diff --git a/Package.swift b/Package.swift
index fc233cd2..73e5cf0a 100644
--- a/Package.swift
+++ b/Package.swift
@@ -39,6 +39,10 @@ let package = Package(
                     name: "Ably",
                     package: "ably-cocoa"
                 ),
+                .product(
+                    name: "AsyncAlgorithms",
+                    package: "swift-async-algorithms"
+                ),
             ]
         ),
         .testTarget(
diff --git a/Sources/AblyChat/RoomLifecycleManager.swift b/Sources/AblyChat/RoomLifecycleManager.swift
index 84c656e3..4d3ae5ce 100644
--- a/Sources/AblyChat/RoomLifecycleManager.swift
+++ b/Sources/AblyChat/RoomLifecycleManager.swift
@@ -1,8 +1,14 @@
-import Ably
+@preconcurrency import Ably
+import AsyncAlgorithms
 
 /// The interface that the lifecycle manager expects its contributing realtime channels to conform to.
 ///
-/// We use this instead of the ``RealtimeChannelProtocol`` interface as its ``attach`` and ``detach`` methods are `async` instead of using callbacks. This makes it easier to write mocks for (since ``RealtimeChannelProtocol`` doesn’t express to the type system that the callbacks it receives need to be `Sendable`, it’s hard to, for example, create a mock that creates a `Task` and then calls the callback from inside this task).
+/// We use this instead of the ``RealtimeChannelProtocol`` interface as:
+///
+/// - its ``attach`` and ``detach`` methods are `async` instead of using callbacks
+/// - it uses `AsyncSequence` to emit state changes instead of using callbacks
+///
+/// This makes it easier to write mocks for (since ``RealtimeChannelProtocol`` doesn’t express to the type system that the callbacks it receives need to be `Sendable`, it’s hard to, for example, create a mock that creates a `Task` and then calls the callback from inside this task).
 ///
 /// We choose to also mark the channel’s mutable state as `async`. This is a way of highlighting at the call site of accessing this state that, since `ARTRealtimeChannel` mutates this state on a separate thread, it’s possible for this state to have changed since the last time you checked it, or since the last time you performed an operation that might have mutated it, or since the last time you recieved an event informing you that it changed. To be clear, marking these as `async` doesn’t _solve_ these issues; it just makes them a bit more visible. We’ll decide how to address them in https://github.com/ably-labs/ably-chat-swift/issues/49.
 internal protocol RoomLifecycleContributorChannel: Sendable {
@@ -11,24 +17,80 @@ internal protocol RoomLifecycleContributorChannel: Sendable {
 
     var state: ARTRealtimeChannelState { get async }
     var errorReason: ARTErrorInfo? { get async }
+
+    /// Equivalent to subscribing to a `RealtimeChannelProtocol` object’s state changes via its `on(_:)` method. The subscription should use the ``BufferingPolicy.unbounded`` buffering policy.
+    ///
+    /// It is marked as `async` purely to make it easier to write mocks for this method (i.e. to use an actor as a mock).
+    func subscribeToState() async -> Subscription<ARTChannelStateChange>
 }
 
 /// A realtime channel that contributes to the room lifecycle.
-internal protocol RoomLifecycleContributor: Sendable {
+///
+/// The identity implied by the `Identifiable` conformance must distinguish each of the contributors passed to a given ``RoomLifecycleManager`` instance.
+internal protocol RoomLifecycleContributor: Identifiable, Sendable {
     associatedtype Channel: RoomLifecycleContributorChannel
 
