Hunk video pipeline

Source-checkout only: the pipeline lives in scripts/launch-video/, which never ships to npm. It can be used for pull-request demos as well as maintainer release videos. Unix-only — the capture scripts exec /bin/bash.

Generates product videos where every terminal frame is the real Hunk TUI — no screen recording, no mockups. Three stages:

capture.ts   (bun)               drive Hunk over a PTY, snap styled keyframes to PNG
compose.mjs  (node + Playwright) render each PNG on a 1920x1080 HTML stage in Chromium
ffmpeg                           encode the composited PNGs at 30fps to mp4/webm

Playwright controls headless Chromium: for each planned frame it loads the terminal PNG onto the HTML stage, applies the window chrome, cards, captions, and transition state, then screenshots the completed stage back to PNG. ffmpeg sequences those composited screenshots into the final videos.

The generic machinery (PTY driving, keyframe rendering, storyboard planning, Chromium compositing, the stage template) is the @hunk/term-video workspace package in packages/term-video/; scripts/launch-video/ holds only Hunk's scenes, captions, and cards on top of it.

Choosing a recipe

The pipeline is not release-specific. Choose the editorial scope, then use the same capture → composite → encode stages:

• Single feature: a short demonstration of one capability or workflow. Use

the single-feature recipe below and capture only the required scene.

• Full release: a multi-feature roundup based on a release's changelog or

highlights. Use the full-release recipe and update the canonical storyboard.

• Custom video: author any set of scenes and SHOTS for tutorials,

comparisons, announcements, or workflow explainers; follow the scene and storyboard rules below.

Creating a video

Expect ~3–6 min for capture and ~2–4 min for compose — run both with a long timeout (or in the background); each logs per-snap / per-shot progress. compose.mjs needs node ≥ 18 on PATH (bun alone is not enough).

# 0. dependencies (tuistory is a devDependency; ghostty-opentui arrives transitively)
bun install    # if a postinstall hook fails in a sandbox, retry with --ignore-scripts

# 1. capture keyframes. Output defaults to <repo>/.video-work/ regardless of
#    cwd (pass a path argument to override), but the PROCESS must run from the
#    repo root — see gotchas.
bun run scripts/launch-video/capture.ts

# 2. one-time portable compositor setup. Playwright installs a Chromium build
#    that exactly matches its browser driver (see gotchas to reuse a system or
#    sandbox browser instead).
printf '{"name":"hunk-video-work","private":true}\n' > .video-work/package.json
cd .video-work
bun add playwright playwright-core
bunx playwright install chromium
cd ..

# 3. composite the storyboard
node scripts/launch-video/compose.mjs .video-work

# 4. encode
cd .video-work
ffmpeg -y -f concat -safe 0 -i concat.txt -vf "fps=30,format=yuv420p" \
  -c:v libx264 -preset slow -crf 18 -movflags +faststart launch.mp4
ffmpeg -y -f concat -safe 0 -i concat.txt -vf "fps=30,format=yuv420p" \
  -c:v libvpx-vp9 -b:v 0 -crf 32 -row-mt 1 launch.webm

Iterate on one scene without re-capturing the rest:

SCENES=review bun run scripts/launch-video/capture.ts   # comma-separated scene names

Scene names are the wants("...") guards in capture.ts's main(). Note SCENES= only narrows capture; compose.mjs preflights that every frame its SHOTS table references exists in frames/ and fails fast listing any missing ones, so a full composite still needs every scene captured at least once.

Single-feature recipe

For a short test, demo, or one-feature announcement, capture and composite only the scene for that feature:

1. Pick one user-visible capability and find its scene name in the

wants("...") guards. If it does not have a scene, author one using the guidance below. Capture only that scene:

``sh SCENES=review bun run scripts/launch-video/capture.ts ``

1. Make a scratch compositor beside the canonical one so its imports and

repo-relative paths continue to work:

``sh cp scripts/launch-video/compose.mjs scripts/launch-video/compose-one-feature.mjs ``

1. In the scratch copy, trim SHOTS to an opening card, only the selected

feature's frames, and an outro card. Rewrite those cards and captions for the scoped cut. Sequence lengths must still match the captured frame names.

1. Composite into the same work directory, then run the normal ffmpeg commands

with descriptive output names:

``sh node scripts/launch-video/compose-one-feature.mjs .video-work cd .video-work ffmpeg -y -f concat -safe 0 -i concat.txt -vf "fps=30,format=yuv420p" \ -c:v libx264 -preset slow -crf 18 -movflags +faststart hunk-feature-demo.mp4 ffmpeg -y -f concat -safe 0 -i concat.txt -vf "fps=30,format=yuv420p" \ -c:v libvpx-vp9 -b:v 0 -crf 32 -row-mt 1 hunk-feature-demo.webm cd .. rm scripts/launch-video/compose-one-feature.mjs ``

Keep the scratch compositor uncommitted. The canonical compose.mjs remains the checked-in reference storyboard. If you added a capture scene only to make PR evidence, revert that scene after encoding; retain it only when it is useful checked-in demo coverage and belongs to the submitted change.

