Unity rendering pipelines (Built-in / URP / HDRP), Shader Graph, Renderer Features, Volume framework, post-processing, materials, lighting, and GPU Resident Drawer. USE WHEN: choosing or migrating rendering pipeline, writing/editing shaders (Shader Graph, HLSL, ShaderLab), tuning lighting, debugging draw calls, configuring Volume profiles, custom render passes. DO NOT USE FOR: 2D Renderer specifics (use `unity-2d-lighting`); UI Toolkit rendering (use `unity-input-ui`); profiling-only questions (use `unity-performance`).

Winston - versatile logging library for Node.js with multiple transports, custom formatting, and log rotation. Supports structured logging, custom levels, and enterprise integration. USE WHEN: user mentions "winston", "node.js logging", "multiple transports", "log rotation", asks about "how to log to multiple destinations", "rotate log files in Node.js", "custom log formats" DO NOT USE FOR: Pino logging - use `pino` instead, Python logging - use `python-logging` instead, Java logging - use `slf4j` or `logback` instead

Selecting accelerators for AI workloads: GPU vs TPU vs NPU vs FPGA vs CPU, and the metrics that actually decide it — memory capacity & bandwidth, TOPS/ FLOPS, interconnect, and cost/Watt. Architect-level hardware-fit reasoning. USE WHEN: choosing AI hardware/accelerators, "which GPU", "TPU vs GPU", "NPU", "FPGA", "HBM/memory bandwidth", "TOPS", "cost per token", VRAM sizing for a model, training vs inference hardware, accelerator interconnect. DO NOT USE FOR: serving software topology (use `inference-serving-topology`); on-device runtimes (use `edge-inference`); generic CPU perf (use systems/hardware-aware-design).

Angular Material and CDK for UI components, theming, and custom components. Covers standalone Material components and custom themes. USE WHEN: user mentions "Angular Material", "Material CDK", "mat-table", "mat-dialog", "Angular UI components", "Material theming", "Angular CDK" DO NOT USE FOR: Bootstrap - use CSS framework skills, PrimeNG or other Angular UI libs

Angular Router with lazy loading, guards, resolvers, and route params. Covers standalone route configuration and functional guards. USE WHEN: user mentions "Angular routing", "lazy loading", "route guards", "resolvers", "navigation", "Angular routes", "canActivate", "loadChildren" DO NOT USE FOR: React Router - use `react-router`, Vue Router - use `vue-composition`, Next.js routing - use `nextjs`

Angular testing with TestBed, ComponentFixture, service testing, and HttpTestingController. Covers standalone component testing and signal testing. USE WHEN: user mentions "Angular testing", "TestBed", "ComponentFixture", "Angular unit test", "HttpTestingController", "testing Angular components", "Angular service test" DO NOT USE FOR: Playwright E2E tests - use `playwright`, React testing - use `react-testing` or `testing-library`

API gateway patterns and implementations. Kong, AWS API Gateway, NGINX as gateway, rate limiting, request routing, authentication offloading, and request/response transformation. USE WHEN: user mentions "API gateway", "Kong", "AWS API Gateway", "NGINX gateway", "gateway pattern", "request routing", "BFF" DO NOT USE FOR: reverse proxy basics - use infrastructure skills; service mesh - use `service-mesh`; rate limiting in app - use `rate-limiting`

ASP.NET Core validation with FluentValidation, Data Annotations, and model validation. Covers custom validators and validation pipeline. USE WHEN: user mentions "FluentValidation", "Data Annotations", "model validation", ".NET validation", "input validation", "validator", "validation pipeline" DO NOT USE FOR: Spring Validation - use `spring-validation`, Zod/Yup - use frontend validation skills

Audit logging for compliance and security. Structured audit events, immutable logs, user action tracking, database change tracking, and regulatory compliance (SOC2, HIPAA, GDPR). USE WHEN: user mentions "audit log", "audit trail", "activity log", "change tracking", "compliance logging", "who changed what", "SOC2 logging" DO NOT USE FOR: application logging - use logging skills; error tracking - use observability skills

AWS SDK integration for Node.js (v3) and Python (boto3). Core services: S3, Lambda, DynamoDB, SQS, SNS, CloudWatch, IAM. Configuration, credentials, and production patterns. USE WHEN: user mentions "AWS", "Amazon Web Services", "Lambda", "DynamoDB", "SQS", "SNS", "CloudWatch", "IAM", "boto3", "aws-sdk" DO NOT USE FOR: S3 file operations - use `cloud-storage`; SQS messaging patterns - use `sqs`; Azure/GCP - use respective skills

axe-core - accessibility testing engine for automated WCAG compliance checks. USE WHEN: user mentions "axe", "automated accessibility testing", "a11y tests", asks about "integrating accessibility checks", "CI/CD accessibility", "Playwright accessibility", "Jest accessibility", "Vitest axe" DO NOT USE FOR: manual accessibility audits - use `wcag` skill instead

