# Configuration Reference

This page documents the configuration keys that `prek` understands.

## Global config file

`prek` reads an optional user-level global config from:

- Linux and macOS: `~/.config/prek/prek.toml` (or `$XDG_CONFIG_HOME/prek/prek.toml` when `XDG_CONFIG_HOME` is set)
- Windows: `%APPDATA%\prek\prek.toml`

This file stores user-level `prek` settings and does not define project hooks.

### Global `auto_update.cooldown_days`

Default cooldown for [`prek auto-update`](../cli/#prek-auto-update).

- Type: integer days, `0` to `255`
- Default: `0`
- CLI override: [`prek auto-update --cooldown-days <DAYS>`](../cli/#prek-auto-update)

```toml
[auto_update]
cooldown_days = 7
```

The age is computed from the tag creation timestamp for annotated tags, or from the tagged commit timestamp for lightweight tags. A value of `0` disables the cooldown check.

Cooldowns never downgrade

If the current `rev` is newer than the latest cooldown-eligible tag, [`prek auto-update`](../cli/#prek-auto-update) keeps the current `rev` instead of downgrading it.

Project configs can also set [`auto_update.cooldown_days`](#auto_updatecooldown_days). The effective precedence is:

1. [`prek auto-update --cooldown-days <DAYS>`](../cli/#prek-auto-update)
1. project config
1. user-level global config
1. default `0`

## Top-level keys

### `repos` (required)

A list of hook repositories.

Each entry is one of:

- a remote repository (typically a git URL)
- `repo: local` for hooks defined directly in your repository
- `repo: meta` for built-in meta hooks
- `repo: builtin` for `prek`'s built-in fast hooks

See [Repo entries](#repo-entries).

### `files`

Global *include* regex applied before hook-level filtering.

- Type: regex string (default, pre-commit compatible) **or** a prek-only glob pattern mapping
- Default: no global include filter

This is usually used to narrow down the universe of files in large repositories.

What path is matched? (workspace + nested projects)

`files` (and `exclude`) are matched against the file path **relative to the project root** — i.e. the directory containing the configuration file.

- For the root project, this is the workspace root.
- For a nested project, this is the nested project directory.

Example (workspace mode):

- Root project config: `./.pre-commit-config.yaml`
- Nested project config: `./nested/.pre-commit-config.yaml`

For a file at `nested/excluded_by_project`:

- Root project sees the path as `nested/excluded_by_project`
- Nested project sees the path as `excluded_by_project`

This matters most for anchored patterns like `^...$`.

Regex matching

When `files` / `exclude` are regex strings, they are matched with *search* semantics (the pattern can match anywhere in the path). Use `^` to anchor at the beginning and `$` at the end.

`prek` uses the Rust [`fancy-regex`](https://github.com/fancy-regex/fancy-regex) engine. Most typical patterns are portable to upstream `pre-commit`, but very advanced regex features may differ from Python’s `re`.

prek-only globs

In addition to regex strings, `prek` supports glob patterns via:

- `files: { glob: "..." }` (single glob)
- `files: { glob: ["...", "..."] }` (glob list)

This is a `prek` extension. Upstream `pre-commit` expects regex strings here.

For more information on the glob syntax, refer to the [globset documentation](https://docs.rs/globset/latest/globset/#syntax).

Examples:

```toml
# Regex (portable to pre-commit)
files = "\\.rs$"

# Glob (prek-only)
files = { glob = "src/**/*.rs" }

# Glob list (prek-only; matches if any glob matches)
files = { glob = ["src/**/*.rs", "crates/**/src/**/*.rs"] }
```

```yaml
# Regex (portable to pre-commit)
files: "\\.rs$"

# Glob (prek-only)
files:
  glob: "src/**/*.rs"

# Glob list (prek-only; matches if any glob matches)
files:
  glob:
    - "src/**/*.rs"
    - "crates/**/src/**/*.rs"
```

### `exclude`

Global *exclude* regex applied before hook-level filtering.

- Type: regex string (default, pre-commit compatible) **or** a prek-only glob pattern mapping
- Default: no global exclude filter

`exclude` is useful for generated folders, vendored code, or build outputs.

What path is matched?

