _ = kill(-child, SIGKILL)
+        if !reaped {
+          var status: Int32 = 0
+          _ = waitpid(child, &status, 0)
+        }
+      }
+      try? FileManager.default.removeItem(at: directory)
+    }.value
+  }
+
+  private func freePort() throws -> Int {
+    let descriptor = socket(AF_INET, SOCK_STREAM, 0)
+    guard descriptor >= 0 else { throw RuntimeError.failed }
+    defer { close(descriptor) }
+    var address = sockaddr_in()
+    address.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
+    address.sin_family = sa_family_t(AF_INET)
+    address.sin_addr.s_addr = inet_addr("127.0.0.1")
+    let bound = withUnsafePointer(to: &address) {
+      $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
+        bind(descriptor, $0, socklen_t(MemoryLayout<sockaddr_in>.size))
+      }
+    }
+    guard bound == 0 else { throw RuntimeError.failed }
+    var length = socklen_t(MemoryLayout<sockaddr_in>.size)
+    let read = withUnsafeMutablePointer(to: &address) {
+      $0.withMemoryRebound(to: sockaddr.self, capacity: 1) { getsockname(descriptor, $0, &length) }
+    }
+    guard read == 0 else { throw RuntimeError.failed }
+    return Int(UInt16(bigEndian: address.sin_port))
+  }
+
+  private func spawn(_ config: URL) throws -> pid_t {
+    var attributes: posix_spawnattr_t?
+    posix_spawnattr_init(&attributes)
+    defer { posix_spawnattr_destroy(&attributes) }
+    posix_spawnattr_setflags(&attributes, Int16(POSIX_SPAWN_SETPGROUP))
+    posix_spawnattr_setpgroup(&attributes, 0)
+    var actions: posix_spawn_file_actions_t?
+    posix_spawn_file_actions_init(&actions)
+    defer { posix_spawn_file_actions_destroy(&actions) }
+    // Child output can contain plugin options and credentials; discard it.
+    for descriptor in [STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO] {
+      posix_spawn_file_actions_addopen(&actions, descriptor, "/dev/null", O_RDWR, 0)
+    }
+    let strings = [executable.path, "-c", config.path].map { strdup($0) }
+    defer { strings.forEach { free($0) } }
+    var argv = strings + [nil]
+    var pid: pid_t = 0
+    let status = argv.withUnsafeMutableBufferPointer {
+      posix_spawn(&pid, executable.path, &actions, &attributes, $0.baseAddress!, environ)
+    }
+    guard status == 0 else { throw RuntimeError.failed }
+    return pid
+  }
+
+  private enum RuntimeError: Error { case failed }
+}
diff --git a/ShadowsocksX-NG2/App/Application/Connectivity/ServerConnectivity.swift b/ShadowsocksX-NG2/App/Application/Connectivity/ServerConnectivity.swift
new file mode 100644
index 00000000..8378ff5a
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/Connectivity/ServerConnectivity.swift
@@ -0,0 +1,235 @@
+import Combine
+import Foundation
+
+/// Process-lifetime observations. Secrets stay inside the configuration adapter.
+@MainActor
+final class ServerConnectivity: ObservableObject {
+  enum Outcome: Equatable, Sendable {
+    case success(milliseconds: Int)
+    case unsupported, preparationTimeout, requestTimeout, configuration, startup, network
+    case http(Int)
+  }
+  enum ConfigurationFailure: Error { case unsupported }
+  struct Record: Equatable, Identifiable {
+    let id = UUID()
+    let finishedAt: Date
+    let outcome: Outcome
+    var networkExpired = false
+    func isExpired(at date: Date) -> Bool {
+      networkExpired || date.timeIntervalSince(finishedAt) >= 300
+    }
+  }
+  struct Batch {
+    let targets: [NodeID]
+    let cooling: [NodeID]
+    var completedIDs: Set<NodeID> = []
+    var completed: Int { completedIDs.count }
+  }
+  struct Summary {
+    let serverID: NodeID?
+    let record: Record?
+    let hasResults: Bool
+    let isTesting: Bool
+  }
+  static let defaultURL = URL(string: "http://www.gstatic.com/generate_204")!
+  @Published private(set) var testing: Set<NodeID> = []
+  @Published private var records: [NodeID: [Record]] = [:]
+  @Published private var batches: [UUID: Batch] = [:]
+  private var versions: [NodeID: String] = [:]
+  private var cooldown: [NodeID: Date] = [:]
+  private var jobs: [NodeID: Task<Void, Never>] = [:]
+  private var queue: [(NodeID, UUID)] = []
+  private var tokens: [NodeID: UUID] = [:]
+  private var running = 0
+  private var generation = 0
+  private var stopped = false
+  private var targetURL: URL? = defaultURL
+  private let revision: (NodeID) -> String
+  private let configuration: (NodeID) throws -> SslocalServerDocument
+  private let now: () -> Date
+  private let measure: (SslocalServerDocument, URL, ContinuousClock.Instant) async -> Outcome
+
+  init(
+    configuration: @escaping (NodeID) throws -> SslocalServerDocument,
+    revision: ((NodeID) -> String)? = nil,
+    now: @escaping () -> Date = Date.init,
+    measure: @escaping (SslocalServerDocument, URL, ContinuousClock.Instant) async -> Outcome
+  ) {
+    self.configuration = configuration
+    self.revision =
+      revision ?? { id in
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = [.sortedKeys]
+        guard let server = try? configuration(id), let data = try? encoder.encode(server) else {
+          return "invalid"
+        }
+        return ProxyACLDocument.digest(data)
+      }
+    self.now = now
+    self.measure = measure
+  }
+
+  static func validURL(_ raw: String) -> URL? {
+    guard let url = URL(string: raw.trimmingCharacters(in: .whitespacesAndNewlines)),
+      ["http", "https"].contains(url.scheme?.lowercased() ?? ""),
+      let host = url.host, !host.isEmpty, url.fragment == nil
+    else { return nil }
+    return url
+  }
+
+  func history(for id: NodeID) -> [Record] { records[id] ?? [] }
+  func batch(_ id: UUID) -> Batch? { batches[id] }
+  func isCooling(_ id: NodeID) -> Bool { cooldown[id].map { now() < $0 } ?? false }
+
+  /// Captures target identities, reuses queued work, and skips cooling identities.
+  @discardableResult
+  func test(_ ids: [NodeID]) -> UUID {
+    configurationsChanged()
+    let batchID = UUID()
+    var seen = Set<NodeID>()
+    let ids = ids.filter { seen.insert($0).inserted }
+    let skipped = ids.filter { !testing.contains($0) && isCooling($0) }
+    let targets = stopped ? [] : ids.filter { !skipped.contains($0) }
+    batches[batchID] = Batch(targets: targets, cooling: skipped)
+    // Bound transient batch metadata; active batches are retained.
+    if batches.count > 100 {
+      for (key, value) in batches where value.completed == value.targets.count && key != batchID {
+        batches.removeValue(forKey: key)
+      }
+    }
+    for id in targets where !testing.contains(id) {
+      let token = UUID()
+      versions[id] = revision(id)
+      tokens[id] = token
+      testing.insert(id)
+      queue.append((id, token))
+    }
+    pump()
+    return batchID
+  }
+
+  func wait(for batchID: UUID) async {
+    while let batch = batches[batchID], batch.completed < batch.targets.count {
+      await Task.yield()
+    }
+  }
+
+  func summary(for ids: [NodeID], at date: Date) -> Summary {
+    let values = ids.compactMap { id in records[id]?.first.map { (id, $0) } }
+    let successes = values.filter {
+      if case .success = $0.1.outcome { return true }
+      return false
+    }
+    let fresh = successes.filter { !$0.1.isExpired(at: date) }
+    let candidates = fresh.isEmpty ? successes : fresh
+    let fastest = candidates.min { lhs, rhs in
+      guard case .success(let leftMilliseconds) = lhs.1.outcome,
+        case .success(let rightMilliseconds) = rhs.1.outcome
+      else {
+        return false
+      }
+      return leftMilliseconds < rightMilliseconds
+    }
+    return Summary(
+      serverID: fastest?.0, record: fastest?.1,
+      hasResults: !values.isEmpty, isTesting: ids.contains { testing.contains($0) })
+  }
+
+  /// Re-read values, including secrets with unchanged references and plugin mappings.
+  func configurationsChanged() {
+    for (id, previous) in versions where revision(id) != previous { invalidate(id) }
+  }
+
+  func setURL(_ url: URL?) {
+    guard url != targetURL else { return }
+    targetURL = url
+    generation += 1
+    records = [:]
+    for id in testing { invalidate(id) }
+  }
+
+  func networkChanged() {
+    generation += 1
+    for id in records.keys {
+      records[id] = records[id]?.map { record in
+        var copy = record
+        copy.networkExpired = true
+        return copy
+      }
+    }
+    for id in testing { jobs[id]?.cancel() }
+  }
+
+  func shutdown() async {
+    stopped = true
+    generation += 1
+    for id in testing { invalidate(id) }
+    let active = Array(jobs.values)
+    for job in active { await job.value }
+  }
+
+  private func invalidate(_ id: NodeID) {
+    records.removeValue(forKey: id)
+    versions.removeValue(forKey: id)
+    jobs[id]?.cancel()
+    // Queued identities are completed internally and enter cooldown too.
