diff --git a/src/db/schema.ts b/src/db/schema.ts
index 67b6b8a..d182609 100644
--- a/src/db/schema.ts
+++ b/src/db/schema.ts
@@ -33,6 +33,9 @@ export const threads = sqliteTable("threads", {
   name: text("name").notNull(),
   status: text("status").notNull().default("active"),
   resolvedCandidateId: integer("resolved_candidate_id"),
+  categoryId: integer("category_id")
+    .notNull()
+    .references(() => categories.id),
   createdAt: integer("created_at", { mode: "timestamp" })
     .notNull()
     .$defaultFn(() => new Date()),
diff --git a/src/shared/schemas.ts b/src/shared/schemas.ts
index d73a1c9..724a48b 100644
--- a/src/shared/schemas.ts
+++ b/src/shared/schemas.ts
@@ -27,10 +27,12 @@ export const updateCategorySchema = z.object({
 // Thread schemas
 export const createThreadSchema = z.object({
   name: z.string().min(1, "Thread name is required"),
+  categoryId: z.number().int().positive(),
 });
 
 export const updateThreadSchema = z.object({
   name: z.string().min(1).optional(),
+  categoryId: z.number().int().positive().optional(),
 });
 
 // Candidate schemas (same fields as items)
diff --git a/tests/helpers/db.ts b/tests/helpers/db.ts
index a500b35..1de3956 100644
--- a/tests/helpers/db.ts
+++ b/tests/helpers/db.ts
@@ -37,6 +37,7 @@ export function createTestDb() {
       name TEXT NOT NULL,
       status TEXT NOT NULL DEFAULT 'active',
       resolved_candidate_id INTEGER,
+      category_id INTEGER NOT NULL REFERENCES categories(id),
       created_at INTEGER NOT NULL DEFAULT (unixepoch()),
       updated_at INTEGER NOT NULL DEFAULT (unixepoch())
     )