app/models/team.ts

@@ -1,4 +1,4 @@
-import { eq, and, isNull } from "drizzle-orm";
+import { eq, and, isNull, ne, sql } from "drizzle-orm";
 import { database } from "~/database/context";
 import * as schema from "~/database/schema";
 import { generateFlagConfig } from "~/lib/flag-generator";
@@ -61,6 +61,21 @@ export async function findTeamByOwnerAndSeason(
   });
 }
 
+export async function findTeamByNameInSeason(
+  seasonId: string,
+  name: string,
+  excludeTeamId?: string
+): Promise<Team | undefined> {
+  const db = database();
+  return await db.query.teams.findFirst({
+    where: and(
+      eq(schema.teams.seasonId, seasonId),
+      sql`lower(${schema.teams.name}) = lower(${name})`,
+      excludeTeamId ? ne(schema.teams.id, excludeTeamId) : undefined
+    ),
+  });
+}
+
 export async function findAvailableTeams(seasonId: string): Promise<Team[]> {
   const db = database();
   return await db.query.teams.findMany({

app/routes/leagues/$leagueId.settings.server.ts

@@ -19,7 +19,7 @@ import { deleteSeasonTimers } from "~/models/draft-timer";
 import { findCurrentSeasonWithSports, type NewSeason, updateSeason } from "~/models/season";
 import { linkMultipleSportsToSeason, unlinkSportFromSeason } from "~/models/season-sport";
 import { findDraftableSportsSeasons, findSportsSeasonsByIds } from "~/models/sports-season";
-import { claimTeam, deleteTeam, findTeamById, findTeamsBySeasonId, removeTeamOwner, renameTeam } from "~/models/team";
+import { claimTeam, deleteTeam, findTeamById, findTeamByNameInSeason, findTeamsBySeasonId, removeTeamOwner, renameTeam } from "~/models/team";
 import { findUserById, findUsersByIds, getUserDisplayName, isUserAdmin } from "~/models/user";
 import { logCommissionerAction } from "~/models/audit-log";
 import { parseDraftSpeed } from "~/lib/draft-timer";
@@ -417,6 +417,10 @@ export async function action(args: Route.ActionArgs) {
         if (username) {
           const strippedName = stripOwnerFromTeamName(team.name, username);
           if (strippedName !== team.name) {
+            const nameConflict = await findTeamByNameInSeason(team.seasonId, strippedName, teamId);
+            if (nameConflict) {
+              return { error: "Cannot remove owner: the resulting team name is already taken in this season." };
+            }
             await renameTeam(teamId, strippedName);
           }
           await removeTeamOwner(teamId);
@@ -478,6 +482,10 @@ export async function action(args: Route.ActionArgs) {
         targetTeam.name,
         assignedUser.username ?? assignedUser.displayName ?? "Member"
       );
+      const nameConflict = await findTeamByNameInSeason(season.id, teamName, teamId);
+      if (nameConflict) {
+        return { error: "Cannot assign owner: the resulting team name is already taken in this season." };
+      }
       await claimTeam(teamId, assignedUserId, teamName);
 
       return { success: true, message: "Owner assigned successfully" };

app/routes/teams/$teamId.settings.tsx

@@ -4,6 +4,7 @@ import type { Route } from "./+types/$teamId.settings";
 
 import {
   findTeamById,
+  findTeamByNameInSeason,
   updateTeam,
   removeTeamOwner,
 } from "~/models/team";
@@ -156,8 +157,17 @@ export async function action(args: Route.ActionArgs) {
       return { error: "Team name is required" };
     }
 
+    const trimmedName = name.trim();
+    if (!trimmedName) {
+      return { error: "Team name is required" };
+    }
+    const conflict = await findTeamByNameInSeason(team.seasonId, trimmedName, teamId);
+    if (conflict) {
+      return { error: "A team with that name already exists in this season." };
+    }
+
     await updateTeam(teamId, {
-      name: name.trim(),
+      name: trimmedName,
     });
     await syncPrivateBracktParticipants(team.seasonId);
 

database/schema.ts

@@ -246,7 +246,9 @@ export const teams = pgTable("teams", {
   ownerId: varchar("owner_id", { length: 255 }), // UUID → users.id, nullable
   createdAt: timestamp("created_at").defaultNow().notNull(),
   updatedAt: timestamp("updated_at").defaultNow().notNull(),
-});
+}, (t) => [
+  uniqueIndex("teams_season_id_lower_name_unique").on(t.seasonId, sql`lower(${t.name})`),
+]);
 
 export const draftSlots = pgTable("draft_slots", {
   id: uuid("id").primaryKey().defaultRandom(),

drizzle/0113_bent_banshee.sql

@@ -0,0 +1 @@
+CREATE UNIQUE INDEX IF NOT EXISTS "teams_season_id_lower_name_unique" ON "teams" USING btree ("season_id",lower("name"));

drizzle/meta/_journal.json

@@ -792,6 +792,13 @@
       "when": 1779318579169,
       "tag": "0112_married_captain_midlands",
       "breakpoints": true
+    },
+    {
+      "idx": 113,
+      "version": "7",
+      "when": 1779579877169,
+      "tag": "0113_bent_banshee",
+      "breakpoints": true
     }
   ]
 }