architect-loop: Claude Fable 5 as Architect, GPT-5.5 Codex as Builder

Single-model AI coding is hitting a ceiling. Claude Code, Cursor, Aider, Copilot - all great for small tasks, all start to break down on complex multi-file features. The hallucination rate goes up, the architectural coherence drops, and you spend more time fixing than building.

architect-loop attacks this problem with role separation: one model plans, the other builds. Claude Fable 5 (the architect) reads your codebase, designs the change, produces a detailed plan with file-by-file diffs. GPT-5.5 Codex (the builder) implements the plan. The result is then reviewed by Claude again before commit.

Why this works

Different models have different strengths. Claude is good at understanding context, maintaining coherence, and following architectural intent. GPT-5.5 Codex is fast at code generation but loses the thread on large codebases. By splitting the work, you get the best of both.

The loop in practice

You describe the feature in plain English. The architect (Claude) reads your repo, asks clarifying questions, produces a plan. You review the plan. The builder (GPT) implements. The architect reviews the diff. You commit or request changes.

Verdict

For complex features (multi-file refactors, new subsystems, API design), architect-loop is noticeably better than single-model. For small changes, it's overkill. Use it when the architectural decisions matter more than typing speed.