diff --git a/apps/web/e2e/admin.spec.ts b/apps/web/e2e/admin.spec.ts
index 9874703..9c46c59 100644
--- a/apps/web/e2e/admin.spec.ts
+++ b/apps/web/e2e/admin.spec.ts
@@ -920,6 +920,10 @@ test.describe("admin route guards", () => {
     await expect(page.getByTestId("auth-restore-failed")).toBeVisible();
     await expect(page.getByRole("heading", { name: "관리자 권한이 사라진 것이 아닙니다." })).toBeVisible();
     await expect(page.locator("#vignette-boot-diagnostic")).toHaveCount(0);
+    // 관리자 auth 복구 UI(.vg-route-error)는 3.5초/8초 watchdog 뒤에도
+    // 정상적인 오류 복구 화면으로 남고 부트 진단과 겹치지 않는다.
+    await page.waitForTimeout(8_600);
+    await expect(page.locator("#vignette-boot-diagnostic")).toHaveCount(0);
 
     await page.getByTestId("auth-restore-retry").click();
 
@@ -1073,7 +1077,22 @@ test.describe("admin route guards", () => {
     await expect(page.locator(".aic-chart__day").last()).toContainText("≤$3.56");
     await expect(page.locator(".aic-cache-score")).toContainText("80%");
     await expect(page.getByLabel("AI 기본 모델")).toHaveValue("gateway-default");
-    await expect(page.getByLabel("AI 엔진 공급자").locator("option")).toHaveCount(6);
+    expect(
+      await page
+        .getByLabel("AI 엔진 공급자")
+        .locator("option")
+        .evaluateAll((options) => options.map((option) => option.value)),
+    ).toEqual([
+      "claude_cli",
+      "claude_api",
+      "codex_cli",
+      "codex_api",
+      "agy_cli",
+      "antigravity_api",
+      "openai",
+      "openrouter",
+      "solar",
+    ]);
 
     const usageRequest = page.waitForRequest((request) =>
       request.url().includes("/api/admin/usage?window_days=7"),
diff --git a/apps/web/e2e/full-sweep-admin-ai.spec.ts b/apps/web/e2e/full-sweep-admin-ai.spec.ts
index 2ec2ef9..976b97a 100644
--- a/apps/web/e2e/full-sweep-admin-ai.spec.ts
+++ b/apps/web/e2e/full-sweep-admin-ai.spec.ts
@@ -86,6 +86,24 @@ interface AdminEngineConfigResponse {
   updated_at: number | null;
 }
 
+interface EngineCapabilitiesResponse {
+  provider: string;
+  available: boolean;
+  source: string;
+  models: Array<{
+    id: string;
+    label: string;
+    description: string;
+    reasoning_efforts: string[];
+    default_reasoning_effort: string | null;
+    is_default: boolean;
+  }>;
+  default_model: string;
+  default_reasoning_effort: string | null;
+  detail: string;
+  fetched_at: number;
+}
+
 function usageFixture(
   days: number,
   overrides: Partial<AdminUsageResponse> = {},
@@ -154,9 +172,14 @@ interface AdminAiMockState {
   usageForWindow: (days: number) => AdminUsageResponse;
   /** usage 응답을 지연시키는 게이트. 반환된 promise가 resolve될 때까지 응답을 보류한다. */
   usageGate?: (days: number) => Promise<void> | undefined;
+  usageStatus?: (days: number) => number | undefined;
   engineConfig: AdminEngineConfigResponse;
   /** 설정 시 GET /admin/engine-config 를 해당 status의 FastAPI 오류로 응답한다. */
   engineConfigStatus?: number;
+  engineConfigGate?: () => Promise<void> | undefined;
+  capabilityGate?: (provider: string, engineUrl: string) => Promise<void> | undefined;
+  capabilityStatus?: (provider: string, engineUrl: string) => number | undefined;
+  capabilityFor?: (provider: string, engineUrl: string) => EngineCapabilitiesResponse;
 }
 
 function createMockState(overrides: Partial<AdminAiMockState> = {}): AdminAiMockState {
@@ -211,6 +234,11 @@ async function mockAdminAiSession(page: Page, state: AdminAiMockState) {
       const days = Number(url.searchParams.get("window_days") ?? 30);
       const gate = state.usageGate?.(days);
       if (gate) await gate;
+      const status = state.usageStatus?.(days);
+      if (status) {
+        await fulfillJson({ detail: `usage ${days} unavailable` }, status);
+        return;
+      }
       await fulfillJson(state.usageForWindow(days));
       return;
     }
@@ -238,7 +266,15 @@ async function mockAdminAiSession(page: Page, state: AdminAiMockState) {
     if (method === "GET" && path.endsWith("/admin/engine-capabilities")) {
       state.counts.capabilities += 1;
       const provider = url.searchParams.get("engine_mode") ?? state.engineConfig.engine_mode;
-      await fulfillJson({
+      const engineUrl = url.searchParams.get("engine_url") ?? state.engineConfig.engine_url;
+      const gate = state.capabilityGate?.(provider, engineUrl);
+      if (gate) await gate;
+      const status = state.capabilityStatus?.(provider, engineUrl);
+      if (status) {
+        await fulfillJson({ detail: `capability ${provider} unavailable` }, status);
+        return;
+      }
+      await fulfillJson(state.capabilityFor?.(provider, engineUrl) ?? {
         provider,
         available: true,
         source: "live_cli",
@@ -262,6 +298,8 @@ async function mockAdminAiSession(page: Page, state: AdminAiMockState) {
 
     if (method === "GET" && path.endsWith("/admin/engine-config")) {
       state.counts.engine += 1;
+      const gate = state.engineConfigGate?.();
+      if (gate) await gate;
       if (state.engineConfigStatus) {
         await fulfillJson({ detail: "engine config unavailable" }, state.engineConfigStatus);
         return;
@@ -374,7 +412,7 @@ test.describe("full sweep: admin ai operations", () => {
   });
 
   // checklist: admin-ai-error-alert, admin-ai-engine-loading-empty
-  test("shows a role=alert banner with the engine panel placeholder on load failure and clears it on refresh", async ({
+  test("shows an explicit engine state after an engine-config failure and recovers on refresh", async ({
     page,
   }) => {
     const state = createMockState({ engineConfigStatus: 500 });
@@ -382,29 +420,151 @@ test.describe("full sweep: admin ai operations", () => {
 
     await page.goto("/admin/ai");
 
