diff --git a/.github/workflows/test-edot.yml b/.github/workflows/test-edot.yml
index bf763f10..b17376da 100644
--- a/.github/workflows/test-edot.yml
+++ b/.github/workflows/test-edot.yml
@@ -33,13 +33,9 @@ jobs:
           - '22'
           - '22.0'
           - '20'
-          - '20.0'
+          - '20.6.0'
           - '18'
-          - '18.0'
-          - '16'
-          - '16.0'
-          - '14'
-          - '14.18.0'
+          - '18.19.0'
 
     runs-on: ubuntu-24.04
 
diff --git a/packages/opentelemetry-node/hook.mjs b/examples/openai/chat.mjs
similarity index 68%
rename from packages/opentelemetry-node/hook.mjs
rename to examples/openai/chat.mjs
index d16b2de8..f2bf6ac6 100644
--- a/packages/opentelemetry-node/hook.mjs
+++ b/examples/openai/chat.mjs
@@ -17,9 +17,18 @@
  * under the License.
  */
 
-export {
-    load,
-    resolve,
-    getFormat,
-    getSource,
-} from '@opentelemetry/instrumentation/hook.mjs';
+import {OpenAI} from 'openai';
+
+let chatModel = process.env.CHAT_MODEL ?? 'gpt-4o-mini';
+
+const client = new OpenAI();
+const completion = await client.chat.completions.create({
+  model: chatModel,
+  messages: [
+    {
+      role: 'user',
+      content: 'Answer in up to 3 words: Which ocean contains Bouvet Island?',
+    },
+  ],
+});
+console.log(completion.choices[0].message.content);
diff --git a/examples/openai/package.json b/examples/openai/package.json
index 6b438820..cfdc09d0 100644
--- a/examples/openai/package.json
+++ b/examples/openai/package.json
@@ -8,7 +8,8 @@
   },
   "scripts": {
     "chat": "node --env-file .env --require @elastic/opentelemetry-node chat.js",
-    "embeddings": "node --env-file .env --require @elastic/opentelemetry-node embeddings.js"
+    "embeddings": "node --env-file .env --require @elastic/opentelemetry-node embeddings.js",
+    "chat:esm": "node --env-file .env --import @elastic/opentelemetry-node chat.mjs"
   },
   "dependencies": {
     "@elastic/opentelemetry-node": "*",
diff --git a/packages/opentelemetry-node/CHANGELOG.md b/packages/opentelemetry-node/CHANGELOG.md
index 6f704595..4a07ba47 100644
--- a/packages/opentelemetry-node/CHANGELOG.md
+++ b/packages/opentelemetry-node/CHANGELOG.md
@@ -2,12 +2,39 @@
 
 ## Unreleased
 
+- BREAKING CHANGE: Bump min-supported node to `^18.19.0 || >=20.6.0`.
+  This raises the minimum-supported Node.js to the same as coming releases of OpenTelemetry JS.
+  This base version range ensures that `module.register()` is available for improved ES module
+  (ESM) auto-instrumentation.
+  This drops support for Node.js 14 and 16.
+
+- feat: Improve ES module (ESM) instrumentation.
+
+  As part of this change, using `--require @elastic/opentelemetry-node` will
+  *no longer* setup a module hook for instrumenting ES modules; only using
+  `--import @elastic/opentelemetry-node` will do so. **The recommendation now
+  is to use `--import @elastic/opentelemetry-node` to start EDOT Node.js.**
+  Using `--require ...` is still fine when you know your application is only
+  using CommonJS modules.
+
+  Implementation details: The underlying module hook mechanism for ESM has been
+  changed to only hook modules that will potentially be patched by configured
+  instrumentations.  This allows some instrumentations to work that could not
+  before due to some ESM files not being hookable (at least via the imperfect
+  mechanism for hooking ES modules). One such example is
+  `@elastic/instrumentation-openai`.  See
+  <https://github.com/nodejs/import-in-the-middle/pull/146> for internal
+  details.
+
 - feat: Add `@opentelemetry/instrumentation-mysql` to the default set
   of instrumentations. See <https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/plugins/node/opentelemetry-instrumentation-mysql#readme>
+
 - feat: Add `@opentelemetry/instrumentation-mysql2` to the default set
   of instrumentations. See <https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/plugins/node/opentelemetry-instrumentation-mysql2#readme>
+
 - feat: Add `@opentelemetry/instrumentation-cassandra-driver` to the default set
   of instrumentations. See <https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/plugins/node/opentelemetry-instrumentation-cassandra#readme>
+
 - test: Test that the native instrumentation in `@elastic/elasticsearch@8.15.0` and later works.
