Implement RTN23 idle-transport detection and the recovery spec points around it by AndyTWF · Pull Request #1331 · ably/ably-pubsub-dotnet

AndyTWF · 2026-09-02T07:46:29Z

Implements RTN23 — dead-transport detection — and the recovery-path spec points that
auditing the constant it had been misusing turned up. Detection latency drops from 120s
to ~25s.

To keep the change set bounded, this is deliberately not a general spec update. Nothing outside the connection-recovery paths above is touched, and the protocol version is unchanged — protocol stays at 6 upstream and this SDK still sends v=2.

Where a clause on those paths has since been superseded, I've brought that one clause forward rather than implement the version it replaced. That is the only reason RTN14h appears here: the pre-6.1.0 resume semantics it replaces were the direct cause of several of the bugs above, so preserving them would have meant knowingly implementing behaviour the spec has already retired. Fast-forwarding is scoped to the clauses these fixes already have their hands on, not pursued for its own sake.

PUB-3824

Implemented (not previously present)

RTN23a — disconnect a transport idle longer than maxIdleInterval + realtimeRequestTimeout. The monitor was measuring against connectionStateTtl.
RTN23b — send heartbeats=true so protocol HEARTBEATs are contractual rather than an undocumented server default.
CD2h — maxIdleInterval parsed from connectionDetails; previously never read.
TO3l11 — realtimeRequestTimeout is now a public, validated ClientOptions property; it was internal.

Corrected

RTN15c6 / RTN15c7 / RTN16f — continuation is now detected positively; a connection cleared per RTN15g reconnects with a new connectionId and no error, which the old test read as a continuation.
RTN19a1 / RTN19a2 — serials kept on a successful resume, renumbered on a failed one, and publish order preserved across the requeue.
RTN7b / RTN7d / RTN7e — RTL6c2 queue failed alongside RTL6c1; failures now report the reason for the state change.
RTN24 — a connection update no longer churns channels (was 4 spurious protocol messages per reauth).
RTL3d / RTL3d1 — reattach unconditional on entering CONNECTED, and ordered before external listeners.
RTL3b / RTL3c / RTN11b / RTP5a — channels detach when the connection goes away, so presence members no longer survive a close.
RTL5l — a channel detaches immediately whenever the connection is not CONNECTED.
RTL11 — queued presence messages fail with an ErrorInfo rather than a bare exception.
RTL15b2 — channelSerial no longer cleared on SUSPENDED.
RTN14d — retryIn reports the delay actually waited.
RTN14e — the suspend deadline is evaluated on every path into DISCONNECTED, including the token/auth paths that never suspended.
RTB1 / RTB1a / RTB1b — backoff coefficients, jitter and the connectionStateTtl clamp.
RTN15a / RTN15h3 — immediate reconnect for a non-token DISCONNECTED.
RTN17 / RTN17i / RTN17j — fallbacks consulted on every attempt, immediate retry bounded (was ~65 attempts/sec), connectivity checked once per attempt.
RTN11d — full reinitialisation on connect() from CLOSED, FAILED or CLOSING.
RTN12b — close timeout is realtimeRequestTimeout, not a hardcoded 1s.
RTN8d / RTN9d — key and id cleared only in the terminal states the clauses name, cleared before the state change is emitted, and cleared even when a transition throws.
RTN21 — connectionDetails overrides only the attributes it carries.
RSA4c / RSA4c1 — the auth callback invocation is bounded, and cause is set per the clause.

