Dot Skills

Knip dead code detection best practices for JavaScript and TypeScript projects. Use when configuring Knip, analyzing unused code, setting up CI integration, or cleaning up codebases. Triggers on knip.json, dead code, unused exports, unused dependencies, bundle optimization.

Ruby on Rails Hotwire best practices for building interactive applications with Turbo Drive, Turbo Frames, Turbo Streams, Turbo 8 morphing, and Stimulus controllers. This skill should be used when writing, reviewing, or refactoring Hotwire-powered Rails code to ensure optimal patterns for navigation, partial page updates, real-time broadcasting, morphing, Stimulus controller design, error handling, and progressive enhancement. Triggers on tasks involving Turbo Frames, Turbo Streams, Turbo Drive, broadcasts, morphing, Stimulus controllers, ActionCable, turbo_stream_from, turbo_frame_tag, data-controller, data-action, or Hotwire performance. Complementary to rails-dev, rails-testing, rails-design-system, ruby-optimise, and ruby-refactor skills.

Migrates a nuqs codebase off pre-v2.5 patterns — deprecated `throttleMs`, hand-rolled setTimeout/useState debounce around `useQueryState`, unchecked `parseAsJson` casts, unversioned `nuqs/adapters/react-router` imports, or `ParserBuilder<T>` type references. Scans the repo, produces a dry-run report, asks for confirmation, applies AST codemods, then runs `tsc --noEmit` + the user's lint as a gate. Trigger even if the user only mentions "upgrade nuqs" or "migrate to nuqs v2.5+" without naming the specific patterns — they almost always exist in pre-v2.5 codebases.

Designing CLIs that AI agents will invoke — non-interactive flags, layered --help with examples, stdin/pipeline composition, actionable errors, idempotency, dry-run, destructive-action safety, and predictable command structure. Use when designing, building, or reviewing a command-line tool that AI agents or automation will invoke. Trigger even if the user doesn't explicitly say "agent-friendly" — apply whenever they are writing `--help` text, adding a new subcommand, designing error messages, or reviewing a CLI's UX.

Drizzle ORM targeting SQLite (better-sqlite3, libsql/Turso, bun:sqlite, Cloudflare D1, expo-sqlite, op-sqlite). Covers schema definition (column modes, primary keys, foreign keys, indexes), drizzle-kit migrations (generate vs push, renames, custom SQL), the query builder (selects, upserts, returning, EXPLAIN), the relational query builder (relations(), `with`, partial columns), transactions and `db.batch()`, prepared statements with `sql.placeholder()`, connection pragmas (WAL, foreign_keys, busy_timeout), and Drizzle type inference (`$inferSelect`, `$inferInsert`, `$type<>`, drizzle-zod). Use when writing, reviewing, or refactoring Drizzle code for SQLite. Trigger even if the user doesn't say "performance" — schema/migration choices made now are expensive to reverse later, and SQLite-specific traps (single-writer model, no native booleans/dates, ALTER TABLE limits, FK pragma off by default) catch teams who reach for Drizzle without reading the SQLite docs.

Write Go CLIs that manage processes and workloads — daemons, supervisors, job runners, deploy tools, anything that spawns or controls other processes. Use when writing, reviewing, or refactoring Go that handles OS signals, runs children via os/exec, fans out concurrent work, threads context for cancellation, returns exit codes, or builds a flag/cobra command surface. Covers the footguns the standard library makes easy to hit — SIGTERM vs Ctrl-C, SIGKILL-by-default children, orphaned process groups, pipe deadlocks, goroutine leaks, zombie reaping, and os.FindProcess lying about liveness. Triggers whenever the task touches process lifecycle, graceful shutdown, subprocess control, or concurrent workload supervision in Go — even if not named.

Opinionated SwiftUI navigation enforcement for iOS 26 / Swift 6.2 clinic modular MVVM-C apps. Enforces Domain coordinator protocols, App-target `DependencyContainer` + concrete coordinators + route shells, `NavigationPath` ownership, coordinator-owned modal state, deep-link/state-restoration readiness, and stale-while-revalidate/optimistic queued flow compatibility. Use when designing or refactoring clinic navigation flows.

