This decomposition breaks the diagrams-as-code CLI tool into 15 issues organized in 6 levels that maximize parallelism while respecting dependencies. **Level 0** establishes the build system foundation (project-scaffold). **Level 1** builds foundational types in parallel (types-module, error-module). **Level 2** creates three independent parsing modules (lexer, parser, validator) that can be developed simultaneously after types/errors are defined. **Level 3** adds layout computation which depends on types and parsing modules. **Level 4** includes a lightweight smoke-test for early verification, plus two independent renderers (svg, ascii) that can be built in parallel. **Level 5** orchestrates everything through app and cli modules. **Level 6** adds comprehensive testing, documentation, and final verification. The critical path is: scaffold → types → parser → layout → renderer → app → cli → tests (8 sequential steps), but many issues run in parallel (lexer/parser/validator, svg/ascii) reducing wall-clock time. Each issue is atomic (completable in one focused session), has clear acceptance criteria traceable to PRD requirements, includes concrete testing strategies with specific test file paths and frameworks, and specifies exact files created/modified. No file conflicts exist between parallel issues. The architecture document is the source of truth for all type signatures and interfaces—issues reference architecture sections rather than duplicating code. Early smoke-test verification (issue 9) catches integration problems before rendering complexity. All 12 PRD acceptance criteria map to specific issues: AC1→scaffold+all, AC2→cli, AC3→svg+integration, AC4→ascii+integration, AC5→error+validator+integration, AC6→svg+integration, AC7→final-verification, AC8→final-verification, AC9→parser, AC10→integration-tests, AC11→all modules, AC12→documentation. This plan enables autonomous agents to work in parallel with confidence that components will integrate successfully.