windbag

A pre-commit linter that catches comments narrating a change — a ticket number, what the code used to do, hedging about whether it works — instead of documenting the constraint that makes the current code correct. Checks Python, JavaScript/TypeScript, Terraform/HCL, Rust, Go, Java, and SQL (including dbt and SQLMesh templates), plus the markup formats that carry comments: YAML, HTML, and Markdown.

What it detects

error rules fail the check; warn rules are reported but don't block.

Markup files

YAML comments (#) come from the YAML grammar, so a # inside a quoted scalar stays data rather than becoming a comment. HTML and Markdown are checked through <!-- ... -->; in Markdown, anything inside a fenced code block is sample markup, not a comment, and is skipped.

The content rules — TICKET_ID, HISTORY_NARRATION, HEDGE_LANGUAGE, CROSS_FILE_REF — carry the weight here. VERBOSE_COMMENT does not apply: a few lines of explanation above a one-line config key is the idiomatic shape in a config file, not a comment outgrowing its code.

SQL files

.sql files are read as Jinja-templated SQL, which is what dbt and SQLMesh models are. --, /* */, and Jinja {# ... #} comments are all checked. A marker inside a 'string', a "quoted identifier", a $$ ... $$ body, or a {{ ... }} / {% ... %} tag is data the template emits, not a comment. The scanner is dialect-agnostic, so Snowflake, Postgres, BigQuery, and the rest all work; MySQL-style # line comments are the one form it does not read.

A comment is measured against the statement below it: the non-blank lines that follow, through the first one ending in ;.

Install

From PyPI — prebuilt wheels for macOS, Linux, and Windows, no Rust toolchain required:

pip install windbag
# or
uv tool install windbag

Run it without installing anything:

uvx windbag check --all

Building from source instead needs a Rust toolchain. If you don't have one:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
. "$HOME/.cargo/env"    # and add this line to ~/.zshrc

Then, from a checkout:

cargo install --path .

That puts windbag in ~/.cargo/bin, which must be on your PATH. This repo builds as a Python wheel via maturin's bindings = "bin" mode, which just wraps the compiled binary — there's no Python code here, and import windbag doesn't work:

uvx maturin build --release
uvx --from target/wheels/windbag-*.whl windbag check --all

Use

windbag init                  # write windbag.toml with generic defaults
windbag check --staged        # check what's about to be committed
windbag check --all           # check every git-tracked file in the repo
windbag check --json --staged # machine-readable output
windbag check --new-only f.py # only comments on lines the working tree adds over HEAD

When run interactively, bulk --all and --staged checks show progress on stderr. Progress is suppressed for --json, CI, hooks, and other non-terminal callers so their output remains machine-readable.

Pre-commit:

- repo: local
  hooks:
    - id: windbag
      name: windbag
      entry: windbag check --staged
      language: system
      pass_filenames: false
      types_or: [python, javascript, jsx, ts, tsx, terraform, rust, yaml, markdown, html, sql, go, java]

(windbag needs to already be on PATH — language: system doesn't install it for you.)

Claude Code plugin

Pre-commit catches slop after it's written. The plugin catches it as it's written: a PostToolUse hook runs windbag on every file Claude edits and exits non-zero on a violation, so the findings go straight back to Claude as a blocking error and it rewrites the comment before moving on. A SessionStart hook states the rules up front so most edits never trip the linter at all.

/plugin marketplace add scale-venture-partners/windbag
/plugin install windbag@windbag

The plugin ships the hooks, not the linter, so the binary also has to be on PATH. The SessionStart hook installs it automatically on first use, via whichever of uv tool install windbag, pipx install windbag, or pip install --user windbag it finds first; if none of those are on PATH either, it exits quietly and the PostToolUse hook stays a no-op until windbag shows up some other way. To install it yourself instead — a locked-down machine with no package-manager network access, say — see Install.

To turn it on for everyone working in a given repo, commit this to that repo's .claude/settings.json. Anyone who opens the repo is prompted to trust the marketplace, and the hooks apply from their next session:

{
  "extraKnownMarketplaces": {
    "windbag": {
      "source": { "source": "github", "repo": "scale-venture-partners/windbag" }
    }
  },
  "enabledPlugins": { "windbag@windbag": true }
}

Working on the plugin itself? /plugin marketplace add /path/to/windbag points at a local checkout instead. Either way the install copies plugin/ into ~/.claude/plugins/cache/ — keeping it out of the repo root is what keeps target/ out of the copy. That copy is a snapshot: after editing a hook, reinstall to pick up the change.

The hook needs windbag on PATH (or WINDBAG_BIN set) and jq installed; without either it exits quietly rather than breaking the session.

Only comments on lines the working tree adds over HEAD are reported, so editing a file doesn't re-litigate comments that were already there. Claude is told not to silence a rule with windbag: ignore on its own — a false positive should surface to you, not get suppressed.

/windbag sweeps the whole repo and fixes what it finds.

Suppress a false positive inline:

# Was missing until v2 (LEGACY-1) — kept for the changelog.  windbag: ignore[TICKET_ID]

Config lives in windbag.toml; see examples/scalevp.toml for narrowing TICKET_ID to a real tracker prefix instead of the generic default.

Examples

main.tf:218  error TICKET_ID          comment references a ticket ID (SCA-533) — that
                                       context belongs in the commit message or PR
                                       description, not the code
main.tf:218  error HISTORY_NARRATION  comment narrates the change ("was missing")
                                       instead of the current state — describe the
                                       constraint, not the history
main.tf:218  warn  VERBOSE_COMMENT    comment block is long relative to what it
                                       documents (7 comment lines, 7.0x the 1 attached
                                       code line(s))

# Was missing entirely (SCA-533): this used to silently no-op.  <- TICKET_ID, HISTORY_NARRATION
value = fetch_value()

# This should work but I'm not sure why it fails sometimes.       <- HEDGE_LANGUAGE
retry(fetch_value)

# increment the counter                                           <- OBVIOUS_COMMENT
counter += 1

# TODO(SCA-600): revisit after Q3 pricing model ships              <- clean, exempt
schedule_followup()

# Sorted DESC because the caller assumes the first row is newest.  <- clean, real WHY
return sorted(items, reverse=True)

# Was missing (SCA-533): the deploy no longer fails.  <- TICKET_ID, HISTORY_NARRATION
steps:
  - checkout

# Pinned because the orb syntax below requires 2.1.   <- clean, real WHY
version: 2.1

In Markdown, a comment shown as sample markup inside a fence is content:

<!-- Was missing (SCA-533): renders wrong without it. -->   <- TICKET_ID, HISTORY_NARRATION

```html
<!-- Was missing (SCA-901): this one is an example. -->     <- clean, inside a fence
```

License

MIT © Scale Venture Partners.

About Scale Venture Partners

We back the few who can go the distance. Scale Venture Partners partners with early-stage AI companies on the journey from founder-led growth to a go-to-market machine. scalevp.com