Legacy interoperability skill for Storyboard and Interface Builder maintenance in iOS 26 / Swift 6.2 clinic codebases. Use only for migration or maintenance of existing storyboard screens; not for new SwiftUI clinic feature development. Triggers on Auto Layout, segues, size classes, IB accessibility, storyboard merge conflicts, and storyboard-to-SwiftUI migration tasks.

Portuguese personal income tax (IRS / Código do IRS) and Modelo 3 filing — determining tax residency (Art. 16), classifying income by category (rental/Anexo F, capital gains/Anexo G, employment/Anexo A, self-employment/Anexo B, pensions, foreign income/Anexo J), choosing the right annexes, applying current Art. 72 autonomous rates, and meeting Portal das Finanças deadlines. Covers residents and non-residents, including landlords with Portuguese-source rental income and double-taxation relief. Portugal-specific; not a substitute for a contabilista certificado.

Application-level React performance optimization covering React Compiler mastery, bundle optimization, rendering performance, data fetching, Core Web Vitals, state subscriptions, profiling, and memory management. Use when optimizing React app performance, analyzing bundle size, improving Core Web Vitals, or profiling render bottlenecks. Complements the react skill (API-level patterns) with holistic performance strategies. Does NOT cover React 19 API usage (see react skill) or Next.js-specific features (see nextjs-16-app-router skill).

Architectural refactoring guide for React applications covering component architecture, state architecture, hook patterns, component decomposition, coupling and cohesion, data flow, and refactoring safety. Use when refactoring React codebases, reviewing PRs for architectural issues, decomposing oversized components, or improving module boundaries. Does NOT cover React 19 API usage (see react skill) or performance optimization (see react-optimise skill).

Swift 6.2 and SwiftUI performance optimization for iOS 26 clinic architecture codebases. Covers async/await concurrency patterns, Sendable/actor isolation, view/render performance, and animation performance while preserving modular MVVM-C boundaries across App, Feature, Domain, and Data layers. Use when profiling or optimizing Swift/SwiftUI behavior in clinic modules.

Swift and SwiftUI refactoring patterns aligned with the iOS 26 / Swift 6.2 clinic modular MVVM-C architecture (Airbnb + OLX SPM layout). Enforces @Observable ViewModels/coordinators, App-target `DependencyContainer` + route shells, Domain repository/coordinator/error-routing protocols, and Data-owned I/O with stale-while-revalidate plus optimistic queued sync boundaries. Use when refactoring existing SwiftUI code into the clinic architecture.

37signals Rails coding principles and conventions from DHH, Jorge Manrubia, and the Fizzy/Basecamp/HEY codebase. This skill should be used when writing, reviewing, or refactoring Ruby on Rails code following the 37signals philosophy — vanilla Rails, CRUD controllers, rich domain models, concerns, no service objects, Hotwire, Turbo, Stimulus, Solid Queue, Solid Cache, Solid Cable, multi-tenancy, Minitest, custom auth, or DHH conventions.

Use this skill to gate DDD and ubiquitous-language quality with a pass/fail adversarial review — a single blind reviewer subagent judges a diff, a module/bounded context, or a DSL/semantic-model surface against 20 decidable rules across glossary lifecycle (a recorded ubiquitous language is required once domain concepts exist — absence is FAIL; code must conform; entries stay live and carry business meaning), language consistency (one name per concept, one meaning per name, no Manager/Helper/Data names on domain rules, transitions named as operations, one vocabulary across code, tests, docs, UI copy), domain model integrity (anemic models, valid-on-construction, value types over primitives, named states over flag piles), context boundaries (foreign-model reach, vendor-type absorption, infrastructure in the domain, multiple writers), and DSL surfaces. Language-agnostic; repeated runs converge code, team, and stakeholders on one recorded vocabulary. Verdicts only.

Use this skill to gate Zod 4 schema code in TypeScript and TanStack Start apps with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 24 decidable rules covering silent Zod 3-to-4 semantic breaks (defaults, enum-keyed records, boolean coercion), removed APIs (including the z.interface hallucination), unified error customization, deprecated method forms, recursion and codec composition, adapter-free TanStack Start validators, and packaging. Trigger it before merging Zod schema work, when asked to gate, adversarially review, or pass/fail Zod usage, or as a currency check that agent-authored schemas use the latest Zod 4.x surface. It renders verdicts only and never fixes the work; for teaching-style Zod feedback use the curated zod skill instead.

