diff --git a/lib/api/comments.ts b/lib/api/comments.ts
index 732bc0a..7ef6cc5 100644
--- a/lib/api/comments.ts
+++ b/lib/api/comments.ts
@@ -112,6 +112,59 @@ export const commentsRoutes = new Elysia({
         return { error: guard.error }
       }
 
+      // ── Anti-spam: content length cap ──────────────────────────
+      const contentStr = JSON.stringify(body.content)
+      if (contentStr.length > 50000) {
+        set.status = 413
+        return { error: "Comment content exceeds maximum size (50KB)" }
+      }
+
+      // ── Anti-spam: duplicate detection ─────────────────────────
+      const fiveMinutesAgo = new Date(Date.now() - 5 * 60 * 1000)
+      const [duplicate] = await db
+        .select({ id: gameComments.id })
+        .from(gameComments)
+        .where(
+          and(
+            eq(gameComments.gameId, params.gameId),
+            eq(gameComments.userId, guard.user.id),
+            eq(gameComments.isRemoved, false),
+            sql`${gameComments.createdAt} >= ${fiveMinutesAgo}`,
+          ),
+        )
+        .limit(1)
+
+      if (duplicate) {
+        const [recent] = await db
+          .select({ content: gameComments.content })
+          .from(gameComments)
+          .where(eq(gameComments.id, duplicate.id))
+          .limit(1)
+
+        if (recent && JSON.stringify(recent.content) === contentStr) {
+          set.status = 409
+          return { error: "Duplicate comment detected — you posted identical content in the last 5 minutes" }
+        }
+      }
+
+      // ── Anti-spam: per-user hourly cap ─────────────────────────
+      const oneHourAgo = new Date(Date.now() - 60 * 60 * 1000)
+      const [{ count: recentCount }] = await db
+        .select({ count: sql<number>`count(*)::int` })
+        .from(gameComments)
+        .where(
+          and(
+            eq(gameComments.userId, guard.user.id),
+            eq(gameComments.isRemoved, false),
+            sql`${gameComments.createdAt} >= ${oneHourAgo}`,
+          ),
+        )
+
+      if (recentCount >= 30) {
+        set.status = 429
+        return { error: "Too many comments — you've reached the hourly limit of 30" }
+      }
+
       // If parentId is provided, verify it exists and belongs to the same game
       if (body.parentId) {
         const [parent] = await db