From 1ade07d705d3dd2ad8168923f96d1188d5bcd996 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 9 Jun 2021 16:31:20 -0600
Subject: [PATCH 01/22] fix mismatched proposer test names

---
 .../test_process_proposer_slashing.py            | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py
index b9becc1fd..48bc5ba3d 100644
--- a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py
+++ b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py
@@ -35,6 +35,14 @@ def run_proposer_slashing_processing(spec, state, proposer_slashing, valid=True)
 @with_all_phases
 @spec_state_test
 def test_success(spec, state):
+    proposer_slashing = get_valid_proposer_slashing(spec, state, signed_1=True, signed_2=True)
+
+    yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
+
+
+@with_all_phases
+@spec_state_test
+def test_success_slashed_and_proposer_index_the_same(spec, state):
     # Get proposer for next slot
     block = build_empty_block_for_next_slot(spec, state)
     proposer_index = block.proposer_index
@@ -47,14 +55,6 @@ def test_success(spec, state):
     yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
 
 
-@with_all_phases
-@spec_state_test
-def test_success_slashed_and_proposer_index_the_same(spec, state):
-    proposer_slashing = get_valid_proposer_slashing(spec, state, signed_1=True, signed_2=True)
-
-    yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
-
-
 @with_all_phases
 @spec_state_test
 @always_bls

From a5762cbad8502945d762cffaaa5a927dec656c43 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 9 Jun 2021 16:56:32 -0600
Subject: [PATCH 02/22] add attestesr slashing for proposer, and some future
 slashing tests woo

---
 .../test/helpers/proposer_slashings.py        |  5 ++-
 .../test_process_attester_slashing.py         | 39 ++++++++++++++++++-
 .../test_process_proposer_slashing.py         |  8 ++++
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/helpers/proposer_slashings.py b/tests/core/pyspec/eth2spec/test/helpers/proposer_slashings.py
index a783d2517..ac0a1cce2 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/proposer_slashings.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/proposer_slashings.py
@@ -73,12 +73,13 @@ def check_proposer_slashing_effect(spec, pre_state, state, slashed_index, block=
 
 
 def get_valid_proposer_slashing(spec, state, random_root=b'\x99' * 32,
-                                slashed_index=None, signed_1=False, signed_2=False):
+                                slashed_index=None, slot=None, signed_1=False, signed_2=False):
     if slashed_index is None:
         current_epoch = spec.get_current_epoch(state)
         slashed_index = spec.get_active_validator_indices(state, current_epoch)[-1]
     privkey = pubkey_to_privkey[state.validators[slashed_index].pubkey]
-    slot = state.slot
+    if slot is None:
+        slot = state.slot
 
     header_1 = spec.BeaconBlockHeader(
         slot=slot,
diff --git a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py
index 940bc47fb..b620a7342 100644
--- a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py
+++ b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py
@@ -6,8 +6,10 @@ from eth2spec.test.context import (
     low_balances, misc_balances,
 )
 from eth2spec.test.helpers.attestations import sign_indexed_attestation
-from eth2spec.test.helpers.attester_slashings import get_valid_attester_slashing, \
-    get_indexed_attestation_participants, get_attestation_2_data, get_attestation_1_data
+from eth2spec.test.helpers.attester_slashings import (
+    get_valid_attester_slashing, get_valid_attester_slashing_by_indices,
+    get_indexed_attestation_participants, get_attestation_2_data, get_attestation_1_data,
+)
 from eth2spec.test.helpers.proposer_slashings import get_min_slashing_penalty_quotient
 from eth2spec.test.helpers.state import (
     get_balance,
@@ -126,6 +128,39 @@ def test_success_already_exited_recent(spec, state):
     yield from run_attester_slashing_processing(spec, state, attester_slashing)
 
 
+@with_all_phases
+@spec_state_test
+@always_bls
+def test_success_proposer_index_slashed(spec, state):
+    # Transition past genesis slot because generally doesn't have a proposer
+    next_epoch_via_block(spec, state)
+
+    proposer_index = spec.get_beacon_proposer_index(state)
+    attester_slashing = get_valid_attester_slashing_by_indices(
+        spec, state,
+        [proposer_index],
+        signed_1=True, signed_2=True,
+    )
+
+    yield from run_attester_slashing_processing(spec, state, attester_slashing)
+
+
+@with_all_phases
+@spec_state_test
+def test_success_attestation_from_future(spec, state):
+    # Transition state to future to enable generation of a "future" attestation
+    future_state = state.copy()
+    next_epoch_via_block(spec, future_state)
+    # Generate slashing using the future state
+    attester_slashing = get_valid_attester_slashing(
+        spec, future_state,
+        slot=state.slot + 5,  # Slot is in the future wrt `state`
+        signed_1=True, signed_2=True
+    )
+
+    yield from run_attester_slashing_processing(spec, state, attester_slashing)
+
+
 @with_all_phases
 @with_custom_state(balances_fn=low_balances, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)
 @spec_test
diff --git a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py
index b9becc1fd..3f01bc841 100644
--- a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py
+++ b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_proposer_slashing.py
@@ -55,6 +55,14 @@ def test_success_slashed_and_proposer_index_the_same(spec, state):
     yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
 
 
+@with_all_phases
+@spec_state_test
+def test_success_block_header_from_future(spec, state):
+    proposer_slashing = get_valid_proposer_slashing(spec, state, slot=state.slot + 5, signed_1=True, signed_2=True)
+
+    yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
+
+
 @with_all_phases
 @spec_state_test
 @always_bls

From 95775e1b904b1f97d19ec69669bd6ddc1114aef4 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Fri, 11 Jun 2021 16:05:19 +0600
Subject: [PATCH 03/22] Add randao to execution payload

---
 specs/merge/beacon-chain.md                   | 10 +++-
 specs/merge/validator.md                      | 25 ++++++---
 .../pyspec/eth2spec/test/helpers/block.py     | 11 +++-
 .../test/helpers/execution_payload.py         |  7 +--
 .../test_process_execution_payload.py         | 51 +++++++++----------
 5 files changed, 66 insertions(+), 38 deletions(-)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 697bd0c96..c19a406f0 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -105,6 +105,7 @@ class ExecutionPayload(Container):
     timestamp: uint64
     receipt_root: Bytes32
     logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
+    randao: Bytes32  # 'difficulty' in the yellow paper
     transactions: List[OpaqueTransaction, MAX_EXECUTION_TRANSACTIONS]
 ```
 
@@ -126,6 +127,7 @@ class ExecutionPayloadHeader(Container):
     timestamp: uint64
     receipt_root: Bytes32
     logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
+    randao: Bytes32
     transactions_root: Root
 ```
 
@@ -198,7 +200,9 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_operations(state, block.body)
     # Pre-merge, skip execution payload processing
     if is_execution_enabled(state, block):
-        process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE)  # [New in Merge]
+        # [New in Merge]
+        randao_mix = get_randao_mix(state, get_current_epoch(state))
+        process_execution_payload(state, block.body.execution_payload, randao_mix, EXECUTION_ENGINE)
 ```
 
 #### Execution payload processing
@@ -208,6 +212,7 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
 ```python
 def process_execution_payload(state: BeaconState,
                               execution_payload: ExecutionPayload,
+                              randao_mix: Bytes32,
                               execution_engine: ExecutionEngine) -> None:
     """
     Note: This function is designed to be able to be run in parallel with the other `process_block` sub-functions
@@ -215,6 +220,7 @@ def process_execution_payload(state: BeaconState,
     if is_transition_completed(state):
         assert execution_payload.parent_hash == state.latest_execution_payload_header.block_hash
         assert execution_payload.number == state.latest_execution_payload_header.number + 1
+        assert execution_payload.randao == randao_mix
 
     assert execution_payload.timestamp == compute_time_at_slot(state, state.slot)
 
@@ -231,6 +237,7 @@ def process_execution_payload(state: BeaconState,
         timestamp=execution_payload.timestamp,
         receipt_root=execution_payload.receipt_root,
         logs_bloom=execution_payload.logs_bloom,
+        randao=execution_payload.randao,
         transactions_root=hash_tree_root(execution_payload.transactions),
     )
 ```
@@ -289,6 +296,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
         timestamp=eth1_timestamp,
         receipt_root=Bytes32(),
         logs_bloom=ByteVector[BYTES_PER_LOGS_BLOOM](),
+        randao=eth1_block_hash,
         transactions_root=Root(),
     )
 
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index c5a7a4c78..6b86aae75 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -49,7 +49,7 @@ The body of this function is implementation dependent.
 The Consensus API may be used to implement this with an external execution engine.
 
 ```python
-def assemble_block(self: ExecutionEngine, block_hash: Hash32, timestamp: uint64) -> ExecutionPayload:
+def assemble_block(self: ExecutionEngine, block_hash: Hash32, timestamp: uint64, randao: Bytes32) -> ExecutionPayload:
     ...
 ```
 
@@ -70,8 +70,23 @@ Let `get_pow_chain_head() -> PowBlock` be the function that returns the head of
 * Set `block.body.execution_payload = get_execution_payload(state, transition_store, execution_engine)` where:
 
 ```python
+def compute_randao_mix(state: BeaconState, randao_reveal: BLSSignature) -> Bytes32:
+    epoch = get_current_epoch(state)
+    return xor(get_randao_mix(state, epoch), hash(randao_reveal))
+
+
+def produce_execution_payload(state: BeaconState,
+                              parent_hash: Hash32,
+                              randao_reveal: BLSSignature,
+                              execution_engine: ExecutionEngine) -> ExecutionPayload:
+    timestamp = compute_time_at_slot(state, state.slot)
+    randao = compute_randao_mix(state, randao_reveal)
+    return execution_engine.assemble_block(parent_hash, timestamp, randao)
+
+
 def get_execution_payload(state: BeaconState,
                           transition_store: TransitionStore,
+                          randao_reveal: BLSSignature,
                           execution_engine: ExecutionEngine) -> ExecutionPayload:
     if not is_transition_completed(state):
         pow_block = get_pow_chain_head()
@@ -80,11 +95,9 @@ def get_execution_payload(state: BeaconState,
             return ExecutionPayload()
         else:
             # Signify merge via producing on top of the last PoW block
-            timestamp = compute_time_at_slot(state, state.slot)
-            return execution_engine.assemble_block(pow_block.block_hash, timestamp)
+            return produce_execution_payload(state, pow_block.block_hash, timestamp, randao_reveal)
 