-    // engine-config 로드 실패 → role=alert 배너에 오류 메시지 노출.
-    const alert = page.locator(".aic-alert[role='alert']");
-    await expect(alert).toBeVisible();
-    await expect(alert).toContainText("engine config unavailable");
-    // 엔진 패널은 폼 대신 로딩/빈 상태 문구를 표시한다.
-    await expect(page.getByText("현재 AI 엔진 설정을 불러오는 중입니다.")).toBeVisible();
+    const enginePanel = page.locator(".aic-engine");
+    await expect(enginePanel.getByRole("alert")).toContainText("engine config unavailable");
+    await expect(
+      enginePanel.getByText("현재 AI 엔진 설정을 불러오지 못했습니다. 새로고침 후 다시 시도해 주세요."),
+    ).toBeVisible();
     await expect(page.getByLabel("AI 연결 주소")).toHaveCount(0);
 
-    // 다음 요청이 시작되면 오류 배너가 초기화된다: 응답을 보류한 채 새로고침.
     state.engineConfigStatus = undefined;
     let gate: ReturnType<typeof deferred> | null = deferred();
     state.usageGate = () => gate?.promise;
     await page.getByRole("button", { name: "새로고침", exact: true }).click();
-    await expect(alert).toHaveCount(0);
+    await expect(page.getByLabel("AI 연결 주소")).toHaveValue("http://127.0.0.1:9099");
+    await expect(enginePanel.getByRole("alert")).toHaveCount(0);
 
     gate.resolve();
     gate = null;
-    // 성공 응답 이후에도 배너는 없고 엔진 설정 폼이 렌더된다.
-    await expect(page.getByLabel("AI 연결 주소")).toHaveValue("http://127.0.0.1:9099");
-    await expect(page.getByLabel("AI 기본 모델")).toHaveValue("gateway-default");
-    await expect(alert).toHaveCount(0);
   });
 
+  test("shows engine config before a slow usage response completes", async ({ page }) => {
+    const usageGate = deferred();
+    const state = createMockState({ usageGate: () => usageGate.promise });
+    await mockAdminAiSession(page, state);
+
+    await page.goto("/admin/ai");
+
+    await expect(page.getByLabel("AI 연결 주소")).toHaveValue("http://127.0.0.1:9099");
+    await expect(page.locator('[data-testid="admin-ai-page"]')).toHaveAttribute("aria-busy", "true");
+
+    usageGate.resolve();
+    await expect(page.locator('[data-testid="admin-ai-page"]')).toHaveAttribute("aria-busy", "false");
+  });
+
+  test("shows a retryable Korean error when engine-config read times out", async ({ page }) => {
+    test.setTimeout(30_000);
+    const engineGate = deferred();
+    const state = createMockState({ engineConfigGate: () => engineGate.promise });
+    await mockAdminAiSession(page, state);
+
+    await page.goto("/admin/ai");
+
+    await expect(
+      page.locator(".aic-engine").getByText(
+        "AI 엔진 설정 조회 시간이 초과되었습니다. 잠시 후 다시 시도해 주세요.",
+      ),
+    ).toBeVisible({ timeout: 20_000 });
+    engineGate.resolve();
+  });
+
+  test("keeps the latest provider selection when an earlier capability request finishes late", async ({
+    page,
+  }) => {
+    const claudeGate = deferred();
+    const state = createMockState({
+      capabilityGate: (provider) => (provider === "claude_api" ? claudeGate.promise : undefined),
+      capabilityFor: (provider) => ({
+        provider,
+        available: true,
+        source: "live_cli",
+        models: [
+          {
+            id: `${provider}-model`,
+            label: `${provider} 모델`,
+            description: "테스트 모델",
+            reasoning_efforts: ["medium"],
+            default_reasoning_effort: "medium",
+            is_default: true,
+          },
+        ],
+        default_model: `${provider}-model`,
+        default_reasoning_effort: "medium",
+        detail: "테스트 모델 목록",
+        fetched_at: 1_785_142_800,
+      }),
+    });
+    await mockAdminAiSession(page, state);
+
+    await page.goto("/admin/ai");
+    const provider = page.getByLabel("AI 엔진 공급자");
+    const model = page.getByLabel("AI 기본 모델");
+    await expect(model.getByRole("option", { name: "openai 모델" })).toBeAttached();
+
+    const lateCapabilityResponse = page.waitForResponse((response) => {
+      const url = new URL(response.url());
+      return (
+        url.pathname.endsWith("/admin/engine-capabilities") &&
+        url.searchParams.get("engine_mode") === "claude_api"
+      );
+    });
+    await provider.selectOption("claude_api");
+    await provider.selectOption("openrouter");
+    await expect(model).toHaveValue("openrouter-model");
+
+    await page.getByRole("button", { name: "새로고침", exact: true }).click();
+    await expect(provider).toHaveValue("openrouter");
+    await expect(model).toHaveValue("openrouter-model");
+
+    claudeGate.resolve();
+    await lateCapabilityResponse;
+    await page.evaluate(() => new Promise<void>((resolve) => requestAnimationFrame(() => resolve())));
+    await expect(model).toHaveValue("openrouter-model");
+  });
+  test("clears prior capability models when refresh changes the engine URL and lookup fails", async ({
+    page,
+  }) => {
+    const state = createMockState({
+      capabilityFor: (provider, engineUrl) => ({
+        provider,
+        available: true,
+        source: "live_cli",
+        models: [
+          {
+            id: `model-${engineUrl}`,
+            label: `모델 ${engineUrl}`,
+            description: "테스트 모델",
+            reasoning_efforts: ["medium"],
+            default_reasoning_effort: "medium",
+            is_default: true,
+          },
+        ],
+        default_model: `model-${engineUrl}`,
+        default_reasoning_effort: "medium",
+        detail: "테스트 모델 목록",
+        fetched_at: 1_785_142_800,
+      }),
+    });
+    await mockAdminAiSession(page, state);
+
+    await page.goto("/admin/ai");
+    const model = page.getByLabel("AI 기본 모델");
+    await expect(model.getByRole("option", { name: "모델 http://127.0.0.1:9099" })).toBeAttached();
+
+    state.engineConfig = engineConfigFixture({
+      engine_url: "http://127.0.0.1:9100",
+      model: "restored-model",
+    });
+    state.capabilityStatus = () => 500;
+    await page.getByRole("button", { name: "새로고침", exact: true }).click();
+
+    await expect(page.getByLabel("AI 연결 주소")).toHaveValue("http://127.0.0.1:9100");
+    await expect(model).toHaveValue("restored-model");
+    await expect(model.getByRole("option", { name: "모델 http://127.0.0.1:9099" })).toHaveCount(0);
+    await expect(page.locator(".aic-engine").getByRole("alert")).toContainText(
+      "capability openai unavailable",
+    );
+  });
   // checklist: admin-ai-window-toggle
   test("refetches only usage on window change and ignores a stale late response", async ({
     page,
@@ -457,6 +617,30 @@ test.describe("full sweep: admin ai operations", () => {
     expect(state.counts.capabilities).toBe(1);
   });
 