PlantUML diagram quality on the agent-uml collaborative canvas — three tiers: rendering safety (syntax that prevents HTTP 400 blank canvas), conversation mechanics (when to push a version vs ask a question, what to write in the message parameter), and design effectiveness (decomposition thresholds, cross-diagram traceability, export readiness). Trigger whenever calling agent-uml MCP tools (design_create, diagram_upsert, design_feedback, design_export) — even when the task seems simple, since a missing `as alias` makes elements un-annotatable and a skinparam mismatch makes diagrams unreadable.

User-facing copy — UI strings, documentation, marketing, release notes, error messages, onboarding flows, blog posts, or anything that a person will read. Distilled from the Apple Style Guide (June 2025): voice and tone (active voice, present tense, second person, no jargon), punctuation, capitalization, hyphenation rules for compound modifiers, when to spell out numbers, units of measure, UI vocabulary (button vs control vs sheet vs popover), Apple product and feature naming, technical notation for developer docs, and international style for localization. Trigger when writing, editing, or reviewing copy — even if the user doesn't explicitly mention "style guide" or "copywriting," any time the deliverable is human-readable text the rules here apply. Especially valuable when the user is writing instructions, naming UI elements, or deciding how to format a number, date, or unit.

Principal-level SwiftUI UI review and refactoring patterns for iOS 26 / Swift 6.2 clinic-architecture apps, grounded in Rams, Segall, and Edson principles. Use when auditing or improving existing SwiftUI screens, transitions, animations, and visual systems while preserving brand identity and respecting clinic Domain/Data/App boundaries.

nginx C module development guidelines based on the official nginx development guide. This skill should be used when writing, reviewing, or refactoring nginx C modules to ensure correct memory management, request lifecycle handling, and event-driven patterns. Triggers on tasks involving nginx module development, ngx_http_module_t, handler/filter/upstream implementation, pool allocation, or nginx configuration directives.

Audits a Next.js (App Router, 14/15+) codebase for React Hook Form anti-patterns — watch() at form root, Controller inlined in parent, async submit without try/catch, missing setError on server failures, RHF in non-"use client" files, RHF mixed with useActionState, schemas defined inside components, useFieldArray without field.id keys, register({ disabled }) for visual disabling, useFieldArray({ disabled }) that silently no-ops mutations, useEffect+reset(data) instead of the values prop. Read-only; emits a markdown report with file:line citations linking back to the companion `react-hook-form` distillation skill. Trigger when the user asks to audit/review/lint RHF usage, find form anti-patterns, or run a quality check on forms — even if they don't say "react-hook-form" by name; if they mention auditing forms in a Next.js project, use this skill.

Use this skill to gate Elixir/OTP systems on BEAM runtime architecture with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 23 decidable rules covering supervision and failure design (restart strategy vs child dependencies, blocking init, durability in terminate, restart amnesia, unsupervised fire-and-forget), backpressure (cast on externally-driven ingest, push pipelines without demand, silenced or retried call timeouts, unbounded fan-out), event delivery semantics (PubSub treated as durable, jobs enqueued outside the creating transaction, non-idempotent consumers under at-least-once delivery, cross-source ordering, telemetry handlers that block or detach), shared-state races (check-then-act on ETS/Registry, hot reads through one mailbox, persistent_term churn), distribution (global singletons in netsplits, node-local uniqueness assumed cluster-wide), and runtime mechanics (wall-clock durations, sub-binary leaks, minted atoms). Verdicts only, never fixes.

Use this skill when reviewing or refactoring existing Rust code that carries an alien mental model — OO/enterprise ceremony from Java/C#, garbage-collected object graphs, exception-style control flow, or imperative loops ported onto the borrow checker. It is the adversarial, architecture-level counterpart to greenfield idiom advice — it names the paradigm the code betrays and prescribes the deep refactor that collapses it, up to deleting whole layers (single-impl DI traits, Deref inheritance, Manager/Service structs, reflexive builders, Rc<RefCell> webs, clone-until-it-compiles, bool/String state machines, sentinel returns, catch_unwind try/catch, reflexive Box<dyn>, blocking calls inside async, fire-and-forget spawns). Every rule is grounded in the codex-rs production workspace (openai/codex) — the prescriptions are what that codebase actually does and lint-enforces. Applies whenever the work is "make this Rust actually Rust", "flatten this architecture", or a pedantic review of code fighting the language.