     # Post-merge, normal payload
-    execution_parent_hash = state.latest_execution_payload_header.block_hash
-    timestamp = compute_time_at_slot(state, state.slot)
-    return execution_engine.assemble_block(execution_parent_hash, timestamp)
+    parent_hash = state.latest_execution_payload_header.block_hash
+    return produce_execution_payload(state, parent_hash, timestamp, randao_reveal)
 ```
diff --git a/tests/core/pyspec/eth2spec/test/helpers/block.py b/tests/core/pyspec/eth2spec/test/helpers/block.py
index 0dd9dc98e..3781f0d50 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/block.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/block.py
@@ -35,6 +35,11 @@ def apply_randao_reveal(spec, state, block, proposer_index=None):
     block.body.randao_reveal = bls.Sign(privkey, signing_root)
 
 
+def compute_randao_mix(spec, state, randao_reveal):
+    epoch = spec.get_current_epoch(state)
+    return spec.xor(spec.get_randao_mix(state, epoch), spec.hash(randao_reveal))
+
+
 # Fully ignore the function if BLS is off, beacon-proposer index calculation is slow.
 @only_with_bls()
 def apply_sig(spec, state, signed_block, proposer_index=None):
@@ -93,13 +98,15 @@ def build_empty_block(spec, state, slot=None):
     empty_block.body.eth1_data.deposit_count = state.eth1_deposit_index
     empty_block.parent_root = parent_block_root
 
+    apply_randao_reveal(spec, state, empty_block)
+
     if is_post_altair(spec):
         empty_block.body.sync_aggregate.sync_committee_signature = spec.G2_POINT_AT_INFINITY
 
     if is_post_merge(spec):
-        empty_block.body.execution_payload = build_empty_execution_payload(spec, state)
+        randao_mix = compute_randao_mix(spec, state, empty_block.body.randao_reveal)
+        empty_block.body.execution_payload = build_empty_execution_payload(spec, state, randao_mix)
 
-    apply_randao_reveal(spec, state, empty_block)
     return empty_block
 
 
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 7774aa4d9..661abe964 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -1,4 +1,4 @@
-def build_empty_execution_payload(spec, state):
+def build_empty_execution_payload(spec, state, randao_mix):
     """
     Assuming a pre-state of the same slot, build a valid ExecutionPayload without any transactions.
     """
@@ -17,6 +17,7 @@ def build_empty_execution_payload(spec, state):
         timestamp=timestamp,
         receipt_root=b"no receipts here" + b"\x00" * 16,  # TODO: root of empty MPT may be better.
         logs_bloom=spec.ByteVector[spec.BYTES_PER_LOGS_BLOOM](),  # TODO: zeroed logs bloom for empty logs ok?
+        randao=randao_mix,
         transactions=empty_txs,
     )
     # TODO: real RLP + block hash logic would be nice, requires RLP and keccak256 dependency however.
@@ -24,7 +25,6 @@ def build_empty_execution_payload(spec, state):
 
     return payload
 
-
 def get_execution_payload_header(spec, execution_payload):
     return spec.ExecutionPayloadHeader(
         block_hash=execution_payload.block_hash,
@@ -37,6 +37,7 @@ def get_execution_payload_header(spec, execution_payload):
         timestamp=execution_payload.timestamp,
         receipt_root=execution_payload.receipt_root,
         logs_bloom=execution_payload.logs_bloom,
+        randao=execution_payload.randao,
         transactions_root=spec.hash_tree_root(execution_payload.transactions)
     )
 
@@ -46,7 +47,7 @@ def build_state_with_incomplete_transition(spec, state):
 
 
 def build_state_with_complete_transition(spec, state):
-    pre_state_payload = build_empty_execution_payload(spec, state)
+    pre_state_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
     payload_header = get_execution_payload_header(spec, pre_state_payload)
 
     return build_state_with_execution_payload_header(spec, state, payload_header)
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index 5edd31960..04fb0df30 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -7,8 +7,7 @@ from eth2spec.test.helpers.execution_payload import (
 from eth2spec.test.context import spec_state_test, expect_assertion_error, with_merge_and_later
 from eth2spec.test.helpers.state import next_slot
 
-
-def run_execution_payload_processing(spec, state, execution_payload, valid=True, execution_valid=True):
+def run_execution_payload_processing(spec, state, execution_payload, randao_mix, valid=True, execution_valid=True):
     """
     Run ``process_execution_payload``, yielding:
       - pre-state ('pre')
@@ -32,11 +31,11 @@ def run_execution_payload_processing(spec, state, execution_payload, valid=True,
             return execution_valid
 
     if not valid:
-        expect_assertion_error(lambda: spec.process_execution_payload(state, execution_payload, TestEngine()))
+        expect_assertion_error(lambda: spec.process_execution_payload(state, execution_payload, randao_mix, TestEngine()))
         yield 'post', None
         return
 
-    spec.process_execution_payload(state, execution_payload, TestEngine())
+    spec.process_execution_payload(state, execution_payload, randao_mix, TestEngine())
 
     # Make sure we called the engine
     assert called_new_block
@@ -54,9 +53,9 @@ def test_success_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
 
-    yield from run_execution_payload_processing(spec, state, execution_payload)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
 
 
 @with_merge_and_later
@@ -67,9 +66,9 @@ def test_success_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
 
-    yield from run_execution_payload_processing(spec, state, execution_payload)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
 
 
 @with_merge_and_later
@@ -81,9 +80,9 @@ def test_success_first_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
 
-    yield from run_execution_payload_processing(spec, state, execution_payload)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
 
 
 @with_merge_and_later
@@ -95,9 +94,9 @@ def test_success_regular_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
 
-    yield from run_execution_payload_processing(spec, state, execution_payload)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
 
 
 @with_merge_and_later
@@ -110,9 +109,9 @@ def test_bad_execution_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False, execution_valid=False)
 
 
 @with_merge_and_later
@@ -125,9 +124,9 @@ def test_bad_execution_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False, execution_valid=False)
 
 
 @with_merge_and_later
@@ -138,10 +137,10 @@ def test_bad_parent_hash_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
     execution_payload.parent_hash = spec.Hash32()
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
 
 
 @with_merge_and_later
@@ -152,10 +151,10 @@ def test_bad_number_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
     execution_payload.number = execution_payload.number + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
 
 
 @with_merge_and_later
@@ -166,11 +165,11 @@ def test_bad_everything_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
     execution_payload.parent_hash = spec.Hash32()
     execution_payload.number = execution_payload.number + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
 
 
 @with_merge_and_later
@@ -181,10 +180,10 @@ def test_bad_timestamp_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
     execution_payload.timestamp = execution_payload.timestamp + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
 
 
 @with_merge_and_later
@@ -195,7 +194,7 @@ def test_bad_timestamp_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
     execution_payload.timestamp = execution_payload.timestamp + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)

From 7d617bc7c0351ce581726c6ea5a5dcc9ea0e9936 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Fri, 11 Jun 2021 22:46:24 +0600
Subject: [PATCH 04/22] Fix timestamp passed to produce_execution_payload

---
 specs/merge/validator.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 6b86aae75..d196d8fae 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -95,9 +95,9 @@ def get_execution_payload(state: BeaconState,
             return ExecutionPayload()
         else:
             # Signify merge via producing on top of the last PoW block
-            return produce_execution_payload(state, pow_block.block_hash, timestamp, randao_reveal)
+            return produce_execution_payload(state, pow_block.block_hash, randao_reveal)
 
     # Post-merge, normal payload
     parent_hash = state.latest_execution_payload_header.block_hash
-    return produce_execution_payload(state, parent_hash, timestamp, randao_reveal)
+    return produce_execution_payload(state, parent_hash, randao_reveal)
 ```

From 2e87a6b44e71a0f399c1aaf8fd4c94cea44adea9 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Fri, 11 Jun 2021 22:50:11 +0600
Subject: [PATCH 05/22] Apply review comments

---
 specs/merge/beacon-chain.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index c19a406f0..2265844e6 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -198,9 +198,8 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_randao(state, block.body)
     process_eth1_data(state, block.body)
     process_operations(state, block.body)
-    # Pre-merge, skip execution payload processing
+    # [New in Merge] Pre-merge, skip execution payload processing
     if is_execution_enabled(state, block):
-        # [New in Merge]
         randao_mix = get_randao_mix(state, get_current_epoch(state))
         process_execution_payload(state, block.body.execution_payload, randao_mix, EXECUTION_ENGINE)
 ```
@@ -252,6 +251,7 @@ This helper function is only for initializing the state for pure Merge testnets
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                       eth1_timestamp: uint64,
                                       deposits: Sequence[Deposit]) -> BeaconState:
+    randao_seed = eth1_block_hash
     fork = Fork(
         previous_version=GENESIS_FORK_VERSION,
         current_version=MERGE_FORK_VERSION,  # [Modified in Merge]
@@ -262,7 +262,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
         fork=fork,
         eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
         latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
-        randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR,  # Seed RANDAO with Eth1 entropy
+        randao_mixes=[randao_seed] * EPOCHS_PER_HISTORICAL_VECTOR,  # Seed RANDAO with Eth1 entropy
     )
 
     # Process deposits
@@ -296,7 +296,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
         timestamp=eth1_timestamp,
         receipt_root=Bytes32(),
         logs_bloom=ByteVector[BYTES_PER_LOGS_BLOOM](),
-        randao=eth1_block_hash,
+        randao=randao_seed,
         transactions_root=Root(),
     )
 

From cc20b80103c8d55c05cb624e28b631eb852d9644 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Tue, 15 Jun 2021 14:55:06 +0600
Subject: [PATCH 06/22] Fix linter, add more test helpers

---
 setup.py                                      |  2 +-
 specs/merge/validator.md                      |  4 +-
 .../test/helpers/execution_payload.py         |  5 ++
 .../test_process_execution_payload.py         | 53 ++++++++++---------
 4 files changed, 36 insertions(+), 28 deletions(-)

diff --git a/setup.py b/setup.py
index 9ecf8261f..24ac6dd0c 100644
--- a/setup.py
+++ b/setup.py
@@ -532,7 +532,7 @@ class NoopExecutionEngine(ExecutionEngine):
     def finalize_block(self, block_hash: Hash32) -> bool:
         return True
 
-    def assemble_block(self, block_hash: Hash32, timestamp: uint64) -> ExecutionPayload:
+    def assemble_block(self, block_hash: Hash32, timestamp: uint64, randao: Bytes32) -> ExecutionPayload:
         raise NotImplementedError("no default block production")
 
 
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index d196d8fae..adbf63e84 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -95,9 +95,9 @@ def get_execution_payload(state: BeaconState,
             return ExecutionPayload()
         else:
             # Signify merge via producing on top of the last PoW block
-            return produce_execution_payload(state, pow_block.block_hash, randao_reveal)
+            return produce_execution_payload(state, pow_block.block_hash, randao_reveal, execution_engine)
 
     # Post-merge, normal payload
     parent_hash = state.latest_execution_payload_header.block_hash
-    return produce_execution_payload(state, parent_hash, randao_reveal)
+    return produce_execution_payload(state, parent_hash, randao_reveal, execution_engine)
 ```
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 661abe964..a84494e74 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -1,3 +1,7 @@
+def build_empty_execution_payload_with_randao(spec, state):
+    return build_empty_execution_payload(spec, state, spec.Bytes32())
+
+
 def build_empty_execution_payload(spec, state, randao_mix):
     """
     Assuming a pre-state of the same slot, build a valid ExecutionPayload without any transactions.
@@ -25,6 +29,7 @@ def build_empty_execution_payload(spec, state, randao_mix):
 
     return payload
 
+
 def get_execution_payload_header(spec, execution_payload):
     return spec.ExecutionPayloadHeader(
         block_hash=execution_payload.block_hash,
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index 04fb0df30..d5e3a796e 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -1,5 +1,5 @@
 from eth2spec.test.helpers.execution_payload import (
-    build_empty_execution_payload,
+    build_empty_execution_payload_with_randao,
     get_execution_payload_header,
     build_state_with_incomplete_transition,
     build_state_with_complete_transition,
@@ -7,7 +7,8 @@ from eth2spec.test.helpers.execution_payload import (
 from eth2spec.test.context import spec_state_test, expect_assertion_error, with_merge_and_later
 from eth2spec.test.helpers.state import next_slot
 
