182 published skills · page 2 of 2
- ▌ Adversarial Python · pproenca bundleUse 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.
- ▌ Datadog Dashboards · pproenca bundleCorrects 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.
- ▌ Expo Design System · pproenca bundleAirbnb-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.
- ▌ Staff Level Elixir · pproenca bundleUse 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.
- ▌ Swift UI Architect · pproenca bundleOpinionated 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.
- ▌ Adversarial Reactor · pproenca bundleUse 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.
- ▌ Clean Code TS React · pproenca bundleUse 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 Optimise · pproenca bundleDockerfile 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.
- ▌ Expo IOS Hig Verify · pproenca bundleStatic 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.
- ▌ Harness Engineering · pproenca bundleSet 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.
- ▌ Nextjs Ppr Patterns · pproenca bundleNext.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 Perf · pproenca bundlenginx 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.
- ▌ Rails Design System · pproenca bundleRuby 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 Macos26 Docs · pproenca bundleSearch 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 Refactor · pproenca bundleTypeScript 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).
- ▌ Adversarial Swift UI · pproenca bundleUse 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.
- ▌ Adversarial Tanstack · pproenca bundleUse 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 Voice Recovery · pproenca bundleAudio 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.
- ▌ Better Auth Scaffold · pproenca bundleScaffolds 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.
- ▌ Complexity Optimizer · pproenca bundleAnalyze 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.
- ▌ Emilkowal Animations · pproenca bundleEmil 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.
- ▌ Language Spec Author · pproenca bundleTurn 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".
- ▌ Nginx C Module Debug · pproenca bundlenginx C module debugging guidelines based on the official nginx development guide. This skill should be used when debugging nginx C module crashes, memory bugs, request flow issues, or production problems. Triggers on tasks involving segfault analysis, coredump debugging, GDB inspection, memory leak detection, request phase tracing, AddressSanitizer setup, or nginx module troubleshooting.
- ▌ Tailwind UI Refactor · pproenca bundleRefactoring UI design patterns for Tailwind CSS applications. This skill should be used when writing, reviewing, or refactoring HTML with Tailwind utility classes to improve visual hierarchy, spacing, typography, color, depth, and polish. Triggers on tasks involving UI cleanup, design review, Tailwind refactoring, component styling, or visual improvements.
- ▌ Nginx C Module Design · pproenca bundlenginx C module directive design guidelines for creating admin-friendly configuration interfaces. This skill should be used when designing nginx module directives — deciding what to expose vs hardcode, naming conventions, scope placement, default values, variable design, and validation patterns. Triggers on tasks involving ngx_command_t design, directive naming, configuration API design, nginx module public interface, or directive deprecation.
- ▌ React Native Elements · pproenca bundleReact Native Elements UI component library best practices for performance, theming, and proper component usage. Use when building React Native apps with RNE, configuring themes, optimizing lists with ListItem, or reviewing RNE component code.
- ▌ React Testing Library · pproenca bundleReact Testing Library best practices for writing maintainable, user-centric tests. Use when writing, reviewing, or refactoring RTL tests. Triggers on test files, testing patterns, getBy/queryBy queries, userEvent, waitFor, and component testing.
- ▌ Theory Of Constraints · pproenca bundleApply the Theory of Constraints (Goldratt's Five Focusing Steps) to find and fix the single bottleneck that caps a process, workflow, pipeline, or Agent Skill/plugin's throughput. Use whenever optimizing speed, lead time, cost, or token/context budget of a system — CI/build pipelines, dev value streams (idea→review→merge→ship), an Agent Skill's trigger/context flow, or runtime code paths — ESPECIALLY when you don't know where to optimize, a local speedup didn't improve the whole, work piles up at a stage, everything is busy but little ships, adding capacity didn't help, or a policy/rule (not a resource) is the limiter. It locates the constraint with measurement, then prescribes exploit → subordinate → elevate → repeat, and stops you optimizing non-constraints (the "mirage of the non-bottleneck"). Trigger even when the user just says "speed this up", "why is this slow", or "make this more efficient" without mentioning constraints or bottlenecks.
- ▌ Deterministic Metric Design · pproenca bundleInventing deterministic metrics — turning a fuzzy property like 'maintainability', 'risk', or 'how reducible this code is' into a deterministic, computable number an agent can trust and optimize. Covers the path from construct to adoption — operationalizing the construct, confronting computability limits (Kolmogorov, Rice) with sound proxies, picking the right measurement scale, proving properties (monotonicity, invariance, the Weyuker/Briand axioms), guaranteeing determinism, establishing construct validity (not just LOC in disguise), and hardening against Goodhart-style gaming when an agent optimizes the metric. Trigger when designing, reviewing, or validating a quantitative metric, score, measure, or index — and even when the user doesn't say 'metric' but wants to quantify, score, rank, or measure code/behavior, build a deterministic optimization target, or invent a measure for something previously unquantified (e.g., behavior-preserving codebase-size reduction).
- ▌ Adversarial IOS Design · pproenca bundleUse this skill to gate iOS SwiftUI design and UX with a pass/fail adversarial review — a single blind reviewer subagent judges screens, diffs, or features against 56 decidable HIG-derived rules, working backwards from mandatory rendered evidence, simulator screenshots (light, dark, accessibility text size) and interaction recordings tiled into filmstrips. Covers navigation/IA (tab bars, five tabs max, system Back), modality and flow grammar (sheets, alerts, unsaved-content protection), layout (44pt targets, safe areas, Dynamic Type), color and contrast, typography floors, Liquid Glass, feedback states (empty, loading, error, launch), motion — filmstrip-primary except the spring-curve and Reduce Motion checks, so code alone never prescribes an unseen animation, and gratuitous decoration fails — plus haptics and craft. Fixes must be the minimal change, removal preferred over addition. Trigger before merging user-facing SwiftUI work. Verdicts only, never fixes; targets without a SwiftUI UI surface abort.