Migrates React UI code to Base UI (`@base-ui/react`) — replacing bespoke modals, custom dropdowns, raw `<dialog>`/`<select>` elements, ad-hoc popovers/menus/tooltips, or other component libraries (Radix UI, Headless UI, Reach UI). Ships a 37-component catalog (snapshotted from base-ui.com/llms.txt) and scripts to refresh it, scan for migration candidates, and verify the migration compiles. Triggers on phrases like "migrate to base-ui", "use base-ui instead of X", "replace this dialog/popover/menu with base-ui", or when scanning a React codebase for components Base UI can replace. Trigger even if the user only mentions one component (e.g., "swap this modal for base-ui dialog") — the workflow scales from one file to a whole repo.

Entry point for MCP server development — interrogates the user about their use case, determines the right deployment model (remote HTTP, MCPB, local stdio), picks a tool-design pattern, and hands off to specialized skills. Triggers when the user asks to "build an MCP server", "create an MCP", "make an MCP integration", "wrap an API for Claude", "expose tools to Claude", "make an MCP app", or discusses building something with the Model Context Protocol.

Interactive UI rendered inside ChatGPT or Claude — OpenAI Apps SDK apps, MCP Apps (the @modelcontextprotocol/ext-apps standard), or MCP-UI components, with a Next.js/React server. Covers the MCP tool and resource architecture, the window.openai / ui-bridge data flow, widget state, sandbox/CSP security, display modes, visual design, and directory submission. Trigger when building, reviewing, or designing such apps — even when the user only says "chat app", "ChatGPT widget", "Claude app", "render UI in chat", "window.openai", "createUIResource", "outputTemplate", or "MCP app UI" without naming a specific SDK.

Discovers business domains in a Swift codebase by tracing what users can DO — not by reading folder names or architecture docs. Maps each domain's vertical slice (Types → Config → Repo → Service → Runtime → UI), identifies providers (external SDK bridges), and separates cross-cutting concerns. Produces a domain map that drives all downstream decisions: folder structure, SPM targets, enforcement specs, migration plans. Use this skill whenever the user wants to understand their codebase domains, find what's cross-cutting vs domain-specific, restructure a Swift project, figure out where code belongs, or map a product's capabilities to architectural boundaries. Triggers on "what are my domains", "where does this belong", "map this codebase", "what's cross-cutting", "organize this project", "is this a domain or infra", "restructure this", "architecture review", or any request to understand the business domain structure of a Swift codebase.

Fog of war, field of view, line of sight, and tile visibility in JavaScript or TypeScript games — roguelikes, RTS, top-down, or strategy maps. Covers efficient FOV algorithms (recursive and symmetric shadowcasting, DDA raycasting, 2D visibility polygons), update scheduling and multi-viewer reference counting, typed-array and bitset state, canvas and WebGL fog rendering, memory and large-map scaling, hot-loop geometry math, and visibility correctness. Trigger when implementing, reviewing, or optimizing such code — even when the user only says "fog of war", "reveal the map", "what can this unit see", "shadowcasting", or "visibility grid" without mentioning performance — the naive raycast-per-cell-every-frame approach is usually what needs replacing. Prefer these patterns when writing new visibility code or refactoring slow or buggy fog.

Crash-hunter skill for iOS 26 / Swift 6.2 clinic-architecture codebases that finds and fixes concurrency, memory, and I/O bugs using TDD. Covers data races, actor isolation, retain cycles, SwiftData context misuse, and sync-related failures in Domain/Data/App boundaries. Use when debugging crashes or hard-to-reproduce failures in ios-* and swift-* clinic modules.