     /// The room feature that this contributor corresponds to. Used only for choosing which error to throw when a contributor operation fails.
     var feature: RoomFeature { get }
     var channel: Channel { get }
+
+    /// Informs the contributor that there has been a break in channel continuity, which it should inform library users about.
+    ///
+    /// It is marked as `async` purely to make it easier to write mocks for this method (i.e. to use an actor as a mock).
+    func emitDiscontinuity(_ error: ARTErrorInfo) async
 }
 
 internal actor RoomLifecycleManager<Contributor: RoomLifecycleContributor> {
+    /// Stores manager state relating to a given contributor.
+    private struct ContributorAnnotation {
+        // TODO: Not clear whether there can be multiple or just one (asked in https://github.com/ably/specification/pull/200/files#r1781927850)
+        var pendingDiscontinuityEvents: [ARTErrorInfo] = []
+    }
+
     internal private(set) var current: RoomLifecycle
     internal private(set) var error: ARTErrorInfo?
+    // TODO: This currently allows the the tests to inject a value in order to test the spec points that are predicated on whether “a channel lifecycle operation is in progress”. In https://github.com/ably-labs/ably-chat-swift/issues/52 we’ll set this property based on whether there actually is a lifecycle operation in progress.
+    private let hasOperationInProgress: Bool
+    /// Manager state that relates to individual contributors, keyed by contributors’ ``Contributor.id``. Stored separately from ``contributors`` so that the latter can be a `let`, to make it clear that the contributors remain fixed for the lifetime of the manager.
+    private var contributorAnnotations: ContributorAnnotations
+
+    /// Provides a `Dictionary`-like interface for storing manager state about individual contributors.
+    private struct ContributorAnnotations {
+        private var storage: [Contributor.ID: ContributorAnnotation]
+
+        init(contributors: [Contributor]) {
+            storage = contributors.reduce(into: [:]) { result, contributor in
+                result[contributor.id] = .init()
+            }
+        }
+
+        /// It is a programmer error to call this subscript getter with a contributor that was not one of those passed to ``init(contributors:pendingDiscontinuityEvents)``.
+        subscript(_ contributor: Contributor) -> ContributorAnnotation {
+            get {
+                guard let annotation = storage[contributor.id] else {
+                    preconditionFailure("Expected annotation for \(contributor)")
+                }
+                return annotation
+            }
+
+            set {
+                storage[contributor.id] = newValue
+            }
+        }
+
+        mutating func clearPendingDiscontinuityEvents() {
+            storage = storage.mapValues { annotation in
+                var newAnnotation = annotation
+                newAnnotation.pendingDiscontinuityEvents = []
+                return newAnnotation
+            }
+        }
+    }
 
     private let logger: InternalLogger
     private let clock: SimpleClock
     private let contributors: [Contributor]
+    private var listenForStateChangesTask: Task<Void, Never>!
 
     internal init(
         contributors: [Contributor],
@@ -37,6 +99,7 @@ internal actor RoomLifecycleManager<Contributor: RoomLifecycleContributor> {
     ) async {
         await self.init(
             current: nil,
+            hasOperationInProgress: nil,
             contributors: contributors,
             logger: logger,
             clock: clock
@@ -46,12 +109,14 @@ internal actor RoomLifecycleManager<Contributor: RoomLifecycleContributor> {
     #if DEBUG
         internal init(
             testsOnly_current current: RoomLifecycle? = nil,
+            testsOnly_hasOperationInProgress hasOperationInProgress: Bool? = nil,
             contributors: [Contributor],
             logger: InternalLogger,
             clock: SimpleClock
         ) async {
             await self.init(
                 current: current,
+                hasOperationInProgress: hasOperationInProgress,
                 contributors: contributors,
                 logger: logger,
                 clock: clock
@@ -61,16 +126,55 @@ internal actor RoomLifecycleManager<Contributor: RoomLifecycleContributor> {
 
