diff --git a/src/content/market/api-client.ts b/src/content/market/api-client.ts
new file mode 100644
index 0000000..f070e76
--- /dev/null
+++ b/src/content/market/api-client.ts
@@ -0,0 +1,136 @@
+import { normalizeRateDisplay } from "../../shared/rate-normalizer";
+import type { MarketApiResult } from "./types";
+
+interface FetchResponseLike {
+  json(): Promise<unknown>;
+  ok: boolean;
+}
+
+type FetchLike = (
+  input: string,
+  init?: RequestInit
+) => Promise<FetchResponseLike>;
+
+interface MarketApiClientOptions {
+  baseUrl?: string;
+  fetchImpl?: FetchLike;
+  timeoutMs?: number;
+}
+
+export function createMarketApiClient(options: MarketApiClientOptions = {}) {
+  const baseUrl = options.baseUrl ?? resolveBaseUrl();
+  const fetchImpl = options.fetchImpl ?? defaultFetch;
+  const timeoutMs = options.timeoutMs ?? 8000;
+
+  return {
+    async loadAuthorAseInfo(authorId: string): Promise<MarketApiResult> {
+      const controller = new AbortController();
+      const timeoutId = setTimeout(() => controller.abort(), timeoutMs);
+
+      try {
+        const response = await fetchImpl(
+          buildAuthorAseInfoUrl(authorId, baseUrl),
+          {
+            credentials: "include",
+            method: "GET",
+            signal: controller.signal
+          }
+        );
+
+        if (!response.ok) {
+          return {
+            success: false,
+            reason: "request-failed"
+          };
+        }
+
+        return mapAuthorAseInfoResponse(await response.json());
+      } catch (error) {
+        if (isAbortError(error) || controller.signal.aborted) {
+          return {
+            success: false,
+            reason: "timeout"
+          };
+        }
+
+        return {
+          success: false,
+          reason: "request-failed"
+        };
+      } finally {
+        clearTimeout(timeoutId);
+      }
+    }
+  };
+}
+
+export function buildAuthorAseInfoUrl(authorId: string, baseUrl: string): string {
+  const url = new URL("/gw/api/aggregator/get_author_ase_info", baseUrl);
+  url.searchParams.set("author_id", authorId);
+  url.searchParams.set("range", "30");
+  return url.toString();
+}
+
+export function mapAuthorAseInfoResponse(payload: unknown): MarketApiResult {
+  const data = getPayloadData(payload);
+  if (!data) {
+    return {
+      success: false,
+      reason: "bad-response"
+    };
+  }
+
+  const singleVideoAfterSearchRate = readNormalizedRate(
+    data.avg_search_after_view_rate
+  );
+  const personalVideoAfterSearchRate = readNormalizedRate(
+    data.personal_avg_search_after_view_rate
+  );
+
+  if (!singleVideoAfterSearchRate || !personalVideoAfterSearchRate) {
+    return {
+      success: false,
+      reason: "missing-rate"
+    };
+  }
+
+  return {
+    success: true,
+    rates: {
+      singleVideoAfterSearchRate,
+      personalVideoAfterSearchRate
+    }
+  };
+}
+
+function getPayloadData(payload: unknown): Record<string, unknown> | null {
+  if (!isRecord(payload)) {
+    return null;
+  }
+
+  return isRecord(payload.data) ? payload.data : payload;
+}
+
+function readNormalizedRate(value: unknown): string | null {
+  return typeof value === "string" ? normalizeRateDisplay(value) : null;
+}
+
+function resolveBaseUrl(): string {
+  if (typeof location !== "undefined" && location.origin) {
+    return location.origin;
+  }
+
+  return "https://xingtu.cn";
+}
+
+async function defaultFetch(input: string, init?: RequestInit) {
+  return fetch(input, init);
+}
+
+function isAbortError(error: unknown): boolean {
+  return error instanceof Error && error.name === "AbortError";
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null;
+}
diff --git a/src/content/market/types.ts b/src/content/market/types.ts
new file mode 100644
index 0000000..c73989e
--- /dev/null
+++ b/src/content/market/types.ts
@@ -0,0 +1,22 @@
+export interface AfterSearchRates {
+  personalVideoAfterSearchRate?: string;
+  singleVideoAfterSearchRate?: string;
+}
+
+export type MarketApiFailureReason =
+  | "bad-response"
+  | "missing-rate"
+  | "request-failed"
+  | "timeout";
+
+export type MarketApiSuccessResult = {
+  success: true;
+  rates: Required<AfterSearchRates>;
+};
+
+export type MarketApiFailureResult = {
+  success: false;
+  reason: MarketApiFailureReason;
+};
+
+export type MarketApiResult = MarketApiSuccessResult | MarketApiFailureResult;
diff --git a/tests/market-api-client.test.ts b/tests/market-api-client.test.ts
new file mode 100644
index 0000000..cfb0f7e
--- /dev/null
+++ b/tests/market-api-client.test.ts
@@ -0,0 +1,75 @@
+import { describe, expect, test } from "vitest";
+
+import {
+  buildAuthorAseInfoUrl,
+  createMarketApiClient,
+  mapAuthorAseInfoResponse
+} from "../src/content/market/api-client";
+
+describe("market-api-client", () => {
+  test("builds the author ase info url with author id and range", () => {
+    expect(
+      buildAuthorAseInfoUrl("123", "https://xingtu.cn")
+    ).toBe(
+      "https://xingtu.cn/gw/api/aggregator/get_author_ase_info?author_id=123&range=30"
+    );
+  });
+
+  test("maps a valid ASE payload into normalized rates", () => {
+    expect(
+      mapAuthorAseInfoResponse({
+        data: {
+          avg_search_after_view_rate: "<0.02%",
+          personal_avg_search_after_view_rate: "0.02 - 0.1%"
+        }
+      })
+    ).toMatchObject({
+      success: true,
+      rates: {
+        singleVideoAfterSearchRate: "<0.02%",
+        personalVideoAfterSearchRate: "0.02% - 0.1%"
+      }
+    });
+  });
+
+  test("returns a missing-rate failure when the payload omits a required field", () => {
+    expect(
+      mapAuthorAseInfoResponse({
+        data: {
+          avg_search_after_view_rate: "<0.02%"
+        }
+      })
+    ).toMatchObject({
+      success: false,
+      reason: "missing-rate"
+    });
+  });
+
+  test("returns a request-failed result for non-ok responses", async () => {
+    const client = createMarketApiClient({
+      fetchImpl: async () => ({
+        ok: false,
+        json: async () => ({})
+      })
+    });
+
+    await expect(client.loadAuthorAseInfo("123")).resolves.toMatchObject({
+      success: false,
+      reason: "request-failed"
+    });
+  });
+
+  test("returns a timeout result when the request aborts", async () => {
+    const client = createMarketApiClient({
+      fetchImpl: async () => {
+        throw new DOMException("Timed out", "AbortError");
+      },
+      timeoutMs: 1
+    });
+
+    await expect(client.loadAuthorAseInfo("123")).resolves.toMatchObject({
+      success: false,
+      reason: "timeout"
+    });
+  });
+});