PR Demo Creation

Overview

Create polished terminal demos for PRs using asciinema recordings converted to GIF. The workflow: script → record → convert → embed.

Tool Selection

| Goal | Tool Chain | Output | |------|------------|--------| | CLI demo for GitHub PR | asciinema → agg | GIF (< 5MB) | | Smaller file needed | asciinema → svg-term-cli | SVG (< 500KB) | | TUI screenshot | tmux → freeze | SVG/PNG |

Default choice: asciinema + agg (best compatibility, GitHub renders GIFs natively)

Prerequisites

bash
# Install tools (macOS)
brew install asciinema
cargo install --git https://github.com/asciinema/agg
npm install -g svg-term-cli  # Optional: for SVG output

Workflow

1. Script Your Demo (REQUIRED)

Before recording, write a brief script:

markdown
## Demo: [feature name]
Duration: ~20-30 seconds

1. [0-3s] Show command being typed
2. [3-10s] Command executes, show key output
3. [10-25s] Highlight the "aha moment" - what makes this valuable
4. [25-30s] Clean exit or final state

Keep it short. 20-30 seconds max. Show ONE thing well.

2. Prepare Environment

bash
# Clean terminal state
clear
export PS1='$ '                    # Simple prompt
export TERM=xterm-256color         # Consistent colors
# Hide sensitive info (API keys, paths with usernames)

Terminal size: 100x24 (readable when scaled down)

3. Record

bash
# Record to .cast file
asciinema rec demo.cast --cols 100 --rows 24

# Execute your scripted demo
# Press Ctrl+D or type 'exit' when done

Tips:

• Type at readable speed (not too fast)
• Pause briefly after key moments
• If you make a mistake, start over (editing is harder than re-recording)

4. Convert to GIF

bash
# Basic conversion (recommended)
agg demo.cast demo.gif

# With speed adjustment (1.5x faster)
agg --speed 1.5 demo.cast demo.gif

# With custom font size for readability
agg --font-size 14 demo.cast demo.gif

Alternative - SVG (smaller files):

bash
svg-term --in demo.cast --out demo.svg --window

5. Validate (Self-Validation)

Claude can self-validate demos using three approaches:

A. Automated Checks (run these first)

bash
# Check file size (must be < 5MB for GitHub)
ls -lh demo.gif

# Check recording duration from .cast metadata
head -1 demo.cast | jq '.duration // "check manually"'

B. Visual Validation (LLM-as-judge)

Extract a static frame for Claude to analyze:

bash
# Option 1: Use svg-term to render a specific timestamp (e.g., 15 seconds in)
svg-term --in demo.cast --out demo-preview.svg --at 15000

# Option 2: Use asciinema cat + freeze for a snapshot
asciinema cat demo.cast | head -500 | freeze -o demo-preview.png

# Option 3: Just convert to GIF and use the file directly
# Claude can read GIF files with the Read tool

Then ask Claude to analyze using the Read tool on the image:

Validation prompt:

Analyze this terminal demo screenshot. Check:
1. Is the text readable (not too small/blurry)?
2. Is the command being demonstrated visible?
3. Is there any sensitive info (API keys, /Users/username paths)?
4. Does the terminal look clean (simple prompt, no clutter)?
5. Is the "aha moment" visible - what value does this demo show?

Rate: PASS or FAIL with specific issues.

C. Content Validation (parse .cast file)

The .cast file is JSON lines - validate the content programmatically:

bash
# Check what commands were typed (input events)
grep '"i"' demo.cast | head -20

# Check recording duration
head -1 demo.cast | jq -r '.duration | floor'
# Should be 20-30 seconds

# Look for sensitive patterns
grep -iE '(api.?key|password|secret|/Users/[a-z])' demo.cast && echo "WARNING: Sensitive data found!"

D. Full Validation Checklist

After running the above, verify:

• ] File size < 5MB (automated)
• ] Duration 20-30 seconds (automated)
• ] No sensitive info in .cast (automated)
• ] Text readable in preview frame (visual/LLM)
• ] Demo shows feature clearly (visual/LLM)
• ] Clean terminal appearance (visual/LLM)

6. Embed in PR

markdown
## Demo

![feature demo](./docs/demos/feature-demo.gif)

*Shows: [one-sentence description of what the demo shows]*

Store demos in docs/demos/ or assets/ directory.

Quick Reference

| Setting | Recommended Value | |---------|------------------| | Duration | 20-30 seconds | | Terminal size | 100x24 | | Speed multiplier | 1.0-1.5x | | Target file size | < 2MB ideal, < 5MB max | | Font size (agg) | 14-16 |

Common Mistakes

| Mistake | Fix | |---------|-----| | Demo too long | Script it first, show ONE thing | | Text unreadable | Use --font-size 14+, terminal 100x24 | | File too large | Use svg-term-cli instead, or increase speed | | Cluttered terminal | Clean PS1, clear history, hide paths | | No context in PR | Add one-line description below GIF |

File Organization

docs/demos/
├── feature-name.gif      # The demo
├── feature-name.cast     # Source recording (optional, for re-rendering)
└── README.md             # Recording instructions for future maintainers