@facebook

Use when you have lint errors, formatting issues, or before committing code to ensure it passes CI.

Use when you need to run tests for React core. Supports source, www, stable, and experimental channels.

Use when you need to run Flow type checking, or when seeing Flow type errors in React code.

Use when you need to check feature flag states, compare channels, or debug why a feature behaves differently across release channels.

Use when you want to validate changes before committing, or when you need to check all React contribution requirements.

Use when feature flag tests fail, flags need updating, understanding @gate pragmas, debugging channel-specific test failures, or adding new flags to React.

Use when adding new error messages to React, or seeing "unknown error code" warnings.

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.

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/, or API/hermes/.

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 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.

Reviews a comma separated pyrefly diff according to the pyrefly review best practices.

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.

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.

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.

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

Develop and iterate on IWSDK PanelUI components. Use when the user wants to create, modify, debug, or improve UI panels in their IWSDK application. Covers UIKITML editing, full-screen preview with ScreenSpace, and visual verification.

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.

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

Test XR session lifecycle and mode transitions. Use when verifying XR enter/exit behavior, testing mode-dependent features, or debugging session state issues.

Find and click a target object in XR. Use when testing UI interactions, clicking buttons, or verifying interactable elements work correctly.

Ray-based interactions in the WebXR scene — click objects, press UI buttons, or distance-grab with DistanceGrabbable. Use when the user wants to point at and interact with something at a distance, click a UI button, or test ray-based selection.

Grab an object in the WebXR scene using emulated controllers. Use when the user wants to pick up, move, or test grabbing an object. Supports OneHandGrabbable and TwoHandsGrabbable components which use proximity-based grip (squeeze button), not trigger.

Debug continuous behavior in WebXR scenes — physics, animations, collisions, game loops, or any real-time interaction that happens too fast for an agent to observe. Uses ECS pause/step/snapshot/diff to freeze time and inspect state frame by frame.

Guide for implementing physics in IWSDK projects. Use when adding physics simulation, configuring rigid bodies, collision shapes, applying forces, creating grabbable physics objects, or troubleshooting physics behavior.

Develop and iterate on IWSDK UI panels efficiently. Use when working on PanelUI components, debugging UI layout, or improving UI design in IWSDK applications.

Test UI system (PanelUI, ScreenSpace) against the poke example using mcp-call.mjs WebSocket CLI.

Parallel test orchestrator. Runs all 9 test suites concurrently via Task sub-agents and mcp-call.mjs. Handles build, example setup, dev servers, agent launch, polling, retries, and result aggregation.

Test grab system (distance grab, one-hand grab, two-hand grab) against the grab example using mcp-call.mjs WebSocket CLI.

Test level system (LevelRoot, LevelTag, default lighting, scene hierarchy) against the poke example using mcp-call.mjs WebSocket CLI.

Test audio system (AudioSource loading, playback state, stop, spatial audio) against the audio example using mcp-call.mjs WebSocket CLI.

Test Havok physics system (gravity, rigid bodies, static vs dynamic) against the physics example using mcp-call.mjs WebSocket CLI.

Test locomotion system (slide, snap turn, teleport, jump) against the locomotion example using mcp-call.mjs WebSocket CLI.

Test environment system (DomeGradient, IBLGradient, default lighting, component schemas) against the poke example using mcp-call.mjs WebSocket CLI.