diff --git a/pkg/filestore/filestore.go b/pkg/filestore/filestore.go
index 9617158..b07134d 100644
--- a/pkg/filestore/filestore.go
+++ b/pkg/filestore/filestore.go
@@ -3,7 +3,9 @@ package filestore
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"io"
 	"os"
 
 	"github.com/ethereum/go-ethereum/core/types"
@@ -15,9 +17,20 @@ func SaveLogsAsync(ctx context.Context, logChan <-chan types.Log, filePath strin
 	if err != nil {
 		return fmt.Errorf("error creating file: %w", err)
 	}
-	defer file.Close()
+	return saveLogs(ctx, logChan, file)
+}
+
+func saveLogs(ctx context.Context, logChan <-chan types.Log, w io.WriteCloser) (err error) {
+	// OS-buffered writes can surface a failure only when the file is flushed
+	// at close time, so a swallowed Close error would report an incomplete
+	// export as success.
+	defer func() {
+		if cerr := w.Close(); cerr != nil {
+			err = errors.Join(err, fmt.Errorf("error closing file: %w", cerr))
+		}
+	}()
 
-	encoder := json.NewEncoder(file)
+	encoder := json.NewEncoder(w)
 
 	for {
 		select {
diff --git a/pkg/filestore/filestore_internal_test.go b/pkg/filestore/filestore_internal_test.go
new file mode 100644
index 0000000..3cd0653
--- /dev/null
+++ b/pkg/filestore/filestore_internal_test.go
@@ -0,0 +1,44 @@
+package filestore
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// closeFailWriter accepts all writes but fails on Close, mimicking a file
+// whose OS-buffered data cannot be flushed (disk full, quota, network fs).
+type closeFailWriter struct{ closeErr error }
+
+func (w *closeFailWriter) Write(p []byte) (int, error) { return len(p), nil }
+func (w *closeFailWriter) Close() error                { return w.closeErr }
+
+func TestSaveLogsReportsCloseError(t *testing.T) {
+	closeErr := errors.New("flush to disk failed")
+
+	logChan := make(chan types.Log, 1)
+	logChan <- types.Log{BlockNumber: 1}
+	close(logChan)
+
+	err := saveLogs(context.Background(), logChan, &closeFailWriter{closeErr: closeErr})
+	if !errors.Is(err, closeErr) {
+		t.Fatalf("got %v, want close error %v", err, closeErr)
+	}
+}
+
+func TestSaveLogsKeepsContextErrorOnCloseFailure(t *testing.T) {
+	closeErr := errors.New("flush to disk failed")
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	err := saveLogs(ctx, make(chan types.Log), &closeFailWriter{closeErr: closeErr})
+	if !errors.Is(err, context.Canceled) {
+		t.Fatalf("got %v, want context.Canceled", err)
+	}
+	if !errors.Is(err, closeErr) {
+		t.Fatalf("got %v, want close error %v", err, closeErr)
+	}
+}
diff --git a/pkg/filestore/filestore_test.go b/pkg/filestore/filestore_test.go
new file mode 100644
index 0000000..8add67e
--- /dev/null
+++ b/pkg/filestore/filestore_test.go
@@ -0,0 +1,61 @@
+package filestore_test
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethersphere/batch-export/pkg/filestore"
+)
+
+func TestSaveLogsAsyncWritesNDJSON(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "export.ndjson")
+
+	logChan := make(chan types.Log, 2)
+	for i := uint64(1); i <= 2; i++ {
+		logChan <- types.Log{
+			Address:     common.HexToAddress("0x000000000000000000000000000000000000bEEF"),
+			Topics:      []common.Hash{common.HexToHash("0x11")},
+			Data:        []byte{0xde, 0xad},
+			BlockNumber: i,
+		}
+	}
+	close(logChan)
+
+	if err := filestore.SaveLogsAsync(context.Background(), logChan, path); err != nil {
+		t.Fatalf("SaveLogsAsync: %v", err)
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		t.Fatalf("open output: %v", err)
+	}
+	defer file.Close()
+
+	var got []types.Log
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		var l types.Log
+		if err := json.Unmarshal(scanner.Bytes(), &l); err != nil {
+			t.Fatalf("decode line %d: %v", len(got)+1, err)
+		}
+		got = append(got, l)
+	}
+	if err := scanner.Err(); err != nil {
+		t.Fatalf("scan output: %v", err)
+	}
+
+	if len(got) != 2 {
+		t.Fatalf("got %d logs, want 2", len(got))
+	}
+	for i, l := range got {
+		if l.BlockNumber != uint64(i+1) {
+			t.Errorf("log %d: blockNumber got %d want %d", i, l.BlockNumber, i+1)
+		}
+	}
+}
diff --git a/pkg/gzipstore/gzipstore.go b/pkg/gzipstore/gzipstore.go
index 6763ad0..2b079ed 100644
--- a/pkg/gzipstore/gzipstore.go
+++ b/pkg/gzipstore/gzipstore.go
@@ -2,6 +2,7 @@ package gzipstore
 
 import (
 	"compress/gzip"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -23,14 +24,22 @@ func CompressFile(inputFilePath string, outputFilePath string) error {
 	}
 	defer outputFile.Close()
 
