feat: Add Antigravity provider integration + fix native mode startup

- Added Antigravity AI provider with Google OAuth authentication
- New integration client (antigravity.ts) with automatic endpoint fallback
- API routes for /api/antigravity/* (models, auth-status, test, chat)
- AntigravitySettings.tsx for Advanced Settings panel
- Updated session-api.ts and session-actions.ts for provider routing
- Updated opencode.jsonc with Antigravity plugin and 11 models:
  - Gemini 3 Pro Low/High, Gemini 3 Flash
  - Claude Sonnet 4.5 (+ thinking variants)
  - Claude Opus 4.5 (+ thinking variants)
  - GPT-OSS 120B Medium

- Fixed native mode startup error (was trying to launch __nomadarch_native__ as binary)
- Native mode workspaces now skip binary launch and are immediately ready

packages/opencode-config/opencode.jsonc

@@ -1,3 +1,204 @@
 {
-  "$schema": "https://opencode.ai/config.json"
+  "$schema": "https://opencode.ai/config.json",
+  // Antigravity plugin for Google OAuth (Gemini + Claude models via Antigravity)
+  "plugin": [
+    "opencode-antigravity-auth@1.2.6"
+  ],
+  "provider": {
+    // Antigravity models (via Google OAuth)
+    "google": {
+      "models": {
+        // Gemini Models
+        "gemini-3-pro-low": {
+          "name": "Gemini 3 Pro Low (Antigravity)",
+          "limit": {
+            "context": 1048576,
+            "output": 65535
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "gemini-3-pro-high": {
+          "name": "Gemini 3 Pro High (Antigravity)",
+          "limit": {
+            "context": 1048576,
+            "output": 65535
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "gemini-3-flash": {
+          "name": "Gemini 3 Flash (Antigravity)",
+          "limit": {
+            "context": 1048576,
+            "output": 65536
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        // Claude Models (via Antigravity)
+        "claude-sonnet-4-5": {
+          "name": "Claude Sonnet 4.5 (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "claude-sonnet-4-5-thinking-low": {
+          "name": "Claude Sonnet 4.5 Thinking Low (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "claude-sonnet-4-5-thinking-medium": {
+          "name": "Claude Sonnet 4.5 Thinking Medium (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "claude-sonnet-4-5-thinking-high": {
+          "name": "Claude Sonnet 4.5 Thinking High (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "claude-opus-4-5-thinking-low": {
+          "name": "Claude Opus 4.5 Thinking Low (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "claude-opus-4-5-thinking-medium": {
+          "name": "Claude Opus 4.5 Thinking Medium (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        "claude-opus-4-5-thinking-high": {
+          "name": "Claude Opus 4.5 Thinking High (Antigravity)",
+          "limit": {
+            "context": 200000,
+            "output": 64000
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        },
+        // Other Models
+        "gpt-oss-120b-medium": {
+          "name": "GPT-OSS 120B Medium (Antigravity)",
+          "limit": {
+            "context": 131072,
+            "output": 32768
+          },
+          "modalities": {
+            "input": [
+              "text",
+              "image",
+              "pdf"
+            ],
+            "output": [
+              "text"
+            ]
+          }
+        }
+      }
+    }
+  }
 }

