opencode-sub2api-haiku-fix

A focused OpenCode plugin that fixes Claude Haiku request-shape failures through Sub2API without changing Sub2API, OpenCode core, or OMO.

It is intentionally narrow: it only applies to the built-in anthropic provider when the model id contains haiku.

Why

In this setup, Opus and Sonnet can work through the same Sub2API account while Haiku fails with:

You're out of extra usage. Add more at claude.ai/settings/usage and keep going.

That message is misleading here. The account and Sub2API route are usable; Haiku is being rejected because the final request fingerprint does not look enough like Claude Code.

This plugin restores the missing Claude Code-style request shape on the OpenCode side.

What It Changes

• Preserves Haiku thinking with thinking: { type: "enabled", budget_tokens }.
• Rewrites the final Haiku wire body into a Claude Code-style 3-block system shape:
  • billing attribution
  • Claude Code identity
  • cached general CLI prompt block
• Moves the original OpenCode system prompt into the opening messages so local instructions are not lost.
• Adds Claude Code-style metadata.user_id, x-client-request-id, and x-claude-code-session-id.
• Rewrites Haiku headers to the current Claude Code-compatible Anthropic shape.
• Adds ?beta=true to Haiku /v1/messages URLs.
• Removes fields that break this Haiku path, including context_management and output_config.effort.
• Caps Haiku tool definitions to OPENCODE_HAIKU_MAX_TOOLS, defaulting to 32.

It does not rewrite Sonnet or Opus requests. It does not implement auth, OAuth, token refresh, keychain access, account switching, or a proxy.

Install

Add the npm package to ~/.config/opencode/opencode.jsonc:

{
  "plugin": [
    "opencode-sub2api-haiku-fix@latest"
  ]
}

Restart OpenCode after changing the plugin list.

Verify

npm test

The test suite covers:

• current OpenCode chat.params shape
• final Anthropic fetch-body rewrite
• Haiku thinking preservation
• non-Haiku requests staying untouched

Links

• npm: https://www.npmjs.com/package/opencode-sub2api-haiku-fix
• Project site: https://mjshao.fun/opencode-sub2api-haiku-fix/
• Portfolio entry: https://mjshao.fun/work/opencode-sub2api-haiku-fix
• Release: https://github.com/nxxxsooo/opencode-sub2api-haiku-fix/releases/tag/v1.0.3

Credits

Inspired by:

• Vacbo/opencode-anthropic-fix
• marco-jardim/opencode-anthropic-fix
• dotCipher/opencode-claude-bridge
• ianjwhite99/opencode-with-claude
• Wei-Shaw/sub2api, whose Claude Code mimicry work made the failure mode diagnosable

这是什么

opencode-sub2api-haiku-fix 是一个聚焦的 OpenCode 插件，用来修复 OpenCode 通过 Sub2API 调用 Claude Haiku 时的请求形状问题。

它不改 Sub2API，不改 OpenCode core，不改 OMO，也不处理任何账号或鉴权。它只在 OpenCode 侧，把已经要发给 anthropic provider 的 Haiku 请求改成更接近 Claude Code CLI 的 wire shape。

为什么需要

同一个 Sub2API 账号、同一个后端下，Opus 和 Sonnet 可以正常工作，但 Haiku 可能报：

You're out of extra usage. Add more at claude.ai/settings/usage and keep going.

在这个场景里，这句话不是额度结论，而是请求指纹被上游判进了错误路径。Haiku 的 system body、metadata、thinking shape 和 beta/header 组合需要更像 Claude Code。

它具体做什么

• 保住 Haiku 的 manual thinking。
• 把 Haiku 最终请求改成 Claude Code 风格的三段 system：
  • billing attribution
  • Claude Code identity
  • 带缓存断点的通用 CLI prompt block
• 把原始 OpenCode system prompt 移进开头 messages，避免本地指令丢失。
• 注入 metadata.user_id、x-client-request-id、x-claude-code-session-id。
• 对齐 Claude Code 风格 headers 和 beta flags。
• 给 /v1/messages 增加 ?beta=true。
• 去掉这条 Haiku 路径上会出问题的 context_management 和 output_config.effort。
• 将 Haiku tools 数量限制到 OPENCODE_HAIKU_MAX_TOOLS，默认 32。

它不会改 Sonnet 或 Opus 请求。

安装

在 ~/.config/opencode/opencode.jsonc 里添加：

{
  "plugin": [
    "opencode-sub2api-haiku-fix@latest"
  ]
}

改完后重启 OpenCode。

验证

npm test

测试覆盖 current OpenCode hook 形状、最终 fetch body 改写、Haiku thinking 保留，以及非 Haiku 请求不被改动。

License

MIT