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romanett 87c35b84b6 Fix Opc.Ua.Client audit findings (security fallback, reconnect, subscriptions, redundancy, browse, files, WebApi) (#4572)
## Summary

Fixes the findings of a bug audit of `Opc.Ua.Client` and
`Opc.Ua.Client.ComplexTypes`, done on master plus #4516 (now merged).

- **Audit:** 82 findings across 12 areas, each checked against the OPC
UA specification. Final severities: 2 High, 37 Medium, 43 Low.
- **Fixes:** 76 fixed, 4 partial, 2 skipped (see [Not
fixed](#not-fixed--partial)).
- **Review:** a follow-up review of the fixes found 15 more defects in
them, all fixed here.
- **Tests:** every fix has a regression test, except a few races that
cannot be reproduced deterministically; the commit messages say which.

The finding IDs (`L<area>-<n>` for the audit, `G<n>` for the review)
appear in the commit titles.

## Behaviour and user-facing changes

### Security and endpoint selection
- **Reconnect no longer drops to weaker security (L3-1, High).** When
the server rejects the configured security policy or mode during
reconnect, `SessionReconnectHandler` no longer switches to whatever
endpoint the server advertises, None included. It only picks an endpoint
at least as strong as the configured one, judged by a locally computed
security level. The server-advertised `SecurityLevel` is not trusted. If
nothing qualifies, reconnect fails with the original error (new log
event `SessionReconnectHandler + 13`) and keeps retrying with the
original settings.
- **`CoreClientUtils.SelectEndpoint(useSecurity: true)` never returns a
SecurityMode None endpoint over opc.tcp (L9-9, High).** It now returns
`null` when no secure endpoint matches.
- When the discovery URL is `https`/`opc.https`, an HTTPS endpoint with
SecurityMode None is still accepted as a last resort, because TLS
protects it (Part 6 §7.4.1) (G17).
  - Endpoints with SecurityMode `Invalid` no longer count as secure.
- `GlobalDiscoveryServerClient` and `ServerPushConfigurationClient` now
throw `BadSecurityPolicyRejected` when no secure endpoint matches,
instead of passing `null` on. The ConsoleReferenceClient sample reports
this with a clear error.
- **No Bearer/Basic credentials over `http://` (L12-2).**
`WebApiClient.Create` and WebApi channel open/reconnect reject them with
`BadSecurityChecksFailed`. The public `WebApiClient(HttpClient, …)`
constructor also rejects them when the client's `BaseAddress` is not
https, and every send checks the address it actually goes to (covers a
`BaseAddress` set later).

### Session, keep-alive and identity
- **Faster detection of a silent server (L1-1).** The keep-alive Read is
now bounded by its `TimeoutHint` (2 × `KeepAliveInterval`), which is
what Part 4 §7.32 says the client should do. It then fails with
`BadNoCommunication`, so reconnect starts after about 2 ×
`KeepAliveInterval` instead of `OperationTimeout` (120 s by default).
- **Operations fail fast during a channel-manager recovery (L1-2, G9).**
`UpdateIdentityAsync`, `TransferSubscriptionsAsync` and
`ReactivateSubscriptionsAsync` fail with `BadSecureChannelClosed`
(retryable) instead of deadlocking. This covers the operation holding
the reconnect lock and any queued behind it.
- **Closing or disposing from a handler no longer waits on itself (L1-3,
G5, G6).**
- `Session` and `ManagedSession` Close/Dispose from a Notification
handler no longer wait 30 s for their own background drain.
- Disposing a `ManagedSession` from a keep-alive `PublishStatusChanged`
handler no longer deadlocks.
- Tasks spawned by a handler no longer count as "the handler" (the owner
marker is scoped to the work item).
- **Switching to an ECC user-token policy takes two ActivateSession
calls (L1-4, G4).** This follows Part 6 §6.8.2 (fetch the ephemeral key,
then activate).
- If the server returns no key, the switch fails with
`BadSecurityPolicyRejected`.
- If the second activation is rejected, the old identity stays on the
override policy with the key just fetched. Restoring the old key was
tried: against the reference server the next reconnect then failed to
decrypt the identity token.
- **`ManagedSession.ConfiguredEndpoint` follows failover (L2-6).** It
now reports the inner session's endpoint, so it changes after a failover
or network-path rotation.
- **An explicit identity update replaces the identity provider (L2-7).**
`ManagedSession.UpdateSessionAsync(identity)` stops the provider's
refresh loop and drops the provider for good. If the update fails, the
loop is restarted.
- **Reconnect waits for in-flight calls on a healthy channel (L2-3,
G8a).** Reconnect/failover on a healthy channel (certificate or
trust-list change, manual reconnect) waits for in-flight service calls.
The wait is bounded (max(`KeepAliveInterval`, 1 s)) only once the
channel is unhealthy (keep-alive stopped, channel not Ready), so a dead
channel no longer holds recovery for `OperationTimeout`.
- **Smaller fixes:**
- Restore reads the server certificate as a chain; this failed on macOS
(L1-5).
  - Session recovery can no longer run twice at once (L1-6).
  - Identity expiries more than 49.7 days out no longer throw (L2-2).
- Keep-alive reconnect suppression is recalculated on a lease swap
(L2-4).

