fix(core): externalize https-proxy-agent to fix proxy support

[sotokisehiro]

fix(core): inject proxy agent statically to fix Vertex AI proxy support

Summary

Fix TypeError: HttpsProxyAgent is not a constructor that occurs when calling Vertex AI / Gemini API through an HTTP/HTTPS proxy (HTTPS_PROXY / HTTP_PROXY). The bug is a P1 blocker for proxy users — particularly enterprise Vertex AI users.

This PR is a follow-up to the original review feedback by @scidomino: instead of externalizing the proxy package from the esbuild bundle, we statically import HttpsProxyAgent / HttpProxyAgent and inject the pre-instantiated agent into GoogleGenAI's underlying transporter.

Root cause

esbuild's splitting: true + format: 'esm' causes CJS packages resolved via dynamic import() to lose named exports. gaxios@7.x (used by google-auth-library → @google/genai) dynamically imports https-proxy-agent:

this.#proxyAgent ||= (await import('https-proxy-agent')).HttpsProxyAgent;

esbuild generates an ESM chunk with only a default export, so .HttpsProxyAgent resolves to undefined, and new this.#proxyAgent(...) throws.

Fix

Statically import both proxy agents in packages/core/src/core/contentGenerator.ts and pre-instantiate the agent before constructing GoogleGenAI. The agent is injected via googleAuthOptions.clientOptions.transporterOptions.agent, which causes gaxios to skip its dynamic import path entirely (gaxios checks opts.agent and uses it if present, falling through to dynamic import only when absent).

import { HttpProxyAgent } from 'http-proxy-agent';
import { HttpsProxyAgent } from 'https-proxy-agent';

// inside createContentGenerator (GoogleGenAI branch):
const proxyUrl = config.proxy?.trim();
const proxyAgent = proxyUrl
  ? baseUrl?.startsWith('http://')
    ? new HttpProxyAgent(proxyUrl)
    : new HttpsProxyAgent(proxyUrl)
  : undefined;

const googleGenAI = new GoogleGenAI({
  apiKey,
  vertexai,
  httpOptions,
  ...(proxyAgent && {
    googleAuthOptions: {
      clientOptions: {
        transporterOptions: { agent: proxyAgent },
      },
    },
  }),
});

Agent selection is based on the destination URL (baseUrl), not the proxy URL — HttpsProxyAgent is required for HTTPS destinations (which both Gemini API and Vertex AI use by default), regardless of the proxy's own scheme.

Changed files

File	Change
packages/core/src/core/contentGenerator.ts	Static imports + agent construction + injection via googleAuthOptions
packages/core/src/core/contentGenerator.test.ts	5 new test cases covering https/http proxy URL, http baseUrl, whitespace trimming, and no-proxy case
packages/core/package.json	Add http-proxy-agent: ^7.0.2 (was already a transitive dep; making it explicit)
package.json	Add http-proxy-agent and https-proxy-agent to root dependencies for consistency
package-lock.json	Regenerated

No esbuild or bundle script changes are needed with this approach — by avoiding the dynamic import path entirely, we don't need to externalize anything from the bundle.

Related issues

• Fixes Proxy defined in environment broken: "TypeError: HttpsProxyAgent is not a constructor" when using proxy options #24471
• Related to Proxy broken: HttpsProxyAgent is not a constructor (esbuild CJS interop) #25169

How to validate

1. Build:

   npm run bundle

2. Verify under proxy (should succeed without TypeError):

   HTTPS_PROXY=http://<your-proxy>:<port> npm start -- --prompt "hello"

3. Verify without proxy (regression check):

   npm start -- --prompt "hello"

4. Run unit tests for the proxy injection:

   cd packages/core && npx vitest run src/core/contentGenerator.test.ts

   Expected: all 39 tests pass (5 new + 34 existing).

Pre-Merge Checklist

• Updated relevant documentation and README (N/A — internal implementation only)
• Added/updated tests (5 new unit tests in contentGenerator.test.ts)
• Noted breaking changes (none)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

This PR unblocks all users who are currently unable to access Vertex AI due to proxy issues.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[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 critical issue where proxy support fails due to how esbuild handles dynamic imports of CommonJS modules in an ESM bundle. By externalizing the proxy agent and ensuring its dependencies are included in the final distribution, the fix restores functionality for users operating behind HTTP/HTTPS proxies.

