From 5582490364031ca014f79084b36ce14a52358899 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Wed, 14 Jul 2021 13:40:34 +0200
Subject: [PATCH 01/19] Apply missing spec_test decorators, to handle
 generator_mode flag

---
 .../altair/block_processing/test_process_sync_aggregate.py     | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
index b9ac8a954..ad285f43c 100644
--- a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
+++ b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
@@ -26,6 +26,7 @@ from eth2spec.test.context import (
     with_presets,
     spec_state_test,
     always_bls,
+    spec_test,
 )
 from eth2spec.utils.hash_function import hash
 
@@ -534,6 +535,7 @@ def test_random_all_but_one_participating_with_duplicates(spec, state):
 
 @with_altair_and_later
 @with_presets([MAINNET], reason="to create duplicate committee")
+@spec_test
 @with_custom_state(balances_fn=misc_balances, threshold_fn=default_activation_threshold)
 @single_phase
 def test_random_misc_balances_and_half_participation_with_duplicates(spec, state):
@@ -596,6 +598,7 @@ def test_random_all_but_one_participating_without_duplicates(spec, state):
 
 @with_altair_and_later
 @with_presets([MINIMAL], reason="to create nonduplicate committee")
+@spec_test
 @with_custom_state(balances_fn=misc_balances, threshold_fn=default_activation_threshold)
 @single_phase
 def test_random_misc_balances_and_half_participation_without_duplicates(spec, state):

From c420968f664d6400ebfadab56ebdc9a3bb66e93a Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 14 Jul 2021 11:08:54 -0600
Subject: [PATCH 02/19] fix last beta.1 mainnet test

---
 .../altair/epoch_processing/test_process_inactivity_updates.py  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py b/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py
index fd1bf3c57..634c7bc48 100644
--- a/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py
+++ b/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py
@@ -218,7 +218,7 @@ def test_some_slashed_zero_scores_full_participation(spec, state):
 @spec_state_test
 @leaking()
 def test_some_slashed_zero_scores_full_participation_leaking(spec, state):
-    slash_some_validators(spec, state, rng=Random(33221))
+    slash_some_validators(spec, state, rng=Random(332243))
     yield from run_inactivity_scores_test(
         spec, state,
         set_full_participation, zero_inactivity_scores,

From a4a050e97af47bde6ee1aa0d1a8facec6c4fed6d Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Fri, 16 Jul 2021 19:16:32 +0600
Subject: [PATCH 03/19] Enforce terminal PoW block to be on the cusp

---
 setup.py                   | 2 +-
 specs/merge/fork-choice.md | 9 ++++++---
 specs/merge/validator.md   | 3 ++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/setup.py b/setup.py
index fa73e0824..c9b22b1a9 100644
--- a/setup.py
+++ b/setup.py
@@ -509,7 +509,7 @@ ExecutionState = Any
 
 
 def get_pow_block(hash: Bytes32) -> PowBlock:
-    return PowBlock(block_hash=hash, is_valid=True, is_processed=True,
+    return PowBlock(block_hash=hash, parent_hash=Bytes32(), is_valid=True, is_processed=True,
                     total_difficulty=uint256(0), difficulty=uint256(0))
 
 
diff --git a/specs/merge/fork-choice.md b/specs/merge/fork-choice.md
index d0f327137..e21b54a7e 100644
--- a/specs/merge/fork-choice.md
+++ b/specs/merge/fork-choice.md
@@ -82,6 +82,7 @@ class TransitionStore(object):
 @dataclass
 class PowBlock(object):
     block_hash: Hash32
+    parent_hash: Hash32
     is_processed: boolean
     is_valid: boolean
     total_difficulty: uint256
@@ -99,9 +100,10 @@ Let `get_pow_block(block_hash: Hash32) -> PowBlock` be the function that given t
 Used by fork-choice handler, `on_block`.
 
 ```python
-def is_valid_terminal_pow_block(transition_store: TransitionStore, block: PowBlock) -> bool:
+def is_valid_terminal_pow_block(transition_store: TransitionStore, block: PowBlock, parent: PowBlock) -> bool:
     is_total_difficulty_reached = block.total_difficulty >= transition_store.transition_total_difficulty
-    return block.is_valid and is_total_difficulty_reached
+    is_parent_total_difficulty_valid = parent.total_difficulty < transition_store.transition_total_difficulty
+    return block.is_valid and is_total_difficulty_reached and is_parent_total_difficulty_valid
 ```
 
 ## Updated fork-choice handlers
@@ -130,8 +132,9 @@ def on_block(store: Store, signed_block: SignedBeaconBlock, transition_store: Tr
     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)
+        pow_parent = get_pow_block(pow_block.parent_hash)
         assert pow_block.is_processed
-        assert is_valid_terminal_pow_block(transition_store, pow_block)
+        assert is_valid_terminal_pow_block(transition_store, pow_block, pow_parent)
 
     # Check the block is valid and compute the post-state
     state = pre_state.copy()
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 97e6a1deb..be8f8b274 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -90,7 +90,8 @@ def get_execution_payload(state: BeaconState,
                           execution_engine: ExecutionEngine) -> ExecutionPayload:
     if not is_merge_complete(state):
         pow_block = get_pow_chain_head()
-        if not is_valid_terminal_pow_block(transition_store, pow_block):
+        pow_parent = get_pow_block(pow_block.parent_hash)
+        if not is_valid_terminal_pow_block(transition_store, pow_block, pow_parent):
             # Pre-merge, empty payload
             return ExecutionPayload()
         else:

From f668b2b43342e3fe0c93c24f91357a3f62111fc9 Mon Sep 17 00:00:00 2001
From: Adrian Sutton <adrian.sutton@consensys.net>
Date: Sat, 17 Jul 2021 16:26:18 +1000
Subject: [PATCH 04/19] Add tests for SyncAggregate with no participants and
 all zero signature.

---
 .../test_process_sync_aggregate.py                | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
index ad285f43c..effd01047 100644
--- a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
+++ b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
@@ -113,6 +113,21 @@ def test_invalid_signature_missing_participant(spec, state):
     yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
 
 
+@with_altair_and_later
+@spec_state_test
+@always_bls
+def test_invalid_signature_no_participants(spec, state):
+    committee_indices = compute_committee_indices(spec, state, state.current_sync_committee)
+
+    block = build_empty_block_for_next_slot(spec, state)
+    # Exclude one participant whose signature was included.
+    block.body.sync_aggregate = spec.SyncAggregate(
+        sync_committee_bits=[False for _ in committee_indices],
+        sync_committee_signature=b'\x00' * 96
+    )
+    yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
+
+
 @with_altair_and_later
 @spec_state_test
 @always_bls

From add00ad2e090baba86971f3b68b13f9ecd15c72c Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Sat, 17 Jul 2021 12:33:06 +0600
Subject: [PATCH 05/19] Replace get_pow_chain_head with
 get_pow_block_at_total_difficulty in validator.md

