From de4c8cbe45eb05c58ea2765d65a9b7bdf991d415 Mon Sep 17 00:00:00 2001
From: Pietro Marchini <pietro.marchini94@gmail.com>
Date: Fri, 13 Feb 2026 15:24:13 +0100
Subject: [PATCH] test_runner: support runner bailout at files level

---
 doc/api/cli.md                                |  16 ++
 doc/api/test.md                               |  36 +++++
 doc/node-config-schema.json                   |   3 +
 doc/node.1                                    |   9 ++
 lib/internal/test_runner/harness.js           |   2 +
 lib/internal/test_runner/reporter/spec.js     |   6 +-
 lib/internal/test_runner/reporter/utils.js    |   4 +
 lib/internal/test_runner/runner.js            |  80 ++++++++--
 lib/internal/test_runner/test.js              |  12 +-
 lib/internal/test_runner/tests_stream.js      |   9 ++
 lib/internal/test_runner/utils.js             |   2 +
 src/node_options.cc                           |   6 +
 src/node_options.h                            |   1 +
 .../test-runner/bail/bail-test-1-pass.js      |  12 ++
 .../test-runner/bail/bail-test-2-fail.js      |  11 ++
 .../test-runner/bail/bail-test-3-pass.js      |  10 ++
 .../test-runner/bail/bail-test-4-pass.js      |   6 +
 .../test-runner/output/bail_concurrency_1.js  |  13 ++
 .../output/bail_concurrency_1.snapshot        |  55 +++++++
 .../bail_concurrency_1_isolation_none.js      |  13 ++
 ...bail_concurrency_1_isolation_none.snapshot |  39 +++++
 test/parallel/test-runner-bail.js             | 137 ++++++++++++++++++
 .../test-runner-run-bail-isolation-none.mjs   |  55 +++++++
 test/parallel/test-runner-run-bail.mjs        |  73 ++++++++++
 ...tput-bail-spec-reporter-isolation-none.mjs |  10 ++
 .../test-output-bail-spec-reporter.mjs        |  10 ++
 26 files changed, 617 insertions(+), 13 deletions(-)
 create mode 100644 test/fixtures/test-runner/bail/bail-test-1-pass.js
 create mode 100644 test/fixtures/test-runner/bail/bail-test-2-fail.js
 create mode 100644 test/fixtures/test-runner/bail/bail-test-3-pass.js
 create mode 100644 test/fixtures/test-runner/bail/bail-test-4-pass.js
 create mode 100644 test/fixtures/test-runner/output/bail_concurrency_1.js
 create mode 100644 test/fixtures/test-runner/output/bail_concurrency_1.snapshot
 create mode 100644 test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.js
 create mode 100644 test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.snapshot
 create mode 100644 test/parallel/test-runner-bail.js
 create mode 100644 test/parallel/test-runner-run-bail-isolation-none.mjs
 create mode 100644 test/parallel/test-runner-run-bail.mjs
 create mode 100644 test/test-runner/test-output-bail-spec-reporter-isolation-none.mjs
 create mode 100644 test/test-runner/test-output-bail-spec-reporter.mjs

diff --git a/doc/api/cli.md b/doc/api/cli.md
index 52e9cf6cb8615c..40a42864fba80a 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -2614,6 +2614,21 @@ Starts the Node.js command line test runner. This flag cannot be combined with
 See the documentation on [running tests from the command line][]
 for more details.
 
+### `--test-bail`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1.0 - Early development
+
+Stops the test runner after the first test failure.
+
+Behavior depends on `--test-isolation`.
+See the [test runner execution model][] section for details.
+
+This flag cannot be combined with `--watch`.
+
 ### `--test-concurrency`
 
 <!-- YAML
@@ -3679,6 +3694,7 @@ one is included in the list below.
 * `--secure-heap-min`
 * `--secure-heap`
 * `--snapshot-blob`
+* `--test-bail`
 * `--test-coverage-branches`
 * `--test-coverage-exclude`
 * `--test-coverage-functions`
diff --git a/doc/api/test.md b/doc/api/test.md
index b12e6c9212af3b..a2b442c803b084 100644
--- a/doc/api/test.md
+++ b/doc/api/test.md
@@ -611,6 +611,16 @@ each other in ways that are not possible when isolation is enabled. For example,
 if a test relies on global state, it is possible for that state to be modified
 by a test originating from another file.
 
