From b530e017619b79b7a8c4d9105177c3425d5d9770 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Mon, 20 Sep 2021 20:57:45 +0600
Subject: [PATCH 01/14] Update calls to execution_engine

---
 setup.py                                      | 19 ++--
 specs/merge/beacon-chain.md                   | 28 ++++--
 specs/merge/fork-choice.md                    | 32 ++-----
 specs/merge/validator.md                      | 92 +++++++++++++------
 .../test_process_execution_payload.py         |  2 +-
 5 files changed, 107 insertions(+), 66 deletions(-)

diff --git a/setup.py b/setup.py
index 6e55cfdde..1d647c2a1 100644
--- a/setup.py
+++ b/setup.py
@@ -522,16 +522,23 @@ def get_pow_chain_head() -> PowBlock:
 
 class NoopExecutionEngine(ExecutionEngine):
 
-    def on_payload(self, execution_payload: ExecutionPayload) -> bool:
+    def execute_payload(self, execution_payload: ExecutionPayload) -> bool:
         return True
 
-    def set_head(self, block_hash: Hash32) -> bool:
-        return True
+    def consensus_validated(self: ExecutionEngine, execution_payload: ExecutionPayload) -> None:
+        pass
 
-    def finalize_block(self, block_hash: Hash32) -> bool:
-        return True
+    def forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
+        pass
 
-    def assemble_block(self, block_hash: Hash32, timestamp: uint64, random: Bytes32) -> ExecutionPayload:
+    def prepare_payload(self: ExecutionEngine,
+                        parent_hash: Hash32,
+                        timestamp: uint64,
+                        random: Bytes32,
+                        feeRecipient: Bytes20) -> uint64:
+        raise NotImplementedError("no default block production")
+
+    def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
         raise NotImplementedError("no default block production")
 
 
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 03bf01155..a5fc4101d 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -31,7 +31,8 @@
     - [`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)
+    - [`execute_payload`](#execute_payload)
+    - [`consensus_validated`](#consensus_validated)
   - [Block processing](#block-processing)
   - [Execution payload processing](#execution-payload-processing)
     - [`is_valid_gas_limit`](#is_valid_gas_limit)
@@ -237,19 +238,31 @@ def compute_timestamp_at_slot(state: BeaconState, slot: Slot) -> uint64:
 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`
+* a state transition function `self.execute_payload` which applies changes to the `self.execution_state`
+* a method `self.consensus_validated` which notifies that the block holding the execution payload
+is valid with respect to the consensus rule set
 
-#### `on_payload`
+#### `execute_payload`
 
 ```python
-def on_payload(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
+def execute_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.
+#### `consensus_validated`
+
+```python
+def consensus_validated(self: ExecutionEngine, execution_payload: ExecutionPayload) -> None:
+    ...
+```
+
+The above functions are accessed through the `EXECUTION_ENGINE` module which instantiates the `ExecutionEngine` protocol.
+
+The body of each of these functions is implementation dependent.
+The Engine API may be used to implement them with an external execution engine.
 
 ### Block processing
 
@@ -264,6 +277,9 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_eth1_data(state, block.body)
     process_operations(state, block.body)
     process_sync_aggregate(state, block.body.sync_aggregate)
+    if is_execution_enabled(state, block.body):
+        # Notify the block is valid with respect to the consensus state transition function
+        EXECUTION_ENGINE.consensus_validated(block.body.execution_payload)  # [New in Merge]
 ```
 
 ### Execution payload processing
@@ -304,7 +320,7 @@ def process_execution_payload(state: BeaconState, payload: ExecutionPayload, exe
     # Verify timestamp
     assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
     # Verify the execution payload is valid
-    assert execution_engine.on_payload(payload)
+    assert execution_engine.execute_payload(payload)
     # Cache execution payload header
     state.latest_execution_payload_header = ExecutionPayloadHeader(
         parent_hash=payload.parent_hash,
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index 8051ab3eb..d8b3426ea 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -10,8 +10,7 @@
 - [Introduction](#introduction)
 - [Protocols](#protocols)
   - [`ExecutionEngine`](#executionengine)
-    - [`set_head`](#set_head)
-    - [`finalize_block`](#finalize_block)
+    - [`forkchoice_updated`](#forkchoice_updated)
 - [Helpers](#helpers)
   - [`PowBlock`](#powblock)
   - [`get_pow_block`](#get_pow_block)
@@ -34,36 +33,19 @@ This is the modification of the fork choice according to the executable beacon c
 
 The following methods are added to the `ExecutionEngine` protocol for use in the fork choice:
 
