From 6c986259672262f86c933243adf9f19fb6be3aa9 Mon Sep 17 00:00:00 2001
From: Potuz <potuz@prysmaticlabs.com>
Date: Fri, 6 Mar 2026 11:02:54 -0300
Subject: [PATCH 01/15] Add a PTC Lookbehind slice in the state

---
 specs/gloas/beacon-chain.md | 60 ++++++++++++++++++++++++++++++-------
 1 file changed, 50 insertions(+), 10 deletions(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 6731919605..9ff1d7b4bd 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -54,6 +54,7 @@
     - [New `compute_balance_weighted_selection`](#new-compute_balance_weighted_selection)
     - [New `compute_balance_weighted_acceptance`](#new-compute_balance_weighted_acceptance)
     - [Modified `compute_proposer_indices`](#modified-compute_proposer_indices)
+    - [New `compute_ptc`](#new-compute_ptc)
   - [Beacon state accessors](#beacon-state-accessors)
     - [Modified `get_next_sync_committee_indices`](#modified-get_next_sync_committee_indices)
     - [Modified `get_attestation_participation_flag_indices`](#modified-get_attestation_participation_flag_indices)
@@ -67,6 +68,7 @@
   - [Epoch processing](#epoch-processing)
     - [Modified `process_epoch`](#modified-process_epoch)
     - [New `process_builder_pending_payments`](#new-process_builder_pending_payments)
+    - [New `process_ptc_lookbehind`](#new-process_ptc_lookbehind)
   - [Block processing](#block-processing)
     - [Withdrawals](#withdrawals)
       - [New `get_builder_withdrawals`](#new-get_builder_withdrawals)
@@ -384,6 +386,8 @@ class BeaconState(Container):
     latest_block_hash: Hash32
     # [New in Gloas:EIP7732]
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
+    # [New in Gloas:EIP7732]
+    ptc_lookbehind: Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]
 ```
 
 ## Dataclasses
@@ -630,6 +634,26 @@ def compute_proposer_indices(
     ]
 ```
 
+#### New `compute_ptc`
+
+```python
+def compute_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
+    """
+    Get the payload timeliness committee for the given ``slot``.
+    """
+    epoch = compute_epoch_at_slot(slot)
+    seed = hash(get_seed(state, epoch, DOMAIN_PTC_ATTESTER) + uint_to_bytes(slot))
+    indices: List[ValidatorIndex] = []
+    # Concatenate all committees for this slot in order
+    committees_per_slot = get_committee_count_per_slot(state, epoch)
+    for i in range(committees_per_slot):
+        committee = get_beacon_committee(state, slot, CommitteeIndex(i))
+        indices.extend(committee)
+    return compute_balance_weighted_selection(
+        state, indices, seed, size=PTC_SIZE, shuffle_indices=False
+    )
+```
+
 ### Beacon state accessors
 
 #### Modified `get_next_sync_committee_indices`
@@ -711,16 +735,10 @@ def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     Get the payload timeliness committee for the given ``slot``.
     """
     epoch = compute_epoch_at_slot(slot)
-    seed = hash(get_seed(state, epoch, DOMAIN_PTC_ATTESTER) + uint_to_bytes(slot))
-    indices: List[ValidatorIndex] = []
-    # Concatenate all committees for this slot in order
-    committees_per_slot = get_committee_count_per_slot(state, epoch)
-    for i in range(committees_per_slot):
-        committee = get_beacon_committee(state, slot, CommitteeIndex(i))
-        indices.extend(committee)
-    return compute_balance_weighted_selection(
-        state, indices, seed, size=PTC_SIZE, shuffle_indices=False
-    )
+    state_epoch = get_current_epoch(state)
+    if epoch < state_epoch:
+        return state.ptc_lookbehind[slot % SLOTS_PER_EPOCH]
+    return state.ptc_lookbehind[SLOTS_PER_EPOCH + slot % SLOTS_PER_EPOCH]
 ```
 
 #### New `get_indexed_payload_attestation`
@@ -815,6 +833,9 @@ def process_slot(state: BeaconState) -> None:
 
 #### Modified `process_epoch`
 
+*Note*: The function `process_epoch` is modified inGloas to call the new helpers
+`process_builder_pending_payments` and `process_ptc_lookbehind`.
+
 ```python
 def process_epoch(state: BeaconState) -> None:
     process_justification_and_finalization(state)
@@ -834,6 +855,8 @@ def process_epoch(state: BeaconState) -> None:
     process_participation_flag_updates(state)
     process_sync_committee_updates(state)
     process_proposer_lookahead(state)
+    # [New in Gloas:EIP7732]
+    process_ptc_lookbehind(state)
 ```
 
 #### New `process_builder_pending_payments`
@@ -853,6 +876,23 @@ def process_builder_pending_payments(state: BeaconState) -> None:
     state.builder_pending_payments = old_payments + new_payments
 ```
 
+#### New `process_ptc_lookbehind`
+
+```python
+def process_ptc_lookbehind(state: BeaconState) -> None:
+    """
+    Get the payload timeliness committee for the given ``slot``.
+    """
+    # Shift out ptc members in the first epoch
+    state.ptc_lookbehind[:SLOTS_PER_EPOCH] = state.ptc_lookbehind[SLOTS_PER_EPOCH:]
+    # Fill in the last epoch withnew ptc indices
+    start_slot = state.slot + 1 - SLOTS_PER_EPOCH
+    last_epoch_committees = [
+        compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
+    ]
+    state.ptc_lookbehind[SLOTS_PER_EPOCH:] = last_epoch_committees
+```
+
 ### Block processing
 
 ```python

From 37f1c0e09d51e15b0df6ab1047675ed0efecc312 Mon Sep 17 00:00:00 2001
From: Potuz <potuz@potuz.net>
Date: Fri, 6 Mar 2026 15:21:13 +0100
Subject: [PATCH 02/15] Update specs/gloas/beacon-chain.md

Co-authored-by: Justin Traglia <95511699+jtraglia@users.noreply.github.com>
---
 specs/gloas/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 9ff1d7b4bd..030b07a395 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -833,7 +833,7 @@ def process_slot(state: BeaconState) -> None:
 
 #### Modified `process_epoch`
 
-*Note*: The function `process_epoch` is modified inGloas to call the new helpers
+*Note*: The function `process_epoch` is modified in Gloas to call the new helpers
 `process_builder_pending_payments` and `process_ptc_lookbehind`.
 