 
 
diff --git a/packages/opentelemetry-node/README.md b/packages/opentelemetry-node/README.md
index fb49e710..8120a85c 100644
--- a/packages/opentelemetry-node/README.md
+++ b/packages/opentelemetry-node/README.md
@@ -31,7 +31,7 @@ npm install --save @elastic/opentelemetry-node
 ## Run
 
 ```sh
-node -r @elastic/opentelemetry-node my-service.js
+node --import @elastic/opentelemetry-node my-service.js
 ```
 
 ## Read the docs
diff --git a/packages/opentelemetry-node/docs/get-started.md b/packages/opentelemetry-node/docs/get-started.md
index 99450dc3..9deba7f0 100644
--- a/packages/opentelemetry-node/docs/get-started.md
+++ b/packages/opentelemetry-node/docs/get-started.md
@@ -92,11 +92,11 @@ for example, before `express` or `http` are loaded.
 
 <!-- ✅ Step-by-step instructions -->
 The recommended way to get the
-distro started is by using the `-r, --require` Node.js
-[CLI option](https://nodejs.org/api/cli.html#-r---require-module):
+distro started is by using the `--import` Node.js
+[CLI option](https://nodejs.org/api/cli.html#--importmodule):
 
 ```sh
-node --require @elastic/opentelemetry-node my-service.js
+node --import @elastic/opentelemetry-node my-service.js
 ```
 
 EDOT Node.js will automatically instrument popular modules (listed in [Supported technologies](./supported-technologies.md))
diff --git a/packages/opentelemetry-node/docs/metrics.md b/packages/opentelemetry-node/docs/metrics.md
index 245f71a7..09cc8bfa 100644
--- a/packages/opentelemetry-node/docs/metrics.md
+++ b/packages/opentelemetry-node/docs/metrics.md
@@ -21,7 +21,7 @@ variable `ELASTIC_OTEL_METRICS_DISABLED` to the string `true`.
 export OTEL_EXPORTER_OTLP_ENDPOINT="${ELASTIC_APM_SERVER_URL}"
 export OTEL_EXPORTER_OTLP_HEADERS="Authorization=Bearer ${ELASTIC_APM_SECRET_TOKEN}"
 export ELASTIC_OTEL_METRICS_DISABLED=true
-node -r @elastic/opentelemetry-node/start.js my-app.js
+node --import @elastic/opentelemetry-node/start.js my-app.js
 ```
 
 ## Advanced configuration
@@ -57,4 +57,4 @@ issues when doing an overview of the instrumented service. These are:
 
 
 If your service is instrumented by EDOT Node.js, or by custom instrumentation that includes the packages mentioned above, Kibana will
-display them as part of the [service metrics](https://www.elastic.co/guide/en/observability/current/apm-metrics.html) in its UI.
\ No newline at end of file
+display them as part of the [service metrics](https://www.elastic.co/guide/en/observability/current/apm-metrics.html) in its UI.
diff --git a/packages/opentelemetry-node/docs/supported-technologies.md b/packages/opentelemetry-node/docs/supported-technologies.md
index 129b6403..d3984f5e 100644
--- a/packages/opentelemetry-node/docs/supported-technologies.md
+++ b/packages/opentelemetry-node/docs/supported-technologies.md
@@ -13,13 +13,13 @@ Elastic Stack, so it is strongly recommended to be using a recent 8.x version.
 
 ## Node.js versions
 
-EDOT Node.js supports Node.js v14.18.0 and later.
+EDOT Node.js supports Node.js 18.19.0, 20.6.0, or later.
 This follows from the [OpenTelemetry JS supported runtimes](https://github.com/open-telemetry/opentelemetry-js#supported-runtimes).
 
 <!--
 Dev Notes on supported Node.js versions:
-- v14.18.0 or later is required for `node:`-prefixed core module loading, as
-  used by gaxios@6.7.0, a transitive dep of `@opentelemetry/resource-detector-gcp`.
+- `^18.19.0 || >=20.6.0` is required for `module.register()` support for ESM
+  instrumentation.
