From 289399f8ec12fa9fbed4182844c6c462ea29288a Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Fri, 21 Nov 2025 08:29:35 +0100
Subject: [PATCH 1/3] src: rename config file testRunner to test

PR-URL: https://github.com/nodejs/node/pull/60798
Reviewed-By: Jacob Smith <jacob@frende.me>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Signed-off-by: Marco Ippolito <marcoippolito54@gmail.com>
---
 doc/api/cli.md                                |  4 +--
 doc/node-config-schema.json                   |  2 +-
 src/node_config_file.cc                       | 14 +++++++++-
 src/node_options.h                            |  2 +-
 .../options-as-flags/test-config.json         |  2 +-
 .../rc/deprecated-testrunner-namespace.json   |  5 ++++
 .../node.config.json                          |  2 +-
 test/fixtures/rc/empty-valid-namespace.json   |  2 +-
 test/fixtures/rc/namespace-with-array.json    |  2 +-
 .../rc/namespace-with-disallowed-envvar.json  |  2 +-
 test/fixtures/rc/namespaced/node.config.json  |  2 +-
 test/fixtures/rc/override-namespace.json      |  2 +-
 .../override-node-option-with-namespace.json  |  2 +-
 test/fixtures/rc/unknown-flag-namespace.json  |  2 +-
 .../options-propagation/node.config.json      |  2 +-
 test/parallel/test-config-file.js             | 14 +++++++++-
 test/parallel/test-runner-flag-propagation.js | 26 +++++++++----------
 17 files changed, 58 insertions(+), 29 deletions(-)
 create mode 100644 test/fixtures/rc/deprecated-testrunner-namespace.json

diff --git a/doc/api/cli.md b/doc/api/cli.md
index 1a6844b1f9dad9..4ca461f263b319 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -986,7 +986,7 @@ in the `$schema` must be replaced with the version of Node.js you are using.
     "watch-path": "src",
     "watch-preserve-output": true
   },
-  "testRunner": {
+  "test": {
     "test-isolation": "process"
   },
   "watch": {
@@ -999,7 +999,7 @@ The configuration file supports namespace-specific options:
 
 * The `nodeOptions` field contains CLI flags that are allowed in [`NODE_OPTIONS`][].
 
-* Namespace fields like `testRunner` contain configuration specific to that subsystem.
+* Namespace fields like `test` contain configuration specific to that subsystem.
 
 No-op flags are not supported.
 Not all V8 flags are currently supported.
diff --git a/doc/node-config-schema.json b/doc/node-config-schema.json
index 2b4f228eaa57d5..71df22b020cf46 100644
--- a/doc/node-config-schema.json
+++ b/doc/node-config-schema.json
@@ -816,7 +816,7 @@
         }
       }
     },
-    "testRunner": {
+    "test": {
       "type": "object",
       "additionalProperties": false,
       "required": [],
diff --git a/src/node_config_file.cc b/src/node_config_file.cc
index b3f5feb53d73c0..d1503bb45b3aff 100644
--- a/src/node_config_file.cc
+++ b/src/node_config_file.cc
@@ -260,8 +260,20 @@ ParseResult ConfigReader::ParseConfig(const std::string_view& config_path) {
       return ParseResult::InvalidContent;
     }
 
-    // Check if this field is a valid namespace
     std::string namespace_name(field_name);
+
+    // TODO(@marco-ippolito): Remove warning for testRunner namespace
+    if (namespace_name == "testRunner") {
+      FPrintF(stderr,
+              "the \"testRunner\" namespace has been removed. "
+              "Use \"test\" instead.\n");
+      // Better to throw an error than to ignore it
+      // Otherwise users might think their test suite is green
+      // when it's not running
+      return ParseResult::InvalidContent;
+    }
+
+    // Check if this field is a valid namespace
     if (!valid_namespaces.contains(namespace_name)) {
       // If not, skip it
       continue;
diff --git a/src/node_options.h b/src/node_options.h
index 6ffa6bf5531d84..77423b8bcd441b 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -423,7 +423,7 @@ std::vector<std::string> MapAvailableNamespaces();
 // Define all namespace entries
 #define OPTION_NAMESPACE_LIST(V)                                               \
   V(kNoNamespace, "")                                                          \
-  V(kTestRunnerNamespace, "testRunner")                                        \
+  V(kTestRunnerNamespace, "test")                                              \
   V(kWatchNamespace, "watch")                                                  \
   V(kPermissionNamespace, "permission")
 
