diff --git a/cmd/fireantelope/main.go b/cmd/fireantelope/main.go
index b0cc04f..e1e9805 100644
--- a/cmd/fireantelope/main.go
+++ b/cmd/fireantelope/main.go
@@ -60,6 +60,7 @@ func Chain() *firecore.Chain[*pbantelope.Block] {
 				//toolsCmd.AddCommand(newToolsBackfillCmd(zlog))
 				parent.AddCommand(newPollerCmd(zlog, tracer))
 				parent.AddCommand(newSilkwormPollerCmd(zlog, tracer))
+				parent.AddCommand(newCheckBlocksCmd(zlog))
 
 				return nil
 			},
diff --git a/cmd/fireantelope/tools_fix_invalid_utf8.go b/cmd/fireantelope/tools_fix_invalid_utf8.go
new file mode 100644
index 0000000..86d16eb
--- /dev/null
+++ b/cmd/fireantelope/tools_fix_invalid_utf8.go
@@ -0,0 +1,109 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	pbantelope "github.com/pinax-network/firehose-antelope/types/pb/sf/antelope/type/v1"
+	"github.com/spf13/cobra"
+	"github.com/streamingfast/bstream"
+	"github.com/streamingfast/dstore"
+	firecore "github.com/streamingfast/firehose-core"
+	"go.uber.org/zap"
+	"io"
+)
+
+func newCheckBlocksCmd(logger *zap.Logger) *cobra.Command {
+	return &cobra.Command{
+		Use:   "check-blocks <src-blocks-store> <start-block> <stop-block>",
+		Short: "checks all blocks for decoding issues (detects the invalid UTF-8 issue).",
+		Args:  cobra.ExactArgs(3),
+		RunE:  createCheckBlocksE(logger),
+	}
+}
+
+func createCheckBlocksE(logger *zap.Logger) firecore.CommandExecutor {
+	return func(cmd *cobra.Command, args []string) error {
+		ctx := cmd.Context()
+
+		srcStore, err := dstore.NewDBinStore(args[0])
+		if err != nil {
+			return fmt.Errorf("unable to create source store: %w", err)
+		}
+
+		start := mustParseUint64(args[1])
+		stop := mustParseUint64(args[2])
+
+		if stop <= start {
+			return fmt.Errorf("stop block must be greater than start block")
+		}
+
+		logger.Info("checking antelope blocks", zap.Uint64("start_block", start), zap.Uint64("stop_block", stop))
+
+		lastFileProcessed := ""
+		startWalkFrom := fmt.Sprintf("%010d", start-(start%100))
+		err = srcStore.WalkFrom(ctx, "", startWalkFrom, func(filename string) error {
+			logger.Debug("checking merged block file", zap.String("filename", filename))
+
+			startBlock := mustParseUint64(filename)
+
+			if startBlock > stop {
+				logger.Debug("stopping at merged block file above stop block", zap.String("filename", filename), zap.Uint64("stop", stop))
+				return io.EOF
+			}
+
+			if startBlock+100 < start {
+				logger.Debug("skipping merged block file below start block", zap.String("filename", filename))
+				return nil
+			}
+
+			rc, err := srcStore.OpenObject(ctx, filename)
+			if err != nil {
+				return fmt.Errorf("failed to open %s: %w", filename, err)
+			}
+			defer rc.Close()
+
+			br, err := bstream.NewDBinBlockReader(rc)
+			if err != nil {
+				return fmt.Errorf("creating block reader: %w", err)
+			}
+
+			i := 0
+			for {
+				block, err := br.Read()
+				if err == io.EOF {
+					break
+				}
+
+				var antelopeBlock pbantelope.Block
+				err = block.Payload.UnmarshalTo(&antelopeBlock)
+				if err != nil {
+					fmt.Printf("block_num: %d - unable to decode: %s\n", block.Number, err)
+				} else {
+					logger.Debug("successfully decoded antelope block", zap.Any("block_num", block.Number))
+				}
+
+				i++
+			}
+
+			if i != 100 {
+				return fmt.Errorf("expected to have read 100 blocks, we have read %d. Bailing out.", i)
+			}
+
+			lastFileProcessed = filename
+			logger.Info("finished merged block", zap.String("filename", filename))
+
+			return nil
+		})
+		fmt.Printf("Last file processed: %s.dbin.zst\n", lastFileProcessed)
+
+		if errors.Is(err, io.EOF) {
+			return nil
+		}
+
+		if err != nil {
+			return err
+		}
+
+		return nil
+	}
+}
diff --git a/cmd/fireantelope/util.go b/cmd/fireantelope/util.go
new file mode 100644
index 0000000..e65fca8
--- /dev/null
+++ b/cmd/fireantelope/util.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func mustParseUint64(in string) uint64 {
+	out, err := strconv.ParseUint(in, 10, 64)
+	if err != nil {
+		panic(fmt.Errorf("unable to parse %q as uint64: %w", in, err))
+	}
+
+	return out
+}
diff --git a/codec/block.go b/codec/block.go
deleted file mode 100644
index 41c15bf..0000000
--- a/codec/block.go
+++ /dev/null
@@ -1,50 +0,0 @@
-// Copyright 2019 dfuse Platform Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package codec
-
-// todo legacy function, bstream.StartBlockResolver has been removed, not sure if and how we need to replace
-//func BlockstoreStartBlockResolver(blocksStore dstore.Store) bstream.StartBlockResolver {
-//	var errFound = errors.New("found")
-//
-//	return func(ctx context.Context, targetBlockNum uint64) (uint64, string, error) {
-//		var dposLibNum uint32
-//		num := uint32(targetBlockNum)
-//
-//		handlerFunc := bstream.HandlerFunc(func(block *bstream.Block, _ interface{}) error {
-//			if block.Number == uint64(num) {
-//				dposLibNum = uint32(block.LibNum)
-//				return errFound
-//			}
-//
-//			return nil
-//		})
-//
-//		fs := bstream.NewFileSource(blocksStore, targetBlockNum, handlerFunc, zlog, nil)
-//
-//		go fs.Run()
-//
-//		select {
-//		case <-ctx.Done():
-//			fs.Shutdown(context.Canceled)
-//			return 0, "", ctx.Err()
-//		case <-fs.Terminated():
-//		}
-//
-//		if dposLibNum != 0 {
-//			return uint64(dposLibNum), "", nil
-//		}
-//		return 0, "", fs.Err()
-//	}
-//}
diff --git a/codec/init.go b/codec/init.go
deleted file mode 100644
index 2dc40be..0000000
--- a/codec/init.go
+++ /dev/null
@@ -1,11 +0,0 @@
-package codec
-
-//func init() {
-//	bstream.GetBlockWriterFactory = bstream.BlockWriterFactoryFunc(BlockWriterFactory)
-//	bstream.GetBlockReaderFactory = bstream.BlockReaderFactoryFunc(BlockReaderFactory)
-//	bstream.GetBlockDecoder = bstream.BlockDecoderFunc(BlockDecoder)
-//	bstream.GetProtocolFirstStreamableBlock = 2
-//	// todo legacy option, check if needs replacement
-//	// bstream.GetProtocolGenesisBlock = 1
-//	bstream.GetBlockWriterHeaderLen = 10
-//}