 -->
 
 ## TypeScript versions
@@ -83,7 +83,7 @@ node --import @elastic/opentelemetry-node my-app.js
 
 ## ECMAScript Modules (ESM)
 
-This Distro includes **limited and experimental** support for instrumenting [ECMAScript module imports](https://nodejs.org/api/esm.html#modules-ecmascript-modules), i.e. modules that are loaded via `import ...` statements and `import('...')` (dynamic import).
+This Distro includes **limited and experimental** support for instrumenting [ECMAScript module (ESM) imports](https://nodejs.org/api/esm.html#modules-ecmascript-modules), i.e. modules that are loaded via `import ...` statements and `import('...')` (dynamic import). To enable ESM instrumentation, use `node --import @elastic/opentelemetry-node ...` to start the SDK. (Using `node --require @elastic/opentelemetry-node ...` will not enable ESM instrumentation. It is intended to signal that only CommonJS module usage should be instrumented.)
 
 <!--
 TODO: add this to the above paragraph once we have an esm.md doc:
@@ -92,5 +92,5 @@ See the [ECMAScript module support](./esm.md) document for details.
 
 Limitations:
 
-* For Node.js `>=20.6.0 || >=18.19.0`, support for hooking `import`s is automatically enabled. For earlier versions of Node.js, you must manually enable the `import`-hook via the `--experimental-loader=@elastic/opentelemetry-node/hook.mjs` option, e.g.: `node --experimental-loader=@elastic/opentelemetry-node/hook.mjs --require=@elastic/opentelemetry-node app.js`.
+* ESM instrumentation is only support for Node.js versions `^18.19.0 || >=20.6.0`. These are the versions that include `module.register()` support. Using the older `node --experimental-loader=...` option is not supported.
 * Currently only a subset of instrumentations support ESM: `express`, `ioredis`, `koa`, `pg`, `pino`. See [this OpenTelemetry JS tracking issue](https://github.com/open-telemetry/opentelemetry-js-contrib/issues/1942) for progress.
diff --git a/packages/opentelemetry-node/import.mjs b/packages/opentelemetry-node/import.mjs
index f3d014b2..5502bc16 100644
--- a/packages/opentelemetry-node/import.mjs
+++ b/packages/opentelemetry-node/import.mjs
@@ -20,52 +20,28 @@
 // Register ESM hook and start the SDK.
 // This is called for `--import @elastic/opentelemetry-node`.
 
-import * as module from 'node:module';
+import {register} from 'node:module';
 import {isMainThread} from 'node:worker_threads';
 
-import {log} from './lib/logging.js';
+// TODO: Update @opentelemetry/instrumentation exports to use it rather than IITM directly, if can.
+import {createAddHookMessageChannel} from 'import-in-the-middle';
 
-/**
- * Return true iff it looks like the `@elastic/opentelemetry-node/hook.mjs`
- * was loaded via node's `--experimental-loader` option.
- *
- * Dev Note: keep this in sync with "require.js".
- */
-function haveHookFromExperimentalLoader() {
-    const USED_LOADER_OPT =
-        /--(experimental-)?loader(\s+|=)@elastic\/opentelemetry-node\/hook.mjs/;
-    for (let i = 0; i < process.execArgv.length; i++) {
-        const arg = process.execArgv[i];
-        const nextArg = process.execArgv[i + 1];
-        if (
-            (arg === '--loader' || arg === '--experimental-loader') &&
-            nextArg === '@elastic/opentelemetry-node/hook.mjs'
-        ) {
-            log.trace('bootstrap-import: --loader hook args used');
-            return true;
-        } else if (USED_LOADER_OPT.test(arg)) {
-            log.trace('bootstrap-import: --loader hook arg used');
-            return true;
-        }
-    }
-    if (
-        process.env.NODE_OPTIONS &&
-        USED_LOADER_OPT.test(process.env.NODE_OPTIONS)
-    ) {
-        log.trace('bootstrap-import: --loader arg used in NODE_OPTIONS');
-        return true;
-    }
-    return false;
-}
+import {log} from './lib/logging.js';
 
 if (isMainThread) {
-    if (
-        typeof module.register === 'function' &&
-        !haveHookFromExperimentalLoader()
-    ) {
-        log.trace('bootstrap-import: registering module hook');
-        module.register('./hook.mjs', import.meta.url);
-    }
+    // Note: If there are *multiple* installations of import-in-the-middle, then
+    // only those instrumentations using this same one will be hooked.