- ▌ Code Map Visualization · pproenca bundleRendering and perception layer for codebase-as-geohash-map visualisations — choosing what to encode on colour/size/position, picking perceptually honest colour scales (viridis/OKLCH, not rainbow), drawing tens of thousands of cells on Canvas2D + WebGL/deck.gl inside a 16ms frame budget, placing and decluttering labels, GPU or spatial-index picking, camera animation and level-of-detail crossfades, and keyboard plus screen-reader accessibility for the canvas. Sits on top of geohash-spatial-code-maps, which owns the geohash encoding, projection, tiling, and navigation math. Also covers nature-inspired rendering — Voronoi, circle packing, phyllotaxis, metaball hulls, edge bundling. Trigger even when the user does not say "visualisation" — if the work involves drawing, colouring, labelling, animating, or making navigable a code map, spatial heatmap, or large cell/point layer on the web, this is the skill.
- ▌ Codemod React Pipeline · pproenca bundleGuided, scripted pipeline for running JSX/TSX/React codemods safely across large legacy codebases. Use when you need to scaffold a codemod, dry-run it, validate its findings, and apply it across many files (50 to 100k+) without breaking the build. Walks the full inner/outer loop with the Codemod CLI (JSSG, ast-grep, workflows). Triggers on large-scale refactor, legacy React migration, codemod a prop/API change, migrate components across the codebase, run a codemod safely, batched/resumable codemod apply, dry-run a codemod.
- ▌ Mlflow Mlops Migration · pproenca bundleGuided workflow for taking any ML codebase — including one with no experiment tracking at all, or one full of MLflow 2-era idioms — to a production-grade open-source MLflow 3 setup with dev/staging/prod environments, registry-based promotion, and served models. Walks seven phases with a developer who may have zero MLflow 3 experience — assess the codebase (scripted read-only audit), model the registry domain (per-environment model names, aliases, gates), stand up tracking per environment, restructure training code to MLflow 3 idioms, wire evaluation-gated promotion, serve and smoke-test, then run the ongoing MLOps loop. Use when asked to set up MLflow, migrate to MLflow 3, productionize model training and serving, or design a dev/staging/prod MLOps cycle. Pairs with the sibling mlflow-3 rule pack for every API decision.
- ▌ Same Results Less Code · pproenca bundleSame behaviour in fewer, clearer lines — covers the judgment gaps that linters cannot catch (reinvention, wrong frame, hidden duplication, derived state, procedural rebuilds, speculative generality, defensive excess, type-system underuse). Trigger when reviewing, refactoring, or simplifying code — and even when the user doesn't explicitly ask for "simplification" but is reviewing code, refactoring, or asking "is there a shorter way to write this?". Complements knip/eslint/ruff/tsc by focusing on the conceptual modelling layer those tools cannot see.
- ▌ Sonarqube AI Slop Gate · pproenca bundleCorrects the wrong defaults a model has when standing up self-hosted SonarQube Server as a continuous gate on AI-generated code, verified against docs.sonarsource.com in July 2026 (Server 2026.3, LTA 2026.1). Use when configuring SonarQube, designing a quality gate, or wiring a scan step into CI for AI-assisted work. Covers the setups that run green while measuring almost nothing — the fudge factor skips duplication and coverage conditions below 20 new lines and is on by default; duplication is never measured on test code; no `new_cognitive_complexity` metric exists to gate on; `sonar.host.url` now defaults to sonarcloud.io rather than localhost; a shallow clone degrades new-code attribution to timestamps. Also covers AI Code Assurance — the project flag, gate qualification, the deprecated Copilot autodetection — and that Community Build cannot analyze pull requests at all. NOT for SonarQube Cloud, IDE connected mode, or authoring custom analyzer rules.
- ▌ Tailwind Responsive UI · pproenca bundleResponsive UI transformation patterns for Tailwind CSS applications. This skill should be used when making interfaces responsive, refactoring layouts for multiple screen sizes, or reviewing responsive Tailwind code. Triggers on tasks involving breakpoint strategy, layout adaptation, responsive spacing, fluid typography, mobile navigation, touch interaction, responsive media, or data table responsiveness.
- ▌ Webpack Plugin Recipes · pproenca bundleUse whenever you face a webpack-build problem that ends with needing to write a plugin — 26 production-shaped recipes covering bundle-size budgets, forbidden architectural imports, env-var validation, secret-leak prevention, build-info injection, asset manifests, license walking, SRI hashes, virtual modules (Vite-style), filesystem routing (Next.js-style), generated barrels, runtime-driven TS types, library replacement (react→preact), debug-stripping, conditional polyfills, dynamic banners, feature flags, build-duration regression tracking, desktop/Slack notifications, changed-chunks diffing, browser auto-open, gzip/brotli pre-compression, image optimization, type-based dist layout, empty-chunk cleanup, cache-busting query strings. Each recipe is a complete working plugin drawn from production patterns at Next.js, Storybook, webpack-contrib. Trigger when the user asks how to do X with webpack or whether a plugin exists for X. Companion to webpack-plugin-authoring.
- ▌ Wxt Browser Extensions · pproenca bundleWXT browser extension performance optimization guidelines. This skill should be used when writing, reviewing, or refactoring WXT browser extension code to ensure optimal performance patterns. Triggers on tasks involving WXT, browser extensions, content scripts, service workers, messaging, and extension APIs.