+When bail is enabled (via [`--test-bail`][] or `run({ bail: true })`),
+isolation mode changes how execution stops:
+
+* In `'process'` isolation, no new test files are started after the first
+  failure, and test files that have already started are not forcibly
+  terminated. Within already-started files, tests that have not started yet
+  may still be aborted by bailout.
+* In `'none'` isolation, no new tests are started and queued tests are
+  cancelled.
+
 #### Child process option inheritance
 
 When running tests in process isolation mode (the default), spawned child processes
@@ -1505,6 +1515,15 @@ changes:
   * `argv` {Array} An array of CLI flags to pass to each test file when spawning the
     subprocesses. This option has no effect when `isolation` is `'none'`.
     **Default:** `[]`.
+  * `bail` {boolean} Stops the test run after the first failure.
+    If `isolation` is `'process'`, no new test files are started after the
+    first failure, and files that have already started are not forcibly
+    terminated. Within already-started files, tests that have not started yet
+    may still be aborted by bailout.
+    If `isolation` is `'none'`, no new tests are started and queued tests are
+    cancelled.
+    This option cannot be used together with `watch`.
+    **Default:** `false`.
   * `signal` {AbortSignal} Allows aborting an in-progress test execution.
   * `testNamePatterns` {string|RegExp|Array} A String, RegExp or a RegExp Array,
     that can be used to only run tests whose name matches the provided pattern.
@@ -3232,6 +3251,22 @@ are defined, while others are emitted in the order that the tests execute.
 
 Emitted when code coverage is enabled and all tests have completed.
 
+### Event: `'test:bail'`
+
+* `data` {Object}
+  * `column` {number|undefined} The column number where the bailout originated,
+    or `undefined` if it was run through the REPL.
+  * `file` {string|undefined} The path of the test file, `undefined` if test
+    was run through the REPL.
+  * `line` {number|undefined} The line number where the bailout originated, or
+    `undefined` if it was run through the REPL.
+  * `nesting` {number} The nesting level of the test.
+  * `test` {string} The bailout message.
+
+Emitted when bail is enabled and the first failure triggers bailout behavior.
+In `'process'` isolation this means no new test files are started, while in
+`'none'` isolation no new tests are started and queued tests are cancelled.
+
 ### Event: `'test:complete'`
 
 * `data` {Object}
@@ -4096,6 +4131,7 @@ Can be used to abort test subtasks when the test has been aborted.
 [`--experimental-test-module-mocks`]: cli.md#--experimental-test-module-mocks
 [`--import`]: cli.md#--importmodule
 [`--no-strip-types`]: cli.md#--no-strip-types
+[`--test-bail`]: cli.md#--test-bail
 [`--test-concurrency`]: cli.md#--test-concurrency
 [`--test-coverage-exclude`]: cli.md#--test-coverage-exclude
 [`--test-coverage-include`]: cli.md#--test-coverage-include
diff --git a/doc/node-config-schema.json b/doc/node-config-schema.json
index 22f52952af54d4..9a79ebdae2f9bc 100644
--- a/doc/node-config-schema.json
+++ b/doc/node-config-schema.json
@@ -671,6 +671,9 @@
         "test": {
           "type": "boolean"
         },
+        "test-bail": {
+          "type": "boolean"
+        },
         "test-concurrency": {
           "type": "number"
         },
diff --git a/doc/node.1 b/doc/node.1
index c97004d48f6a4a..2b1ee50a6587c1 100644
--- a/doc/node.1
+++ b/doc/node.1
@@ -471,6 +471,15 @@ Specify the minimum allocation from the OpenSSL secure heap. The default is 2. T
 .It Fl -test
 Starts the Node.js command line test runner.
 .
+.It Fl -test-bail
+Stops the test runner after the first test failure.
+This option is in early development.
+Behavior depends on the selected
+.Fl -test-isolation
+mode.
+This flag cannot be combined with
+.Fl -watch .
+.
 .It Fl -test-concurrency
 The maximum number of test files that the test runner CLI will execute
 concurrently.
diff --git a/lib/internal/test_runner/harness.js b/lib/internal/test_runner/harness.js
index 6b3b13b2c88d65..ecdbd1d41608c6 100644
--- a/lib/internal/test_runner/harness.js
+++ b/lib/internal/test_runner/harness.js
@@ -52,6 +52,8 @@ function createTestTree(rootTestOptions, globalOptions) {
     buildSuites: [],
     isWaitingForBuildPhase: false,
     watching: false,
+    bail: globalOptions.bail,
+    bailedOut: false,
     config: globalOptions,
     coverage: null,
     resetCounters() {
diff --git a/lib/internal/test_runner/reporter/spec.js b/lib/internal/test_runner/reporter/spec.js
index 14c447f316492f..572271bceac32a 100644
--- a/lib/internal/test_runner/reporter/spec.js
+++ b/lib/internal/test_runner/reporter/spec.js
@@ -11,7 +11,7 @@ const {
 const assert = require('assert');
 const Transform = require('internal/streams/transform');
 const colors = require('internal/util/colors');
-const { kSubtestsFailed } = require('internal/test_runner/test');
+const { kSubtestsFailed, kBailedOut } = require('internal/test_runner/test');
 const { getCoverageReport } = require('internal/test_runner/utils');
 const { relative } = require('path');
 const {
@@ -78,8 +78,10 @@ class SpecReporter extends Transform {
   }
   #handleEvent({ type, data }) {
     switch (type) {
+      case 'test:bail':
+        return `${reporterColorMap['test:bail']}${reporterUnicodeSymbolMap[type]}Bailing out!${colors.white}\n`;
       case 'test:fail':
-        if (data.details?.error?.failureType !== kSubtestsFailed) {
+        if (data.details?.error?.failureType !== kSubtestsFailed && data.details?.error?.failureType !== kBailedOut) {
           ArrayPrototypePush(this.#failedTests, data);
         }
         return this.#handleTestReportEvent(type, data);
diff --git a/lib/internal/test_runner/reporter/utils.js b/lib/internal/test_runner/reporter/utils.js
index 26e4a2d1a5c36c..f152028f1dcb57 100644
--- a/lib/internal/test_runner/reporter/utils.js
+++ b/lib/internal/test_runner/reporter/utils.js
@@ -24,6 +24,7 @@ const reporterUnicodeSymbolMap = {
   'test:coverage': '\u2139 ',
   'arrow:right': '\u25B6 ',
   'hyphen:minus': '\uFE63 ',
+  'test:bail': '\u26A0 ',
 };
 