Highlights

• Externalize https-proxy-agent: Added 'https-proxy-agent' to the esbuild external configuration to prevent runtime errors caused by dynamic import resolution issues in the bundled ESM output.
• Dependency Management: Included 'https-proxy-agent' as a direct dependency in package.json to ensure it is available for the application.
• Build Script Update: Updated the bundle asset copy script to include 'https-proxy-agent' and its transitive dependencies, ensuring they are correctly packaged for binary distribution.

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[gemini-code-assist]

Code Review

This pull request introduces proxy support by adding https-proxy-agent as a dependency and updating the build scripts to externalize and copy it into the bundle. Feedback indicates that the a2a-server bundle may fail at runtime due to missing dependencies, the hardcoded list of transitive dependencies in the copy script is fragile, and the build should fail explicitly if these required packages are not found.

[gemini-code-assist]

The script currently skips copying if a package is missing from node_modules. Since these packages are required for proxy support (a P1 fix), the build should fail explicitly if they cannot be found to prevent shipping a broken bundle.

  if (!existsSync(pkgSrc)) {
    console.error("Error: Required package " + pkg + " not found in node_modules. Ensure dependencies are installed.");
    process.exit(1);
  }
  mkdirSync(pkgDest, { recursive: true });
  cpSync(pkgSrc, pkgDest, { recursive: true, dereference: true });
  console.log("Copied " + pkg + " to bundle/node_modules/");

[sotokisehiro]

Agreed — this is a critical dependency for proxy support, so the build should fail explicitly if these packages are missing. Updated to use console.error + process.exit(1), consistent with the chrome-devtools-mcp copy in section 6.

[sotokisehiro]

This comment was on the previous externalize-based approach. The PR has since been reworked to use static imports (per @scidomino's suggestion); the external entries and the bundle-copy script changes have been removed entirely. No longer applicable.

[sotokisehiro]

@google-cla check

[sotokisehiro]

I have confirmed that it works in a Windows environment.

[sotokisehiro]

@gemini-cli-robot This PR unblocks all users who are currently unable to access Vertex AI due to proxy issues.

[sotokisehiro]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces proxy support by adding https-proxy-agent as an external dependency and updating the asset copying script to include it and its transitive dependencies in the bundle. Feedback indicates that hardcoding transitive dependencies is fragile and suggests using dynamic resolution instead. Additionally, there is a concern that the a2a-server distribution will lack these dependencies at runtime since they are currently only copied to the CLI bundle directory.

[sotokisehiro]

@gemini-code-assist
My pull request and the other pull request (#26551) seem to be duplicates, don't they?

[gemini-code-assist]

I do not have access to view other pull requests, so I am unable to confirm if your PR is a duplicate of #26551. I recommend comparing the changes in both pull requests to see if they address the same issue in the same way. If you find that they are indeed duplicates, it would be best to reach out to the repository maintainers to discuss which PR should be merged.

[sotokisehiro]

@gemini-code-assist I got it.

[gemini-code-assist]

Understood. Since you are now aware of the potential duplication, please proceed with comparing the two pull requests. If you determine that they are indeed duplicates, it is best to coordinate with the repository maintainers to decide which one should move forward. If you have any further questions or need assistance with the code in this PR, feel free to ask.

[sotokisehiro]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces proxy support by adding 'https-proxy-agent' as a dependency and configuring the build system to include it in the bundle. Changes include marking the package as external in the esbuild configuration and updating the asset copying script to manually move the package and its dependencies into the bundle's node_modules. A review comment suggests refactoring the asset copying script to dynamically traverse the dependency tree instead of using a hardcoded list of packages, which would make the build process more resilient to dependency updates.

[sotokisehiro]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces proxy support for the GoogleGenAI client by integrating http-proxy-agent and https-proxy-agent, including logic to select the appropriate agent based on the destination protocol and unit tests for verification. Feedback suggests externalizing the new http-proxy-agent dependency in the build configuration to prevent runtime errors. Additionally, it is recommended to define a local interface for the undocumented googleAuthOptions property and to consider using a custom httpClient to ensure consistent proxy behavior across all API calls.

[sotokisehiro]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces proxy support for the Gemini CLI by adding http-proxy-agent and https-proxy-agent as dependencies. The createContentGenerator function in packages/core was updated to detect and configure the appropriate proxy agent based on the destination URL's protocol, ensuring that requests are correctly routed when a proxy is configured. Additionally, new unit tests were implemented to verify the proxy agent injection logic, including handling of different protocols and whitespace trimming in proxy URLs. I have no feedback to provide as there were no review comments.