+  test("does not let a superseded usage response clear a newer usage error", async ({ page }) => {
+    const slowWindow = deferred();
+    const state = createMockState({
+      usageGate: (days) => (days === 90 ? slowWindow.promise : undefined),
+      usageStatus: (days) => (days === 7 ? 500 : undefined),
+    });
+    await mockAdminAiSession(page, state);
+
+    await page.goto("/admin/ai");
+    const staleResponse = page.waitForResponse((response) =>
+      response.url().includes("/api/admin/usage?window_days=90"),
+    );
+    await page.getByRole("button", { name: "90일" }).click();
+    await page.getByRole("button", { name: "7일" }).click();
+    const alert = page.getByRole("alert").filter({ hasText: "usage 7 unavailable" });
+    await expect(alert).toContainText("usage 7 unavailable");
+    await expect(page.locator('[data-testid="admin-ai-page"]')).toHaveAttribute("aria-busy", "false");
+
+    slowWindow.resolve();
+    await staleResponse;
+    await page.evaluate(() => new Promise<void>((resolve) => requestAnimationFrame(() => resolve())));
+    await expect(alert).toContainText("usage 7 unavailable");
+    await expect(page.locator('[data-testid="admin-ai-page"]')).toHaveAttribute("aria-busy", "false");
+  });
   // checklist: admin-ai-coverage-track, admin-ai-daily-chart, admin-ai-cache-panel
   test("renders the coverage track, daily cost chart, and evaluator cache panel from metered usage", async ({
     page,
diff --git a/apps/web/e2e/full-sweep-shell.spec.ts b/apps/web/e2e/full-sweep-shell.spec.ts
index e8ecef7..fa62081 100644
--- a/apps/web/e2e/full-sweep-shell.spec.ts
+++ b/apps/web/e2e/full-sweep-shell.spec.ts
@@ -232,9 +232,15 @@ test.describe("full sweep — shared shell, GNB, and routing guards", () => {
 
     await page.goto("/learn");
 
-    await expect(page.getByText(BOOT_SCREEN_TEXT)).toBeVisible();
+    const bootScreen = page.getByText(BOOT_SCREEN_TEXT);
+    await expect(bootScreen).toBeVisible();
+    await expect(bootScreen).toHaveAttribute("data-vignette-boot-loading", "true");
     // 부트스트랩이 끝나지 않는 동안은 로그인으로 이동하지 않는다
     await expect(page).toHaveURL(/\/learn$/);
+    // 3.5초와 8초 watchdog은 화면에 실제로 보이는 bounded BootScreen을
+    // 빈 React root로 오인하지 않는다.
+    await page.waitForTimeout(8_600);
+    await expect(page.locator("#vignette-boot-diagnostic")).toHaveCount(0);
 
     releaseMe();
 
@@ -242,6 +248,154 @@ test.describe("full sweep — shared shell, GNB, and routing guards", () => {
     await expect(page.getByRole("button", { name: /Google 계정으로 로그인/ })).toBeVisible();
   });
 
