# Description
Fix incomplete-message buffering, channel cleanup, session resource
accounting, and enforcement of existing transport admission settings.
- Share a targeted `ChunkReassemblyBudget` across server listeners. The
reference default is 64 MiB, with a 32 MiB global occupancy threshold
for sessionless intermediate chunks. This is priority headroom for
activated sessions, not a guaranteed bootstrap partition. Single/final
chunks and unrelated response/client buffers remain outside this budget.
- Retain precise incoming/final payload quotas, valid Abort handling
without channel teardown, terminal late-final rejection, and
exactly-once buffer/reservation cleanup.
- Use one assembly timer per quota/clock scope, asynchronous cleanup, a
fixed deadline, a 30-second fallback for non-positive lifetimes, and
best-effort ERR `BadTimeout` before closure.
- Apply negotiated TCP/WebSocket/Pipe receive limits and size pipe
rentals to actual chunks.
- Add the optional `ISessionBindingProvider` and immutable
`SessionBindingContext` seam. Managed membership counts distinct
committed sessions, not responses, and handles reactivation, transfer,
closure, expiry, restoration and shutdown. Read-only snapshots require
token/channel/security validation and never replace service
authorization.
- Wire default and explicitly injected binding providers through raw
TCP, Kestrel and UACP WebSockets; preserve existing callback/manager
interfaces and direct construction.
- Enforce existing `ConnectionRateLimiter` and channel capacity settings
on Kestrel TCP and UACP WebSocket admission, with physical-transport
leases surviving reverse handoff and releasing on cancellation, close,
failed attachment and stop. HTTP/JSON requests are not treated as UASC
channels.
- Add regression coverage and documentation. Stabilize the CI
cancellation test by waiting for the resolver to enter before canceling.
This is the foundation only. New Balanced/FairShare/TrustedReservations
policies, tenant isolation and guaranteed bootstrap reserves belong in
the separate stacked follow-up, not this PR.
## Related Issues
Fixes#4521.
## Validation
| Scope | Result |
| --- | --- |
| Core transport, budget, binding-context and DI tests, net10.0 | 717
passed |
| Core transport, budget, binding-context and DI tests, net48 | 664
passed, 6 platform-specific skips |
| Session bindings, transfer/security/expiry/restore and hosted DI,
net10.0 | 69 passed |
| Same focused Server suite, net48 | 69 passed |
| ServerRedundancyHandlerTests, Release/net48 | 39 passed |
| ConsoleReferenceServer net10.0 | Build succeeded, zero warnings/errors
|
| Server and HTTPS binding netstandard2.1 | Both builds succeeded, zero
warnings/errors |
The new admission fixtures also passed five repeated runs after
correcting asynchronous connection-context disposal. Full-solution
validation, coverage comparison and CI for this update remain pending.
## 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.
- [ ] 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.
Marc Schier