The .NET 10 LTS Upgrade Playbook for 2026

.NET 10 LTS is here as of November 11, 2025, and it’s the release most teams will standardize on for the next three years. If you own a web or API estate, this isn’t just another patch day—it’s the moment to align runtime, language, and tooling so your 2026 roadmap isn’t built on expiring support. This playbook lays out what’s new, the business case, and a pragmatic 30/60/90‑day plan to move to .NET 10 LTS without stalling feature work.

What actually shipped—and why it matters

.NET 10 is a Long‑Term Support release with support through November 2028. You get the usual annual runtime performance bumps plus real quality‑of‑life in the language and web stack:

C# 14. Field‑backed properties, extension members (including extension properties), null‑conditional assignment, more flexible Span conversions, and modifiers on simple lambda parameters cut boilerplate and make hot paths safer to optimize. These are small, sharp tools you’ll use daily rather than flashy features you forget in a week.

ASP.NET Core 10. Useful defaults and operations work landed: identity and auth metrics out of the box, smarter local binding (\*.localhost resolves to loopback by default), and automatic memory‑pool eviction in Kestrel/IIS/HTTP.sys to lower idle RAM. Add improved diagnostics and OpenAPI ergonomics, and the web stack feels more observable and more forgiving under load.

EF Core 10. If you’re on Azure SQL or SQL Server 2025, EF10’s support for the new vector type and distance functions lets you keep semantic search and RAG‑adjacent workloads inside the database instead of gluing on a sidecar. JSON type support on SQL Server 2025 reduces the impedance mismatch when you model semi‑structured data.

Tooling. Visual Studio 2026 shipped alongside .NET 10 and is the supported IDE for targeting .NET 10. If you’re on VS 2022, plan an upgrade for your IDE images and developer workstations. CI runners and container images need a corresponding SDK/runtime bump too.

Why .NET 10 LTS now: support, safety, and signal

Here’s the thing: both .NET 8 LTS and .NET 9 STS end support on November 10, 2026. With .NET’s annual cadence and STS now at 24 months, the safe planning window is shorter than it looks. If you start your migration in Q1, you’ll have time to soak in production before those dates loom. Waiting until late 2026 compresses testing and multiplies risk.

Security also argues for “sooner.” The Kestrel HTTP stack saw high‑severity fixes in 2025; moving to a fully supported runtime means you’ll keep getting monthly patches without juggling backports across multiple app pools and base images. Operationally, that’s fewer unique snowflakes to harden and monitor.

Our 30/60/90‑day .NET 10 LTS migration plan

Use this as a starting line; trim or add steps to fit your org. The goal is parallel progress: upgrade the platform while unblocking developers and keeping features shipping.

Days 0–30: Inventory, standards, and a pilot

Make upgrades boring by making them uniform.

• Baseline the platform. Lock on a .NET 10 SDK and runtime version, Visual Studio 2026 channel, and base container images. Pin versions across dev, CI, and prod.
• Inventory apps and dependencies. For each app: target framework, hosting model, ASP.NET middleware, EF provider version, auth mechanism, third‑party packages, and container base. Flag anything still on net6.0/net7.0 and packages that lag a major version.
• Pick one pilot service. Choose a low‑blast‑radius API with good tests. Create an upgrade branch; retarget to net10.0; bump EF/ASP.NET packages; address build breaks. Validate local debugging in VS 2026 and a containerized build in CI.
• Add guardrails. Update CI matrices to include net10.0, enable analyzers, and turn on nullable and warnings‑as‑errors where realistic. Bake SCA to catch vulnerable transitive packages.
• Observability first. Standardize metrics and logs. In ASP.NET Core 10, wire up the new auth/identity metrics to your dashboard so you can compare before/after behavior.

Days 31–60: Tackle the middle 60%

• Factory‑upgrade services. Run the pilot changes as a template across similar APIs. Script the retarget, package updates, and common code fixes (for example, JSON changes or obsolete APIs).
• Database edge cases. If you use EF Core, validate provider readiness. For SQL Server 2025/Azure SQL, test vector/JSON features behind feature flags. Keep the default paths unchanged until benchmarks prove net wins.
• Auth and identity. If you use ASP.NET Core Identity, test passkeys and MFA flows end‑to‑end. Map the new metrics to your SLOs.
• Performance baselines. Measure cold starts, p95 latency, CPU, and working‑set changes under representative load. Kestrel’s automatic memory‑pool eviction typically trims idle RAM; prove it with your traffic.

Days 61–90: Production rollout and cleanup

• Stage gradually. Ship canaries, then 10%, 25%, and 50% traffic with error‑budget gates. Roll back on regression, fix, and retry; do not pile on “just one more fix” in prod.
• Unify images. Consolidate on a single base image per OS/arch. Remove legacy .NET runtimes from hosts to reduce attack surface and patching load.
• Debt burndown. Turn temporary compatibility shims into backlog items with owners and dates. Close the loop with post‑migration docs: what broke, how you fixed it, and what to avoid next time.

A simple risk scorecard for upgrade readiness

Use a red/yellow/green snapshot to decide ordering:

• Framework risk. net6.0 or older (red), net8.0/9.0 (yellow), net10.0 (green).
• Data access. Legacy EF6 or old provider (red); EF Core < 9 (yellow); EF Core 10 on supported providers (green).
• Auth stack. Custom cookies/JWT without modern middleware (red); ASP.NET Core Identity pre‑10 (yellow); Identity on 10 with passkey/MFA tested (green).
• Observability. No SLOs (red); logs only (yellow); metrics/tracing with baselines (green).
• Release discipline. Manual deploys (red); basic CI (yellow); CI/CD with staged rollouts and automated rollback (green).