+  test("removes a watchdog panel when the delayed boot screen becomes visible", async ({ page }) => {
+    test.setTimeout(15_000);
+    let releaseMain!: () => void;
+    const mainGate = new Promise<void>((resolve) => {
+      releaseMain = resolve;
+    });
+    let releaseMe!: () => void;
+    const meGate = new Promise<void>((resolve) => {
+      releaseMe = resolve;
+    });
+    await page.route("**/src/main.tsx*", async (route) => {
+      await mainGate;
+      await route.continue();
+    });
+    await page.route("**/api/auth/me", async (route) => {
+      await meGate;
+      await route.fulfill({
+        status: 401,
+        contentType: "application/json",
+        body: JSON.stringify({ detail: "not authenticated" }),
+      });
+    });
+
+    await page.goto("/learn", { waitUntil: "commit" });
+    await expect(page.locator("#root")).toBeEmpty();
+    await expect(page.locator("#vignette-boot-diagnostic")).toBeVisible({ timeout: 4_500 });
+
+    releaseMain();
+
+    await expect(page.getByText(BOOT_SCREEN_TEXT)).toHaveAttribute(
+      "data-vignette-boot-loading",
+      "true",
+    );
+    await expect(page.locator("#vignette-boot-diagnostic")).toHaveCount(0, { timeout: 1_500 });
+
+    releaseMe();
+    await expect(page.getByRole("button", { name: /Google 계정으로 로그인/ })).toBeVisible();
+  });
+
+  test("reports a boot screen that remains visible through the 20-second watchdog", async ({ page }) => {
+    test.setTimeout(35_000);
+    let releaseChunk!: () => void;
+    const gate = new Promise<void>((resolve) => {
+      releaseChunk = resolve;
+    });
+    await page.route("**/src/pages/Login.tsx*", async (route) => {
+      await gate;
+      await route.continue();
+    });
+    await page.route("**/api/auth/me", async (route) => {
+      await route.fulfill({
+        status: 401,
+        contentType: "application/json",
+        body: JSON.stringify({ detail: "not authenticated" }),
+      });
+    });
+
+    await page.route("**/api/auth/config", async (route) => {
+      await route.fulfill({
+        status: 200,
+        contentType: "application/json",
+        body: JSON.stringify({
+          google_oauth_configured: true,
+          saml_configured: false,
+          providers: [
+            {
+              provider: "google",
+              configured: true,
+              enabled: true,
+              login_path: "/auth/login?provider=google",
+            },
+          ],
+          allowed_email_domains: [],
+          redirect_uri: "http://127.0.0.1:8000/auth/callback",
+          dev_login_enabled: false,
+        }),
+      });
+    });
+    const meResolved = page.waitForResponse((response) => response.url().includes("/api/auth/me"));
+    await page.goto("/login", { waitUntil: "domcontentloaded" });
+    await meResolved;
+    await expect(page.getByText(BOOT_SCREEN_TEXT).filter({ visible: true })).toHaveAttribute(
+      "data-vignette-boot-loading",
+      "true",
+    );
+    await page.waitForTimeout(8_600);
+    await expect(page.locator("#vignette-boot-diagnostic")).toHaveCount(0);
+    await expect(page.locator("#vignette-boot-diagnostic")).toBeVisible({ timeout: 14_000 });
+    await expect(page.locator("#vignette-boot-diagnostic")).toHaveAttribute(
+      "data-vignette-boot-reason",
+      "watchdog",
+    );
+
+    releaseChunk();
+    await expect(page.getByRole("button", { name: /Google 계정으로 로그인/ })).toBeVisible();
+  });
+
+  test("keeps manual and runtime diagnostics when a delayed boot screen appears after watchdog", async ({ page }) => {
+    test.setTimeout(15_000);
+    let releaseMain!: () => void;
+    const mainGate = new Promise<void>((resolve) => {
+      releaseMain = resolve;
+    });
+    let releaseMe!: () => void;
+    const meGate = new Promise<void>((resolve) => {
+      releaseMe = resolve;
+    });
+    await page.route("**/src/main.tsx*", async (route) => {
+      await mainGate;
+      await route.continue();
+    });
+    await page.route("**/api/auth/me", async (route) => {
+      await meGate;
+      await route.fulfill({
+        status: 401,
+        contentType: "application/json",
+        body: JSON.stringify({ detail: "not authenticated" }),
+      });
+    });
+
+    await page.goto("/learn", { waitUntil: "commit" });
+    const diagnostic = page.locator("#vignette-boot-diagnostic");
+    await expect(diagnostic).toBeVisible({ timeout: 4_500 });
+    await expect(diagnostic).toHaveAttribute("data-vignette-boot-reason", "watchdog");
+
+    await page.evaluate(() => {
+      (window as Window & { __VIGNETTE_BOOT_DIAG__?: { check(): void } }).__VIGNETTE_BOOT_DIAG__?.check();
+    });
+    await expect(diagnostic).toHaveAttribute("data-vignette-boot-reason", "manual");
+    await page.evaluate(() => {
+      window.dispatchEvent(new ErrorEvent("error", { message: "boot diagnostic runtime fixture" }));
+    });
+    await expect(diagnostic).toHaveAttribute("data-vignette-boot-reason", "runtime-error");
+
+    releaseMain();
+    await expect(page.getByText(BOOT_SCREEN_TEXT)).toHaveAttribute(
+      "data-vignette-boot-loading",
+      "true",
+    );
+    await page.waitForTimeout(250);
+    await expect(diagnostic).toBeVisible();
+    await expect(diagnostic).toHaveAttribute("data-vignette-boot-reason", "runtime-error");
+    await expect(diagnostic.locator("dd").first()).toHaveText("runtime-error");
+
+    releaseMe();
+    await expect(page.getByRole("button", { name: /Google 계정으로 로그인/ })).toBeVisible();
+  });
+
   // checklist: shell-suspense-fallback
   // 모든 페이지가 lazy import이므로 라우트 청크가 로드되는 동안
   // Suspense fallback(BootScreen)이 표시된다. Vite dev 모듈 URL을 지연시켜 재현.
@@ -254,7 +408,35 @@ test.describe("full sweep — shared shell, GNB, and routing guards", () => {
       await gate;
       await route.continue();
     });
+    await page.route("**/api/auth/me", async (route) => {
+      await route.fulfill({
+        status: 401,
+        contentType: "application/json",
+        body: JSON.stringify({ detail: "not authenticated" }),
+      });
+    });
 
+    await page.route("**/api/auth/config", async (route) => {
+      await route.fulfill({
+        status: 200,
+        contentType: "application/json",
+        body: JSON.stringify({
+          google_oauth_configured: true,
+          saml_configured: false,
+          providers: [
+            {
+              provider: "google",
+              configured: true,
+              enabled: true,
+              login_path: "/auth/login?provider=google",
+            },
+          ],
+          allowed_email_domains: [],
+          redirect_uri: "http://127.0.0.1:8000/auth/callback",
+          dev_login_enabled: false,
+        }),
+      });
+    });
     const meResolved = page.waitForResponse(
       (res) => res.url().includes("/api/auth/me"),
       { timeout: 15_000 },
@@ -285,7 +467,35 @@ test.describe("full sweep — shared shell, GNB, and routing guards", () => {
     page.on("request", (request) => {
       if (request.isNavigationRequest()) documentRequests += 1;
     });
+    await page.route("**/api/auth/me", async (route) => {
+      await route.fulfill({
+        status: 401,
+        contentType: "application/json",
+        body: JSON.stringify({ detail: "not authenticated" }),
+      });
+    });
 
