diff --git a/.github/workflows/external-plugin-pr-quality-gates.yml b/.github/workflows/external-plugin-pr-quality-gates.yml
index 3010788b8..6978738e6 100644
--- a/.github/workflows/external-plugin-pr-quality-gates.yml
+++ b/.github/workflows/external-plugin-pr-quality-gates.yml
@@ -214,6 +214,34 @@ jobs:
                 .replace(/>/g, '>')
                 .replace(/"/g, '"')
                 .replace(/'/g, ''');
+            const escapeMarkdownTableCell = (value) =>
+              String(value ?? '')
+                .replace(/\r\n?|\n/g, '\n')
+                .split('\n')
+                .map((line) =>
+                  Array.from(line, (character) =>
+                    /^[A-Za-z0-9 .-]$/.test(character)
+                      ? character
+                      : `&#${character.codePointAt(0)};`
+                  ).join('')
+                )
+                .join('<br>');
+            const normalizeGitHubUrl = (value) => {
+              const raw = String(value || '').trim();
+              if (!raw) {
+                return '';
+              }
+
+              try {
+                const parsed = new URL(raw);
+                if (parsed.protocol !== 'https:' || parsed.hostname !== 'github.com') {
+                  return '';
+                }
+                return parsed.toString();
+              } catch {
+                return '';
+              }
+            };
             const TRUNCATED_OUTPUT_MARKER = '\n...output truncated...';
             const truncateGateOutput = (rawOutput) => {
               const normalized = escapeHtml(String(rawOutput || '').trim());
@@ -243,12 +271,17 @@ jobs:
 
             const rows = checkedPlugins.length > 0
               ? checkedPlugins.map((entry) => {
-                  const name = String(entry?.name || 'unknown');
+                  const name = escapeMarkdownTableCell(entry?.name || 'unknown');
                   const quality = entry?.quality || {};
-                  const sourceUrl = String(entry?.source_tree_url || '');
-                  const locator = String(entry?.source?.sha || entry?.source?.ref || 'repository');
-                  const sourceCell = sourceUrl ? `[${locator}](${sourceUrl})` : locator;
-                  return `| ${name} | ${quality.vally_lint_status || 'not_run'} | ${quality.smoke_status || 'not_run'} | ${quality.version_match_status || 'not_run'} | ${quality.canvas_structure_status || 'not_run'} | ${quality.overall_status || 'not_run'} | ${sourceCell} |`;
+                  const sourceUrl = normalizeGitHubUrl(entry?.source_tree_url || '');
+                  const locator = escapeMarkdownTableCell(entry?.source?.sha || entry?.source?.ref || 'repository');
+                  const sourceCell = sourceUrl ? `[${locator}](<${sourceUrl}>)` : locator;
+                  const vallyLintStatus = escapeMarkdownTableCell(quality.vally_lint_status || 'not_run');
+                  const smokeStatus = escapeMarkdownTableCell(quality.smoke_status || 'not_run');
+                  const versionMatchStatus = escapeMarkdownTableCell(quality.version_match_status || 'not_run');
+                  const canvasStructureStatus = escapeMarkdownTableCell(quality.canvas_structure_status || 'not_run');
+                  const overallStatus = escapeMarkdownTableCell(quality.overall_status || 'not_run');
+                  return `| ${name} | ${vallyLintStatus} | ${smokeStatus} | ${versionMatchStatus} | ${canvasStructureStatus} | ${overallStatus} | ${sourceCell} |`;
                 })
               : ['| _none_ | not_run | not_run | not_run | not_run | not_run | _n/a_ |'];
             const failureDetails = checkedPlugins.flatMap((entry) => {
@@ -296,7 +329,9 @@ jobs:
                     '',
                   ]
                 : []),
-              String(qualityResult.summary || '').trim() || '_No summary provided._',
+              String(qualityResult.summary || '').trim()
+                ? `<pre><code>${escapeHtml(String(qualityResult.summary).trim())}</code></pre>`
+                : '_No summary provided._',
             ].join('\n');
 
             await intakeState.upsertExternalPluginIntakeComment({
diff --git a/eng/external-plugin-pr-quality-gates.mjs b/eng/external-plugin-pr-quality-gates.mjs
index 85cd6d9c0..07d4a3308 100644
--- a/eng/external-plugin-pr-quality-gates.mjs
+++ b/eng/external-plugin-pr-quality-gates.mjs
@@ -1,6 +1,7 @@
 #!/usr/bin/env node
 
 import { runExternalPluginQualityGates } from "./external-plugin-quality-gates.mjs";
+import { validateExternalPlugin } from "./external-plugin-validation.mjs";
 
 function normalizePluginPath(pluginPath) {
   if (!pluginPath || pluginPath === "/") {
@@ -66,13 +67,33 @@ function aggregateResultStatus(pluginResults) {
   };
 }
 
+function createValidationFailureQuality(errors) {
+  const output = errors.map((error) => `- ${error}`).join("\n");
+  return {
+    overall_status: "fail",
+    vally_lint_status: "fail",
+    smoke_status: "not_run",
+    version_match_status: "not_run",
+    canvas_structure_status: "not_run",
+    failure_class: "submitter_fixes",
+    summary: "Plugin entry failed external.json validation. Fix the listed errors and re-run quality checks.",
+    vally_lint_output: output,
+    smoke_output: "Install smoke test skipped due to external.json validation errors.",
+    version_match_output: "Version match skipped due to external.json validation errors.",
+    canvas_structure_output: "Canvas structure check skipped due to external.json validation errors.",
+  };
+}
+
 export async function runExternalPluginPrQualityGates(plugins) {
   if (!Array.isArray(plugins)) {
     throw new Error("plugins must be an array");
   }
 
   const checkedPlugins = await Promise.all(plugins.map(async (plugin) => {
-    const quality = await runExternalPluginQualityGates(plugin);
+    const validation = validateExternalPlugin(plugin, "changed-plugin", { policy: "marketplace" });
+    const quality = validation.errors.length > 0
+      ? createValidationFailureQuality(validation.errors)
+      : await runExternalPluginQualityGates(plugin);
     return {
       name: plugin?.name ?? "unknown",
       source: plugin?.source ?? {},
diff --git a/eng/external-plugin-validation.mjs b/eng/external-plugin-validation.mjs
index 846458832..0a5ce2c13 100644
--- a/eng/external-plugin-validation.mjs
+++ b/eng/external-plugin-validation.mjs
@@ -60,12 +60,20 @@ function validatePluginName(name, prefix, errors) {
     return;
   }
 
-  if (name.length > 50) {
-    errors.push(`${prefix}: "name" must be 50 characters or fewer`);
+  if (name.length > 64) {
+    errors.push(`${prefix}: "name" must be 64 characters or fewer`);
   }
 
-  if (!/^[a-z0-9-]+$/.test(name)) {
-    errors.push(`${prefix}: "name" must contain only lowercase letters, numbers, and hyphens`);
+  if (!/^[a-z0-9.-]+$/.test(name)) {
+    errors.push(`${prefix}: "name" must contain only lowercase letters, numbers, hyphens, and periods`);
+  }
+
+  if (!/^[a-z0-9].*[a-z0-9]$/.test(name) && !/^[a-z0-9]$/.test(name)) {
+    errors.push(`${prefix}: "name" must start and end with a lowercase letter or number`);
+  }
+
+  if (name.includes("--") || name.includes("..")) {
+    errors.push(`${prefix}: "name" must not contain consecutive hyphens or periods`);
   }
 }