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IWSDK project planning and best practices guide. Use when planning new IWSDK features, designing systems/components, reviewing IWSDK code architecture, or when the user asks about IWSDK patterns, ECS design, signals, or reactive programming in this codebase.

MUST read this skill BEFORE developing VR/MR/browser-first 3D applications using IWSDK (Immersive Web SDK). Covers project scaffolding, headless browser setup, CLI tools, reference system, ECS debugging, XR emulation, verification workflows, deployment, and known issues.

Test audio system (AudioSource loading, playback state, stop, spatial audio) against the audio example using the iwsdk CLI.

Test ECS core functionality (system registration, components, Transform sync, pause/step/resume, system toggle, entity discovery, snapshots) against the poke example using the iwsdk CLI.

Test environment system (DomeGradient, IBLGradient, default lighting, component schemas) against the poke example using the iwsdk CLI.

Test grab system (distance grab, one-hand grab, two-hand grab) against the grab example using the iwsdk CLI.

Test XR interactions (ray, poke/touch, dual-mode, audio, UI panel) against the poke example using the iwsdk CLI.

Test level system (LevelRoot, LevelTag, default lighting, scene hierarchy) against the poke example using the iwsdk CLI.

Stream, video frames, photo capture, resolution/frame rate configuration

Swift patterns, async/await, naming conventions, key types for DAT SDK iOS development

Display capability setup, display-capable device selection, UI DSL, icons, buttons, images, and video playback

SDK setup, Swift Package Manager integration, Info.plist configuration, and first connection to Meta glasses

MockDeviceKit for testing without physical glasses hardware

Building a complete DAT app with camera streaming and photo capture

Common issues, Developer Mode, version compatibility, state machine diagnosis

App registration with Meta AI, camera permission flows

Session and Stream capability setup, video frames, photo capture, resolution and frame rate configuration

Kotlin patterns, DatResult, session and capability conventions for DAT SDK Android development

Common issues, Developer Mode, version compatibility, and session and stream diagnosis

Display capability setup, display-capable device selection, UI DSL, icons, buttons, images, and video playback

SDK setup, Gradle integration, AndroidManifest configuration, and first connection to Meta glasses

MockDeviceKit for testing without physical glasses hardware

App registration with Meta AI and device permission flows

Building a complete DAT app with session creation, camera streaming, and photo capture

Rules for writing and reviewing GC-safe C++ code in the Hermes VM runtime. Use when writing, modifying, or reviewing C++ runtime VM code that uses internal Hermes VM APIs (as opposed to code using JSI). This includes working with GC-managed types (HermesValue, Handle, PinnedValue, JSObject, StringPrimitive, etc.), Locals, GCScope, PseudoHandle, CallResult, or any function with _RJS suffix. Typically in lib/VM/, include/hermes/VM/, API/hermes/, or API/napi/.

Guide for adding new JSI functionality to the JavaScript Interface (JSI) layer. Use when the user asks to add, create, or implement new methods or features in the JSI Runtime interface. Covers all required files across JSI core, Hermes implementation, and SynthTrace replay support.

This skill should be used when the user wants to analyze hermesvm binary size changes across a range of commits. Use when the user mentions "binary size", "size analysis", "size regression", "size increase", or asks to measure how commits affect the hermesvm library size.

Use when needing to reorder, split, drop, or amend git commits that are not the top commit, without interactive editor access. Covers programmatic rebase via GIT_SEQUENCE_EDITOR, commit splitting with automated hunk selection, and metadata changes (author, message, dates) on any commit in a range.

Guide for adding a new IR instruction to the Hermes compiler. Use when the user asks to add, create, or define a new IR instruction (Inst/Instruction) in the Hermes intermediate representation. Covers all required files and the patterns for each.

Use when running, debugging, updating, or creating Pysa end-to-end integration tests. Use when taint analysis tests fail, when expected output files need updating, or when working with .models, .cg, .hofcg, .overrides files under `source/interprocedural_analyses/taint/test/integration`.

Use when you need to understand the Pyre or Pysa codebase architecture, find where specific functionality is implemented, or navigate the source directory structure. Use when working on OCaml code, debugging type checking or taint analysis issues, or exploring the codebase.

Use when creating commits or diffs to apply the correct title prefix, reviewer, and test plan based on the area of the codebase being changed.

Use when debugging a Pysa false negative (missing taint issue), comparing two Pysa output directories, or finding where taint flow is lost.

Use when reading, writing, or debugging Pysa JSON model output (.models files). Use when working with taint models that describe sources, sinks, TITO, sanitizers, or issues in JSON format.

Create a Mononoke server-side hook with 3-diff split (tests, wiring, implementation), unit tests, and integration tests

Add or review structured error logging in EdenFS daemon (C++) — the ErrorLogger / EdenErrorInfo system that feeds the edenfs_errors table. Use when writing a catch block or handling a boxed/async exception (folly::Try / exception_wrapper / .thenError), instrumenting a failure path, or debugging a wrong stack trace or wrong component. Covers throw-site trace rules, component choice, errorType, noise filtering, gating, and testing.

Triage systemd-managed EdenFS issues on Linux devservers and OnDemands. Use when investigating EdenFS service failures, unexpected restarts, systemctl errors, edenfs_upgrade/edenfs_restarter problems, or when a user reports EdenFS is down on a systemd-enabled host. Also use when someone asks how systemd-managed EdenFS works, how to monitor it, or how to check its health. Use when asked to build a timeline of EdenFS lifecycle events, show edenfs restart history, or understand how edenfs reached its current state. Trigger on mentions of edenfs systemd, edenfs@ service, edenfs_upgrade timer, edenfs auto-restart, eden status --debug, systemctl edenfs, edenfs lifecycle management, edenfs timeline, edenfs restart history, or "what happened to edenfs".