+    await page.route("**/api/auth/config", async (route) => {
+      await route.fulfill({
+        status: 200,
+        contentType: "application/json",
+        body: JSON.stringify({
+          google_oauth_configured: true,
+          saml_configured: false,
+          providers: [
+            {
+              provider: "google",
+              configured: true,
+              enabled: true,
+              login_path: "/auth/login?provider=google",
+            },
+          ],
+          allowed_email_domains: [],
+          redirect_uri: "http://127.0.0.1:8000/auth/callback",
+          dev_login_enabled: false,
+        }),
+      });
+    });
     await page.goto("/login");
     await expect(page.getByRole("button", { name: /Google 계정으로 로그인/ })).toBeVisible();
     expect(documentRequests).toBe(1);
diff --git a/apps/web/index.html b/apps/web/index.html
index 3800010..1c40263 100644
--- a/apps/web/index.html
+++ b/apps/web/index.html
@@ -127,6 +127,13 @@
           );
           return nodes.filter(isVisiblyRendered).length;
         }
+        function hasVisibleBootLoading(root) {
+          if (!root) return false;
+          var nodes = Array.prototype.slice.call(
+            root.querySelectorAll("[data-vignette-boot-loading]"),
+          );
+          return nodes.some(isVisiblyRendered);
+        }
         function appHealth() {
           var root = document.getElementById("root");
           var path = window.location.pathname;
@@ -138,7 +145,13 @@
                 "[data-vignette-admin-root],[data-vignette-admin-diagnostic],[data-testid='admin-ai-page']",
               )
             : null;
-          var hasAdminContent = !isAdmin || isVisiblyRendered(adminContent);
+          var adminRecovery = root
+            ? root.querySelector(
+                ".vg-route-error[data-testid='auth-restore-retrying'],.vg-route-error[data-testid='auth-restore-failed']",
+              )
+            : null;
+          var hasAdminContent =
+            !isAdmin || isVisiblyRendered(adminContent) || isVisiblyRendered(adminRecovery);
           return {
             healthy: Boolean(
               root &&
@@ -148,13 +161,26 @@
                 hasAdminContent,
             ),
             visible: visible,
+            bootLoading: hasVisibleBootLoading(root),
           };
         }
         function dismissDiagnosticIfHealthy() {
-          if (!appHealth().healthy) return false;
           var panel = document.getElementById("vignette-boot-diagnostic");
-          if (panel) panel.remove();
-          return true;
+          var health = appHealth();
+          if (health.healthy) {
+            if (panel) panel.remove();
+            return true;
+          }
+          if (
+            panel &&
+            panel.getAttribute("data-vignette-boot-reason") === "watchdog" &&
+            health.bootLoading &&
+            Date.now() - loadedAt < 20000
+          ) {
+            panel.remove();
+            return true;
+          }
+          return false;
         }
         function scheduleHealthyCheck() {
           if (healthyCheckTimer !== null) window.clearTimeout(healthyCheckTimer);
@@ -241,6 +267,13 @@
           var path = window.location.pathname;
           var text = (document.body && document.body.innerText ? document.body.innerText : "").trim();
           var health = appHealth();
+          if (
+            reason === "watchdog" &&
+            health.bootLoading &&
+            Date.now() - loadedAt < 20000
+          ) {
+            return;
+          }
           if (health.healthy && reason !== "manual") {
             if (reason !== "watchdog") {
               sendDiagnostic(reason, text.length, health.visible);
@@ -265,12 +298,22 @@
               "position:fixed;z-index:2147483647;inset:24px auto auto 24px;max-width:min(760px,calc(100vw - 48px));padding:18px;border:1px solid #d59b47;border-radius:8px;background:#fffaf0;color:#21312e;box-shadow:0 18px 48px rgba(10,20,18,.18);font:13px/1.5 system-ui,-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;white-space:normal;";
             document.body.appendChild(panel);
           }
+          var currentReason = panel.getAttribute("data-vignette-boot-reason");
+          var effectiveReason = reason;
+          if (
+            reason !== "watchdog" ||
+            (currentReason !== "runtime-error" && currentReason !== "manual")
+          ) {
+            panel.setAttribute("data-vignette-boot-reason", reason);
+          } else {
+            effectiveReason = currentReason;
+          }
           var lines = [
             "<b style=\"display:block;font-size:18px;margin-bottom:6px\">Vignette 화면 진단</b>",
             "<div>React 화면이 정상 콘텐츠를 표시하지 못해서 HTML 부트스트랩 진단을 띄웠습니다.</div>",
             "<dl style=\"display:grid;grid-template-columns:132px minmax(0,1fr);gap:0;margin:12px 0 0;border:1px solid rgba(0,0,0,.12);border-radius:8px;overflow:hidden\">",
             "<dt style=\"padding:7px 9px;background:rgba(0,0,0,.04);font-weight:700\">reason</dt><dd style=\"margin:0;padding:7px 9px;overflow-wrap:anywhere\">" +
-              reason +
+              effectiveReason +
               "</dd>",
             "<dt style=\"padding:7px 9px;background:rgba(0,0,0,.04);font-weight:700\">path</dt><dd style=\"margin:0;padding:7px 9px;overflow-wrap:anywhere\">" +
               path +
@@ -320,6 +363,9 @@
         window.setTimeout(function () {
           render("watchdog");
         }, 8000);
+        window.setTimeout(function () {
+          render("watchdog");
+        }, 20000);
       })();
     </script>
   </head>
diff --git a/apps/web/src/App.tsx b/apps/web/src/App.tsx
index 71602bc..92eb02c 100644
--- a/apps/web/src/App.tsx
+++ b/apps/web/src/App.tsx
@@ -66,6 +66,8 @@ const Settings = lazy(() => import("./pages/Settings"));
 function BootScreen() {
   return (
     <div
+      role="status"
+      data-vignette-boot-loading="true"
       style={{
         minHeight: "100dvh",
         display: "grid",
diff --git a/apps/web/src/lib/api.ts b/apps/web/src/lib/api.ts
index ed9cff7..ce34b6b 100644
--- a/apps/web/src/lib/api.ts
+++ b/apps/web/src/lib/api.ts
@@ -616,6 +616,7 @@ export type AdminUptimeResponse = ApiSchema<"AdminUptimeResponse">;
 export type AdminSupportTicket = ApiSchema<"AdminSupportTicketResponse">;
 export type AdminTicketsResponse = ApiSchema<"AdminTicketsResponse">;
 export type AdminTicketPatchRequest = ApiSchema<"AdminTicketPatch">;
+type AdminReadOptions = Pick<RequestOptions, "signal">;
 export type AdminTicketFilters = {
   status?: AdminSupportTicket["status"] | "";
   category?: AdminSupportTicket["category"] | "";
@@ -628,8 +629,9 @@ export type AdminTicketFilters = {
 };
 
 export const adminApi = {
-  health: () => api.get<AdminHealthResponse>("/admin/health"),
-  usage: (windowDays = 7) => api.get<AdminUsageResponse>(`/admin/usage?window_days=${windowDays}`),
+  health: (options?: AdminReadOptions) => api.get<AdminHealthResponse>("/admin/health", options),
+  usage: (windowDays = 7, options?: AdminReadOptions) =>
+    api.get<AdminUsageResponse>(`/admin/usage?window_days=${windowDays}`, options),
   uptime: (windowHours = 24) =>
     api.get<AdminUptimeResponse>(`/admin/uptime?window_hours=${windowHours}`),
   tickets: (filters: AdminTicketFilters = {}) => {
@@ -828,14 +830,19 @@ export type AdminProviderOAuthStartResponse =
   ApiSchema<"AdminProviderOAuthStartResponse">;
 