packages/server/src/integrations/antigravity.ts

@@ -0,0 +1,495 @@
+/**
+ * Antigravity API Integration for Binary-Free Mode
+ * Provides direct access to Antigravity models (Gemini, Claude, GPT-OSS) via Google OAuth
+ * Based on the opencode-antigravity-auth plugin: https://github.com/NoeFabris/opencode-antigravity-auth
+ * 
+ * This integration enables access to:
+ * - Gemini 3 Pro/Flash models
+ * - Claude Sonnet 4.5 / Opus 4.5 (with thinking variants)
+ * - GPT-OSS 120B
+ * 
+ * Uses Google OAuth credentials stored via the Antigravity OAuth flow
+ */
+
+import { z } from "zod"
+
+// Configuration schema for Antigravity
+export const AntigravityConfigSchema = z.object({
+    enabled: z.boolean().default(true),
+    // Multiple endpoints for automatic fallback (daily → autopush → prod)
+    endpoints: z.array(z.string()).default([
+        "https://daily.antigravity.dev/v1beta",
+        "https://autopush.antigravity.dev/v1beta",
+        "https://antigravity.dev/v1beta"
+    ]),
+    apiKey: z.string().optional()
+})
+
+export type AntigravityConfig = z.infer<typeof AntigravityConfigSchema>
+
+// Antigravity Model schema
+export const AntigravityModelSchema = z.object({
+    id: z.string(),
+    name: z.string(),
+    family: z.enum(["gemini", "claude", "gpt-oss"]).optional(),
+    reasoning: z.boolean().optional(),
+    tool_call: z.boolean().optional(),
+    limit: z.object({
+        context: z.number(),
+        output: z.number()
+    }).optional()
+})
+
+export type AntigravityModel = z.infer<typeof AntigravityModelSchema>
+
+// Chat message schema (OpenAI-compatible)
+export const ChatMessageSchema = z.object({
+    role: z.enum(["user", "assistant", "system", "tool"]),
+    content: z.string().optional(),
+    tool_calls: z.array(z.object({
+        id: z.string(),
+        type: z.literal("function"),
+        function: z.object({
+            name: z.string(),
+            arguments: z.string()
+        })
+    })).optional(),
+    tool_call_id: z.string().optional()
+})
+
+export type ChatMessage = z.infer<typeof ChatMessageSchema>
+
+// Tool Definition Schema
+export const ToolDefinitionSchema = z.object({
+    type: z.literal("function"),
+    function: z.object({
+        name: z.string(),
+        description: z.string(),
+        parameters: z.object({
+            type: z.literal("object"),
+            properties: z.record(z.any()),
+            required: z.array(z.string()).optional()
+        })
+    })
+})
+
+export type ToolDefinition = z.infer<typeof ToolDefinitionSchema>
+
+// Chat request schema
+export const ChatRequestSchema = z.object({
+    model: z.string(),
+    messages: z.array(ChatMessageSchema),
+    stream: z.boolean().default(true),
+    temperature: z.number().optional(),
+    max_tokens: z.number().optional(),
+    tools: z.array(ToolDefinitionSchema).optional(),
+    tool_choice: z.union([
+        z.literal("auto"),
+        z.literal("none"),
+        z.object({
+            type: z.literal("function"),
+            function: z.object({ name: z.string() })
+        })
+    ]).optional(),
+    workspacePath: z.string().optional(),
+    enableTools: z.boolean().optional()
+})
+
+export type ChatRequest = z.infer<typeof ChatRequestSchema>
+
+// Chat response chunk schema
+export const ChatChunkSchema = z.object({
+    id: z.string().optional(),
+    object: z.string().optional(),
+    created: z.number().optional(),
+    model: z.string().optional(),
+    choices: z.array(z.object({
+        index: z.number(),
+        delta: z.object({
+            role: z.string().optional(),
+            content: z.string().optional(),
+            reasoning_content: z.string().optional()
+        }).optional(),
+        message: z.object({
+            role: z.string(),
+            content: z.string()
+        }).optional(),
+        finish_reason: z.string().nullable().optional()
+    }))
+})
+
+export type ChatChunk = z.infer<typeof ChatChunkSchema>
+
+// Available Antigravity models with their specifications
+export const ANTIGRAVITY_MODELS: AntigravityModel[] = [
+    // Gemini Models
+    {
+        id: "gemini-3-pro-low",
+        name: "Gemini 3 Pro Low (Antigravity)",
+        family: "gemini",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 1048576, output: 65535 }
+    },
+    {
+        id: "gemini-3-pro-high",
+        name: "Gemini 3 Pro High (Antigravity)",
+        family: "gemini",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 1048576, output: 65535 }
+    },
+    {
+        id: "gemini-3-flash",
+        name: "Gemini 3 Flash (Antigravity)",
+        family: "gemini",
+        reasoning: false,
+        tool_call: true,
+        limit: { context: 1048576, output: 65536 }
+    },
+    // Claude Models
+    {
+        id: "claude-sonnet-4-5",
+        name: "Claude Sonnet 4.5 (Antigravity)",
+        family: "claude",
+        reasoning: false,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    {
+        id: "claude-sonnet-4-5-thinking-low",
+        name: "Claude Sonnet 4.5 Thinking Low (Antigravity)",
+        family: "claude",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    {
+        id: "claude-sonnet-4-5-thinking-medium",
+        name: "Claude Sonnet 4.5 Thinking Medium (Antigravity)",
+        family: "claude",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    {
+        id: "claude-sonnet-4-5-thinking-high",
+        name: "Claude Sonnet 4.5 Thinking High (Antigravity)",
+        family: "claude",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    {
+        id: "claude-opus-4-5-thinking-low",
+        name: "Claude Opus 4.5 Thinking Low (Antigravity)",
+        family: "claude",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    {
+        id: "claude-opus-4-5-thinking-medium",
+        name: "Claude Opus 4.5 Thinking Medium (Antigravity)",
+        family: "claude",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    {
+        id: "claude-opus-4-5-thinking-high",
+        name: "Claude Opus 4.5 Thinking High (Antigravity)",
+        family: "claude",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 200000, output: 64000 }
+    },
+    // Other Models
+    {
+        id: "gpt-oss-120b-medium",
+        name: "GPT-OSS 120B Medium (Antigravity)",
+        family: "gpt-oss",
+        reasoning: true,
+        tool_call: true,
+        limit: { context: 131072, output: 32768 }
+    }
+]
+
+// Token storage key for Antigravity OAuth
+const ANTIGRAVITY_TOKEN_KEY = "antigravity_oauth_token"
+
+export interface AntigravityToken {
+    access_token: string
+    refresh_token?: string
+    expires_in: number
+    created_at: number
+    project_id?: string
+}
+
+export class AntigravityClient {
+    private config: AntigravityConfig
+    private currentEndpointIndex: number = 0
+    private modelsCache: AntigravityModel[] | null = null
+    private modelsCacheTime: number = 0
+    private readonly CACHE_TTL_MS = 5 * 60 * 1000 // 5 minutes
+
+    constructor(config?: Partial<AntigravityConfig>) {
+        this.config = AntigravityConfigSchema.parse(config || {})
+    }
+
+    /**
+     * Get the current active endpoint with automatic fallback
+     */
+    private getEndpoint(): string {
+        const endpoints = this.config.endpoints
+        return endpoints[this.currentEndpointIndex] || endpoints[0]
+    }
+
+    /**
+     * Rotate to next endpoint on failure
+     */
+    private rotateEndpoint(): void {
+        this.currentEndpointIndex = (this.currentEndpointIndex + 1) % this.config.endpoints.length
+        console.log(`Antigravity: Rotating to endpoint ${this.getEndpoint()}`)
+    }
+
+    /**
+     * Get stored OAuth token from localStorage (browser context)
+     */
+    getStoredToken(): AntigravityToken | null {
+        if (typeof window === "undefined") return null
+        try {
+            const raw = window.localStorage.getItem(ANTIGRAVITY_TOKEN_KEY)
+            if (!raw) return null
+            return JSON.parse(raw)
+        } catch {
+            return null
+        }
+    }
+
+    /**
+     * Check if the stored token is still valid
+     */
+    isTokenValid(token: AntigravityToken | null): boolean {
