> ## Documentation Index
> Fetch the complete documentation index at: https://docs.decktalk.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Build in CI and offline

> Run DeckTalk in GitHub Actions or any CI with a silent build and cue verification, cache Chromium and ffmpeg, and render equations offline with the vendored KaTeX.

A silent build needs no API key and no network once the tools are cached, so a project
can be built and verified on every push. This is how DeckTalk's own repository does it.

## The commands

```console theme={null}
decktalk setup                            # Chromium, ffmpeg, and KaTeX, into per-user caches
decktalk doctor                           # exits 1 when a tool is missing
DECKTALK_VIDEO_PRESET=veryfast decktalk build --silent
decktalk verify 3:3.1eq 3:3.1p1 5:5.1a     # exits 1 when a cue did not land
decktalk shots                            # one PNG per step, worth uploading as an artifact
```

On Linux, `setup` passes `--with-deps` to Playwright so that Chromium's system libraries
are installed too. The verify command with a list of `SECTION:CUE` checks is the test:
`build` verifies section starts and cuts, and the cue checks measure each reveal in the
finished mp4. A silent build's placeholder track carries a click at every word start, so
the cue table also reports an `a/v` column, the picture's first change measured against
the click nearest the cue, and the job fails when the finished file's audio and picture
disagree by more than `max_offset_frames`. That makes a silent build a test of the whole
chain, not only of the cues.
[How it works](/concepts/how-it-works#what-verify-measures) explains the columns.

## A GitHub Actions job

```yaml .github/workflows/video.yml theme={null}
jobs:
  video:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7
      - uses: astral-sh/setup-uv@v10.1.0
      - run: uv tool install decktalk
      - name: Cache Chromium and ffmpeg
        uses: actions/cache@v4
        with:
          path: |
            ~/.cache/ms-playwright
            ~/.cache/decktalk
          key: browsers-${{ runner.os }}
      - run: decktalk setup
      - run: decktalk doctor
      - run: decktalk build --silent
        env:
          DECKTALK_VIDEO_PRESET: veryfast
      - run: decktalk verify 3:3.1eq 3:3.1p1 5:5.1a
      - uses: actions/upload-artifact@v7
        with:
          name: video
          path: build/out/*.mp4
```

Chromium lives in Playwright's cache, which is `~/.cache/ms-playwright` on Linux,
`~/Library/Caches/ms-playwright` on macOS, and `%LOCALAPPDATA%\ms-playwright` on Windows.
KaTeX lives in DeckTalk's own cache, which follows the same platform rule under a
`decktalk` directory, and `DECKTALK_CACHE_DIR` moves it. ffmpeg arrives with the
`static-ffmpeg` package, so it is cached with the Python environment.

To build a voiced video in CI, put `ELEVENLABS_API_KEY` and `ELEVENLABS_VOICE_ID` in the
job's secrets and export them. DeckTalk never prints either.

## Two flags that do not mix

The `--strict` flag makes a missing clip, a missing recording, or a loudness miss an
error. A silent build's mix is clicks and silence, so its loudness report is meaningless
and `--strict` would fail on it. Use `--strict` on voiced builds only.

## The project directory

Every project command takes `--project DIR`, and the `DECKTALK_PROJECT` variable sets
the default, so a job can run from the repository root.

```console theme={null}
DECKTALK_PROJECT=lessons/derivatives decktalk build --silent
```

## Offline

After `decktalk setup`, nothing needs the network. `decktalk init` copies the cached
KaTeX into `deck/katex/`, and the scaffold's page loads it from there. A project created
before `setup` ran loads KaTeX from a CDN instead, which fails offline and leaves every
equation as plain text with a `KATEX?` verdict in the check table. Run `setup`, then
either run `init` again into a fresh directory or copy the cached `katex` directory into
`deck/` and point the two tags at it.

```html deck/index.html theme={null}
<link rel="stylesheet" href="./katex/katex.min.css">
<script src="./katex/katex.min.js"></script>
```

A corporate proxy that blocks Playwright's download can be pointed elsewhere with
`PLAYWRIGHT_DOWNLOAD_HOST`, as Playwright documents.

## Next

[The CLI reference](/reference/cli#exit-codes) lists every exit code, and
[Troubleshooting](/help/troubleshooting) explains each verdict that a check can print.