 ```python

From 2bdbf018b624fb83fa8a43eeff7c6328b169c136 Mon Sep 17 00:00:00 2001
From: Potuz <potuz@potuz.net>
Date: Fri, 6 Mar 2026 15:25:47 +0100
Subject: [PATCH 03/15] Update specs/gloas/beacon-chain.md

Co-authored-by: Justin Traglia <95511699+jtraglia@users.noreply.github.com>
---
 specs/gloas/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 030b07a395..1998744446 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -885,7 +885,7 @@ def process_ptc_lookbehind(state: BeaconState) -> None:
     """
     # Shift out ptc members in the first epoch
     state.ptc_lookbehind[:SLOTS_PER_EPOCH] = state.ptc_lookbehind[SLOTS_PER_EPOCH:]
-    # Fill in the last epoch withnew ptc indices
+    # Fill in the last epoch with new ptc indices
     start_slot = state.slot + 1 - SLOTS_PER_EPOCH
     last_epoch_committees = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)

From fd398a6251af5457130f5b728fdbcbcde2509c1f Mon Sep 17 00:00:00 2001
From: Potuz <potuz@prysmaticlabs.com>
Date: Fri, 6 Mar 2026 11:32:20 -0300
Subject: [PATCH 04/15] lint

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

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 1998744446..789b972194 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -833,8 +833,8 @@ def process_slot(state: BeaconState) -> None:
 
 #### Modified `process_epoch`
 
-*Note*: The function `process_epoch` is modified in Gloas to call the new helpers
-`process_builder_pending_payments` and `process_ptc_lookbehind`.
+*Note*: The function `process_epoch` is modified in Gloas to call the new
+helpers `process_builder_pending_payments` and `process_ptc_lookbehind`.
 
 ```python
 def process_epoch(state: BeaconState) -> None:

From 10e5813d4f259a30c22715ba241ac9a7754bf6cc Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Fri, 6 Mar 2026 08:57:45 -0600
Subject: [PATCH 05/15] Fix off-by-1 issue in process_ptc_lookahead

---
 specs/gloas/beacon-chain.md                   |  9 +++--
 .../test_process_ptc_lookbehind.py            | 40 +++++++++++++++++++
 2 files changed, 45 insertions(+), 4 deletions(-)
 create mode 100644 tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 789b972194..64337e8365 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -881,12 +881,13 @@ def process_builder_pending_payments(state: BeaconState) -> None:
 ```python
 def process_ptc_lookbehind(state: BeaconState) -> None:
     """
-    Get the payload timeliness committee for the given ``slot``.
+    Update the cached PTC window for the previous and current epochs.
     """
-    # Shift out ptc members in the first epoch
+    # Shift out PTC members in the first epoch
     state.ptc_lookbehind[:SLOTS_PER_EPOCH] = state.ptc_lookbehind[SLOTS_PER_EPOCH:]
-    # Fill in the last epoch with new ptc indices
-    start_slot = state.slot + 1 - SLOTS_PER_EPOCH
+    # Fill in the last epoch with the PTC for the epoch that starts after this boundary
+    next_epoch = Epoch(get_current_epoch(state) + 1)
+    start_slot = compute_start_slot_at_epoch(next_epoch)
     last_epoch_committees = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
     ]
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py
new file mode 100644
index 0000000000..267e686c89
--- /dev/null
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py
@@ -0,0 +1,40 @@
+from eth_consensus_specs.test.context import (
+    single_phase,
+    spec_state_test,
+    with_phases,
+)
+from eth_consensus_specs.test.helpers.constants import GLOAS
+from eth_consensus_specs.test.helpers.epoch_processing import run_epoch_processing_with
+
+
+def _compute_epoch_ptc(spec, state, epoch):
+    start_slot = spec.compute_start_slot_at_epoch(epoch)
+    return [
+        spec.compute_ptc(state, spec.Slot(slot))
+        for slot in range(start_slot, start_slot + spec.SLOTS_PER_EPOCH)
+    ]
+
+
+@with_phases([GLOAS])
+@spec_state_test
+@single_phase
+def test_process_ptc_lookbehind_rotates_to_next_epoch(spec, state):
+    spec.process_slots(state, state.slot + spec.SLOTS_PER_EPOCH - 1)
+
+    current_epoch = spec.get_current_epoch(state)
+    current_epoch_ptc = _compute_epoch_ptc(spec, state, current_epoch)
+    state.ptc_lookbehind = current_epoch_ptc + current_epoch_ptc
+
+    next_epoch = spec.Epoch(current_epoch + 1)
+    next_epoch_ptc = _compute_epoch_ptc(spec, state, next_epoch)
+
+    yield from run_epoch_processing_with(spec, state, "process_ptc_lookbehind")
+
+    assert list(state.ptc_lookbehind[: spec.SLOTS_PER_EPOCH]) == current_epoch_ptc
+    assert list(state.ptc_lookbehind[spec.SLOTS_PER_EPOCH :]) == next_epoch_ptc
+
+    # run_epoch_processing_with does not increment the slot
+    state.slot += 1
+
+    assert spec.get_ptc(state, spec.Slot(state.slot - 1)) == current_epoch_ptc[-1]
+    assert spec.get_ptc(state, state.slot) == next_epoch_ptc[0]

From a7bd06c092094da81f84e9a89d1757a0cc7a05bd Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Fri, 6 Mar 2026 09:17:19 -0600
Subject: [PATCH 06/15] Make necessary changes to fork specs

---
 specs/gloas/fork.md                           | 23 +++++++++++++++++++
 specs/heze/beacon-chain.md                    |  1 +
 specs/heze/fork.md                            |  1 +
 .../test_process_payload_attestation.py       |  2 ++
 .../test/helpers/genesis.py                   |  1 +
 5 files changed, 28 insertions(+)

diff --git a/specs/gloas/fork.md b/specs/gloas/fork.md
index 88184ae982..e3e5b3ee71 100644
--- a/specs/gloas/fork.md
+++ b/specs/gloas/fork.md
@@ -7,6 +7,7 @@
 - [Introduction](#introduction)
 - [Configuration](#configuration)
 - [Helpers](#helpers)
+  - [New `initialize_ptc_lookbehind`](#new-initialize_ptc_lookbehind)
   - [New `onboard_builders_from_pending_deposits`](#new-onboard_builders_from_pending_deposits)
 - [Fork to Gloas](#fork-to-gloas)
   - [Fork trigger](#fork-trigger)
@@ -29,6 +30,26 @@ Warning: this configuration is not definitive.
 
 ## Helpers
 
+### New `initialize_ptc_lookbehind`
+
+```python
+def initialize_ptc_lookbehind(
+    state: BeaconState,
+) -> Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]:
+    """
+    Return the cached PTC window starting from the current epoch.
+    Used to initialize the ``ptc_lookbehind`` field in the beacon state at genesis and after forks.
+    """
+    current_epoch = get_current_epoch(state)
+    start_slot = compute_start_slot_at_epoch(current_epoch)
+    empty_previous_epoch = [
+        Vector[ValidatorIndex, PTC_SIZE]([ValidatorIndex(0) for _ in range(PTC_SIZE)])
+        for _ in range(SLOTS_PER_EPOCH)
+    ]
+    current_epoch_ptc = [compute_ptc(state, Slot(start_slot + i)) for i in range(SLOTS_PER_EPOCH)]
+    return empty_previous_epoch + current_epoch_ptc
+```
+
 ### New `onboard_builders_from_pending_deposits`
 
 ```python
@@ -159,6 +180,8 @@ def upgrade_to_gloas(pre: fulu.BeaconState) -> BeaconState:
         latest_block_hash=pre.latest_execution_payload_header.block_hash,
         # [New in Gloas:EIP7732]
         payload_expected_withdrawals=[],
+        # [New in Gloas:EIP7732]
+        ptc_lookbehind=initialize_ptc_lookbehind(pre),
     )
 
     # [New in Gloas:EIP7732]
diff --git a/specs/heze/beacon-chain.md b/specs/heze/beacon-chain.md
index a82797401f..8ca64b5d12 100644
--- a/specs/heze/beacon-chain.md
+++ b/specs/heze/beacon-chain.md
@@ -150,6 +150,7 @@ class BeaconState(Container):
     builder_pending_withdrawals: List[BuilderPendingWithdrawal, BUILDER_PENDING_WITHDRAWALS_LIMIT]
     latest_block_hash: Hash32
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
+    ptc_lookbehind: Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]
 ```
 
