diff --git a/benchmark-proxy/main.go b/benchmark-proxy/main.go
index 50216858..0e02c9e9 100644
--- a/benchmark-proxy/main.go
+++ b/benchmark-proxy/main.go
@@ -231,6 +231,8 @@ type ChainHeadMonitor struct {
 	chainHeads         map[string]*ChainHead // backend name -> chain head info
 	primaryChainID     string                // Chain ID of primary backend
 	enabledBackends    map[string]bool       // Track which backends are enabled
+	blockHashCache     map[string]uint64     // block hash -> block number cache (last 128 blocks from primary)
+	blockHashOrder     []string              // ordered list of block hashes (oldest first)
 	wsDialer           *websocket.Dialer
 	stopChan           chan struct{}
 	enableDetailedLogs bool
@@ -339,6 +341,31 @@ func parseRequestInfo(body []byte) (*RequestInfo, error) {
 		// which needs special handling
 	}
 
+	// Methods that use block hashes as parameters
+	methodsWithBlockHashes := map[string]int{
+		"eth_getBlockByHash":                    0, // first param
+		"eth_getBlockTransactionCountByHash":    0, // first param
+		"eth_getTransactionByBlockHashAndIndex": 0, // first param
+		"eth_getUncleByBlockHashAndIndex":       0, // first param
+		"eth_getUncleCountByBlockHash":          0, // first param
+		"debug_traceBlockByHash":                0, // first param
+	}
+
+	// Check for block hash methods first
+	paramPos, hasBlockHash := methodsWithBlockHashes[req.Method]
+	if hasBlockHash && info.HasParams {
+		// Parse params as array
+		var params []json.RawMessage
+		if err := json.Unmarshal(req.Params, &params); err == nil && len(params) > paramPos {
+			// Try to parse as string (block hash)
+			var blockHash string
+			if err := json.Unmarshal(params[paramPos], &blockHash); err == nil {
+				info.BlockTag = blockHash
+				return info, nil
+			}
+		}
+	}
+
 	paramPos, hasBlockTag := methodsWithBlockTags[req.Method]
 	if !hasBlockTag || !info.HasParams {
 		return info, nil
@@ -561,6 +588,62 @@ func canUseSecondaryForLatest(blockTag string, backendName string, chainHeadMoni
 	return secondaryHead.BlockNumber == primaryHead.BlockNumber
 }
 
+// canUseSecondaryForBlockTag checks if secondary backend can be used for a given block tag
+func canUseSecondaryForBlockTag(blockTag string, backendName string, chainHeadMonitor *ChainHeadMonitor) bool {
+	if chainHeadMonitor == nil {
+		// No monitor, can't verify - be conservative
+		return false
+	}
+
+	// Get chain head status
+	chainStatus := chainHeadMonitor.GetStatus()
+
+	primaryHead, primaryExists := chainStatus["primary"]
+	if !primaryExists || !primaryHead.IsHealthy {
+		// Primary not healthy, allow secondary
+		return true
+	}
+
+	secondaryHead, secondaryExists := chainStatus[backendName]
+	if !secondaryExists || !secondaryHead.IsHealthy {
+		// Secondary not healthy
+		return false
+	}
+
+	// Handle "latest" tag - secondary must be at EXACTLY the same block height
+	if blockTag == "latest" {
+		return secondaryHead.BlockNumber == primaryHead.BlockNumber
+	}
+
+	// Handle "earliest" tag - always allowed
+	if blockTag == "earliest" {
+		return true
+	}
+
+	// Check if it's a block hash (0x followed by 64 hex chars)
+	if len(blockTag) == 66 && strings.HasPrefix(blockTag, "0x") {
+		// Try to look up the block number from our cache
+		if blockNumber, exists := chainHeadMonitor.GetBlockNumberForHash(blockTag); exists {
+			// We know this block number, check if secondary has it
+			return secondaryHead.BlockNumber >= blockNumber
+		}
+		// Unknown block hash - be conservative and route to primary
+		return false
+	}
+
+	// Check if it's a numeric block tag (hex number)
+	if strings.HasPrefix(blockTag, "0x") {
+		blockNumber, err := strconv.ParseUint(strings.TrimPrefix(blockTag, "0x"), 16, 64)
+		if err == nil {
+			// Valid block number - check if secondary has reached it
+			return secondaryHead.BlockNumber >= blockNumber
+		}
+	}
+
+	// Unknown block tag format - be conservative
+	return false
+}
+
 func NewStatsCollector(summaryInterval time.Duration, hasSecondaryBackends bool) *StatsCollector {
 	now := time.Now()
 	sc := &StatsCollector{
@@ -1209,6 +1292,12 @@ func (sc *StatsCollector) printSummary() {
 