- ▌ Adversarial TS Patterns · pproenca bundleUse this skill to gate TypeScript and React application code with a pass/fail adversarial review of design-pattern usage — a single blind reviewer subagent judges a diff or file set against 18 decidable rules covering implicit state machines (boolean-flag lifecycles, useEffect chains, stored derived state, non-exhaustive union matches) and over-engineered OO/enterprise ports (getInstance singletons, factory and builder classes, single-method strategy classes, State/Visitor hierarchies, event buses inside a React tree, pass-through repositories, DI containers, single-implementation interfaces, component inheritance, logic-only HOCs, static-only classes, trivial accessors). Trigger it before merging TS/React work, when asked to gate or pass/fail pattern usage, or as a check that agent-authored code is not porting Java/C# idioms. It renders verdicts only; for teaching-style guidance use implementation-design-patterns or implementation-functional-patterns.
- ▌ Drizzle Nextjs Postgres · pproenca bundleDrizzle ORM against PostgreSQL inside a Next.js App Router app. Covers client construction (globalThis singleton across HMR, serverless pool sizing, `prepare:false` behind PgBouncer/Supavisor, driver choice when you need interactive transactions, `server-only`), reads in Server Components under Next.js 16 Cache Components (`use cache` superseding `unstable_cache` and the `revalidate`/`dynamic` segment configs, Suspense boundaries, React `cache()` dedupe), Server Actions (authorization inside the action, `updateTag` vs `revalidateTag`, `after()`), Postgres schema types (timestamptz, identity vs serial, jsonb, numeric-as-string, bigint modes), drizzle-kit migrations (generate vs push, CONCURRENTLY outside the migrator, NOT VALID constraints, rename prompts), transactions and pooled connections, and Postgres query traps (keyset pagination, count cost, driver-dependent `db.execute()` shape, NOT IN nulls, prepared statements). Use when writing or reviewing Drizzle + Postgres code in Next.js.
- ▌ Drizzle Sqlite Scaffold · pproenca bundleScaffolds Drizzle ORM + SQLite boilerplate — a new `drizzle.config.ts`, a singleton client with the right pragmas, per-table schema files with explicit primary keys/indexed foreign keys/relations()/inferred types, per-table repository modules with `.returning()` + `inArray()` + `.onConflictDoUpdate()`, or drizzle-zod validators. Produces convention-enforced templates for three drivers (better-sqlite3, libsql/Turso, bun:sqlite). Trigger even when the user doesn't say "scaffold" — phrases like "add a table for X", "set up Drizzle in this project", "wire up SQLite", "create a CRUD module for X", or "bootstrap the DB layer" should pull this in. Pairs with the `drizzle-sqlite` skill, which covers the 45 rules these templates encode — read it when an exception is required.
- ▌ Elixir Meta Programming · pproenca bundleUse this skill when building an Elixir macro or a declarative DSL — a schema/spec/route/workflow language in the shape of Ecto.Schema, Absinthe, Plug.Router, or ExUnit — with quote/unquote, __using__, module attributes, and @before_compile. It corrects the wrong defaults a model makes once it commits to metaprogramming — putting logic inside the quote block, re-evaluating unquoted expressions, forgetting Macro.escape, fighting hygiene with var!, generating code ad hoc instead of accumulating declarations, and validating the DSL at runtime rather than at compile time. Applies to writing or reviewing macro/DSL code. NOT for deciding whether to use a macro at all — that gate belongs to staff-level-elixir and adversarial-elixir, which say prefer plain functions.
- ▌ Expo React Native Coder · pproenca bundleComprehensive Expo React Native feature development guide. This skill should be used when building mobile app screens, navigation, data fetching, authentication, deep linking, or native UX patterns with Expo. Triggers on tasks involving Expo Router, React Native components, mobile forms, or app configuration.
- ▌ Inngest Nextjs Patterns · pproenca bundleInngest event-driven functions in a Next.js (App Router) project — creating the client, the /api/inngest route handler, typed events with Zod schemas, durable event-triggered functions, scheduled cron functions, or fan-out orchestrators. Trigger when scaffolding Inngest patterns — and even if the user just says "add a background job", "process this async", "schedule X every hour", or "send an event when Y happens" in a Next.js codebase. Also trigger when reviewing existing Inngest code to enforce event-naming, function-id stability, and step-idempotency conventions.
- ▌ Nextjs Bundle Optimizer · pproenca bundleNext.js 16 bundle-size and build-time optimization — runs a data-driven iteration loop: measure baseline → analyze top offenders → apply ONE recipe → re-measure → verify nothing broke (build + types + tests + no regression) → commit or revert. Built for Next.js 16 with Turbopack default, and falls back to webpack-mode tooling when the project hasn't migrated yet. Triggers on phrases like "First Load JS is huge", "bundle size", "build takes too long", "page is slow to TTI", "reduce bundle", "tree-shake", or when the user shares output from `next experimental-analyze` / `@next/bundle-analyzer` — even if the user doesn't say "optimize" explicitly.
- ▌ React 19 Component Scaffolder · pproenca bundleScaffolds React 19 / React 19.2 code in TypeScript — components, Server Component pages, client islands, form actions with useActionState, context providers, custom hooks, reducers, or document metadata + resource hints. Generates production-grade code that follows React 19 idioms (ref-as-prop, <Context value={...}>, useActionState, inline metadata, useSyncExternalStore) and refuses deprecated React 18 patterns (forwardRef, <Context.Provider>, useFormState, react-dom/test-utils). Trigger even when the user says "create a component", "new page", "add a form", "new hook", or "scaffold X" without explicitly mentioning React 19.
