Impl — Codex Self-Sufficient 15-Phase Workflow

Cooperative Phase: Implementation (any step — self-sufficient) Self-sufficient. If research, requirements, or design missing, does them first (phases 1-5).

Tools

• Simple MCP — query codebase structure, module graph
• Simple LSP MCP — symbol lookup, type checking, go-to-definition
• Context7 MCP — external library documentation

Prerequisites Check

If ALL exist, skip to Phase 8 (Implementation).

Phases

Phases 1-3: Research + Requirements

Skip if exist, otherwise do inline. See research skill for details.

Phases 4-5: Plan + Design + Architecture

Skip if exist. See design skill for details.

Phases 6-7: System Test + Doc Consistency

• Write SSpec BDD tests from design
• Verify doc cross-references are intact
• Built-in matchers only (see design skill for list)

Phase 8: Implementation

• Implement in src/**/<feature>.spl
• Follow /coding rules strictly
• Reference: doc/07_guide/quick_reference/syntax_quick_reference.md

Phases 9-10: Unit + Integration Tests

• 80%+ branch coverage target
• Write unit tests alongside implementation
• Write integration tests for cross-module interactions
• Add doctests for public API functions

Phases 11-13: Bug Reports + Duplication Check + Refactoring

• Run bin/simple bug-add for any discovered bugs
• Check for code duplication across src/
• Refactor: files > 800 lines must be split

Phase 14: Full Test Suite

bash
1bin/simple test && bin/simple build lint

Phase 15: Verify + VCS Sync

• Run verify skill — must show STATUS: PASS
• If src/compiler/**, src/lib/**, src/app/mcp/**, src/app/simple_lsp_mcp/**, or MCP packaging files changed, run:
  • sh scripts/check-core-runtime-smoke.shs <runtime>
  • SIMPLE_BINARY=<runtime> sh scripts/check-mcp-native-smoke.shs
  • If publish/package flow changed: sh scripts/check-mcp-package-smoke.shs
• VCS sync: jj commit -m "feat: <feature description>"

Stub Prevention Gate

STUB001 = HARD FAIL. No pass_todo in final code.

Before declaring implementation complete, verify:

• No pass_todo anywhere in new/modified files
• No pass_do_nothing / pass_dn unless intentional no-op (documented)
• No hardcoded returns without logic
• No commented-out code blocks
• No empty function bodies

Artifacts Produced

Multi-LLM Collaboration

• If other LLMs produced research/design/tests, build on them
• Never overwrite existing artifacts — extend or improve
• Tag Codex-produced code with # codex-impl comment on module header if needed

Rules

• All code in .spl — no Python, no Bash
• Generics use <> not [] — Option<T>, List<Int>
• Pattern binding: if val not if let
• Constructors: Point(x: 3, y: 4) not .new()
• ? is operator only — never in names; use .? over is_* predicates
• NO inheritance — use composition, alias forwarding, traits, or mixins
• Use Result<T, E> + ? for error handling (no try/catch/throw)
• Reserved keywords: gen, val, def, exists, actor, assert, join, pass_todo, pass_do_nothing, pass_dn
• NEVER over-engineer — only make requested changes
• NEVER add unused code — delete completely
• NEVER convert TODO/FIXME to NOTE — implement or delete
• Production MCP or LSP wrappers must execute cached compiled artifacts, not raw source entrypoints
• Do not place full-tree scans or repeated file rereads in request handlers when a cache or index is viable
• When cached or indexed data depends on writable files, implement explicit invalidation on create, edit, move, delete, rename, template application, and bulk replace flows
• Add perf smoke coverage for startup and representative hot requests when changing performance-sensitive tooling
• After compiler/core/lib changes, verify MCP/LSP source-native startup before finishing the task; after packaging/release changes, verify isolated npm install startup too