# Description

The catch block in OnPublishComplete reads m_subscriptions.Count and
m_subscriptions.Any(s => s.Created) without holding m_lock, while all
other accesses (AddSubscription, RemoveSubscriptionAsync,
RemoveTransferredSubscription) correctly lock before modifying the list.

This causes an InvalidOperationException ("Collection was modified;
enumeration operation may not execute") when a publish response errors
concurrently with a subscription being removed during reconnect.

Snapshot both values under m_lock, consistent with all other call sites.

## Related Issues

- Fixes #3835

## Checklist

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after opening the PR._

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- [ ] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
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- [x] I have verified that my changes do not introduce (new) build or
analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
at least .net **framework** and .net **10**, and all passed.
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
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…e ReportAuditCancelEvent call from CancelRequests. (#3853)

# Description

Use request.SessionId instead of request.Session.Id in the
ReportAuditCancelEvent call from CancelRequests to avoid accessing
Session in case ActivateSession.

Cancel service is returning BadUnexpectedError because audit reporting
crashes on request.Session.Id in case the ActivateSession service call
is in-flight and its cancelation is requested becasue Session is null.

## Related Issues

- Fixes issue 3850 on branch master378

## Checklist

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doc.
- [ ] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
- [ ] I have added all necessary documentation.
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analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
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…only. (#3843)

Keep the generated children that belong on instances, and prune the
extra decoded children that should stay on the type definition only,
such as Optional/Mandatory placeholders and ones that do not have
Mandatory/Optional ModellingRules.

# Description

Currently child nodes that are type definition detailes such as ones
that do not have Mandatory/Optional ModellingRules are instantiated in
the runtime instance of such type definitions. This PR proposes to
correct this behaviour during NodeState creation as an alternative from
it being fixed by the ModelCompiler.

## Related Issues

- Fixes #3770 

## Checklist

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after opening the PR._

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and read the
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doc.
- [ ] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
- [ ] I have added all necessary documentation.
- [ ] I have verified that my changes do not introduce (new) build or
analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
at least .net **framework** and .net **10**, and all passed.
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.

# Description

`ConditionState.m_branches` (a plain `Dictionary`) was read and written
from multiple threads without synchronization. A state change on a
background thread could mutate the dictionary while readers
(`GetRetainState`/`UpdateRetainState`, `ConditionRefresh`, `GetBranch`)
enumerated it, yielding torn entries and native access violations
(observed as `IsBranch` on a null `this`). This ports the master378 fix
to `master`, where the type lives at
`Stack/Opc.Ua.Core.Types/State/ConditionState.cs` and uses
`ByteString`/nullable refs.

- **Lock all branch access**: added a private `m_branchesLock` guarding
every read/write of `m_branches` (`CreateBranch`, `GetBranch`,
`ReplaceBranchEvent`, `RemoveBranchEvent`, `ClearBranches`,
`GetBranchCount`).
- **Snapshot enumeration**: `GetBranches()` now returns a copy taken
under the lock, so internal readers and
`AlarmHolder.GetBranchesForConditionRefresh` iterate a stable collection
while other threads mutate the live one. Public signature is unchanged.
- **Test**: added `ConcurrentBranchAccessIsThreadSafe`, stressing
concurrent create/clear writers against enumerate/count readers.

`lock` is used rather than `SemaphoreSlim` because all affected methods
are synchronous. Each `ConditionState` holds its own lock, so the
recursive `UpdateRetainState` traversal across branches neither contends
nor deadlocks. `ConcurrentDictionary` was rejected: it would change the
public return type and still leave compound read-modify-write sequences
(e.g. `ReplaceBranchEvent`) unprotected.

## Related Issues

## Checklist

_Put an `x` in the boxes that apply. You can complete these step by step
after opening the PR._

- [ ] I have signed the
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and read the
[CONTRIBUTING](https://github.com/OPCFoundation/UA-.NETStandard/blob/master/CONTRIBUTING.md)
doc.
- [x] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
- [ ] I have added all necessary documentation.
- [x] I have verified that my changes do not introduce (new) build or
analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
at least .net **framework** and .net **10**, and all passed.
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: Marc Schier <[email protected]>
Co-authored-by: Copilot Autofix powered by AI <[email protected]>
Co-authored-by: Suciu Mircea Adrian <[email protected]>