diff --git a/api.integration.test.ts b/api.integration.test.ts
new file mode 100644
index 0000000..b9d2d28
--- /dev/null
+++ b/api.integration.test.ts
@@ -0,0 +1,323 @@
+import { describe, expect, it } from "vitest";
+
+const BASE_URL = "https://elyos-interview-907656039105.europe-west2.run.app";
+const API_KEY = process.env["ELYOS_API_KEY"] ?? "";
+const REQUEST_TIMEOUT_MS = 30_000;
+
+// Helper: raw fetch with full control over headers and params
+const get = async (
+  path: string,
+  params: Record<string, string> = {},
+  headers: Record<string, string> = { "X-API-Key": API_KEY },
+): Promise<{ status: number; body: string; ms: number }> => {
+  const url = new URL(path, BASE_URL);
+  for (const [k, v] of Object.entries(params)) url.searchParams.set(k, v);
+  const start = Date.now();
+  const res = await fetch(url.toString(), {
+    headers,
+    signal: AbortSignal.timeout(REQUEST_TIMEOUT_MS),
+  });
+  const body = await res.text();
+  return { status: res.status, body, ms: Date.now() - start };
+};
+
+// ---------------------------------------------------------------------------
+// Authentication
+// ---------------------------------------------------------------------------
+
+describe("authentication", () => {
+  it("weather: missing API key returns non-200 status", async () => {
+    const { status } = await get("/weather", { location: "London" }, {});
+    expect(status).not.toBe(200);
+  });
+
+  it("weather: invalid API key returns non-200 status", async () => {
+    const { status } = await get(
+      "/weather",
+      { location: "London" },
+      { "X-API-Key": "invalid-key-xyz" },
+    );
+    expect(status).not.toBe(200);
+  });
+
+  it("research: missing API key returns non-200 status", async () => {
+    const { status } = await get("/research", { topic: "solar energy" }, {});
+    expect(status).not.toBe(200);
+  }, 15_000);
+
+  it("research: invalid API key returns non-200 status", async () => {
+    const { status } = await get(
+      "/research",
+      { topic: "solar energy" },
+      { "X-API-Key": "invalid-key-xyz" },
+    );
+    expect(status).not.toBe(200);
+  }, 15_000);
+});
+
+// ---------------------------------------------------------------------------
+// Weather endpoint – happy path
+// ---------------------------------------------------------------------------
+
+describe("GET /weather – happy path", () => {
+  it("returns 200 for a valid city", async () => {
+    const { status, body } = await get("/weather", { location: "London" });
+    expect(status).toBe(200);
+    expect(body.trim()).not.toBe("");
+  });
+
+  it("response is not an empty JSON object {}", async () => {
+    const { body } = await get("/weather", { location: "London" });
+    // cli.ts retries on empty `{}` – confirm it doesn't happen in normal usage
+    expect(body.trim()).not.toBe("{}");
+  });
+
+  it("response body can be parsed as JSON", async () => {
+    const { body } = await get("/weather", { location: "London" });
+    expect(() => JSON.parse(body)).not.toThrow();
+  });
+
+  it("response contains weather-related data for the requested city", async () => {
+    const { body } = await get("/weather", { location: "London" });
+    const lower = body.toLowerCase();
+    // Expect at least one of: temperature, weather, humidity, wind, degrees
+    const weatherKeywords = [
+      "temperature",
+      "weather",
+      "humidity",
+      "wind",
+      "celsius",
+      "fahrenheit",
+      "cloud",
+      "rain",
+      "sunny",
+      "forecast",
+      "°",
+    ];
+    const hasWeatherData = weatherKeywords.some((kw) => lower.includes(kw));
+    expect(hasWeatherData).toBe(true);
+  });
+
+  it("response references the requested city (London)", async () => {
+    const { body } = await get("/weather", { location: "London" });
+    expect(body.toLowerCase()).toContain("london");
+  });
+
+  it("city with spaces (New York) returns 200 with data", async () => {
+    const { status, body } = await get("/weather", {
+      location: "New York",
+    });
+    expect(status).toBe(200);
+    expect(body.trim()).not.toBe("");
+  });
+
+  it("response references the multi-word city (New York)", async () => {
+    const { body } = await get("/weather", { location: "New York" });