-#### `set_head`
+#### `forkchoice_updated`
 
-Re-organizes the execution payload chain and corresponding state to make `block_hash` the head.
-
-The body of this function is implementation dependent.
-The Consensus API may be used to implement this with an external execution engine.
+* Re-organizes the execution payload chain and corresponding state to make `head_block_hash` the head.
+* Applies finality to the execution state: it irreversibly persists the chain of all execution payloads
+and corresponding state, up to and including `finalized_block_hash`.
 
 ```python
-def set_head(self: ExecutionEngine, block_hash: Hash32) -> bool:
-    """
-    Returns True if the ``block_hash`` was successfully set as head of the execution payload chain.
-    """
+def forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
     ...
 ```
 
-#### `finalize_block`
-
-Applies finality to the execution state: it irreversibly persists the chain of all execution payloads
-and corresponding state, up to and including `block_hash`.
-
 The body of this function is implementation dependent.
-The Consensus API may be used to implement this with an external execution engine.
-
-```python
-def finalize_block(self: ExecutionEngine, block_hash: Hash32) -> bool:
-    """
-    Returns True if the data up to and including ``block_hash`` was successfully finalized.
-    """
-    ...
-```
+The Engine API may be used to implement this with an external execution engine.
 
 ## Helpers
 
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 645e1967b..7dfcecbc1 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -12,11 +12,12 @@
 - [Prerequisites](#prerequisites)
 - [Protocols](#protocols)
   - [`ExecutionEngine`](#executionengine)
-    - [`assemble_block`](#assemble_block)
+    - [`prepare_payload`](#prepare_payload)
+    - [`get_payload`](#get_payload)
 - [Beacon chain responsibilities](#beacon-chain-responsibilities)
   - [Block proposal](#block-proposal)
     - [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
-      - [Execution Payload](#execution-payload)
+      - [ExecutionPayload](#executionpayload)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -39,19 +40,39 @@ Please see related Beacon Chain doc before continuing and use them as a referenc
 
 The following methods are added to the `ExecutionEngine` protocol for use as a validator:
 
-#### `assemble_block`
+#### `prepare_payload`
 
-Produces a new instance of an execution payload, with the specified `timestamp`,
-on top of the execution payload chain tip identified by `block_hash`.
-
-The body of this function is implementation dependent.
-The Consensus API may be used to implement this with an external execution engine.
+Given the set of execution payload attributes initiates a process of building an execution payload
+on top of the execution chain tip identified by `parent_hash`.
 
 ```python
-def assemble_block(self: ExecutionEngine, block_hash: Hash32, timestamp: uint64, random: Bytes32) -> ExecutionPayload:
+def prepare_payload(self: ExecutionEngine,
+                    parent_hash: Hash32,
+                    timestamp: uint64,
+                    random: Bytes32,
+                    fee_recipient: Bytes20) -> uint64:
+    """
+    Returns ``payload_id`` that is used to obtain the execution payload in a subsequent ``get_payload`` call.
+    """
     ...
 ```
 
+#### `get_payload`
+
+Given the `payload_id` returns the most recent version of the execution payload that
+has been built since the corresponding call to `prepare_payload` method.
+
+```python
+def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
+    """
+    Returns ``execution_payload`` object.
+    """
+    ...
+```
+
+The body of each of these functions is implementation dependent.
+The Engine API may be used to implement them with an external execution engine.
+
 ## Beacon chain responsibilities
 
 All validator responsibilities remain unchanged other than those noted below. Namely, the transition block handling and the addition of `ExecutionPayload`.
@@ -60,9 +81,14 @@ All validator responsibilities remain unchanged other than those noted below. Na
 