 export const adminEngineApi = {
-  get: () => api.get<AdminEngineConfigResponse>("/admin/engine-config"),
-  capabilities: (engineMode: string, force = false, engineUrl?: string) => {
+  get: (options?: AdminReadOptions) =>
+    api.get<AdminEngineConfigResponse>("/admin/engine-config", options),
+  capabilities: (
+    engineMode: string,
+    force = false,
+    engineUrl?: string,
+    options?: AdminReadOptions,
+  ) => {
     const query = new URLSearchParams({ engine_mode: engineMode, force: String(force) });
     if (engineUrl?.trim()) query.set("engine_url", engineUrl.trim());
-    return (
-    api.get<EngineCapabilitiesResponse>(
-        `/admin/engine-capabilities?${query.toString()}`,
-      )
+    return api.get<EngineCapabilitiesResponse>(
+      `/admin/engine-capabilities?${query.toString()}`,
+      options,
     );
   },
   update: (body: AdminEngineConfigPatchRequest) =>
diff --git a/apps/web/src/pages/AdminAi.tsx b/apps/web/src/pages/AdminAi.tsx
index f19f957..60f34a4 100644
--- a/apps/web/src/pages/AdminAi.tsx
+++ b/apps/web/src/pages/AdminAi.tsx
@@ -188,11 +188,33 @@ function healthStatusLabel(status?: string): string {
   return "확인 불가";
 }
 
+const ADMIN_READ_TIMEOUT_MS = 15_000;
+const CAPABILITIES_READ_TIMEOUT_MS = 25_000;
+
+class AdminReadTimeoutError extends Error {
+  constructor(label: string) {
+    super(`${label} 조회 시간이 초과되었습니다. 잠시 후 다시 시도해 주세요.`);
+    this.name = "AdminReadTimeoutError";
+  }
+}
+
+function adminReadError(cause: unknown, label: string): string {
+  if (cause instanceof AdminReadTimeoutError) return cause.message;
+  if (cause instanceof Error) return cause.message;
+  return `${label}을 불러오지 못했습니다. 잠시 후 다시 시도해 주세요.`;
+}
+
+function capabilitiesScope(engineMode: string, engineUrl: string): string {
+  return `${engineMode}\u0000${engineUrl.trim()}`;
+}
+
 export default function AdminAi() {
   const [windowDays, setWindowDays] = useState<(typeof WINDOW_OPTIONS)[number]>(30);
   const [usage, setUsage] = useState<AdminUsageResponse | null>(null);
   const [health, setHealth] = useState<AdminHealthResponse | null>(null);
   const [engine, setEngine] = useState<AdminEngineConfigResponse | null>(null);
+  const [engineLoading, setEngineLoading] = useState(true);
+  const [engineError, setEngineError] = useState<string | null>(null);
   const [capabilities, setCapabilities] = useState<EngineCapabilitiesResponse | null>(null);
   const [capabilitiesLoading, setCapabilitiesLoading] = useState(false);
   const [capabilitiesError, setCapabilitiesError] = useState<string | null>(null);
@@ -200,100 +222,257 @@ export default function AdminAi() {
   const [saving, setSaving] = useState(false);
   const [saved, setSaved] = useState(false);
   const [error, setError] = useState<string | null>(null);
-  const initialLoad = useRef(true);
+  const mounted = useRef(false);
+  const loadGeneration = useRef(0);
+  const displayRequestId = useRef(0);
+  const usageRequestId = useRef(0);
+  const healthRequestId = useRef(0);
   const capabilityRequestId = useRef(0);
+  const engineDraftRevision = useRef(0);
+  const loadedEngineRevision = useRef(0);
+  const loadedCapabilitiesScope = useRef<string | null>(null);
+  const activeControllers = useRef(new Set<AbortController>());
+  const loadRef = useRef<() => Promise<void>>(async () => undefined);
+  const loadedWindowDays = useRef(windowDays);
+
+  useEffect(() => {
+    mounted.current = true;
+    return () => {
+      mounted.current = false;
+      loadGeneration.current += 1;
+      capabilityRequestId.current += 1;
+      for (const controller of activeControllers.current) controller.abort();
+      activeControllers.current.clear();
+    };
+  }, []);
+
+  const runTimedRead = useCallback(
+    async <T,>(
+      timeoutMs: number,
+      label: string,
+      request: (signal: AbortSignal) => Promise<T>,
+    ): Promise<T> => {
+      const controller = new AbortController();
+      activeControllers.current.add(controller);
+      let timedOut = false;
+      const timeout = window.setTimeout(() => {
+        timedOut = true;
+        controller.abort();
+      }, timeoutMs);
+      try {
+        return await request(controller.signal);
+      } catch (cause) {
+        if (timedOut) throw new AdminReadTimeoutError(label);
+        throw cause;
+      } finally {
+        window.clearTimeout(timeout);
+        activeControllers.current.delete(controller);
+      }
+    },
+    [],
+  );
+
+  const updateEngineDraft = useCallback(
+    (updater: (current: AdminEngineConfigResponse) => AdminEngineConfigResponse): number => {
+      const revision = ++engineDraftRevision.current;
+      setEngine((current) => (current ? updater(current) : current));
+      return revision;
+    },
+    [],
+  );
 
