diff --git a/.agents/skills/marketplace-architect/scripts/validate.sh b/.agents/skills/marketplace-architect/scripts/validate.sh
index 83595f4..aec062b 100755
--- a/.agents/skills/marketplace-architect/scripts/validate.sh
+++ b/.agents/skills/marketplace-architect/scripts/validate.sh
@@ -224,12 +224,14 @@ ROOT="$(cd "$ROOT" && pwd)"
 
 # ── validate marketplace.json ─────────────────────────────────────────────────
 
+CLAUDE_MARKETPLACE="$ROOT/.claude-plugin/marketplace.json"
+COPILOT_MARKETPLACE="$ROOT/.github/plugin/marketplace.json"
 MARKETPLACE_JSON=""
-for mp in "$ROOT/.claude-plugin/marketplace.json" "$ROOT/.github/plugin/marketplace.json"; do
+
+for mp in "$CLAUDE_MARKETPLACE" "$COPILOT_MARKETPLACE"; do
   if [[ -f "$mp" ]]; then
-    MARKETPLACE_JSON="$mp"
+    [[ -z "$MARKETPLACE_JSON" ]] && MARKETPLACE_JSON="$mp"
     validate_marketplace_json "$mp"
-    break
   fi
 done
 
@@ -237,6 +239,57 @@ if [[ -z "$MARKETPLACE_JSON" ]]; then
   warn "No marketplace.json found. Expected at .claude-plugin/marketplace.json"
 fi
 
+# Marketplace sync check — shared identity fields must match; description/version
+# legitimately differ in structure (Claude: top-level; Copilot: under metadata)
+if [[ -f "$CLAUDE_MARKETPLACE" && -f "$COPILOT_MARKETPLACE" ]]; then
+  cm_val=$(jq -r '.name // empty' "$CLAUDE_MARKETPLACE")
+  cp_val=$(jq -r '.name // empty' "$COPILOT_MARKETPLACE")
+  if [[ "$cm_val" != "$cp_val" ]]; then
+    error "marketplace: 'name' differs — .claude-plugin ('$cm_val') vs .github/plugin ('$cp_val')"
+  fi
+
+  cm_val=$(jq -r '.owner.name // empty' "$CLAUDE_MARKETPLACE")
+  cp_val=$(jq -r '.owner.name // empty' "$COPILOT_MARKETPLACE")
+  if [[ ( -n "$cm_val" || -n "$cp_val" ) && "$cm_val" != "$cp_val" ]]; then
+    error "marketplace: 'owner.name' differs — '$cm_val' vs '$cp_val'"
+  fi
+
+  # description: Claude top-level, Copilot under metadata — compare values regardless of path
+  cm_val=$(jq -r '.description // .metadata.description // empty' "$CLAUDE_MARKETPLACE")
+  cp_val=$(jq -r '.metadata.description // .description // empty' "$COPILOT_MARKETPLACE")
+  if [[ ( -n "$cm_val" || -n "$cp_val" ) && "$cm_val" != "$cp_val" ]]; then
+    error "marketplace: description differs between .claude-plugin/marketplace.json and .github/plugin/marketplace.json"
+  fi
+
+  # version: same structural divergence as description
+  cm_val=$(jq -r '.version // .metadata.version // empty' "$CLAUDE_MARKETPLACE")
+  cp_val=$(jq -r '.metadata.version // .version // empty' "$COPILOT_MARKETPLACE")
+  if [[ ( -n "$cm_val" || -n "$cp_val" ) && "$cm_val" != "$cp_val" ]]; then
+    error "marketplace: version differs — '$cm_val' vs '$cp_val'"
+  fi
+
+  # Plugin catalog must be identical across both files
+  cm_plugins=$(jq -r '.plugins[].name' "$CLAUDE_MARKETPLACE" 2>/dev/null | sort)
+  cp_plugins=$(jq -r '.plugins[].name' "$COPILOT_MARKETPLACE" 2>/dev/null | sort)
+  if [[ "$cm_plugins" != "$cp_plugins" ]]; then
+    error "marketplace: plugin lists differ between .claude-plugin/marketplace.json and .github/plugin/marketplace.json"
+  else
+    while IFS= read -r pname; do
+      [[ -z "$pname" ]] && continue
+      cm_val=$(jq -r --arg n "$pname" '.plugins[] | select(.name==$n) | .source // empty' "$CLAUDE_MARKETPLACE")
+      cp_val=$(jq -r --arg n "$pname" '.plugins[] | select(.name==$n) | .source // empty' "$COPILOT_MARKETPLACE")
+      if [[ "$cm_val" != "$cp_val" ]]; then
+        error "marketplace plugin '$pname': source differs — '$cm_val' vs '$cp_val'"
+      fi
+      cm_val=$(jq -r --arg n "$pname" '.plugins[] | select(.name==$n) | .description // empty' "$CLAUDE_MARKETPLACE")
+      cp_val=$(jq -r --arg n "$pname" '.plugins[] | select(.name==$n) | .description // empty' "$COPILOT_MARKETPLACE")
+      if [[ ( -n "$cm_val" || -n "$cp_val" ) && "$cm_val" != "$cp_val" ]]; then
+        error "marketplace plugin '$pname': description differs between the two marketplace.json files"
+      fi
+    done <<< "$cm_plugins"
+  fi
+fi
+
 # ── validate plugins ──────────────────────────────────────────────────────────
 
 if [[ -n "$PLUGIN_ONLY" ]]; then
diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
index 9f0e857..ab381a8 100644
--- a/.claude-plugin/marketplace.json
+++ b/.claude-plugin/marketplace.json
@@ -1,5 +1,6 @@
 {
   "name": "holocron",
+  "owner": { "name": "Your Name", "email": "you@example.com" },
   "description": "AI development skills for Claude Code and GitHub Copilot CLI — factory, design, implement, review, and cross-cutting workflows.",
   "version": "0.1.0",
   "plugins": [
diff --git a/.github/plugin/marketplace.json b/.github/plugin/marketplace.json
index 9f0e857..17d4d93 100644
--- a/.github/plugin/marketplace.json
+++ b/.github/plugin/marketplace.json
@@ -1,7 +1,10 @@
 {
   "name": "holocron",
-  "description": "AI development skills for Claude Code and GitHub Copilot CLI — factory, design, implement, review, and cross-cutting workflows.",
-  "version": "0.1.0",
+  "owner": { "name": "Your Name", "email": "you@example.com" },
+  "metadata": {
+    "description": "AI development skills for Claude Code and GitHub Copilot CLI — factory, design, implement, review, and cross-cutting workflows.",
+    "version": "0.1.0"
+  },
   "plugins": [
     {
       "name": "hello-world",