-def run_execution_payload_processing(spec, state, execution_payload, randao_mix, valid=True, execution_valid=True):
+
+def run_execution_payload_processing(spec, state, execution_payload, valid=True, execution_valid=True):
     """
     Run ``process_execution_payload``, yielding:
       - pre-state ('pre')
@@ -21,6 +22,7 @@ def run_execution_payload_processing(spec, state, execution_payload, randao_mix,
     yield 'execution', {'execution_valid': execution_valid}
     yield 'execution_payload', execution_payload
 
+    randao_mix = spec.Bytes32()
     called_new_block = False
 
     class TestEngine(spec.NoopExecutionEngine):
@@ -31,7 +33,8 @@ def run_execution_payload_processing(spec, state, execution_payload, randao_mix,
             return execution_valid
 
     if not valid:
-        expect_assertion_error(lambda: spec.process_execution_payload(state, execution_payload, randao_mix, TestEngine()))
+        expect_assertion_error(
+            lambda: spec.process_execution_payload(state, execution_payload, randao_mix, TestEngine()))
         yield 'post', None
         return
 
@@ -53,9 +56,9 @@ def test_success_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
+    yield from run_execution_payload_processing(spec, state, execution_payload)
 
 
 @with_merge_and_later
@@ -66,9 +69,9 @@ def test_success_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
+    yield from run_execution_payload_processing(spec, state, execution_payload)
 
 
 @with_merge_and_later
@@ -80,9 +83,9 @@ def test_success_first_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
+    yield from run_execution_payload_processing(spec, state, execution_payload)
 
 
 @with_merge_and_later
@@ -94,9 +97,9 @@ def test_success_regular_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32())
+    yield from run_execution_payload_processing(spec, state, execution_payload)
 
 
 @with_merge_and_later
@@ -109,9 +112,9 @@ def test_bad_execution_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False, execution_valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
 
 
 @with_merge_and_later
@@ -124,9 +127,9 @@ def test_bad_execution_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False, execution_valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
 
 
 @with_merge_and_later
@@ -137,10 +140,10 @@ def test_bad_parent_hash_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
     execution_payload.parent_hash = spec.Hash32()
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
 
 
 @with_merge_and_later
@@ -151,10 +154,10 @@ def test_bad_number_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
     execution_payload.number = execution_payload.number + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
 
 
 @with_merge_and_later
@@ -165,11 +168,11 @@ def test_bad_everything_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
     execution_payload.parent_hash = spec.Hash32()
     execution_payload.number = execution_payload.number + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
 
 
 @with_merge_and_later
@@ -180,10 +183,10 @@ def test_bad_timestamp_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
     execution_payload.timestamp = execution_payload.timestamp + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
 
 
 @with_merge_and_later
@@ -194,7 +197,7 @@ def test_bad_timestamp_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    execution_payload = build_empty_execution_payload_with_randao(spec, state)
     execution_payload.timestamp = execution_payload.timestamp + 1
 
-    yield from run_execution_payload_processing(spec, state, execution_payload, spec.Bytes32(), valid=False)
+    yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)

From 27889860f098f92a60b7e543d61c5c156aeecb44 Mon Sep 17 00:00:00 2001
From: ericsson <avv49@mail.ru>
Date: Wed, 16 Jun 2021 12:03:20 +0300
Subject: [PATCH 07/22] fix typo: sometimes `change()` invoked on `ShardWork`
 itself, should be invoked on its `status` field

---
 specs/sharding/beacon-chain.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index 98feba22b..d57e97752 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -576,12 +576,12 @@ def update_pending_shard_work(state: BeaconState, attestation: Attestation) -> N
         # TODO In Altair: set participation bit flag for voters of this early winning header
         if pending_header.commitment == DataCommitment():
             # The committee voted to not confirm anything
-            state.shard_buffer[buffer_index][attestation_shard].change(
+            state.shard_buffer[buffer_index][attestation_shard].status.change(
                 selector=SHARD_WORK_UNCONFIRMED,
                 value=None,
             )
         else:
-            state.shard_buffer[buffer_index][attestation_shard].change(
+            state.shard_buffer[buffer_index][attestation_shard].status.change(
                 selector=SHARD_WORK_CONFIRMED,
                 value=pending_header.commitment,
             )
@@ -785,7 +785,7 @@ def reset_pending_shard_work(state: BeaconState) -> None:
             shard = (start_shard + committee_index) % active_shards
             # a committee is available, initialize a pending shard-header list
             committee_length = len(get_beacon_committee(state, slot, committee_index))
-            state.shard_buffer[buffer_index][shard].change(
+            state.shard_buffer[buffer_index][shard].status.change(
                 selector=SHARD_WORK_PENDING,
                 value=List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD](
                     PendingShardHeader(

From d83ca352d5b89a1b11aedeb290f3c3730766d331 Mon Sep 17 00:00:00 2001
From: ericsson <avv49@mail.ru>
Date: Wed, 16 Jun 2021 13:33:56 +0300
Subject: [PATCH 08/22] Fix typing problem: `append` is invoked on a
 `ShardWork` instance

---
 specs/sharding/beacon-chain.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index 98feba22b..e6137748c 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -608,7 +608,7 @@ def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeade
     assert committee_work.status.selector == SHARD_WORK_PENDING
 
     # Check that this header is not yet in the pending list
-    current_headers: Sequence[PendingShardHeader] = committee_work.status.value
+    current_headers: MutableSequence[PendingShardHeader] = committee_work.status.value
     header_root = hash_tree_root(header)
     assert header_root not in [pending_header.root for pending_header in current_headers]
 
@@ -640,7 +640,7 @@ def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeade
     )
 
     # Include it in the pending list
-    state.shard_buffer[header.slot % SHARD_STATE_MEMORY_SLOTS][header.shard].append(pending_header)
+    current_headers.append(pending_header)
 ```
 
 The degree proof works as follows. For a block `B` with length `l` (so `l`  values in `[0...l - 1]`, seen as a polynomial `B(X)` which takes these values),

From 5b4f89875c26d4a15b3a83bc8eb5d255a328179e Mon Sep 17 00:00:00 2001
From: ericsson <avv49@mail.ru>
Date: Wed, 16 Jun 2021 14:06:17 +0300
Subject: [PATCH 09/22] use `List[PendingShardHeader,...]` instead of
 `MutableSequence`, since `remerkleable.List` does not implement the latter

---
 specs/sharding/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index e6137748c..6a6772690 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -608,7 +608,7 @@ def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeade
     assert committee_work.status.selector == SHARD_WORK_PENDING
 
     # Check that this header is not yet in the pending list
-    current_headers: MutableSequence[PendingShardHeader] = committee_work.status.value
+    current_headers: List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD] = committee_work.status.value
     header_root = hash_tree_root(header)
     assert header_root not in [pending_header.root for pending_header in current_headers]
 

From 22b2a73615591cc60be95e85033d89ba4ded32ec Mon Sep 17 00:00:00 2001
From: ericsson <avv49@mail.ru>
Date: Wed, 16 Jun 2021 19:07:24 +0300
Subject: [PATCH 10/22] convert `int` to `CommitteeIndex` when passing to
 `get_beacon_committee`

---
 specs/sharding/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index 98feba22b..56d18b0e7 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -784,7 +784,7 @@ def reset_pending_shard_work(state: BeaconState) -> None:
         for committee_index in range(committees_per_slot):
             shard = (start_shard + committee_index) % active_shards
             # a committee is available, initialize a pending shard-header list
-            committee_length = len(get_beacon_committee(state, slot, committee_index))
+            committee_length = len(get_beacon_committee(state, slot, CommitteeIndex(committee_index)))
             state.shard_buffer[buffer_index][shard].change(
                 selector=SHARD_WORK_PENDING,
                 value=List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD](

From 67f1c2c2bd9ba1d408c66a7938c527752fdd585a Mon Sep 17 00:00:00 2001
From: Nishant Das <nish1993@hotmail.com>
Date: Thu, 17 Jun 2021 23:05:23 +0800
Subject: [PATCH 11/22] Update validator.md

---
 specs/altair/validator.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/validator.md b/specs/altair/validator.md
index f193e3591..53ef2ec60 100644
--- a/specs/altair/validator.md
+++ b/specs/altair/validator.md
@@ -265,7 +265,7 @@ This process occurs each slot.
 
 ##### Prepare sync committee message
 
-If a validator is in the current sync committee (i.e. `is_assigned_to_sync_committee()` above returns `True`), then for every `slot` in the current sync committee period, the validator should prepare a `SyncCommitteeMessage` for the previous slot (`slot - 1`) according to the logic in `get_sync_committee_message` as soon as they have determined the head block of `slot - 1`.
+If a validator is in the current sync committee (i.e. `is_assigned_to_sync_committee()` above returns `True`), then for every `slot` in the current sync committee period, the validator should prepare a `SyncCommitteeMessage` for the previous slot (`slot - 1`) according to the logic in `get_sync_committee_message` as soon as they have determined the head block of `slot - 1`. This would mean that a validator assigned to `slot` would have to prepare and broadcast their `SyncCommitteeMessage` in `slot-1 ` instead of `slot`.   
 
 This logic is triggered upon the same conditions as when producing an attestation.
 Meaning, a sync committee member should produce and broadcast a `SyncCommitteeMessage` either when (a) the validator has received a valid block from the expected block proposer for the current `slot` or (b) one-third of the slot has transpired (`SECONDS_PER_SLOT / 3` seconds after the start of the slot) -- whichever comes first.

From 6e86d8a6968ab705ec95e16fc43e7dc20ec6edbb Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 17 Jun 2021 21:20:17 +0600
Subject: [PATCH 12/22] Rename randao->random, other fixes as per review

---
 setup.py                                      |  2 +-
 specs/merge/beacon-chain.md                   | 10 ++++----
 specs/merge/validator.md                      |  6 ++---
 .../pyspec/eth2spec/test/helpers/block.py     |  7 +-----
 .../test/helpers/execution_payload.py         |  8 +++----
 .../test_process_execution_payload.py         | 24 +++++++++----------
 6 files changed, 26 insertions(+), 31 deletions(-)

diff --git a/setup.py b/setup.py
index 24ac6dd0c..2abd363bf 100644
--- a/setup.py
+++ b/setup.py
@@ -532,7 +532,7 @@ class NoopExecutionEngine(ExecutionEngine):
     def finalize_block(self, block_hash: Hash32) -> bool:
         return True
 
-    def assemble_block(self, block_hash: Hash32, timestamp: uint64, randao: Bytes32) -> ExecutionPayload:
+    def assemble_block(self, block_hash: Hash32, timestamp: uint64, random: Bytes32) -> ExecutionPayload:
         raise NotImplementedError("no default block production")
 
 
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 2265844e6..b1bbb57e6 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -105,7 +105,7 @@ class ExecutionPayload(Container):
     timestamp: uint64
     receipt_root: Bytes32
     logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
-    randao: Bytes32  # 'difficulty' in the yellow paper
+    random: Bytes32  # 'difficulty' in the yellow paper
     transactions: List[OpaqueTransaction, MAX_EXECUTION_TRANSACTIONS]
 ```
 
