diff --git a/examples/papi/chain-exporter.ts b/examples/papi/chain-exporter.ts
new file mode 100644
index 00000000..c0d77aa7
--- /dev/null
+++ b/examples/papi/chain-exporter.ts
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Domain-state Prometheus exporter for paritytech/web3-storage#267.
+ *
+ * The chain nodes already expose standard Substrate Prometheus metrics (block
+ * time, weight, txpool). What no metric covers is the pallet's own domain
+ * state: provider balances and stake, agreement counts, pending challenges,
+ * checkpoint accruals, and per-class block weight (the on_finalize sweep spike
+ * that Substrate's own Prometheus does not expose). This sidecar polls that
+ * state per finalized block and exports it as Prometheus gauges, plus counters
+ * accumulated from lifecycle events, so a stress run (see
+ * `challenge-saturation.ts`) is observable on a dashboard. It is the first
+ * consumer of the telemetry work in #214 and the scrape target the
+ * `monitoring/` stack (a follow-up) will chart.
+ *
+ * Per-provider metrics are labelled; their cardinality is bounded by the small
+ * `MaxPrimaryProviders` / `MaxMembers`. Aggregate counts (agreements,
+ * challenges) are exported as totals, not per-entry, so a saturation run does
+ * not blow up label cardinality.
+ *
+ * Values are float64 (Prometheus' only numeric type), so balances above 2^53
+ * lose low-order precision. Fine for monitoring; do not treat as exact.
+ *
+ * Usage:
+ *   pnpm --filter web3-storage-papi-demo run chain-exporter -- [options]
+ *
+ *   --chain-rpc <url>   default ws://127.0.0.1:2222
+ *   --port <n>          metrics HTTP port, default 9700
+ */
+
+import { createServer } from "node:http";
+import { parseArgs } from "node:util";
+
+import {
+  connect,
+  syncSs58Prefix,
+  waitForChainReady,
+  type ChainConnection,
+  type ParachainApi,
+} from "@web3-storage/sdk";
+
+function parseCli() {
+  const { values } = parseArgs({
+    options: {
+      "chain-rpc": { type: "string", default: "ws://127.0.0.1:2222" },
+      port: { type: "string", default: "9700" },
+      help: { type: "boolean", default: false },
+    },
+  });
+  if (values.help) {
+    console.log(USAGE);
+    process.exit(0);
+  }
+  const port = Number(values.port);
+  if (!Number.isInteger(port) || port < 1 || port > 65535) {
+    throw new Error(`--port must be 1..65535, got ${values.port}`);
+  }
+  return { chainRpc: values["chain-rpc"], port };
+}
+
+const USAGE = `chain-exporter: Prometheus exporter for web3-storage pallet domain state
+
+  --chain-rpc <url>   default ws://127.0.0.1:2222
+  --port <n>          metrics HTTP port, default 9700
+
+Serves /metrics (Prometheus text) and /health.`;
+
+// ── Metric registry ──────────────────────────────────────────────────────────
+
+type Sample = { labels: Record<string, string>; value: number };
+
+interface Metric {
+  help: string;
+  type: "gauge" | "counter";
+  samples: Sample[];
+}
+
+const PREFIX = "web3storage_";
+
+/** Minimal Prometheus registry: gauges are replaced each scrape, counters persist. */
+class Registry {
+  private metrics = new Map<string, Metric>();
+
+  private ensure(name: string, type: Metric["type"], help: string): Metric {
+    let m = this.metrics.get(name);
+    if (!m) {
+      m = { help, type, samples: [] };
+      this.metrics.set(name, m);
+    }
+    return m;
+  }
+
+  /** Replace a gauge's samples for this scrape. */
+  setGauge(name: string, value: number, labels: Record<string, string> = {}) {
+    const m = this.ensure(name, "gauge", GAUGE_HELP[name] ?? name);
+    m.samples.push({ labels, value });
+  }
+
+  clearGauge(name: string) {
+    const m = this.metrics.get(name);
+    if (m && m.type === "gauge") m.samples = [];
+  }
+
+  incCounter(name: string, by = 1) {
+    const m = this.ensure(name, "counter", COUNTER_HELP[name] ?? name);
+    if (m.samples.length === 0) m.samples.push({ labels: {}, value: 0 });
+    m.samples[0].value += by;
+  }
