diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index 232a2de..f04b1ca 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -6,8 +6,8 @@ on:
   workflow_dispatch:
   repository_dispatch:
     types: [repl-released]
-  schedule:
-    - cron: '0 6 * * *'
+#  schedule:
+#    - cron: '0 6 * * *'
 
 permissions:
   contents: read
diff --git a/.github/workflows/validate-docs.yml b/.github/workflows/validate-docs.yml
new file mode 100644
index 0000000..ab4eb49
--- /dev/null
+++ b/.github/workflows/validate-docs.yml
@@ -0,0 +1,63 @@
+name: Validate docs
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout website
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: npm
+
+      - name: Install npm dependencies
+        run: npm ci
+
+      - name: Validate documentation invariants
+        run: npm run docs:validate
+
+      # The Astro build needs generated API-reference content (src/generated/api-reference.json),
+      # produced by `docs:api` from DocFX metadata over the Repl source — mirrors the Repl source
+      # checkout and DocFX setup already proven in .github/workflows/deploy.yml.
+      - name: Resolve latest Repl release tag
+        id: latest-tag
+        run: |
+          tag=$(gh release list --repo yllibed/repl --limit 1 --json tagName -q '.[0].tagName')
+          echo "Resolved tag: $tag"
+          echo "tag=$tag" >> "$GITHUB_OUTPUT"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Checkout Repl source at release tag
+        uses: actions/checkout@v4
+        with:
+          repository: yllibed/repl
+          ref: ${{ steps.latest-tag.outputs.tag }}
+          path: ./repl-source
+          fetch-depth: 0
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.x'
+
+      - name: Install DocFX
+        run: dotnet tool install -g docfx
+
+      - name: Build API reference and Astro site
+        run: npm run build
+        env:
+          ASTRO_TELEMETRY_DISABLED: '1'
diff --git a/package.json b/package.json
index 3d4b6b2..30ba80a 100644
--- a/package.json
+++ b/package.json
@@ -9,6 +9,7 @@
     "start": "astro dev",
     "docs:api": "node ./scripts/build-api-docs.mjs",
     "docs:api:mdx": "node ./scripts/generate-api-mdx.mjs",
+    "docs:validate": "node ./scripts/validate-docs.mjs",
     "prebuild": "npm run docs:api",
     "build": "astro build",
     "preview": "astro preview",
diff --git a/scripts/validate-docs.mjs b/scripts/validate-docs.mjs
new file mode 100644
index 0000000..9e86474
--- /dev/null
+++ b/scripts/validate-docs.mjs
@@ -0,0 +1,184 @@
+#!/usr/bin/env node
+import fs from 'node:fs';
+import path from 'node:path';
+
+const repoRoot = process.cwd();
+const errors = [];
+const replMcpAsServerPattern = /`?Repl\.Mcp`?[\s`'".,;:)\]]+\bis\s+(?:an?|the)\s+MCP server/i;
+
+function fail(file, line, message) {
+  const location = line ? `${file}:${line}` : file;
+  errors.push(`${location}\n  ${message}`);
+}
+
+function readText(file) {
+  return fs.readFileSync(path.join(repoRoot, file), 'utf8');
+}
+
+function walk(dir) {
+  const absolute = path.join(repoRoot, dir);
+  if (!fs.existsSync(absolute)) return [];
+  const entries = fs.readdirSync(absolute, { withFileTypes: true });
+  const files = [];
+  for (const entry of entries) {
+    const relative = path.join(dir, entry.name);
+    if (entry.isDirectory()) {
+      if (['.git', 'node_modules', 'dist', '.astro'].includes(entry.name)) continue;
+      files.push(...walk(relative));
+    } else if (/\.(mdx|md|txt)$/.test(entry.name)) {
+      files.push(relative.replaceAll(path.sep, '/'));
+    }
+  }
+  return files;
+}
+
+function extractJsonBlocks(file, text) {
+  const lines = text.split(/\r?\n/);
+  const blocks = [];
+  let inJson = false;
+  let startLine = 0;
+  let buffer = [];
+
+  for (let index = 0; index < lines.length; index += 1) {
+    const line = lines[index];
+    const trimmed = line.trim();
+
+    if (!inJson && /^```json\b/.test(trimmed)) {
+      inJson = true;
+      startLine = index + 2;
+      buffer = [];
+      continue;
+    }
+
+    if (inJson && trimmed === '```') {
+      blocks.push({ file, startLine, text: buffer.join('\n') });
+      inJson = false;
+      buffer = [];
+      continue;
+    }
+
+    if (inJson) buffer.push(line);
+  }
+
+  if (inJson) {
+    fail(file, startLine - 1, 'JSON code fence must be closed with ``` before end of file.');
+  }
+
+  return blocks;
+}
+
