diff --git a/example/convex/_generated/api.d.ts b/example/convex/_generated/api.d.ts
index 7a9c3698..6739088c 100644
--- a/example/convex/_generated/api.d.ts
+++ b/example/convex/_generated/api.d.ts
@@ -233,6 +233,7 @@ export declare const components: {
             vectors: Array<Array<number> | null>;
           };
           failPendingSteps?: boolean;
+          hideFromUserIdSearch?: boolean;
           messages: Array<{
             error?: string;
             fileIds?: Array<string>;
@@ -836,6 +837,22 @@ export declare const components: {
           }>;
         }
       >;
+      cloneThread: FunctionReference<
+        "action",
+        "internal",
+        {
+          batchSize?: number;
+          copyUserIdForVectorSearch?: boolean;
+          excludeToolMessages?: boolean;
+          insertAtOrder?: number;
+          limit?: number;
+          sourceThreadId: string;
+          statuses?: Array<"pending" | "success" | "failed">;
+          targetThreadId: string;
+          upToAndIncludingMessageId?: string;
+        },
+        number
+      >;
       deleteByIds: FunctionReference<
         "mutation",
         "internal",
diff --git a/src/component/_generated/api.d.ts b/src/component/_generated/api.d.ts
index 3257e2f7..ca538cff 100644
--- a/src/component/_generated/api.d.ts
+++ b/src/component/_generated/api.d.ts
@@ -141,6 +141,7 @@ export type Mounts = {
           vectors: Array<Array<number> | null>;
         };
         failPendingSteps?: boolean;
+        hideFromUserIdSearch?: boolean;
         messages: Array<{
           error?: string;
           fileIds?: Array<string>;
@@ -662,6 +663,22 @@ export type Mounts = {
         }>;
       }
     >;
+    cloneThread: FunctionReference<
+      "action",
+      "public",
+      {
+        batchSize?: number;
+        copyUserIdForVectorSearch?: boolean;
+        excludeToolMessages?: boolean;
+        insertAtOrder?: number;
+        limit?: number;
+        sourceThreadId: string;
+        statuses?: Array<"pending" | "success" | "failed">;
+        targetThreadId: string;
+        upToAndIncludingMessageId?: string;
+      },
+      number
+    >;
     deleteByIds: FunctionReference<
       "mutation",
       "public",
diff --git a/src/component/messages.ts b/src/component/messages.ts
index 380e1022..9af93fd8 100644
--- a/src/component/messages.ts
+++ b/src/component/messages.ts
@@ -24,6 +24,7 @@ import { api, internal } from "./_generated/api.js";
 import type { Doc, Id } from "./_generated/dataModel.js";
 import {
   action,
+  internalMutation,
   internalQuery,
   mutation,
   type MutationCtx,
@@ -130,6 +131,9 @@ const addMessagesArgs = {
   failPendingSteps: v.optional(v.boolean()),
   // A pending message to update. If the pending message failed, abort.
   pendingMessageId: v.optional(v.id("messages")),
+  // if set to true, these messages will not show up in text or vector search
+  // results for the userId
+  hideFromUserIdSearch: v.optional(v.boolean()),
 };
 export const addMessages = mutation({
   args: addMessagesArgs,
@@ -153,6 +157,7 @@ async function addMessagesHandler(
     messages,
     promptMessageId,
     pendingMessageId,
+    hideFromUserIdSearch,
     ...rest
   } = args;
   const promptMessage = promptMessageId && (await ctx.db.get(promptMessageId));
@@ -219,7 +224,7 @@ async function addMessagesHandler(
         vector: embeddings.vectors[i]!,
         model: embeddings.model,
         table: "messages",
-        userId,
+        userId: hideFromUserIdSearch ? undefined : userId,
         threadId,
       });
     }
@@ -230,7 +235,7 @@ async function addMessagesHandler(
       parentMessageId: promptMessageId,
       userId,
       tool: isTool(message.message),
-      text: extractText(message.message),
+      text: hideFromUserIdSearch ? undefined : extractText(message.message),
       status: fail ? "failed" : (message.status ?? "success"),
       error: fail ? error : message.error,
     } satisfies Omit<
@@ -432,64 +437,216 @@ export const updateMessage = mutation({
   },
 });
 
-export const listMessagesByThreadId = query({
+const cloneMessageArgs = {
+  sourceThreadId: v.id("threads"),
+  targetThreadId: v.id("threads"),
+  // defaults to false, so searching for a message by userId will not find
+  // these copies
+  copyUserIdForVectorSearch: v.optional(v.boolean()),
+  // defaults to false, so tool calls & responses will be copied
+  excludeToolMessages: v.optional(v.boolean()),
+  // defaults to copying all messages, but you could just copy success messages.