diff --git a/test/fixtures/options-as-flags/test-config.json b/test/fixtures/options-as-flags/test-config.json
index c80ffa4069fbf5..aa6355c37a1681 100644
--- a/test/fixtures/options-as-flags/test-config.json
+++ b/test/fixtures/options-as-flags/test-config.json
@@ -3,7 +3,7 @@
     "experimental-transform-types": true,
     "max-http-header-size": 8192
   },
-  "testRunner": {
+  "test": {
     "test-isolation": "none"
   }
 }
diff --git a/test/fixtures/rc/deprecated-testrunner-namespace.json b/test/fixtures/rc/deprecated-testrunner-namespace.json
new file mode 100644
index 00000000000000..d8a01949418cf7
--- /dev/null
+++ b/test/fixtures/rc/deprecated-testrunner-namespace.json
@@ -0,0 +1,5 @@
+{
+  "testRunner": {
+    "test-isolation": "none"
+  }
+}
diff --git a/test/fixtures/rc/duplicate-namespace-option/node.config.json b/test/fixtures/rc/duplicate-namespace-option/node.config.json
index 4d948fbd33961d..948dc4e6c5570b 100644
--- a/test/fixtures/rc/duplicate-namespace-option/node.config.json
+++ b/test/fixtures/rc/duplicate-namespace-option/node.config.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
         "test-name-pattern": "first-pattern",
         "test-name-pattern": "second-pattern"
     }
diff --git a/test/fixtures/rc/empty-valid-namespace.json b/test/fixtures/rc/empty-valid-namespace.json
index dbeb33d7aa8b59..c267aa9bde2918 100644
--- a/test/fixtures/rc/empty-valid-namespace.json
+++ b/test/fixtures/rc/empty-valid-namespace.json
@@ -1,3 +1,3 @@
 {
-    "testRunner": {}
+    "test": {}
 }
diff --git a/test/fixtures/rc/namespace-with-array.json b/test/fixtures/rc/namespace-with-array.json
index 056a4291e9b666..1cddcdfd6c4ccd 100644
--- a/test/fixtures/rc/namespace-with-array.json
+++ b/test/fixtures/rc/namespace-with-array.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
         "test-coverage-exclude": ["config-pattern1", "config-pattern2"]
     }
 }
diff --git a/test/fixtures/rc/namespace-with-disallowed-envvar.json b/test/fixtures/rc/namespace-with-disallowed-envvar.json
index 6152684e0583f4..f545f0ff62781f 100644
--- a/test/fixtures/rc/namespace-with-disallowed-envvar.json
+++ b/test/fixtures/rc/namespace-with-disallowed-envvar.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
        "test-concurrency": 1,
        "experimental-test-coverage": true
     }
diff --git a/test/fixtures/rc/namespaced/node.config.json b/test/fixtures/rc/namespaced/node.config.json
index df929d25c10b52..0870c4c86033b2 100644
--- a/test/fixtures/rc/namespaced/node.config.json
+++ b/test/fixtures/rc/namespaced/node.config.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
         "test-isolation": "none"
     }
 }
diff --git a/test/fixtures/rc/override-namespace.json b/test/fixtures/rc/override-namespace.json
index acb37b2eec485c..be79cf5d4415b5 100644
--- a/test/fixtures/rc/override-namespace.json
+++ b/test/fixtures/rc/override-namespace.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
         "test-isolation": "process"
     },
     "nodeOptions": {
diff --git a/test/fixtures/rc/override-node-option-with-namespace.json b/test/fixtures/rc/override-node-option-with-namespace.json
index 2db9e1a47f07ea..e5912da99590b4 100644
--- a/test/fixtures/rc/override-node-option-with-namespace.json
+++ b/test/fixtures/rc/override-node-option-with-namespace.json
@@ -2,7 +2,7 @@
     "nodeOptions": {
         "test-isolation": "none"
     },
-    "testRunner": {
+    "test": {
         "test-isolation": "process"
     }
 }
diff --git a/test/fixtures/rc/unknown-flag-namespace.json b/test/fixtures/rc/unknown-flag-namespace.json
index b5d87ad8dd3acd..01dd62824cf2b9 100644
--- a/test/fixtures/rc/unknown-flag-namespace.json
+++ b/test/fixtures/rc/unknown-flag-namespace.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
         "unknown-flag": true
     }
 }
diff --git a/test/fixtures/test-runner/options-propagation/node.config.json b/test/fixtures/test-runner/options-propagation/node.config.json
index 98a35b7d3eebd2..7bb3d5c80fe0e5 100644
--- a/test/fixtures/test-runner/options-propagation/node.config.json
+++ b/test/fixtures/test-runner/options-propagation/node.config.json
@@ -1,5 +1,5 @@
 {
-    "testRunner": {
+    "test": {
         "experimental-test-coverage": true
     }
 }
diff --git a/test/parallel/test-config-file.js b/test/parallel/test-config-file.js
index 79d2ef7cdc4b64..94593a9b8f6efa 100644
--- a/test/parallel/test-config-file.js
+++ b/test/parallel/test-config-file.js
@@ -429,7 +429,7 @@ describe('namespace-scoped options', () => {
       fixtures.path('rc/unknown-flag-namespace.json'),
       '-p', '"Hello, World!"',
     ]);
-    assert.match(result.stderr, /Unknown or not allowed option unknown-flag for namespace testRunner/);
+    assert.match(result.stderr, /Unknown or not allowed option unknown-flag for namespace test/);
     assert.strictEqual(result.stdout, '');
     assert.strictEqual(result.code, 9);
   });
@@ -550,4 +550,16 @@ describe('namespace-scoped options', () => {
     assert.strictEqual(result.stdout, '2\n');
     assert.strictEqual(result.code, 0);
   });
+
+  it('should throw an error for removed "testRunner" namespace', async () => {
+    const result = await spawnPromisified(process.execPath, [
+      '--no-warnings',
+      '--experimental-config-file',
+      fixtures.path('rc/deprecated-testrunner-namespace.json'),
+      '-p', '"Hello, World!"',
+    ]);
+    assert.match(result.stderr, /the "testRunner" namespace has been removed\. Use "test" instead\./);
+    assert.strictEqual(result.stdout, '');
+    assert.strictEqual(result.code, 9);
+  });
 });
diff --git a/test/parallel/test-runner-flag-propagation.js b/test/parallel/test-runner-flag-propagation.js
index 3f742850a9fae7..f4e9849cce77d0 100644
--- a/test/parallel/test-runner-flag-propagation.js
+++ b/test/parallel/test-runner-flag-propagation.js
@@ -68,19 +68,19 @@ describe('test runner flag propagation', () => {
 
   describe('via config file', () => {
     const configFilePropagationTests = [
-      ['--test-concurrency', 2, 2, 'testRunner'],
-      ['--test-timeout', 5000, 5000, 'testRunner'],
-      ['--test-coverage-branches', 100, 100, 'testRunner'],
-      ['--test-coverage-functions', 100, 100, 'testRunner'],
-      ['--test-coverage-lines', 100, 100, 'testRunner'],
-      ['--experimental-test-coverage', true, false, 'testRunner'],
-      ['--test-coverage-exclude', 'test/**', 'test/**', 'testRunner'],
-      ['--test-coverage-include', 'src/**', 'src/**', 'testRunner'],
-      ['--test-update-snapshots', true, true, 'testRunner'],
-      ['--test-concurrency', 3, 3, 'testRunner'],
-      ['--test-timeout', 2500, 2500, 'testRunner'],
-      ['--test-coverage-branches', 90, 90, 'testRunner'],
-      ['--test-coverage-functions', 85, 85, 'testRunner'],
+      ['--test-concurrency', 2, 2, 'test'],
+      ['--test-timeout', 5000, 5000, 'test'],
+      ['--test-coverage-branches', 100, 100, 'test'],
+      ['--test-coverage-functions', 100, 100, 'test'],
+      ['--test-coverage-lines', 100, 100, 'test'],
+      ['--experimental-test-coverage', true, false, 'test'],
+      ['--test-coverage-exclude', 'test/**', 'test/**', 'test'],
+      ['--test-coverage-include', 'src/**', 'src/**', 'test'],
+      ['--test-update-snapshots', true, true, 'test'],
+      ['--test-concurrency', 3, 3, 'test'],
+      ['--test-timeout', 2500, 2500, 'test'],
+      ['--test-coverage-branches', 90, 90, 'test'],
+      ['--test-coverage-functions', 85, 85, 'test'],
     ];
 
     for (const [flagName, configValue, expectedValue, namespace] of configFilePropagationTests) {

From 4869f1f8d23906610eb86810c64a86197e66639f Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Fri, 21 Nov 2025 08:49:24 +0100
Subject: [PATCH 2/3] src: add test flag to config file

PR-URL: https://github.com/nodejs/node/pull/60798
Reviewed-By: Jacob Smith <jacob@frende.me>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Signed-off-by: Marco Ippolito <marcoippolito54@gmail.com>
---
 doc/node-config-schema.json | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/doc/node-config-schema.json b/doc/node-config-schema.json
index 71df22b020cf46..d2d8e3a2f11bc4 100644
--- a/doc/node-config-schema.json
+++ b/doc/node-config-schema.json
@@ -833,6 +833,9 @@
           "type": "boolean",
           "description": "launch test runner on startup"
         },
+        "test": {
+          "type": "boolean"
+        },
         "test-concurrency": {
           "type": "number",
           "description": "specify test runner concurrency"

From c28ce0d6f3276b6a1904224d3f8a55f5e94f57f3 Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Thu, 16 Apr 2026 07:31:35 +0100
Subject: [PATCH 3/3] src: allow empty --experimental-config-file