+    if jobs[id] == nil, testing.contains(id) { finish(id) }
+  }
+
+  private func pump() {
+    while running < 3, !queue.isEmpty, !stopped {
+      let (id, token) = queue.removeFirst()
+      guard tokens[id] == token else { continue }
+      let preparationDeadline = ContinuousClock.now.advanced(by: .seconds(10))
+      guard versions[id] == revision(id) else {
+        records.removeValue(forKey: id)
+        finish(id)
+        continue
+      }
+      running += 1
+      let epoch = generation
+      let url = targetURL
+      let version = versions[id]
+      let server: SslocalServerDocument?
+      let failure: Outcome
+      do {
+        server = try configuration(id)
+        failure = .configuration
+      } catch ConfigurationFailure.unsupported {
+        server = nil
+        failure = .unsupported
+      } catch {
+        server = nil
+        failure = .configuration
+      }
+      jobs[id] = Task { [self] in
+        let result: Outcome
+        if let server, let url {
+          result =
+            ContinuousClock.now >= preparationDeadline
+            ? .preparationTimeout : await measure(server, url, preparationDeadline)
+        } else {
+          result = url == nil ? .configuration : failure
+        }
+        let current = revision(id)
+        if !Task.isCancelled, epoch == generation, tokens[id] == token, current == version {
+          let record = Record(finishedAt: now(), outcome: result)
+          records[id] = Array(([record] + (records[id] ?? [])).prefix(10))
+        }
+        running -= 1
+        jobs.removeValue(forKey: id)
+        finish(id)
+        pump()
+      }
+    }
+  }
+
+  private func finish(_ id: NodeID) {
+    tokens.removeValue(forKey: id)
+    testing.remove(id)
+    cooldown[id] = now().addingTimeInterval(10)
+    for key in batches.keys where batches[key]?.targets.contains(id) == true {
+      batches[key]?.completedIDs.insert(id)
+    }
+  }
+}
diff --git a/ShadowsocksX-NG2/App/Application/ProxyRuntime/ProxyRuntimeController+SettingsSync.swift b/ShadowsocksX-NG2/App/Application/ProxyRuntime/ProxyRuntimeController+SettingsSync.swift
index a099b4bc..dd68476d 100644
--- a/ShadowsocksX-NG2/App/Application/ProxyRuntime/ProxyRuntimeController+SettingsSync.swift
+++ b/ShadowsocksX-NG2/App/Application/ProxyRuntime/ProxyRuntimeController+SettingsSync.swift
@@ -72,11 +72,16 @@ extension ProxyRuntimeController {
   /// status remains observable through the controller's status stream.
   func updateSettings(_ proposed: ProxySettings) async throws {
     let catalog = catalogSnapshotReader.catalogSnapshot
+    var connectionIndependent = settings
+    connectionIndependent.connectivityURLReference = proposed.connectivityURLReference
+    let onlyTestURLChanged =
+      settings.connectivityURLReference != proposed.connectivityURLReference
+      && connectionIndependent == proposed
     try settingsStore.save(proposed)
     settings = proposed
     listenSettingsUnreadable = false
     settingsUnreadable = false
-    guard state != .off else { return }
+    guard state != .off, !onlyTestURLChanged else { return }
     await convergeToReexpanded(catalog)
   }
 
diff --git a/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow+Connectivity.swift b/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow+Connectivity.swift
new file mode 100644
index 00000000..13d405a6
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow+Connectivity.swift
@@ -0,0 +1,39 @@
+import Foundation
+
+extension SettingsWorkflow {
+  func beginConnectivityURLEditing() throws -> String {
+    guard let reference = committing.committedSettings.connectivityURLReference else {
+      return ServerConnectivity.defaultURL.absoluteString
+    }
+    guard let secret = try credentials.secret(for: reference),
+      ServerConnectivity.validURL(secret) != nil
+    else {
+      throw ServerFormLoadError.credentialsUnavailable
+    }
+    return secret
+  }
+
+  /// Each custom URL gets a fresh secret; failed preference saves roll it back.
+  func saveConnectivityURL(_ raw: String) async -> Bool {
+    guard let url = ServerConnectivity.validURL(raw), startCommit() else { return false }
+    defer { finishCommit() }
+    let previous = committing.committedSettings.connectivityURLReference
+    let reference: CredentialReference? = url == ServerConnectivity.defaultURL ? nil : .fresh()
+    do {
+      if let reference { try credentials.save(url.absoluteString, for: reference) }
+      var proposed = committing.committedSettings
+      proposed.connectivityURLReference = reference
+      let outcome = await persistSettings(proposed)
+      guard outcome == .persisted else {
+        if let reference { try? credentials.delete(reference) }
+        return false
+      }
+      connectivityURLDidChange?(url)
+      if let previous { try? credentials.delete(previous) }
+      return true
+    } catch {
+      if let reference { try? credentials.delete(reference) }
+      return false
+    }
+  }
+}
diff --git a/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow.swift b/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow.swift
index a4f21b29..892aab18 100644
--- a/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow.swift
+++ b/ShadowsocksX-NG2/App/Application/SettingsWorkflow/SettingsWorkflow.swift
@@ -20,6 +20,8 @@ final class SettingsWorkflow: ObservableObject {
   /// Typed persistence failure for the editor to present.
   @Published private(set) var lastFailure: SettingsWorkflowFailure?
 
+  var connectivityURLDidChange: ((URL) -> Void)?
+
   let committing: SettingsCommitting
   let credentials: CredentialStoring
   let occupancyProbe: PortOccupancyProbing
diff --git a/ShadowsocksX-NG2/App/Composition/ConnectivityLifecycle.swift b/ShadowsocksX-NG2/App/Composition/ConnectivityLifecycle.swift
new file mode 100644
index 00000000..1a1566bf
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Composition/ConnectivityLifecycle.swift
@@ -0,0 +1,43 @@
+import AppKit
+import Network
+
+/// Held by the composition, independently of workspace windows.
+@MainActor
+final class ConnectivityLifecycle: NSObject, NSApplicationDelegate {
+  let module: ServerConnectivity
+  private let monitor = NWPathMonitor()
+  private var receivedInitialPath = false
+  private var terminating = false
+
+  init(module: ServerConnectivity) {
+    self.module = module
+    super.init()
+    monitor.pathUpdateHandler = { [weak self] _ in
+      Task { @MainActor in
+        guard let self else { return }
+        if self.receivedInitialPath { self.module.networkChanged() }
+        self.receivedInitialPath = true
+      }
+    }
+    monitor.start(queue: DispatchQueue(label: "connectivity.network"))
+  }
+
+  func applicationShouldTerminate(_ sender: NSApplication) -> NSApplication.TerminateReply {
+    guard !terminating else { return .terminateLater }
+    terminating = true
+    monitor.cancel()
+    Task {
+      await module.shutdown()
+      sender.reply(toApplicationShouldTerminate: true)
+    }
+    return .terminateLater
+  }
+}
+
+@MainActor
+final class ConnectivityApplicationDelegate: NSObject, NSApplicationDelegate {
+  var lifecycle: ConnectivityLifecycle?