 const reporterColorMap = {
@@ -37,6 +38,9 @@ const reporterColorMap = {
   get 'test:diagnostic'() {
     return colors.blue;
   },
+  get 'test:bail'() {
+    return colors.yellow;
+  },
   get 'info'() {
     return colors.blue;
   },
diff --git a/lib/internal/test_runner/runner.js b/lib/internal/test_runner/runner.js
index a9b3cfb93c8abb..6f29c68a2c2145 100644
--- a/lib/internal/test_runner/runner.js
+++ b/lib/internal/test_runner/runner.js
@@ -22,6 +22,8 @@ const {
   SafePromiseAll,
   SafePromiseAllReturnVoid,
   SafePromiseAllSettledReturnVoid,
+  SafePromisePrototypeFinally,
+  SafePromiseRace,
   SafeSet,
   StringPrototypeIndexOf,
   StringPrototypeSlice,
@@ -147,6 +149,7 @@ function getRunArgs(path, { forceExit,
                             testNamePatterns,
                             testSkipPatterns,
                             only,
+                            bail,
                             argv: suppliedArgs,
                             execArgv,
                             rerunFailuresFilePath,
@@ -185,6 +188,9 @@ function getRunArgs(path, { forceExit,
   if (only === true) {
     ArrayPrototypePush(runArgs, '--test-only');
   }
+  if (bail === true) {
+    ArrayPrototypePush(runArgs, '--test-bail');
+  }
   if (timeout != null) {
     ArrayPrototypePush(runArgs, `--test-timeout=${timeout}`);
   }
@@ -271,9 +277,13 @@ class FileTest extends Test {
     this.reporter[kEmitMessage](item.type, item.data);
   }
   #accumulateReportItem(item) {
-    if (item.type !== 'test:pass' && item.type !== 'test:fail') {
+    if (item.type !== 'test:pass' && item.type !== 'test:fail' && item.type !== 'test:bail') {
       return;
     }
+    // If a test failure occurred and bail is enabled, emit a bail event after reporting the failure
+    if (item.type === 'test:bail' && this.root.harness?.bail && !this.root.harness.bailedOut) {
+      this.root.harness.bailedOut = true;
+    }
     this.#reportedChildren++;
     if (item.data.nesting === 0 && item.type === 'test:fail') {
       this.failedSubtests = true;
@@ -604,6 +614,7 @@ function run(options = kEmptyObject) {
   } = options;
   const {
     concurrency,
+    bail,
     timeout,
     signal,
     files,
@@ -747,7 +758,9 @@ function run(options = kEmptyObject) {
     functionCoverage: functionCoverage,
     cwd,
     globalSetupPath,
+    bail,
   };
+  
   const root = createTestTree(rootTestOptions, globalOptions);
   let testFiles = files ?? createTestFileList(globPatterns, cwd);
   const { isTestRunner } = globalOptions;
@@ -756,10 +769,18 @@ function run(options = kEmptyObject) {
     testFiles = ArrayPrototypeFilter(testFiles, (_, index) => index % shard.total === shard.index - 1);
   }
 
+  if (bail) {
+    validateBoolean(bail, 'options.bail');
+    if (watch) {
+      throw new ERR_INVALID_ARG_VALUE('options.bail', watch, 'bail not supported with watch mode');
+    }
+  }
+
   let teardown;
   let postRun;
   let filesWatcher;
   let runFiles;
+
   const opts = {
     __proto__: null,
     root,
@@ -770,6 +791,7 @@ function run(options = kEmptyObject) {
     hasFiles: files != null,
     globPatterns,
     only,
+    bail,
     forceExit,
     cwd,
     isolation,
@@ -792,15 +814,53 @@ function run(options = kEmptyObject) {
       teardown = () => root.harness.teardown();
     }
 