Axios - promise-based HTTP client for browser and Node.js USE WHEN: user mentions "Axios", "HTTP requests", "API calls", "interceptors", "Axios instance", asks about "how to make HTTP calls", "configure Axios", "add auth header", "handle HTTP errors" DO NOT USE FOR: Fetch API - use `http-clients` instead; ky/ofetch - use `http-clients` instead; GraphQL clients - use `graphql-codegen` instead; tRPC - use `trpc` instead

Azure cloud services SDK integration. Azure Functions, Cosmos DB, Blob Storage, Service Bus, Azure AD (Entra ID), and Key Vault. Node.js and .NET SDKs. USE WHEN: user mentions "Azure", "Azure Functions", "Cosmos DB", "Blob Storage", "Service Bus", "Azure AD", "Entra ID", "Key Vault", "Azure SDK" DO NOT USE FOR: AWS services - use `aws`; GCP services - use `gcp`; Terraform for Azure - use `terraform`

Adaptor signatures: pre-signature paired with a "secret" such that publishing a valid signature reveals the secret, and vice versa. Foundational for atomic swaps, scriptless scripts, DLCs, Submarine Swaps trustless variants, PTLCs (Point Time-Locked Contracts). USE WHEN: designing atomic swaps, evaluating PTLCs vs HTLCs, building DLCs, understanding scriptless scripts.

Bitcoin Core JSON-RPC interface: authentication (cookie, rpcauth), wallet vs node RPCs, common verbs (getblockchaininfo, getrawtransaction, scantxoutset, importdescriptors, walletprocesspsbt, submitpackage, testmempoolaccept), error handling. USE WHEN: scripting bitcoind, integrating a service, debugging RPC errors.

Discreet Log Contracts: smart contracts on Bitcoin via oracle attestations + adaptor signatures. Oracle publishes nonces upfront, reveals signed outcomes; CETs (Contract Execution Transactions) enforce payouts. No on-chain footprint of the contract logic. USE WHEN: building betting / prediction markets, parametric insurance, derivatives, oracle-driven settlements on Bitcoin.

FROST (Flexible Round-Optimised Schnorr Threshold): t-of-n threshold signing on secp256k1. n participants share a key via Distributed Key Generation (DKG) or trusted dealer; any t can produce a Schnorr signature. Differs from MuSig2 (which is n-of-n). USE WHEN: t-of-n threshold custody (e.g., 3-of-5 board signatures) with single-sig appearance on chain, federated services, multi-sig with availability.

Miniscript: structured subset of Bitcoin Script with fragment types, satisfaction analysis, malleability resistance. Policy → Miniscript → Script compilation. Used in descriptors (wsh + tr) and modern wallets to express spending conditions safely. USE WHEN: composing complex spending conditions, deriving the cheapest satisfaction, ensuring scripts are non-malleable.

Bitcoin P2P network protocol: messages, version handshake, addr/addrv2, compact blocks (BIP152), compact block filters (BIP157/158), v2 transport encryption (BIP324), wtxid relay (BIP339), Erlay (BIP330), Dandelion++ (BIP156). USE WHEN: implementing/debugging a node, integrating with bitcoind P2P, understanding address gossip, designing privacy-preserving propagation.

BIP331 package relay + accompanying mempool policy: package validation, ancestor/descendant limits, submitpackage RPC, package CPFP, sibling eviction with TRUC v3 (BIP431), ephemeral anchors. Critical for Lightning fee bumping and any multi-tx workflow. USE WHEN: implementing CPFP, designing fee-bump strategies, debugging "why won't my child confirm", reasoning about Lightning anchor pinning.

Application caching patterns. Redis caching, in-memory caches, HTTP caching, cache invalidation strategies, cache-aside, write-through, and CDN caching. USE WHEN: user mentions "caching", "cache invalidation", "Redis cache", "HTTP cache", "CDN caching", "cache-aside", "write-through", "TTL", "stale-while-revalidate" DO NOT USE FOR: Redis as database/queue - use `redis` or `job-queues`; browser storage - use frontend skills

Chart and data visualization libraries. Recharts, Chart.js, D3.js, Victory, Nivo, ECharts. Common chart types, responsive design, and real-time updates. USE WHEN: user mentions "chart", "graph", "data visualization", "Recharts", "Chart.js", "D3", "ECharts", "Victory", "bar chart", "line chart", "dashboard" DO NOT USE FOR: PDF report generation - use `pdf-generation`; data export - use `data-export`

Contract testing for API consumers and providers. Pact framework, Spring Cloud Contract, consumer-driven contracts, provider verification, and contract broker setup. USE WHEN: user mentions "contract testing", "Pact", "consumer-driven contract", "Spring Cloud Contract", "API contract", "provider verification" DO NOT USE FOR: OpenAPI validation - use `openapi-contract`; integration testing - use integration test skills

CORS configuration and HTTP security headers. CORS middleware, preflight requests, Content-Security-Policy, CSRF protection, Helmet.js, and secure cookie configuration. USE WHEN: user mentions "CORS", "cross-origin", "CSP", "Content-Security-Policy", "CSRF", "security headers", "Helmet", "preflight", "Access-Control" DO NOT USE FOR: authentication tokens - use `jwt` or `oauth2`; encryption - use `cryptography`

Reference for major DCS/PLC platforms - ABB Freelance, Siemens PCS7/TIA Portal, Emerson DeltaV, Honeywell Experion. Use when comparing platforms, mapping function blocks across vendors, or designing cross-platform solutions.

