diff --git a/packages/core/src/build/configAndIndexingFunctions.test.ts b/packages/core/src/build/configAndIndexingFunctions.test.ts
index 77cc5c0a9..0b739e9af 100644
--- a/packages/core/src/build/configAndIndexingFunctions.test.ts
+++ b/packages/core/src/build/configAndIndexingFunctions.test.ts
@@ -42,8 +42,7 @@ test("buildConfigAndIndexingFunctions() builds topics for multiple events", asyn
         network: { mainnet: {} },
         abi: [event0, event1],
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
@@ -72,8 +71,7 @@ test("buildConfigAndIndexingFunctions() handles overloaded event signatures and
         network: { mainnet: {} },
         abi: [event1, event1Overloaded],
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
@@ -102,8 +100,7 @@ test("buildConfigAndIndexingFunctions() handles multiple addresses", async () =>
         network: {
           mainnet: {
             address: [address1, address3],
-            startBlock: 16370000,
-            endBlock: 16370020,
+            blocks: [16370000, 16370020],
           },
         },
         abi: [event1, event1Overloaded],
@@ -163,8 +160,7 @@ test("buildConfigAndIndexingFunctions() builds topics for event filter", async (
           },
         },
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
@@ -203,8 +199,7 @@ test("buildConfigAndIndexingFunctions() builds topics for multiple event filters
           },
         ],
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
@@ -237,8 +232,7 @@ test("buildConfigAndIndexingFunctions() overrides default values with network-sp
       a: {
         abi: [event0],
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
         network: {
           mainnet: {
             address: address2,
@@ -266,8 +260,7 @@ test("buildConfigAndIndexingFunctions() handles network name shortcut", async ()
         network: "mainnet",
         abi: [event0],
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
@@ -441,7 +434,7 @@ test("buildConfigAndIndexingFunctions() validates address length", async () => {
   );
 });
 
-test("buildConfigAndIndexingFunctions() coerces NaN startBlock to undefined", async () => {
+test("buildConfigAndIndexingFunctions() coerces NaN startBlock to 0", async () => {
   const config = createConfig({
     networks: {
       mainnet: { chainId: 1, transport: http("http://127.0.0.1:8545") },
@@ -450,7 +443,7 @@ test("buildConfigAndIndexingFunctions() coerces NaN startBlock to undefined", as
       a: {
         network: { mainnet: {} },
         abi: [event0, event1],
-        startBlock: Number.NaN,
+        blocks: [Number.NaN, 16370020],
       },
     },
   });
@@ -460,7 +453,7 @@ test("buildConfigAndIndexingFunctions() coerces NaN startBlock to undefined", as
     rawIndexingFunctions: [{ name: "a:Event0", fn: () => {} }],
   });
 
-  expect(sources[0]?.filter.fromBlock).toBe(undefined);
+  expect(sources[0]?.filter.fromBlock).toBe(0);
 });
 
 test("buildConfigAndIndexingFunctions() includeTransactionReceipts", async () => {
@@ -565,7 +558,7 @@ test("buildConfigAndIndexingFunctions() includeCallTraces with factory", async (
   expect(shouldGetTransactionReceipt(sources[0]!.filter)).toBe(false);
 });
 
-test("buildConfigAndIndexingFunctions() coerces NaN endBlock to undefined", async () => {
+test("buildConfigAndIndexingFunctions() coerces NaN endBlock to Number.MAX_SAFE_INTEGER", async () => {
   const config = createConfig({
     networks: {
       mainnet: { chainId: 1, transport: http("http://127.0.0.1:8545") },
@@ -574,7 +567,7 @@ test("buildConfigAndIndexingFunctions() coerces NaN endBlock to undefined", asyn
       a: {
         network: { mainnet: {} },
         abi: [event0, event1],
-        endBlock: Number.NaN,
+        blocks: [16370000, Number.NaN],
       },
     },
   });
@@ -584,7 +577,58 @@ test("buildConfigAndIndexingFunctions() coerces NaN endBlock to undefined", asyn
     rawIndexingFunctions: [{ name: "a:Event0", fn: () => {} }],
   });
 
-  expect(sources[0]!.filter.toBlock).toBe(undefined);
+  expect(sources[0]!.filter.toBlock).toBe(Number.MAX_SAFE_INTEGER);
+});
+
+test("buildConfigAndIndexingFunctions() resolves overlapping block ranges", async () => {
+  const config = createConfig({
+    networks: {
+      mainnet: { chainId: 1, transport: http("http://127.0.0.1:8545") },
+    },
+    contracts: {
+      a: {
+        network: { mainnet: {} },
+        abi: [event0, event1],
+        blocks: [
+          [16370000, 16370020],
+          [16370010, 16370030],
+        ],
+      },
+    },
+  });
+
+  const { sources } = await buildConfigAndIndexingFunctions({
+    config,
+    rawIndexingFunctions: [{ name: "a:Event0", fn: () => {} }],
+  });
+
+  expect(sources[0]!.filter.fromBlock).toBe(16370000);
+  expect(sources[0]!.filter.toBlock).toBe(16370030);
+});
+
+test("buildConfigAndIndexingFunctions() multiple block ranges", async () => {
+  const config = createConfig({
+    networks: {
+      mainnet: { chainId: 1, transport: http("http://127.0.0.1:8545") },
+    },
+    contracts: {
+      a: {
+        network: { mainnet: {} },
+        abi: [event0, event1],
+        blocks: [
+          [16370000, 16370020],
+          [16370040, 16370060],
+        ],
+      },
+    },
+  });
+
+  const { sources } = await buildConfigAndIndexingFunctions({
+    config,
+    rawIndexingFunctions: [{ name: "a:Event0", fn: () => {} }],
+  });
+
+  expect(sources).toHaveLength(2);
 });
 
