diff --git a/src/lib/metrics-poller.ts b/src/lib/metrics-poller.ts
new file mode 100644
index 0000000..0c39973
--- /dev/null
+++ b/src/lib/metrics-poller.ts
@@ -0,0 +1,116 @@
+import { fetchMetrics, type LlamaSwapConfig } from "./llamaswap";
+import { gpuInfos, parseGpuMetrics, type GpuMetricKind, type GpuSample } from "./metrics-parser";
+
+const RING_SIZE = 60;
+
+function avg(values: number[]): number {
+  return values.reduce((a, b) => a + b, 0) / (values.length || 1);
+}
+function max(values: number[]): number {
+  return values.reduce((a, b) => Math.max(a, b), -Infinity);
+}
+function sum(values: number[]): number {
+  return values.reduce((a, b) => a + b, 0);
+}
+
+const AGGREGATE: Record<GpuMetricKind, (values: number[]) => number> = {
+  util_percent: avg,
+  memory_util_percent: avg,
+  temperature: max,
+  power: sum,
+  fan: avg,
+};
+
+function key(gpuId: string, kind: GpuMetricKind): string {
+  return `${gpuId}|${kind}`;
+}
+
+type FetchFn = (cfg: LlamaSwapConfig) => Promise<string>;
+
+export class MetricsPoller {
+  private buffers = new Map<string, number[]>();
+  private gpuName = new Map<string, string>();
+  private gpuIds: string[] = [];
+  private listeners = new Set<() => void>();
+  private timer?: ReturnType<typeof setInterval>;
+  private lastError?: string;
+
+  constructor(
+    private cfg: LlamaSwapConfig,
+    private intervalMs = 5000,
+    private fetchFn: FetchFn = fetchMetrics,
+  ) {}
+
+  start(): void {
+    void this.tick();
+    this.timer = setInterval(() => void this.tick(), this.intervalMs);
+  }
+
+  stop(): void {
+    if (this.timer) clearInterval(this.timer);
+    this.timer = undefined;
+  }
+
+  on(listener: () => void): () => void {
+    this.listeners.add(listener);
+    return () => {
+      this.listeners.delete(listener);
+    };
+  }
+
+  async tick(): Promise<void> {
+    try {
+      const text = await this.fetchFn(this.cfg);
+      this.apply(parseGpuMetrics(text));
+      this.lastError = undefined;
+    } catch (err) {
+      this.lastError = err instanceof Error ? err.message : String(err);
+    } finally {
+      for (const listener of this.listeners) listener();
+    }
+  }
+
+  private apply(samples: GpuSample[]): void {
+    const byKind = new Map<GpuMetricKind, Map<string, number>>();
+    for (const s of samples) {
+      if (!byKind.has(s.kind)) byKind.set(s.kind, new Map());
+      byKind.get(s.kind)!.set(s.id, s.value);
+      if (!this.gpuName.has(s.id)) this.gpuName.set(s.id, s.name);
+    }
+    this.gpuIds = [...this.gpuName.keys()].sort((a, b) => parseInt(a, 10) - parseInt(b, 10));
+
+    for (const [kind, values] of byKind) {
+      for (const [id, value] of values) this.push(key(id, kind), value);
+      const all = [...values.values()];
+      if (all.length > 0) this.push(key("all", kind), AGGREGATE[kind](all));
+    }
+  }
+
+  private push(k: string, value: number): void {
+    let ring = this.buffers.get(k);
+    if (!ring) {
+      ring = [];
+      this.buffers.set(k, ring);
+    }
+    ring.push(value);
+    if (ring.length > RING_SIZE) ring.shift();
+  }
+
+  getValue(gpuId: string, kind: GpuMetricKind): number | undefined {
