Memory.cloneThread()

The .cloneThread() method creates a copy of an existing conversation thread, including all its messages. This enables creating divergent conversation paths from a specific point in a conversation. When semantic recall is enabled, the method also creates vector embeddings for the cloned messages.

Usage Example

const { thread, clonedMessages } = await memory.cloneThread({
  sourceThreadId: "original-thread-123",
});

Parameters

sourceThreadId:

string

The ID of the thread to clone

newThreadId?:

string

Optional custom ID for the cloned thread. If not provided, one will be generated.

resourceId?:

string

Optional resource ID for the cloned thread. Defaults to the source thread's resourceId.

title?:

string

Optional title for the cloned thread. Defaults to '[source title] (Copy)'.

metadata?:

Record<string, unknown>

Optional metadata to merge with the source thread's metadata. Clone metadata is automatically added.

options?:

CloneOptions

Optional filtering options for the clone operation.

Options Parameters

messageLimit?:

number

Maximum number of messages to clone. When set, clones the most recent N messages.

messageFilter?:

MessageFilter

Filter criteria for selecting which messages to clone.

MessageFilter Parameters

startDate?:

Date

Only clone messages created on or after this date.

endDate?:

Date

Only clone messages created on or before this date.

messageIds?:

string[]

Only clone messages with these specific IDs.

Returns

thread:

StorageThreadType

The newly created cloned thread with clone metadata.

clonedMessages:

MastraDBMessage[]

Array of the cloned messages with new IDs assigned to the new thread.

Clone Metadata

The cloned thread's metadata includes a clone property with:

sourceThreadId:

string

The ID of the original thread that was cloned.

clonedAt:

Date

Timestamp when the clone was created.

lastMessageId?:

string

The ID of the last message in the source thread at the time of cloning.

Extended Usage Example

src/test-clone.ts

import { mastra } from "./mastra";

const agent = mastra.getAgent("agent");
const memory = await agent.getMemory();

// Clone a thread with all messages
const { thread: fullClone } = await memory.cloneThread({
  sourceThreadId: "original-thread-123",
  title: "Alternative Conversation Path",
});

// Clone with a custom ID
const { thread: customIdClone } = await memory.cloneThread({
  sourceThreadId: "original-thread-123",
  newThreadId: "my-custom-clone-id",
});

// Clone only the last 5 messages
const { thread: partialClone, clonedMessages } = await memory.cloneThread({
  sourceThreadId: "original-thread-123",
  options: {
    messageLimit: 5,
  },
});

// Clone messages from a specific date range
const { thread: dateFilteredClone } = await memory.cloneThread({
  sourceThreadId: "original-thread-123",
  options: {
    messageFilter: {
      startDate: new Date("2024-01-01"),
      endDate: new Date("2024-01-31"),
    },
  },
});

// Continue conversation on the cloned thread
const response = await agent.generate("Let's try a different approach", {
  threadId: fullClone.id,
  resourceId: fullClone.resourceId,
});

Vector Embeddings

When the Memory instance has semantic recall enabled (with a vector store and embedder configured), cloneThread() automatically creates vector embeddings for all cloned messages. This ensures that semantic search works correctly on the cloned thread.

import { Memory } from "@mastra/memory";
import { LibSQLStore, LibSQLVector } from "@mastra/libsql";

const memory = new Memory({
  storage: new LibSQLStore({ url: "file:./memory.db" }),
  vector: new LibSQLVector({ connectionUrl: "file:./vector.db" }),
  embedder: embeddingModel,
  options: {
    semanticRecall: true,
  },
});

// Clone will also create embeddings for cloned messages
const { thread } = await memory.cloneThread({
  sourceThreadId: "original-thread",
});

// Semantic search works on the cloned thread
const results = await memory.recall({
  threadId: thread.id,
  vectorSearchString: "search query",
});

Related

• Memory Class Reference
• createThread
• Clone Utility Methods
• recall
• Semantic Recall