+    const {registerOptions, waitForAllMessagesAcknowledged} =
+        createAddHookMessageChannel();
+
+    log.trace('import.mjs: registering module hook');
+    register('import-in-the-middle/hook.mjs', import.meta.url, registerOptions);
 
     await import('./lib/start.js');
+
+    // Ensure that the loader has acknowledged all the modules before we allow
+    // execution to continue.
+    await waitForAllMessagesAcknowledged();
+} else {
+    log.trace('import.mjs: skipping EDOT Node.js bootstrap on non-main thread');
 }
diff --git a/packages/opentelemetry-node/package-lock.json b/packages/opentelemetry-node/package-lock.json
index 645a1cd8..3e510eb7 100644
--- a/packages/opentelemetry-node/package-lock.json
+++ b/packages/opentelemetry-node/package-lock.json
@@ -19,7 +19,6 @@
         "@opentelemetry/exporter-metrics-otlp-http": "^0.57.1",
         "@opentelemetry/exporter-metrics-otlp-proto": "^0.57.1",
         "@opentelemetry/host-metrics": "^0.35.0",
-        "@opentelemetry/instrumentation": "^0.57.1",
         "@opentelemetry/instrumentation-aws-sdk": "^0.49.0",
         "@opentelemetry/instrumentation-bunyan": "^0.45.0",
         "@opentelemetry/instrumentation-cassandra-driver": "^0.45.0",
@@ -66,6 +65,7 @@
         "@opentelemetry/sdk-logs": "^0.57.1",
         "@opentelemetry/sdk-node": "^0.57.1",
         "@opentelemetry/winston-transport": "^0.10.0",
+        "import-in-the-middle": "^1.12.0",
         "safe-stable-stringify": "^2.4.3"
       },
       "devDependencies": {
@@ -103,7 +103,7 @@
         "winston": "^3.13.1"
       },
       "engines": {
-        "node": ">=14.18.0"
+        "node": "^18.19.0 || >=20.6.0"
       }
     },
     "../mockotlpserver": {
@@ -6570,9 +6570,10 @@
       ]
     },
     "node_modules/import-in-the-middle": {
-      "version": "1.9.0",
-      "resolved": "https://registry.npmjs.org/import-in-the-middle/-/import-in-the-middle-1.9.0.tgz",
-      "integrity": "sha512-Ng1SJINJDBzyUEkx9Mj32XD8G0TQCUb5TMoL9V91CTn6F3wYZLygLuhNFrv0cNMBZaeptnL1zecV6XrIdHJ+xQ==",
+      "version": "1.12.0",
+      "resolved": "https://registry.npmjs.org/import-in-the-middle/-/import-in-the-middle-1.12.0.tgz",
+      "integrity": "sha512-yAgSE7GmtRcu4ZUSFX/4v69UGXwugFFSdIQJ14LHPOPPQrWv8Y7O9PHsw8Ovk7bKCLe4sjXMbZFqGFcLHpZ89w==",
+      "license": "Apache-2.0",
       "dependencies": {
         "acorn": "^8.8.2",
         "acorn-import-attributes": "^1.9.5",
@@ -14492,9 +14493,9 @@
       "dev": true
     },
     "import-in-the-middle": {
-      "version": "1.9.0",
-      "resolved": "https://registry.npmjs.org/import-in-the-middle/-/import-in-the-middle-1.9.0.tgz",
-      "integrity": "sha512-Ng1SJINJDBzyUEkx9Mj32XD8G0TQCUb5TMoL9V91CTn6F3wYZLygLuhNFrv0cNMBZaeptnL1zecV6XrIdHJ+xQ==",
+      "version": "1.12.0",
+      "resolved": "https://registry.npmjs.org/import-in-the-middle/-/import-in-the-middle-1.12.0.tgz",
+      "integrity": "sha512-yAgSE7GmtRcu4ZUSFX/4v69UGXwugFFSdIQJ14LHPOPPQrWv8Y7O9PHsw8Ovk7bKCLe4sjXMbZFqGFcLHpZ89w==",
       "requires": {
         "acorn": "^8.8.2",
         "acorn-import-attributes": "^1.9.5",
diff --git a/packages/opentelemetry-node/package.json b/packages/opentelemetry-node/package.json
index 19a09b93..f80b2bd5 100644
--- a/packages/opentelemetry-node/package.json
+++ b/packages/opentelemetry-node/package.json