---
 setup.py                 |  1 +
 specs/merge/validator.md | 28 +++++++++++++++++-----------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/setup.py b/setup.py
index c9b22b1a9..69ae05666 100644
--- a/setup.py
+++ b/setup.py
@@ -496,6 +496,7 @@ class MergeSpecBuilder(Phase0SpecBuilder):
 from typing import Protocol
 from eth2spec.phase0 import {preset_name} as phase0
 from eth2spec.utils.ssz.ssz_typing import Bytes20, ByteList, ByteVector, uint256, Union
+from typing import Union as PyUnion
 '''
 
     @classmethod
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index be8f8b274..22569887e 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -19,7 +19,6 @@
   - [Block proposal](#block-proposal)
     - [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
       - [Execution Payload](#execution-payload)
-        - [`get_pow_chain_head`](#get_pow_chain_head)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -63,13 +62,20 @@ All validator responsibilities remain unchanged other than those noted below. Na
 
 ##### Execution Payload
 
-###### `get_pow_chain_head`
-
-Let `get_pow_chain_head() -> PowBlock` be the function that returns the head of the PoW chain. The body of the function is implementation specific.
-
-* Set `block.body.execution_payload = get_execution_payload(state, transition_store, execution_engine)` where:
+* Set `block.body.execution_payload = get_execution_payload(state, transition_store, execution_engine, pow_chain)` where:
 
 ```python
+def get_pow_block_at_total_difficulty(total_difficulty: uint256,
+                                      pow_chain: Sequence[PowBlock]) -> PyUnion[PowBlock, None]:
+    # `pow_chain` abstractly represents all blocks in the PoW chain
+    for block in pow_chain:
+        parent = get_pow_block(block.parent_hash)
+        if block.total_difficulty >= total_difficulty and parent.total_difficulty < total_difficulty:
+            return block
+
+    return None
+
+
 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))
@@ -87,16 +93,16 @@ def produce_execution_payload(state: BeaconState,
 def get_execution_payload(state: BeaconState,
                           transition_store: TransitionStore,
                           randao_reveal: BLSSignature,
-                          execution_engine: ExecutionEngine) -> ExecutionPayload:
+                          execution_engine: ExecutionEngine,
+                          pow_chain: Sequence[PowBlock]) -> ExecutionPayload:
     if not is_merge_complete(state):
-        pow_block = get_pow_chain_head()
-        pow_parent = get_pow_block(pow_block.parent_hash)
-        if not is_valid_terminal_pow_block(transition_store, pow_block, pow_parent):
+        terminal_pow_block = get_pow_block_at_total_difficulty(transition_store.transition_total_difficulty, pow_chain)
+        if terminal_pow_block is None:
             # Pre-merge, empty payload
             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, execution_engine)
+            return produce_execution_payload(state, terminal_pow_block.block_hash, randao_reveal, execution_engine)
 
     # Post-merge, normal payload
     parent_hash = state.latest_execution_payload_header.block_hash

From 11d54af89d382ea14de42593f87eaf82890c3d49 Mon Sep 17 00:00:00 2001
From: Adrian Sutton <adrian.sutton@consensys.net>
Date: Sat, 17 Jul 2021 16:34:41 +1000
Subject: [PATCH 06/19] Add test to confirm infinite signature is invalid when
 there are participants.

---
 .../test_process_sync_aggregate.py                | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
index effd01047..2557715e4 100644
--- a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
+++ b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
@@ -128,6 +128,21 @@ def test_invalid_signature_no_participants(spec, state):
     yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
 
 
+@with_altair_and_later
+@spec_state_test
+@always_bls
+def test_invalid_signature_infinite_signature_with_participants(spec, state):
+    committee_indices = compute_committee_indices(spec, state, state.current_sync_committee)
+
+    block = build_empty_block_for_next_slot(spec, state)
+    # Exclude one participant whose signature was included.
+    block.body.sync_aggregate = spec.SyncAggregate(
+        sync_committee_bits=[True for _ in committee_indices],
+        sync_committee_signature=spec.G2_POINT_AT_INFINITY
+    )
+    yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
+
+
 @with_altair_and_later
 @spec_state_test
 @always_bls

From f16cfe7c3a5933876d0e2b2006a8d5a57b9f3d03 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Sat, 17 Jul 2021 14:46:25 +0200
Subject: [PATCH 07/19] update sync aggregate tests

---
 .../test_process_sync_aggregate.py            | 29 +++++++++++++------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
index 2557715e4..e4176ee58 100644
--- a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
+++ b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py
@@ -117,27 +117,38 @@ def test_invalid_signature_missing_participant(spec, state):
 @spec_state_test
 @always_bls
 def test_invalid_signature_no_participants(spec, state):
-    committee_indices = compute_committee_indices(spec, state, state.current_sync_committee)
-
     block = build_empty_block_for_next_slot(spec, state)
-    # Exclude one participant whose signature was included.
+    # No participants is an allowed case, but needs a specific signature, not the full-zeroed signature.
     block.body.sync_aggregate = spec.SyncAggregate(
-        sync_committee_bits=[False for _ in committee_indices],
+        sync_committee_bits=[False] * len(block.body.sync_aggregate.sync_committee_bits),
         sync_committee_signature=b'\x00' * 96
     )
     yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
 
+# No-participants, with valid signature, is tested in test_sync_committee_rewards_empty_participants already.
+
+
+@with_altair_and_later
+@spec_state_test
+@always_bls
+def test_invalid_signature_infinite_signature_with_all_participants(spec, state):
+    block = build_empty_block_for_next_slot(spec, state)
+    # Include all participants, try the special-case signature for no-participants
+    block.body.sync_aggregate = spec.SyncAggregate(
+        sync_committee_bits=[True] * len(block.body.sync_aggregate.sync_committee_bits),
+        sync_committee_signature=spec.G2_POINT_AT_INFINITY
+    )
+    yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
+
 
 @with_altair_and_later
 @spec_state_test
 @always_bls
-def test_invalid_signature_infinite_signature_with_participants(spec, state):
-    committee_indices = compute_committee_indices(spec, state, state.current_sync_committee)
-
+def test_invalid_signature_infinite_signature_with_single_participant(spec, state):
     block = build_empty_block_for_next_slot(spec, state)
-    # Exclude one participant whose signature was included.
+    # Try include a single participant with the special-case signature for no-participants.
     block.body.sync_aggregate = spec.SyncAggregate(
-        sync_committee_bits=[True for _ in committee_indices],
+        sync_committee_bits=[True] + ([False] * (len(block.body.sync_aggregate.sync_committee_bits) - 1)),
         sync_committee_signature=spec.G2_POINT_AT_INFINITY
     )
     yield from run_sync_committee_processing(spec, state, block, expect_exception=True)

From 5ad36bd3d5272eff047cfcd42cc1e7f01b22168e Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Sat, 17 Jul 2021 15:55:38 +0200
Subject: [PATCH 08/19] Update remerkleable to v0.1.22: list lookup speed
 improvement

---
 setup.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/setup.py b/setup.py
index fa73e0824..1b9cbefbb 100644
--- a/setup.py
+++ b/setup.py
@@ -1024,7 +1024,7 @@ setup(
         "py_ecc==5.2.0",
         "milagro_bls_binding==1.6.3",
         "dataclasses==0.6",
-        "remerkleable==0.1.21",
+        "remerkleable==0.1.22",
         RUAMEL_YAML_VERSION,
         "lru-dict==1.1.6",
         MARKO_VERSION,

From 1e484b8d98fc55afbe686e2e4e635d6b3f1d19ef Mon Sep 17 00:00:00 2001
From: Piotr Chromiec <tworec@golem.network>
Date: Mon, 19 Jul 2021 14:48:30 +0200
Subject: [PATCH 09/19] README typo fix

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

diff --git a/README.md b/README.md
index d1a0b2876..f5ac598b6 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ This repository hosts the current Eth2 specifications. Discussions about design
 
 [![GitHub release](https://img.shields.io/github/v/release/ethereum/eth2.0-specs)](https://github.com/ethereum/eth2.0-specs/releases/) [![PyPI version](https://badge.fury.io/py/eth2spec.svg)](https://badge.fury.io/py/eth2spec)
 
-Core specifications for Eth2 clients be found in [specs](specs/). These are divided into features.
+Core specifications for Eth2 clients can be found in [specs](specs/). These are divided into features.
 Features are researched and developed in parallel, and then consolidated into sequential upgrades when ready.
 
 The current features are:

From 758b828ecb5520f6821cdb57d60be0c8bb982ffa Mon Sep 17 00:00:00 2001
From: Alex Stokes <r.alex.stokes@gmail.com>
Date: Mon, 19 Jul 2021 14:19:44 -0700
Subject: [PATCH 10/19] Update slashing helper to avoid proposer.

Fixes #2521.
---
 .../test_process_inactivity_updates.py        | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py b/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py
index 634c7bc48..f7d2fa9c8 100644
--- a/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py
+++ b/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py
@@ -195,17 +195,24 @@ def test_random_inactivity_scores_full_participation_leaking(spec, state):
     assert spec.is_in_inactivity_leak(state)
 
 
-def slash_some_validators(spec, state, rng=Random(40404040)):
+def slash_some_validators_for_inactivity_scores_test(spec, state, rng=Random(40404040)):
+    # ``run_inactivity_scores_test`` runs at the next epoch from `state`.
+    # We retrieve the proposer of this future state to avoid
+    # accidentally slashing that validator
+    future_state = state.copy()
+    next_epoch_via_block(spec, future_state)
+
+    proposer_index = spec.get_beacon_proposer_index(future_state)
     # Slash ~1/4 of validaors
     for validator_index in range(len(state.validators)):
-        if rng.choice(range(4)) == 0:
+        if rng.choice(range(4)) == 0 and validator_index != proposer_index:
             spec.slash_validator(state, validator_index)
 
 
 @with_altair_and_later
 @spec_state_test
 def test_some_slashed_zero_scores_full_participation(spec, state):
-    slash_some_validators(spec, state, rng=Random(33429))
+    slash_some_validators_for_inactivity_scores_test(spec, state, rng=Random(33429))
     yield from run_inactivity_scores_test(
         spec, state,
         set_full_participation, zero_inactivity_scores,
@@ -218,7 +225,7 @@ def test_some_slashed_zero_scores_full_participation(spec, state):
 @spec_state_test
 @leaking()
 def test_some_slashed_zero_scores_full_participation_leaking(spec, state):
-    slash_some_validators(spec, state, rng=Random(332243))
+    slash_some_validators_for_inactivity_scores_test(spec, state, rng=Random(332243))
     yield from run_inactivity_scores_test(
         spec, state,
         set_full_participation, zero_inactivity_scores,
@@ -239,7 +246,7 @@ def test_some_slashed_zero_scores_full_participation_leaking(spec, state):
 @spec_state_test
 def test_some_slashed_full_random(spec, state):
     rng = Random(1010222)
-    slash_some_validators(spec, state, rng=rng)
+    slash_some_validators_for_inactivity_scores_test(spec, state, rng=rng)
     yield from run_inactivity_scores_test(
         spec, state,
         randomize_attestation_participation, randomize_inactivity_scores, rng=rng,
@@ -251,7 +258,7 @@ def test_some_slashed_full_random(spec, state):
 @leaking()
 def test_some_slashed_full_random_leaking(spec, state):
     rng = Random(1102233)
-    slash_some_validators(spec, state, rng=rng)
+    slash_some_validators_for_inactivity_scores_test(spec, state, rng=rng)
     yield from run_inactivity_scores_test(
         spec, state,
         randomize_previous_epoch_participation, randomize_inactivity_scores, rng=rng,

From 65f6aa1b33b84a94b613a76fc9c6f3122e0e0344 Mon Sep 17 00:00:00 2001
From: Mikhail Kalinin <noblesse.knight@gmail.com>
Date: Tue, 20 Jul 2021 17:37:52 +0600
Subject: [PATCH 11/19] Replace PyUnion with Optional

---
 setup.py                 | 1 -
 specs/merge/validator.md | 3 +--
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/setup.py b/setup.py
index 69ae05666..c9b22b1a9 100644
--- a/setup.py
+++ b/setup.py
@@ -496,7 +496,6 @@ class MergeSpecBuilder(Phase0SpecBuilder):
 from typing import Protocol
 from eth2spec.phase0 import {preset_name} as phase0
 from eth2spec.utils.ssz.ssz_typing import Bytes20, ByteList, ByteVector, uint256, Union
-from typing import Union as PyUnion
 '''
 
     @classmethod
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 22569887e..2fd7bcc22 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -65,8 +65,7 @@ All validator responsibilities remain unchanged other than those noted below. Na
 * Set `block.body.execution_payload = get_execution_payload(state, transition_store, execution_engine, pow_chain)` where:
 