Full-release recipe

1. Read the release section in CHANGELOG.md. If it has a hand-written

Highlights list (0.18.0 has one; Changesets does not generate them), use that list as the storyboard. Otherwise distill 4–6 user-visible headlines from the Minor Changes — per-PR entries are too granular to shoot — and confirm the shortlist with the user before capturing.

1. Rewrite the canonical storyboard's editorial surface (next section), adding

or adjusting capture scenes as needed (see "Authoring scenes").

1. Capture every scene referenced by the full storyboard, composite it, and

encode both formats using the main workflow above.

1. Verify the complete cut (see "Verification") and deliver both files. When hunk-release invoked this workflow, return the approved MP4 and WebM to that skill for versioned naming and GitHub user-attachment embedding; do not upload or edit the public release without its confirmation gate.

Per-video editorial surface

The capture machinery is reusable, but the storyboard is editorial content for one video. Rewrite it to match the video's scope. As of this writing, the checked-in reference storyboard is the full 0.18.0 release video:

• compose.mjs: the whole SHOTS table; OPEN_CARD (version badge);

OUTROCARD (headline, install commands, footer); EXTENSIONSCARD; every <span class="badge">NEW</span> in captions — a NEW badge is a claim about this release, so drop or move them as features age.

• capture.ts: the scene functions and the wants() guards in main() are

the current storyboard's scene list, plus hunk-side glue (launchHunk, launchHunkShell, createDemoRepo, the keyboard probe).

Reusable machinery lives in @hunk/term-video (packages/term-video/) — extend it there, don't fork it into the scripts: createKeyframer, launchApp/launchShell, createCommandWrapper, typeCommand, ensureKeyboardIsLive, makeSceneFilter (src/capture.ts); the unit-tested storyboard planner with the caption/timing semantics (src/plan.mjs); composeStoryboard with font/Chromium resolution and the missing-keyframe preflight (src/compose.mjs); and the stage template (src/stage.html).

Environment gotchas

Sandbox-specific bullets are marked; each cost real debugging time.

• Run capture.ts with bun from the repo root. tuistory uses subpath

self-imports (tuistory/pty) that only resolve inside this repo's node_modules; running the script from elsewhere resolves tuistory from bun's global cache and crashes. (Output location is unaffected — it defaults to <repo>/.video-work/ via import.meta.url.)

• ghostty-opentui is a transitive dep (via tuistory) with an exports map:

import "ghostty-opentui/image" (not .../dist/image.js), resolved relative to tuistory — @hunk/term-video/capture's createKeyframer does the Bun.resolveSync dance.

• Playwright must match the Chromium it drives. The portable setup above

installs playwright and playwright-core together, then downloads their matching Chromium build. It works on macOS and Linux and is preferred when bandwidth and browser downloads are available; leave CHROMIUM_PATH unset so Playwright uses that managed browser. On Linux, if Chromium reports missing system libraries, run bunx playwright install-deps chromium (it may require sudo) before retrying.

To reuse an existing system, CI, or sandbox Chromium instead, install the playwright-core version provided by that environment and set its executable explicitly:

``sh cd .video-work bun add playwright-core@<matching-version> cd .. CHROMIUM_PATH=/path/to/chromium node scripts/launch-video/compose.mjs .video-work ``

Common executable locations include $(command -v chromium) or $(command -v google-chrome) on Linux and /Applications/Google Chrome.app/Contents/MacOS/Google Chrome on macOS. In an environment with a preinstalled Playwright toolchain, read that toolchain's package.json to get the exact driver version. For example, the Anthropic sandbox exposes it through /opt/pw-browsers/.links/*:

``sh cat "$(cat /opt/pw-browsers/.links/* | head -1)/package.json" | grep '"version"' # e.g. "1.56.1" -> bun add [email protected] ``

compose.mjs picks its browser as $CHROMIUM_PATH, then /opt/pw-browsers/chromium when present, then Playwright's managed browser.

• Give .video-work/ its own package.json before bun add. Without

one, bun walks up and installs into the repo's package.json — revert with git checkout package.json bun.lock if that happens.

• Chromium needs --allow-file-access-from-files (already in

compose.mjs): the stage samples each keyframe through a canvas to color-match the window background, and file:// images taint the canvas without it.

• mp4 needs an ffmpeg with libx264. Sandbox: apt-get install ffmpeg

(run apt-get update first if packages 404). macOS: brew install ffmpeg. Verify ffmpeg -encoders | grep -E 'libx264|libvpx-vp9' shows both before encoding — playwright's bundled ffmpeg-*/ffmpeg-linux only does VP8/WebM and cannot produce the mp4.

• Caption font: JetBrains Mono ships inside ghostty-opentui;

findCaptionFont in packages/term-video/src/compose.mjs searches bun's isolated layout (nodemodules/.bun/nodemodules/…) then a hoisted nodemodules/…. If it still throws caption font not found, locate the file with find nodemodules -name jetbrains-mono-nerd.ttf and pass it as fontPath to composeStoryboard.

