@cloudflare

Control headless Chrome via Cloudflare Browser Rendering CDP WebSocket. Use for screenshots, page navigation, scraping, and video capture when browser automation is needed in a Cloudflare Workers environment. Requires CDP_SECRET env var and cdpUrl configured in browser.profiles.

Use when investigating bugs, crashes, assertions, or unexpected behavior - requires writing a reproducing test early instead of over-analyzing source code; concrete experiments over mental models

Detailed guide for authoring .wd-test files in workerd, with examples of bindings, Durable Objects, multi-service configs, TypeScript tests, and network access.

Use when about to claim work is complete, fixed, or passing, before committing or creating PRs - requires running verification commands and confirming output before making any success claims; evidence before assertions always

Memory safety, thread safety, concurrency, and critical detection patterns for workerd code review. Covers V8/KJ boundary hazards, lifetime management, cross-thread safety, and coroutine pitfalls. Load this skill when reviewing any C++ code.

How to find, build, and run tests in workerd. Covers wd-test, kj_test target naming, bazel query patterns, and common flags. Also covers parent project integration tests if workerd is used as a submodule. Load this skill when you need to locate or run a test and aren't sure of the exact target name or invocation.

Structured scratch document for tracking investigation state during bug hunts - prevents re-reading code, losing context, and rabbit holes; maintains external memory so you don't re-derive conclusions

Performance optimization, API design & compatibility, security vulnerabilities, and standards spec compliance for workerd code review. Covers tcmalloc-aware perf analysis, compat flags, autogates, web standards adherence, and security patterns. Load this skill when reviewing API changes, performance-sensitive code, security-relevant code, or standards implementations.

Step-by-step guide for updating the V8 JavaScript engine in workerd, including patch rebasing, dependency updates, integrity hashes, and verification. Load this skill when performing or assisting with a V8 version bump.

JS/TS style guidelines and review checklist for workerd. Covers TypeScript strictness, import conventions, export patterns, private field syntax, error handling, feature gating, and test structure. Load this skill when reviewing or writing JavaScript or TypeScript code in src/node/, src/cloudflare/, or JS/TS test files under src/workerd/.

KJ/workerd C++ style guidelines for code review. Covers naming, type usage, memory management, error handling, inheritance, constness, and formatting conventions. Load this skill when reviewing or writing C++ code in the workerd codebase.

Rust code review for workerd. Covers CXX FFI safety, unsafe code patterns, JSG resource conventions, error handling, and a review checklist adapted from the C++ review skills. Load this skill when reviewing Rust code in src/rust/.

Step-by-step guide for adding a new autogate to workerd for gradual rollout of risky changes, including enum registration, string mapping, usage pattern, and testing.

Step-by-step guide for adding a new compatibility flag to workerd, including capnp schema, C++ usage, testing, and documentation requirements.

Guidelines for posting pull request review comments via GitHub CLI, including suggested edits format, handling unresolved comments, etiquette, and report/issue tracking. Load this skill when reviewing a PR via GitHub and posting inline comments.

Use markdown formatting when drafting content intended for external systems (GitHub issues/PRs, Jira tickets, wiki pages, design docs, etc.) so formatting is preserved when the user copies it. Load this skill before producing any draft the user will paste elsewhere.

Commit categorization rules for changelogs and "what's new" summaries. MUST be loaded before categorizing commits in changelog or whats-new commands. Provides the canonical path-based category table used to group commits by area.

Identifies the local user's GitHub account and git identity before performing code reviews. Load this skill at the start of any PR review, code review, or commit log analysis so findings can be framed relative to the user's own prior comments, commits, and approval status.

Bootstrap skill for discovering additional skills and context from a parent project when workerd is used as a submodule. Load this skill when tasks span project boundaries (e.g., Sentry/production investigation, integration testing, cross-repo debugging).

Use when receiving code review feedback, before implementing suggestions, especially if feedback seems unclear or technically questionable - requires technical rigor and verification, not performative agreement or blind implementation

After completing any task that took more than ~5 tool calls, or after long-running builds/tests finish, load this skill and deliver a dad joke to lighten the mood. Also load before any user-requested joke, pun, or limerick. Never improvise jokes without loading this skill first.

Migrates Next.js projects to vinext (Vite-based Next.js reimplementation). Load when asked to migrate, convert, or switch from Next.js to vinext. Handles compatibility scanning, package replacement, Vite config generation, ESM conversion, and deployment setup (Cloudflare Workers natively, other platforms via Nitro).

