diff --git a/.env.example b/.env.example
index 44d5b700..782f4cee 100644
--- a/.env.example
+++ b/.env.example
@@ -38,6 +38,10 @@ GATEWAY_INTERNAL_API_URL=http://127.0.0.1:13000
 ACCOUNT_ICON_RESET_RECONCILE_INTERVAL_MS=30000
 WEB_PUSH_OUTBOX_POLL_MS=1000
 GATEWAY_PUBLIC_URL=http://localhost:13000
+# Gateway authentication protection shares atomic 60s counters under this prefix.
+# Defaults: 10 login attempts/account, 600 auth requests/socket peer, 1200 globally;
+# expensive auth work is capped at 4/process. Forwarded headers are not trusted.
+# These are security defaults in auth/attemptBudget.ts, not disable-able env toggles.
 GATEWAY_REDIS_PREFIX=sammo:gateway
 GATEWAY_DB_SCHEMA=public
 GATEWAY_WORKSPACE_ROOT=/path/to/core2026
diff --git a/app/gateway-api/src/auth/attemptBudget.ts b/app/gateway-api/src/auth/attemptBudget.ts
new file mode 100644
index 00000000..86278f20
--- /dev/null
+++ b/app/gateway-api/src/auth/attemptBudget.ts
@@ -0,0 +1,187 @@
+import { createHmac } from 'node:crypto';
+
+export interface AuthCounter {
+    key: string;
+    limit: number;
+    windowMs: number;
+}
+
+export interface AuthCounterStore {
+    readonly available?: boolean;
+    /** Atomically check every counter, then charge them only when accepted. */
+    consume(counters: AuthCounter[]): Promise<number>;
+}
+
+export class AuthBudgetError extends Error {
+    constructor(
+        readonly reason: 'limited' | 'unavailable',
+        readonly retryAfterSeconds = 1
+    ) {
+        super(
+            reason === 'limited'
+                ? 'Authentication attempts are temporarily limited.'
+                : 'Authentication protection is unavailable.'
+        );
+    }
+}
+
+const CONSUME_SCRIPT = `
+local retry = 0
+for i, key in ipairs(KEYS) do
+    local count = tonumber(redis.call('GET', key) or '0')
+    if count >= tonumber(ARGV[i * 2 - 1]) then
+        local ttl = redis.call('PTTL', key)
+        if ttl < 0 then
+            return -1
+        end
+        retry = math.max(retry, math.max(ttl, 1))
+    end
+end
+if retry > 0 then return retry end
+for i, key in ipairs(KEYS) do
+    local count = redis.call('INCR', key)
+    if count == 1 then redis.call('PEXPIRE', key, ARGV[i * 2]) end
+end
+return 0
+`;
+
+export class RedisAuthCounterStore implements AuthCounterStore {
+    constructor(
+        private readonly client: {
+            readonly isReady?: boolean;
+            withAbortSignal?: (signal: AbortSignal) => {
+                eval: (script: string, options: { keys: string[]; arguments: string[] }) => Promise<unknown>;
+            };
+            eval: (script: string, options: { keys: string[]; arguments: string[] }) => Promise<unknown>;
+        }
+    ) {}
+
+    get available(): boolean {
+        return this.client.isReady !== false;
+    }
+
+    async consume(counters: AuthCounter[]): Promise<number> {
+        if (this.client.isReady === false) throw new AuthBudgetError('unavailable');
+        const client = this.client.withAbortSignal?.(AbortSignal.timeout(2000)) ?? this.client;
+        const result = await client.eval(CONSUME_SCRIPT, {
+            keys: counters.map((counter) => counter.key),
+            arguments: counters.flatMap((counter) => [String(counter.limit), String(counter.windowMs)]),
+        });
+        if (typeof result !== 'number' || !Number.isFinite(result) || result < 0) {
+            throw new AuthBudgetError('unavailable');
+        }
+        return result;
+    }
+}
+
+/** Direct callers/tests have a bounded local store; the HTTP server always injects Redis. */
+export class InMemoryAuthCounterStore implements AuthCounterStore {
+    private readonly entries = new Map<string, { count: number; expiresAt: number }>();
+
+    async consume(counters: AuthCounter[]): Promise<number> {
+        const now = Date.now();
+        for (const [key, entry] of this.entries) if (entry.expiresAt <= now) this.entries.delete(key);
+        if (this.entries.size + counters.filter((counter) => !this.entries.has(counter.key)).length > 8192) {
+            throw new AuthBudgetError('unavailable');
+        }
+        let retryMs = 0;
+        for (const counter of counters) {
+            const entry = this.entries.get(counter.key);
+            if (entry && entry.count >= counter.limit) retryMs = Math.max(retryMs, entry.expiresAt - now);
+        }
+        if (retryMs > 0) return retryMs;
+        for (const counter of counters) {
+            const entry = this.entries.get(counter.key) ?? { count: 0, expiresAt: now + counter.windowMs };
+            entry.count += 1;
+            this.entries.set(counter.key, entry);
+        }
+        return 0;
+    }
+}
+
+const EXPENSIVE_ACTIONS = new Set([
+    'auth.bootstrapLocal',
+    'auth.kakaoExchange',
+    'auth.kakaoResolveAccount',
+    'auth.kakaoSetPassword',
+    'auth.register',
+    'auth.registerLocal',
+    'auth.login',
+    'auth.kakaoOtp',
+    'account.changePassword',
+    'account.scheduleDeletion',
+]);
+const PUBLIC_ACTIONS = new Set(['auth.passwordKey', 'auth.checkRegistrationField', 'auth.kakaoStart']);
+
+export const isBudgetedAuthAction = (action: string): boolean =>
+    EXPENSIVE_ACTIONS.has(action) || PUBLIC_ACTIONS.has(action);
+
+export class AuthAttemptBudget {
+    private active = 0;
+    private pendingChecks = 0;
+
+    constructor(
+        private readonly store: AuthCounterStore,
+        private readonly prefix: string,
+        private readonly secret: string
+    ) {}
+
+    private key(kind: string, value: string): string {
+        const digest = createHmac('sha256', this.secret).update(`auth-budget-v1:${kind}:${value}`).digest('hex');
+        return `${this.prefix}:auth-budget:v1:${kind}:${digest}`;
+    }
+
+    async run<T>(
+        action: string,
+        client: string,
+        subject: string | undefined | (() => Promise<string | undefined>),
+        work: () => Promise<T>
+    ): Promise<T> {
+        if (this.store.available === false || this.pendingChecks >= 32) throw new AuthBudgetError('unavailable');
+        const expensive = EXPENSIVE_ACTIONS.has(action);
+        if (expensive && this.active >= 4) throw new AuthBudgetError('limited');
+        if (expensive) this.active += 1;
+        try {
+            const consume = async (): Promise<number> => {
+                const resolvedSubject = typeof subject === 'function' ? await subject() : subject;
+                const counters: AuthCounter[] = [
+                    { key: this.key('global', 'all'), limit: 1200, windowMs: 60_000 },
+                    { key: this.key('client', client), limit: 600, windowMs: 60_000 },
+                ];
+                if (resolvedSubject)
+                    counters.push({ key: this.key('subject', resolvedSubject), limit: 10, windowMs: 60_000 });
+                return this.store.consume(counters);
+            };
+            this.pendingChecks += 1;
+            const checking = consume();
+            // A caller timeout does not prove the underlying Redis/actor read settled.