 ```python
-def get_pow_block_at_total_difficulty(total_difficulty: uint256,
-                                      pow_chain: Sequence[PowBlock]) -> PyUnion[PowBlock, None]:
+def get_pow_block_at_total_difficulty(total_difficulty: uint256, pow_chain: Sequence[PowBlock]) -> Optional[PowBlock]:
     # `pow_chain` abstractly represents all blocks in the PoW chain
     for block in pow_chain:
         parent = get_pow_block(block.parent_hash)

From 02a9fc460e4bbb806e7b18ae80e0bbaac810651b Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 21 Jul 2021 11:03:19 -0600
Subject: [PATCH 12/19] require aggregation bits to have at least one
 participant in sync contributions

---
 specs/altair/p2p-interface.md | 2 ++
 specs/altair/validator.md     | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/specs/altair/p2p-interface.md b/specs/altair/p2p-interface.md
index e5e391ff5..ba8d09c04 100644
--- a/specs/altair/p2p-interface.md
+++ b/specs/altair/p2p-interface.md
@@ -139,6 +139,8 @@ def get_sync_subcommittee_pubkeys(state: BeaconState, subcommittee_index: uint64
 
 - _[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`.
+- _[REJECT]_ The contribution has participants --
+  that is, `len(set(bit for bit in contribution.aggregation_bits if bit == True)) >= 1`.
 - _[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)`.
diff --git a/specs/altair/validator.md b/specs/altair/validator.md
index 8742900bc..badef2de5 100644
--- a/specs/altair/validator.md
+++ b/specs/altair/validator.md
@@ -354,7 +354,7 @@ def is_sync_committee_aggregator(signature: BLSSignature) -> bool:
 
 If a validator is selected to aggregate the `SyncCommitteeMessage`s produced on a subnet during a given `slot`, they construct an aggregated `SyncCommitteeContribution`.
 