PR-URL: https://github.com/nodejs/node/pull/61610
Reviewed-By: Pietro Marchini <pietro.marchini94@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Signed-off-by: Marco Ippolito <marcoippolito54@gmail.com>
---
 doc/api/cli.md                                |  13 +-
 doc/api/test.md                               |   2 +-
 doc/node.1                                    |  70 ++++-
 lib/internal/main/watch_mode.js               |   8 +-
 lib/internal/process/pre_execution.js         |   3 +-
 lib/internal/test_runner/runner.js            |   6 +-
 src/node.cc                                   |  14 +-
 src/node_config_file.cc                       |  64 +++--
 src/node_config_file.h                        |   4 +-
 src/node_options.cc                           |   9 +-
 src/node_options.h                            |   1 -
 test/parallel/test-cli-node-options-docs.js   |   1 +
 test/parallel/test-cli-options-as-flags.js    |   6 +-
 test/parallel/test-config-file.js             | 241 +++++++++++-------
 test/parallel/test-permission-config-file.mjs |  27 +-
 test/parallel/test-runner-cli.js              |  43 ++--
 test/parallel/test-runner-flag-propagation.js |  15 +-
 test/sequential/test-watch-mode.mjs           |   4 +-
 18 files changed, 343 insertions(+), 188 deletions(-)

diff --git a/doc/api/cli.md b/doc/api/cli.md
index 4ca461f263b319..c39ab130d9ad7a 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -963,7 +963,7 @@ added: v23.6.0
 
 Enable experimental import support for `.node` addons.
 
-### `--experimental-config-file=config`
+### `--experimental-config-file=path`, `--experimental-config-file`
 
 <!-- YAML
 added: v23.10.0
@@ -972,6 +972,12 @@ added: v23.10.0
 > Stability: 1.0 - Early development
 
 If present, Node.js will look for a configuration file at the specified path.
+If the path is not specified, Node.js will look for a `node.config.json` file
+in the current working directory.
+To specify a custom path, use the `--experimental-config-file=path` form.
+The space-separated `--experimental-config-file path` form is not supported.
+The alias `--experimental-default-config-file` is equivalent to
+`--experimental-config-file` without an argument.
 Node.js will read the configuration file and apply the settings. The
 configuration file should be a JSON file with the following structure. `vX.Y.Z`
 in the `$schema` must be replaced with the version of Node.js you are using.
@@ -1043,9 +1049,10 @@ added: v23.10.0
 
 > Stability: 1.0 - Early development
 
-If the `--experimental-default-config-file` flag is present, Node.js will look for a
+This flag is an alias for `--experimental-config-file` without an argument.
+If present, Node.js will look for a
 `node.config.json` file in the current working directory and load it as a
-as configuration file.
+configuration file.
 
 ### `--experimental-eventsource`
 
diff --git a/doc/api/test.md b/doc/api/test.md
index ee8855adf1b4ef..0ae5220a2e7a1b 100644
--- a/doc/api/test.md
+++ b/doc/api/test.md
@@ -4503,7 +4503,7 @@ test.describe('my suite', (suite) => {
 [`suite()`]: #suitename-options-fn
 [`test()`]: #testname-options-fn
 [code coverage]: #collecting-code-coverage
-[configuration files]: cli.md#--experimental-config-fileconfig
+[configuration files]: cli.md#--experimental-config-filepath---experimental-config-file
 [describe options]: #describename-options-fn
 [it options]: #testname-options-fn
 [module customization hooks]: module.md#customization-hooks
diff --git a/doc/node.1 b/doc/node.1
index 73b1db87bee031..7ac6acb579b9b0 100644
--- a/doc/node.1
+++ b/doc/node.1
@@ -169,11 +169,75 @@ Interpret the entry point as a URL.
 .It Fl -experimental-addon-modules
 Enable experimental addon module support.
 .
-.It Fl -experimental-config-file
-Specifies the configuration file to load.
+.It Fl -experimental-config-file , Fl -experimental-config-file Ns = Ns Ar config , Fl -experimental-default-config-file
+If present, Node.js will look for a configuration file at the specified path.
+If the path is not specified, Node.js will look for a \fBnode.config.json\fR file
+in the current working directory.
+To specify a custom path, use the \fB--experimental-config-file=\fR\fBpath\fR form.
+The space-separated \fB--experimental-config-file path\fR form is not supported.
+Node.js will read the configuration file and apply the settings. The
+configuration file should be a JSON file with the following structure. \fBvX.Y.Z\fR
+in the \fB$schema\fR must be replaced with the version of Node.js you are using.
+.Bd -literal
+{
+  "$schema": "https://nodejs.org/dist/vX.Y.Z/docs/node-config-schema.json",
+  "nodeOptions": {
+    "import": [
+      "amaro/strip"
+    ],
+    "watch-path": "src",
+    "watch-preserve-output": true
+  },
+  "testRunner": {
+    "test-isolation": "process"
+  },
+  "watch": {
+    "watch-preserve-output": true
+  }
+}
+.Ed
+The configuration file supports namespace-specific options:
+.Bl -bullet
+.It
+The \fBnodeOptions\fR field contains CLI flags that are allowed in \fBNODE_OPTIONS\fR.
+.It
+Namespace fields like \fBtestRunner\fR contain configuration specific to that subsystem.
+.El
+No-op flags are not supported.
+Not all V8 flags are currently supported.
+It is possible to use the official JSON schema
+to validate the configuration file, which may vary depending on the Node.js version.
+Each key in the configuration file corresponds to a flag that can be passed
+as a command-line argument. The value of the key is the value that would be
+passed to the flag.
+For example, the configuration file above is equivalent to
+the following command-line arguments:
+.Bd -literal
+node --import amaro/strip --watch-path=src --watch-preserve-output --test-isolation=process
+.Ed
+The priority in configuration is as follows:
+.Bl -bullet
+.It
+NODE_OPTIONS and command-line options
+.It
+Dotenv NODE_OPTIONS
+.It
+Configuration file
+.El
+Values in the configuration file will not override the values in the environment
+variables, command-line options, or the \fBNODE_OPTIONS\fR env file parsed by the
+\fB--env-file\fR flag.
+Keys cannot be duplicated within the same or different namespaces.
+The configuration parser will throw an error if the configuration file contains
+unknown keys or keys that cannot be used in a namespace.
+Node.js will not sanitize or perform validation on the user-provided configuration,
+so \fBNEVER\fR use untrusted configuration files.
 .
 .It Fl -experimental-default-config-file
-Enable support for automatically loading node.config.json.
+This flag is an alias for \fB--experimental-config-file\fR without an argument.
+If present, Node.js will look for a
+\fBnode.config.json\fR file in the current working directory and load it as a
+configuration file.
 .
 .It Fl -experimental-import-meta-resolve
 Enable experimental ES modules support for import.meta.resolve().
diff --git a/lib/internal/main/watch_mode.js b/lib/internal/main/watch_mode.js
index 5e2e97f2fd60f2..63d1b51c815155 100644
--- a/lib/internal/main/watch_mode.js
+++ b/lib/internal/main/watch_mode.js
@@ -1,7 +1,6 @@
 'use strict';
 const {
   ArrayPrototypeForEach,
-  ArrayPrototypeIncludes,
   ArrayPrototypeJoin,
   ArrayPrototypeMap,
   ArrayPrototypePush,
@@ -67,11 +66,8 @@ for (let i = 0; i < process.execArgv.length; i++) {
     }
     continue;
   }
-  if (StringPrototypeStartsWith(arg, '--experimental-config-file')) {
-    if (!ArrayPrototypeIncludes(arg, '=')) {
-      // Skip the flag and the next argument (the config file path)
-      i++;
-    }
+  if (arg === '--experimental-config-file' ||
+      StringPrototypeStartsWith(arg, '--experimental-config-file=')) {
     continue;
   }
   if (arg === '--experimental-default-config-file') {
diff --git a/lib/internal/process/pre_execution.js b/lib/internal/process/pre_execution.js
index e9ab2b2a8958e9..2716c2ae81b642 100644
--- a/lib/internal/process/pre_execution.js
+++ b/lib/internal/process/pre_execution.js
@@ -386,8 +386,7 @@ function setupSQLite() {
 }
 
