Block a user
dohertj2
created branch phase-3-pr70-opcua-client-security-policy in dohertj2/lmxopcua
2026-04-19 01:45:47 -04:00
82f2dfcfa3
Merge pull request 'Phase 3 PR 69 -- OPC UA Client ISubscribable + IHostConnectivityProbe' (#68) from phase-3-pr69-opcua-client-subscribe-probe into v2
0433d3a35e
Phase 3 PR 69 -- OPC UA Client ISubscribable + IHostConnectivityProbe. Completes the OpcUaClientDriver capability surface — now matches the Galaxy + Modbus + S7 driver coverage. ISubscribable: SubscribeAsync creates a new upstream Subscription via the non-obsolete Subscription(ITelemetryContext, SubscriptionOptions) ctor + AddItem/CreateItemsAsync flow, wires each MonitoredItem's Notification event into OnDataChange. Tag strings round-trip through MonitoredItem.Handle so the notification handler can identify which tag changed without a second lookup. Publishing interval floored at 50ms (servers negotiate up anyway; sub-50ms wastes round-trip). SubscriptionOptions uses KeepAliveCount=10, LifetimeCount=1000, TimestampsToReturn=Both so SourceTimestamp passthrough for the cascading-quality rule works through subscription paths too. UnsubscribeAsync calls Subscription.DeleteAsync(silent:true) and tolerates unknown handles (returns cleanly) because the caller's race with server-side cleanup after a session drop shouldn't crash either side. Session shutdown explicitly deletes every remote subscription before closing — avoids BadSubscriptionIdInvalid noise in the upstream server's log on Close. IHostConnectivityProbe: HostName surfaced as the EndpointUrl (not host:port like the Modbus/S7 drivers) so the Admin /hosts dashboard can render the full opc.tcp:// URL as a clickable target back at the remote server. HostState tracked via session.KeepAlive event — OPC UA's built-in keep-alive is authoritative for session liveness (the SDK pings on KeepAliveInterval, sets KeepAliveStopped after N missed pings), strictly better than a driver-side polling probe: no extra wire round-trip, no duplicate semantic with the native protocol. Handler transitions Running on healthy keep-alives and Stopped on any Bad service-result. Initial Running raised at end of InitializeAsync once the session is up; Shutdown transitions back to Unknown + unwires the handler. Unit tests (OpcUaClientSubscribeAndProbeTests, 3 facts): SubscribeAsync_without_initialize_throws_InvalidOperationException, UnsubscribeAsync_with_unknown_handle_is_noop (session-drop-race safety), GetHostStatuses_returns_endpoint_url_row_pre_init (asserts EndpointUrl as the host identity -- the full opc.tcp://plc.example:4840 URL). Live-session subscribe/unsubscribe round-trip + keep-alive state transition coverage lands in a follow-up PR once we scaffold the in-process OPC UA server fixture. 13/13 OpcUaClient.Tests pass. dotnet build clean. All six capability interfaces (IDriver / ITagDiscovery / IReadable / IWritable / ISubscribable / IHostConnectivityProbe) implemented — OPC UA Client driver surface complete.