 ## Helpers
diff --git a/specs/heze/fork.md b/specs/heze/fork.md
index 01333da7a5..a50a628de2 100644
--- a/specs/heze/fork.md
+++ b/specs/heze/fork.md
@@ -103,6 +103,7 @@ def upgrade_to_heze(pre: gloas.BeaconState) -> BeaconState:
         builder_pending_withdrawals=pre.builder_pending_withdrawals,
         latest_block_hash=pre.latest_block_hash,
         payload_expected_withdrawals=pre.payload_expected_withdrawals,
+        ptc_lookbehind=pre.ptc_lookbehind,
     )
 
     return post
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py
index 15532e76dd..4cd3741639 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py
@@ -375,6 +375,8 @@ def test_process_payload_attestation_sampling_not_capped(spec, state):
     low_balance = spec.EFFECTIVE_BALANCE_INCREMENT
     for validator in state.validators:
         validator.effective_balance = low_balance
+    # Direct balance mutations bypass epoch processing, so refresh the cached current-epoch PTC.
+    state.ptc_lookbehind = spec.initialize_ptc_lookbehind(state)
 
     chosen_slot = None
     chosen_index = None
diff --git a/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py b/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py
index 45d25251b0..cb158aa4d0 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py
@@ -252,6 +252,7 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
             spec.BuilderPendingPayment() for _ in range(2 * spec.SLOTS_PER_EPOCH)
         ]
         state.builder_pending_withdrawals = []
+        state.ptc_lookbehind = spec.initialize_ptc_lookbehind(state)
 
     if is_post_fulu(spec):
         # Initialize proposer lookahead list

From dc0b3f41ff0492c248c5954f216193efc0d2c14e Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Fri, 6 Mar 2026 09:46:48 -0600
Subject: [PATCH 07/15] Make some improvements to get_ptc() and add unit tests

---
 specs/gloas/beacon-chain.md                   |   9 +-
 .../gloas/unittests/validator/__init__.py     |   1 +
 .../unittests/validator/test_validator.py     | 102 ++++++++++++++++++
 3 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/__init__.py
 create mode 100644 tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/test_validator.py

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 64337e8365..7aedec1a9f 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -729,6 +729,9 @@ def get_attestation_participation_flag_indices(
 
 #### New `get_ptc`
 
+*Note*: `get_ptc` uses the cached `ptc_lookbehind` for previous and current
+epoch lookups, and computes next-epoch PTC assignments on demand.
+
 ```python
 def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     """
@@ -736,9 +739,13 @@ def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     """
     epoch = compute_epoch_at_slot(slot)
     state_epoch = get_current_epoch(state)
+    assert epoch <= state_epoch + 1
     if epoch < state_epoch:
+        assert epoch + 1 == state_epoch
         return state.ptc_lookbehind[slot % SLOTS_PER_EPOCH]
-    return state.ptc_lookbehind[SLOTS_PER_EPOCH + slot % SLOTS_PER_EPOCH]
+    if epoch == state_epoch:
+        return state.ptc_lookbehind[SLOTS_PER_EPOCH + slot % SLOTS_PER_EPOCH]
+    return compute_ptc(state, slot)
 ```
 
 #### New `get_indexed_payload_attestation`
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/__init__.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/__init__.py
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/__init__.py
@@ -0,0 +1 @@
+
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/test_validator.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/test_validator.py
new file mode 100644
index 0000000000..e828f938b1
--- /dev/null
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/unittests/validator/test_validator.py
@@ -0,0 +1,102 @@
+from eth_consensus_specs.test.context import (
+    expect_assertion_error,
+    single_phase,
+    spec_test,
+    with_phases,
+    with_state,
+)
+from eth_consensus_specs.test.helpers.constants import GLOAS
+from eth_consensus_specs.test.helpers.state import next_epoch
+
+
+def _compute_first_ptc_assignments(spec, state, epoch):
+    assignments = {}
+    start_slot = spec.compute_start_slot_at_epoch(epoch)
+    for slot in range(start_slot, start_slot + spec.SLOTS_PER_EPOCH):
+        for validator_index in spec.compute_ptc(state, spec.Slot(slot)):
+            assignments.setdefault(validator_index, spec.Slot(slot))
+    return assignments
+
+
+def _run_get_ptc_assignments(spec, state, epoch, valid=True, assignments=None):
+    if not valid:
+        expect_assertion_error(
+            lambda: spec.get_ptc_assignment(state, epoch, spec.ValidatorIndex(0))
+        )
+        return
+
+    if assignments is None:
+        assignments = _compute_first_ptc_assignments(spec, state, epoch)
+    _assert_get_ptc_assignments(spec, state, epoch, assignments)
+
+
+def _assert_get_ptc_assignments(spec, state, epoch, assignments):
+    assert len(assignments) > 0
+
+    for validator_index, expected_slot in assignments.items():
+        assert spec.get_ptc_assignment(state, epoch, validator_index) == expected_slot
+
+    unassigned_validator = next(
+        (spec.ValidatorIndex(i) for i in range(len(state.validators)) if i not in assignments),
+        None,
+    )
+    if unassigned_validator is not None:
+        assert spec.get_ptc_assignment(state, epoch, unassigned_validator) is None
+
+
+@with_phases([GLOAS])
+@spec_test
+@with_state
+@single_phase
+def test_get_ptc_assignment__current_epoch_minus_2(spec, state):
+    next_epoch(spec, state)
+    next_epoch(spec, state)
+
+    epoch = spec.Epoch(spec.get_current_epoch(state) - 2)
+    _run_get_ptc_assignments(spec, state, epoch, valid=False)
+
+
+@with_phases([GLOAS])
+@spec_test
+@with_state
+@single_phase
+def test_get_ptc_assignment__current_epoch_minus_1(spec, state):
+    previous_epoch = spec.get_current_epoch(state)
+    previous_assignments = _compute_first_ptc_assignments(spec, state, previous_epoch)
+
+    next_epoch(spec, state)
+
+    _run_get_ptc_assignments(
+        spec,
+        state,
+        previous_epoch,
+        valid=True,
+        assignments=previous_assignments,
+    )
+
+
+@with_phases([GLOAS])
+@spec_test
+@with_state
+@single_phase
+def test_get_ptc_assignment__current_epoch(spec, state):
+    epoch = spec.get_current_epoch(state)
+    _run_get_ptc_assignments(spec, state, epoch, valid=True)
+
+
+@with_phases([GLOAS])
+@spec_test
+@with_state
+@single_phase
+def test_get_ptc_assignment__current_epoch_plus_1(spec, state):
+    epoch = spec.Epoch(spec.get_current_epoch(state) + 1)
+    _run_get_ptc_assignments(spec, state, epoch, valid=True)
+
+
+@with_phases([GLOAS])
+@spec_test
+@with_state
+@single_phase
+def test_get_ptc_assignment__current_epoch_plus_2(spec, state):
+    epoch = spec.Epoch(spec.get_current_epoch(state) + 2)
+    _run_get_ptc_assignments(spec, state, epoch, valid=False)

From 72d5acc495bde927e53571bf2019299584a2bbd7 Mon Sep 17 00:00:00 2001
From: Potuz <potuz@prysmaticlabs.com>
Date: Mon, 23 Mar 2026 11:39:41 -0300
Subject: [PATCH 08/15] Add 3 epochs

---
 specs/gloas/beacon-chain.md | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 7aedec1a9f..87a20375d1 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -387,7 +387,7 @@ class BeaconState(Container):
     # [New in Gloas:EIP7732]
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
     # [New in Gloas:EIP7732]
-    ptc_lookbehind: Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]
+    ptc_lookbehind: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD)* SLOTS_PER_EPOCH]
 ```
 
 ## Dataclasses
@@ -729,8 +729,7 @@ def get_attestation_participation_flag_indices(
 
 #### New `get_ptc`
 
-*Note*: `get_ptc` uses the cached `ptc_lookbehind` for previous and current
-epoch lookups, and computes next-epoch PTC assignments on demand.
+*Note*: `get_ptc` uses the cached `ptc_lookbehind` for lookups. 
 
