fix: handle invalid maxOutputTokens value (0 or undefined)

[Jedeiah]

Issue for this PR

Closes #21858
Closes #21522

Type of change

• Bug fix

What does this PR do?

Fixes maxOutputTokens returning 0 when model.limit.output is 0, undefined, or negative. Returns OUTPUT_TOKEN_MAX (32000) as fallback when model output limit is invalid.

When plugins pass maxOutputTokens=0 via chat.params hook, OpenCode 1.4.0+ requires >= 1, which causes "maxOutputTokens must be >= 1" error for local providers like Ollama.

How did you verify your code works?

• Added 5 unit tests for maxOutputTokens function covering edge cases (undefined, 0, negative, valid values)
• All tests pass

Screenshots / recordings

N/A (not a UI change)

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[wjiuxing]

When will this PR be merged in pls? I try to add limit.context/output into the model info but it doesn't work, as this comment: #22253 (comment)

[Jedeiah]

这个 PR 什么时候能合并？我尝试在模型信息中添加 limit.context/output，但是不起作用，就像这条评论里说的那样：#22253 (comment)

根本原因是 oh-my-openagent 读取到某些模型的能力缓存 limit.output = 0，
没有做防御性校验，直接把 0 透传成 maxOutputTokens=0 发给 OpenCode，
OpenCode 1.4.0+ 要求 maxOutputTokens >= 1 所以报错。

---

以下是合理的临时方案（可丢给Ai让它去解决）：

方案 A（限自定义模型，且要覆盖所有 agent 用到的模型才有效）：

如果你用的是自定义 provider 里声明的模型，可以在 opencode.json 的对应模型
条目下加 limit.output，让 oh-my-openagent 读到正确值而不是缓存里的 0：

{
  "provider": {
    "your-provider": {
      "models": {
        "your-model-id": {
          "limit": {
            "output": 4096,
            "context": 128000
          }
        }
      }
    }
  }
}

注意：oh-my-openagent 会启动多个 agent，每个 agent 用不同模型。
必须给所有涉及的模型都加上 limit.output，漏一个就还会触发。
对 opencode 内置识别的标准模型（如 anthropic/claude-sonnet）无效。

---

方案 B（治本，推荐）：

直接给 oh-my-openagent 的 dist/index.js 打补丁，
在写入和透传 maxOutputTokens 的三个关键路径上过滤掉 <= 0 的值。

文件路径（以 macOS 为例，Windows 路径类似）：
~/.cache/opencode/packages/oh-my-openagent@latest/node_modules/oh-my-openagent/dist/index.js

改动 1 - applySessionPromptParams 写入时（搜 model.maxTokens !== undefined）：

改前：
...model.maxTokens !== undefined ? { maxOutputTokens: model.maxTokens } : {}

改后：
...typeof model.maxTokens === "number" && model.maxTokens > 0 ? { maxOutputTokens: model.maxTokens } : {}

改动 2 - 读取会话参数发请求时（搜 storedPromptParams.maxOutputTokens !== undefined）：

改前：

if (storedPromptParams.maxOutputTokens !== undefined) {
  output.maxOutputTokens = storedPromptParams.maxOutputTokens;
}

改后：

if (typeof storedPromptParams.maxOutputTokens === "number" && storedPromptParams.maxOutputTokens > 0) {
  output.maxOutputTokens = storedPromptParams.maxOutputTokens;
}

改动 3 - compatibility 结果写回时（搜 compatibility.maxTokens !== undefined）：

改前：

if (compatibility.maxTokens !== undefined) {
  output.maxOutputTokens = compatibility.maxTokens;
} else {
  delete output.maxOutputTokens;
}

改后：

if (typeof compatibility.maxTokens === "number" && compatibility.maxTokens > 0) {
  output.maxOutputTokens = compatibility.maxTokens;
} else {
  delete output.maxOutputTokens;
}

改完后删除模型能力缓存再重启：
rm ~/.cache/oh-my-opencode/model-capabilities.json # macOS/Linux
Windows: 删除 %USERPROFILE%\.cache\oh-my-opencode\model-capabilities.json

⚠️ 注意：插件更新后补丁可能会被覆盖，需要重新执行一遍。

[Jedeiah]

Hi @maintainers, this PR has been open for a while and I've resolved the merge conflicts. The code passes all unit tests and meets the contributing guidelines. Could someone please review and merge it? This fixes the maxOutputTokens >= 1 error for issues #21858 and #21522. Thank you!

[Jedeiah]

Hi @thdxr @Brendonovich @kitlangton, this PR has been open for a while and I've resolved the merge conflicts. The code passes all unit tests and meets the contributing guidelines. Could someone please review and merge it? This fixes the maxOutputTokens >= 1 error for issues #21858 and #21522. Thank you!

[Jedeiah]

The unit test failure on Windows () is a pre-existing flaky test in the base branch, not caused by my changes. I verified locally - the test passes on macOS.

This appears to be the same issue mentioned in PR #22587 where the author also noted: 'The unit (windows) CI failure is unrelated to this PR. This appears to be a pre-existing issue on the base branch.'

Could someone approve and merge this PR? Thank you!