Load FIRST before searching code in eden/. Contains component-to-file maps, key type names, and architecture diagrams for EdenFS, Sapling, and Mononoke. Tells you exactly which files to read for any task. References contain per-component quick reference tables.

How to mint real OpenZL frames and chunks for GPU decoder tests using the contrib/gpu/testkit utilities (frame_factory, multichunk_frame, frame_verifier), and how to extract a codec's encoded streams via reflection for differential GPU decode. USE when writing or reviewing GPU-decoder tests that need OpenZL-encoded fixtures.

Design patterns and requirements for OpenZL codecs (located under `src/openzl/codecs/`). **USE AUOMATICALLY** when creating, modifying, or reviewing codecs in OpenZL.

Design documentation for the OpenZL component registry located under tests/registry. **USE AUTOMATICALLY** whenever editing files under tests/registry/.

Use when creating benchmark scenarios for new openzl codec nodes in unitBench - adding kernel-level encode/decode benchmarks or graph-level compress/decompress benchmarks for codecs like bitsplit, delta, transpose, entropy, etc.

FBOSS coding standards and patterns. Auto-loaded when writing code in fboss/ to catch architecture violations, SAI/SDK misuse, thrift_cow pitfalls, platform config errors, and testing gaps. For explicit multi-reviewer review, use /fboss-review instead.

Comprehensive FBOSS code review with 11 parallel reviewers (5 generic + 6 FBOSS-specific). Covers reliability, engineering, code quality, silent failures, agent architecture, SAI/SDK, FSDB/thrift_cow, platform/config, testing, and cross-cutting design. Self-contained alternative to /review-diff for FBOSS diffs. Findings shown to user only, never auto-posted.

Find and remove redundant FBOSS agent_hw_tests without losing coverage. Use when asked to reduce/combine/dedup HW tests, retire non-dataplane (set/get) tests where dataplane tests exist, or cut HW test runtime while keeping coverage. Report-first; applying edits is a separate opt-in step.

Triage a failing FBOSS test by bisecting commits and investigating code changes. Use when a test is broken and you need to find the commit that caused the failure.

Write and run markdown-driven e2e tests for Relay. Covers fixture format, server/client code patterns, interaction DSL, snapshots, and running tests.

Best practices for writing idiomatic Relay code. ALWAYS use this skill when writing or modifying React components that use Relay for data fetching. Covers fragments, queries, mutations, pagination, and common anti-patterns. Use when you see `useFragment`, `useLazyLoadQuery`, `usePreloadedQuery`, `useMutation`, `usePaginationFragment`, `graphql` template literals, `react-relay` imports, or `__generated__/*.graphql` files. Also use when asked to explain Relay concepts, debug Relay issues, or review Relay code.

Performance best practices for Relay applications. Use when optimizing data fetching, reducing re-renders, configuring caching, or improving time to first meaningful paint. Covers query placement, @defer, pagination, fetch policies, garbage collection, fragment granularity, and server-side filtering. Companion to the relay-best-practices skill which covers correctness and architecture.

Port a PyTorch model to use pyrefly's tensor shape type system (Tensor[B, C, H, W], Dim[T]). Use this skill whenever the user wants to add shape annotations to a PyTorch model, type a model with tensor dimensions, port a model to use shape tracking, or annotate model forward methods with tensor shapes. Also use when the user mentions tensor shape ports, Dim types for PyTorch, or pyrefly shape checking on a model file. Invoke BEFORE starting any model port — the skill's gated workflow prevents common failure modes.

Use when adding a new PyTorch model to Pyrefly's shape-tracking example corpus under tensor-shapes/pyrefly-torch-stubs/examples — i.e. importing a model as a tested, corpus-quality reference port. This is maintainer-facing fbsource work. For porting your own model elsewhere, use the porting skill directly; for fixing a wrong/missing shape rule, use modify-shaped-array-dsl.

Use when Pyrefly computes a wrong tensor shape (or is missing one that can't be expressed in a stub signature) and you need to add or fix a shape-DSL rule. Requires a Pyrefly checkout (fbsource or a clone); not usable from a pip/site-packages install.

Performance testing CLI for the rebalancer solver (algopt/rebalancer/). Use when benchmarking solver performance, comparing commits for regressions, profiling solver execution, running A/B tests, or querying the rebalancer_runs Scuba table. Covers local, Skycastle (distributed), and ServiceLab (isolated hardware) execution environments. Also handles replaying saved solver configs and managing predefined run collections like the pareto golden set. Only for the rebalancer project — not for general ServiceLab benchmarks, non-rebalancer services, or functional correctness testing.

Debugging tool for rebalancer constraint violations and move failures using eval_move, list_server_moves, and query_mip CLIs.

Use when GitHub Actions CI is failing, when investigating build or test failures on a branch or PR, when the user asks about CI status, or when you need to diagnose why a workflow failed, or when you need to examine GHA build logs (e.g. sccache stats, cache usage, build timing). Triggers on keywords like "CI", "GHA", "GitHub Actions", "build failure", "tests failing", "pipeline broken", "build logs", "sccache", "cache stats", "build performance".

Guide users through writing their first Buck2 rule to learn fundamental concepts including rules, actions, targets, configurations, analysis, and select(). Use this skill when users want to learn Buck2 basics hands-on or need help understanding rule writing.