Use this skill to gate Swift language code with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 36 decidable rules covering concurrency (unresumed continuations, cancellation checks, async let, TaskGroup, @concurrent), property invariants (stored-derived state, private(set), observers skipped in init, discard self), error handling (underlying errors preserved, rethrows, Result.get(),

Black-box CLI grading harness — runs a test suite against a target CLI and reports per-rule pass/fail from the cli-for-agents 45-rule catalog. Use when reviewing, auditing, or grading a command-line tool for agent-friendliness. Trigger even if the user doesn't explicitly say "agent-friendly" — apply whenever they ask "is mycli good for agents?", "review this CLI", "grade my cli against the rules", "check if this tool is safe to automate", or "audit command-line design". Companion to the cli-for-agents distillation skill.

Adversarial pass/fail review gate that enforces the feature-arch skill's React feature-based architecture rules. Use when a diff, branch, PR, or src/ tree must be judged for architecture conformance before merge — feature folder structure, import boundaries, cross-feature isolation, data-fetching, state, testing, and naming rules. A single blind reviewer renders per-rule PASS/FAIL verdicts with cited evidence, and the reviewer's structured output is the verdict fail-closed. Use the feature-arch skill itself to design or migrate an architecture; use this gate to judge whether work conforms to it.

Clinic-architecture-aligned iOS design system engineering for SwiftUI (iOS 26 / Swift 6.2) covering token architecture, color/typography/spacing systems, component style libraries, asset governance, and theming. Enforces @Equatable on views and keeps design-system usage compatible with Feature-to-Domain+DesignSystem boundaries. Use when building or refactoring DesignSystem infrastructure for the clinic modular MVVM-C stack.

Drafting Python Enhancement Proposals (PEPs) — proposing a Python language feature, a standard library change, an interoperability standard, or an informational/process document for the Python community. Covers all three PEP types (Standards Track, Informational, Process): choosing the right type, scaffolding a valid reStructuredText pep-NNNN file, filling each required section to the acceptance bar, linting the headers, and navigating the sponsor / submission / Steering Council review process. Trigger on "write a PEP", "draft a PEP", "propose a Python feature", "create a Python Enhancement Proposal", "PEP template", or when someone is preparing a proposal for the Python Discourse or python-dev. Use it even if the user only says "PEP" or doesn't mention reStructuredText — the headers, sections, and process are exactly what trips PEP authors up.

Search and inspect local iOS 26 SDK documentation and Swift interfaces, especially SwiftUI and SwiftUICore. Use when Codex needs current iOS 26 SwiftUI APIs, Liquid Glass components, view modifiers, availability, signatures, deprecations, symbol docs, or SDK-only facts and should not rely on memory or public web docs being available.

Tailwind CSS code refactoring patterns for v4 migration and anti-pattern cleanup. This skill should be used when refactoring Tailwind utility classes, migrating from v3 to v4, cleaning up deprecated utilities, consolidating verbose class patterns, or removing code smells — all without changing the visual output. Triggers on tasks involving Tailwind CSS cleanup, v4 migration, class refactoring, @apply removal, or utility modernization.

Write, revise, or review software design documents using Malte Ubl's "Design Docs at Google" guidance. Use when Codex needs to draft a design doc, technical design, RFC, engineering review doc, architecture proposal, mini design doc, or design-doc review focused on context, goals, non-goals, trade-offs, alternatives, cross-cutting concerns, review lifecycle, and deciding whether a design doc is warranted.

Use this skill to gate Elixir, OTP, Ecto, and Phoenix code with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 19 decidable rules that catch architecture ported from an alien paradigm, covering enterprise layering (repository wrappers over Ecto, service-object tiers, DI behaviours with a single implementation, logic trapped in effectful callbacks), processes as objects (GenServer-per-entity, Agents as mutable variables, leaked message protocols, singleton managers), anemic data (bare maps as entities, boolean-flag state, hand-rolled type dispatch, 32+-field structs), defensive control flow (raise/rescue as branching, nil-guard swallowing, raw input past the boundary), transliterated loops, and needless metaprogramming (macro DSLs for data, use-as-import, compile-time coupling). Trigger it before merging Elixir work, or to check agent-authored code. It renders verdicts only, never fixes; Ecto-dependent rules go N/A without Ecto.