 #### Constructing the `BeaconBlockBody`
 
-##### Execution Payload
+##### ExecutionPayload
 
-* Set `block.body.execution_payload = get_execution_payload(state, execution_engine, pow_chain)` where:
+To obtain an execution payload a proposer of a block must take the following actions:
+
+1. Set `payload_id = prepare_execution_payload(state, pow_chain, fee_recipient, execution_engine)`, where:
+    * `state` is the state for which `is_proposer(state, validator_index)` returns `True`
+    * `pow_chain` is a list that abstractly represents all blocks in the PoW chain
+    * `fee_recipient` is the value suggested to be used for the `coinbase` field of the execution payload
 
 ```python
 def get_pow_block_at_total_difficulty(total_difficulty: uint256, pow_chain: Sequence[PowBlock]) -> Optional[PowBlock]:
@@ -75,27 +101,37 @@ def get_pow_block_at_total_difficulty(total_difficulty: uint256, pow_chain: Sequ
     return None
 
 
-def produce_execution_payload(state: BeaconState,
-                              parent_hash: Hash32,
-                              execution_engine: ExecutionEngine) -> ExecutionPayload:
-    timestamp = compute_timestamp_at_slot(state, state.slot)
-    randao_mix = get_randao_mix(state, get_current_epoch(state))
-    return execution_engine.assemble_block(parent_hash, timestamp, randao_mix)
-
-
-def get_execution_payload(state: BeaconState,
-                          execution_engine: ExecutionEngine,
-                          pow_chain: Sequence[PowBlock]) -> ExecutionPayload:
+def prepare_execution_payload(state: BeaconState,
+                              pow_chain: Sequence[PowBlock],
+                              fee_recipient: Bytes20,
+                              execution_engine: ExecutionEngine) -> Optional[uint64]:
     if not is_merge_complete(state):
         terminal_pow_block = get_pow_block_at_total_difficulty(TERMINAL_TOTAL_DIFFICULTY, pow_chain)
         if terminal_pow_block is None:
-            # Pre-merge, empty payload
-            return ExecutionPayload()
+            # Pre-merge, no prepare payload call is needed
+            return None
         else:
             # Signify merge via producing on top of the last PoW block
-            return produce_execution_payload(state, terminal_pow_block.block_hash, execution_engine)
+            parent_hash = terminal_pow_block.block_hash
+    else:
+        # Post-merge, normal payload
+        parent_hash = state.latest_execution_payload_header.block_hash
 
-    # Post-merge, normal payload
-    parent_hash = state.latest_execution_payload_header.block_hash
-    return produce_execution_payload(state, parent_hash, execution_engine)
+    timestamp = compute_timestamp_at_slot(state, state.slot)
+    random = get_randao_mix(state, get_current_epoch(state))
+    return execution_engine.prepare_payload(parent_hash, timestamp, random, fee_recipient)
 ```
+
+2. Set `block.body.execution_payload = get_execution_payload(payload_id, execution_engine)`, where:
+
+```python
+def get_execution_payload(payload_id: Optional[uint64], execution_engine: ExecutionEngine) -> ExecutionPayload:
+    if payload_id is None:
+        # Pre-merge, empty payload
+        return ExecutionPayload()
+    else:
+        return execution_engine.get_payload(payload_id)
+```
+
+*Note*: It is recommended for a validator to call `prepare_execution_payload` as soon as input parameters become known,
+and make subsequent calls to this function if any of these parameters has been updated.
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 4c68034d4..a3aadc470 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 on_payload(self, payload) -> bool:
+        def execute_payload(self, payload) -> bool:
             nonlocal called_new_block, execution_valid
             called_new_block = True
             assert payload == execution_payload

From 18bfe3555f7b6b7f856096af0678085fdde30357 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Wed, 22 Sep 2021 17:45:26 +0600
Subject: [PATCH 02/14] Apply suggestions from code review

Co-authored-by: Danny Ryan <dannyjryan@gmail.com>
---
 specs/merge/beacon-chain.md | 2 +-
 specs/merge/fork-choice.md  | 1 +
 specs/merge/validator.md    | 6 +++---
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index a5fc4101d..6a5a2730b 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -239,7 +239,7 @@ The implementation-dependent `ExecutionEngine` protocol encapsulates the executi
 
 * a state object `self.execution_state` of type `ExecutionState`
 * a state transition function `self.execute_payload` which applies changes to the `self.execution_state`
-* a method `self.consensus_validated` which notifies that the block holding the execution payload
+* a method `self.consensus_validated` which signals that the beacon block containing the execution payload
 is valid with respect to the consensus rule set
 
 #### `execute_payload`
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index d8b3426ea..15d47a650 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -35,6 +35,7 @@ The following methods are added to the `ExecutionEngine` protocol for use in the
 
 #### `forkchoice_updated`
 
+This method performs two actions *atomically*:
 * Re-organizes the execution payload chain and corresponding state to make `head_block_hash` the head.
 * Applies finality to the execution state: it irreversibly persists the chain of all execution payloads
 and corresponding state, up to and including `finalized_block_hash`.
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 7dfcecbc1..a84384dd6 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -42,7 +42,7 @@ The following methods are added to the `ExecutionEngine` protocol for use as a v
 
 #### `prepare_payload`
 
-Given the set of execution payload attributes initiates a process of building an execution payload
+Given the set of execution payload attributes, `prepare_payload` initiates a process of building an execution payload
 on top of the execution chain tip identified by `parent_hash`.
 
 ```python
@@ -59,7 +59,7 @@ def prepare_payload(self: ExecutionEngine,
 
 #### `get_payload`
 
-Given the `payload_id` returns the most recent version of the execution payload that
+Given the `payload_id`, `get_payload` returns the most recent version of the execution payload that
 has been built since the corresponding call to `prepare_payload` method.
 