 			fmt.Printf("  %s: %s (%s)\n", name, status, details)
 		}
+
+		// Show block hash cache stats
+		sc.chainHeadMonitor.mu.RLock()
+		cacheSize := len(sc.chainHeadMonitor.blockHashCache)
+		sc.chainHeadMonitor.mu.RUnlock()
+		fmt.Printf("  Block hash cache: %d entries (max 128)\n", cacheSize)
 	}
 
 	if sc.hasSecondaryBackends && sc.skippedSecondaryRequests > 0 {
@@ -2351,10 +2440,10 @@ func handleRequest(w http.ResponseWriter, r *http.Request, backends []Backend, c
 			// Check all block tags in the request
 			canUseSecondary := true
 			for _, blockTag := range batchInfo.BlockTags {
-				if !canUseSecondaryForLatest(blockTag, backend.Name, chainHeadMonitor) {
+				if !canUseSecondaryForBlockTag(blockTag, backend.Name, chainHeadMonitor) {
 					canUseSecondary = false
 					if enableDetailedLogs {
-						log.Printf("Skipping secondary backend %s for block tag '%s' - not at same height as primary",
+						log.Printf("Skipping secondary backend %s for block tag '%s' - not at required height",
 							backend.Name, blockTag)
 					}
 					break
@@ -2971,6 +3060,8 @@ func NewChainHeadMonitor(backends []Backend, enableDetailedLogs bool) *ChainHead
 		backends:        backends,
 		chainHeads:      make(map[string]*ChainHead),
 		enabledBackends: make(map[string]bool),
+		blockHashCache:  make(map[string]uint64),
+		blockHashOrder:  make([]string, 0, 128),
 		wsDialer: &websocket.Dialer{
 			ReadBufferSize:  1024 * 1024, // 1MB
 			WriteBufferSize: 1024 * 1024, // 1MB
@@ -3200,6 +3291,11 @@ func (m *ChainHeadMonitor) readNewHeads(conn *websocket.Conn, backendName string
 
 			m.updateBackendStatus(backendName, head, "")
 
+			// Cache block hash if this is from primary backend
+			if backendName == "primary" && notification.Params.Result.Hash != "" {
+				m.cacheBlockHash(notification.Params.Result.Hash, blockNumber)
+			}
+
 			if m.enableDetailedLogs {
 				log.Printf("Backend %s at block %d (hash: %s...)",
 					backendName, blockNumber, head.BlockHash[:8])
@@ -3364,3 +3460,35 @@ func (m *ChainHeadMonitor) GetStatus() map[string]ChainHead {
 	}
 	return status
 }
+
+// cacheBlockHash adds a block hash to the cache, maintaining a maximum of 128 entries
+func (m *ChainHeadMonitor) cacheBlockHash(blockHash string, blockNumber uint64) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// Check if hash already exists
+	if _, exists := m.blockHashCache[blockHash]; exists {
+		return
+	}
+
+	// Add to cache
+	m.blockHashCache[blockHash] = blockNumber
+	m.blockHashOrder = append(m.blockHashOrder, blockHash)
+
+	// Maintain maximum cache size of 128 blocks
+	if len(m.blockHashOrder) > 128 {
+		// Remove oldest entry
+		oldestHash := m.blockHashOrder[0]
+		delete(m.blockHashCache, oldestHash)
+		m.blockHashOrder = m.blockHashOrder[1:]
+	}
+}
+
+// GetBlockNumberForHash returns the block number for a given hash if it's in the cache
+func (m *ChainHeadMonitor) GetBlockNumberForHash(blockHash string) (uint64, bool) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	blockNumber, exists := m.blockHashCache[blockHash]
+	return blockNumber, exists
+}