add fee-aware mining, coinbase validation, and reorg-safe orphan handling

Mining: blocks now include mempool txs, select spendable txs by fee, and pay coinbase as base reward + fees in main.c.
 - Consensus: block validation now enforces coinbase accounting and rejects invalid coinbase placement, including coinbase on amount2, in block.c and transaction.c.
 - Chain state: rollback now rebuilds currentSupply/currentReward, and block addition preflights spendability before mutating balances in chain.c.
 - Orphans/reorgs: orphan retry is safer, rollback-triggered sync reattaches orphans immediately, and transient orphan failures no longer drop blocks in orphan_pool.c and main.c.
 - Networking/mempool: node lifecycle now initializes the mempool, broadcasts can exclude one peer, and mempool snapshotting supports mining selection in net_node.c and txmempool.c.
 - Ledger simulation: added non-mutating spendable-transaction selection for block assembly in balance_sheet.c.

TODO.txt

@@ -17,6 +17,11 @@ A loophole in the reorg penalty system could potentially exist where someone bro
 TO TEST:
 Implement Horizen's "Reorg Penalty" system to make it harder for the young chain to be attacked by a powerful miner.
 
+NOTE:
+Because tx sizes are currently fixed, mining can use raw fee ordering for now. If tx sizes ever become dynamic, revisit selection to consider fee/byte instead.
+
+Mempool snapshotting for mining should hold the lock only long enough to copy pending txs, but if the mempool grows very large that copy may still be non-trivial.
+
 DONE:
 I want to move away from the Monero emission. I want to do something a bit radical for cryptocurrency, but I feel like it's necessary to make it more like money:
 a constant inflation rate of 1.5% per year. It's lower than fiat (USD is ~2.8% per year), and it additionally doesn't fluctuate during crisis. It's constant.

include/balance_sheet.h

@@ -8,6 +8,7 @@
 #include <stdio.h>
 #include <khash/khash.h>
 #include <crypto/crypto.h>
+#include <block/transaction.h>
 #include <string.h>
 #include <utils.h>
 #include <uint256.h>
@@ -29,4 +30,12 @@ bool BalanceSheet_LoadFromFile(const char* inPath);
 void BalanceSheet_Print();
 void BalanceSheet_Destroy();
 
+bool BalanceSheet_SelectSpendableTransactions(
+    const signed_transaction_t* candidates,
+    size_t candidateCount,
+    signed_transaction_t** outAccepted,
+    size_t* outAcceptedCount,
+    uint64_t* outTotalFees
+);
+
 #endif

include/block/block.h

@@ -36,6 +36,7 @@ void Block_AddTransaction(block_t* block, signed_transaction_t* tx);
 void Block_RemoveTransaction(block_t* block, uint8_t* txHash);
 bool Block_HasValidProofOfWork(const block_t* block);
 bool Block_AllTransactionsValid(const block_t* block);
+bool Block_ValidateCoinbaseAndFees(const block_t* block, uint64_t expectedCoinbaseAmount, uint64_t* outTotalFees);
 bool Block_IsFullyValid(const block_t* block);
 void Block_ShutdownPowContext(void);
 void Block_Destroy(block_t* block);

include/nets/net_node.h

@@ -57,7 +57,7 @@ int Node_ConnectPeer(net_node_t* node, const char* ip, unsigned short port);
 int Node_ConnectStartupPeers(net_node_t* node, const char** ips, const unsigned short* ports, size_t peersCount);
 
 int Node_SendPacket(net_node_t* node, tcp_connection_t* conn, packet_type_t packetType, const void* payload, size_t payloadLen);
-int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx);
+int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx, tcp_connection_t* excludeNode);
 
 // Helpers for outbound peer selection and block broadcast
 int Node_GetBestOutboundPeer(net_node_t* node, tcp_connection_t** outConn, uint64_t* outHeight);

include/txmempool.h

@@ -13,6 +13,7 @@ void TxMempool_Init();
 // Assumed that the transation was confirmed to be valid
 int TxMempool_Insert(signed_transaction_t tx);
 bool TxMempool_Lookup(uint8_t* txHash, signed_transaction_t* out);
+bool TxMempool_Snapshot(signed_transaction_t** outTxs, size_t* outCount);
 void TxMempool_Print();
 void TxMempool_Destroy();
 

src/balance_sheet.c

@@ -4,6 +4,140 @@
 khash_t(balance_sheet_map_m)* sheetMap = NULL;
 static pthread_mutex_t g_sheetLock;
 
