[BUG] Custom provider initialization fails with "fn3 is not a function

Description

Attempting to use a custom provider configuration results in a TypeError: fn3 is not a function during provider initialization. The custom provider feature appears to be incomplete or has compatibility issues.

Reproduction Steps

Add the following to opencode.json:

{
  "provider": {
    "custom": {
      "api": "openai",
      "options": {
        "apiKey": "xxx",
        "baseURL": "http://localhost:8045/v1"
      },
      "models": { ... }
    }
  }
}

Run opencode run "hello" --model custom/model-name
Error occurs during provider initialization

Error Message

ProviderInitError: ProviderInitError
data: { providerID: "custom" }

TypeError: fn3 is not a function

Environment

OS: Windows 11
opencode version: v1.0.150 (also affects v1.0.210)
oh-my-opencode version: v2.14.0

Root Cause

opencode attempts to dynamically load a custom provider module but cannot find the corresponding create* function. The custom provider functionality is either incomplete or has compatibility issues.

Workaround

Use built-in provider with overridden options:

{
  "provider": {
    "anthropic": {
      "options": {
        "apiKey": "your-api-key",
        "baseURL": "http://localhost:8045/v1"
      }
    }
  },
  "model": "anthropic/claude-sonnet-4-5"
}

Expected Behavior

Custom provider should initialize correctly according to the configuration.

Additional Notes

This workaround works for most use cases but limits flexibility when users truly need custom provider definitions.

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response

This issue might be a duplicate of existing issues. Please check:

Custom OpenAI-compatible provider options not being passed to API calls #5674: Custom OpenAI-compatible provider options not being passed to API calls
Custom OpenAI-compatible provider returns no text content #5210: Custom OpenAI-compatible provider returns no text content
LM Studio Missing as Provider, custom provider for LM Studio non-functional. #1555: LM Studio Missing as Provider, custom provider for LM Studio non-functional
need help setting up ollama #4862: Ollama provider initialization fails with 'fn2 is not a function'
[BUG] Schema.ref 'QuestionInfo' was set alongside unsupported fields in v1.1.x #7791: Schema.ref 'QuestionInfo' was set alongside unsupported fields in v1.1.x

These issues all relate to custom provider configuration failures, particularly with @ai-sdk/openai-compatible and other providers. Some report similar 'fnX is not a function' errors during provider initialization, while others report related configuration issues with custom providers.

Feel free to ignore if none of these address your specific case.

Any updates on this ?

To stay organized issues are automatically closed after 90 days of no activity. If the issue is still relevant please open a new one.

same error

{ast login: Mon Apr 27 20:49:18 on console
  "name": "UnknownError",ir ~ % opencode
  "data": {
    "message": "TypeError: fn3 is not a function. (In 'fn3(input)', 'fn3' is an instance of Object)\n    at <anonymous> (src/plugin/index.ts:87:28)\n    at processTicksAndRejections (native:7:39)"
  }
}

same error on most recent version as of posting this with no custom model config afaik, running on void linux:

{
  "name": "UnknownError",
  "data": {
    "message": "TypeError: fn3 is not a function. (In 'fn3(input)', 'fn3' is an instance of Object)\n    at <anonymous> (src/plugin/index.ts:87:28)\n    at processTicksAndRejections (native:7:39)"
  }
}

I forgot to post why it was happening for me. I had custom plugin which was exporting some objects along with main plugin function.
I looked at their plugin implementation and figured out.

I forgot to post why it was happening for me. I had custom plugin which was exporting some objects along with main plugin function. I looked at their plugin implementation and figured out.

The only plugin I have is an old version of ohmyopencode back when it had to be installed via npm/npx, could you please provide a sort of "guide" on where to find plugins, what to search for inside a plugin, and what to do to fix the issue if what you did fixed the fn issue

remove "oh-my-opencode" plugin config work for me ,
vim ~/.config/opencode/opencode.json,
"plugin": ["oh-my-opencode", "opencode-antigravity-auth@1.3.1"],

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[BUG] Custom provider initialization fails with "fn3 is not a function #7792

Description

Description

Reproduction Steps

Error Message

Environment

Root Cause

Workaround

Expected Behavior

Additional Notes

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Operating System

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[BUG] Custom provider initialization fails with "fn3 is not a function #7792

Description

Description

Description

Reproduction Steps

Error Message

Environment

Root Cause

Workaround

Expected Behavior

Additional Notes

Plugins

OpenCode version

Steps to reproduce

Screenshot and/or share link

Operating System

Terminal

Activity

github-actions commented on Jan 11, 2026

adilovcode commented on Jan 12, 2026

thdxr commented on Mar 25, 2026

yuhuoji commented on Apr 27, 2026

viper968 commented on Apr 30, 2026

adilovcode commented on Apr 30, 2026

viper968 commented on May 6, 2026

Jayzhang1995 commented on Jun 9, 2026

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