 ```python
 def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
@@ -739,13 +738,12 @@ def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     """
     epoch = compute_epoch_at_slot(slot)
     state_epoch = get_current_epoch(state)
-    assert epoch <= state_epoch + 1
     if epoch < state_epoch:
         assert epoch + 1 == state_epoch
         return state.ptc_lookbehind[slot % SLOTS_PER_EPOCH]
-    if epoch == state_epoch:
-        return state.ptc_lookbehind[SLOTS_PER_EPOCH + slot % SLOTS_PER_EPOCH]
-    return compute_ptc(state, slot)
+    assert epoch <= state_epoch + MIN_SEED_LOOKAHEAD
+    offset = (epoch - state_epoch + 1) * SLOTS_PER_EPOCH
+    return state.ptc_lookbehind[offset + slot % SLOTS_PER_EPOCH]
 ```
 
 #### New `get_indexed_payload_attestation`
@@ -888,17 +886,18 @@ def process_builder_pending_payments(state: BeaconState) -> None:
 ```python
 def process_ptc_lookbehind(state: BeaconState) -> None:
     """
-    Update the cached PTC window for the previous and current epochs.
+    Update the cached PTC window.
     """
     # Shift out PTC members in the first epoch
-    state.ptc_lookbehind[:SLOTS_PER_EPOCH] = state.ptc_lookbehind[SLOTS_PER_EPOCH:]
+    last_epoch_start = len(state.ptc_lookbehind) - SLOTS_PER_EPOCH
+    state.ptc_lookbehind[:last_epoch_start] = state.ptc_lookbehind[SLOTS_PER_EPOCH:]
     # Fill in the last epoch with the PTC for the epoch that starts after this boundary
-    next_epoch = Epoch(get_current_epoch(state) + 1)
+    next_epoch = Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD + 1)
     start_slot = compute_start_slot_at_epoch(next_epoch)
     last_epoch_committees = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
     ]
-    state.ptc_lookbehind[SLOTS_PER_EPOCH:] = last_epoch_committees
+    state.ptc_lookbehind[last_epoch_start:] = last_epoch_committees
 ```
 
 ### Block processing

From bc6b2c57f56f388a93e26a02097e7a65439ec2b2 Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Mon, 23 Mar 2026 12:29:02 -0500
Subject: [PATCH 09/15] Refactor process_ptc_lookbehind

---
 specs/gloas/beacon-chain.md | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 87a20375d1..e34dc176e8 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -387,7 +387,9 @@ class BeaconState(Container):
     # [New in Gloas:EIP7732]
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
     # [New in Gloas:EIP7732]
-    ptc_lookbehind: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD)* SLOTS_PER_EPOCH]
+    ptc_lookbehind: Vector[
+        Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH
+    ]
 ```
 
 ## Dataclasses
@@ -729,7 +731,7 @@ def get_attestation_participation_flag_indices(
 
 #### New `get_ptc`
 
-*Note*: `get_ptc` uses the cached `ptc_lookbehind` for lookups. 
+*Note*: `get_ptc` uses the cached `ptc_lookbehind` for lookups.
 
 ```python
 def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
@@ -888,16 +890,20 @@ def process_ptc_lookbehind(state: BeaconState) -> None:
     """
     Update the cached PTC window.
     """
-    # Shift out PTC members in the first epoch
-    last_epoch_start = len(state.ptc_lookbehind) - SLOTS_PER_EPOCH
-    state.ptc_lookbehind[:last_epoch_start] = state.ptc_lookbehind[SLOTS_PER_EPOCH:]
-    # Fill in the last epoch with the PTC for the epoch that starts after this boundary
+    prev = 0
+    curr = SLOTS_PER_EPOCH
+    next = 2 * SLOTS_PER_EPOCH
+
+    # Previous epoch: shift in PTC from the current epoch
+    state.ptc_lookbehind[prev:curr] = state.ptc_lookbehind[curr:next]
+    # Current epoch: shift in PTC from the next epoch
+    state.ptc_lookbehind[curr:next] = state.ptc_lookbehind[next:]
+    # Next epoch: compute PTC for the epoch
     next_epoch = Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD + 1)
     start_slot = compute_start_slot_at_epoch(next_epoch)
-    last_epoch_committees = [
+    state.ptc_lookbehind[next:] = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
     ]
-    state.ptc_lookbehind[last_epoch_start:] = last_epoch_committees
 ```
 
 ### Block processing

From 6579ca0862d9e215f1ef628b2df88c3d8295cfee Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Mon, 23 Mar 2026 12:35:26 -0500
Subject: [PATCH 10/15] Rename ptc_lookbehind to ptc_window

---
 specs/gloas/beacon-chain.md                   | 26 +++++++++----------
 specs/gloas/fork.md                           | 10 +++----
 specs/heze/beacon-chain.md                    |  2 +-
 specs/heze/fork.md                            |  2 +-
 .../test_process_payload_attestation.py       |  2 +-
 ...okbehind.py => test_process_ptc_window.py} | 10 +++----
 .../test/helpers/genesis.py                   |  2 +-
 7 files changed, 26 insertions(+), 28 deletions(-)
 rename tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/{test_process_ptc_lookbehind.py => test_process_ptc_window.py} (78%)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index e34dc176e8..2f1c1d3c92 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -68,7 +68,7 @@
   - [Epoch processing](#epoch-processing)
     - [Modified `process_epoch`](#modified-process_epoch)
     - [New `process_builder_pending_payments`](#new-process_builder_pending_payments)
-    - [New `process_ptc_lookbehind`](#new-process_ptc_lookbehind)
+    - [New `process_ptc_window`](#new-process_ptc_window)
   - [Block processing](#block-processing)
     - [Withdrawals](#withdrawals)
       - [New `get_builder_withdrawals`](#new-get_builder_withdrawals)
@@ -387,9 +387,7 @@ class BeaconState(Container):
     # [New in Gloas:EIP7732]
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
     # [New in Gloas:EIP7732]
-    ptc_lookbehind: Vector[
-        Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH
-    ]
+    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]
 ```
 
 ## Dataclasses
@@ -731,7 +729,7 @@ def get_attestation_participation_flag_indices(
 
 #### New `get_ptc`
 
-*Note*: `get_ptc` uses the cached `ptc_lookbehind` for lookups.
+*Note*: `get_ptc` uses the cached `ptc_window` for lookups.
 
 ```python
 def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
@@ -742,10 +740,10 @@ def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     state_epoch = get_current_epoch(state)
     if epoch < state_epoch:
         assert epoch + 1 == state_epoch
-        return state.ptc_lookbehind[slot % SLOTS_PER_EPOCH]
+        return state.ptc_window[slot % SLOTS_PER_EPOCH]
     assert epoch <= state_epoch + MIN_SEED_LOOKAHEAD
     offset = (epoch - state_epoch + 1) * SLOTS_PER_EPOCH
-    return state.ptc_lookbehind[offset + slot % SLOTS_PER_EPOCH]
+    return state.ptc_window[offset + slot % SLOTS_PER_EPOCH]
 ```
 
 #### New `get_indexed_payload_attestation`
@@ -841,7 +839,7 @@ def process_slot(state: BeaconState) -> None:
 #### Modified `process_epoch`
 
 *Note*: The function `process_epoch` is modified in Gloas to call the new
-helpers `process_builder_pending_payments` and `process_ptc_lookbehind`.
+helpers `process_builder_pending_payments` and `process_ptc_window`.
 