 ```python
@@ -83,7 +83,7 @@ All validator responsibilities remain unchanged other than those noted below. Na
 
 ##### ExecutionPayload
 
-To obtain an execution payload a proposer of a block must take the following actions:
+To obtain an execution payload, the proposer of a block must take the following actions:
 
 1. Set `payload_id = prepare_execution_payload(state, pow_chain, fee_recipient, execution_engine)`, where:
     * `state` is the state for which `is_proposer(state, validator_index)` returns `True`

From 06107ce7d8be3a66ef40803bca30c808d1cb13c7 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Wed, 22 Sep 2021 18:10:57 +0600
Subject: [PATCH 03/14] Polish the description of execution engine functions

---
 specs/merge/beacon-chain.md | 12 ++++++------
 specs/merge/fork-choice.md  | 10 +++++-----
 specs/merge/validator.md    | 10 +++++-----
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 3e107b7a9..a1ab61848 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -242,9 +242,14 @@ The implementation-dependent `ExecutionEngine` protocol encapsulates the executi
 
 * a state object `self.execution_state` of type `ExecutionState`
 * a state transition function `self.execute_payload` which applies changes to the `self.execution_state`
-* a method `self.consensus_validated` which signals that the beacon block containing the execution payload
+* a function `self.consensus_validated` which signals that the beacon block containing the execution payload
 is valid with respect to the consensus rule set
 
+*Note*: `execute_payload` and `consensus_validated` are functions accessed through the `EXECUTION_ENGINE` module which instantiates the `ExecutionEngine` protocol.
+
+The body of each of these functions is implementation dependent.
+The Engine API may be used to implement them with an external execution engine.
+
 #### `execute_payload`
 
 ```python
@@ -262,11 +267,6 @@ def consensus_validated(self: ExecutionEngine, execution_payload: ExecutionPaylo
     ...
 ```
 
-The above functions are accessed through the `EXECUTION_ENGINE` module which instantiates the `ExecutionEngine` protocol.
-
-The body of each of these functions is implementation dependent.
-The Engine API may be used to implement them with an external execution engine.
-
 ### Block processing
 
 *Note*: The call to the `process_execution_payload` must happen before the call to the `process_randao` as the former depends on the `randao_mix` computed with the reveal of the previous block.
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index 15d47a650..5adeded16 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -31,11 +31,14 @@ This is the modification of the fork choice according to the executable beacon c
 
 ### `ExecutionEngine`
 
-The following methods are added to the `ExecutionEngine` protocol for use in the fork choice:
+*Note*: The `forkchoice_updated` function is added to the `ExecutionEngine` protocol to signal the fork choice updates.
+
+The body of this function is implementation dependent.
+The Engine API may be used to implement it with an external execution engine.
 
 #### `forkchoice_updated`
 
-This method performs two actions *atomically*:
+This function performs two actions *atomically*:
 * Re-organizes the execution payload chain and corresponding state to make `head_block_hash` the head.
 * Applies finality to the execution state: it irreversibly persists the chain of all execution payloads
 and corresponding state, up to and including `finalized_block_hash`.
@@ -45,9 +48,6 @@ def forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized
     ...
 ```
 
-The body of this function is implementation dependent.
-The Engine API may be used to implement this with an external execution engine.
-
 ## Helpers
 
 ### `PowBlock`
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index a84384dd6..aa5efc8ed 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -38,7 +38,10 @@ Please see related Beacon Chain doc before continuing and use them as a referenc
 
 ### `ExecutionEngine`
 
-The following methods are added to the `ExecutionEngine` protocol for use as a validator:
+*Note*: `prepare_payload` and `get_payload` functions are added to the `ExecutionEngine` protocol for use as a validator.
+
+The body of each of these functions is implementation dependent.
+The Engine API may be used to implement them with an external execution engine.
 
 #### `prepare_payload`
 
@@ -70,9 +73,6 @@ def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
     ...
 ```
 
-The body of each of these functions is implementation dependent.
-The Engine API may be used to implement them with an external execution engine.
-
 ## Beacon chain responsibilities
 
 All validator responsibilities remain unchanged other than those noted below. Namely, the transition block handling and the addition of `ExecutionPayload`.
@@ -134,4 +134,4 @@ def get_execution_payload(payload_id: Optional[uint64], execution_engine: Execut
 ```
 
 *Note*: It is recommended for a validator to call `prepare_execution_payload` as soon as input parameters become known,
-and make subsequent calls to this function if any of these parameters has been updated.
+and make subsequent calls to this function when any of these parameters gets updated.

From 24bacafeee3511b70741c7e7d4196856bcf9eb11 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Wed, 22 Sep 2021 23:52:15 +0600
Subject: [PATCH 04/14] Update consensus_validated description

---
 setup.py                    |  4 ++--
 specs/merge/beacon-chain.md | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/setup.py b/setup.py
index 1d647c2a1..6d75caeb1 100644
--- a/setup.py
+++ b/setup.py
@@ -522,10 +522,10 @@ def get_pow_chain_head() -> PowBlock:
 
 class NoopExecutionEngine(ExecutionEngine):
 
-    def execute_payload(self, execution_payload: ExecutionPayload) -> bool:
+    def execute_payload(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
         return True
 
-    def consensus_validated(self: ExecutionEngine, execution_payload: ExecutionPayload) -> None:
+    def consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool) -> None:
         pass
 
     def forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index a1ab61848..eccb7f047 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -263,10 +263,15 @@ def execute_payload(self: ExecutionEngine, execution_payload: ExecutionPayload)
 #### `consensus_validated`
 
