diff --git a/ncli/resttest-rules.json b/ncli/resttest-rules.json
index ac3396e11..aef11baa9 100644
--- a/ncli/resttest-rules.json
+++ b/ncli/resttest-rules.json
@@ -1973,7 +1973,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "200"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "value": ["phase0", "altair", "bellatrix"], "operator": "oneof"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"version": "", "data": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body": {"randao_reveal": "", "eth1_data": {"deposit_root": "", "deposit_count": "", "block_hash": ""}, "graffiti": "", "proposer_slashings": [{"signed_header_1": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}, "signed_header_2": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}}], "attester_slashings": [{"attestation_1": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}, "attestation_2": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}}], "attestations": [{"aggregation_bits": "", "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}], "deposits": [{"proof": [""], "data": {"pubkey": "", "withdrawal_credentials": "", "amount": "", "signature": ""}}], "voluntary_exits": [{"message": {"epoch": "", "validator_index": ""}, "signature": ""}]}}, "signature": ""}}}]
     }
   },
@@ -1985,7 +1988,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "200"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "value": ["phase0", "altair", "bellatrix"], "operator": "oneof"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"version": "", "data": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body": {"randao_reveal": "", "eth1_data": {"deposit_root": "", "deposit_count": "", "block_hash": ""}, "graffiti": "", "proposer_slashings": [{"signed_header_1": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}, "signed_header_2": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}}], "attester_slashings": [{"attestation_1": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}, "attestation_2": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}}], "attestations": [{"aggregation_bits": "", "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}], "deposits": [{"proof": [""], "data": {"pubkey": "", "withdrawal_credentials": "", "amount": "", "signature": ""}}], "voluntary_exits": [{"message": {"epoch": "", "validator_index": ""}, "signature": ""}]}}, "signature": ""}}}]
     }
   },
@@ -1997,7 +2003,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "200"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "value": ["phase0", "altair", "bellatrix"], "operator": "oneof"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"version": "", "data": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body": {"randao_reveal": "", "eth1_data": {"deposit_root": "", "deposit_count": "", "block_hash": ""}, "graffiti": "", "proposer_slashings": [{"signed_header_1": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}, "signed_header_2": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}}], "attester_slashings": [{"attestation_1": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}, "attestation_2": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}}], "attestations": [{"aggregation_bits": "", "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}], "deposits": [{"proof": [""], "data": {"pubkey": "", "withdrawal_credentials": "", "amount": "", "signature": ""}}], "voluntary_exits": [{"message": {"epoch": "", "validator_index": ""}, "signature": ""}]}}, "signature": ""}}}]
     }
   },
@@ -2009,7 +2018,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "200"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "value": ["phase0", "altair", "bellatrix"], "operator": "oneof"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"version": "", "data": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body": {"randao_reveal": "", "eth1_data": {"deposit_root": "", "deposit_count": "", "block_hash": ""}, "graffiti": "", "proposer_slashings": [{"signed_header_1": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}, "signed_header_2": {"message": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""},"signature": ""}}], "attester_slashings": [{"attestation_1": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}, "attestation_2": {"attesting_indices": [""], "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}}], "attestations": [{"aggregation_bits": "", "signature": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}}], "deposits": [{"proof": [""], "data": {"pubkey": "", "withdrawal_credentials": "", "amount": "", "signature": ""}}], "voluntary_exits": [{"message": {"epoch": "", "validator_index": ""}, "signature": ""}]}}, "signature": ""}}}]
     }
   },
@@ -2021,7 +2033,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "404"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "operator": "notexists"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
@@ -2033,7 +2048,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "400"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "operator": "notexists"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
@@ -2045,7 +2063,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "404"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "operator": "notexists"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
@@ -2057,7 +2078,10 @@
     },
     "response": {
       "status": {"operator": "equals", "value": "400"},
-      "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "operator": "notexists"}
+      ],
       "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
@@ -2685,6 +2709,21 @@
