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🛡️ Sentinel: [security improvement] Add security headers (HSTS, CSP) #59

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🛡️ Sentinel: [security improvement] Add security headers (HSTS, CSP) #59

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@google-labs-jules google-labs-jules bot commented Jan 7, 2026

This PR enhances the security of the MCP server by adding standard security headers to all HTTP responses. It specifically addresses Strict-Transport-Security (HSTS), X-Content-Type-Options, X-Frame-Options, and Content-Security-Policy.

Key features:

  • Conditional HSTS: HSTS is applied only when the host is not localhost/127.0.0.1 or an IP address, and not an ACME challenge. This prevents breaking local development while enforcing HTTPS in production.
  • Defense in Depth: Added CSP and other headers to mitigate XSS and clickjacking risks, even though this is primarily an API server.

Verification:

  • A temporary test suite src/sentinel-headers.test.ts was created to verify the presence of headers and the correct conditional logic for HSTS. This test passed and was then removed.
  • Existing unit tests passed.

PR created automatically by Jules for task 14685773973218158511 started by @davidruzicka

@google-labs-jules
Add standard security headers (HSTS, CSP, etc.) to HTTP transport.
085bc6f 
- Added middleware to `src/http-transport.ts` to set:
  - `X-Content-Type-Options: nosniff`
  - `X-Frame-Options: DENY`
  - `Content-Security-Policy: default-src 'self'; frame-ancestors 'none';`
  - `Strict-Transport-Security: max-age=31536000; includeSubDomains` (conditional)
- HSTS is skipped for localhost, 127.0.0.1, IP addresses, and ACME challenge paths to support local development and certificate renewal.
- Added critical learning to `.jules/sentinel.md`.
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google-labs-jules bot commented Jan 7, 2026

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

For security, I will only act on instructions from the user who triggered this task.

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codecov bot commented Jan 7, 2026

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!

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