diff --git a/Cargo.lock b/Cargo.lock
index ea7c446d..6bf112fd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -138,7 +138,7 @@ dependencies = [
 
 [[package]]
 name = "starcoin-framework"
-version = "11.0.0"
+version = "13.0.0"
 dependencies = [
  "anyhow",
  "include_dir",
diff --git a/Cargo.toml b/Cargo.toml
index a3bc053b..e6811b27 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "starcoin-framework"
-version = "11.0.0"
+version = "13.0.0"
 authors = ["Starcoin Core Dev <dev@starcoin.org>"]
 license = "Apache-2.0"
 publish = false
@@ -14,4 +14,4 @@ once_cell = "1.8.0"
 tempfile = "3.2.0"
 log = "0.4.14"
 
-[dev-dependencies]
\ No newline at end of file
+[dev-dependencies]
diff --git a/integration-tests/block/block_metadata.exp b/integration-tests/block/block_metadata.exp
index 1643c9e6..b44edfa9 100644
--- a/integration-tests/block/block_metadata.exp
+++ b/integration-tests/block/block_metadata.exp
@@ -1,7 +1,13 @@
-processed 3 tasks
+processed 4 tasks
 
 task 2 'run'. lines 5-15:
 {
-  "gas_used": 16339,
+  "gas_used": 23606,
+  "status": "Executed"
+}
+
+task 3 'run'. lines 17-27:
+{
+  "gas_used": 20390,
   "status": "Executed"
 }
diff --git a/integration-tests/block/block_metadata.move b/integration-tests/block/block_metadata.move
index d759ca9e..a8ab3968 100644
--- a/integration-tests/block/block_metadata.move
+++ b/integration-tests/block/block_metadata.move
@@ -13,3 +13,15 @@ script {
     }
 }
 // check: EXECUTED
+
+//# run --signers alice
+script {
+    use StarcoinFramework::Block;
+    use StarcoinFramework::Debug;
+
+    fun get_parents_hash(_account: signer) {
+        let hash = Block::get_parents_hash();
+        Debug::print<vector<u8>>(&hash);
+    }
+}
+// check: EXECUTED
diff --git a/integration-tests/epoch/adjust_epoch_block_time_max.exp b/integration-tests/epoch/adjust_epoch_block_time_max.exp
index 28237215..4a378569 100644
--- a/integration-tests/epoch/adjust_epoch_block_time_max.exp
+++ b/integration-tests/epoch/adjust_epoch_block_time_max.exp
@@ -2,6 +2,6 @@ processed 3 tasks
 
 task 2 'run'. lines 5-40:
 {
-  "gas_used": 26693545,
+  "gas_used": 32458705,
   "status": "Executed"
 }
diff --git a/integration-tests/epoch/adjust_epoch_block_time_min.exp b/integration-tests/epoch/adjust_epoch_block_time_min.exp
index 48ce10b5..da240864 100644
--- a/integration-tests/epoch/adjust_epoch_block_time_min.exp
+++ b/integration-tests/epoch/adjust_epoch_block_time_min.exp
@@ -2,6 +2,6 @@ processed 3 tasks
 
 task 2 'run'. lines 6-37:
 {
-  "gas_used": 26475471,
+  "gas_used": 32240631,
   "status": "Executed"
 }
diff --git a/integration-tests/epoch/adjust_epoch_failed.exp b/integration-tests/epoch/adjust_epoch_failed.exp
index 101e63fe..08d78895 100644
--- a/integration-tests/epoch/adjust_epoch_failed.exp
+++ b/integration-tests/epoch/adjust_epoch_failed.exp
@@ -18,13 +18,13 @@ task 3 'run'. lines 7-19:
 
 task 4 'run'. lines 22-34:
 {
-  "gas_used": 42342,
+  "gas_used": 54350,
   "status": "Executed"
 }
 
 task 5 'run'. lines 37-51:
 {
-  "gas_used": 41667,
+  "gas_used": 53675,
   "status": {
     "MoveAbort": {
       "location": {
@@ -40,7 +40,7 @@ task 5 'run'. lines 37-51:
 
 task 6 'run'. lines 54-67:
 {
-  "gas_used": 38000,
+  "gas_used": 50008,
   "status": {
     "MoveAbort": {
       "location": {
@@ -56,7 +56,7 @@ task 6 'run'. lines 54-67:
 
 task 7 'run'. lines 70-83:
 {
-  "gas_used": 45146,
+  "gas_used": 57286,
   "status": {
     "MoveAbort": {
       "location": {
@@ -72,6 +72,6 @@ task 7 'run'. lines 70-83:
 
