fix(cli): resolve bunx execution -S not found error on Windows

[ilkerozgedik]

Summary

Fixed execution failure on Windows when running bunx @google/gemini-cli. The shebang #!/usr/bin/env -S node --no-warnings=DEP0040 uses the -S flag which is a GNU env extension not supported on Windows, causing:

error: interpreter executable "-S" not found in %PATH%

Details

• Replaced shebang with #!/usr/bin/env node in both entry points (packages/cli/index.ts, packages/a2a-server/src/http/server.ts)
• Moved DEP0040 (punycode deprecation) suppression to a dedicated suppress-warnings.ts module that is imported first — this correctly handles ESM module hoisting, ensuring the override runs before any other module is evaluated

Related Issues

Closes #24654

How to Validate

On a Windows machine:

• Run bunx @google/gemini-cli — should launch without any error
• Previously would fail with: error: interpreter executable "-S" not found in %PATH%

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

[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 addresses a compatibility issue where the use of the -S flag in shebang lines caused execution errors on Windows systems when using tools like bunx. By shifting the suppression of deprecation warnings from the shebang to a runtime programmatic check, the project ensures a more robust and cross-platform execution experience for developers.

Highlights

• Shebang Update: Removed the unsupported -S flag from the shebang lines in executable files to ensure compatibility with Windows environments.
• Warning Suppression: Implemented a programmatic interception of process.emitWarning to suppress DEP0040 (punycode deprecation) warnings, replacing the previous command-line flag approach.

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[gemini-code-assist]

Code Review

This pull request replaces shebang-based warning suppression with a manual override of process.emitWarning in packages/a2a-server/src/http/server.ts and packages/cli/index.ts to ensure compatibility across platforms like Windows. The review feedback correctly identifies that due to ESM hoisting, static imports are evaluated before the suppression logic, which may allow deprecation warnings to leak during the initial module load. The reviewer suggests using dynamic imports or a dedicated initialization module to ensure the override is active before any dependencies are processed.

[gemini-code-assist]

In ECMAScript Modules (ESM), static import statements are hoisted and evaluated before the module body runs. This means the process.emitWarning override will execute only after all static imports (including those on lines 22-23 and their transitive dependencies) have been fully evaluated. If any of these modules trigger the punycode deprecation warning during their evaluation, the suppression will be ineffective.

To correctly suppress warnings during module loading in ESM, you should either:

1. Move the suppression logic to a separate file and import it as the very first import in this file.
2. Use dynamic import() for all dependencies after the override logic.

References

1. When a new file is intended to replace a file that will be deprecated, it is acceptable to duplicate definitions from the old file to avoid creating a dependency on the code that is being phased out.

[gemini-code-assist]

In ESM, static import statements are hoisted and evaluated before the module body. Consequently, the process.emitWarning override will run after the modules on lines 19-21 have been loaded, making the suppression ineffective if they trigger the warning during evaluation. Using dynamic import() ensures the override is active before the modules are loaded.

// Suppress DEP0040 (Punycode deprecation warning) safely, as Windows limits shebang flags.
const originalEmitWarning = process.emitWarning;
process.emitWarning = ((...args: unknown[]) => {
  const [warning, type, code] = args;
  if (type === 'DEP0040' || code === 'DEP0040' || (type === 'DeprecationWarning' && String(warning).includes('punycode'))) {
    return;
  }
  return Reflect.apply(originalEmitWarning, process, args);
}) as typeof process.emitWarning;

const { main } = await import('./src/gemini.js');
const { FatalError, writeToStderr } = await import('@google/gemini-cli-core');
const { runExitCleanup } = await import('./src/utils/cleanup.js');