@@ -127,7 +127,7 @@ class ExecutionPayloadHeader(Container):
     timestamp: uint64
     receipt_root: Bytes32
     logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
-    randao: Bytes32
+    random: Bytes32
     transactions_root: Root
 ```
 
@@ -219,7 +219,7 @@ def process_execution_payload(state: BeaconState,
     if is_transition_completed(state):
         assert execution_payload.parent_hash == state.latest_execution_payload_header.block_hash
         assert execution_payload.number == state.latest_execution_payload_header.number + 1
-        assert execution_payload.randao == randao_mix
+        assert execution_payload.random == randao_mix
 
     assert execution_payload.timestamp == compute_time_at_slot(state, state.slot)
 
@@ -236,7 +236,7 @@ def process_execution_payload(state: BeaconState,
         timestamp=execution_payload.timestamp,
         receipt_root=execution_payload.receipt_root,
         logs_bloom=execution_payload.logs_bloom,
-        randao=execution_payload.randao,
+        random=execution_payload.random,
         transactions_root=hash_tree_root(execution_payload.transactions),
     )
 ```
@@ -296,7 +296,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
         timestamp=eth1_timestamp,
         receipt_root=Bytes32(),
         logs_bloom=ByteVector[BYTES_PER_LOGS_BLOOM](),
-        randao=randao_seed,
+        random=randao_seed,
         transactions_root=Root(),
     )
 
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index adbf63e84..7910132e6 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -49,7 +49,7 @@ The body of this function is implementation dependent.
 The Consensus API may be used to implement this with an external execution engine.
 
 ```python
-def assemble_block(self: ExecutionEngine, block_hash: Hash32, timestamp: uint64, randao: Bytes32) -> ExecutionPayload:
+def assemble_block(self: ExecutionEngine, block_hash: Hash32, timestamp: uint64, random: Bytes32) -> ExecutionPayload:
     ...
 ```
 
@@ -80,8 +80,8 @@ def produce_execution_payload(state: BeaconState,
                               randao_reveal: BLSSignature,
                               execution_engine: ExecutionEngine) -> ExecutionPayload:
     timestamp = compute_time_at_slot(state, state.slot)
-    randao = compute_randao_mix(state, randao_reveal)
-    return execution_engine.assemble_block(parent_hash, timestamp, randao)
+    randao_mix = compute_randao_mix(state, randao_reveal)
+    return execution_engine.assemble_block(parent_hash, timestamp, randao_mix)
 
 
 def get_execution_payload(state: BeaconState,
diff --git a/tests/core/pyspec/eth2spec/test/helpers/block.py b/tests/core/pyspec/eth2spec/test/helpers/block.py
index 3781f0d50..b8f7c4bcb 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/block.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/block.py
@@ -35,11 +35,6 @@ def apply_randao_reveal(spec, state, block, proposer_index=None):
     block.body.randao_reveal = bls.Sign(privkey, signing_root)
 
 
-def compute_randao_mix(spec, state, randao_reveal):
-    epoch = spec.get_current_epoch(state)
-    return spec.xor(spec.get_randao_mix(state, epoch), spec.hash(randao_reveal))
-
-
 # Fully ignore the function if BLS is off, beacon-proposer index calculation is slow.
 @only_with_bls()
 def apply_sig(spec, state, signed_block, proposer_index=None):
@@ -104,7 +99,7 @@ def build_empty_block(spec, state, slot=None):
         empty_block.body.sync_aggregate.sync_committee_signature = spec.G2_POINT_AT_INFINITY
 
     if is_post_merge(spec):
-        randao_mix = compute_randao_mix(spec, state, empty_block.body.randao_reveal)
+        randao_mix = spec.compute_randao_mix(state, empty_block.body.randao_reveal)
         empty_block.body.execution_payload = build_empty_execution_payload(spec, state, randao_mix)
 
     return empty_block
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index a84494e74..d14bdfa88 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -1,8 +1,8 @@
-def build_empty_execution_payload_with_randao(spec, state):
+def build_empty_execution_payload_with_zeroed_random(spec, state):
     return build_empty_execution_payload(spec, state, spec.Bytes32())
 
 
-def build_empty_execution_payload(spec, state, randao_mix):
+def build_empty_execution_payload(spec, state, random):
     """
     Assuming a pre-state of the same slot, build a valid ExecutionPayload without any transactions.
     """
@@ -21,7 +21,7 @@ def build_empty_execution_payload(spec, state, randao_mix):
         timestamp=timestamp,
         receipt_root=b"no receipts here" + b"\x00" * 16,  # TODO: root of empty MPT may be better.
         logs_bloom=spec.ByteVector[spec.BYTES_PER_LOGS_BLOOM](),  # TODO: zeroed logs bloom for empty logs ok?
-        randao=randao_mix,
+        random=random,
         transactions=empty_txs,
     )
     # TODO: real RLP + block hash logic would be nice, requires RLP and keccak256 dependency however.
@@ -42,7 +42,7 @@ def get_execution_payload_header(spec, execution_payload):
         timestamp=execution_payload.timestamp,
         receipt_root=execution_payload.receipt_root,
         logs_bloom=execution_payload.logs_bloom,
-        randao=execution_payload.randao,
+        random=execution_payload.random,
         transactions_root=spec.hash_tree_root(execution_payload.transactions)
     )
 
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index d5e3a796e..e2a2bf663 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -1,5 +1,5 @@
 from eth2spec.test.helpers.execution_payload import (
-    build_empty_execution_payload_with_randao,
+    build_empty_execution_payload_with_zeroed_random,
     get_execution_payload_header,
     build_state_with_incomplete_transition,
     build_state_with_complete_transition,
@@ -56,7 +56,7 @@ def test_success_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -69,7 +69,7 @@ def test_success_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -83,7 +83,7 @@ def test_success_first_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -97,7 +97,7 @@ def test_success_regular_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -112,7 +112,7 @@ def test_bad_execution_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
 
@@ -127,7 +127,7 @@ def test_bad_execution_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
 
@@ -140,7 +140,7 @@ def test_bad_parent_hash_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
     execution_payload.parent_hash = spec.Hash32()
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
@@ -154,7 +154,7 @@ def test_bad_number_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
     execution_payload.number = execution_payload.number + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
@@ -168,7 +168,7 @@ def test_bad_everything_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
     execution_payload.parent_hash = spec.Hash32()
     execution_payload.number = execution_payload.number + 1
 
@@ -183,7 +183,7 @@ def test_bad_timestamp_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
     execution_payload.timestamp = execution_payload.timestamp + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
@@ -197,7 +197,7 @@ def test_bad_timestamp_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_randao(spec, state)
+    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
     execution_payload.timestamp = execution_payload.timestamp + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)

From 878b15df6ab8d56dd4499c45e2ddec4faa570910 Mon Sep 17 00:00:00 2001
From: Justin <drakefjustin@gmail.com>
Date: Fri, 18 Jun 2021 11:09:30 +0100
Subject: [PATCH 13/22] polish merge/beacon-chain.md (#2472)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Polish `merge/beacon-chain.md` with mostly non-substantive changes.

**Non-substantive changes**

* rename `MAX_EXECUTION_TRANSACTIONS` to `MAX_TRANSACTIONS_PER_PAYLOAD`
	- rename "execution transaction" to just "transaction" as per discussion with Danny
* rename `compute_time_at_slot` to `compute_timestamp_at_slot`
	- the function returns a Unix timestamp
	- "timestamp" matches `execution_payload.timestamp`
* be explicit about `ExecutionEngine.execution_state` for clarity
* rename `ExecutionPayload.number` to `ExecutionPayload.block_number`
	- more specific ("number" is pretty vague)
	- consistent with `ExecutionPayload.block_hash`
* rename `new_block` to `on_payload`
	- the `on_` prefix is consistent with other event handlers (e.g. see `on_tick`, `on_block`, `on_attestation` [here](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/fork-choice.md#handlers))
	- the `_payload` suffix is more to the point given the function accepts an `execution_payload`
	- avoids conflict with `on_block` which is already used in the fork choice
* rework the table of contents for consistency
* order `is_execution_enabled` after `is_transition_completed` and `is_transition_block`
	- `is_execution_enabled` refers to `is_transition_completed` and `is_transition_block`
* rename "transition" to "merge"
	- "transition" is a bit vague—we will have other transitions at future hard forks
	- there is no need for two words to refer to the same concept
* add a bunch of inline comments, e.g. in `process_execution_payload`
* make the `process_execution_payload` signature consistent with the other `process_` functions in `process_block` which take as arguments `state` and `block.body`
* remove `TRANSITION_TOTAL_DIFFICULTY`
	- to be put in `merge/fork-choice.md` where it is used
* various misc cleanups

**Substantive changes**

* reorder `ExecutionPayload` fields
	- for consistency with yellow paper and Eth1
	- same for `ExecutionPayloadHeader`
	- added comments separating out the execution block header fields from the extra fields (cosmetic)
---
 setup.py                                      |  18 +-
 specs/merge/beacon-chain.md                   | 233 ++++++++----------
 specs/merge/fork-choice.md                    |   2 +-
 specs/merge/validator.md                      |   2 +-
 .../test/helpers/execution_payload.py         |  18 +-
 .../test_process_execution_payload.py         |   6 +-
 6 files changed, 129 insertions(+), 150 deletions(-)

diff --git a/setup.py b/setup.py
index 9ecf8261f..4430ccec0 100644
--- a/setup.py
+++ b/setup.py
@@ -223,7 +223,7 @@ def get_spec(file_name: Path, preset: Dict[str, str], config: Dict[str, str]) ->
 
                     if not _is_constant_id(name):
                         # Check for short type declarations
-                        if value.startswith("uint") or value.startswith("Bytes") or value.startswith("ByteList"):
+                        if value.startswith("uint") or value.startswith("Bytes") or value.startswith("ByteList") or value.startswith("Union"):
                             custom_types[name] = value
                         continue
 
