diff --git a/packages/cosmic-swingset/test/prometheus.test.js b/packages/cosmic-swingset/test/prometheus.test.js
new file mode 100644
index 00000000000..63c052b1a69
--- /dev/null
+++ b/packages/cosmic-swingset/test/prometheus.test.js
@@ -0,0 +1,71 @@
+import test from 'ava';
+
+import fs from 'node:fs';
+import path from 'node:path';
+
+import { q, Fail } from '@endo/errors';
+import tmp from 'tmp';
+
+import { promisify } from '@agoric/internal/src/js-utils.js';
+import { makeFakeStorageKit } from '@agoric/internal/src/storage-test-utils.js';
+
+import { makeLaunchChain } from '../src/chain-main.js';
+import { defaultBootstrapMessage } from '../tools/test-kit.js';
+
+const tmpDir = promisify(tmp.dir);
+
+test('Prometheus metric definitions', async t => {
+  const OTEL_EXPORTER_PROMETHEUS_PORT = '12345';
+  // @ts-expect-error
+  const { storagePort } = defaultBootstrapMessage;
+  const [dbDir, cleanupDB] = await tmpDir({
+    prefix: 'testdb',
+    unsafeCleanup: true,
+  });
+  t.teardown(cleanupDB);
+
+  const fakeStorageKit = makeFakeStorageKit('');
+  const { toStorage: handleVstorage } = fakeStorageKit;
+  const fakeAgcc = {
+    send: (destPort, msgJson) => {
+      const msg = JSON.parse(msgJson);
+      if (destPort === storagePort) return JSON.stringify(handleVstorage(msg));
+      throw Fail`port ${q(destPort)} not implemented for message ${msg}`;
+    },
+  };
+  const launchChain = makeLaunchChain(fakeAgcc, dbDir, {
+    env: {
+      OTEL_EXPORTER_PROMETHEUS_PORT,
+      CHAIN_BOOTSTRAP_VAT_CONFIG:
+        '@agoric/vm-config/decentral-core-config.json',
+    },
+    fs,
+    path,
+  });
+
+  const { shutdown } = await launchChain(defaultBootstrapMessage);
+  t.teardown(shutdown);
+
+  const response = await fetch(
+    `http://localhost:${OTEL_EXPORTER_PROMETHEUS_PORT}/metrics`,
+  );
+  const text = await response.text();
+  // Normalize text:
+  // https://prometheus.io/docs/instrumenting/exposition_formats/#text-format-details
+  // * Set telemetry_sdk_version and service_instance_id to "%s".
+  // * Replace integer values with "%d" and floating-point values with "%f".
+  // * Replace trailing milliseconds-since-epoch timestamps with "%@".
+  const normalizedText = text
+    .replace(/^.*(telemetry_sdk_version|service_instance_id).*$/m, line =>
+      line.replaceAll(
+        /(telemetry_sdk_version|service_instance_id)="([^""\\]|\\.)*"/g,
+        '$1="%s"',
+      ),
+    )
+    .replaceAll(
+      /^([^#].*?) (?:([0-9]+)|([0-9]*[.][0-9]+))( [0-9]{13,})?$/gm,
+      (_substring, prefix, intValue, floatValue, timestamp) =>
+        `${prefix} ${intValue ? '%d' : '%f'}${timestamp ? ' %@' : ''}`,
+    );
+  t.snapshot(normalizedText);
+});
diff --git a/packages/internal/src/js-utils.js b/packages/internal/src/js-utils.js
index 70cd6d19c4b..9c906d99a7b 100644
--- a/packages/internal/src/js-utils.js
+++ b/packages/internal/src/js-utils.js
@@ -5,6 +5,48 @@
  *   dependent upon a hardened environment.
  */
 
+/**
+ * Pick the last type from an array.
+ *
+ * @template {unknown[]} A
+ * @typedef {A extends [...infer P, infer X] ? X : never} Last
+ */
+/**
+ * Collect up to 8 function overloads into a union.
