feat: show rejoin link when bot is already in a fight

- Track active fight IDs per bot in orchestrator (Set → Map)
- Return fightId in "already in fight" error responses (409)
- Frontend shows "REJOIN FIGHT" link instead of generic error

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/engine/orchestrator.ts

@@ -47,7 +47,8 @@ interface WebhookResponse {
 import { MAX_ROUNDS, KO_THRESHOLD, MAX_RESPONSE_BYTES, STARTING_HP, ELO_K_FACTOR, ELO_K_FACTOR_MOCK, MAX_ANSWER_LENGTH, MAX_TRASH_TALK_LENGTH } from '../lib/constants.js'
 
 // Track bots currently in a fight to prevent concurrent fights
-const activeFighters = new Set<string>()
+// Maps botId → fightId so we can direct users to their active fight
+const activeFighters = new Map<string, string>()
 
 export function getActiveFighterCount(): number {
   return activeFighters.size
@@ -57,6 +58,10 @@ export function isInFight(botId: string): boolean {
   return activeFighters.has(botId)
 }
 
+export function getActiveFightId(botId: string): string | undefined {
+  return activeFighters.get(botId)
+}
+
 function emit(fightId: string, type: string, data: Record<string, unknown>) {
   fightEvents.emit({
     fightId,
@@ -621,13 +626,13 @@ export async function runFight(botAId: string, botBId: string, mode: 'free' | 'r
   if (activeFighters.has(botAId)) throw new Error(`Bot ${botAId} is already in a fight`)
   if (activeFighters.has(botBId)) throw new Error(`Bot ${botBId} is already in a fight`)
 
-  activeFighters.add(botAId)
-  activeFighters.add(botBId)
+  const [botA, botB] = await loadBots(botAId, botBId)
+  const arena = randomArena()
+  const fightId = await createFightRecord(botA, botB, arena, mode)
+  activeFighters.set(botAId, fightId)
+  activeFighters.set(botBId, fightId)
 
   try {
-    const [botA, botB] = await loadBots(botAId, botBId)
-    const arena = randomArena()
-    const fightId = await createFightRecord(botA, botB, arena, mode)
     await executeFightRounds(fightId, botA, botB, arena, mode)
     return fightId
   } finally {
@@ -644,12 +649,11 @@ export async function runFightAsync(botAId: string, botBId: string, mode: 'free'
   if (activeFighters.has(botAId)) throw new Error(`Bot ${botAId} is already in a fight`)
   if (activeFighters.has(botBId)) throw new Error(`Bot ${botBId} is already in a fight`)
 
-  activeFighters.add(botAId)
-  activeFighters.add(botBId)
-
   const [botA, botB] = await loadBots(botAId, botBId)
   const arena = randomArena()
   const fightId = await createFightRecord(botA, botB, arena, mode)
+  activeFighters.set(botAId, fightId)
+  activeFighters.set(botBId, fightId)
 
   executeFightRounds(fightId, botA, botB, arena, mode)
     .catch(err => {

server/src/engine/queue.ts

@@ -1,7 +1,7 @@
 import { db, schema } from '../db/index.js'
 import { logger } from '../lib/logger.js'
 import { eq } from 'drizzle-orm'
-import { runFightAsync, isInFight } from './orchestrator.js'
+import { runFightAsync, isInFight, getActiveFightId } from './orchestrator.js'
 import { seedMockBots } from './mock.js'
 
 interface QueueEntry {
@@ -55,9 +55,12 @@ export async function joinQueue(botId: string): Promise<string> {
     throw new Error(`Cooldown active. Wait ${waitSec}s.`)
   }
 
-  // Check if already in a fight
+  // Check if already in a fight — return the fight ID so frontend can redirect
   if (isInFight(botId)) {
-    throw new Error('Bot is already in a fight.')
+    const activeFightId = getActiveFightId(botId)
+    const err = new Error('Bot is already in a fight.')
+    ;(err as any).fightId = activeFightId
+    throw err
   }
 
   // Load bot

server/src/routes/fights.ts

@@ -7,7 +7,7 @@ import { eq, desc, inArray } from 'drizzle-orm'
 import { ARENAS } from '../engine/arenas.js'
 import { runMockFight, isClassicBot } from '../engine/mock.js'
 import { startFightLoop } from '../engine/fight-loop.js'
-import { runFight, runFightAsync, isInFight } from '../engine/orchestrator.js'
+import { runFight, runFightAsync, isInFight, getActiveFightId } from '../engine/orchestrator.js'
 import { fightEvents } from '../engine/events.js'
 import { botRateLimit } from '../middleware/rate-limit.js'
 import { getPendingChallenge, getPendingAnswers, submitHumanResponse } from '../engine/human-responses.js'
@@ -233,7 +233,7 @@ fightsRouter.post('/matchmake/:botId', botRateLimit(10_000), async (c) => {
   }
 
   if (isInFight(botId)) {
-    return c.json({ error: 'Bot is already in a fight.' }, 400)
+    return c.json({ error: 'Bot is already in a fight.', fightId: getActiveFightId(botId) }, 409)
   }
 
   const allBots = await db.select()
@@ -285,7 +285,7 @@ fightsRouter.post('/practice/:botId', botRateLimit(10_000), async (c) => {
   const bot = botRows[0]
 
   if (isInFight(botId)) {
-    return c.json({ error: 'Bot is already in a fight.' }, 400)
+    return c.json({ error: 'Bot is already in a fight.', fightId: getActiveFightId(botId) }, 409)
   }
 
   // Find all classic bots

server/src/routes/queue.ts

@@ -31,9 +31,10 @@ queueRouter.post('/join/:botId', async (c) => {
   try {
     const fightId = await joinQueue(botId)
     return c.json({ fightId, message: 'Matched! Fight starting.' })
-  } catch (err) {
+  } catch (err: any) {
     const message = err instanceof Error ? err.message : 'Queue error'
-    return c.json({ error: message }, 500)
+    const status = message.includes('already in a fight') ? 409 : 500
+    return c.json({ error: message, fightId: err?.fightId || undefined }, status)
   }
 })