Adopted from specification 6.1.0

RTN14h, replacing RTN15g — the client always attempts a resume and lets the server decide whether continuity survives, rather than discarding its connection state once connectionStateTtl has passed. Verified against the live sandbox: a resume is still honoured well beyond the advertised TTL, so the old gate was throwing away resumes the server would have accepted.
RTN27c — a reconnect from DISCONNECTED is now genuinely a resume attempt; clearing the key on every failed attempt had made that false from the second attempt onwards.
RTN15g1 / RTN15g2 / RTN15g3 and RTL4j / RTL4j1 / RTL4j2 — deleted at 6.1.0. The TTL freshness check and ATTACH_RESUME go with them; channelSerial (RTL4c1, kept across a suspend by RTL15b2) already carries the continuity signal.
RTN16g3, replacing RTN16g2 — createRecoveryKey() now returns a key while SUSPENDED, where it previously returned empty. RTN8d/RTN9d keep the connectionKey through SUSPENDED because RTN14h always attempts a resume, so the connection is still recoverable there and the key has to be available to hand over. Not yet in the published spec — ably/specification#511 adds RTN16g3 and tombstones RTN16g2 — but implemented here because it is the direct consequence of RTN14h above, and splitting the two would mean two behaviour changes for callers instead of one. ably-js has behaved this way since 2.27.0.

One clause the 6.1.0 edit missed

RTN27d is contradicted by this and deliberately not followed. It still calls SUSPENDED a state whose next connect attempt is "a clean connection (not a resume attempt)", where we now resume — as RTN14h, RTN8d, RTN9d and DF1a require between them. This adheres to the ably-js implementation.

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Summary by CodeRabbit

New Features
- Added configurable realtime request timeout validation.
- Added server-provided idle intervals and protocol heartbeats, with caller overrides preserved.
- Improved connection recovery, channel reattachment, serial continuity, and suspended-state recovery.
- Added immediate reconnect handling and fallback connectivity checks.
Bug Fixes
- Auth callbacks now respect request timeouts and report underlying failure details.
- Queued callbacks continue processing after an application callback error.
- Retry and close timers now reflect configured timeout values accurately.
- Improved connection and channel state handling during failures and transitions.

coderabbitai · 2026-09-02T07:46:38Z

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📒 Files selected for processing (4)

src/IO.Ably.Shared/Realtime/Workflows/RealtimeState.cs
src/IO.Ably.Shared/Realtime/Workflows/RealtimeWorkflow.cs
src/IO.Ably.Shared/Transport/ConnectionManager.cs
src/IO.Ably.Tests.Shared/Realtime/RealtimeWorkflowSpecs.cs

Walkthrough

The change adds server-provided idle limits, timeout validation, bounded authentication callbacks, revised reconnect handling, connection continuity, safer queue cleanup, and updated channel transitions.

Changes

Realtime lifecycle changes

Layer / File(s)	Summary
Idle, timeout, and authentication contracts `src/IO.Ably.Shared...`, `src/IO.Ably.Tests.Shared/Realtime/...`	`ConnectionDetails` and `ConnectionInfo` carry `MaxIdleInterval`. `RealtimeRequestTimeout` enforces a one-millisecond minimum and timer-safe maximum. Auth callbacks use the configured timeout. Protocol heartbeats are requested by default and remain caller-overridable.
Connection retry and state workflow `src/IO.Ably.Shared/Realtime/Workflows/`, `src/IO.Ably.Shared/Transport/`, `src/IO.Ably.Tests.Shared/Realtime/...`	Immediate retries are counted and bounded. Connectivity answers move through commands. Retry delays report actual timer values and respect state TTLs. Connection continuity, queue cleanup, and teardown behavior are updated.
Channel and presence lifecycle `src/IO.Ably.Shared/Realtime/RealtimeChannel.cs`, `src/IO.Ably.Shared/Realtime/RealtimeChannels.cs`, `src/IO.Ably.Shared/Realtime/Presence.cs`, `src/IO.Ably.Shared/Realtime/Connection.cs`, `src/IO.Ably.Tests.Shared/Realtime/...`	Suspended channels retain serials and recovery keys. Channel transitions handle reconnect, close, suspend, and detach states. Presence callbacks no longer stop queue cleanup.
Lifecycle regression coverage `src/IO.Ably.Tests.Shared/Realtime/...`, `src/IO.Ably.Tests.Shared/Infrastructure/...`	Tests cover serialization, timeout limits, retry timing, fallback checks, recovery keys, idle monitoring, channel transitions, connection continuity, and fake transport creation.

