Initial support for reloading extensions in the CLI - mcp servers only by jakemac53 · Pull Request #12239 · google-gemini/gemini-cli

jakemac53 · 2025-10-29T18:07:10Z

Summary

Adds support for unloading and reloading extensions MCP servers within the interactive CLI, based on events sent from the ExtensionLoader.

Details

The only time this can happen today is in response to an /extensions update command, which causes an "unload" and then "load" event.

On "unload" or "disable" we will shut down all previous MCP servers from an extension, and clear the tools from the tool manager and gemini chat context.

On "load" or "enable" we start up any MCP servers from an extension, and add its tools to the tool manager and gemini chat context.

This functionality is guarded behind an experimental.extensionReloading setting.

I also updated the discovery state management in the McpClientManager to avoid race conditions.

Because this is so intertwined across different systems, I wrote an integration test instead of unit tests. If you would like, I could also add unit tests for some of it, but they won't be very valuable imo.

Related Issues

First part of #11108

How to Validate

Install an extension, add an update to it (add a new mcp server), and update it using /extensions update <your-extension>. You should see its status show as updated, and if running /mcp list you should see the new mcp server connected. You should also be able to use gemini to invoke those tools.

Pre-Merge Checklist

…disabled or unloaded/loaded

…rnal gemini state for tools

gemini-code-assist · 2025-10-29T18:07:37Z

Summary of Changes

Hello @jakemac53, 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 implements initial support for dynamically reloading extensions in the interactive CLI, specifically for MCP (Model Context Protocol) servers. This enhancement allows the CLI to respond to extension updates, enabling, or disabling by seamlessly unloading and reloading the affected MCP servers and their associated tools without needing a full application restart. The feature is opt-in via an experimental setting and includes robust handling for discovery state management to ensure stability during these dynamic operations.

Highlights

Dynamic Extension Reloading: Introduced the capability to unload and reload extensions for MCP servers within the interactive CLI without requiring a full application restart.
Event-Driven Reloading: Reloading is triggered by events from the ExtensionLoader, such as those occurring after an /extensions update command.
MCP Server Management: Unload/disable events now correctly shut down associated MCP servers and clear their tools from the tool manager and Gemini chat context. Conversely, load/enable events start MCP servers and integrate their tools.
Experimental Feature Flag: This new functionality is controlled by an experimental.extensionReloading setting, allowing for controlled rollout.
Race Condition Prevention: The McpClientManager's discovery state management has been updated to prevent race conditions during extension loading and unloading.
Integration Test Coverage: A new integration test (extensions-reload.test.ts) has been added to validate the end-to-end reloading process, covering the complex interactions between different systems.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	`/gemini review`	Performs a code review for the current pull request in its current state.
Pull Request Summary	`/gemini summary`	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	`/gemini help`	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

gemini-code-assist

Code Review

This pull request introduces experimental support for reloading extensions in the interactive CLI, which is a great enhancement for developer experience. The implementation correctly wires the new extensionReloading setting through the configuration and UI components. The addition of an integration test is also very valuable for such a cross-cutting feature.

My review focuses on a couple of critical race conditions in the McpClientManager that could lead to incorrect state when loading or unloading extensions with multiple MCP servers. I've also pointed out a potential bug in the UI that could display "undefined" to the user, and a source of potential flakiness in the new integration test. Addressing these issues will make the feature more robust.

gemini-code-assist · 2025-10-29T18:09:22Z

+  await run.expectText(
+    'Extension "test-extension" successfully updated: 0.0.1 → 0.0.2',
+  );
+  await new Promise((resolve) => setTimeout(resolve, 1000));


Using a fixed setTimeout can lead to flaky tests, especially in a CI environment where performance can vary. If the reload operation takes longer than 1 second, the test will fail. Conversely, if it's much faster, the test is unnecessarily slow.

A more robust approach would be to poll for a specific condition that indicates the reload is complete. For instance, you could repeatedly run /extensions list and check the output until the version is v0.0.2 or the status is (updated). Your TestRig or InteractiveRun could be enhanced with a polling helper for this purpose.

chrstnb · 2025-10-29T18:24:55Z

+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { expect, test } from 'vitest';


Can you test when env vars are changed?

Oh interesting, so like if the extension has settings, and on update you have to add new settings, does it pick those up?

chrstnb · 2025-10-29T18:28:58Z

+  }
+
+  /**
+   * For all the MCP servers associated with this extension:


Wondering if we can/should store session IDs for http connections to persist

Hmm yeah that could be interesting but I think probably isn't worth the complexity right now. But, worth filing a bug to track?

Sg-- I think unexpectedly losing state for a user is something we'd want to be careful to avoid

chrstnb · 2025-10-29T18:31:33Z

How can we ensure the prompt is accurate and not polluted by the previous state?

jakemac53 · 2025-10-29T18:32:55Z

How can we ensure the prompt is accurate and not polluted by the previous state?

