# Fix the locale QA agent browser automation failing on RTL screenshot comparison

## TL;DR

RTL screenshots differ in expected ways, so normalize direction before comparing. Mirrored layouts are correct, not failures, and naive pixel diffs flag every one. Compare structural similarity with mirroring awareness, or diff against an RTL baseline instead of the LTR screenshot.

## The error

```text
Locale QA agent: RTL screenshot comparison failed, 400 diff regions
all of them are correct mirroring, no real bugs
```

## Fix it

### Step 1: Confirm the diffs are mirroring, not bugs

```bash
node -e "console.log('open the diff image, check whether each region is just the mirrored counterpart')"
```

Expected: The diffs are expected mirroring.

### Step 2: Compare RTL against an RTL baseline

```bash
node -e "console.log('capture the baseline in RTL once, approved by a human, diff future RTL runs against it')"
```

Expected: Mirroring stops counting as failure.

### Step 3: Or mirror-normalize before diffing

```bash
node -e "console.log('flip the RTL screenshot horizontally before comparing to the LTR baseline -- true bugs survive the flip')"
```

Expected: Real bugs still show, mirroring cancels out.

### Step 4: Re-run the comparison

```bash
node scripts/qa-screenshots.js --locale ar | tail -3
```

Expected: The comparison passes on correct mirroring.

## When to use this

- RTL screenshot comparisons fail on correct mirroring
- A QA agent flags every RTL screenshot

## When NOT to use this

- The screenshots show real RTL bugs, fix those
- LTR comparisons fail, different problem

## Tool and version compatibility

- Any screenshot diffing in QA agents
- RTL baselines or mirror normalization

## Variant phrasings

### no RTL baseline exists yet

Capture one and have a human approve it. The first baseline is manual, the rest are automatic.

### text rendering differs beyond mirroring

Fonts shape Arabic differently per platform. That needs font normalization, not mirroring logic.

## Why it happens

Pixel diffs compare images, not layouts. A correctly mirrored RTL page differs from the LTR screenshot in nearly every pixel, so the diff reports hundreds of regions that are all correct behavior.

## Edge cases

- Mirror normalization hides asymmetric bugs, keep some unmirrored checks too
- Approve baselines carefully, a bad baseline bakes in bugs
- Threshold tuning is not a substitute for the right baseline

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_-eeUPZNWwRK1H0eCr9dLmA