Code Assistant is a Rust-based AI coding assistant that can run as both a CLI/GUI application and a headless MCP server to be consumed by MCP clients such as Claude Desktop. It offers a multi-interface architecture: a modern GUI based on Zed's GPUI framework, a terminal interface, and a headless MCP server mode for integration with external tools. The MCP server implements compatibility with the Agent Client Protocol (ACP), using JSON-RPC over stdin/stdout in ACP mode to support pending messages, real-time streaming, and tool execution with proper permission handling. It supports adaptive tool invocation modes to accommodate different LLM capabilities: native function calling, XML-style streaming tags, and triple-caret blocks. Real-time streaming processors display tool invocations as they stream, with smart filtering to avoid unsafe tool combinations. Each chat session is linked to a specific project with persistent state, working memory, and draft messages (attachments supported), and sessions are anchored to the initial project context. The system can automatically load repository guidance by inserting AGENTS.md (or CLAUDE.md fallback) into the model's system context to align behavior with repo-specific instructions. Additional features include session compaction and ACP-compatible tooling behavior.