perf(cli): cache loadSettings to reduce redundant disk I/O at startup

[sehoon38]

Summary

This PR caches the results of loadSettings to reduce redundant disk I/O and configuration merging overhead during CLI startup and initialization.

Details

• Implemented an in-memory cache with a 30-second TTL for loadSettings in packages/cli/src/config/settings.ts using the core createCache utility. This covers the burst of reads that happen natively when launching the CLI or executing a sub-process.
• saveSettings now clears the cache to ensure that changes take effect immediately.
• Added resetSettingsCacheForTesting() for test isolation.
• Added robust unit testing for the cache hit rates and clearing logic in packages/cli/src/config/settings.test.ts.

Related Issues

Fixes #17988

How to Validate

1. Run the test suite:
   npm test -w @google/gemini-cli -- src/config/settings.test.ts
2. Start the CLI normally and ensure there's no functionality degradation.

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-cli]

Hi @sehoon38, 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 focuses on enhancing the performance of the CLI by introducing a caching layer for configuration loading. The primary goal is to minimize repetitive disk I/O operations and reduce the computational overhead associated with merging various configuration settings, thereby leading to a faster and more efficient startup experience for the command-line interface.

Highlights

• Performance Improvement: Implemented an in-memory cache for loadSettings with a 5-second TTL to significantly reduce redundant disk I/O and configuration merging overhead during CLI startup.
• Cache Management: Modified saveSettings to automatically clear the loadSettings cache, ensuring that any configuration changes are immediately reflected in subsequent loads.
• Testability and Validation: Introduced a dedicated resetSettingsCacheForTesting() function for improved test isolation and added comprehensive unit tests to validate the new caching logic and its behavior.

Changelog

• packages/cli/src/config/settings.test.ts
  • Imported the new resetSettingsCacheForTesting utility.
  • Added a call to resetSettingsCacheForTesting() in the beforeEach hook to ensure test isolation.
  • Introduced a new test suite specifically for the caching mechanism, covering scenarios like cache hits, separate caches for different workspaces, and cache invalidation upon saving settings.
• packages/cli/src/config/settings.ts
  • Imported the createCache utility from @google/gemini-cli-core.
  • Defined and initialized settingsCache as an in-memory cache with a 5-second Time-To-Live (TTL).
  • Exported resetSettingsCacheForTesting() to allow clearing the cache, primarily for testing purposes.
  • Refactored loadSettings to utilize the settingsCache, retrieving existing settings or delegating to a new internal function for initial loading.
  • Renamed the original implementation of loadSettings to _doLoadSettings and made it a private function.
  • Added a call to settingsCache.clear() within saveSettings to ensure the cache is invalidated when settings are modified and saved.

Activity

• No specific activity has been recorded for this pull request yet.

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[gemini-code-assist]

Code Review

This pull request introduces an in-memory cache for loadSettings to improve startup performance by reducing disk I/O. The implementation correctly uses a cache with a 5-second TTL and invalidates it when settings are saved. The associated tests are well-written and cover the new caching logic. I have one suggestion to make the cache invalidation more granular for an even greater performance benefit, aligning with our caching guidelines.

[github-actions]

Size Change: +336 B (0%)

Total Size: 26 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.6 MB	+336 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

_{compressed-size-action}

[scidomino]

I'm worried that caching is not the right way to do this. There are a lot of processes that load the settings after modifying them and this would make it break if you try to do that twice within 30 seconds (like uninstalling and reinstalling an extension).

[scidomino]

To keep things simple, we should just invalidate the entire cache every time. The extra complexity is not worth it.