+ *
+ * @template {(...args: any[]) => unknown} F
+ * @typedef {F extends {
+ *   (...args: infer A1): infer R1;
+ *   (...args: infer A2): infer R2;
+ *   (...args: infer A3): infer R3;
+ *   (...args: infer A4): infer R4;
+ *   (...args: infer A5): infer R5;
+ *   (...args: infer A6): infer R6;
+ *   (...args: infer A7): infer R7;
+ * }
+ *   ?
+ *       | ((...args: A1) => R1)
+ *       | ((...args: A2) => R2)
+ *       | ((...args: A3) => R3)
+ *       | ((...args: A4) => R4)
+ *       | ((...args: A5) => R5)
+ *       | ((...args: A6) => R6)
+ *       | ((...args: A7) => R7)
+ *   : never} Overloads
+ */
+/**
+ * Pick the type of a function's last parameter.
+ *
+ * @template {(...args: any[]) => unknown} F
+ * @typedef {Last<Parameters<Overloads<F>>>} LastParameter
+ */
+
+const { defineProperties } = Object;
+
+/** @type {<F>(name: string, fn: F) => F} */
+export const defineName = (name, fn) =>
+  defineProperties(fn, { name: { value: name } });
+
 /**
  * Deep-copy a value by round-tripping it through JSON (which drops
  * function/symbol/undefined values and properties that are non-enumerable
@@ -87,3 +129,45 @@ export const makeMeasureSeconds = currentTimeMillisec => {
   };
   return measureSeconds;
 };
+
+/**
+ * Generalize Node.js util.promisify to support callbacks with multiple
+ * post-error parameters, which fulfill the returned promise as an array rather
+ * than as a single value.
+ *
+ * @template {(...args: any[]) => unknown} F function whose last parameter is an
+ *   error-first callback
+ * @template {Parameters<LastParameter<F>> extends [Error | null, ...infer R]
+ *     ? R
+ *     : never} R
+ * @param {F} fn
+ */
+export const promisify = fn => {
+  /**
+   * @typedef {Parameters<Overloads<F>> extends [...infer P, infer CB]
+   *     ? (
+   *         ...args: P
+   *       ) => Promise<
+   *         Parameters<LastParameter<F>> extends [unknown, unknown] ? R[0] : R
+   *       >
+   *     : never} Promisified
+   */
+  const promisified = /** @type {Promisified} */ (
+    (...args) =>
+      // eslint-disable-next-line no-restricted-syntax
+      new Promise((resolve, reject) => {
+        /** @type {(err: Error, ...result: R) => void} */
+        const callback = (err, ...result) => {
+          if (err) {
+            reject(err);
+          } else if (result.length === 1) {
+            resolve(/** @type {any} */ (result[0]));
+          } else {
+            resolve(result);
+          }
+        };
+        fn(...args, callback);
+      })
+  );
+  return defineName(fn.name && `promisified ${fn.name}`, promisified);
+};
diff --git a/packages/internal/test/snapshots/exports.test.js.md b/packages/internal/test/snapshots/exports.test.js.md
index 06f69a7e5d7..8dda4e41e1d 100644
--- a/packages/internal/test/snapshots/exports.test.js.md
+++ b/packages/internal/test/snapshots/exports.test.js.md
@@ -26,6 +26,7 @@ Generated by [AVA](https://avajs.dev).
       'deepCopyJsonable',
       'deepMapObject',
       'deeplyFulfilledObject',
+      'defineName',
       'forever',
       'fromUniqueEntries',
       'getMethodNames',
@@ -35,6 +36,7 @@ Generated by [AVA](https://avajs.dev).
       'mustMatch',
       'objectMap',
       'objectMetaMap',
+      'promisify',
       'pureDataMarshaller',
       'synchronizedTee',
       'untilTrue',
diff --git a/packages/internal/test/snapshots/exports.test.js.snap b/packages/internal/test/snapshots/exports.test.js.snap
index a952ead7268..2dd2c7b078e 100644
Binary files a/packages/internal/test/snapshots/exports.test.js.snap and b/packages/internal/test/snapshots/exports.test.js.snap differ