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Mapping 200 internal REST endpoints to 200 MCP tools puts 200 KB of JSON schema in front of every request. The 2026-07-28 spec also made the usual escape hatch illegal: tools/list MUST NOT vary per-connection, so per-session dynamic registration is gone. Here are the three levers that still work, with measured wire sizes and verified code on @modelcontextprotocol/server 2.0.0.

Microsoft.Extensions.AI 10.9.0 adds RoutingChatClient, OrderedFailoverChatClient, and SemanticRoutingChatClient. Verified against the real package: what fails over, what does not, and why MEAI001 breaks your build.

.NET 11 Preview 7 adds an opt-in package that pauses interactive Server circuits when the browser tab is hidden, freeing memory and SignalR connections held by users who are not actually there.

blazor.server.js 404s on .NET 10 because the script stopped being an embedded resource. Add RequiresAspNetWebAssets to the host project, or make sure it has a .razor file.

MSB4057 means a target ran against the outer cross-targeting build of a multi-targeted MAUI project. Pass a TFM, or guard the target with a TargetFramework condition.

Test Explorer drives xUnit v3 through Microsoft.Testing.Platform server mode over a JSON-RPC socket, dotnet test does not. Set UseMicrosoftTestingPlatformRunner so both paths are the same code, or set DisableTestingPlatformServerCapability to fall back to VSTest.

Tightening a team's default permission mode to Manual is a one-line settings change interactively and a silent outage in CI, because headless runs turn every ask into a deny and still report success. Measured on Claude Code 2.1.224, including the trust gate that drops your allowlist but keeps your mode.

Labeled break and continue landed in the C# section of .NET 11 Preview 7. You can now put a label on a loop and jump straight to it, which retires the bool flag and goto workarounds for nested loops.

Every way dotnet tool install --global dotnet-ef fails on the .NET 10 SDK, with the exact message and exit code for each: already installed, version not found, downgrade blocked, shim conflict, dead NuGet feed, and the runtime mismatch that only breaks after the install succeeds.

CS9137 comes from the Microsoft.AspNetCore.OpenApi source generator. Add InterceptorsNamespaces to every project that calls AddOpenApi, not just the one holding the PackageReference.