Same as [`files`](#top-level-files): the pattern is evaluated against the file path **relative to the project root** (the directory containing the config).

prek-only globs

Like [`files`](#top-level-files), `exclude` supports `glob` (single glob or glob list) as a `prek` extension. For glob syntax details, see the [globset documentation](https://docs.rs/globset/latest/globset/#syntax).

Examples:

```toml
# Regex (portable to pre-commit)
exclude = "^target/"

# Glob (prek-only)
exclude = { glob = "target/**" }

# Glob list (prek-only)
exclude = { glob = ["target/**", "dist/**"] }
```

```yaml
# Regex (portable to pre-commit)
exclude: "^target/"

# Glob (prek-only)
exclude:
  glob: "target/**"

# Glob list (prek-only)
exclude:
  glob:
    - "target/**"
    - "dist/**"
```

Verbose regex example (useful for long allow/deny lists):

```toml
# `(?x)` enables "verbose" regex mode (whitespace and newlines are ignored).
exclude = """(?x)^(
  docs/|
  vendor/|
  target/
)"""
```

```yaml
# `(?x)` enables "verbose" regex mode (whitespace and newlines are ignored).
exclude: |
  (?x)^(
    docs/|
    vendor/|
    target/
  )
```

### `fail_fast`

Stop the run after the first failing hook.

- Type: boolean
- Default: `false`

This is a global default; individual hooks can also set `fail_fast`.

### `default_language_version`

Map a language name to the default [`language_version`](#language_version) used by hooks of that language.

- Type: map
- Default: none (hooks fall back to `language_version: default`)

Example:

```toml
default_language_version.python = "3.12"
default_language_version.node = "20"
```

```yaml
default_language_version:
  python: "3.12"
  node: "20"
```

`prek` treats [`language_version`](#language_version) as a version request (often a semver-like selector) and may install toolchains automatically. See [Difference from pre-commit](../../diff/).

### `default_stages`

Default [`stages`](#stages) used when a hook does not specify its own.

- Type: list of stage names
- Default: all stages

Allowed values:

- `manual`
- `commit-msg`
- `post-checkout`
- `post-commit`
- `post-merge`
- `post-rewrite`
- `pre-commit`
- `pre-merge-commit`
- `pre-push`
- `pre-rebase`
- `prepare-commit-msg`

### `default_install_hook_types`

Default Git shim name(s) installed by [`prek install`](../cli/#prek-install) when you don’t pass `--hook-type`.

- Type: list of `--hook-type` values
- Default: `[pre-commit]`

This controls which Git shims are installed (for example `pre-commit` vs `pre-push`). It is separate from a hook’s [`stages`](#stages), which controls when a particular hook is eligible to run.

Allowed values:

- `pre-commit`
- `pre-push`
- `commit-msg`
- `prepare-commit-msg`
- `post-checkout`
- `post-commit`
- `post-merge`
- `post-rewrite`
- `pre-merge-commit`
- `pre-rebase`

### `auto_update.cooldown_days`

prek-only

This top-level key is a `prek` extension and is not recognized by upstream `pre-commit`.

Project default cooldown for [`prek auto-update`](../cli/#prek-auto-update).

- Type: integer days, `0` to `255`
- Default: inherited from the user-level global config, or `0`
- CLI override: [`prek auto-update --cooldown-days <DAYS>`](../cli/#prek-auto-update)

```toml
[auto_update]
cooldown_days = 7
```

```yaml
auto_update:
  cooldown_days: 7
```

In workspace mode, this setting is scoped to the project config file that defines it. It applies only to that project and is not inherited by nested projects. Sub-projects use their own `auto_update` setting, then the user-level global config, then the default. If two projects use the same repo URL with different cooldown settings, [`prek auto-update`](../cli/#prek-auto-update) fetches the repo once but evaluates each project with its own cooldown.

### `minimum_prek_version`

prek-only

This key is a `prek` extension. Upstream `pre-commit` uses `minimum_pre_commit_version`, which `prek` intentionally ignores.

Require a minimum `prek` version for this config.

- Type: string (version)
- Default: unset

If the installed `prek` is older than the configured minimum, `prek` exits with an error.

Example:

```toml
minimum_prek_version = "0.2.0"
```

```yaml
minimum_prek_version: "0.2.0"
```

### `orphan`

prek-only

`orphan` is a `prek` workspace-mode feature and is not recognized by upstream `pre-commit`.