-Given all of the (valid) collected `sync_committee_messages: Set[SyncCommitteeMessage]` from the `sync_committee_{subnet_id}` gossip during the selected `slot` with an equivalent `beacon_block_root` to that of the aggregator, the aggregator creates a `contribution: SyncCommitteeContribution` with the following fields:
+Collect all of the (valid) `sync_committee_messages: Set[SyncCommitteeMessage]` from the `sync_committee_{subnet_id}` gossip during the selected `slot` with an equivalent `beacon_block_root` to that of the aggregator. If `len(sync_committee_messages) > 0`, the aggregator creates a `contribution: SyncCommitteeContribution` with the following fields:
 
 ###### Slot
 

From f7a2a973acd9005a64abbf5f164d6b879cb1d6d9 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 21 Jul 2021 15:51:59 -0600
Subject: [PATCH 13/19] Update specs/altair/p2p-interface.md

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>
---
 specs/altair/p2p-interface.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/p2p-interface.md b/specs/altair/p2p-interface.md
index ba8d09c04..6820fd10a 100644
--- a/specs/altair/p2p-interface.md
+++ b/specs/altair/p2p-interface.md
@@ -140,7 +140,7 @@ def get_sync_subcommittee_pubkeys(state: BeaconState, subcommittee_index: uint64
 - _[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`.
 - _[REJECT]_ The contribution has participants --
-  that is, `len(set(bit for bit in contribution.aggregation_bits if bit == True)) >= 1`.
+  that is, `any(contribution.aggregation_bits)`.
 - _[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)`.

From 17fad2dea2ee7e0747d346cf600590721b9b9c59 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Thu, 22 Jul 2021 16:36:41 +0200
Subject: [PATCH 14/19] rebase The Merge onto Altair base functionality

---
 setup.py                                      | 28 ++++-----
 specs/merge/beacon-chain.md                   | 58 +++++++++++++++++--
 specs/merge/fork.md                           | 21 ++++---
 specs/merge/validator.md                      |  8 +--
 specs/sharding/beacon-chain.md                | 21 +++----
 specs/sharding/p2p-interface.md               |  3 +-
 tests/core/pyspec/eth2spec/test/context.py    | 20 ++-----
 .../eth2spec/test/helpers/block_processing.py |  1 +
 .../eth2spec/test/helpers/epoch_processing.py |  2 +-
 .../pyspec/eth2spec/test/helpers/genesis.py   | 14 +++--
 .../eth2spec/test/helpers/merge/fork.py       |  8 ++-
 .../test/merge/fork/test_merge_fork_basic.py  | 16 ++---
 .../test/merge/fork/test_merge_fork_random.py | 20 +++----
 13 files changed, 132 insertions(+), 88 deletions(-)

diff --git a/setup.py b/setup.py
index 552c69740..4c6969a26 100644
--- a/setup.py
+++ b/setup.py
@@ -447,7 +447,7 @@ class AltairSpecBuilder(Phase0SpecBuilder):
     @classmethod
     def imports(cls, preset_name: str) -> str:
         return super().imports(preset_name) + '\n' + f'''
-from typing import NewType, Union
+from typing import NewType, Union as PyUnion
 
 from eth2spec.phase0 import {preset_name} as phase0
 from eth2spec.utils.ssz.ssz_typing import Path
@@ -463,7 +463,7 @@ GeneralizedIndex = NewType('GeneralizedIndex', int)
     @classmethod
     def sundry_functions(cls) -> str:
         return super().sundry_functions() + '\n\n' + '''
-def get_generalized_index(ssz_class: Any, *path: Sequence[Union[int, SSZVariableName]]) -> GeneralizedIndex:
+def get_generalized_index(ssz_class: Any, *path: Sequence[PyUnion[int, SSZVariableName]]) -> GeneralizedIndex:
     ssz_path = Path(ssz_class)
     for item in path:
         ssz_path = ssz_path / item
@@ -487,14 +487,14 @@ def get_generalized_index(ssz_class: Any, *path: Sequence[Union[int, SSZVariable
 #
 # MergeSpecBuilder
 #
-class MergeSpecBuilder(Phase0SpecBuilder):
+class MergeSpecBuilder(AltairSpecBuilder):
     fork: str = MERGE
 
     @classmethod
     def imports(cls, preset_name: str):
         return super().imports(preset_name) + f'''
 from typing import Protocol
-from eth2spec.phase0 import {preset_name} as phase0
+from eth2spec.altair import {preset_name} as altair
 from eth2spec.utils.ssz.ssz_typing import Bytes20, ByteList, ByteVector, uint256, Union
 '''
 
@@ -844,19 +844,15 @@ class PySpecCommand(Command):
         if len(self.md_doc_paths) == 0:
             print("no paths were specified, using default markdown file paths for pyspec"
                   " build (spec fork: %s)" % self.spec_fork)
-            if self.spec_fork == PHASE0:
+            if self.spec_fork in (PHASE0, ALTAIR, MERGE):
                 self.md_doc_paths = """
                     specs/phase0/beacon-chain.md
                     specs/phase0/fork-choice.md
                     specs/phase0/validator.md
                     specs/phase0/weak-subjectivity.md
                 """
-            elif self.spec_fork == ALTAIR:
-                self.md_doc_paths = """
-                    specs/phase0/beacon-chain.md
-                    specs/phase0/fork-choice.md
-                    specs/phase0/validator.md
-                    specs/phase0/weak-subjectivity.md
+            if self.spec_fork in (ALTAIR, MERGE):
+                self.md_doc_paths += """
                     specs/altair/beacon-chain.md
                     specs/altair/bls.md
                     specs/altair/fork.md
@@ -864,18 +860,14 @@ class PySpecCommand(Command):
                     specs/altair/p2p-interface.md
                     specs/altair/sync-protocol.md
                 """
-            elif self.spec_fork == MERGE:
-                self.md_doc_paths = """
-                    specs/phase0/beacon-chain.md
-                    specs/phase0/fork-choice.md
-                    specs/phase0/validator.md
-                    specs/phase0/weak-subjectivity.md
+            if self.spec_fork == MERGE:
+                self.md_doc_paths += """
                     specs/merge/beacon-chain.md
                     specs/merge/fork.md
                     specs/merge/fork-choice.md
                     specs/merge/validator.md
                 """
-            else:
+            if len(self.md_doc_paths) == 0:
                 raise Exception('no markdown files specified, and spec fork "%s" is unknown', self.spec_fork)
 
         self.parsed_md_doc_paths = self.md_doc_paths.split()
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 59ec3ce48..aa2e3b334 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -1,7 +1,5 @@
 # Ethereum 2.0 The Merge
 
-**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.
 
