Audit BREAKING_CHANGES_V1.6.md against v1.5.71 and catch up through #8698

[Aaronontheweb]

Audits BREAKING_CHANGES_V1.6.md against the last stable v1.5 release, catches it up with the ## Breaking changes sections of PRs merged since 2026-09-20, and adds the breaking changes that landed before the ledger existed. Only that file changes.

Definition used

Baseline: 1.5.71 (newest 1.5.* tag; no 1.6.0-* tag exists). A change is breaking if it isn't binary compatible, source compatible (trim-analyzer warnings noted briefly), or behaviorally compatible for an existing app with existing config. Not listed: Akka.DynamicTypeLoading-off-only behavior (except #8608, which turns it off for trimmed/AOT apps), fixes, comparisons with dev states that never shipped, refactors, new APIs, and .Internal / [InternalApi] types (per docs/community/contributing/api-changes-compatibility.md). The preamble now says this, and says breaking changes go in the PR body's ## Breaking changes section and get batched here.

Rows: 39 before, 22 after.

Removed (26 rows)

• Folded into the two consolidated rows (7): AOT: module serializer table for Akka.Cluster (#8626, part 3a) #8666, AOT: module serializer tables for Akka.Remote and Akka.Streams (#8626, part 2) #8658, AOT (4/7): core serializers and bindings from a built-in table; serialization-identifiers matched by name — canary goes green #8604 (core serializers), AOT (5/7): built-in routers and guardian strategy, guarded dispatcher/executor fallbacks, generic Expression.Lambda in the Props argument parser #8605 (Props parser), AOT (2/7): built-in mailbox types, mailbox requirement map, MailboxType/Mailboxes trimming annotations #8602 and AOT (1/7): Akka.DynamicTypeLoading feature switch, canary app, built-in tables for formatter/stdout logger/scheduler #8601 into the TargetInvocationException row (their settings-block cases are fixes; switch-off parts excluded); AOT (3/7): Props/actor-type trimming annotations, akka.loggers from a built-in table, Akka.DependencyInjection ripple #8603 into the trim-analyzer row
• AOT: first-party logger table so Akka.Hosting's LoggerFactoryLogger resolves without reflection #8654: fix (versioned Hosting logger name now resolves) / switch-off only
• AOT M1-G: one matching rule for every built-in type name #8613: switch-off only
• AOT (6/7): remove UDP buffer pooling, keep the DNS provider configurable through a built-in table #8606 (DNS provider): switch-off only
• AOT (5/7): built-in routers and guardian strategy, guarded dispatcher/executor fallbacks, generic Expression.Lambda in the Props argument parser #8605 (routers, guardian strategy, dispatchers): switch-off only
• AOT (4/7): core serializers and bindings from a built-in table; serialization-identifiers matched by name — canary goes green #8604 (serialization-identifiers matched by name): fix; the widening only matters for duplicate FullNames
• ClusterClient: arm the reconnect deadline per establishing phase via IWithTimers #8510 ClusterClient timers: fix; adds an interface and property to a sealed class
• perf: stop retaining ConsistentHash ring's SortedDictionary (#8293) #8324 ConsistentHash: old behavior was inconsistent; a null dictionary fails either way
• Akka.Cluster: gossip removal tombstones - stop resurrecting removed members #8484 gossip tombstones: additive proto field, fix (moved to "Not breaking, for the record")
• Milestone 3.5: widen system/address UID int32 -> int64 (Artery prerequisite) #8317 wire row: same varint encoding (folded into the Milestone 3.5: widen system/address UID int32 -> int64 (Artery prerequisite) #8317 API row and the "for the record" note)
• Artery: TestConductor blackhole and passThrough support (test-mode) #8378 system-UID RNG: fix
• Artery-only, and Artery isn't in 1.5.71 (9): Artery: flush outbound streams on graceful shutdown #8486, Artery: port InboundQuarantineCheck #8416, Artery: order DaemonMsgCreate ahead of Watch and retry early inbound resolves #8414, Artery: keep outbound-lanes in-flight messages alive across transient connection faults #8368, Artery: outbound lanes for parallel outbound encoding (ships at 1) #8357, Artery: inbound lanes for parallel inbound message processing (ships at 1) #8356, Artery: raise Akka.IO pipe watermarks on Artery TCP connections #8345, Artery: fix control-queue sizing, overflow observability, and shutdown races #8346 (x2)

The #8594 row (Hosting net10.0 + Microsoft.Extensions 10) is not removed but merged into the single net10.0 row below, so net10-only is stated once.

Added from PR bodies

• Serialization: built-in serializers declare their ids in code (#8676, part 1) #8694: built-in serializer ids can no longer be overridden via serialization-identifiers
• Serialization: module tables carry aliases and bindings (#8676, part 2) #8698: a second alias for a built-in Akka.Remote/Akka.Cluster/... serializer type shares the built-in instance (can change PrimitiveSerializers manifests); core json/bytes are unaffected
• Consolidated TargetInvocationException row (AOT (1/7): Akka.DynamicTypeLoading feature switch, canary app, built-in tables for formatter/stdout logger/scheduler #8601, AOT (2/7): built-in mailbox types, mailbox requirement map, MailboxType/Mailboxes trimming annotations #8602, AOT (4/7): core serializers and bindings from a built-in table; serialization-identifiers matched by name — canary goes green #8604, AOT (5/7): built-in routers and guardian strategy, guarded dispatcher/executor fallbacks, generic Expression.Lambda in the Props argument parser #8605, AOT: module serializer tables for Akka.Remote and Akka.Streams (#8626, part 2) #8658, AOT: module serializer table for Akka.Cluster (#8626, part 3a) #8666, AOT: module serializer tables for the Cluster contrib family (#8626, part 3b) #8669, AOT: module serializer table for Akka.Persistence (#8626, part 4) #8695)
• Consolidated trim-analyzer row (AOT (2/7): built-in mailbox types, mailbox requirement map, MailboxType/Mailboxes trimming annotations #8602, AOT (3/7): Props/actor-type trimming annotations, akka.loggers from a built-in table, Akka.DependencyInjection ripple #8603, Hosting: register WithExtension<T> through ExtensionsSetup #8649, Akka.Hosting: add missing trimming annotations for Native AOT #8655, AOT: serializers resolve their own manifests; guard the TypeCache fallback #8697), including Hosting's AddAkka<T>, WithHealthCheck<T>, WithDefaultLogMessageFormatter<T>

