feat: add Google Antigravity authentication support

- Add 'antigravity' as new auth choice in onboard and configure wizards
- Implement Google Antigravity OAuth flow using loginAntigravity from pi-ai
- Update writeOAuthCredentials to accept any OAuthProvider (not just 'anthropic')
- Add schema sanitization for Google Cloud Code Assist API to fix tool call errors
- Default model set to google-antigravity/claude-opus-4-5 after successful auth

The schema sanitization removes unsupported JSON Schema keywords (patternProperties,
const, anyOf, etc.) that Google's Cloud Code Assist API doesn't understand.

patches/@mariozechner__pi-ai.patch

@@ -1,5 +1,90 @@
+diff --git a/dist/providers/google-shared.js b/dist/providers/google-shared.js
+index ff9cbcfebfac6b4370d85dc838f5cacf2a60ed64..42096c82aec925b412258348a36ba4a7025b283b 100644
+--- a/dist/providers/google-shared.js
++++ b/dist/providers/google-shared.js
+@@ -140,6 +140,71 @@ export function convertMessages(model, context) {
+     }
+     return contents;
+ }
++/**
++ * Sanitize JSON Schema for Google Cloud Code Assist API.
++ * Removes unsupported keywords like patternProperties, const, anyOf, etc.
++ * and converts to a format compatible with Google's function declarations.
++ */
++function sanitizeSchemaForGoogle(schema) {
++    if (!schema || typeof schema !== 'object') {
++        return schema;
++    }
++    // If it's an array, sanitize each element
++    if (Array.isArray(schema)) {
++        return schema.map(item => sanitizeSchemaForGoogle(item));
++    }
++    const sanitized = {};
++    // List of unsupported JSON Schema keywords that Google's API doesn't understand
++    const unsupportedKeywords = [
++        'patternProperties',
++        'const',
++        'anyOf',
++        'oneOf',
++        'allOf',
++        'not',
++        '$schema',
++        '$id',
++        '$ref',
++        '$defs',
++        'definitions',
++        'if',
++        'then',
++        'else',
++        'dependentSchemas',
++        'dependentRequired',
++        'unevaluatedProperties',
++        'unevaluatedItems',
++        'contentEncoding',
++        'contentMediaType',
++        'contentSchema',
++        'deprecated',
++        'readOnly',
++        'writeOnly',
++        'examples',
++        '$comment',
++        'additionalProperties',
++    ];
++    for (const [key, value] of Object.entries(schema)) {
++        // Skip unsupported keywords
++        if (unsupportedKeywords.includes(key)) {
++            continue;
++        }
++        // Recursively sanitize nested objects
++        if (key === 'properties' && typeof value === 'object' && value !== null) {
++            sanitized[key] = {};
++            for (const [propKey, propValue] of Object.entries(value)) {
++                sanitized[key][propKey] = sanitizeSchemaForGoogle(propValue);
++            }
++        } else if (key === 'items' && typeof value === 'object') {
++            sanitized[key] = sanitizeSchemaForGoogle(value);
++        } else if (typeof value === 'object' && value !== null && !Array.isArray(value)) {
++            sanitized[key] = sanitizeSchemaForGoogle(value);
++        } else {
++            sanitized[key] = value;
++        }
++    }
++    return sanitized;
++}
+ /**
+  * Convert tools to Gemini function declarations format.
+  */
+@@ -151,7 +216,7 @@ export function convertTools(tools) {
+             functionDeclarations: tools.map((tool) => ({
+                 name: tool.name,
+                 description: tool.description,
+-                parameters: tool.parameters,
++                parameters: sanitizeSchemaForGoogle(tool.parameters),
+             })),
+         },
+     ];
 diff --git a/dist/providers/openai-responses.js b/dist/providers/openai-responses.js
-index 20fb0a22aaa28f7ff7c2f44a8b628fa1d9d7d936..c2bc63f483f3285b00755901ba97db810221cea6 100644
+index 20fb0a22aaa28f7ff7c2f44a8b628fa1d9d7d936..31bae0aface1319487ce62d35f1f3b6ed334863e 100644
 --- a/dist/providers/openai-responses.js
 +++ b/dist/providers/openai-responses.js
 @@ -486,7 +486,6 @@ function convertTools(tools) {