@@ -495,7 +495,7 @@ class MergeSpecBuilder(Phase0SpecBuilder):
         return super().imports(preset_name) + f'''
 from typing import Protocol
 from eth2spec.phase0 import {preset_name} as phase0
-from eth2spec.utils.ssz.ssz_typing import Bytes20, ByteList, ByteVector, uint256
+from eth2spec.utils.ssz.ssz_typing import Bytes20, ByteList, ByteVector, uint256, Union
 '''
 
     @classmethod
@@ -523,7 +523,7 @@ def get_pow_chain_head() -> PowBlock:
 
 class NoopExecutionEngine(ExecutionEngine):
 
-    def new_block(self, execution_payload: ExecutionPayload) -> bool:
+    def on_payload(self, execution_payload: ExecutionPayload) -> bool:
         return True
 
     def set_head(self, block_hash: Hash32) -> bool:
@@ -553,6 +553,10 @@ spec_builders = {
 }
 
 
+def is_spec_defined_type(value: str) -> bool:
+    return value.startswith('ByteList') or value.startswith('Union')
+
+
 def objects_to_spec(preset_name: str,
                     spec_object: SpecObject,
                     builder: SpecBuilder,
@@ -565,15 +569,15 @@ def objects_to_spec(preset_name: str,
             [
                 f"class {key}({value}):\n    pass\n"
                 for key, value in spec_object.custom_types.items()
-                if not value.startswith('ByteList')
+                if not is_spec_defined_type(value)
             ]
         )
-        + ('\n\n' if len([key for key, value in spec_object.custom_types.items() if value.startswith('ByteList')]) > 0 else '')
+        + ('\n\n' if len([key for key, value in spec_object.custom_types.items() if is_spec_defined_type(value)]) > 0 else '')
         + '\n\n'.join(
             [
                 f"{key} = {value}\n"
                 for key, value in spec_object.custom_types.items()
-                if value.startswith('ByteList')
+                if is_spec_defined_type(value)
             ]
         )
     )
@@ -1020,7 +1024,7 @@ setup(
         "py_ecc==5.2.0",
         "milagro_bls_binding==1.6.3",
         "dataclasses==0.6",
-        "remerkleable==0.1.20",
+        "remerkleable==0.1.21",
         RUAMEL_YAML_VERSION,
         "lru-dict==1.1.6",
         MARKO_VERSION,
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 697bd0c96..562adaab4 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -1,6 +1,6 @@
 # Ethereum 2.0 The Merge
 
-**Warning:** This document is currently based on [Phase 0](../phase0/beacon-chain.md) but will be rebased to [Altair](../altair/beacon-chain.md) once the latter is shipped.
+**Warning**: This document is currently based on [Phase 0](../phase0/beacon-chain.md) and will be rebased on [Altair](../altair/beacon-chain.md).
 
 **Notice**: This document is a work-in-progress for researchers and implementers.
 
@@ -21,35 +21,36 @@
   - [New containers](#new-containers)
     - [`ExecutionPayload`](#executionpayload)
     - [`ExecutionPayloadHeader`](#executionpayloadheader)
-- [Protocols](#protocols)
-  - [`ExecutionEngine`](#executionengine)
-    - [`new_block`](#new_block)
 - [Helper functions](#helper-functions)
-  - [Misc](#misc)
+  - [Predicates](#predicates)
+    - [`is_merge_complete`](#is_merge_complete)
+    - [`is_merge_block`](#is_merge_block)
     - [`is_execution_enabled`](#is_execution_enabled)
-    - [`is_transition_completed`](#is_transition_completed)
-    - [`is_transition_block`](#is_transition_block)
-    - [`compute_time_at_slot`](#compute_time_at_slot)
+  - [Misc](#misc)
+    - [`compute_timestamp_at_slot`](#compute_timestamp_at_slot)
+- [Beacon chain state transition function](#beacon-chain-state-transition-function)
+  - [Execution engine](#execution-engine)
+    - [`on_payload`](#on_payload)
   - [Block processing](#block-processing)
-    - [Execution payload processing](#execution-payload-processing)
-      - [`process_execution_payload`](#process_execution_payload)
-- [Initialize state for pure Merge testnets and test vectors](#initialize-state-for-pure-merge-testnets-and-test-vectors)
+  - [Execution payload processing](#execution-payload-processing)
+    - [`process_execution_payload`](#process_execution_payload)
+- [Testing](#testing)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
 
 ## Introduction
 
-This is a patch implementing the executable beacon chain proposal. 
-It enshrines transaction execution and validity as a first class citizen at the core of the beacon chain.
+This patch adds transaction execution to the beacon chain as part of the Merge fork.
 
 ## Custom types
 
-We define the following Python custom types for type hinting and readability:
+*Note*: The `Transaction` type is a stub which is not final.
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
-| `OpaqueTransaction` | `ByteList[MAX_BYTES_PER_OPAQUE_TRANSACTION]` | a byte-list containing a single [typed transaction envelope](https://eips.ethereum.org/EIPS/eip-2718#opaque-byte-array-rather-than-an-rlp-array) structured as `TransactionType \|\| TransactionPayload` |
+| `OpaqueTransaction` | `ByteList[MAX_BYTES_PER_OPAQUE_TRANSACTION]` | a [typed transaction envelope](https://eips.ethereum.org/EIPS/eip-2718#opaque-byte-array-rather-than-an-rlp-array) structured as `TransactionType \|\| TransactionPayload` |
+| `Transaction` | `Union[OpaqueTransaction]` | a transaction |
 
 ## Constants
 
@@ -58,32 +59,26 @@ We define the following Python custom types for type hinting and readability:
 | Name | Value |
 | - | - |
 | `MAX_BYTES_PER_OPAQUE_TRANSACTION` | `uint64(2**20)` (= 1,048,576) |
-| `MAX_EXECUTION_TRANSACTIONS` | `uint64(2**14)` (= 16,384) |
+| `MAX_TRANSACTIONS_PER_PAYLOAD` | `uint64(2**14)` (= 16,384) |
 | `BYTES_PER_LOGS_BLOOM` | `uint64(2**8)` (= 256) |
 
 ## Containers
 
 ### Extended containers
 
-*Note*: Extended SSZ containers inherit all fields from the parent in the original
-order and append any additional fields to the end.
-
 #### `BeaconBlockBody`
 
-*Note*: `BeaconBlockBody` fields remain unchanged other than the addition of `execution_payload`.
-
 ```python
 class BeaconBlockBody(phase0.BeaconBlockBody):
+    # Execution
     execution_payload: ExecutionPayload  # [New in Merge]
 ```
 
 #### `BeaconState`
 
-*Note*: `BeaconState` fields remain unchanged other than addition of `latest_execution_payload_header`.
-
 ```python
 class BeaconState(phase0.BeaconState):
-    # Execution-layer
+    # Execution
     latest_execution_payload_header: ExecutionPayloadHeader  # [New in Merge]
 ```
 
@@ -91,103 +86,100 @@ class BeaconState(phase0.BeaconState):
 
 #### `ExecutionPayload`
 
-The execution payload included in a `BeaconBlockBody`.
-
 ```python
 class ExecutionPayload(Container):
-    block_hash: Hash32  # Hash of execution block
+    # Execution block header fields
     parent_hash: Hash32
-    coinbase: Bytes20
+    coinbase: Bytes20  # 'beneficiary' in the yellow paper
     state_root: Bytes32
-    number: uint64
+    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
+    receipt_root: Bytes32  # 'receipts root' in the yellow paper
+    block_number: uint64  # 'number' in the yellow paper
     gas_limit: uint64
     gas_used: uint64
     timestamp: uint64
-    receipt_root: Bytes32
-    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
-    transactions: List[OpaqueTransaction, MAX_EXECUTION_TRANSACTIONS]
+    # Extra payload fields
+    block_hash: Hash32  # Hash of execution block
+    transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
 ```
 
 #### `ExecutionPayloadHeader`
 
-The execution payload header included in a `BeaconState`.
-
-*Note:* Holds execution payload data without transaction bodies.
-
 ```python
 class ExecutionPayloadHeader(Container):
-    block_hash: Hash32  # Hash of execution block
+    # Execution block header fields
     parent_hash: Hash32
     coinbase: Bytes20
     state_root: Bytes32
-    number: uint64
+    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
+    receipt_root: Bytes32
+    block_number: uint64
     gas_limit: uint64
     gas_used: uint64
     timestamp: uint64
-    receipt_root: Bytes32
-    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
+    # Extra payload fields
+    block_hash: Hash32  # Hash of execution block
     transactions_root: Root
 ```
 
-## Protocols
-
-### `ExecutionEngine`
-
-The `ExecutionEngine` protocol separates the consensus and execution sub-systems.
-The consensus implementation references an instance of this sub-system with `EXECUTION_ENGINE`. 
-
-The following methods are added to the `ExecutionEngine` protocol for use in the state transition:
-
-#### `new_block`
-
-Verifies the given `execution_payload` with respect to execution state transition, and persists changes if valid.
-
-The body of this function is implementation dependent.
-The Consensus API may be used to implement this with an external execution engine.
-
-```python
-def new_block(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
-    """
-    Returns True if the ``execution_payload`` was verified and processed successfully, False otherwise. 
-    """
-    ...
-```
-
 ## Helper functions
 
-### Misc
+### Predicates
+
+#### `is_merge_complete`
+
+```python
+def is_merge_complete(state: BeaconState) -> bool:
+    return state.latest_execution_payload_header != ExecutionPayloadHeader()
+```
+
+#### `is_merge_block`
+
+```python
+def is_merge_block(state: BeaconState, body: BeaconBlockBody) -> bool:
+    return not is_merge_complete(state) and body.execution_payload != ExecutionPayload()
+```
 
 #### `is_execution_enabled`
 
 ```python
-def is_execution_enabled(state: BeaconState, block: BeaconBlock) -> bool:
-    return is_transition_completed(state) or is_transition_block(state, block)
+def is_execution_enabled(state: BeaconState, body: BeaconBlockBody) -> bool:
+    return is_merge_block(state, body) or is_merge_complete(state)
 ```
 
-#### `is_transition_completed`
+### Misc
 
-```python
-def is_transition_completed(state: BeaconState) -> bool:
-    return state.latest_execution_payload_header != ExecutionPayloadHeader()
-```
-
-#### `is_transition_block`
-
-```python
-def is_transition_block(state: BeaconState, block: BeaconBlock) -> bool:
-    return not is_transition_completed(state) and block.body.execution_payload != ExecutionPayload()
-```
-
-#### `compute_time_at_slot`
+#### `compute_timestamp_at_slot`
 
 *Note*: This function is unsafe with respect to overflows and underflows.
 
 ```python
-def compute_time_at_slot(state: BeaconState, slot: Slot) -> uint64:
+def compute_timestamp_at_slot(state: BeaconState, slot: Slot) -> uint64:
     slots_since_genesis = slot - GENESIS_SLOT
     return uint64(state.genesis_time + slots_since_genesis * SECONDS_PER_SLOT)
 ```
 