 task 8 'run'. lines 86-99:
 {
-  "gas_used": 168736,
+  "gas_used": 180876,
   "status": "Executed"
 }
diff --git a/integration-tests/incubator/SortedLinkedList.exp b/integration-tests/incubator/SortedLinkedList.exp
index 4f0b294d..8e4a83ab 100644
--- a/integration-tests/incubator/SortedLinkedList.exp
+++ b/integration-tests/incubator/SortedLinkedList.exp
@@ -72,19 +72,19 @@ task 19 'run'. lines 504-512:
 
 task 20 'run'. lines 514-523:
 {
-  "gas_used": 167705,
+  "gas_used": 172067,
   "status": "Executed"
 }
 
 task 21 'run'. lines 525-534:
 {
-  "gas_used": 196043,
+  "gas_used": 200405,
   "status": "Executed"
 }
 
 task 22 'run'. lines 536-545:
 {
-  "gas_used": 232559,
+  "gas_used": 236921,
   "status": "Executed"
 }
 
@@ -102,7 +102,7 @@ task 24 'run'. lines 559-568:
 
 task 25 'run'. lines 570-580:
 {
-  "gas_used": 28739,
+  "gas_used": 33101,
   "status": {
     "MoveAbort": {
       "location": "Script",
@@ -113,6 +113,6 @@ task 25 'run'. lines 570-580:
 
 task 32 'run'. lines 595-605:
 {
-  "gas_used": 113223,
+  "gas_used": 117585,
   "status": "Executed"
 }
diff --git a/release/v12/sources/Block.move b/release/v12/sources/Block.move
index ac4328a8..8f6a5cab 100644
--- a/release/v12/sources/Block.move
+++ b/release/v12/sources/Block.move
@@ -1,6 +1,7 @@
 address StarcoinFramework {
 /// Block module provide metadata for generated blocks.
 module Block {
+    use StarcoinFramework::Vector;
     use StarcoinFramework::Event;
     use StarcoinFramework::Timestamp;
     use StarcoinFramework::Signer;
@@ -34,7 +35,40 @@ module Block {
         uncles: u64,
     }
 
+    /// Block metadata struct.
+    // parents_hash is for FLexiDag block
+    struct BlockMetadataV2 has key {
+        /// number of the current block
+        number: u64,
+        /// Hash of the parent block.
+        parent_hash: vector<u8>,
+        /// Author of the current block.
+        author: address,
+        /// number of uncles.
+        uncles: u64,
+        /// An Array of the parents hash for a Dag block.
+        parents_hash: vector<u8>,
+        /// Handle of events when new blocks are emitted
+        new_block_events: Event::EventHandle<Self::NewBlockEventV2>,
+    }
+
+    /// Events emitted when new block generated.
+    // parents_hash is for FLexiDag block
+    struct NewBlockEventV2 has drop, store {
+        number: u64,
+        author: address,
+        timestamp: u64,
+        uncles: u64,
+        parents_hash: vector<u8>,
+    }
+
     const EBLOCK_NUMBER_MISMATCH: u64 = 17;
+    const ERROR_NOT_BLOCK_HEADER: u64 = 19;
+    const ERROR_INTERVAL_TOO_LITTLE: u64 = 20;
+
+    const CHECKPOINT_LENGTH: u64 = 60;
+    const BLOCK_HEADER_LENGTH: u64 = 247;
+    const BLOCK_INTERVAL_NUMBER: u64 = 5;
 
     /// This can only be invoked by the GENESIS_ACCOUNT at genesis
     public fun initialize(account: &signer, parent_hash: vector<u8>) {
@@ -45,7 +79,7 @@ module Block {
             account,
             BlockMetadata {
                 number: 0,
-                parent_hash: parent_hash,
+                parent_hash,
                 author: CoreAddresses::GENESIS_ADDRESS(),
                 uncles: 0,
                 new_block_events: Event::new_event_handle<Self::NewBlockEvent>(account),
@@ -58,63 +92,122 @@ module Block {
         aborts_if exists<BlockMetadata>(Signer::address_of(account));
     }
 