     private init(
         current: RoomLifecycle?,
+        hasOperationInProgress: Bool?,
         contributors: [Contributor],
         logger: InternalLogger,
         clock: SimpleClock
     ) async {
         self.current = current ?? .initialized
+        self.hasOperationInProgress = hasOperationInProgress ?? false
         self.contributors = contributors
+        contributorAnnotations = .init(contributors: contributors)
         self.logger = logger
         self.clock = clock
+
+        // The idea here is to make sure that, before the initializer completes, we are already listening for state changes, so that e.g. tests don’t miss a state change.
+        let subscriptions = await withTaskGroup(of: (contributor: Contributor, subscription: Subscription<ARTChannelStateChange>).self) { group in
+            for contributor in contributors {
+                group.addTask {
+                    await (contributor: contributor, subscription: contributor.channel.subscribeToState())
+                }
+            }
+
+            return await Array(group)
+        }
+
+        // CHA-RL4: listen for state changes from our contributors
+        // TODO: Understand what happens when this task gets cancelled by `deinit`; I’m not convinced that the for-await loops will exit (https://github.com/ably-labs/ably-chat-swift/issues/29)
+        listenForStateChangesTask = Task {
+            await withTaskGroup(of: Void.self) { group in
+                for (contributor, subscription) in subscriptions {
+                    // This `@Sendable` is to make the compiler error "'self'-isolated value of type '() async -> Void' passed as a strongly transferred parameter; later accesses could race" go away. I don’t hugely understand what it means, but given the "'self'-isolated value" I guessed it was something vaguely to do with the fact that `async` actor initializers are actor-isolated and thought that marking it as `@Sendable` would sever this isolation and make the error go away, which it did 🤷. But there are almost certainly consequences that I am incapable of reasoning about with my current level of Swift concurrency knowledge.
+                    group.addTask { @Sendable [weak self] in
+                        for await stateChange in subscription {
+                            await self?.didReceiveStateChange(stateChange, forContributor: contributor)
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    deinit {
+        listenForStateChangesTask.cancel()
     }
 
+    #if DEBUG
+        internal func testsOnly_pendingDiscontinuityEvents(for contributor: Contributor) -> [ARTErrorInfo] {
+            contributorAnnotations[contributor].pendingDiscontinuityEvents
+        }
+    #endif
+
     // TODO: clean up old subscriptions (https://github.com/ably-labs/ably-chat-swift/issues/36)
     private var subscriptions: [Subscription<RoomStatusChange>] = []
 
@@ -80,6 +184,113 @@ internal actor RoomLifecycleManager<Contributor: RoomLifecycleContributor> {
         return subscription
     }
 