+            void checking.then(
+                () => {
+                    this.pendingChecks -= 1;
+                },
+                () => {
+                    this.pendingChecks -= 1;
+                }
+            );
+            let timeout: ReturnType<typeof setTimeout> | undefined;
+            let retryMs: number;
+            try {
+                retryMs = await Promise.race([
+                    checking,
+                    new Promise<never>((_resolve, reject) => {
+                        timeout = setTimeout(() => reject(new AuthBudgetError('unavailable')), 2000);
+                        timeout.unref();
+                    }),
+                ]);
+            } catch {
+                throw new AuthBudgetError('unavailable');
+            } finally {
+                clearTimeout(timeout);
+            }
+            if (retryMs > 0) throw new AuthBudgetError('limited', Math.max(1, Math.ceil(retryMs / 1000)));
+            return await work();
+        } finally {
+            if (expensive) this.active -= 1;
+        }
+    }
+}
diff --git a/app/gateway-api/src/auth/kakaoClient.ts b/app/gateway-api/src/auth/kakaoClient.ts
index 171071d0..4c1cffd6 100644
--- a/app/gateway-api/src/auth/kakaoClient.ts
+++ b/app/gateway-api/src/auth/kakaoClient.ts
@@ -4,6 +4,7 @@ export interface KakaoOAuthConfig {
     redirectUri: string;
     oauthHost?: string;
     apiHost?: string;
+    requestTimeoutMs?: number;
 }
 
 export interface KakaoOAuthToken {
@@ -52,12 +53,57 @@ export class KakaoOAuthClient {
     private readonly redirectUri: string;
     private readonly oauthHost: string;
     private readonly apiHost: string;
+    private readonly requestTimeoutMs: number;
 
     constructor(config: KakaoOAuthConfig) {
         this.restKey = config.restKey;
         this.redirectUri = config.redirectUri;
         this.oauthHost = config.oauthHost ?? 'https://kauth.kakao.com';
         this.apiHost = config.apiHost ?? 'https://kapi.kakao.com';
+        this.requestTimeoutMs = config.requestTimeoutMs ?? 10_000;
+        if (!Number.isInteger(this.requestTimeoutMs) || this.requestTimeoutMs < 50 || this.requestTimeoutMs > 10_000) {
+            throw new Error('Kakao request timeout must be between 50 and 10000 milliseconds.');
+        }
+    }
+
+    private async requestJson(
+        url: URL,
+        init: RequestInit
+    ): Promise<{ response: Response; payload: Record<string, unknown> }> {
+        try {
+            const response = await fetch(url, {
+                ...init,
+                redirect: 'error',
+                signal: AbortSignal.timeout(this.requestTimeoutMs),
+            });
+            if (!response.body) throw new Error('Missing response body.');
+            const reader = response.body.getReader();
+            const chunks: Uint8Array[] = [];
+            let bytes = 0;
+            try {
+                while (true) {
+                    const chunk = await reader.read();
+                    if (chunk.done) break;
+                    bytes += chunk.value.byteLength;
+                    if (bytes > 64 * 1024) {
+                        void reader.cancel().catch(() => undefined);
+                        throw new Error('Response is too large.');
+                    }
+                    chunks.push(chunk.value);
+                }
+            } finally {
+                reader.releaseLock();
+            }
+            const payload: unknown = JSON.parse(
+                new TextDecoder('utf-8', { fatal: true }).decode(Buffer.concat(chunks))
+            );
+            if (!payload || typeof payload !== 'object' || Array.isArray(payload))
+                throw new Error('Invalid response shape.');
+            return { response, payload: payload as Record<string, unknown> };
+        } catch {
+            // Provider/network payloads can include access tokens or account details.
+            throw new Error('Kakao HTTP request failed.');
+        }
     }
 
     buildAuthUrl(state: string, scopes: string[]): string {
@@ -73,7 +119,7 @@ export class KakaoOAuthClient {
     }
 
     async exchangeCode(code: string): Promise<KakaoOAuthToken> {
-        const response = await fetch(new URL('/oauth/token', this.oauthHost), {
+        const { response, payload } = await this.requestJson(new URL('/oauth/token', this.oauthHost), {
             method: 'POST',
             headers: {
                 'Content-Type': 'application/x-www-form-urlencoded',
@@ -85,15 +131,14 @@ export class KakaoOAuthClient {
                 code,
             }),
         });
-        const payload = (await response.json()) as Record<string, unknown>;
         if (!response.ok) {
-            throw new Error(`Kakao OAuth token error: ${JSON.stringify(payload)}`);
+            throw new Error('Kakao OAuth token error.');
         }
         return parseToken(payload);
     }
 
     async refreshToken(refreshToken: string): Promise<KakaoOAuthToken> {
-        const response = await fetch(new URL('/oauth/token', this.oauthHost), {
+        const { response, payload } = await this.requestJson(new URL('/oauth/token', this.oauthHost), {
             method: 'POST',
             headers: {
                 'Content-Type': 'application/x-www-form-urlencoded',
@@ -104,27 +149,25 @@ export class KakaoOAuthClient {
                 refresh_token: refreshToken,
             }),
         });
-        const payload = (await response.json()) as Record<string, unknown>;
         if (!response.ok) {
-            throw new Error(`Kakao OAuth refresh error: ${JSON.stringify(payload)}`);
+            throw new Error('Kakao OAuth refresh error.');
         }
         return parseToken(payload);
     }
 
     async signup(accessToken: string): Promise<KakaoSignupResult> {
-        const response = await fetch(new URL('/v1/user/signup', this.apiHost), {