+
+  render(): string {
+    const lines: string[] = [];
+    for (const [name, m] of this.metrics) {
+      const full = PREFIX + name;
+      lines.push(`# HELP ${full} ${m.help}`);
+      lines.push(`# TYPE ${full} ${m.type}`);
+      for (const s of m.samples) {
+        const labels = Object.entries(s.labels)
+          .map(([k, v]) => `${k}="${escapeLabel(v)}"`)
+          .join(",");
+        lines.push(`${full}${labels ? `{${labels}}` : ""} ${s.value}`);
+      }
+    }
+    return lines.join("\n") + "\n";
+  }
+}
+
+function escapeLabel(v: string): string {
+  return v.replace(/\\/g, "\\\\").replace(/\n/g, "\\n").replace(/"/g, '\\"');
+}
+
+const GAUGE_HELP: Record<string, string> = {
+  finalized_block: "Latest finalized block number scraped",
+  providers_total: "Registered storage providers",
+  buckets_total: "Layer-0 buckets",
+  agreements_total: "Storage agreements (all)",
+  agreements_active: "Storage agreements not past expires_at",
+  agreements_expired: "Storage agreements past expires_at, not yet swept",
+  challenges_pending_total: "Unresolved challenges across all deadlines",
+  checkpoint_rewards_pending_total: "Sum of unclaimed checkpoint rewards (planck)",
+  checkpoint_pool_total: "Sum of checkpoint pool balances (planck)",
+  block_weight_ref_time: "Latest finalized block ref_time by dispatch class (picoseconds)",
+  block_weight_proof_size: "Latest finalized block proof_size (PoV) by dispatch class (bytes)",
+  provider_stake: "Provider bonded stake (planck)",
+  provider_committed_bytes: "Provider committed bytes",
+  provider_free_balance: "Provider free balance (planck)",
+  provider_reserved_balance: "Provider reserved balance (planck)",
+  provider_pending_challenges: "Unresolved challenges against a provider",
+  provider_challenges_received: "Lifetime challenges received (provider stats)",
+  provider_challenges_failed: "Lifetime challenges failed (provider stats)",
+  provider_deregistering: "1 if the provider has announced deregistration",
+  exporter_last_scrape_block: "Block number of the last successful scrape",
+};
+
+const COUNTER_HELP: Record<string, string> = {
+  challenge_created_total: "ChallengeCreated events observed",
+  challenge_defended_total: "ChallengeDefended events observed",
+  challenge_slashed_total: "ChallengeSlashed events observed",
+  provider_checkpoint_submitted_total: "ProviderCheckpointSubmitted events observed",
+  checkpoint_miss_penalized_total: "CheckpointMissPenalized events observed",
+  provider_registered_total: "ProviderRegistered events observed",
+  exporter_scrape_errors_total: "Per-block scrape failures",
+};
+
+/** StorageProvider event type -> counter name. */
+const EVENT_COUNTERS: Record<string, string> = {
+  ChallengeCreated: "challenge_created_total",
+  ChallengeDefended: "challenge_defended_total",
+  ChallengeSlashed: "challenge_slashed_total",
+  ProviderCheckpointSubmitted: "provider_checkpoint_submitted_total",
+  CheckpointMissPenalized: "checkpoint_miss_penalized_total",
+  ProviderRegistered: "provider_registered_total",
+};
+
+// ── Scraping ─────────────────────────────────────────────────────────────────
+
+const num = (b: bigint | number): number => (typeof b === "bigint" ? Number(b) : b);
+
+/** Snapshot the domain-state gauges at a finalized block hash. */
+async function scrapeGauges(
+  api: ParachainApi,
+  reg: Registry,
+  at: string,
+  blockNumber: number,
+): Promise<void> {
+  const [providers, agreements, challenges, buckets, rewards, pools, blockWeight] =
+    await Promise.all([
+      api.query.StorageProvider.Providers.getEntries({ at }),
+      api.query.StorageProvider.StorageAgreements.getEntries({ at }),
+      api.query.StorageProvider.Challenges.getEntries({ at }),
+      api.query.StorageProvider.Buckets.getEntries({ at }),
+      api.query.StorageProvider.CheckpointRewards.getEntries({ at }),
+      api.query.StorageProvider.CheckpointPool.getEntries({ at }),
