Ship Sooner on .NET 10 LTS: The 30‑Day Playbook

.NET 10 LTS is out as of November 11, 2025, with support through November 2028. For most web and API teams, the calculus is simple: the security posture and runtime polish in .NET 10 LTS outweigh the cost of staying put. The question isn’t “if,” it’s “how fast can we move without breaking things.” This guide hits what’s new, what’s risky, and a pragmatic .NET 10 LTS upgrade plan you can run in 30 days.

What’s new in ASP.NET Core 10 that actually moves the needle

The .NET 10 LTS web stack leans into security, diagnostics, and developer productivity. Here’s what changes your day-to-day.

Passkeys in Identity. ASP.NET Core Identity now ships with passkey support based on WebAuthn/FIDO2. If you’ve been waiting for a paved road to passwordless sign‑in that works across browsers and devices, this is it. The Blazor Web App template includes passkey setup and management out of the box.

OpenAPI 3.1. ASP.NET Core’s OpenAPI generator now targets the 3.1 spec (JSON Schema 2020‑12). You’ll see better schema fidelity for union‑ish shapes, nullable handling, and validation metadata. That means cleaner client generation and fewer hand‑written patches in SDKs.

Server‑Sent Events made easy. A typed helper for Server‑Sent Events (SSE) lets you stream updates over a single HTTP connection without leaning on SignalR or spinning up full WebSockets. For dashboards, moderate traffic feeds, and AI streaming responses, SSE is the low‑friction path.

Automatic memory‑pool eviction. Long‑running web apps can “hang on” to memory. ASP.NET Core now evicts unused blocks from its memory pools automatically, lowering steady‑state footprint under real traffic.

New built‑in metrics. Identity, auth, Blazor, and memory pools now emit richer counters and histograms. Pair that with your existing OpenTelemetry setup and you get faster incident triage without extra middleware.

These are incremental, not flashy. But they remove toil you’ve been normalizing for years—and that’s the kind of value LTS releases should deliver.

Blazor quality‑of‑life upgrades

Blazor gets sturdier state persistence, better tracing for Server circuits, and crisper static asset handling (fingerprinting and compression improvements). You’ll notice fewer navigation oddities and easier performance profiling on WebAssembly when you need a memory dump or CPU profile from real users.

Diagnostics you’ll actually use

Between improved problem‑details integration (customizable error responses that align with your validators) and expanded metrics, you can replace a few homegrown filters with supported primitives. That means less custom code in the exception pipeline and more consistent behavior across services.

C# 14: small syntax wins that pay back fast

The language update that ships with .NET 10 LTS is C# 14. The theme: fewer footguns, more expressiveness.

Extension members let you group multiple extensions (including properties and static members) in one place. It’s a tidy way to add behavior without polluting your types or scattering one‑off helper classes.

Field‑backed properties reduce boilerplate for simple guard clauses in getters/setters. It’s a tiny change that cleans up models and DTOs across a codebase.

Implicit Span conversions nudge the compiler toward Span/ReadOnlySpan overloads where appropriate. You’ll win perf on hot paths with less ceremony, especially in parsing and text processing.

Bottom line: C# 14 nudges teams toward clearer, faster code without forcing new paradigms.

EF Core 10: vector search and JSON types are the headline

Entity Framework Core 10 lines up with database features that matter in 2025.

Vector search for Azure SQL and SQL Server 2025. EF Core 10 speaks the vector type and its distance functions, so you can build semantic search into line‑of‑business apps without duct‑taping custom SQL everywhere. If you’re rolling out retrieval‑augmented features, this is the paved path.

First‑class JSON columns in SQL Server 2025/Azure SQL. Prior versions used NVARCHAR for JSON. Now EF maps to the native JSON type where available and supports LINQ against JSON values with proper RETURNING semantics. Read: fewer casts, better indexing options, and fewer surprises.

Migration behavior fixes. EF 10 dials back a change from EF 9 and avoids spanning all migrations in a single transaction—reducing edge‑case failures during long schema evolutions. EF 10 requires .NET 10; there’s no backport to older runtimes or .NET Framework.

.NET 10 LTS lifecycle facts leaders care about

Dates matter. .NET 10 is an LTS release with support through November 2028. .NET’s monthly patch cadence remains “second Tuesday” (Patch Tuesday), which is where you’ll get security updates. Meanwhile, Microsoft extended Standard Term Support (STS) releases like .NET 9 to 24 months—so .NET 9 and .NET 8 both end support on November 10, 2026. If you’re on .NET 9, you’ve got a short runway; if you’re on .NET 8, you have time, but adopting .NET 10 LTS now locks in three years of runway.

A practical note for containerized shops: the default .NET container images track Ubuntu by default in .NET 10. Validate base image changes in your SBOM and vulnerability scans before pushing to prod.

Security context: why “later” is a risk

This fall’s critical Kestrel HTTP request smuggling bug was a reminder that platforms move fast and attackers move faster. Patching was straightforward for supported branches, but teams on older stacks felt the pain. Running an LTS with current patches is the boring, defensible choice—exactly what your auditors and incident postmortems want.

People also ask: should we jump from .NET 8 LTS?

If your estate is on .NET 8 LTS and stable, you could wait until 2026. But there’s little upside. ASP.NET Core 10’s passkeys, diagnostics, and memory improvements plus EF 10’s database support will compound across the next year. Treat the move to .NET 10 LTS as an opportunity to pay down CI debt and standardize on current base images and SDKs.