+        const { response, payload } = await this.requestJson(new URL('/v1/user/signup', this.apiHost), {
             headers: {
                 Authorization: `Bearer ${accessToken}`,
             },
         });
-        const payload = (await response.json()) as Record<string, unknown>;
         if (!response.ok && payload.code === -102 && payload.msg === 'already registered') {
             return {
                 alreadyRegistered: true,
             };
         }
         if (!response.ok) {
-            throw new Error(`Kakao signup error: ${JSON.stringify(payload)}`);
+            throw new Error('Kakao signup error.');
         }
         return {
             id: payload.id ? String(payload.id) : undefined,
@@ -133,15 +176,14 @@ export class KakaoOAuthClient {
     }
 
     async getMe(accessToken: string): Promise<KakaoUserInfo> {
-        const response = await fetch(new URL('/v2/user/me', this.apiHost), {
+        const { response, payload } = await this.requestJson(new URL('/v2/user/me', this.apiHost), {
             method: 'GET',
             headers: {
                 Authorization: `Bearer ${accessToken}`,
             },
         });
-        const payload = (await response.json()) as Record<string, unknown>;
         if (!response.ok) {
-            throw new Error(`Kakao me error: ${JSON.stringify(payload)}`);
+            throw new Error('Kakao me error.');
         }
         const kakaoAccount = (payload.kakao_account ?? {}) as Record<string, unknown>;
         return {
@@ -156,7 +198,7 @@ export class KakaoOAuthClient {
     }
 
     async sendTalkMessage(accessToken: string, message: string, link: string): Promise<void> {
-        const response = await fetch(new URL('/v2/api/talk/memo/default/send', this.apiHost), {
+        const { response, payload } = await this.requestJson(new URL('/v2/api/talk/memo/default/send', this.apiHost), {
             method: 'POST',
             headers: {
                 Authorization: `Bearer ${accessToken}`,
@@ -174,10 +216,9 @@ export class KakaoOAuthClient {
                 }),
             }),
         });
-        const payload = (await response.json()) as Record<string, unknown>;
         const code = Number(payload.code ?? 0);
         if (!response.ok || code < 0) {
-            throw new Error(`Kakao talk message error: ${JSON.stringify(payload)}`);
+            throw new Error('Kakao talk message error.');
         }
     }
 }
diff --git a/app/gateway-api/src/context.ts b/app/gateway-api/src/context.ts
index 6fc94805..abe2792b 100644
--- a/app/gateway-api/src/context.ts
+++ b/app/gateway-api/src/context.ts
@@ -1,3 +1,4 @@
+import { AuthAttemptBudget, InMemoryAuthCounterStore } from './auth/attemptBudget.js';
 import type { GatewayFlushPublisher } from './auth/flushPublisher.js';
 import type { GatewaySessionService } from './auth/sessionService.js';
 import type { UserRepository } from './auth/userRepository.js';
@@ -40,6 +41,8 @@ export interface GatewayApiContext {
     releases: GatewayReleaseRepository;
     orchestrator: GatewayOrchestratorHandle;
     profileStatus: GatewayProfileStatusService;
+    authBudget: AuthAttemptBudget;
+    requestIp: string;
     requestHeaders: Record<string, string | string[] | undefined>;
     prisma: GatewayPrismaClient;
     adminAudit: AdminAuditStore;
@@ -69,6 +72,8 @@ export const createGatewayApiContext = (options: {
     releases?: GatewayReleaseRepository;
     orchestrator: GatewayOrchestratorHandle;
     profileStatus: GatewayProfileStatusService;
+    authBudget?: AuthAttemptBudget;
+    requestIp?: string;
     requestHeaders?: Record<string, string | string[] | undefined>;
     prisma: GatewayPrismaClient;
     adminAudit?: AdminAuditStore;
@@ -95,6 +100,10 @@ export const createGatewayApiContext = (options: {
     releases: options.releases ?? createGatewayReleaseRepository(options.prisma),
     orchestrator: options.orchestrator,
     profileStatus: options.profileStatus,
+    authBudget:
+        options.authBudget ??
+        new AuthAttemptBudget(new InMemoryAuthCounterStore(), 'direct-caller', options.gameTokenSecret),
+    requestIp: options.requestIp ?? 'unknown',
     requestHeaders: options.requestHeaders ?? {},
     prisma: options.prisma,
     adminAudit: options.adminAudit ?? createAdminAuditStore(options.prisma),
diff --git a/app/gateway-api/src/server.ts b/app/gateway-api/src/server.ts
index 04273bcc..d8ee053f 100644
--- a/app/gateway-api/src/server.ts
+++ b/app/gateway-api/src/server.ts
@@ -25,6 +25,7 @@ import { createPasswordEnvelopeService } from './auth/passwordEnvelope.js';
 import { RedisGatewaySessionService } from './auth/redisSessionService.js';
 import { createGatewayOrchestrator } from './orchestrator/orchestratorFactory.js';
 import { createGatewayReleaseRepository } from './orchestrator/gatewayReleaseRepository.js';
+import { AuthAttemptBudget, RedisAuthCounterStore } from './auth/attemptBudget.js';
 import { appRouter } from './router.js';
 import { RepositoryProfileStatusService } from './lobby/profileStatusService.js';
 import { registerAccountIconInternalRoute } from './auth/accountIconInternalRoute.js';
@@ -66,6 +67,11 @@ export const createGatewayApiServer = async () => {
         sessionTtlSeconds: config.sessionTtlSeconds,
         gameSessionTtlSeconds: config.gameSessionTtlSeconds,
     });
+    const authBudget = new AuthAttemptBudget(
+        new RedisAuthCounterStore(redis.client),
+        config.redisKeyPrefix,
+        config.gameTokenSecret
+    );
     const flushPublisher = new RedisGatewayFlushPublisher(redis.client, config.flushChannel);
     const kakaoClient = new KakaoOAuthClient({
         restKey: config.kakaoRestKey,
@@ -91,6 +97,8 @@ export const createGatewayApiServer = async () => {
     );
     const app = fastify({
         logger: safeHttpLoggerOptions,
+        // Count the actual peer; forwarded headers are untrusted without an explicit proxy policy.