 ```python
 def process_epoch(state: BeaconState) -> None:
@@ -863,7 +861,7 @@ def process_epoch(state: BeaconState) -> None:
     process_sync_committee_updates(state)
     process_proposer_lookahead(state)
     # [New in Gloas:EIP7732]
-    process_ptc_lookbehind(state)
+    process_ptc_window(state)
 ```
 
 #### New `process_builder_pending_payments`
@@ -883,10 +881,10 @@ def process_builder_pending_payments(state: BeaconState) -> None:
     state.builder_pending_payments = old_payments + new_payments
 ```
 
-#### New `process_ptc_lookbehind`
+#### New `process_ptc_window`
 
 ```python
-def process_ptc_lookbehind(state: BeaconState) -> None:
+def process_ptc_window(state: BeaconState) -> None:
     """
     Update the cached PTC window.
     """
@@ -895,13 +893,13 @@ def process_ptc_lookbehind(state: BeaconState) -> None:
     next = 2 * SLOTS_PER_EPOCH
 
     # Previous epoch: shift in PTC from the current epoch
-    state.ptc_lookbehind[prev:curr] = state.ptc_lookbehind[curr:next]
+    state.ptc_window[prev:curr] = state.ptc_window[curr:next]
     # Current epoch: shift in PTC from the next epoch
-    state.ptc_lookbehind[curr:next] = state.ptc_lookbehind[next:]
+    state.ptc_window[curr:next] = state.ptc_window[next:]
     # Next epoch: compute PTC for the epoch
     next_epoch = Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD + 1)
     start_slot = compute_start_slot_at_epoch(next_epoch)
-    state.ptc_lookbehind[next:] = [
+    state.ptc_window[next:] = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
     ]
 ```
diff --git a/specs/gloas/fork.md b/specs/gloas/fork.md
index e3e5b3ee71..8245583351 100644
--- a/specs/gloas/fork.md
+++ b/specs/gloas/fork.md
@@ -7,7 +7,7 @@
 - [Introduction](#introduction)
 - [Configuration](#configuration)
 - [Helpers](#helpers)
-  - [New `initialize_ptc_lookbehind`](#new-initialize_ptc_lookbehind)
+  - [New `initialize_ptc_window`](#new-initialize_ptc_window)
   - [New `onboard_builders_from_pending_deposits`](#new-onboard_builders_from_pending_deposits)
 - [Fork to Gloas](#fork-to-gloas)
   - [Fork trigger](#fork-trigger)
@@ -30,15 +30,15 @@ Warning: this configuration is not definitive.
 
 ## Helpers
 
-### New `initialize_ptc_lookbehind`
+### New `initialize_ptc_window`
 
 ```python
-def initialize_ptc_lookbehind(
+def initialize_ptc_window(
     state: BeaconState,
 ) -> Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]:
     """
     Return the cached PTC window starting from the current epoch.
-    Used to initialize the ``ptc_lookbehind`` field in the beacon state at genesis and after forks.
+    Used to initialize the ``ptc_window`` field in the beacon state at genesis and after forks.
     """
     current_epoch = get_current_epoch(state)
     start_slot = compute_start_slot_at_epoch(current_epoch)
@@ -181,7 +181,7 @@ def upgrade_to_gloas(pre: fulu.BeaconState) -> BeaconState:
         # [New in Gloas:EIP7732]
         payload_expected_withdrawals=[],
         # [New in Gloas:EIP7732]
-        ptc_lookbehind=initialize_ptc_lookbehind(pre),
+        ptc_window=initialize_ptc_window(pre),
     )
 
     # [New in Gloas:EIP7732]
diff --git a/specs/heze/beacon-chain.md b/specs/heze/beacon-chain.md
index 8ca64b5d12..a3a2a63f38 100644
--- a/specs/heze/beacon-chain.md
+++ b/specs/heze/beacon-chain.md
@@ -150,7 +150,7 @@ class BeaconState(Container):
     builder_pending_withdrawals: List[BuilderPendingWithdrawal, BUILDER_PENDING_WITHDRAWALS_LIMIT]
     latest_block_hash: Hash32
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
-    ptc_lookbehind: Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]
+    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]
 ```
 
 ## Helpers
diff --git a/specs/heze/fork.md b/specs/heze/fork.md
index a50a628de2..7aef37d7df 100644
--- a/specs/heze/fork.md
+++ b/specs/heze/fork.md
@@ -103,7 +103,7 @@ def upgrade_to_heze(pre: gloas.BeaconState) -> BeaconState:
         builder_pending_withdrawals=pre.builder_pending_withdrawals,
         latest_block_hash=pre.latest_block_hash,
         payload_expected_withdrawals=pre.payload_expected_withdrawals,
-        ptc_lookbehind=pre.ptc_lookbehind,
+        ptc_window=pre.ptc_window,
     )
 
     return post
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py
index 4cd3741639..eef256e508 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_payload_attestation.py
@@ -376,7 +376,7 @@ def test_process_payload_attestation_sampling_not_capped(spec, state):
     for validator in state.validators:
         validator.effective_balance = low_balance
     # Direct balance mutations bypass epoch processing, so refresh the cached current-epoch PTC.
-    state.ptc_lookbehind = spec.initialize_ptc_lookbehind(state)
+    state.ptc_window = spec.initialize_ptc_window(state)
 
     chosen_slot = None
     chosen_index = None
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
similarity index 78%
rename from tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py
rename to tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
index 267e686c89..cefa39b642 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_lookbehind.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
@@ -18,20 +18,20 @@ def _compute_epoch_ptc(spec, state, epoch):
 @with_phases([GLOAS])
 @spec_state_test
 @single_phase
-def test_process_ptc_lookbehind_rotates_to_next_epoch(spec, state):
+def test_process_ptc_window_rotates_to_next_epoch(spec, state):
     spec.process_slots(state, state.slot + spec.SLOTS_PER_EPOCH - 1)
 
     current_epoch = spec.get_current_epoch(state)
     current_epoch_ptc = _compute_epoch_ptc(spec, state, current_epoch)
-    state.ptc_lookbehind = current_epoch_ptc + current_epoch_ptc
+    state.ptc_window = current_epoch_ptc + current_epoch_ptc
 
     next_epoch = spec.Epoch(current_epoch + 1)
     next_epoch_ptc = _compute_epoch_ptc(spec, state, next_epoch)
 
-    yield from run_epoch_processing_with(spec, state, "process_ptc_lookbehind")
+    yield from run_epoch_processing_with(spec, state, "process_ptc_window")
 
-    assert list(state.ptc_lookbehind[: spec.SLOTS_PER_EPOCH]) == current_epoch_ptc
-    assert list(state.ptc_lookbehind[spec.SLOTS_PER_EPOCH :]) == next_epoch_ptc
+    assert list(state.ptc_window[: spec.SLOTS_PER_EPOCH]) == current_epoch_ptc
+    assert list(state.ptc_window[spec.SLOTS_PER_EPOCH :]) == next_epoch_ptc
 
