Desktop custom tools fail with Bun workspace dependencies and Node ESM resolution #33366

Description

OpenCode Desktop v1.17.9 fails to load project-local custom tools in a setup that is valid under the Bun-based OpenCode CLI/runtime expectations documented for custom tools.

There are two related failure modes in Desktop:

1. .opencode/package.json dependencies using the Bun/npm workspace protocol fail during Desktop background dependency installation with NpmInstallFailedError / Unsupported URL Type "workspace:".
2. If a custom tool imports a workspace TypeScript package whose package export points at .ts source, Desktop loads it through Node-style ESM resolution and fails on extensionless relative imports such as export * from "./foo", even though Bun and TypeScript moduleResolution: "Bundler" accept this.

This makes Desktop unable to send prompts in projects with local custom tools, while the same tool graph can load under Bun.

Why this appears Desktop-specific

The CLI path runs under Bun, but Desktop starts an Electron utility sidecar and imports the Node-targeted server bundle from dist/node/node.js. The Desktop sidecar also uses the internal Npm/Arborist dependency installer for config/tool/plugin dependencies. That behavior diverges from the docs, which say local plugin/custom-tool dependencies are installed with Bun and show custom tools using Bun APIs.

Minimal reproduction

Create a project with a Bun workspace package and a project-local custom tool:

// package.json
{
  "private": true,
  "type": "module",
  "workspaces": ["packages/*", ".opencode"]
}

// packages/example-core/package.json
{
  "name": "@example/core",
  "private": true,
  "type": "module",
  "exports": {
    ".": "./src/index.ts"
  }
}

// packages/example-core/src/index.ts
export * from "./message"

// packages/example-core/src/message.ts
export const message = "hello"

// .opencode/package.json
{
  "private": true,
  "type": "module",
  "dependencies": {
    "@example/core": "workspace:*",
    "@opencode-ai/plugin": "1.17.9"
  }
}

// .opencode/tools/example.ts
import { tool } from "@opencode-ai/plugin"
import { message } from "@example/core"

export default tool({
  description: "Return a test message",
  args: {},
  async execute() {
    return message
  },
})

Then open this project in OpenCode Desktop and send any prompt.

Actual behavior

Desktop logs show the background dependency install failure:

background dependency install failed ... NpmInstallFailedError ... Unsupported URL Type "workspace:": workspace:*

If the dependency graph is otherwise present, Desktop can then fail loading the package source with Node-style ESM resolution:

prompt_async failed ... Error [ERR_MODULE_NOT_FOUND]: Cannot find module '.../packages/example-core/src/message' imported from .../packages/example-core/src/index.ts

The UI only reports a generic failure such as:

Failed to send command
Unexpected server error. Check server logs for details.

Expected behavior

Desktop should either:

• load project-local TypeScript custom tools with behavior compatible with the Bun CLI/custom-tool documentation, including Bun workspace dependencies and Bun/TypeScript-style resolution, or
• clearly document that Desktop custom tools must be Node-compatible and cannot use Bun workspace dependencies / Bun-only module resolution, and surface a clear actionable UI error when a tool cannot be loaded.

A project-local custom tool load failure should not make the whole session unable to respond to prompts.

Environment

• OpenCode Desktop: v1.17.9
• OpenCode CLI: v1.17.9
• Bun: 1.3.14
• macOS arm64

Related issues

Possibly related, but not exact duplicates:

• plugin dependency failure causes silent prompt_async crash with ERR_MODULE_NOT_FOUND, no error shown in UI #28286: custom tool dependency failure causes silent prompt_async crash with ERR_MODULE_NOT_FOUND
• Electron sidecar: npm plugins fail to load — peer dep @opencode-ai/plugin resolves as @local #26085 / Windows Desktop 1.14.39 tries to install @opencode-ai/plugin@local #26003 / Server: background dependency install fails every session with @opencode-ai/plugin@local not found #30908 / Desktop app hangs on Windows 11 - @opencode-ai/plugin@local npm install failed #31708: Desktop sidecar dependency install failures involving @opencode-ai/plugin@local