+  func applicationShouldTerminate(_ sender: NSApplication) -> NSApplication.TerminateReply {
+    lifecycle?.applicationShouldTerminate(sender) ?? .terminateNow
+  }
+}
diff --git a/ShadowsocksX-NG2/App/Composition/MainApp.swift b/ShadowsocksX-NG2/App/Composition/MainApp.swift
index ec68c122..9792a3fc 100644
--- a/ShadowsocksX-NG2/App/Composition/MainApp.swift
+++ b/ShadowsocksX-NG2/App/Composition/MainApp.swift
@@ -5,6 +5,8 @@ import SwiftUI
 struct ShadowsocksXNG2App: App {
   /// 进程期强持有（组合根装配一次）。body 不读它：事实发布经各 workflow 的
   /// didChange 通道，不借 @StateObject 订阅控制器变化。
+  @NSApplicationDelegateAdaptor(ConnectivityApplicationDelegate.self) private var appDelegate
+  private let connectivityLifecycle: ConnectivityLifecycle
   private let proxyController: ProxyRuntimeController
   @StateObject private var catalogWorkflow: CatalogWorkflow
   @StateObject private var proxyControl: ProxyControlWorkflow
@@ -28,6 +30,7 @@ struct ShadowsocksXNG2App: App {
 
   init() {
     let composition = AppComposition.make()
+    connectivityLifecycle = composition.connectivityLifecycle
     proxyController = composition.controller
     _catalogWorkflow = StateObject(wrappedValue: composition.catalogWorkflow)
     _proxyControl = StateObject(wrappedValue: composition.proxyControl)
@@ -46,6 +49,7 @@ struct ShadowsocksXNG2App: App {
     // GUI 事件接入内存环形缓冲：独立诊断窗口日志查看器与
     // 诊断导出的来源；wrapper 侧不注册，仍走 stderr → agent.log 收敛。
     RuntimeLog.setSink(RuntimeEventStore.shared)
+    appDelegate.lifecycle = connectivityLifecycle
   }
 
   var body: some Scene {
@@ -141,6 +145,7 @@ private struct StatusMenuLabel: View {
 /// StateObject 状态与 onAppear 副作用在窗口首次打开时才发生。
 @MainActor
 private struct AppComposition {
+  let connectivityLifecycle: ConnectivityLifecycle
   let controller: ProxyRuntimeController
   let catalogWorkflow: CatalogWorkflow
   let proxyControl: ProxyControlWorkflow
@@ -192,6 +197,22 @@ private struct AppComposition {
     // 写入侧经窄缝 SettingsCommitting，运行时控制器薄扩展即生产实现。
     let settingsWorkflow = SettingsWorkflow(
       committing: controller, credentials: controller.credentials)
+    let testRuntime = ConnectivityRuntime(
+      executable: Bundle.main.bundleURL.appendingPathComponent("Contents/Helpers/sslocal"))
+    let connectivity = ServerConnectivity(
+      configuration: { [weak catalogWorkflow] id in
+        guard let catalogWorkflow else { throw ServerFormLoadError.notFound }
+        return try catalogWorkflow.connectivityConfiguration(for: id)
+      },
+      revision: { [weak catalogWorkflow] in
+        catalogWorkflow?.connectivityRevision(for: $0) ?? "missing"
+      },
+      measure: testRuntime.measure)
+    catalogWorkflow.connectivity = connectivity
+    connectivity.setURL(
+      (try? settingsWorkflow.beginConnectivityURLEditing()).flatMap(ServerConnectivity.validURL))
+    settingsWorkflow.connectivityURLDidChange = { [weak connectivity] in connectivity?.setURL($0) }
+    let connectivityLifecycle = ConnectivityLifecycle(module: connectivity)
     // 诊断工作流 module：诊断区唯一 seam，组合根接线一次；进程期
     // 实例供独立诊断窗口使用。
     let diagnosticsWorkflow = DiagnosticsWorkflow(
@@ -226,6 +247,7 @@ private struct AppComposition {
       configurationGroupFileExporter: dependencies.configurationGroupFileExporter,
       qrImageSaver: dependencies.qrImageSaver)
     return AppComposition(
+      connectivityLifecycle: connectivityLifecycle,
       controller: controller,
       catalogWorkflow: catalogWorkflow,
       proxyControl: proxyControl,
diff --git a/ShadowsocksX-NG2/App/Resources/Connectivity.xcstrings b/ShadowsocksX-NG2/App/Resources/Connectivity.xcstrings
new file mode 100644
index 00000000..2c3f315b
--- /dev/null
+++ b/ShadowsocksX-NG2/App/Resources/Connectivity.xcstrings
@@ -0,0 +1,358 @@
+{
+  "sourceLanguage": "zh-Hans",
+  "strings": {
+    "响应延迟": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Response latency"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "响应延迟"
+          }
+        }
+      }
+    },
+    "测试中": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Testing"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "测试中"
+          }
+        }
+      }
+    },
+    "已过期": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Expired"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "已过期"
+          }
+        }
+      }
+    },
+    "无成功结果": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "No successful result"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "无成功结果"
+          }
+        }
+      }
+    },
+    "测试全部": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Test All"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "测试全部"
+          }
+        }
+      }
+    },
+    "已跳过冷却中的服务器": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Skipped servers in cooldown"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "已跳过冷却中的服务器"
+          }
+        }
+      }
+    },
+    "测试连通性": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Test Connectivity"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "测试连通性"
+          }
+        }
+      }
+    },
+    "配置不支持": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Unsupported configuration"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "配置不支持"
+          }
+        }
+      }
+    },
+    "准备超时": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Preparation timed out"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "准备超时"
+          }
+        }
+      }
+    },
+    "请求超时": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Request timed out"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "请求超时"
+          }
+        }
+      }
+    },
+    "配置错误": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Configuration error"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "配置错误"
+          }
+        }
+      }
+    },
+    "启动错误": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Startup error"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "启动错误"
+          }
+        }
+      }
+    },
+    "网络错误": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Network error"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "网络错误"
+          }
+        }
+      }
+    },
+    "最快响应延迟": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Fastest response latency"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "最快响应延迟"
+          }
+        }
+      }
+    },
+    "连通性测试": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Connectivity Test"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "连通性测试"
+          }
+        }
+      }
+    },
+    "测试 URL…": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Test URL…"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "测试 URL…"
+          }
+        }
+      }
+    },
+    "测试 URL": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Test URL"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "测试 URL"
+          }
+        }
+      }
+    },
+    "无法读取或保存测试 URL": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Unable to read or save the test URL"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "无法读取或保存测试 URL"
+          }
+        }
+      }
+    },
+    "经指定服务器发送 GET 请求，2xx 为成功；不跟随重定向。": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Send a GET through the selected server. A 2xx response succeeds. Redirects are not followed."
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "经指定服务器发送 GET 请求，2xx 为成功；不跟随重定向。"
+          }
+        }
+      }
+    },
+    "恢复默认": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Restore Default"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "恢复默认"
+          }
+        }
+      }
+    },
+    "取消": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Cancel"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "取消"
+          }
+        }
+      }
+    },
+    "保存": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Save"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "保存"
+          }
+        }
+      }
+    }
+  },
+  "version": "1.0"
+}
diff --git a/ShadowsocksX-NG2/App/UI/Servers/CatalogNodeDetailView.swift b/ShadowsocksX-NG2/App/UI/Servers/CatalogNodeDetailView.swift
index 70f2574e..2f5cc20a 100644
--- a/ShadowsocksX-NG2/App/UI/Servers/CatalogNodeDetailView.swift
+++ b/ShadowsocksX-NG2/App/UI/Servers/CatalogNodeDetailView.swift
@@ -45,6 +45,10 @@ struct CatalogNodeDetailView: View {
             parameters.reload(load: workflow.serverDetailPluginOptions)
           }
         }
+      } supplement: {
+        if let module = workflow.connectivity {
+          ConnectivityDetailView(module: module, node: node, workflow: workflow)
+        }
       }
       .onAppear {
         if !node.isGroup {
diff --git a/ShadowsocksX-NG2/App/UI/Servers/ConnectivityViews.swift b/ShadowsocksX-NG2/App/UI/Servers/ConnectivityViews.swift
new file mode 100644
index 00000000..80cd0341
--- /dev/null
+++ b/ShadowsocksX-NG2/App/UI/Servers/ConnectivityViews.swift
@@ -0,0 +1,148 @@
+import SwiftUI
+
+/// Observes only the network observations, with a periodic expiry projection.
+struct ConnectivityCell: View {
+  @ObservedObject var module: ServerConnectivity
+  let node: CatalogTreeNode
+  let workflow: CatalogWorkflow
+
+  var body: some View {
+    TimelineView(.periodic(from: .now, by: 1)) { context in
+      let value = presentation(at: context.date)
+      HStack(spacing: 5) {
+        Text(value.text).foregroundStyle(value.expired ? .secondary : .primary)
+        if value.testing { ProgressView().controlSize(.mini) }
+      }
+      .help(value.help)
+      .accessibilityElement(children: .ignore)
+      .accessibilityLabel(Text(ConnectivityCopy.text("响应延迟")))
+      .accessibilityValue(
+        Text(
+          value.text + " " + value.help + (value.testing ? " " + ConnectivityCopy.text("测试中") : ""))
+      )
+    }
+  }
+
+  private struct Presentation {
+    let text: String
+    let help: String
+    let expired: Bool
+    let testing: Bool
+  }
+
+  private func presentation(at date: Date) -> Presentation {
+    let record: ServerConnectivity.Record?
+    let text: String
+    var prefix = ""
+    let summary = module.summary(for: node.connectivityServerIDs, at: date)
+    if node.isGroup {
+      record = summary.record
+      text = record.map { ConnectivityCopy.outcome($0.outcome) } ?? (summary.hasResults ? "—" : "")
+      if let id = summary.serverID { prefix = workflow.displayName(for: id) + " · " }
+    } else {
+      record = module.history(for: node.id).first
+      text = record.map { ConnectivityCopy.outcome($0.outcome) } ?? ""
+    }
+    let expired = record?.isExpired(at: date) ?? false
+    let help =
+      record.map {
+        prefix + $0.finishedAt.formatted(date: .numeric, time: .standard)
+          + (expired ? " · " + ConnectivityCopy.text("已过期") : "")
+      } ?? (summary.hasResults && node.isGroup ? ConnectivityCopy.text("无成功结果") : "")
+    return Presentation(text: text, help: help, expired: expired, testing: summary.isTesting)
+  }
+}
+
+struct ConnectivityBatchButton: View {
+  @ObservedObject var module: ServerConnectivity
+  let targets: [NodeID]
+  @State private var batchID: UUID?