### Reconnect state machine and reverse connect
- **⚠ `MaxTotalReconnectTime = 0` now means "no time limit" (L3-7).
Reviewer decision needed.** Before, 0 disabled reconnect entirely.
Negative values other than `Timeout.InfiniteTimeSpan` now throw
`ArgumentOutOfRangeException` when the state machine is constructed;
before, they crashed the worker. The XML docs of
`ReconnectPolicy`/`ReconnectPolicyOptions` are updated. If 0 should keep
meaning "no reconnect", this is a one-line revert.
- **A close racing the end of the reconnect budget is no longer lost
(L3-4).** It goes through the normal close instead of switching to
failover.
- **The "reconnect worker" marker covers one step only (L2-1).** It
lasts for a single connect/reconnect/failover/close step. Keep-alive,
publish and identity loops started in a step no longer count as the
worker afterwards.
- **Reverse-connect strategies `Undefined` and `Any` alone are removed
after the first callback (L8-1).** This matches the documentation;
before, they behaved like `Always`.
- **`AddEndpoint` for a URL that is already added disposes the replaced
listener (L8-2).**

### Service calls
- **Batched calls clean up after a failed later batch (L3-2).** When a
later batch of
`Browse`/`BrowseNext`/`HistoryRead`/`CreateMonitoredItems` fails, the
continuation points and monitored items created by earlier batches are
released or deleted before the exception is rethrown. This adds one
request. `AddNodes`/`RegisterNodes` are not undone.
- **Batched diagnostic infos point at the right strings (L3-3).** The
string-table indexes are rebased when diagnostics are padded.
- **`ReadBytesAsync` rejects oversized responses (L3-5).** It throws
`BadUnknownResponse` when the server returns more bytes than requested,
and `BadEncodingLimitsExceeded` beyond `int` range.
- **`ReadByteStringInChunksAsync` handles an unknown server limit
(L3-6).** When the server's `MaxByteStringLength` is 0 (absent) or
larger than `int`, it falls back to the client's
`MessageContext.MaxByteStringLength`. It throws only when both are
unknown.