+static bool BalanceSheet_GetSimEntry(
+    khash_t(balance_sheet_map_m)* simMap,
+    const uint8_t address[32],
+    balance_sheet_entry_t* out
+) {
+    if (!simMap || !address || !out) {
+        return false;
+    }
+
+    key32_t key;
+    memcpy(key.bytes, address, 32);
+
+    khiter_t k = kh_get(balance_sheet_map_m, simMap, key);
+    if (k != kh_end(simMap)) {
+        *out = kh_value(simMap, k);
+        return true;
+    }
+
+    if (BalanceSheet_Lookup((uint8_t*)address, out)) {
+        int ret = 0;
+        k = kh_put(balance_sheet_map_m, simMap, key, &ret);
+        if (k == kh_end(simMap)) {
+            return false;
+        }
+        kh_value(simMap, k) = *out;
+        return true;
+    }
+
+    memset(out, 0, sizeof(*out));
+    memcpy(out->address, address, 32);
+    out->balance = uint256_from_u64(0);
+
+    int ret = 0;
+    k = kh_put(balance_sheet_map_m, simMap, key, &ret);
+    if (k == kh_end(simMap)) {
+        return false;
+    }
+
+    kh_value(simMap, k) = *out;
+    return true;
+}
+
+static bool BalanceSheet_StoreSimEntry(
+    khash_t(balance_sheet_map_m)* simMap,
+    const balance_sheet_entry_t* entry
+) {
+    if (!simMap || !entry) {
+        return false;
+    }
+
+    key32_t key;
+    memcpy(key.bytes, entry->address, 32);
+
+    int ret = 0;
+    khiter_t k = kh_put(balance_sheet_map_m, simMap, key, &ret);
+    if (k == kh_end(simMap)) {
+        return false;
+    }
+
+    kh_value(simMap, k) = *entry;
+    return true;
+}
+
+static bool BalanceSheet_ApplyCandidateTransaction(
+    khash_t(balance_sheet_map_m)* simMap,
+    const signed_transaction_t* tx,
+    uint64_t* outFee
+) {
+    if (!simMap || !tx) {
+        return false;
+    }
+
+    if (Address_IsCoinbase(tx->transaction.senderAddress)) {
+        return true;
+    }
+
+    if (!Transaction_Verify(tx)) {
+        return false;
+    }
+
+    balance_sheet_entry_t senderEntry;
+    if (!BalanceSheet_GetSimEntry(simMap, tx->transaction.senderAddress, &senderEntry)) {
+        return false;
+    }
+
+    uint256_t spend = uint256_from_u64(0);
+    if (uint256_add_u64(&spend, tx->transaction.amount1) ||
+        uint256_add_u64(&spend, tx->transaction.amount2) ||
+        uint256_add_u64(&spend, tx->transaction.fee)) {
+        return false;
+    }
+
+    if (uint256_cmp(&senderEntry.balance, &spend) < 0) {
+        return false;
+    }
+
+    if (!uint256_subtract(&senderEntry.balance, &spend)) {
+        return false;
+    }
+    if (!BalanceSheet_StoreSimEntry(simMap, &senderEntry)) {
+        return false;
+    }
+
+    balance_sheet_entry_t recipient1Entry;
+    if (!BalanceSheet_GetSimEntry(simMap, tx->transaction.recipientAddress1, &recipient1Entry)) {
+        return false;
+    }
+    if (uint256_add_u64(&recipient1Entry.balance, tx->transaction.amount1)) {
+        return false;
+    }
+    if (!BalanceSheet_StoreSimEntry(simMap, &recipient1Entry)) {
+        return false;
+    }
+
+    if (tx->transaction.amount2 > 0) {
+        balance_sheet_entry_t recipient2Entry;
+        if (!BalanceSheet_GetSimEntry(simMap, tx->transaction.recipientAddress2, &recipient2Entry)) {
+            return false;
+        }
+        if (uint256_add_u64(&recipient2Entry.balance, tx->transaction.amount2)) {
+            return false;
+        }
+        if (!BalanceSheet_StoreSimEntry(simMap, &recipient2Entry)) {
+            return false;
+        }
+    }
+
+    if (outFee) {
+        *outFee = tx->transaction.fee;
+    }
+
+    return true;
+}
+
 static int BalanceSheet_InsertLocked(balance_sheet_entry_t entry) {
     if (!sheetMap) {
         return -1;
@@ -143,3 +277,64 @@ void BalanceSheet_Destroy() {
     sheetMap = NULL;
     pthread_mutex_destroy(&g_sheetLock);
 }
+
+bool BalanceSheet_SelectSpendableTransactions(
+    const signed_transaction_t* candidates,
+    size_t candidateCount,
+    signed_transaction_t** outAccepted,
+    size_t* outAcceptedCount,
+    uint64_t* outTotalFees
+) {
+    if (!outAccepted || !outAcceptedCount || !outTotalFees) {
+        return false;
+    }
+
+    *outAccepted = NULL;
+    *outAcceptedCount = 0;
+    *outTotalFees = 0;
+
+    if (!candidates || candidateCount == 0) {
+        return true;
+    }
+
+    signed_transaction_t* accepted = (signed_transaction_t*)calloc(candidateCount, sizeof(signed_transaction_t));
+    if (!accepted) {
+        return false;
+    }
+
+    khash_t(balance_sheet_map_m)* simMap = kh_init(balance_sheet_map_m);
+    if (!simMap) {
+        free(accepted);
+        return false;
+    }
+
+    size_t acceptedCount = 0;
+    uint64_t totalFees = 0;
+
+    for (size_t i = 0; i < candidateCount; ++i) {
+        const signed_transaction_t* tx = &candidates[i];
+        if (Address_IsCoinbase(tx->transaction.senderAddress)) {
+            continue;
+        }
+
+        uint64_t fee = 0;
+        if (!BalanceSheet_ApplyCandidateTransaction(simMap, tx, &fee)) {
+            continue;
+        }
+
+        accepted[acceptedCount++] = *tx;
+        totalFees += fee;
+    }
+
+    kh_destroy(balance_sheet_map_m, simMap);
+
+    if (acceptedCount == 0) {
+        free(accepted);
+        accepted = NULL;
+    }
+
+    *outAccepted = accepted;
+    *outAcceptedCount = acceptedCount;
+    *outTotalFees = totalFees;
+    return true;
+}