pnpm-lock.yaml

@@ -9,7 +9,7 @@ overrides:
 
 patchedDependencies:
   '@mariozechner/pi-ai':
-    hash: bf3e904ebaad236b8c3bb48c7d1150a1463735e783acaab6d15d6cd381b43832
+    hash: 9d828603572332a8eba73e7d08d3a32408bc1d87a5c1f27b3f9f8d35c3d2ffb0
     path: patches/@mariozechner__pi-ai.patch
   '@mariozechner/pi-coding-agent@0.31.1':
     hash: d0d5ffa1bfda8a0f9d14a5e73a074014346d3edbdb2ffc91444d3be5119f5745

src/commands/configure.ts

@@ -10,7 +10,11 @@ import {
   spinner,
   text,
 } from "@clack/prompts";
-import { loginAnthropic, type OAuthCredentials } from "@mariozechner/pi-ai";
+import {
+  loginAnthropic,
+  loginAntigravity,
+  type OAuthCredentials,
+} from "@mariozechner/pi-ai";
 
 import type { ClawdisConfig } from "../config/config.js";
 import {
@@ -223,13 +227,17 @@ async function promptAuthConfig(
       message: "Model/auth choice",
       options: [
         { value: "oauth", label: "Anthropic OAuth (Claude Pro/Max)" },
+        {
+          value: "antigravity",
+          label: "Google Antigravity (Claude Opus 4.5, Gemini 3, etc.)",
+        },
         { value: "apiKey", label: "Anthropic API key" },
         { value: "minimax", label: "Minimax M2.1 (LM Studio)" },
         { value: "skip", label: "Skip for now" },
       ],
     }),
     runtime,
-  ) as "oauth" | "apiKey" | "minimax" | "skip";
+  ) as "oauth" | "antigravity" | "apiKey" | "minimax" | "skip";
 
   let next = cfg;
 
@@ -266,6 +274,47 @@ async function promptAuthConfig(
       spin.stop("OAuth failed");
       runtime.error(String(err));
     }
+  } else if (authChoice === "antigravity") {
+    note(
+      [
+        "Browser will open for Google authentication.",
+        "Sign in with your Google account that has Antigravity access.",
+        "The callback will be captured automatically on localhost:51121.",
+      ].join("\n"),
+      "Google Antigravity OAuth",
+    );
+    const spin = spinner();
+    spin.start("Starting OAuth flow…");
+    let oauthCreds: OAuthCredentials | null = null;
+    try {
+      oauthCreds = await loginAntigravity(
+        async ({ url, instructions }) => {
+          spin.message(instructions ?? "Complete sign-in in browser…");
+          await openUrl(url);
+          runtime.log(`Open: ${url}`);
+        },
+        (msg) => spin.message(msg),
+      );
+      spin.stop("Antigravity OAuth complete");
+      if (oauthCreds) {
+        await writeOAuthCredentials("google-antigravity", oauthCreds);
+        // Set default model to Claude Opus 4.5 via Antigravity
+        next = {
+          ...next,
+          agent: {
+            ...next.agent,
+            model: "google-antigravity/claude-opus-4-5",
+          },
+        };
+        note(
+          "Default model set to google-antigravity/claude-opus-4-5",
+          "Model configured",
+        );
+      }
+    } catch (err) {
+      spin.stop("Antigravity OAuth failed");
+      runtime.error(String(err));
+    }
   } else if (authChoice === "apiKey") {
     const key = guardCancel(
       await text({

src/commands/onboard-auth.ts

@@ -1,7 +1,7 @@
 import fs from "node:fs/promises";
 import path from "node:path";
 