@@ -24,7 +24,7 @@
   ],
   "author": "Elastic Observability <https://www.elastic.co/observability>",
   "engines": {
-    "node": ">=14.18.0"
+    "node": "^18.19.0 || >=20.6.0"
   },
   "files": [
     "lib",
@@ -33,7 +33,6 @@
     "LICENSE",
     "NOTICE.md",
     "README.md",
-    "hook.mjs",
     "import.mjs",
     "package.json",
     "require.js"
@@ -45,7 +44,7 @@
     "lint:eslint": "eslint --ext=js,mjs,cjs . # requires node >=16.0.0",
     "lint:types": "rm -rf build/lint-types && tsc --outDir build/lint-types && diff -ur types build/lint-types",
     "lint:fix": "eslint --ext=js,mjs,cjs --fix . # requires node >=16.0.0",
-    "lint:deps": "dependency-check require.js import.mjs hook.mjs 'lib/**/*.js' 'test/**/*.js' '!test/fixtures/a-ts-proj' -e mjs:../../scripts/parse-mjs-source -i @types/tape -i dotenv -i @opentelemetry/winston-transport -i @opentelemetry/exporter-logs-* -i @opentelemetry/exporter-metrics-*",
+    "lint:deps": "dependency-check require.js import.mjs 'lib/**/*.js' 'test/**/*.js' '!test/fixtures/a-ts-proj' -e mjs:../../scripts/parse-mjs-source -i @types/tape -i dotenv -i @opentelemetry/winston-transport -i @opentelemetry/exporter-logs-* -i @opentelemetry/exporter-metrics-*",
     "lint:license-files": "../../scripts/gen-notice.sh --lint .  # requires node >=16",
     "lint:changelog": "../../scripts/extract-release-notes.sh .",
     "test": "NODE_OPTIONS='-r dotenv/config' DOTENV_CONFIG_PATH=./test/test-services.env tape test/**/*.test.js",
@@ -63,7 +62,6 @@
       "types": "./types/sdk.d.ts",
       "default": "./lib/sdk.js"
     },
-    "./hook.mjs": "./hook.mjs",
     "./package.json": "./package.json"
   },
   "dependencies": {
@@ -77,7 +75,6 @@
     "@opentelemetry/exporter-metrics-otlp-http": "^0.57.1",
     "@opentelemetry/exporter-metrics-otlp-proto": "^0.57.1",
     "@opentelemetry/host-metrics": "^0.35.0",
-    "@opentelemetry/instrumentation": "^0.57.1",
     "@opentelemetry/instrumentation-aws-sdk": "^0.49.0",
     "@opentelemetry/instrumentation-bunyan": "^0.45.0",
     "@opentelemetry/instrumentation-cassandra-driver": "^0.45.0",
@@ -124,6 +121,7 @@
     "@opentelemetry/sdk-logs": "^0.57.1",
     "@opentelemetry/sdk-node": "^0.57.1",
     "@opentelemetry/winston-transport": "^0.10.0",
+    "import-in-the-middle": "^1.12.0",
     "safe-stable-stringify": "^2.4.3"
   },
   "devDependencies": {
diff --git a/packages/opentelemetry-node/require.js b/packages/opentelemetry-node/require.js
index 1831fbc6..98b7170e 100644
--- a/packages/opentelemetry-node/require.js
+++ b/packages/opentelemetry-node/require.js
@@ -17,53 +17,19 @@
  * under the License.
  */
 
-// Register ESM hook and start the SDK.
+// Start the SDK for CommonJS usage.
 // This is called for `--require @elastic/opentelemetry-node`.
+//
+// Note: This does *not* register an import hook for ESM instrumentation. Use
+// `--import @elastic/opentelemetry-node` for that.
 
-const register = require('module').register;
-const {pathToFileURL} = require('url');
 const {isMainThread} = require('worker_threads');
 
-const {log} = require('./lib/logging');
-
-/**
- * Return true iff it looks like the `@elastic/opentelemetry-node/hook.mjs`
- * was loaded via node's `--experimental-loader` option.
- *
- * Dev Note: keep this in sync with "import.mjs".
