diff --git a/.github/workflows/website-ci.yml b/.github/workflows/website-ci.yml
index e814a04..ac5f14b 100644
--- a/.github/workflows/website-ci.yml
+++ b/.github/workflows/website-ci.yml
@@ -36,6 +36,8 @@ jobs:
         run: npm ci
 
       - name: Build Next.js application
+        env:
+          MOTORSIGNAL_GIT_SHA: ${{ github.sha }}
         run: npm run build
 
       - name: Run Founder Portal tests
@@ -49,3 +51,6 @@ jobs:
 
       - name: Run Navigation and Auth tests
         run: node tests/navigation-auth.cjs
+
+      - name: Verify deployment revision contract
+        run: node tests/deployment-revision.test.cjs
diff --git a/scripts/deploy-website.ps1 b/scripts/deploy-website.ps1
index 5dbf9e2..0c9b117 100644
--- a/scripts/deploy-website.ps1
+++ b/scripts/deploy-website.ps1
@@ -21,7 +21,22 @@ if ($Key) {
     $SshKeyArgs = @("-i", $Key)
 }
 
+$RepositoryRoot = (Resolve-Path "$PSScriptRoot\..").Path
+$GitSha = (git -C $RepositoryRoot rev-parse HEAD).Trim()
+if ($GitSha -notmatch '^[0-9a-f]{40}$') {
+    Write-Error "Unable to resolve a valid 40-character Git revision."
+    exit 1
+}
+
+# Refuse dirty website inputs before assigning the HEAD revision
+$DirtyWebsite = (git -C $RepositoryRoot status --porcelain -- website).Trim()
+if ($DirtyWebsite) {
+    Write-Error "Cannot deploy website: working tree contains uncommitted changes under website/:`n$DirtyWebsite"
+    exit 1
+}
+
 $Timestamp = Get-Date -Format "yyyyMMdd-HHmmss"
+Write-Host ">>> Deploying website revision $GitSha" -ForegroundColor Cyan
 
 if ($BuildRemote) {
     # Ultra-lean mode: Upload only source files (~100 KB total)
@@ -29,7 +44,7 @@ if ($BuildRemote) {
     $TempTar = "$PSScriptRoot\$TarName"
 
     Write-Host ">>> 1. Packaging source code (~100 KB)..." -ForegroundColor Cyan
-    tar -czf "$TempTar" -C website app components lib public package.json tsconfig.json next.config.ts
+    tar -czf "$TempTar" -C "$RepositoryRoot\website" app components lib public package.json tsconfig.json next.config.ts
 
     Write-Host ">>> 2. Uploading source code to server..." -ForegroundColor Cyan
     scp @SshKeyArgs "$TempTar" "${User}@${HostIp}:/tmp/$TarName"
@@ -48,7 +63,7 @@ rm -f "`$TAR"
 
 cd "`$TARGET"
 echo "Running Next.js production build on server..."
-npm run build
+MOTORSIGNAL_GIT_SHA="$GitSha" npm run build
 
 echo "Restarting motorsignal-website service..."
 sudo systemctl restart motorsignal-website
@@ -60,13 +75,23 @@ echo "Done!"
     # Fast local build: Strip Next.js cache & dev artifacts (~2 MB total instead of 500 MB)
     Write-Host ">>> 1. Building Next.js application locally..." -ForegroundColor Cyan
     Set-Location -Path "$PSScriptRoot\..\website"
-    npm run build
-    Set-Location -Path "$PSScriptRoot\.."
+    $PreviousDeploySha = $env:MOTORSIGNAL_GIT_SHA
+    try {
+        $env:MOTORSIGNAL_GIT_SHA = $GitSha
+        npm run build
+    } finally {
+        if ($null -eq $PreviousDeploySha) {
+            Remove-Item Env:MOTORSIGNAL_GIT_SHA -ErrorAction SilentlyContinue
+        } else {
+            $env:MOTORSIGNAL_GIT_SHA = $PreviousDeploySha
+        }
+        Set-Location -Path $RepositoryRoot
+    }
 
     $TarName = "website-update-$Timestamp.tar.gz"
     $TempTar = "$PSScriptRoot\$TarName"
 
-    tar -czf "$TempTar" --exclude="cache" --exclude="dev" --exclude="standalone" -C website .next/server .next/static .next/types .next/BUILD_ID .next/*.json public package.json app components lib
+    tar -czf "$TempTar" --exclude="cache" --exclude="dev" --exclude="standalone" -C "$RepositoryRoot\website" .next/server .next/static .next/types .next/BUILD_ID .next/*.json public package.json app components lib
 
