diff --git a/backend/src/db/schema.ts b/backend/src/db/schema.ts
index c70dc8a..913ba7f 100644
--- a/backend/src/db/schema.ts
+++ b/backend/src/db/schema.ts
@@ -3,7 +3,6 @@ import {
   uuid,
   text,
   integer,
-  serial,
   timestamp,
   jsonb,
   pgEnum,
@@ -41,7 +40,7 @@ export interface ProgressNote {
 
 export const tasks = pgTable("tasks", {
   id: uuid("id").defaultRandom().primaryKey(),
-  taskNumber: serial("task_number").notNull(),
+  taskNumber: integer("task_number"),
   title: text("title").notNull(),
   description: text("description"),
   source: taskSourceEnum("source").notNull().default("donovan"),
diff --git a/backend/src/index.ts b/backend/src/index.ts
index 7c0ecc2..a6ff7b3 100644
--- a/backend/src/index.ts
+++ b/backend/src/index.ts
@@ -2,9 +2,38 @@ import { Elysia } from "elysia";
 import { cors } from "@elysiajs/cors";
 import { taskRoutes } from "./routes/tasks";
 import { auth } from "./lib/auth";
+import { db } from "./db";
+import { tasks } from "./db/schema";
+import { isNull, asc, sql } from "drizzle-orm";
 
 const PORT = process.env.PORT || 3100;
 
+// Backfill task numbers for existing tasks that don't have one
+async function backfillTaskNumbers() {
+  const unnumbered = await db
+    .select()
+    .from(tasks)
+    .where(isNull(tasks.taskNumber))
+    .orderBy(asc(tasks.createdAt));
+
+  if (unnumbered.length === 0) return;
+
+  const maxNum = await db
+    .select({ max: sql<number>`COALESCE(MAX(${tasks.taskNumber}), 0)` })
+    .from(tasks);
+  let next = (maxNum[0]?.max ?? 0) + 1;
+
+  for (const task of unnumbered) {
+    await db
+      .update(tasks)
+      .set({ taskNumber: next++ })
+      .where(sql`${tasks.id} = ${task.id}`);
+  }
+  console.log(`Backfilled ${unnumbered.length} task numbers (${next - unnumbered.length} to ${next - 1})`);
+}
+
+backfillTaskNumbers().catch(console.error);
+
 const app = new Elysia()
   .use(
     cors({
diff --git a/backend/src/routes/tasks.ts b/backend/src/routes/tasks.ts
index 3330e30..f2adfec 100644
--- a/backend/src/routes/tasks.ts
+++ b/backend/src/routes/tasks.ts
@@ -119,6 +119,12 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
       const maxPos = await db
         .select({ max: sql<number>`COALESCE(MAX(${tasks.position}), 0)` })
         .from(tasks);
+      // Get next task number
+      const maxNum = await db
+        .select({ max: sql<number>`COALESCE(MAX(${tasks.taskNumber}), 0)` })
+        .from(tasks);
+      const nextNumber = (maxNum[0]?.max ?? 0) + 1;
+
       const newTask = await db
         .insert(tasks)
         .values({
@@ -128,6 +134,7 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
           status: body.status || "queued",
           priority: body.priority || "medium",
           position: (maxPos[0]?.max ?? 0) + 1,
+          taskNumber: nextNumber,
           progressNotes: [],
         })
         .returning();