- ▌ Io Bound Data Processing · pproenca bundleProcessing, transforming, or moving datasets that may exceed RAM on a single low-compute box — covers memory discipline (streaming, generators, dtype shrinkage), I/O access patterns (sequential vs random, mmap, async), data formats (Parquet vs CSV vs JSON, predicate pushdown), chunking & batching, spill-to-disk (external merge sort, DuckDB/Polars), pipelining (bounded queues, backpressure, checkpointing), codec selection (zstd/lz4/gzip), concurrency for I/O-bound workloads (asyncio, threads, prefetch), and observability (iowait vs CPU%, rows/sec, py-spy/strace). Trigger on "process a large file", "stream this", "out-of-core", "OOM kill", "this is slow", or code with `pd.read_csv` of multi-GB files, `requests.get(...).content` on big bodies, `BytesIO` on unbounded inputs, per-row INSERTs, sequential `requests.get` loops, falling `tqdm` rates — even if I/O or memory isn't mentioned. Complement to computer-science-algorithms.
- ▌ Relational Data Modeling · pproenca bundleCorrects the wrong defaults a model has when designing a relational schema — the DDL decisions an experienced engineer makes differently. Use when creating or reviewing tables, migrations, ER models, or ORM schema definitions. Covers identity and keys (surrogate vs natural, identity vs serial, uuidv7, composite keys that make cross-tenant references impossible), relationships (polymorphic foreign keys the database cannot enforce, referential actions, unindexed FK columns, disjoint subtypes), invariants the engine can prove instead of application code (EXCLUDE, partial unique indexes, CHECK limits, deferrable cycles, NOT VALID), types (timestamptz, exact money, range types, enum vs lookup table), derived and encoded data (generated columns, JSONB as an escape hatch), and time (events vs in-place updates, soft-delete flags that silently disable constraints, temporal keys). NOT for query tuning, index selection for read paths, or connection pooling.
- ▌ Webpack Plugin Authoring · pproenca bundleWriting webpack 5 plugins — hook selection (compiler vs compilation, tap vs tapAsync, processAssets stages), the asset pipeline (emitAsset, source classes, info metadata, source maps), watch-mode and persistent caching (file/context/missing/buildDependencies), plugin lifecycle (constructor purity, multi-compiler isolation, shutdown cleanup), schema-utils validation, WebpackError reporting, jest-worker parallelism, and compatibility patterns (compiler.webpack namespace, peerDependencies, getCompilationHooks WeakMap). Patterns are drawn from production plugins like mini-css-extract-plugin, terser-webpack-plugin, compression-webpack-plugin, and Next.js's webpack plugins. Trigger when writing, reviewing, or debugging webpack 5 plugins — even if the user doesn't explicitly mention "best practices" — anytime an `apply(compiler)` method is being written, hooks are being tapped, or a plugin imports from `webpack-sources`, the rules in this skill apply.
- ▌ Implementation Design Patterns · pproenca bundleImplementation guide for the 22 Gang of Four design patterns in TypeScript, distilled from refactoring.guru. Use this skill when writing, refactoring, or reviewing TypeScript that exhibits a pattern-shaped problem — class-explosion from inheritance, conditionals switching on type, tight coupling to concrete classes, tree-shaped models, runtime algorithm selection, undo/redo, snapshot-and-restore, state-dependent behavior, subscriber notification, or hiding subsystem complexity. Each pattern entry includes intent, problem, solution, applicability (when to use AND when NOT to use), a runnable TypeScript example, implementation steps, pros/cons, and relations to sibling patterns. Trigger even when no pattern is named — cues like "class getting unwieldy," "giant switch," "swap implementations at runtime," "combinatorial subclasses," "need undo," or "traverse a tree" are pattern-shaped. Covers all 5 Creational, 7 Structural, and 10 Behavioral GoF patterns.
- ▌ Ast Grep Typescript React · pproenca bundleUse this skill when writing, debugging, or reviewing ast-grep patterns, YAML rules, or codemods against TypeScript or React (.ts/.tsx) code — searching for JSX elements, props, hooks, imports, or type constructs, and rewriting them. Covers the TS/React-specific traps — the tsx-vs-typescript language split, JSX and TypeScript node kinds, fragment matching, rewrites, and the @ast-grep/napi API. Complements the general-purpose ast-grep skill (rule mechanics) — reach for this one whenever the target code is TypeScript or React.
- ▌ Geohash Spatial Code Maps · pproenca bundleGeohash encoding/decoding in TypeScript or Rust — bit interleaving, the base32 alphabet, precision and cell geometry, neighbour/adjacency computation, proximity and bounding-box queries, and geohash-backed spatial indexing. Also covers the "codebase as a navigable 2D map" pattern — projecting a codebase into a coordinate plane, geohashing it so prefixes become business-domain regions, and navigating it like Google Maps (zoom, tiles, level-of-detail, clustering, deep links). Trigger when implementing, reviewing, or debugging geohash work — even when the user does not say "geohash" but the work involves spatial hashing, Morton/Z-order codes, proximity search on lat/lon, or mapping and visualising code structure spatially. Contains 42 impact-ordered rules with TypeScript and Rust examples.