+      api.query.System.BlockWeight.getValue({ at }),
+    ]);
+
+  for (const name of PER_PROVIDER_GAUGES) reg.clearGauge(name);
+  for (const { keyArgs, value } of providers) {
+    const provider = keyArgs[0];
+    const [account, pending] = await Promise.all([
+      api.query.System.Account.getValue(provider, { at }),
+      api.query.StorageProvider.PendingChallenges.getValue(provider, { at }),
+    ]);
+    const labels = { provider };
+    reg.setGauge("provider_stake", num(value.stake), labels);
+    reg.setGauge("provider_committed_bytes", num(value.committed_bytes), labels);
+    reg.setGauge("provider_free_balance", num(account.data.free), labels);
+    reg.setGauge("provider_reserved_balance", num(account.data.reserved), labels);
+    reg.setGauge("provider_pending_challenges", num(pending), labels);
+    reg.setGauge("provider_challenges_received", value.stats.challenges_received, labels);
+    reg.setGauge("provider_challenges_failed", value.stats.challenges_failed, labels);
+    reg.setGauge("provider_deregistering", value.deregister_at != null ? 1 : 0, labels);
+  }
+
+  let active = 0;
+  for (const { value } of agreements) {
+    if (value.expires_at > blockNumber) active++;
+  }
+  const rewardsTotal = rewards.reduce((sum, e) => sum + e.value, 0n);
+  const poolTotal = pools.reduce((sum, e) => sum + e.value, 0n);
+
+  reg.clearGauge("finalized_block");
+  reg.setGauge("finalized_block", blockNumber);
+  reg.clearGauge("providers_total");
+  reg.setGauge("providers_total", providers.length);
+  reg.clearGauge("buckets_total");
+  reg.setGauge("buckets_total", buckets.length);
+  reg.clearGauge("agreements_total");
+  reg.setGauge("agreements_total", agreements.length);
+  reg.clearGauge("agreements_active");
+  reg.setGauge("agreements_active", active);
+  reg.clearGauge("agreements_expired");
+  reg.setGauge("agreements_expired", agreements.length - active);
+  reg.clearGauge("challenges_pending_total");
+  reg.setGauge("challenges_pending_total", challenges.length);
+  reg.clearGauge("checkpoint_rewards_pending_total");
+  reg.setGauge("checkpoint_rewards_pending_total", num(rewardsTotal));
+  reg.clearGauge("checkpoint_pool_total");
+  reg.setGauge("checkpoint_pool_total", num(poolTotal));
+
+  // Per-class weight of the latest finalized block. Substrate's own Prometheus
+  // does not expose this; it is the signal that spikes at a challenge-deadline
+  // block (the on_finalize slash sweep is charged to the mandatory class). See
+  // challenge-saturation.ts.
+  reg.clearGauge("block_weight_ref_time");
+  reg.clearGauge("block_weight_proof_size");
+  for (const cls of ["normal", "operational", "mandatory"] as const) {
+    reg.setGauge("block_weight_ref_time", num(blockWeight[cls].ref_time), { class: cls });
+    reg.setGauge("block_weight_proof_size", num(blockWeight[cls].proof_size), { class: cls });
+  }
+}
+
+const PER_PROVIDER_GAUGES = [
+  "provider_stake",
+  "provider_committed_bytes",
+  "provider_free_balance",
+  "provider_reserved_balance",
+  "provider_pending_challenges",
+  "provider_challenges_received",
+  "provider_challenges_failed",
+  "provider_deregistering",
+];
+
+/** Count lifecycle events in one block into the persistent counters. */
+async function scrapeEvents(api: ParachainApi, reg: Registry, at: string): Promise<void> {
+  const records = (await api.query.System.Events.getValue({ at })) as unknown as Array<{
+    event: { type: string; value: { type: string } };
+  }>;
+  for (const r of records) {
+    if (r.event?.type !== "StorageProvider") continue;
+    const counter = EVENT_COUNTERS[r.event.value?.type];
+    if (counter) reg.incCounter(counter);
+  }
+}
+
+// ── Main ─────────────────────────────────────────────────────────────────────
+
+async function main() {
+  const opts = parseCli();
+  const reg = new Registry();
+  // Register counters at 0 up front so they exist before their first event;
+  // `rate()` over a counter that only appears mid-run reads as a gap.