 ```python
-def consensus_validated(self: ExecutionEngine, execution_payload: ExecutionPayload) -> None:
+def consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool) -> None:
     ...
 ```
 
+The call of this function depends on the result of the state transition and must be done when call to the [`state_transition`](../phase0/beacon-chain.md#beacon-chain-state-transition-function) function finishes. The value of the `valid` parameter must be set as follows:
+
+* `True` if `state_transition` function call succeedes
+* `False` if `state_transition` function call fails
+
 ### Block processing
 
 *Note*: The call to the `process_execution_payload` must happen before the call to the `process_randao` as the former depends on the `randao_mix` computed with the reveal of the previous block.
@@ -280,9 +285,6 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_eth1_data(state, block.body)
     process_operations(state, block.body)
     process_sync_aggregate(state, block.body.sync_aggregate)
-    if is_execution_enabled(state, block.body):
-        # Notify the block is valid with respect to the consensus state transition function
-        EXECUTION_ENGINE.consensus_validated(block.body.execution_payload)  # [New in Merge]
 ```
 
 ### Execution payload processing

From 38a4fd907e941d8aabb17fdc3090eb39002c33d6 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Wed, 22 Sep 2021 23:56:10 +0600
Subject: [PATCH 05/14] Fix spelling

Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>
---
 specs/merge/validator.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index aa5efc8ed..115b992b0 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -68,7 +68,7 @@ has been built since the corresponding call to `prepare_payload` method.
 ```python
 def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
     """
-    Returns ``execution_payload`` object.
+    Return ``execution_payload`` object.
     """
     ...
 ```

From f4bd37a10859206d47a1dd0754e4da8067d72544 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Wed, 22 Sep 2021 23:58:04 +0600
Subject: [PATCH 06/14] Fix spelling 2

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

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index eccb7f047..a99036fe5 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -269,7 +269,7 @@ def consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool)
 
 The call of this function depends on the result of the state transition and must be done when call to the [`state_transition`](../phase0/beacon-chain.md#beacon-chain-state-transition-function) function finishes. The value of the `valid` parameter must be set as follows:
 
-* `True` if `state_transition` function call succeedes
+* `True` if `state_transition` function call succeeds
 * `False` if `state_transition` function call fails
 
 ### Block processing

From eada985e9e10c40da7cd9bf773920d0ab93aac7e Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 13:16:18 +0600
Subject: [PATCH 07/14] Better wording for consensus_validated

Co-authored-by: Danny Ryan <dannyjryan@gmail.com>
---
 specs/merge/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index a99036fe5..4a1c9c42f 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -267,7 +267,7 @@ def consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool)
     ...
 ```
 
-The call of this function depends on the result of the state transition and must be done when call to the [`state_transition`](../phase0/beacon-chain.md#beacon-chain-state-transition-function) function finishes. The value of the `valid` parameter must be set as follows:
+The inputs to this function depend on the result of the state transition. A call to `consensus_validated` must be made after the [`state_transition`](../phase0/beacon-chain.md#beacon-chain-state-transition-function) function finishes. The value of the `valid` parameter must be set as follows:
 
 * `True` if `state_transition` function call succeeds
 * `False` if `state_transition` function call fails

From c815f695cd01dbdfe79d80d06bb7570fa38bf7db Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 13:17:55 +0600
Subject: [PATCH 08/14] Polish comment in get_payload body

Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>
---
 specs/merge/validator.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 115b992b0..4500d610c 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -55,7 +55,7 @@ def prepare_payload(self: ExecutionEngine,
                     random: Bytes32,
                     fee_recipient: Bytes20) -> uint64:
     """
-    Returns ``payload_id`` that is used to obtain the execution payload in a subsequent ``get_payload`` call.
+    Return ``payload_id`` that is used to obtain the execution payload in a subsequent ``get_payload`` call.
     """
     ...
 ```

From 7ef938da772886c31cb655e4b4fbd989188a2afb Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 13:37:52 +0600
Subject: [PATCH 09/14] Add notify_ prefix to EE functions sending
 notifications

---
 setup.py                    |  4 ++--
 specs/merge/beacon-chain.md | 12 ++++++------
 specs/merge/fork-choice.md  |  8 ++++----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/setup.py b/setup.py
index 6d75caeb1..39eccad53 100644
--- a/setup.py
+++ b/setup.py
@@ -525,10 +525,10 @@ class NoopExecutionEngine(ExecutionEngine):
     def execute_payload(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
         return True
 
-    def consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool) -> None:
+    def notify_consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool) -> None:
         pass
 