+    public fun initialize_blockmetadata_v2(account: &signer) acquires BlockMetadata {
+        CoreAddresses::assert_genesis_address(account);
+
+        let block_meta_ref = borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
+
+        // create new resource base on current block metadata
+        if (!exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS())) {
+            move_to<BlockMetadataV2>(
+                account,
+                BlockMetadataV2 {
+                    number: block_meta_ref.number,
+                    parent_hash: block_meta_ref.parent_hash,
+                    author: block_meta_ref.author,
+                    uncles: block_meta_ref.uncles,
+                    parents_hash: Vector::empty(),
+                    new_block_events: Event::new_event_handle<Self::NewBlockEventV2>(account),
+                });
+        }
+    }
+
+    spec initialize_blockmetadata_v2 {
+        aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+        aborts_if exists<BlockMetadata>(Signer::address_of(account));
+
+        ensures exists<BlockMetadataV2>(Signer::address_of(account));
+    }
+
     /// Get the current block number
-    public fun get_current_block_number(): u64 acquires BlockMetadata {
-      borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).number
+    public fun get_current_block_number(): u64 acquires BlockMetadataV2 {
+        borrow_global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).number
     }
 
     spec get_current_block_number {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
     }
 
     /// Get the hash of the parent block.
-    public fun get_parent_hash(): vector<u8> acquires BlockMetadata {
-      *&borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).parent_hash
+    public fun get_parent_hash(): vector<u8> acquires BlockMetadataV2 {
+        *&borrow_global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).parent_hash
     }
 
     spec get_parent_hash {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
     }
 
     /// Gets the address of the author of the current block
-    public fun get_current_author(): address acquires BlockMetadata {
-      borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).author
+    public fun get_current_author(): address acquires BlockMetadataV2 {
+        borrow_global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).author
     }
 
     spec get_current_author {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
+    }
+
+    public fun get_parents_hash(): vector<u8> acquires BlockMetadataV2 {
+        *&borrow_global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).parents_hash
+    }
+
+    spec get_parents_hash {
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
     }
 
     /// Call at block prologue
-    public fun process_block_metadata(account: &signer, parent_hash: vector<u8>,author: address, timestamp: u64, uncles:u64, number:u64) acquires BlockMetadata{
+    public fun process_block_metadata(account: &signer,
+                                      parent_hash: vector<u8>,
+                                      author: address,
+                                      timestamp: u64,
+                                      uncles: u64,
+                                      number: u64) acquires BlockMetadataV2 {
+        Self::process_block_metadata_v2(account, parent_hash, author, timestamp, uncles, number, Vector::empty<u8>())
+    }
+
+    spec process_block_metadata {
+        aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if number != global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).number + 1;
+    }
+
+    /// Call at block prologue for flexidag
+    public fun process_block_metadata_v2(account: &signer,
+                                         parent_hash: vector<u8>,
+                                         author: address,
+                                         timestamp: u64,
+                                         uncles: u64,
+                                         number: u64,
+                                         parents_hash: vector<u8>) acquires BlockMetadataV2 {
         CoreAddresses::assert_genesis_address(account);
 
-        let block_metadata_ref = borrow_global_mut<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
+        let block_metadata_ref = borrow_global_mut<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
         assert!(number == (block_metadata_ref.number + 1), Errors::invalid_argument(EBLOCK_NUMBER_MISMATCH));
         block_metadata_ref.number = number;
-        block_metadata_ref.author= author;
+        block_metadata_ref.author = author;
         block_metadata_ref.parent_hash = parent_hash;
         block_metadata_ref.uncles = uncles;
-
-        Event::emit_event<NewBlockEvent>(
-          &mut block_metadata_ref.new_block_events,
-          NewBlockEvent {
-              number: number,
-              author: author,
-              timestamp: timestamp,
-              uncles: uncles,
-          }
+        block_metadata_ref.parents_hash = parents_hash;
+
+        Event::emit_event<NewBlockEventV2>(
+            &mut block_metadata_ref.new_block_events,
+            NewBlockEventV2 {
+                number,
+                author,
+                timestamp,
+                uncles,
+                parents_hash,
+            }
         );
     }
 
-    spec process_block_metadata {
-        aborts_if Signer::address_of(account) != CoreAddresses::SPEC_GENESIS_ADDRESS();
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
-        aborts_if number != global<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS()).number + 1;
+    spec process_block_metadata_v2 {
+        aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if number != global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).number + 1;
     }
 
     spec schema AbortsIfBlockMetadataNotExist {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
     }
 }
-}
\ No newline at end of file
+}
diff --git a/release/v12/sources/TransactionManager.move b/release/v12/sources/TransactionManager.move
index cd9f44e1..0d572f3c 100644
--- a/release/v12/sources/TransactionManager.move
+++ b/release/v12/sources/TransactionManager.move
@@ -229,7 +229,7 @@ module TransactionManager {
 
