fix(cli): fall back to embedded macOS seatbelt profiles if missing

[amelidev]

Summary

This PR resolves the critical startup crash when running Gemini CLI in sandbox mode (-s) on macOS/gMac environments where static Seatbelt .sb profiles are not found in the runfiles or bundle folder.

Details

• The Problem: Non-JS static assets (like .sb seatbelt profiles) are often stripped or omitted from the deployed bundle (e.g. bundle/gemini.js or gemini.mjs in Bazel/google3) because they are not traced by standard JS bundlers/packagers.
• The Solution: We embed the contents of the six built-in macOS seatbelt profiles inside sandboxBuiltinProfiles.ts.
• The Fallback: If fs.existsSync(profileFile) returns false at runtime, we fall back to writing the embedded profile string to a unique, randomized temporary file under os.tmpdir() (gemini-sandbox-macos-${profile}-${rand}.sb).
• Dynamic Cleanup: We register cleanup listeners strictly on the 'exit' event (to avoid signal hijacking / process lockup of SIGINT/SIGTERM handlers) and on spawned child process termination (close, error) to cleanly unlink the temporary file.
• Security Hardening (NODE_OPTIONS Quoting): Escaped/quoted the NODE_OPTIONS argument string via the quote utility inside the sh -c invocation to neutralize potential shell command injection vulnerabilities.
• Backward Compatibility: Original local development behavior remains completely unchanged, as the fallback ONLY triggers if the physical .sb file is missing.

Related Issues

Resolves the issue reported in issue.md.

How to Validate

We have added robust unit test coverage to verify this fallback behavior. Run the targeted tests for the touched module:

npm test -w @google/gemini-cli -- src/utils/sandbox.test.ts

All 22 tests (including our new fallback test) compile, pass, and satisfy all linting rules cleanly!

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
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[github-actions]

📊 PR Size: size/L

• Lines changed: 937
• Additions: +800
• Deletions: -137
• Files changed: 3

[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 resolves a critical startup crash in the Gemini CLI's sandbox mode on macOS, which occurred when static Seatbelt profiles were missing from the bundle. By embedding these profiles directly into the source code, the CLI can now dynamically generate the necessary sandbox configuration at runtime, ensuring consistent behavior across different deployment environments.

Highlights

• Embedded Seatbelt Profiles: Added a new utility file containing the six built-in macOS seatbelt profiles to ensure they are available even when static files are missing from the deployment bundle.
• Runtime Fallback Mechanism: Implemented a fallback in the sandbox initialization logic that writes embedded profiles to a temporary file in the system's temporary directory if the expected .sb file is not found on disk.
• Automatic Cleanup: Added robust cleanup logic to ensure temporary profile files are unlinked upon process exit, termination signals, or child process completion.

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[gemini-code-assist]

Code Review

This pull request implements a fallback mechanism for the macOS seatbelt sandbox, writing embedded profile contents to a temporary file when the profile is missing on disk, and adds corresponding unit tests. Feedback on these changes highlights a potential command injection vulnerability when constructing the shell command with unescaped NODE_OPTIONS. Additionally, the feedback advises against registering custom SIGINT and SIGTERM handlers for temporary file cleanup, as they can hijack termination signals and prevent the CLI process from exiting properly, suggesting to rely solely on the exit event instead.