Priority: ⚪ Not assessed

Estimated code review effort: 5 (Critical) | ~120 minutes

Merge Risk: 🟡 Moderate · up to e5ea9

Changing heartbeat transport options on an active connection can cause a healthy connection to be treated as idle and disconnected. This should be corrected before merge.

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant RealtimeWorkflow
  participant ConnectionState
  participant Transport
  Client->>RealtimeWorkflow: queue heartbeat monitor tick
  RealtimeWorkflow->>ConnectionState: read connection and idle state
  RealtimeWorkflow->>Transport: request disconnect after idle threshold
  Transport->>RealtimeWorkflow: report disconnected state
  RealtimeWorkflow->>RealtimeWorkflow: schedule bounded reconnect

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Title check	✅ Passed	The title clearly identifies the main change: RTN23 idle-transport detection and related recovery specification updates. It is concise and specific.
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_{A rabbit checks the ticking line
Idle clouds drift past in time
Keys stay safe through fields of gray
Channels hop back on their way
Queues clear softly, errors flee
Fresh connections bloom with glee}

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RTN23a - implemented. The monitor measured idleness against connectionStateTtl, so a silently dead transport took 120s to notice instead of ~25s. RTN23b - implemented. heartbeats=true was never sent, so protocol HEARTBEATs relied on an undocumented server default that heartbeats=false would switch off. CD2h - implemented. maxIdleInterval was never parsed from connectionDetails. Scoped to the transport that carried it, so a new transport does not inherit it and an RTN24 update does not withdraw it. RTN21 - fixed. A CONNECTED with no connectionDetails emptied the connectionKey, leaving a live connection with nothing to resume with. RTN15g2 - completed, incidentally. Parsing maxIdleInterval supplies the term the freshness window was missing: the measure is now the gap between the last sign of activity and the sum of connectionStateTtl and maxIdleInterval, not connectionStateTtl alone. Note the clause is deleted as of spec 6.1.0 and replaced by RTN14h, which requires a resume to be attempted regardless of how long it has been - that is not adopted here, and is coupled to the SUSPENDED key clearing in RTN8d/RTN9d. Widening the window does move behaviour toward RTN14h, since connection state is discarded less often than before. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…inue RTN15c6, RTN15c7 - fixed. Continuation required an error on the message, so an RTN15g clear - which returns a new connectionId and no error - read as a continuation and the client kept counting while the server restarted at zero. RTN19a1, RTN19a2 - fixed. Renumbering left the stale WaitingForAck entries behind, so the next ACK matched them too and callbacks ran twice; the requeue appended rather than prepended, reversing publish order on the wire. RTN7e - fixed. Only the RTL6c1 queue was failed, not RTL6c2, so a publish made while disconnected got no callback at all. RTN7b - hardened. A failed transport write could leave one message in both queues. RTN16f - a successful recover keeps the counter it adopted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…nection goes away RTL3d - fixed. The reattach was gated on connectionId having changed, which RTN15g empties before CONNECTING, so the channel stayed locally ATTACHED on a new connection with no server-side attachment - permanently silent, no error. RTL3d1 - fixed. The reattach ran after external listeners had seen CONNECTED. RTN24 - fixed. An update churned channels: four spurious protocol messages per reauth, plus UPDATE events RTL2g does not permit. RTN11b, RTL3b, RTP5a - fixed. Channels never passed through DETACHED on a close, so presence members from the abandoned connection survived into the next one. RTL3c - fixed. A DETACHING channel was left stranded when the connection suspended. RTL5l - fixed. Enumerating the non-connected states let DISCONNECTED through, where the DETACH was queued for the next connection and the callback never fired. RTL11 - fixed. A null reason faulted the task with a bare Exception. RTL15b2 - fixed. channelSerial was cleared on SUSPENDED. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…ect path RTN14d - fixed. retryIn reported the nominal disconnectedRetryTimeout while the timer was started with the RTB1 delay, and reported a wait at all on the skipAttach path where there is none. RTB1a - fixed. The attempt count read `?? 0 + 1`, which C# parses as `?? (0 + 1)`, so a non-null collection was never incremented. RTB1 - fixed. The connectionStateTtl clamp subtracted unguarded operands and overflowed on a backward clock step. RTN14e - fixed. Only the two connection-attempt handlers checked the deadline, and the token and auth retry paths pass through neither, so a client whose token source kept failing never suspended. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…retry RTN17j - fixed. The immediate retry was unbounded: each failed attempt produced another qualifying DISCONNECTED, so RTB1 was never reached and retryIn told the application it would wait while the client retried as fast as the connectivity check allowed. Now bounded by the number of domains there are to traverse. RTN17, RTN17i - fixed. Host selection skipped GetHost for timer-driven retries, so once the retry budget was spent every attempt was pinned to the primary and a client whose primary datacenter was down could never reach a fallback. RTN17j - the connectivity answer is carried on the CONNECTING command, so a cycle takes one check rather than two serialised on the reader thread. RTN15a, RTN15h3 - fixed. The immediate reconnect recognised only an exception or a 500-504 status, which a plain DISCONNECTED carries neither of. Token errors are excluded, since RTN15h2 owns those and already reconnects. RTN14e, RTN17 - fixed. A transport dropping out of CONNECTED recorded no failed attempt: entering CONNECTED clears the attempt collection, and the exception path discarded the failure whenever it was empty. FirstAttempt stayed null so the suspend clock started late, and DisconnectedCount stayed at zero, which feeds fallback host selection. Divergences, all deliberate: - The host list is not swept within a single attempt, as ably-js does. RTN17i's first sentence favours it. - The immediate retry is bounded by domain count and then hands over to RTB1. ably-js instead rate-limits it to one per second and never stops granting it. - The immediate retry stays gated on the connectivity check, as it was before this change. RTN15h3 mandates it unconditionally and RTN17j scopes the check to fallback use, so with no internet we wait out RTB1 where RTN15h3 says reconnect. Pre-existing, widened here to the RTN15h3 case. ably-js does not gate on it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…ardown RTN11d - fixed. Only the channel half ran, so Connection.errorReason, msgSerial and the channel's channelSerial all survived into the new connection. RTN11b - fixed. connect() while CLOSING applied no part of RTN11d. RTN12b - fixed. The close timeout was a hardcoded 1s, not realtimeRequestTimeout, so on a slow link close() could reach CLOSED unacknowledged. TO3l11 - implemented. realtimeRequestTimeout was internal and could not be set. Validated at both ends; the upper bound is Int32.MaxValue ms, the tightest limit across every timer sink on every framework this package ships. RSA4c - fixed. The bound was applied to the task the callback returned, so a callback whose body runs synchronously was never bounded at all. RSA4c1 - fixed. cause was set as InnerException, which is not the spec's field. RTN8d, RTN9d - fixed. A throwing transition skipped the key clear and the transport teardown, leaving a terminal state holding a resumable key and a live transport. Also carries RealtimeWorkflowSpecs.cs in full: its additions are one contiguous insertion of complete test classes and cannot be split across the commits whose spec points they cover. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