-import type { OAuthCredentials } from "@mariozechner/pi-ai";
+import type { OAuthCredentials, OAuthProvider } from "@mariozechner/pi-ai";
 import { discoverAuthStorage } from "@mariozechner/pi-coding-agent";
 
 import { resolveClawdisAgentDir } from "../agents/agent-paths.js";
@@ -9,7 +9,7 @@ import type { ClawdisConfig } from "../config/config.js";
 import { CONFIG_DIR } from "../utils.js";
 
 export async function writeOAuthCredentials(
-  provider: "anthropic",
+  provider: OAuthProvider,
   creds: OAuthCredentials,
 ): Promise<void> {
   const dir = path.join(CONFIG_DIR, "credentials");

src/commands/onboard-interactive.ts

@@ -9,7 +9,11 @@ import {
   spinner,
   text,
 } from "@clack/prompts";
-import { loginAnthropic, type OAuthCredentials } from "@mariozechner/pi-ai";
+import {
+  loginAnthropic,
+  loginAntigravity,
+  type OAuthCredentials,
+} from "@mariozechner/pi-ai";
 
 import type { ClawdisConfig } from "../config/config.js";
 import {
@@ -198,6 +202,10 @@ export async function runInteractiveOnboarding(
       message: "Model/auth choice",
       options: [
         { value: "oauth", label: "Anthropic OAuth (Claude Pro/Max)" },
+        {
+          value: "antigravity",
+          label: "Google Antigravity (Claude Opus 4.5, Gemini 3, etc.)",
+        },
         { value: "apiKey", label: "Anthropic API key" },
         { value: "minimax", label: "Minimax M2.1 (LM Studio)" },
         { value: "skip", label: "Skip for now" },
@@ -239,6 +247,47 @@ export async function runInteractiveOnboarding(
       spin.stop("OAuth failed");
       runtime.error(String(err));
     }
+  } else if (authChoice === "antigravity") {
+    note(
+      [
+        "Browser will open for Google authentication.",
+        "Sign in with your Google account that has Antigravity access.",
+        "The callback will be captured automatically on localhost:51121.",
+      ].join("\n"),
+      "Google Antigravity OAuth",
+    );
+    const spin = spinner();
+    spin.start("Starting OAuth flow…");
+    let oauthCreds: OAuthCredentials | null = null;
+    try {
+      oauthCreds = await loginAntigravity(
+        async ({ url, instructions }) => {
+          spin.message(instructions ?? "Complete sign-in in browser…");
+          await openUrl(url);
+          runtime.log(`Open: ${url}`);
+        },
+        (msg) => spin.message(msg),
+      );
+      spin.stop("Antigravity OAuth complete");
+      if (oauthCreds) {
+        await writeOAuthCredentials("google-antigravity", oauthCreds);
+        // Set default model to Claude Opus 4.5 via Antigravity
+        nextConfig = {
+          ...nextConfig,
+          agent: {
+            ...nextConfig.agent,
+            model: "google-antigravity/claude-opus-4-5",
+          },
+        };
+        note(
+          "Default model set to google-antigravity/claude-opus-4-5",
+          "Model configured",
+        );
+      }
+    } catch (err) {
+      spin.stop("Antigravity OAuth failed");
+      runtime.error(String(err));
+    }
   } else if (authChoice === "apiKey") {
     const key = guardCancel(
       await text({

src/commands/onboard-types.ts

@@ -1,5 +1,5 @@
 export type OnboardMode = "local" | "remote";
-export type AuthChoice = "oauth" | "apiKey" | "minimax" | "skip";
+export type AuthChoice = "oauth" | "antigravity" | "apiKey" | "minimax" | "skip";
 export type GatewayAuthChoice = "off" | "token" | "password";
 export type ResetScope = "config" | "config+creds+sessions" | "full";
 export type GatewayBind = "loopback" | "lan" | "tailnet" | "auto";