 test("buildConfigAndIndexingFunctions() account source", async () => {
@@ -596,8 +640,7 @@ test("buildConfigAndIndexingFunctions() account source", async () => {
       a: {
         network: { mainnet: {} },
         address: address1,
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
@@ -636,8 +679,7 @@ test("buildConfigAndIndexingFunctions() block source", async () => {
     blocks: {
       a: {
         network: { mainnet: {} },
-        startBlock: 16370000,
-        endBlock: 16370020,
+        blocks: [16370000, 16370020],
       },
     },
   });
diff --git a/packages/core/src/build/configAndIndexingFunctions.ts b/packages/core/src/build/configAndIndexingFunctions.ts
index 2e8ebe95c..938a8f1f0 100644
--- a/packages/core/src/build/configAndIndexingFunctions.ts
+++ b/packages/core/src/build/configAndIndexingFunctions.ts
@@ -24,11 +24,23 @@ import {
   defaultTransferFilterInclude,
 } from "@/sync/filter.js";
 import { chains } from "@/utils/chains.js";
+import { type Interval, intervalUnion } from "@/utils/interval.js";
 import { toLowerCase } from "@/utils/lowercase.js";
+import { _eth_getBlockByNumber } from "@/utils/rpc.js";
 import { dedupe } from "@ponder/common";
-import type { Hex, LogTopic } from "viem";
+import { type Hex, type LogTopic, hexToNumber } from "viem";
 import { buildLogFactory } from "./factory.js";
 
+/**
+ * Block intervals with startBlock (inclusive) and endBlock (inclusive).
+ *  - startBlock: `number | "latest"`
+ *  - endBlock: `number | "latest" | "realtime"`
+ *    - `number`: A specific block number.
+ *    - `"latest"`: The latest block number at the startup of the Ponder instance.
+ *    - `"realtime"`: Indefinite/live indexing.
+ */
+type BlockRange = [number | "latest", number | "latest" | "realtime"];
+
 const flattenSources = <
   T extends Config["contracts"] | Config["accounts"] | Config["blocks"],
 >(
@@ -73,7 +85,59 @@ export async function buildConfigAndIndexingFunctions({
 }> {
   const logs: { level: "warn" | "info" | "debug"; msg: string }[] = [];
 
-  const networks: Network[] = await Promise.all(
+  const latestBlockNumbers = new Map<string, Promise<Hex>>();
+
+  const latest = async (network: Network) => {
+    if (latestBlockNumbers.has(network.name)) {
+      return hexToNumber(await latestBlockNumbers.get(network.name)!);
+    }
+
+    const latest: Promise<Hex> = network.transport.request({
+      method: "eth_blockNumber",
+    });
+
+    latestBlockNumbers.set(network.name, latest);
+
+    return hexToNumber(await latest);
+  };
+
+  const resolveBlockRanges = async (
+    blocks: BlockRange[] | BlockRange | undefined,
+    network: Network,
+  ) => {
+    let rawBlockRanges: [number, number | "realtime"][];
+
+    if (blocks === undefined || blocks.length === 0) {
+      rawBlockRanges = [[0, "realtime"]];
+    } else if (blocks.every((b) => Array.isArray(b))) {
+      rawBlockRanges = await Promise.all(
+        blocks.map(async ([fromBlock, toBlock]) => [
+          fromBlock === "latest" ? await latest(network) : fromBlock,
+          toBlock === "latest" ? await latest(network) : toBlock,
+        ]),
+      );
+    } else {
+      rawBlockRanges = [
+        [
+          blocks[0] === "latest" ? await latest(network) : blocks[0],
+          blocks[1] === "latest" ? await latest(network) : blocks[1],
+        ],
+      ];
+    }
+
+    const blockRanges: Interval[] = rawBlockRanges.map(
+      ([rawStartBlock, rawEndBlock]) => [
+        Number.isNaN(rawStartBlock) ? 0 : rawStartBlock,
+        Number.isNaN(rawEndBlock) || rawEndBlock === "realtime"
+          ? Number.MAX_SAFE_INTEGER
+          : (rawEndBlock as number),
+      ],
+    );
+
+    return intervalUnion(blockRanges);
+  };
+
+  const networks = await Promise.all(
     Object.entries(config.networks).map(async ([networkName, network]) => {
       const { chainId, transport } = network;
 
@@ -103,7 +167,7 @@ export async function buildConfigAndIndexingFunctions({
         );
       }
 
-      return {
+      const resolvedNetwork = {
         name: networkName,
         chainId,
         chain,
@@ -113,6 +177,8 @@ export async function buildConfigAndIndexingFunctions({
         finalityBlockCount: getFinalityBlockCount({ chainId }),
         disableCache: network.disableCache ?? false,
       } satisfies Network;
+
+      return resolvedNetwork;
     }),
   );
 
@@ -217,25 +283,6 @@ export async function buildConfigAndIndexingFunctions({
       );
     }
 
-    const startBlockMaybeNan = source.startBlock;
-    const startBlock = Number.isNaN(startBlockMaybeNan)
-      ? undefined
-      : startBlockMaybeNan;
-    const endBlockMaybeNan = source.endBlock;
-    const endBlock = Number.isNaN(endBlockMaybeNan)
-      ? undefined
-      : endBlockMaybeNan;
-
-    if (
-      startBlock !== undefined &&
-      endBlock !== undefined &&
-      endBlock < startBlock
-    ) {
-      throw new Error(
-        `Validation failed: Start block for '${source.name}' is after end block (${startBlock} > ${endBlock}).`,
-      );
-    }
-
     const network = networks.find((n) => n.name === source.network);
     if (!network) {
       throw new Error(
@@ -246,10 +293,58 @@ export async function buildConfigAndIndexingFunctions({
           .join(", ")}].`,
       );
     }
+
+    const blockRanges: [number, number | "realtime"][] =
+      source.blocks === undefined
+        ? [[0, "realtime"]]
+        : source.blocks.every((b) => Array.isArray(b))
+          ? await Promise.all(
+              source.blocks.map(async ([fromBlock, toBlock]) => [
+                fromBlock === "latest" ? await latest(network) : fromBlock,
+                toBlock === "latest" ? await latest(network) : toBlock,
+              ]),
+            )
+          : [
+              [
+                source.blocks[0] === "latest"
+                  ? await latest(network)
+                  : source.blocks[0],
+                source.blocks[1] === "latest"
+                  ? await latest(network)
+                  : source.blocks[1],
+              ],
+            ];
+
+    for (const [rawStartBlock, rawEndBlock] of blockRanges) {
+      const startBlock = Number.isNaN(rawStartBlock) ? 0 : rawStartBlock;
+      const endBlock = Number.isNaN(rawEndBlock) ? "realtime" : rawEndBlock;
+      if (typeof endBlock !== "string" && endBlock < startBlock) {
+        throw new Error(
+          `Validation failed: Start block for '${source.name}' is after end block (${startBlock} > ${endBlock}).`,
+        );
+      }
+
+      if (typeof endBlock === "string" && endBlock !== "realtime") {
+        throw new Error(
+          `Validation failed: End block for '${source.name}' is ${endBlock}. Expected number or "realtime"`,
+        );
+      }
+    }
   }
 