 function initializeConfigFileSupport() {
-  if (getOptionValue('--experimental-default-config-file') ||
-      getOptionValue('--experimental-config-file')) {
+  if (getOptionValue('--experimental-config-file')) {
     emitExperimentalWarning('--experimental-config-file');
   }
 }
diff --git a/lib/internal/test_runner/runner.js b/lib/internal/test_runner/runner.js
index bb3a8868309a94..2033ac16e8ea49 100644
--- a/lib/internal/test_runner/runner.js
+++ b/lib/internal/test_runner/runner.js
@@ -161,7 +161,11 @@ function createTestFileList(patterns, cwd) {
 
 function filterExecArgv(arg, i, arr) {
   return !ArrayPrototypeIncludes(kFilterArgs, arg) &&
-  !ArrayPrototypeSome(kFilterArgValues, (p) => arg === p || (i > 0 && arr[i - 1] === p) || StringPrototypeStartsWith(arg, `${p}=`));
+  !ArrayPrototypeSome(kFilterArgValues, (p) => {
+    return arg === p ||
+      StringPrototypeStartsWith(arg, `${p}=`) ||
+      (p !== '--experimental-config-file' && i > 0 && arr[i - 1] === p);
+  });
 }
 
 function getRunArgs(path, { forceExit,
diff --git a/src/node.cc b/src/node.cc
index 6f899ec0621ada..8b21578eb52b23 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -911,15 +911,21 @@ static ExitCode InitializeNodeWithArgsInternal(
   }
 
   std::string node_options_from_config;
-  if (auto path = per_process::config_reader.GetDataFromArgs(*argv)) {
-    switch (per_process::config_reader.ParseConfig(*path)) {
+  auto config_path = per_process::config_reader.GetDataFromArgs(argv);
+  if (per_process::config_reader.HasInvalidDefaultConfigFileArgument()) {
+    errors->push_back("--experimental-default-config-file does not take an "
+                      "argument");
+    return ExitCode::kInvalidCommandLineArgument;
+  }
+  if (config_path) {
+    switch (per_process::config_reader.ParseConfig(*config_path)) {
       case ParseResult::Valid:
         break;
       case ParseResult::InvalidContent:
-        errors->push_back(std::string(*path) + ": invalid content");
+        errors->push_back(std::string(*config_path) + ": invalid content");
         break;
       case ParseResult::FileError:
-        errors->push_back(std::string(*path) + ": not found");
+        errors->push_back(std::string(*config_path) + ": not found");
         break;
       default:
         UNREACHABLE();
diff --git a/src/node_config_file.cc b/src/node_config_file.cc
index d1503bb45b3aff..e62f1b526da4b0 100644
--- a/src/node_config_file.cc
+++ b/src/node_config_file.cc
@@ -2,39 +2,53 @@
 #include "debug_utils-inl.h"
 #include "simdjson.h"
 
-#include <string>
-
 namespace node {
 
+constexpr std::string_view kConfigFileFlag = "--experimental-config-file";
+constexpr std::string_view kDefaultConfigFileFlag =
+    "--experimental-default-config-file";
+constexpr std::string_view kDefaultConfigFileName = "node.config.json";
+
+inline bool HasEqualsPrefix(std::string_view arg, std::string_view flag) {
+  return arg.size() > flag.size() && arg.starts_with(flag) &&
+         arg[flag.size()] == '=';
+}
+
 std::optional<std::string_view> ConfigReader::GetDataFromArgs(
-    const std::vector<std::string>& args) {
-  constexpr std::string_view flag_path = "--experimental-config-file";
-  constexpr std::string_view default_file =
-      "--experimental-default-config-file";
-
-  bool has_default_config_file = false;
-
-  for (auto it = args.begin(); it != args.end(); ++it) {
-    if (*it == flag_path) {
-      // Case: "--experimental-config-file foo"
-      if (auto next = std::next(it); next != args.end()) {
-        return *next;
+    std::vector<std::string>* args) {
+  std::optional<std::string_view> result;
+  invalid_default_config_file_argument_ = false;
+
+  for (size_t i = 0; i < args->size(); ++i) {
+    std::string& arg = (*args)[i];
+
+    if (arg == kConfigFileFlag) {
+      // --experimental-config-file
+      arg = std::string(kConfigFileFlag) + "=" +
+            std::string(kDefaultConfigFileName);
+      result = kDefaultConfigFileName;
+    } else if (HasEqualsPrefix(arg, kConfigFileFlag)) {
+      // --experimental-config-file=path
+      std::string_view path =
+          std::string_view(arg).substr(kConfigFileFlag.size() + 1);
+      if (!path.empty()) {
+        result = path;
       }
-    } else if (it->starts_with(flag_path)) {
-      // Case: "--experimental-config-file=foo"
-      if (it->size() > flag_path.size() && (*it)[flag_path.size()] == '=') {
-        return std::string_view(*it).substr(flag_path.size() + 1);
-      }
-    } else if (*it == default_file || it->starts_with(default_file)) {
-      has_default_config_file = true;
+    } else if (arg == kDefaultConfigFileFlag) {
+      // --experimental-default-config-file
+      arg = std::string(kConfigFileFlag) + "=" +
+            std::string(kDefaultConfigFileName);
+      result = kDefaultConfigFileName;
+    } else if (HasEqualsPrefix(arg, kDefaultConfigFileFlag)) {
+      invalid_default_config_file_argument_ = true;
     }
   }
 
-  if (has_default_config_file) {
-    return "node.config.json";
-  }
+  return result;
+}
 
-  return std::nullopt;
+bool ConfigReader::HasInvalidDefaultConfigFileArgument() const {
+  return invalid_default_config_file_argument_;
 }
 
 ParseResult ConfigReader::ProcessOptionValue(
diff --git a/src/node_config_file.h b/src/node_config_file.h
index 82874cee8b583f..afe0e84765b8cb 100644
--- a/src/node_config_file.h
+++ b/src/node_config_file.h
@@ -30,7 +30,8 @@ class ConfigReader {
   ParseResult ParseConfig(const std::string_view& config_path);
 
   std::optional<std::string_view> GetDataFromArgs(
-      const std::vector<std::string>& args);
+      std::vector<std::string>* args);
+  bool HasInvalidDefaultConfigFileArgument() const;
 
   std::string GetNodeOptions();
   const std::vector<std::string>& GetNamespaceFlags() const;
@@ -53,6 +54,7 @@ class ConfigReader {
 
   std::vector<std::string> node_options_;
   std::vector<std::string> namespace_options_;
+  bool invalid_default_config_file_argument_ = false;
 
