diff --git a/.github/workflows/validate-index.yml b/.github/workflows/validate-index.yml
index 393be186..b4a33c96 100644
--- a/.github/workflows/validate-index.yml
+++ b/.github/workflows/validate-index.yml
@@ -16,53 +16,5 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
-      - name: Install yq
-        run: |
-          YQ_VERSION="v4.44.1"
-          wget -qO /tmp/yq "https://github.com/mikefarah/yq/releases/download/${YQ_VERSION}/yq_linux_amd64"
-          sudo mv /tmp/yq /usr/local/bin/yq
-          sudo chmod +x /usr/local/bin/yq
-
-      - name: Validate all indexed files exist
-        run: |
-          EXIT_CODE=0
-
-          # Check skill files
-          SKILL_FILES=$(yq eval '.skills[].file' index.yaml)
-          echo "Checking skill files listed in index.yaml..."
-          while IFS= read -r filepath; do
-            if [ -z "$filepath" ] || [ "$filepath" = "null" ]; then
-              continue
-            fi
-            if [ ! -f "$filepath" ]; then
-              echo "MISSING: $filepath"
-              EXIT_CODE=1
-            else
-              echo "OK: $filepath"
-            fi
-          done <<< "$SKILL_FILES"
-
-          # Check role files
-          ROLE_FILES=$(yq eval '.roles[].file' index.yaml)
-          echo ""
-          echo "Checking role files listed in index.yaml..."
-          while IFS= read -r filepath; do
-            if [ -z "$filepath" ] || [ "$filepath" = "null" ]; then
-              continue
-            fi
-            if [ ! -f "$filepath" ]; then
-              echo "MISSING: $filepath"
-              EXIT_CODE=1
-            else
-              echo "OK: $filepath"
-            fi
-          done <<< "$ROLE_FILES"
-
-          if [ "$EXIT_CODE" -ne 0 ]; then
-            echo ""
-            echo "FAIL: One or more files listed in index.yaml do not exist."
-            exit 1
-          fi
-
-          echo ""
-          echo "All indexed files are present."
+      - name: Validate index
+        run: ruby scripts/validate_index.rb
diff --git a/index.yaml b/index.yaml
index f038f59a..7dd3a155 100644
--- a/index.yaml
+++ b/index.yaml
@@ -462,7 +462,7 @@ skills:
     role: [soc-analyst]
     phase: [operate, respond]
     activity: [triage, investigate]
-    frameworks: [MITRE-ATT&CK-v16, NIST-SP-800-61r2]
+    frameworks: [MITRE-ATT&CK-v16, NIST-SP-800-61-Rev2]
     difficulty: beginner
     time_estimate: "10-20min per alert"
     file: skills/secops/alert-triage/SKILL.md
diff --git a/scripts/validate_index.rb b/scripts/validate_index.rb
new file mode 100644
index 00000000..f91f9cc2
--- /dev/null
+++ b/scripts/validate_index.rb
@@ -0,0 +1,196 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "set"
+
+ROOT = File.expand_path("..", __dir__)
+INDEX_PATH = File.join(ROOT, "index.yaml")
+SKILL_GLOB = File.join(ROOT, "skills", "*", "*", "SKILL.md")
+ROLE_GLOB = File.join(ROOT, "roles", "*", "SKILL.md")
+METADATA_FIELDS = %w[tags role phase frameworks difficulty time_estimate].freeze
+
+def rel(path)
+  path.delete_prefix("#{ROOT}#{File::SEPARATOR}")
+end
+
+def parse_value(raw)
+  value = raw.strip
+  return nil if value.empty?
+
+  if value.start_with?("[") && value.end_with?("]")
+    inner = value[1...-1].strip
+    return [] if inner.empty?
+
+    inner.split(",").map { |item| parse_value(item) }
+  elsif (value.start_with?('"') && value.end_with?('"')) ||
+        (value.start_with?("'") && value.end_with?("'"))
+    value[1...-1]
+  elsif value == "true"
+    true
+  elsif value == "false"
+    false
+  else
+    value
+  end
+end
+
+def parse_index(path)
+  section = nil
+  current = nil
+  items = { "skills" => [], "roles" => [] }
+
+  File.readlines(path, chomp: true).each_with_index do |line, index|
+    stripped = line.strip
+    next if stripped.empty? || stripped.start_with?("#")
+
+    if line =~ /^([a-z_]+):\s*$/
+      section = Regexp.last_match(1)
+      current = nil
+      next
+    end
+
+    next unless %w[skills roles].include?(section)
+
+    if line =~ /^  - ([A-Za-z0-9_-]+):\s*(.+?)\s*$/
+      current = { "__line" => index + 1 }
+      items[section] << current
+      current[Regexp.last_match(1)] = parse_value(Regexp.last_match(2))
+    elsif line =~ /^    ([A-Za-z0-9_-]+):\s*(.+?)\s*$/
+      raise "index.yaml line #{index + 1}: field found before list item" unless current
+
+      current[Regexp.last_match(1)] = parse_value(Regexp.last_match(2))
+    end
+  end
+
+  items
+rescue Errno::ENOENT
+  raise "index.yaml not found at #{path}"
+end
+
+def frontmatter_for(path)
+  text = File.read(path)
+  match = text.match(/\A---\s*\n(.*?)\n---\s*(?:\n|\z)/m)
+  raise "missing YAML frontmatter delimited by ---" unless match
+
+  parse_frontmatter(match[1])
+end
+
+def parse_frontmatter(text)
+  fields = {}
+  skip_block = false
+
+  text.each_line(chomp: true) do |line|
+    if skip_block
+      next if line.start_with?(" ") || line.start_with?("\t") || line.strip.empty?