-  const contractSources: ContractSource[] = flattenSources(
-    config.contracts ?? {},
+  const contractSources: ContractSource[] = (
+    await Promise.all(
+      flattenSources(config.contracts ?? {}).map(
+        async ({ blocks, network, ...rest }) => ({
+          blocks: await resolveBlockRanges(
+            blocks,
+            networks.find((n) => n.name === network)!,
+          ),
+          network,
+          ...rest,
+        }),
+      ),
+    )
   )
     .flatMap((source): ContractSource[] => {
       const network = networks.find((n) => n.name === source.network)!;
@@ -377,15 +472,6 @@ export async function buildConfigAndIndexingFunctions({
         });
       }
 
-      const startBlockMaybeNan = source.startBlock;
-      const fromBlock = Number.isNaN(startBlockMaybeNan)
-        ? undefined
-        : startBlockMaybeNan;
-      const endBlockMaybeNan = source.endBlock;
-      const toBlock = Number.isNaN(endBlockMaybeNan)
-        ? undefined
-        : endBlockMaybeNan;
-
       const contractMetadata = {
         type: "contract",
         abi: source.abi,
@@ -407,14 +493,92 @@ export async function buildConfigAndIndexingFunctions({
           ...resolvedAddress,
         });
 
-        const logSources = topicsArray.map(
-          (topics) =>
+        const logSources = topicsArray.flatMap((topics) =>
+          source.blocks.map(
+            ([fromBlock, toBlock]) =>
+              ({
+                ...contractMetadata,
+                filter: {
+                  type: "log",
+                  chainId: network.chainId,
+                  address: logFactory,
+                  topic0: topics.topic0,
+                  topic1: topics.topic1,
+                  topic2: topics.topic2,
+                  topic3: topics.topic3,
+                  fromBlock,
+                  toBlock,
+                  include: defaultLogFilterInclude.concat(
+                    source.includeTransactionReceipts
+                      ? defaultTransactionReceiptInclude
+                      : [],
+                  ),
+                },
+              }) satisfies ContractSource,
+          ),
+        );
+
+        if (source.includeCallTraces) {
+          const callTraceSources = source.blocks.map(
+            ([fromBlock, toBlock]) =>
+              ({
+                ...contractMetadata,
+                filter: {
+                  type: "trace",
+                  chainId: network.chainId,
+                  fromAddress: undefined,
+                  toAddress: logFactory,
+                  callType: "CALL",
+                  functionSelector: registeredFunctionSelectors,
+                  includeReverted: false,
+                  fromBlock,
+                  toBlock,
+                  include: defaultTraceFilterInclude.concat(
+                    source.includeTransactionReceipts
+                      ? defaultTransactionReceiptInclude
+                      : [],
+                  ),
+                },
+              }) satisfies ContractSource,
+          );
+
+          return [...logSources, ...callTraceSources];
+        }
+
+        return logSources;
+      } else if (resolvedAddress !== undefined) {
+        for (const address of Array.isArray(resolvedAddress)
+          ? resolvedAddress
+          : [resolvedAddress]) {
+          if (!address!.startsWith("0x"))
+            throw new Error(
+              `Validation failed: Invalid prefix for address '${address}'. Got '${address!.slice(
+                0,
+                2,
+              )}', expected '0x'.`,
+            );
+          if (address!.length !== 42)
+            throw new Error(
+              `Validation failed: Invalid length for address '${address}'. Got ${address!.length}, expected 42 characters.`,
+            );
+        }
+      }
+
+      const validatedAddress = Array.isArray(resolvedAddress)
+        ? dedupe(resolvedAddress).map((r) => toLowerCase(r))
+        : resolvedAddress !== undefined
+          ? toLowerCase(resolvedAddress)
+          : undefined;
+
+      const logSources = topicsArray.flatMap((topics) =>
+        source.blocks.map(
+          ([fromBlock, toBlock]) =>
             ({
               ...contractMetadata,
               filter: {
                 type: "log",
                 chainId: network.chainId,
-                address: logFactory,
+                address: validatedAddress,
                 topic0: topics.topic0,
                 topic1: topics.topic1,
                 topic2: topics.topic2,
@@ -428,18 +592,23 @@ export async function buildConfigAndIndexingFunctions({
                 ),
               },
             }) satisfies ContractSource,
-        );
+        ),
+      );
 