         // then deal with current block.
         Timestamp::update_global_time(&account, timestamp);
-        Block::process_block_metadata(
+        Block::process_block_metadata_v2(
             &account,
             parent_hash,
             author,
diff --git a/sources/Block.move b/sources/Block.move
index ac4328a8..3b54221a 100644
--- a/sources/Block.move
+++ b/sources/Block.move
@@ -1,6 +1,7 @@
 address StarcoinFramework {
 /// Block module provide metadata for generated blocks.
 module Block {
+    use StarcoinFramework::Vector;
     use StarcoinFramework::Event;
     use StarcoinFramework::Timestamp;
     use StarcoinFramework::Signer;
@@ -34,7 +35,40 @@ module Block {
         uncles: u64,
     }
 
+    /// Block metadata struct.
+    // parents_hash is for FLexiDag block
+    struct BlockMetadataV2 has key {
+        /// number of the current block
+        number: u64,
+        /// Hash of the parent block.
+        parent_hash: vector<u8>,
+        /// Author of the current block.
+        author: address,
+        /// number of uncles.
+        uncles: u64,
+        /// An Array of the parents hash for a Dag block.
+        parents_hash: vector<u8>,
+        /// Handle of events when new blocks are emitted
+        new_block_events: Event::EventHandle<Self::NewBlockEventV2>,
+    }
+
+    /// Events emitted when new block generated.
+    // parents_hash is for FLexiDag block
+    struct NewBlockEventV2 has drop, store {
+        number: u64,
+        author: address,
+        timestamp: u64,
+        uncles: u64,
+        parents_hash: vector<u8>,
+    }
+
     const EBLOCK_NUMBER_MISMATCH: u64 = 17;
+    const ERROR_NOT_BLOCK_HEADER: u64 = 19;
+    const ERROR_INTERVAL_TOO_LITTLE: u64 = 20;
+
+    const CHECKPOINT_LENGTH: u64 = 60;
+    const BLOCK_HEADER_LENGTH: u64 = 247;
+    const BLOCK_INTERVAL_NUMBER: u64 = 5;
 
     /// This can only be invoked by the GENESIS_ACCOUNT at genesis
     public fun initialize(account: &signer, parent_hash: vector<u8>) {
@@ -45,7 +79,7 @@ module Block {
             account,
             BlockMetadata {
                 number: 0,
-                parent_hash: parent_hash,
+                parent_hash,
                 author: CoreAddresses::GENESIS_ADDRESS(),
                 uncles: 0,
                 new_block_events: Event::new_event_handle<Self::NewBlockEvent>(account),
@@ -58,35 +92,95 @@ module Block {
         aborts_if exists<BlockMetadata>(Signer::address_of(account));
     }
 
+    public fun initialize_blockmetadata_v2(account: &signer) acquires BlockMetadata {
+        CoreAddresses::assert_genesis_address(account);
+
+        let block_meta_ref = borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
+
+        // create new resource base on current block metadata
+        move_to<BlockMetadataV2>(
+            account,
+            BlockMetadataV2 {
+                number: block_meta_ref.number,
+                parent_hash: block_meta_ref.parent_hash,
+                author: block_meta_ref.author,
+                uncles: block_meta_ref.uncles,
+                parents_hash: Vector::empty(),
+                new_block_events: Event::new_event_handle<Self::NewBlockEventV2>(account),
+            });
+    }
+
+    spec initialize_blockmetadata_v2 {
+        aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+        aborts_if exists<BlockMetadata>(Signer::address_of(account));
+
+        ensures exists<BlockMetadataV2>(Signer::address_of(account));
+    }
+
     /// Get the current block number
-    public fun get_current_block_number(): u64 acquires BlockMetadata {
-      borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).number
+    public fun get_current_block_number(): u64 acquires BlockMetadataV2, BlockMetadata {
+        let addr = CoreAddresses::GENESIS_ADDRESS();
+        if (exists<BlockMetadataV2>(addr)) {
+            borrow_global<BlockMetadataV2>(addr).number
+        } else {
+            borrow_global<BlockMetadata>(addr).number
+        }
     }
 
     spec get_current_block_number {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
     }
 
     /// Get the hash of the parent block.
-    public fun get_parent_hash(): vector<u8> acquires BlockMetadata {
-      *&borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).parent_hash
+    public fun get_parent_hash(): vector<u8> acquires BlockMetadataV2, BlockMetadata {
+        let addr = CoreAddresses::GENESIS_ADDRESS();
+        if (exists<BlockMetadataV2>(addr)) {
+            *&borrow_global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).parent_hash
+        } else {
+            *&borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).parent_hash
+        }
     }
 
     spec get_parent_hash {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
     }
 
