Checks aws_eks_cluster and azurerm_kubernetes_cluster blocks in your .tf files against the published EKS and AKS Kubernetes version calendars, and tells you which clusters are already paying the extended-support rate, which ones AWS will upgrade on its own, and which AKS clusters ask for Long Term Support on a tier that does not include it.
Web version (same engine, runs in the browser): https://getreadystack.com/tools/aks-eks-support-cliff-lint
Yardstick: an EKS cluster in extended support is billed $0.60 per cluster-hour instead of $0.10 — $365 a month, $4,380 a year, per cluster. AKS Premium tier (required for LTS) is $0.60 per cluster-hour against $0.10 for Standard.
Why this exists
terraform validate and terraform plan accept version = "1.32" on an EKS cluster without comment. When there is no upgrade_policy block, AWS defaults the cluster to EXTENDED, and billing switches to the extended rate at the start of the day standard support ends (UTC). Nothing in the plan output changes. On AKS, support_plan = "AKSLongTermSupport" is only available on sku_tier = "Premium", and a version past community end of life without LTS gets platform support only: no Kubernetes security patches and no new clusters at that version.
What it checks (9 rules)
| Rule |
Severity |
Fires when |
| eks-extended-billing |
error |
EKS version is past end of standard support and the policy is EXTENDED or missing; reports dollars billed so far |
| eks-forced-upgrade-soon |
error |
extended support ends within 90 days |
| eks-past-extended |
error |
version past extended support, or STANDARD policy past standard support (auto-upgrade) |
| eks-cliff-soon |
warning |
standard support ends within 90 days |
| aks-lts-needs-premium |
error |
AKSLongTermSupport without sku_tier = "Premium" |
| aks-out-of-support |
error |
AKS version past community end of life with LTS off |
| aks-lts-ended |
error |
AKS version past its LTS end of life |
| aks-eol-soon |
warning |
community end of life within 90 days, LTS off |
| aks-premium-unused |
info |
Premium tier bought for LTS while the version is still in community support |
Calendars used (checked 2026-09-27)
EKS (end of standard / end of extended): 1.31 2025-11-26 / 2026-11-26 · 1.32 2026-03-23 / 2027-03-23 · 1.33 2026-07-29 / 2027-07-29 · 1.34 2026-12-02 / 2027-12-02 · 1.35 2027-03-27 / 2028-03-27 · 1.36 2027-08-02 / 2028-08-02. Source: docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html
AKS (community end of life / LTS end of life): 1.29 2025-03-31 / 2026-04-30 · 1.30 2025-08-22 / 2026-07-31 · 1.31 2025-11-01 / 2026-11-30 · 1.32 2026-03-31 / 2027-03-31 · 1.33 2026-07-31 / 2027-07-31 · 1.34 2026-11-30 / 2027-11-30 · 1.35 2027-03-31 / 2028-03-31 · 1.36 2027-06-30 / 2028-06-30 · 1.37 2027-10-31 / 2028-10-31. Month-only dates are the last day of that month, as Microsoft defines them. Source: learn.microsoft.com/azure/aks/supported-kubernetes-versions
Worked example (sample file clusters.tf, today = 2026-09-27)
| Line in clusters.tf |
Finding and fix |
payments: version = "1.32", no upgrade_policy |
$2,256 extra since 2026-03-23; move to 1.35 or later |
batch: version = "1.31", EXTENDED |
$3,660 extra since 2025-11-26; move to 1.35 or later |
| batch: extended ends 2026-11-26 |
forced control-plane upgrade in 60 days |
web: version = "1.34", STANDARD |
auto-upgrade on 2026-12-02 (66 days) |
| core: AKSLongTermSupport on Standard |
LTS needs sku_tier = "Premium" |
legacy: kubernetes_version = "1.33.2", no LTS |
past 2026-07-31 end of life |
| analytics: Premium + LTS on 1.35 |
community support until 2027-03-31; Standard saves $365 a month |
Free and full version
Free: lint the open .tf file, all 9 rules, every message, no key. Full version: scan the whole workspace and export a per-cluster CSV of fees, cliff dates and fixes for a platform or FinOps review — get the full version.
Commands
Open the Command Palette and type the extension name to run the check on the active .tf file.
Prices are AWS and Azure list prices per cluster-hour in USD; your contract may differ.