+
+  var body: some View {
+    HStack(spacing: 6) {
+      Button {
+        batchID = module.test(targets)
+      } label: {
+        Label(ConnectivityCopy.text("测试全部"), systemImage: "waveform.path.ecg")
+      }
+      .disabled(targets.isEmpty)
+      if let batchID, let batch = module.batch(batchID) {
+        if batch.completed < batch.targets.count { ProgressView().controlSize(.mini) }
+        Text("\(batch.completed)/\(batch.targets.count)")
+          .monospacedDigit()
+        if !batch.cooling.isEmpty {
+          Text(ConnectivityCopy.text("已跳过冷却中的服务器") + " (\(batch.cooling.count))")
+            .foregroundStyle(.secondary)
+        }
+      }
+    }
+  }
+}
+
+struct ConnectivityTestButton: View {
+  @ObservedObject var module: ServerConnectivity
+  let node: CatalogTreeNode
+  var body: some View {
+    Button(ConnectivityCopy.text("测试连通性")) { module.test(node.connectivityServerIDs) }
+      .disabled(!node.containsServerConfiguration || (!node.isGroup && module.isCooling(node.id)))
+  }
+}
+
+/// Copy is kept at the presentation edge; failures never render raw errors or URLs.
+enum ConnectivityCopy {
+  static func text(_ key: String) -> String {
+    NSLocalizedString(key, tableName: "Connectivity", bundle: .main, comment: "")
+  }
+  static func outcome(_ value: ServerConnectivity.Outcome) -> String {
+    switch value {
+    case .success(let milliseconds): "\(milliseconds) ms"
+    case .unsupported: text("配置不支持")
+    case .preparationTimeout: text("准备超时")
+    case .requestTimeout: text("请求超时")
+    case .configuration: text("配置错误")
+    case .startup: text("启动错误")
+    case .network: text("网络错误")
+    case .http(let status): "HTTP \(status)"
+    }
+  }
+}
+
+struct ConnectivityDetailView: View {
+  @ObservedObject var module: ServerConnectivity
+  let node: CatalogTreeNode
+  let workflow: CatalogWorkflow
+
+  var body: some View {
+    TimelineView(.periodic(from: .now, by: 1)) { context in
+      VStack(alignment: .leading, spacing: 8) {
+        HStack {
+          Text(ConnectivityCopy.text(node.isGroup ? "最快响应延迟" : "连通性测试")).font(.headline)
+          ConnectivityTestButton(module: module, node: node)
+        }
+        if node.isGroup {
+          ConnectivityCell(module: module, node: node, workflow: workflow)
+          let summary = module.summary(for: node.connectivityServerIDs, at: context.date)
+          if let id = summary.serverID, let record = summary.record {
+            Text(workflow.displayName(for: id))
+            Text(timestamp(record, at: context.date)).foregroundStyle(.secondary)
+          } else if summary.hasResults {
+            Text(ConnectivityCopy.text("无成功结果")).foregroundStyle(.secondary)
+          }
+        } else {
+          ForEach(module.history(for: node.id)) { record in
+            HStack {
+              Text(timestamp(record, at: context.date)).foregroundStyle(.secondary)
+              Spacer()
+              Text(ConnectivityCopy.outcome(record.outcome))
+            }
+          }
+        }
+      }
+    }
+  }
+
+  private func timestamp(_ record: ServerConnectivity.Record, at date: Date) -> String {
+    record.finishedAt.formatted(date: .numeric, time: .standard)
+      + (record.isExpired(at: date) ? " · " + ConnectivityCopy.text("已过期") : "")
+  }
+}
diff --git a/ShadowsocksX-NG2/App/UI/Servers/FavoriteServersTable.swift b/ShadowsocksX-NG2/App/UI/Servers/FavoriteServersTable.swift
index 5de998cd..f10d9138 100644
--- a/ShadowsocksX-NG2/App/UI/Servers/FavoriteServersTable.swift
+++ b/ShadowsocksX-NG2/App/UI/Servers/FavoriteServersTable.swift
@@ -37,6 +37,12 @@ struct FavoriteServersTable<MenuContent: View>: View {
         ServerTableNameCell(node: node, activeTargetID: activeTargetID)
       }
       .width(min: 140, ideal: 200)
+      TableColumn(ConnectivityCopy.text("响应延迟")) { node in
+        if let module = workflow.connectivity {
+          ConnectivityCell(module: module, node: node, workflow: workflow)
+        }
+      }
+      .width(min: 90, ideal: 110)
       TableColumn("路径") { node in
         let path = path(for: node)
         Text(path)
diff --git a/ShadowsocksX-NG2/App/UI/Servers/NodeDetailView.swift b/ShadowsocksX-NG2/App/UI/Servers/NodeDetailView.swift
index c97550be..f9d23c65 100644
--- a/ShadowsocksX-NG2/App/UI/Servers/NodeDetailView.swift
+++ b/ShadowsocksX-NG2/App/UI/Servers/NodeDetailView.swift
@@ -1,9 +1,10 @@
 import SwiftUI
 
 /// 只接受展示值与外部动作；不查询节点类型、工作流或凭据。
-struct NodeDetailView<Actions: View>: View {
+struct NodeDetailView<Actions: View, Supplement: View>: View {
   let detail: NodeDetailPresentation
   @ViewBuilder let actions: Actions
+  @ViewBuilder let supplement: Supplement
 
   var body: some View {
     ScrollView {
@@ -40,6 +41,7 @@ struct NodeDetailView<Actions: View>: View {
             }
           }
         }
+        supplement
       }
       .frame(maxWidth: .infinity, alignment: .leading)
       .padding(.horizontal, 16)
diff --git a/ShadowsocksX-NG2/App/UI/Servers/ServerTableNameCell.swift b/ShadowsocksX-NG2/App/UI/Servers/ServerTableNameCell.swift
index c930c899..3ef13d57 100644
--- a/ShadowsocksX-NG2/App/UI/Servers/ServerTableNameCell.swift
+++ b/ShadowsocksX-NG2/App/UI/Servers/ServerTableNameCell.swift
@@ -53,6 +53,9 @@ struct ServerNodeContextMenu: View {
 
   @ViewBuilder
   var body: some View {
+    if let module = workflow.connectivity {
+      ConnectivityTestButton(module: module, node: node)
+    }
     Button("激活") {
       Task { @MainActor in
         do {
diff --git a/ShadowsocksX-NG2/App/UI/Servers/ServersView.swift b/ShadowsocksX-NG2/App/UI/Servers/ServersView.swift
index 95c9d41f..f639ac5a 100644
--- a/ShadowsocksX-NG2/App/UI/Servers/ServersView.swift
+++ b/ShadowsocksX-NG2/App/UI/Servers/ServersView.swift
@@ -154,6 +154,12 @@ struct ServersView: View {
         .padding(.leading, CGFloat(depths[node.id] ?? 0) * 14)
       }
       .width(min: 160, ideal: 240)
+      TableColumn(ConnectivityCopy.text("响应延迟")) { node in
+        if let module = workflow.connectivity {
+          ConnectivityCell(module: module, node: node, workflow: workflow)
+        }
+      }
+      .width(min: 90, ideal: 110)
       TableColumn("收藏") { node in
         Image(systemName: workflow.isFavorite(node.id) ? "star.fill" : "star")
           .accessibilityLabel(Text("收藏"))
@@ -302,6 +308,12 @@ extension ServersView {
 
   @ToolbarContentBuilder
   private var toolbarContent: some ToolbarContent {
+    if let module = workflow.connectivity {
+      ToolbarItem(placement: .primaryAction) {
+        ConnectivityBatchButton(
+          module: module, targets: workflow.connectivityTargets(source: section.source))
+      }
+    }
     if section != .favorites {
       ToolbarItem(placement: .primaryAction) {
         Menu {
diff --git a/ShadowsocksX-NG2/App/UI/Settings/ConnectivityURLSettings.swift b/ShadowsocksX-NG2/App/UI/Settings/ConnectivityURLSettings.swift
new file mode 100644
index 00000000..dbc38b6a
--- /dev/null
+++ b/ShadowsocksX-NG2/App/UI/Settings/ConnectivityURLSettings.swift
@@ -0,0 +1,53 @@
+import SwiftUI
+
+struct ConnectivityURLSettings: View {
+  @ObservedObject var workflow: SettingsWorkflow
+  @State private var editing = false
+  @State private var value = ""
+  @State private var failure = false
+
+  var body: some View {
+    Section {
+      Button(ConnectivityCopy.text("测试 URL…")) {
+        do {
+          value = try workflow.beginConnectivityURLEditing()
+          failure = false
+          editing = true
+        } catch { failure = true }
+      }
+      if failure { Text(ConnectivityCopy.text("无法读取或保存测试 URL")).foregroundStyle(.red) }
+    } header: {
+      Text(ConnectivityCopy.text("连通性测试"))
+    }
+    .sheet(isPresented: $editing) {
+      VStack(alignment: .leading, spacing: 16) {
+        Text(ConnectivityCopy.text("测试 URL")).font(.headline)
+        TextField("HTTP / HTTPS", text: $value).textFieldStyle(.roundedBorder)
+        Text(ConnectivityCopy.text("经指定服务器发送 GET 请求，2xx 为成功；不跟随重定向。"))
+          .font(.caption).foregroundStyle(.secondary)
+        if failure { Text(ConnectivityCopy.text("无法读取或保存测试 URL")).foregroundStyle(.red) }
+        HStack {
+          Button(ConnectivityCopy.text("恢复默认")) {
+            value = ServerConnectivity.defaultURL.absoluteString
+          }
+          Spacer()
+          Button(ConnectivityCopy.text("取消")) { editing = false }.keyboardShortcut(.cancelAction)
+          Button(ConnectivityCopy.text("保存")) {
+            Task {
+              if await workflow.saveConnectivityURL(value) {
+                editing = false
+                failure = false
+              } else {
+                failure = true
+              }
+            }
+          }
+          .keyboardShortcut(.defaultAction)
+          .disabled(ServerConnectivity.validURL(value) == nil || workflow.isCommitting)
+        }
+      }
+      .padding(24).frame(width: 520)
+      .interactiveDismissDisabled(workflow.isCommitting)
+    }
+  }
+}
diff --git a/ShadowsocksX-NG2/App/UI/Settings/SettingsView.swift b/ShadowsocksX-NG2/App/UI/Settings/SettingsView.swift
index 3c7e2e64..6bbcb083 100644
--- a/ShadowsocksX-NG2/App/UI/Settings/SettingsView.swift
+++ b/ShadowsocksX-NG2/App/UI/Settings/SettingsView.swift
@@ -15,6 +15,7 @@ struct SettingsView: View {
     Form {
       generalSection
       endpointSection
+      ConnectivityURLSettings(workflow: workflow)
       systemProxySection
       PluginManagementSection(model: plugins)
     }
diff --git a/ShadowsocksX-NG2/Domain/Settings/ProxySettings.swift b/ShadowsocksX-NG2/Domain/Settings/ProxySettings.swift
index 1a534fcf..1a8341f1 100644
--- a/ShadowsocksX-NG2/Domain/Settings/ProxySettings.swift
+++ b/ShadowsocksX-NG2/Domain/Settings/ProxySettings.swift
@@ -5,6 +5,7 @@ import Foundation
 struct ProxySettings: Equatable, Sendable {
   static let defaultProxyExceptions = ""
 
+  var connectivityURLReference: CredentialReference?