-    def forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
+    def notify_forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
         pass
 
     def prepare_payload(self: ExecutionEngine,
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 4a1c9c42f..9be89fcea 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -32,7 +32,7 @@
 - [Beacon chain state transition function](#beacon-chain-state-transition-function)
   - [Execution engine](#execution-engine)
     - [`execute_payload`](#execute_payload)
-    - [`consensus_validated`](#consensus_validated)
+    - [`notify_consensus_validated`](#notify_consensus_validated)
   - [Block processing](#block-processing)
   - [Execution payload processing](#execution-payload-processing)
     - [`is_valid_gas_limit`](#is_valid_gas_limit)
@@ -242,10 +242,10 @@ The implementation-dependent `ExecutionEngine` protocol encapsulates the executi
 
 * a state object `self.execution_state` of type `ExecutionState`
 * a state transition function `self.execute_payload` which applies changes to the `self.execution_state`
-* a function `self.consensus_validated` which signals that the beacon block containing the execution payload
+* a function `self.notify_consensus_validated` which signals that the beacon block containing the execution payload
 is valid with respect to the consensus rule set
 
-*Note*: `execute_payload` and `consensus_validated` are functions accessed through the `EXECUTION_ENGINE` module which instantiates the `ExecutionEngine` protocol.
+*Note*: `execute_payload` and `notify_consensus_validated` are functions accessed through the `EXECUTION_ENGINE` module which instantiates the `ExecutionEngine` protocol.
 
 The body of each of these functions is implementation dependent.
 The Engine API may be used to implement them with an external execution engine.
@@ -260,14 +260,14 @@ def execute_payload(self: ExecutionEngine, execution_payload: ExecutionPayload)
     ...
 ```
 
-#### `consensus_validated`
+#### `notify_consensus_validated`
 
 ```python
-def consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool) -> None:
+def notify_consensus_validated(self: ExecutionEngine, block_hash: Hash32, valid: bool) -> None:
     ...
 ```
 
-The inputs to this function depend on the result of the state transition. A call to `consensus_validated` must be made after the [`state_transition`](../phase0/beacon-chain.md#beacon-chain-state-transition-function) function finishes. The value of the `valid` parameter must be set as follows:
+The inputs to this function depend on the result of the state transition. A call to `notify_consensus_validated` must be made after the [`state_transition`](../phase0/beacon-chain.md#beacon-chain-state-transition-function) function finishes. The value of the `valid` parameter must be set as follows:
 
 * `True` if `state_transition` function call succeeds
 * `False` if `state_transition` function call fails
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index 5adeded16..7b8643e99 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -10,7 +10,7 @@
 - [Introduction](#introduction)
 - [Protocols](#protocols)
   - [`ExecutionEngine`](#executionengine)
-    - [`forkchoice_updated`](#forkchoice_updated)
+    - [`notify_forkchoice_updated`](#notify_forkchoice_updated)
 - [Helpers](#helpers)
   - [`PowBlock`](#powblock)
   - [`get_pow_block`](#get_pow_block)
@@ -31,12 +31,12 @@ This is the modification of the fork choice according to the executable beacon c
 
 ### `ExecutionEngine`
 
-*Note*: The `forkchoice_updated` function is added to the `ExecutionEngine` protocol to signal the fork choice updates.
+*Note*: The `notify_forkchoice_updated` function is added to the `ExecutionEngine` protocol to signal the fork choice updates.
 
 The body of this function is implementation dependent.
 The Engine API may be used to implement it with an external execution engine.
 
-#### `forkchoice_updated`
+#### `notify_forkchoice_updated`
 
 This function performs two actions *atomically*:
 * Re-organizes the execution payload chain and corresponding state to make `head_block_hash` the head.
@@ -44,7 +44,7 @@ This function performs two actions *atomically*:
 and corresponding state, up to and including `finalized_block_hash`.
 