### Browse and NodeCache
- **Empty browse pages with a continuation point are followed (L9-1,
L9-4, L9-5, G16).** Part 4 §5.9.2.1 allows a server to return an empty
page with a continuation point, so browsing keeps following it. After 10
consecutive empty rounds it gives up with `BadNoData` and releases the
continuation point.
- `BrowseAsync(NodeId)` now throws instead of silently returning a
truncated list.
  - `BrowseStreamAsync` yields a `BadNoData` result for that node.
- The same cap, through one shared helper, now also protects
`RoleManagementClient.ListRolesAsync` and the FileSystem
enumerate/empty-check loops.
- **Continuation points are released on failure (L9-3).**
`BrowseAsync(NodeId)` releases them on any exception, and
`BrowseStreamAsync` releases all points of the current page when the
consumer stops early.
- **NodeCache lookups propagate cancellation (L9-6, L9-8).**
`FindAsync`, `IsKnownAsync`, `FetchNodeAsync`,
`FindReferenceTypeNameAsync`, the reference-table fill and the
type-hierarchy search now let `OperationCanceledException` through.
Before, a cancelled lookup looked like "node does not exist".
- **A NodeClass mismatch fails only that node (L9-7).** It returns
`BadNodeClassInvalid` for that node instead of throwing
`KeyNotFoundException` for the whole batch.
- **Smaller fixes:**
- `MaxNodesPerBrowse` ≥ 2^31 no longer breaks the managed browse (L9-2).
  - Null discovery URLs are skipped (L9-10).
  - `ModelChangeTracker` no longer cancels a joined start (L9-11).
- **Log changes:** `BrowserContinuationPointExistsButBrowse` (Browser +
0) was removed, and `BrowserServerReturnedEmptyReferencesBut` now
includes the round count.

### Subscriptions (default engine)
- **Recovery after a transfer delivers each message exactly once (L5-1,
G22).** Messages already dispatched are acknowledged instead of
republished and delivered again. Messages whose earlier republish failed
are now republished and delivered, with the Republish flag and after
newer messages, instead of being acknowledged and lost.
- **A keep-alive that proves a gap triggers republish at once (L5-5,
G23).** The dedup mark moves only past messages that were actually
recovered, so a failed republish is retried by the next data message.
- **Item changes that fail are retried with backoff (L5-3).** They are
retried on the next apply pass after the state manager's 250 ms–5 s
backoff, instead of six times back to back. The six attempts now span
about 13 s.
- **Extreme revised intervals no longer throw (L5-4, L6-1).** Very large
or NaN intervals and counts revised by the server are capped (NaN falls
back to the requested value). Before, the overflow could stop every
publish worker.
- **`SetTriggeringAsync` from a callback no longer hangs (L5-7, G21).**
While the subscription is deleted, recreated or disposed, it returns
`BadOperationAbandoned`. A cancelled reset no longer makes later calls
fail.
- **Publish responses for unknown subscription ids (L6-3, L6-4, G20).**
The client no longer re-sends acknowledgements the server already
processed. An unknown id seen while a creation is pending is left alone
instead of being deleted.
- **Smaller fixes:**
- A null and an empty `IndexRange` are treated as equal, and restored
snapshots use `null` (L5-6).
  - A failed partition attach during restore is rolled back (L6-2).
- `StreamingSubscription` throws `ObjectDisposedException` after dispose
(L6-6).

### Subscriptions (classic `Subscription`)
- **Republish no longer abandons other missing messages (L7-1).** A
Republish response no longer overwrites `AvailableSequenceNumbers`, so
other missing messages are not given up while the server still holds
them.
- **Late copies are no longer delivered twice (L7-2).** Copies of
already-processed sequence numbers are ignored, and creating a new
server subscription resets the sequence state.
- **Disposing from a keep-alive handler no longer deadlocks (L7-3).**
`Dispose()` from a keep-alive `PublishStatusChanged` handler can return
while that callback is still finishing.
- **Transfer of a restored subscription (L7-4, G27).**
  - It succeeds even when some saved items were never created.
- The server subscription is deleted only when this session's own
TransferSubscriptions just moved it and adoption failed definitively
(item count mismatch or a non-transient status). Transient errors and
`ReactivateSubscriptionsAsync` never delete it.
  - The public `Subscription.TransferAsync` never deletes.
- **Smaller fixes:**
  - Cloned items keep their triggering links (L7-5).
  - `CreateAsync` clears stale server ids (L7-6).
- A `Good_SubscriptionTransferred` for the client's own transfer is
ignored (L7-7).
- An item removed while its create is in flight is deleted afterwards
(L7-8).
- The publish timeout for very long keep-alives no longer overflows
(L7-9).
  - A negative `MaxMessageCount` is handled (L7-10).
  - `LastMessage` tolerates a wrong notification type (L7-11).
  - Pending acks exactly 2^31 away no longer throw (L4-1).
- **Log changes:** new log events `Subscription + 68..70`.

