Prepare the 2.1.0 release - #34

Summary

Prepares DevBrain 2.1.0:

• Directory.Build.props: <Version> 2.0.0 → 2.1.0. This is the single source for assembly versions and the MCP serverInfo version.
• CHANGELOG.md: [Unreleased] becomes [2.1.0] — 2026-10-20, with a summary paragraph and an empty [Unreleased] heading kept above it, matching what 2.0.0 did.
  • New Security section for the System.Security.Cryptography.Xml 10.0.12 → 10.0.13 bump (Bump System.Security.Cryptography.Xml from 10.0.12 to 10.0.13 #32), which also resolves .Pkcs to 10.0.13. It covers CVE-2026-96958, -96959 and -96960 (Xml) and CVE-2026-84008 and -70162 (Pkcs), all .NET denial-of-service vulnerabilities.
  • New Changed section for the project-prefixed key docs (Use project-prefixed keys in the README, usage guide, and project-init docs #29), the usage-guide write guidance (Replace outdated "never patch" guidance in the usage guide #28), and the root AGENTS.md ignore (Ignore a root AGENTS.md for per-deployment agent instructions #31).
  • New Validation section.
  • The provisioning-outputs entry now also lists FRONT_DOOR_ENDPOINT_HOST_NAME and FRONT_DOOR_DOMAIN_VALIDATION_TOKEN.

Why 2.1.0 rather than 2.0.1: main has opt-in features since v2.0.0 (custom domain, Front Door publishing and WAF, the origin check, serverless Cosmos), so this is a minor release. None of them changes behavior unless you set it, and the tool contracts are unchanged.

How deployments get the security fix

DevBrain.Server uses the Web SDK, which leaves System.Security.Cryptography.Xml and .Pkcs out of the build output. At runtime the server loads them from the ASP.NET Core runtime in its mcr.microsoft.com/dotnet/aspnet:10.0 base image. So the package bump fixes restore and the Core and test projects, but a running deployment is patched only when azd deploy rebuilds the image on runtime 10.0.13 (released 2026-10-13). The changelog says so.

Independent review

An independent review agent checked the diff against everything since v2.0.0. All four findings are fixed in this PR:

1. The Validation bullet said the deployment ran "on the 10.0.13 packages". The server loads these assemblies from the runtime, not the package → reworded. The deployed image's base was checked directly: it has ASPNET_VERSION=10.0.13.
2. The Security entry didn't say how deployments get the fix → added the base-image and redeploy note.
3. The FRONT_DOOR_ENDPOINT_HOST_NAME and FRONT_DOOR_DOMAIN_VALIDATION_TOKEN outputs were missing → added.
4. The empty [Unreleased] heading was dropped, unlike 2.0.0 → restored.

The reviewer confirmed the CVE-to-package mapping against the GitHub advisories, that restoring the pre-bump tree fails with NU1903/NU1902 "Warning As Error", the semver choice, and public-repo hygiene.

Validation

• dotnet build has 0 warnings and 0 errors, and dotnet test --solution devbrain.slnx passes 162 tests.
• dotnet list package --vulnerable --include-transitive reports none.
• --deprecated --include-transitive flags only Microsoft.Testing.Platform.MSBuild 2.4.0, a legacy dependency of the test projects. It's left for a follow-up.
• az bicep build --file infra/main.bicep succeeds.
• The built assembly reports InformationalVersion 2.1.0.
• Not in this release: newer patch versions are available (Microsoft.AspNetCore.DataProtection 10.0.13, Microsoft.Azure.Cosmos 3.63.2, ModelContextProtocol.AspNetCore 2.3.0, xunit.v3 4.0.2, and others). Dependabot can pick them up.

After merge

1. Tag v2.1.0 on main and publish the GitHub release from the changelog entry.
2. Redeploy (azd deploy from main) so serverInfo reports 2.1.0.

If this merges after 2026-10-20 (Hawaii time), update the changelog date first.

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