 ```python
-def forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
+def notify_forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, finalized_block_hash: Hash32) -> None:
     ...
 ```
 

From b7deef16293916a0fa03c00544aac0b5ea43540d Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 13:50:46 +0600
Subject: [PATCH 10/14] Clarity which state should be used in prepare_payload
 in a better way

---
 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 4500d610c..dc67997c7 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -83,10 +83,10 @@ All validator responsibilities remain unchanged other than those noted below. Na
 
 ##### ExecutionPayload
 
-To obtain an execution payload, the proposer of a block must take the following actions:
+To obtain an execution payload, a block proposer bulding a block on top of a `state` must take the following actions:
 
 1. Set `payload_id = prepare_execution_payload(state, pow_chain, fee_recipient, execution_engine)`, where:
-    * `state` is the state for which `is_proposer(state, validator_index)` returns `True`
+    * `state` is the state object after applying `process_slots(state, slot)` transition to the resulting state of the parent block processing
     * `pow_chain` is a list that abstractly represents all blocks in the PoW chain
     * `fee_recipient` is the value suggested to be used for the `coinbase` field of the execution payload
 

From 7d577ed422e7504238e7451247806aa1f3e960f7 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 14:35:55 +0600
Subject: [PATCH 11/14] Introduce ExecutionAddress type

---
 setup.py                                                     | 2 +-
 specs/merge/beacon-chain.md                                  | 5 +++--
 specs/merge/validator.md                                     | 4 ++--
 tests/core/pyspec/eth2spec/test/helpers/execution_payload.py | 2 +-
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/setup.py b/setup.py
index 39eccad53..efd4c29d5 100644
--- a/setup.py
+++ b/setup.py
@@ -535,7 +535,7 @@ class NoopExecutionEngine(ExecutionEngine):
                         parent_hash: Hash32,
                         timestamp: uint64,
                         random: Bytes32,
-                        feeRecipient: Bytes20) -> uint64:
+                        feeRecipient: ExecutionAddress) -> uint64:
         raise NotImplementedError("no default block production")
 
     def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 9be89fcea..1be41a81e 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -54,6 +54,7 @@ This patch adds transaction execution to the beacon chain as part of the Merge f
 | - | - | - |
 | `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 |
+| `ExecutionAddress` | `Bytes20` | Address of account on the execution layer |
 
 ## Constants
 
@@ -159,7 +160,7 @@ class BeaconState(Container):
 class ExecutionPayload(Container):
     # Execution block header fields
     parent_hash: Hash32
-    coinbase: Bytes20  # 'beneficiary' in the yellow paper
+    coinbase: ExecutionAddress  # 'beneficiary' in the yellow paper
     state_root: Bytes32
     receipt_root: Bytes32  # 'receipts root' in the yellow paper
     logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
@@ -181,7 +182,7 @@ class ExecutionPayload(Container):
 class ExecutionPayloadHeader(Container):
     # Execution block header fields
     parent_hash: Hash32
-    coinbase: Bytes20
+    coinbase: ExecutionAddress
     state_root: Bytes32
     receipt_root: Bytes32
     logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index dc67997c7..e175a083e 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -53,7 +53,7 @@ def prepare_payload(self: ExecutionEngine,
                     parent_hash: Hash32,
                     timestamp: uint64,
                     random: Bytes32,
-                    fee_recipient: Bytes20) -> uint64:
+                    fee_recipient: ExecutionAddress) -> uint64:
     """
     Return ``payload_id`` that is used to obtain the execution payload in a subsequent ``get_payload`` call.
     """
@@ -103,7 +103,7 @@ def get_pow_block_at_total_difficulty(total_difficulty: uint256, pow_chain: Sequ
 
 def prepare_execution_payload(state: BeaconState,
                               pow_chain: Sequence[PowBlock],
-                              fee_recipient: Bytes20,
+                              fee_recipient: ExecutionAddress,
                               execution_engine: ExecutionEngine) -> Optional[uint64]:
     if not is_merge_complete(state):
         terminal_pow_block = get_pow_block_at_total_difficulty(TERMINAL_TOTAL_DIFFICULTY, pow_chain)
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 6126346a9..0d03447a7 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -11,7 +11,7 @@ def build_empty_execution_payload(spec, state, randao_mix=None):
 
     payload = spec.ExecutionPayload(
         parent_hash=latest.block_hash,
-        coinbase=spec.Bytes20(),
+        coinbase=spec.ExecutionAddress(),
         state_root=latest.state_root,  # no changes to the state
         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?

From 41e06aec1bb093663c9bf28268deacfbce59e899 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 15:03:43 +0600
Subject: [PATCH 12/14] Introduce PayloadId type

---
 setup.py                 |  4 ++--
 specs/merge/validator.md | 15 +++++++++++----
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/setup.py b/setup.py
index efd4c29d5..9c1846737 100644
--- a/setup.py
+++ b/setup.py
@@ -535,10 +535,10 @@ class NoopExecutionEngine(ExecutionEngine):
                         parent_hash: Hash32,
                         timestamp: uint64,
                         random: Bytes32,
-                        feeRecipient: ExecutionAddress) -> uint64:
+                        feeRecipient: ExecutionAddress) -> PayloadId:
         raise NotImplementedError("no default block production")
 
-    def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
+    def get_payload(self: ExecutionEngine, payload_id: PayloadId) -> ExecutionPayload:
         raise NotImplementedError("no default block production")
 
 
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index e175a083e..54ecbb64a 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -10,6 +10,7 @@
 
 - [Introduction](#introduction)
 - [Prerequisites](#prerequisites)
+- [Custom types](#custom-types)
 - [Protocols](#protocols)
   - [`ExecutionEngine`](#executionengine)
     - [`prepare_payload`](#prepare_payload)
@@ -34,6 +35,12 @@ All behaviors and definitions defined in this document, and documents it extends
 All terminology, constants, functions, and protocol mechanics defined in the updated Beacon Chain doc of [The Merge](./beacon-chain.md) are requisite for this document and used throughout.
 Please see related Beacon Chain doc before continuing and use them as a reference throughout.
 
+## Custom types
+
+| Name | SSZ equivalent | Description |
+| - | - | - |
+| `PayloadId` | `uint64` | Identifier of a payload building process |
+
 ## Protocols
 
 ### `ExecutionEngine`
@@ -53,7 +60,7 @@ def prepare_payload(self: ExecutionEngine,
                     parent_hash: Hash32,
                     timestamp: uint64,
                     random: Bytes32,
-                    fee_recipient: ExecutionAddress) -> uint64:
+                    fee_recipient: ExecutionAddress) -> PayloadId:
     """
     Return ``payload_id`` that is used to obtain the execution payload in a subsequent ``get_payload`` call.
     """
@@ -66,7 +73,7 @@ Given the `payload_id`, `get_payload` returns the most recent version of the exe
 has been built since the corresponding call to `prepare_payload` method.
 
