diff --git a/apps/api/src/db/schema.ts b/apps/api/src/db/schema.ts
index 3b25cd6..f875c7f 100644
--- a/apps/api/src/db/schema.ts
+++ b/apps/api/src/db/schema.ts
@@ -1431,6 +1431,7 @@ export const classLesson = pgTable(
      * 没有它。写入侧在 PUT /classroom/lesson 按 lessonLanguageSchema 校验过
      */
     language: text().$type<LessonLanguage>(),
+    /** 这天第一次布置的老师，别的老师「改」也不换（和 createdAt 一样）。看板上写「HH:mm 谁 布置」 */
     createdBy: integer("created_by").notNull(),
     /**
      * 这天第一次布置的时刻，之后「改」只动 updatedAt。清掉（删行）再布置算重新开始。
diff --git a/apps/api/src/routes/classroom.ts b/apps/api/src/routes/classroom.ts
index 130af28..1840e0b 100644
--- a/apps/api/src/routes/classroom.ts
+++ b/apps/api/src/routes/classroom.ts
@@ -105,15 +105,21 @@ async function visibleProblems(ids: number[]) {
   return new Map(rows.map((row) => [row.id, row]))
 }
 
-/** 老师给这个班今天布置的题（problem.id，按输入顺序）、选的语言和布置时刻；没布置为 null */
+/**
+ * 老师给这个班今天布置的题（problem.id，按输入顺序）、选的语言、布置时刻和布置的老师；
+ * 没布置为 null。老师写真名：老师之间认的是名字，用户名（lwp0201、little）认不出是谁
+ */
 async function lessonPlan(className: string, day: string) {
   const [row] = await db
     .select({
       problemIds: schema.classLesson.problemIds,
       language: schema.classLesson.language,
       createdAt: schema.classLesson.createdAt,
+      createdBy: sql<string>`coalesce(nullif(${schema.userProfile.realName}, ''), ${schema.user.username})`,
     })
     .from(schema.classLesson)
+    .innerJoin(schema.user, eq(schema.user.id, schema.classLesson.createdBy))
+    .leftJoin(schema.userProfile, eq(schema.userProfile.userId, schema.classLesson.createdBy))
     .where(and(eq(schema.classLesson.className, className), eq(schema.classLesson.day, day)))
     .limit(1)
   return row?.problemIds.length ? row : null
@@ -142,6 +148,7 @@ async function classLessonProblems(className: string, lookbackDays: number) {
       day: today,
       language: plan.language ?? null,
       assignedAt: plan.createdAt,
+      assignedBy: plan.createdBy,
       problems: planned.flatMap((id) => {
         const problem = problems.get(id)
         if (!problem) return []
@@ -174,6 +181,7 @@ async function classLessonProblems(className: string, lookbackDays: number) {
     // 推断出来的课不知道老师要的是哪种语言，不限
     language: null,
     assignedAt: null,
+    assignedBy: null,
     problems: picked.flatMap((row) => {
       const problem = problems.get(row.problemId)
       return problem
@@ -400,6 +408,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
       source: null,
       language: null,
       assignedAt: null,
+      assignedBy: null,
       lastLanguage: null,
       problems: [],
       students: [],
@@ -603,6 +612,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
     source: lesson.source,
     language: lesson.language,
     assignedAt: lesson.assignedAt,
+    assignedBy: lesson.assignedBy,
     lastLanguage: last?.language ?? null,
     problems: lesson.problems.map((problem) => ({
       problemId: problem.id,
@@ -742,6 +752,7 @@ classroomRoutes.get("/classroom/today", requireTeacher, async (c) => {
         className,
         source: lesson.source,
         assignedAt: lesson.assignedAt,
+        assignedBy: lesson.assignedBy,
         problems: lesson.problems.map((problem) => ({
           problemDisplayId: problem.displayId,
           title: problem.title,
@@ -867,7 +878,8 @@ classroomRoutes.put("/classroom/lesson", requireTeacher, async (c) => {
     })
     .onConflictDoUpdate({
       target: [schema.classLesson.className, schema.classLesson.day],
-      set: { problemIds, language, createdBy: user.id, updatedAt: now },
+      // 「改」不换布置的人，和 createdAt 一样认第一次
+      set: { problemIds, language, updatedAt: now },
     })
   return success(c, null)
 })
diff --git a/apps/web/src/oj/classroom/board.vue b/apps/web/src/oj/classroom/board.vue
index 999174c..f052213 100644
--- a/apps/web/src/oj/classroom/board.vue
+++ b/apps/web/src/oj/classroom/board.vue
@@ -465,7 +465,7 @@ function lastText(student: ClassBoardStudent) {
           {{ problem.problemDisplayId }}
         </span>
         <span v-if="board.assignedAt" class="assigned">
-          {{ parseTime(board.assignedAt, "HH:mm") }} 布置
+          {{ parseTime(board.assignedAt, "HH:mm") }} {{ board.assignedBy }} 布置
         </span>
         <n-button text class="edit" @click="editing = true">
           <template #icon><Icon icon="ph:pencil-simple" /></template>
diff --git a/apps/web/src/oj/home/TeacherHome.vue b/apps/web/src/oj/home/TeacherHome.vue
index 15becf0..f84ee37 100644
--- a/apps/web/src/oj/home/TeacherHome.vue
+++ b/apps/web/src/oj/home/TeacherHome.vue
@@ -53,7 +53,7 @@ function stateOf(row: ClassRow) {
 function metaOf(row: ClassRow) {
   const parts = [
     row.source === "teacher" && row.assignedAt
-      ? `${parseTime(row.assignedAt, "HH:mm")} 布置了 ${row.problems.length} 道`
+      ? `${parseTime(row.assignedAt, "HH:mm")} ${row.assignedBy} 布置了 ${row.problems.length} 道`
       : `做了 ${row.problems.length} 道`,
   ]
   if (row.activeCount) parts.push(`${row.activeCount}/${row.rosterCount} 人交过`)
diff --git a/packages/contract/src/classroom.ts b/packages/contract/src/classroom.ts
index 7d7d2fa..a84d62e 100644
--- a/packages/contract/src/classroom.ts
+++ b/packages/contract/src/classroom.ts
@@ -172,6 +172,8 @@ export const classBoardSchema = z.object({
   language: lessonLanguageSchema,
   /** 今天第一次布置的时刻，之后改题不变；推断出来的课为 null */
   assignedAt: z.string().nullable(),
+  /** 第一次布置的老师（真名，没有真名用用户名）；推断出来的课为 null */
+  assignedBy: z.string().nullable(),
   /** 这个班最近一次布置选的语言（含今天），给语言下拉当默认值；从没选过为 null */
   lastLanguage: lessonLanguageSchema,
   problems: z.array(classBoardProblemSchema),
@@ -210,6 +212,8 @@ export const classTodaySchema = z.object({
       source: z.enum(["teacher", "inferred"]).nullable(),
       /** 老师布置的时刻；推断出来的为 null */
       assignedAt: z.string().nullable(),
+      /** 布置的老师；推断出来的为 null */
+      assignedBy: z.string().nullable(),
       problems: z.array(
         z.object({
           problemDisplayId: z.string(),