Phase 3 PR 69 -- OPC UA Client ISubscribable + IHostConnectivityProbe
Phase 3 PR 69 -- OPC UA Client ISubscribable + IHostConnectivityProbe
dohertj2
created branch phase-3-pr69-opcua-client-subscribe-probe in dohertj2/lmxopcua
2026-04-19 01:23:52 -04:00
dohertj2
pushed to phase-3-pr69-opcua-client-subscribe-probe at dohertj2/lmxopcua
2026-04-19 01:23:52 -04:00
0433d3a35e
Phase 3 PR 69 -- OPC UA Client ISubscribable + IHostConnectivityProbe. Completes the OpcUaClientDriver capability surface — now matches the Galaxy + Modbus + S7 driver coverage. ISubscribable: SubscribeAsync creates a new upstream Subscription via the non-obsolete Subscription(ITelemetryContext, SubscriptionOptions) ctor + AddItem/CreateItemsAsync flow, wires each MonitoredItem's Notification event into OnDataChange. Tag strings round-trip through MonitoredItem.Handle so the notification handler can identify which tag changed without a second lookup. Publishing interval floored at 50ms (servers negotiate up anyway; sub-50ms wastes round-trip). SubscriptionOptions uses KeepAliveCount=10, LifetimeCount=1000, TimestampsToReturn=Both so SourceTimestamp passthrough for the cascading-quality rule works through subscription paths too. UnsubscribeAsync calls Subscription.DeleteAsync(silent:true) and tolerates unknown handles (returns cleanly) because the caller's race with server-side cleanup after a session drop shouldn't crash either side. Session shutdown explicitly deletes every remote subscription before closing — avoids BadSubscriptionIdInvalid noise in the upstream server's log on Close. IHostConnectivityProbe: HostName surfaced as the EndpointUrl (not host:port like the Modbus/S7 drivers) so the Admin /hosts dashboard can render the full opc.tcp:// URL as a clickable target back at the remote server. HostState tracked via session.KeepAlive event — OPC UA's built-in keep-alive is authoritative for session liveness (the SDK pings on KeepAliveInterval, sets KeepAliveStopped after N missed pings), strictly better than a driver-side polling probe: no extra wire round-trip, no duplicate semantic with the native protocol. Handler transitions Running on healthy keep-alives and Stopped on any Bad service-result. Initial Running raised at end of InitializeAsync once the session is up; Shutdown transitions back to Unknown + unwires the handler. Unit tests (OpcUaClientSubscribeAndProbeTests, 3 facts): SubscribeAsync_without_initialize_throws_InvalidOperationException, UnsubscribeAsync_with_unknown_handle_is_noop (session-drop-race safety), GetHostStatuses_returns_endpoint_url_row_pre_init (asserts EndpointUrl as the host identity -- the full opc.tcp://plc.example:4840 URL). Live-session subscribe/unsubscribe round-trip + keep-alive state transition coverage lands in a follow-up PR once we scaffold the in-process OPC UA server fixture. 13/13 OpcUaClient.Tests pass. dotnet build clean. All six capability interfaces (IDriver / ITagDiscovery / IReadable / IWritable / ISubscribable / IHostConnectivityProbe) implemented — OPC UA Client driver surface complete.
141673fc80
Merge pull request 'Phase 3 PR 68 -- OPC UA Client ITagDiscovery (Full browse)' (#67) from phase-3-pr68-opcua-client-discovery into v2
db56a95819
Phase 3 PR 68 -- OPC UA Client ITagDiscovery via recursive browse (Full strategy). Adds ITagDiscovery to OpcUaClientDriver. DiscoverAsync opens a single Remote folder on the IAddressSpaceBuilder and recursively browses from the configured root (default: ObjectsFolder i=85; override via OpcUaClientDriverOptions.BrowseRoot for scoped discovery). Browse uses non-obsolete Session.BrowseAsync(RequestHeader, ViewDescription, uint maxReferences, BrowseDescriptionCollection, ct) with HierarchicalReferences forward, subtypes included, NodeClassMask Object+Variable, ResultMask pulling BrowseName + DisplayName + NodeClass + TypeDefinition. Objects become sub-folders via builder.Folder; Variables become builder.Variable entries with FullName set to the NodeId.ToString() serialization so IReadable/IWritable can round-trip without re-resolving. Three safety caps added to OpcUaClientDriverOptions to bound runaway discovery: (1) MaxBrowseDepth default 10 -- deep enough for realistic OPC UA information models, shallow enough that cyclic graphs can't spin the browse forever. (2) MaxDiscoveredNodes default 10_000 -- caps memory on pathological remote servers. Once the cap is hit, recursion short-circuits and the partially-discovered tree is still projected into the local address space (graceful degradation rather than all-or-nothing). (3) BrowseRoot as an opt-in scope restriction string per driver-specs.md \u00A78 -- defaults to ObjectsFolder but operators with 100k-node servers can point it at a single subtree. Visited-set tracks NodeIds already visited to prevent infinite cycles on graphs with non-strict hierarchy (OPC UA models can have back-references). Transient