     /// Gets the address of the author of the current block
-    public fun get_current_author(): address acquires BlockMetadata {
-      borrow_global<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS()).author
+    public fun get_current_author(): address acquires BlockMetadataV2, BlockMetadata {
+        let addr = CoreAddresses::GENESIS_ADDRESS();
+        if (exists<BlockMetadataV2>(addr)) {
+            *&borrow_global<BlockMetadataV2>(addr).author
+        } else {
+            *&borrow_global<BlockMetadata>(addr).author
+        }
     }
 
     spec get_current_author {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
+    }
+
+    public fun get_parents_hash(): vector<u8> acquires BlockMetadataV2 {
+        let addr = CoreAddresses::GENESIS_ADDRESS();
+        if (exists<BlockMetadataV2>(addr)) {
+            *&borrow_global<BlockMetadataV2>(addr).parents_hash
+        } else {
+            Vector::empty()
+        }
+    }
+
+    spec get_parents_hash {
+        aborts_if !exists<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
     }
 
     /// Call at block prologue
-    public fun process_block_metadata(account: &signer, parent_hash: vector<u8>,author: address, timestamp: u64, uncles:u64, number:u64) acquires BlockMetadata{
+    public fun process_block_metadata(
+        account: &signer,
+        parent_hash: vector<u8>,
+        author: address,
+        timestamp: u64,
+        uncles: u64,
+        number: u64,
+    ) acquires BlockMetadata {
         CoreAddresses::assert_genesis_address(account);
 
         let block_metadata_ref = borrow_global_mut<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
@@ -97,24 +191,75 @@ module Block {
         block_metadata_ref.uncles = uncles;
 
         Event::emit_event<NewBlockEvent>(
-          &mut block_metadata_ref.new_block_events,
-          NewBlockEvent {
-              number: number,
-              author: author,
-              timestamp: timestamp,
-              uncles: uncles,
-          }
+            &mut block_metadata_ref.new_block_events,
+            NewBlockEvent {
+                number: number,
+                author: author,
+                timestamp: timestamp,
+                uncles: uncles,
+            }
         );
     }
 
     spec process_block_metadata {
-        aborts_if Signer::address_of(account) != CoreAddresses::SPEC_GENESIS_ADDRESS();
-        aborts_if !exists<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
-        aborts_if number != global<BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS()).number + 1;
+        aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if number != global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).number + 1;
+    }
+
+    /// Call at block prologue for flexidag
+    public fun process_block_metadata_v2(
+        account: &signer,
+        parent_hash: vector<u8>,
+        author: address,
+        timestamp: u64,
+        uncles: u64,
+        number: u64,
+        parents_hash: vector<u8>
+    ) acquires BlockMetadataV2, BlockMetadata {
+        CoreAddresses::assert_genesis_address(account);
+
+        let account_addr = Signer::address_of(account);
+        if (exists<BlockMetadataV2>(account_addr)) {
+            let block_metadata_ref = borrow_global_mut<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
+            assert!(number == (block_metadata_ref.number + 1), Errors::invalid_argument(EBLOCK_NUMBER_MISMATCH));
+            block_metadata_ref.number = number;
+            block_metadata_ref.author = author;
+            block_metadata_ref.parent_hash = parent_hash;
+            block_metadata_ref.uncles = uncles;
+            block_metadata_ref.parents_hash = parents_hash;
+
+            Event::emit_event<NewBlockEventV2>(
+                &mut block_metadata_ref.new_block_events,
+                NewBlockEventV2 {
+                    number,
+                    author,
+                    timestamp,
+                    uncles,
+                    parents_hash,
+                }
+            );
+        } else {
+            Self::process_block_metadata(
+                account,
+                parent_hash,
+                author,
+                timestamp,
+                uncles,
+                number
+            )
+        }
+
+    }
+
+    spec process_block_metadata_v2 {
+        aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if number != global<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS()).number + 1;
     }
 
