diff --git a/internal/adapter/claudebox/client.go b/internal/adapter/claudebox/client.go
index 92c0c8f..d8af85d 100644
--- a/internal/adapter/claudebox/client.go
+++ b/internal/adapter/claudebox/client.go
@@ -175,6 +175,8 @@ func (c *Client) ExecuteStream(ctx context.Context, req *ExecuteRequest, handler
 
 	// Parse SSE events
 	scanner := bufio.NewScanner(resp.Body)
+	buf := make([]byte, 0, 64*1024)
+	scanner.Buffer(buf, 1024*1024) // 1MB max to match other streaming paths
 	for scanner.Scan() {
 		line := scanner.Text()
 		if !strings.HasPrefix(line, "data: ") {