diff --git a/indexer/lib/advertisement-walker.js b/indexer/lib/advertisement-walker.js
index e752621..6f52ebc 100644
--- a/indexer/lib/advertisement-walker.js
+++ b/indexer/lib/advertisement-walker.js
@@ -311,9 +311,16 @@ export async function fetchAdvertisedPayload (providerAddress, advertisementCid,
     }
   }
 
-  debug('entriesChunk %s %j', entriesCid, entriesChunk.Entries.slice(0, 5))
-  const entryHash = entriesChunk.Entries[0]['/'].bytes
-  const payloadCid = CID.create(1, 0x55 /* raw */, multihash.decode(Buffer.from(entryHash, 'base64'))).toString()
+  let payloadCid
+  try {
+    payloadCid = processEntries(entriesCid, entriesChunk)
+  } catch (err) {
+    debug('Error processing entries: %s', err)
+    return {
+      error: /** @type {const} */('PAYLOAD_CID_NOT_EXTRACTABLE'),
+      previousAdvertisementCid
+    }
+  }
 
   return {
     previousAdvertisementCid,
@@ -326,16 +333,44 @@ export async function fetchAdvertisedPayload (providerAddress, advertisementCid,
  * @param {string} cid
  * @param {object} [options]
  * @param {number} [options.fetchTimeout]
+ * @param {typeof fetch} [options.fetchMethod]
  * @returns {Promise<unknown>}
  */
-async function fetchCid (providerBaseUrl, cid, { fetchTimeout } = {}) {
-  const url = new URL(cid, new URL('/ipni/v1/ad/_cid_placeholder_', providerBaseUrl))
+export async function fetchCid (providerBaseUrl, cid, { fetchTimeout, fetchMethod } = {}) {
+  let url = new URL(providerBaseUrl)
+
+  // Check if the URL already has a path
+  if (!(url.pathname && url.pathname !== '/')) {
+    // If no path, add the standard path with a placeholder
+    url = new URL('/ipni/v1/ad/_cid_placeholder_', providerBaseUrl)
+  } else {
+    // If there's already a path, append the additional path
+    url = new URL(`${url.pathname}/ipni/v1/ad/_cid_placeholder_`, url.origin)
+  }
+  url = new URL(cid, url)
   debug('Fetching %s', url)
   try {
-    const res = await fetch(url, { signal: AbortSignal.timeout(fetchTimeout ?? 30_000) })
+    const res = await (fetchMethod ?? fetch)(url, { signal: AbortSignal.timeout(fetchTimeout ?? 30_000) })
     debug('Response from %s → %s %o', url, res.status, res.headers)
     await assertOkResponse(res)
-    return await res.json()
+
+    // Determine the codec based on the CID
+    const parsedCid = CID.parse(cid)
+    const codec = parsedCid.code
+
+    // List of codecs:
+    // https://github.com/multiformats/multicodec/blob/f18c7ba5f4d3cc74afb51ee79978939abc0e6556/table.csv
+    switch (codec) {
+      case 297: // DAG-JSON
+        return await res.json()
+
+      case 113: { // DAG-CBOR
+        const buffer = await res.arrayBuffer()
+        return cbor.decode(new Uint8Array(buffer)) }
+
+      default:
+        throw new Error(`Unknown codec ${codec} for CID ${cid}`)
+    }
   } catch (err) {
     if (err && typeof err === 'object') {
       Object.assign(err, { url })
@@ -371,3 +406,51 @@ export function parseMetadata (meta) {
     return { protocol }
   }
 }
+
+/**
+ * Process entries from either DAG-JSON or DAG-CBOR format
+ * @param {string} entriesCid - The CID of the entries
+ * @param {{Entries: Array<unknown>}} entriesChunk - The decoded entries
+ * @returns {string} The payload CID
+ */
+export function processEntries (entriesCid, entriesChunk) {
+  if (!entriesChunk.Entries || !entriesChunk.Entries.length) {
+    throw new Error(`No entries found in the response for ${entriesCid}`)
+  }
+  const parsedCid = CID.parse(entriesCid)
+  const codec = parsedCid.code
+  let entryBytes
+  switch (codec) {
+    case 297: {
+      // DAG-JSON
+      // For DAG-JSON format, the entry is a base64 encoded string
+      const entry = entriesChunk.Entries[0]
+      // Check that entry is an object with a '/' property
+      if (!entry || typeof entry !== 'object' || !('/' in entry)) {