Production deployment strategies. Blue-green, canary, rolling update, recreate. Zero-downtime deployments, rollback procedures, database migration coordination, and deployment automation. USE WHEN: user mentions "blue-green", "canary deployment", "rolling update", "zero-downtime", "deployment strategy", "rollback", "deploy pipeline" DO NOT USE FOR: CI/CD pipeline syntax - use `github-actions`; container orchestration - use `kubernetes`; IaC - use `terraform`

Edge / on-device AI inference architecture: running models on MCUs, NPUs, mobile, and mini-PCs; quantization for edge, TOPS/memory/energy budgets, TinyML, and the latency case for on-device vs cloud. Architect-level. USE WHEN: designing on-device/edge AI, "edge inference", "on-device", "NPU", "TinyML", "quantization", "Jetson", "Coral", "Hailo", local LLM on small hardware, offline/low-latency inference, energy-constrained ML. DO NOT USE FOR: cloud GPU serving (use `inference-serving-topology`); choosing datacenter accelerators (use `ai-hardware-selection`); RAG app code (use rag skills).

Error tracking and monitoring integration. Sentry, Datadog RUM, Bugsnag. Source maps, breadcrumbs, release tracking, performance monitoring, and alerting configuration. USE WHEN: user mentions "Sentry", "error tracking", "Bugsnag", "Datadog RUM", "crash reporting", "source maps", "release tracking", "error monitoring" DO NOT USE FOR: application logging - use logging skills; APM/tracing - use `opentelemetry`; structured error responses - use `error-handling`

Complete ABB Freelance DCS file format reference for DMF, PRT, and CSV project files. Use when analyzing, parsing, or generating Freelance engineering files.

Google Cloud Platform SDK integration. Cloud Functions, Firestore, Cloud Storage, Pub/Sub, BigQuery, and Cloud Run. Node.js and Python client libraries. USE WHEN: user mentions "GCP", "Google Cloud", "Cloud Functions", "Firestore", "Cloud Storage", "Pub/Sub", "BigQuery", "Cloud Run", "Firebase" DO NOT USE FOR: AWS services - use `aws`; Azure services - use `azure`; Firebase Auth - use auth skills

gRPC service development. Protocol Buffers (protobuf), service definitions, streaming (unary, server, client, bidirectional), interceptors, and code generation for Node.js, Go, Java, and Python. USE WHEN: user mentions "gRPC", "protobuf", "Protocol Buffers", ".proto", "grpc-js", "tonic", "grpc-java", "service mesh RPC" DO NOT USE FOR: REST APIs - use `rest-api`; GraphQL - use `graphql`; WebSocket - use real-time skills

Health check and graceful shutdown patterns. Liveness and readiness probes, dependency health checks, Kubernetes probes, Spring Actuator health, and zero-downtime shutdown. USE WHEN: user mentions "health check", "liveness", "readiness", "probe", "graceful shutdown", "SIGTERM", "health endpoint", "/healthz" DO NOT USE FOR: monitoring dashboards - use `error-tracking` or `opentelemetry`; deployment strategies - use `deployment-strategies`

Hybrid edge-cloud AI architecture: local-first inference with cloud escalation, model cascading, and splitting the workload across device and datacenter to balance latency, cost, privacy, and quality. Architect-level topology. USE WHEN: designing systems that combine on-device and cloud AI, "local-first", "cloud fallback", "model cascade", "escalation", "hybrid inference", routing by confidence/complexity, edge+cloud trade-offs. DO NOT USE FOR: pure on-device (use `edge-inference`); pure cloud serving (use `inference-serving-topology`); multi-provider API routing (use `model-gateway-routing`).

Image processing and optimization. Sharp (Node.js), Pillow (Python), Cloudinary, responsive images, WebP/AVIF conversion, thumbnails, and CDN-based image transformation. USE WHEN: user mentions "image resize", "thumbnail", "image optimization", "Sharp", "Pillow", "Cloudinary", "WebP", "AVIF", "image upload processing" DO NOT USE FOR: file upload handling - use `file-upload`; cloud storage - use `cloud-storage`; PDF generation - use `pdf-generation`

Background job queue systems. BullMQ (Node.js), Celery (Python), Sidekiq (Ruby), Spring Batch. Job scheduling, retries, priorities, concurrency control, and dead letter queues. USE WHEN: user mentions "job queue", "background job", "BullMQ", "Bull", "Celery", "worker", "async task", "task queue", "Sidekiq" DO NOT USE FOR: cron scheduling without queue - use `cron-scheduling`; message brokers - use messaging skills (Kafka, RabbitMQ)