browse failures on a subtree are swallowed -- the sub-branch stops but the rest of discovery continues, matching the Modbus driver's 'transient poll errors don't kill the loop' pattern. The driver's health surface reflects the network-level cascade via the probe loop (PR 69). Deferred to a follow-up PR: DataType resolution via a batch Session.ReadAsync(Attributes.DataType) after the browse so DriverAttributeInfo.DriverDataType is accurate instead of the current conservative DriverDataType.Int32 default; AccessLevel-derived SecurityClass instead of the current ViewOnly default; array-type detection via Attributes.ValueRank + ArrayDimensions. These need an extra wire round-trip per batch of variables + a NodeId -> DriverDataType mapping table; out of scope for PR 68 to keep browse path landable. Unit tests (OpcUaClientDiscoveryTests, 3 facts): DiscoverAsync_without_initialize_throws_InvalidOperationException (pre-init hits RequireSession); DiscoverAsync_rejects_null_builder (ArgumentNullException); Discovery_caps_are_sensible_defaults (asserts 10000 / 10 / null defaults documented above). NullAddressSpaceBuilder stub implements the full IAddressSpaceBuilder shape including IVariableHandle.MarkAsAlarmCondition (throws NotSupportedException since this PR doesn't wire alarms). Live-browse coverage against a real remote server is deferred to the in-process-server-fixture PR. 10/10 OpcUaClient.Tests pass. dotnet build clean.
Phase 3 PR 68 -- OPC UA Client ITagDiscovery (Full browse)
Phase 3 PR 68 -- OPC UA Client ITagDiscovery (Full browse)
dohertj2
created branch phase-3-pr68-opcua-client-discovery in dohertj2/lmxopcua
2026-04-19 01:19:00 -04:00
dohertj2
pushed to phase-3-pr68-opcua-client-discovery at dohertj2/lmxopcua
2026-04-19 01:19:00 -04:00
db56a95819
Phase 3 PR 68 -- OPC UA Client ITagDiscovery via recursive browse (Full strategy). Adds ITagDiscovery to OpcUaClientDriver. DiscoverAsync opens a single Remote folder on the IAddressSpaceBuilder and recursively browses from the configured root (default: ObjectsFolder i=85; override via OpcUaClientDriverOptions.BrowseRoot for scoped discovery). Browse uses non-obsolete Session.BrowseAsync(RequestHeader, ViewDescription, uint maxReferences, BrowseDescriptionCollection, ct) with HierarchicalReferences forward, subtypes included, NodeClassMask Object+Variable, ResultMask pulling BrowseName + DisplayName + NodeClass + TypeDefinition. Objects become sub-folders via builder.Folder; Variables become builder.Variable entries with FullName set to the NodeId.ToString() serialization so IReadable/IWritable can round-trip without re-resolving. Three safety caps added to OpcUaClientDriverOptions to bound runaway discovery: (1) MaxBrowseDepth default 10 -- deep enough for realistic OPC UA information models, shallow enough that cyclic graphs can't spin the browse forever. (2) MaxDiscoveredNodes default 10_000 -- caps memory on pathological remote servers. Once the cap is hit, recursion short-circuits and the partially-discovered tree is still projected into the local address space (graceful degradation rather than all-or-nothing). (3) BrowseRoot as an opt-in scope restriction string per driver-specs.md \u00A78 -- defaults to ObjectsFolder but operators with 100k-node servers can point it at a single subtree. Visited-set tracks NodeIds already visited to prevent infinite cycles on graphs with non-strict hierarchy (OPC UA models can have back-references). Transient browse failures on a subtree are swallowed -- the sub-branch stops but the rest of discovery continues, matching the Modbus driver's 'transient poll errors don't kill the loop' pattern. The driver's health surface reflects the network-level cascade via the probe loop (PR 69). Deferred to a follow-up PR: DataType resolution via a batch Session.ReadAsync(Attributes.DataType) after the browse so DriverAttributeInfo.DriverDataType is accurate instead of the current conservative DriverDataType.Int32 default; AccessLevel-derived SecurityClass instead of the current ViewOnly default; array-type detection via Attributes.ValueRank + ArrayDimensions. These need an extra wire round-trip per batch of variables + a NodeId -> DriverDataType mapping table; out of scope for PR 68 to keep browse path landable. Unit tests (OpcUaClientDiscoveryTests, 3 facts): DiscoverAsync_without_initialize_throws_InvalidOperationException (pre-init hits RequireSession); DiscoverAsync_rejects_null_builder (ArgumentNullException); Discovery_caps_are_sensible_defaults (asserts 10000 / 10 / null defaults documented above). NullAddressSpaceBuilder stub implements the full IAddressSpaceBuilder shape including IVariableHandle.MarkAsAlarmCondition (throws NotSupportedException since this PR doesn't wire alarms). Live-browse coverage against a real remote server is deferred to the in-process-server-fixture PR. 10/10 OpcUaClient.Tests pass. dotnet build clean.