-    runFiles = () => {
-      root.harness.bootstrapPromise = null;
-      root.harness.buildPromise = null;
-      return SafePromiseAllSettledReturnVoid(testFiles, (path) => {
-        const subtest = runTestFile(path, filesWatcher, opts);
-        filesWatcher?.runningSubtests.set(path, subtest);
-        return subtest;
-      });
-    };
+    if (bail) {
+      runFiles = async () => {
+        root.harness.bootstrapPromise = null;
+        root.harness.buildPromise = null;
+
+        const running = new SafeSet();
+        let index = 0;
+
+        const shouldBail = () => bail && root.harness.bailedOut;
+
+        const enqueueNext = () => {
+          if (index < testFiles.length && !shouldBail()) {
+            const path = testFiles[index++];
+            const subtest = runTestFile(path, filesWatcher, opts);
+            filesWatcher?.runningSubtests.set(path, subtest);
+            running.add(subtest);
+            SafePromisePrototypeFinally(subtest, () => running.delete(subtest));
+          }
+        };
+
+        // Fill initial pool up to root test concurrency
+        // We use root test concurrency here because concurrency logic is handled at test level.
+        while (running.size < root.concurrency && index < testFiles.length && !shouldBail()) {
+          enqueueNext();
+        }
+
+        // As each test completes, enqueue the next one
+        while (running.size > 0) {
+          await SafePromiseRace([...running]);
+
+          // Refill pool after completion(s)
+          while (running.size < root.concurrency && index < testFiles.length && !shouldBail()) {
+            enqueueNext();
+          }
+        }
+      };
+    } else {
+      runFiles = () => {
+        root.harness.bootstrapPromise = null;
+        root.harness.buildPromise = null;
+        return SafePromiseAllSettledReturnVoid(testFiles, (path) => {
+          const subtest = runTestFile(path, filesWatcher, opts);
+          filesWatcher?.runningSubtests.set(path, subtest);
+          return subtest;
+        });
+      };
+    }
   } else if (isolation === 'none') {
     if (watch) {
       const absoluteTestFiles = ArrayPrototypeMap(testFiles, (file) => (isAbsolute(file) ? file : resolve(cwd, file)));
diff --git a/lib/internal/test_runner/test.js b/lib/internal/test_runner/test.js
index e426438faba75f..bc43e2c0a125c0 100644
--- a/lib/internal/test_runner/test.js
+++ b/lib/internal/test_runner/test.js
@@ -78,6 +78,7 @@ const { bigint: hrtime } = process.hrtime;
 const kCallbackAndPromisePresent = 'callbackAndPromisePresent';
 const kCancelledByParent = 'cancelledByParent';
 const kAborted = 'testAborted';
+const kBailedOut = 'bailedOut';
 const kParentAlreadyFinished = 'parentAlreadyFinished';
 const kSubtestsFailed = 'subtestsFailed';
 const kTestCodeFailure = 'testCodeFailure';
@@ -580,7 +581,7 @@ class Test extends AsyncResource {
       }
     }
 
-    switch (typeof concurrency) {
+    switch (typeof concurrency) { // <-- here we are overriding this.concurrency with the value from options!
       case 'number':
         validateUint32(concurrency, 'options.concurrency', true);
         this.concurrency = concurrency;
@@ -780,6 +781,10 @@ class Test extends AsyncResource {
    */
   async processPendingSubtests() {
     while (this.pendingSubtests.length > 0 && this.hasConcurrency()) {
+      if (this.root.harness?.bailedOut) {
+        queueMicrotask( () => this.postRun(new ERR_TEST_FAILURE("Test was aborted due to bailout", kBailedOut)));
+        break;
+      }
       const deferred = ArrayPrototypeShift(this.pendingSubtests);
       const test = deferred.test;
       test.reporter.dequeue(test.nesting, test.loc, test.name, this.reportedType);
@@ -1382,6 +1387,10 @@ class Test extends AsyncResource {
       this.reporter.ok(this.nesting, this.loc, this.testNumber, this.name, report.details, report.directive);
     } else {
       this.reporter.fail(this.nesting, this.loc, this.testNumber, this.name, report.details, report.directive);
+      if (this.root.harness?.bail && !this.root.harness.bailedOut) {
+        this.reporter.bail(this.nesting, this.loc, 'bailing out due to test failure');
+        this.root.harness.bailedOut = true;
+      }
     }
 
     for (let i = 0; i < this.diagnostics.length; i++) {
@@ -1558,6 +1567,7 @@ module.exports = {
   kTestCodeFailure,
   kTestTimeoutFailure,
   kAborted,
+  kBailedOut,
   kUnwrapErrors,
   Suite,
   Test,
diff --git a/lib/internal/test_runner/tests_stream.js b/lib/internal/test_runner/tests_stream.js
index 7b64487696f53f..cc33cb4afd7c79 100644
--- a/lib/internal/test_runner/tests_stream.js
+++ b/lib/internal/test_runner/tests_stream.js
@@ -149,6 +149,15 @@ class TestsStream extends Readable {
     });
   }
 