     spec schema AbortsIfBlockMetadataNotExist {
-        aborts_if !exists<BlockMetadata>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if !exists<BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
     }
 }
-}
\ No newline at end of file
+}
diff --git a/sources/Epoch.move b/sources/Epoch.move
index 81e1d751..9afa3f47 100644
--- a/sources/Epoch.move
+++ b/sources/Epoch.move
@@ -1,12 +1,16 @@
 address StarcoinFramework {
 /// The module provide epoch functionality for starcoin.
 module Epoch {
+    use StarcoinFramework::FlexiDagConfig::FlexiDagConfig;
+    use StarcoinFramework::Math::u64_max;
+    use StarcoinFramework::Config::config_exist_by_address;
+    use StarcoinFramework::Errors;
+    use StarcoinFramework::FlexiDagConfig;
     use StarcoinFramework::Config;
     use StarcoinFramework::Signer;
     use StarcoinFramework::CoreAddresses;
 
     use StarcoinFramework::Event;
-    use StarcoinFramework::Errors;
     use StarcoinFramework::Timestamp;
     use StarcoinFramework::Math;
     use StarcoinFramework::Option;
@@ -153,14 +157,25 @@ module Epoch {
         CoreAddresses::assert_genesis_address(account);
 
         let epoch_ref = borrow_global_mut<Epoch>(CoreAddresses::GENESIS_ADDRESS());
-        assert!(epoch_ref.max_uncles_per_block >= uncles, Errors::invalid_argument(EINVALID_UNCLES_COUNT));
+        let flexidag_fork_height = if (config_exist_by_address<FlexiDagConfig>(CoreAddresses::GENESIS_ADDRESS())) {
+            FlexiDagConfig::effective_height(CoreAddresses::GENESIS_ADDRESS())
+        } else {
+            u64_max()
+        };
+        assert!(
+            block_number > flexidag_fork_height || epoch_ref.max_uncles_per_block >= uncles,
+            Errors::invalid_argument(EINVALID_UNCLES_COUNT)
+        );
 
         let epoch_data = borrow_global_mut<EpochData>(CoreAddresses::GENESIS_ADDRESS());
         let (new_epoch, reward_per_block) = if (block_number < epoch_ref.end_block_number) {
             (false, epoch_ref.reward_per_block)
         } else if (block_number == epoch_ref.end_block_number) {
             //start a new epoch
-            assert!(uncles == 0, Errors::invalid_argument(EINVALID_UNCLES_COUNT));
+            assert!(
+                block_number > flexidag_fork_height || uncles == 0,
+                Errors::invalid_argument(EINVALID_UNCLES_COUNT)
+            );
             // block time target unit is milli_seconds.
             let now_milli_seconds = timestamp;
 