Reviews Workers and Cloudflare Developer Platform code for type correctness, API usage, and configuration validity. Load when reviewing TypeScript/JavaScript using Workers APIs, wrangler.jsonc/toml config, or Cloudflare bindings (KV, R2, D1, Durable Objects, Queues, Vectorize, AI, Hyperdrive).

Creates, updates, and reviews product changelog entries for the Cloudflare documentation site. Load when generating changelog MDX files, editing existing entries, reviewing changelog style, or validating frontmatter.

Reviews documentation PRs and provides GitHub PR suggestions. Load when asked to review, suggest changes, or provide feedback on docs content. Covers MDX, frontmatter, style guide, components, and content accuracy.

Transform technical jargon into clear explanations using before/after comparisons, metaphors, and practical context

Use when working on or reviewing session execution, command handling, shell state, FIFO-based streaming, or stdout/stderr separation. Relevant for session.ts, command handlers, exec/execStream, or anything involving shell process management. (project)

Use when writing or running tests for this project. Covers unit vs E2E test decisions, test file locations, mock patterns, and project-specific testing conventions. (project)

Use when creating git commits to ensure commit messages follow project standards. Applies the 7 rules for great commit messages with focus on conciseness and imperative mood.

Generate hierarchical AGENTS.md knowledge base for a codebase. Creates root + complexity-scored subdirectory documentation.

Comprehensive guide for building OpenAPI endpoints with chanfana - schema definition, request validation, CRUD operations, D1 database integration, and exception handling

Cloudflare Workers CLI for deploying, developing, and managing Workers, KV, R2, D1, Vectorize, Hyperdrive, Workers AI, Containers, Queues, Workflows, Pipelines, and Secrets Store. Load before running wrangler commands to ensure correct syntax and best practices. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Build AI agents on Cloudflare Workers using the Agents SDK. Load when creating stateful agents, durable workflows, real-time WebSocket apps, scheduled tasks, MCP servers, or chat applications. Covers Agent class, state management, callable RPC, Workflows integration, and React hooks. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Guide for using Cloudflare R2 SQL - serverless distributed query engine for Apache Iceberg tables in R2 Data Catalog.

Build sandboxed applications for secure code execution. Load when building AI code execution, code interpreters, CI/CD systems, interactive dev environments, or executing untrusted code. Covers Sandbox SDK lifecycle, commands, files, code interpreter, and preview URLs. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Analyzes web performance using Chrome DevTools MCP. Measures Core Web Vitals (FCP, LCP, TBT, CLS, Speed Index), identifies render-blocking resources, network dependency chains, layout shifts, caching issues, and accessibility gaps. Use when asked to audit, profile, debug, or optimize page load performance, Lighthouse scores, or site speed. Biases towards retrieval from current documentation over pre-trained knowledge.

Reviews and authors Cloudflare Workers code against production best practices. Load when writing new Workers, reviewing Worker code, configuring wrangler.jsonc, or checking for common Workers anti-patterns (streaming, floating promises, global state, secrets, bindings, observability). Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Builds AI agents on Cloudflare using the Agents SDK with state management, real-time WebSockets, scheduled tasks, tool integration, and chat capabilities. Generates production-ready agent code deployed to Workers. Use when: user wants to "build an agent", "AI agent", "chat agent", "stateful agent", mentions "Agents SDK", needs "real-time AI", "WebSocket AI", or asks about agent "state management", "scheduled tasks", or "tool calling". Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Comprehensive Cloudflare platform skill covering Workers, Pages, storage (KV, D1, R2), AI (Workers AI, Vectorize, Agents SDK), networking (Tunnel, Spectrum), security (WAF, DDoS), and infrastructure-as-code (Terraform, Pulumi). Use for any Cloudflare development task. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Create and review Cloudflare Durable Objects. Use when building stateful coordination (chat rooms, multiplayer games, booking systems), implementing RPC methods, SQLite storage, alarms, WebSockets, or reviewing DO code for best practices. Covers Workers integration, wrangler config, and testing with Vitest. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Builds remote MCP (Model Context Protocol) servers on Cloudflare Workers with tools, OAuth authentication, and production deployment. Generates server code, configures auth providers, and deploys to Workers. Use when: user wants to "build MCP server", "create MCP tools", "remote MCP", "deploy MCP", add "OAuth to MCP", or mentions Model Context Protocol on Cloudflare. Also triggers on "MCP authentication" or "MCP deployment". Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

Add new Prometheus metrics to the Cloudflare exporter. Use when adding metrics, implementing new GraphQL/REST queries, or extending metric coverage. Covers the full workflow from schema discovery through client implementation and README updates.