# Description
Nodes created at runtime now get their NodeIds from a single
`DefaultNodeIdFactory` rather than from a `New` override per
NodeManager.
The factory derives a deterministic identifier from a canonical,
length-prefixed browse path, which is injective where the classic
`{parent}_{child}` concatenation was not — `A_B` + `C` and `A` + `B_C`
both produced `A_B_C` — and it also records the parent's identifier type
and qualifies cross-namespace segments by URI, so identifiers no longer
shift with namespace-table ordering.
A NodeManager selects its style declaratively instead of writing
assignment code:
```csharp
NodeIdFactory = NodeIdFactory.WithMode(NodeIdAssignmentMode.Counter);
```
`NodeIdAssignmentMode` offers `String` (the canonical path verbatim, the
default), `Numeric` / `Guid` / `Opaque` (that path through SHA-256),
`Counter` (sequential, for nodes whose browse paths repeat — per-session
diagnostics, inference jobs, rediscovered assets) and `None`. The
counter
starts above `0x40000000`, out of reach of any authored model, so a
long-running server cannot walk a runtime instance onto a type node.
`New` overrides are gone from every NodeManager the stack ships except
two whose identifiers are a domain scheme rather than an assignment
policy: `FileSystemNodeManager`, whose NodeIds encode the file path they
resolve back to, and `RoboticsNodeManager`, whose build coordinator
reserves identifiers across managers with ownership tracking.
**Namespace rule.** Every identifier is minted into the NodeManager's
own
namespace. Neither the parent's namespace nor the browse name's is
consulted: a parent can belong to a companion-specification model whose
NodeIds are fixed by its NodeSet (`DeviceSet` in the DI namespace), and
a
browse name only names the type that declared the child. NodeManagers
whose instance namespace is not their first one rebase with
`WithDefaultNamespaceIndex`.
**Types vs instances.** An authored NodeId on a node that stands on its
own is kept. A node hanging off a parent is re-minted, because it
reached
the factory through `AssignNodeIds` walking a subtree copied from a type
declaration. Keeping those would alias every instance onto the type's
own
nodes, and the predefined-node index takes the last writer, so the type
would quietly become an instance rather than the clash being reported.
New `ISystemContext.CreateInstance(...)` builds an instance of a
generated
type and rebases its subtree through `AssignInstanceNodeId` — the path
the
generated `CreateInstanceOf<Type>` helpers already took. The AI
NodeManager was the one place calling `NodeState.Create` directly, so
its
roots kept the NodeId their state object is born with (the type's own);
it now uses the shared path.
## Breaking changes
- `IAsyncNodeManager` extends `INodeIdFactory` and gains `AddNode` and
`AddRootNotifier`. This lets the fluent surface mint and register
through the interface instead of type-testing for
`AsyncCustomNodeManager` and silently falling back to a concatenated
identifier when the test failed — that fallback was itself a source of
divergent NodeIds.
- `AsyncNodeManagerAdapter` delegates `New` to the wrapped NodeManager,
so
**`CustomNodeManager2` behaves exactly as before**: it mints nothing and
a node keeps whatever NodeId it already has. Servers built on it are
unaffected.
## Notes for reviewers
- `docs/NodeIdAssignment.md` is new and describes the whole mechanism:
the
factory contract, identifier formats, type declarations vs instances,
the generated helpers and their parameters, per-NodeManager behaviour,
and an inventory of every member involved.
- The three commits are independently revertible.
- Two pieces that look redundant are deliberately kept, with the
reasoning
recorded in the doc: `assignInstanceNodeIds` (it *suppresses* minting,
where the rebase rule *forces* it) and the generator's
`NodeId.Equals(TypeNodeIdConstant)` guard (it distinguishes a
caller-assigned NodeId from a declaration's).
- Fluent builder tests previously passed only because of the removed
fallback; they now run against a real `DefaultNodeIdFactory` through a
shared `FluentTestNodeManager` helper.
## Related Issues
_No tracking issue yet._
## Checklist
- [ ] 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.
> Test runs were on **net10.0 only** — .NET Framework was not exercised
> locally. Suites run green on an idle machine: Server 4950/4955, GDS
> 1116/1170, WotCon 1225/1225, Vision 484/485, DI 424/424, AI 174/174,
> ISA95 136/136, Positioning 69/69, RobotIntent 22/22. One unrelated
> pre-existing failure remains in `Opc.Ua.Types.Tests`
> (`EveryEmbeddedExampleMatchesItsRecordedHash`) — a WoT fixture checked
> out with CRLF, fixed by
> `git add --renormalize tests/Opc.Ua.Types.Tests/Wot/Assets`.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
OPC Foundation UA .NET Standard Reference Server
Additional samples
- OPC 10000-21 onboarding registrar/client — loads the generated Onboarding companion model, binds the standard registrar administration methods to an injected ticket store, and drives a secure register/unregister round trip with a PowerShell script.
Introduction
This document is referring to the CTT version 1.04.9.398.
This OPC Server is designed to be the default OPC UA Server when opening the OPC UA Compliance Test Tool and it uses an address-space that matches the design of the UACTT and the requirements for OPC UA compliance testing.
