Context Engineering & Harness Engineering Toolkit for Claude Code

Structured prompts, agent orchestration, and automated pipelines — debugging, code review, UI design, product specs, and more.

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Install

npx devlyn-cli

That's it. The interactive installer handles everything. Claude Code config is installed by default; optional AI CLI instructions can be selected during install. Choose Codex CLI (OpenAI) to install AGENTS.md AND /devlyn:resolve + /devlyn:ideate skills into ~/.codex/skills/ so the same slash commands work inside Codex too. Run it again anytime to update.

How It Works — Two Skills, Full Cycle

devlyn-cli turns Claude Code into a hands-free development pipeline. The product surface is two skills:

ideate (optional)  →  resolve  →  ship

Step 1 (optional) — Plan with /devlyn:ideate

Turn a raw idea into a verifiable spec — single-feature, multi-feature, or "normalize this external doc".

/devlyn:ideate "I want to build a habit tracking app with AI nudges"

Default mode produces a docs/specs/<id>-<slug>/spec.md plus spec.expected.json (mechanical verification block) that /devlyn:resolve --spec consumes directly. Modes:

| Mode | When to use | |---|---| | default | One feature, AI drives focused Q&A | | --quick | One-line goal → assume-and-confirm spec, single-turn (autonomous-pipeline-safe) | | --from-spec <path> | You already wrote a spec; ideate normalizes + lints it | | --project | Multi-feature project: emits plan.md index + N child specs |

Skip ideate entirely if you have a spec or just want to describe the work — /devlyn:resolve accepts free-form goals too.

Step 2 — Resolve with /devlyn:resolve

Hands-free pipeline for any coding task — bug fix, feature, refactor, debug, modify, PR review. Pass a spec, a free-form goal, or a diff to verify.

/devlyn:resolve "fix the login bug"                                # free-form
/devlyn:resolve --spec docs/specs/2026-05-04-auth/spec.md          # spec mode
/devlyn:resolve --verify-only <diff-or-PR-ref> --spec <path>       # verify-only

Internal phases run sequentially with file-based handoff via .devlyn/pipeline.state.json:

PLAN  →  IMPLEMENT  →  BUILD_GATE  →  CLEANUP  →  VERIFY (fresh subagent, findings-only)

• PLAN is the heaviest phase by design — formalizes invariants from the spec/goal and the file list to touch.
• BUILD_GATE runs your project's real compilers, typecheckers, linters, and python3 .claude/skills/_shared/spec-verify-check.py (verification commands literal-match). Auto-detects Next.js, Rust, Go, Solidity, Expo, Swift, and Dockerfiles. Browser flows route through Chrome MCP → Playwright → curl tier.
• VERIFY runs in a fresh subagent context with no code-mutation tools — findings only, structurally independent.
• Git checkpoints at every phase for safe rollback. Fix-loop budget shared across BUILD_GATE and VERIFY (--max-rounds N, default 4).

Common flags: --engine claude|codex|auto (default claude), --bypass build-gate,cleanup, --pair-verify (force pair-mode JUDGE in VERIFY), --perf (per-phase timing).

Engine selection — Claude solo by default

--engine claude (default) is the canonical surface. Every phase routes to Claude.

--engine codex routes IMPLEMENT to Codex; --engine auto opts into the experimental dual-engine routing where applicable. Both are research-only at HEAD: iter-0020 closed Codex BUILD/IMPLEMENT below the quality floor on the 9-fixture suite (L2 vs L1 = −3.6, 3/8 gated fixtures cleared the +5 margin floor — release-readiness FAIL); iter-0033g + iter-0034 closed PLAN-pair as research-only with explicit unblock conditions (container/sandbox infra OR production telemetry capturing positive evidence of subagent introspection). Install the Codex CLI (https://platform.openai.com/docs/codex) and pass the flag explicitly to opt in:

/devlyn:resolve "fix the auth bug" --engine auto   # experimental, research-only

If Codex is absent when --engine auto or --engine codex is requested, the harness silently downgrades to --engine claude and emits a banner in the final report.

/devlyn:ideate now thinks like a world-class Product Owner, and /devlyn:auto-resolve finally honors the spec contract the ideate skill was already designed to produce. Validated with 19 parallel eval subagents, 1.2M tokens of evidence — Customer Frame propagation went from 0/20 to 20/20 across seven test scenarios.

• Jobs-to-be-Done forcing in FRAME — ideate's opening FRAME phase now requires a one-sentence JTBD statement ("When [situation], [user] wants [motivation] so they can [outcome]") before anything else. A bare problem statement is a state description, not a job — downstream specs built without this frame describe system behavior instead of customer progress.
• Customer Frame field on every item spec — item-spec template gains a ## Customer Frame section between Context and Objective that carries the per-item JTBD sentence all the way through to auto-resolve's build agent. The build agent uses this line to resolve ambiguity in Requirements rather than inventing interpretations.
• PHASE 0.5 SPEC PREFLIGHT on auto-resolve — when the task names a docs/roadmap/phase-N/...md spec, auto-resolve now reads it BEFORE BUILD, verifies internal dependencies are status: done, and writes .devlyn/SPEC-CONTEXT.md so downstream phases stop re-deriving what the spec already owns. Un-done deps halt the pipeline with BLOCKED rather than shipping out-of-sequence code.
• Done-criteria verbatim copy — when PHASE 0.5 found a spec, BUILD's Phase B copies the spec's Requirements, Out of Scope, and Verification sections verbatim into .devlyn/done-criteria.md. No silent re-derivation; the ideate CHALLENGE rubric's validation is preserved through the handoff.
• Spec-bounded exploration — BUILD's Phase A uses the spec's Architecture Notes + Dependencies as the exploration boundary instead of re-classifying the task type open-endedly.
• Complexity-gated team ceremony — complexity: low specs with no security/auth/API/data risk keywords skip TeamCreate entirely. Medium/high complexity or risk-flagged specs still assemble the team as before.
• Evidence discipline in ideate EXPLORE — research phase now labels unsourced market/tech claims [UNVERIFIED] inline rather than presenting recall as fact. The CHALLENGE rubric's NO GUESSWORK axis fires on unlabeled authoritative claims.
• Mode tie-break rule — when a request matches two ideate modes (Quick Add vs Expand, Research-first vs Deep-dive), the narrowest mode wins. Deterministic selection replaces intuitive match.
• Bloat removal — three redundant motivational blocks deleted from ideate SKILL.md (<why_this_matters> rationale, duplicate CHALLENGE preamble, external engine-routing pointer). SKILL.md shrank from 529 to 519 lines despite the new features.