[sotokisehiro]

@gemini-code-assist Thanks for the review. Both indications are based on premises that no longer apply to this PR. I'd like to address them inline rather than changing the code:

Re: contentGenerator.ts:344 — externalize http-proxy-agent in esbuild.config.js

This indication is based on the older externalization strategy described in the PR description (which I'll update separately). The current implementation does not externalize either proxy package. We instead statically import them in contentGenerator.ts and inject a pre-instantiated agent into GoogleGenAI. With this approach:

• esbuild bundles both http-proxy-agent and https-proxy-agent inline as part of the chunks (verified via grep "HttpsProxyAgent" bundle/chunk-*.js).
• gaxios's dynamic import('https-proxy-agent') path is never reached (because we provide agent upfront, satisfying gaxios's if (opts.agent) skip branch).
• No external entry or asset-copy step is needed for SEA distribution.

Adding either package to external and copying it via copy_bundle_assets.js would re-introduce exactly the brittleness that maintainer @scidomino flagged in the previous revision. The PR description will be revised to reflect the current design.

Re: contentGenerator.ts:359 — googleAuthOptions undocumented + Gemini API path

Two sub-points to address:

1. googleAuthOptions is a documented public option, not internal.

It's declared on GoogleGenAIOptions in @google/genai@1.30.0's exported type definitions:

class GoogleGenAI {
  constructor(options: GoogleGenAIOptions);
}

interface GoogleGenAIOptions {
  apiKey?: string;
  vertexai?: boolean;
  httpOptions?: HttpOptions;
  googleAuthOptions?: GoogleAuthOptions;  // re-exported from google-auth-library
  // ...
}

The nested chain clientOptions.transporterOptions.agent comes from the google-auth-library types (GoogleAuthOptions → clientOptions: AuthClientOptions → transporterOptions). All of these are public, typed APIs — no as any or local interface workaround is needed.

2. Vertex AI vs Gemini API key path.

You're correct that googleAuthOptions only configures the auth/transporter layer, which is the path used by Vertex AI auth. For Gemini API key auth, the request goes through httpOptions → fetch directly without the gaxios layer.

This is intentional and matches the original bug scope:

• The bug being fixed (Proxy defined in environment broken: "TypeError: HttpsProxyAgent is not a constructor" when using proxy options #24471) is TypeError: HttpsProxyAgent is not a constructor triggered by gaxios@7's dynamic import('https-proxy-agent') inside GoogleAuth.getRequestHeaders(). This code path is only reached on the Vertex AI auth flow — Gemini API key auth doesn't go through gaxios.
• Therefore the Gemini API key path is not affected by this specific TypeError and doesn't need a fix here.
• General proxy support for the Gemini API key path is a separate concern (see Proxy broken: HttpsProxyAgent is not a constructor (esbuild CJS interop) #25169 and related). It would require either a custom httpClient/fetch wrapper or upstream @google/genai exposing an agent field on HttpOptions. That's intentionally out of scope for this PR — this PR is targeted at unblocking Vertex AI users hit by the regression.

I'll update the PR description to make the scope and the no-externalize design explicit.

[gemini-code-assist]

Thank you for the detailed explanation. Your reasoning for moving away from the externalization strategy is sound. By statically importing the proxy agents and injecting them directly into googleAuthOptions, you effectively bypass the dynamic import path that was causing the TypeError in the ESM bundle, while also avoiding the complexity and potential brittleness of managing external dependencies in the build configuration.

Your analysis of the scope—specifically that this fix targets the Vertex AI auth flow where the gaxios dynamic import is triggered—is correct. This approach is a cleaner, more maintainable solution for the reported issue.

Updating the PR description to reflect this design and scope is a great next step. Once that is done, the changes appear to be well-aligned with the goal of unblocking Vertex AI users behind proxies.

[sotokisehiro]

@scidomino Thanks for your earlier review and the suggested approach — you were right that the original external + bundle-copy approach was hacky. The PR has been reworked to use static imports as you recommended (current HEAD: 8e563e199).

A short summary of where it landed and why a couple of details differ slightly from your snippet.