Performance and reliability wins you can bank

Between JIT improvements, NativeAOT refinements, and library work, .NET 10 typically gives you lower CPU per request and smaller allocations on hot paths. On the web tier, the automatic memory‑pool eviction reduces idle working set, which matters for autoscaled fleets and small nodes. If you’re running Arm64 in the cloud, runtime vectorization and GC improvements close more of the gap with x64. These are boring gains, and that’s the point: they stack up across every app.

What breaks—and the fixes that stick

Most upgrades are straightforward, but a few areas deserve attention:

• JSON Patch and System.Text.Json. If your APIs use JSON Patch, validate behavior on the new implementation. It’s faster and leaner, but it’s not a drop‑in for dynamic types. Audit payloads and models, and pin behavior via tests.
• Kestrel and local development. Binding \*.localhost now maps to loopback by default. That’s safer, but it may surface surprises in dev tooling that assumed 0.0.0.0. Update your launchSettings.json and env vars accordingly.
• EF Core 10 runtime requirement. EF10 requires .NET 10. If you planned a gradual runtime upgrade, move EF last—or move the runtime first across the solution, then bump EF. For SQL Server 2025 features (vector/JSON), ensure the server really supports them before flipping switches in code.
• Tooling. Targeting .NET 10 from Visual Studio 2022 isn’t supported. Standardize on Visual Studio 2026 and update containerized build agents to the .NET 10 SDK.

People also ask

Can we skip .NET 9 and go straight to .NET 10 LTS?

Yes. If you’re on 6 or 8 LTS, jumping to 10 LTS is the cleanest path. You’ll pick up C# 14 and ASP.NET Core/EF Core 10 in one move and land on a support window through 2028.

Is .NET 10 LTS stable enough for enterprise?

Yes. It’s the supported baseline for three years, ships with Visual Studio 2026, and receives monthly patches. Treat it like every prior LTS: pilot, measure, then roll out with staged traffic.

How long does a typical migration take?

For a mid‑sized product with 10–20 services, a disciplined team usually finishes in 6–12 weeks: two weeks of pilot, four to eight weeks of parallelized upgrades, and one to two weeks of production soak.

What about security?

Staying on supported runtimes means you keep getting fixes for web‑server and pipeline issues without bespoke mitigations. If you had to chase a high‑severity HTTP stack fix in 2025, you already know the cost of lag.

C# 14: small features that punch above their weight

Field‑backed properties give you a safe path from trivial auto‑props to explicit logic without inventing a backing field. Extension members let you add static and instance members (including properties) to types you don’t own, which is perfect for internal DSLs around domain types. Null‑conditional assignment reduces defensive ceremony in UI and orchestration code. Together with better Span<> conversions and lambda parameter modifiers, these changes incrementally cut allocations and friction.

EF Core 10: pragmatic data options

Even if you don’t plan to touch vectors or the new JSON type on day one, EF10’s provider updates and LINQ/translation improvements will matter. The power move is to isolate “AI‑ish” features behind an interface so you can light up vector search when your database supports it. Meanwhile, keep OLTP paths boring and measured.

Tooling and pipelines: don’t forget the boring work

Upgrade guides often skip the parts that bite at 4 p.m. Friday. Add these to your checklist:

• IDE and images. Roll out Visual Studio 2026 and the .NET 10 SDK. Refresh devcontainer/base images. Verify remote caching and deterministic builds.
• CI/CD. Update build matrices to include net10.0. Re‑sign ClickOnce/MSIX or installer artifacts after the SDK change. Rotate any code signing certs expiring in 2026.
• Observability. Add the new ASP.NET Core metrics to dashboards. Define SLOs on p95 latency and error rate before flipping traffic.
• Security gates. Keep software composition analysis and runtime patching on. Standardize monthly patch cadence tied to .NET’s Patch Tuesday.

Budget and ROI: how to frame the conversation

Executives fund outcomes. Position the upgrade as a risk‑reduction and efficiency project with a capped timeline: fewer supported variants to patch, measurable resource savings from runtime/memory improvements, and a language/tooling baseline that speeds features in H2. If you can carve 5–10% off CPU or RAM per pod, that’s real money across hundreds of pods—especially if autoscaling is tuned.

What to do next

• Pick a pilot service and retarget it to net10.0 this week. Bake in the ASP.NET Core 10 metrics.
• Schedule the Visual Studio 2026 rollout and update CI runners to the .NET 10 SDK.
• Create the inventory and risk scorecard for every app. Sort by green/yellow/red and plan waves.
• Benchmark before/after for CPU, memory, and p95. Tune Kestrel and GC settings only if data says so.
• Lock a team‑level playbook to ship on .NET 10 LTS and make it the default for new services.

Related deep dives

Want the specifics on stacks and trade‑offs? Start here:

• What .NET 10 LTS changes for your web stack
• Move to .NET 10 LTS: What’s New, What Breaks, What Wins
• The .NET 10 LTS Reality Check for 2026 Upgrades
• Why we also care about web performance: Next.js 16 playbook

Final take

Upgrading to .NET 10 LTS in 2026 isn’t about chasing shiny objects; it’s about reducing operational risk while picking up steady gains in throughput, memory, and developer experience. Ship a pilot now, standardize the toolchain, and roll through services with metrics watching your back. Future‑you—in late 2026 when older versions age out—will be very glad you started today.