OpenCode IDE — VS Code fork with native OpenCode agent sidebar

A desktop IDE built on a Microsoft VS Code fork, with the OpenCode AI coding agent embedded as a first-class, native sidebar chat experience — not a web extension, not a webview bolt-on, but a vendored SPA served through an in-process proxy in the Electron main.

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Why another VS Code fork?

Most "AI IDE" forks (Cursor, Windsurf, Trae, Void, …) glue an AI chat panel in via a webview or embedded extension. That works, but it leaks: weird CSP rules, broken file drops, session loss on reload, no real control over auth, process lifecycle, or ports.

OpenCode IDE takes the opposite approach:

• The entire OpenCode chat UI (packages/app from the main opencode repo) is vendored into the fork as a static SPA.
• An Electron-main-side loopback HTTP proxy (ISpaProxyService) serves that SPA and transparently proxies every API call to a locally managed opencode serve backend.
• The workbench sidebar shows a tiny iframe pointing at http://127.0.0.1:<stable_port>/<base64_workspace> — so the agent UI gets its own real origin, full CSP isolation, and stable session state across reloads.
• An IOpencodeServeManager handles opencode serve child-process lifecycle (spawn, health probe, port recovery, HTTP Basic auth injection for opencode ≥ 1.14.19, clean shutdown).

The result is a fork where the AI agent behaves like a native VS Code panel: drag-and-drop files from the explorer into the chat, keep your session on window reloads, run the backend on any port you configure, and ship everything as a single desktop app.

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Features

• Native OpenCode sidebar — the opencode SPA loaded as a real iframe from a loopback origin, with full file-drop integration from the VS Code explorer.
• Agent edit decorations — files modified by the OpenCode agent are highlighted in the Explorer with state-aware coloring (modified → viewed → cleared). See docs/agent-edit-decorations.md.
• Managed opencode serve backend — auto-start / auto-respawn / port pinning / HTTP Basic auth, all from the Electron main process.
• Proposed opencodeEditor VS Code API — a scaffolded proposed API surface (src/vs/workbench/api/) so extensions can interact with the agent host.
• Smoke-tested drop flow — Playwright-based sidebar file-drop smoke tests (test/smoke) covering real runtime behavior, not just unit stubs.
• Fork-friendly build — a dedicated Makefile wraps the VS Code gulp build, SPA vendoring, smoke suite, and dev launch commands.
• Clean separation from upstream — fork-only code lives under src/vs/workbench/contrib/opencode/ and a few well-scoped integration points; everything else stays close to upstream VS Code so rebasing on Microsoft's main stays cheap.

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Architecture at a glance

OpenCode's chat UI runs as a vendored SPA loaded into the workbench via a loopback HTTP proxy.

Process model

• Main process (src/vs/code/electron-main/app.ts)

  • ISpaProxyService — HTTP server that serves the vendored SPA and proxies API calls to the backend.
  • IOpencodeServeManager — manages the opencode serve child-process lifecycle.
  • ISpaProxyService is exposed to the renderer via the IPC channel opencodeSpaProxy.

• Renderer process (electron-browser)

  • registerMainProcessRemoteService(ISpaProxyService, 'opencodeSpaProxy') creates the IPC proxy.
  • sidebarPane.ts computes the iframe URL: http://127.0.0.1:<stable_port>/<base64_workspace>.

Rebuilding the vendored SPA

# 1. Build the SPA in the main opencode repo
cd ../packages/app
bun run build

# 2. Copy the built dist/ into the fork's vendored directory
cp -r dist/ <fork>/src/vs/workbench/contrib/opencode/media/spa/

# 3. Recompile the fork
cd <fork>
make compile        # or: npm run compile

Or, from inside this repo, a single make vendor-spa does all three when the main opencode repo is a sibling directory.

