Polymarket Exchange Upgrade (Apr 28, 2026): What Breaks, What Changes, and a Builder Checklist

Polymarket scheduled a coordinated exchange upgrade for April 28, 2026 (~11:00 UTC). If you run bots, maker strategies, or analytics tooling, treat this like a protocol migration—not a UI refresh.

Key takeaways

• Trading pauses around ~11:00 UTC; maintenance is expected to be roughly an hour.
• All open orders are cleared during the window. You’ll need to re-place limit orders after resume.
• Collateral migrates from USDC.e to pUSD (1:1). The UI handles wrapping with a one-time approval prompt.
• Builders: there’s no backward compatibility—upgrade to the V2 stack before the window ends.

What changes (in plain language)

Polymarket is rolling out new exchange contracts and a rewritten order book. That means assumptions about order IDs, book snapshots, and endpoints may break if you keep old integrations.

Checklist for traders and builders

• Before the window: cancel or record critical orders, export positions, and freeze any unattended bots.
• During downtime: pause automation and avoid repeated retries that can trigger rate limits.
• After resume: re-place limit orders, confirm pUSD approvals, and verify fills/settlement on a small trade first.
• Builders: follow the V2 migration guide, update SDKs, and validate attribution fields (e.g., builder code) if you use them.

Sources

• Polymarket Help Center: Exchange upgrade (Apr 28, 2026)
• Polymarket Docs: Migrating to CLOB V2
• Polymarket Status: maintenance details