Workspace-mode setting to isolate a nested project from parent configs.

- Type: boolean
- Default: `false`

When `orphan: true`, files under this project directory are handled only by this project’s config and are not “seen” by parent projects.

Example:

```toml
orphan = true

[[repos]]
repo = "https://github.com/astral-sh/ruff-pre-commit"
rev = "v0.8.4"
hooks = [{ id = "ruff" }]
```

```yaml
orphan: true
repos:
  - repo: https://github.com/astral-sh/ruff-pre-commit
    rev: v0.8.4
    hooks:
      - id: ruff
```

See [Workspace Mode - File Processing Behavior](../../workspace/#file-processing-behavior) for details.

## Repo entries

Each item under `repos:` is a mapping that always contains a `repo:` key.

### Remote repository

Use this for hooks distributed in a separate repository.

Required keys:

- `repo`: repository location (commonly an https git URL)
- `rev`: version to use (tag, branch, or commit SHA)
- `hooks`: list of hook selections

Remote hook definitions live inside the hook repository itself in the `.pre-commit-hooks.yaml` manifest (at the repo root). Your config only selects hooks by `id` and optionally overrides options. See [Authoring Hooks](../../authoring-hooks/) if you maintain a hook repository.

#### `repo`

Where to fetch hooks from.

In most configs this is a git URL. `prek` also recognizes special values documented separately: `local`, `meta`, and `builtin`.

#### `rev`

The revision to use for the remote repository.

Use a tag or commit SHA for repeatable results. If you use a moving target (like a branch name), runs may change over time.

#### `hooks`

The list of hooks to enable from that repository.

Each item must at least specify `id`. You can also add hook-level options (filters, args, stages, etc.) to customize behavior.

Example:

```toml
[[repos]]
repo = "https://github.com/astral-sh/ruff-pre-commit"
rev = "v0.8.4"
hooks = [{ id = "ruff", args = ["--fix"] }]
```

```yaml
repos:
  - repo: https://github.com/astral-sh/ruff-pre-commit
    rev: v0.8.4
    hooks:
      - id: ruff
        args: [--fix]
```

Notes:

- For reproducibility, prefer immutable pins (tags or commit SHAs).
- [`prek auto-update`](../cli/#prek-auto-update) can help update [`rev`](#rev) values.

### `repo: local`

Define hooks inline inside your repository.

Keys:

- `repo`: must be `local`
- `hooks`: list of **local hook definitions** (see [Local hook definition](#local-hook-definition))

Example:

```toml
[[repos]]
repo = "local"
hooks = [
  {
    id = "cargo-fmt",
    name = "cargo fmt",
    language = "system",
    entry = "cargo fmt",
    files = "\\.rs$",
  },
]
```

```yaml
repos:
  - repo: local
    hooks:
      - id: cargo-fmt
        name: cargo fmt
        language: system
        entry: cargo fmt
        files: "\\.rs$"
```

### `repo: meta`

Use `pre-commit`-style meta hooks that validate and debug your configuration.

`prek` supports the following meta hook ids:

- `check-hooks-apply`
- `check-useless-excludes`
- `identity`

Restrictions:

- `id` is required.
- `entry` is not allowed.
- `language` (if set) must be `system`.

You may still configure normal hook options such as [`files`](#hook-files-exclude), [`exclude`](#hook-files-exclude), [`stages`](#stages), etc.

Example:

```toml
[[repos]]
repo = "meta"
hooks = [{ id = "check-useless-excludes" }]
```

```yaml
repos:
  - repo: meta
    hooks:
      - id: check-useless-excludes
```

### `repo: builtin`

prek-only

`repo: builtin` is specific to `prek` and is not compatible with upstream `pre-commit`.

Use `prek`’s built-in fast hooks (offline, zero setup).

Restrictions:

- `id` is required.
- `entry` is not allowed.
- `language` (if set) must be `system`.

Example:

```toml
[[repos]]
repo = "builtin"
hooks = [
  { id = "trailing-whitespace" },
  { id = "check-yaml" },
]
```

```yaml
repos:
  - repo: builtin
    hooks:
      - id: trailing-whitespace
      - id: check-yaml
```

For the list of available built-in hooks and the “automatic fast path” behavior, see [Built-in Fast Hooks](../../builtin/).