### Redundancy
- **Warm/Hot demotion (L4-2, G1, G3).**
- Without token reuse, the demoted leader closes its session and
reconnects as a fresh standby.
- With token reuse, it abandons the shared server session locally,
without CloseSession, so the new leader can reactivate it and keep its
subscriptions. This uses the new internal methods
`ManagedSession.AbandonServerSessionAsync` and
`Session.AbandonServerSession`.
- `RoleChanged(false)` is now raised before the standby connect and no
longer depends on it, so `CurrentSession` can briefly be `null`.
- Exceptions from `RoleChanged` handlers are logged and do not stop the
teardown.
- **Promotion (L4-3, G2).** A promoted standby that adopts the leader's
session first closes its own server session. A retried promotion keeps
the session it already adopted.
- **Client failover takeover (L4-4, partial).** Subscriptions the backup
prepared in advance (not yet created, `TransferId` set to the active
client's id) are moved through the session's own transfer and keep
publishing. `docs/HighAvailability.md` is updated.
- **`ShouldFailover` through the interface (L4-6).** Calling it through
`IServerRedundancyHandler` no longer fails over away from a server that
is still Healthy.

### Fluent / dependency injection
- **Shared DI session (L10-5).** The shared session from `AddClient` is
reconnected after a caller disposes it, and is disposed with the
container. After that the connect delegate throws
`ObjectDisposedException`.
- **New public API:
`ManagedSessionBuilder.WithServerRedundancyOptions(ServerRedundancyOptions)`
(L10-6).** This is additive. The `Session.ServerRedundancy` options are
now actually applied.
- **`AddDiscoveryAndConnect` rewrites the advertised address (L10-7).**
It replaces the host and port the server advertises with those of the
discovery URL (Part 4 §5.6.2.1, NAT/containers), and prefers endpoints
with the same scheme.

### State machines and role management
- **`GetSubStateMachineAsync` returns the instance's own sub-state
machine (L10-1).** Before, it returned the type's placeholder.
- **`WaitForStateAsync` reports failures with OPC UA status codes
(L10-2).** It throws `BadNotFound` when `CurrentState/Id` cannot be
resolved, and `BadInvalidState` when observation ends without reaching
the state. Before, both surfaced as `OperationCanceledException`.
- **`RoleManagementClient.ListRolesAsync` pages correctly (L10-3).** It
follows continuation points, releases them on any failure, and throws on
a Bad browse status instead of returning an empty list.
- **Role properties are read into the right fields (L10-4).** Properties
whose namespace cannot be resolved are skipped instead of shifting the
other values.

### File system, temporary files and alias names
- **Path escaping (L11-8, G12).**
- Path segments escape `:` and `/` with `&`, and `&` itself as `&&`
before those characters or at the end of a name.
- `Format` and `Parse` round-trip all names. Typed input ending in `&/`
now reads the slash as part of the name.
- A segment without a namespace prefix also matches a namespace-0 child
when nothing matches in the parent's namespace.
- **Stale path cache (L11-1).** When a cached lookup fails,
`GetInfoAsync` retries once from the server. `ExistsAsync` and
`GetFileAsync` report "not found" instead of throwing.
- **`GenerateFileForReadAsync` waits for the file (L11-2).** It waits
until the file-generation state machine reaches ReadTransfer (`Idle`
counts as not started yet), and throws `IOException` if it reports
Error. The wait is bounded only by the caller's token.
- **Non-recursive delete refuses hidden children (L11-3).** It refuses
when the directory holds children that the subtype options hide from
enumeration. Before, the server deleted them all.
- **Alias names (L11-5, L11-6, L11-7).**
- `BadMethodInvalid` maps to `NotSupportedException` for all alias
calls, so `UseVerbose` falls back to `FindAlias`.
  - A duplicate alias name resolves to all its targets.
- If the refresh strategy fails to start, the resolver logs a warning
and keeps working without automatic invalidation. New log event block
`AliasNameResolver = 560`.
- **Null profile entries (L11-4).** Null `ServerProfileArray` entries no
longer crash `GetConformanceInfoAsync`.