JUnit 5 testing framework with Mockito integration. Covers unit tests, mocking, and Spring Boot test integration. USE WHEN: user mentions "junit", "java test", "mockito", asks about "@Test", "@Mock", "@InjectMocks", "unit test java", "spring boot test" DO NOT USE FOR: Integration tests with containers - use `testcontainers`; REST API tests - use `rest-assured`; E2E tests - use Selenium; JavaScript/TypeScript - use `vitest` or `jest`

Load and performance testing. k6 (Grafana), Artillery, Apache JMeter, Locust (Python). Scenario design, thresholds, ramp-up patterns, and CI/CD integration. USE WHEN: user mentions "load test", "performance test", "stress test", "k6", "Artillery", "JMeter", "Locust", "throughput", "benchmarking" DO NOT USE FOR: unit/integration testing - use testing skills; monitoring in production - use `opentelemetry`

Model gateway / LLM router architecture: a control point in front of multiple models/providers for routing (cost/quality/latency), fallback, rate limiting, caching, observability, and governance. Architect-level, multi-provider. USE WHEN: designing an LLM gateway/router, "model router", "LLM gateway", "multi-provider", "fallback", "cost routing", "LiteLLM", "Envoy AI Gateway", semantic cache, central key/quota/observability for LLM calls. DO NOT USE FOR: single-engine serving (use `inference-serving-topology`); edge/cascade (use `hybrid-edge-cloud`); agent orchestration (use `agentic-architecture`).

Multi-tenant architecture patterns. Database-per-tenant, schema-per-tenant, shared-schema with tenant ID, row-level security, tenant resolution, and data isolation. USE WHEN: user mentions "multi-tenant", "multitenancy", "SaaS architecture", "tenant isolation", "row-level security", "tenant ID", "subdomain routing" DO NOT USE FOR: general database design - use database skills; authentication - use auth skills

PDF generation and manipulation. Puppeteer/Playwright HTML-to-PDF, PDFKit, jsPDF, React-PDF, iText (Java), ReportLab (Python). Invoices, reports, and document generation. USE WHEN: user mentions "PDF", "generate PDF", "HTML to PDF", "invoice PDF", "PDFKit", "jsPDF", "Puppeteer PDF", "React-PDF", "iText", "ReportLab" DO NOT USE FOR: PDF parsing/reading - different concern; image generation - different format

Push notifications for web and mobile. Firebase Cloud Messaging (FCM), Apple Push Notification Service (APNs), Web Push API, Expo Notifications, and notification service architecture. USE WHEN: user mentions "push notification", "FCM", "Firebase messaging", "APNs", "web push", "service worker notification", "Expo notifications" DO NOT USE FOR: email notifications - use `email-sending`; in-app real-time updates - use `socket-io` or `sse`

Progressive Web App development. Service workers, Web App Manifest, offline-first strategies, caching with Workbox, push notifications, and installability. USE WHEN: user mentions "PWA", "Progressive Web App", "service worker", "offline-first", "Web App Manifest", "Workbox", "installable web app", "cache-first", "add to home screen" DO NOT USE FOR: native mobile apps - use `react-native`, `flutter`, `expo`; push notification server-side - use `push-notifications`

Rate limiting and throttling. Token bucket, sliding window, fixed window algorithms. Express rate limit, Spring rate limiting, Redis-based distributed rate limiting, and API quota management. USE WHEN: user mentions "rate limit", "throttle", "API quota", "too many requests", "429", "express-rate-limit", "sliding window", "token bucket" DO NOT USE FOR: circuit breaker patterns - use `resilience-patterns`; DDoS protection - use infrastructure/WAF solutions

React Native mobile development. Core components, navigation (React Navigation), platform-specific code, native modules, performance optimization, and debugging. USE WHEN: user mentions "React Native", "react-native", "mobile app with React", "cross-platform mobile", "RN", "react-native-cli" DO NOT USE FOR: Expo-specific features - use `expo`; Flutter - use `flutter`; web React - use `react` skills

Application resilience patterns. Circuit breakers, retries with backoff, bulkheads, timeouts, fallbacks, and health checks. Polly (.NET), resilience4j (Java), cockatiel (Node.js). USE WHEN: user mentions "circuit breaker", "retry", "backoff", "bulkhead", "resilience", "fault tolerance", "Polly", "resilience4j", "fallback" DO NOT USE FOR: error handling basics - use language skills; monitoring - use `opentelemetry`

Serverless computing patterns. AWS Lambda, Azure Functions, GCP Cloud Functions. Deployment frameworks: Serverless Framework, AWS SAM, SST. Cold starts, event sources, and production optimization. USE WHEN: user mentions "serverless", "Lambda", "cloud function", "Azure Functions", "SAM", "SST", "Serverless Framework", "cold start", "FaaS" DO NOT USE FOR: container orchestration - use `kubernetes` or `docker`; always-on servers - use backend framework skills

