[docs] Document Helm v4.2.0+ prerequisite for Kubernetes deployment

[aspire-repo-bot]

Documents changes from microsoft/aspire#17491.

@mitchdenny added an up-front Helm CLI version check to Aspire's Kubernetes deployment pipeline. Aspire now validates that Helm v4.2.0 or later is installed before running helm upgrade --install, replacing cryptic flag failures (unknown flag: --force-conflicts, Flag --force has been deprecated) with a single clear, actionable error message that includes the detected version, required minimum, and a link to the Helm install docs.

Targeting release/13.4 — the latest release branch on microsoft/aspire.dev — because release/13.5 (from the source PR milestone 13.5) does not exist there.

Why this PR is needed

The Helm v4.2.0+ minimum is now enforced at runtime, so users who attempt to deploy with an older Helm will see a validation error. The documentation must surface this requirement before users hit it.

Changes made

• src/frontend/src/content/docs/deployment/kubernetes.mdx — Added a new Prerequisites section listing Helm v4.2.0+ (and kubectl) as required tools, with links to the install docs.
• src/frontend/src/content/docs/integrations/compute/kubernetes.mdx — Added a callout note in the Installation section explaining the Helm v4.2.0+ prerequisite and why it's enforced.

Both pages were updated (not created); the changes are focused on the new minimum-version requirement.

Generated by PR Documentation Check for issue #17491 · ● 9.3M · ◷

[Copilot]

Pull request overview

Updates Aspire Kubernetes documentation to surface the newly enforced minimum Helm CLI version requirement (Helm v4.2.0+) before users hit runtime validation failures.

Changes:

• Added a Helm v4.2.0+ prerequisite callout to the Kubernetes hosting integration installation section.
• Added a Prerequisites section to the Kubernetes deployment overview page listing Helm v4.2.0+ and kubectl.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/frontend/src/content/docs/integrations/compute/kubernetes.mdx	Adds an installation callout describing the Helm v4.2.0+ prerequisite and why it’s enforced.
src/frontend/src/content/docs/deployment/kubernetes.mdx	Adds a Prerequisites section to the Kubernetes deployment overview highlighting Helm v4.2.0+ and kubectl.

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[IEvangelist]

Docs accuracy review

Source of truth: microsoft/aspire@cc4b7eaf (release/13.4, fetched 2026-05-29)
PR head: 9a5ab02db9f098043b1de8fbf70ec646650a6215

Verdict	Count
verified	5
verified-with-nuance	0
unverifiable	0
contradicted	0

Verdict: APPROVE. Every claim matches the implementation at release/13.4.

Doc-tester (UX) notes

Read as a user landing on either page from a fresh repo. The v4.2.0 floor, the actionable-error phrasing, and the helm upgrade --install description are concrete enough that a user who hits a Helm-related failure can map it to the relevant validator. Cross-linking to https://helm.sh/docs/intro/install/ matches the same URL the runtime uses in its error messages, so a user following the doc and a user who hit the runtime error end up at the same install page.

Verified claims (with evidence)

#	Claim	Evidence
1	"Helm v4.2.0 or later"	src/Aspire.Hosting.Kubernetes/Deployment/HelmVersionValidator.cs:28 — public static readonly Version MinimumHelmVersion = new(4, 2, 0);. The class doc-comment (:14-22) explains the v4 rationale (--server-side=true --force-conflicts Helm-4 shape).
2	"Aspire shells out to helm upgrade --install to deploy the generated chart"	HelmDeploymentEngine.cs:433 — arguments.Append(..., $"upgrade --install {releaseName} \"{outputPath}\"") and runs it via IHelmRunner.RunAsync (:458-466). Same string in Aspire.Hosting.Kubernetes/README.md:11.
3	"It validates the Helm version up front"	HelmDeploymentEngine.cs:135-155 enqueues a check-helm-prereqs-{env} pipeline step that calls HelmVersionValidator.EnsureMinimumVersionAsync(helmRunner, ct); the prepare/deploy/uninstall steps all DependsOn it (:155,166,234).
4	"Missing or older versions produce a clear actionable error rather than cryptic flag failures"	HelmVersionValidator.cs:80-83,89-91,96-98,102-109 — each failure mode (helm-not-on-PATH, non-zero exit, unparseable output, too-old version) throws InvalidOperationException with MinimumHelmVersion and InstallDocsUrl in the message. The class doc-comment (:14-22) calls out the exact "cryptic" failures it prevents (unknown flag: --force-conflicts, Flag --force has been deprecated...).
5	"kubectl — Required to interact with your cluster."	Beyond generic Kubernetes use, Aspire actively shells out to kubectl in the deployment pipeline: CertManagerExtensions.cs:462,519 (ClusterIssuer apply/delete), KubernetesEnvironmentResource.cs:1248,1308,1353,1441,1529,1617,1682,1793,1863,1921,1966 (Gateway listener patching and namespace bootstrap), and HelmDeploymentEngine.cs:683 (service inspection for runtime instructions).