+  bail(nesting, loc, test) {
+    this[kEmitMessage]('test:bail', {
+      __proto__: null,
+      nesting,
+      test,
+      ...loc,
+    });
+  }
+
   end() {
     this.#tryPush(null);
   }
diff --git a/lib/internal/test_runner/utils.js b/lib/internal/test_runner/utils.js
index 5b53342933cdcb..58d584f7d905e1 100644
--- a/lib/internal/test_runner/utils.js
+++ b/lib/internal/test_runner/utils.js
@@ -211,6 +211,7 @@ function parseCommandLine() {
   }
 
   const isTestRunner = getOptionValue('--test');
+  const bail = getOptionValue('--test-bail');
   const coverage = getOptionValue('--experimental-test-coverage');
   const forceExit = getOptionValue('--test-force-exit');
   const sourceMaps = getOptionValue('--enable-source-maps');
@@ -341,6 +342,7 @@ function parseCommandLine() {
   globalTestOptions = {
     __proto__: null,
     isTestRunner,
+    bail,
     concurrency,
     coverage,
     coverageExcludeGlobs,
diff --git a/src/node_options.cc b/src/node_options.cc
index 54c6c17c3d007d..e5e823ab21e1d9 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -861,6 +861,12 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             kDisallowedInEnvvar,
             false,
             OptionNamespaces::kTestRunnerNamespace);
+  AddOption("--test-bail",
+            "abort test execution after first failure",
+            &EnvironmentOptions::test_runner_bail,
+            kDisallowedInEnvvar,
+            false,
+            OptionNamespaces::kTestRunnerNamespace);
   AddOption("--test-concurrency",
             "specify test runner concurrency",
             &EnvironmentOptions::test_runner_concurrency,
diff --git a/src/node_options.h b/src/node_options.h
index 25bd23c72f9e3b..cd0b0089ea15b0 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -190,6 +190,7 @@ class EnvironmentOptions : public Options {
   std::vector<std::string> optional_env_file;
   bool has_env_file_string = false;
   bool test_runner = false;
+  bool test_runner_bail = false;
   uint64_t test_runner_concurrency = 0;
   uint64_t test_runner_timeout = 0;
   bool test_runner_coverage = false;
diff --git a/test/fixtures/test-runner/bail/bail-test-1-pass.js b/test/fixtures/test-runner/bail/bail-test-1-pass.js
new file mode 100644
index 00000000000000..f359d8045e8fed
--- /dev/null
+++ b/test/fixtures/test-runner/bail/bail-test-1-pass.js
@@ -0,0 +1,12 @@
+'use strict';
+const { test } = require('node:test');
+const { setTimeout } = require('timers/promises');
+
+test('test 1 passes', async () => {
+  // This should pass
+  await setTimeout(500);
+});
+
+test('test 2 passes', () => {
+  // This should pass
+});
diff --git a/test/fixtures/test-runner/bail/bail-test-2-fail.js b/test/fixtures/test-runner/bail/bail-test-2-fail.js
new file mode 100644
index 00000000000000..ca18420309df5e
--- /dev/null
+++ b/test/fixtures/test-runner/bail/bail-test-2-fail.js
@@ -0,0 +1,11 @@
+'use strict';
+const { test } = require('node:test');
+const assert = require('assert');
+
+test('failing test 1', () => {
+  assert.strictEqual(1, 2, 'This test should fail');
+});
+
+test('failing test 2', () => {
+  assert.strictEqual(3, 4, 'This test fails as well');
+});
diff --git a/test/fixtures/test-runner/bail/bail-test-3-pass.js b/test/fixtures/test-runner/bail/bail-test-3-pass.js
new file mode 100644
index 00000000000000..b1abf5cb975e85
--- /dev/null
+++ b/test/fixtures/test-runner/bail/bail-test-3-pass.js
@@ -0,0 +1,10 @@
+'use strict';
+const { test } = require('node:test');
+
+test('test 3 passes', () => {
+  // This should not run if bail happens in test 2
+});
+
+test('test 4 passes', () => {
+  // This should not run if bail happens in test 2
+});
diff --git a/test/fixtures/test-runner/bail/bail-test-4-pass.js b/test/fixtures/test-runner/bail/bail-test-4-pass.js
new file mode 100644
index 00000000000000..b5a3cbe3fa492b
--- /dev/null
+++ b/test/fixtures/test-runner/bail/bail-test-4-pass.js
@@ -0,0 +1,6 @@
+'use strict';
+const { test } = require('node:test');
+
+test('test 5 passes', () => {
+  // This should not run if bail happens earlier
+});
diff --git a/test/fixtures/test-runner/output/bail_concurrency_1.js b/test/fixtures/test-runner/output/bail_concurrency_1.js
new file mode 100644
index 00000000000000..277abf6f8cef32
--- /dev/null
+++ b/test/fixtures/test-runner/output/bail_concurrency_1.js
@@ -0,0 +1,13 @@
+'use strict';
+const fixtures = require('../../../common/fixtures');
+const { spec } = require('node:test/reporters');
+const { run } = require('node:test');
+
+const files = [