What's in the PR now

The Vertex AI / proxy fix is now contained to 5 files, +192 / -0 — purely the proxy work, nothing unrelated:

packages/core/src/core/contentGenerator.ts       | +16
packages/core/src/core/contentGenerator.test.ts  | +170
packages/core/package.json                       |  +1
package.json                                     |  +2
package-lock.json                                |  +3

The core change in contentGenerator.ts:

import { HttpProxyAgent } from 'http-proxy-agent';
import { HttpsProxyAgent } from 'https-proxy-agent';

// inside createContentGenerator, GoogleGenAI branch:
const proxyUrl = config.proxy?.trim();
const proxyAgent = proxyUrl
  ? baseUrl?.startsWith('http://')
    ? new HttpProxyAgent(proxyUrl)
    : new HttpsProxyAgent(proxyUrl)
  : undefined;

const googleGenAI = new GoogleGenAI({
  apiKey: config.apiKey === '' ? undefined : config.apiKey,
  vertexai: config.vertexai ?? config.authType === AuthType.USE_VERTEX_AI,
  httpOptions,
  ...(apiVersionEnv && { apiVersion: apiVersionEnv }),
  ...(proxyAgent && {
    googleAuthOptions: {
      clientOptions: {
        transporterOptions: { agent: proxyAgent },
      },
    },
  }),
});

The external entries in esbuild.config.js, the Step 8 in copy_bundle_assets.js, and the proxy-agent entries in root package.json dependencies from the previous revision have all been removed — none of them are needed once the agent is provided statically.

Two minor deviations from your snippet (and why)

1. Agent selection is keyed on baseUrl, not proxyUrl.

Your snippet picks the agent class from proxyUrl.startsWith('http://'), but the protocol that actually matters for HTTP-CONNECT semantics is the destination scheme. Both Vertex AI and Gemini API endpoints are HTTPS by default, so HttpsProxyAgent is needed (it tunnels via CONNECT) regardless of whether the proxy itself is reached over http:// or https://. Using HttpProxyAgent for an HTTPS destination would fail the TLS handshake. So the picker reads baseUrl (destination override or default) and falls through to HttpsProxyAgent whenever the destination is HTTPS — which is the common case.

(gemini-code-assist flagged the same point in its automated review, with a clear explanation.)

2. Agent is injected via googleAuthOptions.clientOptions.transporterOptions.agent, not httpOptions.agent.

HttpOptions in @google/genai@1.30.0 doesn't expose an agent field, but the dynamic-import bug actually originates one layer down in google-auth-library → gaxios. Passing the agent via googleAuthOptions propagates it to gaxios.defaults.agent, which makes gaxios skip the await import('https-proxy-agent') branch entirely — so no dynamic import is attempted at runtime and the esbuild ESM bundle issue can't trigger. Net effect is the same as your suggestion (no dynamic import path), it's just hooked into the layer where the bug actually lives.

This intentionally scopes the fix to the Vertex AI / Google Auth path, which is where the original TypeError: HttpsProxyAgent is not a constructor reproduces. Generic proxy support for the Gemini API key path (which doesn't go through gaxios) is a separate concern and would belong in a different PR.

Test coverage

packages/core/src/core/contentGenerator.test.ts gains 5 cases for createContentGenerator (the Vertex AI branch):

• https:// proxy URL → HttpsProxyAgent injected
• http:// proxy URL with default (HTTPS) destination → still HttpsProxyAgent (deviation docs: Add setup instructions for API key to README #1 above)
• http:// baseUrl with http:// proxy URL → HttpProxyAgent
• proxy URL with surrounding whitespace → trimmed before instantiation
• no proxy → no googleAuthOptions on the call

Total contentGenerator.test.ts is 39 / 39 passing.

Verification

• npm run build, npm run bundle ✅
• vitest run on contentGenerator.test.ts → 39/39
• proxy-agent code is bundled inline into chunk files (no bundle/node_modules/{http,https}-proxy-agent left over from the old approach)
• E2E confirmed on Windows under HTTPS_PROXY against Vertex AI

Re: CLA

CLA is now signed and the cla/google check is green.

Could you take another look when you get a chance? Happy to adjust further if anything else jumps out.

[scidomino]

There are a bunch of comments left by Gemini. Please address them and mark them as "resolved". Then I will review.

[scidomino]

ping me when you are done

[sotokisehiro]

@scidomino All Gemini review comments have been addressed and marked as resolved. Ready for your review.

Thanks also for your earlier suggestion — you were right that the original external + bundle-copy approach was hacky. The PR has been reworked to use static imports as you recommended (current HEAD: 8e563e199).

A short summary of where it landed and why a couple of details differ slightly from your snippet.