+        if (!token) return false
+        const createdAt = token.created_at > 1e12 ? Math.floor(token.created_at / 1000) : token.created_at
+        const expiresAt = (createdAt + token.expires_in) * 1000 - 300000 // 5 min buffer
+        return Date.now() < expiresAt
+    }
+
+    /**
+     * Get authorization headers for API requests
+     */
+    private getAuthHeaders(): Record<string, string> {
+        const headers: Record<string, string> = {
+            "Content-Type": "application/json",
+            "User-Agent": "NomadArch/1.0"
+        }
+
+        // Try OAuth token first
+        const token = this.getStoredToken()
+        if (token && this.isTokenValid(token)) {
+            headers["Authorization"] = `Bearer ${token.access_token}`
+        } else if (this.config.apiKey) {
+            headers["Authorization"] = `Bearer ${this.config.apiKey}`
+        }
+
+        return headers
+    }
+
+    /**
+     * Check if the client is authenticated
+     */
+    isAuthenticated(): boolean {
+        const token = this.getStoredToken()
+        return this.isTokenValid(token) || Boolean(this.config.apiKey)
+    }
+
+    /**
+     * Get available Antigravity models
+     */
+    async getModels(): Promise<AntigravityModel[]> {
+        // Return cached models if still valid
+        const now = Date.now()
+        if (this.modelsCache && (now - this.modelsCacheTime) < this.CACHE_TTL_MS) {
+            return this.modelsCache
+        }
+
+        // If authenticated, return full model list
+        if (this.isAuthenticated()) {
+            this.modelsCache = ANTIGRAVITY_MODELS
+            this.modelsCacheTime = now
+            return ANTIGRAVITY_MODELS
+        }
+
+        // Not authenticated - return empty list
+        return []
+    }
+
+    /**
+     * Test connection to Antigravity API
+     */
+    async testConnection(): Promise<boolean> {
+        if (!this.isAuthenticated()) {
+            return false
+        }
+
+        try {
+            // Try a simple models list request to verify connectivity
+            const response = await fetch(`${this.getEndpoint()}/models`, {
+                headers: this.getAuthHeaders(),
+                signal: AbortSignal.timeout(10000)
+            })
+            return response.ok
+        } catch (error) {
+            console.warn("Antigravity connection test failed:", error)
+            // Try next endpoint
+            this.rotateEndpoint()
+            return false
+        }
+    }
+
+    /**
+     * Chat completion (streaming) with automatic endpoint fallback
+     */
+    async *chatStream(request: ChatRequest): AsyncGenerator<ChatChunk> {
+        if (!this.isAuthenticated()) {
+            throw new Error("Antigravity: Not authenticated. Please sign in with Google OAuth.")
+        }
+
+        let lastError: Error | null = null
+        const maxRetries = this.config.endpoints.length
+
+        for (let retry = 0; retry < maxRetries; retry++) {
+            try {
+                const endpoint = this.getEndpoint()
+                const response = await fetch(`${endpoint}/chat/completions`, {
+                    method: "POST",
+                    headers: this.getAuthHeaders(),
+                    body: JSON.stringify({
+                        ...request,
+                        stream: true
+                    })
+                })
+
+                if (!response.ok) {
+                    const errorText = await response.text()
+                    if (response.status === 401 || response.status === 403) {
+                        throw new Error(`Antigravity authentication failed: ${errorText}`)
+                    }
+                    // Try next endpoint for other errors
+                    this.rotateEndpoint()
+                    lastError = new Error(`Antigravity API error (${response.status}): ${errorText}`)
+                    continue
+                }
+
+                if (!response.body) {
+                    throw new Error("Response body is missing")
+                }
+
+                const reader = response.body.getReader()
+                const decoder = new TextDecoder()
+                let buffer = ""
+
+                try {
+                    while (true) {
+                        const { done, value } = await reader.read()
+                        if (done) break
+
+                        buffer += decoder.decode(value, { stream: true })
+                        const lines = buffer.split("\n")
+                        buffer = lines.pop() || ""
+
+                        for (const line of lines) {
+                            const trimmed = line.trim()
+                            if (trimmed.startsWith("data: ")) {
+                                const data = trimmed.slice(6)
+                                if (data === "[DONE]") return
+
+                                try {
+                                    const parsed = JSON.parse(data)
+                                    yield parsed as ChatChunk
+
+                                    // Check for finish
+                                    if (parsed.choices?.[0]?.finish_reason) {
+                                        return
+                                    }
+                                } catch (e) {
+                                    // Skip invalid JSON
+                                }
+                            }
+                        }
+                    }
+                } finally {
+                    reader.releaseLock()
+                }
+                return // Success, exit retry loop
+            } catch (error) {
+                lastError = error instanceof Error ? error : new Error(String(error))
+                if (error instanceof Error && error.message.includes("authentication")) {
+                    throw error // Don't retry auth errors
+                }
+                this.rotateEndpoint()
+            }
+        }
+
+        throw lastError || new Error("Antigravity: All endpoints failed")
+    }
+
+    /**
+     * Chat completion (non-streaming)
+     */
+    async chat(request: ChatRequest): Promise<ChatChunk> {
+        if (!this.isAuthenticated()) {
+            throw new Error("Antigravity: Not authenticated. Please sign in with Google OAuth.")
+        }
+
+        let lastError: Error | null = null
+        const maxRetries = this.config.endpoints.length
+
+        for (let retry = 0; retry < maxRetries; retry++) {
+            try {
+                const endpoint = this.getEndpoint()
+                const response = await fetch(`${endpoint}/chat/completions`, {
+                    method: "POST",
+                    headers: this.getAuthHeaders(),
+                    body: JSON.stringify({
+                        ...request,
+                        stream: false
+                    })
+                })
+
+                if (!response.ok) {
+                    const errorText = await response.text()
+                    if (response.status === 401 || response.status === 403) {
+                        throw new Error(`Antigravity authentication failed: ${errorText}`)
+                    }
+                    this.rotateEndpoint()
+                    lastError = new Error(`Antigravity API error (${response.status}): ${errorText}`)
+                    continue
+                }
+
+                return await response.json()
+            } catch (error) {
+                lastError = error instanceof Error ? error : new Error(String(error))
+                if (error instanceof Error && error.message.includes("authentication")) {
+                    throw error
+                }
+                this.rotateEndpoint()
+            }
+        }
+
+        throw lastError || new Error("Antigravity: All endpoints failed")
+    }
+}
+
+export function getDefaultAntigravityConfig(): AntigravityConfig {
+    return {
+        enabled: true,
+        endpoints: [
+            "https://daily.antigravity.dev/v1beta",
+            "https://autopush.antigravity.dev/v1beta",
+            "https://antigravity.dev/v1beta"
+        ]
+    }
+}