RTN14h - implemented. Replaces RTN15g as of specification 6.1.0. The client discarded its connection state once connectionStateTtl had passed and reconnected fresh, throwing away a resume the server would still have honoured. DF1a settles the scope - the ttl is no longer used to decide whether to resume at all - so the gate is general rather than SUSPENDED-only, which is how ably-js reads it too. RTN27c - fixed. DISCONNECTED is a state where "if the library was previously connected, the next connect attempt will be an RTN15b resume attempt". Clearing the key on every failed attempt made that false from the second attempt onwards. RTN8d, RTN9d - fixed twice over. Both list only CLOSED, CLOSING and FAILED, so SUSPENDED must keep the key and id; it cleared them. And all three of the states they do name cleared after SetState, which is what emits the state change - inline, with no SynchronizationContext installed - so the application was told it had reached a terminal state while Connection.Key still read as a resumable key. The clear now happens before the transition, which also stops it depending on a finally. Only a listener reading during the transition could observe this, so it was inherited rather than introduced here. RTN15g1, RTN15g2, RTN15g3 - deleted at 6.1.0. HasConnectionStateTtlPassed and its tests go with them. The reattach RTN15g3 asked for is already unconditional under RTL3d. RTL4j, RTL4j1, RTL4j2 - deleted at 6.1.0; SDKs need not set ATTACH_RESUME. Safe only because RTL4c1 already sends channelSerial on ATTACH and RTL15b2 keeps it across a suspend, so the reattach still carries a continuity signal. The Flag constant stays, per TR3f. The now-dead clearConnectionKey parameter goes from SetDisconnectedStateCommand and SetSuspendedStateCommand. No caller sets it, and leaving it would let the violation back in unnoticed. SetConnectingStateCommand keeps its own, still used by ConnectionClosingState for RTN11b/RTN11d, where a clean connection is the intent. Two clauses the 6.1.0 edit left describing the old model. They are handled differently, and both deliberately: - RTN27d is not followed. It still calls SUSPENDED a state whose "next connect attempt is a clean connection (not a resume attempt)", which RTN14h, RTN8d, RTN9d and DF1a now all contradict; the commit that made those changes does not touch RTN27 at all. ably-js retains the key in SUSPENDED too, citing RTN8d/RTN9d and RTN14h for it. - RTN16g2 is followed. It says createRecoveryKey returns null in SUSPENDED, which sits oddly beside RTN9d now that a key exists there, but it is what the published spec says and CreateRecoveryKey still complies. ably-js returns a key instead, citing an RTN16g3 that "replaces RTN16g2 as of 6.1.0" and appears nowhere in the published spec. Both worth raising upstream rather than guessing. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

RTN16g3 - implemented. Replaces RTN16g2, which listed SUSPENDED among the states where createRecoveryKey returns null. RTN8d and RTN9d now keep the connectionKey through SUSPENDED because RTN14h always attempts a resume, so the connection is still recoverable there and the key has to be available to hand to another client. Withholding it left the SDK holding a usable recovery key it would not surface, in the one prolonged-outage state where handing recovery over is most useful. RTN16i - fixed alongside it. GetChannelSerials filtered on ChannelState.Attached, and RTL3c puts every channel into SUSPENDED when the connection suspends, so the key would have gone out with no channelSerials at all - connection continuity without message continuity, and nothing to tell the caller. Gated on the serial instead, as ably-js does; RTL15b2 already keeps it through SUSPENDED. RTN16g3 is not yet in the published specification - ably/specification#511 adds it and tombstones RTN16g2. Implemented ahead of that merging because it is the direct consequence of RTN14h in the previous commit, and shipping the two apart would mean two behaviour changes for callers instead of one. ably-js already behaves this way, from 2.27.0. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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Inline comments:
In `@src/IO.Ably.Tests.Shared/Realtime/ConnectionSandBoxSpecs.cs`:
- Line 968: Update WhenDisconnectedPastTTL_ShouldStillResume_AndReattachChannels
so it actually disconnects beyond the configured connectionStateTtl before
reconnecting, restoring a short TTL and delaying in the Disconnected handler
before channels[1].Attach(); preserve the test’s resume and channel-reattachment
assertions.