+    const ring = this.buffers.get(key(gpuId, kind));
+    return ring ? ring[ring.length - 1] : undefined;
+  }
+
+  getHistory(gpuId: string, kind: GpuMetricKind): number[] {
+    const ring = this.buffers.get(key(gpuId, kind));
+    return ring ? [...ring] : [];
+  }
+
+  gpus(): { id: string; name: string }[] {
+    return this.gpuIds.map((id) => ({ id, name: this.gpuName.get(id) ?? "" }));
+  }
+
+  isOffline(): boolean {
+    return this.lastError !== undefined;
+  }
+}
diff --git a/tests/metrics-poller.test.ts b/tests/metrics-poller.test.ts
new file mode 100644
index 0000000..56c4d07
--- /dev/null
+++ b/tests/metrics-poller.test.ts
@@ -0,0 +1,63 @@
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { test } from "node:test";
+import { type LlamaSwapConfig } from "../src/lib/util";
+import { MetricsPoller } from "../src/lib/metrics-poller";
+import { parseGpuMetrics } from "../src/lib/metrics-parser";
+
+const FIXTURE = readFileSync(new URL("./fixtures/metrics.txt", import.meta.url), "utf8");
+const FIXTURE2 = FIXTURE
+  .replace(/llamaswap_gpu_util_percent\{id="0"[^}]*\} 100/, 'llamaswap_gpu_util_percent{id="0",name="RTX PRO 6000"} 30')
+  .replace(/llamaswap_gpu_util_percent\{id="1"[^}]*\} 100/, 'llamaswap_gpu_util_percent{id="1",name="RTX PRO 6000"} 50')
+  .replace(/llamaswap_gpu_util_percent\{id="2"[^}]*\} 100/, 'llamaswap_gpu_util_percent{id="2",name="RTX 5090"} 80');
+
+function stubFetch(bodies: string[]) {
+  let i = 0;
+  return async () => bodies[Math.min(i++, bodies.length - 1)];
+}
+
+const CFG: LlamaSwapConfig = { baseUrl: "http://test" };
+
+test("poller stores per-GPU history and computes aggregates", async () => {
+  const poller = new MetricsPoller(CFG, 5000, stubFetch([FIXTURE, FIXTURE2]));
+  await poller.tick();
+  await poller.tick();
+
+  assert.equal(poller.getValue("0", "util_percent"), 30);
+  assert.deepEqual(poller.getHistory("0", "util_percent"), [100, 30]);
+
+  const allUtil = poller.getValue("all", "util_percent");
+  assert.ok(allUtil !== undefined);
+  assert.ok(Math.abs(allUtil - (30 + 50 + 80) / 3) < 1e-9);
+
+  const allTemp = poller.getValue("all", "temperature");
+  assert.equal(allTemp, 64);
+
+  const allPower = poller.getValue("all", "power");
+  assert.ok(allPower !== undefined);
+  assert.ok(Math.abs(allPower - (316.56 + 336.17 + 377.28)) < 1e-9);
+
+  assert.deepEqual(poller.gpus().map((g) => g.id), ["0", "1", "2"]);
+  assert.equal(poller.gpus()[2].name, "NVIDIA GeForce RTX 5090");
+});
+
+test("poller ring buffer caps at 60 samples", async () => {
+  const poller = new MetricsPoller(CFG, 5000, stubFetch([FIXTURE]));
+  for (let i = 0; i < 70; i++) await poller.tick();
+  assert.equal(poller.getHistory("0", "fan").length, 60);
+});
+
+test("poller reports offline after a fetch failure and recovers", async () => {
+  let fail = true;
+  const fetchFn = async () => {
+    if (fail) throw new Error("boom");
+    return FIXTURE;
+  };
+  const poller = new MetricsPoller(CFG, 5000, fetchFn);
+  await poller.tick();
+  assert.equal(poller.isOffline(), true);
+  fail = false;
+  await poller.tick();
+  assert.equal(poller.isOffline(), false);
+  assert.ok(poller.getValue("0", "util_percent") !== undefined);
+});