-        if (source.includeCallTraces) {
-          return [
-            ...logSources,
-            {
+      if (source.includeCallTraces) {
+        const callTraceSources = source.blocks.map(
+          ([fromBlock, toBlock]) =>
+            ({
               ...contractMetadata,
               filter: {
                 type: "trace",
                 chainId: network.chainId,
                 fromAddress: undefined,
-                toAddress: logFactory,
+                toAddress: Array.isArray(validatedAddress)
+                  ? validatedAddress
+                  : validatedAddress === undefined
+                    ? undefined
+                    : [validatedAddress],
                 callType: "CALL",
                 functionSelector: registeredFunctionSelectors,
                 includeReverted: false,
@@ -451,85 +620,10 @@ export async function buildConfigAndIndexingFunctions({
                     : [],
                 ),
               },
-            } satisfies ContractSource,
-          ];
-        }
-
-        return logSources;
-      } else if (resolvedAddress !== undefined) {
-        for (const address of Array.isArray(resolvedAddress)
-          ? resolvedAddress
-          : [resolvedAddress]) {
-          if (!address!.startsWith("0x"))
-            throw new Error(
-              `Validation failed: Invalid prefix for address '${address}'. Got '${address!.slice(
-                0,
-                2,
-              )}', expected '0x'.`,
-            );
-          if (address!.length !== 42)
-            throw new Error(
-              `Validation failed: Invalid length for address '${address}'. Got ${address!.length}, expected 42 characters.`,
-            );
-        }
-      }
-
-      const validatedAddress = Array.isArray(resolvedAddress)
-        ? dedupe(resolvedAddress).map((r) => toLowerCase(r))
-        : resolvedAddress !== undefined
-          ? toLowerCase(resolvedAddress)
-          : undefined;
-
-      const logSources = topicsArray.map(
-        (topics) =>
-          ({
-            ...contractMetadata,
-            filter: {
-              type: "log",
-              chainId: network.chainId,
-              address: validatedAddress,
-              topic0: topics.topic0,
-              topic1: topics.topic1,
-              topic2: topics.topic2,
-              topic3: topics.topic3,
-              fromBlock,
-              toBlock,
-              include: defaultLogFilterInclude.concat(
-                source.includeTransactionReceipts
-                  ? defaultTransactionReceiptInclude
-                  : [],
-              ),
-            },
-          }) satisfies ContractSource,
-      );
+            }) satisfies ContractSource,
+        );
 
-      if (source.includeCallTraces) {
-        return [
-          ...logSources,
-          {
-            ...contractMetadata,
-            filter: {
-              type: "trace",
-              chainId: network.chainId,
-              fromAddress: undefined,
-              toAddress: Array.isArray(validatedAddress)
-                ? validatedAddress
-                : validatedAddress === undefined
-                  ? undefined
-                  : [validatedAddress],
-              callType: "CALL",
-              functionSelector: registeredFunctionSelectors,
-              includeReverted: false,
-              fromBlock,
-              toBlock,
-              include: defaultTraceFilterInclude.concat(
-                source.includeTransactionReceipts
-                  ? defaultTransactionReceiptInclude
-                  : [],
-              ),
-            },
-          } satisfies ContractSource,
-        ];
+        return [...logSources, ...callTraceSources];
       } else return logSources;
     }) // Remove sources with no registered indexing functions
     .filter((source) => {
@@ -550,19 +644,23 @@ export async function buildConfigAndIndexingFunctions({
       return hasNoRegisteredIndexingFunctions === false;
     });
 
-  const accountSources: AccountSource[] = flattenSources(config.accounts ?? {})
+  const accountSources: AccountSource[] = (
+    await Promise.all(
+      flattenSources(config.accounts ?? {}).map(
+        async ({ blocks, network, ...rest }) => ({
+          blocks: await resolveBlockRanges(
+            blocks,
+            networks.find((n) => n.name === network)!,
+          ),
+          network,
+          ...rest,
+        }),
+      ),
+    )
+  )
     .flatMap((source): AccountSource[] => {
       const network = networks.find((n) => n.name === source.network)!;
 
-      const startBlockMaybeNan = source.startBlock;
-      const fromBlock = Number.isNaN(startBlockMaybeNan)
-        ? undefined
-        : startBlockMaybeNan;
-      const endBlockMaybeNan = source.endBlock;
-      const toBlock = Number.isNaN(endBlockMaybeNan)
-        ? undefined
-        : endBlockMaybeNan;
-
       const resolvedAddress = source?.address;
 
       if (resolvedAddress === undefined) {
@@ -581,7 +679,7 @@ export async function buildConfigAndIndexingFunctions({
           ...resolvedAddress,
         });
 
-        return [
+        const accountSources = source.blocks.flatMap(([fromBlock, toBlock]) => [
           {
             type: "account",
             name: source.name,
@@ -650,7 +748,9 @@ export async function buildConfigAndIndexingFunctions({
               ),
             },
           } satisfies AccountSource,
-        ];
+        ]);
+
+        return accountSources;
       }
 
       for (const address of Array.isArray(resolvedAddress)
@@ -675,7 +775,7 @@ export async function buildConfigAndIndexingFunctions({
           ? toLowerCase(resolvedAddress)
           : undefined;
 
-      return [
+      const accountSources = source.blocks.flatMap(([fromBlock, toBlock]) => [
         {
           type: "account",
           name: source.name,
@@ -744,7 +844,9 @@ export async function buildConfigAndIndexingFunctions({
             ),
           },
         } satisfies AccountSource,
-      ];
+      ]);
+
+      return accountSources;
     })
     .filter((source) => {
       const eventName =
@@ -767,8 +869,21 @@ export async function buildConfigAndIndexingFunctions({
       return hasRegisteredIndexingFunction;
     });
 
-  const blockSources: BlockSource[] = flattenSources(config.blocks ?? {})
-    .map((source) => {
+  const blockSources: BlockSource[] = (
+    await Promise.all(
+      flattenSources(config.blocks ?? {}).map(
+        async ({ blocks, network, ...rest }) => ({
+          blocks: await resolveBlockRanges(
+            blocks,
+            networks.find((n) => n.name === network)!,
+          ),
+          network,
+          ...rest,
+        }),
+      ),
+    )
+  )
+    .flatMap((source) => {
       const network = networks.find((n) => n.name === source.network)!;
 
       const intervalMaybeNan = source.interval ?? 1;
@@ -780,29 +895,23 @@ export async function buildConfigAndIndexingFunctions({
         );
       }
 