+        throw new Error('DAG-JSON entry must have a "/" property')
+      }
+
+      // Verify the '/' property is an object with 'bytes' property
+      // In DAG-JSON, CIDs are represented as objects with a '/' property that contains 'bytes'
+      if (!entry['/'] || typeof entry['/'] !== 'object' || !('bytes' in entry['/'])) {
+        throw new Error('DAG-JSON entry\'s "/" property must be an object with a "bytes" property')
+      }
+
+      const entryHash = entry['/'].bytes
+      if (typeof entryHash !== 'string') {
+        throw new Error('DAG-JSON entry\'s ["/"]["bytes"] property must be a string')
+      }
+      entryBytes = Buffer.from(entryHash, 'base64')
+      break }
+    case 113: {
+      // DAG-CBOR
+      // For DAG-CBOR format, the entry is already a Uint8Array with the multihash
+      entryBytes = entriesChunk.Entries[0]
+      assert(entryBytes instanceof Uint8Array, 'DAG-CBOR entry must be a Uint8Array')
+      break }
+    default:
+      throw new Error(`Unsupported codec ${codec}`)
+  }
+  assert(entryBytes, 'Entry bytes must be set')
+  return CID.create(1, 0x55 /* raw */, multihash.decode(entryBytes)).toString()
+}
diff --git a/indexer/test/advertisement-walker.test.js b/indexer/test/advertisement-walker.test.js
index 3056b8a..ce4c8d8 100644
--- a/indexer/test/advertisement-walker.test.js
+++ b/indexer/test/advertisement-walker.test.js
@@ -1,19 +1,25 @@
 import { RedisRepository } from '@filecoin-station/spark-piece-indexer-repository'
 import { Redis } from 'ioredis'
 import assert from 'node:assert'
-import { after, before, beforeEach, describe, it } from 'node:test'
+import { after, before, beforeEach, describe, it, mock } from 'node:test'
 import { setTimeout } from 'node:timers/promises'
 import {
   fetchAdvertisedPayload,
   processNextAdvertisement,
   walkOneStep
+  , processEntries,
+  fetchCid
 } from '../lib/advertisement-walker.js'
+import pRetry from 'p-retry'
 import { givenHttpServer } from './helpers/http-server.js'
 import { FRISBII_ADDRESS, FRISBII_AD_CID } from './helpers/test-data.js'
 import { assertOkResponse } from '../lib/http-assertions.js'
 import * as stream from 'node:stream'
 import { pipeline } from 'node:stream/promises'
-
+import * as cbor from '@ipld/dag-cbor'
+import { CID } from 'multiformats/cid'
+import * as crypto from 'node:crypto'
+import * as multihash from 'multiformats/hashes/digest'
 /** @import { ProviderInfo, WalkerState } from '../lib/typings.js' */
 
 // TODO(bajtos) We may need to replace this with a mock index provider
@@ -517,3 +523,249 @@ describe('data schema for REST API', () => {
     })
   })
 })
+
+describe('processEntries', () => {
+  // Use a real DAG-JSON CID that will naturally have codec 0x0129 (297)
+  // CIDs that start with 'bagu' are DAG-JSON encoded
+  const dagJsonCid = 'baguqeeraa5mjufqdwuwrrrqboctnn3vhdlq63rj3hce2igpzbmae7sazkfea'
+  // Use a real DAG-CBOR CID that will naturally have codec 0x71 (113)
+  // CIDs that start with 'bafy' are DAG-CBOR encoded
+  const dagCborCid = 'bafyreibpxkmu65ezxy7rynxotbghfz3ktiapjisntepd67hghfn4hde3na'
+  const testData = 'test data for multihash'
+  // Create a proper multihash from this digest
+  const mh = multihash.create(0x12, crypto.createHash('sha256').update(testData).digest())
+  // @ts-ignore
+  const entryBytes = Buffer.from(mh.bytes).toString('base64')
+  const dagJsonChunk = {
+    Entries: [
+      {
+        '/': {
+          bytes: entryBytes
+        }
+      }
+    ]
+  }
+
+  const dagCborChunk = {
+    Entries: [mh.bytes]
+  }
+  it('processes DAG-JSON entries correctly', () => {
+    // Process the entries with the real CID
+    const result = processEntries(dagJsonCid, dagJsonChunk)
+
+    // Verify the result is a valid CID string