   var listen: SslocalListenSettings
   /// User-added system-proxy exceptions; these entries do not become ACL rules.
   var proxyExceptions: String
@@ -22,12 +23,14 @@ struct ProxySettings: Equatable, Sendable {
 
   init(
     listen: SslocalListenSettings = SslocalListenSettings(),
+    connectivityURLReference: CredentialReference? = nil,
     proxyExceptions: String = ProxySettings.defaultProxyExceptions,
     preferredMode: ProxyModeKind = .rule,
     ruleDefaultAction: RuleDefaultAction = .proxyWhenUnmatched,
     agentEnabled: Bool = false,
     systemProxyEnabled: Bool = false
   ) {
+    self.connectivityURLReference = connectivityURLReference
     self.listen = listen
     self.proxyExceptions = proxyExceptions
     self.preferredMode = preferredMode
diff --git a/ShadowsocksX-NG2/Domain/Settings/ProxySettingsFileStore.swift b/ShadowsocksX-NG2/Domain/Settings/ProxySettingsFileStore.swift
index 9a8a208d..c4ffe857 100644
--- a/ShadowsocksX-NG2/Domain/Settings/ProxySettingsFileStore.swift
+++ b/ShadowsocksX-NG2/Domain/Settings/ProxySettingsFileStore.swift
@@ -85,6 +85,7 @@ struct ProxySettingsFileStore: ProxySettingsStoring {
     return try validated(
       ProxySettings(
         listen: listen,
+        connectivityURLReference: record.connectivityURLReference,
         proxyExceptions: record.proxyExceptions,
         preferredMode: record.preferredMode,
         ruleDefaultAction: record.ruleDefaultAction,
@@ -94,6 +95,7 @@ struct ProxySettingsFileStore: ProxySettingsStoring {
 
   private func record(from settings: ProxySettings) -> ProxySettingsRecord {
     var record = ProxySettingsRecord()
+    record.connectivityURLReference = settings.connectivityURLReference
     record.localListen = settings.listen.local
     record.lanListen = settings.listen.lan
     record.proxyExceptions = settings.proxyExceptions
@@ -112,6 +114,7 @@ struct ProxySettingsFileStore: ProxySettingsStoring {
 }
 
 private struct ProxySettingsRecord: Codable, Equatable, Sendable {
+  var connectivityURLReference: CredentialReference?
   var localListen = LocalListeningSettings()
   var lanListen = LANListeningSettings()
   var proxyExceptions: String = ProxySettings.defaultProxyExceptions
@@ -124,6 +127,8 @@ private struct ProxySettingsRecord: Codable, Equatable, Sendable {
 
   init(from decoder: Decoder) throws {
     let container = try decoder.container(keyedBy: CodingKeys.self)
+    connectivityURLReference = try container.decodeIfPresent(
+      CredentialReference.self, forKey: .connectivityURLReference)
     // 未正式发版：忽略旧的单组监听字段，不迁移独立旧监听文件。
     localListen =
       try container.decodeIfPresent(LocalListeningSettings.self, forKey: .localListen)
@@ -156,6 +161,7 @@ private struct ProxySettingsRecord: Codable, Equatable, Sendable {
 
 extension ProxySettingsRecord {
   fileprivate enum CodingKeys: String, CodingKey {
+    case connectivityURLReference
     case localListen, lanListen
     case proxyExceptions
     case preferredMode
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityCatalogTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityCatalogTests.swift
new file mode 100644
index 00000000..29b88c0a
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityCatalogTests.swift
@@ -0,0 +1,49 @@
+import Foundation
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ConnectivityCatalogTests {
+  @Test func targetScopesExpandFavoriteGroupsWithoutChangingCatalogOrActivation() async throws {
+    let subscription = try CatalogFixtures.makeSubscriptionFixture(prefix: UUID().uuidString)
+    var catalog = subscription.catalog
+    let credentials = InMemoryCredentialStore()
+    let group = try catalog.addGroup("Local")
+    let nested = try catalog.addGroup("Nested", to: group)
+    let firstTarget = try ActivationFixture.addPlainServer(
+      "A", to: group, in: &catalog, credentials: credentials)
+    let secondTarget = try ActivationFixture.addPlainServer(
+      "B", to: nested, in: &catalog, credentials: credentials)
+    let directory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: directory) }
+    let store = CatalogFileStore(fileURL: directory.appendingPathComponent("catalog.json"))
+    try store.save(CatalogDocument(catalog: catalog))
+    let runtime = FakeCatalogRuntime()
+    let coordinator = CatalogCommitCoordinator(fileStore: store, runtime: runtime)
+    let workflow = makeCatalogWorkflow(coordinator: coordinator, credentials: credentials)
+    try workflow.setFavorite(group, isFavorite: true)
+    try workflow.setFavorite(secondTarget, isFavorite: true)
+    #expect(workflow.connectivityTargets(source: .manual) == [secondTarget, firstTarget])
+    #expect(
+      workflow.connectivityTargets(source: .subscription)
+        == Array(subscription.serverIDs.reversed()))
+    #expect(workflow.connectivityTargets(source: nil) == [secondTarget, firstTarget])
+    #expect(
+      workflow.tree.node(withID: group)?.connectivityServerIDs == [secondTarget, firstTarget])
+    let before = try Data(contentsOf: store.fileURL)
+    let tree = workflow.tree
+    let version = workflow.connectivityRevision(for: firstTarget)
+    let derived = try workflow.connectivityConfiguration(for: firstTarget)
+    #expect(derived.id == firstTarget.rawValue)
+    #expect(derived.password == "pw-A")
+    #expect(runtime.convergeCount == 0)
+    #expect(workflow.tree == tree)
+    #expect(try Data(contentsOf: store.fileURL) == before)
+    let fields = try #require(catalog.entry(for: firstTarget))
+    guard case .server(let connection) = fields.kind else { return }
+    try credentials.save("different", for: connection.passwordRef)
+    #expect(workflow.connectivityRevision(for: firstTarget) != version)
+    #expect(try workflow.connectivityConfiguration(for: firstTarget).password == "different")
+  }
+}
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityCertificateTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityCertificateTests.swift
new file mode 100644
index 00000000..157794d5
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityCertificateTests.swift
@@ -0,0 +1,104 @@
+import Foundation
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ConnectivityCertificateTests {
+  @Test func HTTPSRejectsUntrustedCertificateThroughRequiredProxy() async throws {
+    let root = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    try FileManager.default.createDirectory(at: root, withIntermediateDirectories: true)
+    defer { try? FileManager.default.removeItem(at: root) }
+    let (cert, key) = try makeCertificate(in: root)
+    let marker = root.appendingPathComponent("tls-error")
+    let script = try writeProxyScript(in: root)
+    let proxy = Process()
+    let output = Pipe()
+    proxy.executableURL = URL(fileURLWithPath: "/usr/bin/env")
+    proxy.arguments = ["python3", script.path, cert.path, key.path, marker.path]
+    proxy.standardOutput = output
+    proxy.standardError = FileHandle.nullDevice
+    try proxy.run()
+    defer {
+      if proxy.isRunning {
+        proxy.terminate()
+        proxy.waitUntilExit()
+      }
+    }
+    var data = Data()
+    while let byte = try output.fileHandleForReading.read(upToCount: 1), !byte.isEmpty {
+      if byte == Data([10]) { break }
+      data.append(byte)
+    }
+    let port = try #require(
+      Int(
+        (String(data: data, encoding: .utf8) ?? "").trimmingCharacters(in: .whitespacesAndNewlines))
+    )
+    let id = NodeID.fresh()
+    let server = SslocalServerDocument(
+      id: "test", server: "example.com", serverPort: 443,
+      password: "test", method: "aes-256-gcm", plugin: nil, pluginOpts: nil)
+    let module = ServerConnectivity(
+      configuration: { _ in server },
+      measure: { _, url, _ in
+        await ConnectivityHTTPRequest().perform(url: url, proxyPort: port)
+      })
+    module.setURL(URL(string: "https://localhost/test")!)
