diff --git a/crates/agentic-core/migrations/0002_add_placeholders.sql b/crates/agentic-core/migrations/0002_add_placeholders.sql
new file mode 100644
index 0000000..849c3ed
--- /dev/null
+++ b/crates/agentic-core/migrations/0002_add_placeholders.sql
@@ -0,0 +1,12 @@
+ALTER TABLE conversations ADD COLUMN tenant_id TEXT;
+ALTER TABLE conversations ADD COLUMN metadata TEXT;
+
+ALTER TABLE items ADD COLUMN tenant_id TEXT;
+ALTER TABLE items ADD COLUMN raw_tokens TEXT;
+
+ALTER TABLE responses ADD COLUMN tenant_id TEXT;
+ALTER TABLE responses ADD COLUMN raw_tokens TEXT;
+
+CREATE INDEX IF NOT EXISTS idx_conversations_tenant_id ON conversations (tenant_id);
+CREATE INDEX IF NOT EXISTS idx_items_tenant_id ON items (tenant_id);
+CREATE INDEX IF NOT EXISTS idx_responses_tenant_id ON responses (tenant_id);
diff --git a/crates/agentic-core/src/storage/models/conversation.rs b/crates/agentic-core/src/storage/models/conversation.rs
index 21a70f6..4d9515a 100644
--- a/crates/agentic-core/src/storage/models/conversation.rs
+++ b/crates/agentic-core/src/storage/models/conversation.rs
@@ -12,6 +12,9 @@ pub struct Conversation {
     /// Unique conversation identifier.
     pub id: String,
 
+    /// Optional metadata as JSON string.
+    pub metadata: Option<String>,
+
     /// Creation timestamp as Unix timestamp in seconds.
     pub created_at: i64,
 }
@@ -69,10 +72,12 @@ mod tests {
     fn test_conversation_basic() {
         let conversation = Conversation {
             id: "conv_1".to_string(),
+            metadata: None,
             created_at: 1_704_067_200,
         };
 
         assert_eq!(conversation.id, "conv_1");
+        assert!(conversation.metadata.is_none());
         assert_eq!(conversation.created_at, 1_704_067_200);
     }
 }
diff --git a/crates/agentic-core/src/storage/models/item.rs b/crates/agentic-core/src/storage/models/item.rs
index 71640dc..c283200 100644
--- a/crates/agentic-core/src/storage/models/item.rs
+++ b/crates/agentic-core/src/storage/models/item.rs
@@ -1,5 +1,7 @@
 //! Conversation history item stored in the database.
 
+use tracing::warn;
+
 use super::super::pool::{DbPool, DbResult, DbTransaction};
 use super::super::types::item::InOutItem;
 use crate::types::io::{InputItem, OutputItem};
@@ -44,9 +46,14 @@ impl Item {
     /// Deserialize data column as either `InputItem` or `OutputItem`.
     #[must_use]
     pub fn as_inout(&self) -> Option<InOutItem> {
-        self.as_input()
-            .map(InOutItem::Input)
-            .or_else(|| self.as_output().map(InOutItem::Output))
+        match (self.as_input(), self.as_output()) {
+            (Some(input), _) if !matches!(input, InputItem::Unknown) => Some(InOutItem::Input(input)),
+            (_, Some(output)) if !matches!(output, OutputItem::Unknown) => Some(InOutItem::Output(output)),
+            _ => {
+                warn!(item_id = %self.id, "unrecognized item type in stored data");
+                None
+            }
+        }
     }
 }
 
diff --git a/crates/agentic-core/src/storage/types/conversation.rs b/crates/agentic-core/src/storage/types/conversation.rs
index c4fbe82..55dc909 100644
--- a/crates/agentic-core/src/storage/types/conversation.rs
+++ b/crates/agentic-core/src/storage/types/conversation.rs
@@ -9,6 +9,8 @@ use super::super::models::Conversation as StorageDbConversation;
 pub struct ConversationData {
     /// Unique conversation identifier
     pub conversation_id: String,
+    /// Optional metadata as JSON string
+    pub metadata: Option<String>,
     /// Creation timestamp as Unix timestamp in seconds
     pub created_at: i64,
 }
@@ -17,6 +19,7 @@ impl From<StorageDbConversation> for ConversationData {
     fn from(row: StorageDbConversation) -> Self {
         Self {
             conversation_id: row.id,
+            metadata: row.metadata,
             created_at: row.created_at,
         }
     }
@@ -26,6 +29,7 @@ impl From<ConversationData> for StorageDbConversation {
     fn from(data: ConversationData) -> Self {
         Self {
             id: data.conversation_id,
+            metadata: data.metadata,
             created_at: data.created_at,
         }
     }
@@ -39,6 +43,7 @@ mod tests {
     fn test_conversation_from_db_conversation() {
         let db_row = StorageDbConversation {
             id: "conv_123".to_string(),
+            metadata: None,
             created_at: 1_704_067_200,
         };
 
@@ -51,11 +56,13 @@ mod tests {
     fn test_conversation_roundtrip() {
         let data = ConversationData {
             conversation_id: "conv_456".to_string(),
+            metadata: Some(r#"{"key":"value"}"#.to_string()),
             created_at: 1_704_067_200,
         };
 
         let db_row: StorageDbConversation = data.into();
         assert_eq!(db_row.id, "conv_456");
+        assert_eq!(db_row.metadata, Some(r#"{"key":"value"}"#.to_string()));
         assert_eq!(db_row.created_at, 1_704_067_200);
     }
 
@@ -63,6 +70,7 @@ mod tests {
     fn test_conversation_data_clone() {
         let data = ConversationData {
             conversation_id: "conv_clone".to_string(),
+            metadata: None,
             created_at: 1_704_067_200,
         };
 
@@ -75,6 +83,7 @@ mod tests {
     fn test_conversation_data_debug_format() {
         let data = ConversationData {
             conversation_id: "conv_debug".to_string(),
+            metadata: None,
             created_at: 1_704_067_200,
         };
 
@@ -87,6 +96,7 @@ mod tests {
     fn test_conversation_bidirectional_conversion() {
         let original = ConversationData {
             conversation_id: "conv_bidir".to_string(),
+            metadata: None,
             created_at: 1_706_790_600,
         };
 
diff --git a/crates/agentic-core/src/types/io.rs b/crates/agentic-core/src/types/io.rs
index 239a9ce..14fd7f9 100644
--- a/crates/agentic-core/src/types/io.rs
+++ b/crates/agentic-core/src/types/io.rs
@@ -51,6 +51,8 @@ pub enum InputItem {
     Message(InputMessage),
     #[serde(rename = "function_call_output")]
     FunctionCallOutput(FunctionToolResultMessage),
+    #[serde(other)]
+    Unknown,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -108,6 +110,8 @@ pub enum OutputItem {
     Message(OutputMessage),
     #[serde(rename = "function_call")]
     FunctionCall(FunctionToolCall),
+    #[serde(other)]
+    Unknown,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]