Service mesh patterns and implementations. Istio, Linkerd, traffic management, mutual TLS, observability, circuit breaking, and canary routing at the infrastructure level. USE WHEN: user mentions "service mesh", "Istio", "Linkerd", "sidecar proxy", "mutual TLS", "mTLS", "traffic splitting", "Envoy", "mesh" DO NOT USE FOR: API gateway patterns - use `api-gateway`; in-app resilience - use `resilience-patterns`; Kubernetes basics - use `kubernetes`

Server-Sent Events for real-time server-to-client streaming. Express, Fastify, FastAPI, Spring WebFlux SSE implementations. Event streams, reconnection, and EventSource API. USE WHEN: user mentions "SSE", "Server-Sent Events", "EventSource", "event stream", "text/event-stream", "live feed", "streaming updates" DO NOT USE FOR: bidirectional communication - use `socket-io`; WebRTC - use `webrtc`; LLM streaming - use AI SDK skills

Storage-engine and database-internals architecture: B-tree vs LSM-tree, write- ahead logging, buffer/page cache, MVCC and concurrency control, durability/fsync, and compaction. Architect-level engine selection and data-path design. USE WHEN: designing or choosing a storage engine, "B-tree vs LSM", "WAL", "buffer pool", "MVCC", "compaction", "write amplification", "fsync/durability", embedded KV store, database internals, read/write-optimized store choice. DO NOT USE FOR: SQL query writing/ORM (use database/orm skills); data pipelines (use `data-intensive`); vector indexes (use vector-stores skills).

Stripe payment processing. Covers Checkout Sessions, Payment Intents, Subscriptions, Webhooks, idempotency, and Stripe.js frontend integration. USE WHEN: user mentions "stripe", "payment", "checkout", "subscription billing", "payment intent", "payment gateway", "credit card", "invoice", "Stripe.js" DO NOT USE FOR: PayPal-only integration; cryptocurrency payments; accounting software

Systems-level networking architecture: kernel-bypass (DPDK, io_uring, eBPF/XDP), zero-copy, the network stack data path, NIC offloads, congestion control, and high-connection-count (C10M) server design. Architect-level, not app HTTP. USE WHEN: designing high-throughput/low-latency networking, packet processing, "kernel bypass", "DPDK", "io_uring", "eBPF", "XDP", "zero-copy", "C10M", "line rate", NIC offload, congestion control, software data plane. DO NOT USE FOR: REST/GraphQL API design (use api-design skills); app websockets (use real-time skills); cloud LB config (use infrastructure skills).

Unity 2D lighting — URP 2D Renderer, Light 2D types (Point/Freeform/Sprite/ Parametric/Global), Shadow Casters 2D, Sprite Mask, Renderer2DData, normal mapped sprites, blend styles. USE WHEN: setting up the URP 2D Renderer, lighting a 2D scene, adding 2D shadows, using Sprite Mask for stencil-like effects, normal-mapped sprites. DO NOT USE FOR: 3D lighting (use `unity-rendering`); UI lighting concepts (UI doesn't normally use Light 2D); 2D animation (use `unity-2d-animation`).

Unity project conventions — folder layout, asmdef structure, naming, source control (.gitignore + LFS + force text serialization), prefab variants, ScriptableObject-based architecture. USE WHEN: starting a new Unity project, refactoring an unhealthy one, setting up source control, organising assets, deciding on naming. DO NOT USE FOR: specific systems (use feature-specific skills).

Unity DOTS — Entities 1.x, Burst-compiled jobs, IJobChunk / IJobEntity, NativeArray / NativeList, SystemBase vs ISystem, baking GameObject to entity, hybrid components. USE WHEN: massive entity counts (RTS, swarms, particles-as-entities), data-oriented refactor of hot simulations, deterministic netcode targets, Burst-friendly math. DO NOT USE FOR: regular GameObject gameplay (use `unity-core`); rendering (DOTS uses Entities Graphics — link from `unity-rendering`); networking with NGO (use `unity-netcode`).

Unity Editor scripting — custom Inspectors, PropertyDrawers, EditorWindow, MenuItems, asset post-processors, Editor Coroutines, automated builds via `-batchmode -executeMethod`. USE WHEN: building tools for designers, custom Inspector UI, gizmos, scene validators, asset import hooks, editor menu commands, headless CI builds. DO NOT USE FOR: runtime UI (use `unity-input-ui`); test runner (use `unity-testing`).

Unity Netcode for GameObjects (NGO) — NetworkBehaviour, NetworkVariable, RPCs (Server/Client/Owner), client-side prediction, lag compensation, Multiplay/Relay/Lobby integration. USE WHEN: building multiplayer (co-op, competitive, MMO-lite), network authority decisions, anti-cheat, matchmaking + relay. DO NOT USE FOR: P2P state-sync without NGO (Mirror, Photon — out of scope); ECS-native networking (NetCode for Entities — adjacent stack).