+## Beacon chain state transition function
+
+### Execution engine
+
+The implementation-dependent `ExecutionEngine` protocol encapsulates the execution sub-system logic via:
+
+* a state object `self.execution_state` of type `ExecutionState`
+* a state transition function `self.on_payload` which mutates `self.execution_state`
+
+#### `on_payload`
+
+```python
+def on_payload(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
+    """
+    Returns ``True`` iff ``execution_payload`` is valid with respect to ``self.execution_state``.
+    """
+    ...
+```
+
+The above function is accessed through the `EXECUTION_ENGINE` module which instantiates the `ExecutionEngine` protocol.
+
 ### Block processing
 
 ```python
@@ -196,50 +188,45 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_randao(state, block.body)
     process_eth1_data(state, block.body)
     process_operations(state, block.body)
-    # Pre-merge, skip execution payload processing
-    if is_execution_enabled(state, block):
+    if is_execution_enabled(state, block.body):
         process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE)  # [New in Merge]
 ```
 
-#### Execution payload processing
+### Execution payload processing
 
-##### `process_execution_payload`
+#### `process_execution_payload`
 
 ```python
-def process_execution_payload(state: BeaconState,
-                              execution_payload: ExecutionPayload,
-                              execution_engine: ExecutionEngine) -> None:
-    """
-    Note: This function is designed to be able to be run in parallel with the other `process_block` sub-functions
-    """
-    if is_transition_completed(state):
-        assert execution_payload.parent_hash == state.latest_execution_payload_header.block_hash
-        assert execution_payload.number == state.latest_execution_payload_header.number + 1
-
-    assert execution_payload.timestamp == compute_time_at_slot(state, state.slot)
-
-    assert execution_engine.new_block(execution_payload)
-
+def process_execution_payload(state: BeaconState, payload: ExecutionPayload, execution_engine: ExecutionEngine) -> None:
+    # Verify consistency of the parent hash and block number
+    if is_merge_complete(state):
+        assert payload.parent_hash == state.latest_execution_payload_header.block_hash
+        assert payload.block_number == state.latest_execution_payload_header.block_number + uint64(1)
+    # Verify timestamp
+    assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
+    # Verify the execution payload is valid
+    assert execution_engine.on_payload(payload)
+    # Cache execution payload
     state.latest_execution_payload_header = ExecutionPayloadHeader(
-        block_hash=execution_payload.block_hash,
-        parent_hash=execution_payload.parent_hash,
-        coinbase=execution_payload.coinbase,
-        state_root=execution_payload.state_root,
-        number=execution_payload.number,
-        gas_limit=execution_payload.gas_limit,
-        gas_used=execution_payload.gas_used,
-        timestamp=execution_payload.timestamp,
-        receipt_root=execution_payload.receipt_root,
-        logs_bloom=execution_payload.logs_bloom,
-        transactions_root=hash_tree_root(execution_payload.transactions),
+        parent_hash=payload.parent_hash,
+        coinbase=payload.coinbase,
+        state_root=payload.state_root,
+        logs_bloom=payload.logs_bloom,
+        receipt_root=payload.receipt_root,
+        block_number=payload.block_number,
+        gas_limit=payload.gas_limit,
+        gas_used=payload.gas_used,
+        timestamp=payload.timestamp,
+        block_hash=payload.block_hash,
+        transactions_root=hash_tree_root(payload.transactions),
     )
 ```
 
-## Initialize state for pure Merge testnets and test vectors
+## Testing
 
-This helper function is only for initializing the state for pure Merge testnets and tests.
+*Note*: The function `initialize_beacon_state_from_eth1` is modified for pure Merge testing only.
 
-*Note*: The function `initialize_beacon_state_from_eth1` is modified: (1) using `MERGE_FORK_VERSION` as the current fork version, (2) utilizing the Merge `BeaconBlockBody` when constructing the initial `latest_block_header`, and (3) adding initial `latest_execution_payload_header`.
+*Note*: The function `initialize_beacon_state_from_eth1` is modified to use `MERGE_FORK_VERSION` and initialize `latest_execution_payload_header`.
 
 ```python
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
@@ -276,21 +263,9 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
     # Set genesis validators root for domain separation and chain versioning
     state.genesis_validators_root = hash_tree_root(state.validators)
 
-    # [New in Merge] Construct execution payload header
-    # Note: initialized with zero block height
-    state.latest_execution_payload_header = ExecutionPayloadHeader(
-        block_hash=eth1_block_hash,
-        parent_hash=Hash32(),
-        coinbase=Bytes20(),
-        state_root=Bytes32(),
-        number=uint64(0),
-        gas_limit=uint64(0),
-        gas_used=uint64(0),
-        timestamp=eth1_timestamp,
-        receipt_root=Bytes32(),
-        logs_bloom=ByteVector[BYTES_PER_LOGS_BLOOM](),
-        transactions_root=Root(),
-    )
+    # [New in Merge] Initialize the execution payload header (with block number set to 0)
+    state.latest_execution_payload_header.block_hash = eth1_block_hash
+    state.latest_execution_payload_header.timestamp = eth1_timestamp
 
     return state
 ```
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index 56345dd90..d0f327137 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -127,7 +127,7 @@ def on_block(store: Store, signed_block: SignedBeaconBlock, transition_store: Tr
     assert get_ancestor(store, block.parent_root, finalized_slot) == store.finalized_checkpoint.root
     
     # [New in Merge]
-    if (transition_store is not None) and is_transition_block(pre_state, block):
+    if (transition_store is not None) and is_merge_block(pre_state, block):
         # Delay consideration of block until PoW block is processed by the PoW node
         pow_block = get_pow_block(block.body.execution_payload.parent_hash)
         assert pow_block.is_processed
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index c5a7a4c78..21668b327 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -73,7 +73,7 @@ Let `get_pow_chain_head() -> PowBlock` be the function that returns the head of
 def get_execution_payload(state: BeaconState,
                           transition_store: TransitionStore,
                           execution_engine: ExecutionEngine) -> ExecutionPayload:
-    if not is_transition_completed(state):
+    if not is_merge_complete(state):
         pow_block = get_pow_chain_head()
         if not is_valid_terminal_pow_block(transition_store, pow_block):
             # Pre-merge, empty payload
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 7774aa4d9..238e2e00f 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -4,19 +4,19 @@ def build_empty_execution_payload(spec, state):
     """
     latest = state.latest_execution_payload_header
     timestamp = spec.compute_time_at_slot(state, state.slot)
-    empty_txs = spec.List[spec.OpaqueTransaction, spec.MAX_EXECUTION_TRANSACTIONS]()
+    empty_txs = spec.List[spec.Transaction, spec.MAX_TRANSACTIONS_PER_PAYLOAD]()
 
     payload = spec.ExecutionPayload(
-        block_hash=spec.Hash32(),
         parent_hash=latest.block_hash,
         coinbase=spec.Bytes20(),
         state_root=latest.state_root,  # no changes to the state
-        number=latest.number + 1,
+        logs_bloom=spec.ByteVector[spec.BYTES_PER_LOGS_BLOOM](),  # TODO: zeroed logs bloom for empty logs ok?
+        receipt_root=b"no receipts here" + b"\x00" * 16,  # TODO: root of empty MPT may be better.
+        block_number=latest.block_number + 1,
         gas_limit=latest.gas_limit,  # retain same limit
         gas_used=0,  # empty block, 0 gas
         timestamp=timestamp,
-        receipt_root=b"no receipts here" + b"\x00" * 16,  # TODO: root of empty MPT may be better.
-        logs_bloom=spec.ByteVector[spec.BYTES_PER_LOGS_BLOOM](),  # TODO: zeroed logs bloom for empty logs ok?
+        block_hash=spec.Hash32(),
         transactions=empty_txs,
     )
     # TODO: real RLP + block hash logic would be nice, requires RLP and keccak256 dependency however.
@@ -27,16 +27,16 @@ def build_empty_execution_payload(spec, state):
 
 def get_execution_payload_header(spec, execution_payload):
     return spec.ExecutionPayloadHeader(
-        block_hash=execution_payload.block_hash,
         parent_hash=execution_payload.parent_hash,
         coinbase=execution_payload.coinbase,
         state_root=execution_payload.state_root,
-        number=execution_payload.number,
+        logs_bloom=execution_payload.logs_bloom,
+        receipt_root=execution_payload.receipt_root,
+        block_number=execution_payload.block_number,
         gas_limit=execution_payload.gas_limit,
         gas_used=execution_payload.gas_used,
         timestamp=execution_payload.timestamp,
-        receipt_root=execution_payload.receipt_root,
-        logs_bloom=execution_payload.logs_bloom,
+        block_hash=execution_payload.block_hash,
         transactions_root=spec.hash_tree_root(execution_payload.transactions)
     )
 
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index 5edd31960..4c68034d4 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -25,7 +25,7 @@ def run_execution_payload_processing(spec, state, execution_payload, valid=True,
     called_new_block = False
 
     class TestEngine(spec.NoopExecutionEngine):
-        def new_block(self, payload) -> bool:
+        def on_payload(self, payload) -> bool:
             nonlocal called_new_block, execution_valid
             called_new_block = True
             assert payload == execution_payload
@@ -153,7 +153,7 @@ def test_bad_number_regular_payload(spec, state):
 
     # execution payload
     execution_payload = build_empty_execution_payload(spec, state)
-    execution_payload.number = execution_payload.number + 1
+    execution_payload.block_number = execution_payload.block_number + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
 
@@ -168,7 +168,7 @@ def test_bad_everything_regular_payload(spec, state):
     # execution payload
     execution_payload = build_empty_execution_payload(spec, state)
     execution_payload.parent_hash = spec.Hash32()
-    execution_payload.number = execution_payload.number + 1
+    execution_payload.block_number = execution_payload.block_number + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
 

From a61aa7968d87c13489f026a64f9510d4392fa36c Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Mon, 21 Jun 2021 12:48:44 -0600
Subject: [PATCH 14/22] clean up

---
 specs/altair/validator.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/validator.md b/specs/altair/validator.md
index 53ef2ec60..9de78638b 100644
--- a/specs/altair/validator.md
+++ b/specs/altair/validator.md
@@ -265,7 +265,7 @@ This process occurs each slot.
 
 ##### Prepare sync committee message
 
-If a validator is in the current sync committee (i.e. `is_assigned_to_sync_committee()` above returns `True`), then for every `slot` in the current sync committee period, the validator should prepare a `SyncCommitteeMessage` for the previous slot (`slot - 1`) according to the logic in `get_sync_committee_message` as soon as they have determined the head block of `slot - 1`. This would mean that a validator assigned to `slot` would have to prepare and broadcast their `SyncCommitteeMessage` in `slot-1 ` instead of `slot`.   
+If a validator is in the current sync committee (i.e. `is_assigned_to_sync_committee()` above returns `True`), then for every `slot` in the current sync committee period, the validator should prepare a `SyncCommitteeMessage` for the previous slot (`slot - 1`) according to the logic in `get_sync_committee_message` as soon as they have determined the head block of `slot - 1`. This means that when assigned to a `slot` a `SyncCommitteeMessage` is prepared and broadcast in `slot-1 ` instead of `slot`.   
 
