From 06a53071609be190563d893742bf4340f5b5fb6b Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Tue, 10 Mar 2026 16:16:12 +0700
Subject: [PATCH] feat(gemini-cli): add proper User-Agent and X-Goog-Api-Client
 headers

Match native GeminiCLI client fingerprint to avoid upstream rejection.
Also fix base executor to call transformRequest before buildHeaders so
subclasses can store model context for header generation.

Made-with: Cursor
---
 open-sse/config/constants.js     | 28 ++++++++++++++++++++++++++++
 open-sse/executors/base.js       |  2 +-
 open-sse/executors/gemini-cli.js |  8 ++++++--
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/open-sse/config/constants.js b/open-sse/config/constants.js
index e5d15ad6..63f29919 100644
--- a/open-sse/config/constants.js
+++ b/open-sse/config/constants.js
@@ -19,6 +19,34 @@ function mapStainlessArch() {
   }
 }
 
+// === Gemini CLI Version Constants ===
+export const GEMINI_CLI_VERSION = "0.31.0";
+export const GEMINI_CLI_API_CLIENT = "google-genai-sdk/1.41.0 gl-node/v22.19.0";
+
+function mapGeminiCLIOs() {
+  switch (platform()) {
+    case "darwin": return "darwin";
+    case "win32": return "windows";
+    case "linux": return "linux";
+    case "freebsd": return "freebsd";
+    default: return platform();
+  }
+}
+
+function mapGeminiCLIArch() {
+  switch (arch()) {
+    case "x64": return "x64";
+    case "arm64": return "arm64";
+    case "ia32": return "x86";
+    default: return arch();
+  }
+}
+
+/** Returns User-Agent matching native Gemini CLI format: GeminiCLI/<version>/<model> (<os>; <arch>) */
+export function geminiCLIUserAgent(model = "unknown") {
+  return `GeminiCLI/${GEMINI_CLI_VERSION}/${model || "unknown"} (${mapGeminiCLIOs()}; ${mapGeminiCLIArch()})`;
+}
+
 // === GitHub Copilot Version Constants ===
 export const GITHUB_COPILOT = {
   VSCODE_VERSION: "1.110.0",
diff --git a/open-sse/executors/base.js b/open-sse/executors/base.js
index 7fc96496..17f351de 100644
--- a/open-sse/executors/base.js
+++ b/open-sse/executors/base.js
@@ -84,8 +84,8 @@ export class BaseExecutor {
 
     for (let urlIndex = 0; urlIndex < fallbackCount; urlIndex++) {
       const url = this.buildUrl(model, stream, urlIndex, credentials);
-      const headers = this.buildHeaders(credentials, stream);
       const transformedBody = this.transformRequest(model, body, stream, credentials);
+      const headers = this.buildHeaders(credentials, stream);
 
       if (!retryAttemptsByUrl[urlIndex]) retryAttemptsByUrl[urlIndex] = 0;
 
diff --git a/open-sse/executors/gemini-cli.js b/open-sse/executors/gemini-cli.js
index 0fbe2c66..e6fe3d35 100644
--- a/open-sse/executors/gemini-cli.js
+++ b/open-sse/executors/gemini-cli.js
@@ -1,5 +1,5 @@
 import { BaseExecutor } from "./base.js";
-import { PROVIDERS, OAUTH_ENDPOINTS } from "../config/constants.js";
+import { PROVIDERS, OAUTH_ENDPOINTS, GEMINI_CLI_API_CLIENT, geminiCLIUserAgent } from "../config/constants.js";
 
 export class GeminiCLIExecutor extends BaseExecutor {
   constructor() {
@@ -15,11 +15,15 @@ export class GeminiCLIExecutor extends BaseExecutor {
     return {
       "Content-Type": "application/json",
       "Authorization": `Bearer ${credentials.accessToken}`,
-      ...(stream && { "Accept": "text/event-stream" })
+      "User-Agent": geminiCLIUserAgent(this._currentModel),
+      "X-Goog-Api-Client": GEMINI_CLI_API_CLIENT,
+      "Accept": stream ? "text/event-stream" : "application/json"
     };
   }
 
   transformRequest(model, body, stream, credentials) {
+    // Store model for use in buildHeaders (called by base.execute after transformRequest)
+    this._currentModel = model;
     if (!body.project && credentials?.projectId) {
       body.project = credentials.projectId;
     }