src/block/block.c

@@ -214,23 +214,88 @@ bool Block_AllTransactionsValid(const block_t* block) {
 
     for (size_t i = 0; i < DynArr_size(block->transactions); i++) {
         signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(block->transactions, i);
+        if (!Transaction_Verify(tx)) {
+            return false;
+        }
+
         if (tx && Address_IsCoinbase(tx->transaction.senderAddress)) {
             if (hasCoinbase) {
-                return false; // More than one coinbase transaction
+                return false;
             }
 
             hasCoinbase = true;
-            continue; // Coinbase transactions are valid since the miner has the right to create coins. Only rule is one per block.
-        }
-        
-        if (!Transaction_Verify(tx)) {
-            return false;
         }
     }
 
     return true && hasCoinbase && DynArr_size(block->transactions) > 0; // Every block must have at least one transaction (the coinbase)
 }
 
+bool Block_ValidateCoinbaseAndFees(const block_t* block, uint64_t expectedCoinbaseAmount, uint64_t* outTotalFees) {
+    if (!block || !block->transactions) {
+        return false;
+    }
+
+    bool hasCoinbase = false;
+    uint64_t totalFees = 0;
+    uint8_t zeroAddress[32] = {0};
+
+    for (size_t i = 0; i < DynArr_size(block->transactions); ++i) {
+        signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(block->transactions, i);
+        if (!tx) {
+            return false;
+        }
+
+        if (Address_IsCoinbase(tx->transaction.senderAddress)) {
+            if (hasCoinbase) {
+                return false;
+            }
+
+            hasCoinbase = true;
+
+            if (!Transaction_Verify(tx)) {
+                return false;
+            }
+
+            if (tx->transaction.fee != 0 || tx->transaction.amount2 != 0) {
+                return false;
+            }
+
+            if (tx->transaction.amount1 != expectedCoinbaseAmount) {
+                return false;
+            }
+
+            if (Address_IsCoinbase(tx->transaction.recipientAddress1)) {
+                return false;
+            }
+
+            if (memcmp(tx->transaction.recipientAddress2, zeroAddress, sizeof(zeroAddress)) != 0) {
+                return false;
+            }
+
+            continue;
+        }
+
+        if (!Transaction_Verify(tx)) {
+            return false;
+        }
+
+        if (UINT64_MAX - totalFees < tx->transaction.fee) {
+            return false;
+        }
+        totalFees += tx->transaction.fee;
+    }
+
+    if (!hasCoinbase) {
+        return false;
+    }
+
+    if (outTotalFees) {
+        *outTotalFees = totalFees;
+    }
+
+    return true;
+}
+
 bool Block_IsFullyValid(const block_t* block) {
     bool merkleValid = false;
     uint8_t calculatedMerkleRoot[32];

src/block/chain.c

@@ -97,6 +97,37 @@ static bool DebitAddress(const uint8_t address[32], const uint256_t* amount) {
     return BalanceSheet_Insert(entry) >= 0;
 }
 