+  fixtures.path('test-runner', 'bail', 'bail-test-1-pass.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-2-fail.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-3-pass.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-4-pass.js'),
+];
+
+run({ bail: true, concurrency: 1, files }).compose(spec).compose(process.stdout);
diff --git a/test/fixtures/test-runner/output/bail_concurrency_1.snapshot b/test/fixtures/test-runner/output/bail_concurrency_1.snapshot
new file mode 100644
index 00000000000000..319c5397794afa
--- /dev/null
+++ b/test/fixtures/test-runner/output/bail_concurrency_1.snapshot
@@ -0,0 +1,55 @@
+✔ test 1 passes (*ms)
+✔ test 2 passes (*ms)
+✖ failing test 1 (*ms)
+Bailing out! no new test files will be started!
+✖ failing test 2 (*ms)
+ℹ tests 4
+ℹ suites 0
+ℹ pass 2
+ℹ fail 2
+ℹ cancelled 0
+ℹ skipped 0
+ℹ todo 0
+ℹ duration_ms *
+
+✖ failing tests:
+
+*
+✖ failing test 1 (*ms)
+  AssertionError [ERR_ASSERTION]: This test should fail
+  
+  1 !== 2
+  
+      *
+      *
+      *
+      *
+      * {
+    generatedMessage: false,
+    code: 'ERR_ASSERTION',
+    actual: 1,
+    expected: 2,
+    operator: 'strictEqual',
+    diff: 'simple'
+  }
+
+*
+✖ failing test 2 (*ms)
+  AssertionError [ERR_ASSERTION]: This test fails as well
+  
+  3 !== 4
+  
+      *
+      *
+      *
+      *
+      *
+      *
+      * {
+    generatedMessage: false,
+    code: 'ERR_ASSERTION',
+    actual: 3,
+    expected: 4,
+    operator: 'strictEqual',
+    diff: 'simple'
+  }
diff --git a/test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.js b/test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.js
new file mode 100644
index 00000000000000..3d3aecc00f85cb
--- /dev/null
+++ b/test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.js
@@ -0,0 +1,13 @@
+'use strict';
+const fixtures = require('../../../common/fixtures');
+const { spec } = require('node:test/reporters');
+const { run } = require('node:test');
+
+const files = [
+  fixtures.path('test-runner', 'bail', 'bail-test-1-pass.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-2-fail.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-3-pass.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-4-pass.js'),
+];
+
+run({ bail: true, concurrency: 1, isolation: 'none', files }).compose(spec).compose(process.stdout);
diff --git a/test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.snapshot b/test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.snapshot
new file mode 100644
index 00000000000000..26e338227a87e8
--- /dev/null
+++ b/test/fixtures/test-runner/output/bail_concurrency_1_isolation_none.snapshot
@@ -0,0 +1,39 @@
+✔ test 1 passes (*ms)
+✔ test 2 passes (*ms)
+✖ failing test 1 (*ms)
+⚠ Bailing out!
+✖ failing test 2
+✖ test 3 passes
+✖ test 4 passes
+✖ test 5 passes
+ℹ tests 7
+ℹ suites 0
+ℹ pass 2
+ℹ fail 1
+ℹ cancelled 4
+ℹ skipped 0
+ℹ todo 0
+ℹ duration_ms *
+
+✖ failing tests:
+
+*
+✖ failing test 1 (*ms)
+  AssertionError [ERR_ASSERTION]: This test should fail
+  
+  1 !== 2
+  
+      *
+      *
+      *
+      *
+      *
+      *
+      * {
+    generatedMessage: false,
+    code: 'ERR_ASSERTION',
+    actual: 1,
+    expected: 2,
+    operator: 'strictEqual',
+    diff: 'simple'
+  }
diff --git a/test/parallel/test-runner-bail.js b/test/parallel/test-runner-bail.js
new file mode 100644
index 00000000000000..299ddb65732eca
--- /dev/null
+++ b/test/parallel/test-runner-bail.js
@@ -0,0 +1,137 @@
+'use strict';
+require('../common');
+const { test } = require('node:test');
+const assert = require('node:assert');
+const { spawn } = require('node:child_process');
+const { once } = require('node:events');
+const fixtures = require('../common/fixtures');
+
+const runTest = async (args, cwd = process.cwd()) => {
+  const child = spawn(process.execPath, args, {
+    cwd,
+    stdio: 'pipe',
+    env: { ...process.env },
+  });
+
+  const stdout = [];
+  const stderr = [];
+
+  child.stdout.on('data', (chunk) => stdout.push(chunk));
+  child.stderr.on('data', (chunk) => stderr.push(chunk));
+
+  const [code] = await once(child, 'exit');
+
+  return {
+    code,
+    stdout: Buffer.concat(stdout).toString('utf8'),
+    stderr: Buffer.concat(stderr).toString('utf8'),
+  };
+};
+
+test('bail stops test execution on first failure with isolation=process', async () => {
+  const fixturesDir = fixtures.path('test-runner', 'bail');
+  const result = await runTest([
+    '--test-bail',
+    '--test-concurrency=1', // <-- fixed concurrency to ensure predictable order of test execution
+    '--test',