- ▌ Metric Validation Harness · pproenca bundleEmpirically validates a software metric before trusting or optimizing it — point it at any candidate metric (a command that takes a path and prints one number) plus a corpus, and it runs experiments that try to falsify each property a good metric must have. Checks determinism (same input, same number across runs and hash seeds), invariance to cosmetic edits (also an anti-gaming probe), monotonicity under construct-increasing edits, discrimination, robustness on edge inputs, near-linear tractability, and construct validity (convergent, discriminant vs LOC, predictive AUC, lift over a baseline). Trigger whenever someone proposes, reviews, tunes, or ships a metric, score, or index, asks "is this metric any good", suspects a score tracks LOC or jumps between runs, or builds a deterministic optimization target. It is the empirical companion to the deterministic-metric-design skill and is read-only.
- ▌ Design To React Algorithms · pproenca bundleReverse-engineering a Sketch file (or Figma export with similar shape) into pixel-perfect React + CSS — the iteration mental model, tree reconstruction, layout inference algorithms, geometry math, visual-regression diffing, and the style/typography/path conversions that make "improvement without regression" enforceable. Trigger even if the user doesn't explicitly mention "algorithms" but is converting a design source into web code, building a design-to-code pipeline, or struggling to make incremental fidelity improvements without breaking previously-converted output.
- ▌ Expo IOS Screen Scaffolder · pproenca bundleScaffolds Expo (React Native) iOS screens that follow Apple Human Interface Guidelines by construction — list, detail, form, modal sheet, native tabs layout, and settings screens, each wired with native navigation, FlashList, safe-area insets, semantic colors, SF Symbols, haptics, and empty/loading states. Generated code follows the expo-ios-hig rules so it passes expo-ios-hig-verify without rework. Each screen is TSX for Expo Router, not Swift. Trigger whenever the user wants to create, add, generate, or scaffold a new Expo screen, route, tab layout, or form for iOS — even if they don't mention HIG.
- ▌ Openai Codex Rust Patterns · pproenca bundleOpenAI Codex Rust coding patterns distilled from the codex-rs workspace. Use this skill whenever writing, reviewing, or refactoring Rust code — especially for async agents, CLI tools, sandboxing, secret handling, Ratatui TUIs, JSON-RPC protocols, tokio-based services, or any codebase that needs defensive panic discipline. Trigger even when the user does not explicitly mention Codex, because the patterns generalize to any production Rust workspace. Covers async cancellation, error enum design, process sandboxing, DNS-rebinding defense, credential hardening (zeroize/mlock/ctor), Cargo workspace architecture, wiremock-based fakes, insta snapshot testing, OpenTelemetry tracing, and Ratatui rendering.
- ▌ React Fetch Cache Patterns · pproenca bundleReact data-fetching patterns at scale — recommender carousels, infinite feeds, pages with many parallel fetches, dashboards. Covers request orchestration (parallelism, batching, deduplication), cache strategy (keys, normalization, staleTime, SWR), backend protection (concurrency caps, debounce/throttle, jittered retries, circuit breakers), prefetching (route loaders, hover/intent, idle, server hydration), failure resilience (AbortController, timeouts, error boundaries, stale fallback, idempotent mutations), and feed/carousel patterns (virtualization, cursor pagination, summary/detail split). Includes 5 ready-to-use scaffolding templates (resource query hook, carousel data loader, infinite feed, hover-prefetch link, request collapser). Trigger when building, reviewing, or refactoring React components that fetch data — even if the user doesn't explicitly mention "performance" or "scale".
- ▌ Relational Database Design · pproenca bundleDistills a logical relational-database design methodology into rules an agent applies while designing or reviewing a schema. Covers the design sequence (mission → tables → fields → keys → relationships → business rules → views → integrity review), one-subject-per-table decomposition, atomic single-valued fields, candidate/primary/foreign keys, relationship types with deletion rules and participation, the four levels of data integrity, database-vs-application business rules, validation tables, views for derived data, and the flat-file / spreadsheet / RDBMS-driven antipatterns to avoid. The structure is logical and RDBMS-agnostic, and normalized by construction. Use when designing a new relational schema, reviewing or refactoring an existing one, resolving redundant or repeating data, choosing keys, modeling relationships, or deciding where a constraint belongs.
- ▌ Acceptance Pipeline Catalog · pproenca bundleUse when implementing, reviewing, or debugging a Gherkin acceptance-test pipeline with mutation testing. Covers parser, JSON IR, generator, runtime, step handlers, test runner, mutator, value mutation rules, execution, result classification, reporting, project layout, conformance, and agent setup. Based on Uncle Bob's Acceptance Pipeline Specification. Trigger even when the user mentions Gherkin parsing, acceptance test generation, mutation testing for acceptance tests, or building a portable test pipeline.
- ▌ Computer Science Algorithms · pproenca bundleChoosing or implementing an algorithm or data structure — asymptotic complexity, data-structure selection, sorting & searching, dynamic programming, graph algorithms, divide & conquer, greedy algorithms, string/sequence algorithms, and the at-scale toolbox (Bloom filters, HyperLogLog, Count-Min Sketch, reservoir sampling, consistent hashing, external merge sort, Aho-Corasick, MinHash/LSH). Trigger on tasks involving "what's the right algorithm for…", performance-critical code, code with nested loops over the same input, recursive solutions, shortest-path / scheduling / matching / DP problems, code review for accidental O(n²) blowup, and any "how do I do X at scale / on a stream / without enough RAM" question — even if the user doesn't explicitly mention "algorithm" or "complexity."
- ▌ Marketplace Personalisation · pproenca bundlePersonalisation and recommendation systems for a two-sided trust marketplace built on AWS Personalize — event tracking, dataset and schema design, two-sided matching, cold start, feedback loops, bias control, recipe selection, serving-time re-ranking, observability, and a diagnostic playbook for existing systems. Trigger when designing, building, debugging, reviewing, or improving such a system — and even when the user does not explicitly mention "AWS Personalize" but is working on recommendations, ranking, search, homepage personalisation, or anything that matches seekers and providers across a trust-based catalog.