-      const startBlockMaybeNan = source.startBlock;
-      const fromBlock = Number.isNaN(startBlockMaybeNan)
-        ? undefined
-        : startBlockMaybeNan;
-      const endBlockMaybeNan = source.endBlock;
-      const toBlock = Number.isNaN(endBlockMaybeNan)
-        ? undefined
-        : endBlockMaybeNan;
-
-      return {
-        type: "block",
-        name: source.name,
-        network,
-        filter: {
-          type: "block",
-          chainId: network.chainId,
-          interval: interval,
-          offset: (fromBlock ?? 0) % interval,
-          fromBlock,
-          toBlock,
-          include: defaultBlockFilterInclude,
-        },
-      } satisfies BlockSource;
+      return source.blocks.map(
+        ([fromBlock, toBlock]) =>
+          ({
+            type: "block",
+            name: source.name,
+            network,
+            filter: {
+              type: "block",
+              chainId: network.chainId,
+              interval: interval,
+              offset: fromBlock % interval,
+              fromBlock,
+              toBlock,
+              include: defaultBlockFilterInclude,
+            },
+          }) satisfies BlockSource,
+      );
     })
     .filter((blockSource) => {
       const hasRegisteredIndexingFunction =
diff --git a/packages/core/src/config/index.test.ts b/packages/core/src/config/index.test.ts
index 05dd94959..56c5373a0 100644
--- a/packages/core/src/config/index.test.ts
+++ b/packages/core/src/config/index.test.ts
@@ -25,12 +25,12 @@ test("createConfig basic", () => {
       c1: {
         abi: [event1],
         network: "mainnet",
-        startBlock: 0,
+        blocks: [0, Number.POSITIVE_INFINITY],
       },
       c2: {
         abi: [event1],
         network: "optimism",
-        startBlock: 0,
+        blocks: [0, Number.POSITIVE_INFINITY],
       },
     },
   });
@@ -185,7 +185,7 @@ test("createConfig network overrides", () => {
       c1: {
         abi: [event1],
         network: "mainnet",
-        startBlock: 0,
+        blocks: [0, Number.POSITIVE_INFINITY],
       },
       c2: {
         abi: [event0, event1],
@@ -200,7 +200,7 @@ test("createConfig network overrides", () => {
             },
           },
         },
-        startBlock: 0,
+        blocks: [0, Number.POSITIVE_INFINITY],
       },
     },
   });
diff --git a/packages/core/src/config/index.ts b/packages/core/src/config/index.ts
index 3dfd31b10..5d849bdc3 100644
--- a/packages/core/src/config/index.ts
+++ b/packages/core/src/config/index.ts
@@ -61,10 +61,17 @@ type DatabaseConfig =
 // base
 
 type BlockConfig = {
-  /** Block number at which to start indexing events (inclusive). If `undefined`, events will be processed from block 0. Default: `undefined`. */
-  startBlock?: number;
-  /** Block number at which to stop indexing events (inclusive). If `undefined`, events will be processed in real-time. Default: `undefined`. */
-  endBlock?: number;
+  /**
+   * Block intervals with startBlock (inclusive) and endBlock (inclusive).
+   *  - startBlock: `number | "latest"`
+   *  - endBlock: `number | "latest" | "realtime"`
+   *    - `number`: A specific block number.
+   *    - `"latest"`: The latest block number at the startup of the Ponder instance.
+   *    - `"realtime"`: Indefinite/live indexing.
+   */
+  blocks?:
+    | [number | "latest", number | "realtime" | "latest"][]
+    | [number | "latest", number | "realtime" | "latest"];
 };
 
 type TransactionReceiptConfig = {
@@ -210,11 +217,7 @@ type AccountsConfig<networks, accounts> = {} extends accounts
 
 // blocks
 
-type BlockFilterConfig = {
-  /** Block number at which to start indexing events (inclusive). If `undefined`, events will be processed from block 0. Default: `undefined`. */
-  startBlock?: number;
-  /** Block number at which to stop indexing events (inclusive). If `undefined`, events will be processed in real-time. Default: `undefined`. */
-  endBlock?: number;
+type BlockFilterConfig = BlockConfig & {
   interval?: number;
 };
 
diff --git a/packages/core/src/internal/types.ts b/packages/core/src/internal/types.ts
index 634ee7f4a..1bdfaed98 100644
--- a/packages/core/src/internal/types.ts
+++ b/packages/core/src/internal/types.ts
@@ -69,8 +69,8 @@ export type LogFilter<
   topic1: LogTopic;
   topic2: LogTopic;
   topic3: LogTopic;
-  fromBlock: number | undefined;
-  toBlock: number | undefined;
+  fromBlock: number;
+  toBlock: number;
   include:
     | (
         | `block.${keyof Block}`
@@ -86,8 +86,8 @@ export type BlockFilter = {
   chainId: number;
   interval: number;
   offset: number;
-  fromBlock: number | undefined;
-  toBlock: number | undefined;
+  fromBlock: number;
+  toBlock: number;
   include: `block.${keyof Block}`[] | undefined;
 };
 
@@ -100,8 +100,8 @@ export type TransferFilter<
   fromAddress: FilterAddress<fromFactory>;
   toAddress: FilterAddress<toFactory>;
   includeReverted: boolean;
-  fromBlock: number | undefined;
-  toBlock: number | undefined;
+  fromBlock: number;
+  toBlock: number;
   include:
     | (
         | `block.${keyof Block}`
@@ -121,8 +121,8 @@ export type TransactionFilter<
   fromAddress: FilterAddress<fromFactory>;
   toAddress: FilterAddress<toFactory>;
   includeReverted: boolean;
-  fromBlock: number | undefined;
-  toBlock: number | undefined;
+  fromBlock: number;
+  toBlock: number;
   include:
     | (
         | `block.${keyof Block}`
@@ -143,8 +143,8 @@ export type TraceFilter<
   functionSelector: Hex | Hex[] | undefined;
   callType: Trace["type"] | undefined;
   includeReverted: boolean;
-  fromBlock: number | undefined;
-  toBlock: number | undefined;
+  fromBlock: number;
+  toBlock: number;
   include:
     | (
         | `block.${keyof Block}`
diff --git a/packages/core/src/sync-historical/index.ts b/packages/core/src/sync-historical/index.ts
index 5c0e79dca..b5c98fdcc 100644
--- a/packages/core/src/sync-historical/index.ts
+++ b/packages/core/src/sync-historical/index.ts
@@ -758,16 +758,13 @@ export const createHistoricalSync = async (
       // is only partially synced.
 