+    #if DEBUG
+        // TODO: clean up old subscriptions (https://github.com/ably-labs/ably-chat-swift/issues/36)
+        /// Supports the ``testsOnly_subscribeToHandledContributorStateChanges()`` method.
+        private var stateChangeHandledSubscriptions: [Subscription<ARTChannelStateChange>] = []
+
+        /// Returns a subscription which emits the contributor state changes that have been handled by the manager.
+        ///
+        /// A contributor state change is considered handled once the manager has performed all of the side effects that it will perform as a result of receiving this state change. Specifically, once:
+        ///
+        /// - the manager has recorded all pending discontinuity events provoked by the state change (you can retrieve these using ``testsOnly_pendingDiscontinuityEventsForContributor(at:)``)
+        /// - the manager has performed all status changes provoked by the state change
+        /// - the manager has performed all contributor actions provoked by the state change, namely calls to ``RoomLifecycleContributorChannel.detach()`` or ``RoomLifecycleContributor.emitDiscontinuity(_:)``
+        internal func testsOnly_subscribeToHandledContributorStateChanges() -> Subscription<ARTChannelStateChange> {
+            let subscription = Subscription<ARTChannelStateChange>(bufferingPolicy: .unbounded)
+            stateChangeHandledSubscriptions.append(subscription)
+            return subscription
+        }
+    #endif
+
+    /// Implements CHA-RL4b’s contributor state change handling.
+    private func didReceiveStateChange(_ stateChange: ARTChannelStateChange, forContributor contributor: Contributor) async {
+        logger.log(message: "Got state change \(stateChange) for contributor \(contributor)", level: .info)
+
+        // TODO: The spec, which is written for a single-threaded environment, is presumably operating on the assumption that the channel is currently in the state given by `stateChange.current` (https://github.com/ably-labs/ably-chat-swift/issues/49)
+        switch stateChange.event {
+        case .update:
+            // CHA-RL4a1 — if RESUMED then no-op
+            guard !stateChange.resumed else {
+                break
+            }
+
+            guard let reason = stateChange.reason else {
+                // TODO: Decide the right thing to do here (https://github.com/ably-labs/ably-chat-swift/issues/74)
+                preconditionFailure("State change event with resumed == false should have a reason")
+            }
+
+            if hasOperationInProgress {
+                // CHA-RL4a3
+                logger.log(message: "Recording pending discontinuity event for contributor \(contributor)", level: .info)
+
+                contributorAnnotations[contributor].pendingDiscontinuityEvents.append(reason)
+            } else {
+                // CHA-RL4a4
+                logger.log(message: "Emitting discontinuity event for contributor \(contributor)", level: .info)
+
+                await contributor.emitDiscontinuity(reason)
+            }
+        case .attached:
+            if hasOperationInProgress {
+                if !stateChange.resumed {
+                    // CHA-RL4b1
+                    logger.log(message: "Recording pending discontinuity event for contributor \(contributor)", level: .info)
+
+                    guard let reason = stateChange.reason else {
+                        // TODO: Decide the right thing to do here (https://github.com/ably-labs/ably-chat-swift/issues/74)
+                        preconditionFailure("State change event with resumed == false should have a reason")
+                    }
+
+                    contributorAnnotations[contributor].pendingDiscontinuityEvents.append(reason)
+                }
+            } else if current != .attached {
+                if await (contributors.async.map { await $0.channel.state }.allSatisfy { $0 == .attached }) {
+                    // CHA-RL4b8
+                    logger.log(message: "Now that all contributors are ATTACHED, transitioning room to ATTACHED", level: .info)
+                    changeStatus(to: .attached)
+                }
+            }
+        case .failed:
+            if !hasOperationInProgress {
+                // CHA-RL4b5
+                guard let reason = stateChange.reason else {
+                    // TODO: Decide the right thing to do here (https://github.com/ably-labs/ably-chat-swift/issues/74)
+                    preconditionFailure("FAILED state change event should have a reason")
+                }
+
+                changeStatus(to: .failed, error: reason)
+
+                // TODO: CHA-RL4b5 is a bit unclear about how to handle failure, and whether they can be detached concurrently (asked in https://github.com/ably/specification/pull/200/files#r1777471810)
+                for contributor in contributors {
+                    do {
+                        try await contributor.channel.detach()
+                    } catch {
+                        logger.log(message: "Failed to detach contributor \(contributor), error \(error)", level: .info)
+                    }
+                }
+            }
+        case .suspended:
+            if !hasOperationInProgress {
+                // CHA-RL4b9
+                guard let reason = stateChange.reason else {
+                    // TODO: Decide the right thing to do here (https://github.com/ably-labs/ably-chat-swift/issues/74)
+                    preconditionFailure("SUSPENDED state change event should have a reason")
+                }
+
+                changeStatus(to: .suspended, error: reason)
+            }
+        default:
+            break
+        }
+
+        #if DEBUG
+            for subscription in stateChangeHandledSubscriptions {
+                subscription.emit(stateChange)
+            }
+        #endif
+    }
+
     /// Updates ``current`` and ``error`` and emits a status change event.
     private func changeStatus(to new: RoomLifecycle, error: ARTErrorInfo? = nil) {
         logger.log(message: "Transitioning from \(current) to \(new), error \(String(describing: error))", level: .info)
diff --git a/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributor.swift b/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributor.swift
index d1a0d2af..e008fd28 100644
--- a/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributor.swift
+++ b/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributor.swift
@@ -1,11 +1,18 @@
+import Ably
 @testable import AblyChat
 
 actor MockRoomLifecycleContributor: RoomLifecycleContributor {
     nonisolated let feature: RoomFeature
     nonisolated let channel: MockRoomLifecycleContributorChannel
 