+        trustProxy: false,
         routerOptions: gatewayFastifyRouterOptions,
     });
     app.setErrorHandler(safeHttpErrorHandler);
@@ -154,6 +162,8 @@ export const createGatewayApiServer = async () => {
                     releases,
                     orchestrator,
                     profileStatus,
+                    authBudget,
+                    requestIp: req.ip,
                     requestHeaders: req.headers,
                     prisma: postgres.prisma as GatewayPrismaClient,
                     navigationConfig,
diff --git a/app/gateway-api/src/trpc.ts b/app/gateway-api/src/trpc.ts
index 739369e5..4b551851 100644
--- a/app/gateway-api/src/trpc.ts
+++ b/app/gateway-api/src/trpc.ts
@@ -1,9 +1,36 @@
 import { safeTrpcErrorFormatter } from '@sammo-ts/common';
-import { initTRPC } from '@trpc/server';
+import { AuthBudgetError, isBudgetedAuthAction } from './auth/attemptBudget.js';
+import { initTRPC, TRPCError } from '@trpc/server';
 
 import type { GatewayApiContext } from './context.js';
 
 const t = initTRPC.context<GatewayApiContext>().create({ errorFormatter: safeTrpcErrorFormatter });
 
 export const router = t.router;
-export const procedure = t.procedure;
+export const procedure = t.procedure.use(async ({ ctx, path, getRawInput, next }) => {
+    if (!isBudgetedAuthAction(path)) return next();
+    const raw: unknown = await getRawInput();
+    const input = raw && typeof raw === 'object' ? (raw as Record<string, unknown>) : {};
+    const resolveSubject = async (): Promise<string | undefined> => {
+        if (path === 'auth.login' && typeof input.username === 'string' && input.username.length <= 64) {
+            return `login:${input.username.trim().toLocaleLowerCase('en-US')}`;
+        }
+        if (path.startsWith('account.') && typeof input.sessionToken === 'string' && input.sessionToken.length <= 256) {
+            const session = await ctx.sessions.getSession(input.sessionToken);
+            if (session) return `account:${session.userId}`;
+        }
+        return undefined;
+    };
+    try {
+        return await ctx.authBudget.run(path, ctx.requestIp, resolveSubject, () => next());
+    } catch (error) {
+        if (!(error instanceof AuthBudgetError)) throw error;
+        throw new TRPCError({
+            code: error.reason === 'limited' ? 'TOO_MANY_REQUESTS' : 'SERVICE_UNAVAILABLE',
+            message:
+                error.reason === 'limited'
+                    ? `인증 요청이 많습니다. ${error.retryAfterSeconds}초 후 다시 시도해 주세요.`
+                    : '인증 보호 서비스를 사용할 수 없습니다. 잠시 후 다시 시도해 주세요.',
+        });
+    }
+});
diff --git a/app/gateway-api/test/authAttemptBudget.integration.test.ts b/app/gateway-api/test/authAttemptBudget.integration.test.ts
new file mode 100644
index 00000000..76ea2239
--- /dev/null
+++ b/app/gateway-api/test/authAttemptBudget.integration.test.ts
@@ -0,0 +1,53 @@
+import { randomUUID } from 'node:crypto';
+import { createClient } from 'redis';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { RedisAuthCounterStore } from '../src/auth/attemptBudget.js';
+
+const redisUrl = process.env.GATEWAY_AUTH_REDIS_TEST_URL;
+
+describe.skipIf(!redisUrl)('Redis authentication budget atomicity', () => {
+    const client = createClient({ url: redisUrl });
+    const prefix = `auth-budget-test:${randomUUID()}`;
+    const store = new RedisAuthCounterStore(client);
+    const keys = ['subject', 'global', 'expires', 'invalid'].map((kind) => `${prefix}:${kind}`);
+    beforeAll(async () => {
+        await client.connect();
+    });
+    afterAll(async () => {
+        await client.del(keys);
+        await client.quit();
+    });
+
+    it('admits exactly ten concurrent attempts and does not charge other buckets on rejection', async () => {
+        const attempts = await Promise.all(
+            Array.from({ length: 100 }, () =>
+                store.consume([
+                    { key: keys[0]!, limit: 10, windowMs: 60_000 },
+                    { key: keys[1]!, limit: 1000, windowMs: 60_000 },
+                ])
+            )
+        );
+        expect(attempts.filter((retry) => retry === 0)).toHaveLength(10);
+        expect(attempts.filter((retry) => retry > 0)).toHaveLength(90);
+        expect(await client.get(keys[0]!)).toBe('10');
+        expect(await client.get(keys[1]!)).toBe('10');
+        expect(await client.pTTL(keys[0]!)).toBeGreaterThan(0);
+    });
+
+    it('keeps the original expiry under repeated rejected attempts and permits recovery', async () => {
+        const counters = [{ key: keys[2]!, limit: 1, windowMs: 120 }];
+        expect(await store.consume(counters)).toBe(0);
+        const before = await client.pTTL(keys[2]!);
+        expect(await store.consume(counters)).toBeGreaterThan(0);
+        expect(await client.pTTL(keys[2]!)).toBeLessThanOrEqual(before);
+        await expect.poll(() => client.exists(keys[2]!), { interval: 20, timeout: 1000 }).toBe(0);
+        expect(await store.consume(counters)).toBe(0);
+    });
+
+    it('rejects a malformed counter without an expiry instead of permanently locking the account', async () => {
+        await client.set(keys[3]!, '10');
+        await expect(store.consume([{ key: keys[3]!, limit: 10, windowMs: 60_000 }])).rejects.toMatchObject({
+            reason: 'unavailable',
+        });
+    });
+});
diff --git a/app/gateway-api/test/authAttemptBudget.test.ts b/app/gateway-api/test/authAttemptBudget.test.ts
new file mode 100644
index 00000000..086ab981
--- /dev/null
+++ b/app/gateway-api/test/authAttemptBudget.test.ts
@@ -0,0 +1,131 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { AuthAttemptBudget, AuthBudgetError, InMemoryAuthCounterStore } from '../src/auth/attemptBudget.js';
+
+describe('authentication attempt and resource budgets', () => {
+    afterEach(() => {
+        vi.useRealTimers();
+    });
+
+    it('shares a login subject across clients without exposing account or address in keys', async () => {
+        const store = new InMemoryAuthCounterStore();
+        const consume = vi.spyOn(store, 'consume');
+        const budget = new AuthAttemptBudget(store, 'fixture', 'fixture-secret');
+        for (let i = 0; i < 10; i++)
+            await budget.run('auth.login', `client-${i}`, 'login:fixture-user', async () => 'ok');
+        const work = vi.fn(async () => 'must not run');
+        await expect(budget.run('auth.login', 'another-client', 'login:fixture-user', work)).rejects.toMatchObject({
+            reason: 'limited',
+            retryAfterSeconds: 60,
+        });
+        expect(work).not.toHaveBeenCalled();