Use this skill to gate Python code (floors 3.10+, rules verified through 3.14) with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 20 decidable rules hunting two failure modes. First, code modern Python makes unnecessary — branch ladders over match/registries, hand-written init/repr/eq over dataclasses, TypeVar ritual over PEP 695, typing.Optional over PEP 604 unions, os.path over pathlib, hand-rolled stdlib batteries, deprecated utcnow, orphan create_task over TaskGroup. Second, legacy-pattern propagation — single-implementation ABCs, pass-through layers, single-method classes, concrete-inheritance reuse, boolean-forked functions, shapeless payloads and parameter clumps — judged as if greenfield; consistency with legacy code is not PASS evidence. A version probe reads the target's Python floor, marks rules above it N/A, and fetches the official what's-new delta when the floor exceeds the verified version. Verdicts only, never fixes.

Corrects the wrong defaults a model has when building Datadog dashboards, verified against Datadog's docs in July 2026. Use when creating, editing, or reviewing a Datadog dashboard — choosing widgets, writing metric/log/span queries, or emitting widget JSON. Covers the queries that render a plausible number and are still wrong — `.as_count()` is appended automatically in the graph editor but never through the API, so programmatic counts silently average; `p95` resolves only on distribution metrics, and averaging one is an average of averages; ratios need `.as_count()` on both sides or they divide interpolated averages. Also covers grounding queries in metrics that exist rather than invented names, wire type strings that diverge from UI names (Pie Chart is `sunburst`, Table is `query_table`), and Datadog's own layout standard. Assumes the Datadog MCP server is connected. NOT for Terraform or raw Dashboard API management, monitor and SLO authoring, or non-Datadog observability tools.

Airbnb-DLS-aligned design system engineering for Expo / React Native apps targeting both web and native iOS, built on Unistyles v3, Reanimated, Skia, and FlashList. Use whenever building, reviewing, or refactoring shared UI — design tokens, theming, variant-driven component APIs, typography, spacing, cross-platform web/iOS parity, native-feel performance, or complex surfaces like calendars and drawing canvases (examples use a clinic app). Covers token architecture, theming, component API contracts (variants over style props), web/iOS parity (Unistyles `_web` hover/focus/cursor, Platform splits, one shared theme), the Unistyles styling engine, and governance. Trigger even when the user does not say "design system" but is creating or changing reusable React Native components, tokens, theme code, or making a component behave natively on both web and iOS. Teaches how to BUILD the design system; pair with expo-react-native-coder for features and expo-ios-hig for iOS native-feel decisions.

Use this skill when writing, reviewing, or refactoring Elixir, OTP, Ecto, or Phoenix/LiveView code. It corrects the staff-level judgment calls a capable model gets wrong by default — reaching for a GenServer as the universal tool, rescuing instead of letting processes crash, N+1 Ecto access, non-atomic writes, unbounded/linked Task fan-out, atom exhaustion from user input, eager Enum where Stream fits, and calling Repo from the web layer. Applies whenever the work touches process design, error handling, concurrency, data access, or LiveView, even if the user doesn't name them.

Opinionated SwiftUI architecture enforcement for iOS 26 / Swift 6.2 clinic modular MVVM-C apps using local SPM package boundaries. Enforces App-target `DependencyContainer` + route shells, @Observable ViewModels/coordinators, Domain repository/coordinator/error-routing protocols, Data-owned I/O, stale-while-revalidate reads, and optimistic queued sync. Use when writing, reviewing, or refactoring SwiftUI architecture, navigation, dependency wiring, or repository boundaries.

Use this skill to gate Elixir code built on the Reactor orchestration library (~> 1.0) with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 28 decidable rules covering saga compensation and undo (side effects without undo, cleanup in the wrong callback, compensate returns that roll back vs continue, non-idempotent undo), retry discipline (uncapped retries under the max_retries infinity default, retrying business failures, missing backoff), dependency and data flow (lexical-order assumptions, context smuggling, missing return), step contracts (invalid run/3 returns, halt misused as failure, guard/where confusion, side effects in inline fns), composition (Reactor.run inside steps instead of compose, Enum loops over map steps, case over switch, unbounded recurse), concurrency (serial-by-default map, sandbox tests left async, process-context loss), and middleware contracts. Verdicts only, never fixes.

