We don't have a repomap or codebase summary - right now we're relying on .voidrules and Gather/Agent mode to look around to implement large edits, and we find that works decently well, although we might add something like an auto-summary or Aider's repomap before exiting Beta.
Regarding context - you can customize the context window and reserved amount of token space for each model. You can also use "@ to mention" to include entire files and folders, limited to the context window length. (you can also customize the model's reasoning ability, think tags to parse, tool use format (gemini/openai/anthropic), FIM support, etc).