 ## Table of contents
@@ -69,7 +67,17 @@ This patch adds transaction execution to the beacon chain as part of the Merge f
 #### `BeaconBlockBody`
 
 ```python
-class BeaconBlockBody(phase0.BeaconBlockBody):
+class BeaconBlockBody(Container):
+    randao_reveal: BLSSignature
+    eth1_data: Eth1Data  # Eth1 data vote
+    graffiti: Bytes32  # Arbitrary data
+    # Operations
+    proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
+    attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
+    attestations: List[Attestation, MAX_ATTESTATIONS]
+    deposits: List[Deposit, MAX_DEPOSITS]
+    voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
+    sync_aggregate: SyncAggregate
     # Execution
     execution_payload: ExecutionPayload  # [New in Merge]
 ```
@@ -77,7 +85,41 @@ class BeaconBlockBody(phase0.BeaconBlockBody):
 #### `BeaconState`
 
 ```python
-class BeaconState(phase0.BeaconState):
+class BeaconState(altair.BeaconState):
+    # Versioning
+    genesis_time: uint64
+    genesis_validators_root: Root
+    slot: Slot
+    fork: Fork
+    # History
+    latest_block_header: BeaconBlockHeader
+    block_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
+    state_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
+    historical_roots: List[Root, HISTORICAL_ROOTS_LIMIT]
+    # Eth1
+    eth1_data: Eth1Data
+    eth1_data_votes: List[Eth1Data, EPOCHS_PER_ETH1_VOTING_PERIOD * SLOTS_PER_EPOCH]
+    eth1_deposit_index: uint64
+    # Registry
+    validators: List[Validator, VALIDATOR_REGISTRY_LIMIT]
+    balances: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
+    # Randomness
+    randao_mixes: Vector[Bytes32, EPOCHS_PER_HISTORICAL_VECTOR]
+    # Slashings
+    slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR]  # Per-epoch sums of slashed effective balances
+    # Participation
+    previous_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT]
+    current_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT]
+    # Finality
+    justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH]  # Bit set for every recent justified epoch
+    previous_justified_checkpoint: Checkpoint
+    current_justified_checkpoint: Checkpoint
+    finalized_checkpoint: Checkpoint
+    # Inactivity
+    inactivity_scores: List[uint64, VALIDATOR_REGISTRY_LIMIT]
+    # Sync
+    current_sync_committee: SyncCommittee
+    next_sync_committee: SyncCommittee
     # Execution
     latest_execution_payload_header: ExecutionPayloadHeader  # [New in Merge]
 ```
@@ -190,6 +232,7 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_randao(state, block.body)
     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):
         process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE)  # [New in Merge]
 ```
@@ -232,7 +275,7 @@ def process_execution_payload(state: BeaconState, payload: ExecutionPayload, exe
 
 *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 to use `MERGE_FORK_VERSION` and initialize `latest_execution_payload_header`.
+*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) initialize `latest_execution_payload_header`.
 
 ```python
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
@@ -269,6 +312,11 @@ 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)
 
+    # Fill in sync committees
+    # Note: A duplicate committee is assigned for the current and next committee at genesis
+    state.current_sync_committee = get_next_sync_committee(state)
+    state.next_sync_committee = get_next_sync_committee(state)
+
     # [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
diff --git a/specs/merge/fork.md b/specs/merge/fork.md
index 1f2ea7fff..5c5c40a64 100644
--- a/specs/merge/fork.md
+++ b/specs/merge/fork.md
@@ -43,15 +43,18 @@ Note that for the pure Merge networks, we don't apply `upgrade_to_merge` since i
 
 ### Upgrading the state
 
-If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == MERGE_FORK_EPOCH`, an irregular state change is made to upgrade to Merge.
+As with the Phase0-to-Altair upgrade, the `state_transition` is modified to upgrade the `BeaconState`.
+The `BeaconState` upgrade runs as part of `process_slots`, slots with missing block proposals do not affect the upgrade time.
 
+If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == MERGE_FORK_EPOCH`, an irregular state change is made to upgrade to Merge.
 The upgrade occurs after the completion of the inner loop of `process_slots` that sets `state.slot` equal to `MERGE_FORK_EPOCH * SLOTS_PER_EPOCH`.
-Care must be taken when transitioning through the fork boundary as implementations will need a modified [state transition function](../phase0/beacon-chain.md#beacon-chain-state-transition-function) that deviates from the Phase 0 document.
-In particular, the outer `state_transition` function defined in the Phase 0 document will not expose the precise fork slot to execute the upgrade in the presence of skipped slots at the fork boundary. Instead the logic must be within `process_slots`.
+
+When multiple upgrades are scheduled for the same epoch (common for test-networks),
+all the upgrades run in sequence before resuming the regular state transition.
 
 ```python
-def upgrade_to_merge(pre: phase0.BeaconState) -> BeaconState:
-    epoch = phase0.get_current_epoch(pre)
+def upgrade_to_merge(pre: altair.BeaconState) -> BeaconState:
+    epoch = altair.get_current_epoch(pre)
     post = BeaconState(
         # Versioning
         genesis_time=pre.genesis_time,
@@ -78,14 +81,16 @@ def upgrade_to_merge(pre: phase0.BeaconState) -> BeaconState:
         randao_mixes=pre.randao_mixes,
         # Slashings
         slashings=pre.slashings,
-        # Attestations
-        previous_epoch_attestations=pre.previous_epoch_attestations,
-        current_epoch_attestations=pre.current_epoch_attestations,
+        # Participation
+        previous_epoch_participation=pre.previous_epoch_participation,
+        current_epoch_participation=pre.current_epoch_participation,
         # Finality
         justification_bits=pre.justification_bits,
         previous_justified_checkpoint=pre.previous_justified_checkpoint,
         current_justified_checkpoint=pre.current_justified_checkpoint,
         finalized_checkpoint=pre.finalized_checkpoint,
+        # Inactivity
+        inactivity_scores=pre.inactivity_scores,
         # Execution-layer
         latest_execution_payload_header=ExecutionPayloadHeader(),
     )
diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 2fd7bcc22..baf716760 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -1,7 +1,5 @@
 # Ethereum 2.0 The Merge
 
-**Warning:** This document is currently based on [Phase 0](../phase0/validator.md) but will be rebased to [Altair](../altair/validator.md) once the latter is shipped.
-
 **Notice**: This document is a work-in-progress for researchers and implementers.
 
 ## Table of contents
@@ -29,9 +27,11 @@ This document represents the changes to be made in the code of an "honest valida
 
 ## Prerequisites
 
-This document is an extension of the [Phase 0 -- Validator](../phase0/validator.md). All behaviors and definitions defined in the Phase 0 doc carry over unless explicitly noted or overridden.
+This document is an extension of the [Altair -- Honest Validator](../altair/validator.md) guide.
+All behaviors and definitions defined in this document, and documents it extends, carry over unless explicitly noted or overridden.
 
-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.
+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.
 
 ## Protocols
 
diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index 5a460855b..4e88a8971 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -179,7 +179,7 @@ class BeaconBlockBody(merge.BeaconBlockBody):  # [extends The Merge block body]
 ### `BeaconState`
 