packages/server/src/server/http-server.ts

@@ -22,6 +22,7 @@ import { registerOllamaRoutes } from "./routes/ollama"
 import { registerQwenRoutes } from "./routes/qwen"
 import { registerZAIRoutes } from "./routes/zai"
 import { registerOpenCodeZenRoutes } from "./routes/opencode-zen"
+import { registerAntigravityRoutes } from "./routes/antigravity"
 import { registerSkillsRoutes } from "./routes/skills"
 import { registerContextEngineRoutes } from "./routes/context-engine"
 import { registerNativeSessionsRoutes } from "./routes/native-sessions"
@@ -131,6 +132,7 @@ export function createHttpServer(deps: HttpServerDeps) {
   registerQwenRoutes(app, { logger: deps.logger })
   registerZAIRoutes(app, { logger: deps.logger })
   registerOpenCodeZenRoutes(app, { logger: deps.logger })
+  registerAntigravityRoutes(app, { logger: deps.logger })
   registerSkillsRoutes(app)
   registerContextEngineRoutes(app)
 

packages/server/src/server/routes/antigravity.ts

@@ -0,0 +1,336 @@
+import { FastifyInstance } from "fastify"
+import { AntigravityClient, type ChatRequest, getDefaultAntigravityConfig, type ChatMessage } from "../../integrations/antigravity"
+import { Logger } from "../../logger"
+import { CORE_TOOLS, executeTools, type ToolCall, type ToolResult } from "../../tools/executor"
+import { getMcpManager } from "../../mcp/client"
+
+interface AntigravityRouteDeps {
+    logger: Logger
+}
+
+// Maximum number of tool execution loops
+const MAX_TOOL_LOOPS = 10
+
+export async function registerAntigravityRoutes(
+    app: FastifyInstance,
+    deps: AntigravityRouteDeps
+) {
+    const logger = deps.logger.child({ component: "antigravity-routes" })
+
+    // Create shared client
+    const client = new AntigravityClient(getDefaultAntigravityConfig())
+
+    // List available Antigravity models
+    app.get('/api/antigravity/models', async (request, reply) => {
+        try {
+            const models = await client.getModels()
+
+            return {
+                models: models.map(m => ({
+                    id: m.id,
+                    name: m.name,
+                    family: m.family,
+                    provider: "antigravity",
+                    free: false, // These require Google OAuth
+                    reasoning: m.reasoning,
+                    tool_call: m.tool_call,
+                    limit: m.limit
+                }))
+            }
+        } catch (error) {
+            logger.error({ error }, "Failed to list Antigravity models")
+            return reply.status(500).send({ error: "Failed to list models" })
+        }
+    })
+
+    // Check authentication status
+    app.get('/api/antigravity/auth-status', async (request, reply) => {
+        try {
+            const authenticated = client.isAuthenticated()
+            return { authenticated }
+        } catch (error) {
+            logger.error({ error }, "Antigravity auth status check failed")
+            return reply.status(500).send({ error: "Auth status check failed" })
+        }
+    })
+
+    // Test connection
+    app.get('/api/antigravity/test', async (request, reply) => {
+        try {
+            const connected = await client.testConnection()
+            return { connected }
+        } catch (error) {
+            logger.error({ error }, "Antigravity connection test failed")
+            return reply.status(500).send({ error: "Connection test failed" })
+        }
+    })
+
+    // Chat completion endpoint WITH MCP TOOL SUPPORT
+    app.post('/api/antigravity/chat', async (request, reply) => {
+        try {
+            const chatRequest = request.body as ChatRequest & {
+                workspacePath?: string
+                enableTools?: boolean
+            }
+
+            // Extract workspace path for tool execution
+            const workspacePath = chatRequest.workspacePath || process.cwd()
+            const enableTools = chatRequest.enableTools !== false
+
+            logger.info({
+                workspacePath,
+                receivedWorkspacePath: chatRequest.workspacePath,
+                enableTools,
+                model: chatRequest.model
+            }, "Antigravity chat request received")
+
+            // Handle streaming with tool loop
+            if (chatRequest.stream) {
+                reply.raw.writeHead(200, {
+                    'Content-Type': 'text/event-stream',
+                    'Cache-Control': 'no-cache',
+                    'Connection': 'keep-alive',
+                })
+
+                try {
+                    await streamWithToolLoop(
+                        client,
+                        chatRequest,
+                        workspacePath,
+                        enableTools,
+                        reply.raw,
+                        logger
+                    )
+                    reply.raw.end()
+                } catch (streamError) {
+                    logger.error({ error: streamError }, "Antigravity streaming failed")
+                    reply.raw.write(`data: ${JSON.stringify({ error: String(streamError) })}\n\n`)
+                    reply.raw.end()
+                }
+            } else {
+                // Non-streaming with tool loop
+                const response = await chatWithToolLoop(
+                    client,
+                    chatRequest,
+                    workspacePath,
+                    enableTools,
+                    logger
+                )
+                return response
+            }
+        } catch (error) {
+            logger.error({ error }, "Antigravity chat request failed")
+            return reply.status(500).send({ error: "Chat request failed" })
+        }
+    })
+
+    logger.info("Antigravity routes registered with MCP tool support - Google OAuth required!")
+}
+
+/**
+ * Streaming chat with tool execution loop
+ */
+async function streamWithToolLoop(
+    client: AntigravityClient,
+    request: ChatRequest,
+    workspacePath: string,
+    enableTools: boolean,
+    rawResponse: any,
+    logger: Logger
+): Promise<void> {
+    let messages = [...request.messages]
+    let loopCount = 0
+
+    // Load MCP tools from workspace config
+    let allTools = [...CORE_TOOLS]
+    if (enableTools && workspacePath) {
+        try {
+            const mcpManager = getMcpManager()
+            await mcpManager.loadConfig(workspacePath)
+            const mcpTools = await mcpManager.getToolsAsOpenAIFormat()
+            allTools = [...CORE_TOOLS, ...mcpTools]
+            if (mcpTools.length > 0) {
+                logger.info({ mcpToolCount: mcpTools.length }, "Loaded MCP tools for Antigravity")
+            }
+        } catch (mcpError) {
+            logger.warn({ error: mcpError }, "Failed to load MCP tools")
+        }
+    }
+
+    // Inject tools if enabled
+    const requestWithTools: ChatRequest = {
+        ...request,
+        tools: enableTools ? allTools : undefined,
+        tool_choice: enableTools ? "auto" : undefined
+    }
+
+    while (loopCount < MAX_TOOL_LOOPS) {
+        loopCount++
+
+        // Accumulate tool calls from stream
+        let accumulatedToolCalls: { [index: number]: { id: string; name: string; arguments: string } } = {}
+        let hasToolCalls = false
+        let textContent = ""
+
+        // Stream response
+        for await (const chunk of client.chatStream({ ...requestWithTools, messages })) {
+            // Write chunk to client
+            rawResponse.write(`data: ${JSON.stringify(chunk)}\n\n`)
+
+            const choice = chunk.choices[0]
+            if (!choice) continue
+
+            // Accumulate text content
+            if (choice.delta?.content) {
+                textContent += choice.delta.content
+            }
+
+            // Accumulate tool calls from delta (if API supports it)
+            const deltaToolCalls = (choice.delta as any)?.tool_calls
+            if (deltaToolCalls) {
+                hasToolCalls = true
+                for (const tc of deltaToolCalls) {
+                    const idx = tc.index ?? 0
+                    if (!accumulatedToolCalls[idx]) {
+                        accumulatedToolCalls[idx] = { id: tc.id || "", name: "", arguments: "" }
+                    }
+                    if (tc.id) accumulatedToolCalls[idx].id = tc.id
+                    if (tc.function?.name) accumulatedToolCalls[idx].name += tc.function.name
+                    if (tc.function?.arguments) accumulatedToolCalls[idx].arguments += tc.function.arguments
+                }
+            }
+
+            // Check if we should stop
+            if (choice.finish_reason === "stop") {
+                rawResponse.write('data: [DONE]\n\n')
+                return
+            }
+        }
+
+        // If no tool calls, we're done
+        if (!hasToolCalls || !enableTools) {
+            rawResponse.write('data: [DONE]\n\n')
+            return
+        }
+
+        // Convert accumulated tool calls
+        const toolCalls: ToolCall[] = Object.values(accumulatedToolCalls).map(tc => ({
+            id: tc.id,
+            type: "function" as const,
+            function: {
+                name: tc.name,
+                arguments: tc.arguments
+            }
+        }))
+
+        if (toolCalls.length === 0) {
+            rawResponse.write('data: [DONE]\n\n')
+            return
+        }
+
+        logger.info({ toolCalls: toolCalls.map(tc => tc.function.name) }, "Executing tool calls")
+
+        // Add assistant message with tool calls
+        const assistantMessage: ChatMessage = {
+            role: "assistant",
+            content: textContent || undefined,
+            tool_calls: toolCalls
+        }
+        messages.push(assistantMessage)
+
+        // Execute tools
+        const toolResults = await executeTools(workspacePath, toolCalls)
+
+        // Notify client about tool execution via special event
+        for (const result of toolResults) {
+            const toolEvent = {
+                type: "tool_result",
+                tool_call_id: result.tool_call_id,
+                content: result.content
+            }
+            rawResponse.write(`data: ${JSON.stringify(toolEvent)}\n\n`)
+        }
+
+        // Add tool results to messages
+        for (const result of toolResults) {
+            const toolMessage: ChatMessage = {
+                role: "tool",
+                content: result.content,
+                tool_call_id: result.tool_call_id
+            }
+            messages.push(toolMessage)
+        }
+
+        logger.info({ loopCount, toolsExecuted: toolResults.length }, "Tool loop iteration complete")
+    }
+
+    logger.warn({ loopCount }, "Max tool loops reached")
+    rawResponse.write('data: [DONE]\n\n')
+}
+
+/**
+ * Non-streaming chat with tool execution loop
+ */
+async function chatWithToolLoop(
+    client: AntigravityClient,
+    request: ChatRequest,
+    workspacePath: string,
+    enableTools: boolean,
+    logger: Logger
+): Promise<any> {
+    let messages = [...request.messages]
+    let loopCount = 0
+    let lastResponse: any = null
+
+    // Inject tools if enabled
+    const requestWithTools: ChatRequest = {
+        ...request,
+        tools: enableTools ? CORE_TOOLS : undefined,
+        tool_choice: enableTools ? "auto" : undefined
+    }
+
+    while (loopCount < MAX_TOOL_LOOPS) {
+        loopCount++
+
+        const response = await client.chat({ ...requestWithTools, messages, stream: false })
+        lastResponse = response
+
+        const choice = response.choices[0]
+        if (!choice) break
+
+        const toolCalls = (choice.message as any)?.tool_calls
+
+        // If no tool calls, return
+        if (!toolCalls || toolCalls.length === 0 || !enableTools) {
+            return response
+        }
+
+        logger.info({ toolCalls: toolCalls.map((tc: any) => tc.function.name) }, "Executing tool calls")
+
+        // Add assistant message
+        const assistantMessage: ChatMessage = {
+            role: "assistant",
+            content: (choice.message as any).content || undefined,
+            tool_calls: toolCalls
+        }
+        messages.push(assistantMessage)
+
+        // Execute tools
+        const toolResults = await executeTools(workspacePath, toolCalls)
+
+        // Add tool results
+        for (const result of toolResults) {
+            const toolMessage: ChatMessage = {
+                role: "tool",
+                content: result.content,
+                tool_call_id: result.tool_call_id
+            }
+            messages.push(toolMessage)
+        }
+
+        logger.info({ loopCount, toolsExecuted: toolResults.length }, "Tool loop iteration complete")
+    }
+
+    logger.warn({ loopCount }, "Max tool loops reached")
+    return lastResponse
+}

packages/server/src/workspaces/manager.ts

@@ -68,6 +68,8 @@ export class WorkspaceManager {
   }
 
   async create(folder: string, name?: string): Promise<WorkspaceDescriptor> {
+    // Special constant for Native mode (no OpenCode binary)
+    const NATIVE_MODE_PATH = "__nomadarch_native__"
 
     const id = `${Date.now().toString(36)}`
     const binary = this.options.binaryRegistry.resolveDefault()
@@ -75,7 +77,15 @@ export class WorkspaceManager {
     const workspacePath = path.isAbsolute(folder) ? folder : path.resolve(this.options.rootDir, folder)
     clearWorkspaceSearchCache(workspacePath)
 
