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Backfill and live-stream any set of smart contract events over a simple HTTP API. A stream is one URL for a chain and a filter: contract addresses and event topics. Start with the quickstart to read your first page.

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Backfill, then follow live

Start at any block, including genesis (from=0). Streams delivers pages in block order, then follows the tip on the same connection. For contract logs, choose addresses and topics; for block headers, use the blocks source without filters. You hold the position, so each consumer can restart or replay independently. Pages contain complete blocks. Reorgs arrive as correction pages that start lower. Apply the transaction rule to replace affected rows. Each page also carries the chain’s safe and finalized block marks when available. Use finalized marks to gate irreversible side effects. Both transports deliver the same pages. No SDK is required.

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Access and authentication

Streams is an allowlisted beta. Your account must have Streams access and an enabled account RPC API key. The read URL embeds that key: https://lasso.sh/streams/k/{key}/{chain}/logs. Keep the full URL in your secret store and out of logs. RPC profile and strategy segments do not apply. A saved dashboard stream is a credential-free recipe, not a running consumer. It stores neither a key nor your cursor. You can also build the read URL directly. Management APIs use the account’s management Bearer token, not its RPC key.

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Pricing

Delivery costs $0.10 per million events**, with a **$0.10 minimum per account per active UTC day, drawn from the account’s USD balance. Pro included RPC usage does not pay for Streams. Check the current versioned tariff in service discovery. Live, historical, replay and correction items count. Each block header counts as one event. Empty pages, errors, keepalives and blocks scanned are free. Empty pages do not activate a day. Passive dashboard samples are free; the Test reader uses the billable public endpoint. The beta has no free interactive reads. Billing records complete pages successfully written by the server, not client acknowledgments. A fully written frame may be billable even if you disconnect before consuming it. Failed or truncated writes are free; replay deliveries bill again.

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Limits

The beta serves Ethereum (ethereum or 1), Base (base or 8453), and Arbitrum (arbitrum or 42161). Each key allows 10 concurrent readers and two concurrent history builds. Account request-rate limits also apply.

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