cli-demo-generator

CLI Demo Generator

Create professional animated CLI demos. Four approaches, from fully automated to pixel-precise manual control.

Quick Start

Simplest path — give commands, get GIF:

python3 ${CLAUDE_SKILL_DIR}/scripts/auto_generate_demo.py \
  -c "npm install my-package" \
  -c "npm run build" \
  -o demo.gif

Self-bootstrapping demo — for repeatable recordings that clean their own state:

python3 ${CLAUDE_SKILL_DIR}/scripts/auto_generate_demo.py \
  -c "npm install my-package" \
  -c "npm run build" \
  -o demo.gif \
  --bootstrap "npm uninstall my-package 2>/dev/null" \
  --speed 2

Critical: VHS Parser Limitations

VHS Type strings cannot contain $, \", or backticks. These cause parse errors:

# FAILS — VHS parser rejects special chars
Type "echo \"hello $USER\""
Type "claude() { command claude \"$@\"; }"

Workaround: base64 encode the command, decode at runtime:

# 1. Encode your complex command
echo 'claude() { command claude "$@" 2>&1 | grep -v "noise"; }' | base64
# Output: Y2xhdWRlKCkgey4uLn0K

# 2. Use in tape
Type "echo Y2xhdWRlKCkgey4uLn0K | base64 -d > /tmp/wrapper.sh && source /tmp/wrapper.sh"

This pattern is essential for output filtering, function definitions, and any command with shell special characters.

Approaches

1. Automated Generation (Recommended)

python3 ${CLAUDE_SKILL_DIR}/scripts/auto_generate_demo.py \
  -c "command1" -c "command2" \
  -o output.gif \
  --title "My Demo" \
  --theme "Catppuccin Latte" \
  --font-size 24 \
  --width 1400 --height 600

Flag	Default	Description
-c	required	Command to include (repeatable)
-o	required	Output GIF path
--title	none	Title shown at start
--theme	Dracula	VHS theme name
--font-size	16	Font size in pt
--width	1400	Terminal width px
--height	700	Terminal height px
--bootstrap	none	Hidden setup command (repeatable)
--filter	none	Regex pattern to filter from output
--speed	1	Playback speed multiplier (uses gifsicle)
--no-execute	false	Generate .tape only

Smart timing: install/build/test/deploy → 3s, ls/pwd/echo → 1s, others → 2s.

2. Batch Generation

Create multiple demos from one config:

# demos.yaml
demos:
  - name: "Install"
    output: "install.gif"
    commands: ["npm install my-package"]
  - name: "Usage"
    output: "usage.gif"
    commands: ["my-package --help", "my-package run"]

python3 ${CLAUDE_SKILL_DIR}/scripts/batch_generate.py demos.yaml --output-dir ./gifs

3. Interactive Recording

Record a live terminal session:

bash ${CLAUDE_SKILL_DIR}/scripts/record_interactive.sh output.gif --theme "Catppuccin Latte"
# Type commands naturally, Ctrl+D when done

Requires asciinema (brew install asciinema).

4. Manual Tape File

For maximum control, write a tape directly. Templates in assets/templates/:

• basic.tape — simple command sequence
• interactive.tape — typing simulation
• self-bootstrap.tape — self-cleaning demo with hidden setup (recommended for repeatable demos)

Advanced Patterns

These patterns come from production use. See references/advanced_patterns.md for full details.

Self-Bootstrapping Demos

Demos that clean previous state, set up environment, and hide all of it from the viewer:

Hide
Type "cleanup-previous-state 2>/dev/null"
Enter
Sleep 2s
Type "clear"
Enter
Sleep 500ms
Show

Type "the-command-users-see"
Enter
Sleep 3s

The Hide → commands → clear → Show sequence is critical. clear wipes the terminal buffer so hidden commands don't leak into the GIF.

Output Noise Filtering

Filter noisy progress lines from commands that produce verbose output:

# Hidden: create a wrapper function that filters noise
Hide
Type "echo <base64-encoded-wrapper> | base64 -d > /tmp/w.sh && source /tmp/w.sh"
Enter
Sleep 500ms
Type "clear"
Enter
Sleep 500ms
Show

# Visible: clean command, filtered output
Type "my-noisy-command"
Enter
Sleep 3s

Frame Verification

After recording, verify GIF content by extracting key frames:

# Extract frames at specific positions
ffmpeg -i demo.gif -vf "select=eq(n\,100)" -frames:v 1 /tmp/frame.png -y 2>/dev/null

# View the frame (Claude can read images)
# Use Read tool on /tmp/frame.png to verify content

Post-Processing Speed-Up

Use gifsicle to speed up recordings without re-recording:

# 2x speed (halve frame delay)
gifsicle -d2 original.gif "#0-" > fast.gif

# 1.5x speed
gifsicle -d4 original.gif "#0-" > faster.gif

Template Placeholder Pattern

Keep tape files generic with placeholders, replace at build time:

# In tape file
Type "claude plugin marketplace add MARKETPLACE_REPO"

# In build script
sed "s|MARKETPLACE_REPO|$DETECTED_REPO|g" template.tape > rendered.tape
vhs rendered.tape

Timing & Sizing Reference

Context	Width	Height	Font	Duration
README/docs	1400	600	16-20	10-20s
Presentation	1800	900	24	15-30s
Compact embed	1200	600	14-16	10-15s
Wide output	1600	800	16	15-30s

See references/best_practices.md for detailed guidelines.

Troubleshooting

Problem	Solution
VHS not installed	brew install charmbracelet/tap/vhs
gifsicle not installed	brew install gifsicle
GIF too large	Reduce dimensions, sleep times, or use --speed 2
Text wraps/breaks	Increase --width or decrease --font-size
VHS parse error on $ or \"	Use base64 encoding (see Critical section above)
Hidden commands leak into GIF	Add clear + Sleep 500ms before Show
Commands execute before previous finishes	Increase Sleep duration

Tape File Syntax

references/vhs_syntax.md is the full VHS tape-file reference — every command, setting, and key name, with the argument forms each accepts. Read it when writing a tape by hand, when a tape parses but behaves unexpectedly, or when you need a command this SKILL.md does not show an example of.

Dependencies

Required: VHS (brew install charmbracelet/tap/vhs)

Optional: gifsicle (speed-up), asciinema (interactive recording), ffmpeg (frame verification), PyYAML (batch YAML configs)