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src/IO.Ably.Tests.Shared/Realtime/ConnectionSandBoxSpecs.cs
src/IO.Ably.Tests.Shared/Realtime/ConnectionSpecs/ConnectionFailuresOnceConnectedSpecs.cs
src/IO.Ably.Tests.Shared/Realtime/ConnectionSpecs/ConnectionParameterSpecs.cs
src/IO.Ably.Tests.Shared/Realtime/ConnectionStateTests/DisconnectedStateSpecs.cs
src/IO.Ably.Tests.Shared/Realtime/RealtimeWorkflowSpecs.cs

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RTN15b, RTN15c6 - covered. The universal test suite specifies both halves of a successful resume in one case, realtime/unit/RTN15b/successful-resume-0: the reconnect carries the connectionKey in the resume query param, and the server signals success by answering with the same connectionId. WhenTransportCloses_ShouldResumeConnection already pins the first half, but feeds back a CONNECTED with no connectionId, so nothing pinned the second - and neither did the RTN15c6 work in this branch, which is about the message serial sequence rather than connection identity. Tagged with that UTS id, so the case is claimed by a test that implements all of it.

A UTS tag is a machine-readable claim that a test implements a specific case, so a tag on a test that asserts something else makes the suite report coverage it does not have. The tags added earlier were placed by reading each case's requirement table, which is a summary; the binding part is its Assertions block. Read against those, most of them over-claimed. Strengthened to assert what their case asserts: - RTL5l detach-attached-when-disconnected-1: no DETACH on the wire, not just an empty outbound queue. - RTN7e error-represents-reason-4: the publisher's error agrees with Connection.ErrorReason, which is the point of the clause. - RTN16f recover-initializes-msgserial-0: the serial on a published frame, not only the internal counter. - RTN15c7 failed-resume-new-id-0: new id, updated key, errorReason and still CONNECTED. Now routed through DISCONNECTED, as a refused resume actually arrives - reconnecting from CONNECTED trips UpdateState's same-state early return and the error never reaches Connection.ErrorReason. - RTN15h3 non-token-error-resume-0: followed through to CONNECTED, checking the resume went out and the id survived. The clause is "reconnect with a resume attempt" and only the reconnect half was covered. - RTN14h resume-after-ttl-0: every reconnection attempt carries the resume, not just the most recent one. RTN23a idle-timeout-reconnect-1 asserts the whole cycle - two attempts, an ordered state sequence, a new connectionId - so it moved to a new test that drives it. The existing test still pins what the monitor decides, which is worth keeping but is not that case. RTB1 disconnected-retry-delay-0 asserts the coefficient sequence and its cap across five retries. ReconnectionStrategyTest already did exactly that and predates this branch, so the tag moved there; the single-retry StartTimer test cannot exercise the curve, because FakeConnectionContext has no client and the attempt count is always one. Two tags removed rather than fixed: - realtime/proxy/RTN14h/resume-after-ttl-expiry-0 needs the fault-injecting proxy harness, which this repo does not have. - the second realtime/unit/RTN16f/recover-initializes-msgserial-0 - the case has no failure path, and ids must be unique per uts/docs/writing-test-specs.md. FakeTransportFactory gains CreatedTransports, since LastCreatedTransport cannot answer how many attempts were made or whether each carried a resume.

Copilot

Pull request overview

Implements RTN23 idle-transport detection and broadens realtime connection recovery behavior.

Changes:

Adds configurable realtime timeout, idle monitoring, and protocol heartbeats.
Revises reconnection, fallback, serial continuity, channel teardown, and recovery behavior.
Expands unit and sandbox coverage for affected specification clauses.