+    private(set) var emitDiscontinuityArguments: [ARTErrorInfo] = []
+
     init(feature: RoomFeature, channel: MockRoomLifecycleContributorChannel) {
         self.feature = feature
         self.channel = channel
     }
+
+    func emitDiscontinuity(_ error: ARTErrorInfo) async {
+        emitDiscontinuityArguments.append(error)
+    }
 }
diff --git a/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributorChannel.swift b/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributorChannel.swift
index d23539af..3ef81e5c 100644
--- a/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributorChannel.swift
+++ b/Tests/AblyChatTests/Mocks/MockRoomLifecycleContributorChannel.swift
@@ -1,4 +1,4 @@
-import Ably
+@preconcurrency import Ably
 @testable import AblyChat
 
 final actor MockRoomLifecycleContributorChannel: RoomLifecycleContributorChannel {
@@ -7,6 +7,8 @@ final actor MockRoomLifecycleContributorChannel: RoomLifecycleContributorChannel
 
     var state: ARTRealtimeChannelState
     var errorReason: ARTErrorInfo?
+    // TODO: clean up old subscriptions (https://github.com/ably-labs/ably-chat-swift/issues/36)
+    private var subscriptions: [Subscription<ARTChannelStateChange>] = []
 
     private(set) var attachCallCount = 0
     private(set) var detachCallCount = 0
@@ -92,4 +94,16 @@ final actor MockRoomLifecycleContributorChannel: RoomLifecycleContributorChannel
             throw error
         }
     }
+
+    func subscribeToState() -> Subscription<ARTChannelStateChange> {
+        let subscription = Subscription<ARTChannelStateChange>(bufferingPolicy: .unbounded)
+        subscriptions.append(subscription)
+        return subscription
+    }
+
+    func emitStateChange(_ stateChange: ARTChannelStateChange) {
+        for subscription in subscriptions {
+            subscription.emit(stateChange)
+        }
+    }
 }
diff --git a/Tests/AblyChatTests/RoomLifecycleManagerTests.swift b/Tests/AblyChatTests/RoomLifecycleManagerTests.swift
index e2c477b8..c7f93c2b 100644
--- a/Tests/AblyChatTests/RoomLifecycleManagerTests.swift
+++ b/Tests/AblyChatTests/RoomLifecycleManagerTests.swift
@@ -1,4 +1,4 @@
-import Ably
+@preconcurrency import Ably
 @testable import AblyChat
 import Testing
 
@@ -29,11 +29,13 @@ struct RoomLifecycleManagerTests {
 
     private func createManager(
         forTestingWhatHappensWhenCurrentlyIn current: RoomLifecycle? = nil,
+        forTestingWhatHappensWhenHasOperationInProgress hasOperationInProgress: Bool? = nil,
         contributors: [MockRoomLifecycleContributor] = [],
         clock: SimpleClock = MockSimpleClock()
     ) async -> RoomLifecycleManager<MockRoomLifecycleContributor> {
         await .init(
             testsOnly_current: current,
+            testsOnly_hasOperationInProgress: hasOperationInProgress,
             contributors: contributors,
             logger: TestLogger(),
             clock: clock
@@ -56,6 +58,14 @@ struct RoomLifecycleManagerTests {
         )
     }
 
+    /// Given a room lifecycle manager and a channel state change, this method will return once the manager has performed all of the side effects that it will perform as a result of receiving this state change. You can provide a function which will be called after ``waitForManager`` has started listening for the manager’s “state change handled” notifications.
+    func waitForManager(_ manager: RoomLifecycleManager<some RoomLifecycleContributor>, toHandleContributorStateChange stateChange: ARTChannelStateChange, during action: () async -> Void) async {
+        let subscription = await manager.testsOnly_subscribeToHandledContributorStateChanges()
+        async let handledSignal = subscription.first { $0 === stateChange }
+        await action()
+        _ = await handledSignal
+    }
+
     // MARK: - Initial state
 