+  for (const name of Object.values(EVENT_COUNTERS)) reg.incCounter(name, 0);
+  reg.incCounter("exporter_scrape_errors_total", 0);
+
+  const conn = connect(opts.chainRpc);
+  const { papi, api } = conn;
+  await waitForChainReady(api);
+  await syncSs58Prefix(api);
+
+  const server = createServer((req, res) => {
+    if (req.url === "/metrics") {
+      res.writeHead(200, { "content-type": "text/plain; version=0.0.4" });
+      res.end(reg.render());
+    } else if (req.url === "/health") {
+      res.writeHead(200, { "content-type": "application/json" });
+      res.end(JSON.stringify({ status: "ok" }));
+    } else {
+      res.writeHead(404).end("not found\n");
+    }
+  });
+  server.listen(opts.port, () => {
+    console.log(`chain-exporter on :${opts.port}/metrics, chain ${opts.chainRpc}`);
+  });
+
+  // Gauges track the latest finalized block; counters catch up over every block
+  // since the last one so a finalization jump does not drop events.
+  let lastEventBlock = -1;
+  // Skip a block if the previous scrape is still running: overlapping runs would
+  // corrupt the cleared-then-set gauge samples. The event catch-up loop reads
+  // from lastEventBlock+1, so a skipped block's events are counted next time.
+  let scraping = false;
+  const sub = papi.finalizedBlock$.subscribe({
+    next: async (block) => {
+      if (scraping) return;
+      scraping = true;
+      try {
+        await scrapeGauges(api, reg, block.hash, block.number);
+        if (lastEventBlock < 0) lastEventBlock = block.number - 1;
+        for (let n = lastEventBlock + 1; n <= block.number; n++) {
+          const hash =
+            n === block.number
+              ? block.hash
+              : await papi._request<string>("chain_getBlockHash", [n]);
+          if (hash) await scrapeEvents(api, reg, hash);
+        }
+        lastEventBlock = block.number;
+        reg.clearGauge("exporter_last_scrape_block");
+        reg.setGauge("exporter_last_scrape_block", block.number);
+      } catch (err) {
+        reg.incCounter("exporter_scrape_errors_total");
+        console.error(`scrape failed at #${block.number}: ${(err as Error)?.message ?? err}`);
+      } finally {
+        scraping = false;
+      }
+    },
+    error: (err) => console.error(`finalizedBlock$ error: ${err}`),
+  });
+
+  const shutdown = () => {
+    sub.unsubscribe();
+    server.close();
+    (conn as ChainConnection).papi.destroy();
+    process.exit(0);
+  };
+  process.on("SIGINT", shutdown);
+  process.on("SIGTERM", shutdown);
+}
+
+main().catch((err) => {
+  console.error(`❌ ${err?.message ?? err}`);
+  process.exit(1);
+});
diff --git a/examples/papi/package.json b/examples/papi/package.json
index 3b816761..d311a7a6 100644
--- a/examples/papi/package.json
+++ b/examples/papi/package.json
@@ -10,6 +10,7 @@
     "demo:checkpoint-missed": "node --import tsx checkpoint-missed.ts",
     "demo:sc-flow": "node --import tsx sc-flow.ts",
     "e2e": "node --import tsx e2e/runner.bin.ts",
+    "chain-exporter": "node --import tsx chain-exporter.ts",
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {