Crates

The workspace ships 49 crates under crates/. They split into four functional groups: the linter, the formatter, the type checker (ty), and shared infrastructure that everyone consumes.

Group: shared infrastructure (Ruff- and ty-side)

Crate	Role
ruff_python_parser	Handwritten Python parser.
ruff_python_ast	Typed AST + visitor traits. Re-exported as ast::*.
ruff_python_trivia	Whitespace and comment scanning.
ruff_python_index	Pre-pass indexing of definitions / references.
ruff_python_codegen	Renders AST nodes back to source (used by autofixes).
ruff_python_literal	String/number literal parsing helpers.
ruff_python_stdlib	Lookup tables for Python standard library names.
ruff_python_importer	Insertion of from x import y statements when an autofix needs them.
ruff_python_semantic	Name resolution, scope graph, semantic model.
ruff_text_size	TextSize / TextRange byte-offset types.
ruff_source_file	SourceFile, line tables, byte ↔ line/column conversion.
ruff_db	Salsa database building blocks, System file abstraction, file IDs.
ruff_diagnostics	Diagnostic, Fix, severity, applicability.
ruff_annotate_snippets	Forked annotate-snippets-rs for diagnostic rendering.
ruff_macros	Proc-macros: derive(Options), rule metadata, codegen.
ruff_options_metadata	Reflection metadata for configuration options.
ruff_cache	Cache key + serialization helpers.
ruff_notebook	Jupyter notebook (.ipynb) reading/writing.
ruff_markdown	Markdown helpers (used by docs and mdtest).
ruff_memory_usage	Allocation accounting helpers.
ruff_benchmark	Criterion benchmark harness for the linter.
mdtest	Markdown-driven test harness used by ty.

Group: Ruff (linter + formatter)

Crate	Role
ruff_linter	All 900+ lint rules, checkers, registry, fixers.
ruff_python_formatter	Python code formatter.
ruff_formatter	The general-purpose formatter engine (a fork of rome_formatter).
ruff_workspace	Settings model, pyproject.toml / ruff.toml resolution.
ruff_graph	Import graph for ruff analyze graph.
ruff_server	Ruff LSP.
ruff_wasm	Browser bindings for the linter and formatter.
ruff_dev	Internal cargo dev CLI (codegen, debugging, snapshots).

The ruff and ty binary crates compose these; see Apps.

Group: ty (type checker)

Crate	Role
ty_python_semantic	Type system, inference, lints. The biggest ty crate.
ty_python_core	Core Python value/type helpers shared between subsystems.
ty_module_resolver	Resolves import statements across stubs, site-packages, vendored.
ty_project	Project (workspace) configuration and file discovery.
ty_ide	IDE-only queries (hover, completion, rename, references).
ty_server	ty LSP.
ty_site_packages	Discovery of installed-package metadata.
ty_vendored	Bundled typeshed stubs.
ty_static	Static asset bundle.
ty_combine	Type combination helpers.
ty_completion_bench, ty_completion_eval	Benchmarks and quality eval for completions.
ty_test	Test scaffolding for ty.
ty_wasm	Browser bindings for ty.

Cross-cutting reading order

If you're new, read in this order:

1. ruff_python_parser — to understand the input shape.
2. ruff_python_ast — to read the data the parser produces.
3. ruff_python_semantic — to see how the linter and ty answer "what does this name refer to?"
4. ruff_linter — for how rules are organized and dispatched.
5. ruff_python_formatter — separate pipeline; useful as a contrast.
6. ty_python_semantic — once you understand the shared layers.

Per-crate pages cover internal layout, key abstractions, integration points, and where to start modifying.