+    // Expect the response to mention New York, not a different city
+    const lower = body.toLowerCase();
+    expect(lower).toContain("new york");
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Weather endpoint – case sensitivity
+// ---------------------------------------------------------------------------
+
+describe("GET /weather – case sensitivity", () => {
+  it("lowercase and mixed-case city produce the same result", async () => {
+    const [r1, r2] = await Promise.all([
+      get("/weather", { location: "london" }),
+      get("/weather", { location: "London" }),
+    ]);
+    expect(r1.status).toBe(200);
+    expect(r2.status).toBe(200);
+    // Both should be non-empty and contain the same essential data
+    expect(r1.body.toLowerCase()).toContain("london");
+    expect(r2.body.toLowerCase()).toContain("london");
+  });
+
+  it("all-uppercase city returns 200", async () => {
+    const { status } = await get("/weather", { location: "LONDON" });
+    expect(status).toBe(200);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Weather endpoint – edge cases / quirks
+// ---------------------------------------------------------------------------
+
+describe("GET /weather – edge cases", () => {
+  it("non-existent city returns a clear error or non-200 status (not silent success)", async () => {
+    const { status, body } = await get("/weather", {
+      location: "Qxzplorf99999",
+    });
+    // Either status should indicate failure, or body should mention error/not found
+    const isErrorStatus = status >= 400;
+    const isErrorBody = /error|not found|unknown|invalid/i.test(body);
+    expect(isErrorStatus || isErrorBody).toBe(true);
+  });
+
+  it("empty location string does not return weather data as if it were valid", async () => {
+    const { status, body } = await get("/weather", { location: "" });
+    const isErrorStatus = status >= 400;
+    const isErrorBody =
+      /error|not found|unknown|invalid|required|missing/i.test(body);
+    // Empty location should result in an error (not a 200 with data)
+    expect(isErrorStatus || isErrorBody).toBe(true);
+  });
+
+  it("missing location parameter returns a non-200 status or error body", async () => {
+    const { status, body } = await get("/weather");
+    const isErrorStatus = status >= 400;
+    const isErrorBody = /error|missing|required|parameter/i.test(body);
+    expect(isErrorStatus || isErrorBody).toBe(true);
+  });
+
+  it("numeric string as location returns an error or empty data (not real weather)", async () => {
+    const { status, body } = await get("/weather", { location: "12345" });
+    // A numeric string is not a valid city name
+    const isErrorStatus = status >= 400;
+    const isErrorBody = /error|not found|unknown|invalid/i.test(body);
+    expect(isErrorStatus || isErrorBody).toBe(true);
+  });
+
+  it("SQL injection attempt in location does not cause server error (500)", async () => {
+    const { status } = await get("/weather", {
+      location: "'; DROP TABLE locations; --",
+    });
+    expect(status).not.toBe(500);
+  });
+
+  it("consecutive calls for same city return consistent (non-empty) responses", async () => {
+    const r1 = await get("/weather", { location: "Tokyo" });
+    const r2 = await get("/weather", { location: "Tokyo" });
+    expect(r1.body.trim()).not.toBe("");
+    expect(r2.body.trim()).not.toBe("");
+    // Core data (at minimum both should reference the city)
+    expect(r1.body.toLowerCase()).toContain("tokyo");
+    expect(r2.body.toLowerCase()).toContain("tokyo");
+  });
+
+  it("non-ASCII city name (Zürich) returns 200 or graceful error", async () => {
+    const { status } = await get("/weather", { location: "Zürich" });
+    // Should either work (200) or return a clean 4xx, not a 500
+    expect(status).not.toBe(500);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Research endpoint – happy path
+// ---------------------------------------------------------------------------
+
+describe("GET /research – happy path", () => {
+  it("returns 200 for a valid topic", async () => {
+    const { status, body } = await get("/research", {
+      topic: "solar energy",
+    });
+    expect(status).toBe(200);
+    expect(body.trim()).not.toBe("");
+  }, 15_000);
+
+  it("response is not an empty JSON object {}", async () => {
