Feature Request: Context Control for Subagents

Problem

Subagents currently receive full repository context even for focused tasks, which:

• Increases token usage for small models (e.g., llama3.2:1b)
• Degrades performance for specialised, narrow-scope tasks
• Makes it difficult to optimise local models for specific use cases
• Wastes resources when only a minimal prompt is needed

Use Case

When using lightweight local models (1B-7B parameters) as subagents for focused tasks like:

• doc-reader: Extract key points from a single documentation file
• codegen: Generate a small code snippet
• log-analyser: Analyse a specific log file
• editor: Refine a single paragraph

These tasks require only the prompt and perhaps a single file reference, yet the subagent receives the entire repository context including:

• Full project structure
• Git history
• All configuration files
• Build scripts
• Documentation files

This is particularly problematic for resource-constrained local models where context window size directly impacts inference speed and quality.

Proposed Solution

Add a context configuration option in agent definitions to control what contextual information is passed to subagents:

{
  "agent": {
    "doc-reader": {
      "mode": "subagent",
      "model": "ollama/llama3.2:1b",
      "context": {
        "repo": false,           // Disable full repository context
        "files": "prompt-only",  // Only include files mentioned in the prompt
        "maxTokens": 2000,       // Maximum context tokens to pass
        "git": false,            // Exclude git history
        "config": false          // Exclude configuration files
      }
    }
  }
}

Configuration Options

• repo (boolean, default: true): Include full repository structure
• files (string, default: "all"): Control which files to include
  • "all": All repository files
  • "prompt-only": Only files explicitly mentioned in the prompt
  • "none": No file context
• maxTokens (number, optional): Hard limit on context tokens
• git (boolean, default: true): Include git history and metadata
• config (boolean, default: true): Include configuration files

Alternative: Markdown Configuration

---
description: Reads documentation and summarises key insights
mode: subagent
model: ollama/llama3.2:1b
temperature: 0.1
context:
  repo: false
  files: prompt-only
  maxTokens: 2000
---

Extract key points, APIs, and caveats from documentation.
Provide a short summary and a Q&A with likely follow-ups.

Benefits

1. Performance: Faster inference for small local models
2. Cost: Reduced token usage for API-based models
3. Quality: Less noise, more focused responses
4. Flexibility: Different subagents can have different context requirements
5. Resource optimisation: Better support for constrained environments

Real-World Example

Current configuration (16 subagents using llama3.2:1b):

{
  "doc-reader": {
    "mode": "subagent",
    "model": "ollama/llama3.2:1b",
    "prompt": "Extract key points, APIs, and caveats from documentation.\nProvide a short summary and a Q&A with likely follow-ups.",
    "tools": {
      "write": false,
      "edit": false,
      "bash": false
    }
  }
}

When invoked with:

@doc-reader summarise the authentication section in README.md

Current behaviour: Receives entire repository context (potentially 50,000+ tokens)
Desired behaviour: Receives only the prompt + README.md content (~2,000 tokens)

This would make local small models significantly more practical for production use.

Compatibility

This would be a backwards-compatible addition:

• Default behaviour remains unchanged (full context)
• Existing agents continue to work without modification
• New context option is entirely optional

Related Work

Similar context control exists in other AI systems:

• LangChain's context_window parameter
• LlamaIndex's chunk_size configuration
• Anthropic's explicit context management in Claude

Would this feature align with OpenCode's roadmap? Happy to provide additional details or contribute to implementation if helpful.