 This logic is triggered upon the same conditions as when producing an attestation.
 Meaning, a sync committee member should produce and broadcast a `SyncCommitteeMessage` either when (a) the validator has received a valid block from the expected block proposer for the current `slot` or (b) one-third of the slot has transpired (`SECONDS_PER_SLOT / 3` seconds after the start of the slot) -- whichever comes first.

From fc1012b6326b76dec3ba7ee87daae212e16f0812 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Mon, 21 Jun 2021 12:49:41 -0600
Subject: [PATCH 15/22] typo

---
 specs/altair/validator.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/validator.md b/specs/altair/validator.md
index 9de78638b..49146da00 100644
--- a/specs/altair/validator.md
+++ b/specs/altair/validator.md
@@ -265,7 +265,7 @@ This process occurs each slot.
 
 ##### Prepare sync committee message
 
-If a validator is in the current sync committee (i.e. `is_assigned_to_sync_committee()` above returns `True`), then for every `slot` in the current sync committee period, the validator should prepare a `SyncCommitteeMessage` for the previous slot (`slot - 1`) according to the logic in `get_sync_committee_message` as soon as they have determined the head block of `slot - 1`. This means that when assigned to a `slot` a `SyncCommitteeMessage` is prepared and broadcast in `slot-1 ` instead of `slot`.   
+If a validator is in the current sync committee (i.e. `is_assigned_to_sync_committee()` above returns `True`), then for every `slot` in the current sync committee period, the validator should prepare a `SyncCommitteeMessage` for the previous slot (`slot - 1`) according to the logic in `get_sync_committee_message` as soon as they have determined the head block of `slot - 1`. This means that when assigned to `slot` a `SyncCommitteeMessage` is prepared and broadcast in `slot-1 ` instead of `slot`.   
 
 This logic is triggered upon the same conditions as when producing an attestation.
 Meaning, a sync committee member should produce and broadcast a `SyncCommitteeMessage` either when (a) the validator has received a valid block from the expected block proposer for the current `slot` or (b) one-third of the slot has transpired (`SECONDS_PER_SLOT / 3` seconds after the start of the slot) -- whichever comes first.

From ac19aa3e2d1533d933d504661b39341b18f086ad Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Tue, 22 Jun 2021 14:23:26 +0600
Subject: [PATCH 16/22] Accept polishing suggested by Justin

---
 specs/merge/beacon-chain.md                   | 18 +++++-------
 .../test/helpers/execution_payload.py         | 11 ++++---
 .../test_process_execution_payload.py         | 29 +++++++++----------
 3 files changed, 26 insertions(+), 32 deletions(-)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 47e69e918..7823a664d 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -191,25 +191,22 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_eth1_data(state, block.body)
     process_operations(state, block.body)
     if is_execution_enabled(state, block.body):
-        # [New in Merge]
-        randao_mix = get_randao_mix(state, get_current_epoch(state))
-        process_execution_payload(state, block.body.execution_payload, randao_mix, EXECUTION_ENGINE)
+        process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE)  # [New in Merge]
 ```
 
 ### Execution payload processing
 
 #### `process_execution_payload`
 
+*Note:* This function depends on `process_randao` function call as it retrieves the most recent randao mix from the `state`. Implementations that are considering parallel processing of execution payload with respect to beacon chain state transition function should work around this dependency.
+
 ```python
-def process_execution_payload(state: BeaconState,
-                              payload: ExecutionPayload,
-                              randao_mix: Bytes32,
-                              execution_engine: ExecutionEngine) -> None:
+def process_execution_payload(state: BeaconState, payload: ExecutionPayload, execution_engine: ExecutionEngine) -> None:
     # Verify consistency of the parent hash, block number and random
     if is_merge_complete(state):
         assert payload.parent_hash == state.latest_execution_payload_header.block_hash
         assert payload.block_number == state.latest_execution_payload_header.block_number + uint64(1)
-        assert payload.random == randao_mix
+        assert payload.random == get_randao_mix(state, get_current_epoch(state))
     # Verify timestamp
     assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
     # Verify the execution payload is valid
@@ -241,7 +238,6 @@ def process_execution_payload(state: BeaconState,
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                       eth1_timestamp: uint64,
                                       deposits: Sequence[Deposit]) -> BeaconState:
-    randao_seed = eth1_block_hash
     fork = Fork(
         previous_version=GENESIS_FORK_VERSION,
         current_version=MERGE_FORK_VERSION,  # [Modified in Merge]
@@ -252,7 +248,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
         fork=fork,
         eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
         latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
-        randao_mixes=[randao_seed] * EPOCHS_PER_HISTORICAL_VECTOR,  # Seed RANDAO with Eth1 entropy
+        randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR,  # Seed RANDAO with Eth1 entropy
     )
 
     # Process deposits
@@ -276,7 +272,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
     # [New in Merge] Initialize the execution payload header (with block number set to 0)
     state.latest_execution_payload_header.block_hash = eth1_block_hash
     state.latest_execution_payload_header.timestamp = eth1_timestamp
-    state.latest_execution_payload_header.random = randao_seed
+    state.latest_execution_payload_header.random = eth1_block_hash
 
     return state
 ```
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 41fa3117d..1ef63eaaf 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -1,8 +1,4 @@
-def build_empty_execution_payload_with_zeroed_random(spec, state):
-    return build_empty_execution_payload(spec, state, spec.Bytes32())
-
-
-def build_empty_execution_payload(spec, state, random):
+def build_empty_execution_payload(spec, state, randao_mix=None):
     """
     Assuming a pre-state of the same slot, build a valid ExecutionPayload without any transactions.
     """
@@ -10,6 +6,9 @@ def build_empty_execution_payload(spec, state, random):
     timestamp = spec.compute_time_at_slot(state, state.slot)
     empty_txs = spec.List[spec.Transaction, spec.MAX_TRANSACTIONS_PER_PAYLOAD]()
 
+    if randao_mix is None:
+        randao_mix = spec.get_randao_mix(state, spec.get_current_epoch(state))
+
     payload = spec.ExecutionPayload(
         parent_hash=latest.block_hash,
         coinbase=spec.Bytes20(),
@@ -17,7 +16,7 @@ def build_empty_execution_payload(spec, state, random):
         receipt_root=b"no receipts here" + b"\x00" * 16,  # TODO: root of empty MPT may be better.
         logs_bloom=spec.ByteVector[spec.BYTES_PER_LOGS_BLOOM](),  # TODO: zeroed logs bloom for empty logs ok?
         block_number=latest.block_number + 1,
-        random=random,
+        random=randao_mix,
         gas_limit=latest.gas_limit,  # retain same limit
         gas_used=0,  # empty block, 0 gas
         timestamp=timestamp,
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index 4f6c98705..15c69f2dd 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -1,5 +1,5 @@
 from eth2spec.test.helpers.execution_payload import (
-    build_empty_execution_payload_with_zeroed_random,
+    build_empty_execution_payload,
     get_execution_payload_header,
     build_state_with_incomplete_transition,
     build_state_with_complete_transition,
@@ -22,7 +22,6 @@ def run_execution_payload_processing(spec, state, execution_payload, valid=True,
     yield 'execution', {'execution_valid': execution_valid}
     yield 'execution_payload', execution_payload
 
-    randao_mix = spec.Bytes32()
     called_new_block = False
 
     class TestEngine(spec.NoopExecutionEngine):
@@ -34,11 +33,11 @@ def run_execution_payload_processing(spec, state, execution_payload, valid=True,
 
     if not valid:
         expect_assertion_error(
-            lambda: spec.process_execution_payload(state, execution_payload, randao_mix, TestEngine()))
+            lambda: spec.process_execution_payload(state, execution_payload, TestEngine()))
         yield 'post', None
         return
 
-    spec.process_execution_payload(state, execution_payload, randao_mix, TestEngine())
+    spec.process_execution_payload(state, execution_payload, TestEngine())
 
     # Make sure we called the engine
     assert called_new_block
@@ -56,7 +55,7 @@ def test_success_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -69,7 +68,7 @@ def test_success_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -83,7 +82,7 @@ def test_success_first_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -97,7 +96,7 @@ def test_success_regular_payload_with_gap_slot(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload)
 
@@ -112,7 +111,7 @@ def test_bad_execution_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
 
@@ -127,7 +126,7 @@ def test_bad_execution_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False, execution_valid=False)
 
@@ -140,7 +139,7 @@ def test_bad_parent_hash_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
     execution_payload.parent_hash = spec.Hash32()
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
@@ -154,7 +153,7 @@ def test_bad_number_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
     execution_payload.block_number = execution_payload.block_number + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
@@ -168,7 +167,7 @@ def test_bad_everything_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
     execution_payload.parent_hash = spec.Hash32()
     execution_payload.block_number = execution_payload.block_number + 1
 
@@ -183,7 +182,7 @@ def test_bad_timestamp_first_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
     execution_payload.timestamp = execution_payload.timestamp + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)
@@ -197,7 +196,7 @@ def test_bad_timestamp_regular_payload(spec, state):
     next_slot(spec, state)
 
     # execution payload
-    execution_payload = build_empty_execution_payload_with_zeroed_random(spec, state)
+    execution_payload = build_empty_execution_payload(spec, state)
     execution_payload.timestamp = execution_payload.timestamp + 1
 
     yield from run_execution_payload_processing(spec, state, execution_payload, valid=False)

From e5c01061af230ad2651097576c5900cb719b1fbd Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Tue, 22 Jun 2021 14:26:38 +0600
Subject: [PATCH 17/22] Add couple of cosmetic fixes

---
 tests/core/pyspec/eth2spec/test/helpers/execution_payload.py   | 2 +-
 .../merge/block_processing/test_process_execution_payload.py   | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 1ef63eaaf..c41a05079 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -51,7 +51,7 @@ def build_state_with_incomplete_transition(spec, state):
 
 
 def build_state_with_complete_transition(spec, state):
-    pre_state_payload = build_empty_execution_payload(spec, state, spec.Bytes32())
+    pre_state_payload = build_empty_execution_payload(spec, state)
     payload_header = get_execution_payload_header(spec, pre_state_payload)
 
     return build_state_with_execution_payload_header(spec, state, payload_header)
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index 15c69f2dd..4c68034d4 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -32,8 +32,7 @@ def run_execution_payload_processing(spec, state, execution_payload, valid=True,
             return execution_valid
 
     if not valid:
-        expect_assertion_error(
-            lambda: spec.process_execution_payload(state, execution_payload, TestEngine()))
+        expect_assertion_error(lambda: spec.process_execution_payload(state, execution_payload, TestEngine()))
         yield 'post', None
         return
 

From c61eeb8a27370fbb98c317404fcfc770ba29dd0d Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Tue, 22 Jun 2021 12:31:02 -0600
Subject: [PATCH 18/22] optimize sync committee message gossip and caches

---
 specs/altair/p2p-interface.md | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/specs/altair/p2p-interface.md b/specs/altair/p2p-interface.md
index fc0a8a35f..6945704f4 100644
--- a/specs/altair/p2p-interface.md
+++ b/specs/altair/p2p-interface.md
@@ -137,13 +137,14 @@ def get_sync_subcommittee_pubkeys(state: BeaconState, subcommittee_index: uint64
     return sync_committee.pubkeys[i:i + sync_subcommittee_size]
 ```
 