   // Cache for fast lookup of environment options
   std::unordered_map<std::string, options_parser::OptionMappingDetails>
diff --git a/src/node_options.cc b/src/node_options.cc
index b7062241d590e3..ab050b123f61a4 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -851,11 +851,10 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             &EnvironmentOptions::optional_env_file);
   Implies("--env-file-if-exists", "[has_env_file_string]");
   AddOption("--experimental-config-file",
-            "set config file from supplied file",
-            &EnvironmentOptions::experimental_config_file_path);
-  AddOption("--experimental-default-config-file",
-            "set config file from default config file",
-            &EnvironmentOptions::experimental_default_config_file);
+            "set config file path",
+            &EnvironmentOptions::experimental_config_file_path,
+            kDisallowedInEnvvar);
+  AddAlias("--experimental-default-config-file", "--experimental-config-file");
   AddOption("--test",
             "launch test runner on startup",
             &EnvironmentOptions::test_runner,
diff --git a/src/node_options.h b/src/node_options.h
index 77423b8bcd441b..8117345a6ca43a 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -269,7 +269,6 @@ class EnvironmentOptions : public Options {
   bool report_exclude_env = false;
   bool report_exclude_network = false;
   std::string experimental_config_file_path;
-  bool experimental_default_config_file = false;
 
   inline DebugOptions* get_debug_options() { return &debug_options_; }
   inline const DebugOptions& debug_options() const { return debug_options_; }
diff --git a/test/parallel/test-cli-node-options-docs.js b/test/parallel/test-cli-node-options-docs.js
index 80caa29d4263ef..534c99c04de964 100644
--- a/test/parallel/test-cli-node-options-docs.js
+++ b/test/parallel/test-cli-node-options-docs.js
@@ -122,5 +122,6 @@ for (const [, envVar, config] of nodeOptionsCC.matchAll(addOptionRE)) {
 
 // add alias handling
 manPagesOptions.delete('-trace-events-enabled');
+manPagesOptions.delete('-experimental-default-config-file');
 
 assert.strictEqual(manPagesOptions.size, 0, `Man page options not documented: ${[...manPagesOptions]}`);
diff --git a/test/parallel/test-cli-options-as-flags.js b/test/parallel/test-cli-options-as-flags.js
index 403a18d162ca61..b61e98847dc38f 100644
--- a/test/parallel/test-cli-options-as-flags.js
+++ b/test/parallel/test-cli-options-as-flags.js
@@ -55,8 +55,7 @@ describe('getOptionsAsFlagsFromBinding', () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
       '--expose-internals',
-      '--experimental-config-file',
-      configFile,
+      `--experimental-config-file=${configFile}`,
       fixtureFile,
     ]);
 
@@ -76,8 +75,7 @@ describe('getOptionsAsFlagsFromBinding', () => {
       '--no-warnings',
       '--expose-internals',
       '--stack-trace-limit=512',
-      '--experimental-config-file',
-      configFile,
+      `--experimental-config-file=${configFile}`,
       fixtureFile,
     ]);
 
diff --git a/test/parallel/test-config-file.js b/test/parallel/test-config-file.js
index 94593a9b8f6efa..6aac042b0c6c2a 100644
--- a/test/parallel/test-config-file.js
+++ b/test/parallel/test-config-file.js
@@ -24,8 +24,7 @@ const onlyWithInspectorAndNodeOptions = {
 
 test('should handle non existing json', async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--experimental-config-file',
-    'i-do-not-exist.json',
+    '--experimental-config-file=i-do-not-exist.json',
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Cannot read configuration from i-do-not-exist\.json: no such file or directory/);
@@ -36,8 +35,7 @@ test('should handle non existing json', async () => {
 
 test('should handle empty json', async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--experimental-config-file',
-    fixtures.path('rc/empty.json'),
+    `--experimental-config-file=${fixtures.path('rc/empty.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Can't parse/);
@@ -49,8 +47,7 @@ test('should handle empty json', async () => {
 test('should handle empty object json', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/empty-object.json'),
+    `--experimental-config-file=${fixtures.path('rc/empty-object.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -60,8 +57,7 @@ test('should handle empty object json', async () => {
 
 test('should parse boolean flag', onlyWithAmaroAndNodeOptions, async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--experimental-config-file',
-    fixtures.path('rc/transform-types.json'),
+    `--experimental-config-file=${fixtures.path('rc/transform-types.json')}`,
     fixtures.path('typescript/ts/transformation/test-enum.ts'),
   ]);
   assert.match(result.stderr, /--experimental-config-file is an experimental feature and might change at any time/);
@@ -71,8 +67,7 @@ test('should parse boolean flag', onlyWithAmaroAndNodeOptions, async () => {
 
