11.9Pattern 8: Visual Regression (Screenshot Comparison)

Use screenshots to detect visual changes.

# Capture baseline
playwright-cli goto https://app.example.com/dashboard
playwright-cli screenshot            # → path in .playwright-cli/; copy to baseline/

# ... after code change ...

# Capture current
playwright-cli goto https://app.example.com/dashboard
playwright-cli screenshot            # → copy to current/

# Agent compares screenshots (via vision or a pixel-diff tool)

Note the disk-first advantage here: screenshots never enter the model context unless the agent chooses to look. A pixel-diff tool can compare hundreds of PNG pairs for zero tokens; the agent only reads the images that actually differ.

Agent's Added Value

With vision capabilities, the agent can:

• Identify specific visual differences
• Classify changes as intentional vs regression
• Describe what changed in natural language