Unity performance — Profiler, Frame Debugger, Memory Profiler, GC allocation hunting, object pooling, IL2CPP build settings, Burst, batching, LOD, GPU Resident Drawer. USE WHEN: frame drops, GC spikes, long load times, memory growth, draw-call storms, mobile thermal/battery issues, profiling captures. DO NOT USE FOR: gameplay logic refactoring (use `unity-core`); pipeline selection (use `unity-rendering`).

Unity 3D physics (Rigidbody, Collider, Joints) and animation (Animator state machines, parameters, layers, Animation Rigging, Humanoid retargeting, blend trees). USE WHEN: tuning rigidbody movement, designing Animator state machines, blending animations, layer collision matrix, joints/constraints, motion warping, IK setups. DO NOT USE FOR: 2D physics or 2D animation (use `unity-2d-physics` / `unity-2d-animation`); ECS physics (use `unity-dots`).

Unity XR — XR Interaction Toolkit 3.x (Interactor/Interactable/Manipulation), AR Foundation (planes, anchors, image tracking, body tracking), OpenXR, hand tracking on Quest/Vision OS. USE WHEN: VR/AR/MR projects, integrating XR controllers, AR plane detection, XR locomotion, hand tracking, eye tracking, OpenXR features. DO NOT USE FOR: regular 3D gameplay (use `unity-physics-anim`); rendering pipeline (use `unity-rendering` — XR has URP-specific considerations).

Vector database integration for embeddings and similarity search. Pinecone, Weaviate, Qdrant, ChromaDB, pgvector. Index management, metadata filtering, hybrid search, and production optimization. USE WHEN: user mentions "vector database", "embeddings", "similarity search", "Pinecone", "Weaviate", "Qdrant", "ChromaDB", "pgvector", "HNSW", "ANN" DO NOT USE FOR: LangChain integration - use `langchain`; RAG architecture - use `rag-patterns`; traditional databases - use database skills

Virtualization and isolation architecture: hypervisors (type-1/type-2), container internals (namespaces, cgroups), microVMs, and the isolation-vs-overhead spectrum. Architect-level choice of isolation boundary. USE WHEN: choosing an isolation/virtualization boundary, "hypervisor", "KVM", "type-1/type-2", "container", "namespaces", "cgroups", "microVM", "Firecracker", "gVisor", "Kata", multi-tenant isolation, sandboxing untrusted workloads. DO NOT USE FOR: Kubernetes/Docker operational config (use infrastructure skills); OS internals (use `os-kernel-architecture`).

Webhook patterns for sending and receiving. Signature verification, retry logic, idempotency, payload design, and webhook infrastructure. Covers Stripe, GitHub, Slack webhook consumption and custom webhook dispatch. USE WHEN: user mentions "webhook", "webhook endpoint", "webhook signature", "event callback", "HTTP callback", "webhook retry", "webhook dispatch" DO NOT USE FOR: WebSocket real-time - use `socket-io` or `sse`; message queues - use messaging skills

xUnit.net testing framework with Fact, Theory, fixtures, DI, and mocking with Moq and NSubstitute. Covers .NET testing best practices. USE WHEN: user mentions "xUnit", ".NET testing", "Fact", "Theory", "InlineData", "Moq", "NSubstitute", "C# unit test" DO NOT USE FOR: NUnit - use `nunit`, Vitest - use `vitest`, Jest - use `jest`, Playwright - use `playwright`

Angular Reactive Forms with validators, FormArray, and dynamic forms. Covers typed forms, custom validators, and form patterns. USE WHEN: user mentions "Angular forms", "reactive forms", "FormGroup", "FormArray", "validators", "form validation", "Angular form patterns" DO NOT USE FOR: React forms - use `react-hook-form` or `react-forms`, template-driven forms for simple cases

Angular HttpClient with interceptors, error handling, retry, and caching patterns. Covers functional interceptors and typed responses. USE WHEN: user mentions "HttpClient", "Angular HTTP", "interceptors", "API calls", "Angular REST", "HTTP error handling", "auth interceptor" DO NOT USE FOR: Axios - use `axios` skill, Fetch API directly, backend HTTP frameworks

Angular SSR with @angular/ssr, hydration, and prerendering. Covers server-side rendering setup, transfer state, and deployment. USE WHEN: user mentions "Angular SSR", "server-side rendering", "Angular Universal", "@angular/ssr", "hydration", "prerendering", "Angular SEO" DO NOT USE FOR: Next.js SSR - use `nextjs`, Nuxt SSR - use `vue-composition`, SvelteKit SSR - use `svelte`

Apache POI for Excel file manipulation in Java applications. USE WHEN: user mentions "Apache POI", "Excel generation", asks about "Java Excel", "XLSX export", "Excel import", "POI workbook", "spreadsheet generation" DO NOT USE FOR: CSV files - use OpenCSV or standard Java CSV libraries

ASP.NET Core Identity for authentication, roles, claims, and external providers. Covers Identity setup, customization, and token-based auth. USE WHEN: user mentions "ASP.NET Identity", "user authentication", ".NET auth", "roles and claims", "Identity scaffolding", "external login providers" DO NOT USE FOR: JWT-only auth without Identity, Spring Security - use `spring-security`

