Cannot load custom providers from local file paths #4324

Description

OpenCode fails to load custom providers when using local file paths, always attempting to install them from npm registry instead. This prevents important use cases like local development, private/internal providers, and custom integrations.

Current Behavior

When configuring a custom provider with a local path:

{
  "provider": {
    "my-custom-provider": {
      "name": "My Custom Provider",
      "npm": "/path/to/my-provider",
      "models": {
        "custom-model": { "name": "Custom Model" }
      }
    }
  }
}

OpenCode attempts to install it via npm:

bun add --force --exact /path/to/my-provider@latest

This fails with:

ProviderInitError: ProviderInitError
  data: {
    providerId: "my-custom-provider"
  }

BunInstallFailedError: BunInstallFailedError
  data: {
    pkg: "/path/to/my-provider",
    version: "latest"
  }

What could work:

OpenCode should detect local file paths and import them directly without attempting npm installation, similar to how other configuration options (like plugins and tools) support local paths.

Expected to work:

• Absolute paths: "/path/to/provider"
• Relative paths: "./providers/my-provider"
• File URLs: "file://./providers/my-provider"

what problems does this cause?

I'm trying to use opencode as a harness for generating information using llm's. We have a custom llm gateway that we use to handle all of the auth around different models. However, I'm unable to use the AI SDK as I cant make my own custom provider.

I've submitted PR #4323 with a proposed fix for this issue.

OpenCode version

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Steps to reproduce

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Screenshot and/or share link

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Operating System

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Terminal

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