+static bool Chain_RecomputeRuntimeState(blockchain_t* chain) {
+    if (!chain) {
+        return false;
+    }
+
+    uint256_t rebuiltSupply = uint256_from_u64(0);
+    for (size_t i = 0; i < chain->size; ++i) {
+        block_t* blk = (block_t*)DynArr_at(chain->blocks, i);
+        if (!blk || !blk->transactions) {
+            return false;
+        }
+
+        for (size_t j = 0; j < DynArr_size(blk->transactions); ++j) {
+            signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(blk->transactions, j);
+            if (!tx) {
+                return false;
+            }
+
+            if (Address_IsCoinbase(tx->transaction.senderAddress)) {
+                if (uint256_add_u64(&rebuiltSupply, tx->transaction.amount1)) {
+                    return false;
+                }
+            }
+        }
+    }
+
+    currentSupply = rebuiltSupply;
+    currentReward = CalculateBlockReward(currentSupply, chain);
+    return true;
+}
+
 static void Chain_ClearBlocks(blockchain_t* chain) {
     if (!chain || !chain->blocks) {
         return;
@@ -161,34 +192,65 @@ bool Chain_AddBlock(blockchain_t* chain, block_t* block) {
     }
 
     do {
-        // First pass: ensure all non-coinbase senders can cover the full spend
-        // (amount1 + amount2 + fee) before mutating the chain or balance sheet.
         size_t txCount = DynArr_size(block->transactions);
+        signed_transaction_t* candidateTxs = (signed_transaction_t*)calloc(txCount, sizeof(signed_transaction_t));
+        if (!candidateTxs) {
+            ok = false;
+            break;
+        }
+
+        size_t nonCoinbaseCount = 0;
         for (size_t i = 0; i < txCount; ++i) {
             signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(block->transactions, i);
             if (!tx) {
-                ok = false; break;
+                ok = false;
+                break;
             }
 
-            if (Address_IsCoinbase(tx->transaction.senderAddress)) {
-                continue;
-            }
-
-            uint256_t spend;
-            if (!BuildSpendAmount(tx, &spend)) { ok = false; break; }
-
-            balance_sheet_entry_t senderEntry;
-            if (!BalanceSheet_Lookup(tx->transaction.senderAddress, &senderEntry)) {
-                fprintf(stderr, "Error: Sender address not found in balance sheet during block addition. Bailing!\n");
-                ok = false; break;
-            }
-
-            if (uint256_cmp(&senderEntry.balance, &spend) < 0) {
-                fprintf(stderr, "Error: Sender balance insufficient for block transaction. Bailing!\n");
-                ok = false; break;
+            candidateTxs[i] = *tx;
+            if (!Address_IsCoinbase(tx->transaction.senderAddress)) {
+                ++nonCoinbaseCount;
             }
         }
-        if (!ok) break;
+
+        if (!ok) {
+            free(candidateTxs);
+            break;
+        }
+
+        signed_transaction_t* spendableTxs = NULL;
+        size_t spendableCount = 0;
+        uint64_t totalFees = 0;
+        if (!BalanceSheet_SelectSpendableTransactions(candidateTxs, txCount, &spendableTxs, &spendableCount, &totalFees)) {
+            free(candidateTxs);
+            ok = false;
+            break;
+        }
+
+        free(candidateTxs);
+
+        if (spendableCount != nonCoinbaseCount) {
+            free(spendableTxs);
+            ok = false;
+            break;
+        }
+
+        uint64_t expectedCoinbaseAmount = currentReward;
+        if (UINT64_MAX - expectedCoinbaseAmount < totalFees) {
+            free(spendableTxs);
+            ok = false;
+            break;
+        }
+        expectedCoinbaseAmount += totalFees;
+
+        uint64_t observedFees = 0;
+        if (!Block_ValidateCoinbaseAndFees(block, expectedCoinbaseAmount, &observedFees) || observedFees != totalFees) {
+            free(spendableTxs);
+            ok = false;
+            break;
+        }
+
+        free(spendableTxs);
 
         // Push the block only after validation succeeds.
         block_t* blk = (block_t*)DynArr_push_back(chain->blocks, block);
@@ -434,6 +496,12 @@ bool Chain_RollbackToHeight(blockchain_t* chain, size_t height) {
         }
     }
 
