[Feature Request] Support model-level parameters (reasoningEffort, temperature, top_p) in Custom Agent (.agent.md) configuration

[liuzgiqing]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Copilot in GitHub

Body

Summary

Currently, VS Code Copilot's Custom Agent (.agent.md) configuration only supports specifying a model name via model: "deepseek-v4-pro", but does NOT support model-level parameters like reasoningEffort, temperature, top_p, etc.

Other coding agents like OpenCode already support these parameters in their agent configuration:

{
  "agent": {
    "deep-thinker": {
      "model": "openai/gpt-5",
      "reasoningEffort": "high",
      "textVerbosity": "low"
    }
  }
}

Current State (VS Code Copilot .agent.md)

The current frontmatter only supports:

---
description: "..."
name: "Agent Name"
model: "deepseek-v4-pro"
tools: [read, edit, search, execute]
user-invocable: true
---

No reasoningEffort, temperature, top_p, maxTokens, or similar model parameters are available.

Feature Request

Add support for model-level parameters in Custom Agent (.agent.md) frontmatter, such as:

Parameter	Values	Purpose
reasoningEffort	none, minimal, low, medium, high, xhigh	Control reasoning depth for reasoning models
temperature	0.0 ~ 1.0	Control response randomness/creativity
top_p	0.0 ~ 1.0	Control response diversity
maxTokens	number	Limit max output tokens

Proposed frontmatter example:

---
description: "Use when: complex architecture design requiring deep reasoning"
name: "Deep Thinker"
model: "deepseek-v4-pro"
reasoningEffort: "high"
temperature: 0.1
maxTokens: 8000
tools: [read, edit, search, execute]
user-invocable: true
---

Use Case

Different agents have different needs:

• A planning agent needs temperature: 0.1 for deterministic analysis
• A brainstorming agent needs temperature: 0.8 for creativity
• A deep reasoning agent needs reasoningEffort: "high" for complex problems
• A quick agent needs maxTokens: 2000 to limit costs

Reference

• OpenCode agent configuration supports these: https://opencode.ai/docs/zh-cn/agents/#additional
• Anthropic/OpenAI APIs natively support these parameters

[github-actions[bot]]

💬 Your Product Feedback Has Been Submitted 🎉

Thank you for taking the time to share your insights with us! Your feedback is invaluable as we build a better GitHub experience for all our users.

Here's what you can expect moving forward ⏩

• Your input will be carefully reviewed and cataloged by members of our product teams. 
  • Due to the high volume of submissions, we may not always be able to provide individual responses.
  • Rest assured, your feedback will help chart our course for product improvements.
• Other users may engage with your post, sharing their own perspectives or experiences. 
• GitHub staff may reach out for further clarification or insight. 
  • We may 'Answer' your discussion if there is a current solution, workaround, or roadmap/changelog post related to the feedback.

Where to look to see what's shipping 👀

• Read the Changelog for real-time updates on the latest GitHub features, enhancements, and calls for feedback.
• Explore our Product Roadmap, which details upcoming major releases and initiatives.

What you can do in the meantime 💻

• Upvote and comment on other user feedback Discussions that resonate with you.
• Add more information at any point! Useful details include: use cases, relevant labels, desired outcomes, and any accompanying screenshots.

As a member of the GitHub community, your participation is essential. While we can't promise that every suggestion will be implemented, we want to emphasize that your feedback is instrumental in guiding our decisions and priorities.

Thank you once again for your contribution to making GitHub even better! We're grateful for your ongoing support and collaboration in shaping the future of our platform. ⭐