Naming conventions

Names follow each language's standard style, plus the project choices below. When this page doesn't cover a case, copy what the nearest existing code does, and add the case here in the same PR. Formatters and linters (cargo fmt, clippy, ESLint) enforce layout; this page covers what they can't.

Branch, commit and pull-request names are in DEVELOPMENT_WORKFLOW.md.

General

Use the domain words from the glossary, such as lease, coverage, validator and checkpoint. One concept has one name across Rust, TypeScript, docs and the UI contract. Don't use synonyms such as chunk for a lease or resumeData for a checkpoint.
Spell words out (download, not dl). Common abbreviations are fine: url, id, http, io, ui.
Booleans read as a question: is_paused, has_validator, canResume.
Units go in the name when the type doesn't carry them: timeout_ms, size_bytes, rateBytesPerSec.

Rust

These follow the Rust API guidelines on naming.

Item	Style	Example
Crates	`kebab-case` with a `velocity-` prefix	`velocity-core`, `velocity-desktop-v2`
Modules and files	`snake_case`	`validation.rs`, `database/migrations.rs`
Types, traits, enum variants	`UpperCamelCase`	`AppInfo`, `DirectTransfer`, `DownloadStatus::Paused`
Functions, methods, variables	`snake_case`	`app_info()`, `select_checks`
Constants and statics	`SCREAMING_SNAKE_CASE`	`PRODUCT_NAME`, `MAX_URL_LEN`
Conversions	`as_`/`to_`/`into_` by cost and ownership; `from_` constructors	`to_record()`, `from_metadata()`
Fallible constructors	`parse_…` or `try_…`, returning `Result`	`parse_content_range()`
Unit tests	In `#[cfg(test)] mod tests` beside the code; the name states the behaviour	`identifier_differs_from_v1`
Integration tests	`crates/<crate>/tests/<behaviour>.rs`	`tests/range_probe.rs`

TypeScript and React

Item	Style	Example
Components and their files	`PascalCase`, one component per file	`App.tsx`, `DownloadList.tsx`
Other modules	`camelCase`	`appInfo.ts`, `formatSize.ts`
Hooks	`useCamelCase`	`useDownloads()`
Functions and variables	`camelCase`	`parseAppInfo()`, `windowHeading()`
Types and interfaces	`PascalCase`, no `I` prefix	`AppInfo`
Constants	`SCREAMING_SNAKE_CASE` for true constants, `camelCase` otherwise	`MAX_VISIBLE_ROWS`
Tests	Next to the code as `<module>.test.ts(x)`. `describe` names the unit, `it` states the behaviour	`appInfo.test.ts`, `it('rejects a response without a version')`

The UI contract (between Rust and TypeScript)

Item	Style	Example
Tauri commands	`snake_case`, verb first	`app_info`, `add_downloads`, `get_snapshot`
Events	`velocity://` plus a `kebab-case` noun	`velocity://snapshot`
Error codes	`SCREAMING_SNAKE_CASE`, stable once released; they describe the cause, not the screen	`INTEGRITY_CHECK_FAILED`
Fields crossing the boundary	`snake_case` in Rust. The TypeScript side mirrors them as the contract (#25) decides	—

Scripts, files and docs

Item	Style	Example
`package.json` scripts	`group:action`	`check:fast`, `test:focused`
Node scripts	`kebab-case.mjs`, tests as `<name>.test.mjs`	`check-pr.mjs`, `checks-lib.test.mjs`
Top-level docs	`UPPER_SNAKE_CASE.md`	`DEVELOPMENT_WORKFLOW.md`
Decision records	`NNNN-kebab-title.md`	`0001-v2-direction.md`
Research	`YYYY-MM-DD-kebab-title.md`	`2026-10-21-libcurl-engine-research-r2.md`
Environment variables	`VELOCITY_` plus `SCREAMING_SNAKE_CASE`	`VELOCITY_DATA_DIR`