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Getting started

As a global tool:

dotnet tool install -g Nullean.Curb

Ships as a native-AOT binary for linux-x64, linux-arm64, win-x64, win-arm64 and osx-arm64, with a portable fallback for everything else. About 10 ms to start. Installing requires the .NET 10 SDK.

To have your build do the formatting instead — which is usually what you want — see the build integration.

curb format ./src
curb check ./src
  1. rewrite files in place
  2. exit non-zero if anything would change

Out of the box Curb uses Roslyn's defaults, which are the same defaults Visual Studio and Rider use. On a repository that is already IDE0055-clean, curb format should change nothing.

Reflow is opt-in. Add max_line_length = 120 to your .editorconfig and Curb wraps long lines; omit it and line lengths are never changed. The first run on an existing repository is a large commit. See Reflow for what the key does, what each mode costs, and which ReSharper wrapping keys need a width.

There is no second config file to learn. Curb reads your .editorconfig:

[*.cs]
indent_style = tab
max_line_length = 120
csharp_new_line_before_open_brace = all
csharp_space_after_cast = false
csharp_preserve_single_line_blocks = true
csharp_prefer_braces = true
csharp_style_namespace_declarations = file_scoped
  1. omit, or set off, for no reflow and preserved line breaks

All 39 IDE0055 formatting options are supported, plus the 8 core EditorConfig keys, plus a set of syntax-level code style and wrapping options — around 90 keys in total.

Unrecognised or not-yet-implemented keys are reported, not silently ignored, with a "did you mean" suggestion for likely typos. Semantic code style keys are passed over deliberately, because they belong to a tool that loads a compilation.

When output surprises you, this is the first thing to run:

curb print-config Program.cs

It prints every resolved option for that specific file, the value in force, and any diagnostics — so you can see what your .editorconfig cascade actually produced rather than what you expected. Options are resolved per file, not per directory, because a section can discriminate on filename.

Command What it does
curb format <path> Format files in place.
curb check <path> Exit non-zero if anything would change. Writes nothing.
curb print-config <file> Show every resolved option for a file, and any diagnostics.
curb doc-tree <file> Dump the internal document IR. A debugging aid.
curb --version
Flag Applies to What it does
-f, --files <path> format, check Work on only these files, instead of walking a directory. Repeatable.
--msbuild-list-file <path> format, check Work on the paths listed in this file, one per line, instead of walking a directory. What the build integration passes, since a compile set can be too long for a command line.
-c, --cache <path> format, check Skip files a previous run watched format to themselves. The caller names the path — there is no ambient cache. The build integration uses obj/curb.cache; a pre-commit hook uses .git/curb.cache. Ignored with --coverage.
--coverage check Report which syntax kinds are still emitted verbatim, and how often.
--no-verify format, check Skip re-parsing the output to prove the token stream is unchanged. Not recommended — see Safety.

obj/ and bin/ are skipped automatically.

Code Meaning
0 Success.
1 check found files that would change.
2 Unknown command.
3 A file failed verification, or a named path did not exist.

Only 1 means "your code needs formatting". Anything else means Curb did not do its job, which is why the build integration treats them differently.

  • Why Curb — why it's fast, why it doesn't fight dotnet format, and why running inside the build matters.
  • The two passes — what Curb will and will not touch.
  • Integrations — the argument for putting this in your build rather than in your agent's instructions.