Added bounds checking after calculating startIdx.

Problem: Race condition in cache lookup logic:
Thread A reads cache metadata (17+ records, endOffset = 32)
Thread B modifies/truncates the cache to 17 records
Thread A calculates startIdx = 19 based on old metadata
Slice operation consumedRecords[19:17] panics

weed/mq/kafka/integration/broker_client_subscribe.go

@@ -271,6 +271,12 @@ func (bc *BrokerClient) ReadRecordsFromOffset(ctx context.Context, session *Brok
 		if requestedOffset >= cacheStartOffset && requestedOffset <= cacheEndOffset {
 			// Found in cache
 			startIdx := int(requestedOffset - cacheStartOffset)
+			// CRITICAL: Bounds check to prevent race condition where cache is modified between checks
+			if startIdx < 0 || startIdx >= len(session.consumedRecords) {
+				glog.V(2).Infof("[FETCH] Cache index out of bounds (race condition): startIdx=%d, cache size=%d, falling through to normal read",
+					startIdx, len(session.consumedRecords))
+				// Cache was modified, fall through to normal read path
+			} else {
 				endIdx := startIdx + maxRecords
 				if endIdx > len(session.consumedRecords) {
 					endIdx = len(session.consumedRecords)
@@ -280,6 +286,7 @@ func (bc *BrokerClient) ReadRecordsFromOffset(ctx context.Context, session *Brok
 				return session.consumedRecords[startIdx:endIdx], nil
 			}
 		}
+	}
 
 	// CRITICAL FIX for Schema Registry: Keep subscriber alive across multiple fetch requests
 	// Schema Registry expects to make multiple poll() calls on the same consumer connection