- ▌ Opinionated Nextjs Patterns · pproenca bundleOpinionated, backend-agnostic Next.js 16 (App Router) architecture — authorization at the data layer, server-side loading with cache()+Promise.all, mutations through next-safe-action + typed route handlers, client/server boundaries ('use client' at leaves + TanStack Query), forms with RHF + Zod, UI via shadcn/ui + Tailwind + Base UI + next-intl, request handling in proxy.ts (Next.js 16's renamed middleware), and a Turbo monorepo of @app/* packages confining the backend behind one data-access package. Examples use Supabase but every rule states the transferable principle. Use when writing, reviewing, or refactoring Next.js 16 code. Trigger on server actions, route handlers, RSC vs 'use client' placement, TanStack Query, RHF/Zod, proxy.ts, or monorepo package layout — even when the user doesn't say 'patterns' or 'best practices'.
- ▌ Rails Application UI Blocks · pproenca bundleCompose new Rails backend pages and refactor existing Rails UI to use premium blocks from templates/application-ui. Use when requests mention ERB views, Rails partials, admin/dashboard screens, Tailwind UI assembly, or replacing custom markup with existing premium blocks while preserving behavior, accessibility, and Turbo/Stimulus hooks.
- ▌ Adversarial Phoenix Liveview · pproenca bundleUse this skill to gate Phoenix LiveView realtime UIs with a pass/fail adversarial review — a single blind reviewer subagent judges a diff or file set against 32 decidable rules covering state ownership and lifecycle (patch vs remount, callback load placement, connected-mount guards, form recovery), realtime data flow (broadcast placement, scoped topics, presence mechanisms), async responsiveness (blocking external calls, socket-copying closures, lifecycle-owned tasks, rendered failure states), render and wire efficiency (the constructs that silently disable HEEx change tracking), streams (growing collections in assigns, the stream DOM contract, bounded infinite scroll), component and context boundaries, client trust (per-event authorization, scoped lookups, live_session boundaries, revocation disconnects), and mechanism-presence interaction feedback (JS commands, in-flight feedback, debounce, hook contracts, overlay focus). Verdicts only, never fixes.
- ▌ Typescript Advanced Patterns · pproenca bundleAdvanced TypeScript — type-level programming, library/DSL APIs, declaration merging, modern language features at depth (decorators, using, const T, NoInfer, variance), and feature implementation patterns built on advanced types. Trigger on tasks involving recursive conditional types, infer patterns, mapped-type key remapping, variadic tuples, fluent builders with phantom state, schema-first inference (Zod/Valibot), end-to-end-typed API clients, finite state machines, module augmentation, and library-publishing concerns. Trigger even when the user does not say "advanced" — if the work involves type-level algorithms, library-author API design, or going beyond surface-level uses of TS 5.x features, this is the skill. Assumes the reader has absorbed the `typescript-refactor` skill — this one extends those patterns at depth, never restates them.
- ▌ Implementation Functional Patterns · pproenca bundleTypeScript's functional answers to the 22 Gang of Four classes — factory functions (Factory Method, Abstract Factory, Prototype, Memento), module-scope singletons, fluent immutable builders, wrapper functions (Adapter, Facade), native Proxy, WeakMap caches (Flyweight), discriminated unions with exhaustive match (State, Visitor, Composite), event emitters and signals (Mediator, Observer), pipelines and composition (CoR, Decorator), stream methods (Iterator), closures-as-commands, higher-order strategies, lambda placement. Use when reviewing TypeScript that has a class-shaped problem the GoF catalog solves with a hierarchy but where idiomatic TS reaches for a function, a tagged union, or a data structure. Each rule names the GoF pattern(s) it replaces and when the class form still wins. Trigger on "factory class", "singleton getInstance", "state machine class", "observer pattern", "AST visitor", "where do I put this lambda". Sibling to implementation-design-patterns.
- ▌ Algorithmic Complexity Review · pproenca bundleAlgorithmic complexity (Big-O) review — finding nested loops, N+1 queries, exponential recursion, quadratic string builds, and other accidental complexity blowups. Covers Python, JavaScript/TypeScript, Java, Go, and similar languages. Use whenever writing, reviewing, or refactoring code where Big-O matters. Trigger even when the user doesn't mention "Big-O" explicitly — if they're reviewing code for performance, refactoring a hot path, asking "why is this slow," or working with data that scales (loops, recursions, collections, ORM access), apply this skill to classify the time/space complexity and suggest the fix. Especially trigger on tasks like "review for performance," "find slow code," "make this faster," "this code is O(n²)," or when reading code that processes collections.
- ▌ Expo Design System Scaffolder · pproenca bundleScaffolds Expo / React Native design system components that obey the expo-design-system rules by construction — a variant-driven pressable primitive, a slot-based card surface, a typed text primitive, a labeled form field, a FlashList entity screen, a theme token group, and a Storybook variant catalog. Generated code uses Unistyles v3 variants instead of style props, ref-as-prop, design tokens, built-in accessibility, and web/iOS parity (`_web` hover/focus/cursor on interactive primitives), so it follows expo-design-system without rework. Output is TSX/TS using react-native-unistyles. Trigger whenever the user wants to create, add, generate, or scaffold a new shared UI component, primitive, design token group, or screen for the clinic mobile app — even if they don't mention the design system.