+    if (!Chain_RecomputeRuntimeState(chain)) {
+        pthread_mutex_unlock(&balanceSheetLock);
+        pthread_rwlock_unlock(&chainLock);
+        return false;
+    }
+
     pthread_mutex_unlock(&balanceSheetLock);
     pthread_rwlock_unlock(&chainLock);
 

src/block/transaction.c

@@ -42,7 +42,23 @@ bool Transaction_Verify(const signed_transaction_t* tx) {
     }
 
     if (Address_IsCoinbase(tx->transaction.senderAddress)) {
-        // Coinbase transactions are valid if the signature is correct for the block (handled in Block_Verify)
+        if (tx->transaction.amount1 == 0) {
+            return false;
+        }
+
+        if (tx->transaction.amount2 != 0) {
+            return false;
+        }
+
+        if (Address_IsCoinbase(tx->transaction.recipientAddress1) || Address_IsCoinbase(tx->transaction.recipientAddress2)) {
+            return false;
+        }
+
+        uint8_t zeroAddress[32] = {0};
+        if (memcmp(tx->transaction.recipientAddress2, zeroAddress, 32) != 0) {
+            return false;
+        }
+
         return true;
     }
 

src/main.c

@@ -147,6 +147,63 @@ static void AddCoinbaseTransaction(block_t* block, const uint8_t minerAddress[32
     Block_AddTransaction(block, &coinbaseTx);
 }
 
+static int CompareTransactionPriority(const void* lhs, const void* rhs) {
+    const signed_transaction_t* left = (const signed_transaction_t*)lhs;
+    const signed_transaction_t* right = (const signed_transaction_t*)rhs;
+
+    if (left->transaction.fee > right->transaction.fee) {
+        return -1;
+    }
+    if (left->transaction.fee < right->transaction.fee) {
+        return 1;
+    }
+
+    uint8_t leftHash[32];
+    uint8_t rightHash[32];
+    Transaction_CalculateHash(left, leftHash);
+    Transaction_CalculateHash(right, rightHash);
+    return memcmp(leftHash, rightHash, sizeof(leftHash));
+}
+
+static bool BuildSpendableMempoolSelection(
+    signed_transaction_t** outAcceptedTxs,
+    size_t* outAcceptedCount,
+    uint64_t* outTotalFees
+) {
+    if (!outAcceptedTxs || !outAcceptedCount || !outTotalFees) {
+        return false;
+    }
+
+    *outAcceptedTxs = NULL;
+    *outAcceptedCount = 0;
+    *outTotalFees = 0;
+
+    signed_transaction_t* snapshot = NULL;
+    size_t snapshotCount = 0;
+    if (!TxMempool_Snapshot(&snapshot, &snapshotCount)) {
+        return false;
+    }
+
+    if (snapshot && snapshotCount > 1) {
+        qsort(snapshot, snapshotCount, sizeof(signed_transaction_t), CompareTransactionPriority);
+    }
+
+    signed_transaction_t* acceptedTxs = NULL;
+    size_t acceptedCount = 0;
+    uint64_t totalFees = 0;
+    bool ok = BalanceSheet_SelectSpendableTransactions(snapshot, snapshotCount, &acceptedTxs, &acceptedCount, &totalFees);
+    free(snapshot);
+    if (!ok) {
+        free(acceptedTxs);
+        return false;
+    }
+
+    *outAcceptedTxs = acceptedTxs;
+    *outAcceptedCount = acceptedCount;
+    *outTotalFees = totalFees;
+    return true;
+}
+
 static void PrintBlockDetail(const block_t* block, size_t txCount, const uint8_t canonicalHash[32], const uint8_t powHash[32]) {
     if (!block) {
         return;
@@ -301,6 +358,46 @@ static bool ComputeHistoricalAutolykosHashFromDisk(const char* chainDataDir, uin
     return ok;
 }
 
