// Draft a commit message for a Velox commit. Use when the user asks to write, draft, or compose a commit message for a Velox change. Encodes the project's content rules so the draft is showable without a separate review pass.
Review Velox pull requests for code quality, memory safety, performance, and correctness. Use when reviewing PRs, when asked to review code changes, or when the user mentions "/pr-review".
Answer questions about the Velox codebase or pull requests. Use when asked a question via "/query" or when the user wants to understand code, architecture, or implementation details.
| name | write-commit-message |
| description | Draft a commit message for a Velox commit. Use when the user asks to write, draft, or compose a commit message for a Velox change. Encodes the project's content rules so the draft is showable without a separate review pass. |
Drafts a commit message that follows the rules in CODING_STYLE.md and CLAUDE.md at the repo root. The rules there are authoritative — this skill is the workflow for applying them.
Read the rules — Open CODING_STYLE.md and CLAUDE.md and re-read the commit-message sections. Do not draft from memory.
Gather facts from the diff itself — Never draft from the conversation alone. The conversation has scaffolding; the diff is the truth.
Draft — Match length to the change. Each paragraph is one long line (no hard wraps). The right shape depends on what the diff actually does:
Title: [velox] type(scope): Description or [velox][PR] type(scope): Description for GitHub-originated PRs — capital start, no trailing period, ≤67 chars. Type ∈ {feat, fix, refactor, test, docs}. Scope optional.
Body paragraphs (include only those that carry weight for this change):
Prose clarity — write so a tired reader gets each sentence on first read.
Prefer short sentences. If a sentence has two clauses joined by "so", "because", "but", "even though", "although", or a comma + participle, consider splitting it. Contrastive joiners ("but X", "even though Y") are especially risky when both halves introduce a fact the reader does not already have — pack two new facts into one sentence and the reader stalls. State each rule in its own sentence, then connect them.
Avoid stacked abstractions like "left the outer scope advertising the column as X" or "the projection inherits the source's reverseLookup names". Replace with a concrete chain.
Avoid compiler/optimizer/execution-engine jargon ("outer reference", "outer scope", "binding context", "name resolution scope", "vector encoding") unless the rest of the paragraph already established it. If you must use it, define it inline with a tiny example.
Prefer plain verbs (used, dropped, kept) over jargon verbs (advertise, surface, propagate, materialize) unless the jargon is the precise term.
Avoid hyphenated compound-noun stacks ("user-written case", "lookup-based fallback", "context-aware resolver"). They require the reader to unpack a modifier chain before getting to the noun. Rewrite as a relative clause ("the case the user wrote") or a single concrete noun.
Prefer the word with one obvious meaning in this context. "Case" can mean legal case, match case, or upper/lower case — use "capitalization" when you mean letter case. Similarly: "operator" vs "function", "key" vs "column", "type" vs "kind" — pick the one a SQL reader and a C++ reader both interpret the same way.
Show a complete example query or input that demonstrates the failure, paired with the resulting error. Don't describe an input in prose ("a vector of nulls passed to X") when you can show one (makeFlatVector<int64_t>({1, null, 2})); the example carries the meaning without the reader holding context across sentences.
Break any long code, query, or error string out into a fenced block on its own line. "Long" means more than ~6 words or anything that wraps the surrounding paragraph awkwardly. This applies whether the long string is paired with another or stands alone — a single long error string embedded mid-sentence still overloads the reader. Patterns:
Lead with the error, then explain:
The query failed with:
Function not registered: my_func(BIGINT)
This happened because the function was registered only under the Presto namespace.
Query + result:
For example:
SELECT my_func(c0) FROM (VALUES 1, 2) AS t(c0)
fails with `Function not registered` because ...
Short fragments (a single column name, a flag, a 2-3-word error name) stay inline.
When in doubt, read the paragraph aloud. If you pause mid-sentence to decode it, split or simplify it.
Self-check before showing — Walk every item; do not skip any.
[velox] type(scope): Description or [velox][PR] type(scope): Description, capital, no period, ≤67 chars.\`escaped\`.If any item fails, fix the draft before showing.
Show the draft — Present the final draft. Mention any facts you could not verify and want the user to confirm.
These are the patterns drafts most often hit, and that this skill exists to prevent:
foo(), we now do A. In bar(), we adjust B." The reviewer reads the diff for that. Collapse into the single mechanism.Foo, Bar, Baz, Qux, and Quux." or "Updated across N call sites." The diff is the source of truth for scope. Naming the touched symbols eats space without informing the reader. Exception: name a specific file only when its role in the change is not obvious from the title (e.g., the test file that needed expectation updates, or the one production file the rest of the diff supports).For all other Velox commit-message work — drafting, revising, or rewriting — invoke this skill.