- */
-function haveHookFromExperimentalLoader() {
-    const USED_LOADER_OPT =
-        /--(experimental-)?loader(\s+|=)@elastic\/opentelemetry-node\/hook.mjs/;
-    for (let i = 0; i < process.execArgv.length; i++) {
-        const arg = process.execArgv[i];
-        const nextArg = process.execArgv[i + 1];
-        if (
-            (arg === '--loader' || arg === '--experimental-loader') &&
-            nextArg === '@elastic/opentelemetry-node/hook.mjs'
-        ) {
-            log.trace('bootstrap-require: --loader hook args used');
-            return true;
-        } else if (USED_LOADER_OPT.test(arg)) {
-            log.trace('bootstrap-require: --loader hook arg used');
-            return true;
-        }
-    }
-    if (
-        process.env.NODE_OPTIONS &&
-        USED_LOADER_OPT.test(process.env.NODE_OPTIONS)
-    ) {
-        log.trace('bootstrap-require: --loader arg used in NODE_OPTIONS');
-        return true;
-    }
-    return false;
-}
-
 if (isMainThread) {
-    if (typeof register === 'function' && !haveHookFromExperimentalLoader()) {
-        log.trace('bootstrap-require: registering module hook');
-        register('./hook.mjs', pathToFileURL(__filename).toString());
-    }
-
     require('./lib/start.js');
+} else {
+    const {log} = require('./lib/logging');
+    log.trace(
+        'require.mjs: skipping EDOT Node.js bootstrap on non-main thread'
+    );
 }
diff --git a/packages/opentelemetry-node/test/esm-usage.test.js b/packages/opentelemetry-node/test/esm-usage.test.js
index 6082693a..75513fa9 100644
--- a/packages/opentelemetry-node/test/esm-usage.test.js
+++ b/packages/opentelemetry-node/test/esm-usage.test.js
@@ -17,9 +17,7 @@
  * under the License.
  */
 
-// Sanity test the various ways that ESM support can be enabled via --require,
-// --import, and --experimental-loader (also --loader) in the various versions
-// of Node.js
+// Sanity test the various ways that ESM support can be enabled.
 
 const test = require('tape');
 const {filterOutDnsNetSpans, runTestFixtures} = require('./testutils');
@@ -35,23 +33,10 @@ if (skip) {
 
 /** @type {import('./testutils').TestFixture[]} */
 const testFixtures = [
-    {
-        name: 'ESM via --require',
-        versionRanges: {
-            // TODO: issue on node docs that https://nodejs.org/api/all.html#all_module_moduleregisterspecifier-parenturl-options history doesn't show backport to v18.19.0
-            node: '^18.19.0 || >=20.6.0', // when `module.register()` was added
-        },
-        args: ['./fixtures/use-ioredis.mjs'],
-        cwd: __dirname,
-        env: {
-            NODE_OPTIONS: '--require=@elastic/opentelemetry-node',
-        },
-        verbose: true,
-        checkTelemetry: assertUseIoredisMjsSpans,
-    },
     {
         name: 'ESM via --import',
         versionRanges: {
+            // TODO: issue on node docs that https://nodejs.org/api/all.html#all_module_moduleregisterspecifier-parenturl-options history doesn't show backport to v18.19.0
             node: '^18.19.0 || >=20.6.0', // when `module.register()` was added
         },
         args: ['./fixtures/use-ioredis.mjs'],
@@ -61,96 +46,16 @@ const testFixtures = [
             NODE_NO_WARNINGS: '1',
         },
         verbose: true,
-        checkTelemetry: assertUseIoredisMjsSpans,
-    },
-
-    // Test the cases where the Node.js version means `--experimental-loader`
-    // is needed to register the `import`-hook.
-    {
-        name: 'ESM via --require & --experimental-loader for older Node.js',
-        versionRanges: {
-            node: [
-                // The minimum versions where `--experimental-loader` works at all.
-                '^12.20.0 || ^14.13.1 || ^16.0.0 || ^18.1.0 || >=20.2.0',
-                // The Node.js versions before `module.register()` existed.
-                '<18.19.0 || >=20.0.0 <20.6.0',
-            ],
+        checkTelemetry: function assertUseIoredisMjsSpans(t, col) {
+            // Assert that we got the two redis spans expected from 'use-ioredis.mjs'.
+            const spans = filterOutDnsNetSpans(col.sortedSpans);
+            t.equal(spans[1].name, 'set');
+            t.equal(spans[1].attributes['db.system'], 'redis');
+            t.equal(spans[2].name, 'get');
         },
-        args: ['./fixtures/use-ioredis.mjs'],
-        cwd: __dirname,
-        env: {
-            NODE_OPTIONS:
-                '--require=@elastic/opentelemetry-node --experimental-loader=@elastic/opentelemetry-node/hook.mjs',
-            NODE_NO_WARNINGS: '1',
-        },
-        verbose: true,
-        checkTelemetry: assertUseIoredisMjsSpans,
-    },
-    {
-        name: 'ESM via --import & --experimental-loader for older Node.js',
-        versionRanges: {
-            node: [
-                // The minimum versions where `--experimental-loader` works at all.