+        expect(JSON.stringify(consume.mock.calls)).not.toContain('fixture-user');
+        expect(JSON.stringify(consume.mock.calls)).not.toContain('client-');
+        await expect(budget.run('auth.login', 'another-client', 'login:other-user', async () => 'ok')).resolves.toBe(
+            'ok'
+        );
+    });
+
+    it('does not extend a blocked account window and admits it after expiry', async () => {
+        vi.useFakeTimers();
+        const budget = new AuthAttemptBudget(new InMemoryAuthCounterStore(), 'fixture', 'secret');
+        for (let i = 0; i < 10; i++) await budget.run('auth.login', 'client', 'login:user', async () => null);
+        await vi.advanceTimersByTimeAsync(59_000);
+        await expect(budget.run('auth.login', 'client', 'login:user', async () => null)).rejects.toMatchObject({
+            retryAfterSeconds: 1,
+        });
+        await vi.advanceTimersByTimeAsync(1000);
+        await expect(budget.run('auth.login', 'client', 'login:user', async () => 'recovered')).resolves.toBe(
+            'recovered'
+        );
+    });
+
+    it('limits public auth traffic per peer and across peers without charging rejected requests', async () => {
+        const budget = new AuthAttemptBudget(new InMemoryAuthCounterStore(), 'fixture', 'secret');
+        for (let i = 0; i < 600; i++) await budget.run('auth.passwordKey', 'peer-a', undefined, async () => null);
+        await expect(budget.run('auth.kakaoStart', 'peer-a', undefined, async () => null)).rejects.toMatchObject({
+            reason: 'limited',
+        });
+        for (let i = 0; i < 600; i++) await budget.run('auth.passwordKey', 'peer-b', undefined, async () => null);
+        await expect(budget.run('auth.kakaoStart', 'peer-c', undefined, async () => null)).rejects.toMatchObject({
+            reason: 'limited',
+        });
+    });
+
+    it('bounds expensive work and releases capacity after resolver failures', async () => {
+        const budget = new AuthAttemptBudget(new InMemoryAuthCounterStore(), 'fixture', 'secret');
+        let release!: () => void;
+        const pending = new Promise<void>((resolve) => {
+            release = resolve;
+        });
+        const work = vi.fn(async () => {
+            await pending;
+            throw new Error('fixture resolver failure');
+        });
+        const running = Array.from({ length: 4 }, () =>
+            budget.run('auth.login', 'client', undefined, work).catch(() => null)
+        );
+        await vi.waitFor(() => expect(work).toHaveBeenCalledTimes(4));
+        const rejected = vi.fn(async () => null);
+        await expect(budget.run('auth.registerLocal', 'client', undefined, rejected)).rejects.toBeInstanceOf(
+            AuthBudgetError
+        );
+        expect(rejected).not.toHaveBeenCalled();
+        release();
+        await Promise.all(running);
+        await expect(budget.run('auth.login', 'client', undefined, async () => 'ok')).resolves.toBe('ok');
+    });
+
+    it('bounds unfinished checks after caller timeouts and recovers only after they settle', async () => {
+        vi.useFakeTimers();
+        let release!: (retry: number) => void;
+        const waiting = new Promise<number>((resolve) => {
+            release = resolve;
+        });
+        const store = { consume: vi.fn(() => waiting) };
+        const budget = new AuthAttemptBudget(store, 'fixture', 'secret');
+        const work = vi.fn(async () => 'ok');
+        const requests = Array.from({ length: 32 }, () =>
+            budget.run('auth.passwordKey', 'client', undefined, work).catch((error: unknown) => error)
+        );
+        await vi.advanceTimersByTimeAsync(2001);
+        expect(
+            (await Promise.all(requests)).every(
+                (error) => error instanceof AuthBudgetError && error.reason === 'unavailable'
+            )
+        ).toBe(true);
+        const actorLookup = vi.fn(async () => undefined);
+        await expect(budget.run('auth.login', 'client', actorLookup, work)).rejects.toMatchObject({
+            reason: 'unavailable',
+        });
+        expect(actorLookup).not.toHaveBeenCalled();
+        expect(work).not.toHaveBeenCalled();
+        expect(store.consume).toHaveBeenCalledTimes(32);
+        release(0);
+        await Promise.resolve();
+        await Promise.resolve();
+        await expect(budget.run('auth.login', 'client', undefined, work)).resolves.toBe('ok');
+        expect(work).toHaveBeenCalledTimes(1);
+    });
+
+    it('fails closed before credential work when the counter backend errors or stalls', async () => {
+        const work = vi.fn(async () => null);
+        const failing = new AuthAttemptBudget(
+            {
+                consume: async () => {
+                    throw new Error('private-backend-error');
+                },
+            },
+            'fixture',
+            'secret'
+        );
+        await expect(failing.run('auth.login', 'client', undefined, work)).rejects.toMatchObject({
+            reason: 'unavailable',
+        });
+        vi.useFakeTimers();
+        const stalled = new AuthAttemptBudget({ consume: () => new Promise(() => {}) }, 'fixture', 'secret');
+        const result = stalled.run('auth.login', 'client', undefined, work).catch((error: unknown) => error);
+        await vi.advanceTimersByTimeAsync(2001);
+        expect(await result).toMatchObject({ reason: 'unavailable' });
+        expect(work).not.toHaveBeenCalled();
+    });
+});
diff --git a/app/gateway-api/test/authBudgetHttp.integration.test.ts b/app/gateway-api/test/authBudgetHttp.integration.test.ts
new file mode 100644
index 00000000..f2315d12
--- /dev/null
+++ b/app/gateway-api/test/authBudgetHttp.integration.test.ts
@@ -0,0 +1,238 @@
+import { constants, publicEncrypt, randomUUID } from 'node:crypto';
+import fastify, { type FastifyRequest } from 'fastify';
+import { fastifyTRPCPlugin } from '@trpc/server/adapters/fastify';
+import { createClient } from 'redis';
+import { afterAll, beforeAll, describe, expect, it, vi } from 'vitest';
+import { trpcJsonBodyHttpServerOptions } from '@sammo-ts/common';
+import { createGatewayApiContext } from '../src/context.js';
+import { appRouter } from '../src/router.js';
+import { AuthAttemptBudget, RedisAuthCounterStore } from '../src/auth/attemptBudget.js';
+import { createInMemoryUserRepository } from '../src/auth/inMemoryUserRepository.js';
+import { InMemoryGatewaySessionService } from '../src/auth/inMemorySessionService.js';
+import { createPasswordEnvelopeService } from '../src/auth/passwordEnvelope.js';
+
