Enforce Activation Rate Limit at Fork Transition

specs/_features/eip7251/beacon-chain.md

@@ -51,6 +51,7 @@
     - [Updated  `initiate_validator_exit`](#updated--initiate_validator_exit)
     - [New `switch_to_compounding_validator`](#new-switch_to_compounding_validator)
     - [New `queue_excess_active_balance`](#new-queue_excess_active_balance)
+    - [New `queue_entire_balance_and_reset_validator`](#new-queue_entire_balance_and_reset_validator)
     - [New `compute_exit_epoch_and_update_churn`](#new-compute_exit_epoch_and_update_churn)
     - [New `compute_consolidation_epoch_and_update_churn`](#new-compute_consolidation_epoch_and_update_churn)
     - [Updated `slash_validator`](#updated-slash_validator)
@@ -526,6 +527,19 @@ def queue_excess_active_balance(state: BeaconState, index: ValidatorIndex) -> No
         )
 ```
 
+#### New `queue_entire_balance_and_reset_validator`
+```python
+def queue_entire_balance_and_reset_validator(state: BeaconState, index: ValidatorIndex) -> None:
+    balance = state.balances[index]
+    state.balances[index] = 0
+    validator = state.validators[index]
+    validator.effective_balance = 0
+    validator.activation_eligibility_epoch = FAR_FUTURE_EPOCH
+    state.pending_balance_deposits.append(
+        PendingBalanceDeposit(index=index, amount=balance)
+    )
+```
+
 #### New `compute_exit_epoch_and_update_churn`
 
 ```python

specs/_features/eip7251/fork.md

@@ -128,6 +128,23 @@ def upgrade_to_eip7251(pre: deneb.BeaconState) -> BeaconState:
         pending_consolidations=[],
     )
 
+    activation_queue = []
+    pre_activation_queue = []
+    below_minimum = []
+    for index, validator in enumerate(post.validators):
+        if validator.activation_epoch == FAR_FUTURE_EPOCH:
+            if validator.activation_eligibility_epoch != FAR_FUTURE_EPOCH:
+                activation_queue.append(index)
+            else:
+                if validator.effective_balance >= MIN_ACTIVATION_BALANCE:
+                    pre_activation_queue.append(index)
+                else:
+                    below_minimum.append(index)
+
+    activation_queue.sort(key=lambda index: (post.validators[index].activation_eligibility_epoch, index))
+    for index in activation_queue + pre_activation_queue + below_minimum:
+        queue_entire_balance_and_reset_validator(post, ValidatorIndex(index))
+
     # Ensure early adopters of compounding credentials go through the activation churn
     for index, validator in enumerate(post.validators):
         if has_compounding_withdrawal_credential(validator):