architect

1# /architect — Implementation Architecture from PRD
2 
3## When to Use
4 
5**Don't use when:** you already have an architecture and want to implement it (use /marshal or /archon); you need a PRD first (use /prd before /architect).
6 
7- After /prd produces an approved PRD (greenfield or feature mode)
8- When the user has a clear direction + existing codebase (no PRD needed)
9- When /do routes a build request
10- When the user has a spec and wants a build plan
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12## Inputs
13 
14One of:
151. A PRD file path (from /prd) — preferred, contains structured requirements
162. A user-provided spec or description + an existing codebase — sufficient
173. Neither — suggest /prd first, but don't hard-gate. If the user has a clear
18   direction ("add auth to my app"), that + the existing code IS the input.
19 
20## Mode Detection
21 
22**Greenfield mode**: PRD exists with `Mode: greenfield`, or no existing source files.
23Produces a complete architecture from scratch.
24 
25**Feature mode**: PRD exists with `Mode: feature`, OR the user describes a feature
26and the project has existing source files. The architecture describes changes to
27existing code, not a standalone system.
28 
29In feature mode:
30- Read the existing file tree FIRST — understand the current architecture before planning changes
31- Read key files (package.json, tsconfig, main entry points, existing patterns)
32- The File Tree section shows ONLY new and modified files, not the entire project
33- Phases include a Phase 0: "Baseline" that records current typecheck/test state
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