 ```python
-class BeaconState(merge.BeaconState):  # [extends The Merge state]
+class BeaconState(merge.BeaconState):
     # [Updated fields] (Warning: this changes with Altair, Sharding will rebase to use participation-flags)
     previous_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
     current_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
@@ -494,9 +494,9 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     process_randao(state, block.body)
     process_eth1_data(state, block.body)
     process_operations(state, block.body)  # [Modified in Sharding]
-    # 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]
+    process_sync_aggregate(state, block.body.sync_aggregate)
+    # is_execution_enabled is omitted, execution is enabled by default. 
+    process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE)
 ```
 
 #### Operations
@@ -527,7 +527,7 @@ def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
 
 ```python
 def process_attestation(state: BeaconState, attestation: Attestation) -> None:
-    phase0.process_attestation(state, attestation)
+    altair.process_attestation(state, attestation)
     update_pending_shard_work(state, attestation)
 ```
 
@@ -681,25 +681,26 @@ This epoch transition overrides the Merge epoch transition:
 
 ```python
 def process_epoch(state: BeaconState) -> None:
-    # Sharding
+    # Sharding pre-processing
     process_pending_shard_confirmations(state)
     charge_confirmed_shard_fees(state)
     reset_pending_shard_work(state)
 
-    # Phase0
+    # Base functionality
     process_justification_and_finalization(state)
+    process_inactivity_updates(state)
     process_rewards_and_penalties(state)
     process_registry_updates(state)
     process_slashings(state)
-
-    # Final updates
     process_eth1_data_reset(state)
     process_effective_balance_updates(state)
     process_slashings_reset(state)
     process_randao_mixes_reset(state)
     process_historical_roots_update(state)
-    process_participation_record_updates(state)
+    process_participation_flag_updates(state)
+    process_sync_committee_updates(state)
 
