## TL;DR
The runner image does not ship reviewdog. Install it in a step before the review step, pin the version so builds stay reproducible, and the command resolves. This is a missing tool, not a config bug.

## The error
```text
error: reviewdog: not found: install reviewdog before running the review step
```

## Steps

### 1. Confirm it is really missing
Add a debug step or check the log for the command resolution:
```bash
which reviewdog || echo "not installed"
```
Expected output: "not installed", confirming the diagnosis.

### 2. Install with the official setup action
Add this step before the review step:
```yaml
- uses: reviewdog/action-setup@v1
  with:
    reviewdog_version: v0.17.2
```
Expected output: reviewdog lands on PATH at the pinned version.

### 3. Or install with go install
On runners with Go available:
```bash
go install github.com/reviewdog/reviewdog/cmd/reviewdog@v0.17.2
```
Make sure the Go bin directory is on PATH afterward.
Expected output: `reviewdog --version` prints v0.17.2.

### 4. Pin the version everywhere
Use the same pinned version in every workflow that calls reviewdog. Unpinned installs drift and break flag compatibility.
Expected output: all review steps report the same version.

### 5. Re-run the review step
Expected output: reviewdog runs instead of the not-found error.

## When to use
- The exact "reviewdog: not found" error
- New workflows or new runner images
- Self-hosted runners with minimal tooling

## When not to use
- reviewdog flag or usage errors (it installed but the call is wrong)
- Diff, filter, or annotation failures
- Permission errors posting reviews

## Tool compatibility
- reviewdog/action-setup v1
- Go toolchain 1.20 and later for go install
- GitHub-hosted and self-hosted runners

## Variant phrasings
### reviewdog command not found in GitHub Actions
Same fix. The hosted images do not include it.

### install reviewdog in CI pipeline
The setup action is the shortest path. Pin the version.

### reviewdog version mismatch between jobs
Pin one version in a shared workflow or a central env var and reference it everywhere.

## Why it happens
GitHub-hosted runner images include common tools but not reviewdog. A step that calls it directly fails at command resolution before reviewdog ever runs, which is why the error message tells you to install it first.

## Edge cases
- Self-hosted runners: install once on the image instead of per run to save time.
- PATH issues: go install puts the binary in the Go bin dir. Add it to PATH or the next step still cannot find it.
- Version drift: a floating install can pull a release that renames flags. Pinning avoids surprise breakage.
- Caching: cache the tool directory on self-hosted runners to keep installs fast.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_ODWMkxp0zeuJkGIaIvyWFw