Authoring scenes (capture.ts)

• Shared geometry is 140x32 cells rendered at fontSize 16 / dpr 2 → 2688x1536

PNGs. Keep every scene at this size so all frames fit one window.

• Helpers: createDemoRepo() and launchHunkShell() are hunk-side glue in

the script (git repo built from examples/2-mini-app-refactor; interactive bash with a real hunk command on PATH and a clean ❯ prompt); snap, typeCommand, launchApp/launchShell, and createCommandWrapper come from @hunk/term-video/capture.

• Always waitForText on scene-specific content before the first snap, and

call ensureKeyboardIsLive() before scripted keypresses — the first key after startup can be dropped (real race, the helper toggles ? to prove keys land).

• Animation = one snap per keypress. Cursor walks and typing effects are

just every j/k/character captured as its own frame and played back at 0.2–0.3s per frame. Prefer this over sparse keyframes: three stills read as a slideshow, per-press frames read as motion.

• renderTerminalToImage auto-trims trailing blank rows, so short outputs

(CLI scenes) produce short PNGs — the stage handles this by sampling the image's bottom-left pixel and painting the window body to match.

• manifest.json is a capture-side inventory of the current run only;

compose.mjs ignores it (frames resolve by name from SHOTS), and after a SCENES= run it is partial while frames/ stays cumulative.

• Demo content that must exist: STML notes come from

examples/9-agent-markup-notes (launch with --experimental), extension scenes from examples/extensions/ loaded via --extension <path> (explicit paths skip the repo trust prompt). The pager pipe is git diff | hunk pager — bare hunk on piped stdin prints help. Sidebar toggle is s; comment draft is c, save with Ctrl+S (\x13).

Storyboard model (compose.mjs)

• SHOTS is the whole edit: one entry per shot, dur in seconds, played as

unique frames + per-frame durations in an ffmpeg concat list (holds cost one frame, so runtime is dominated by transitions, not length).

• capKey is caption identity: the caption slides in only when capKey

changes, and continuation shots that share a capKey without restating caption keep the previous caption on screen. Sequences (walks, typing) are generated with Array.from spreads.

• Sequence lengths must match capture loop bounds: walk("j", 10) in

capture.ts produces review-walk-00..09, consumed by Array.from({length: 9}) (+ the opening frame) in SHOTS. Change one side and the other breaks — the preflight check names any frame that's missing.

• enter: true fades/scales the surface in — use it for cards and the first

terminal shot only.

• Caption HTML vocabulary: <span class="badge">NEW</span> amber pill,

<span class="hl"> amber highlight, <span class="dim"> muted. Cards use badge / h1/h2 / sub / cmds+cmd / foot classes from packages/term-video/src/stage.html.

• Target pacing: money shots hold 3–4s, context shots 2–3s, typing/walk frames

0.2–0.6s; keep the total near 60s.

Content accuracy (learned the hard way)

• Verify install commands against reality, not the README: check

npm view hunkdiff dist-tags. A prerelease needs npm i -g hunkdiff@beta; brew install hunk only serves stable (homebrew-core Autobump, lags npm) — omit brew on prerelease cards.

• Label demo extensions as examples. The triage board, CSS palette, and

semver views are examples/extensions/, not shipped features — caption them with a dimmed example: prefix. The real features are the APIs (sidebars, file views, commands, dialogs).

• Window titles are decorative but must not lie: the shell scenes run bash,

so keep their titles generic (shell — …) rather than naming a shell the capture doesn't launch.

• STML requires --experimental; say so on the outro card.
• The video is silent — never imply audio in the video or its announcement copy.

Verification and delivery

• Eyeball keyframes in .video-work/frames/ (Read renders PNGs) after

capture — especially new scenes — before compositing.

• After encoding, return to the repository root, set VIDEO to the produced

MP4, and inspect a mid-animation point, each new scene, and the outro:

``sh VIDEO=.video-work/hunk-feature-demo.mp4 # or .video-work/launch.mp4 ffmpeg -y -ss 2 -i "$VIDEO" -frames:v 1 .video-work/check.png ffprobe -show_entries format=duration "$VIDEO" ``

Captions must persist through the extracted animation frames.

• Outputs stay under .video-work/: the full-release recipe creates

launch.mp4/launch.webm, while the single-feature recipe above creates hunk-feature-demo.mp4/hunk-feature-demo.webm. .video-work/ is gitignored — never commit the video or its frames. For a standalone video request, send both files to the user directly (mp4: social/Slack; webm: web embeds), report duration and file sizes, and flag if the mp4 exceeds ~10 MB (Slack) or ~15 MB (X). When invoked by hunk-release, hand both files back to that workflow instead; it owns versioned filenames, GitHub's user-attachment limit, public embedding, and inline-player verification. Copy them elsewhere only if the user names a destination.