+    # Sharding post-processing
     process_shard_epoch_increment(state)
 ```
 
diff --git a/specs/sharding/p2p-interface.md b/specs/sharding/p2p-interface.md
index 51dbfd5a6..baf9494f2 100644
--- a/specs/sharding/p2p-interface.md
+++ b/specs/sharding/p2p-interface.md
@@ -29,8 +29,7 @@
 
 ## Introduction
 
-The specification of these changes continues in the same format as the [Phase0](../phase0/p2p-interface.md) and
-[Altair](../altair/p2p-interface.md) network specifications, and assumes them as pre-requisite.
+The specification of these changes continues in the same format as the network specifications of previous upgrades, and assumes them as pre-requisite.
 The adjustments and additions for Shards are outlined in this document.
 
 ## Constants
diff --git a/tests/core/pyspec/eth2spec/test/context.py b/tests/core/pyspec/eth2spec/test/context.py
index 362f64abf..7fddc0762 100644
--- a/tests/core/pyspec/eth2spec/test/context.py
+++ b/tests/core/pyspec/eth2spec/test/context.py
@@ -347,10 +347,6 @@ def with_phases(phases, other_phases=None):
                 preset_name = kw.pop('preset')
             targets = spec_targets[preset_name]
 
-            # TODO: test state is dependent on phase0 but is immediately transitioned to later phases.
-            #  A new state-creation helper for later phases may be in place, and then tests can run without phase0
-            available_phases.add(PHASE0)
-
             # Populate all phases for multi-phase tests
             phase_dir = {}
             if PHASE0 in available_phases:
@@ -433,23 +429,15 @@ def with_config_overrides(config_overrides):
 
 
 def is_post_altair(spec):
-    if spec.fork == MERGE:  # TODO: remove parallel Altair-Merge condition after rebase.
-        return False
-    if spec.fork in FORKS_BEFORE_ALTAIR:
-        return False
-    return True
+    return spec.fork not in FORKS_BEFORE_ALTAIR
 
 
 def is_post_merge(spec):
-    if spec.fork == ALTAIR:  # TODO: remove parallel Altair-Merge condition after rebase.
-        return False
-    if spec.fork in FORKS_BEFORE_MERGE:
-        return False
-    return True
+    return spec.fork not in FORKS_BEFORE_MERGE
 
 
-with_altair_and_later = with_phases([ALTAIR])  # TODO: include Merge, but not until Merge work is rebased.
-with_merge_and_later = with_phases([MERGE])
+with_altair_and_later = with_phases([ALTAIR, MERGE])
+with_merge_and_later = with_phases([MERGE])  # TODO: include sharding when spec stabilizes.
 
 
 def fork_transition_test(pre_fork_name, post_fork_name, fork_epoch=None):
diff --git a/tests/core/pyspec/eth2spec/test/helpers/block_processing.py b/tests/core/pyspec/eth2spec/test/helpers/block_processing.py
index d2ec4a111..e82f62ed0 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/block_processing.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/block_processing.py
@@ -30,6 +30,7 @@ def get_process_calls(spec):
         # Merge
         'process_application_payload':
             lambda state, block: spec.process_application_payload(state, block.body),
+        # TODO: add sharding processing functions when spec stabilizes.
         # Custody Game
         'process_custody_game_operations':
             lambda state, block: spec.process_custody_game_operations(state, block.body),
diff --git a/tests/core/pyspec/eth2spec/test/helpers/epoch_processing.py b/tests/core/pyspec/eth2spec/test/helpers/epoch_processing.py
index c783692fc..eed259e81 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/epoch_processing.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/epoch_processing.py
@@ -28,7 +28,7 @@ def get_process_calls(spec):
             'process_participation_record_updates'
         ),
         'process_sync_committee_updates',  # altair
-        'process_shard_epoch_increment'  # sharding
+        # TODO: add sharding processing functions when spec stabilizes.
     ]
 
 
diff --git a/tests/core/pyspec/eth2spec/test/helpers/genesis.py b/tests/core/pyspec/eth2spec/test/helpers/genesis.py
index 8617ce9f3..a9eb59f67 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/genesis.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/genesis.py
@@ -1,7 +1,6 @@
 from eth2spec.test.helpers.constants import (
-    ALTAIR,
-    FORKS_BEFORE_ALTAIR,
-    MERGE,
+    ALTAIR, MERGE,
+    FORKS_BEFORE_ALTAIR, FORKS_BEFORE_MERGE,
 )
 from eth2spec.test.helpers.keys import pubkeys
 
@@ -25,11 +24,13 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
     deposit_root = b'\x42' * 32
 
     eth1_block_hash = b'\xda' * 32
+    previous_version = spec.config.GENESIS_FORK_VERSION
     current_version = spec.config.GENESIS_FORK_VERSION
 
     if spec.fork == ALTAIR:
         current_version = spec.config.ALTAIR_FORK_VERSION
     elif spec.fork == MERGE:
+        previous_version = spec.config.ALTAIR_FORK_VERSION
         current_version = spec.config.MERGE_FORK_VERSION
 
     state = spec.BeaconState(
@@ -41,7 +42,7 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
             block_hash=eth1_block_hash,
         ),
         fork=spec.Fork(
-            previous_version=spec.config.GENESIS_FORK_VERSION,
+            previous_version=previous_version,
             current_version=current_version,
             epoch=spec.GENESIS_EPOCH,
         ),
@@ -73,4 +74,9 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
         state.current_sync_committee = spec.get_next_sync_committee(state)
         state.next_sync_committee = spec.get_next_sync_committee(state)
 
+    if spec.fork not in FORKS_BEFORE_MERGE:
+        # Initialize the execution payload header (with block number and genesis time set to 0)
+        state.latest_execution_payload_header.block_hash = eth1_block_hash
+        state.latest_execution_payload_header.random = eth1_block_hash
+
     return state
diff --git a/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py b/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py
index 9b7f89366..3a55dc88c 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py
@@ -24,10 +24,14 @@ def run_fork_test(post_spec, pre_state):
         'randao_mixes',
         # Slashings
         'slashings',
-        # Attestations
-        'previous_epoch_attestations', 'current_epoch_attestations',
+        # Participation
+        'previous_epoch_participation', 'current_epoch_participation',
         # Finality
         'justification_bits', 'previous_justified_checkpoint', 'current_justified_checkpoint', 'finalized_checkpoint',
+        # Inactivity
+        'inactivity_scores',
+        # Sync
+        'current_sync_committee', 'next_sync_committee'
     ]
     for field in stable_fields:
         assert getattr(pre_state, field) == getattr(post_state, field)
diff --git a/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_basic.py b/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_basic.py
index 066a656a8..d92b0015c 100644
--- a/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_basic.py
+++ b/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_basic.py
@@ -7,7 +7,7 @@ from eth2spec.test.context import (
 )
 from eth2spec.test.utils import with_meta_tags
 from eth2spec.test.helpers.constants import (
-    PHASE0, MERGE,
+    ALTAIR, MERGE,
     MINIMAL,
 )
 from eth2spec.test.helpers.state import (
@@ -20,7 +20,7 @@ from eth2spec.test.helpers.merge.fork import (
 )
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -28,7 +28,7 @@ def test_fork_base_state(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -37,7 +37,7 @@ def test_fork_next_epoch(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -46,7 +46,7 @@ def test_fork_next_epoch_with_block(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -56,7 +56,7 @@ def test_fork_many_next_epoch(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @with_custom_state(balances_fn=low_balances, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)
 @spec_test
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -64,7 +64,7 @@ def test_fork_random_low_balances(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @with_custom_state(balances_fn=misc_balances, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)
 @spec_test
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -72,7 +72,7 @@ def test_fork_random_misc_balances(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @with_presets([MINIMAL],
               reason="mainnet config leads to larger validator set than limit of public/private keys pre-generated")
 @with_custom_state(balances_fn=large_validator_set, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)
diff --git a/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py b/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py
index d790acd3a..cabde150f 100644
--- a/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py
+++ b/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py
@@ -9,7 +9,7 @@ from eth2spec.test.context import (
 )
 from eth2spec.test.utils import with_meta_tags
 from eth2spec.test.helpers.constants import (
-    PHASE0, MERGE,
+    ALTAIR, MERGE,
     MINIMAL,
 )
 from eth2spec.test.helpers.merge.fork import (
@@ -22,7 +22,7 @@ from eth2spec.test.helpers.random import (
 )
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -31,7 +31,7 @@ def test_merge_fork_random_0(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -40,7 +40,7 @@ def test_merge_fork_random_1(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -49,7 +49,7 @@ def test_merge_fork_random_2(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -58,7 +58,7 @@ def test_merge_fork_random_3(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -69,7 +69,7 @@ def test_merge_fork_random_duplicate_attestations(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_state
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -91,7 +91,7 @@ def test_merge_fork_random_mismatched_attestations(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state_0)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_custom_state(balances_fn=low_balances, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -100,7 +100,7 @@ def test_merge_fork_random_low_balances(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_custom_state(balances_fn=misc_balances, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)
 @with_meta_tags(MERGE_FORK_TEST_META_TAGS)
@@ -109,7 +109,7 @@ def test_merge_fork_random_misc_balances(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[PHASE0], other_phases=[MERGE])
+@with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @with_presets([MINIMAL],
               reason="mainnet config leads to larger validator set than limit of public/private keys pre-generated")
 @spec_test

From bb0848b6f6d07ff0eaad16c039e9010f93c85514 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Thu, 22 Jul 2021 19:58:10 +0200
Subject: [PATCH 15/19] carry over current and previous_sync_committee in Merge
 state upgrader, review from @djrtwo

---
 specs/merge/fork.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/specs/merge/fork.md b/specs/merge/fork.md
index 5c5c40a64..c89e00cf9 100644
--- a/specs/merge/fork.md
+++ b/specs/merge/fork.md
@@ -91,6 +91,9 @@ def upgrade_to_merge(pre: altair.BeaconState) -> BeaconState:
         finalized_checkpoint=pre.finalized_checkpoint,
         # Inactivity
         inactivity_scores=pre.inactivity_scores,
+        # Sync
+        current_sync_committee=pre.current_sync_committee,
+        next_sync_committee=pre.next_sync_committee,
         # Execution-layer
         latest_execution_payload_header=ExecutionPayloadHeader(),
     )

From 8318441474c045255deb48e708f6ebfd43edc240 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Thu, 22 Jul 2021 19:59:15 +0200
Subject: [PATCH 16/19] Fix remaining merge-rebase-altair tests

---
 .../pyspec/eth2spec/test/helpers/constants.py |  7 +---
 .../eth2spec/test/helpers/merge/fork.py       |  3 --
 .../test/merge/fork/test_merge_fork_random.py | 38 +------------------
 3 files changed, 3 insertions(+), 45 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/helpers/constants.py b/tests/core/pyspec/eth2spec/test/helpers/constants.py
index 8f116dc3d..5ab847327 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/constants.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/constants.py
@@ -18,12 +18,9 @@ DAS = SpecForkName('das')
 ALL_PHASES = (PHASE0, ALTAIR, MERGE)
 # The forks that output to the test vectors.
 TESTGEN_FORKS = (PHASE0, ALTAIR, MERGE)
-# TODO: everything runs in parallel to Altair.
-# After features are rebased on the Altair fork, this can be reduced to just PHASE0.
-FORKS_BEFORE_ALTAIR = (PHASE0, MERGE, SHARDING, CUSTODY_GAME, DAS)
 
-# TODO: when rebasing Merge onto Altair, add ALTAIR to this tuple.
-FORKS_BEFORE_MERGE = (PHASE0,)
+FORKS_BEFORE_ALTAIR = (PHASE0,)
+FORKS_BEFORE_MERGE = (PHASE0, ALTAIR)
 
 #
 # Config
diff --git a/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py b/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py
index 3a55dc88c..5a45e8565 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/merge/fork.py
@@ -4,9 +4,6 @@ MERGE_FORK_TEST_META_TAGS = {
 
 
 def run_fork_test(post_spec, pre_state):
-    # Clean up state to be more realistic
-    pre_state.current_epoch_attestations = []
-
     yield 'pre', pre_state
 
     post_state = post_spec.upgrade_to_merge(pre_state)
diff --git a/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py b/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py
index cabde150f..20101fac4 100644
--- a/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py
+++ b/tests/core/pyspec/eth2spec/test/merge/fork/test_merge_fork_random.py
@@ -16,10 +16,7 @@ from eth2spec.test.helpers.merge.fork import (
     MERGE_FORK_TEST_META_TAGS,
     run_fork_test,
 )
-from eth2spec.test.helpers.random import (
-    randomize_state,
-    randomize_attestation_participation,
-)
+from eth2spec.test.helpers.random import randomize_state
 
 
 @with_phases(phases=[ALTAIR], other_phases=[MERGE])
@@ -58,39 +55,6 @@ def test_merge_fork_random_3(spec, phases, state):
     yield from run_fork_test(phases[MERGE], state)
 
 
-@with_phases(phases=[ALTAIR], other_phases=[MERGE])
-@spec_test
-@with_state
-@with_meta_tags(MERGE_FORK_TEST_META_TAGS)
-def test_merge_fork_random_duplicate_attestations(spec, phases, state):
-    randomize_state(spec, state, rng=Random(1111))
-    # Note: `run_fork_test` empties `current_epoch_attestations`
-    state.previous_epoch_attestations = state.previous_epoch_attestations + state.previous_epoch_attestations
-    yield from run_fork_test(phases[MERGE], state)
-
-
-@with_phases(phases=[ALTAIR], other_phases=[MERGE])
-@spec_test
-@with_state
-@with_meta_tags(MERGE_FORK_TEST_META_TAGS)
-def test_merge_fork_random_mismatched_attestations(spec, phases, state):
-    # Create a random state
-    randomize_state(spec, state, rng=Random(2222))
-
-    # Now make two copies
-    state_0 = state.copy()
-    state_1 = state.copy()
-
-    # Randomize attestation participation of both
-    randomize_attestation_participation(spec, state_0, rng=Random(3333))
-    randomize_attestation_participation(spec, state_1, rng=Random(4444))
-
-    # Note: `run_fork_test` empties `current_epoch_attestations`
-    # Use pending attestations from both random states in a single state for testing
-    state_0.previous_epoch_attestations = state_0.previous_epoch_attestations + state_1.previous_epoch_attestations
-    yield from run_fork_test(phases[MERGE], state_0)
-
-
 @with_phases(phases=[ALTAIR], other_phases=[MERGE])
 @spec_test
 @with_custom_state(balances_fn=low_balances, threshold_fn=lambda spec: spec.config.EJECTION_BALANCE)

From bf6ad465ce63b05d067dc8207dea96e8958f01b4 Mon Sep 17 00:00:00 2001
From: protolambda <proto@protolambda.com>
Date: Thu, 22 Jul 2021 20:01:50 +0200
Subject: [PATCH 17/19] remove old BeaconState extension

---
 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 aa2e3b334..01c54e017 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -85,7 +85,7 @@ class BeaconBlockBody(Container):
 #### `BeaconState`
 
