diff --git a/dataforge-io/dataforge-io-yaml/src/main/kotlin/hep/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt b/dataforge-io/dataforge-io-yaml/src/main/kotlin/hep/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt
index 9306b336..db701625 100644
--- a/dataforge-io/dataforge-io-yaml/src/main/kotlin/hep/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt
+++ b/dataforge-io/dataforge-io-yaml/src/main/kotlin/hep/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt
@@ -2,20 +2,18 @@ package hep.dataforge.io.yaml
 
 import hep.dataforge.context.Context
 import hep.dataforge.io.*
-import hep.dataforge.meta.*
+import hep.dataforge.meta.DFExperimental
+import hep.dataforge.meta.EmptyMeta
+import hep.dataforge.meta.Meta
 import kotlinx.io.core.*
 import kotlinx.serialization.toUtf8Bytes
 
 @DFExperimental
 class FrontMatterEnvelopeFormat(
     val io: IOPlugin,
-    val metaType: String = YamlMetaFormat.name.toString(),
     meta: Meta = EmptyMeta
 ) : EnvelopeFormat {
 
-    val metaFormat = io.metaFormat(metaType, meta)
-        ?: error("Meta format with type $metaType could not be resolved in $io")
-
     override fun Input.readPartial(): PartialEnvelope {
         var line: String = ""
         var offset = 0u
@@ -60,11 +58,12 @@ class FrontMatterEnvelopeFormat(
         return SimpleEnvelope(meta, data)
     }
 
-    override fun Output.writeObject(obj: Envelope) {
+    override fun Output.writeEnvelope(envelope: Envelope, metaFormatFactory: MetaFormatFactory, formatMeta: Meta) {
+        val metaFormat = metaFormatFactory(formatMeta, io.context)
         writeText("$SEPARATOR\r\n")
-        metaFormat.run { writeObject(obj.meta) }
+        metaFormat.run { writeObject(envelope.meta) }
         writeText("$SEPARATOR\r\n")
-        obj.data?.read { copyTo(this@writeObject) }
+        envelope.data?.read { copyTo(this@writeEnvelope) }
     }
 
     companion object : EnvelopeFormatFactory {
@@ -73,8 +72,7 @@ class FrontMatterEnvelopeFormat(
         private val metaTypeRegex = "---(\\w*)\\s*".toRegex()
 
         override fun invoke(meta: Meta, context: Context): EnvelopeFormat {
-            val metaFormatName: String = meta["name"].string ?: YamlMetaFormat.name.toString()
-            return FrontMatterEnvelopeFormat(context.io, metaFormatName, meta)
+            return FrontMatterEnvelopeFormat(context.io,  meta)
         }
 
         override fun peekFormat(io: IOPlugin, input: Input): EnvelopeFormat? {
diff --git a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeFormat.kt
index 4c5c5839..c52b9e1d 100644
--- a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeFormat.kt
@@ -2,6 +2,7 @@ package hep.dataforge.io
 
 import hep.dataforge.context.Context
 import hep.dataforge.io.EnvelopeFormatFactory.Companion.ENVELOPE_FORMAT_TYPE
+import hep.dataforge.meta.EmptyMeta
 import hep.dataforge.meta.Meta
 import hep.dataforge.names.Name
 import hep.dataforge.names.asName
@@ -18,11 +19,15 @@ data class PartialEnvelope(val meta: Meta, val dataOffset: UInt, val dataSize: U
 
 
 interface EnvelopeFormat : IOFormat<Envelope> {
+    val defaultMetaFormat: MetaFormatFactory get() = JsonMetaFormat
+
     fun Input.readPartial(): PartialEnvelope
 
+    fun Output.writeEnvelope(envelope: Envelope, metaFormatFactory: MetaFormatFactory, formatMeta: Meta = EmptyMeta)
+
     override fun Input.readObject(): Envelope
 
-    override fun Output.writeObject(obj: Envelope)
+    override fun Output.writeObject(obj: Envelope): Unit = writeEnvelope(obj, defaultMetaFormat)
 }
 
 @Type(ENVELOPE_FORMAT_TYPE)
diff --git a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaggedEnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaggedEnvelopeFormat.kt
index 97a23fb9..cce3eade 100644
--- a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaggedEnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaggedEnvelopeFormat.kt
@@ -13,12 +13,11 @@ import kotlinx.io.core.*
 @ExperimentalUnsignedTypes
 class TaggedEnvelopeFormat(
     val io: IOPlugin,
-    private val metaFormatKey: Short,
     val version: VERSION = TaggedEnvelopeFormat.VERSION.DF02
 ) : EnvelopeFormat {
 
-    private val metaFormat = io.metaFormat(metaFormatKey)
-        ?: error("Meta format with key $metaFormatKey could not be resolved in $io")
+//    private val metaFormat = io.metaFormat(metaFormatKey)
+//        ?: error("Meta format with key $metaFormatKey could not be resolved in $io")
 
 
     private fun Tag.toBytes(): ByteReadPacket = buildPacket(24) {
@@ -37,13 +36,14 @@ class TaggedEnvelopeFormat(
         writeText(END_SEQUENCE)
     }
 