     // @spec CHA-RS2a
@@ -675,4 +685,249 @@ struct RoomLifecycleManagerTests {
 
         #expect(await manager.current == .released)
     }
+
+    // MARK: - Handling contributor UPDATE events
+
+    // @spec CHA-RL4a1
+    @Test
+    func contributorUpdate_withResumedTrue_doesNothing() async throws {
+        // Given: A RoomLifecycleManager
+        let contributor = createContributor()
+        let manager = await createManager(contributors: [contributor])
+
+        // When: A contributor emits an UPDATE event with `resumed` flag set to true
+        let contributorStateChange = ARTChannelStateChange(
+            current: .attached, // arbitrary
+            previous: .attached, // arbitrary
+            event: .update,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: true
+        )
+
+        await waitForManager(manager, toHandleContributorStateChange: contributorStateChange) {
+            await contributor.channel.emitStateChange(contributorStateChange)
+        }
+
+        // Then: The manager does not record a pending discontinuity event for this contributor, nor does it call `emitDiscontinuity` on the contributor (this is my interpretation of "no action should be taken" in CHA-RL4a1; i.e. that the actions described in CHA-RL4a2 and CHA-RL4a3 shouldn’t happen) (TODO: get clarification; have asked in https://github.com/ably/specification/pull/200#discussion_r1777385499)
+        #expect(await manager.testsOnly_pendingDiscontinuityEvents(for: contributor).isEmpty)
+        #expect(await contributor.emitDiscontinuityArguments.isEmpty)
+    }
+
+    // @spec CHA-RL4a3
+    @Test
+    func contributorUpdate_withResumedFalse_withOperationInProgress_recordsPendingDiscontinuityEvent() async throws {
+        // Given: A RoomLifecycleManager, with a room lifecycle operation in progress
+        let contributor = createContributor()
+        let manager = await createManager(forTestingWhatHappensWhenHasOperationInProgress: true, contributors: [contributor])
+
+        // When: A contributor emits an UPDATE event with `resumed` flag set to false
+        let contributorStateChange = ARTChannelStateChange(
+            current: .attached, // arbitrary
+            previous: .attached, // arbitrary
+            event: .update,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false
+        )
+
+        await waitForManager(manager, toHandleContributorStateChange: contributorStateChange) {
+            await contributor.channel.emitStateChange(contributorStateChange)
+        }
+
+        // Then: The manager records a pending discontinuity event for this contributor, and this discontinuity event has error equal to the contributor UPDATE event’s `reason`
+        let pendingDiscontinuityEvents = await manager.testsOnly_pendingDiscontinuityEvents(for: contributor)
+        try #require(pendingDiscontinuityEvents.count == 1)
+
+        let pendingDiscontinuityEvent = pendingDiscontinuityEvents[0]
+        #expect(pendingDiscontinuityEvent === contributorStateChange.reason)
+    }
+
+    // @spec CHA-RL4a4
+    @Test
+    func contributorUpdate_withResumedTrue_withNoOperationInProgress_emitsDiscontinuityEvent() async throws {
+        // Given: A RoomLifecycleManager, with no room lifecycle operation in progress
+        let contributor = createContributor()
+        let manager = await createManager(forTestingWhatHappensWhenHasOperationInProgress: false, contributors: [contributor])
+
+        // When: A contributor emits an UPDATE event with `resumed` flag set to false
+        let contributorStateChange = ARTChannelStateChange(
+            current: .attached, // arbitrary
+            previous: .attached, // arbitrary
+            event: .update,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false
+        )
+
+        await waitForManager(manager, toHandleContributorStateChange: contributorStateChange) {
+            await contributor.channel.emitStateChange(contributorStateChange)
+        }
+
+        // Then: The manager calls `emitDiscontinuity` on the contributor, with error equal to the contributor UPDATE event’s `reason`
+        let emitDiscontinuityArguments = await contributor.emitDiscontinuityArguments
+        try #require(emitDiscontinuityArguments.count == 1)
+
+        let discontinuity = emitDiscontinuityArguments[0]
+        #expect(discontinuity === contributorStateChange.reason)