   const loadCapabilities = useCallback(
     async (
       engineMode: string,
       engineUrl: string,
-      options: { force?: boolean; applyDefault?: boolean } = {},
+      options: { force?: boolean; applyDefault?: boolean; draftRevision?: number } = {},
     ) => {
       const requestId = ++capabilityRequestId.current;
+      const draftRevision = options.draftRevision ?? engineDraftRevision.current;
+      const scope = capabilitiesScope(engineMode, engineUrl);
       setCapabilitiesLoading(true);
       setCapabilitiesError(null);
       try {
-        const next = await adminEngineApi.capabilities(
-          engineMode,
-          options.force ?? false,
-          engineUrl,
+        const next = await runTimedRead(
+          CAPABILITIES_READ_TIMEOUT_MS,
+          "모델 목록",
+          (signal) =>
+            adminEngineApi.capabilities(engineMode, options.force ?? false, engineUrl, { signal }),
         );
-        if (requestId !== capabilityRequestId.current) return;
+        if (
+          !mounted.current ||
+          requestId !== capabilityRequestId.current ||
+          draftRevision !== engineDraftRevision.current
+        ) {
+          return;
+        }
         setCapabilities(next);
+        loadedCapabilitiesScope.current = scope;
         if (options.applyDefault && next.available && next.default_model) {
           setEngine((current) => {
             if (!current || current.engine_mode !== engineMode) return current;
             return {
               ...current,
               model: next.default_model ?? "",
-              reasoning_effort: next.default_reasoning_effort,
+              reasoning_effort: next.default_reasoning_effort ?? null,
             };
           });
         }
       } catch (cause) {
-        if (requestId !== capabilityRequestId.current) return;
-        setCapabilities(null);
-        setCapabilitiesError(
-          cause instanceof Error ? cause.message : "모델 목록을 불러오지 못했습니다.",
-        );
+        if (
+          !mounted.current ||
+          requestId !== capabilityRequestId.current ||
+          draftRevision !== engineDraftRevision.current
+        ) {
+          return;
+        }
+        setCapabilitiesError(adminReadError(cause, "모델 목록"));
       } finally {
-        if (requestId === capabilityRequestId.current) setCapabilitiesLoading(false);
+        if (mounted.current && requestId === capabilityRequestId.current) {
+          setCapabilitiesLoading(false);
+        }
       }
     },
-    [],
+    [runTimedRead],
+  );
+
+  const loadUsage = useCallback(
+    async (days: number): Promise<{ requestId: number; error: string | null }> => {
+      const requestId = ++usageRequestId.current;
+      try {
+        const next = await runTimedRead(
+          ADMIN_READ_TIMEOUT_MS,
+          "AI 사용량",
+          (signal) => adminApi.usage(days, { signal }),
+        );
+        if (!mounted.current || requestId !== usageRequestId.current) {
+          return { requestId, error: null };
+        }
+        setUsage(next);
+        return { requestId, error: null };
+      } catch (cause) {
+        if (!mounted.current || requestId !== usageRequestId.current) {
+          return { requestId, error: null };
+        }
+        return { requestId, error: adminReadError(cause, "AI 사용량") };
+      }
+    },
+    [runTimedRead],
+  );
+
+  const loadHealth = useCallback(
+    async (): Promise<{ requestId: number; error: string | null }> => {
+      const requestId = ++healthRequestId.current;
+      try {
+        const next = await runTimedRead(
+          ADMIN_READ_TIMEOUT_MS,
+          "엔진 상태",
+          (signal) => adminApi.health({ signal }),
+        );
+        if (!mounted.current || requestId !== healthRequestId.current) {
+          return { requestId, error: null };
+        }
+        setHealth(next);
+        return { requestId, error: null };
+      } catch (cause) {
+        if (!mounted.current || requestId !== healthRequestId.current) {
+          return { requestId, error: null };
+        }
+        return { requestId, error: adminReadError(cause, "엔진 상태") };
+      }
+    },
+    [runTimedRead],
   );
 
   const load = useCallback(async () => {
+    const generation = ++loadGeneration.current;
+    const displayRequest = ++displayRequestId.current;
+    const draftRevision = engineDraftRevision.current;
+    capabilityRequestId.current += 1;
+    setCapabilitiesLoading(false);
     setLoading(true);
     setError(null);
-    try {
-      const [usageResult, healthResult, engineResult] = await Promise.allSettled([
-        adminApi.usage(windowDays),
-        adminApi.health(),
-        adminEngineApi.get(),
-      ]);
-      if (usageResult.status === "fulfilled") setUsage(usageResult.value);
-      if (healthResult.status === "fulfilled") setHealth(healthResult.value);
-      if (engineResult.status === "fulfilled") {
-        setEngine(engineResult.value);
-        await loadCapabilities(engineResult.value.engine_mode, engineResult.value.engine_url);
-      }
-      const failures = [usageResult, healthResult, engineResult]
-        .filter((result): result is PromiseRejectedResult => result.status === "rejected")
-        .map((result) =>
-          result.reason instanceof Error ? result.reason.message : "일부 운영 정보를 불러오지 못했습니다.",
-        );
-      if (failures.length > 0) setError([...new Set(failures)].join(" · "));
-    } finally {
-      setLoading(false);
-    }
-  }, [loadCapabilities, windowDays]);
+    setEngineLoading(true);
+    setEngineError(null);
 