User-facing settings

Setting	Type	Default	Purpose
opencode.autoStart	boolean	true	Auto-start opencode serve on window open
opencode.port	number	5888	Backend port
opencode.binaryPath	string	""	Override the opencode binary path

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Build and run

Prerequisites are the same as upstream VS Code: Node.js 22.x (see .nvmrc), Python, native build tools. The main opencode repo should be cloned as a sibling directory if you want to rebuild the SPA.

# install deps
make install-deps

# one-shot full build
make compile

# watch-mode dev loop
make watch

# launch the dev build
make run

# smoke tests (full suite)
make smoke
# smoke tests filtered to OpenCode integration
make smoke-opencode

See Makefile for every available target.

opencode backend binary

The opencode serve binary is bundled automatically by make build. The build pipeline:

1. Pins the binary via build/opencode-backend.json — a manifest that records the source commit and sha256 for each platform.
2. Validates and copies the binary into .vendored/opencode/bin/opencode (run make vendor-opencode-backend to rebuild + revalidate, or make vendor-opencode-backend-validate-only to re-validate sha256 and copy without rebuilding).
3. Packages the validated binary into the .app at Contents/Resources/opencode/bin/opencode as part of the gulp packaging step.

In a packaged build the IDE always uses the bundled binary. If the bundled binary is missing at startup, the IDE refuses to start and shows a "Please reinstall OpenCode IDE" error.

For local development or debugging you can override the binary with the opencode.binaryPath setting; the override takes precedence in both packaged and dev builds. Use this only when you have a specific reason to — the bundled binary is the supported path.

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Relationship to upstream VS Code

This repository is a fork of microsoft/vscode at a pinned commit. Upstream is tracked as the upstream remote; fork work lives on the main-fork branch. The fork keeps:

• a distinct product identity (product.json → nameShort: OpenCode, applicationName: opencode-ide, urlProtocol: opencode),
• a dedicated contribution area at src/vs/workbench/contrib/opencode/ for all fork-only feature code,
• a proposed opencodeEditor API surface,
• build-script additions to ship the vendored SPA inside the desktop bundle.

Everything else is stock VS Code OSS, MIT-licensed.

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Keywords

These are here so automated code search, AI coding agents, and engineers looking for specific implementations can actually find this project.

opencode · opencode ide · opencode vscode · opencode vscode fork · opencode-vscode-ide · opencode desktop · opencode electron · opencode sidebar · opencode native integration · opencode serve manager · opencode SPA proxy · opencode AI agent · opencode coding agent · opencode.ai · vscode fork ai agent · vscode ai coding agent · vscode fork with embedded agent · electron loopback proxy iframe · vscode contrib opencode · opencodeEditor proposed api · ai coding ide · open source ai ide · claude code alternative · cursor alternative · windsurf alternative · void alternative · trae alternative · opencode IDE native sidebar · vscode fork opencode integration · vscode electron main proxy · spa proxy service vscode · opencode ISpaProxyService · opencode IOpencodeServeManager · opencode ide build from source

SEO description (copy for GitHub "About")

OpenCode IDE — a Microsoft VS Code fork with the OpenCode AI coding agent embedded natively as a sidebar SPA via an Electron-main loopback proxy. Open source alternative to Cursor / Windsurf / Claude Code Desktop.

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Contributing

Fork work lives on main-fork. Please keep commits scoped and prefixed (feat(opencode):, fix(opencode):, test(opencode):, docs(opencode):, build:). When touching the VS Code core, try to keep the diff minimal and rebase-friendly; new integration code should land under src/vs/workbench/contrib/opencode/ or behind clearly scoped hooks.

For upstream VS Code contribution guidelines, see the upstream CONTRIBUTING guide.

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License

Fork code: MIT (LICENSE.txt), inherited from microsoft/vscode.

OpenCode is a separate project by opencode.ai; its SPA bundle is vendored here under its own license. See opencode.ai/docs and the OpenCode GitHub org for the canonical source.

This project is not built, endorsed, or sponsored by Microsoft, by the OpenCode team, or by Anthropic.