89bd726fa8
Merge pull request 'Phase 3 PR 67 -- OPC UA Client IReadable + IWritable' (#66) from phase-3-pr67-opcua-client-read-write into v2
238748bc98
Phase 3 PR 67 -- OPC UA Client IReadable + IWritable via Session.ReadAsync/WriteAsync. Adds IReadable + IWritable capabilities to OpcUaClientDriver, routing reads/writes through the session's non-obsolete ReadAsync(RequestHeader, maxAge, TimestampsToReturn, ReadValueIdCollection, ct) and WriteAsync(RequestHeader, WriteValueCollection, ct) overloads (the sync and BeginXxx/EndXxx patterns are all [Obsolete] in SDK 1.5.378). Serializes on the shared Gate from PR 66 so reads + writes + future subscribe + probe don't race on the single session. NodeId parsing: fullReferences use OPC UA's standard serialized NodeId form -- ns=2;s=Demo.Counter, i=2253, ns=4;g=... for GUID, ns=3;b=... for opaque. TryParseNodeId calls NodeId.Parse with the session's MessageContext which honours the server-negotiated namespace URI table. Malformed input surfaces as BadNodeIdInvalid (0x80330000) WITHOUT a wire round-trip -- saves a request for a fault the driver can detect locally. Cascading-quality implementation per driver-specs.md \u00A78: upstream StatusCode, SourceTimestamp, and ServerTimestamp pass through VERBATIM. Bad codes from the remote server stay as the same Bad code (not translated to generic BadInternalError) so downstream clients can distinguish 'upstream value unavailable' from 'local driver bug'. SourceTimestamp is preserved verbatim (null on MinValue guard) so staleness is visible; ServerTimestamp falls back to DateTime.UtcNow if the upstream omitted it, never overwriting a non-zero value. Wire-level exceptions in the Read batch -- transport / timeout / session-dropped -- fan out BadCommunicationError (0x80050000) across every tag in the batch, not BadInternalError, so operators distinguish network reachability from driver faults. Write-side same pattern: successful WriteAsync maps each upstream StatusCode.Code verbatim into the local WriteResult.StatusCode; transport-layer failure fans out BadCommunicationError across the whole batch. WriteValue carries AttributeId=Value + DataValue wrapping Variant(writeValue) -- the SDK handles the type-to-Variant mapping for common CLR types (bool, int, float, string, etc.) so the driver doesn't need a per-type switch. Name disambiguation: the SDK has its own Opc.Ua.WriteRequest type which collides with ZB.MOM.WW.OtOpcUa.Core.Abstractions.WriteRequest; method signature uses the fully-qualified Core.Abstractions.WriteRequest. Unit tests (OpcUaClientReadWriteTests, 2 facts): ReadAsync_without_initialize_throws_InvalidOperationException + WriteAsync_without_initialize_throws_InvalidOperationException -- pre-init calls hit RequireSession and fail uniformly. Wire-level round-trip coverage against a live remote server lands in a follow-up PR once we scaffold an in-process OPC UA server fixture (the existing Server project in the solution is a candidate host). 7/7 OpcUaClient.Tests pass (5 scaffold + 2 read/write). dotnet build clean. Scope: ITagDiscovery (browse) + ISubscribable + IHostConnectivityProbe remain deferred to PRs 68-69 which also need namespace-index remapping and reference-counted MonitoredItem forwarding per driver-specs.md \u00A78.