+const redisUrl = process.env.GATEWAY_AUTH_REDIS_TEST_URL;
+
+describe.skipIf(!redisUrl)('authentication budgets over real HTTP and Redis', () => {
+    const client = createClient({ url: redisUrl });
+    const prefix = `auth-budget-http-test:${randomUUID()}`;
+    const envelope = createPasswordEnvelopeService();
+    beforeAll(async () => {
+        await client.connect();
+    });
+    afterAll(async () => {
+        const keys: string[] = [];
+        for await (const page of client.scanIterator({ MATCH: `${prefix}:*`, COUNT: 100 })) keys.push(...page);
+        if (keys.length) await client.del(keys);
+        await client.quit();
+    });
+    const credential = (password: string) => {
+        const key = envelope.getPublicKey();
+        return {
+            keyId: key.keyId,
+            ciphertext: publicEncrypt(
+                { key: key.publicKeyPem, padding: constants.RSA_PKCS1_OAEP_PADDING, oaepHash: 'sha256' },
+                Buffer.from(password)
+            ).toString('base64'),
+        };
+    };
+    const fixture = async (available = true) => {
+        const users = createInMemoryUserRepository();
+        await users.createUser({ username: 'target-user', password: 'correct-password' });
+        await users.createUser({ username: 'other-user', password: 'correct-password' });
+        const requestIps = new Set<string>();
+        const peer = (request: FastifyRequest): string => {
+            requestIps.add(request.ip);
+            return request.ip;
+        };
+        const verify = vi.spyOn(users, 'verifyPassword');
+        const open = vi.fn(envelope.open);
+        const sessions = new InMemoryGatewaySessionService({ sessionTtlSeconds: 600, gameSessionTtlSeconds: 600 });
+        const authBudget = new AuthAttemptBudget(
+            new RedisAuthCounterStore(available ? client : client.duplicate()),
+            `${prefix}:${randomUUID()}`,
+            'synthetic-budget-key'
+        );
+        const app = fastify({ trustProxy: false });
+        await app.register(fastifyTRPCPlugin, {
+            prefix: '/trpc',
+            trpcOptions: {
+                router: appRouter,
+                ...trpcJsonBodyHttpServerOptions,
+                createContext: ({ req }: { req: FastifyRequest }) =>
+                    createGatewayApiContext({
+                        users,
+                        sessions,
+                        passwordEnvelope: { ...envelope, open },
+                        authBudget,
+                        requestIp: peer(req),
+                        requestHeaders: req.headers,
+                        flushPublisher: { publishUserFlush: async () => {} },
+                        gameTokenSecret: 'synthetic-game-key',
+                        gameSessionTtlSeconds: 600,
+                        kakaoClient: {} as never,
+                        oauthSessions: {} as never,
+                        publicBaseUrl: 'http://localhost',
+                        adminLocalAccountEnabled: true,
+                        localRegistrationEnabled: true,
+                        localAccountGraceDays: 7,
+                        profiles: {} as never,
+                        orchestrator: {} as never,
+                        profileStatus: {} as never,
+                        prisma: {} as never,
+                    }),
+            },
+        });
+        const address = await app.listen({ host: '127.0.0.1', port: 0 });
+        const post = (operation: string, input: unknown, headers: Record<string, string> = {}) =>
+            fetch(`${address}/trpc/${operation}`, {
+                method: 'POST',
+                headers: { 'content-type': 'application/json', ...headers },
+                body: JSON.stringify(input),
+            });
+        return { app, address, post, users, sessions, verify, open, requestIps };
+    };
+
+    it('blocks an eleventh normalized account attempt before RSA/Argon2 despite spoofed forwarding headers', async () => {
+        const f = await fixture();
+        try {
+            for (let i = 0; i < 10; i++) {
+                const response = await f.post(
+                    'auth.login',
+                    { username: i % 2 ? ' TARGET-USER ' : 'target-user', credential: credential('wrong-password') },
+                    { 'x-forwarded-for': `198.51.100.${i + 1}` }
+                );
+                expect(response.status).toBe(401);
+            }
+            expect(f.requestIps.size).toBe(1);
+            expect(f.requestIps.has('127.0.0.1')).toBe(true);
+            expect(f.verify).toHaveBeenCalledTimes(10);
+            expect(f.open).toHaveBeenCalledTimes(10);
+            const denied = await f.post(
+                'auth.login',
+                { username: 'target-user', credential: credential('correct-password') },
+                { 'x-forwarded-for': '203.0.113.99' }
+            );
+            expect(denied.status).toBe(429);
+            expect(JSON.stringify(await denied.json())).not.toContain('stack');
+            expect(f.verify).toHaveBeenCalledTimes(10);
+            expect(f.open).toHaveBeenCalledTimes(10);
+            expect(
+                (await f.post('auth.login', { username: 'other-user', credential: credential('correct-password') }))
+                    .status
+            ).toBe(200);
+        } finally {
+            await f.app.close();
+        }
+    });
+
+    it('charges each operation in a tRPC batch instead of granting one budget per HTTP request', async () => {
+        const f = await fixture();
+        try {
+            const statuses: number[] = [];
+            for (let round = 0; round < 4; round++) {
+                const input = Object.fromEntries(
+                    Array.from({ length: 3 }, (_value, i) => [
+                        String(i),
+                        { username: 'target-user', credential: credential('wrong-password') },
+                    ])
+                );
+                const response = await f.post('auth.login,auth.login,auth.login?batch=1', input);
+                const body = (await response.json()) as Array<{ error: { data: { httpStatus: number } } }>;
+                statuses.push(...body.map((entry) => entry.error.data.httpStatus));
+            }
+            expect(statuses.filter((status) => status === 401)).toHaveLength(10);
+            expect(statuses.filter((status) => status === 429)).toHaveLength(2);
+            expect(f.verify).toHaveBeenCalledTimes(10);
+        } finally {
+            await f.app.close();
+        }
+    });
+