@@ -377,4 +392,4 @@ module Epoch {
     }
 
 }
-}
\ No newline at end of file
+}
diff --git a/sources/FlexiDagConfig.move b/sources/FlexiDagConfig.move
new file mode 100644
index 00000000..4ac2c486
--- /dev/null
+++ b/sources/FlexiDagConfig.move
@@ -0,0 +1,52 @@
+address StarcoinFramework {
+    module FlexiDagConfig {
+
+        use StarcoinFramework::Config;
+        use StarcoinFramework::CoreAddresses;
+        use StarcoinFramework::Signer;
+
+        spec module {
+            pragma verify = false;
+            pragma aborts_if_is_strict;
+        }
+
+        /// The struct to hold all config data needed for Flexidag.
+        struct FlexiDagConfig has copy, drop, store {
+            // todo: double check, epoch might be better?
+            // the height of dag genesis block
+            effective_height:  u64,
+        }
+
+        /// Create a new configuration for flexidag, mainly used in DAO.
+        public fun new_flexidag_config(effective_height: u64): FlexiDagConfig {
+            FlexiDagConfig {
+                effective_height,
+            }
+        }
+
+        public fun initialize(account: &signer, effective_height: u64) {
+            CoreAddresses::assert_genesis_address(account);
+            Config::publish_new_config<FlexiDagConfig>(account, new_flexidag_config(effective_height));
+        }
+
+        spec initialize {
+            aborts_if Signer::address_of(account) != CoreAddresses::GENESIS_ADDRESS();
+            aborts_if exists<Config::Config<FlexiDagConfig>>(Signer::address_of(account));
+            aborts_if exists<Config::ModifyConfigCapabilityHolder<FlexiDagConfig>>(Signer::address_of(account));
+            ensures exists<Config::Config<FlexiDagConfig>>(Signer::address_of(account));
+            ensures
+                exists<Config::ModifyConfigCapabilityHolder<FlexiDagConfig>>(
+                    Signer::address_of(account),
+                );
+        }
+
+        public fun effective_height(account: address): u64 {
+            let flexi_dag_config = Config::get_by_address<FlexiDagConfig>(account);
+            flexi_dag_config.effective_height
+        }
+
+        spec effective_height {
+            include Config::AbortsIfConfigNotExist<FlexiDagConfig> { addr: account };
+        }
+    }
+}
diff --git a/sources/Genesis.move b/sources/Genesis.move
index 93328f81..92d0b9ca 100644
--- a/sources/Genesis.move
+++ b/sources/Genesis.move
@@ -104,6 +104,7 @@ module Genesis {
         ChainId::initialize(&genesis_account, chain_id);
         ConsensusStrategy::initialize(&genesis_account, strategy);
         Block::initialize(&genesis_account, parent_hash);
+
         TransactionPublishOption::initialize(
             &genesis_account,
             script_allowed,
@@ -447,7 +448,12 @@ module Genesis {
             GenesisNFT::initialize(&genesis_account, merkle_root, 1639u64, image);
         };
         StdlibUpgradeScripts::do_upgrade_from_v6_to_v7_with_language_version(&genesis_account, 6);
-        StdlibUpgradeScripts::do_upgrade_from_v11_to_v12(&genesis_account);
+
+        // stdlib_version == 0 is StdlibVersion::Latest
+        if (stdlib_version >= 12 || stdlib_version == 0) {
+            StdlibUpgradeScripts::do_upgrade_from_v11_to_v12(&genesis_account);
+        };
+
         // Initialize Frozen strategy
         FrozenConfigStrategy::do_initialize(&association);
         //Start time, Timestamp::is_genesis() will return false. this call should at the end of genesis init.
@@ -559,4 +565,4 @@ module Genesis {
         );
     }
 }
-}
\ No newline at end of file
+}
diff --git a/sources/OnChainConfigScripts.move b/sources/OnChainConfigScripts.move
index 4ce105e9..7bc0bc29 100644
--- a/sources/OnChainConfigScripts.move
+++ b/sources/OnChainConfigScripts.move
@@ -1,5 +1,6 @@
 address StarcoinFramework {
 module OnChainConfigScripts {
+    use StarcoinFramework::FlexiDagConfig;
     use StarcoinFramework::ConsensusConfig;
     use StarcoinFramework::OnChainConfigDao;
     use StarcoinFramework::STC;
@@ -119,6 +120,15 @@ module OnChainConfigScripts {
         pragma verify = false;
     }
 
+    public entry fun propose_update_flexi_dag_effective_height(account: signer, new_height: u64, exec_delay: u64) {
+        let config = FlexiDagConfig::new_flexidag_config(new_height);
+        OnChainConfigDao::propose_update<STC::STC, FlexiDagConfig::FlexiDagConfig>(&account, config, exec_delay);
+    }
+
+    spec propose_update_flexi_dag_effective_height {
+        pragma verify = false;
+    }
+
     public entry fun execute_on_chain_config_proposal<ConfigT: copy + drop + store>(account: signer, proposal_id: u64) {
         OnChainConfigDao::execute<STC::STC, ConfigT>(Signer::address_of(&account), proposal_id);
     }
diff --git a/sources/StdlibUpgradeScripts.move b/sources/StdlibUpgradeScripts.move
index 34f5260c..3e34cbb2 100644
--- a/sources/StdlibUpgradeScripts.move
+++ b/sources/StdlibUpgradeScripts.move
@@ -2,12 +2,15 @@ address StarcoinFramework {
 /// The module for StdlibUpgrade init scripts
 module StdlibUpgradeScripts {
 
+    use StarcoinFramework::Block;
     use StarcoinFramework::Errors;
     use StarcoinFramework::Signer;
     use StarcoinFramework::ChainId;
     use StarcoinFramework::Vector;
     use StarcoinFramework::ACL;
     use StarcoinFramework::FrozenConfigStrategy;
+        use StarcoinFramework::Math::u64_max;
+        use StarcoinFramework::FlexiDagConfig;
         use StarcoinFramework::CoreAddresses;
         use StarcoinFramework::STC::{Self, STC};
         use StarcoinFramework::Token::{Self, LinearTimeMintKey};
@@ -120,7 +123,11 @@ module StdlibUpgradeScripts {
         while (i < Vector::length(&acl_vec)) {
             STC::burn(Account::withdraw_illegal_token<STC>(sender, *Vector::borrow(&acl_vec, i), 0));
             i = i + 1;
-        }
+        };
+
+        FlexiDagConfig::initialize(sender, u64_max());
+        Block::initialize_blockmetadata_v2(sender);
+        OnChainConfigDao::plugin<STC, FlexiDagConfig::FlexiDagConfig>(sender);
     }
 