-- _[IGNORE]_ The contribution's slot is for the current slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance), i.e. `contribution.slot == current_slot`.
-- _[IGNORE]_ The block being signed over (`contribution.beacon_block_root`) has been seen (via both gossip and non-gossip sources).
+- _[IGNORE]_ The contribution's slot is for the current slot (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance), i.e. `contribution.slot == current_slot`.
 - _[REJECT]_ The subcommittee index is in the allowed range, i.e. `contribution.subcommittee_index < SYNC_COMMITTEE_SUBNET_COUNT`.
-- _[IGNORE]_ The sync committee contribution is the first valid contribution received for the aggregator with index `contribution_and_proof.aggregator_index` for the slot `contribution.slot` and subcommittee index `contribution.subcommittee_index`.
 - _[REJECT]_ `contribution_and_proof.selection_proof` selects the validator as an aggregator for the slot -- i.e. `is_sync_committee_aggregator(contribution_and_proof.selection_proof)` returns `True`.
 - _[REJECT]_ The aggregator's validator index is in the declared subcommittee of the current sync committee --
   i.e. `state.validators[contribution_and_proof.aggregator_index].pubkey in get_sync_subcommittee_pubkeys(state, contribution.subcommittee_index)`.
+- _[IGNORE]_ The sync committee contribution is the first valid contribution received for the aggregator with index `contribution_and_proof.aggregator_index`
+  for the slot `contribution.slot` and subcommittee index `contribution.subcommittee_index`
+  (this requires maintaining a cache of size `SYNC_COMMITTEE_SIZE` for this topic that can be flushed after each slot).
 - _[REJECT]_ The `contribution_and_proof.selection_proof` is a valid signature of the `SyncAggregatorSelectionData` derived from the `contribution` by the validator with index `contribution_and_proof.aggregator_index`.
 - _[REJECT]_ The aggregator signature, `signed_contribution_and_proof.signature`, is valid.
 - _[REJECT]_ The aggregate signature is valid for the message `beacon_block_root` and aggregate pubkey derived from the participation info in `aggregation_bits` for the subcommittee specified by the `contribution.subcommittee_index`.
@@ -158,12 +159,12 @@ The `sync_committee_{subnet_id}` topics are used to propagate unaggregated sync
 
 The following validations MUST pass before forwarding the `sync_committee_message` on the network:
 
-- _[IGNORE]_ The signature's slot is for the current slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance), i.e. `sync_committee_message.slot == current_slot`.
-- _[IGNORE]_ The block being signed over (`sync_committee_message.beacon_block_root`) has been seen (via both gossip and non-gossip sources).
-- _[IGNORE]_ There has been no other valid sync committee signature for the declared `slot` for the validator referenced by `sync_committee_message.validator_index`.
-  Note this validation is _per topic_ so that for a given `slot`, multiple messages could be forwarded with the same `validator_index` as long as the `subnet_id`s are distinct.
+- _[IGNORE]_ The signature's slot is for the current slot (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance), i.e. `sync_committee_message.slot == current_slot`.
 - _[REJECT]_ The `subnet_id` is valid for the given validator, i.e. `subnet_id in compute_subnets_for_sync_committee(state, sync_committee_message.validator_index)`.
   Note this validation implies the validator is part of the broader current sync committee along with the correct subcommittee.
+- _[IGNORE]_ There has been no other valid sync committee signature for the declared `slot` for the validator referenced by `sync_committee_message.validator_index`
+  (this requires maintaining a cache of size `SYNC_COMMITTEE_SIZE // SYNC_COMMITTEE_SUBNET_COUNT` for each subnet that can be flushed after each slot).
+  Note this validation is _per topic_ so that for a given `slot`, multiple messages could be forwarded with the same `validator_index` as long as the `subnet_id`s are distinct.
 - _[REJECT]_ The `signature` is valid for the message `beacon_block_root` for the validator referenced by `validator_index`.
 
 #### Sync committees and aggregation

From e8136cb62ceb2985fdb454b7746ecf26135de12f Mon Sep 17 00:00:00 2001
From: vbuterin <v@buterin.com>
Date: Tue, 22 Jun 2021 18:15:56 -0500
Subject: [PATCH 19/22] Update merge description to signal more progress

---
 README.md | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/README.md b/README.md
index a9a840bde..d1a0b2876 100644
--- a/README.md
+++ b/README.md
@@ -35,8 +35,7 @@ The current features are:
 
 ### Merge
 
-The merge is still actively in R&D. The specifications outline a general direction for engineering work,
-while the details are in review and may change.
+The merge is still actively in development. The exact specification has not been formally accepted as final and details are still subject to change.
 
 * Background material:
   * An [ethresear.ch](https://ethresear.ch) post [describing the basic mechanism](https://ethresear.ch/t/the-eth1-eth2-transition/6265)

From 989c9620c7185da64537b7b6bea57021000a754c Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 23 Jun 2021 08:32:52 -0600
Subject: [PATCH 20/22] bump VERSION.txt to 1.1.0-alpha.8

---
 tests/core/pyspec/eth2spec/VERSION.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/core/pyspec/eth2spec/VERSION.txt b/tests/core/pyspec/eth2spec/VERSION.txt
index e79b1b4ae..a40920e99 100644
--- a/tests/core/pyspec/eth2spec/VERSION.txt
+++ b/tests/core/pyspec/eth2spec/VERSION.txt
@@ -1 +1 @@
-1.1.0-alpha.7
\ No newline at end of file
+1.1.0-alpha.8
\ No newline at end of file

From dbf7fbd3d041717f606052424d06e60b933f9843 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Thu, 24 Jun 2021 17:13:36 +0200
Subject: [PATCH 21/22] encode, decode and randomize ssz Union types

---
 tests/core/pyspec/eth2spec/debug/decode.py     | 13 ++++++++++++-
 tests/core/pyspec/eth2spec/debug/encode.py     |  8 +++++++-
 .../core/pyspec/eth2spec/debug/random_value.py | 18 +++++++++++++++++-
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/debug/decode.py b/tests/core/pyspec/eth2spec/debug/decode.py
index 871748d54..30bfd487b 100644
--- a/tests/core/pyspec/eth2spec/debug/decode.py
+++ b/tests/core/pyspec/eth2spec/debug/decode.py
@@ -2,7 +2,7 @@ from typing import Any
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import (
     uint, Container, List, boolean,
-    Vector, ByteVector, ByteList
+    Vector, ByteVector, ByteList, Union, View
 )
 
 
@@ -27,5 +27,16 @@ def decode(data: Any, typ):
             assert (data["hash_tree_root"][2:] ==
                     hash_tree_root(ret).hex())
         return ret
+    elif issubclass(typ, Union):
+        selector = int(data["selector"])
+        options = typ.options()
+        value_typ = options[selector]
+        value: View
+        if value_typ is None:  # handle the "nil" type case
+            assert data["value"] is None
+            value = None
+        else:
+            value = decode(data["value"], value_typ)
+        return typ(selector=selector, value=value)
     else:
         raise Exception(f"Type not recognized: data={data}, typ={typ}")
diff --git a/tests/core/pyspec/eth2spec/debug/encode.py b/tests/core/pyspec/eth2spec/debug/encode.py
index 10bf4bedd..d93f7cf5e 100644
--- a/tests/core/pyspec/eth2spec/debug/encode.py
+++ b/tests/core/pyspec/eth2spec/debug/encode.py
@@ -1,7 +1,7 @@
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root, serialize
 from eth2spec.utils.ssz.ssz_typing import (
     uint, boolean,
-    Bitlist, Bitvector, Container, Vector, List
+    Bitlist, Bitvector, Container, Vector, List, Union
 )
 
 
@@ -31,5 +31,11 @@ def encode(value, include_hash_tree_roots=False):
         if include_hash_tree_roots:
             ret["hash_tree_root"] = '0x' + hash_tree_root(value).hex()
         return ret
+    elif isinstance(value, Union):
+        inner_value = value.value()
+        return {
+            'selector': int(value.selector()),
+            'value': None if inner_value is None else encode(inner_value, include_hash_tree_roots)
+        }
     else:
         raise Exception(f"Type not recognized: value={value}, typ={type(value)}")
diff --git a/tests/core/pyspec/eth2spec/debug/random_value.py b/tests/core/pyspec/eth2spec/debug/random_value.py
index 33eb25c0c..f8cb5701e 100644
--- a/tests/core/pyspec/eth2spec/debug/random_value.py
+++ b/tests/core/pyspec/eth2spec/debug/random_value.py
@@ -5,7 +5,7 @@ from typing import Type
 
 from eth2spec.utils.ssz.ssz_typing import (
     View, BasicView, uint, Container, List, boolean,
-    Vector, ByteVector, ByteList, Bitlist, Bitvector
+    Vector, ByteVector, ByteList, Bitlist, Bitvector, Union
 )
 
 # in bytes
@@ -115,6 +115,22 @@ def get_random_ssz_object(rng: Random,
                 get_random_ssz_object(rng, field_type, max_bytes_length, max_list_length, mode, chaos)
             for field_name, field_type in fields.items()
         })
+    elif issubclass(typ, Union):
+        options = typ.options()
+        selector: int
+        if mode == RandomizationMode.mode_zero:
+            selector = 0
+        elif mode == RandomizationMode.mode_max:
+            selector = len(options)-1
+        else:
+            selector = rng.randrange(0, len(options))
+        elem_type = options[selector]
+        elem: View
+        if elem_type is None:
+            elem = None
+        else:
+            elem = get_random_ssz_object(rng, elem_type, max_bytes_length, max_list_length, mode, chaos)
+        return typ(selector=selector, value=elem)
     else:
         raise Exception(f"Type not recognized: typ={typ}")
 

From 44a3113ce176358ab69a0648aed883a23e7039a6 Mon Sep 17 00:00:00 2001
From: Alex Stokes <r.alex.stokes@gmail.com>
Date: Thu, 24 Jun 2021 09:24:58 -0700
Subject: [PATCH 22/22] fix spacing for linter

---
 tests/core/pyspec/eth2spec/debug/random_value.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/core/pyspec/eth2spec/debug/random_value.py b/tests/core/pyspec/eth2spec/debug/random_value.py
index f8cb5701e..ff80ee0f4 100644
--- a/tests/core/pyspec/eth2spec/debug/random_value.py
+++ b/tests/core/pyspec/eth2spec/debug/random_value.py
@@ -121,7 +121,7 @@ def get_random_ssz_object(rng: Random,
         if mode == RandomizationMode.mode_zero:
             selector = 0
         elif mode == RandomizationMode.mode_max:
-            selector = len(options)-1
+            selector = len(options) - 1
         else:
             selector = rng.randrange(0, len(options))
         elem_type = options[selector]