+    await module.wait(for: module.test([id]))
+    #expect(module.history(for: id).first?.outcome == .network)
+    #expect(FileManager.default.fileExists(atPath: marker.path))
+    if FileManager.default.fileExists(atPath: marker.path) {
+      let failure = try String(contentsOf: marker, encoding: .utf8)
+      #expect(failure.contains("UNKNOWN_CA") || failure.contains("CERTIFICATE_UNKNOWN"))
+    }
+  }
+  private func makeCertificate(in root: URL) throws -> (URL, URL) {
+    let cert = root.appendingPathComponent("cert.pem")
+    let key = root.appendingPathComponent("key.pem")
+    let openssl = Process()
+    openssl.executableURL = URL(fileURLWithPath: "/usr/bin/openssl")
+    openssl.arguments = [
+      "req", "-x509", "-newkey", "rsa:2048", "-nodes", "-keyout", key.path,
+      "-out", cert.path, "-days", "1", "-subj", "/CN=localhost", "-addext",
+      "subjectAltName=DNS:localhost",
+    ]
+    openssl.standardOutput = FileHandle.nullDevice
+    openssl.standardError = FileHandle.nullDevice
+    try openssl.run()
+    openssl.waitUntilExit()
+    #expect(openssl.terminationStatus == 0)
+    return (cert, key)
+  }
+
+  private func writeProxyScript(in root: URL) throws -> URL {
+    let script = root.appendingPathComponent("proxy.py")
+    try """
+    import socket, ssl, sys, pathlib
+    context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+    context.load_cert_chain(sys.argv[1], sys.argv[2])
+    server = socket.socket()
+    server.bind(('127.0.0.1', 0)); server.listen()
+    print(server.getsockname()[1], flush=True)
+    while True:
+        connection, _ = server.accept()
+        request = b''
+        while b'\\r\\n\\r\\n' not in request:
+            data = connection.recv(4096)
+            if not data: break
+            request += data
+        if not request.startswith(b'CONNECT localhost:443 '):
+            connection.close(); continue
+        connection.sendall(b'HTTP/1.1 200 Connection Established\\r\\n\\r\\n')
+        try:
+            secured = context.wrap_socket(connection, server_side=True)
+            secured.recv(4096)
+            secured.sendall(b'HTTP/1.1 204 No Content\\r\\n\\r\\n')
+            secured.close()
+        except ssl.SSLError as error:
+            pathlib.Path(sys.argv[3]).write_text(str(error))
+            connection.close()
+    """.write(to: script, atomically: true, encoding: .utf8)
+    return script
+  }
+
+}
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityFormalRuntimeTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityFormalRuntimeTests.swift
new file mode 100644
index 00000000..88c8e75e
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityFormalRuntimeTests.swift
@@ -0,0 +1,53 @@
+import Foundation
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ConnectivityFormalRuntimeTests {
+  @Test func changingTestURLDoesNotConvergeTheRunningFormalProxy() async throws {
+    let runtime = ProxyRuntimeFixture.makeTemporaryRuntime()
+    defer { try? FileManager.default.removeItem(at: runtime.directory) }
+    let credentials = InMemoryCredentialStore()
+    let agent = ProxyRuntimeFixture.FakeLaunchAgent()
+    let systemProxy = ProxyRuntimeFixture.FakeSystemProxy()
+    let store = SettingsWorkflowTests.InMemorySettingsStore()
+    let fileStore = RuntimeFileStore(fileURL: runtime.contract)
+    agent.onRegister = {
+      if let document = fileStore.loadDocument() {
+        try? fileStore.writeRuntimeReceipt(for: document, processID: 42)
+      }
+    }
+    let controller = ProxyRuntimeController(
+      catalogSnapshotReader: ProxyRuntimeFixture.catalogSnapshotReader(
+        at: runtime.directory.appendingPathComponent("catalog.json")),
+      activationFileStore: ActivationStateFileStore(
+        fileURL: runtime.directory.appendingPathComponent("activation.json")),
+      runtimeFileStore: fileStore, credentials: credentials, plugins: ActivationFixture.plugins,
+      listenRestore: RestoredListenSettings(
+        settings: ActivationFixture.listen, unreadableError: nil),
+      settingsStore: store,
+      customRuleStore: CustomRuleStore(
+        fileURL: runtime.directory.appendingPathComponent("rules.json")),
+      appBundle: AppArtifact.bundle,
+      ruleSnapshots: BuiltinRuleSnapshots(loader: ProxyRuntimeFixture.controlFlowRuleSnapshot),
+      agent: agent,
+      probe: ProxyRuntimeFixture.FakeProbe.reachable(), systemProxy: systemProxy,
+      systemProxyHelper: ProxyRuntimeFixture.FakeSystemProxyHelperService(),
+      launchHealthTimeoutSeconds: 0.05,
+      sendSignal: { _, _ in 0 }, processIsAlive: { $0 == 42 })
+    await controller.setAgentEnabled(true)
+    let state = controller.state
+    let calls = agent.registerCount
+    let target = controller.activeTargetID
+    let document = try Data(contentsOf: runtime.contract)
+    let workflow = SettingsWorkflow(committing: controller, credentials: credentials)
+    #expect(await workflow.saveConnectivityURL("https://example.com/probe?token=private"))
+    #expect(controller.state == state)
+    #expect(controller.activeTargetID == target)
+    #expect(agent.registerCount == calls)
+    #expect(agent.unregisterCount == 0)
+    #expect(systemProxy.applied.isEmpty)
+    #expect(try Data(contentsOf: runtime.contract) == document)
+  }
+}
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityHTTPTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityHTTPTests.swift
new file mode 100644
index 00000000..ead4c9aa
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityHTTPTests.swift
@@ -0,0 +1,130 @@
+import Foundation
+import Network
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ConnectivityHTTPTests {
+  @Test(arguments: [204, 200, 302, 500])
+  func sendsGETThroughProxyAndStopsAtHeaders(status: Int) async throws {
+    let proxy = try HeaderProxy(status: status)
+    defer { proxy.stop() }
+    let port = try await proxy.start()
+    let started = ContinuousClock.now
+    // This name cannot resolve; a successful response proves proxy routing.
+    let id = NodeID.fresh()
+    let module = ServerConnectivity(
+      configuration: { _ in Self.server },
+      measure: { _, url, _ in
+        await ConnectivityHTTPRequest().perform(url: url, proxyPort: port)
+      })
+    module.setURL(URL(string: "http://target.invalid/test")!)
+    await module.wait(for: module.test([id]))
+    let value = try #require(module.history(for: id).first?.outcome)
+    if (200..<300).contains(status) {
+      guard case .success = value else {
+        Issue.record("Expected successful proxy response, got \(value)")
+        return
+      }
+    } else {
+      #expect(value == .http(status))
+    }
+    #expect(ContinuousClock.now - started < .seconds(2))
+    #expect(proxy.requests.count == 1)
+    #expect(proxy.requests.first?.hasPrefix("GET http://target.invalid/test HTTP/") == true)
+  }
+
+  @Test func requestHasOneFiveSecondDeadline() async throws {
+    let proxy = try HeaderProxy(status: nil)
+    defer { proxy.stop() }
+    let port = try await proxy.start()
+    let id = NodeID.fresh()
+    let module = ServerConnectivity(
+      configuration: { _ in Self.server },
+      measure: { _, url, _ in
+        await ConnectivityHTTPRequest().perform(url: url, proxyPort: port)
+      })
+    module.setURL(URL(string: "http://target.invalid/slow")!)