+    'bail-test-1-pass.js',
+    'bail-test-2-fail.js',
+    'bail-test-3-pass.js',
+    'bail-test-4-pass.js',
+  ], fixturesDir);
+
+  // Should exit with non-zero code due to failure
+  assert.notStrictEqual(result.code, 0);
+
+  // bail-test-1-pass.js should run (2 tests)
+  assert.match(result.stdout, /test 1 passes/);
+  assert.match(result.stdout, /test 2 passes/);
+
+  // bail-test-2-fail.js should run and fail
+  assert.match(result.stdout, /failing test 1/);
+
+  // Files after failure should NOT run
+  assert.doesNotMatch(result.stdout, /test 3 passes/);
+  assert.doesNotMatch(result.stdout, /test 4 passes/);
+  assert.doesNotMatch(result.stdout, /test 5 passes/);
+});
+
+test.todo('bail stops test execution on first failure with isolation=none');
+
+test('bail stops test execution on first failure with isolation=none', async () => {
+  const fixturesDir = fixtures.path('test-runner', 'bail');
+  const result = await runTest([
+    '--test-bail',
+    '--test-reporter=spec',
+    '--test-concurrency=1', // <-- fixed concurrency to ensure predictable order of test execution
+    '--test-isolation=none',
+    '--test',
+    'bail-test-1-pass.js',
+    'bail-test-2-fail.js',
+    'bail-test-3-pass.js',
+    'bail-test-4-pass.js',
+  ], fixturesDir);
+
+  // Should exit with non-zero code due to failure
+  assert.notStrictEqual(result.code, 0);
+
+  // bail-test-1-pass.js should run (2 tests)
+  assert.match(result.stdout, /✔ test 1 passes/);
+  assert.match(result.stdout, /✔ test 2 passes/);
+
+  // bail-test-2-fail.js first test should run and fail
+  assert.match(result.stdout, /✖ failing test 1/);
+
+  // Bail event should be emitted
+  assert.match(result.stdout, /Bailing out!/);
+
+  // Remaining tests after failure should be cancelled
+  assert.match(result.stdout, /✖ failing test 2/);
+  assert.match(result.stdout, /✖ test 3 passes/);
+  assert.match(result.stdout, /✖ test 4 passes/);
+  assert.match(result.stdout, /✖ test 5 passes/);
+
+  // Verify counters: 2 passed, 1 failed, 4 cancelled
+  assert.match(result.stdout, /pass 2/);
+  assert.match(result.stdout, /fail 1/);
+  assert.match(result.stdout, /cancelled 4/);
+});
+
+test('bail throws error when combined with watch mode', async () => {
+  const fixturesDir = fixtures.path('test-runner', 'bail');
+  const result = await runTest([
+    '--test',
+    '--test-bail',
+    '--watch',
+    'bail-test-1-pass.js',
+  ], fixturesDir);
+
+  // Should exit with error
+  assert.notStrictEqual(result.code, 0);
+
+  // Should contain error message about bail+watch incompatibility
+  assert.match(result.stderr, /not supported with watch mode/);
+});
+
+test('without bail, all tests run even after failure', async () => {
+  const fixturesDir = fixtures.path('test-runner', 'bail');
+  const result = await runTest([
+    '--test',
+    'bail-test-1-pass.js',
+    'bail-test-2-fail.js',
+    'bail-test-3-pass.js',
+  ], fixturesDir);
+
+  // Should exit with non-zero code due to failure
+  assert.notStrictEqual(result.code, 0);
+
+  // All tests should run
+  assert.match(result.stdout, /test 1 passes/);
+  assert.match(result.stdout, /test 2 passes/);
+  assert.match(result.stdout, /failing test 1/);
+  assert.match(result.stdout, /test 3 passes/);
+  assert.match(result.stdout, /test 4 passes/);
+
+  // Should NOT contain bail event
+  assert.doesNotMatch(result.stdout, /test:bail/);
+});
diff --git a/test/parallel/test-runner-run-bail-isolation-none.mjs b/test/parallel/test-runner-run-bail-isolation-none.mjs
new file mode 100644
index 00000000000000..0e11984e7454cd
--- /dev/null
+++ b/test/parallel/test-runner-run-bail-isolation-none.mjs
@@ -0,0 +1,55 @@
+import * as common from '../common/index.mjs';
+import assert from 'node:assert';
+import { test, run } from 'node:test';
+import * as fixtures from '../common/fixtures.mjs';
+
+const files = [
+  fixtures.path('test-runner', 'bail', 'bail-test-1-pass.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-2-fail.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-3-pass.js'),
+  fixtures.path('test-runner', 'bail', 'bail-test-4-pass.js'),
+];
+
+async function runScenario() {
+  const stream = run({ bail: true, isolation: 'none', concurrency: 1, files });
+
+  let testCount = 0;
+  let failCount = 0;
+  let bailCount = 0;
+  let bailedOutCount = 0;
+
+  stream.on('test:bail', common.mustCall(() => {
+    bailCount++;
+  }));
+
+  stream.on('test:pass', () => {
+    testCount++;
+  });
+
+  stream.on('test:fail', (item) => {