## Hook entries

Hook items under `repos[*].hooks` have slightly different shapes depending on the repo type.

### Remote hook selection

For a remote repo, the hook entry must include:

- `id` (required): selects the hook from the repository

All other hook keys are optional overrides (for example [`args`](#args), [`files`](#hook-files-exclude), [`exclude`](#hook-files-exclude), [`stages`](#stages), …).

Advanced overrides

`prek` also supports overriding `name`, `entry`, and `language` for remote hooks. This can be useful for experimentation, but it may reduce portability to the original `pre-commit`.

### Local hook definition

For `repo: local`, the hook entry is a full definition and must include:

- `id` (required): stable identifier used by [`prek run <id>`](../cli/#prek-run) and selectors
- `name` (required): label shown in output
- `entry` (required): command to execute
- `language` (required): how `prek` sets up and runs the hook

### Builtin/meta hook selection

For `repo: builtin` and `repo: meta`, the hook entry must include `id`. You can optionally provide `name` and normal hook options (filters, [`stages`](#stages), etc), but not `entry`.

## Common hook options

These keys can appear on hooks (remote/local/builtin/meta), subject to the restrictions above.

### `id`

The stable identifier of the hook.

- For remote hooks, this must match a hook id defined by the remote repository.
- For local hooks, you choose it.

`id` is also used for CLI selection (for example [`prek run <id>`](../cli/#prek-run) and [`PREK_SKIP`](../environment-variables/#prek_skip)).

Hook ids containing `:`

If your hook id contains `:` (for example `id: lint:ruff`), `prek run lint:ruff` will not select that hook. `prek` interprets `lint:ruff` as the selector `<project-path>:<hook-id>`, with project `lint` and hook `ruff`. To select the hook id `lint:ruff`, add a leading `:` and run `prek run :lint:ruff`.

### `name`

Human-friendly label shown in output.

- Required for `repo: local` hooks.
- Optional as an override for remote/meta/builtin hooks.

### `entry`

The command line to execute for the hook.

- Required for `repo: local` hooks.
- Optional override for remote hooks.
- Not allowed for `repo: meta` and `repo: builtin`.

If [`pass_filenames`](#pass_filenames) is `true`, `prek` appends matching filenames to this command when running.

### `shell`

prek-only

`shell` is a `prek` extension and may not be recognized by upstream `pre-commit`.

Run `entry` through a predefined shell adapter.

- Type: one of `sh`, `bash`, `pwsh`, `powershell`, `cmd`
- Default: `null` (run `entry` directly without a shell)

When `shell` is omitted, `prek` preserves the default no-shell behavior: it parses `entry` into argv, invokes the command directly, and appends [`args`](#args) and matching filenames as process arguments.

When `shell` is set, `entry` is treated as source for that shell. `prek` writes the source to a temporary script file, runs it with the selected shell adapter, and passes hook [`args`](#args) followed by matching filenames as script arguments.

| `shell`      | Adapter command                                        | Script arguments |
| ------------ | ------------------------------------------------------ | ---------------- |
| `bash`       | `bash --noprofile --norc -eo pipefail <script>`        | `"$@"`           |
| `sh`         | `sh -e <script>`                                       | `"$@"`           |
| `pwsh`       | `pwsh -NoProfile -NonInteractive -File <script>`       | `$args`          |
| `powershell` | `powershell -NoProfile -NonInteractive -File <script>` | `$args`          |
| `cmd`        | `cmd /D /E:ON /V:OFF /S /C CALL <script>`              | `%*`             |

```toml
[[repos]]
repo = "local"
hooks = [
  {
    id = "test-all",
    name = "test-all",
    language = "system",
    entry = """
    uv run --python=3.10 --isolated pytest
    uv run --python=3.11 --isolated pytest
    """,
    shell = "bash",
    pass_filenames = false,
  },
]
```

```yaml
repos:
  - repo: local
    hooks:
      - id: test-all
        name: test-all
        language: system
        entry: |
          uv run --python=3.10 --isolated pytest
          uv run --python=3.11 --isolated pytest
        shell: bash
        pass_filenames: false
```

