EKS Upgrade Readiness Skill

Overview

This skill assesses your live EKS cluster's readiness for a Kubernetes version upgrade. It connects to your cluster via AWS CLI and kubectl, runs automated checks across 8 assessment areas, calculates a readiness score (0-100%), and produces a detailed report with prioritized remediation steps and pre-filled AWS CLI commands.

This skill is laser-focused on upgrade safety — answering the question: "Is it safe to upgrade this cluster to the next version?"

Read-only / assessment-only — hard rule. This skill ONLY inspects the cluster; it MUST NOT modify it. Every aws, kubectl, and MCP call it issues must be a read/list/describe operation. NEVER run mutating verbs (apply, create, delete, patch, edit, replace, annotate, label, set, scale, cordon, drain, update-*, --force, etc.), and NEVER execute a remediation snippet. Any mutating command embedded in a steering file is a recommendation for the user to run themselves — surface it as text, do not execute it.

What Gets Assessed

Readiness Score

The skill calculates a weighted readiness score:

Hard Blocker Override: If any hard blocker is detected (e.g., incompatible Karpenter, critical add-on DEGRADED, cluster subnets collectively cannot place control-plane ENIs, cluster not ACTIVE), the score is capped at ≤ 59% (NOT READY) regardless of other findings. See references/report-generation.md for the full list.

Score Interpretation:

• 90-100: READY — Safe to proceed
• 80-89: GOOD — Minor issues, can proceed with caution
• 70-79: FAIR — Several issues need attention first
• 60-69: RISKY — Significant issues, not recommended yet
• 0-59: NOT READY — Critical blockers, must resolve first

Prerequisites

1. AWS credentials configured — aws configure or ~/.aws/credentials with EKS access
2. kubectl access to the target cluster (for Kubernetes API queries)
3. Required AWS Permissions:
   • eks:DescribeCluster, eks:ListClusters, eks:ListNodegroups, eks:DescribeNodegroup
   • eks:ListAddons, eks:DescribeAddon, eks:DescribeAddonVersions, eks:ListInsights, eks:DescribeInsight
   • ec2:DescribeSubnets

MCP Server Setup

This skill works without any MCP server — it falls back to AWS CLI and kubectl commands. That fallback path is the default in apex.

For richer EKS operations (live cluster reads, upgrade insights, K8s resource introspection), enable the EKS MCP server via the apex eks-mcp-server skill — it walks you through both AWS-hosted and self-hosted setup options. Once configured, this skill will prefer MCP tools over CLI for EKS operations.

Note: Apex does NOT ship a project-root .mcp.json. MCP setup is opt-in and user-driven through the eks-mcp-server skill.

Configuration

The skill uses your existing AWS credentials. No additional configuration needed if aws eks list-clusters works from your terminal.

To use a specific profile or region, set environment variables:

export AWS_PROFILE=your-profile-name
export AWS_REGION=your-region

Getting Started

Invoke the skill: /eks-upgrade-check

Or simply ask: "Run an EKS upgrade readiness assessment"

The skill will discover your clusters, ask which one to assess and what target version, then run the full assessment.

Assessment Workflow

Step 0: Pre-flight

Action 1 — List clusters (test connectivity & discover clusters)

Run aws eks list-clusters to discover available clusters.

Region caveat. aws eks list-clusters is region-scoped (it lists only the current/--region region) and returns names only, not regions. An empty result means "no clusters in this region," NOT "no clusters in the account" — before treating zero clusters as terminal, confirm the intended region (echo $AWS_REGION) and, if the region is ambiguous, list the likely regions. Any "name + region" shown to the user pairs the returned name with the region actually queried.

• ✅ Success → Show the cluster list. Ask which cluster to assess. If only one cluster, confirm it.
• ❌ Failure → STOP. Do NOT retry more than once. Show:

Cannot access EKS clusters. Try these steps:

1. Check that AWS credentials are configured: aws sts get-caller-identity
2. Check your region: aws eks list-clusters --region <region>
3. Check that MCP servers are enabled in Claude Code

Wait for the user to resolve the issue.

Action 2 — Describe the selected cluster

Run aws eks describe-cluster --name <cluster> and show: cluster name, Kubernetes version, platform version, region, status, account ID.

Account ID hygiene: the account ID (from aws sts get-caller-identity / the cluster ARN) is sensitive. If the report will be shared outside the account, mask or omit the account ID before sharing.

Action 2b — Validate cluster status

Check the status field from the cluster description. If status is NOT ACTIVE:

• CREATING/UPDATING/DELETING → STOP. Show: "Cluster is currently in <status> state. The EKS API will reject an upgrade request. Wait for the operation to complete, then re-run this assessment."
• FAILED → STOP. Show: "Cluster is in FAILED state. This is a hard blocker — the cluster must be recovered before an upgrade can be attempted. Contact AWS Support if the cluster is stuck in FAILED."

