workerd

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.

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.

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.

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.

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

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

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.

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.

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.

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.

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

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