-    this.options.logger.info({ workspaceId: id, folder: workspacePath, binary: resolvedBinaryPath }, "Creating workspace")
+    // Check if we're in native mode
+    const isNativeMode = resolvedBinaryPath === NATIVE_MODE_PATH || binary.path === NATIVE_MODE_PATH
+
+    this.options.logger.info({
+      workspaceId: id,
+      folder: workspacePath,
+      binary: resolvedBinaryPath,
+      isNativeMode
+    }, "Creating workspace")
 
     const proxyPath = `/workspaces/${id}/instance`
 
@@ -87,13 +97,14 @@ export class WorkspaceManager {
       status: "starting",
       proxyPath,
       binaryId: resolvedBinaryPath,
-      binaryLabel: binary.label,
-      binaryVersion: binary.version,
+      binaryLabel: isNativeMode ? "NomadArch Native" : binary.label,
+      binaryVersion: isNativeMode ? "Native" : binary.version,
       createdAt: new Date().toISOString(),
       updatedAt: new Date().toISOString(),
     }
 
-    if (!descriptor.binaryVersion) {
+    // Native mode doesn't need binary version detection
+    if (!isNativeMode && !descriptor.binaryVersion) {
       descriptor.binaryVersion = this.detectBinaryVersion(resolvedBinaryPath)
     }
 
@@ -102,6 +113,31 @@ export class WorkspaceManager {
 
     this.options.eventBus.publish({ type: "workspace.created", workspace: descriptor })
 
+    // In native mode, we don't launch a binary - the workspace is immediately ready
+    // and uses native session management APIs instead
+    if (isNativeMode) {
+      this.options.logger.info({ workspaceId: id }, "Starting native mode workspace (no binary)")
+
+      // Native mode is immediately ready - no process to launch
+      descriptor.status = "ready"
+      descriptor.updatedAt = new Date().toISOString()
+      // No pid or port for native mode - it uses the server's own APIs
+
+      this.options.eventBus.publish({ type: "workspace.started", workspace: descriptor })
+      this.options.logger.info({ workspaceId: id }, "Native mode workspace ready")
+
+      // Trigger Context-Engine indexing (non-blocking)
+      const contextEngine = getContextEngineService()
+      if (contextEngine) {
+        contextEngine.indexPath(workspacePath).catch((error) => {
+          this.options.logger.warn({ workspaceId: id, error }, "Context-Engine indexing failed")
+        })
+      }
+
+      return descriptor
+    }
+
+    // SDK/binary mode - launch the OpenCode process
     const preferences = this.options.configStore.get().preferences ?? {}
     const userEnvironment = preferences.environmentVariables ?? {}
     const opencodeConfigDir = ensureWorkspaceOpencodeConfig(id)

packages/server/src/workspaces/runtime.ts

@@ -33,6 +33,12 @@ export class WorkspaceRuntime {
   async launch(options: LaunchOptions): Promise<{ pid: number; port: number; exitPromise: Promise<ProcessExitInfo>; getLastOutput: () => string }> {
     this.validateFolder(options.folder)
 
+    // Native mode should not use the runtime - it uses native session management instead
+    const NATIVE_MODE_PATH = "__nomadarch_native__"
+    if (options.binaryPath === NATIVE_MODE_PATH) {
+      throw new Error(`Native mode does not use binary launches. Use native session management APIs instead.`)
+    }
+
     // Check if binary exists before attempting to launch
     try {
       accessSync(options.binaryPath, constants.F_OK)

packages/ui/src/components/advanced-settings-modal.tsx

@@ -6,6 +6,7 @@ import OllamaCloudSettings from "./settings/OllamaCloudSettings"
 import QwenCodeSettings from "./settings/QwenCodeSettings"
 import ZAISettings from "./settings/ZAISettings"
 import OpenCodeZenSettings from "./settings/OpenCodeZenSettings"
+import AntigravitySettings from "./settings/AntigravitySettings"
 
 interface AdvancedSettingsModalProps {
   open: boolean
@@ -75,6 +76,15 @@ const AdvancedSettingsModal: Component<AdvancedSettingsModalProps> = (props) =>
                 >
                   Z.AI
                 </button>
+                <button
+                  class={`px-4 py-2 text-sm font-medium border-b-2 whitespace-nowrap ${activeTab() === "antigravity"
+                    ? "border-purple-500 text-purple-400"
+                    : "border-transparent hover:border-gray-300"
+                    }`}
+                  onClick={() => setActiveTab("antigravity")}
+                >
+                  🚀 Antigravity
+                </button>
               </div>
             </div>
 
@@ -115,6 +125,10 @@ const AdvancedSettingsModal: Component<AdvancedSettingsModalProps> = (props) =>
               <Show when={activeTab() === "zai"}>
                 <ZAISettings />
               </Show>
+
+              <Show when={activeTab() === "antigravity"}>
+                <AntigravitySettings />
+              </Show>
             </div>
 
             <div class="px-6 py-4 border-t flex justify-end" style={{ "border-color": "var(--border-base)" }}>