 test('should parse boolean flag defaulted to true', onlyIfNodeOptionsSupport, async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--experimental-config-file',
-    fixtures.path('rc/warnings-false.json'),
+    `--experimental-config-file=${fixtures.path('rc/warnings-false.json')}`,
     '-p', 'process.emitWarning("A warning")',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -83,9 +78,8 @@ test('should parse boolean flag defaulted to true', onlyIfNodeOptionsSupport, as
 test('should throw an error when a flag is declared twice', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/override-property.json'),
-    fixtures.path('typescript/ts/transformation/test-enum.ts'),
+    `--experimental-config-file=${fixtures.path('rc/override-property.json')}`,
+    '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Option --experimental-transform-types is already defined/);
   assert.strictEqual(result.stdout, '');
@@ -95,8 +89,7 @@ test('should throw an error when a flag is declared twice', async () => {
 test('should not override env-file', onlyWithAmaroAndNodeOptions, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/transform-types.json'),
+    `--experimental-config-file=${fixtures.path('rc/transform-types.json')}`,
     '--env-file', fixtures.path('dotenv/node-options-no-tranform.env'),
     fixtures.path('typescript/ts/transformation/test-enum.ts'),
   ]);
@@ -108,8 +101,7 @@ test('should not override env-file', onlyWithAmaroAndNodeOptions, async () => {
 test('should not override NODE_OPTIONS', onlyWithAmaro, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/transform-types.json'),
+    `--experimental-config-file=${fixtures.path('rc/transform-types.json')}`,
     fixtures.path('typescript/ts/transformation/test-enum.ts'),
   ], {
     env: {
@@ -126,8 +118,7 @@ test('should not override CLI flags', onlyWithAmaro, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
     '--no-experimental-transform-types',
-    '--experimental-config-file',
-    fixtures.path('rc/transform-types.json'),
+    `--experimental-config-file=${fixtures.path('rc/transform-types.json')}`,
     fixtures.path('typescript/ts/transformation/test-enum.ts'),
   ]);
   assert.match(result.stderr, /ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX/);
@@ -138,8 +129,7 @@ test('should not override CLI flags', onlyWithAmaro, async () => {
 test('should parse array flag correctly', onlyIfNodeOptionsSupport, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/import.json'),
+    `--experimental-config-file=${fixtures.path('rc/import.json')}`,
     '--eval', 'setTimeout(() => console.log("D"),99)',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -150,8 +140,7 @@ test('should parse array flag correctly', onlyIfNodeOptionsSupport, async () =>
 test('should validate invalid array flag', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/invalid-import.json'),
+    `--experimental-config-file=${fixtures.path('rc/invalid-import.json')}`,
     '--eval', 'setTimeout(() => console.log("D"),99)',
   ]);
   assert.match(result.stderr, /invalid-import\.json: invalid content/);
@@ -162,8 +151,7 @@ test('should validate invalid array flag', async () => {
 test('should validate array flag as string', onlyIfNodeOptionsSupport, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/import-as-string.json'),
+    `--experimental-config-file=${fixtures.path('rc/import-as-string.json')}`,
     '--eval', 'setTimeout(() => console.log("B"),99)',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -174,8 +162,7 @@ test('should validate array flag as string', onlyIfNodeOptionsSupport, async ()
 test('should throw at unknown flag', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/unknown-flag.json'),
+    `--experimental-config-file=${fixtures.path('rc/unknown-flag.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Unknown or not allowed option some-unknown-flag for namespace nodeOptions/);
@@ -186,8 +173,7 @@ test('should throw at unknown flag', async () => {
 test('should throw at flag not available in NODE_OPTIONS', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/not-node-options-flag.json'),
+    `--experimental-config-file=${fixtures.path('rc/not-node-options-flag.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Unknown or not allowed option test for namespace nodeOptions/);
@@ -198,8 +184,7 @@ test('should throw at flag not available in NODE_OPTIONS', async () => {
 test('unsigned flag should be parsed correctly', onlyIfNodeOptionsSupport, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/numeric.json'),
+    `--experimental-config-file=${fixtures.path('rc/numeric.json')}`,
     '-p', 'http.maxHeaderSize',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -210,8 +195,7 @@ test('unsigned flag should be parsed correctly', onlyIfNodeOptionsSupport, async
 test('numeric flag should not allow negative values', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/negative-numeric.json'),
+    `--experimental-config-file=${fixtures.path('rc/negative-numeric.json')}`,
     '-p', 'http.maxHeaderSize',
   ]);
   assert.match(result.stderr, /Invalid value for --max-http-header-size/);
@@ -223,8 +207,7 @@ test('numeric flag should not allow negative values', async () => {
 test('v8 flag should not be allowed in config file', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/v8-flag.json'),
+    `--experimental-config-file=${fixtures.path('rc/v8-flag.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /V8 flag --abort-on-uncaught-exception is currently not supported/);
@@ -236,8 +219,7 @@ test('string flag should be parsed correctly', onlyIfNodeOptionsSupport, async (
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
     '--test',
-    '--experimental-config-file',
-    fixtures.path('rc/string.json'),
+    `--experimental-config-file=${fixtures.path('rc/string.json')}`,
     fixtures.path('rc/test.js'),
   ]);
   assert.strictEqual(result.stderr, '');
@@ -249,8 +231,7 @@ test('host port flag should be parsed correctly', onlyWithInspectorAndNodeOption
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
     '--expose-internals',
-    '--experimental-config-file',
-    fixtures.path('rc/host-port.json'),
+    `--experimental-config-file=${fixtures.path('rc/host-port.json')}`,
     '-p', 'require("internal/options").getOptionValue("--inspect-port").port',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -261,8 +242,7 @@ test('host port flag should be parsed correctly', onlyWithInspectorAndNodeOption
 test('--inspect=true should be parsed correctly', onlyWithInspectorAndNodeOptions, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/inspect-true.json'),
+    `--experimental-config-file=${fixtures.path('rc/inspect-true.json')}`,
     '--inspect-port', '0',
     '-p', 'require("node:inspector").url()',
   ]);
@@ -274,8 +254,7 @@ test('--inspect=true should be parsed correctly', onlyWithInspectorAndNodeOption
 test('--inspect=false should be parsed correctly', { skip: !process.features.inspector }, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/inspect-false.json'),
+    `--experimental-config-file=${fixtures.path('rc/inspect-false.json')}`,
     '-p', 'require("node:inspector").url()',
   ]);
   assert.strictEqual(result.stderr, '');
@@ -286,8 +265,7 @@ test('--inspect=false should be parsed correctly', { skip: !process.features.ins
 test('no op flag should throw', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/no-op.json'),
+    `--experimental-config-file=${fixtures.path('rc/no-op.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /No-op flag --http-parser is currently not supported/);
@@ -299,8 +277,7 @@ test('no op flag should throw', async () => {
 test('should not allow users to sneak in a flag', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/sneaky-flag.json'),
+    `--experimental-config-file=${fixtures.path('rc/sneaky-flag.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /The number of NODE_OPTIONS doesn't match the number of flags in the config file/);
@@ -311,8 +288,7 @@ test('should not allow users to sneak in a flag', async () => {
 test('non object root', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/non-object-root.json'),
+    `--experimental-config-file=${fixtures.path('rc/non-object-root.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Root value unexpected not an object for/);
@@ -323,8 +299,7 @@ test('non object root', async () => {
 test('non object node options', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/non-object-node-options.json'),
+    `--experimental-config-file=${fixtures.path('rc/non-object-node-options.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /"nodeOptions" value unexpected for/);
@@ -335,8 +310,7 @@ test('non object node options', async () => {
 test('should throw correct error when a json is broken', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/broken.json'),
+    `--experimental-config-file=${fixtures.path('rc/broken.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Can't parse/);
@@ -348,8 +322,7 @@ test('should throw correct error when a json is broken', async () => {
 test('broken value in node_options', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
-    '--experimental-config-file',
-    fixtures.path('rc/broken-node-options.json'),
+    `--experimental-config-file=${fixtures.path('rc/broken-node-options.json')}`,
     '-p', '"Hello, World!"',
   ]);
   assert.match(result.stderr, /Can't parse/);
@@ -371,12 +344,83 @@ test('should use node.config.json as default', onlyIfNodeOptionsSupport, async (
   assert.strictEqual(result.code, 0);
 });
 