-                '^12.20.0 || ^14.13.1 || ^16.0.0 || ^18.1.0 || >=20.2.0',
-                // The Node.js versions before `module.register()` existed,
-                // plus --import was added in v18.18.0.
-                '>=18.18.0 <18.19.0 || >=20.0.0 <20.6.0',
-            ],
-        },
-        args: ['./fixtures/use-ioredis.mjs'],
-        cwd: __dirname,
-        env: {
-            NODE_OPTIONS:
-                '--import=@elastic/opentelemetry-node --experimental-loader=@elastic/opentelemetry-node/hook.mjs',
-            NODE_NO_WARNINGS: '1',
-        },
-        verbose: true,
-        checkTelemetry: assertUseIoredisMjsSpans,
-    },
-
-    // Test a couple cases where, with newer Node.js versions that support
-    // `module.register()`, we could possibly *double-register* the hook if
-    // the user also registered the hook via `--experimental-loader=...`.
-    {
-        name: 'ESM via --import with possible double-hooking',
-        versionRanges: {
-            node: '^18.19.0 || >=20.6.0', // when `module.register()` was added
-        },
-        args: ['./fixtures/use-ioredis.mjs'],
-        cwd: __dirname,
-        env: {
-            NODE_OPTIONS:
-                '--import=@elastic/opentelemetry-node --experimental-loader=@elastic/opentelemetry-node/hook.mjs',
-            NODE_NO_WARNINGS: '1',
-        },
-        verbose: true,
-        checkTelemetry: assertUseIoredisMjsSpans,
-    },
-    {
-        name: 'ESM via --require with possible double-hooking',
-        versionRanges: {
-            node: '^18.19.0 || >=20.6.0', // when `module.register()` was added
-        },
-        args: ['./fixtures/use-ioredis.mjs'],
-        cwd: __dirname,
-        env: {
-            NODE_OPTIONS:
-                '--require=@elastic/opentelemetry-node --experimental-loader=@elastic/opentelemetry-node/hook.mjs',
-            NODE_NO_WARNINGS: '1',
-        },
-        verbose: true,
-        checkTelemetry: assertUseIoredisMjsSpans,
     },
 ];
 
-function assertUseIoredisMjsSpans(t, col) {
-    // Assert that we got the two redis spans expected from 'use-ioredis.mjs'.
-    const spans = filterOutDnsNetSpans(col.sortedSpans);
-    t.equal(spans[1].name, 'set');
-    t.equal(spans[1].attributes['db.system'], 'redis');
-    t.equal(spans[2].name, 'get');
-}
-
 test('ESM usage', {skip}, (suite) => {
     runTestFixtures(suite, testFixtures);
     suite.end();
diff --git a/packages/opentelemetry-node/test/fixtures/use-fetch.mjs b/packages/opentelemetry-node/test/fixtures/use-fetch.mjs
index 6621b00c..30d74729 100644
--- a/packages/opentelemetry-node/test/fixtures/use-fetch.mjs
+++ b/packages/opentelemetry-node/test/fixtures/use-fetch.mjs
@@ -17,7 +17,7 @@
  * under the License.
  */
 
-// Usage: node -r @elastic/opentelemetry-node use-fetch.mjs
+// Usage: node --import @elastic/opentelemetry-node use-fetch.mjs
 
 const res = await fetch('http://www.google.com/');
 console.log(
diff --git a/packages/opentelemetry-node/test/fixtures/use-ioredis.mjs b/packages/opentelemetry-node/test/fixtures/use-ioredis.mjs
index f81106af..9dce1e9b 100644
--- a/packages/opentelemetry-node/test/fixtures/use-ioredis.mjs
+++ b/packages/opentelemetry-node/test/fixtures/use-ioredis.mjs
@@ -17,7 +17,7 @@
  * under the License.
  */
 
-// Usage: node -r @elastic/opentelemetry-node use-ioredis.mjs
+// Usage: node --import @elastic/opentelemetry-node use-ioredis.mjs
 
 import {trace} from '@opentelemetry/api';
 
diff --git a/packages/opentelemetry-node/test/fixtures/use-redis.mjs b/packages/opentelemetry-node/test/fixtures/use-redis.mjs
index 4cd6e2ab..e19ee052 100644
--- a/packages/opentelemetry-node/test/fixtures/use-redis.mjs
+++ b/packages/opentelemetry-node/test/fixtures/use-redis.mjs
@@ -17,7 +17,7 @@
  * under the License.