### WebApi transport
- **Failures come back as `ServiceResultException` (L12-1).**
  - A timeout becomes `BadRequestTimeout`.
- HTTP 429/503 becomes `BadServerTooBusy` with the Retry-After hint, on
every target framework. `WebApiClient` checks the status itself (reusing
`HttpsTransportChannel.CreateServerTooBusyException`), so callers of
`WebApiClient` also get a `ServiceResultException` instead of an
`HttpRequestException` for these two statuses (G15).
  - An IO error becomes `BadNotConnected`.
- **Timeouts (L12-1, G14).**
- `OperationTimeout` applies to each request. When `RequestTimeout` is
unset, HttpClient's 100 s default no longer cuts off long Publish
requests.
- The GetEndpoints call at open is bounded by `OperationTimeout`, and
cancelling the open now throws.
- **Core change:** `HttpsTransportChannel.MapRequestFailure` went from
private to internal so the WebApi channel can reuse it.

### ComplexTypes
- **Out-of-range union selector (L12-3).** A union whose SwitchField is
larger than its field count now fails with `BadDecodingError` when
decoded and `BadEncodingError` when encoded (Part 6 §5.2.8).
- **Verbose JSON unions (L12-4).** They now decode their selected field
instead of `null`.

## Not fixed / partial
- **L2-5 (skipped):** an identity provider combined with a
caller-supplied reverse connection still can't connect to an
undiscovered endpoint. Fixing it means choosing the identity after
CreateSession, a design change.
- **L4-5 (skipped):** the one-time KeyCredential token needs a fresh
token on each reactivation. Today reactivation fails and the client
falls back to a new session.
- **L4-4 (partial):** only subscriptions the backup prepared in advance
survive a takeover.
- **L3-2 (partial):** `AddNodes`/`RegisterNodes` batches are not rolled
back.
- **L2-3 (partial):** service calls still hold the session lock for
their whole round trip.
- **Known from the review, not fixed here:**
  - G7: the batch cleanup request can't be cancelled.
- G11: the DI session's close at host shutdown never reaches the server,
and a closed session keeps being handed out.
- G13: a file renamed by another client is still found under its old
path.
  - G25: a clone-based transfer doesn't mark the original subscriptions.
  - G27b: the transfer item check matches by count, not by ID.
- **Outside this PR:** the reference server ignores `ECDHPolicyUri` on
ActivateSession (`SessionSecurityPolicyHelper`), which breaks Part 6
§6.8.2. As a result, the L1-4 two-step ECC switch ends in
`BadSecurityPolicyRejected` against our own server.

## Testing
All suites on net10.0, on the branch before the master merge. Every
suite had 0 failures:

| Suite | Passed | Skipped |
|---|---|---|
| Opc.Ua.Client.Tests | 2698 | 0 |
| Opc.Ua.Redundancy.Client.Tests | 134 | 0 |
| Opc.Ua.Subscriptions.Classic.Tests | 57 | 0 |
| Opc.Ua.Bindings.Https.WebApi.Tests | 385 | 0 |
| Opc.Ua.Sessions.Tests | 782 | 379 |
| Opc.Ua.Subscriptions.Tests | 640 | 6 |
| Opc.Ua.Client.ComplexTypes.Tests | 2858 | 0 |

After merging current master (net10.0), every suite had 0 failures
except one, a flaky new test fixed in 9f52952b2:

| Suite | Passed | Skipped | Failed |
|---|---|---|---|
| Opc.Ua.Client.Tests | 2719 | 0 | 1 (the flaky test) |
| Opc.Ua.Redundancy.Client.Tests | 134 | 0 | 0 |
| Opc.Ua.Client.ComplexTypes.Tests | 2858 | 0 | 0 |
| Opc.Ua.Subscriptions.Classic.Tests | 57 | 0 | 0 |
| Opc.Ua.Bindings.Https.WebApi.Tests | 397 | 0 | 0 |
| Opc.Ua.Sessions.Tests | 790 | 379 | 0 |
| Opc.Ua.Subscriptions.Tests | 640 | 6 | 0 |

