Google C++ Style Guide rules for writing clean, maintainable C++ code. Use when writing C++, reviewing code, discussing naming conventions, formatting, class design, or any C++ best practices. Covers headers, scoping, classes, functions, naming, comments, and formatting.

Build ClickHouse with various configurations (Release, Debug, ASAN, TSAN, etc.). Use when the user wants to compile ClickHouse.

Show a report of open ClickHouse PRs whose only non-green CI check is "CH Inc sync" (or that are fully green) — i.e. effectively ready to merge. Groups by your authored PRs, PRs assigned to you (authored by others), and PRs by tracked authors (default groeneai). Shows the CH Inc sync state and whether each PR was ever approved; excludes already-merged PRs. Use when asked for "good PRs", merge-ready PRs, or PRs blocked only on the sync job.

Review a ClickHouse Pull Request for correctness, safety, performance, and compliance. Use when the user wants to review a PR or diff.

Bisect a ClickHouse regression using pre-built master binaries from CI. Use when the user wants to find the commit that introduced a bug.

Fix the "CH Inc sync" job in a pull request. Diagnoses the failure as one of three types — conflicts found, build failed, or tests failed — and handles each accordingly.

Continue work on an existing PR - resolve conflicts, fix CI failures, address reviewer feedback, and push updates. Use when the user wants to pick up and advance a pull request.

In-browser review of pending changes before committing or opening a PR. Starts a local server on localhost:3000 that renders the working-tree diff with @pierre/diffs CodeView, opens the user's browser, and waits for their line comments — which must then be read back and addressed. Works from a browser on the same machine, or from the user's own machine through an SSH-forwarded port (the server prints the `ssh -L` command); where nobody opens the page within 120 s, it exits on its own. Use when the user asks for a browser review of the changes.

Profile a ClickHouse query using the sampling query profiler and system.trace_log. Use when the user wants to find CPU hotspots, analyze where time is spent in a query, or investigate performance bottlenecks.

Analyze CI performance comparison reports for a ClickHouse PR. Lists all regressions and improvements, cross-references with master history to distinguish real changes from flaky tests.

Analyze a jemalloc (or other) allocation profile in collapsed stack format. Use when the user wants to analyze memory allocations, find top allocators, or understand memory usage patterns from a .collapsed profile file.

Update a ClickHouse third-party library (contrib submodule) to a new version. Handles fork management, submodule pointer bumps, CMake adaptation, and source code fixes. Use when the user wants to bump a dependency.

Investigate a ClickHouse CI failure end-to-end from a PR or S3 report URL. Fetches the failed tests and their output, classifies each as flaky vs a real regression using play.clickhouse.com master history, and for every failure searches for both an existing tracking GitHub issue and an existing fix (open/merged PR) — reporting, per failure, whether an issue still needs to be created and whether a fix exists with its status (WIP, merged, already in this branch or not). Downloads and reads the harness artifacts only for failures that history does not explain, and reports a root-cause hypothesis. Read-only first pass — never commits, pushes, or edits.

Edit an auto-generated ClickHouse release changelog into the form that gets committed to CHANGELOG.md. Use when the user has the output of `utils/changelog/changelog.py` and wants it cleaned up and re-categorized for a release.

Evaluate ClickHouse performance test results from existing CI/dashboard data or local perf.py runs. Use to check PR performance changes, run local performance tests, compare with history, assess flakiness, inspect coverage/PR relevance, and summarize whether a result is actionable.

Create a ClickHouse git worktree with submodules hardlinked from the main repo. Use when the user wants to create a new worktree for ClickHouse development.

Share a Claude Code session to pastila.nl and return a viewer link. Shares the current session by default, or a session specified as a transcript path, a session id, or a project. Use when the user asks to share, publish, or get a link to this conversation or to a session/transcript.