+    let started = ContinuousClock.now
+    await module.wait(for: module.test([id]))
+    #expect(module.history(for: id).first?.outcome == .requestTimeout)
+    #expect(ContinuousClock.now - started >= .seconds(5))
+    #expect(ContinuousClock.now - started < .seconds(6))
+    #expect(proxy.requests.count == 1)
+  }
+
+  @Test func cancellationEndsRequestWithoutWaitingForHeaders() async throws {
+    let proxy = try HeaderProxy(status: nil)
+    defer { proxy.stop() }
+    let port = try await proxy.start()
+    let id = NodeID.fresh()
+    let module = ServerConnectivity(
+      configuration: { _ in Self.server },
+      measure: { _, url, _ in
+        await ConnectivityHTTPRequest().perform(url: url, proxyPort: port)
+      })
+    module.setURL(URL(string: "http://target.invalid/test")!)
+    let batch = module.test([id])
+    for _ in 0..<20 { await Task.yield() }
+    await module.shutdown()
+    await module.wait(for: batch)
+    #expect(module.history(for: id).isEmpty)
+    #expect(module.isCooling(id))
+  }
+  private static var server: SslocalServerDocument {
+    SslocalServerDocument(
+      id: "test", server: "example.com", serverPort: 443,
+      password: "test", method: "aes-256-gcm", plugin: nil, pluginOpts: nil)
+  }
+}
+
+/// Controlled HTTP proxy: headers arrive, but the declared body never does.
+private final class HeaderProxy: @unchecked Sendable {
+  private let listener: NWListener
+  private let status: Int?
+  private let lock = NSLock()
+  private var received: [String] = []
+  private var connections: [NWConnection] = []
+  var requests: [String] { lock.withLock { received } }
+
+  init(status: Int?) throws {
+    self.status = status
+    listener = try NWListener(using: .tcp, on: .any)
+  }
+
+  func start() async throws -> Int {
+    listener.newConnectionHandler = { [self] connection in
+      lock.withLock { connections.append(connection) }
+      connection.start(queue: DispatchQueue(label: UUID().uuidString))
+      connection.receive(minimumIncompleteLength: 1, maximumLength: 65536) { [self] data, _, _, _ in
+        if let data { lock.withLock { received.append(String(data: data, encoding: .utf8) ?? "") } }
+        guard let status else { return }
+        let headers =
+          "HTTP/1.1 \(status) Response\r\nLocation: http://another.invalid/redirect\r\nContent-Length: 99999\r\n\r\n"
+        connection.send(content: Data(headers.utf8), completion: .contentProcessed { _ in })
+      }
+    }
+    return try await withCheckedThrowingContinuation { continuation in
+      listener.stateUpdateHandler = { [self] state in
+        switch state {
+        case .ready:
+          listener.stateUpdateHandler = nil
+          continuation.resume(returning: Int(listener.port!.rawValue))
+        case .failed(let error):
+          listener.stateUpdateHandler = nil
+          continuation.resume(throwing: error)
+        default: break
+        }
+      }
+      listener.start(queue: DispatchQueue(label: UUID().uuidString))
+    }
+  }
+
+  func stop() {
+    listener.cancel()
+    listener.newConnectionHandler = nil
+    let connections = lock.withLock { self.connections }
+    connections.forEach { $0.cancel() }
+  }
+}
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityRuntimeTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityRuntimeTests.swift
new file mode 100644
index 00000000..621195e2
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivityRuntimeTests.swift
@@ -0,0 +1,44 @@
+import Darwin
+import Foundation
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ConnectivityRuntimeTests {
+  @Test func preparationTimeoutKillsProcessGroupAndRemovesSecretsBeforeCompleting() async throws {
+    let root = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: root) }
+    try FileManager.default.createDirectory(at: root, withIntermediateDirectories: true)
+    let environments = root.appendingPathComponent("environments")
+    let pidFile = root.appendingPathComponent("pid")
+    let script = root.appendingPathComponent("fake-sslocal")
+    // Ignore TERM so this test exercises the two-second force termination path.
+    let text = "#!/bin/sh\ntrap '' TERM\necho $$ > '\(pidFile.path)'\nsleep 60 &\nwait\n"
+    try text.write(to: script, atomically: true, encoding: .utf8)
+    try FileManager.default.setAttributes([.posixPermissions: 0o700], ofItemAtPath: script.path)
+    let adapter = ConnectivityRuntime(executable: script, temporaryRoot: environments)
+    let id = NodeID.fresh()
+    let server = SslocalServerDocument(
+      id: id.rawValue, server: "example.com", serverPort: 443,
+      password: "private", method: "aes-256-gcm", plugin: nil, pluginOpts: nil)
+    let module = ServerConnectivity(
+      configuration: { _ in server },
+      measure: { server, url, _ in
+        await adapter.measure(
+          server, url: url, preparationDeadline: .now.advanced(by: .milliseconds(100)))
+      })
+    let started = ContinuousClock.now
+    await module.wait(for: module.test([id]))
+    #expect(module.history(for: id).first?.outcome == .preparationTimeout)
+    #expect(ContinuousClock.now - started >= .seconds(2))
+    #expect(try FileManager.default.contentsOfDirectory(atPath: environments.path).isEmpty)
+    let pid = try #require(
+      Int32(
+        String(contentsOf: pidFile, encoding: .utf8).trimmingCharacters(in: .whitespacesAndNewlines)
+      ))
+    #expect(kill(pid, 0) != 0)
+    #expect(module.testing.isEmpty)
+    #expect(module.isCooling(id))
+  }
+}
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ConnectivitySettingsTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivitySettingsTests.swift
new file mode 100644
index 00000000..0315a31c
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ConnectivitySettingsTests.swift
@@ -0,0 +1,39 @@
+import Foundation
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ConnectivitySettingsTests {
+  @Test func customURLIsSecretAndFailureDoesNotPublishOrChangeSavedURL() async throws {
+    let committer = FakeSettingsCommitter()
+    let credentials = InMemoryCredentialStore()
+    let workflow = SettingsWorkflow(committing: committer, credentials: credentials)
+    var published = 0
+    workflow.connectivityURLDidChange = { _ in published += 1 }
+    let secretURL = "https://example.com/probe?token=private"
+    #expect(await workflow.saveConnectivityURL(secretURL))
+    #expect(try workflow.beginConnectivityURLEditing() == secretURL)
+    #expect(credentials.storageCount == 1)
+    let saved = committer.committedSettings
+    let directory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    let file = directory.appendingPathComponent("settings.json")
+    defer { try? FileManager.default.removeItem(at: directory) }
+    let store = ProxySettingsFileStore(fileURL: file)
+    try store.save(saved)
+    #expect(try store.load() == saved)
+    let text = try String(contentsOf: file, encoding: .utf8)
+    #expect(!text.contains("private"))
+    #expect(!text.contains("example.com"))
+    committer.updateError = ProxySettingsStoreError.ioFailure(detail: "fixture")
+    #expect(await !workflow.saveConnectivityURL("http://example.com/new"))
+    #expect(committer.committedSettings == saved)
+    #expect(credentials.storageCount == 1)
+    #expect(published == 1)
+    #expect(try workflow.beginConnectivityURLEditing() == secretURL)
+    committer.updateError = nil
+    #expect(await workflow.saveConnectivityURL(ServerConnectivity.defaultURL.absoluteString))
+    #expect(committer.committedSettings.connectivityURLReference == nil)
+    #expect(credentials.storageCount == 0)
+  }
+}
diff --git a/ShadowsocksX-NG2/Tests/Connectivity/ServerConnectivityTests.swift b/ShadowsocksX-NG2/Tests/Connectivity/ServerConnectivityTests.swift
new file mode 100644
index 00000000..29447a48
--- /dev/null
+++ b/ShadowsocksX-NG2/Tests/Connectivity/ServerConnectivityTests.swift
@@ -0,0 +1,190 @@
+import Foundation
+import Testing
+
+@testable import ShadowsocksX_NG2
+
+@MainActor
+struct ServerConnectivityTests {
+  @Test func repeatedRequestsShareWorkAndCoolingDoesNotAddHistory() async {
+    let id = NodeID(rawValue: UUID().uuidString)
+    var calls = 0
+    var now = Date(timeIntervalSince1970: 100)
+    let module = ServerConnectivity(
+      configuration: { _ in .fixture }, now: { now },
+      measure: { _, _, _ in
+        calls += 1
+        await Task.yield()
+        return .success(milliseconds: 42)
+      })
+    let batch = module.test([id, id])
+    _ = module.test([id])
+    await module.wait(for: batch)
+    #expect(calls == 1)
+    #expect(module.history(for: id).count == 1)
+    let skipped = module.test([id])
+    #expect(module.batch(skipped)?.cooling == [id])
+    #expect(module.history(for: id).count == 1)
+    now.addTimeInterval(10)
+    await module.wait(for: module.test([id]))
+    #expect(calls == 2)
+  }
+
+  @Test func overlappingBatchesShareThreeSlotsUntilCleanupCompletes() async {
+    let ids = (0..<7).map { _ in NodeID.fresh() }
+    let gate = AsyncGate()
+    var active = 0
+    var peak = 0
+    var calls = 0
+    let module = ServerConnectivity(
+      configuration: { _ in .fixture },
+      measure: { _, _, _ in
+        active += 1
+        calls += 1
+        peak = max(peak, active)
+        await gate.wait()
+        active -= 1
+        return .success(milliseconds: 12)
+      })
+    let firstTarget = module.test(Array(ids.prefix(5)))
+    let secondTarget = module.test(Array(ids.suffix(5)))
+    for _ in 0..<100 { await Task.yield() }
+    #expect(calls == 3)
+    #expect(module.testing.count == 7)
+    gate.release()
+    await module.wait(for: firstTarget)
+    await module.wait(for: secondTarget)
+    #expect(peak == 3)
+    #expect(calls == 7)
+    #expect(ids.allSatisfy { module.history(for: $0).count == 1 })
+  }
+
+  @Test func credentialValueChangesSuppressLateResultsAndPreserveCooldown() async {
+    let id = NodeID.fresh()
+    var server = SslocalServerDocument.fixture
+    let gate = AsyncGate()
+    let module = ServerConnectivity(
+      configuration: { _ in server },
+      measure: { _, _, _ in
+        await gate.wait()
+        return .success(milliseconds: 9)
+      })
+    let batch = module.test([id])
+    await Task.yield()
+    server = SslocalServerDocument(
+      id: "test", server: "example.com", serverPort: 443,
+      password: "changed", method: "aes-256-gcm", plugin: nil, pluginOpts: nil)
+    module.configurationsChanged()
+    gate.release()
+    await module.wait(for: batch)
+    #expect(module.history(for: id).isEmpty)
+    #expect(module.isCooling(id))
+    module.setURL(URL(string: "https://example.com/check")!)