Unsupported languages

`shell` is rejected for language backends that do not run `entry` through the shell-aware entry resolver, and for `repo: meta` and `repo: builtin` hooks.

| Language                         | Why `shell` is unsupported                                                                                |
| -------------------------------- | --------------------------------------------------------------------------------------------------------- |
| `docker`, `docker_image`         | `entry` participates in container image or entrypoint selection instead of direct host process execution. |
| `dart`                           | Dart package config injection requires `entry` to resolve to a direct `dart` command.                     |
| `fail`                           | `entry` is the failure message body.                                                                      |
| `julia`, `rust`                  | `entry` participates in install/runtime package resolution and is split before execution.                 |
| `pygrep`                         | `entry` is the regex pattern.                                                                             |
| `conda`, `coursier`, `perl`, `r` | The language backend is not implemented yet.                                                              |

### `language`

How `prek` should run the hook (and whether it should create a managed environment).

- Required for `repo: local` hooks.
- Optional override for remote hooks.
- Not allowed (except as `system`) for `repo: meta` and `repo: builtin`.

Common values include `system`, `python`, `node`, `rust`, `golang`, `ruby`, and `docker`.

See [Language Support](../../languages/) for per-language behavior, supported values, and [`language_version`](#language_version) details.

Language name aliases

For compatibility with upstream `pre-commit`, the following legacy language names are also accepted:

- `unsupported` is treated as `system`
- `unsupported_script` is treated as `script`

### `alias`

An alternate identifier for selecting the hook from the CLI.

If set, you can run the hook via either [`prek run <id>`](../cli/#prek-run) or [`prek run <alias>`](../cli/#prek-run).

### `args`

Extra arguments appended to the hook’s `entry`.

- Type: list of strings

Example:

```toml
hooks = [{ id = "ruff", args = ["--fix"] }]
```

```yaml
hooks:
  - id: ruff
    args: [--fix]
```

### `env`

prek-only

`env` is a `prek` extension and may not be recognized by upstream `pre-commit`.

Extra runtime environment variables for the hook process.

- Type: map of string to string

Values override the existing process environment (including variables such as `PATH`). They are applied when the hook runs, not when `prek` installs or prepares the hook environment.

For remote hooks, `env` may also be set by the hook author in `.pre-commit-hooks.yaml`. Values from the project configuration are merged with manifest values and override duplicate keys.

For `docker` / `docker_image` hooks, these variables are passed into the container rather than being applied to the container runtime command.

Example:

```toml
[[repos]]
repo = "local"
hooks = [
  {
    id = "cargo-doc",
    name = "cargo doc",
    language = "system",
    entry = "cargo doc --all-features --workspace --no-deps",
    env = { RUSTDOCFLAGS = "-Dwarnings" },
    pass_filenames = false,
  },
]
```

```yaml
repos:
  - repo: local
    hooks:
      - id: cargo-doc
        name: cargo doc
        language: system
        entry: cargo doc --all-features --workspace --no-deps
        env:
          RUSTDOCFLAGS: -Dwarnings
        pass_filenames: false
```

### `files` / `exclude`

Filters applied to candidate filenames.

- `files` selects which files are eligible for the hook.
- `exclude` removes files matched by `files`.

If you use both global and hook-level filters, the effective behavior is “global filter first, then hook filter”.

By default (and for compatibility with upstream `pre-commit`), these are regex strings. As a `prek` extension, you can also specify globs using `glob` or a glob list.

See [Top-level `files`](#top-level-files) and [Top-level `exclude`](#top-level-exclude) for syntax notes and examples.

### `types` / `types_or` / `exclude_types`

File-type filters based on [`identify`](https://pre-commit.com/#filtering-files-with-types) tags.

Tip

Use [`prek util identify <path>`](../cli/#prek-util-identify) to see how prek tags a file when you’re troubleshooting `types` filters.

Compared to regex-only filtering ([`files` / `exclude`](#hook-files-exclude)), tag-based filtering is often easier and more robust:

- tags can match by **file extension** *and* by **shebang** (for extensionless scripts)
- you can easily exclude things like **symlinks** or **binary files**

Common tags include:

- `file`, `text`, `binary`, `symlink`, `executable`
- language-ish tags such as `python`, `rust`, `javascript`, `yaml`, `toml`, ...
- `types`: all listed tags must match (logical AND)
- `types_or`: at least one listed tag must match (logical OR)
- `exclude_types`: tags that disqualify a file

How these combine:

- [`files` / `exclude`](#hook-files-exclude), `types`, and `types_or` are combined with **AND**.
- Tags within `types` are combined with **AND**.
- Tags within `types_or` are combined with **OR**.