+    const { body } = await get("/research", { topic: "solar energy" });
+    expect(body.trim()).not.toBe("{}");
+  }, 15_000);
+
+  it("response body can be parsed as JSON", async () => {
+    const { body } = await get("/research", { topic: "climate change" });
+    expect(() => JSON.parse(body)).not.toThrow();
+  }, 15_000);
+
+  it("response contains content relevant to the researched topic", async () => {
+    const { body } = await get("/research", { topic: "solar energy" });
+    const lower = body.toLowerCase();
+    // Solar energy research should mention relevant keywords
+    const relevantKeywords = [
+      "solar",
+      "energy",
+      "sun",
+      "panel",
+      "photovoltaic",
+      "renewable",
+      "electricity",
+      "power",
+    ];
+    const hasRelevantContent = relevantKeywords.some((kw) =>
+      lower.includes(kw),
+    );
+    expect(hasRelevantContent).toBe(true);
+  }, 15_000);
+});
+
+// ---------------------------------------------------------------------------
+// Research endpoint – response timing
+// ---------------------------------------------------------------------------
+
+describe("GET /research – response timing", () => {
+  it("response time is at least 3 seconds (as documented)", async () => {
+    const { ms } = await get("/research", { topic: "quantum computing" });
+    expect(ms).toBeGreaterThanOrEqual(3_000);
+  }, 20_000);
+
+  it("response time does not exceed 8 seconds (as documented)", async () => {
+    const { ms } = await get("/research", { topic: "machine learning" });
+    // Documented maximum is 8 seconds; allow 2s of network overhead
+    expect(ms).toBeLessThanOrEqual(10_000);
+  }, 20_000);
+});
+
+// ---------------------------------------------------------------------------
+// Research endpoint – edge cases / quirks
+// ---------------------------------------------------------------------------
+
+describe("GET /research – edge cases", () => {
+  it("empty topic string does not return research data as if valid", async () => {
+    const { status, body } = await get("/research", { topic: "" });
+    const isErrorStatus = status >= 400;
+    const isErrorBody = /error|not found|invalid|required|missing/i.test(body);
+    expect(isErrorStatus || isErrorBody).toBe(true);
+  }, 15_000);
+
+  it("missing topic parameter returns a non-200 status or error body", async () => {
+    const { status, body } = await get("/research");
+    const isErrorStatus = status >= 400;
+    const isErrorBody = /error|missing|required|parameter/i.test(body);
+    expect(isErrorStatus || isErrorBody).toBe(true);
+  }, 15_000);
+
+  it("two requests for the same topic return consistent (non-empty) responses", async () => {
+    const [r1, r2] = await Promise.all([
+      get("/research", { topic: "solar energy" }),
+      get("/research", { topic: "solar energy" }),
+    ]);
+    expect(r1.body.trim()).not.toBe("");
+    expect(r2.body.trim()).not.toBe("");
+    // Both results should be about solar energy
+    expect(r1.body.toLowerCase()).toMatch(/solar|energy|renewable/);
+    expect(r2.body.toLowerCase()).toMatch(/solar|energy|renewable/);
+  }, 20_000);
+
+  it("different topics return different content", async () => {
+    const [r1, r2] = await Promise.all([
+      get("/research", { topic: "solar energy" }),
+      get("/research", { topic: "ocean biology" }),
+    ]);
+    // Responses should not be identical for unrelated topics
+    expect(r1.body).not.toBe(r2.body);
+  }, 20_000);
+
+  it("research on an obscure topic returns a meaningful (non-empty) response", async () => {
+    const { status, body } = await get("/research", {
+      topic: "knot theory in topology",
+    });
+    expect(status).toBe(200);
+    expect(body.trim().length).toBeGreaterThan(50);
+  }, 15_000);
+
+  it("SQL injection attempt in topic does not cause server error (500)", async () => {
+    const { status } = await get("/research", {
+      topic: "'; DROP TABLE research; --",
+    });
+    expect(status).not.toBe(500);
+  }, 15_000);
+});
diff --git a/vitest.config.ts b/vitest.config.ts
index 77a73cf..2c01d68 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from "vitest/config";
 
 export default defineConfig({
-  test: {},
+  test: {
+    testTimeout: 30_000,
+  },
 });