+    assert(CID.parse(result), 'Result should be a parseable CID')
+  })
+
+  it('processes DAG-CBOR entries correctly', () => {
+    // Process the entries with the real CID
+    const result = processEntries(dagCborCid, dagCborChunk)
+
+    // Verify the result is a valid CID string
+    assert(CID.parse(result), 'Result should be a parseable CID')
+  })
+
+  // Error handling tests
+  it('throws an error when entries array is empty', () => {
+    assert.throws(
+      () => processEntries(dagCborCid, { Entries: [] }),
+      /No entries found/
+    )
+  })
+
+  it('throws an error when Entries field is missing', () => {
+    assert.throws(
+      // @ts-ignore
+      () => processEntries(dagCborCid, {}),
+      /No entries found/
+    )
+  })
+
+  it('throws an error for unsupported codec', () => {
+    // Use a CID with an unsupported codec
+    const unsupportedCid = 'bafkreigrnnl64xuevvkhknbhrcqzbdvvmqnchp7ae2a4ulninsjoc5svoq'
+
+    assert.throws(
+      () => processEntries(unsupportedCid, dagJsonChunk),
+      /Unsupported codec/
+    )
+  })
+
+  // Data integrity test using real multihash operations
+  it('correctly creates a CID from entry data', () => {
+    // Process the entries
+    const result = processEntries(dagJsonCid, dagJsonChunk)
+
+    // Create the expected CID directly
+    const expectedCid = CID.create(1, 0x55, mh).toString()
+
+    // They should match
+    assert.strictEqual(result, expectedCid, 'CID should match the one created directly')
+  })
+
+  // Test with entries from CBOR encoding/decoding
+  it('correctly handles DAG-CBOR entries serialized with @ipld/dag-cbor', () => {
+    // Process the entries
+    const result = processEntries(dagCborCid, dagCborChunk)
+
+    // Create the expected CID directly
+    const expectedCid = CID.create(1, 0x55, mh).toString()
+
+    // They should match
+    assert.strictEqual(result, expectedCid, 'CID should match the one created directly')
+  })
+
+  // Error case tests with real data
+  it('handles malformed base64 in DAG-JSON gracefully', () => {
+    const malformedChunk = {
+      Entries: [
+        {
+          '/': {
+            bytes: 'This-is-not-valid-base64!'
+          }
+        }
+      ]
+    }
+
+    // We expect an error when processing this malformed data
+    assert.throws(
+      () => processEntries(dagJsonCid, malformedChunk),
+      /Incorrect length/
+    )
+  })
+
+  it('handles invalid multihash in DAG-CBOR gracefully', () => {
+    const invalidChunk = {
+      Entries: [new Uint8Array([0, 1, 2, 3])] // Too short to be a valid multihash
+    }
+
+    // We expect an error when processing this invalid multihash
+    assert.throws(
+      () => processEntries(dagCborCid, invalidChunk),
+      /Incorrect length/
+    )
+  })
+})
+
+describe('fetchCid', () => {
+  // Use a real DAG-JSON CID that will naturally have codec 0x0129 (297)
+  // CIDs that start with 'bagu' are DAG-JSON encoded
+  const dagJsonCid = 'baguqeerayzpbdctxk4iyps45uldgibsvy6zro33vpfbehggivhcxcq5suaia'
+  // Sample JSON response
+  const testResponse = { test: 'value' }
+  // Use a real DAG-CBOR CID that will naturally have codec 0x71 (113)
+  // CIDs that start with 'bafy' are DAG-CBOR encoded
+  const dagCborCid = 'bafyreictdikh363qfxsmjp63i6kup6aukjqfpd4r6wbhbiz2ctuji4bofm'
+
+  it('uses DAG-JSON codec (0x0129) to parse response as JSON', async () => {
+    // Mock fetch to return JSON
+    // @ts-ignore
+    const mockFetch = mock.fn(() => Promise.resolve({
+      ok: true,
+      status: 200,
+      json: () => Promise.resolve(testResponse),
+      arrayBuffer: () => { throw new Error('Should not call arrayBuffer for JSON') }
+    }))
+
+    const parsedCid = CID.parse(dagJsonCid)
+    assert.strictEqual(parsedCid.code, 297)
+
+    // @ts-ignore