+  statuses: v.optional(v.array(vMessageStatus)),
+  // stop at this message id
+  upToAndIncludingMessageId: v.optional(v.id("messages")),
+  // defaults to 0. the messages will be inserted starting at this order.
+  insertAtOrder: v.optional(v.number()),
+};
+export const cloneMessageBatch = internalMutation({
   args: {
-    threadId: v.id("threads"),
-    excludeToolMessages: v.optional(v.boolean()),
-    /** What order to sort the messages in. To get the latest, use "desc". */
-    order: v.union(v.literal("asc"), v.literal("desc")),
-    paginationOpts: v.optional(paginationOptsValidator),
-    statuses: v.optional(v.array(vMessageStatus)),
-    upToAndIncludingMessageId: v.optional(v.id("messages")),
+    ...cloneMessageArgs,
+    paginationOpts: paginationOptsValidator,
   },
-  handler: async (ctx, args) => {
-    const statuses =
-      args.statuses ?? vMessageStatus.members.map((m) => m.value);
-    const last =
-      args.upToAndIncludingMessageId &&
-      (await ctx.db.get(args.upToAndIncludingMessageId));
-    assert(
-      !last || last.threadId === args.threadId,
-      "upToAndIncludingMessageId must be a message in the thread",
-    );
-    const toolOptions = args.excludeToolMessages ? [false] : [true, false];
-    const order = args.order ?? "desc";
-    const streams = toolOptions.flatMap((tool) =>
-      statuses.map((status) =>
-        stream(ctx.db, schema)
-          .query("messages")
-          .withIndex("threadId_status_tool_order_stepOrder", (q) => {
-            const qq = q
-              .eq("threadId", args.threadId)
-              .eq("status", status)
-              .eq("tool", tool);
-            if (last) {
-              return qq.lte("order", last.order);
-            }
-            return qq;
-          })
-          .order(order)
-          .filterWith(
-            // We allow all messages on the same order.
-            async (m) =>
-              !last || m.order < last.order || m.order === last.order,
-          ),
-      ),
-    );
-    const messages = await mergedStream(streams, [
-      "order",
-      "stepOrder",
-    ]).paginate(
-      args.paginationOpts ?? {
-        numItems: DEFAULT_RECENT_MESSAGES,
-        cursor: null,
-      },
+  handler: async (
+    ctx,
+    args,
+  ): Promise<{
+    numCopied: number;
+    continueCursor: string;
+    isDone: boolean;
+  }> => {
+    const orderOffset = args.insertAtOrder ?? 0;
+    const result = await listMessagesByThreadIdHandler(ctx, {
+      threadId: args.sourceThreadId,
+      excludeToolMessages: args.excludeToolMessages,
+      order: "desc",
+      paginationOpts: args.paginationOpts,
+      statuses: args.statuses,
+      upToAndIncludingMessageId: args.upToAndIncludingMessageId,
+    });
+
+    const existing =
+      result.page.length === 0
+        ? []
+        : await mergedStream(
+            [true, false].flatMap((tool) =>
+              messageStatuses.map((status) =>
+                stream(ctx.db, schema)
+                  .query("messages")
+                  .withIndex("threadId_status_tool_order_stepOrder", (q) =>
+                    q
+                      .eq("threadId", args.targetThreadId)
+                      .eq("status", status)
+                      .eq("tool", tool)
+                      .gte("order", result.page[0].order)
+                      .lte("order", result.page[result.page.length - 1].order),
+                  ),
+              ),
+            ),
+            ["order", "stepOrder"],
+          ).collect();
+
+    await Promise.all(
+      result.page
+        .filter(
+          (m) =>
+            !existing.some(
+              (e) => e.order === m.order && e.stepOrder === m.stepOrder,
+            ),
+        )
+        .map(async (m) => {
+          // update file refs
+          if (m.fileIds) {
+            await changeRefcount(ctx, [], m.fileIds);
+          }
+          let embeddingId: VectorTableId | undefined = undefined;
+          if (m.embeddingId) {
+            const vector = await ctx.db.get(m.embeddingId);
+            assert(vector, `Vector ${m.embeddingId} not found`);
+            const dimension = vector.vector.length;
+            validateVectorDimension(dimension);