     /// Burned by user account
@@ -136,4 +143,4 @@ module StdlibUpgradeScripts {
         STC::burn(token);
     }
 }
-}
\ No newline at end of file
+}
diff --git a/sources/TransactionManager.move b/sources/TransactionManager.move
index bc9c726d..84517fb3 100644
--- a/sources/TransactionManager.move
+++ b/sources/TransactionManager.move
@@ -220,6 +220,28 @@ module TransactionManager {
         number: u64,
         chain_id: u8,
         parent_gas_used: u64,
+    ) {
+        Self::block_prologue_v2(account, parent_hash, timestamp, author, auth_key_vec, uncles, number, chain_id, parent_gas_used, Vector::empty<u8>())
+    }
+
+    spec block_prologue {
+        pragma verify = false;//fixme : timeout
+    }
+
+    /// Set the metadata for the current block and distribute transaction fees and block rewards.
+    /// The runtime always runs this before executing the transactions in a block.
+    /// For Flexidag block
+    public fun block_prologue_v2(
+        account: signer,
+        parent_hash: vector<u8>,
+        timestamp: u64,
+        author: address,
+        auth_key_vec: vector<u8>,
+        uncles: u64,
+        number: u64,
+        chain_id: u8,
+        parent_gas_used: u64,
+        parents_hash: vector<u8>,
     ) {
         // Can only be invoked by genesis account
         CoreAddresses::assert_genesis_address(&account);
@@ -232,20 +254,21 @@ module TransactionManager {
 
         // then deal with current block.
         Timestamp::update_global_time(&account, timestamp);
-        Block::process_block_metadata(
+        Block::process_block_metadata_v2(
             &account,
             parent_hash,
             author,
             timestamp,
             uncles,
             number,
+            parents_hash,
         );
         let reward = Epoch::adjust_epoch(&account, number, timestamp, uncles, parent_gas_used);
         // pass in previous block gas fees.
         BlockReward::process_block_reward(&account, number, reward, author, auth_key_vec, txn_fee);
     }
 
-    spec block_prologue {
+    spec block_prologue_v2 {
         pragma verify = false;//fixme : timeout
     }
 }
diff --git a/sources/TransactionTimeout.move b/sources/TransactionTimeout.move
index a4ff2b63..09c21da6 100644
--- a/sources/TransactionTimeout.move
+++ b/sources/TransactionTimeout.move
@@ -35,16 +35,16 @@ module TransactionTimeout {
     current_block_time < txn_timestamp && txn_timestamp < max_txn_time
   }
   spec is_valid_transaction_timestamp {
-    aborts_if !exists<Timestamp::CurrentTimeMilliseconds>(CoreAddresses::SPEC_GENESIS_ADDRESS());
-    aborts_if !exists<Block::BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+    aborts_if !exists<Timestamp::CurrentTimeMilliseconds>(CoreAddresses::GENESIS_ADDRESS());
+    aborts_if !exists<Block::BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
     include Timestamp::AbortsIfTimestampNotExists;
     aborts_if Block::get_current_block_number() != 0 && Timestamp::now_seconds() + TransactionTimeoutConfig::duration_seconds() > max_u64();
     aborts_if Block::get_current_block_number() != 0 && !exists<Config::Config<TransactionTimeoutConfig::TransactionTimeoutConfig>>(CoreAddresses::SPEC_GENESIS_ADDRESS());
   }
 
     spec schema AbortsIfTimestampNotValid {
-        aborts_if !exists<Timestamp::CurrentTimeMilliseconds>(CoreAddresses::SPEC_GENESIS_ADDRESS());
-        aborts_if !exists<Block::BlockMetadata>(CoreAddresses::SPEC_GENESIS_ADDRESS());
+        aborts_if !exists<Timestamp::CurrentTimeMilliseconds>(CoreAddresses::GENESIS_ADDRESS());
+        aborts_if !exists<Block::BlockMetadataV2>(CoreAddresses::GENESIS_ADDRESS());
         include Timestamp::AbortsIfTimestampNotExists;
         aborts_if Block::get_current_block_number() != 0 && Timestamp::now_seconds() + TransactionTimeoutConfig::duration_seconds() > max_u64();
         aborts_if Block::get_current_block_number() != 0 && !exists<Config::Config<TransactionTimeoutConfig::TransactionTimeoutConfig>>(CoreAddresses::SPEC_GENESIS_ADDRESS());