       for (const { filter } of args.sources) {
-        if (
-          (filter.fromBlock !== undefined && filter.fromBlock > _interval[1]) ||
-          (filter.toBlock !== undefined && filter.toBlock < _interval[0])
-        ) {
+        if (filter.fromBlock > _interval[1] || filter.toBlock < _interval[0]) {
           continue;
         }
 
         const interval: Interval = [
-          Math.max(filter.fromBlock ?? 0, _interval[0]),
-          Math.min(filter.toBlock ?? Number.POSITIVE_INFINITY, _interval[1]),
+          Math.max(filter.fromBlock, _interval[0]),
+          Math.min(filter.toBlock, _interval[1]),
         ];
 
         const completedIntervals = intervalsCache.get(filter)!;
diff --git a/packages/core/src/sync-realtime/bloom.ts b/packages/core/src/sync-realtime/bloom.ts
index 2d636872e..3c1a5178f 100644
--- a/packages/core/src/sync-realtime/bloom.ts
+++ b/packages/core/src/sync-realtime/bloom.ts
@@ -43,8 +43,8 @@ export function isFilterInBloom({
 }): boolean {
   // Return `false` for out of range blocks
   if (
-    hexToNumber(block.number) < (filter.fromBlock ?? 0) ||
-    hexToNumber(block.number) > (filter.toBlock ?? Number.POSITIVE_INFINITY)
+    hexToNumber(block.number) < filter.fromBlock ||
+    hexToNumber(block.number) > filter.toBlock
   ) {
     return false;
   }
diff --git a/packages/core/src/sync-store/index.test.ts b/packages/core/src/sync-store/index.test.ts
index 2d78c753d..418c16052 100644
--- a/packages/core/src/sync-store/index.test.ts
+++ b/packages/core/src/sync-store/index.test.ts
@@ -80,8 +80,8 @@ test("getIntervals() empty", async (context) => {
     chainId: 1,
     interval: 1,
     offset: 0,
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies BlockFilter;
 
@@ -93,11 +93,11 @@ test("getIntervals() empty", async (context) => {
     Map {
       {
         "chainId": 1,
-        "fromBlock": undefined,
+        "fromBlock": 0,
         "include": [],
         "interval": 1,
         "offset": 0,
-        "toBlock": undefined,
+        "toBlock": Infinity,
         "type": "block",
       } => [
         {
@@ -124,8 +124,8 @@ test("getIntervals() returns intervals", async (context) => {
     chainId: 1,
     interval: 1,
     offset: 0,
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies BlockFilter;
 
@@ -147,11 +147,11 @@ test("getIntervals() returns intervals", async (context) => {
     Map {
       {
         "chainId": 1,
-        "fromBlock": undefined,
+        "fromBlock": 0,
         "include": [],
         "interval": 1,
         "offset": 0,
-        "toBlock": undefined,
+        "toBlock": Infinity,
         "type": "block",
       } => [
         {
@@ -183,8 +183,8 @@ test("getIntervals() merges intervals", async (context) => {
     chainId: 1,
     interval: 1,
     offset: 0,
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies BlockFilter;
 
@@ -215,11 +215,11 @@ test("getIntervals() merges intervals", async (context) => {
     Map {
       {
         "chainId": 1,
-        "fromBlock": undefined,
+        "fromBlock": 0,
         "include": [],
         "interval": 1,
         "offset": 0,
-        "toBlock": undefined,
+        "toBlock": Infinity,
         "type": "block",
       } => [
         {
@@ -254,8 +254,8 @@ test("getIntervals() adjacent intervals", async (context) => {
     topic2: null,
     topic3: null,
     address: [zeroAddress],
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies LogFilter;
 
@@ -290,9 +290,9 @@ test("getIntervals() adjacent intervals", async (context) => {
           "0x0000000000000000000000000000000000000000",
         ],
         "chainId": 1,
-        "fromBlock": undefined,
+        "fromBlock": 0,
         "include": [],
-        "toBlock": undefined,
+        "toBlock": Infinity,
         "topic0": null,
         "topic1": null,
         "topic2": null,
@@ -332,8 +332,8 @@ test("insertIntervals() merges duplicates", async (context) => {
     chainId: 1,
     interval: 1,
     offset: 0,
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies BlockFilter;
 
@@ -369,11 +369,11 @@ test("insertIntervals() merges duplicates", async (context) => {
     Map {
       {
         "chainId": 1,
-        "fromBlock": undefined,
+        "fromBlock": 0,
         "include": [],
         "interval": 1,
         "offset": 0,
-        "toBlock": undefined,
+        "toBlock": Infinity,
         "type": "block",
       } => [
         {
@@ -408,8 +408,8 @@ test("insertIntervals() preserves fragments", async (context) => {
     topic2: null,
     topic3: null,
     address: [zeroAddress, ALICE],
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies LogFilter;
 