It uses the OPC Foundation UA .NET Standard Library. Therefore it supports both the opc.tcp and https transports. There is a .NET framework based server with UI and a .NET Core console version of the server which runs on any OS supporting .NET Standard 2.1 or .NET 8.0 and later.
How to build and run the Windows OPC UA Reference Server with UACTT
- Open the solution UA.slnx with Visual Studio 2026.
- Choose the project
Reference Serverin the Solution Explorer and set it with a right click asStartup Project. - Hit
F5to build and execute the sample.
How to build and run the console OPC UA Reference Server on Windows, Linux and iOS
This section describes how to run the ConsoleReferenceServer.
Please follow instructions in this article to setup the dotnet command line environment for your platform.
Start the server
- Open a command prompt.
- Navigate to the folder samples/Reference/ConsoleReferenceServer.
- To run the server sample type
dotnet run --project ConsoleReferenceServer.csproj. The server is now running and waiting for the connection of the UACTT.
UACTT test certificates
The reference server always rejects new client certificates and requires that the UACTT certificates are in appropriate folders.
- The console server certificates are stored in %LocalApplicationData%/OPC Foundation/pki.
- The Windows .NET framework server stores the certificates in %CommonApplicationData%\OPC Foundation\pki.
- %CommonApplicationData% maps to the path set by the environment variable ProgramData on Windows.
- %LocalApplicationData% maps to a hidden location in the user home folder and depends on the target platform. See Certificates for more information.
Certificate stores
Under pki, the following stores contain certificates under certs, CRLs under crl or private keys under private.
- own contains the reference server public certificate and private key.
- rejected contains the rejected client certificates. To trust a client certificate, copy the rejected certificate to the trusted/certs folder.
- trusted contains trusted client and CAs certificates and CRLs.
- issuer contains CAs certificates and CRLs needed for validation.
- trustedUser contains trusted user and user CA certificates and CRLs.
- issuerUser contains user CA certificates and CRLs needed for validation of the certificate chains.
Placing the UACTT certificates
CTT creates a PKI folder in a new project. There is a subfolder copyToServer which contains the application and user identity certificates. Copy the ApplicationInstance_PKI certificates for testing with the UACTT to the following stores:
- trusted/certs: trusted certificates
- trusted/crl: revocation lists of trusted certificates
- issuer/certs: issuer certificates
- issuer/crl: revocation lists of issuer certificates
Copy the X509UserIdentity_PKI certificates for testing with the UACTT to the following stores:
- trustedUser/certs: trusted user certificates
- trustedUser/crl: revocation lists of trusted user certificates
- issuerUser/certs: user issuer certificates
- issuerUser/crl: revocation lists of user issuer certificates
UACTT Testing
Download and install the OPC UA Compliance Test Tool.
Note: Access to the UACTT is granted to OPC Foundation Corporate Members.
UACTT sample configuration
A sample configuration for the UACTT Version 1.04.9.398 can be found in UAReferenceServer.ctt.xml. Originally the reference server was certified only against the Standard UA Server profile, the Method Server Facet and the DataAccess Server Facet, in addition to all security related profiles. During release testing all Conformance Units should be enabled / checked.
Enabling Alarms & Conditions
The address space for Alarms contains a Start method which needs to be called to produce alarms for CTT testing. The method is called from a connected client.
The ConsoleReferenceServer has also a command line option -ctt which starts the Alarms when the server is started. The following Alarm instances are available for monitoring:
AlarmConditionTypeDiscrepancyAlarmTypeLimitAlarmTypeExclusiveLimitAlarmTypeExclusiveDeviationAlarmTypeExclusiveRateOfChangeAlarmTypeNonExclusiveLimitAlarmTypeNonExclusiveDeviationAlarmTypeNonExclusiveRateOfChangeAlarmTypeDiscreteAlarmTypeSystemOffNormalAlarmTypeExclusiveLevelAlarmTypeNonExclusiveLevelAlarmTypeOffNormalAlarmType
Known missing Tests and Issues
Depending on the setup in the provided project configuration, unsupported profiles should be skipped. At the time of writing (1.4.368) the following tests, profiles or facets are not yet covered or not configured due to issues:
- no support for events, historian and only a few basic Alarms & Conditions.
- Decimal type causes crash of CTT (needs investigation)
- no Image / Enumeration scalar test cases
- Arrays may not include Variant (needs investigation)
- no ArrayItemType implemented
- multiple hierarchical references test node missing
- deprecated security profiles support for SHA1/1k RSA keys implemented not according to certification. SHA1/1k keys can only be turned on/off for all profiles, not just for the deprecated profiles.
- Monitored Items with array are failing a few test cases.
It is recommended to run the server as retail build with disabled logging, to avoid side effects due to timing artifacts when log entries are written to a disk drive.
Running the CTT against a Docker container
Please refer to the Docker container of the Reference Server documentation page. Once setup to map the certificate store and the configuration to a local folder, follow the instructions above to copy the certificates to the PKI and get started.
Finding the Address Space Configuration Code
- Project: Reference Server
- File: ReferenceNodeManager.cs
- Method: CreateAddressSpace
Finding the UA Services
- Project: Opc.Ua.Server
- File: StandardServer.cs