- ▌ Expo React Native Performance · pproenca bundleExpo React Native performance optimization guidelines. This skill should be used when writing, reviewing, or refactoring Expo React Native code to ensure optimal performance patterns. Triggers on tasks involving React Native components, lists, animations, images, or performance improvements.
- ▌ Library Reference Distillation · pproenca bundleMethodology for starting a new library-reference distillation skill — one that turns an external library (nuqs, zod, framer-motion, msw, react-hook-form, emilkowal-animations) into an idiomatic-usage rule pack — or evolving one against a new upstream release. Distills the conventions empirically shared across shipped library-ref skills in this repo — the source-priority ladder (docs → blog/changelog → issues → types → examples), version pinning that inverts with API velocity, the universal 4-tier category ladder (CRITICAL setup → HIGH isolation → MEDIUM composition → LOW edge cases), the 4-slot When-to-Apply template, the failure-gap exemplar heuristic (privilege production lessons over API restatement), and metadata.references[] as cite-set checksum. Triggers on "I want to write a skill for library X", "refresh against new upstream", "where should I source rules from", "what categories should this skill have", and on /dev-skill:new for a library-reference distillation.
- ▌ Linguistic Semantic Algorithms · pproenca bundleMapping out an unfamiliar codebase via NLP and graph algorithms — 40 algorithms across topic modelling, semantic embeddings, code graphs, repository mining, clone detection, IR-based bug localization, identifier linguistics, and complexity metrics. Trigger when hunting bugs across many files, scoping a new feature, identifying domain entities, or analyzing commit history — even if the user doesn't explicitly mention algorithms — apply when they ask "where does X live in this codebase?", "what is this codebase about?", "find duplicated logic", "what changed recently?", "who owns this code?", or "is this function risky?".
- ▌ Migrate JS To Modern Typescript · pproenca bundleMigrating a JavaScript codebase to TypeScript — converting .js files to .ts, adding types to existing JS, or tightening a loosely-typed TS project toward strict mode. Covers tsconfig and allowJs strategy, incremental strict-flag ratcheting (noImplicitAny, strictNullChecks, noUncheckedIndexedAccess), typing public surfaces, replacing `any` and unsafe casts with `unknown` and narrowing, validating runtime boundaries (JSON, env, API responses), converting CommonJS to ESM and prototypes to classes, and the build/CI changes a migration needs. Trigger even when the user only says "add types", "turn on strict mode", or "convert this file to TypeScript", and especially on a mixed JS/TS repo. Distinct from general TypeScript refactoring — this is the migration act itself, performed file by file while keeping the build green.
- ▌ Stripe Inspired API Design Rules · pproenca bundleJSON HTTP API design rules distilled from Stripe — resource modeling, identifier schemes, URL structure, request/response wire format, pagination, errors, idempotency, versioning, naming, webhooks, and authentication. Triggers on tasks involving OpenAPI specs, API design reviews, schema decisions, endpoint shaping, error envelope design, webhook delivery, or any "is this API well-designed" question. Apply when designing, reviewing, or refactoring a JSON HTTP API — even when the user doesn't mention Stripe by name, since the rules are general API-design principles distilled from the industry's most-copied reference.
- ▌ Codebase Comprehension Algorithms · pproenca bundleMapping an unfamiliar codebase into feature/business domains — answering "what is this about", "which files implement feature X", "where is the architectural spine", or reviewing a refactor that crosses module boundaries. 47 algorithms across 9 categories — graph construction (omnipresent filter, multilayer, SCC), lexical preprocessing (Samurai, TF-IDF), community detection (Leiden, Infomap, SBM, MCL, Walktrap, spectral, HDBSCAN), architecture recovery (Bunch+MQ, ACDC, Limbo, Reflexion, DSM), topic modelling (LDA, LSI, NMF, HDP), evolutionary coupling (Gall, ROSE), information-theoretic (NCD, MI, MDL, naturalness), centrality (PageRank, HITS, betweenness, TextRank), validation (MoJoFM, ARI/NMI, resolution limit, consensus, co-change prediction, ablation). Trigger without explicit "clustering" mention — codebase grokking, dependency mapping, domain extraction, architecture-recovery validation all apply.
- ▌ Acceptance Pipeline Feature Design · pproenca bundleDesigns new features, extensions, or modifications to Uncle Bob's Acceptance Pipeline Specification — new mutation strategies, Gherkin syntax support, report formats, pipeline stages, IR fields, or handler patterns. Trigger when someone asks "how would I add X to the acceptance pipeline" or discusses spec-level changes to the parser, generator, runtime, mutator, or reporter components — even if they don't explicitly say "feature design." Works in tandem with the acceptance-pipeline-catalog skill, which provides the baseline spec reference.
- ▌ Marketplace Search Recsys Planning · pproenca bundleSearch and recommendation system planning for a two-sided trust marketplace built on OpenSearch — user-intent framing, product-surface architecture, index design, query understanding, retrieval strategy, ranking, search-plus-recs blending, measurement, and a dashboard-and-alerting layer for ongoing decision making. Triggers on tasks involving marketplace search, homefeeds, ranking, relevance tuning, OpenSearch query DSL, analyzers, synonyms, golden sets, NDCG, A/B testing, or diagnosing an existing retrieval system. Use this skill BEFORE marketplace-personalisation when planning new work; hand off when the diagnosed bottleneck is personalisation-specific.
