The popular AI pair-programming tool Aider has released version 0.90 with a new "Architect mode" that separates the planning step from the editing step across two distinct model calls. In architect mode, a high-capability model (such as o3 or Claude Opus) first produces a detailed implementation plan describing which files to change and how, and then a faster, cheaper model (such as DeepSeek V3 or Qwen3-32B) executes the actual code edits. This two-stage approach significantly reduces hallucinations on complex multi-file changes while cutting costs by 60–70% compared to using a single frontier model throughout. Aider v0.90 also introduces improved repo-map generation that handles monorepos more gracefully.