Add OpenCode integration for Sandbox SDK

Adds support for running OpenCode (AI coding agent) inside Sandbox
containers with two usage patterns:

1. Programmatic SDK access via createOpencode():
   - Returns typed client from @opencode-ai/sdk
   - Custom fetch adapter routes requests through container
   - Automatic server lifecycle management

2. Web UI proxy via proxyToOpencode():
   - Exposes OpenCode's web interface through Workers
   - Handles localhost redirect for proper API routing

Features:
- Process reuse: detects existing OpenCode server on port
- Provider auth: extracts API keys from config to env vars
- Peer dependency on @opencode-ai/sdk (optional install)

Includes example worker demonstrating both patterns.

Author: ghostwriternr

examples/opencode/.dev.vars.example

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+ANTHROPIC_API_KEY=<YOUR-KEY-HERE>

examples/opencode/.gitignore

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+# Created by https://www.toptal.com/developers/gitignore/api/macos,node,git
+# Edit at https://www.toptal.com/developers/gitignore?templates=macos,node,git
+
+### Git ###
+# Created by git for backups. To disable backups in Git:
+# $ git config --global mergetool.keepBackup false
+*.orig
+
+# Created by git when using merge tools for conflicts
+*.BACKUP.*
+*.BASE.*
+*.LOCAL.*
+*.REMOTE.*
+*_BACKUP_*.txt
+*_BASE_*.txt
+*_LOCAL_*.txt
+*_REMOTE_*.txt
+
+### macOS ###
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+### macOS Patch ###
+# iCloud generated files
+*.icloud
+
+### Node ###
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional stylelint cache
+.stylelintcache
+
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variable files
+.env
+.env.development.local
+.env.test.local
+.env.production.local
+.env.local
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+out
+
+# Nuxt.js build / generate output
+.nuxt
+dist
+
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
+# vuepress build output
+.vuepress/dist
+
+# vuepress v2.x temp and cache directory
+.temp
+
+# Docusaurus cache and generated files
+.docusaurus
+
+# Serverless directories
+.serverless/
+
+# FuseBox cache
+.fusebox/
+
+# DynamoDB Local files
+.dynamodb/
+
+# TernJS port file
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+.vscode-test
+
+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*
+
+### Node Patch ###
+# Serverless Webpack directories
+.webpack/
+
+# Optional stylelint cache
+
+# SvelteKit build / generate output
+.svelte-kit
+
+# End of https://www.toptal.com/developers/gitignore/api/macos,node,git
+
+### Wrangler ###
+.wrangler/
+.env*
+!.env.example
+.dev.vars*
+!.dev.vars.example

examples/opencode/Dockerfile

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+FROM docker.io/cloudflare/sandbox:0.6.3
+
+# Add opencode install location to PATH before installation
+ENV PATH="/root/.opencode/bin:${PATH}"
+
+# Install OpenCode CLI
+# Download script first, then run - this shows errors instead of failing silently
+RUN curl -fsSL https://opencode.ai/install -o /tmp/install-opencode.sh \
+    && bash /tmp/install-opencode.sh \
+    && rm /tmp/install-opencode.sh \
+    && opencode --version
+
+# Expose OpenCode server port
+EXPOSE 4096

examples/opencode/README.md

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+# OpenCode + Sandbox SDK
+
+Run OpenCode inside Cloudflare Sandboxes! Just open the worker URL in your browser to get the full OpenCode web experience.
+
+## Quick Start
+
+1. Copy `.dev.vars.example` to `.dev.vars` and add your Anthropic API key:
+
+```bash
+cp .dev.vars.example .dev.vars
+# Edit .dev.vars with your ANTHROPIC_API_KEY
+```
+
+2. Install dependencies and run:
+
+```bash
+npm install
+npm run dev
+```
+
+3. Open http://localhost:8787 in your browser - you'll see the OpenCode web UI!
+
+## How It Works
+
+The worker acts as a transparent proxy to OpenCode running in the container:
+
+```
+Browser → Worker → Sandbox DO → Container :4096 → OpenCode Server
+                                                       ↓
+                                    Proxies UI from desktop.dev.opencode.ai
+```
+
+OpenCode handles everything:
+
+- API routes (`/session/*`, `/event`, etc.)
+- Web UI (proxied from `desktop.dev.opencode.ai`)
+- WebSocket for terminal
+
+## Key Benefits
+
+- **Web UI** - Full browser-based OpenCode experience
+- **Isolated execution** - Code runs in secure sandbox containers
+- **Persistent sessions** - Sessions survive across requests
+
+Happy hacking!

