OpenCode: Add OpenCode as a new provider

The OpenCode provider allows using a variety of models with an agent
harness that can gather more information from the codebase as required
(like with claude-code, codex, or gemini-cli).

This is an alternative to using OpenRouter directly, where the api
provider is more like a chatbot and cannot gather any additional context
beyond what was handed to it.

src/config/init.ts

@@ -34,6 +34,13 @@ export const AVAILABLE_REVIEWERS: ReviewerOption[] = [
     description: 'Uses your Gemini CLI (Google account, no API key needed)',
     needsApiKey: false
   },
+  {
+    id: 'antigravity',
+    name: 'Antigravity CLI',
+    model: 'antigravity',
+    description: 'Uses your Antigravity CLI (agy) — Google account, no API key needed',
+    needsApiKey: false
+  },
   {
     id: 'opencode-cli',
     name: 'OpenCode (via OpenRouter)',

src/providers/antigravity.ts

@@ -0,0 +1,194 @@
+import { spawn } from 'child_process'
+import type { AIProvider, Message, CliProviderOptions } from './types.js'
+import { CliSessionHelper } from './session-helper.js'
+import { preparePromptForCli } from '../utils/prompt-file.js'
+import { withRetry } from '../utils/retry.js'
+
+// Antigravity (`agy`) is Google's rebrand of the Gemini CLI. Compared to `gemini`:
+//  - auto-approve is `--dangerously-skip-permissions` (was `-y`)
+//  - print mode emits plain text on stdout (no `-o json` / `-o stream-json`)
+//  - there is no `--model` flag; agy pins its own model, so cliModel is ignored
+//
+// Unlike gemini-cli, this provider is stateless: agy's `--conversation` resume
+// re-prints the *entire* assistant transcript on every turn, which would duplicate
+// prior responses. Instead each call runs a fresh conversation with the full
+// message history in the prompt (the same approach the API providers use), so each
+// run returns exactly one response. We therefore expose no session id.
+export class AntigravityCliProvider implements AIProvider {
+  name = 'antigravity'
+  private cwd: string
+  private timeout: number  // ms, 0 = no timeout
+  private formatter = new CliSessionHelper()
+
+  constructor(_options?: CliProviderOptions) {
+    // No API key needed (uses Google account). agy has no --model flag, so cliModel is ignored.
+    this.cwd = process.cwd()
+    this.timeout = 15 * 60 * 1000  // 15 minutes default
+  }
+
+  setCwd(cwd: string) {
+    this.cwd = cwd
+  }
+
+  async chat(messages: Message[], systemPrompt?: string): Promise<string> {
+    const prompt = this.formatter.buildPrompt(messages, systemPrompt)
+    return withRetry(() => this.runAgy(prompt))
+  }
+
+  async *chatStream(messages: Message[], systemPrompt?: string): AsyncGenerator<string, void, unknown> {
+    const prompt = this.formatter.buildPrompt(messages, systemPrompt)
+    yield* this.runAgyStream(prompt)
+  }
+
+  private buildArgs(): string[] {
+    const args = ['--dangerously-skip-permissions']
+    if (this.timeout > 0) {
+      args.push('--print-timeout', `${Math.max(1, Math.ceil(this.timeout / 60000))}m`)
+    }
+    // Prompt is read from stdin via the `-` sentinel
+    args.push('--print', '-')
+    return args
+  }
+
+  private runAgy(prompt: string): Promise<string> {
+    const { prompt: stdinPrompt, cleanup } = preparePromptForCli(prompt)
+
+    return new Promise((resolve, reject) => {
+      const child = spawn('agy', this.buildArgs(), {
+        cwd: this.cwd,
+        stdio: ['pipe', 'pipe', 'pipe']
+      })
+
+      // Suppress EPIPE: if child exits early, close handler reports the real error
+      child.stdin.on('error', () => {})
+      child.stdin.write(stdinPrompt)
+      child.stdin.end()
+
+      let output = ''
+      let error = ''
+
+      child.stdout.on('data', (data) => {
+        output += data.toString()
+      })
+
+      child.stderr.on('data', (data) => {
+        error += data.toString()
+      })
+
+      child.on('close', (code) => {
+        cleanup()
+        if (code !== 0) {