@@ -435,9 +435,9 @@ test("insertIntervals() preserves fragments", async (context) => {
           "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266",
         ],
         "chainId": 1,
-        "fromBlock": undefined,
+        "fromBlock": 0,
         "include": [],
-        "toBlock": undefined,
+        "toBlock": Infinity,
         "topic0": null,
         "topic1": null,
         "topic2": null,
@@ -1404,8 +1404,8 @@ test("getEvents() returns events", async (context) => {
     topic1: null,
     topic2: null,
     topic3: null,
-    fromBlock: undefined,
-    toBlock: undefined,
+    fromBlock: 0,
+    toBlock: Number.POSITIVE_INFINITY,
     include: [],
   } satisfies LogFilter;
 
diff --git a/packages/core/src/sync/filter.ts b/packages/core/src/sync/filter.ts
index dc40f84ab..9777850a8 100644
--- a/packages/core/src/sync/filter.ts
+++ b/packages/core/src/sync/filter.ts
@@ -124,8 +124,8 @@ export const isLogFilterMatched = ({
 }): boolean => {
   // Return `false` for out of range blocks
   if (
-    hexToNumber(block.number) < (filter.fromBlock ?? 0) ||
-    hexToNumber(block.number) > (filter.toBlock ?? Number.POSITIVE_INFINITY)
+    hexToNumber(block.number) < filter.fromBlock ||
+    hexToNumber(block.number) > filter.toBlock
   ) {
     return false;
   }
@@ -176,8 +176,8 @@ export const isTransactionFilterMatched = ({
 }): boolean => {
   // Return `false` for out of range blocks
   if (
-    hexToNumber(block.number) < (filter.fromBlock ?? 0) ||
-    hexToNumber(block.number) > (filter.toBlock ?? Number.POSITIVE_INFINITY)
+    hexToNumber(block.number) < filter.fromBlock ||
+    hexToNumber(block.number) > filter.toBlock
   ) {
     return false;
   }
@@ -260,8 +260,8 @@ export const isTraceFilterMatched = ({
 }): boolean => {
   // Return `false` for out of range blocks
   if (
-    hexToNumber(block.number) < (filter.fromBlock ?? 0) ||
-    hexToNumber(block.number) > (filter.toBlock ?? Number.POSITIVE_INFINITY)
+    hexToNumber(block.number) < filter.fromBlock ||
+    hexToNumber(block.number) > filter.toBlock
   ) {
     return false;
   }
@@ -345,8 +345,8 @@ export const isTransferFilterMatched = ({
 }): boolean => {
   // Return `false` for out of range blocks
   if (
-    hexToNumber(block.number) < (filter.fromBlock ?? 0) ||
-    hexToNumber(block.number) > (filter.toBlock ?? Number.POSITIVE_INFINITY)
+    hexToNumber(block.number) < filter.fromBlock ||
+    hexToNumber(block.number) > filter.toBlock
   ) {
     return false;
   }
@@ -422,8 +422,8 @@ export const isBlockFilterMatched = ({
 }): boolean => {
   // Return `false` for out of range blocks
   if (
-    hexToNumber(block.number) < (filter.fromBlock ?? 0) ||
-    hexToNumber(block.number) > (filter.toBlock ?? Number.POSITIVE_INFINITY)
+    hexToNumber(block.number) < filter.fromBlock ||
+    hexToNumber(block.number) > filter.toBlock
   ) {
     return false;
   }
diff --git a/packages/core/src/sync/index.ts b/packages/core/src/sync/index.ts
index 5f727e43e..4ada0e0cd 100644
--- a/packages/core/src/sync/index.ts
+++ b/packages/core/src/sync/index.ts
@@ -82,7 +82,7 @@ export type RealtimeEvent =
 
 export type SyncProgress = {
   start: SyncBlock | LightBlock;
-  end: SyncBlock | LightBlock | undefined;
+  end: SyncBlock | LightBlock;
   cached: SyncBlock | LightBlock | undefined;
   current: SyncBlock | LightBlock | undefined;
   finalized: SyncBlock | LightBlock;
@@ -119,7 +119,7 @@ export const blockToCheckpoint = (
  * sync progress has reached the final end block.
  */
 const isSyncEnd = (syncProgress: SyncProgress) => {
-  if (syncProgress.end === undefined || syncProgress.current === undefined) {
+  if (syncProgress.current === undefined) {
     return false;
   }
 
@@ -145,12 +145,10 @@ const isSyncFinalized = (syncProgress: SyncProgress) => {
 const getHistoricalLast = (
   syncProgress: Pick<SyncProgress, "finalized" | "end">,
 ) => {
-  return syncProgress.end === undefined
+  return hexToNumber(syncProgress.end.number) >
+    hexToNumber(syncProgress.finalized.number)
     ? syncProgress.finalized
-    : hexToNumber(syncProgress.end.number) >
-        hexToNumber(syncProgress.finalized.number)
-      ? syncProgress.finalized
-      : syncProgress.end;
+    : syncProgress.end;
 };
 
 /** Compute the minimum checkpoint, filtering out undefined */
@@ -199,10 +197,6 @@ export const getChainCheckpoint = ({
   network: Network;
   tag: "start" | "current" | "finalized" | "end";
 }): string | undefined => {
-  if (tag === "end" && syncProgress.end === undefined) {
-    return undefined;
-  }
-
   if (tag === "current" && isSyncEnd(syncProgress)) {
     return undefined;
   }
@@ -371,10 +365,6 @@ export const createSync = async (args: CreateSyncParameters): Promise<Sync> => {
         getChainCheckpoint({ syncProgress, network, tag }),
     );
 
-    if (tag === "end" && checkpoints.some((c) => c === undefined)) {
-      return undefined;
-    }
-
     if (tag === "current" && checkpoints.every((c) => c === undefined)) {
       return undefined;
     }
@@ -1010,14 +1000,9 @@ export const syncDiagnostic = async ({
   requestQueue: RequestQueue;
 }) => {
   /** Earliest `startBlock` among all `filters` */
-  const start = Math.min(...sources.map(({ filter }) => filter.fromBlock ?? 0));
-  /**
-   * Latest `endBlock` among all filters. `undefined` if at least one
-   * of the filters doesn't have an `endBlock`.
-   */
-  const end = sources.some(({ filter }) => filter.toBlock === undefined)
-    ? undefined
-    : Math.max(...sources.map(({ filter }) => filter.toBlock!));
+  const start = Math.min(...sources.map(({ filter }) => filter.fromBlock));
+  /** Latest `endBlock` among all `filters`. */
+  const end = Math.max(...sources.map(({ filter }) => filter.toBlock));
 