+static bool Block_GetCoinbaseAndFeeTotals(const block_t* block, uint64_t* outCoinbaseAmount, uint64_t* outTotalFees) {
+    if (!block || !block->transactions || !outCoinbaseAmount || !outTotalFees) {
+        return false;
+    }
+
+    bool hasCoinbase = false;
+    uint64_t coinbaseAmount = 0;
+    uint64_t totalFees = 0;
+
+    for (size_t i = 0; i < DynArr_size(block->transactions); ++i) {
+        signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(block->transactions, i);
+        if (!tx) {
+            return false;
+        }
+
+        if (Address_IsCoinbase(tx->transaction.senderAddress)) {
+            if (hasCoinbase) {
+                return false;
+            }
+
+            hasCoinbase = true;
+            coinbaseAmount = tx->transaction.amount1;
+            continue;
+        }
+
+        if (UINT64_MAX - totalFees < tx->transaction.fee) {
+            return false;
+        }
+        totalFees += tx->transaction.fee;
+    }
+
+    if (!hasCoinbase) {
+        return false;
+    }
+
+    *outCoinbaseAmount = coinbaseAmount;
+    *outTotalFees = totalFees;
+    return true;
+}
+
 static bool MineAndAppendBlock(blockchain_t* chain,
                                block_t* block,
                                uint256_t* currentSupply,
@@ -404,6 +501,7 @@ static bool VerifyChainFully(blockchain_t* chain) {
     blockchain_t* prevChain = Chain_Create();
     if (!prevChain) { return false; }
 
+    uint256_t replaySupply = uint256_from_u64(0);
     uint32_t expectedDifficulty = INITIAL_DIFFICULTY;
     for (size_t i = 0; i < chainSize; ++i) {
         block_t* blk = NULL;
@@ -480,12 +578,31 @@ static bool VerifyChainFully(blockchain_t* chain) {
             return false;
         }
 
+        uint64_t expectedReward = 0;
+        uint64_t savedReward = currentReward;
+        expectedReward = CalculateBlockReward(replaySupply, prevChain);
+        currentReward = savedReward;
+
         if (!Block_AllTransactionsValid(blk)) {
             Block_Destroy(blk);
             Chain_Destroy(prevChain);
             return false;
         }
 
+        uint64_t coinbaseAmount = 0;
+        uint64_t totalFees = 0;
+        if (!Block_GetCoinbaseAndFeeTotals(blk, &coinbaseAmount, &totalFees)) {
+            Block_Destroy(blk);
+            Chain_Destroy(prevChain);
+            return false;
+        }
+
+        if (UINT64_MAX - expectedReward < totalFees || coinbaseAmount != (expectedReward + totalFees)) {
+            Block_Destroy(blk);
+            Chain_Destroy(prevChain);
+            return false;
+        }
+
         uint8_t expectedMerkle[32];
         Block_CalculateMerkleRoot(blk, expectedMerkle);
         if (memcmp(blk->header.merkleRoot, expectedMerkle, sizeof(expectedMerkle)) != 0) {
@@ -508,6 +625,8 @@ static bool VerifyChainFully(blockchain_t* chain) {
         headerOnly.transactions = NULL;
         (void)DynArr_push_back(prevChain->blocks, &headerOnly);
 
+        (void)uint256_add_u64(&replaySupply, coinbaseAmount);
+
         Block_Destroy(blk);
     }
 
@@ -746,14 +865,38 @@ int main(int argc, char* argv[]) {
             printf("Mining %llu block(s)...\n", requested);
             bool minedAll = true;
             for (unsigned long long i = 0; i < requested; ++i) {
-                block_t* block = BuildNextBlock(chain, difficultyTarget);
-                if (!block) {
-                    fprintf(stderr, "failed to create block\n");
+                signed_transaction_t* acceptedTxs = NULL;
+                size_t acceptedTxCount = 0;
+                uint64_t totalFees = 0;
+                if (!BuildSpendableMempoolSelection(&acceptedTxs, &acceptedTxCount, &totalFees)) {
+                    fprintf(stderr, "failed to select spendable transactions from mempool\n");
                     minedAll = false;
                     break;
                 }
 
-                AddCoinbaseTransaction(block, minerAddress, currentReward);
+                block_t* block = BuildNextBlock(chain, difficultyTarget);
+                if (!block) {
+                    fprintf(stderr, "failed to create block\n");
+                    free(acceptedTxs);
+                    minedAll = false;
+                    break;
+                }
+
+                uint64_t coinbaseAmount = currentReward;
+                if (UINT64_MAX - coinbaseAmount < totalFees) {
+                    free(acceptedTxs);
+                    Block_Destroy(block);
+                    minedAll = false;
+                    break;
+                }
+                coinbaseAmount += totalFees;
+
+                AddCoinbaseTransaction(block, minerAddress, coinbaseAmount);
+
+                for (size_t txIndex = 0; txIndex < acceptedTxCount; ++txIndex) {
+                    Block_AddTransaction(block, &acceptedTxs[txIndex]);
+                }
+                free(acceptedTxs);
 
                 if (!MineAndAppendBlock(chain, block, &currentSupply, &currentReward, &difficultyTarget)) {
                     Block_Destroy(block);
@@ -822,7 +965,8 @@ int main(int argc, char* argv[]) {
                 continue;
             }
 