-test('should override node.config.json when specificied', onlyIfNodeOptionsSupport, async () => {
+test('should use node.config.json when --experimental-config-file has no argument',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file',
+         '-p', 'http.maxHeaderSize',
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, '10\n');
+       assert.strictEqual(result.code, 0);
+     });
+
+test('should not treat the script path as a config file argument',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file',
+         fixtures.path('printA.js'),
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, 'A\n');
+       assert.strictEqual(result.code, 0);
+     });
+
+test('should treat a space-separated config file path as the script',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file',
+         fixtures.path('rc/empty.json'),
+         fixtures.path('printA.js'),
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.strictEqual(result.stdout, '');
+       assert.match(result.stderr, /SyntaxError/);
+       assert.match(result.stderr, /Unexpected end of JSON input/);
+       assert.doesNotMatch(result.stderr, /Can't parse/);
+       assert.doesNotMatch(result.stderr, /requires an argument/);
+       assert.strictEqual(result.code, 1);
+     });
+
+test('should error when --experimental-config-file= has empty argument',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file=',
+         '-p', 'http.maxHeaderSize',
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.match(result.stderr, /--experimental-config-file= requires an argument/);
+       assert.strictEqual(result.code, 9);
+     });
+
+test('should error when --experimental-default-config-file has an explicit argument',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-default-config-file=node.config.json',
+         '-p', 'http.maxHeaderSize',
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.match(result.stderr, /--experimental-default-config-file does not take an argument/);
+       assert.strictEqual(result.code, 9);
+     });
+
+test('should override node.config.json when specified', onlyIfNodeOptionsSupport, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
     '--experimental-default-config-file',
-    '--experimental-config-file',
-    fixtures.path('rc/default/override.json'),
+    `--experimental-config-file=${fixtures.path('rc/default/override.json')}`,
     '-p', 'http.maxHeaderSize',
   ], {
     cwd: fixtures.path('rc/default'),
@@ -385,6 +429,46 @@ test('should override node.config.json when specificied', onlyIfNodeOptionsSuppo
   assert.strictEqual(result.stdout, '20\n');
   assert.strictEqual(result.code, 0);
 });
+
+test('should work with --experimental-config-file=path',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         `--experimental-config-file=${fixtures.path('rc/default/node.config.json')}`,
+         '-p', 'http.maxHeaderSize',
+       ]);
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, '10\n');
+       assert.strictEqual(result.code, 0);
+     });
+
+test('should use last config file when multiple are specified',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         `--experimental-config-file=${fixtures.path('rc/default/node.config.json')}`,
+         `--experimental-config-file=${fixtures.path('rc/default/override.json')}`,
+         '-p', 'http.maxHeaderSize',
+       ]);
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, '20\n');
+       assert.strictEqual(result.code, 0);
+     });
+
+test('should use default when next argument starts with dash',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file',
+         '-p', 'http.maxHeaderSize',
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, '10\n');
+       assert.strictEqual(result.code, 0);
+     });
+
 // Skip on windows because it doesn't support chmod changing read permissions
 // Also skip if user is root because it would have read permissions anyway
 test('should throw an error when the file is non readable', {
@@ -413,8 +497,7 @@ describe('namespace-scoped options', () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
       '--expose-internals',
-      '--experimental-config-file',
-      fixtures.path('rc/namespaced/node.config.json'),
+      `--experimental-config-file=${fixtures.path('rc/namespaced/node.config.json')}`,
       '-p', 'require("internal/options").getOptionValue("--test-isolation")',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -425,8 +508,7 @@ describe('namespace-scoped options', () => {
   it('should throw an error when a namespace-scoped option is not recognised', async () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
-      '--experimental-config-file',
-      fixtures.path('rc/unknown-flag-namespace.json'),
+      `--experimental-config-file=${fixtures.path('rc/unknown-flag-namespace.json')}`,
       '-p', '"Hello, World!"',
     ]);
     assert.match(result.stderr, /Unknown or not allowed option unknown-flag for namespace test/);
@@ -437,8 +519,7 @@ describe('namespace-scoped options', () => {
   it('should not throw an error when a namespace is not recognised', async () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
-      '--experimental-config-file',
-      fixtures.path('rc/unknown-namespace.json'),
+      `--experimental-config-file=${fixtures.path('rc/unknown-namespace.json')}`,
       '-p', '"Hello, World!"',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -449,8 +530,7 @@ describe('namespace-scoped options', () => {
   it('should handle an empty namespace valid namespace', async () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
-      '--experimental-config-file',
-      fixtures.path('rc/empty-valid-namespace.json'),
+      `--experimental-config-file=${fixtures.path('rc/empty-valid-namespace.json')}`,
       '-p', '"Hello, World!"',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -462,8 +542,7 @@ describe('namespace-scoped options', () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
       '--expose-internals',
-      '--experimental-config-file',
-      fixtures.path('rc/override-node-option-with-namespace.json'),
+      `--experimental-config-file=${fixtures.path('rc/override-node-option-with-namespace.json')}`,
       '-p', 'require("internal/options").getOptionValue("--test-isolation")',
     ]);
     assert.match(result.stderr, /Option --test-isolation is already defined/);
@@ -475,8 +554,7 @@ describe('namespace-scoped options', () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
       '--expose-internals',
-      '--experimental-config-file',
-      fixtures.path('rc/override-namespace.json'),
+      `--experimental-config-file=${fixtures.path('rc/override-namespace.json')}`,
       '-p', 'require("internal/options").getOptionValue("--test-isolation")',
     ]);
     assert.match(result.stderr, /Option --test-isolation is already defined/);
@@ -489,8 +567,7 @@ describe('namespace-scoped options', () => {
       '--no-warnings',
       '--expose-internals',
       '--test-isolation', 'process',
-      '--experimental-config-file',
-      fixtures.path('rc/namespaced/node.config.json'),
+      `--experimental-config-file=${fixtures.path('rc/namespaced/node.config.json')}`,
       '-p', 'require("internal/options").getOptionValue("--test-isolation")',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -504,8 +581,7 @@ describe('namespace-scoped options', () => {
       '--expose-internals',
       '--test-coverage-exclude', 'cli-pattern1',
       '--test-coverage-exclude', 'cli-pattern2',
-      '--experimental-config-file',
-      fixtures.path('rc/namespace-with-array.json'),
+      `--experimental-config-file=${fixtures.path('rc/namespace-with-array.json')}`,
       '-p', 'JSON.stringify(require("internal/options").getOptionValue("--test-coverage-exclude"))',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -526,8 +602,7 @@ describe('namespace-scoped options', () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
       '--expose-internals',
-      '--experimental-config-file',
-      fixtures.path('rc/namespace-with-disallowed-envvar.json'),
+      `--experimental-config-file=${fixtures.path('rc/namespace-with-disallowed-envvar.json')}`,
       '-p', 'require("internal/options").getOptionValue("--test-concurrency")',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -542,8 +617,7 @@ describe('namespace-scoped options', () => {
       '--no-warnings',
       '--expose-internals',
       '--test-concurrency', '2',
-      '--experimental-config-file',
-      fixtures.path('rc/namespace-with-disallowed-envvar.json'),
+      `--experimental-config-file=${fixtures.path('rc/namespace-with-disallowed-envvar.json')}`,
       '-p', 'require("internal/options").getOptionValue("--test-concurrency")',
     ]);
     assert.strictEqual(result.stderr, '');
@@ -551,15 +625,4 @@ describe('namespace-scoped options', () => {
     assert.strictEqual(result.code, 0);
   });
 
-  it('should throw an error for removed "testRunner" namespace', async () => {
-    const result = await spawnPromisified(process.execPath, [
-      '--no-warnings',
-      '--experimental-config-file',
-      fixtures.path('rc/deprecated-testrunner-namespace.json'),
-      '-p', '"Hello, World!"',
-    ]);
-    assert.match(result.stderr, /the "testRunner" namespace has been removed\. Use "test" instead\./);
-    assert.strictEqual(result.stdout, '');
-    assert.strictEqual(result.code, 9);
-  });
 });
diff --git a/test/parallel/test-permission-config-file.mjs b/test/parallel/test-permission-config-file.mjs
index bb67e27bb2dd7b..b6eaf2e60ba646 100644
--- a/test/parallel/test-permission-config-file.mjs
+++ b/test/parallel/test-permission-config-file.mjs
@@ -13,8 +13,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        readOnlyConfigPath,
+        `--experimental-config-file=${readOnlyConfigPath}`,
         readTestPath,
       ]);
       assert.strictEqual(result.code, 0);
@@ -23,8 +22,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        readWriteConfigPath,
+        `--experimental-config-file=${readWriteConfigPath}`,
         writeTestPath,
       ]);
       assert.strictEqual(result.code, 0);
@@ -33,8 +31,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        readOnlyConfigPath,
+        `--experimental-config-file=${readOnlyConfigPath}`,
         writeTestPath,
       ]);
       assert.strictEqual(result.code, 1);
@@ -50,8 +47,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        configPath,
+        `--experimental-config-file=${configPath}`,
         childTestPath,
       ]);
       assert.strictEqual(result.code, 0);
@@ -60,8 +56,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        readOnlyConfigPath,
+        `--experimental-config-file=${readOnlyConfigPath}`,
         childTestPath,
       ]);
       assert.strictEqual(result.code, 1, result.stderr);
@@ -76,8 +71,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        configPath,
+        `--experimental-config-file=${configPath}`,
         '-p',
         'process.permission.has("wasi") && process.permission.has("inspector")',
       ]);
@@ -88,8 +82,7 @@ describe('Permission model config file support', () => {
     {
       const result = await spawnPromisified(process.execPath, [
         '--permission',
-        '--experimental-config-file',
-        readOnlyConfigPath,
+        `--experimental-config-file=${readOnlyConfigPath}`,
         '-p',
         'process.permission.has("wasi") + process.permission.has("inspector")',
       ]);
@@ -103,8 +96,7 @@ describe('Permission model config file support', () => {
 