+    #expect(module.isCooling(id))
+  }
+
+  @Test func latestFailureReplacesSuccessAndHistoryIsBounded() async {
+    let id = NodeID.fresh()
+    var now = Date(timeIntervalSince1970: 100)
+    var outcome = ServerConnectivity.Outcome.success(milliseconds: 11)
+    let module = ServerConnectivity(
+      configuration: { _ in .fixture }, now: { now },
+      measure: { _, _, _ in outcome })
+    await module.wait(for: module.test([id]))
+    outcome = .http(302)
+    for _ in 0..<12 {
+      now.addTimeInterval(10)
+      await module.wait(for: module.test([id]))
+    }
+    #expect(module.history(for: id).count == 10)
+    #expect(module.history(for: id).first?.outcome == .http(302))
+    let summary = module.summary(for: [id], at: now)
+    #expect(summary.hasResults)
+    #expect(summary.record == nil)
+    #expect(!summary.isTesting)
+  }
+
+  @Test func freshResultsBeatStaleAndTiesUseCatalogOrder() async {
+    let ids = (0..<3).map { _ in NodeID.fresh() }
+    var now = Date(timeIntervalSince1970: 100)
+    var latency = 1
+    let module = ServerConnectivity(
+      configuration: { _ in .fixture }, now: { now },
+      measure: { _, _, _ in .success(milliseconds: latency) })
+    await module.wait(for: module.test([ids[0]]))
+    now.addTimeInterval(300)
+    latency = 20
+    await module.wait(for: module.test(Array(ids.suffix(2))))
+    #expect(module.summary(for: ids, at: now).serverID == ids[1])
+    module.networkChanged()
+    #expect(module.summary(for: ids, at: now).serverID == ids[0])
+    #expect(module.summary(for: ids, at: now).record?.isExpired(at: now) == true)
+    module.setURL(URL(string: "https://example.com/new")!)
+    #expect(!module.summary(for: ids, at: now).hasResults)
+  }
+
+  @Test func URLAndNetworkChangesSuppressInFlightAndShutdownDrainsQueuedWork() async {
+    let ids = (0..<5).map { _ in NodeID.fresh() }
+    let gate = AsyncGate()
+    let module = ServerConnectivity(
+      configuration: { _ in .fixture },
+      measure: { _, _, _ in
+        await gate.wait()
+        return .success(milliseconds: 9)
+      })
+    let batch = module.test(ids)
+    await Task.yield()
+    module.networkChanged()
+    let shutdown = Task { await module.shutdown() }
+    await Task.yield()
+    #expect(!module.testing.isEmpty)
+    gate.release()
+    await shutdown.value
+    await module.wait(for: batch)
+    #expect(module.testing.isEmpty)
+    #expect(ids.allSatisfy { module.history(for: $0).isEmpty && module.isCooling($0) })
+  }
+
+  @Test func queuedConfigurationIsRecheckedBeforeLaunching() async {
+    let ids = (0..<4).map { _ in NodeID.fresh() }
+    let gate = AsyncGate()
+    var changed = false
+    var calls = 0
+    let module = ServerConnectivity(
+      configuration: { id in
+        if changed && id == ids[3] { throw ServerFormLoadError.notFound }
+        return .fixture
+      },
+      measure: { _, _, _ in
+        calls += 1
+        await gate.wait()
+        return .success(milliseconds: 5)
+      })
+    let batch = module.test(ids)
+    for _ in 0..<100 { await Task.yield() }
+    changed = true
+    gate.release()
+    await module.wait(for: batch)
+    #expect(calls == 3)
+    #expect(module.history(for: ids[3]).isEmpty)
+    #expect(module.isCooling(ids[3]))
+  }
+
+  @Test func URLValidationAllowsHTTPAndHTTPSOnly() {
+    #expect(ServerConnectivity.validURL("http://example.com/check") != nil)
+    #expect(ServerConnectivity.validURL("https://example.com/check?q=secret") != nil)
+    for value in [
+      "file:///tmp/check", "ftp://example.com", "https:///", "example.com", "http://x/#fragment",
+    ] {
+      #expect(ServerConnectivity.validURL(value) == nil)
+    }
+  }
+
+}
+
+extension SslocalServerDocument {
+  fileprivate static var fixture: Self {
+    Self(
+      id: "test", server: "example.com", serverPort: 443, password: "secret",
+      method: "aes-256-gcm", plugin: nil, pluginOpts: nil)
+  }
+}
diff --git a/ShadowsocksX-NG2/project.yml b/ShadowsocksX-NG2/project.yml
index 5f77f5d9..e26fc2df 100644
--- a/ShadowsocksX-NG2/project.yml
+++ b/ShadowsocksX-NG2/project.yml
@@ -138,6 +138,7 @@ targets:
         # 模块名让位给 Core 镜像库（ShadowsocksX_NG2）：两者 swiftmodule 都落
         # 共享 Products 目录，重名会互相覆盖；app 可执行自身不 import 任何
         # 消费方，改名零影响。
+        SWIFT_OBJC_BRIDGING_HEADER: App/Application/Connectivity/ConnectivityHTTPTransport.h
         PRODUCT_MODULE_NAME: ShadowsocksX_NG2App
         ASSETCATALOG_COMPILER_APPICON_NAME: AppIcon
         MARKETING_VERSION: "2.0.0"
@@ -163,6 +164,7 @@ targets:
         - name: ShadowsocksX-NG2Tests
           parallelizable: true
     dependencies:
+      - sdk: libcurl.tbd
       # 代理运行时 wrapper（BundleProgram）：以独立可执行文件装入
       # Contents/MacOS，由 LaunchAgent plist 以 bundle 相对路径引用。
       - target: ShadowsocksX-NG2Agent
@@ -197,9 +199,12 @@ targets:
     settings:
       base:
         PRODUCT_NAME: ShadowsocksX-NG2Core
+        SWIFT_OBJC_BRIDGING_HEADER: App/Application/Connectivity/ConnectivityHTTPTransport.h
         PRODUCT_MODULE_NAME: ShadowsocksX_NG2
         # 静态库产物不签名（app 的 DevID 身份不适用）。
         CODE_SIGNING_ALLOWED: NO
+    dependencies:
+      - sdk: libcurl.tbd
   ShadowsocksX-NG2Agent:
     type: tool
     platform: macOS
@@ -264,6 +269,7 @@ targets:
       path: Tests/Info.plist
       properties: {}
     dependencies:
+      - sdk: libcurl.tbd
       # 去宿主化（ADR 0021）：单测链 Core 静态库镜像而非 app 可执行，测试在
       # 独立 xctest runner 中运行，宿主 app 不再被启动。
       - target: ShadowsocksX-NG2Core
@@ -283,6 +289,7 @@ targets:
       path: Tests/Smoke/Info.plist
       properties: {}
     dependencies:
+      - sdk: libcurl.tbd
       # 去宿主化（ADR 0021）：smoke 同样链 Core 镜像库；真实 sslocal/agent 从
       # scheme 构建的 app 产物取（AppArtifact），宿主 app 不再被启动。
       - target: ShadowsocksX-NG2Core