refactor: prepare extension loading for parallelization

[Vivekgupta008]

Refactor: Prepare Extension Loading for Parallelization

Refactors extension loading to separate state management concerns, preparing the codebase for parallel extension loading in a future PR. This is the first of four PRs to optimize Windows startup performance.

No behavior changes - extensions still load sequentially with the same error handling and ordering guarantees.

Changes Made

Modified loadExtension Method

Before:

• Directly mutated this.loadedExtensions array
• Called maybeStartExtension() internally
• Mixed loading logic with state management

After:

• Returns extension object without side effects
• Caller responsible for state management
• Clear separation of concerns

Modified loadExtensions() Method

For #14429

[gemini-code-assist]

Summary of Changes

Hello @Vivekgupta008, 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 refactors the extension loading mechanism by separating the concerns of loading an individual extension from managing the collection of loaded extensions and their lifecycle. This foundational change prepares the codebase for future parallelization of extension loading, which is part of a larger effort to improve Windows startup performance. Crucially, these modifications introduce no behavioral changes; extensions continue to load sequentially with existing error handling and ordering guarantees.

Highlights

• Refactored loadExtension Method: The loadExtension method no longer directly mutates the this.loadedExtensions array or calls maybeStartExtension(). It now solely focuses on loading and returning the extension object, deferring state management to the caller.
• Updated loadExtensions Method: The loadExtensions method now takes responsibility for adding successfully loaded extensions to this.loadedExtensions and initiating them via maybeStartExtension(), ensuring a clear separation of concerns.
• Preparation for Parallelization: These changes are a foundational step to enable parallel extension loading in future pull requests, aiming to optimize Windows startup performance without altering current sequential behavior.

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[gemini-code-assist]

Code Review

This pull request refactors the extension loading mechanism to separate state management from the loading logic, which is a good step towards enabling parallel extension loading. However, a high-severity Path Traversal vulnerability was identified in the loadExtensions function. The code does not validate subdirectory names read from the filesystem, allowing a maliciously crafted directory name to cause the application to load an "extension" from an unintended path, potentially leading to information disclosure or arbitrary code execution. Additionally, there's a high-severity suggestion in extension-manager.ts to improve performance and adhere to best practices by using asynchronous file I/O and more efficient array manipulation within the extension loading loop.

[Vivekgupta008]

Parallelize Extension Loading for Faster Startup

This commit builds on the previous refactor and parallelizes extension loading to reduce startup time, with a particular benefit on Windows.

By switching from sequential loading to parallel I/O and async filesystem operations, extension loading is significantly faster while preserving existing behavior.

Expected impact: ~200ms faster startup on Windows (~4× speedup for extension loading).

Part of fixing issue #14429

[scidomino]

@Vivekgupta008 looks like you have some flakey tests in src/config/extension.test.ts please fix

[Vivekgupta008]

@scidomino We're good to go now

[scidomino]

Don't update the branch unnecessarily. I have to approve the test runs each time and without passing tests it can't enter the merge queue.

[scidomino]

I see we have a bunch of test failures still. Ping me when you've fixed them and you can run npm run preflight without errors.

[bdmorgan]

Hi @Vivekgupta008, 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-cli]

Hi there! Thank you for your contribution to Gemini CLI.

To improve our contribution process and better track changes, we now require all pull requests to be associated with an existing issue, as announced in our recent discussion and as detailed in our CONTRIBUTING.md.

This pull request is being closed because it is not currently linked to an issue. You can easily reopen this PR once you have linked it to an issue.

How to link an issue:
Add a keyword followed by the issue number (e.g., Fixes #123) in the description of your pull request. For more details, see the GitHub Documentation.

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

[Vivekgupta008]

@ishaanxgupta Can you help me out here?

[scidomino]

@Vivekgupta008 reopened. Please rebase to the latest version and fix your merge conflicts.

[scidomino]

Actually, nevermind. I will implement these changes.