Use when writing, reviewing, or refactoring TypeScript or React code for craftsmanship — naming, function and component shape, error handling, data modeling, tests, and abstraction. Translates Robert C. Martin's Clean Code principles into modern TS+React idioms (TS 5.x, React 19), with first-class "When NOT to apply" guidance and a Meta category for principle conflicts (DRY vs SRP, small functions vs deep modules, type safety vs ergonomics). Triggers on code review, refactoring for clarity, naming, function/component design, "is this clean?", "make this more readable", "right abstraction?" — even when the user doesn't say "clean code". Does NOT cover React-specific APIs (RSC, hooks API surface) — use the `react` skill. Does NOT cover TS compiler perf or tsconfig — use the `typescript` skill.

Dockerfile optimization guidelines from official Docker documentation. This skill should be used when writing, reviewing, or refactoring Dockerfiles to ensure optimal build time, image size, security, and robustness. Triggers on tasks involving Dockerfile creation, Docker image builds, container optimization, multi-stage builds, build cache, or Docker security hardening.

Static scan of an Expo / React Native iOS app for non-native patterns — Material component kits, JS navigators instead of native stack/tabs, PanResponder, disabled font scaling, hardcoded hex colors, unvirtualized lists — reports each violation with file:line and a link to the rule. Trigger when the user asks to check, lint, audit, or review an Expo iOS app for HIG compliance or "native feel," or before shipping/merging Expo iOS UI. Pairs with the expo-ios-hig rules skill (it checks what that skill teaches) and the expo-ios-screen-scaffolder.

Set up or update the agent-first engineering harness for any repository. Implements the complete scaffolding that makes AI coding agents effective: knowledge maps (AGENTS.md as a concise TOC), structured documentation, architecture boundaries, enforcement rules (.harness/*.yml specs), quality scoring, and process patterns for agent-driven development. Use this skill whenever someone wants to make a repo agent-ready, set up AGENTS.md or docs/ structure, define domain boundaries or golden principles, generate .harness/ configuration, audit agent readiness, or update an existing harness. Also trigger when a user reports problems with agent effectiveness, context management, or architectural drift — these are symptoms of a missing or stale harness. Trigger on: "harness this repo", "set up harness", "agent-first setup", "make this agent-ready", "update the harness", "assess agent readiness", "set up AGENTS.md", "organize for agents", or any discussion about structuring a codebase for AI agent workflows.

Next.js 16 App Router pages mixing static and dynamic content — Partial Prerendering (PPR) under the Cache Components model. Covers enabling it with cacheComponents (the removed experimental.ppr / experimental_ppr flags), the dynamic-by-default rendering inversion, the Suspense static-shell/dynamic-hole boundary, the 'use cache' directive (automatic keys, cacheLife/cacheTag, children/action pass-through, runtime values as props, serverless durability), async runtime APIs and connection() for non-determinism, page composition from a single hole to parallel dashboards to streaming a Promise into a Client Component with use(), and forms/wizards with updateTag read-your-writes and Activity state preservation. Triggers on PPR, cacheComponents, 'use cache', Suspense streaming, partial prerendering, or static-shell work even when not named explicitly.

nginx C module performance optimization and reliability guidelines based on the official nginx development guide. This skill should be used when optimizing nginx C modules for throughput, latency, memory efficiency, and operational resilience. Triggers on tasks involving buffer optimization, connection tuning, shared memory contention, error recovery, timeout strategy, caching implementation, worker process tuning, or logging performance in nginx C modules.

Ruby on Rails design system guidelines for building consistent, maintainable UI with minimal abstraction. This skill should be used when creating or refactoring Rails views, partials, components, form builders, helpers, Stimulus controllers, Turbo Frames, Turbo Streams, or design tokens. Triggers on tasks involving ERB partials, Turbo navigation, Turbo Streams, ViewComponent, Phlex, Tailwind design tokens, custom form builders, view helpers, Stimulus behaviors, Import Maps, Lookbook previews, or design system consistency audits.

Search and inspect local macOS 26 SDK documentation and Swift interfaces, especially SwiftUI, SwiftUICore, and AppKit. Use when Codex needs current macOS 26 APIs, Liquid Glass components, window, scene, menu, toolbar, AppKit bridging, availability, signatures, deprecations, symbol docs, or SDK-only facts and should not rely on memory or public web docs being available.

