Summary

Add GitHub Copilot optimization headers (x-initiator, Openai-Intent, Copilot-Vision-Request, anthropic-beta) to reduce request usage and improve billing accuracy for GitHub Copilot subscriptions.

Context

GitHub Copilot uses specific HTTP headers to optimize request counting and billing.

• x-initiator: Distinguishes between user-initiated vs agent-initiated requests
• Openai-Intent: Signals conversation context for billing optimization
• Copilot-Vision-Request: Enables vision model optimizations when images are present
• anthropic-beta: Required when Copilot proxies Anthropic Claude models

Changes

• Added initiator field to Context struct to track who initiated a conversation
• Modified AgentExecutor to mark agent-spawned conversations with initiator: "agent"
• Implemented GitHub Copilot-specific header injection in OpenAIProvider
• Added vision content detection to set Copilot-Vision-Request header
• Added Anthropic model detection to inject required beta flag
• Updated ContextRecord for proper JSON serialization of initiator field
• Added comprehensive test coverage for all header scenarios

Key Implementation Details

The headers are only added for GITHUB_COPILOT provider, ensuring no impact on other providers (OpenAI, Anthropic, ZAI, etc.). The initiator field is stored within the JSON-serialized Context in the existing database column - no schema migration required.

Header Logic:

1. x-initiator: Uses request.initiator if set, otherwise falls back to detecting from the last message role (non-User = agent)
2. Openai-Intent: Always "conversation-edits" for GitHub Copilot
3. Copilot-Vision-Request: "true" when image content is detected in messages
4. anthropic-beta: Added when model name contains "claude"

Use Cases

• Subagent tool calls: Automatically marked as x-initiator: agent for proper billing categorization
• Direct user interactions: Default to x-initiator: user when no initiator is set
• Vision requests: Images in messages trigger Copilot-Vision-Request: true for model optimization
• Anthropic models: Claude models get required beta flag for extended thinking

Testing

# Run provider tests to verify header generation
cargo test --package forge_repo -- test_get_headers

# Run all tests for modified packages
cargo test --package forge_repo --package forge_app --package forge_domain

All 272 tests pass, including 4 new tests specifically for GitHub Copilot headers:

• test_get_headers_with_request_github_copilot_user_initiated
• test_get_headers_with_request_github_copilot_agent_initiated
• test_get_headers_with_request_github_copilot_vision_content
• test_get_headers_with_request_non_github_copilot_no_extra_headers

Links

• Files changed:
  • crates/forge_repo/src/provider/openai.rs - Header generation
  • crates/forge_domain/src/context.rs - Added initiator field
  • crates/forge_app/src/agent_executor.rs - Subagent initiator marking
  • crates/forge_repo/src/conversation/conversation_record.rs - Serialization support

Co-Authored-By: ForgeCode noreply@forgecode.dev