       "body": [{"operator": "jstructcmps", "start": ["data"], "value": {"genesis_time": "", "genesis_validators_root": "", "slot": "", "fork": {"previous_version": "", "current_version": "", "epoch": ""}, "latest_block_header": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""}, "block_roots": [""], "state_roots": [""], "historical_roots": [""], "eth1_data": {"deposit_root": "", "deposit_count": "", "block_hash": ""}, "eth1_data_votes": [{"deposit_root": "", "deposit_count": "", "block_hash": ""}], "eth1_deposit_index": "", "validators": [{"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}], "balances": [""], "randao_mixes": [""], "slashings": [""], "previous_epoch_attestations": [{"aggregation_bits": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}, "inclusion_delay": "", "proposer_index": ""}], "current_epoch_attestations": [{"aggregation_bits": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}, "inclusion_delay": "", "proposer_index": ""}], "justification_bits": "", "previous_justified_checkpoint": {"epoch": "", "root": ""}, "current_justified_checkpoint": {"epoch": "", "root": ""}, "finalized_checkpoint": {"epoch": "", "root": ""}}}]
     }
   },
+  {
+    "topics": ["debug", "beacon_states_head_slow", "slow"],
+    "request": {
+      "url": "/eth/v2/debug/beacon/states/head",
+      "headers": {"Accept": "application/json"}
+    },
+    "response": {
+      "status": {"operator": "equals", "value": "200"},
+      "headers": [
+        {"key": "Content-Type", "value": "application/json", "operator": "equals"},
+        {"key": "Eth-Consensus-Version", "value": ["phase0", "altair", "bellatrix"], "operator": "oneof"}
+      ],
+      "body": [{"operator": "jstructcmps", "start": ["data"], "value": {"genesis_time": "", "genesis_validators_root": "", "slot": "", "fork": {"previous_version": "", "current_version": "", "epoch": ""}, "latest_block_header": {"slot": "", "proposer_index": "", "parent_root": "", "state_root": "", "body_root": ""}, "block_roots": [""], "state_roots": [""], "historical_roots": [""], "eth1_data": {"deposit_root": "", "deposit_count": "", "block_hash": ""}, "eth1_data_votes": [{"deposit_root": "", "deposit_count": "", "block_hash": ""}], "eth1_deposit_index": "", "validators": [{"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}], "balances": [""], "randao_mixes": [""], "slashings": [""], "previous_epoch_attestations": [{"aggregation_bits": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}, "inclusion_delay": "", "proposer_index": ""}], "current_epoch_attestations": [{"aggregation_bits": "", "data": {"slot": "", "index": "", "beacon_block_root": "", "source": {"epoch": "", "root": ""}, "target": {"epoch": "", "root": ""}}, "inclusion_delay": "", "proposer_index": ""}], "justification_bits": "", "previous_justified_checkpoint": {"epoch": "", "root": ""}, "current_justified_checkpoint": {"epoch": "", "root": ""}, "finalized_checkpoint": {"epoch": "", "root": ""}}}]
+    }
+  },
   {
     "topics": ["node"],
     "request": {
diff --git a/ncli/resttest.nim b/ncli/resttest.nim
index e2610e0a1..8ad0bdbc4 100644
--- a/ncli/resttest.nim
+++ b/ncli/resttest.nim
@@ -1,3 +1,10 @@
+# beacon_chain
+# Copyright (c) 2021-2022 Status Research & Development GmbH
+# Licensed and distributed under either of
+#   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
+#   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
+# at your option. This file may not be copied, modified, or distributed except according to those terms.
+
 import std/[strutils, os, options, uri, json, tables]
 import stew/[results, io2, base10]
 import confutils, chronicles, httputils,
@@ -24,7 +31,7 @@ type
     Equals, OneOf, Inside, InsideOrEq
 
   HeaderOperatorKind {.pure.} = enum
-    Exists, Equals, OneOf, Substr
+    Exists, NotExists, Equals, OneOf, Substr
 
   BodyOperatorKind {.pure.} = enum
     Exists, JsonStructCmpS, JsonStructCmpNS
@@ -574,6 +581,8 @@ proc getResponseHeadersExpect(rule: JsonNode): Result[HeadersExpect, cstring] =
           case toLowerAscii(jop.str)
           of "exists":
             HeaderOperatorKind.Exists
+          of "notexists":
+            HeaderOperatorKind.NotExists
           of "equals":
             HeaderOperatorKind.Equals
           of "oneof":
@@ -586,24 +595,25 @@ proc getResponseHeadersExpect(rule: JsonNode): Result[HeadersExpect, cstring] =
       block:
         var vres: seq[string]
         let jvalue = jitem.getOrDefault("value")
-        case jvalue.kind
-        of JArray:
-          if len(jvalue.elems) == 0:
-            return err("`response.header` element has an empty array value")
-          for jelem in jvalue.elems:
-            case jelem.kind
-            of JString:
-              vres.add(jvalue.str)
-            of JInt:
-              vres.add(Base10.toString(uint64(jvalue.num)))
-            else:
-              return err("`response.header` element has incorrect value")
-        of JString:
-          vres.add(jvalue.str)
-        of JInt:
-          vres.add(Base10.toString(uint64(jvalue.num)))
-        else:
-          return err("`response.header` element has incorrect value")
+        if not isnil(jvalue):
+          case jvalue.kind
+          of JArray:
+            if len(jvalue.elems) == 0:
+              return err("`response.header` element has an empty array value")
+            for jelem in jvalue.elems:
+              case jelem.kind
+              of JString:
+                vres.add(jelem.str)
+              of JInt:
+                vres.add(Base10.toString(uint64(jvalue.num)))
+              else:
+                return err("`response.header` element has incorrect value")
+          of JString:
+            vres.add(jvalue.str)
+          of JInt:
+            vres.add(Base10.toString(uint64(jvalue.num)))
+          else:
+            return err("`response.header` element has incorrect value")
         vres
     res.add(HeaderExpect(key: key, value: value, kind: operator))
   ok(HeadersExpect(headers: res))
@@ -704,6 +714,9 @@ proc validateHeaders(resp: HttpResponseHeader, expect: HeadersExpect): bool =
       of HeaderOperatorKind.Exists:
         if item.key notin resp:
           return false
+      of HeaderOperatorKind.NotExists:
+        if item.key in resp:
+          return false
       of HeaderOperatorKind.Equals:
         if item.key notin resp:
           return false