The touched test projects also build on net48 with 0 warnings.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: marcschier <11168470+marcschier@users.noreply.github.com>
Co-authored-by: Marc Schier <marcschier@users.noreply.github.com>
2026-09-29 09:34:03 +00:00
romanett ea93c86da2 Fix the Opc.Ua.Client defects reported by the client stack audit (#4471)
# Description

Fixes the 78 `Opc.Ua.Client` findings of a read-only bug audit of
`Opc.Ua.Client` / `Opc.Ua.Types` / `Opc.Ua.SourceGeneration` taken at
a05a36055, plus the regressions a subsequent review of those fixes
turned up. Every behavioural change was checked against the OPC UA
specification, and the citations are in the code comments.

## Session, reconnect and failover

- The reconnect `finally` re-acquired `m_reconnectLock` with the
caller's token, so a cancelled reconnect left the session stuck in
`Reconnecting` forever and every later reconnect failed. It now uses
`CancellationToken.None`.
- An in-place session recreate tore down subscriptions it should not
have: `transferred` is all-or-nothing, so a single failed transfer reset
and recreated the ones the server had just taken over, orphaning them on
the new session. `TransferSubscriptions` now reports the
per-subscription outcome and only the subscriptions the server did not
take over are recreated. A token-reuse failover keeps the same server
session, so nothing is transferred or reset there at all.
- In-place recreate only tears down the channel it created itself; a
caller-supplied channel or a channel-manager lease is left to its owner.
- `Snapshot(out SessionState)` went through the `SessionOptions` record
copy constructor, which drops every member declared on `SessionState`,
so the paired `Snapshot`/`Restore` API could not round-trip.
- The user-token policy override restored the policy URI on failure but
had already disposed the ECC ephemeral key the previous identity needs,
so the identity the rollback claims to preserve could no longer be
reactivated. The key is now parked and restored.
- `SetTriggering` batching sliced the remove list past its end when a
call had more adds than removes (Part 5 §6.3.11 bounds the *sum* of both
arrays, so an individual list may be shorter than the limit).
- The certificate-less `None` attempt dropped the request header, and
with it the ECDH ephemeral key that travels in `additionalHeader` (Part
4 §7.1/§7.15).
- `Session.Equals` compared a `ConfiguredEndpoint` against an
`EndpointDescription`, so a session did not equal a session on the same
endpoint.

## Managed session, pool and connection state machine

- `ManagedSession.Dispose()` blocked on the connection state machine's
worker, which raises `ConnectionStateChanged` synchronously — disposing
from that handler deadlocked permanently. The machine now recognises its
own flow and completes the teardown as the worker's continuation.
- `ManagedSessionFactory` dropped `updateBeforeConnect`, `connection`
and `reverseConnectManager` on all four `CreateAsync` overloads.
- The session pool ran its shared connect on no token at all, so once
the only caller gave up nothing could abort it and
`RemoveAsync`/`DisposeAsync` waited out the whole reconnect budget. Each
entry now owns the token that aborts its connect, and removal closes
*and* disposes the session.
- An explicit `engineFactory` was silently ignored for
`DefaultSessionFactory` subclasses, which quietly downgraded the session
to the classic subscription engine.

## Subscriptions

- Fixed a lock-order inversion between `m_subscriptionLock` and the
partition locks in `CompleteAsync` and `DisposeAsync`.
- `OwnsSubscriptionId` stopped at the first registered subscription
carrying the id — but in the very case it guards, the asker still holds
its own retired id, so the answer depended on `HashSet` enumeration
order and the delete could still tear down a sibling that had been
handed the recycled id.
- `MessageProcessor`'s republish gap walk was unbounded; it is now
bounded by the server's retransmission queue (Part 4 §5.14.5).
- A publish acknowledgement is sent even when a notification handler
throws — the ack means "the server may delete the message" (Part 4
§5.14.5.2), not "I processed it".
- Loaded monitored items did not raise the process-wide client-handle
counter, so a fresh process minted handles that collided with the loaded
ones; a transfer-restored item was also stamped `BadOperationAbandoned`
and left at the default monitoring mode.
- `AutoSetQueueSize` was not idempotent, so the queue size ratcheted up
on every subscription state change.
- The snapshot dropped the partition and recovery options entirely, and
clamped the sampling interval and the secondary-partition idle timeout
to zero — turning the Part 4 §7.21 "use the publishing interval"
sentinel and "never delete an idle partition" into something else.
- The state stream is positional OPC UA binary and the reader cannot
detect an absent field, so appending the partition options would have
mis-decoded every previously saved file. The stream now carries a format
version and the first format is decoded through a frozen copy of its
shape.

