diff --git a/tests/waku_rln_relay/test_rln_group_manager_onchain.nim b/tests/waku_rln_relay/test_rln_group_manager_onchain.nim
index f9137cb08..e8527e4e2 100644
--- a/tests/waku_rln_relay/test_rln_group_manager_onchain.nim
+++ b/tests/waku_rln_relay/test_rln_group_manager_onchain.nim
@@ -333,7 +333,7 @@ suite "Onchain group manager":
     debug "epoch in bytes", epochHex = epoch.inHex()
 
     # generate proof
-    let validProofRes = manager.generateProof(
+    let validProofRes = await manager.generateProof(
       data = messageBytes, epoch = epoch, messageId = MessageId(1)
     )
 
@@ -367,10 +367,13 @@ suite "Onchain group manager":
     debug "epoch in bytes", epochHex = epoch.inHex()
 
     # generate proof
-    let validProof = manager.generateProof(
+    let validProofRes = await manager.generateProof(
       data = messageBytes, epoch = epoch, messageId = MessageId(0)
-    ).valueOr:
-      raiseAssert $error
+    )
+
+    check:
+      validProofRes.isOk()
+    let validProof = validProofRes.get()
 
     # validate the root (should be false)
     let validated = manager.validateRoot(validProof.merkleRoot)
@@ -410,10 +413,13 @@ suite "Onchain group manager":
     debug "epoch in bytes", epochHex = epoch.inHex()
 
     # generate proof
-    let validProof = manager.generateProof(
+    let validProofRes = await manager.generateProof(
       data = messageBytes, epoch = epoch, messageId = MessageId(0)
-    ).valueOr:
-      raiseAssert $error
+    )
+
+    check:
+      validProofRes.isOk()
+    let validProof = validProofRes.get()
 
     # verify the proof (should be true)
     let verified = manager.verifyProof(messageBytes, validProof).valueOr:
@@ -454,7 +460,7 @@ suite "Onchain group manager":
     debug "epoch in bytes", epochHex = epoch.inHex()
 
     # generate proof
-    let invalidProofRes = manager.generateProof(
+    let invalidProofRes = await manager.generateProof(
       data = messageBytes, epoch = epoch, messageId = MessageId(0)
     )
 
diff --git a/waku/waku_rln_relay/group_manager/on_chain/group_manager.nim b/waku/waku_rln_relay/group_manager/on_chain/group_manager.nim
index 38c657534..4cb7fdbc9 100644
--- a/waku/waku_rln_relay/group_manager/on_chain/group_manager.nim
+++ b/waku/waku_rln_relay/group_manager/on_chain/group_manager.nim
@@ -64,6 +64,30 @@ type
     keystorePassword*: Option[string]
     registrationHandler*: Option[RegistrationHandler]
     validRootBuffer*: Deque[MerkleNode]
+    latestProcessedBlock*: BlockNumber
+
+proc setMetadata*(
+    g: OnchainGroupManager, lastProcessedBlock = none(BlockNumber)
+): GroupManagerResult[void] =
+  let normalizedBlock =
+    if lastProcessedBlock.isSome():
+      lastProcessedBlock.get()
+    else:
+      g.latestProcessedBlock
+  try:
+    let metadataSetRes = g.rlnInstance.setMetadata(
+      RlnMetadata(
+        lastProcessedBlock: normalizedBlock.uint64,
+        chainId: g.chainId,
+        contractAddress: g.ethContractAddress,
+        validRoots: g.validRootBuffer.toSeq(),
+      )
+    )
+    if metadataSetRes.isErr():
+      return err("failed to persist rln metadata: " & metadataSetRes.error)
+  except CatchableError:
+    return err("failed to persist rln metadata: " & getCurrentExceptionMsg())
+  return ok()
 
 proc fetchMerkleProofElements*(
     g: OnchainGroupManager
@@ -369,6 +393,12 @@ method verifyProof*(
   else:
     return ok(true)
 
+method onRegister*(g: OnchainGroupManager, cb: OnRegisterCallback) {.gcsafe.} =
+  g.registerCb = some(cb)
+
+method onWithdraw*(g: OnchainGroupManager, cb: OnWithdrawCallback) {.gcsafe.} =
+  g.withdrawCb = some(cb)
+
 method init*(g: OnchainGroupManager): Future[GroupManagerResult[void]] {.async.} =
   # check if the Ethereum client is reachable
   var ethRpc: Web3