[release-notes] ASP.NET Core in .NET 11 Preview 4 by danroth27 · Pull Request #10389 · dotnet/core

danroth27 · 2026-04-30T04:20:29Z

ASP.NET Core release notes for .NET 11 Preview 4.

Targets the milestone base branch #10388. Merging this PR
into release-notes/11.0-preview4 adds aspnetcore.md to the milestone.

Generated end-to-end by the release-notes skill. AI-authored content;
please review for accuracy, resolve any inline  placeholders,
and then mark this PR ready for review.

cc @danroth27

Live-tested every feature against the installed 11.0.100-preview.4.26224.122 build with reflection + sample apps: * Resolve TLS TODO: confirm ITlsHandshakeFeature.Exception property name. * OpenAPI file results: note .Produces<FileContentHttpResult>() annotation is required for the binary schema to appear (PR #64562 fires from metadata, not auto-inference). * Endpoint filter on binding failure: drop the inaccurate ValueTask<object?> claim (PR #64539 applies to any return type), and call out RouteHandlerOptions.ThrowOnBadRequest = false so the filter observes the 400 in Development mode. Filed dotnet/aspnetcore#66541 for a Virtualize prepend edge case (scroll-anchor regression when `_itemsBefore == 0`); release-notes claim left as-is — the bug only affects the case where the user has not yet scrolled the rendered window past index 0. Circuit-pause and `mcpserver` template remain documented; both PRs were merged late in the cycle and are expected to land in a Preview 4 servicing build. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* HTTP QUERY (#65714) is OpenAPI-only; reword and rename heading. * Virtualize: clarify #65951 covers height-changes-above-viewport (no API change). Add separate section for #66521's new AnchorMode parameter, including ItemComparer guidance for reference-type items. * Add a Runtime-async section for #66449 (backport of #66200). Removes the pre-filtering note that excluded it. Feedback from BrennanConroy and ilonatommy on #10389. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Missed in initial pass: dotnet/aspnetcore#65885 fixes the Blazor Web Worker template failing in published WASM apps because workers don't inherit the page's import map. Belongs alongside the existing WebWorker template entries. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Drop backport PR # (use original #66200 only) * Add a call to action for developers to test their apps and report regressions caused by runtime-async enablement. Feedback from BrennanConroy on #10389. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…eal CircuitHandler pattern Verified against 11.0.0-preview.4.26230.115: there is no public registry of active circuits. The supported discovery path is CircuitHandler.OnConnectionUpAsync. Updated the example to track circuits in a CircuitHandler and drain them via the captured references. Also clarify return-value semantics and that onPauseRequested is a JS-side option on Blazor.start(). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Documents how to opt in to the new Blazor Gateway (PR dotnet/aspnetcore#65982) in a standalone Blazor WebAssembly app: swapping the DevServer reference for Microsoft.AspNetCore.Components.Gateway, configuring YARP proxying to backend APIs, and exposing a runtime config endpoint to the client. Links to the GatewayDemo sample in danroth27/AspNetCore11Samples for an end-to-end setup. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Sample was restructured to live in BlazorWasmFeatures/ alongside sibling BackendApi/ and Gateway/ projects (replacing the GatewayDemo/ subtree). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The Microsoft.AspNetCore.Components.Gateway package isn't being produced on the build feeds (the Web SDK defaults IsPackable to false, silently no-op'ing Pack). A fix is up at dotnet/aspnetcore#66579 but won't make Preview 4, so remove the section and TOC entry; we'll bring it back when the package ships. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

danroth27 · 2026-05-05T04:19:13Z

Update: pulling the Blazor Gateway section back out of the Preview 4 release notes for now. The package isn't being produced on the build feeds — root cause turned out to be that Microsoft.NET.Sdk.Web defaults IsPackable to false, so the Gateway project's Pack target silently no-ops despite IsShippingPackage=true and a custom NuspecFile. One-line fix is up at dotnet/aspnetcore#66579, but it won't make Preview 4. We'll bring the content back once the package actually ships.

BrennanConroy · 2026-05-06T00:37:46Z

+
+Apps that use OpenTelemetry or hot reload aren't affected — the feature switches default on in those configurations.
+
+## Runtime-async enabled for shared framework libraries


cc @agocke in case you want to provide input on the messaging here.

@kilifu

- Remove duplicate 'Thank you @kilifu' line in HTTP QUERY section. - Add UseTlsClientHelloListener snippet to the TLS section. - Split 'OpenAPI and minimal API improvements' into two sections so the endpoint-filter bullet (not OpenAPI-related) stands on its own. - Remove the agent-generated 'Filtered features' HTML comment block. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

@halter73

- HTTP QUERY: replace 'first-class' with 'known' (per @halter73), and expand with OpenAPI 3.2 'query' Path Item field details and the 'OpenApiVersion'/'x-oai-additionalOperations' note (per @mikekistler). - HTTP QUERY follow-up sentence: lowercase 'get'/'post' to match OpenAPI spec casing (per @mikekistler). - TLS section: replace standalone snippet with combined snippet that also demonstrates 'ITlsHandshakeFeature.Exception' via connection middleware, and ensures 'UseTlsClientHelloListener' is called before 'UseHttps' (per @DeagleGross + @halter73 + @BrennanConroy). - Endpoint filters: drop the redundant short-circuit sentence, clarify 'ThrowOnBadRequest' default in non-Development environments, and call out the 10.0.8 backport (per @halter73). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Expand HTTP QUERY snippet with OpenApiVersion=3.2 setup and show generated output for both 3.2 (inline `query`) and 3.0/3.1 (`x-oai-additionalOperations`). - Fix article agreement: `a x-oai-additionalOperations` -> `an x-oai-additionalOperations`. - Correct the Virtualize AnchorMode descriptions to match the XML doc comments on the enum (Beginning = news feed/notification UX, End = chat/log auto-scroll UX, default is Beginning, `[Flags]` so they can be combined). Update the example to use `notifications` to match the corrected scenario. - Promote the Blazor Web Worker template rename + `InvokeVoidAsync` + cancellation/ timeout additions to its own section instead of a Bug fixes bullet. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The two JSON snippets above already show exactly where QUERY appears in the generated document for both 3.2 and 3.0/3.1, so the trailing prose is now redundant. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

mikekistler

Looks good. 👍

I spent a bunch of time looking at the File results type item. I think it is correct but I think we will want to expand on this when we put this into the docs.

danroth27 · 2026-04-30T04:20:29Z