-            AddCoinbaseTransaction(block, minerAddress, currentReward);
+            uint64_t coinbaseAmount = currentReward;
+            AddCoinbaseTransaction(block, minerAddress, coinbaseAmount);
 
             signed_transaction_t spendTx;
             Transaction_Init(&spendTx);
@@ -865,7 +1009,7 @@ int main(int argc, char* argv[]) {
             
             printf("transaction added to mempool, broadcasting...\n");
 
-            if (Node_BroadcastTransaction(node, &spendTx) == 0) {
+            if (Node_BroadcastTransaction(node, &spendTx, NULL) == 0) {
                 printf("transaction broadcast to peers\n");
             } else {
                 printf("failed to broadcast transaction to peers\n");
@@ -1031,6 +1175,11 @@ int main(int argc, char* argv[]) {
                                     break;
                                 }
 
+                                size_t reattached = OrphanPool_AttemptAttach(chain);
+                                if (reattached > 0) {
+                                    printf("Reorg rollback attached %zu orphan(s)\n", reattached);
+                                }
+
                                 // Apply additional penalty by shrinking end and restart window from current Chain_Size
                                 if (peerHeight > reorgPenalty) {
                                     end = peerHeight - reorgPenalty;

src/nets/net_node.c

@@ -177,6 +177,20 @@ static node_block_accept_result_t Node_ParseAndAcceptBlock(const unsigned char*
         return NODE_BLOCK_REJECTED;
     }
 
+    uint64_t coinbaseAmount = 0;
+    if (blk->transactions) {
+        for (size_t i = 0; i < DynArr_size(blk->transactions); ++i) {
+            signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(blk->transactions, i);
+            if (tx && Address_IsCoinbase(tx->transaction.senderAddress)) {
+                coinbaseAmount = tx->transaction.amount1;
+                break;
+            }
+        }
+    }
+
+    (void)uint256_add_u64(&currentSupply, coinbaseAmount);
+    currentReward = CalculateBlockReward(currentSupply, currentChain);
+
     // Persist on accept if requested
     if (persist) {
         Chain_SaveToFile(currentChain, chainDataDir, currentSupply, currentReward);
@@ -387,7 +401,7 @@ int Node_SendPacket(net_node_t* node, tcp_connection_t* conn, packet_type_t pack
     return rc;
 }
 
-int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx) {
+int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx, tcp_connection_t* excludeNode) {
     if (!node || !tx) {
         return -1;
     }
@@ -403,8 +417,9 @@ int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx) {
     // Broadcast to all outbound peers
     pthread_mutex_lock(&node->outboundLock);
     for (size_t i = 0; i < MAX_CONS; ++i) {
-        if (node->outboundClients[i].connection) {
-            (void)Node_SendPacket(node, node->outboundClients[i].connection, PACKET_TYPE_BROADCAST_TX, payload, payloadLen);
+        tcp_connection_t* connection = node->outboundClients[i].connection;
+        if (connection && connection != excludeNode) {
+            (void)Node_SendPacket(node, connection, PACKET_TYPE_BROADCAST_TX, payload, payloadLen);
         }
     }
     pthread_mutex_unlock(&node->outboundLock);
@@ -646,7 +661,7 @@ void Node_Server_OnData(tcp_connection_t* client) {
                         // Broadcast to other peers
                         net_node_t* node = Node_FromConnection(client);
                         if (node) {
-                            Node_BroadcastTransaction(node, &tx);
+                            Node_BroadcastTransaction(node, &tx, client);
                         }
                     } else {
                         printf("Failed to add transaction %s from node %u to mempool\n", txHashHex, client ? client->connectionId : 0U);

src/nets/orphan_pool.c

@@ -197,13 +197,8 @@ size_t OrphanPool_AttemptAttach(blockchain_t* chain) {
                     i = (size_t)-1; // reset outer loop
                     break;
                 } else {
-                    // Chain_AddBlock rejected it (maybe invalid). Drop it.
-                    Block_Destroy(e->block);
-                    DynArr_remove(g_orphans, i);
-                    n = DynArr_size(g_orphans);
-                    i = (size_t)-1;
-                    madeProgress = true;
-                    break;
+                    // Keep the orphan around; rejection may be temporary while the local tip is being reorged.
+                    continue;
                 }
             }
         }