     # run_epoch_processing_with does not increment the slot
     state.slot += 1
diff --git a/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py b/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py
index cb158aa4d0..2130c8eff0 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/helpers/genesis.py
@@ -252,7 +252,7 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
             spec.BuilderPendingPayment() for _ in range(2 * spec.SLOTS_PER_EPOCH)
         ]
         state.builder_pending_withdrawals = []
-        state.ptc_lookbehind = spec.initialize_ptc_lookbehind(state)
+        state.ptc_window = spec.initialize_ptc_window(state)
 
     if is_post_fulu(spec):
         # Initialize proposer lookahead list

From b7c1794903d7deea5fed836b3f2061b5f87520aa Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Mon, 23 Mar 2026 12:45:32 -0500
Subject: [PATCH 11/15] Update initialize_ptc_window & fix a test

---
 specs/gloas/fork.md                           | 12 ++++---
 .../test_process_ptc_window.py                | 35 +++++++++++++------
 2 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/specs/gloas/fork.md b/specs/gloas/fork.md
index 8245583351..85b9414da7 100644
--- a/specs/gloas/fork.md
+++ b/specs/gloas/fork.md
@@ -35,19 +35,23 @@ Warning: this configuration is not definitive.
 ```python
 def initialize_ptc_window(
     state: BeaconState,
-) -> Vector[Vector[ValidatorIndex, PTC_SIZE], 2 * SLOTS_PER_EPOCH]:
+) -> Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]:
     """
     Return the cached PTC window starting from the current epoch.
     Used to initialize the ``ptc_window`` field in the beacon state at genesis and after forks.
     """
     current_epoch = get_current_epoch(state)
-    start_slot = compute_start_slot_at_epoch(current_epoch)
     empty_previous_epoch = [
         Vector[ValidatorIndex, PTC_SIZE]([ValidatorIndex(0) for _ in range(PTC_SIZE)])
         for _ in range(SLOTS_PER_EPOCH)
     ]
-    current_epoch_ptc = [compute_ptc(state, Slot(start_slot + i)) for i in range(SLOTS_PER_EPOCH)]
-    return empty_previous_epoch + current_epoch_ptc
+    current_start = compute_start_slot_at_epoch(current_epoch)
+    current_epoch_ptc = [
+        compute_ptc(state, Slot(current_start + i)) for i in range(SLOTS_PER_EPOCH)
+    ]
+    next_start = compute_start_slot_at_epoch(Epoch(current_epoch + MIN_SEED_LOOKAHEAD))
+    next_epoch_ptc = [compute_ptc(state, Slot(next_start + i)) for i in range(SLOTS_PER_EPOCH)]
+    return empty_previous_epoch + current_epoch_ptc + next_epoch_ptc
 ```
 
 ### New `onboard_builders_from_pending_deposits`
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
index cefa39b642..dd5ac79b81 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
@@ -18,23 +18,38 @@ def _compute_epoch_ptc(spec, state, epoch):
 @with_phases([GLOAS])
 @spec_state_test
 @single_phase
-def test_process_ptc_window_rotates_to_next_epoch(spec, state):
-    spec.process_slots(state, state.slot + spec.SLOTS_PER_EPOCH - 1)
+def test_process_ptc_window_shifts_all_three_epochs(spec, state):
+    """
+    Verify that process_ptc_window shifts prev/curr/next correctly
+    and that get_ptc returns the right committees afterwards.
+    """
+    spec.process_slots(state, state.slot + 2 * spec.SLOTS_PER_EPOCH - 1)
 
     current_epoch = spec.get_current_epoch(state)
-    current_epoch_ptc = _compute_epoch_ptc(spec, state, current_epoch)
-    state.ptc_window = current_epoch_ptc + current_epoch_ptc
+    prev_epoch_ptc = _compute_epoch_ptc(spec, state, spec.Epoch(current_epoch - 1))
+    curr_epoch_ptc = _compute_epoch_ptc(spec, state, current_epoch)
+    next_epoch_ptc = _compute_epoch_ptc(spec, state, spec.Epoch(current_epoch + 1))
 
-    next_epoch = spec.Epoch(current_epoch + 1)
-    next_epoch_ptc = _compute_epoch_ptc(spec, state, next_epoch)
+    # Set up the 3-epoch window: [prev, curr, next]
+    state.ptc_window = prev_epoch_ptc + curr_epoch_ptc + next_epoch_ptc
+
+    # Compute what the new next epoch should be after the shift
+    new_next_epoch = spec.Epoch(current_epoch + spec.MIN_SEED_LOOKAHEAD + 1)
+    new_next_epoch_ptc = _compute_epoch_ptc(spec, state, new_next_epoch)
 
     yield from run_epoch_processing_with(spec, state, "process_ptc_window")
 
-    assert list(state.ptc_window[: spec.SLOTS_PER_EPOCH]) == current_epoch_ptc
-    assert list(state.ptc_window[spec.SLOTS_PER_EPOCH :]) == next_epoch_ptc
+    # After shift: [curr, next, new_next]
+    SPE = spec.SLOTS_PER_EPOCH
+    assert list(state.ptc_window[:SPE]) == curr_epoch_ptc
+    assert list(state.ptc_window[SPE : 2 * SPE]) == next_epoch_ptc
+    assert list(state.ptc_window[2 * SPE :]) == new_next_epoch_ptc
 
-    # run_epoch_processing_with does not increment the slot
+    # run_epoch_processing_with does not increment the slot, so do it manually
     state.slot += 1
 
-    assert spec.get_ptc(state, spec.Slot(state.slot - 1)) == current_epoch_ptc[-1]
+    # Now state_epoch = current_epoch + 1
+    # Previous epoch lookup (current_epoch) should hit the first section
+    assert spec.get_ptc(state, spec.Slot(state.slot - 1)) == curr_epoch_ptc[-1]
+    # Current epoch lookup should hit the second section
     assert spec.get_ptc(state, state.slot) == next_epoch_ptc[0]

From 41d963c4304ccac3a86916d78cded61e02910196 Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Mon, 23 Mar 2026 13:13:33 -0500
Subject: [PATCH 12/15] Hardcode ptc_window to be prev/curr/next epochs

---
 specs/gloas/beacon-chain.md                   |  8 +++----
 specs/gloas/fork.md                           | 10 ++++----
 specs/heze/beacon-chain.md                    |  2 +-
 .../test_process_ptc_window.py                | 24 +++----------------
 4 files changed, 13 insertions(+), 31 deletions(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 2f1c1d3c92..5dc2a00d1e 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -387,7 +387,7 @@ class BeaconState(Container):
     # [New in Gloas:EIP7732]
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
     # [New in Gloas:EIP7732]
-    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]
+    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], 3 * SLOTS_PER_EPOCH]
 ```
 
 ## Dataclasses
@@ -741,7 +741,7 @@ def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     if epoch < state_epoch:
         assert epoch + 1 == state_epoch
         return state.ptc_window[slot % SLOTS_PER_EPOCH]
-    assert epoch <= state_epoch + MIN_SEED_LOOKAHEAD
+    assert epoch <= state_epoch + 1
     offset = (epoch - state_epoch + 1) * SLOTS_PER_EPOCH
     return state.ptc_window[offset + slot % SLOTS_PER_EPOCH]
 ```
@@ -889,7 +889,7 @@ def process_ptc_window(state: BeaconState) -> None:
     Update the cached PTC window.
     """
     prev = 0
-    curr = SLOTS_PER_EPOCH
+    curr = 1 * SLOTS_PER_EPOCH
     next = 2 * SLOTS_PER_EPOCH
 