+    it('shares the password/deletion subject across sessions of the same authenticated actor', async () => {
+        const f = await fixture();
+        const user = await f.users.findByUsername('target-user');
+        try {
+            for (let i = 0; i < 10; i++) {
+                const session = await f.sessions.createSession(user!);
+                const response = await f.post(i % 2 ? 'account.changePassword' : 'account.scheduleDeletion', {
+                    sessionToken: session.sessionToken,
+                    currentCredential: credential('wrong-password'),
+                    newCredential: credential('new-password'),
+                });
+                expect(response.status).toBe(401);
+            }
+            const session = await f.sessions.createSession(user!);
+            expect(
+                (
+                    await f.post('account.scheduleDeletion', {
+                        sessionToken: session.sessionToken,
+                        currentCredential: credential('correct-password'),
+                    })
+                ).status
+            ).toBe(429);
+            expect(f.verify).toHaveBeenCalledTimes(10);
+            expect(f.open).toHaveBeenCalledTimes(10);
+            expect((await f.users.findById(user!.id))?.deleteAfter).toBeUndefined();
+        } finally {
+            await f.app.close();
+        }
+    });
+
+    it('fails closed on unavailable protection while keeping logout independent of its counters', async () => {
+        const f = await fixture(false);
+        try {
+            expect(
+                (await f.post('auth.login', { username: 'target-user', credential: credential('correct-password') }))
+                    .status
+            ).toBe(503);
+            expect(f.open).not.toHaveBeenCalled();
+            expect(f.verify).not.toHaveBeenCalled();
+            const user = await f.users.findByUsername('target-user');
+            const session = await f.sessions.createSession(user!);
+            expect((await f.post('auth.logout', { sessionToken: session.sessionToken })).status).toBe(200);
+            expect(await f.sessions.getSession(session.sessionToken)).toBeNull();
+            expect(
+                (await f.post('auth.login', { username: 123, credential: credential('correct-password') })).status
+            ).toBe(503);
+            const malformed = await fetch(`${f.address}/trpc/auth.login`, {
+                method: 'POST',
+                headers: { 'content-type': 'application/json' },
+                body: '{',
+            });
+            expect(malformed.status).toBe(400);
+        } finally {
+            await f.app.close();
+        }
+    });
+
+    it('bounds parallel credential work and admits a subsequent request after all failures settle', async () => {
+        const f = await fixture();
+        let release!: () => void;
+        const waiting = new Promise<void>((resolve) => {
+            release = resolve;
+        });
+        f.verify.mockImplementation(async () => {
+            await waiting;
+            return false;
+        });
+        const input = { username: 'target-user', credential: credential('wrong-password') };
+        const pending = Array.from({ length: 4 }, () => f.post('auth.login', input));
+        try {
+            await vi.waitFor(() => expect(f.verify).toHaveBeenCalledTimes(4));
+            expect((await f.post('auth.login', input)).status).toBe(429);
+            expect(f.open).toHaveBeenCalledTimes(4);
+            release();
+            expect((await Promise.all(pending)).map((r) => r.status)).toEqual([401, 401, 401, 401]);
+            f.verify.mockRestore();
+            expect(
+                (await f.post('auth.login', { username: 'target-user', credential: credential('correct-password') }))
+                    .status
+            ).toBe(200);
+        } finally {
+            release();
+            await Promise.allSettled(pending);
+            await f.app.close();
+        }
+    });
+});
diff --git a/app/gateway-api/test/kakaoClient.test.ts b/app/gateway-api/test/kakaoClient.test.ts
index 12b9b9d0..73c00215 100644
--- a/app/gateway-api/test/kakaoClient.test.ts
+++ b/app/gateway-api/test/kakaoClient.test.ts
@@ -25,11 +25,16 @@ describe('Kakao OAuth HTTP transport', () => {
         await expect(createClient().signup('access-token')).resolves.toEqual({
             alreadyRegistered: true,
         });
-        expect(fetchMock).toHaveBeenCalledWith(new URL('https://kapi.example.test/v1/user/signup'), {
-            headers: {
-                Authorization: 'Bearer access-token',
-            },
-        });
+        expect(fetchMock).toHaveBeenCalledWith(
+            new URL('https://kapi.example.test/v1/user/signup'),
+            expect.objectContaining({
+                headers: {
+                    Authorization: 'Bearer access-token',
+                },
+                redirect: 'error',
+                signal: expect.any(AbortSignal),
+            })
+        );
     });
 
     it('continues to reject unrelated Kakao signup errors', async () => {
@@ -40,8 +45,6 @@ describe('Kakao OAuth HTTP transport', () => {
             })
         );
 
-        await expect(createClient().signup('access-token')).rejects.toThrow(
-            'Kakao signup error: {"msg":"invalid request","code":-201}'
-        );
+        await expect(createClient().signup('access-token')).rejects.toThrow('Kakao signup error.');
     });
 });
diff --git a/app/gateway-api/test/kakaoTransportLimits.test.ts b/app/gateway-api/test/kakaoTransportLimits.test.ts
new file mode 100644
index 00000000..01030c11
--- /dev/null
+++ b/app/gateway-api/test/kakaoTransportLimits.test.ts
@@ -0,0 +1,95 @@
+import { createServer, type Server, type ServerResponse } from 'node:http';
+import { gzipSync } from 'node:zlib';
+import { afterEach, describe, expect, it } from 'vitest';
+import { KakaoOAuthClient } from '../src/auth/kakaoClient.js';
+
+describe('bounded Kakao provider transport', () => {
+    const servers: Server[] = [];
+    afterEach(async () => {
+        for (const server of servers.splice(0)) {
+            server.closeAllConnections();
+            await new Promise<void>((resolve) => server.close(() => resolve()));
+        }
+    });
+    const provider = async (respond: (response: ServerResponse) => void, requestTimeoutMs = 1000) => {
+        const server = createServer((_request, response) => respond(response));
+        servers.push(server);
+        await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve));
+        const address = server.address();