- ▌ Implementation Design Patterns Python · pproenca bundleImplementation guide for the 22 Gang of Four design patterns in idiomatic modern Python (3.10+), distilled from refactoring.guru. Use when writing, refactoring, or reviewing Python with a pattern-shaped problem — class-explosion from inheritance, conditionals switching on type, tight coupling to concrete classes, tree-shaped models, runtime algorithm selection, undo/redo, state-dependent behavior, or hiding subsystem complexity. Each entry leads with the Pythonic form (functions, dataclasses, Protocol, singledispatch, match, generators, copy/replace) and falls back to the class-based GoF structure only when identity, state, or dispatch require it. Includes intent, applicability (when to use AND when NOT to), a runnable example, steps, pros/cons, and relations. Trigger even when no pattern is named — cues like "too many constructor params," "giant if/elif," "swap behavior at runtime," "need undo," or "walk a tree" are pattern-shaped. Covers all 5 Creational, 7 Structural, and 10 Behavioral GoF patterns.
- ▌ Marketplace Pre Member Personalisation · pproenca bundlePre-member journey of a two-sided trust marketplace — from anonymous landing through onboarding, registration, and the paid-membership paywall. Covers anonymous signal inference, what pet owners specifically need to validate before paying (safety, availability, competence, effort, local cost comparison), what pet sitters specifically need to validate (opportunity, first-stay path, daily commitment, hidden costs), information-asymmetry closure, progressive profile building, social proof, conversion psychology, onboarding intent capture, identity stitching, and pre-member measurement. Triggers on tasks involving visitor-to-member conversion, anonymous personalisation, onboarding flow design, paywall timing, pre-member ranking, or any question about what a pet owner or pet sitter needs to see before paying. Use this skill BEFORE marketplace-personalisation and marketplace-search-recsys-planning.
- ▌ Marketplace Recsys Feature Engineering · pproenca bundleFeature engineering for marketplace recommenders — what to extract from raw marketplace assets (listing photos, owner-entered listing metadata, sitter wizard responses) to power item-to-item (similar listings), user-to-item (homefeed ranking), or user-to-user (mutual-fit matching) recommenders. Covers asset auditing, first-principles feature decomposition, vision-feature extraction (CLIP, room-type, amenities, aesthetics), listing text and metadata encoding, sitter wizard design, derived-composition patterns for i2i / u2i / u2u (ANN shelves, two-tower, mutual-fit), feature quality governance (training-serving parity, drift, PII), and incremental value proof (ablation A/B, kill reviews, feature-free baseline). Trigger even when the user does not explicitly say "feature engineering" but is asking how to get more signal out of listing photos, listing metadata, or the sitter onboarding wizard, or how to improve i2i / u2i / u2u quality without blindly ingesting a new model.
- ▌ Opensearch Function Scoring Algorithms · pproenca bundleSearch relevance and ranking on OpenSearch/Elasticsearch for a two-sided marketplace — candidate retrieval (hybrid BM25 + kNN, RRF, two-tower EBR), base relevance (BM25F, multi_match, LambdaMART), quality signals (Wilson lower bound, Bayesian average, rank_feature saturation/sigmoid), personalization (listing/user/session embeddings), spatial/temporal decay (gauss/exp), marketplace balance (conversion-weighted ranking, supply fairness, Pareto multi-objective), bias correction (IPS, click models, Thompson sampling), empirical evaluation (judgment sets, NDCG, ablation, A/B sizing, CUPED, regression suites), and diversity (MMR, DPP, max-per-host). Triggers on function_score, rank_feature, script_score, kNN, hybrid query, learning-to-rank, two-sided ranking, exposure fairness, NDCG, A/B testing, judgment set construction, ranking ablation, or "why is my OpenSearch ranking bad". Applies to Elasticsearch too — same APIs.
- ▌ Opensearch Personalize Caching Strategies · pproenca bundleCaching strategies in front of AWS OpenSearch (Elasticsearch) or AWS Personalize — search, recommenders, multi-recommender pages, anon vs logged-in traffic. Covers ROI decision (TPS/minProvisionedTPS, Zipf, amplification), key design (canonicalisation, cohort vs user, solution-version pinning, bucketing), personalisation boundary (anon/logged split, fan-out coalescing), strategies (cache-aside, refresh-ahead, write-through, batch precompute, L1+L2), TTL (volatility, soft/hard, jitter, event-driven invalidation), stampede protection (single-flight, XFetch, stale-while-revalidate, circuit breaker), observability (hit-rate, cost-per-1k, cardinality drift, log-replay), defensive caching (negative, Bloom filter), and tier composition (LRU, ElastiCache Redis, CloudFront, OpenSearch request/filter cache). Triggers on cache hit rate, Personalize throttling, stampede, single-flight, L1/L2, ElastiCache sizing. Complements opensearch-function-scoring-algorithms.
- ▌ Django Recommender Search Backend Patterns · pproenca bundleDjango backend patterns for recommendation services (AWS Personalize, Databricks Model Serving, internal microservices) and OpenSearch-backed search/feed endpoints. Covers fan-out orchestration (asyncio.gather, deadline propagation, partial results, async client reuse), external service protection (timeouts, circuit breakers, jittered retry, bulkheads, rate limits), OpenSearch query patterns (search_after, _source filtering, function_score, aliases, routing, bool.filter), result blending (score normalization, MMR, dedup, cold-start), Redis caching (stampede protection, model-versioned keys, two-tier, negative), resilience (partial-response envelope, stale-on-error, graceful degradation), async (sync_to_async, async ORM, uvicorn, contextvars, disconnect cancellation), and DRF response shape (cursor pagination, ETag, throttling). Use when building, reviewing, or refactoring such a Django backend. Triggers even without explicit "scale" cues. Includes 5 scaffolding templates.