ASP.NET Core custom middleware, pipeline order, exception handling middleware, and request/response manipulation. USE WHEN: user mentions "middleware", "request pipeline", "exception middleware", "ASP.NET middleware", "UseMiddleware", "pipeline order" DO NOT USE FOR: Express middleware - use `express`, NestJS middleware - use `nestjs`

ASP.NET Core Minimal API endpoints, route groups, filters, and typed results. Covers modern .NET 8+ endpoint patterns. USE WHEN: user mentions "Minimal API", "MapGet", "MapPost", "route groups", "endpoint filters", ".NET minimal", "lambda endpoints" DO NOT USE FOR: Controller-based APIs (use `aspnet-core`), Express.js (use `express`), FastAPI (use `fastapi`)

ASP.NET Core SignalR for real-time hubs, clients, groups, and streaming. Covers strongly-typed hubs and hub filters. USE WHEN: user mentions "SignalR", "real-time", "WebSocket", "hubs", "real-time notifications", ".NET WebSocket", "push notifications" DO NOT USE FOR: Spring WebSocket - use `spring-websocket`, Socket.IO - use Angular/React WebSocket patterns

BIP32 hierarchical deterministic key derivation: master key from seed, hardened vs unhardened derivation, xpub/xprv encoding, fingerprints, child-key chaining, key origin paths. USE WHEN: building HD wallets, deriving addresses, parsing xpubs, validating descriptors with key origin.

Coin selection algorithms: branch-and-bound (BnB), knapsack, single random draw (SRD), Murch's waste metric, change avoidance. Determines which UTXOs to spend for a given target. USE WHEN: implementing wallet send flow, choosing which UTXOs to consolidate, optimizing fees, designing privacy-preserving selection.

Running Bitcoin Core in production: bitcoin.conf reference, sections, pruning, signet, dbcache, mempool tuning, network bind, Tor, IBD considerations, debug.log analysis. USE WHEN: deploying a node, tuning performance, debugging IBD issues, configuring multi-network nodes.

Output descriptors: BIP380-385 family. Descriptor language for declaring scriptPubKey templates with key origin info, ranges, checksums. Functions: pkh, wpkh, sh, wsh, tr, multi, sortedmulti, multi_a, addr, raw, combo, rawtr. USE WHEN: importing watch-only wallets, defining multisig, declaring scan ranges, exchanging key info between wallets.

Generic Bitcoin message signing: BIP137 (legacy P2PKH-only) and BIP322 (modern, supports any output type). Used for proof-of-ownership, withdraw verification, federated authentication, exchange KYC-free attestation. USE WHEN: implementing "sign this message with your Bitcoin address", verifying ownership of an address, building auth via signing.

Soft-fork proposals NOT activated on mainnet: CTV (BIP119), APO/APOAS (BIP118), OP_VAULT (BIP345), OP_CAT reactivation, drivechains (BIP300/301), spacechains, CISA. Status, mechanics, controversy per proposal. USE WHEN: discussing covenants, evaluating L2 design that depends on unactivated opcodes, understanding the soft-fork pipeline.

HD wallet implementation: BIP32 derivation, BIP39 mnemonic seed (with passphrase), BIP44/49/84/86 derivation paths, account structure, gap limit, watch-only via xpub. USE WHEN: building/restoring an HD wallet, choosing derivation paths, debugging address generation, importing mnemonics.

Cron and scheduled task management. node-cron, cron expressions, Spring @Scheduled, APScheduler (Python), and distributed scheduling patterns. USE WHEN: user mentions "cron", "scheduled task", "cron job", "node-cron", "@Scheduled", "APScheduler", "periodic task", "crontab" DO NOT USE FOR: job queues with workers - use `job-queues`; one-off delayed tasks - use `job-queues`

Application-level cryptography. Password hashing (bcrypt, argon2), encryption (AES-GCM), digital signatures, key management, and secure random generation. USE WHEN: user mentions "encryption", "hashing", "bcrypt", "argon2", "AES", "cryptography", "digital signature", "key management", "HMAC" DO NOT USE FOR: TLS/HTTPS configuration - use infrastructure skills; JWT tokens - use `jwt`; OAuth flows - use `oauth2`

Data export to CSV, Excel (XLSX), and JSON. ExcelJS, SheetJS (xlsx), Papa Parse, Apache POI (Java), openpyxl (Python). Streaming exports for large datasets. USE WHEN: user mentions "export CSV", "export Excel", "XLSX generation", "download spreadsheet", "ExcelJS", "SheetJS", "Papa Parse", "data export" DO NOT USE FOR: PDF generation - use `pdf-generation`; file upload/download - use `file-upload`/`cloud-storage`

Expo framework for React Native. Managed and bare workflows, Expo Router, EAS Build/Submit/Update, config plugins, and Expo SDK modules. USE WHEN: user mentions "Expo", "expo-router", "EAS Build", "expo-cli", "app.json", "expo-config-plugin", "Expo Go" DO NOT USE FOR: bare React Native without Expo - use `react-native`; Flutter - use `flutter`

