cloudflare

Load when working with the module registry in workerd — reading, modifying, debugging, or reviewing module resolution, compilation, evaluation, or registration code. Provides pointers to three reference documents covering the legacy registry, V8 module internals, and the new registry design.

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.

Mandatory rules for running bazel tests during development. Load this skill before running any bazel test command, especially when validating fixes or verifying regression tests. Prevents false confidence from cached results, filter flags that silently match nothing, and partial test runs that miss breakage.

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

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.

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.

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/.

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.

Comprehensive Cloudflare platform skill covering Workers, Pages, storage (KV, D1, R2), AI (Workers AI, Vectorize, Agents SDK), feature flags (Flagship), 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.

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.

Send and receive transactional emails with Cloudflare Email Service (Email Sending + Email Routing). Use when building email sending (Workers binding or REST API), email routing, Agents SDK email handling, or integrating email into any app — Workers, Node.js, Python, Go, etc. Also use for email deliverability, SPF/DKIM/DMARC, wrangler email setup, MCP email tools, or when a coding agent needs to send emails. Even for simple requests like "add email to my Worker" — this skill has critical config details.

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, chat applications, voice agents, or browser automation. Covers Agent class, state management, callable RPC, Workflows, durable execution, queues, retries, observability, and React hooks. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

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 (LCP, INP, CLS) and supplementary metrics (FCP, TBT, 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.

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.

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.

Use when you need to exercise a real, running Sandbox deployment via HTTP — for example to validate SDK changes against a live container, reproduce a user-reported issue, or experiment with the API (including FUSE bucket mounts) without spinning up `wrangler dev`. Documents the Sandbox bridge worker reachable via `SANDBOX_WORKER_URL` + `SANDBOX_API_KEY` when the host injects them.

Use when creating a changeset, preparing a release, or bumping versions. Covers which packages to reference, how to write user-facing changeset descriptions, the release automation flow, and the npm/Docker version sync requirement. (project)

Use when navigating the codebase for the first time, adding a new client method, adding a new container handler/service, or understanding how a request flows from Worker through the Sandbox DO into the container. Covers the three-layer architecture, client pattern, container runtime structure, and monorepo layout. (project)

Use when writing or reviewing TypeScript in this repo. Covers the no-`any` rule and where to put new types, the uppercase-acronym style guide, and the rules for code comments (no historical context). (project)

Use when working in the examples/ directory, running an example with wrangler dev, adding a new example, or answering questions about EXPOSE directives and the local Docker dev loop. (project)

Use when adding logs, debugging, or working with the Logger across the SDK and container runtime. Covers the constructor-injection pattern, child loggers, env-var configuration, and test mocking. (project)

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)

Evaluate a GitHub issue or pull request and decide if it is spam or clearly off-topic for cloudflare/cloudflare-docs.

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 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).

Analyzes a Dependabot PR to determine what actually changed in each bumped package and whether those changes affect this repo. Reports changed APIs/methods, which doc pages use them, and the realistic probability of any visible impact on the docs site.

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.

Creates and updates GitHub pull requests for cloudflare-docs changes. Load when asked to open, create, submit, update, edit, or write a title or description for a PR. Covers title conventions, PR body structure, and the documentation checklist template.

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

Add or maintain PolyStella in an existing Astro project. Use when integrating AI-driven build-time content localization, configuring R2 caching, wiring locale-prefixed routes, or debugging an existing PolyStella setup in a downstream project.

Edit the PolyStella package source. Use when adding a file-format adapter, adding a CLI subcommand, adding a translation provider, modifying the cache contract, debugging a translation regression, or otherwise working on the package itself (not consuming it).

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.

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).

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

Mounts Git remotes with ArtifactFS as local working trees without a full clone. Use when asked to mount a remote repo, explain committed state versus dirty overlay state, or mount multiple repos under one daemon.

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

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.