-  useEffect(() => {
-    if (initialLoad.current) {
-      initialLoad.current = false;
-      void load();
-      return;
-    }
-    let active = true;
-    setLoading(true);
-    setError(null);
-    void adminApi.usage(windowDays)
-      .then((nextUsage) => {
-        if (active) setUsage(nextUsage);
+    const usagePromise = loadUsage(windowDays);
+    const healthPromise = loadHealth();
+    void runTimedRead(
+      ADMIN_READ_TIMEOUT_MS,
+      "AI 엔진 설정",
+      (signal) => adminEngineApi.get({ signal }),
+    )
+      .then((next) => {
+        if (
+          !mounted.current ||
+          generation !== loadGeneration.current ||
+          draftRevision !== engineDraftRevision.current ||
+          draftRevision !== loadedEngineRevision.current
+        ) {
+          return;
+        }
+        const scope = capabilitiesScope(next.engine_mode, next.engine_url);
+        if (loadedCapabilitiesScope.current !== scope) {
+          setCapabilities(null);
+          setCapabilitiesError(null);
+        }
+        setEngine(next);
+        loadedEngineRevision.current = draftRevision;
+        setEngineError(null);
+        void loadCapabilities(next.engine_mode, next.engine_url, { draftRevision });
       })
       .catch((cause) => {
-        if (active) {
-          setError(cause instanceof Error ? cause.message : "AI 사용량을 불러오지 못했습니다.");
-        }
+        if (!mounted.current || generation !== loadGeneration.current) return;
+        setEngineError(adminReadError(cause, "AI 엔진 설정"));
       })
       .finally(() => {
-        if (active) setLoading(false);
+        if (mounted.current && generation === loadGeneration.current) setEngineLoading(false);
       });
-    return () => {
-      active = false;
-    };
-  }, [windowDays]);
+
+    const [usageResult, healthResult] = await Promise.all([usagePromise, healthPromise]);
+    if (
+      !mounted.current ||
+      generation !== loadGeneration.current ||
+      displayRequest !== displayRequestId.current ||
+      usageResult.requestId !== usageRequestId.current ||
+      healthResult.requestId !== healthRequestId.current
+    ) {
+      return;
+    }
+    const errors = [usageResult.error, healthResult.error].filter((item): item is string => Boolean(item));
+    setError(errors.length ? [...new Set(errors)].join(" · ") : null);
+    setLoading(false);
+  }, [loadCapabilities, loadHealth, loadUsage, runTimedRead, windowDays]);
+
+  useEffect(() => {
+    loadRef.current = load;
+  }, [load]);
+
+  useEffect(() => {
+    const timer = window.setTimeout(() => {
+      void loadRef.current();
+    }, 0);
+    return () => window.clearTimeout(timer);
+  }, []);
+
+  useEffect(() => {
+    if (windowDays === loadedWindowDays.current) return;
+    loadedWindowDays.current = windowDays;
+    const displayRequest = ++displayRequestId.current;
+    setLoading(true);
+    setError(null);
+    void loadUsage(windowDays).then((usageResult) => {
+      if (
+        !mounted.current ||
+        displayRequest !== displayRequestId.current ||
+        usageResult.requestId !== usageRequestId.current
+      ) {
+        return;
+      }
+      setError(usageResult.error);
+      setLoading(false);
+    });
+  }, [loadUsage, windowDays]);
 
   const saveEngine = async () => {
     if (!engine || !engine.engine_url.trim() || !engine.model.trim()) return;
@@ -307,9 +486,11 @@ export default function AdminAi() {
         model: engine.model.trim(),
         reasoning_effort: engine.reasoning_effort,
       });
-      setEngine(next);
+      const savedRevision = updateEngineDraft(() => next);
+      loadedEngineRevision.current = savedRevision;
       setSaved(true);
-      setHealth(await adminApi.health().catch(() => health));
+      const healthResult = await loadHealth();
+      if (healthResult.error) setError(healthResult.error);
       window.setTimeout(() => setSaved(false), 2400);
     } catch (cause) {
       setError(cause instanceof Error ? cause.message : "AI 운영 설정을 저장하지 못했습니다.");
@@ -317,7 +498,6 @@ export default function AdminAi() {
       setSaving(false);
     }
   };
-
   const usageCostBasis = readCostBasis(usage);
   const budgetCostBasis = readCostBasis(usage?.budget, usageCostBasis);
   const daily = usage?.daily_cost ?? [];
@@ -710,6 +890,14 @@ export default function AdminAi() {
                   {healthStatusLabel(engineService?.status)}
                 </span>
               </div>
+              {engineError ? (
+                <div className="aic-capability is-unavailable" role="alert">
+                  <div>
+                    <b>엔진 설정을 확인할 수 없음</b>
+                    <span>{engineError}</span>
+                  </div>
+                </div>
+              ) : null}
               {engine ? (
                 <>
                   <Field
@@ -726,15 +914,17 @@ export default function AdminAi() {
                         const engineMode = event.target
                           .value as AdminEngineConfigResponse["engine_mode"];
                         setCapabilities(null);
-                        setEngine({
-                          ...engine,
+                        loadedCapabilitiesScope.current = null;
+                        const draftRevision = updateEngineDraft((current) => ({
+                          ...current,
                           engine_mode: engineMode,
                           model: "",
                           reasoning_effort: null,
-                        });
+                        }));
                         void loadCapabilities(engineMode, engine.engine_url, {
                           force: true,
                           applyDefault: true,
+                          draftRevision,
                         });
                       }}
                     >
@@ -750,8 +940,12 @@ export default function AdminAi() {
                       id="aic-engine-url"
                       value={engine.engine_url}
                       onChange={(event) => {
-                        setEngine({ ...engine, engine_url: event.target.value });
+                        updateEngineDraft((current) => ({
+                          ...current,
+                          engine_url: event.target.value,
+                        }));
                         setCapabilities(null);
+                        loadedCapabilitiesScope.current = null;
                         setCapabilitiesError(
                           "연결 주소가 바뀌었습니다. 새 주소의 모델 목록을 확인하세요.",
                         );
@@ -771,11 +965,11 @@ export default function AdminAi() {
                       onChange={(event) => {
                         const model = event.target.value;
                         const option = capabilityModels.find((item) => item.id === model);
-                        setEngine({
-                          ...engine,
+                        updateEngineDraft((current) => ({
+                          ...current,
                           model,
                           reasoning_effort: option?.default_reasoning_effort ?? null,
-                        });
+                        }));
                       }}
                       aria-label="AI 기본 모델"
                       disabled={capabilitiesLoading || !capabilities?.available}
@@ -805,11 +999,11 @@ export default function AdminAi() {
                       aria-label="AI 추론 강도"
                       disabled={capabilitiesLoading || !selectedModel}
                       onChange={(event) =>
-                        setEngine({
-                          ...engine,
+                        updateEngineDraft((current) => ({
+                          ...current,
                           reasoning_effort: (event.target.value ||
                             null) as AdminEngineConfigResponse["reasoning_effort"],
-                        })
+                        }))
                       }
                     >
                       {selectedEfforts.length ? null : (
@@ -858,6 +1052,7 @@ export default function AdminAi() {
                         void loadCapabilities(engine.engine_mode, engine.engine_url, {
                           force: true,
                           applyDefault: !selectedModel,
+                          draftRevision: engineDraftRevision.current,
                         })
                       }
                       disabled={capabilitiesLoading}
@@ -889,7 +1084,11 @@ export default function AdminAi() {
                   </div>
                 </>
               ) : (
-                <div className="aic-empty">현재 AI 엔진 설정을 불러오는 중입니다.</div>
+                <div className="aic-empty">
+                  {engineLoading
+                    ? "현재 AI 엔진 설정을 불러오는 중입니다."
+                    : "현재 AI 엔진 설정을 불러오지 못했습니다. 새로고침 후 다시 시도해 주세요."}
+                </div>
               )}
             </section>