+            embeddingId = await insertVector(ctx, dimension, {
+              ...pick(vector, ["model", "table", "vector"]),
+              userId: args.copyUserIdForVectorSearch
+                ? vector.userId
+                : undefined,
+              threadId: args.targetThreadId,
+            });
+          }
+          await ctx.db.insert("messages", {
+            ...omit(m, [
+              "_id",
+              "_creationTime",
+              "threadId",
+              "order",
+              "embeddingId",
+            ]),
+            embeddingId,
+            threadId: args.targetThreadId,
+            order: orderOffset + m.order,
+          });
+        }),
     );
+    return {
+      numCopied: result.page.length,
+      continueCursor: result.continueCursor,
+      isDone: result.isDone,
+    };
+  },
+});
+
+export const cloneThread = action({
+  args: {
+    ...cloneMessageArgs,
+    batchSize: v.optional(v.number()),
+    // how many messages to copy
+    limit: v.optional(v.number()),
+  },
+  returns: v.number(),
+  handler: async (ctx, args) => {
+    let cursor: string | null = null;
+    let copiedSoFar = 0;
+    while (copiedSoFar < (args.limit ?? Infinity)) {
+      const numToCopy = Math.min(
+        args.batchSize ?? DEFAULT_RECENT_MESSAGES,
+        args.limit ?? Infinity - copiedSoFar,
+      );
+      const result: {
+        numCopied: number;
+        continueCursor: string;
+        isDone: boolean;
+      } = await ctx.runMutation(internal.messages.cloneMessageBatch, {
+        ...args,
+        paginationOpts: {
+          cursor,
+          numItems: numToCopy,
+        },
+      });
+      copiedSoFar += result.numCopied;
+      cursor = result.continueCursor;
+      if (result.isDone) {
+        break;
+      }
+    }
+    return copiedSoFar;
+  },
+});
+
+export const listMessagesByThreadIdArgs = {
+  threadId: v.id("threads"),
+  excludeToolMessages: v.optional(v.boolean()),
+  /** What order to sort the messages in. To get the latest, use "desc". */
+  order: v.union(v.literal("asc"), v.literal("desc")),
+  paginationOpts: v.optional(paginationOptsValidator),
+  statuses: v.optional(v.array(vMessageStatus)),
+  upToAndIncludingMessageId: v.optional(v.id("messages")),
+};
+export const listMessagesByThreadId = query({
+  args: listMessagesByThreadIdArgs,
+  handler: async (ctx, args) => {
+    const messages = await listMessagesByThreadIdHandler(ctx, args);
     return { ...messages, page: messages.page.map(publicMessage) };
   },
   returns: vPaginationResult(vMessageDoc),
 });
 
+async function listMessagesByThreadIdHandler(
+  ctx: QueryCtx,
+  args: ObjectType<typeof listMessagesByThreadIdArgs>,
+) {
+  const statuses = args.statuses ?? vMessageStatus.members.map((m) => m.value);
+  const last =
+    args.upToAndIncludingMessageId &&
+    (await ctx.db.get(args.upToAndIncludingMessageId));
+  assert(
+    !last || last.threadId === args.threadId,
+    "upToAndIncludingMessageId must be a message in the thread",
+  );
+  const toolOptions = args.excludeToolMessages ? [false] : [true, false];
+  const order = args.order ?? "desc";
+  const streams = toolOptions.flatMap((tool) =>
+    statuses.map((status) =>
+      stream(ctx.db, schema)
+        .query("messages")
+        .withIndex("threadId_status_tool_order_stepOrder", (q) => {
+          const qq = q
+            .eq("threadId", args.threadId)
+            .eq("status", status)
+            .eq("tool", tool);
+          if (last) {
+            return qq.lte("order", last.order);
+          }
+          return qq;
+        })
+        .order(order)
+        .filterWith(
+          // We allow all messages on the same order.
+          async (m) => !last || m.order <= last.order,
+        ),
+    ),
+  );
+  const messages = await mergedStream(streams, ["order", "stepOrder"]).paginate(
+    args.paginationOpts ?? {
+      numItems: DEFAULT_RECENT_MESSAGES,
+      cursor: null,
+    },
+  );
+  if (messages.page.length === 0) {
+    messages.isDone = true;
+  }
+  return messages;
+}
+
 export const getMessagesByIds = query({
   args: { messageIds: v.array(v.id("messages")) },
   handler: async (ctx, args) => {