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[FEATURE]: Support custom system prompt per model in config #18177
Description
Feature hasn't been suggested before.
- I have verified this feature I'm about to request hasn't been suggested before.
There are earlier issues, but they don't follow the template and seem dead.
Describe the enhancement you want to request
When configuring custom models via opencode.json, there's no way to specify a model-specific system prompt. The default behavior matches model IDs to built-in prompts (claude, gemini, gpt, etc.), but unknown models fall back to a generic prompt with no way to customize it.
The existing agent-level prompt field isn't sufficient here because agents and models are orthogonal concepts. A single model can be used across multiple agents, and a single agent can be switched between models. The system prompt should follow the model, not the agent — for example, a custom model may need specific formatting instructions or persona regardless of which agent uses it.
A prompt field on the model config would let users define a system prompt tailored to their model.
Activity
github-actions commentedon Mar 19, 2026
This issue doesn't fully meet our contributing guidelines.
What needs to be fixed:
[FEATURE]:(e.g.[FEATURE]: Support custom system prompt per model in config)Please edit this issue to address the above within 2 hours, or it will be automatically closed.
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[-]Support custom system prompt per model in config[/-][+][FEATURE]: Support custom system prompt per model in config[/+]github-actions commentedon Mar 19, 2026
Thanks for updating the issue! It now meets our contributing guidelines. Appreciate you taking the time to fix it.
github-actions commentedon May 19, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.