+        if (!address || typeof address === 'string') throw new Error('Fixture provider listener failed.');
+        const origin = `http://127.0.0.1:${address.port}`;
+        return new KakaoOAuthClient({
+            restKey: 'synthetic-key',
+            redirectUri: `${origin}/callback`,
+            apiHost: origin,
+            oauthHost: origin,
+            requestTimeoutMs,
+        });
+    };
+
+    it('retains successful token/account responses and documented recovery responses', async () => {
+        const client = await provider((res) =>
+            res.end(
+                JSON.stringify({
+                    id: 42,
+                    access_token: 'synthetic-token',
+                    expires_in: 3600,
+                    kakao_account: {
+                        has_email: true,
+                        email: 'fixture@example.test',
+                        is_email_valid: true,
+                        is_email_verified: true,
+                    },
+                })
+            )
+        );
+        expect(await client.exchangeCode('synthetic-code')).toMatchObject({
+            accessToken: 'synthetic-token',
+            accessTokenExpiresIn: 3600,
+        });
+        expect(await client.getMe('synthetic-token')).toMatchObject({
+            id: '42',
+            kakaoAccount: { email: 'fixture@example.test', isEmailVerified: true },
+        });
+    });
+
+    it('aborts both header and response-body stalls within the configured deadline', async () => {
+        const silent = await provider(() => {}, 100);
+        await expect(silent.getMe('synthetic-token')).rejects.toThrow('Kakao HTTP request failed.');
+        const partial = await provider((res) => {
+            res.writeHead(200, { 'content-type': 'application/json' });
+            res.write('{');
+        }, 100);
+        await expect(partial.getMe('synthetic-token')).rejects.toThrow('Kakao HTTP request failed.');
+    });
+
+    it('limits decompressed response bytes and rejects malformed JSON without exposing payloads', async () => {
+        const oversized = await provider((res) => {
+            res.writeHead(200, { 'content-type': 'application/json', 'content-encoding': 'gzip' });
+            res.end(gzipSync(JSON.stringify({ payload: 'x'.repeat(2 * 1024 * 1024) })));
+        });
+        await expect(oversized.getMe('synthetic-token')).rejects.toThrow('Kakao HTTP request failed.');
+        const malformed = await provider((res) => res.end('synthetic-sensitive-provider-data'));
+        await expect(malformed.getMe('synthetic-token')).rejects.toThrow('Kakao HTTP request failed.');
+    });
+
+    it('does not follow redirects or expose provider error details', async () => {
+        let destinationRequests = 0;
+        const destination = await provider((res) => {
+            destinationRequests += 1;
+            res.end('{}');
+        });
+        const destinationUrl = new URL(destination.buildAuthUrl('state', []));
+        const redirect = await provider((res) => {
+            res.writeHead(302, { location: destinationUrl.origin });
+            res.end();
+        });
+        await expect(redirect.getMe('synthetic-token')).rejects.toThrow('Kakao HTTP request failed.');
+        expect(destinationRequests).toBe(0);
+        const failure = await provider((res) => {
+            res.writeHead(400);
+            res.end(JSON.stringify({ msg: 'synthetic-provider-secret', code: -201 }));
+        });
+        await expect(failure.signup('synthetic-token')).rejects.toThrow('Kakao signup error.');
+    });
+});
diff --git a/docs/release-operations.md b/docs/release-operations.md
index 32b1ed08..ec6760d4 100644
--- a/docs/release-operations.md
+++ b/docs/release-operations.md
@@ -566,3 +566,54 @@ message는 일반 문구로 치환한다. 4xx의 사용자용 검증/권한 문
 이 정책은 HTTP API 로그의 범위이며 release builder의 관리자 build log를
 일괄 숨기지 않는다. 장애 조사 시 request ID·route·status·code와 별도 격리 재현을
 사용하며 운영 HTTP 로그에 credential이나 raw error payload를 다시 추가하지 않는다.
+
+## 온라인 인증 시도와 비용 제한 (2026-10-09)
+
+Gateway HTTP server는 기존 전용 Redis와 `GATEWAY_REDIS_PREFIX`에 인증 counter를
+공유한다. 별도 credential이나 비활성화 env key는 추가하지 않는다. 각 procedure
+실행 전에 원자적으로 모든 counter를 검사하고 허용된 요청만 차감한다. 같은 tRPC
+batch의 항목도 각각 차감한다. 기본 창은 최초 허용 요청부터 60초이며 다음과 같다.
+
+| 경계                                                                    | 기본 상한              |
+| ----------------------------------------------------------------------- | ---------------------- |
+| 정규화한 로그인 계정명, peer와 무관                                     | 10회/60초              |
+| 같은 인증 actor의 비밀번호 변경·탈퇴, session을 바꿔도 공유             | 10회/60초              |
+| 인증 시작·등록·자격 증명·OTP와 public key/가입 필드 검사, socket peer별 | 600회/60초             |
+| 위 인증 procedure 전체, 같은 Gateway Redis namespace                    | 1200회/60초            |
+| RSA/Argon2/provider 호출이 있는 인증 작업, API 프로세스별               | 동시 4개, 대기 큐 없음 |
+
+계정 counter는 존재하지 않는 이름과 성공/실패를 동일하게 차감하고 성공 직후에도
+초기화하지 않는다. 거절된 시도는 TTL이나 다른 counter를 갱신하지 않으므로 공격자가
+고정된 창을 연장할 수 없다. 계정 자체를 DB에서 잠그거나 sanction을 만들지 않으며
+기존 session·OAuth 시작/복구·logout은 계정명 counter와 별도다. 계속되는 공격이
+매 새 창의 예산을 소진하면 password login은 일시 제한될 수 있다. account 중심
+제한의 가용성 tradeoff로 기록하고 운영자는 인증 정책을 지워서 해결하지 않는다.
+
+Fastify `trustProxy:false`를 유지해 임의 `X-Forwarded-For`로 peer counter를 바꿀 수
+없다. 현재 Docker의 Caddy 뒤에서는 이 counter가 해당 proxy를 공유하는 사용자들의
+합계다. 이를 인터넷 client별 제한이라고 보고하지 않는다. 원래 client IP를 써야
+한다면 실제 두 proxy 경계와 덮어쓰기 규칙, 좁은 trusted proxy allowlist를 먼저
+결정해야 하며 `trustProxy:true`나 단순 hop 수를 켜지 않는다. global/account counter와
+동시 비용 상한은 forwarded header에 의존하지 않는다.
+
+아직 끝나지 않은 counter/actor 확인은 프로세스당 32개로 제한한다. 요청의 2초
+시간 초과 뒤에도 이 자리는 실제 확인 Promise가 끝날 때까지 유지한다. backend가
+멈춘 동안 대기하는 payload가 계속 늘어나지 않게 하며 확인이 끝나면 정상 복구한다.
+
+Redis 확인은 2초 안에 끝나야 하고 unready/error/잘못된 counter는 503으로 fail
+closed 처리한다. 한도를 넘으면 429와 재시도 초를 포함한 메시지를 보낸다.
+Redis namespace 내 key는 purpose를 나눈 HMAC으로 식별해 계정명/IP 원문을 저장하지
+않으며 모두 TTL이 있다. key namespace 때문에 secret rotation은 남은 최대 60초의
+시도 counter의 key 식별자를 전환한다. 내부 직접 caller/test의 기본 context는
+bounded memory store를 사용하지만 실제 HTTP server는 공유 Redis budget을 주입한다.
+
+Kakao transport는 각 HTTP 요청의 header와 body 전체에 10초 deadline, decoded JSON
+응답 64 KiB 상한과 redirect 거절을 적용한다. provider payload·token·account 정보를
+오류 문구에 넣지 않는다. `-102 already registered`의 명시적 복구 분기는 유지한다.
+여러 요청을 순차 수행하는 OAuth flow의 전체 시간이 10초라는 뜻은 아니다. 상한은
+게임 시간·OTP 만료·기존 session lifetime·Argon2 강도와 무관하다.
+
+이 단계는 온라인 자격 증명/가입 비용을 보호하며 established session의 일반 조회,
+logout과 game-session 교환에 동일한 인증 시작 budget을 강제로 적용하지 않는다.
+임시 운영 stack과 공개 운영/개발 stack은 Redis와 prefix를 공유하지 않으며 새 코드의
+검증 결과를 실제 공개 배포 근거로 사용하지 않는다.