What's in the PR now

The Vertex AI / proxy fix is now contained to 5 files, +192 / -0 — purely the proxy work, nothing unrelated:

packages/core/src/core/contentGenerator.ts       | +16
packages/core/src/core/contentGenerator.test.ts  | +170
packages/core/package.json                       |  +1
package.json                                     |  +2
package-lock.json                                |  +3

The core change in contentGenerator.ts:

import { HttpProxyAgent } from 'http-proxy-agent';
import { HttpsProxyAgent } from 'https-proxy-agent';

// inside createContentGenerator, GoogleGenAI branch:
const proxyUrl = config.proxy?.trim();
const proxyAgent = proxyUrl
  ? baseUrl?.startsWith('http://')
    ? new HttpProxyAgent(proxyUrl)
    : new HttpsProxyAgent(proxyUrl)
  : undefined;

const googleGenAI = new GoogleGenAI({
  apiKey: config.apiKey === '' ? undefined : config.apiKey,
  vertexai: config.vertexai ?? config.authType === AuthType.USE_VERTEX_AI,
  httpOptions,
  ...(apiVersionEnv && { apiVersion: apiVersionEnv }),
  ...(proxyAgent && {
    googleAuthOptions: {
      clientOptions: {
        transporterOptions: { agent: proxyAgent },
      },
    },
  }),
});

The external entries in esbuild.config.js, the Step 8 in copy_bundle_assets.js, and the proxy-agent entries in root package.json dependencies from the previous revision have all been removed — none of them are needed once the agent is provided statically.

Two minor deviations from your snippet (and why)

1. Agent selection is keyed on baseUrl, not proxyUrl.

Your snippet picks the agent class from proxyUrl.startsWith('http://'), but the protocol that actually matters for HTTP-CONNECT semantics is the destination scheme. Both Vertex AI and Gemini API endpoints are HTTPS by default, so HttpsProxyAgent is needed (it tunnels via CONNECT) regardless of whether the proxy itself is reached over http:// or https://. Using HttpProxyAgent for an HTTPS destination would fail the TLS handshake. So the picker reads baseUrl (destination override or default) and falls through to HttpsProxyAgent whenever the destination is HTTPS — which is the common case.

(gemini-code-assist flagged the same point in its automated review, with a clear explanation.)

2. Agent is injected via googleAuthOptions.clientOptions.transporterOptions.agent, not httpOptions.agent.

HttpOptions in @google/genai@1.30.0 doesn't expose an agent field, but the dynamic-import bug actually originates one layer down in google-auth-library → gaxios. Passing the agent via googleAuthOptions propagates it to gaxios.defaults.agent, which makes gaxios skip the await import('https-proxy-agent') branch entirely — so no dynamic import is attempted at runtime and the esbuild ESM bundle issue can't trigger. Net effect is the same as your suggestion (no dynamic import path), it's just hooked into the layer where the bug actually lives.

This intentionally scopes the fix to the Vertex AI / Google Auth path, which is where the original TypeError: HttpsProxyAgent is not a constructor reproduces. Generic proxy support for the Gemini API key path (which doesn't go through gaxios) is a separate concern and would belong in a different PR.

Test coverage

packages/core/src/core/contentGenerator.test.ts gains 5 cases for createContentGenerator (the Vertex AI branch):

• https:// proxy URL → HttpsProxyAgent injected
• http:// proxy URL with default (HTTPS) destination → still HttpsProxyAgent (deviation docs: Add setup instructions for API key to README #1 above)
• http:// baseUrl with http:// proxy URL → HttpProxyAgent
• proxy URL with surrounding whitespace → trimmed before instantiation
• no proxy → no googleAuthOptions on the call

Total contentGenerator.test.ts is 39 / 39 passing.

Verification

• npm run build, npm run bundle ✅
• vitest run on contentGenerator.test.ts → 39/39
• proxy-agent code is bundled inline into chunk files (no bundle/node_modules/{http,https}-proxy-agent left over from the old approach)
• E2E confirmed on Windows under HTTPS_PROXY against Vertex AI

Re: CLA

CLA is now signed and the cla/google check is green.

Could you take another look when you get a chance? Happy to adjust further if anything else jumps out.

[scidomino]

You mentioned that the proxy-agent entries in the root package.json dependencies were removed, but they are still present in the current diff for package.json. Since this is a monorepo, we only need these dependencies defined in the workspace that uses them (packages/core/package.json). Please remove them from the root package.json and regenerate the lockfile.

Also, try to keep the PR comments concise. I can only read so much text in one sitting 😄

[sotokisehiro]

Sorry about the inconsistency in my last comment — you're right. Removed both http-proxy-agent and https-proxy-agent from the root package.json and regenerated the lockfile in 4f796edc1. They remain only in packages/core/package.json where they're actually imported.

Will keep replies tight from here on 👍

[sotokisehiro]

Thank you for your cooperation!