   const [remoteChainId, startBlock, latestBlock] = await Promise.all([
     requestQueue.request({ method: "eth_chainId" }),
@@ -1026,16 +1011,14 @@ export const syncDiagnostic = async ({
   ]);
 
   const endBlock =
-    end === undefined
-      ? undefined
-      : end > hexToBigInt(latestBlock.number)
-        ? ({
-            number: toHex(end),
-            hash: "0x",
-            parentHash: "0x",
-            timestamp: toHex(maxCheckpoint.blockTimestamp),
-          } as LightBlock)
-        : await _eth_getBlockByNumber(requestQueue, { blockNumber: end });
+    end > hexToBigInt(latestBlock.number)
+      ? ({
+          number: toHex(end),
+          hash: "0x",
+          parentHash: "0x",
+          timestamp: toHex(maxCheckpoint.blockTimestamp),
+        } as LightBlock)
+      : await _eth_getBlockByNumber(requestQueue, { blockNumber: end });
 
   // Warn if the config has a different chainId than the remote.
   if (hexToNumber(remoteChainId) !== network.chainId) {
@@ -1073,8 +1056,8 @@ export const getCachedBlock = ({
 }): Promise<SyncBlock | LightBlock> | undefined => {
   const latestCompletedBlocks = sources.map(({ filter }) => {
     const requiredInterval = [
-      filter.fromBlock ?? 0,
-      filter.toBlock ?? Number.POSITIVE_INFINITY,
+      filter.fromBlock,
+      filter.toBlock,
     ] satisfies Interval;
     const fragmentIntervals = historicalSync.intervalsCache.get(filter)!;
 
@@ -1090,7 +1073,7 @@ export const getCachedBlock = ({
     if (completedIntervals.length === 0) return undefined;
 
     const earliestCompletedInterval = completedIntervals[0]!;
-    if (earliestCompletedInterval[0] !== (filter.fromBlock ?? 0)) {
+    if (earliestCompletedInterval[0] !== filter.fromBlock) {
       return undefined;
     }
     return earliestCompletedInterval[1];
@@ -1109,8 +1092,7 @@ export const getCachedBlock = ({
   if (
     latestCompletedBlocks.every(
       (block, i) =>
-        block !== undefined ||
-        (sources[i]!.filter.fromBlock ?? 0) > minCompletedBlock,
+        block !== undefined || sources[i]!.filter.fromBlock > minCompletedBlock,
     )
   ) {
     return _eth_getBlockByNumber(requestQueue, {
@@ -1177,15 +1159,7 @@ export async function* localHistoricalSyncGenerator({
     historicalSync.intervalsCache.entries(),
   ).flatMap(([filter, fragmentIntervals]) =>
     intervalDifference(
-      [
-        [
-          filter.fromBlock ?? 0,
-          Math.min(
-            filter.toBlock ?? Number.POSITIVE_INFINITY,
-            totalInterval[1],
-          ),
-        ],
-      ],
+      [[filter.fromBlock, Math.min(filter.toBlock, totalInterval[1])]],
       intervalIntersectionMany(
         fragmentIntervals.map(({ intervals }) => intervals),
       ),
diff --git a/packages/core/src/types/virtual.test-d.ts b/packages/core/src/types/virtual.test-d.ts
index bfa28130a..00575b583 100644
--- a/packages/core/src/types/virtual.test-d.ts
+++ b/packages/core/src/types/virtual.test-d.ts
@@ -55,7 +55,7 @@ const config = createConfig({
       abi: [event0, func0],
       network: "mainnet",
       address: "0x",
-      startBlock: 0,
+      blocks: [0, Number.POSITIVE_INFINITY],
       includeTransactionReceipts: false,
       includeCallTraces: true,
     },
@@ -64,7 +64,7 @@ const config = createConfig({
       address: "0x69",
       network: {
         mainnet: {
-          startBlock: 1,
+          blocks: [1, Number.POSITIVE_INFINITY],
           includeTransactionReceipts: true,
           includeCallTraces: true,
         },
@@ -81,7 +81,7 @@ const config = createConfig({
   blocks: {
     b1: {
       interval: 2,
-      startBlock: 1,
+      blocks: [1, Number.POSITIVE_INFINITY],
       network: "mainnet",
     },
   },
@@ -283,18 +283,14 @@ test("Context contracts", () => {
   //   ^?
 
   type expectedAbi = [Event1, Event1Overloaded, Func1, Func1Overloaded];
-  type expectedStartBlock = 1 | undefined;
-  type expectedEndBlock = undefined;
+  type expectedBlocks = [1, number] | undefined;
   type expectedAddress = "0x69";
 
   assertType<a["abi"]>({} as any as expectedAbi);
   assertType<expectedAbi>({} as any as a["abi"]);
 
-  assertType<a["startBlock"]>({} as any as expectedStartBlock);
-  assertType<expectedStartBlock>({} as any as a["startBlock"]);
-
-  assertType<a["endBlock"]>({} as any as expectedEndBlock);
-  assertType<expectedEndBlock>({} as any as a["endBlock"]);
+  assertType<a["blocks"]>({} as any as expectedBlocks);
+  assertType<expectedBlocks>({} as any as a["blocks"]);
 
   assertType<a["address"]>({} as any as expectedAddress);
   assertType<expectedAddress>({} as any as a["address"]);
diff --git a/packages/core/src/types/virtual.ts b/packages/core/src/types/virtual.ts
index b2309428d..436c135f7 100644
--- a/packages/core/src/types/virtual.ts
+++ b/packages/core/src/types/virtual.ts
@@ -189,13 +189,9 @@ export namespace Virtual {
           config["contracts"][_contractName],
           "address"
         >;
-        startBlock: ExtractOverridenProperty<
+        blocks: ExtractOverridenProperty<
           config["contracts"][_contractName],
-          "startBlock"
-        >;
-        endBlock: ExtractOverridenProperty<
-          config["contracts"][_contractName],
-          "endBlock"
+          "blocks"
         >;
       };
     };