Do NOT proceed with the assessment if cluster status is not ACTIVE. This is a hard blocker (see report-generation.md).

Cluster status gates the whole assessment; node group status gates node readiness. If a node group's lifecycle status == UPDATING (mid-rotation), the assessment can still run but node readings may be a transient old/new mix — flag it as potentially unstable and recommend re-running after rotation (see node-readiness.md §5.1).

Action 3 — Validate permissions (AWS + Kubernetes)

3a — AWS API preflight. After describing the cluster, verify key AWS permissions by attempting:

1. aws eks list-nodegroups --cluster-name <cluster>
2. aws eks list-addons --cluster-name <cluster>
3. aws eks describe-addon-versions --kubernetes-version <current> (add-on compatibility — addon-compatibility.md marks this a MUST-run read)
4. aws eks list-insights --cluster-name <cluster>
5. aws ec2 describe-subnets --subnet-ids <cluster subnet ids> (node-readiness subnet-IP hard-blocker input)

eks:DescribeCluster / eks:DescribeNodegroup / eks:DescribeAddon / eks:DescribeInsight are exercised implicitly by the assessment steps themselves; the probes above cover the list/describe reads that gate scoring inputs.

3b — Kubernetes RBAC preflight. The high-weight assessment categories read Kubernetes objects, not just AWS APIs. Verify cluster read access with kubectl auth can-i before scanning:

kubectl auth can-i list deployments -A          # workloads (workload-risks, deprecated-apis)
kubectl auth can-i list daemonsets -A           # workloads
kubectl auth can-i list statefulsets -A         # workloads
kubectl auth can-i list validatingwebhookconfigurations   # webhooks (breaking-changes)
kubectl auth can-i list mutatingwebhookconfigurations     # webhooks
kubectl auth can-i list horizontalpodautoscalers -A       # HPA (deprecated-apis)
kubectl auth can-i list nodepools.karpenter.sh            # Karpenter nodepools (node-readiness, addon-compat)

If kubectl auth can-i itself errors (not a clean yes/no), treat the read as denied.

Denied-read discipline (same for the AWS and Kubernetes preflights). If any probe above returns AccessDenied (AWS) or no (kubectl) → surface exactly which read is denied and the IAM action or RBAC verb/resource needed, then ask the user whether to (a) fix the permission and re-run the probe, or (b) continue with a partial assessment. A denied read is NOT a hard stop and NOT a silent 0: the affected category is reported UNKNOWN / not-scored and listed in ## Unassessed, per references/report-generation.md. A partial assessment can NEVER yield an uncaveated READY — the headline verdict carries the partial marker and is capped below READY. The guarantee this preflight gives extends only to the reads it actually probes.

Action 4 — Determine target version

Ask: "Your cluster is on v[current]. The next version is v[current+1]. Shall I assess upgrade readiness to v[current+1]?"

If the user specifies a version more than 1 minor version ahead, explain that EKS requires one-version-at-a-time upgrades and show the required path (e.g., 1.29 → 1.30 → 1.31 → 1.32). Offer to assess the first hop.

Action 5 — Confirm and proceed

Steps 1-8: Run Assessment

Read each steering file in order from ${CLAUDE_SKILL_DIR}/references/. For each section:

1. Read the steering file
2. Execute the checks described in it using AWS CLI and kubectl commands
3. Collect findings with severity ratings

Steering file loading guide:

Step 9: Calculate Score & Generate Report

Read ${CLAUDE_SKILL_DIR}/references/report-generation.md and produce the report.

Tool Usage Rules

1. Do NOT call any tools when this skill is first activated. Wait for the user to ask.
2. Do NOT hardcode or guess cluster names. Always discover by listing first.
3. Do NOT retry a failed command more than once.
4. Always read the relevant steering file before executing checks for that section.
5. Use aws CLI and kubectl for cluster queries. If MCP servers are available, prefer them for EKS operations.

Data Files

• OSS Add-on Registry: ${CLAUDE_SKILL_DIR}/data/oss_addon_registry.json — identifiers and authoritative upstream URLs for common OSS add-ons. This file does NOT contain compatibility data. Compatibility is always verified live via the registry's compatibility_url and releases_url fields. If an add-on is not in the registry or the upstream source is unreachable, report UNKNOWN — never guess.
• HTML Converter: ${CLAUDE_SKILL_DIR}/tools/md_to_html.py — converts markdown reports to HTML

Report Output

• Markdown: EKS-Upgrade-Assessment-<cluster>-<current>-to-<target>-<YYYY-MM-DD>-<HHMM>.md
• HTML: Run python3 ${CLAUDE_SKILL_DIR}/tools/md_to_html.py <report>.md to convert

Do NOT generate HTML manually. Always use the conversion script.