     # Previous epoch: shift in PTC from the current epoch
@@ -897,7 +897,7 @@ def process_ptc_window(state: BeaconState) -> None:
     # Current epoch: shift in PTC from the next epoch
     state.ptc_window[curr:next] = state.ptc_window[next:]
     # Next epoch: compute PTC for the epoch
-    next_epoch = Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD + 1)
+    next_epoch = Epoch(get_current_epoch(state) + 2)
     start_slot = compute_start_slot_at_epoch(next_epoch)
     state.ptc_window[next:] = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
diff --git a/specs/gloas/fork.md b/specs/gloas/fork.md
index 85b9414da7..285aef49e7 100644
--- a/specs/gloas/fork.md
+++ b/specs/gloas/fork.md
@@ -35,23 +35,23 @@ Warning: this configuration is not definitive.
 ```python
 def initialize_ptc_window(
     state: BeaconState,
-) -> Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]:
+) -> Vector[Vector[ValidatorIndex, PTC_SIZE], 3 * SLOTS_PER_EPOCH]:
     """
     Return the cached PTC window starting from the current epoch.
     Used to initialize the ``ptc_window`` field in the beacon state at genesis and after forks.
     """
-    current_epoch = get_current_epoch(state)
-    empty_previous_epoch = [
+    previous_epoch_ptc = [
         Vector[ValidatorIndex, PTC_SIZE]([ValidatorIndex(0) for _ in range(PTC_SIZE)])
         for _ in range(SLOTS_PER_EPOCH)
     ]
+    current_epoch = get_current_epoch(state)
     current_start = compute_start_slot_at_epoch(current_epoch)
     current_epoch_ptc = [
         compute_ptc(state, Slot(current_start + i)) for i in range(SLOTS_PER_EPOCH)
     ]
-    next_start = compute_start_slot_at_epoch(Epoch(current_epoch + MIN_SEED_LOOKAHEAD))
+    next_start = compute_start_slot_at_epoch(Epoch(current_epoch + 1))
     next_epoch_ptc = [compute_ptc(state, Slot(next_start + i)) for i in range(SLOTS_PER_EPOCH)]
-    return empty_previous_epoch + current_epoch_ptc + next_epoch_ptc
+    return previous_epoch_ptc + current_epoch_ptc + next_epoch_ptc
 ```
 
 ### New `onboard_builders_from_pending_deposits`
diff --git a/specs/heze/beacon-chain.md b/specs/heze/beacon-chain.md
index a3a2a63f38..c6f53aea25 100644
--- a/specs/heze/beacon-chain.md
+++ b/specs/heze/beacon-chain.md
@@ -150,7 +150,7 @@ class BeaconState(Container):
     builder_pending_withdrawals: List[BuilderPendingWithdrawal, BUILDER_PENDING_WITHDRAWALS_LIMIT]
     latest_block_hash: Hash32
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
-    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]
+    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], 3 * SLOTS_PER_EPOCH]
 ```
 
 ## Helpers
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
index dd5ac79b81..5c297d0ebc 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
@@ -7,14 +7,6 @@
 from eth_consensus_specs.test.helpers.epoch_processing import run_epoch_processing_with
 
 
-def _compute_epoch_ptc(spec, state, epoch):
-    start_slot = spec.compute_start_slot_at_epoch(epoch)
-    return [
-        spec.compute_ptc(state, spec.Slot(slot))
-        for slot in range(start_slot, start_slot + spec.SLOTS_PER_EPOCH)
-    ]
-
-
 @with_phases([GLOAS])
 @spec_state_test
 @single_phase
@@ -25,25 +17,15 @@ def test_process_ptc_window_shifts_all_three_epochs(spec, state):
     """
     spec.process_slots(state, state.slot + 2 * spec.SLOTS_PER_EPOCH - 1)
 
-    current_epoch = spec.get_current_epoch(state)
-    prev_epoch_ptc = _compute_epoch_ptc(spec, state, spec.Epoch(current_epoch - 1))
-    curr_epoch_ptc = _compute_epoch_ptc(spec, state, current_epoch)
-    next_epoch_ptc = _compute_epoch_ptc(spec, state, spec.Epoch(current_epoch + 1))
-
-    # Set up the 3-epoch window: [prev, curr, next]
-    state.ptc_window = prev_epoch_ptc + curr_epoch_ptc + next_epoch_ptc
-
-    # Compute what the new next epoch should be after the shift
-    new_next_epoch = spec.Epoch(current_epoch + spec.MIN_SEED_LOOKAHEAD + 1)
-    new_next_epoch_ptc = _compute_epoch_ptc(spec, state, new_next_epoch)
+    SPE = spec.SLOTS_PER_EPOCH
+    curr_epoch_ptc = list(state.ptc_window[SPE : 2 * SPE])
+    next_epoch_ptc = list(state.ptc_window[2 * SPE :])
 
     yield from run_epoch_processing_with(spec, state, "process_ptc_window")
 
     # After shift: [curr, next, new_next]
-    SPE = spec.SLOTS_PER_EPOCH
     assert list(state.ptc_window[:SPE]) == curr_epoch_ptc
     assert list(state.ptc_window[SPE : 2 * SPE]) == next_epoch_ptc
-    assert list(state.ptc_window[2 * SPE :]) == new_next_epoch_ptc
 
     # run_epoch_processing_with does not increment the slot, so do it manually
     state.slot += 1

From 31745d0d05571d346267ac0a148e597062f340b2 Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Mon, 23 Mar 2026 15:30:24 -0500
Subject: [PATCH 13/15] Add back MIN_SEED_LOOKAHEAD to ptc_window

---
 specs/gloas/beacon-chain.md                   | 20 +++++++------------
 specs/gloas/fork.md                           | 19 +++++++++---------
 specs/gloas/validator.md                      |  4 ++--
 specs/heze/beacon-chain.md                    |  2 +-
 .../test_process_ptc_window.py                |  5 +++--
 5 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/specs/gloas/beacon-chain.md b/specs/gloas/beacon-chain.md
index 5dc2a00d1e..3c6d040406 100644
--- a/specs/gloas/beacon-chain.md
+++ b/specs/gloas/beacon-chain.md
@@ -387,7 +387,7 @@ class BeaconState(Container):
     # [New in Gloas:EIP7732]
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
     # [New in Gloas:EIP7732]
-    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], 3 * SLOTS_PER_EPOCH]
+    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]
 ```
 