+    const result = await fetchCid('http://example.com', dagJsonCid, { fetchMethod: mockFetch })
+
+    // Verify we got the JSON response
+    assert.deepStrictEqual(result, testResponse)
+  })
+
+  it('uses DAG-CBOR codec (0x71) to parse response as CBOR', async () => {
+    const cborData = cbor.encode(testResponse)
+
+    // Mock fetch to return ArrayBuffer
+    // @ts-ignore
+    const mockFetch = mock.fn(() => Promise.resolve({
+      ok: true,
+      status: 200,
+      json: () => { throw new Error('Should not call json for CBOR') },
+      arrayBuffer: () => Promise.resolve(cborData.buffer)
+    })
+    )
+
+    const parsedCid = CID.parse(dagCborCid)
+    assert.strictEqual(parsedCid.code, 113)
+
+    // @ts-ignore
+    const result = await fetchCid('http://example.com', dagCborCid, { fetchMethod: mockFetch })
+
+    // Verify we got the decoded CBOR data
+    assert.deepStrictEqual(result, testResponse)
+  })
+
+  it('throws an error for unknown codec', async () => {
+    // Mock fetch to return JSON
+
+    // @ts-ignore
+    const mockFetch = mock.fn(() => Promise.resolve({
+      ok: true,
+      status: 200,
+      json: () => { throw new Error('Should not call json for CBOR') },
+      arrayBuffer: () => { throw new Error('Should not call arrayBuffer for fallback') }
+    })
+    )
+
+    // Use a CID with a codec that is neither DAG-JSON (0x0129) nor DAG-CBOR (0x71)
+    // This is a raw codec (0x55) CID
+    const unknownCodecCid = 'bafkreigrnnl64xuevvkhknbhrcqzbdvvmqnchp7ae2a4ulninsjoc5svoq'
+    const parsedCid = CID.parse(unknownCodecCid)
+    assert.strictEqual(parsedCid.code, 85)
+    const errorMessage = 'Unknown codec 85'
+    try {
+      // @ts-ignore
+      await fetchCid('http://example.com', unknownCodecCid, { fetchMethod: mockFetch })
+      assert.fail('fetchCid should have thrown an error')
+    } catch (error) {
+      // @ts-ignore
+      assert.ok(error.message.includes(errorMessage), `Error message should include: ${errorMessage}`)
+    }
+  })
+  it('correctly fetches and processes real DAG-CBOR data from Curio provider', async function () {
+    // Use a real Curio provider and known DAG-CBOR CID
+    const curioProviderUrl = 'https://f03303347-market.duckdns.org/ipni-provider/12D3KooWJ91c6xQshrNe7QAXPFAaeRrHWq2UrgXGPf8UmMZMwyZ5'
+    const dagCborCid = 'baguqeeracgnw2ecmhaa6qkb3irrgjjk5zt5fes7wwwpb4aymoaogzyvvbrma'
+    /** @type {unknown} */
+    let result = await pRetry(
+      () =>
+        (
+          fetchCid(curioProviderUrl, dagCborCid)
+        )
+    )
+
+    // Verify the result has the expected structure for DAG-CBOR entries
+    assert(result, 'Expected a non-null result')
+    assert(typeof result === 'object' && result !== null, 'Result should be an object')
+
+    /** @type {Record<string, unknown>} */
+    const resultObj = /** @type {Record<string, unknown>} */ (result)
+    assert('Entries' in resultObj, 'Result should have Entries property')
+    assert(typeof resultObj.Entries === 'object' && resultObj.Entries !== null, 'Entries should be an object')
+
+    /** @type {Record<string, unknown>} */
+    const entries = /** @type {Record<string, unknown>} */ (resultObj.Entries)
+    assert('/' in entries, 'Entries should have a "/" property')
+
+    const entriesCid = entries['/']
+    assert(typeof entriesCid === 'string', 'Entries CID should be a string')
+
+    /** @type {unknown} */
+    result = await pRetry(
+      () =>
+        (
+          fetchCid(curioProviderUrl, entriesCid)
+        )
+    )
+    /** @type {{ Entries: unknown[]; }} */
+    const entriesChunk = /** @type {{ Entries: unknown[]; }} */ (result)
+    const payloadCid = processEntries(entriesCid, entriesChunk)
+    console.log(payloadCid)
+    assert.deepStrictEqual(payloadCid, 'bafkreiefrclz7c6w57yl4u7uiq4kvht4z7pits5jpcj3cajbvowik3rvhm')
+  })
+})