Checked and not added: #8695/#8669/#8666 (beyond the unwrapping row), #8697/#8671/#8670 (switch-off only; #8670's provider spelling fix is folded into the #8599 row), #8674, #8668, #8665, #8664, #8663 (restores v1.5), #8661, #8655 (trim row only), #8653, #8652/#8650 (fix), #8648 (additive), #8647, #8645, #8636, #8635, #8630 (fixes to the unreleased TCP rewrite), #8628, #8218 (additive).

Added from the pre-ledger pass and review

Scope: everything on dev since it diverged from v1.5 (merge-base 1f14b74ce, 2025-08-15) up to the ledger's creation (#8260, 2026-06-12), enumerated with git log --first-parent 1f14b74ce..akkadotnet/dev --before=2026-06-13 (277 commits) plus the pre-fork v1.6 work that came in through #7761. Most of those PRs also shipped in v1.5.x, so each candidate was checked against 1.5.71. Cross-checks over the full range: the *.DotNet.verified.txt API approvals (1.5.71 vs dev, normalized for the newer generator's rendering), every shipped .conf, the .proto files, and project TFMs / package references.

• Modernize Akka.IO TCP: ByteString removal, Stream+Pipe transport, ReadOnlySequence<byte> migration, .NET 10 TFM #8132 + Forward-port #8591 to dev: Akka.Hosting in the akka.net repository, net10.0 only #8594 (+ dependency bumps Bump FSharp.Core from 6.0.5 to 10.1.300 #8228/Build: pin SDK-implicit FSharp.Core and bump FsharpVersion to 10.1.302 (fixes repo-wide NU1605) #8386, Bump Google.Protobuf from 3.26.1 to 3.35.0 #8229/Bump Google.Protobuf from 3.35.1 to 3.36.1 #8577, Bump LightningDB from 0.16.0 to 0.21.0 #8236/Bump LightningDB from 0.21.0 to 0.22.0 #8338): every package, Akka.Hosting included, targets net10.0 only; Hosting ships at the Akka.NET version; dependency minimums rise (Microsoft.Extensions 10.0, Google.Protobuf 3.36.1, FSharp.Core 10.1.302, LightningDB 0.22.0)
• Modernize Akka.IO TCP: ByteString removal, Stream+Pipe transport, ReadOnlySequence<byte> migration, .NET 10 TFM #8132: Akka.IO.ByteString removed; TCP data and the Streams byte APIs use ReadOnlySequence<byte>, TCP write helpers also take ReadOnlyMemory<byte>/byte[], UDP uses ReadOnlyMemory<byte>; ByteOrder moved to Akka.Util
• Modernize Akka.IO TCP: ByteString removal, Stream+Pipe transport, ReadOnlySequence<byte> migration, .NET 10 TFM #8132: TCP connects to a DnsEndPoint bypass akka.io.dns and use the OS resolver
• Add SerializerV2 foundation #8222: Serializer gains FromBinary(byte[], string) / Manifest(object) (CS0121 on FromBinary(bytes, null), CS0114 in subclasses); ByteArraySerializer.IncludeManifest becomes a sealed true
• Use explicit hostname in DotNetty certificate validator #8465: ValidateHostname(expectedHostname) now checks the certificate against that name
• Remove System.ConfigurationManager support from .NET 6+ #7456 (via [v1.6] flip dev to v1.6 #7761): App.config HOCON loading removed (ConfigurationFactory.Load(), AkkaConfigurationSection and friends, Akka.FSharp Configuration.load)

Not listed:

• Remove obsolete addorset from the API #7622 (Akka.Util.Internal.Extensions.AddOrSet): an .Internal, already-obsolete API.
• [V3] ReceiveActor - Removing MatchBuilder and making use of handlers. Deleted all MatchHandler code #7557 (via [v1.6] flip dev to v1.6 #7761): Receive(typeof(object), Func<object, bool>) without a predicate blocking later Receive* registrations is a regression that is being fixed in a separate PR (branch fix/receiveactor-func-object-handler), not documented here.

Rewritten

Every kept row cut to one or two sentences plus a one-sentence migration, and set to Merged with its PR (branch names replaced: #8599, #8594, #8545, #8510, #8484, #8445, #8486, #8416, #8414, #8378, #8368, #8357, #8356, #8359, #8345, #8346, #8263). Kept: #8649, #8660, #8646 (reframed against v1.5: write-commands-queue-max-size now caps one write, not a registered connection's backlog), #8608, #8606 (UDP pool), #8599 (+#8670), #8545, #8445, #8378 (cut to the Player change: unapplied throttles now fail; the Artery test-mode part is dropped), #8359, #8317 (API), #8263. The "for the record" note also covers the always-registered artery-control serializer (id 23, reserved range) and #8561 (TestKit-only DotNetty batching). List markers use * (MD004); markdownlint passes.