packages/ui/src/components/settings/AntigravitySettings.tsx

@@ -0,0 +1,428 @@
+import { Component, createSignal, onMount, For, Show } from 'solid-js'
+import { Rocket, CheckCircle, XCircle, Loader, Sparkles, LogIn, LogOut, Shield } from 'lucide-solid'
+import { getUserScopedKey } from '../../lib/user-storage'
+
+interface AntigravityModel {
+    id: string
+    name: string
+    family?: string
+    reasoning?: boolean
+    tool_call?: boolean
+    limit?: {
+        context: number
+        output: number
+    }
+}
+
+interface AntigravityToken {
+    access_token: string
+    refresh_token?: string
+    expires_in: number
+    created_at: number
+}
+
+const ANTIGRAVITY_TOKEN_KEY = "antigravity_oauth_token"
+const GOOGLE_OAUTH_CLIENT_ID = "782068742485-pf45b4gldtk7q847g3v5ercqfl31nkud.apps.googleusercontent.com" // Antigravity/Gemini CLI client
+
+const AntigravitySettings: Component = () => {
+    const [models, setModels] = createSignal<AntigravityModel[]>([])
+    const [isLoading, setIsLoading] = createSignal(true)
+    const [connectionStatus, setConnectionStatus] = createSignal<'idle' | 'testing' | 'connected' | 'failed'>('idle')
+    const [authStatus, setAuthStatus] = createSignal<'unknown' | 'authenticated' | 'unauthenticated'>('unknown')
+    const [isAuthenticating, setIsAuthenticating] = createSignal(false)
+    const [error, setError] = createSignal<string | null>(null)
+
+    // Check stored token on mount
+    onMount(async () => {
+        checkAuthStatus()
+        await loadModels()
+        await testConnection()
+    })
+
+    const getStoredToken = (): AntigravityToken | null => {
+        if (typeof window === "undefined") return null
+        try {
+            const raw = window.localStorage.getItem(getUserScopedKey(ANTIGRAVITY_TOKEN_KEY))
+            if (!raw) return null
+            return JSON.parse(raw)
+        } catch {
+            return null
+        }
+    }
+
+    const isTokenValid = (token: AntigravityToken | null): boolean => {
+        if (!token) return false
+        const createdAt = token.created_at > 1e12 ? Math.floor(token.created_at / 1000) : token.created_at
+        const expiresAt = (createdAt + token.expires_in) * 1000 - 300000 // 5 min buffer
+        return Date.now() < expiresAt
+    }
+
+    const checkAuthStatus = () => {
+        const token = getStoredToken()
+        if (isTokenValid(token)) {
+            setAuthStatus('authenticated')
+        } else {
+            setAuthStatus('unauthenticated')
+        }
+    }
+
+    const loadModels = async () => {
+        setIsLoading(true)
+        try {
+            const response = await fetch('/api/antigravity/models')
+            if (response.ok) {
+                const data = await response.json()
+                setModels(data.models || [])
+                setError(null)
+            } else {
+                throw new Error('Failed to load models')
+            }
+        } catch (err) {
+            console.error('Failed to load Antigravity models:', err)
+            setError('Failed to load models')
+        } finally {
+            setIsLoading(false)
+        }
+    }
+
+    const testConnection = async () => {
+        setConnectionStatus('testing')
+        try {
+            const response = await fetch('/api/antigravity/test')
+            if (response.ok) {
+                const data = await response.json()
+                setConnectionStatus(data.connected ? 'connected' : 'failed')
+            } else {
+                setConnectionStatus('failed')
+            }
+        } catch (err) {
+            setConnectionStatus('failed')
+        }
+    }
+
+    const startGoogleOAuth = async () => {
+        setIsAuthenticating(true)
+        setError(null)
+
+        try {
+            // Open Google OAuth in a new window
+            const redirectUri = `${window.location.origin}/auth/antigravity/callback`
+            const scope = encodeURIComponent("openid email profile https://www.googleapis.com/auth/cloud-platform")
+            const state = crypto.randomUUID()
+
+            // Store state for verification
+            window.localStorage.setItem('antigravity_oauth_state', state)
+
+            const authUrl = `https://accounts.google.com/o/oauth2/v2/auth?` +
+                `client_id=${GOOGLE_OAUTH_CLIENT_ID}&` +
+                `redirect_uri=${encodeURIComponent(redirectUri)}&` +
+                `response_type=token&` +
+                `scope=${scope}&` +
+                `state=${state}&` +
+                `prompt=consent`
+
+            // Open popup
+            const width = 500
+            const height = 600
+            const left = (window.screen.width - width) / 2
+            const top = (window.screen.height - height) / 2
+
+            const popup = window.open(
+                authUrl,
+                'antigravity-oauth',
+                `width=${width},height=${height},left=${left},top=${top}`
+            )
+
+            if (!popup) {
+                throw new Error('Failed to open authentication window. Please allow popups.')
+            }
+
+            // Poll for token in URL hash
+            const checkClosed = setInterval(() => {
+                try {
+                    if (popup.closed) {
+                        clearInterval(checkClosed)
+                        setIsAuthenticating(false)
+                        checkAuthStatus()
+                        loadModels()
+                    } else {
+                        // Check if we can access the popup location (same origin after redirect)
+                        const hash = popup.location.hash
+                        if (hash && hash.includes('access_token')) {
+                            const params = new URLSearchParams(hash.substring(1))
+                            const accessToken = params.get('access_token')
+                            const expiresIn = parseInt(params.get('expires_in') || '3600', 10)
+
+                            if (accessToken) {
+                                const token: AntigravityToken = {
+                                    access_token: accessToken,
+                                    expires_in: expiresIn,
+                                    created_at: Date.now()
+                                }
+
+                                window.localStorage.setItem(
+                                    getUserScopedKey(ANTIGRAVITY_TOKEN_KEY),
+                                    JSON.stringify(token)
+                                )
+
+                                popup.close()
+                                clearInterval(checkClosed)
+                                setIsAuthenticating(false)
+                                setAuthStatus('authenticated')
+                                loadModels()
+                            }
+                        }
+                    }
+                } catch (e) {
+                    // Cross-origin error - popup is on Google's domain, still waiting
+                }
+            }, 500)
+
+            // Cleanup after 5 minutes
+            setTimeout(() => {
+                clearInterval(checkClosed)
+                if (!popup.closed) {
+                    popup.close()
+                }
+                setIsAuthenticating(false)
+            }, 300000)
+
+        } catch (err: any) {
+            console.error('OAuth error:', err)
+            setError(err.message || 'Authentication failed')
+            setIsAuthenticating(false)
+        }
+    }
+
+    const signOut = () => {
+        window.localStorage.removeItem(getUserScopedKey(ANTIGRAVITY_TOKEN_KEY))
+        setAuthStatus('unauthenticated')
+        setModels([])
+    }
+
+    const formatNumber = (num: number): string => {
+        if (num >= 1000000) return `${(num / 1000000).toFixed(1)}M`
+        if (num >= 1000) return `${(num / 1000).toFixed(0)}K`
+        return num.toString()
+    }
+
+    const getModelFamily = (model: AntigravityModel): { label: string; color: string } => {
+        if (model.id.startsWith('gemini')) return { label: 'Gemini', color: 'bg-blue-500/20 text-blue-400' }
+        if (model.id.startsWith('claude')) return { label: 'Claude', color: 'bg-orange-500/20 text-orange-400' }
+        if (model.id.startsWith('gpt')) return { label: 'GPT', color: 'bg-green-500/20 text-green-400' }
+        return { label: model.family || 'Other', color: 'bg-zinc-700 text-zinc-400' }
+    }
+
+    return (
+        <div class="space-y-6 p-6">
+            {/* Header */}
+            <div class="flex items-center justify-between">
+                <div class="flex items-center gap-3">
+                    <div class="p-2 bg-gradient-to-br from-purple-500/20 to-blue-500/20 rounded-lg">
+                        <Rocket class="w-6 h-6 text-purple-400" />
+                    </div>
+                    <div>
+                        <h2 class="text-xl font-semibold text-white">Antigravity</h2>
+                        <p class="text-sm text-zinc-400">Premium models via Google OAuth</p>
+                    </div>
+                </div>
+
+                <div class="flex items-center gap-2">
+                    {connectionStatus() === 'testing' && (
+                        <span class="flex items-center gap-2 text-sm text-zinc-400">
+                            <Loader class="w-4 h-4 animate-spin" />
+                            Testing...
+                        </span>
+                    )}
+                    {connectionStatus() === 'connected' && (
+                        <span class="flex items-center gap-2 text-sm text-emerald-400">
+                            <CheckCircle class="w-4 h-4" />
+                            Connected
+                        </span>
+                    )}
+                    {connectionStatus() === 'failed' && (