## Browse, node cache and the remaining clients

- Managed browse wrote a retry pass's status into whatever node happened
to sit at that offset in the caller's list, and retried
continuation-point errors without any bound. It now keeps the caller's
slot and gives up on passes that make no progress — a fixed pass cap
would cut short a large browse against a conforming server with a small
continuation-point quota.
- Continuation points are released when a consumer stops enumerating
early, as Part 4 §5.9.3.2 requires.
- The node cache reordered its batched results relative to the inputs,
which mispairs them for every consumer that matches positionally; its
supertype walks could also spin forever on a server whose `HasSubtype`
chain loops back on itself.
- A browse error was cached as "this node has no references"; it is now
surfaced to the direct caller, while the bulk and hierarchy walks treat
the node as having no references for that one operation without caching
it, so a single un-browsable node cannot fail a whole batch.
- `WebApiClient` mutated a caller-supplied (typically
`IHttpClientFactory`-pooled) `HttpClient`, which throws once that client
has sent its first request; those instances are configured per request
instead.
- `PathCache` was not thread-safe.

## Review follow-ups

The last two commits are the result of reviewing the audit fixes
themselves. Worth calling out: the `Task.WaitAsync(CancellationToken)`
polyfill in `Opc.Ua.Types` never checked `IsCompleted`, so an
already-finished task plus an already-cancelled token reported
cancellation on every pre-net8.0 target where the BCL overload returns
the result. It is now aligned with the BCL and pinned by a test.

## Related Issues

- No tracking issue; this PR is the result of a read-only audit of the
client stack.

## Checklist

- [x] I have signed the
[CLA](https://opcfoundation.org/license/cla/ContributorLicenseAgreementv1.0.pdf)
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.
- [x] 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.

### Verification

35 regression tests were added under
`tests/Opc.Ua.Client.Tests/AuditRegressions/` (category
`AuditRegression`), one per fixed defect where the defect is observable
at unit level; most were mutation-checked by reintroducing the bug and
confirming the test fails.

Locally on **net10.0**: `Opc.Ua.Client.Tests` 2252/2252,
`Opc.Ua.Client.ComplexTypes.Tests` 2773/2773,
`Opc.Ua.Bindings.Https.WebApi.Tests` 346/346, and all 23 library and
test projects that reference `Opc.Ua.Client` build clean.
`Opc.Ua.Client` also builds clean for **netstandard2.1**, the target
that actually compiles the `WaitAsync` polyfill. The full **UA.slnx**
solution and the .NET Framework targets have not been run locally — left
to CI.

One pre-existing failure in `Opc.Ua.Types.Tests` is unrelated to this
branch:
`WotSpecFixtureManifestTests.EveryEmbeddedExampleMatchesItsRecordedHash`
(embedded WoT fixture hashes) fails identically with these changes
reverted.

### Notes for reviewers

- Two review findings were deliberately left unfixed and are documented
in the code: `ManagedSession.CreateAsync` has to write the engine choice
onto a caller-supplied `DefaultSessionFactory` subclass (the only
alternative is changing the `ISessionFactory.Create` contract), and the
connection state machine's "am I on my own worker" flag is an
`AsyncLocal`, so it also flows into work a `StateChanged` handler
spawns. The previous behaviour in that second case was a hard deadlock.
- `Session.Dispose()`'s single `GetAwaiter().GetResult()` bridge to
`CloseAsync` is left as is: `Dispose(bool)` must be synchronous and
`DisposeAsync` already exists.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
2026-09-14 08:22:28 +02:00
Marc Schier 7cec2d614d Move repository files to the consolidated layout 2026-07-16 06:25:54 +02:00