diff --git a/api/src/server.ts b/api/src/server.ts
index bc15dfd..9ca3321 100644
--- a/api/src/server.ts
+++ b/api/src/server.ts
@@ -3395,6 +3395,27 @@ async function getLatestBudgetSession(app: any, userId: string) {
   });
 }
 
+async function ensureBudgetSession(app: any, userId: string, fallbackAvailableCents = 0) {
+  const existing = await getLatestBudgetSession(app, userId);
+  if (existing) return existing;
+
+  const now = new Date();
+  const start = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), 1, 0, 0, 0, 0));
+  const end = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth() + 1, 1, 0, 0, 0, 0));
+
+  return app.prisma.budgetSession.create({
+    data: {
+      userId,
+      periodStart: start,
+      periodEnd: end,
+      totalBudgetCents: BigInt(Math.max(0, fallbackAvailableCents)),
+      allocatedCents: 0n,
+      fundedCents: 0n,
+      availableCents: BigInt(Math.max(0, fallbackAvailableCents)),
+    },
+  });
+}
+
 app.post("/variable-categories", mutationRateLimit, async (req, reply) => {
   const parsed = CatBody.safeParse(req.body);
   if (!parsed.success) {
@@ -3527,14 +3548,13 @@ app.post("/variable-categories/rebalance", mutationRateLimit, async (req, reply)
 
 app.get("/variable-categories/manual-rebalance", async (req, reply) => {
   const userId = req.userId;
-  const session = await getLatestBudgetSession(app, userId);
-  if (!session) return reply.code(400).send({ ok: false, code: "NO_BUDGET_SESSION" });
-
   const cats = await app.prisma.variableCategory.findMany({
     where: { userId },
     orderBy: [{ priority: "asc" }, { name: "asc" }],
     select: { id: true, name: true, percent: true, isSavings: true, balanceCents: true },
   });
+  const totalBalance = cats.reduce((s, c) => s + Number(c.balanceCents ?? 0n), 0);
+  const session = await ensureBudgetSession(app, userId, totalBalance);
 
   return reply.send({
     ok: true,
@@ -3550,10 +3570,6 @@ app.post("/variable-categories/manual-rebalance", async (req, reply) => {
     return reply.code(400).send({ ok: false, code: "INVALID_BODY" });
   }
 
-  const session = await getLatestBudgetSession(app, userId);
-  if (!session) return reply.code(400).send({ ok: false, code: "NO_BUDGET_SESSION" });
-  const availableCents = Number(session.availableCents ?? 0n);
-
   const cats = await app.prisma.variableCategory.findMany({
     where: { userId },
     orderBy: [{ priority: "asc" }, { name: "asc" }],
@@ -3561,6 +3577,10 @@ app.post("/variable-categories/manual-rebalance", async (req, reply) => {
   });
   if (cats.length === 0) return reply.code(400).send({ ok: false, code: "NO_CATEGORIES" });
 
+  const totalBalance = cats.reduce((s, c) => s + Number(c.balanceCents ?? 0n), 0);
+  const session = await ensureBudgetSession(app, userId, totalBalance);
+  const availableCents = Number(session.availableCents ?? 0n);
+
   const targetMap = new Map<string, number>();
   for (const t of parsed.data.targets) {
     if (targetMap.has(t.id)) return reply.code(400).send({ ok: false, code: "DUPLICATE_ID" });