Feature flag management. LaunchDarkly, Unleash, Flagsmith, and custom implementations. Gradual rollouts, A/B testing, kill switches, and flag lifecycle management. USE WHEN: user mentions "feature flag", "feature toggle", "LaunchDarkly", "Unleash", "Flagsmith", "gradual rollout", "A/B test", "canary release", "kill switch" DO NOT USE FOR: CI/CD deployment strategies - use `github-actions`; environment config - use environment variable patterns

Internationalization and localization. i18next (React, Node.js), next-intl, vue-i18n, ICU message format, pluralization, date/number formatting, and RTL support. USE WHEN: user mentions "i18n", "internationalization", "localization", "l10n", "i18next", "translation", "next-intl", "vue-i18n", "ICU format", "RTL" DO NOT USE FOR: character encoding - general programming; currency/payment formatting - use `stripe`

ISA-5.1 tag naming, ISA-88 batch control, ISA-95 enterprise integration, ISA-18.2 alarm management, and ISA-101 HMI standards reference. Use when working with instrument tags, naming conventions, or plant hierarchy.

JaCoCo Java code coverage tool USE WHEN: user mentions "JaCoCo", "Java coverage", "code coverage", asks about "coverage threshold", "jacoco-maven-plugin", "coverage report", "LINE coverage", "BRANCH coverage" DO NOT USE FOR: JavaScript/TypeScript coverage - use Vitest skill, SonarQube analysis - use `sonarqube` skill, test execution - use testing skills

JSDoc - documentation generator for JavaScript with type annotations. USE WHEN: user mentions "JSDoc", "JavaScript documentation", asks about "documenting JavaScript", "type hints", "jsdoc comments", "API documentation generation" DO NOT USE FOR: TypeScript - use `jsdoc-tsdoc` skill for TypeScript/TSDoc

Core Lightning (CLN, formerly c-lightning) by Blockstream: lightningd, lightning-cli, plugin architecture (Python pyln-client, Rust cln-plugin, Go glightning), commando, BOLT12 leadership. USE WHEN: integrating with CLN, writing plugins, debugging CLN-specific behaviour, leveraging BOLT12 features.

Consumer Lightning wallet integration patterns: Phoenix, Breez SDK, Mutiny, Zeus, BlueWallet (LN), Aqua. Custodial vs non-custodial, LSP partnerships, mobile-specific UX (push notifications, background sync). USE WHEN: integrating with consumer wallets, designing self-custodial mobile UX, evaluating wallet SDK options.

HTLC (Hash Time-Locked Contract) lifecycle: offered/received, fulfill via preimage, fail/timeout, 2nd-stage txs. Modern variant PTLCs (Point Time-Locked Contracts) with adaptor signatures. USE WHEN: implementing payment forwarding, debugging stuck HTLCs, reasoning about CLTV deltas in routes.

LDK (Lightning Dev Kit) by Lightning Labs: modular Rust crates for building custom Lightning apps. ldk-node for opinionated quick-start. ChannelManager, ChainMonitor, Router, async signer, persistence. USE WHEN: embedding Lightning into mobile/desktop apps, building custom Lightning logic, scaling beyond LND-style daemon.

LNURL: bech32-encoded HTTP URL fetched by wallet to enable payment flows. LUDs (LNURL specs): LUD-01 (encoding), LUD-04 (auth), LUD-06 (pay), LUD-09 (success action), LUD-12 (comment), LUD-16 (lightning address), LUD-21 (verify). USE WHEN: implementing LNURL servers/clients, building Lightning Address resolver, designing pay/withdraw/auth flows.

Phoenixd by ACINQ: headless server build of Phoenix wallet for self-hosting. Single-node Lightning daemon with batteries-included ACINQ swap-in / swap-out, BOLT12 receive, WebSocket payments API. USE WHEN: deploying a self-hosted minimal Lightning daemon for a service (point-of-sale, donation page, micro-merchant), avoiding full LND/CLN complexity.

Lightning pathfinding and routing: cost models, MPP / AMP / trampoline, blinded paths (BOLT 4 update), apriori probability, pickhardt-payments. USE WHEN: implementing/tuning a routing algorithm, debugging "no route" errors, evaluating pathfinding strategies.

OWASP security guidelines and Top 10 vulnerabilities USE WHEN: user mentions "OWASP", "security audit", "vulnerability scan", asks about "injection", "XSS", "CSRF", "access control", "authentication security" DO NOT USE FOR: OWASP Top 10:2025 specific - use `owasp-top-10` instead

API pagination patterns. Offset-based, cursor-based, keyset pagination. Filtering, sorting, and page metadata. REST and GraphQL pagination implementations. USE WHEN: user mentions "pagination", "paginate", "cursor", "offset", "page size", "next page", "infinite scroll API", "list endpoint" DO NOT USE FOR: frontend infinite scroll UI - use frontend framework skills; database query optimization - use database skills