 ## Dataclasses
@@ -741,7 +741,7 @@ def get_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     if epoch < state_epoch:
         assert epoch + 1 == state_epoch
         return state.ptc_window[slot % SLOTS_PER_EPOCH]
-    assert epoch <= state_epoch + 1
+    assert epoch <= state_epoch + MIN_SEED_LOOKAHEAD
     offset = (epoch - state_epoch + 1) * SLOTS_PER_EPOCH
     return state.ptc_window[offset + slot % SLOTS_PER_EPOCH]
 ```
@@ -888,18 +888,12 @@ def process_ptc_window(state: BeaconState) -> None:
     """
     Update the cached PTC window.
     """
-    prev = 0
-    curr = 1 * SLOTS_PER_EPOCH
-    next = 2 * SLOTS_PER_EPOCH
-
-    # Previous epoch: shift in PTC from the current epoch
-    state.ptc_window[prev:curr] = state.ptc_window[curr:next]
-    # Current epoch: shift in PTC from the next epoch
-    state.ptc_window[curr:next] = state.ptc_window[next:]
-    # Next epoch: compute PTC for the epoch
-    next_epoch = Epoch(get_current_epoch(state) + 2)
+    # Shift all epochs forward by one
+    state.ptc_window[: len(state.ptc_window) - SLOTS_PER_EPOCH] = state.ptc_window[SLOTS_PER_EPOCH:]
+    # Fill in the last epoch
+    next_epoch = Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD + 1)
     start_slot = compute_start_slot_at_epoch(next_epoch)
-    state.ptc_window[next:] = [
+    state.ptc_window[len(state.ptc_window) - SLOTS_PER_EPOCH :] = [
         compute_ptc(state, Slot(slot)) for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH)
     ]
 ```
diff --git a/specs/gloas/fork.md b/specs/gloas/fork.md
index 285aef49e7..ea0970fb11 100644
--- a/specs/gloas/fork.md
+++ b/specs/gloas/fork.md
@@ -35,23 +35,24 @@ Warning: this configuration is not definitive.
 ```python
 def initialize_ptc_window(
     state: BeaconState,
-) -> Vector[Vector[ValidatorIndex, PTC_SIZE], 3 * SLOTS_PER_EPOCH]:
+) -> Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]:
     """
     Return the cached PTC window starting from the current epoch.
     Used to initialize the ``ptc_window`` field in the beacon state at genesis and after forks.
     """
-    previous_epoch_ptc = [
+    empty_previous_epoch = [
         Vector[ValidatorIndex, PTC_SIZE]([ValidatorIndex(0) for _ in range(PTC_SIZE)])
         for _ in range(SLOTS_PER_EPOCH)
     ]
+
+    ptcs = []
     current_epoch = get_current_epoch(state)
-    current_start = compute_start_slot_at_epoch(current_epoch)
-    current_epoch_ptc = [
-        compute_ptc(state, Slot(current_start + i)) for i in range(SLOTS_PER_EPOCH)
-    ]
-    next_start = compute_start_slot_at_epoch(Epoch(current_epoch + 1))
-    next_epoch_ptc = [compute_ptc(state, Slot(next_start + i)) for i in range(SLOTS_PER_EPOCH)]
-    return previous_epoch_ptc + current_epoch_ptc + next_epoch_ptc
+    for e in range(1 + MIN_SEED_LOOKAHEAD):
+        epoch = Epoch(current_epoch + e)
+        start_slot = compute_start_slot_at_epoch(epoch)
+        ptcs += [compute_ptc(state, Slot(start_slot + i)) for i in range(SLOTS_PER_EPOCH)]
+
+    return empty_previous_epoch + ptcs
 ```
 
 ### New `onboard_builders_from_pending_deposits`
diff --git a/specs/gloas/validator.md b/specs/gloas/validator.md
index d1d95f72a0..7ec2b57494 100644
--- a/specs/gloas/validator.md
+++ b/specs/gloas/validator.md
@@ -62,8 +62,8 @@ def get_ptc_assignment(
     index ``validator_index`` is a member of the PTC. Returns None if no
     assignment is found.
     """
-    next_epoch = Epoch(get_current_epoch(state) + 1)
-    assert epoch <= next_epoch
+    max_epoch = Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD)
+    assert epoch <= max_epoch
 
     start_slot = compute_start_slot_at_epoch(epoch)
     for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH):
diff --git a/specs/heze/beacon-chain.md b/specs/heze/beacon-chain.md
index c6f53aea25..a3a2a63f38 100644
--- a/specs/heze/beacon-chain.md
+++ b/specs/heze/beacon-chain.md
@@ -150,7 +150,7 @@ class BeaconState(Container):
     builder_pending_withdrawals: List[BuilderPendingWithdrawal, BUILDER_PENDING_WITHDRAWALS_LIMIT]
     latest_block_hash: Hash32
     payload_expected_withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
-    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], 3 * SLOTS_PER_EPOCH]
+    ptc_window: Vector[Vector[ValidatorIndex, PTC_SIZE], (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH]
 ```
 
 ## Helpers
diff --git a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
index 5c297d0ebc..8ff53b843a 100644
--- a/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
+++ b/tests/core/pyspec/eth_consensus_specs/test/gloas/epoch_processing/test_process_ptc_window.py
@@ -10,7 +10,7 @@
 @with_phases([GLOAS])
 @spec_state_test
 @single_phase
-def test_process_ptc_window_shifts_all_three_epochs(spec, state):
+def test_process_ptc_window__shifts_all_epochs(spec, state):
     """
     Verify that process_ptc_window shifts prev/curr/next correctly
     and that get_ptc returns the right committees afterwards.
@@ -18,8 +18,9 @@ def test_process_ptc_window_shifts_all_three_epochs(spec, state):
     spec.process_slots(state, state.slot + 2 * spec.SLOTS_PER_EPOCH - 1)
 
     SPE = spec.SLOTS_PER_EPOCH
+    # Save current and next epoch sections before the shift
     curr_epoch_ptc = list(state.ptc_window[SPE : 2 * SPE])
-    next_epoch_ptc = list(state.ptc_window[2 * SPE :])
+    next_epoch_ptc = list(state.ptc_window[2 * SPE : 3 * SPE])
 
     yield from run_epoch_processing_with(spec, state, "process_ptc_window")
 

From e7b191044449c73f0b6117bfac6e0e49008dd5f1 Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Tue, 24 Mar 2026 12:58:09 -0500
Subject: [PATCH 14/15] Fix epoch restrictions in paragraph

---
 specs/gloas/validator.md | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/specs/gloas/validator.md b/specs/gloas/validator.md
index 7ec2b57494..94e23d2ee3 100644
--- a/specs/gloas/validator.md
+++ b/specs/gloas/validator.md
@@ -49,9 +49,10 @@ validator" to implement Gloas.
 
 A validator may be a member of the new Payload Timeliness Committee (PTC) for a
 given slot. To check for PTC assignments, use
-`get_ptc_assignment(state, epoch, validator_index)` where `epoch <= next_epoch`,
-as PTC committee selection is only stable within the context of the current and
-next epoch.
+`get_ptc_assignment(state, epoch, validator_index)` where
+`epoch <= get_current_epoch(state) + MIN_SEED_LOOKAHEAD`, as PTC committee
+selection is only stable within the context of the current and next epochs the
+lookahead.
 
 ```python
 def get_ptc_assignment(

From 89ce53b0918d36a1e17e09e1a65b0d121edbbf6b Mon Sep 17 00:00:00 2001
From: Justin Traglia <jtraglia@pm.me>
Date: Tue, 24 Mar 2026 16:24:01 -0500
Subject: [PATCH 15/15] Fix typo

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

diff --git a/specs/gloas/validator.md b/specs/gloas/validator.md
index 94e23d2ee3..b898a15c4e 100644
--- a/specs/gloas/validator.md
+++ b/specs/gloas/validator.md
@@ -51,8 +51,8 @@ A validator may be a member of the new Payload Timeliness Committee (PTC) for a
 given slot. To check for PTC assignments, use
 `get_ptc_assignment(state, epoch, validator_index)` where
 `epoch <= get_current_epoch(state) + MIN_SEED_LOOKAHEAD`, as PTC committee
-selection is only stable within the context of the current and next epochs the
-lookahead.
+selection is only stable within the context of the current and next epochs in
+the lookahead.
 
 ```python
 def get_ptc_assignment(