From 58fad516dca130e3f6a211eada9f04c0335df6c9 Mon Sep 17 00:00:00 2001
From: jeevan-sid <g1siddharthr@gmail.com>
Date: Mon, 16 Feb 2026 19:03:31 +0530
Subject: [PATCH] feat: implement getTransactionByNonceAndSender

---
 eth/api_backend.go         | 27 +++++++++++++++++++++++++++
 ethclient/ethclient.go     | 10 ++++++++++
 internal/ethapi/api.go     |  9 +++++++++
 internal/ethapi/backend.go |  1 +
 4 files changed, 47 insertions(+)

diff --git a/eth/api_backend.go b/eth/api_backend.go
index 3f826b7861..2594cdc925 100644
--- a/eth/api_backend.go
+++ b/eth/api_backend.go
@@ -215,6 +215,33 @@ func (b *EthAPIBackend) BlockByNumberOrHash(ctx context.Context, blockNrOrHash r
 	return nil, errors.New("invalid arguments; neither block nor hash specified")
 }
 
+// GetTransactionBySenderAndNonce returns the hash of a transaction for the given sender and nonce.
+// It checks the pool, then enforces a nonce check against the current state, and finally checks the historical TxSenderNonce index.
+func (b *EthAPIBackend) GetTransactionBySenderAndNonce(ctx context.Context, sender common.Address, nonce uint64) (*common.Hash, error) {
+
+	if pool := b.eth.TxPool(); pool != nil {
+		if tx := pool.GetTxBySenderAndNonce(sender, nonce); tx != nil {
+			hash := tx.Hash()
+			return &hash, nil
+		}
+	}
+
+	state, _, err := b.StateAndHeaderByNumberOrHash(ctx, rpc.BlockNumberOrHashWithNumber(rpc.LatestBlockNumber))
+	if err != nil {
+		return nil, err
+	}
+	currentNonce := state.GetNonce(sender)
+
+	// If the requested nonce is greater than or equal to the current nonce,
+	// and we already confirmed it's NOT in the pool, then the transaction
+	// definitely does not exist.
+	if nonce >= currentNonce {
+		return nil, nil
+	}
+	hash := rawdb.ReadTxSenderNonceEntry(b.eth.ChainDb(), sender, nonce)
+	return hash, nil
+}
+
 func (b *EthAPIBackend) Pending() (*types.Block, types.Receipts, *state.StateDB) {
 	return b.eth.miner.Pending()
 }
diff --git a/ethclient/ethclient.go b/ethclient/ethclient.go
index bc4eaad6fa..967fd7e58e 100644
--- a/ethclient/ethclient.go
+++ b/ethclient/ethclient.go
@@ -288,6 +288,16 @@ func (ec *Client) TransactionByHash(ctx context.Context, hash common.Hash) (tx *
 	return json.tx, json.BlockNumber == nil, nil
 }
 
+// TransactionHashBySenderAndNonce returns the transaction hash for the given sender and nonce.
+func (ec *Client) TransactionHashBySenderAndNonce(ctx context.Context, sender common.Address, nonce uint64) (*common.Hash, error) {
+	var hash *common.Hash
+	err := ec.c.CallContext(ctx, &hash, "eth_getTransactionBySenderAndNonce", sender, nonce)
+	if err != nil {
+		return nil, err
+	}
+	return hash, nil
+}
+
 // TransactionSender returns the sender address of the given transaction. The transaction
 // must be known to the remote node and included in the blockchain at the given block and
 // index. The sender is the one derived by the protocol at the time of inclusion.
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index 5fbe7db694..b034badcd1 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -1449,6 +1449,15 @@ func (api *TransactionAPI) GetTransactionByHash(ctx context.Context, hash common
 	return newRPCTransaction(tx, blockHash, blockNumber, header.Time, index, header.BaseFee, api.b.ChainConfig()), nil
 }
 
+// GetTransactionBySenderAndNonce returns the hash of a transaction for the given sender and nonce.
+func (s *TransactionAPI) GetTransactionBySenderAndNonce(ctx context.Context, sender common.Address, nonce uint64) (*common.Hash, error) {
+	hash, err := s.b.GetTransactionBySenderAndNonce(ctx, sender, nonce)
+	if err != nil {
+		return nil, err
+	}
+	return hash, nil
+}
+
 // GetRawTransactionByHash returns the bytes of the transaction for the given hash.
 func (api *TransactionAPI) GetRawTransactionByHash(ctx context.Context, hash common.Hash) (hexutil.Bytes, error) {
 	// Retrieve a finalized transaction, or a pooled otherwise
diff --git a/internal/ethapi/backend.go b/internal/ethapi/backend.go
index af3d592b82..754a771ab3 100644
--- a/internal/ethapi/backend.go
+++ b/internal/ethapi/backend.go
@@ -66,6 +66,7 @@ type Backend interface {
 	BlockByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Block, error)
 	BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error)
 	BlockByNumberOrHash(ctx context.Context, blockNrOrHash rpc.BlockNumberOrHash) (*types.Block, error)
+	GetTransactionBySenderAndNonce(ctx context.Context, sender common.Address, nonce uint64) (*common.Hash, error)
 	StateAndHeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*state.StateDB, *types.Header, error)
 	StateAndHeaderByNumberOrHash(ctx context.Context, blockNrOrHash rpc.BlockNumberOrHash) (*state.StateDB, *types.Header, error)
 	Pending() (*types.Block, types.Receipts, *state.StateDB)