examples/opencode/package.json

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+{
+  "name": "@cloudflare/sandbox-opencode-example",
+  "version": "1.0.0",
+  "type": "module",
+  "private": true,
+  "description": "Example of running OpenCode web UI inside Sandbox",
+  "scripts": {
+    "deploy": "wrangler deploy",
+    "dev": "wrangler dev",
+    "start": "wrangler dev",
+    "types": "wrangler types",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@opencode-ai/sdk": "^1.0.0"
+  },
+  "devDependencies": {
+    "@cloudflare/sandbox": "*",
+    "@types/node": "^24.10.1",
+    "typescript": "^5.9.3",
+    "wrangler": "^4.50.0"
+  },
+  "author": "",
+  "license": "MIT"
+}

examples/opencode/src/index.ts

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+/**
+ * OpenCode + Sandbox SDK Example
+ *
+ * This example demonstrates both ways to use OpenCode with Sandbox:
+ * 1. Web UI - Browse to / for the full OpenCode web experience
+ * 2. Programmatic - POST to /api/test for SDK-based automation
+ */
+import { getSandbox } from '@cloudflare/sandbox';
+import { createOpencode, proxyToOpencode } from '@cloudflare/sandbox/opencode';
+import type { OpencodeClient } from '@opencode-ai/sdk';
+
+export default {
+  async fetch(request: Request, env: Env): Promise<Response> {
+    const url = new URL(request.url);
+    const sandbox = getSandbox(env.Sandbox, 'opencode');
+
+    // Programmatic SDK test endpoint
+    if (request.method === 'POST' && url.pathname === '/api/test') {
+      return handleSdkTest(sandbox, env);
+    }
+
+    // Everything else: Web UI proxy
+    return proxyToOpencode(request, sandbox, {
+      config: {
+        provider: {
+          anthropic: {
+            apiKey: env.ANTHROPIC_API_KEY
+          }
+        }
+      }
+    });
+  }
+};
+
+/**
+ * Test the programmatic SDK access
+ */
+async function handleSdkTest(
+  sandbox: ReturnType<typeof getSandbox>,
+  env: Env
+): Promise<Response> {
+  try {
+    // Clone a repo to give the agent something to work with
+    await sandbox.gitCheckout('https://github.com/cloudflare/agents.git', {
+      targetDir: '/home/user/agents'
+    });
+
+    // Get typed SDK client
+    const { client } = await createOpencode<OpencodeClient>(sandbox, {
+      config: {
+        provider: {
+          anthropic: {
+            apiKey: env.ANTHROPIC_API_KEY
+          }
+        }
+      }
+    });
+
+    // Create a session
+    const session = await client.session.create({
+      body: { title: 'Test Session' },
+      query: { directory: '/home/user/agents' }
+    });
+
+    if (!session.data) {
+      throw new Error(`Failed to create session: ${JSON.stringify(session)}`);
+    }
+
+    // Send a prompt using the SDK
+    const promptResult = await client.session.prompt({
+      path: { id: session.data.id },
+      query: { directory: '/home/user/agents' },
+      body: {
+        model: {
+          providerID: 'anthropic',
+          modelID: 'claude-haiku-4-5'
+        },
+        parts: [
+          {
+            type: 'text',
+            text: 'Summarize the README.md file in 2-3 sentences. Be concise.'
+          }
+        ]
+      }
+    });
+
+    // Extract text response from result
+    const parts = promptResult.data?.parts ?? [];
+    const textPart = parts.find((p: { type: string }) => p.type === 'text') as
+      | { text?: string }
+      | undefined;
+
+    return new Response(textPart?.text ?? 'No response', {
+      headers: { 'Content-Type': 'text/plain' }
+    });
+  } catch (error) {
+    console.error('SDK test error:', error);
+    const message = error instanceof Error ? error.message : 'Unknown error';
+    const stack = error instanceof Error ? error.stack : undefined;
+    return Response.json(
+      { success: false, error: message, stack },
+      { status: 500 }
+    );
+  }
+}
+
+// Export Sandbox DO for wrangler
+export { Sandbox } from '@cloudflare/sandbox';