eks-upgrade-check

name	eks-upgrade-check
description	Assess EKS cluster upgrade readiness - run automated checks across 8 areas, calculate a readiness score (0-100%), and generate a report with remediation steps. Assessment-only: all checks are strictly read-only and never modify the cluster. Use when (in the context of a Kubernetes version upgrade): EKS upgrade, cluster upgrade, upgrade readiness, deprecated API, version skew, addon compatibility, Karpenter version, node upgrade, control plane upgrade.
allowed-tools	Bash, Read, Write, Grep, Glob, WebFetch, WebSearch

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

#	Section	Key Checks
01	Version Validation	Upgrade path validity, version skew policy, support status
02	Breaking Changes	Version-specific API removals, behavioral changes, resource impact
03	Deprecated API Detection	Live scan of cluster resources for deprecated/removed APIs
04	Add-on Compatibility	Core add-on versions, OSS add-on matrix, Karpenter compatibility
05	Node Readiness	Node version skew, AL2→AL2023 migration, AMI compatibility
06	Workload Risks	Single replicas, missing PDBs, health probes, resource requests
07	AWS Upgrade Insights	Official EKS pre-upgrade checks and recommendations
08	Upgrade Plan	Pre-filled CLI commands, step-by-step upgrade sequence

Readiness Score

The skill calculates a weighted readiness score:

Category	Max Deduction	Rationale
Breaking Changes	25 pts	Highest risk — can break apps
Deprecated APIs	20 pts	Actionable, fixable pre-upgrade
Node Readiness (skew + subnet IPs)	20 pts	Can block upgrade entirely
Unsupported Version	15 pts	No security patches, urgent upgrade needed
Add-on Compatibility	15 pts	Critical > optional add-ons
Karpenter	10 pts	Only if installed
Workload Risks	10 pts	Best-practice, not blockers
AWS Upgrade Insights	10 pts	Official AWS checks
AL2 Nodes / Behavioral	10 pts	Informational

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 steering/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 uses two MCP servers, both pre-configured in .mcp.json at the project root:

• awslabs.eks-mcp-server — connects to your EKS cluster
• awslabs.aws-documentation-mcp-server — looks up AWS documentation during assessment

On first launch, Claude Code will prompt you to enable both servers. If MCP servers are not available, the skill falls back to AWS CLI and kubectl commands.

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 steering/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}/steering/. 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:

User Request	Steering File(s)
Full upgrade assessment	ALL files in order
Version / upgrade path	steering/version-validation.md
Breaking changes / API removals	steering/breaking-changes.md
Deprecated APIs	steering/deprecated-apis.md
Add-on compatibility / Karpenter	steering/addon-compatibility.md
Node readiness / AL2 / AMI	steering/node-readiness.md
Workload risks / PDB / probes	steering/workload-risks.md
AWS Insights	steering/upgrade-insights.md
Generate report	steering/report-generation.md

Step 9: Calculate Score & Generate Report

Read ${CLAUDE_SKILL_DIR}/steering/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.