feat(ai): add PI_AI_ANTIGRAVITY_VERSION env var override

Allows users to override the Antigravity User-Agent version when Google
updates their version requirements, avoiding the need to wait for a
package release.

Fixes #1129

packages/ai/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added `PI_AI_ANTIGRAVITY_VERSION` environment variable to override the Antigravity User-Agent version when Google updates their version requirements ([#1129](https://github.com/badlogic/pi-mono/issues/1129))
+
 ## [0.50.8] - 2026-02-01
 
 ### Added

packages/ai/README.md

@@ -911,6 +911,14 @@ const response = await complete(model, context, {
 });
 ```
 
+#### Antigravity Version Override
+
+Set `PI_AI_ANTIGRAVITY_VERSION` to override the Antigravity User-Agent version when Google updates their requirements:
+
+```bash
+export PI_AI_ANTIGRAVITY_VERSION="1.23.0"
+```
+
 #### Cache Retention
 
 Set `PI_CACHE_RETENTION=long` to extend prompt cache retention:

packages/ai/src/providers/google-gemini-cli.ts

@@ -72,15 +72,20 @@ const GEMINI_CLI_HEADERS = {
 };
 
 // Headers for Antigravity (sandbox endpoint) - requires specific User-Agent
-const ANTIGRAVITY_HEADERS = {
-	"User-Agent": "antigravity/1.15.8 darwin/arm64",
-	"X-Goog-Api-Client": "google-cloud-sdk vscode_cloudshelleditor/0.1",
-	"Client-Metadata": JSON.stringify({
-		ideType: "IDE_UNSPECIFIED",
-		platform: "PLATFORM_UNSPECIFIED",
-		pluginType: "GEMINI",
-	}),
-};
+const DEFAULT_ANTIGRAVITY_VERSION = "1.15.8";
+
+function getAntigravityHeaders() {
+	const version = process.env.PI_AI_ANTIGRAVITY_VERSION || DEFAULT_ANTIGRAVITY_VERSION;
+	return {
+		"User-Agent": `antigravity/${version} darwin/arm64`,
+		"X-Goog-Api-Client": "google-cloud-sdk vscode_cloudshelleditor/0.1",
+		"Client-Metadata": JSON.stringify({
+			ideType: "IDE_UNSPECIFIED",
+			platform: "PLATFORM_UNSPECIFIED",
+			pluginType: "GEMINI",
+		}),
+	};
+}
 
 // Antigravity system instruction (ported from CLIProxyAPI v6.6.89).
 const ANTIGRAVITY_SYSTEM_INSTRUCTION = `<identity>
@@ -430,7 +435,7 @@ export const streamGoogleGeminiCli: StreamFunction<"google-gemini-cli", GoogleGe
 
 			const requestBody = buildRequest(model, context, projectId, options, isAntigravity);
 			options?.onPayload?.(requestBody);
-			const headers = isAntigravity ? ANTIGRAVITY_HEADERS : GEMINI_CLI_HEADERS;
+			const headers = isAntigravity ? getAntigravityHeaders() : GEMINI_CLI_HEADERS;
 
 			const requestHeaders = {
 				Authorization: `Bearer ${accessToken}`,

packages/coding-agent/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Added
 
 - Added `titlebar-spinner.ts` example extension that shows a braille spinner animation in the terminal title while the agent is working.
+- Added `PI_AI_ANTIGRAVITY_VERSION` environment variable documentation to help text ([#1129](https://github.com/badlogic/pi-mono/issues/1129))
 
 ## [0.50.8] - 2026-02-01
 

packages/coding-agent/src/cli/args.ts

@@ -288,6 +288,7 @@ ${chalk.bold("Environment Variables:")}
   AWS_REGION                       - AWS region for Amazon Bedrock (e.g., us-east-1)
   ${ENV_AGENT_DIR.padEnd(32)} - Session storage directory (default: ~/${CONFIG_DIR_NAME}/agent)
   PI_SHARE_VIEWER_URL              - Base URL for /share command (default: https://buildwithpi.ai/session/)
+  PI_AI_ANTIGRAVITY_VERSION        - Override Antigravity User-Agent version (e.g., 1.23.0)
 
 ${chalk.bold("Available Tools (default: read, bash, edit, write):")}
   read   - Read file contents