-    override fun Output.writeObject(obj: Envelope) {
-        val metaBytes = metaFormat.writeBytes(obj.meta)
-        val tag = Tag(metaFormatKey, metaBytes.size.toUInt() + 2u, obj.data?.size ?: 0.toULong())
+    override fun Output.writeEnvelope(envelope: Envelope, metaFormatFactory: MetaFormatFactory, formatMeta: Meta) {
+        val metaFormat = metaFormatFactory.invoke(formatMeta, io.context)
+        val metaBytes = metaFormat.writeBytes(envelope.meta)
+        val tag = Tag(metaFormatFactory.key, metaBytes.size.toUInt() + 2u, envelope.data?.size ?: 0.toULong())
         writePacket(tag.toBytes())
         writeFully(metaBytes)
         writeText("\r\n")
-        obj.data?.read { copyTo(this@writeObject) }
+        envelope.data?.read { copyTo(this@writeEnvelope) }
         flush()
     }
 
@@ -102,7 +102,7 @@ class TaggedEnvelopeFormat(
             val metaFormatFactory = io.metaFormatFactories.find { it.name == metaFormatName }
                 ?: error("Meta format could not be resolved")
 
-            return TaggedEnvelopeFormat(io, metaFormatFactory.key)
+            return TaggedEnvelopeFormat(io)
         }
 
         private fun Input.readTag(version: VERSION): Tag {
@@ -124,9 +124,9 @@ class TaggedEnvelopeFormat(
         override fun peekFormat(io: IOPlugin, input: Input): EnvelopeFormat? {
             return try {
                 val header = input.readTextExactBytes(6)
-                when(header.substring(2..5)){
-                    VERSION.DF02.name-> TaggedEnvelopeFormat(io, JsonMetaFormat.key,VERSION.DF02)
-                    VERSION.DF03.name-> TaggedEnvelopeFormat(io, JsonMetaFormat.key,VERSION.DF03)
+                when (header.substring(2..5)) {
+                    VERSION.DF02.name -> TaggedEnvelopeFormat(io, VERSION.DF02)
+                    VERSION.DF03.name -> TaggedEnvelopeFormat(io, VERSION.DF03)
                     else -> null
                 }
             } catch (ex: Exception) {
diff --git a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt
index 8e7c9e2b..14d871db 100644
--- a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt
@@ -8,33 +8,30 @@ import kotlinx.serialization.toUtf8Bytes
 
 class TaglessEnvelopeFormat(
     val io: IOPlugin,
-    val metaType: String = JsonMetaFormat.name.toString(),
     meta: Meta = EmptyMeta
 ) : EnvelopeFormat {
 
     private val metaStart = meta[META_START_PROPERTY].string ?: DEFAULT_META_START
     private val dataStart = meta[DATA_START_PROPERTY].string ?: DEFAULT_DATA_START
 
-    val metaFormat = io.metaFormat(metaType, meta)
-        ?: error("Meta format with type $metaType could not be resolved in $io")
-
     private fun Output.writeProperty(key: String, value: Any) {
         writeText("#? $key: $value;\r\n")
     }
 
-    override fun Output.writeObject(obj: Envelope) {
+    override fun Output.writeEnvelope(envelope: Envelope, metaFormatFactory: MetaFormatFactory, formatMeta: Meta) {
+        val metaFormat = metaFormatFactory(formatMeta, io.context)
 
         //printing header
         writeText(TAGLESS_ENVELOPE_HEADER + "\r\n")
 
         //printing all properties
-        writeProperty(META_TYPE_PROPERTY, metaType)
+        writeProperty(META_TYPE_PROPERTY, metaFormatFactory.type)
         //TODO add optional metaFormat properties
-        writeProperty(DATA_LENGTH_PROPERTY, obj.data?.size ?: 0)
+        writeProperty(DATA_LENGTH_PROPERTY, envelope.data?.size ?: 0)
 
         //Printing meta
-        if (!obj.meta.isEmpty()) {
-            val metaBytes = metaFormat.writeBytes(obj.meta)
+        if (!envelope.meta.isEmpty()) {
+            val metaBytes = metaFormat.writeBytes(envelope.meta)
             writeProperty(META_LENGTH_PROPERTY, metaBytes.size)
             writeText(metaStart + "\r\n")
             writeFully(metaBytes)
@@ -42,7 +39,7 @@ class TaglessEnvelopeFormat(
         }
 
         //Printing data
-        obj.data?.let { data ->
+        envelope.data?.let { data ->
             writeText(dataStart + "\r\n")
             writeFully(data.toBytes())
         }
@@ -170,8 +167,7 @@ class TaglessEnvelopeFormat(
         override val name = TAGLESS_ENVELOPE_TYPE.asName()
 
         override fun invoke(meta: Meta, context: Context): EnvelopeFormat {
-            val metaFormatName: String = meta["name"].string ?: JsonMetaFormat.name.toString()
-            return TaglessEnvelopeFormat(context.io, metaFormatName, meta)
+            return TaglessEnvelopeFormat(context.io, meta)
         }
 
         val default by lazy { invoke() }