Migrate your Flashblocks integration to 200ms blocks.
200ms native blocks are live on Vibenet for experimental developer testing. This deployment may change, and you should not rely on it for production decisions.Denim activated on Base Sepolia on October 21, 2026 at 18:00 UTC, so 200ms native blocks are also live there. Base Mainnet is targeting November 2026. That date is a planning target, not an activation timestamp, and may change. The base-reth-node and base-consensus versions required for Base Mainnet are not yet published. Check the Upgrades overview for the latest schedule.
Use this guide if your application consumes Flashblocks. Denim replaces Flashblocks with canonical 200ms blocks, so Flashblocks subscriptions and pending state are unavailable after activation.
Inventory every Flashblocks subscription and RPC request that uses the "pending" block tag before Denim. Replace each integration using the table below.
Use eth_subscribe("newHeads"), then fetch transactions for each canonical block.
eth_getBlockByNumber("pending", ...)
Use normal RPC calls to read the latest canonical blocks.
eth_getBalance(..., "pending")
Use normal RPC calls to read the latest canonical state.
eth_getTransactionCount(..., "pending", ...)
Use normal RPC calls to read the latest canonical state.
eth_call(..., "pending")
Use normal RPC calls to read the latest canonical state.
eth_estimateGas(..., "pending")
Use normal RPC calls to read the latest canonical state.
eth_simulateV1(..., "pending")
Use normal RPC calls to read the latest canonical state.
eth_getLogs with a range ending at "pending"
Use normal RPC calls to query logs from canonical blocks.
eth_getBlockTransactionCountByNumber("pending")
Use normal RPC calls to read the latest canonical block.
Bridge or proof flow that reads historical block hashes or beacon roots
Review its history assumptions. The retained number of values is unchanged, but 200ms blocks mean that history covers less elapsed time.
The "pending" block tag and Flashblocks preconfirmation state have no direct equivalent after Denim. The replacements above return canonical data from 200ms blocks, not preconfirmed or pending data.
Test your migrated integration on Vibenet. For the protocol design and RPC behavior, see 200ms Native Blocks.
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This deployment may change, and you should not rely on it for production decisions.`]}),_jsxs(_components.p,{children:[`Denim activated on Base Sepolia on October 21, 2026 at 18:00 UTC, so 200ms native blocks are also live there. Base Mainnet is targeting November 2026. That date is a planning target, not an activation timestamp, and may change. The `,_jsx(_components.code,{children:`base-reth-node`}),` and `,_jsx(_components.code,{children:`base-consensus`}),` versions required for Base Mainnet are not yet published. Check the `,_jsx(_components.a,{href:`/upgrades/overview`,children:`Upgrades overview`}),` for the latest schedule.`]})]}),`\n`,_jsx(Heading,{level:`2`,id:`summary`,children:`Summary`}),`\n`,_jsx(_components.p,{children:`Use this guide if your application consumes Flashblocks. 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Replace each integration using the table below.`]}),`\n`,_jsx(Heading,{level:`2`,id:`update-integrations-for-denim`,children:`Update Integrations for Denim`}),`\n`,_jsxs(Table,{children:[_jsx(_components.thead,{children:_jsxs(_components.tr,{children:[_jsx(_components.th,{children:`Integration to review`}),_jsx(_components.th,{children:`Action for Denim`})]})}),_jsxs(_components.tbody,{children:[_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_subscribe(\"newFlashblocks\")`})}),_jsxs(_components.td,{children:[`Use `,_jsx(_components.code,{children:`eth_subscribe(\"newHeads\")`}),`.`]})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_subscribe(\"pendingLogs\")`})}),_jsxs(_components.td,{children:[`Use `,_jsx(_components.code,{children:`eth_subscribe(\"logs\")`}),`.`]})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_subscribe(\"newFlashblockTransactions\")`})}),_jsxs(_components.td,{children:[`Use `,_jsx(_components.code,{children:`eth_subscribe(\"newHeads\")`}),`, then fetch transactions for each canonical block.`]})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_getBlockByNumber(\"pending\", ...)`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical blocks.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_getBalance(..., \"pending\")`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical state.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_getTransactionCount(..., \"pending\", ...)`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical state.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_call(..., \"pending\")`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical state.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_estimateGas(..., \"pending\")`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical state.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_simulateV1(..., \"pending\")`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical state.`})]}),_jsxs(_components.tr,{children:[_jsxs(_components.td,{children:[_jsx(_components.code,{children:`eth_getLogs`}),` with a range ending at `,_jsx(_components.code,{children:`\"pending\"`})]}),_jsx(_components.td,{children:`Use normal RPC calls to query logs from canonical blocks.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:_jsx(_components.code,{children:`eth_getBlockTransactionCountByNumber(\"pending\")`})}),_jsx(_components.td,{children:`Use normal RPC calls to read the latest canonical block.`})]}),_jsxs(_components.tr,{children:[_jsx(_components.td,{children:`Bridge or proof flow that reads historical block hashes or beacon roots`}),_jsx(_components.td,{children:`Review its history assumptions. The retained number of values is unchanged, but 200ms blocks mean that history covers less elapsed time.`})]})]})]}),`\n`,_jsx(Warning,{children:_jsxs(_components.p,{children:[`The `,_jsx(_components.code,{children:`\"pending\"`}),` block tag and Flashblocks preconfirmation state have no direct equivalent after Denim. The replacements above return canonical data from 200ms blocks, not preconfirmed or pending data.`]})}),`\n`,_jsx(Heading,{level:`2`,id:`test-on-vibenet`,children:`Test on Vibenet`}),`\n`,_jsxs(_components.p,{children:[`Test your migrated integration on `,_jsx(_components.a,{href:`/build-on-base/test-on-vibenet`,children:`Vibenet`}),`. For the protocol design and RPC behavior, see `,_jsx(_components.a,{href:`/upgrades/denim/200ms-blocks`,children:`200ms Native Blocks`}),`.`]})]})}function MDXContent(props={}){const{wrapper:MDXLayout}={..._provideComponents(),...props.components};return MDXLayout?_jsx(MDXLayout,{...props,children:_jsx(_createMdxContent,{...props})}):_createMdxContent(props)}return{default:MDXContent};function _missingMdxReference(id,component){throw new Error(`Expected `+(component?`component`:`object`)+\" `\"+id+\"` to be defined: you likely forgot to import, pass, or provide it.\")}","frontmatter":{},"scope":{"config":{},"pageMetadata":{"title":"Migrate From Flashblocks","description":"Migrate your Flashblocks integration to 200ms blocks.","href":"/upgrades/denim/migrate-from-flashblocks"}}},"mdxSourceWithNoJs":null},"mdxExtracts":{"tableOfContents":[{"title":"Summary","slug":"summary","depth":2,"children":[]},{"title":"Recommended 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