+function validateServerConfig(block) {
+  const relevant = /"(?:mcpServers|servers)"|McpServerSample\.csproj/.test(block.text);
+  if (!relevant) return;
+
+  let parsed;
+  try {
+    parsed = JSON.parse(block.text);
+  } catch (error) {
+    fail(block.file, block.startLine, `MCP host JSON must be valid copy/paste JSON: ${error.message}`);
+    return;
+  }
+
+  validateServerMap(block, parsed.mcpServers, 'mcpServers');
+  validateServerMap(block, parsed.servers, 'servers');
+}
+
+function validateServerMap(block, serverMap, key) {
+  if (!serverMap || typeof serverMap !== 'object' || Array.isArray(serverMap)) return;
+
+  for (const [name, server] of Object.entries(serverMap)) {
+    if (!server || typeof server !== 'object') continue;
+
+    if (key === 'servers' && server.command && server.type !== 'stdio') {
+      fail(
+        block.file,
+        block.startLine,
+        `VS Code-style server "${name}" uses top-level "servers" but is missing "type": "stdio".`
+      );
+    }
+
+    const command = server.command;
+    const args = Array.isArray(server.args) ? server.args : [];
+    const launchesDotnetProject = command === 'dotnet'
+      && args.includes('run')
+      && args.includes('--project')
+      && args.some((arg) => typeof arg === 'string' && arg.endsWith('.csproj'));
+
+    if (launchesDotnetProject) {
+      const noBuildIndex = args.indexOf('--no-build');
+      const dashDashIndex = args.indexOf('--');
+      const hasNoBuildOption = noBuildIndex !== -1 && (dashDashIndex === -1 || noBuildIndex < dashDashIndex);
+      if (!hasNoBuildOption) {
+        fail(
+          block.file,
+          block.startLine,
+          `MCP host server "${name}" runs a .csproj with dotnet run but does not include "--no-build" before the "--" application-argument separator.`
+        );
+      }
+    }
+  }
+}
+
+function validateMcpHostDocs(file, text) {
+  if (replMcpAsServerPattern.test(text)) {
+    fail(file, findLine(text, 'Repl.Mcp'), 'Describe Repl.Mcp as the component used to build MCP servers, not as the MCP server itself.');
+  }
+
+  if (file.endsWith('cookbook/mcp-server.mdx') && text.includes('## Agent-host setup')) {
+    const section = text.split('## Agent-host setup', 2)[1].split('\n## ', 1)[0];
+
+    if (!section.includes('dotnet build samples/08-mcp-server/McpServerSample.csproj')) {
+      fail(file, findLine(text, '## Agent-host setup'), 'Agent-host setup should tell users to build the local sample before configuring an MCP host.');
+    }
+
+    if (!section.includes('"--no-build"')) {
+      fail(file, findLine(text, '## Agent-host setup'), 'Agent-host setup must use "--no-build" for dotnet-run host configs.');
+    }
+
+    if (!section.includes('"repl-contacts-sample"')) {
+      fail(file, findLine(text, '## Agent-host setup'), 'Agent-host setup should use the shared sample server name "repl-contacts-sample".');
+    }
+
+    if (section.includes('.vscode/mcp.json') && !section.includes('"servers"')) {
+      fail(file, findLine(text, '.vscode/mcp.json'), 'VS Code .vscode/mcp.json examples must use top-level "servers", not only "mcpServers".');
+    }
+  }
+}
+
+function validateLlmsTxt(file, text) {
+  if (!file.endsWith('llms.txt')) return;
+
+  if (text.includes('For Coding Agents') && !text.includes('/getting-started/for-coding-agents/')) {
+    fail(file, findLine(text, 'For Coding Agents'), 'llms.txt mentions For Coding Agents but does not link the canonical page.');
+  }
+
+  if (replMcpAsServerPattern.test(text)) {
+    fail(file, findLine(text, 'Repl.Mcp'), 'llms.txt should say Repl.Mcp is the component; the app is the MCP server.');
+  }
+}
+
+function findLine(text, needle) {
+  const lines = text.split(/\r?\n/);
+  const index = lines.findIndex((line) => line.includes(needle));
+  return index === -1 ? 1 : index + 1;
+}
+
+const files = [
+  ...walk('src/content/docs'),
+  ...walk('public'),
+].sort();
+
+for (const file of files) {
+  const text = readText(file);
+  validateMcpHostDocs(file, text);
+  validateLlmsTxt(file, text);
+  for (const block of extractJsonBlocks(file, text)) validateServerConfig(block);
+}
+
+if (errors.length > 0) {
+  console.error(`Documentation validation failed with ${errors.length} issue(s):\n`);
+  for (const error of errors) console.error(`- ${error}\n`);
+  process.exit(1);
+}
+
+console.log(`Documentation validation passed (${files.length} files checked).`);