Phase 3 PR 67 -- OPC UA Client IReadable + IWritable
Phase 3 PR 67 -- OPC UA Client IReadable + IWritable
dohertj2
created branch phase-3-pr67-opcua-client-read-write in dohertj2/lmxopcua
2026-04-19 01:15:13 -04:00
dohertj2
pushed to phase-3-pr67-opcua-client-read-write at dohertj2/lmxopcua
2026-04-19 01:15:13 -04:00
238748bc98
Phase 3 PR 67 -- OPC UA Client IReadable + IWritable via Session.ReadAsync/WriteAsync. Adds IReadable + IWritable capabilities to OpcUaClientDriver, routing reads/writes through the session's non-obsolete ReadAsync(RequestHeader, maxAge, TimestampsToReturn, ReadValueIdCollection, ct) and WriteAsync(RequestHeader, WriteValueCollection, ct) overloads (the sync and BeginXxx/EndXxx patterns are all [Obsolete] in SDK 1.5.378). Serializes on the shared Gate from PR 66 so reads + writes + future subscribe + probe don't race on the single session. NodeId parsing: fullReferences use OPC UA's standard serialized NodeId form -- ns=2;s=Demo.Counter, i=2253, ns=4;g=... for GUID, ns=3;b=... for opaque. TryParseNodeId calls NodeId.Parse with the session's MessageContext which honours the server-negotiated namespace URI table. Malformed input surfaces as BadNodeIdInvalid (0x80330000) WITHOUT a wire round-trip -- saves a request for a fault the driver can detect locally. Cascading-quality implementation per driver-specs.md \u00A78: upstream StatusCode, SourceTimestamp, and ServerTimestamp pass through VERBATIM. Bad codes from the remote server stay as the same Bad code (not translated to generic BadInternalError) so downstream clients can distinguish 'upstream value unavailable' from 'local driver bug'. SourceTimestamp is preserved verbatim (null on MinValue guard) so staleness is visible; ServerTimestamp falls back to DateTime.UtcNow if the upstream omitted it, never overwriting a non-zero value. Wire-level exceptions in the Read batch -- transport / timeout / session-dropped -- fan out BadCommunicationError (0x80050000) across every tag in the batch, not BadInternalError, so operators distinguish network reachability from driver faults. Write-side same pattern: successful WriteAsync maps each upstream StatusCode.Code verbatim into the local WriteResult.StatusCode; transport-layer failure fans out BadCommunicationError across the whole batch. WriteValue carries AttributeId=Value + DataValue wrapping Variant(writeValue) -- the SDK handles the type-to-Variant mapping for common CLR types (bool, int, float, string, etc.) so the driver doesn't need a per-type switch. Name disambiguation: the SDK has its own Opc.Ua.WriteRequest type which collides with ZB.MOM.WW.OtOpcUa.Core.Abstractions.WriteRequest; method signature uses the fully-qualified Core.Abstractions.WriteRequest. Unit tests (OpcUaClientReadWriteTests, 2 facts): ReadAsync_without_initialize_throws_InvalidOperationException + WriteAsync_without_initialize_throws_InvalidOperationException -- pre-init calls hit RequireSession and fail uniformly. Wire-level round-trip coverage against a live remote server lands in a follow-up PR once we scaffold an in-process OPC UA server fixture (the existing Server project in the solution is a candidate host). 7/7 OpcUaClient.Tests pass (5 scaffold + 2 read/write). dotnet build clean. Scope: ITagDiscovery (browse) + ISubscribable + IHostConnectivityProbe remain deferred to PRs 68-69 which also need namespace-index remapping and reference-counted MonitoredItem forwarding per driver-specs.md \u00A78.