src/txmempool.c

@@ -1,14 +1,21 @@
 #include <txmempool.h>
+#include <pthread.h>
+
+static pthread_mutex_t g_txMempoolLock;
+static bool g_txMempoolLockInitialized = false;
 
 khash_t(tx_mempool_map_m)* txMempool = NULL;
 
 void TxMempool_Init() {
     txMempool = kh_init(tx_mempool_map_m);
+    pthread_mutex_init(&g_txMempoolLock, NULL);
+    g_txMempoolLockInitialized = true;
 }
 
 int TxMempool_Insert(signed_transaction_t tx) {
     if (!txMempool) { return -1; }
 
+    pthread_mutex_lock(&g_txMempoolLock);
     uint8_t txHash[32];
     Transaction_CalculateHash(&tx, txHash);
 
@@ -18,17 +25,21 @@ int TxMempool_Insert(signed_transaction_t tx) {
     int ret;
     khiter_t k = kh_put(tx_mempool_map_m, txMempool, key, &ret);
     if (k == kh_end(txMempool)) {
+        pthread_mutex_unlock(&g_txMempoolLock);
         return -1;
     }
 
     kh_value(txMempool, k) = tx;
 
+    pthread_mutex_unlock(&g_txMempoolLock);
+
     return ret;
 }
 
 bool TxMempool_Lookup(uint8_t* txHash, signed_transaction_t* out) {
     if (!txMempool || !txHash || !out) { return false; }
     
+    pthread_mutex_lock(&g_txMempoolLock);
     key32_t key;
     memcpy(key.bytes, txHash, 32);
 
@@ -36,15 +47,65 @@ bool TxMempool_Lookup(uint8_t* txHash, signed_transaction_t* out) {
     if (k != kh_end(txMempool)) {
         signed_transaction_t tx = kh_value(txMempool, k);
         memcpy(out, &tx, sizeof(signed_transaction_t));
+        pthread_mutex_unlock(&g_txMempoolLock);
         return true;
     }
 
+    pthread_mutex_unlock(&g_txMempoolLock);
     return false;
 }
 
+bool TxMempool_Snapshot(signed_transaction_t** outTxs, size_t* outCount) {
+    if (!outTxs || !outCount) {
+        return false;
+    }
+
+    *outTxs = NULL;
+    *outCount = 0;
+
+    if (!txMempool) {
+        return true;
+    }
+
+    pthread_mutex_lock(&g_txMempoolLock);
+
+    size_t count = 0;
+    khiter_t k;
+    for (k = kh_begin(txMempool); k != kh_end(txMempool); ++k) {
+        if (kh_exist(txMempool, k)) {
+            ++count;
+        }
+    }
+
+    if (count == 0) {
+        pthread_mutex_unlock(&g_txMempoolLock);
+        return true;
+    }
+
+    signed_transaction_t* snapshot = (signed_transaction_t*)malloc(count * sizeof(signed_transaction_t));
+    if (!snapshot) {
+        pthread_mutex_unlock(&g_txMempoolLock);
+        return false;
+    }
+
+    size_t index = 0;
+    for (k = kh_begin(txMempool); k != kh_end(txMempool); ++k) {
+        if (kh_exist(txMempool, k)) {
+            snapshot[index++] = kh_value(txMempool, k);
+        }
+    }
+
+    pthread_mutex_unlock(&g_txMempoolLock);
+
+    *outTxs = snapshot;
+    *outCount = count;
+    return true;
+}
+
 void TxMempool_Print() {
     if (!txMempool) { return; }
 
+    pthread_mutex_lock(&g_txMempoolLock);
     khiter_t k;
     for (k = kh_begin(txMempool); k != kh_end(txMempool); ++k) {
         if (kh_exist(txMempool, k)) {
@@ -62,10 +123,19 @@ void TxMempool_Print() {
                 (unsigned long long)tx.transaction.fee);
         }
     }
+    pthread_mutex_unlock(&g_txMempoolLock);
 }
 
 void TxMempool_Destroy() {
     if (txMempool) {
+        pthread_mutex_lock(&g_txMempoolLock);
         kh_destroy(tx_mempool_map_m, txMempool);
+        txMempool = NULL;
+        pthread_mutex_unlock(&g_txMempoolLock);
+    }
+
+    if (g_txMempoolLockInitialized) {
+        pthread_mutex_destroy(&g_txMempoolLock);
+        g_txMempoolLockInitialized = false;
     }
 }