Description
The Custom Instructions feature documented at https://opencode.ai/docs/rules/#custom-instructions does not work with Anthropic models.
From docs:
"You can specify custom instruction files in your opencode.json [...] This allows you and your team to reuse existing rules rather than having to duplicate them to AGENTS.md."
"All instruction files are combined with your AGENTS.md files."
Expected behavior
Files specified in instructions array are automatically combined with AGENTS.md and included in the LLM context. The model should follow these rules.
Actual behavior
Anthropic models (Claude Sonnet 4.5, Opus 4.5, Haiku 4.5) completely ignore content from instructions array. The same configuration works correctly with OpenAI and Groq models.
Reproduction
// opencode.json
{
"$schema": "https://opencode.ai/config.json",
"instructions": ["my-rules.md"]
}
- Add any rule to my-rules.md
- Start opencode, select Anthropic model
- Ask a question where the rule should apply
- Rule is ignored
Switch to OpenAI/Groq → rule is applied.
Environment
- opencode v1.1.21
- macOS
- Tested with multiple Anthropic models
Description
The Custom Instructions feature documented at https://opencode.ai/docs/rules/#custom-instructions does not work with Anthropic models.
From docs:
Expected behavior
Files specified in
instructionsarray are automatically combined with AGENTS.md and included in the LLM context. The model should follow these rules.Actual behavior
Anthropic models (Claude Sonnet 4.5, Opus 4.5, Haiku 4.5) completely ignore content from
instructionsarray. The same configuration works correctly with OpenAI and Groq models.Reproduction
Switch to OpenAI/Groq → rule is applied.
Environment