I was trying to avoid using the model in these tests but I could actually make it call into the model - basically ask it to make a tool call to the old tool, and check that it can't do that. Or, ask it what tools it has available.

jakemac53 · 2025-10-29T18:35:44Z

Another option regarding the tests is I could try setting up a unit test but one that doesn't many or even any mocks, and then I could potentially validate the internals a bit better (like the exact tool list available to the GeminiChat).

…appears and can be missed

github-actions · 2025-10-29T20:00:51Z

Size Change: +5.06 kB (+0.02%)

Total Size: 20.3 MB

Filename	Size	Change
`./bundle/gemini.js`	20.3 MB	+5.06 kB (+0.02%)

ℹ️ View Unchanged

Filename	Size
`./bundle/sandbox-macos-permissive-closed.sb`	1.03 kB
`./bundle/sandbox-macos-permissive-open.sb`	890 B
`./bundle/sandbox-macos-permissive-proxied.sb`	1.31 kB
`./bundle/sandbox-macos-restrictive-closed.sb`	3.29 kB
`./bundle/sandbox-macos-restrictive-open.sb`	3.36 kB
`./bundle/sandbox-macos-restrictive-proxied.sb`	3.56 kB

_{compressed-size-action}

jakemac53 · 2025-10-29T21:56:36Z

Ok, I took a look at trying to do more of a unit test but I ran into a number of issues. Abandoning that for now, integration test it is.

…he CLI - mcp servers only (google-gemini#12239)

jakemac53 added 6 commits October 28, 2025 19:43

disconnect and reconnect extension mcp servers when they are enabled/…

078957c

…disabled or unloaded/loaded

fix potential race conditions for the mcp discovery state, reset inte…

f4735d8

…rnal gemini state for tools

reset the mcpServer config variable as well

e0bd22d

add experimental extension reloading setting

2f96ee6

make sure to unregister the tools in the mcp client as well

50ed615

revert debugging change to app container

d1f6e9a

jakemac53 requested a review from chrstnb October 29, 2025 18:07

jakemac53 requested a review from a team as a code owner October 29, 2025 18:07

Merge branch 'main' into reload-mcp-servers

707db7c

gemini-code-assist Bot reviewed Oct 29, 2025

View reviewed changes

chrstnb reviewed Oct 29, 2025

View reviewed changes

remove the check for the mcp server connections because that text dis…

2bb87de

…appears and can be missed

fix up some test mocks

c17e73f

fix the at command processor test as well

b30c41b

chrstnb approved these changes Oct 30, 2025

View reviewed changes

jakemac53 added 4 commits October 30, 2025 15:52

ensure we always send the batch update ended notification

b042669

run in debug mode

efd2576

skip extension reload test in sandbox mode

ad2950f

skip on windows also

0dffbff

jakemac53 enabled auto-merge October 30, 2025 17:58

jakemac53 added this pull request to the merge queue Oct 30, 2025

Merged via the queue into main with commit cc08133 Oct 30, 2025
22 checks passed

jakemac53 deleted the reload-mcp-servers branch October 30, 2025 18:15

thacio added a commit to thacio/auditaria that referenced this pull request Oct 31, 2025

Merge Commit 'cc08133': Initial support for reloading extensions in t…

30d8473

…he CLI - mcp servers only (google-gemini#12239)

chrstnb mentioned this pull request Dec 4, 2025

Allow reloading hooks to support whole-extension reloading #14531

Closed

Conversation

jakemac53 commented Oct 29, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Details

Related Issues

How to Validate

Pre-Merge Checklist

Uh oh!

gemini-code-assist Bot commented Oct 29, 2025

Summary of Changes

Highlights

Footnotes

Uh oh!

gemini-code-assist Bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

Uh oh!

Uh oh!

gemini-code-assist Bot Oct 29, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!

chrstnb Oct 29, 2025

Choose a reason for hiding this comment

Uh oh!

jakemac53 Oct 29, 2025

Choose a reason for hiding this comment

Uh oh!

chrstnb Oct 29, 2025

Choose a reason for hiding this comment

Uh oh!

jakemac53 Oct 29, 2025

Choose a reason for hiding this comment

Uh oh!

chrstnb Oct 29, 2025

Choose a reason for hiding this comment

Uh oh!

chrstnb commented Oct 29, 2025

Uh oh!

jakemac53 commented Oct 29, 2025

Uh oh!

jakemac53 commented Oct 29, 2025

Uh oh!

github-actions Bot commented Oct 29, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

jakemac53 commented Oct 29, 2025

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

jakemac53 commented Oct 29, 2025 •

edited

Loading

github-actions Bot commented Oct 29, 2025 •

edited

Loading