TypeScript and TSX refactoring and modernization guidelines from a principal specialist perspective, current to TypeScript 6.0 and React 19. This skill should be used when refactoring, reviewing, or modernizing TypeScript or React/TSX code for type safety, compiler performance, and idiomatic patterns. Triggers on tasks involving type architecture, narrowing, generics, discriminated unions, error handling, React component and hook typing, or migration to modern TypeScript features (satisfies, using, const type parameters, inferred type predicates, isolatedDeclarations, erasable syntax, import attributes).

Use this skill to gate SwiftUI code with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 31 decidable rules — data modeling and observation (@Observable over ObservableObject, @State ownership, task(id:) re-init guards, environment closures and high-frequency values), view update cost (computed-var extraction, whole-model dependencies, init side effects, uncached derivations, structs on rows), structural identity (applyIf branching, AnyLayout), task lifecycle (.task over onAppear+Task, scalar ids, @concurrent offloading), lists and geometry (ForEach view count, AnyView rows, GeometryReader measurement, feedback loops, visualEffect), animation scope, and accessibility (button semantics, style protocols, accessibilityRepresentation, semantic styling, ScaledMetric spacing). Trigger before merging SwiftUI work or to audit agent-authored views. Verdicts only, never fixes; targets without a SwiftUI surface abort.

Use this skill to gate TanStack Start plus TypeScript web-app changes with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 22 decidable rules covering client/server boundary leaks, server-function and server-route usage, auth and security, SSR data loading, boundary type safety, and compiler config. Trigger it before merging TanStack Start work, when asked to gate, adversarially review, or pass/fail a Start or TanStack codebase, or as a final check on agent-authored Start features. It renders verdicts only and never fixes the work; for teaching-style review feedback use a distillation skill instead.

Audio forensics and voice recovery guidelines for CSI-level audio analysis. This skill should be used when recovering voice from low-quality or low-volume audio, enhancing degraded recordings, performing forensic audio analysis, or transcribing difficult audio. Triggers on tasks involving audio enhancement, noise reduction, voice isolation, forensic authentication, or audio transcription.

Scaffolds a Better Auth setup in a Next.js (App Router) + Drizzle project — lib/auth.ts, lib/auth-client.ts, the /api/auth/[...all] route handler, middleware.ts, .env.example, and a permissions module. Produces convention-enforced templates for three plugin presets (minimal, social, advanced with twoFactor+magicLink). Trigger even when the user doesn't explicitly say "scaffold" — phrases like "set up Better Auth", "wire up auth", "initialize auth in this project", or "add auth to Next.js" should pull this in. Pairs with the `better-auth` skill, which covers the rules these templates encode.

Analyze a software codebase for algorithmic complexity and performance hotspots, then propose or implement safe optimizations without breaking behavior. Use when the user asks to scan many files, find inefficient loops, nested iteration, repeated scans, costly rendering/recomputation, N+1 queries, avoidable O(n^2) or O(n) operations, or reduce complexity such as O(n^2) to O(n log n) / O(n), while preserving tests, APIs, outputs, and maintainability.

Emil Kowalski's animation best practices for web interfaces. Use when writing, reviewing, or implementing animations in React, CSS, or Framer Motion. Triggers on tasks involving transitions, easing, gestures, toasts, drawers, or motion.

Turn a rough idea for a language into a complete, implementable specification — a DSL, query, config/data, template, or protocol language — by interviewing the author dimension by dimension until another developer could build a conforming implementation from the document alone. It grills for the decisions authors skip: lexical rules (whitespace, case, comments, literals), grammar with precedence and ambiguity resolution, a semantic/type model, validation rules with counter-examples, execution algorithms and the error model, the output/serialization format, and RFC 2119 conformance. The completeness bar and formal notation (lexical vs syntactic grammar, function-style algorithms) are distilled from the GraphQL specification. Trigger on "spec out my language", "design a DSL / query language", "write a language or grammar spec", "formalize this syntax", or when someone has a language idea that needs to become an implementable spec — even if they only say "spec" or "grammar".