Generate multiple deck variants from the same configuration and compare them side by side.
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## Overview
Build X and Compare lets you run 1–10 deck builds with the same commander, themes, and settings in parallel. Use it to explore variance across builds, find the most consistent card inclusions, and produce an optimized "best-of" deck via the Synergy Builder.
Enable with `ENABLE_BATCH_BUILD=1` (default: on).
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## Starting a Batch Build
1. In the **New Deck modal**, increase the **Build count** slider from 1 to your desired number (max 10).
2. Configure the rest of the build (commander, themes, bracket, budget) as normal.
3. Click **Build**. Builds run in parallel (max 5 concurrent) with a real-time progress bar and dynamic time estimates.
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## Results View
After all builds complete, the results page shows:
- Individual build cards, each with a summary (card count, estimated cost, theme coverage).
- **Card overlap statistics**: how many cards appeared in N of N builds, sorted by frequency.
- A **Rebuild** button to re-run with the same configuration (locks and include/exclude lists are preserved).
- A **ZIP export** button to download all builds (CSV, TXT, and summary JSON for each).
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## Synergy Builder
The Synergy Builder analyzes all builds in the batch and produces an optimized single deck scored by three factors:
| Factor | Description |
|--------|-------------|
| Frequency | Cards that appeared in more builds score higher |