People also ask: what breaks when moving to .NET 10 LTS?

There aren’t many sharp edges, but don’t skip this checklist:

• ASP.NET Core: cookie login redirects are disabled for known API endpoints (APIs return 401/403 rather than redirecting to login); legacy WebHost/IWebHost is obsolete; OpenAPI analyzers and some older WithOpenApi extension points are deprecated.
• Language/compiler: C# 14 tweaks overload resolution toward Span/ReadOnlySpan in some cases and treats certain lambda parameter modifiers (like scoped) more strictly.
• Containers: default .NET images use Ubuntu—re‑verify your distro‑specific tooling and CA bundles.
• Networking and crypto: certificate and revocation defaults continue to tighten—review any custom handlers that assumed permissive defaults.

Run your test suite under the .NET 10 SDK before flipping target frameworks to catch behavioral drift early.

.NET 10 LTS upgrade playbook: 30 days to production

You can get a typical mid‑sized service platform (10–50 services) upgraded in four weeks with the right sequencing.

Week 0: inventory and guardrails

Make a single source of truth:

• List every app/service, target framework, container base, CI workflow, and owning team.
• Establish a pre‑prod upgrade ring with real traffic (shadow or limited audience) and rollback controls.
• Freeze new framework‑level features for two weeks to avoid moving targets.

If you want a deeper sprint template, use our practical walkthrough in .NET 10 LTS: What’s New and the 30‑Day Upgrade Plan.

Week 1: SDKs, toolchains, and CI

• Install the .NET 10 SDK on all build agents and developer machines. Pin with global.json in the repo.
• Upgrade IDEs—Visual Studio 2026 for Windows or current C# extensions on VS Code.
• Update container bases to mcr.microsoft.com/dotnet/aspnet:10.0 and mcr.microsoft.com/dotnet/sdk:10.0. Run your SBOM and vulnerability scans.
• Harden CI secrets and permissions. If you’re still using risky pull request triggers, our GitHub Actions pull_request_target Playbook explains safer patterns.

Week 2: target framework, compile, and smoke

• Flip projects to TargetFramework = net10.0. For multi‑TFMs, keep prior TFMs temporarily to publish dual artifacts if you need rollback.
• Remove obsolete WebHost usage (IWebHost, WebHostBuilder). Move to the Generic Host if you haven’t already.
• Adopt OpenAPI 3.1 generation. Validate clients regenerate cleanly and update schema compliance tests.
• Turn on Identity passkeys in one pilot app. Measure sign‑in success and support tickets before broad rollout.

Week 3: EF Core 10 and data surface

• Bump to EF Core 10. Run migrations in a staging database. Validate long‑running migration behavior and transaction boundaries for your environment.
• If you’re on Azure SQL or SQL Server 2025, test vector search and native JSON types behind feature flags. Add indexes early; measure query plans under real load.
• Review data access code that relied on text JSON columns—map to the new type and re‑run serialization tests.

Week 4: load tests, observability, and cutover

• Exercise the new ASP.NET Core metrics in your telemetry stack. Build SLO dashboards for auth, request durations, and memory.
• Run a realistic load test using production traffic patterns. Compare p95 latency and memory footprint to your baseline.
• Gradually raise traffic to the upgraded ring. If error budgets hold steady for 48 hours, promote to general availability.

Want a frank view of what teams underestimate? Read The .NET 10 LTS Upgrade Reality Check.

Let’s get practical: a pre‑flight checklist you can copy

• Project files: <TargetFramework>net10.0</TargetFramework>, remove legacy WebHost references, update analyzers and SDK‑style packages.
• NuGet: align Microsoft.* package versions to 10.x; trim transitive packages that are now in‑box.
• Auth: enable passkeys (pilot first), verify cookie redirect behavior for API endpoints, confirm OIDC handler settings.
• OpenAPI: regenerate clients against 3.1; fix nullable and oneOf/anyOf mismatches.
• EF Core: test migrations and scaffolding; evaluate vector/JSON types if on Azure SQL/SQL Server 2025.
• Containers: move base images to 10.0; verify distro assumptions and CA bundles; rebuild with repeatable Dockerfile stages.
• Observability: enable new metrics; ensure logs/metrics/traces share correlation IDs; pin dashboards.
• CI/CD: matrix builds across Linux/Windows; enforce signed builds; revisit PR permissions with our pull_request_target changes playbook.

ROI: what your team gets for doing this now

For product leaders, the win is compounding: lower auth friction with passkeys, less memory waste under load, clearer diagnostics when things go sideways, and a supported runtime through November 2028. For engineers, the win is velocity: C# 14’s polish, fewer custom filters, better OpenAPI output, and cleaner EF Core primitives for modern data.

People also ask: is C# 14 mandatory with .NET 10 LTS?

No. Your code compiles fine without touching new features. You can even pin a different language version in your project file. But most teams should let the default ride and adopt features opportunistically—especially field‑backed properties and extension members in shared libraries.

What to do next

• Pick one service and run the Week 1–2 steps today. Measure, don’t guess.
• Schedule a 90‑minute architecture review to identify breaking changes that actually apply to you.
• Add an error budget gate to your cutover plan so business stakeholders can green‑light confidently.
• Bring in help where it pays back. Our modernization playbooks and .NET upgrade services are designed for fast, low‑risk cutovers. See our portfolio for examples.

If you want ongoing guidance on platform shifts like this, bookmark the Bybowu blog. The best upgrades feel boring—and that’s exactly how .NET 10 LTS should feel by the time you ship.