Defaults:

- `types`: `[file]` (matches all files)
- `types_or`: `[]`
- `exclude_types`: `[]`

These filters are applied in addition to regex filtering.

Examples:

```toml
[[repos]]
repo = "local"
hooks = [
  # AND: must be under `src/` AND have the `python` tag
  {
    id = "lint-py",
    name = "Lint (py)",
    language = "system",
    entry = "python -m ruff check",
    files = "^src/",
    types = ["python"],
    exclude_types = ["symlink"]
  },

  # OR: match any of the listed tags under `web/`
  {
    id = "lint-web",
    name = "Lint (web)",
    language = "system",
    entry = "npm run lint",
    files = "^web/",
    types_or = ["javascript", "jsx", "ts", "tsx"]
  },
]
```

```yaml
repos:
  - repo: local
    hooks:
      - id: lint-py
        name: Lint (py)
        language: system
        entry: python -m ruff check
        files: ^src/
        types: [python]
        exclude_types: [symlink]

      - id: lint-web
        name: Lint (web)
        language: system
        entry: npm run lint
        files: ^web/
        types_or: [javascript, jsx, ts, tsx]
```

If you need to match a path pattern that doesn’t align with a hook’s default `types` (common when reusing an existing hook in a nonstandard way), override it back to “all files” and use [`files`](#hook-files-exclude):

```toml
[[repos]]
repo = "meta"
hooks = [
  {
    id = "check-hooks-apply",
    types = ["file"],
    files = "\\.(yaml|yml|myext)$"
  },
]
```

```yaml
repos:
  - repo: meta
    hooks:
      - id: check-hooks-apply
        types: [file]
        files: \.(yaml|yml|myext)$
```

### `always_run`

Run the hook even when no files match.

- Type: boolean
- Default: `false`

This is commonly used for hooks that check repository-wide state (for example, running a test suite) rather than operating on specific files.

### `pass_filenames`

Controls whether `prek` appends the matching filenames to the command line.

- Type: boolean or positive integer
- Default: `true` which passes all matching filenames

Set `pass_filenames: false` for hooks that don’t accept file arguments (or that discover files themselves).

Set `pass_filenames: n` (a positive integer) to limit each invocation to at most `n` filenames. When there are more matching files than `n`, `prek` splits them across multiple invocations. Those invocations may run concurrently unless [`require_serial`](#require_serial) is `true`. This is useful for tools that can only process a limited number of files at once.

Prek will automatically limit the number of filenames to ensure command lines don’t exceed the OS limit, even when `pass_filenames: true`.

prek-only

`pass_filenames: n` with a positive integer is a `prek` extension. Upstream `pre-commit` only accepts a boolean value.

### `stages`

Declare which stages a hook is eligible to run in.

- Type: list of stage names
- Default: all stages

Allowed values:

- `manual`
- `commit-msg`
- `post-checkout`
- `post-commit`
- `post-merge`
- `post-rewrite`
- `pre-commit`
- `pre-merge-commit`
- `pre-push`
- `pre-rebase`
- `prepare-commit-msg`

When you run [`prek run --hook-stage <stage>`](../cli/#prek-run), only hooks configured for that stage are considered.

### `require_serial`

Force a hook to run without parallel invocations (one in-flight process for that hook at a time).

- Type: boolean
- Default: `false`

This is useful for tools that use global caches/locks or otherwise can’t handle concurrent execution.

### `priority`

prek-only

`priority` controls `prek`'s scheduler and does not exist in upstream `pre-commit`.

Each hook can set an explicit `priority` (a non-negative integer) that controls when it runs and with which hooks it may execute in parallel.

Scope:

- `priority` is evaluated **within a single configuration file** and is compared across **all hooks in that file**, even if they appear under different `repos:` entries.
- `priority` does **not** coordinate across different config files. In workspace mode, each project’s config file is scheduled independently.