b21d550836
Merge pull request 'Phase 3 PR 66 -- OPC UA Client (gateway) driver scaffold' (#65) from phase-3-pr66-opcua-client-scaffold into v2
91eaf534c8
Phase 3 PR 66 -- OPC UA Client (gateway) driver project scaffold + IDriver session lifecycle. First driver that CONSUMES OPC UA rather than PUBLISHES it -- connects to a remote server and re-exposes its address space through the local OtOpcUa server per driver-specs.md \u00A78. Uses the same OPCFoundation.NetStandard.Opc.Ua.Client package the existing Client.Shared ships (bumped to 1.5.378.106 to match). Builds its own ApplicationConfiguration (cert stores under %LocalAppData%/OtOpcUa/pki so multiple driver instances in one OtOpcUa server process share a trust anchor) rather than reusing Client.Shared -- Client.Shared is oriented at the interactive CLI with different session-lifetime needs (this driver is always-on, needs keep-alive + session transfer on reconnect + multi-year uptime). Navigated the post-refactor 1.5.378 SDK surface: every Session.Create* static is now [Obsolete] in favour of DefaultSessionFactory; CoreClientUtils.SelectEndpoint got the sync overloads deprecated in favour of SelectEndpointAsync with a required ITelemetryContext parameter. Driver passes telemetry: null! to both SelectEndpointAsync + new DefaultSessionFactory(telemetry: null!) -- the SDK's internal default sink handles null gracefully and plumbing a telemetry context through the driver options surface is out of scope (the driver emits its own logs via the DriverHealth surface anyway). ApplicationInstance default ctor is also obsolete; wrapped in #pragma warning disable CS0618 rather than migrate to the ITelemetryContext overload for the same reason. OpcUaClientDriverOptions models driver-specs.md \u00A78 settings: EndpointUrl (default opc.tcp://localhost:4840 IANA-assigned port), SecurityPolicy/SecurityMode/AuthType enums, Username/Password, SessionTimeout=120s + KeepAliveInterval=5s + ReconnectPeriod=5s (defaults from spec), AutoAcceptCertificates=false (production default; dev turns on for self-signed servers), ApplicationUri + SessionName knobs for certificate SAN matching and remote-server session-list identification. OpcUaClientDriver : IDriver: InitializeAsync builds the ApplicationConfiguration, resolves + creates cert if missing via app.CheckApplicationInstanceCertificatesAsync, selects endpoint via CoreClientUtils.SelectEndpointAsync, builds UserIdentity (Anonymous or Username with UTF-8-encoded password bytes -- the legacy string-password ctor went away; Certificate auth deferred), creates session via DefaultSessionFactory.CreateAsync. Health transitions Unknown -> Initializing -> Healthy on success or -> Faulted on failure with best-effort Session.CloseAsync cleanup. ShutdownAsync (async now, not Task.CompletedTask) closes the session + disposes. Internal Session + Gate expose to the test project via InternalsVisibleTo so PRs 67-69 can stack read/write/discovery/subscribe on the same serialization. Scaffold tests (OpcUaClientDriverScaffoldTests, 5 facts): Default_options_target_standard_opcua_port_and_anonymous_auth (4840 + None mode + Anonymous + AutoAccept=false production default), Default_timeouts_match_driver_specs_section_8 (120s/5s/5s), Driver_reports_type_and_id_before_connect (DriverType=OpcUaClient, DriverInstanceId round-trip, pre-init Unknown health), Initialize_against_unreachable_endpoint_transitions_to_Faulted_and_throws, Reinitialize_against_unreachable_endpoint_re_throws. Uses opc.tcp://127.0.0.1:1 as the 'guaranteed-unreachable' target -- RFC 5737 reserved IPs get black-holed and time out only after the SDK's internal retry/backoff fully elapses (~60s), while port 1 on loopback refuses immediately with TCP RST which keeps the test suite snappy (5 tests / 8s). 5/5 pass. dotnet build clean. Scope boundary: ITagDiscovery / IReadable / IWritable / ISubscribable / IHostConnectivityProbe deliberately NOT in this PR -- they need browse + namespace remapping + reference-counted MonitoredItem forwarding + keep-alive probing and land in PRs 67-69.