-	// create a new gzip writer that writes to the output file
-	gzipWriter := gzip.NewWriter(outputFile)
-	defer gzipWriter.Close()
+	return compress(outputFile, inputFile)
+}
 
-	// copy the contents from the input file to the gzip writer
-	_, err = io.Copy(gzipWriter, inputFile)
-	if err != nil {
-		return fmt.Errorf("failed to write compressed data to '%s': %w", outputFilePath, err)
+func compress(dst io.Writer, src io.Reader) (err error) {
+	gzipWriter := gzip.NewWriter(dst)
+	// Close flushes the remaining compressed bytes and the gzip footer; a
+	// swallowed error here would report a truncated archive as success.
+	defer func() {
+		if cerr := gzipWriter.Close(); cerr != nil {
+			err = errors.Join(err, fmt.Errorf("failed to finalize gzip stream: %w", cerr))
+		}
+	}()
+
+	// copy the contents from the source to the gzip writer
+	if _, err := io.Copy(gzipWriter, src); err != nil {
+		return fmt.Errorf("failed to write compressed data: %w", err)
 	}
 
 	return nil
diff --git a/pkg/gzipstore/gzipstore_internal_test.go b/pkg/gzipstore/gzipstore_internal_test.go
new file mode 100644
index 0000000..5da04ff
--- /dev/null
+++ b/pkg/gzipstore/gzipstore_internal_test.go
@@ -0,0 +1,31 @@
+package gzipstore
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+// headerOnlyWriter accepts the first write (the gzip header) and fails every
+// write after it, so the compressed payload flush at Close is what fails.
+type headerOnlyWriter struct {
+	writes int
+	err    error
+}
+
+func (w *headerOnlyWriter) Write(p []byte) (int, error) {
+	w.writes++
+	if w.writes > 1 {
+		return 0, w.err
+	}
+	return len(p), nil
+}
+
+func TestCompressReportsFlushError(t *testing.T) {
+	writeErr := errors.New("disk full")
+
+	err := compress(&headerOnlyWriter{err: writeErr}, strings.NewReader("payload"))
+	if !errors.Is(err, writeErr) {
+		t.Fatalf("got %v, want flush error %v", err, writeErr)
+	}
+}
diff --git a/pkg/gzipstore/gzipstore_test.go b/pkg/gzipstore/gzipstore_test.go
new file mode 100644
index 0000000..61a173a
--- /dev/null
+++ b/pkg/gzipstore/gzipstore_test.go
@@ -0,0 +1,47 @@
+package gzipstore_test
+
+import (
+	"bytes"
+	"compress/gzip"
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/ethersphere/batch-export/pkg/gzipstore"
+)
+
+func TestCompressFileRoundTrip(t *testing.T) {
+	dir := t.TempDir()
+	inputPath := filepath.Join(dir, "in.ndjson")
+	outputPath := filepath.Join(dir, "out.gzip")
+
+	content := []byte("{\"blockNumber\":\"0x1\"}\n{\"blockNumber\":\"0x2\"}\n")
+	if err := os.WriteFile(inputPath, content, 0o644); err != nil {
+		t.Fatalf("write input: %v", err)
+	}
+
+	if err := gzipstore.CompressFile(inputPath, outputPath); err != nil {
+		t.Fatalf("CompressFile: %v", err)
+	}
+
+	file, err := os.Open(outputPath)
+	if err != nil {
+		t.Fatalf("open output: %v", err)
+	}
+	defer file.Close()
+
+	gzipReader, err := gzip.NewReader(file)
+	if err != nil {
+		t.Fatalf("gzip reader: %v", err)
+	}
+	defer gzipReader.Close()
+
+	got, err := io.ReadAll(gzipReader)
+	if err != nil {
+		t.Fatalf("decompress: %v", err)
+	}
+	if !bytes.Equal(got, content) {
+		t.Errorf("round trip mismatch: got %q want %q", got, content)
+	}
+}