+          reject(new Error(`Antigravity CLI exited with code ${code}: ${error}`))
+        } else {
+          resolve(output.trim())
+        }
+      })
+
+      child.on('error', (err) => {
+        cleanup()
+        reject(new Error(`Failed to run agy CLI: ${err.message}`))
+      })
+    })
+  }
+
+  private async *runAgyStream(prompt: string): AsyncGenerator<string, void, unknown> {
+    const { prompt: stdinPrompt, cleanup } = preparePromptForCli(prompt)
+
+    const child = spawn('agy', this.buildArgs(), {
+      cwd: this.cwd,
+      stdio: ['pipe', 'pipe', 'pipe']
+    })
+
+    const chunks: string[] = []
+    let resolveNext: ((value: { chunk: string | null }) => void) | null = null
+    let done = false
+    let error: Error | null = null
+    let lastActivity = Date.now()
+    let stderrBuf = ''
+
+    // Timeout checker - kill if no activity for too long
+    const timeoutChecker = this.timeout > 0 ? setInterval(() => {
+      if (Date.now() - lastActivity > this.timeout) {
+        child.kill('SIGTERM')
+        // Force kill if SIGTERM is ignored
+        const forceKill = setTimeout(() => {
+          try { child.kill('SIGKILL') } catch {}
+        }, 5000)
+        forceKill.unref()
+        done = true
+        const stderr = stderrBuf.trim()
+        error = new Error(`Antigravity CLI timed out after ${this.timeout / 1000}s of inactivity${stderr ? ': ' + stderr.slice(-500) : ''}`)
+        if (resolveNext) {
+          resolveNext({ chunk: null })
+        }
+      }
+    }, 10000) : null  // Check every 10s
+
+    const pushChunk = (chunk: string) => {
+      if (resolveNext) {
+        resolveNext({ chunk })
+        resolveNext = null
+      } else {
+        chunks.push(chunk)
+      }
+    }
+
+    // Print mode streams the plain-text response on stdout — yield chunks as-is
+    child.stdout.on('data', (data) => {
+      lastActivity = Date.now()
+      pushChunk(data.toString())
+    })
+
+    child.stderr.on('data', (data) => {
+      lastActivity = Date.now()  // Activity on stderr also counts
+      stderrBuf += data.toString()
+      if (stderrBuf.length > 10000) stderrBuf = stderrBuf.slice(-10000)
+    })
+
+    child.on('close', (code) => {
+      cleanup()
+      if (timeoutChecker) clearInterval(timeoutChecker)
+      done = true
+      if (code !== 0 && !error) {
+        const stderr = stderrBuf.trim()
+        error = new Error(`Antigravity CLI exited with code ${code}${stderr ? ': ' + stderr.slice(-500) : ''}`)
+      }
+      if (resolveNext) {
+        resolveNext({ chunk: null })
+      }
+    })
+
+    child.on('error', (err) => {
+      cleanup()
+      if (timeoutChecker) clearInterval(timeoutChecker)
+      done = true
+      error = new Error(`Failed to run agy CLI: ${err.message}`)
+      if (resolveNext) {
+        resolveNext({ chunk: null })
+      }
+    })
+
+    // Write prompt to stdin and close
+    // Suppress EPIPE: if child exits early, close handler reports the real error
+    child.stdin.on('error', () => {})
+    child.stdin.write(stdinPrompt)
+    child.stdin.end()
+
+    while (!done || chunks.length > 0) {
+      if (chunks.length > 0) {
+        yield chunks.shift()!
+      } else if (!done) {
+        const result = await new Promise<{ chunk: string | null }>((resolve) => {
+          resolveNext = resolve
+        })
+        if (result.chunk !== null) {
+          yield result.chunk
+        }
+      }
+    }
+
+    if (error) {
+      throw error
+    }
+  }
+}

src/providers/factory.ts

@@ -6,6 +6,7 @@ import { OpenAIProvider } from './openai.js'
 import { ClaudeCodeProvider } from './claude-code.js'
 import { CodexCliProvider } from './codex-cli.js'
 import { GeminiCliProvider } from './gemini-cli.js'
+import { AntigravityCliProvider } from './antigravity.js'
 import { GeminiProvider } from './gemini.js'
 import { OpencodeCliProvider } from './opencode-cli.js'
 import { QwenCodeProvider } from './qwen-code.js'
@@ -15,7 +16,7 @@ import { checkCliBinary } from './cli-check.js'
 