     const result = await spawnPromisified(process.execPath, [
       '--permission',
-      '--experimental-config-file',
-      configPath,
+      `--experimental-config-file=${configPath}`,
       '--allow-fs-read=*',
       '-p',
       'process.permission.has("addon") && process.permission.has("wasi")',
@@ -118,8 +110,7 @@ describe('Permission model config file support', () => {
 
     const result = await spawnPromisified(process.execPath, [
       '--permission',
-      '--experimental-config-file',
-      configPath,
+      `--experimental-config-file=${configPath}`,
       '--allow-child-process',
       '--allow-fs-write=*',
       '-p',
diff --git a/test/parallel/test-runner-cli.js b/test/parallel/test-runner-cli.js
index 287e97861c9285..2a8abf8f86a277 100644
--- a/test/parallel/test-runner-cli.js
+++ b/test/parallel/test-runner-cli.js
@@ -431,30 +431,37 @@ for (const isolation of ['none', 'process']) {
 }
 
 {
-  // Should not propagate --experimental-config-file option to sub test in isolation process
+  // Should not propagate config file options to sub tests in isolation process.
   const fixturePath = join(testFixtures, 'options-propagation');
-  const args = [
-    '--test-reporter=tap',
-    '--no-warnings',
-    `--experimental-config-file=node.config.json`,
-    '--expose-internals',
-    '--test',
+  const configFlagVariants = [
+    ['--experimental-config-file=node.config.json'],
+    ['--experimental-config-file'],
+    ['--experimental-default-config-file'],
   ];
-  const child = spawnSync(process.execPath, args, { cwd: fixturePath });
 
-  assert.strictEqual(child.stderr.toString(), '');
-  const stdout = child.stdout.toString();
+  for (const configArgs of configFlagVariants) {
+    const args = [
+      '--test-reporter=tap',
+      '--no-warnings',
+      ...configArgs,
+      '--expose-internals',
+      '--test',
+    ];
+    const child = spawnSync(process.execPath, args, { cwd: fixturePath });
 
-  assert.match(stdout, /tests 1/);
-  assert.match(stdout, /suites 0/);
-  assert.match(stdout, /pass 1/);
-  assert.match(stdout, /fail 0/);
-  assert.match(stdout, /cancelled 0/);
-  assert.match(stdout, /skipped 0/);
-  assert.match(stdout, /todo 0/);
+    assert.strictEqual(child.stderr.toString(), '');
+    const stdout = child.stdout.toString();
 
+    assert.match(stdout, /tests 1/);
+    assert.match(stdout, /suites 0/);
+    assert.match(stdout, /pass 1/);
+    assert.match(stdout, /fail 0/);
+    assert.match(stdout, /cancelled 0/);
+    assert.match(stdout, /skipped 0/);
+    assert.match(stdout, /todo 0/);
 
-  assert.strictEqual(child.status, 0);
+    assert.strictEqual(child.status, 0);
+  }
 }
 
 {
diff --git a/test/parallel/test-runner-flag-propagation.js b/test/parallel/test-runner-flag-propagation.js
index f4e9849cce77d0..055d8b6d67c9b5 100644
--- a/test/parallel/test-runner-flag-propagation.js
+++ b/test/parallel/test-runner-flag-propagation.js
@@ -15,8 +15,10 @@ const runner = path.join(fixtureDir, 'runner.mjs');
 describe('test runner flag propagation', () => {
   describe('via command line', () => {
     const flagPropagationTests = [
-      ['--experimental-config-file', 'node.config.json', ''],
-      ['--experimental-default-config-file', '', false],
+      ['--experimental-config-file=node.config.json', '', '', '--experimental-config-file',
+       'should not propagate --experimental-config-file to child tests'],
+      ['--experimental-default-config-file', '', '', '--experimental-config-file',
+       'should not propagate --experimental-default-config-file to child tests'],
       ['--env-file', '.env', '.env'],
       ['--env-file-if-exists', '.env', '.env'],
       ['--test-concurrency', '2', '2'],
@@ -32,8 +34,11 @@ describe('test runner flag propagation', () => {
       ['--require', './index.js', './index.js'],
     ];
 
-    for (const [flagName, testValue, expectedValue] of flagPropagationTests) {
-      const testDescription = `should propagate ${flagName} to child tests as expected`;
+    for (const [flagName,
+                testValue,
+                expectedValue,
+                propagatedFlag = flagName,
+                testDescription = `should propagate ${flagName} to child tests as expected`] of flagPropagationTests) {
 
       it(testDescription, () => {
         const args = [
@@ -45,7 +50,7 @@ describe('test runner flag propagation', () => {
           // Use the runner fixture
           runner,
           // Pass parameters to the fixture
-          `--flag=${flagName}`,
+          `--flag=${propagatedFlag}`,
           `--expected=${expectedValue}`,
           `--description="${testDescription}"`,
         ].filter(Boolean);
diff --git a/test/sequential/test-watch-mode.mjs b/test/sequential/test-watch-mode.mjs
index 39ad7ef72ada00..707210a021f944 100644
--- a/test/sequential/test-watch-mode.mjs
+++ b/test/sequential/test-watch-mode.mjs
@@ -826,7 +826,7 @@ process.on('message', (message) => {
     const file = createTmpFile();
     const configFile = createTmpFile(JSON.stringify({ watch: { 'watch': true } }), '.json');
     const { stderr, stdout } = await runWriteSucceed({
-      file, watchedFile: file, args: ['--experimental-config-file', configFile, file], options: {
+      file, watchedFile: file, args: [`--experimental-config-file=${configFile}`, file], options: {
         timeout: 10000,
       },
     });
@@ -850,7 +850,7 @@ process.on('message', (message) => {
     const watchedFile = createTmpFile('', '.js', dir);
     const configFile = createTmpFile(JSON.stringify({ watch: { 'watch-path': [dir] } }), '.json', dir);
 
-    const args = ['--experimental-config-file', configFile, file];
+    const args = [`--experimental-config-file=${configFile}`, file];
     const { stderr, stdout } = await runWriteSucceed({ file, watchedFile, args });
 
     assert.strictEqual(stderr, '');