 ```python
-class BeaconState(altair.BeaconState):
+class BeaconState(Container):
     # Versioning
     genesis_time: uint64
     genesis_validators_root: Root

From 06b8bb1a5785bfd928b0cf907203ef660305cc91 Mon Sep 17 00:00:00 2001
From: Anton Nashatyrev <anton.nashatyrev@gmail.com>
Date: Mon, 21 Jun 2021 20:27:29 +0300
Subject: [PATCH 18/19] Simplify get_start_shard function

---
 specs/sharding/beacon-chain.md | 33 ++++-----------------------------
 1 file changed, 4 insertions(+), 29 deletions(-)

diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index 4e88a8971..517892b8c 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -58,7 +58,6 @@
     - [`process_pending_shard_confirmations`](#process_pending_shard_confirmations)
     - [`charge_confirmed_shard_fees`](#charge_confirmed_shard_fees)
     - [`reset_pending_shard_work`](#reset_pending_shard_work)
-    - [`process_shard_epoch_increment`](#process_shard_epoch_increment)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -187,7 +186,6 @@ class BeaconState(merge.BeaconState):
     # A ring buffer of the latest slots, with information per active shard.
     shard_buffer: Vector[List[ShardWork, MAX_SHARDS], SHARD_STATE_MEMORY_SLOTS]
     shard_gasprice: uint64
-    current_epoch_start_shard: Shard
 ```
 
 ## New containers
@@ -447,22 +445,10 @@ def get_start_shard(state: BeaconState, slot: Slot) -> Shard:
     """
     Return the start shard at ``slot``.
     """
-    current_epoch_start_slot = compute_start_slot_at_epoch(get_current_epoch(state))
-    shard = state.current_epoch_start_shard
-    if slot > current_epoch_start_slot:
-        # Current epoch or the next epoch lookahead
-        for _slot in range(current_epoch_start_slot, slot):
-            committee_count = get_committee_count_per_slot(state, compute_epoch_at_slot(Slot(_slot)))
-            active_shard_count = get_active_shard_count(state, compute_epoch_at_slot(Slot(_slot)))
-            shard = (shard + committee_count) % active_shard_count
-    elif slot < current_epoch_start_slot:
-        # Previous epoch
-        for _slot in list(range(slot, current_epoch_start_slot))[::-1]:
-            committee_count = get_committee_count_per_slot(state, compute_epoch_at_slot(Slot(_slot)))
-            active_shard_count = get_active_shard_count(state, compute_epoch_at_slot(Slot(_slot)))
-            # Ensure positive
-            shard = (shard + active_shard_count - committee_count) % active_shard_count
-    return Shard(shard)
+    epoch = compute_epoch_at_slot(Slot(_slot))
+    committee_count = get_committee_count_per_slot(state, epoch)
+    active_shard_count = get_active_shard_count(state, epoch)
+    return committee_count * slot % active_shard_count 
 ```
 
 #### `compute_shard_from_committee_index`
@@ -699,9 +685,6 @@ def process_epoch(state: BeaconState) -> None:
     process_historical_roots_update(state)
     process_participation_flag_updates(state)
     process_sync_committee_updates(state)
-
-    # Sharding post-processing
-    process_shard_epoch_increment(state)
 ```
 
 #### `process_pending_shard_confirmations`
@@ -800,11 +783,3 @@ def reset_pending_shard_work(state: BeaconState) -> None:
             )
         # a shard without committee available defaults to SHARD_WORK_UNCONFIRMED.
 ```
-
-#### `process_shard_epoch_increment`
-
-```python
-def process_shard_epoch_increment(state: BeaconState) -> None:
-    # Update current_epoch_start_shard
-    state.current_epoch_start_shard = get_start_shard(state, Slot(state.slot + 1))
-```

From 37da2018a3ea860c3661b2d516d923e03a15aa7d Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Fri, 23 Jul 2021 08:22:53 -0600
Subject: [PATCH 19/19] bump VERSION.txt to 1.1.0-beta.2

---
 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 854663a0e..fd5a6fed6 100644
--- a/tests/core/pyspec/eth2spec/VERSION.txt
+++ b/tests/core/pyspec/eth2spec/VERSION.txt
@@ -1 +1 @@
-1.1.0-beta.1
\ No newline at end of file
+1.1.0-beta.2
\ No newline at end of file