     $SizeMb = [math]::Round(((Get-Item "$TempTar").Length / 1MB), 2)
     Write-Host ">>> 3. Uploading $SizeMb MB to server..." -ForegroundColor Cyan
@@ -92,7 +117,15 @@ echo "Service restarted."
     ssh -t @SshKeyArgs "${User}@${HostIp}" $RemoteCmd
 }
 
-Write-Host ">>> 5. Checking website response..." -ForegroundColor Green
+Write-Host ">>> 5. Checking deployed revision..." -ForegroundColor Green
 Start-Sleep -Seconds 2
-$StatusCode = (Invoke-WebRequest -Uri "https://motorsignal.app/account" -Method Head -UseBasicParsing).StatusCode
-Write-Host ">>> Deployed successfully! HTTP Status: $StatusCode" -ForegroundColor Green
+$Version = Invoke-RestMethod -Uri "https://motorsignal.app/api/version" -Method Get
+if ($Version.status -ne "ok" -or $Version.service -ne "motorsignal-website") {
+    Write-Error "Website version endpoint returned an unhealthy response."
+    exit 1
+}
+if ($Version.revision -ne $GitSha) {
+    Write-Error "Deployment revision mismatch. Expected $GitSha but production reports $($Version.revision)."
+    exit 1
+}
+Write-Host ">>> Deployed successfully! Verified revision: $($Version.shortRevision)" -ForegroundColor Green
diff --git a/website/app/api/version/route.ts b/website/app/api/version/route.ts
new file mode 100644
index 0000000..b9e19e5
--- /dev/null
+++ b/website/app/api/version/route.ts
@@ -0,0 +1,21 @@
+import { NextResponse } from 'next/server';
+
+export const dynamic = 'force-dynamic';
+
+export function GET() {
+  const revision = process.env.MOTORSIGNAL_DEPLOY_REVISION || 'unknown';
+
+  return NextResponse.json(
+    {
+      status: 'ok',
+      service: 'motorsignal-website',
+      revision,
+      shortRevision: revision === 'unknown' ? 'unknown' : revision.slice(0, 12),
+    },
+    {
+      headers: {
+        'Cache-Control': 'no-store, max-age=0',
+      },
+    },
+  );
+}
diff --git a/website/next.config.ts b/website/next.config.ts
index fa1e26a..307fce8 100644
--- a/website/next.config.ts
+++ b/website/next.config.ts
@@ -1,9 +1,15 @@
 import type { NextConfig } from 'next';
 
+const deployRevision = process.env.MOTORSIGNAL_GIT_SHA?.trim() || 'unknown';
+
 const nextConfig: NextConfig = {
   output: 'standalone',
   poweredByHeader: false,
   reactStrictMode: true,
+  env: {
+    // Embedded at build time so /api/version identifies the exact deployed source.
+    MOTORSIGNAL_DEPLOY_REVISION: deployRevision,
+  },
 };
 
 export default nextConfig;
diff --git a/website/tests/deployment-revision.test.cjs b/website/tests/deployment-revision.test.cjs
new file mode 100644
index 0000000..6d63223
--- /dev/null
+++ b/website/tests/deployment-revision.test.cjs
@@ -0,0 +1,23 @@
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const root = path.resolve(__dirname, '..', '..');
+const route = fs.readFileSync(path.join(root, 'website/app/api/version/route.ts'), 'utf8');
+const config = fs.readFileSync(path.join(root, 'website/next.config.ts'), 'utf8');
+const deploy = fs.readFileSync(path.join(root, 'scripts/deploy-website.ps1'), 'utf8');
+
+assert.match(config, /MOTORSIGNAL_GIT_SHA/);
+assert.match(config, /MOTORSIGNAL_DEPLOY_REVISION/);
+assert.match(route, /service: 'motorsignal-website'/);
+assert.match(route, /revision/);
+assert.match(route, /Cache-Control/);
+assert.match(route, /no-store/);
+assert.match(deploy, /git -C \$RepositoryRoot rev-parse HEAD/);
+assert.match(deploy, /MOTORSIGNAL_GIT_SHA/);
+assert.match(deploy, /https:\/\/motorsignal\.app\/api\/version/);
+assert.match(deploy, /Deployment revision mismatch/);
+assert.match(deploy, /status --porcelain -- website/);
+assert.match(deploy, /working tree contains uncommitted changes/);
+
+console.log('PASS: website deployment revision contract verified.');