Hooks run in ascending priority order: **lower `priority` values run earlier**. Hooks that share the same `priority` value run concurrently, subject to the global concurrency limit.

When `priority` is omitted, `prek` assigns an implicit value based on hook order to preserve sequential behavior.

Example:

```toml
[[repos]]
repo = "local"
hooks = [
  {
    id = "format",
    name = "Format",
    language = "system",
    entry = "python3 -m ruff format",
    always_run = true,
    priority = 0,
  },
  {
    id = "lint",
    name = "Lint",
    language = "system",
    entry = "python3 -m ruff check",
    always_run = true,
    priority = 10,
  },
  {
    id = "tests",
    name = "Tests",
    language = "system",
    entry = "just test",
    always_run = true,
    priority = 20,
  },
]
```

```yaml
repos:
  - repo: local
    hooks:
      - id: format
        name: Format
        language: system
        entry: python3 -m ruff format
        always_run: true
        priority: 0

      - id: lint
        name: Lint
        language: system
        entry: python3 -m ruff check
        always_run: true
        priority: 10

      - id: tests
        name: Tests
        language: system
        entry: just test
        always_run: true
        priority: 20
```

Parallel hooks modifying files

If two hooks run in the same priority group and both mutate the same files (or depend on shared state), results are undefined. Use separate priorities to avoid overlap.

Hooks modifying files without a non-zero exit code

If a hook modifies files without emitting a non-zero exit code (e.g. `ruff format`), the priority group as a whole will fail. It is not possible for prek to attribute the failure to a specific hook in the group which modified files. Use separate priorities for clearer failure attribution.

`require_serial` is different

[`require_serial`](#require_serial) set to `true` prevents concurrent invocations of the *same hook*. It does not prevent other hooks from running alongside it; use a unique `priority` if you need exclusivity.

### `fail_fast`

Hook-level fail-fast behavior.

- Type: boolean
- Default: `false`

If `true`, a failure in this hook stops the run immediately.

### `verbose`

Print hook output even when the hook succeeds.

- Type: boolean
- Default: `false`

### `log_file`

Write hook output to a file when the hook fails (and also when `verbose: true`).

- Type: string path

### `description`

Free-form description shown in listings / metadata.

- Type: string

### `language_version`

Choose the language/toolchain version request for this hook.

- Type: string
- Default: `default`

If not set, `prek` may use [`default_language_version`](#default_language_version) for the hook’s language.

prek-only

`language_version` is treated as a **version request**, not a single pinned value. For languages that use semver requests, you can specify ranges (for example `^1.2`, `>=1.5, <2.0`).

Special values:

- `default`: use the language’s default resolution logic.
- `system`: require a system-installed toolchain (no downloads).

Language-specific behavior:

- Python: passed to the Python resolver (for example `python3` or `python3.12`). May trigger toolchain download.
- Node: passed to the Node resolver (for example `20`, `18.19.0`). May trigger toolchain download.
- Go: uses Go version strings such as `1.22.1` (downloaded if missing).
- Rust: supports rustup toolchains such as `stable`, `beta`, `nightly`, or versioned toolchains.
- Other languages: parsed as a semver request and matched against the installed toolchain version.

Examples:

```toml
hooks = [
  { id = "ruff", language = "python", language_version = "3.12" },
  { id = "eslint", language = "node", language_version = "20" },
  { id = "cargo-fmt", language = "rust", language_version = "stable" },
  { id = "my-tool", language = "system", language_version = "system" },
]
```

```yaml
hooks:
  - id: ruff
    language: python
    language_version: "3.12"

  - id: eslint
    language: node
    language_version: "20"

  - id: cargo-fmt
    language: rust
    language_version: stable

  - id: my-tool
    language: system
    language_version: system
```

### `additional_dependencies`

Extra dependencies for hooks that run inside a managed environment (for example Python or Node hooks).

- Type: list of strings

If you set this for a language that doesn’t support dependency installation, `prek` fails with a configuration error.

### `minimum_prek_version`

prek-only

This is a `prek`-specific requirement gate. Upstream `pre-commit` does not have a hook-level minimum version key.

Require a minimum `prek` version for this specific hook.

- Type: string (version)
- Default: unset

For process environment controls, see the [Environment Variable Reference](../environment-variables/).