+                        <span class="flex items-center gap-2 text-sm text-red-400">
+                            <XCircle class="w-4 h-4" />
+                            Offline
+                        </span>
+                    )}
+                </div>
+            </div>
+
+            {/* Info Banner */}
+            <div class="bg-gradient-to-r from-purple-500/10 via-blue-500/10 to-purple-500/10 border border-purple-500/20 rounded-xl p-4">
+                <div class="flex items-start gap-3">
+                    <Sparkles class="w-5 h-5 text-purple-400 mt-0.5" />
+                    <div>
+                        <h3 class="font-semibold text-purple-300 mb-1">Premium AI Models via Google</h3>
+                        <p class="text-sm text-zinc-300">
+                            Antigravity provides access to Gemini 3 Pro/Flash, Claude Sonnet 4.5, Claude Opus 4.5,
+                            and GPT-OSS 120B through Google's rate limits. Sign in with your Google account to get started.
+                        </p>
+                    </div>
+                </div>
+            </div>
+
+            {/* Authentication Section */}
+            <div class="bg-zinc-900/50 border border-zinc-800 rounded-xl p-4">
+                <div class="flex items-center justify-between">
+                    <div class="flex items-center gap-3">
+                        <Shield class="w-5 h-5 text-zinc-400" />
+                        <div>
+                            <h4 class="font-medium text-white">Google OAuth Authentication</h4>
+                            <p class="text-xs text-zinc-500">
+                                {authStatus() === 'authenticated'
+                                    ? 'You are signed in and can use Antigravity models'
+                                    : 'Sign in with Google to access premium models'}
+                            </p>
+                        </div>
+                    </div>
+
+                    <Show when={authStatus() === 'unauthenticated'}>
+                        <button
+                            onClick={startGoogleOAuth}
+                            disabled={isAuthenticating()}
+                            class="flex items-center gap-2 px-4 py-2 bg-purple-600 hover:bg-purple-500 disabled:bg-purple-600/50 text-white rounded-lg transition-colors"
+                        >
+                            {isAuthenticating() ? (
+                                <>
+                                    <Loader class="w-4 h-4 animate-spin" />
+                                    Signing in...
+                                </>
+                            ) : (
+                                <>
+                                    <LogIn class="w-4 h-4" />
+                                    Sign in with Google
+                                </>
+                            )}
+                        </button>
+                    </Show>
+
+                    <Show when={authStatus() === 'authenticated'}>
+                        <div class="flex items-center gap-3">
+                            <span class="flex items-center gap-2 px-3 py-1.5 bg-emerald-500/20 text-emerald-400 rounded-lg text-sm">
+                                <CheckCircle class="w-4 h-4" />
+                                Authenticated
+                            </span>
+                            <button
+                                onClick={signOut}
+                                class="flex items-center gap-2 px-3 py-1.5 text-sm text-zinc-400 hover:text-white bg-zinc-800 hover:bg-zinc-700 rounded-lg transition-colors"
+                            >
+                                <LogOut class="w-4 h-4" />
+                                Sign out
+                            </button>
+                        </div>
+                    </Show>
+                </div>
+            </div>
+
+            {/* Error Display */}
+            <Show when={error()}>
+                <div class="p-4 bg-red-500/10 border border-red-500/30 rounded-lg text-red-400 text-sm">
+                    {error()}
+                </div>
+            </Show>
+
+            {/* Models Grid */}
+            <div class="space-y-4">
+                <div class="flex items-center justify-between">
+                    <h3 class="text-lg font-medium text-white">Available Models</h3>
+                    <button
+                        onClick={loadModels}
+                        disabled={isLoading()}
+                        class="flex items-center gap-2 px-3 py-1.5 text-sm bg-zinc-800 hover:bg-zinc-700 rounded-lg transition-colors"
+                    >
+                        {isLoading() ? <Loader class="w-4 h-4 animate-spin" /> : null}
+                        Refresh
+                    </button>
+                </div>
+
+                <Show when={isLoading()}>
+                    <div class="flex items-center justify-center py-12">
+                        <div class="flex items-center gap-3 text-zinc-400">
+                            <Loader class="w-6 h-6 animate-spin" />
+                            <span>Loading models...</span>
+                        </div>
+                    </div>
+                </Show>
+
+                <Show when={!isLoading() && models().length > 0}>
+                    <div class="grid grid-cols-1 md:grid-cols-2 gap-4">
+                        <For each={models()}>
+                            {(model) => {
+                                const family = getModelFamily(model)
+                                return (
+                                    <div class="group bg-zinc-900/50 border border-zinc-800 hover:border-purple-500/50 rounded-xl p-4 transition-all">
+                                        <div class="flex items-start justify-between mb-3">
+                                            <div>
+                                                <h4 class="font-semibold text-white group-hover:text-purple-300 transition-colors">
+                                                    {model.name}
+                                                </h4>
+                                                <p class="text-xs text-zinc-500 font-mono">{model.id}</p>
+                                            </div>
+                                            <span class={`px-2 py-0.5 text-[10px] font-bold uppercase rounded ${family.color}`}>
+                                                {family.label}
+                                            </span>
+                                        </div>
+
+                                        <div class="flex flex-wrap gap-2 mb-3">
+                                            {model.reasoning && (
+                                                <span class="px-2 py-0.5 text-[10px] bg-purple-500/20 text-purple-400 rounded">
+                                                    Thinking
+                                                </span>
+                                            )}
+                                            {model.tool_call && (
+                                                <span class="px-2 py-0.5 text-[10px] bg-blue-500/20 text-blue-400 rounded">
+                                                    Tool Use
+                                                </span>
+                                            )}
+                                        </div>
+
+                                        {model.limit && (
+                                            <div class="flex items-center gap-4 text-xs text-zinc-500">
+                                                <span>Context: {formatNumber(model.limit.context)}</span>
+                                                <span>Output: {formatNumber(model.limit.output)}</span>
+                                            </div>
+                                        )}
+                                    </div>
+                                )
+                            }}
+                        </For>
+                    </div>
+                </Show>
+
+                <Show when={!isLoading() && models().length === 0 && authStatus() === 'authenticated'}>
+                    <div class="text-center py-12 text-zinc-500">
+                        <p>No models available at this time.</p>
+                        <button
+                            onClick={loadModels}
+                            class="mt-4 px-4 py-2 text-sm bg-purple-500/20 text-purple-400 hover:bg-purple-500/30 rounded-lg transition-colors"
+                        >
+                            Try Again
+                        </button>
+                    </div>
+                </Show>
+
+                <Show when={!isLoading() && models().length === 0 && authStatus() === 'unauthenticated'}>
+                    <div class="text-center py-12 text-zinc-500">
+                        <p>Sign in with Google to see available models.</p>
+                    </div>
+                </Show>
+            </div>
+
+            {/* Usage Info */}
+            <div class="bg-zinc-900/50 border border-zinc-800 rounded-xl p-4">
+                <h4 class="font-medium text-white mb-2">How to Use</h4>
+                <ul class="text-sm text-zinc-400 space-y-1">
+                    <li>• Sign in with your Google account above</li>
+                    <li>• Select any Antigravity model from the model picker in chat</li>
+                    <li>• Models include Gemini 3, Claude Sonnet/Opus 4.5, and GPT-OSS</li>
+                    <li>• Thinking-enabled models show step-by-step reasoning</li>
+                    <li>• Uses Google's rate limits for maximum throughput</li>
+                </ul>
+            </div>
+        </div>
+    )
+}
+
+export default AntigravitySettings