Phase 3 PR 66 -- OPC UA Client (gateway) driver scaffold
Phase 3 PR 66 -- OPC UA Client (gateway) driver scaffold
dohertj2
pushed to phase-3-pr66-opcua-client-scaffold at dohertj2/lmxopcua
2026-04-19 01:09:37 -04:00
91eaf534c8
Phase 3 PR 66 -- OPC UA Client (gateway) driver project scaffold + IDriver session lifecycle. First driver that CONSUMES OPC UA rather than PUBLISHES it -- connects to a remote server and re-exposes its address space through the local OtOpcUa server per driver-specs.md \u00A78. Uses the same OPCFoundation.NetStandard.Opc.Ua.Client package the existing Client.Shared ships (bumped to 1.5.378.106 to match). Builds its own ApplicationConfiguration (cert stores under %LocalAppData%/OtOpcUa/pki so multiple driver instances in one OtOpcUa server process share a trust anchor) rather than reusing Client.Shared -- Client.Shared is oriented at the interactive CLI with different session-lifetime needs (this driver is always-on, needs keep-alive + session transfer on reconnect + multi-year uptime). Navigated the post-refactor 1.5.378 SDK surface: every Session.Create* static is now [Obsolete] in favour of DefaultSessionFactory; CoreClientUtils.SelectEndpoint got the sync overloads deprecated in favour of SelectEndpointAsync with a required ITelemetryContext parameter. Driver passes telemetry: null! to both SelectEndpointAsync + new DefaultSessionFactory(telemetry: null!) -- the SDK's internal default sink handles null gracefully and plumbing a telemetry context through the driver options surface is out of scope (the driver emits its own logs via the DriverHealth surface anyway). ApplicationInstance default ctor is also obsolete; wrapped in #pragma warning disable CS0618 rather than migrate to the ITelemetryContext overload for the same reason. OpcUaClientDriverOptions models driver-specs.md \u00A78 settings: EndpointUrl (default opc.tcp://localhost:4840 IANA-assigned port), SecurityPolicy/SecurityMode/AuthType enums, Username/Password, SessionTimeout=120s + KeepAliveInterval=5s + ReconnectPeriod=5s (defaults from spec), AutoAcceptCertificates=false (production default; dev turns on for self-signed servers), ApplicationUri + SessionName knobs for certificate SAN matching and remote-server session-list identification. OpcUaClientDriver : IDriver: InitializeAsync builds the ApplicationConfiguration, resolves + creates cert if missing via app.CheckApplicationInstanceCertificatesAsync, selects endpoint via CoreClientUtils.SelectEndpointAsync, builds UserIdentity (Anonymous or Username with UTF-8-encoded password bytes -- the legacy string-password ctor went away; Certificate auth deferred), creates session via DefaultSessionFactory.CreateAsync. Health transitions Unknown -> Initializing -> Healthy on success or -> Faulted on failure with best-effort Session.CloseAsync cleanup. ShutdownAsync (async now, not Task.CompletedTask) closes the session + disposes. Internal Session + Gate expose to the test project via InternalsVisibleTo so PRs 67-69 can stack read/write/discovery/subscribe on the same serialization. Scaffold tests (OpcUaClientDriverScaffoldTests, 5 facts): Default_options_target_standard_opcua_port_and_anonymous_auth (4840 + None mode + Anonymous + AutoAccept=false production default), Default_timeouts_match_driver_specs_section_8 (120s/5s/5s), Driver_reports_type_and_id_before_connect (DriverType=OpcUaClient, DriverInstanceId round-trip, pre-init Unknown health), Initialize_against_unreachable_endpoint_transitions_to_Faulted_and_throws, Reinitialize_against_unreachable_endpoint_re_throws. Uses opc.tcp://127.0.0.1:1 as the 'guaranteed-unreachable' target -- RFC 5737 reserved IPs get black-holed and time out only after the SDK's internal retry/backoff fully elapses (~60s), while port 1 on loopback refuses immediately with TCP RST which keeps the test suite snappy (5 tests / 8s). 5/5 pass. dotnet build clean. Scope boundary: ITagDiscovery / IReadable / IWritable / ISubscribable / IHostConnectivityProbe deliberately NOT in this PR -- they need browse + namespace remapping + reference-counted MonitoredItem forwarding + keep-alive probing and land in PRs 67-69.