perf(sandbox): optimize Windows sandbox initialization via native ACL application

[ehedlund]

Summary

This PR optimizes the Windows sandbox initialization performance by offloading file system ACL modifications from Node.js to the native C# helper (GeminiSandbox.exe). This eliminates the overhead of spawning multiple icacls.exe processes.

Details

• Native ACL Application: Updated GeminiSandbox.cs to apply ACLs natively using .NET's FileSystemSecurity and P/Invoke (SetNamedSecurityInfo).
• Bulk Processing via Manifests: WindowsSandboxManager.ts now aggregates allowed and forbidden paths into temporary manifest files, which are passed to the helper via --allowed-manifest and --forbidden-manifest flags.
• Improved Isolation: The native helper now sets the "Low Mandatory Level" integrity label and adds explicit "Deny FullControl" rules for forbidden/secret files directly in the process setup phase.

Related Issues

N/A

How to Validate

Execute the unit and integration tests on a Windows environment:

npm run test -w @google/gemini-cli-core -- src/sandbox/windows
npm run test -w @google/gemini-cli-core -- src/services/sandboxManager.integration.test.ts

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
  • Windows
    • npm run
    • npx
    • Docker
  • Linux

[gemini-cli]

Hi @ehedlund, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly optimizes Windows sandbox initialization by replacing the previous Node.js-driven icacls process spawning with a native C# implementation. By aggregating path permissions into manifest files and performing bulk ACL operations within the native helper, the system achieves a more performant and robust initialization process while maintaining strict security boundaries.

Highlights

• Native ACL Application: Offloaded file system ACL modifications from Node.js to the native C# helper, reducing initialization overhead from O(N) to O(1).
• Bulk Manifest Processing: Implemented manifest-based path communication between Node.js and the native helper to efficiently handle allowed and forbidden paths.
• Enhanced Security: Improved sandbox isolation by natively setting Low Mandatory Level integrity labels and applying explicit Deny rules for sensitive files.
• Test Modernization: Updated the test suite to validate manifest generation and content, replacing reliance on external icacls process monitoring.

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[github-actions]

Size Change: -2.14 kB (-0.01%)

Total Size: 34 MB

Filename	Size	Change
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[gemini-code-assist]

Code Review

This pull request refactors the Windows sandbox security implementation by replacing individual icacls calls with a manifest-based approach. It introduces a C# helper to apply bulk ACLs and updates the TypeScript manager to generate forbidden and allowed path manifests. I have provided feedback regarding the optimization of P/Invoke calls and the use of GetLongPathName for security, as well as a suggestion to parallelize secret file scanning.

[spencer426]

Left a couple of comments regarding synchronous file system operations and the manifest file encoding.

[spencer426]

LGTM