Core pipeline skills (ideate, auto-resolve, preflight) rewritten against Anthropic's Opus 4.7 prompting guidance, validated by multi-round comprehension and quality-grading subagents.

• 4.7 prompt patterns — <investigate_before_answering> on evaluator and challenge, <coverage_over_filtering> with per-finding confidence, 3 few-shot examples in the Challenge phase, <orchestrator_context> (auto-compaction + xhigh effort), <use_parallel_tool_calls> in ideate EXPLORE and preflight Phase 0.
• --with-codex consolidated into --engine auto — auto covers BUILD/FIX + team roles + ideate CHALLENGE critic. Legacy flag still accepted with a graceful handoff. (Note: post iter-0020 close-out, --engine auto is experimental research-only; default is --engine claude.)
• Bug fixes — PHASE 1.5 BLOCKED browser failures re-route correctly via PHASE 2.5; PHASE 1.4-fix and PHASE 2.5 share one global round counter; preflight PHASE 1 numbering fixed; build-gate-exhausted now produces a graceful final report.
• CLAUDE.md refresh (shipped to npx installers) — Quick Start pointing to ideate → auto-resolve → preflight, Context Window Management updated for Opus 4.7 auto-compaction, terminology refresh (TodoWrite → task tools, Task agents → Agent subagents).

Optional Power-User Skills

Two creative skills have moved to optional-skills/ — install them via the interactive installer when you need them.

| Command | Use When | |---|---| | /devlyn:design-system | Extract exact design tokens (colors, type scale, spacing) from a chosen UI style | | /devlyn:team-design-ui | Multi-perspective design team generates 5 distinct UI style explorations |

Earlier versions of devlyn-cli shipped 16+ skills (auto-resolve / preflight / evaluate / review / team-review / clean / update-docs / browser-validate / product-spec / feature-spec / recommend-features / discover-product / design-ui / implement-ui). These were consolidated into /devlyn:resolve (which folds verification, review, and cleanup into its phases) plus /devlyn:ideate (which absorbs the planning surfaces) in the iter-0034 Phase 4 cutover (2026-05-04). Upgrades automatically remove the legacy skill directories from ~/.claude/skills/.

Auto-Activated Skills

These activate automatically — no commands needed. They shape how Claude thinks during relevant tasks.

| Skill | Activates During | |---|---| | root-cause-analysis | Debugging — enforces 5 Whys, evidence standards | | code-review-standards | Reviews — severity framework, approval criteria | | ui-implementation-standards | UI work — design fidelity, accessibility, responsiveness | | code-health-standards | Maintenance — dead code prevention, complexity thresholds |

Optional Add-ons

Selected during install. Run npx devlyn-cli again to add more.

| Skill | Description | |---|---| | asset-creator | AI pixel art game asset pipeline — generate, chroma-key, catalog | | cloudflare-nextjs-setup | Cloudflare Workers + Next.js with OpenNext | | generate-skill | Create Claude Code skills following Anthropic best practices | | prompt-engineering | Claude 4 prompt optimization | | better-auth-setup | Better Auth + Hono + Drizzle + PostgreSQL | | pyx-scan | Check if an AI agent skill is safe before installing | | dokkit | Document template filling for DOCX/HWPX | | devlyn:pencil-pull | Pull Pencil designs into code | | devlyn:pencil-push | Push codebase UI to Pencil canvas | | devlyn:reap | Safely reap orphaned MCP / codex / Superset child processes | | devlyn:design-system | Extract design tokens from a chosen UI style for exact reproduction | | devlyn:team-design-ui | 5 distinct UI style explorations from a full design team |

| Pack | Description | |---|---| | vercel-labs/agent-skills | React, Next.js, React Native best practices | | supabase/agent-skills | Supabase integration patterns | | coreyhaines31/marketingskills | Marketing automation and content skills | | anthropics/skills | Official Anthropic skill-creator with eval framework | | Leonxlnx/taste-skill | Premium frontend design skills |

| Server | Description | |---|---| | playwright | Playwright MCP — powers /devlyn:resolve BUILD_GATE browser tier (Chrome MCP → Playwright → curl fallback) |

--engine auto/codex uses the local codex CLI binary, not MCP. Install from https://platform.openai.com/docs/codex; the harness silently downgrades to --engine claude if the CLI is missing.

Want to add a pack? Open a PR adding it to the OPTIONAL_ADDONS array in bin/devlyn.js.

Requirements

• Node.js 18+
• Claude Code installed and configured

Contributing

• Add a skill — directory in config/skills/ with SKILL.md
• Add optional skill — add to optional-skills/ and OPTIONAL_ADDONS in bin/devlyn.js
• Suggest a pack — PR to the pack list

Star History

License

MIT — Nocodecat @ Donut Studio