 ```python
-def get_payload(self: ExecutionEngine, payload_id: uint64) -> ExecutionPayload:
+def get_payload(self: ExecutionEngine, payload_id: PayloadId) -> ExecutionPayload:
     """
     Return ``execution_payload`` object.
     """
@@ -104,7 +111,7 @@ def get_pow_block_at_total_difficulty(total_difficulty: uint256, pow_chain: Sequ
 def prepare_execution_payload(state: BeaconState,
                               pow_chain: Sequence[PowBlock],
                               fee_recipient: ExecutionAddress,
-                              execution_engine: ExecutionEngine) -> Optional[uint64]:
+                              execution_engine: ExecutionEngine) -> Optional[PayloadId]:
     if not is_merge_complete(state):
         terminal_pow_block = get_pow_block_at_total_difficulty(TERMINAL_TOTAL_DIFFICULTY, pow_chain)
         if terminal_pow_block is None:
@@ -125,7 +132,7 @@ def prepare_execution_payload(state: BeaconState,
 2. Set `block.body.execution_payload = get_execution_payload(payload_id, execution_engine)`, where:
 
 ```python
-def get_execution_payload(payload_id: Optional[uint64], execution_engine: ExecutionEngine) -> ExecutionPayload:
+def get_execution_payload(payload_id: Optional[PayloadId], execution_engine: ExecutionEngine) -> ExecutionPayload:
     if payload_id is None:
         # Pre-merge, empty payload
         return ExecutionPayload()

From 0e2eb506751c99e82f4e004d2a95aa5a41020c8c Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Thu, 23 Sep 2021 15:30:14 +0600
Subject: [PATCH 13/14] Fix spelling

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

diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 54ecbb64a..1bc36b02d 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -90,7 +90,7 @@ All validator responsibilities remain unchanged other than those noted below. Na
 
 ##### ExecutionPayload
 
-To obtain an execution payload, a block proposer bulding a block on top of a `state` must take the following actions:
+To obtain an execution payload, a block proposer building a block on top of a `state` must take the following actions:
 
 1. Set `payload_id = prepare_execution_payload(state, pow_chain, fee_recipient, execution_engine)`, where:
     * `state` is the state object after applying `process_slots(state, slot)` transition to the resulting state of the parent block processing

From 11840ce51ff69614d19747e546e8c1fa351a1a37 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Fri, 24 Sep 2021 16:31:09 +0600
Subject: [PATCH 14/14] Map EE calls on the PoS events defined in EIP-3675

---
 specs/merge/beacon-chain.md | 2 ++
 specs/merge/fork-choice.md  | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 1be41a81e..053c829f1 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -273,6 +273,8 @@ The inputs to this function depend on the result of the state transition. A call
 * `True` if `state_transition` function call succeeds
 * `False` if `state_transition` function call fails
 
+*Note*: The call of the `notify_consensus_validated` function with `valid = True` maps on the `POS_CONSENSUS_VALIDATED` event defined in the [EIP-3675](https://eips.ethereum.org/EIPS/eip-3675#definitions).
+
 ### Block processing
 
 *Note*: The call to the `process_execution_payload` must happen before the call to the `process_randao` as the former depends on the `randao_mix` computed with the reveal of the previous block.
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index 7b8643e99..4cf413b10 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -48,6 +48,8 @@ def notify_forkchoice_updated(self: ExecutionEngine, head_block_hash: Hash32, fi
     ...
 ```
 
+*Note*: The call of the `notify_forkchoice_updated` function maps on the `POS_FORKCHOICE_UPDATED` event defined in the [EIP-3675](https://eips.ethereum.org/EIPS/eip-3675#definitions).
+
 ## Helpers
 
 ### `PowBlock`