+    }
+
+    // @specPartial CHA-RL4b1 - I don’t know the meaning of "and the particular contributor has been attached previously" so haven’t implemented that part of the spec point (TODO: asked in https://github.com/ably/specification/pull/200/files#r1775552624)
+    @Test
+    func contributorAttachEvent_withResumeFalse_withOperationInProgress_recordsPendingDiscontinuityEvent() async throws {
+        // Given: A RoomLifecycleManager, with a room lifecycle operation in progress
+        let contributor = createContributor()
+        let manager = await createManager(forTestingWhatHappensWhenHasOperationInProgress: true, contributors: [contributor])
+
+        // When: A contributor emits an ATTACHED event with `resumed` flag set to false
+        let contributorStateChange = ARTChannelStateChange(
+            current: .attached,
+            previous: .attaching, // arbitrary
+            event: .attached,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false
+        )
+
+        await waitForManager(manager, toHandleContributorStateChange: contributorStateChange) {
+            await contributor.channel.emitStateChange(contributorStateChange)
+        }
+
+        // Then: The manager records a pending discontinuity event for this contributor, and this discontinuity event has error equal to the contributor ATTACHED event’s `reason`
+        let pendingDiscontinuityEvents = await manager.testsOnly_pendingDiscontinuityEvents(for: contributor)
+        try #require(pendingDiscontinuityEvents.count == 1)
+
+        let pendingDiscontinuityEvent = pendingDiscontinuityEvents[0]
+        #expect(pendingDiscontinuityEvent === contributorStateChange.reason)
+    }
+
+    // @specPartial CHA-RL4b5 - Haven’t implemented the part that refers to "transient disconnect timeouts"; TODO do this (https://github.com/ably-labs/ably-chat-swift/issues/48)
+    @Test
+    func contributorFailedEvent_withNoOperationInProgress() async throws {
+        // Given: A RoomLifecycleManager, with no room lifecycle operation in progress
+        let contributors = [
+            // TODO: The .success is currently arbitrary since the spec doesn’t say what to do if detach fails (have asked in https://github.com/ably/specification/pull/200#discussion_r1777471810)
+            createContributor(detachBehavior: .success),
+            createContributor(detachBehavior: .success),
+        ]
+        let manager = await createManager(forTestingWhatHappensWhenHasOperationInProgress: false, contributors: contributors)
+
+        let roomStatusSubscription = await manager.onChange(bufferingPolicy: .unbounded)
+        async let failedStatusChange = roomStatusSubscription.first { $0.current == .failed }
+
+        // When: A contributor emits an FAILED event
+        let contributorStateChange = ARTChannelStateChange(
+            current: .failed,
+            previous: .attached, // arbitrary
+            event: .failed,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false // arbitrary
+        )
+
+        await waitForManager(manager, toHandleContributorStateChange: contributorStateChange) {
+            await contributors[0].channel.emitStateChange(contributorStateChange)
+        }
+
+        // Then:
+        // - the room status transitions to failed, with the error of the status change being the `reason` of the contributor FAILED event
+        // - and it calls `detach` on all contributors
+        _ = try #require(await failedStatusChange)
+        #expect(await manager.current == .failed)
+
+        for contributor in contributors {
+            #expect(await contributor.channel.detachCallCount == 1)
+        }
+    }
+
+    // @specOneOf(1/2) CHA-RL4b8
+    @Test
+    func contributorAttachedEvent_withNoOperationInProgress_roomNotAttached_allContributorsAttached() async throws {
+        // Given: A RoomLifecycleManager, not in the ATTACHED state, all of whose contributors are in the ATTACHED state (to satisfy the condition of CHA-RL4b8; for the purposes of this test I don’t care that they’re in this state even _before_ the state change of the When)
+        let contributors = [
+            createContributor(initialState: .attached),
+            createContributor(initialState: .attached),
+        ]
+
+        let manager = await createManager(
+            forTestingWhatHappensWhenCurrentlyIn: .initialized, // arbitrary non-ATTACHED