Reviewed changes

Copilot reviewed 37 out of 37 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
`ReconnectionStrategyTest.cs`	Adds RTB1 trait coverage.
`RealtimeWorkflowSpecs.cs`	Tests recovery, queues, channels, and idle detection.
`ProtocolMessageTests.cs`	Tests max-idle JSON parsing.
`DisconnectedStateSpecs.cs`	Tests retry timing and backoff.
`ClosingStateSpecs.cs`	Tests configurable close timeout.
`ConnectionRecoverySpecs.cs`	Tests suspended recovery keys.
`ConnectionParameterSpecs.cs`	Tests heartbeat transport parameters.
`ConnectionFallbackSpecs.cs`	Tests bounded fallback retries.
`ConnectionFailureSpecs.cs`	Updates immediate-retry expectations.
`ConnectionFailuresOnceConnectedSpecs.cs`	Tests resume, auth, and timeout behavior.
`ConnectionSandBoxSpecs.cs`	Updates live recovery behavior coverage.
`ChannelsSpecs.cs`	Removes obsolete attach-resume tests.
`ChannelSpecs.cs`	Tests channel transition ordering.
`ChannelSandboxSpecs.cs`	Removes superseded attach-resume cases.
`FakeTransportFactory.cs`	Tracks all created transports.
`AblyRealtimeSpecs.cs`	Exposes created transports to tests.
`ErrorInfo.cs`	Adds idle-timeout error details.
`ConnectionDetails.cs`	Adds `MaxIdleInterval`.
`TransportParams.cs`	Requests protocol heartbeats.
`ConnectionStateBase.cs`	Allows workflow retry-time updates.
`ConnectionDisconnectedState.cs`	Applies backoff, jitter, and TTL clamping.
`ConnectionConnectedState.cs`	Delegates immediate reconnect handling.
`ConnectionClosingState.cs`	Uses configured close timeout.
`ConnectionManager.cs`	Uses configured auth-update timeout.
`ConnectionInfo.cs`	Carries maximum idle interval.
`ConnectionAttemptsInfo.cs`	Tracks bounded immediate retries.
`RealtimeWorkflow.cs`	Implements idle detection and recovery changes.
`RealtimeState.cs`	Stores idle limits and updates connection data.
`RealtimeCommands.cs`	Extends reconnect and monitor commands.
`RealtimeChannels.cs`	Reinitializes channels and preserves serials.
`RealtimeChannel.cs`	Revises reattach, detach, and suspend behavior.
`Presence.cs`	Safely fails queued presence callbacks.
`Connection.cs`	Allows recovery keys while suspended.
`ClientOptions.cs`	Makes realtime timeout public and validated.
`AuthOptions.cs`	Documents callback timeout behavior.
`AblyAuth.cs`	Bounds callbacks and records causes.
`IO_Ably_ConnectionDetailsMessageSerializer.cs`	Adds MessagePack idle-interval support.

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AndyTWF · 2026-09-09T10:33:16Z

+                    if (State.Connection.State == ConnectionState.Closed ||
+                        State.Connection.State == ConnectionState.Failed)


@sacOO7 I don't think this one is correct.

The spec points are as follows:

(RTN11b) If the state is CLOSING, the client should make a new connection with a new transport instance and remove all references to the old one. In particular, it should make sure that, when the CLOSED ProtocolMessage arrives for the old connection, it doesn’t affect the new one. Additionally, the client should ensure that all channels first transition to DETACHED, following RTL3b, and then reinitialize channels per RTN11d. (RTN11d) If the state is CLOSED or FAILED, transitions all the channels to INITIALIZED and unsets their RealtimeChannel.errorReason, clear all internal connection data (including in particular Connection.errorReason) and resets the msgSerial to 0

RTN11b makes no particular reference to resetting the error reason or the message serial. It only references RTN11d insofar as reinitializing the channels.

As it turns out, we don't lose anything by this exclusion because entering closing empties the connection ID in key for RTN8d and RTN9d. When the next connect arrives, there's no ID that needs to be matched, and the message serial is reset. This happens at connected, which is, if you take the spec literally, where it should happen. Ably JS is not a good reference here, as it also doesn't appear to follow the spec in any useful way.

Admittedly, though, the comment in the code is misleading, so I've adjusted the comment to be closer to what the spec actually says.