 // Parse CLI model string: 'gemini-cli:gemini-2.5-pro' → { provider: 'gemini-cli', cliModel: 'gemini-2.5-pro' }
 // Plain 'gemini-cli' → { provider: 'gemini-cli', cliModel: undefined }
-const CLI_PROVIDERS = ['claude-code', 'codex-cli', 'gemini-cli', 'opencode-cli', 'qwen-code'] as const
+const CLI_PROVIDERS = ['claude-code', 'codex-cli', 'gemini-cli', 'antigravity', 'opencode-cli', 'qwen-code'] as const
 type CliProviderName = typeof CLI_PROVIDERS[number]
 
 const OPENROUTER_PREFIX = 'openrouter/'
@@ -47,7 +48,7 @@ export function isCliModel(model: string): boolean {
   return (CLI_PROVIDERS as readonly string[]).includes(provider)
 }
 
-export function getProviderForModel(model: string): 'anthropic' | 'openai' | 'google' | 'claude-code' | 'codex-cli' | 'gemini-cli' | 'opencode-cli' | 'qwen-code' | 'minimax' | 'mock' | 'openrouter' {
+export function getProviderForModel(model: string): 'anthropic' | 'openai' | 'google' | 'claude-code' | 'codex-cli' | 'gemini-cli' | 'antigravity' | 'opencode-cli' | 'qwen-code' | 'minimax' | 'mock' | 'openrouter' {
   if (model.startsWith(OPENROUTER_PREFIX)) {
     return 'openrouter'
   }
@@ -101,6 +102,12 @@ export function createProvider(model: string, config: MagpieConfig): AIProvider
     return new GeminiCliProvider({ cliModel })
   }
 
+  // Antigravity CLI (`agy`) doesn't need API key config (uses Google account)
+  if (providerName === 'antigravity') {
+    checkCliBinary('agy', 'Antigravity')
+    return new AntigravityCliProvider({ cliModel })
+  }
+
   // Qwen Code CLI doesn't need API key config (uses OAuth)
   if (providerName === 'qwen-code') {
     checkCliBinary('qwen', 'Qwen Code')

src/utils/context-loader.ts

@@ -6,6 +6,7 @@ import { homedir } from 'os'
 const PROVIDER_CONTEXT_MAP: Record<string, string[]> = {
   'claude-code': ['CLAUDE.md', 'AGENTS.md', 'GEMINI.md'],
   'gemini-cli':  ['GEMINI.md', 'AGENTS.md', 'CLAUDE.md'],
+  'antigravity': ['GEMINI.md', 'AGENTS.md', 'CLAUDE.md'],
   'codex-cli':   ['AGENTS.md', 'CLAUDE.md', 'GEMINI.md'],
 }
 const DEFAULT_CONTEXT_FILES = ['CLAUDE.md', 'AGENTS.md', 'GEMINI.md']

tests/providers/factory.test.ts

@@ -44,6 +44,10 @@ describe('Provider Factory', () => {
       expect(getProviderForModel('codex-cli')).toBe('codex-cli')
     })
 
+    it('should return antigravity for antigravity model', () => {
+      expect(getProviderForModel('antigravity')).toBe('antigravity')
+    })
+
     it('should return opencode-cli for opencode-cli model (with and without :model suffix)', () => {
       expect(getProviderForModel('opencode-cli')).toBe('opencode-cli')
       expect(getProviderForModel('opencode-cli:openrouter/anthropic/claude-sonnet-4')).toBe('opencode-cli')
@@ -91,6 +95,11 @@ describe('Provider Factory', () => {
       expect(provider.name).toBe('codex-cli')
     })
 
+    it('should create antigravity provider', () => {
+      const provider = createProvider('antigravity', mockConfig)
+      expect(provider.name).toBe('antigravity')
+    })
+
     it('should create opencode-cli provider with no extra config', () => {
       const provider = createProvider('opencode-cli', mockConfig)
       expect(provider.name).toBe('opencode-cli')