+            forTestingWhatHappensWhenHasOperationInProgress: false,
+            contributors: contributors
+        )
+
+        let roomStatusSubscription = await manager.onChange(bufferingPolicy: .unbounded)
+        async let maybeAttachedRoomStatusChange = roomStatusSubscription.first { $0.current == .attached }
+
+        // When: A contributor emits a state change to ATTACHED
+        let contributorStateChange = ARTChannelStateChange(
+            current: .attached,
+            previous: .attaching, // arbitrary
+            event: .attached,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false // arbitrary
+        )
+
+        await contributors[0].channel.emitStateChange(contributorStateChange)
+
+        // Then: The room status transitions to ATTACHED
+        _ = try #require(await maybeAttachedRoomStatusChange)
+        #expect(await manager.current == .attached)
+    }
+
+    // @specOneOf(2/2) CHA-RL4b8 - Tests that the specified side effect doesn’t happen if part of the condition (i.e. all contributors now being ATTACHED) is not met
+    @Test
+    func contributorAttachedEvent_withNoOperationInProgress_roomNotAttached_notAllContributorsAttached() async throws {
+        // Given: A RoomLifecycleManager, not in the ATTACHED state, one of whose contributors is not in the ATTACHED state state (to simulate the condition of CHA-RL4b8 not being met; for the purposes of this test I don’t care that they’re in this state even _before_ the state change of the When)
+        let contributors = [
+            createContributor(initialState: .attached),
+            createContributor(initialState: .detached),
+        ]
+
+        let initialManagerState = RoomLifecycle.initialized // arbitrary non-ATTACHED
+        let manager = await createManager(
+            forTestingWhatHappensWhenCurrentlyIn: initialManagerState,
+            forTestingWhatHappensWhenHasOperationInProgress: false,
+            contributors: contributors
+        )
+
+        // When: A contributor emits a state change to ATTACHED
+        let contributorStateChange = ARTChannelStateChange(
+            current: .attached,
+            previous: .attaching, // arbitrary
+            event: .attached,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false // arbitrary
+        )
+
+        await waitForManager(manager, toHandleContributorStateChange: contributorStateChange) {
+            await contributors[0].channel.emitStateChange(contributorStateChange)
+        }
+
+        // Then: The room status does not change
+        #expect(await manager.current == initialManagerState)
+    }
+
+    // @specPartial CHA-RL4b9 - Haven’t implemented the part that refers to "transient disconnect timeouts"; TODO do this (https://github.com/ably-labs/ably-chat-swift/issues/48). Nor have I implemented "the room enters the RETRY loop"; TODO do this (https://github.com/ably-labs/ably-chat-swift/issues/51)
+    @Test
+    func contributorSuspendedEvent_withNoOperationInProgress() async throws {
+        // Given: A RoomLifecycleManager with no lifecycle operation in progress
+        let contributor = createContributor()
+        let manager = await createManager(forTestingWhatHappensWhenHasOperationInProgress: false, contributors: [contributor])
+
+        let roomStatusSubscription = await manager.onChange(bufferingPolicy: .unbounded)
+        async let maybeSuspendedRoomStatusChange = roomStatusSubscription.first { $0.current == .suspended }
+
+        // When: A contributor emits a state change to SUSPENDED
+        let contributorStateChange = ARTChannelStateChange(
+            current: .suspended,
+            previous: .attached, // arbitrary
+            event: .suspended,
+            reason: ARTErrorInfo(domain: "SomeDomain", code: 123), // arbitrary
+            resumed: false // arbitrary
+        )
+
+        await contributor.channel.emitStateChange(contributorStateChange)
+
+        // Then: The room transitions to SUSPENDED, and this state change has error equal to the contributor state change’s `reason`
+        let suspendedRoomStatusChange = try #require(await maybeSuspendedRoomStatusChange)
+        #expect(suspendedRoomStatusChange.error === contributorStateChange.reason)
+
+        #expect(await manager.current == .suspended)
+        #expect(await manager.error === contributorStateChange.reason)
+    }
 }