TO3l11 - the lower bound was zero, which let a positive sub-millisecond value through. CountdownTimer hands the delay to System.Threading.Timer as (int)TotalMilliseconds, so anything under a millisecond truncates to a zero delay timer - the same hot loop a literal zero produces, and just as quiet. The bound is now one millisecond. RTN23b - the heartbeats guard was answered once and cached for the client's lifetime, on the belief that TransportParams is fixed at construction. It is not: ClientOptions.TransportParams is a mutable dictionary the client keeps a reference to, and TransportParams.Create reads it afresh for every transport. A cached answer can therefore describe a param the current transport never sent, arming the monitor against heartbeats nobody asked for or standing it down while they are being sent. Recomputed per tick; the cost is a scan of a dictionary that is normally empty. RTN14h - the sandbox test named for a past-ttl reconnect was not reaching one. A live endpoint reconnects inside the ttl, so an implementation that restored the old RTN15g gate would still have passed. It now holds the attempts in CONNECTING until the ttl is spent and the client suspends - SUSPENDED being the state RTN14h names - then lets them complete, and asserts the key and id survive that. The connectionId is deliberately no longer asserted either way: whether the server still honours the resume after the ttl is its decision, and asserting it made the test depend on server retention rather than on client behaviour. Also states, on both sides, why RTN11d's connection level reset covers CLOSED and FAILED but not CLOSING: RTN11b asks only that channels be reinitialised from CLOSING, and the operations table maps that column to RTN11b rather than RTN11d. The previous wording said RTN11b "routes connect() through RTN11d", which reads as all of it.

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In `@src/IO.Ably.Tests.Shared/Realtime/RealtimeWorkflowSpecs.cs`:
- Line 1931: Update the Realtime workflow test so the existing connected
transport remains configured with heartbeats disabled. After changing
client.Options.TransportParams["heartbeats"] to "true", create a new transport
and verify it sends heartbeats=true before asserting the idle monitor arms;
ensure heartbeat settings are recalculated for each transport.

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src/IO.Ably.Shared/ClientOptions.cs
src/IO.Ably.Shared/Realtime/RealtimeChannels.cs
src/IO.Ably.Shared/Realtime/Workflows/RealtimeWorkflow.cs
src/IO.Ably.Tests.Shared/Realtime/ConnectionSandBoxSpecs.cs
src/IO.Ably.Tests.Shared/Realtime/ConnectionSpecs/ConnectionFailuresOnceConnectedSpecs.cs
src/IO.Ably.Tests.Shared/Realtime/RealtimeWorkflowSpecs.cs

🚧 Files skipped from review as they are similar to previous changes (3)

src/IO.Ably.Tests.Shared/Realtime/ConnectionSandBoxSpecs.cs
src/IO.Ably.Shared/Realtime/RealtimeChannels.cs
src/IO.Ably.Shared/Realtime/Workflows/RealtimeWorkflow.cs

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The guard asked ClientOptions.TransportParams whether protocol heartbeats had been requested. That is the wrong source: the params are rebuilt for every transport, and the dictionary is public and mutable, so a caller changing it retuned the monitor for a transport already on the wire. Armed against one that went out with heartbeats=false, the monitor measures against pings ClientWebSocket cannot see and disconnects a healthy connection; stood down against one that did ask, it never detects a dead one. ConnectionManager.CreateTransport now records the answer from the params the transport is actually built with, read after the merge, and the monitor consults that. Being per transport is the whole point, so it is stored per transport on the connection state. This deletes ComputeProtocolHeartbeatsNotRequested, whose job was to predict what DictionaryExtensions.Merge would do to the caller's entry - including the case-insensitive key match that lets "Heartbeats" displace ours while Ably reads neither. Asking the merged result answers all of that directly, so the reimplementation and its case analysis go, and the warning moves to transport creation where it fires once per transport rather than once per client.

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Provision each sandbox test environment once, atomically #1337

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Implement RTN23 idle-transport detection and the recovery spec points around it - #1331

Implement RTN23 idle-transport detection and the recovery spec points around it#1331
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		if (State.Connection.State == ConnectionState.Closed \|\|
		State.Connection.State == ConnectionState.Failed)

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Adopted from specification 6.1.0

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