  */
 
-// Usage: node -r @elastic/opentelemetry-node use-redis.mjs
+// Usage: node --import @elastic/opentelemetry-node use-redis.mjs
 
 import {trace} from '@opentelemetry/api';
 
diff --git a/packages/opentelemetry-node/test/instr-ioredis.test.js b/packages/opentelemetry-node/test/instr-ioredis.test.js
index 01fc8f4b..10195ab0 100644
--- a/packages/opentelemetry-node/test/instr-ioredis.test.js
+++ b/packages/opentelemetry-node/test/instr-ioredis.test.js
@@ -64,19 +64,18 @@ const testFixtures = [
         },
     },
 
-    // This duplicates the "ESM via --require" test case in esm-usage.test.js,
+    // This duplicates the test case in esm-usage.test.js,
     // but it is useful to have the ESM ioredis sanity test here as well when
     // working on instr-ioredis.
     {
-        name: 'use-ioredis.mjs (ESM via --require)',
+        name: 'use-ioredis.mjs (ESM)',
         versionRanges: {
-            // TODO: issue on node docs that https://nodejs.org/api/all.html#all_module_moduleregisterspecifier-parenturl-options history doesn't show backport to v18.19.0
             node: '^18.19.0 || >=20.6.0', // when `module.register()` was added
         },
         args: ['./fixtures/use-ioredis.mjs'],
         cwd: __dirname,
         env: {
-            NODE_OPTIONS: '--require=@elastic/opentelemetry-node',
+            NODE_OPTIONS: '--import=@elastic/opentelemetry-node',
         },
         verbose: true,
         checkTelemetry: assertUseIoredisMjsSpans,
diff --git a/packages/opentelemetry-node/test/instr-mongoose.test.js b/packages/opentelemetry-node/test/instr-mongoose.test.js
index c4ae061f..6c31d997 100644
--- a/packages/opentelemetry-node/test/instr-mongoose.test.js
+++ b/packages/opentelemetry-node/test/instr-mongoose.test.js
@@ -43,7 +43,7 @@ const testFixtures = [
             // Ref: https://github.com/mongodb/node-mongodb-native/blob/a8370367f7470962a834ddf36f9a6c62621d6345/package.json#L118
             node: '>=16.20.1',
         },
-        // verbose: true,
+        verbose: true,
         checkTelemetry: (t, col) => {
             // We expect spans like this
             // ------ trace 5527d1 (13 spans) ------
diff --git a/packages/opentelemetry-node/test/instr-redis-4.test.js b/packages/opentelemetry-node/test/instr-redis-4.test.js
index 0271cd04..5848c01e 100644
--- a/packages/opentelemetry-node/test/instr-redis-4.test.js
+++ b/packages/opentelemetry-node/test/instr-redis-4.test.js
@@ -65,14 +65,14 @@ const testFixtures = [
     },
     // ESM redis sanity test
     {
-        name: 'use-redis.mjs (ESM via --require)',
+        name: 'use-redis.mjs (ESM)',
         versionRanges: {
             node: '^18.19.0 || >=20.6.0', // when `module.register()` was added
         },
         args: ['./fixtures/use-redis.mjs'],
         cwd: __dirname,
         env: {
-            NODE_OPTIONS: '--require=@elastic/opentelemetry-node',
+            NODE_OPTIONS: '--import=@elastic/opentelemetry-node',
         },
         verbose: true,
         checkTelemetry: (t, col) => {
diff --git a/packages/opentelemetry-node/test/instr-undici.test.js b/packages/opentelemetry-node/test/instr-undici.test.js
index d4ce97d3..fadf064b 100644
--- a/packages/opentelemetry-node/test/instr-undici.test.js
+++ b/packages/opentelemetry-node/test/instr-undici.test.js
@@ -91,6 +91,9 @@ const testFixtures = [
         args: ['./fixtures/use-fetch.mjs'],
         cwd: __dirname,
         env: {
+            // Typically '--import' usage is required for ESM instrumention.
+            // However undici instrumentation uses diagnostics_channel, so it
+            // is an exception.
             NODE_OPTIONS: '--require=@elastic/opentelemetry-node',
         },
         // verbose: true,