+
+      skip_block = false
+    end
+
+    next if line.strip.empty? || line.start_with?("#")
+    next unless line =~ /^([A-Za-z0-9_-]+):\s*(.*?)\s*$/
+
+    key = Regexp.last_match(1)
+    raw = Regexp.last_match(2)
+    if %w[| > |- >- |+ >+].include?(raw)
+      skip_block = true
+      next
+    end
+
+    fields[key] = parse_value(raw)
+  end
+
+  fields
+end
+
+def duplicate_values(items, field)
+  counts = Hash.new(0)
+  items.each { |item| counts[item[field]] += 1 if item[field] }
+  counts.select { |_value, count| count > 1 }.keys
+end
+
+def compare_metadata(entry_type, id, indexed, frontmatter, errors)
+  expected_name = frontmatter["name"]
+  errors << "#{entry_type} #{id}: indexed id does not match frontmatter name '#{expected_name}'" if id != expected_name
+
+  METADATA_FIELDS.each do |field|
+    next unless indexed.key?(field) && frontmatter.key?(field)
+
+    next if indexed[field] == frontmatter[field]
+
+    errors << "#{entry_type} #{id}: #{field} mismatch; index=#{indexed[field].inspect}, frontmatter=#{frontmatter[field].inspect}"
+  end
+end
+
+def validate_entries(entry_type, entries, discovered_files, errors)
+  indexed_files = entries.map { |entry| entry["file"] }.compact.sort
+
+  duplicate_values(entries, "id").each do |id|
+    errors << "#{entry_type} #{id}: duplicate id in index.yaml"
+  end
+
+  duplicate_values(entries, "file").each do |file|
+    errors << "#{entry_type} file #{file}: duplicate file in index.yaml"
+  end
+
+  entries.each do |entry|
+    id = entry["id"]
+    file = entry["file"]
+    line = entry["__line"]
+
+    errors << "#{entry_type} entry at index.yaml line #{line}: missing id" unless id
+    unless file
+      errors << "#{entry_type} #{id || "entry at index.yaml line #{line}"}: missing file"
+      next
+    end
+
+    absolute = File.join(ROOT, file)
+    unless File.file?(absolute)
+      errors << "#{entry_type} #{id || file}: indexed file does not exist: #{file}"
+      next
+    end
+
+    begin
+      compare_metadata(entry_type, id, entry, frontmatter_for(absolute), errors) if id
+    rescue StandardError => e
+      errors << "#{entry_type} #{id || file}: #{file}: #{e.message}"
+    end
+  end
+
+  missing_from_index = discovered_files - indexed_files
+  missing_from_index.each do |file|
+    errors << "#{entry_type} #{file}: file exists but is missing from index.yaml"
+  end
+
+  stale_index_entries = indexed_files - discovered_files
+  stale_index_entries.each do |file|
+    errors << "#{entry_type} #{file}: indexed file is outside expected #{entry_type} path set"
+  end
+end
+
+def validate_role_skill_references(roles, skill_ids, errors)
+  roles.each do |role|
+    role.fetch("skills", []).each do |skill_id|
+      next if skill_ids.include?(skill_id)
+
+      errors << "role #{role['id']}: references unknown skill id '#{skill_id}'"
+    end
+  end
+end
+
+errors = []
+index = parse_index(INDEX_PATH)
+skill_files = Dir.glob(SKILL_GLOB).map { |path| rel(path) }.sort
+role_files = Dir.glob(ROLE_GLOB).map { |path| rel(path) }.sort
+
+validate_entries("skill", index["skills"], skill_files, errors)
+validate_entries("role", index["roles"], role_files, errors) unless index["roles"].empty?
+validate_role_skill_references(index["roles"], index["skills"].map { |entry| entry["id"] }.compact.to_set, errors)
+
+if errors.empty?
+  puts "OK: index.yaml matches #{skill_files.size} skills and #{role_files.size} roles."
+else
+  puts "FAIL: index.yaml validation failed."
+  errors.each { |error| puts "  - #{error}" }
+end
+
+exit(errors.empty? ? 0 : 1)