packages/ui/src/stores/session-actions.ts

@@ -1116,6 +1116,144 @@ async function streamZAIChat(
   })
 }
 
+async function streamAntigravityChat(
+  instanceId: string,
+  sessionId: string,
+  providerId: string,
+  modelId: string,
+  messages: ExternalChatMessage[],
+  messageId: string,
+  assistantMessageId: string,
+  assistantPartId: string,
+): Promise<void> {
+  const controller = new AbortController()
+  const timeoutId = setTimeout(() => controller.abort(), STREAM_TIMEOUT_MS)
+
+  // Get workspace path for tool execution
+  const instance = instances().get(instanceId)
+  const workspacePath = instance?.folder || ""
+
+  const response = await fetch("/api/antigravity/chat", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    signal: controller.signal,
+    body: JSON.stringify({
+      model: modelId,
+      messages,
+      stream: true,
+      workspacePath,
+      enableTools: true,
+    }),
+  })
+
+  if (!response.ok) {
+    const errorText = await response.text().catch(() => "")
+    throw new Error(errorText || `Antigravity chat failed (${response.status})`)
+  }
+
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.beginStreamingUpdate()
+  let fullText = ""
+  let lastUpdateAt = 0
+
+  try {
+    await readSseStream(response, (data) => {
+      try {
+        const chunk = JSON.parse(data)
+        if (chunk?.error) throw new Error(chunk.error)
+
+        // Handle tool execution results (special events from backend)
+        if (chunk?.type === "tool_result") {
+          const toolResult = `\n\n✅ **Tool Executed:** ${chunk.content}\n\n`
+          fullText += toolResult
+          store.applyPartUpdate({
+            messageId: assistantMessageId,
+            part: { id: assistantPartId, type: "text", text: fullText } as any,
+          })
+
+          // Dispatch file change event to refresh sidebar
+          if (typeof window !== "undefined") {
+            console.log(`[EVENT] Dispatching FILE_CHANGE_EVENT for ${instanceId}`);
+            window.dispatchEvent(new CustomEvent(FILE_CHANGE_EVENT, { detail: { instanceId } }))
+          }
+
+          // Auto-trigger preview for HTML file writes
+          const content = chunk.content || ""
+          if (content.includes("Successfully wrote") &&
+            (content.includes(".html") || content.includes("index.") || content.includes(".htm"))) {
+            if (typeof window !== "undefined") {
+              const htmlMatch = content.match(/to\s+([^\s]+\.html?)/)
+              if (htmlMatch) {
+                const relativePath = htmlMatch[1]
+                const origin = typeof window !== "undefined" ? window.location.origin : "http://localhost:3000"
+                const apiOrigin = origin.replace(":3000", ":9898")
+                const previewUrl = `${apiOrigin}/api/workspaces/${instanceId}/serve/${relativePath}`
+
+                console.log(`[EVENT] Auto-preview triggered for ${previewUrl}`);
+                window.dispatchEvent(new CustomEvent(BUILD_PREVIEW_EVENT, {
+                  detail: { url: previewUrl, instanceId }
+                }))
+              }
+            }
+          }
+
+          return
+        }
+
+        const delta =
+          chunk?.choices?.[0]?.delta?.content ??
+          chunk?.choices?.[0]?.message?.content
+        if (typeof delta !== "string" || delta.length === 0) return
+        fullText += delta
+
+        const now = Date.now()
+        if (now - lastUpdateAt > 40) { // Limit to ~25 updates per second
+          lastUpdateAt = now
+          store.applyPartUpdate({
+            messageId: assistantMessageId,
+            part: { id: assistantPartId, type: "text", text: fullText } as any,
+          })
+        }
+      } catch (e) {
+        if (e instanceof Error) throw e
+      }
+    })
+
+    // Always apply final text update
+    store.applyPartUpdate({
+      messageId: assistantMessageId,
+      part: { id: assistantPartId, type: "text", text: fullText } as any,
+    })
+  } finally {
+    clearTimeout(timeoutId)
+    store.endStreamingUpdate()
+  }
+
+  store.upsertMessage({
+    id: assistantMessageId,
+    sessionId,
+    role: "assistant",
+    status: "complete",
+    updatedAt: Date.now(),
+    isEphemeral: false,
+  })
+  store.setMessageInfo(assistantMessageId, {
+    id: assistantMessageId,
+    role: "assistant",
+    providerID: providerId,
+    modelID: modelId,
+    time: { created: store.getMessageInfo(assistantMessageId)?.time?.created ?? Date.now(), completed: Date.now() },
+  } as any)
+  store.upsertMessage({
+    id: messageId,
+    sessionId,
+    role: "user",
+    status: "sent",
+    updatedAt: Date.now(),
+    isEphemeral: false,
+  })
+}
+
 async function sendMessage(
   instanceId: string,
   sessionId: string,
@@ -1264,7 +1402,7 @@ async function sendMessage(
     addDebugLog(`Merge System Instructions: ${Math.round(tPre2 - tPre1)}ms`, "warn")
   }
 
-  if (providerId === "ollama-cloud" || providerId === "qwen-oauth" || providerId === "opencode-zen" || providerId === "zai") {
+  if (providerId === "ollama-cloud" || providerId === "qwen-oauth" || providerId === "opencode-zen" || providerId === "zai" || providerId === "antigravity") {
     const store = messageStoreBus.getOrCreate(instanceId)
     const now = Date.now()
     const assistantMessageId = createId("msg")
@@ -1347,6 +1485,17 @@ async function sendMessage(
           assistantMessageId,
           assistantPartId,
         )
+      } else if (providerId === "antigravity") {
+        await streamAntigravityChat(
+          instanceId,
+          sessionId,
+          providerId,
+          effectiveModel.modelId,
+          externalMessages,
+          messageId,
+          assistantMessageId,
+          assistantPartId,
+        )
       } else {
         const qwenManager = new QwenOAuthManager()
         const token = await qwenManager.getValidToken()
@@ -1428,7 +1577,9 @@ async function sendMessage(
               ? "Z.AI request failed"
               : providerId === "opencode-zen"
                 ? "OpenCode Zen request failed"
-                : "Qwen request failed",
+                : providerId === "antigravity"
+                  ? "Antigravity request failed"
+                  : "Qwen request failed",
         message: error?.message || "Request failed",
         variant: "error",
         duration: 8000,

packages/ui/src/stores/session-api.ts

@@ -249,14 +249,83 @@ async function fetchZAIProvider(): Promise<Provider | null> {
   }
 }
 
+function getStoredAntigravityToken():
+  | { access_token: string; expires_in: number; created_at: number }
+  | null {
+  if (typeof window === "undefined") return null
+  try {
+    const raw = window.localStorage.getItem(getUserScopedKey("antigravity_oauth_token"))
+    if (!raw) return null
+    return JSON.parse(raw)
+  } catch {
+    return null
+  }
+}
+
+function isAntigravityTokenValid(token: { expires_in: number; created_at: number } | null): boolean {
+  if (!token) return false
+  const createdAt = token.created_at > 1e12 ? Math.floor(token.created_at / 1000) : token.created_at
+  const expiresAt = (createdAt + token.expires_in) * 1000 - 300000
+  return Date.now() < expiresAt
+}
+
+async function fetchAntigravityProvider(): Promise<Provider | null> {
+  // Check if user is authenticated with Antigravity (Google OAuth)
+  const token = getStoredAntigravityToken()
+  if (!isAntigravityTokenValid(token)) {
+    // Not authenticated - try to fetch models anyway (they show as available but require auth)
+    try {
+      const data = await fetchJson<{ models?: Array<{ id: string; name: string; limit?: Model["limit"] }> }>(
+        "/api/antigravity/models",
+      )
+      const models = Array.isArray(data?.models) ? data?.models ?? [] : []
+      if (models.length === 0) return null
+
+      return {
+        id: "antigravity",
+        name: "Antigravity (Google OAuth)",
+        models: models.map((model) => ({
+          id: model.id,
+          name: model.name,
+          providerId: "antigravity",
+          limit: model.limit,
+        })),
+        defaultModelId: "gemini-3-pro-high",
+      }
+    } catch {
+      return null
+    }
+  }
+
+  // User is authenticated - fetch full model list
+  const data = await fetchJson<{ models?: Array<{ id: string; name: string; limit?: Model["limit"] }> }>(
+    "/api/antigravity/models",
+  )
+  const models = Array.isArray(data?.models) ? data?.models ?? [] : []
+  if (models.length === 0) return null
+
+  return {
+    id: "antigravity",
+    name: "Antigravity (Google OAuth)",
+    models: models.map((model) => ({
+      id: model.id,
+      name: model.name,
+      providerId: "antigravity",
+      limit: model.limit,
+    })),
+    defaultModelId: "gemini-3-pro-high",
+  }
+}
+
 async function fetchExtraProviders(): Promise<Provider[]> {
-  const [ollama, zen, qwen, zai] = await Promise.all([
+  const [ollama, zen, qwen, zai, antigravity] = await Promise.all([
     fetchOllamaCloudProvider(),
     fetchOpenCodeZenProvider(),
     fetchQwenOAuthProvider(),
     fetchZAIProvider(),
+    fetchAntigravityProvider(),
   ])
-  return [ollama, zen, qwen, zai].filter((provider): provider is Provider => Boolean(provider))
+  return [ollama, zen, qwen, zai, antigravity].filter((provider): provider is Provider => Boolean(provider))
 }
 
 function removeDuplicateProviders(base: Provider[], extras: Provider[]): Provider[] {