+    if (item.details?.error?.failureType === 'bailedOut') {
+      bailedOutCount++;
+    } else {
+      failCount++;
+    }
+  });
+
+  // eslint-disable-next-line no-unused-vars, no-empty
+  for await (const _ of stream) {}
+
+  return { testCount, failCount, bailCount, bailedOutCount };
+}
+
+test('it should bail in isolation none mode', async () => {
+  const { testCount, failCount, bailCount, bailedOutCount } = await runScenario();
+
+  // 2 tests pass (from bail-test-1-pass.js)
+  assert.strictEqual(testCount, 2);
+  // 1 test actually fails (first test in bail-test-2-fail.js)
+  assert.strictEqual(failCount, 1);
+  // 1 bail event is emitted
+  assert.strictEqual(bailCount, 1);
+  // 4 tests are cancelled due to bailout
+  // (failing test 2, test 3 passes, test 4 passes, test 5 passes)
+  assert.strictEqual(bailedOutCount, 4);
+});
diff --git a/test/parallel/test-runner-run-bail.mjs b/test/parallel/test-runner-run-bail.mjs
new file mode 100644
index 00000000000000..931cf213521d0a
--- /dev/null
+++ b/test/parallel/test-runner-run-bail.mjs
@@ -0,0 +1,73 @@
+import * as common from '../common/index.mjs';
+import assert from 'node:assert';
+import { test, run } from 'node:test';
+import * as fixtures from '../common/fixtures.mjs';
+
+test('bail option validation', async () => {
+  // Test that bail rejects watch mode
+  assert.throws(() => {
+    run({ bail: true, watch: true, files: [] });
+  }, {
+    code: 'ERR_INVALID_ARG_VALUE',
+    message: /not supported with watch mode/,
+  });
+});
+
+test('bail stops test execution on first failure', async () => {
+  const files = [
+    fixtures.path('test-runner', 'bail', 'bail-test-1-pass.js'),
+    fixtures.path('test-runner', 'bail', 'bail-test-2-fail.js'),
+    fixtures.path('test-runner', 'bail', 'bail-test-3-pass.js'),
+    fixtures.path('test-runner', 'bail', 'bail-test-4-pass.js'),
+  ];
+
+  const stream = run({ bail: true, concurrency: 1, files });
+
+  let testCount = 0;
+  let failCount = 0;
+
+  stream.on('test:bail', common.mustCall((data) => {
+    assert.ok(data.file);
+  }));
+
+  stream.on('test:pass', () => {
+    testCount++;
+  });
+
+  stream.on('test:fail', () => {
+    failCount++;
+  });
+
+  // eslint-disable-next-line no-unused-vars, no-empty
+  for await (const event of stream) {}
+
+  assert.strictEqual(failCount, 2);
+  assert.strictEqual(testCount, 2);
+});
+
+test('without bail, all tests run even after failure', async () => {
+  const files = [
+    fixtures.path('test-runner', 'bail', 'bail-test-1-pass.js'),
+    fixtures.path('test-runner', 'bail', 'bail-test-2-fail.js'),
+    fixtures.path('test-runner', 'bail', 'bail-test-3-pass.js'),
+  ];
+
+  const stream = run({ bail: false, files });
+
+  let bailEventReceived = false;
+  let testCount = 0;
+
+  stream.on('test:bail', () => {
+    bailEventReceived = true;
+  });
+
+  stream.on('test:pass', () => {
+    testCount++;
+  });
+
+  // eslint-disable-next-line no-unused-vars, no-empty
+  for await (const _ of stream) {}
+
+  assert.strictEqual(bailEventReceived, false);
+  assert.strictEqual(testCount, 4);
+});
diff --git a/test/test-runner/test-output-bail-spec-reporter-isolation-none.mjs b/test/test-runner/test-output-bail-spec-reporter-isolation-none.mjs
new file mode 100644
index 00000000000000..ac2c21f146b533
--- /dev/null
+++ b/test/test-runner/test-output-bail-spec-reporter-isolation-none.mjs
@@ -0,0 +1,10 @@
+// Test that the output of test-runner/output/bail_concurrency_1_isolation_none.js matches test-runner/output/bail_concurrency_1_isolation_none.snapshot
+import '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import { spawnAndAssert, specTransform, ensureCwdIsProjectRoot } from '../common/assertSnapshot.js';
+
+ensureCwdIsProjectRoot();
+await spawnAndAssert(
+  fixtures.path('test-runner/output/bail_concurrency_1_isolation_none.js'),
+  specTransform,
+);
diff --git a/test/test-runner/test-output-bail-spec-reporter.mjs b/test/test-runner/test-output-bail-spec-reporter.mjs
new file mode 100644
index 00000000000000..97b4240b1691d7
--- /dev/null
+++ b/test/test-runner/test-output-bail-spec-reporter.mjs
@@ -0,0 +1,10 @@
+// Test that the output of test-runner/output/bail_concurrency_1.js matches test-runner/output/bail_concurrency_1.snapshot
+import '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import { spawnAndAssert, specTransform, ensureCwdIsProjectRoot } from '../common/assertSnapshot.js';
+
+ensureCwdIsProjectRoot();
+await spawnAndAssert(
+  fixtures.path('test-runner/output/bail_concurrency_1.js'),
+  specTransform,
+);