diff --git a/.github/workflows/probe-etherscan-base.yml b/.github/workflows/probe-etherscan-base.yml
new file mode 100644
index 0000000..216060b
--- /dev/null
+++ b/.github/workflows/probe-etherscan-base.yml
@@ -0,0 +1,22 @@
+name: probe etherscan base deployment
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - '.github/workflows/probe-etherscan-base.yml'
+      - 'scripts/probe-etherscan-base-deployment.ts'
+      - 'src/app.ts'
+jobs:
+  probe:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Probe Etherscan V2 Base getcontractcreation
+        run: npx tsx scripts/probe-etherscan-base-deployment.ts
+        env:
+          ETHERSCAN_API_KEY: ${{ secrets.ETHERSCAN_API_KEY }}
diff --git a/scripts/probe-etherscan-base-deployment.ts b/scripts/probe-etherscan-base-deployment.ts
new file mode 100644
index 0000000..59e4e5b
--- /dev/null
+++ b/scripts/probe-etherscan-base-deployment.ts
@@ -0,0 +1,73 @@
+/**
+ * One-off probe: verify Etherscan V2 getcontractcreation works for Base
+ * with the addresses from issue #806 / the failing Blockscout batch.
+ *
+ * Usage (CI): npx tsx scripts/probe-etherscan-base-deployment.ts
+ */
+import { Address } from 'viem'
+import { base } from 'viem/chains'
+import EtherscanApi from '../src/services/etherscanApi'
+
+const ADDRESSES = [
+    '0xb6862ada846003e66e2bc2de1e1acc4687f2ccb3',
+    '0x1be88d8b5696a69378973729523f3a135921854b',
+    '0x586d1d28d5f8aed81da8aef7016c4108f7a4ce51', // rate provider from issue #806
+    '0xe32ba1c7546cf0793ce88ddcb7883d37fba83789',
+    '0x9c2dcdbdb3f0a0f628d1112bbcabd9ae75353df3', // asset from issue #806
+] as Address[]
+
+async function probeRaw(apiKey: string) {
+    const url =
+        `https://api.etherscan.io/v2/api?chainid=${base.id}` +
+        `&module=contract&action=getcontractcreation` +
+        `&contractaddresses=${ADDRESSES.join(',')}` +
+        `&apikey=${apiKey}`
+
+    const response = await fetch(url)
+    const data = await response.json()
+    console.log(`HTTP ${response.status}`)
+    console.log(`status=${data.status} message=${data.message}`)
+    console.log(`result_type=${Array.isArray(data.result) ? 'array' : typeof data.result}`)
+    if (typeof data.result === 'string') {
+        console.log(`result=${data.result}`)
+    } else if (Array.isArray(data.result)) {
+        console.log(`result_len=${data.result.length}`)
+    }
+    return data
+}
+
+async function main() {
+    const apiKey = process.env.ETHERSCAN_API_KEY
+    if (!apiKey) {
+        throw new Error('ETHERSCAN_API_KEY is not set')
+    }
+
+    console.log(`Probing Etherscan V2 getcontractcreation on Base for ${ADDRESSES.length} addresses...`)
+    const raw = await probeRaw(apiKey)
+
+    if (raw.status !== '1' || !Array.isArray(raw.result)) {
+        throw new Error(
+            `Etherscan V2 Base getcontractcreation failed: status=${raw.status} message=${raw.message} result=${typeof raw.result === 'string' ? raw.result : JSON.stringify(raw.result)?.slice(0, 200)}`,
+        )
+    }
+
+    const api = new EtherscanApi(base, apiKey)
+    const results = await api.getDeploymentTxHashAndBlock(ADDRESSES)
+
+    for (const result of results) {
+        const ok = Boolean(result.deploymentTxHash)
+        console.log(
+            `${ok ? 'OK' : 'MISSING'} ${result.address} tx=${result.deploymentTxHash || 'n/a'} block=${result.blockNumber || 'n/a'}`,
+        )
+        if (!ok) {
+            throw new Error(`Missing deployment tx for ${result.address}`)
+        }
+    }
+
+    console.log(`SUCCESS: Etherscan V2 returned deployment data for all ${results.length} Base addresses`)
+}
+
+main().catch((error) => {
+    console.error('PROBE FAILED:', error instanceof Error ? error.message : error)
+    process.exit(1)
+})
diff --git a/src/app.ts b/src/app.ts
index 6d45abb..81b173a 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -97,10 +97,36 @@ class RateProviderDataService {
     public async getDeploymentBlocks(addresses: Address[]): Promise<{ address: Address; deploymentTxHash: Hex }[]> {
         const chainApi = this.getApiForFunction('getDeploymentBlocks')
 
-        // The addresses length can be arbitrary but the etherscan API only allows 5 addresses at a time
-        // so we need to chunk the addresses and call the API sequentially
+        try {
+            return await this.fetchDeploymentBlocksFromApi(chainApi, addresses)
+        } catch (error) {
+            // Base/Optimism use Blockscout for getDeploymentBlocks, but that endpoint is often
+            // flaky (HTTP 500) or rate-limited. Fall back to Etherscan V2 when a key is available.
+            const canFallbackToEtherscan =
+                (this.chain.id === base.id || this.chain.id === optimism.id) && Boolean(this.apiKey)
+
+            if (!canFallbackToEtherscan) {
+                throw error
+            }
+
+            console.warn(
+                `Blockscout getDeploymentBlocks failed for ${this.chain.name}; falling back to Etherscan V2:`,
+                error instanceof Error ? error.message : error,
+            )
+            return await this.fetchDeploymentBlocksFromApi(new EtherscanApi(this.chain, this.apiKey), addresses)
+        }
+    }
+
+    /**
+     * Chunks addresses and fetches deployment info from the given explorer API.
+     * Explorer APIs typically allow at most 5 addresses per getcontractcreation call.
+     */
+    private async fetchDeploymentBlocksFromApi(
+        chainApi: ChainApi,
+        addresses: Address[],
+    ): Promise<{ address: Address; deploymentTxHash: Hex }[]> {
         const chunkSize = 5
-        const txHashes = []
+        const txHashes: { address: Address; deploymentTxHash: Hex }[] = []
 
         for (let i = 0; i < addresses.length; i += chunkSize) {
             const chunk = addresses.slice(i, i + chunkSize)