DataDog · thomas-lebeau · Jun 16, 2026 · Jun 11, 2026 · Jun 12, 2026 · Jun 12, 2026
@@ -46,6 +46,8 @@ const pathsWithSideEffect = new Set([
 // Those packages are known to have no side effects when evaluated
 const packagesWithoutSideEffect = new Set([
   '@datadog/js-core/time',
+  '@datadog/js-core/util',
+  '@datadog/js-core/monitor',
   '@datadog/browser-core',
   '@datadog/browser-rum-core',
   '@datadog/browser-rum-react/internal',

@@ -101,6 +101,9 @@
     "webpack-dev-middleware": "8.0.3",
     "ws": "8.21.0"
   },
+  "resolutions": {
+    "rolldown": "1.1.1"
+  },
   "volta": {
     "node": "26.3.0",
     "yarn": "4.16.0"

@@ -0,0 +1,21 @@
+# `@datadog/browser-core` package
+
+`@datadog/browser-core` is primarily consumed by other `@datadog/browser-*` packages within this
+monorepo. It is published to npm but **not supported for external use** and carries **no semver
+stability guarantee**.
+
+## Breaking changes are allowed
+
+External consumers exist but are unsupported — we do not guarantee compatibility for them. You may
+freely:
+
+- Remove or rename exported symbols
+- Change function signatures (parameters, return types, arity)
+- Reorganize modules and re-exports
+
+When migrating code from `@datadog/browser-core` to `@datadog/js-core`, do **not** keep a
+backward-compatible re-export in `browser-core` just to avoid a "breaking change" — there is no
+breaking change here. Move the code and update all internal call sites directly.
+
+Review comments that warn about "breaking changes" in this package (e.g. removed exports,
+signature changes) are **not applicable** and should be disregarded.
@@ -1,5 +1,5 @@
+import { setDebugMode } from '@datadog/js-core/util'
 import { catchUserErrors } from '../tools/catchUserErrors'
-import { setDebugMode } from '../tools/monitor'
 import { display } from '../tools/display'
 
 // replaced at build time

@@ -1,10 +1,10 @@
 import { clocksNow } from '@datadog/js-core/time'
+import { ConsoleApiName } from '@datadog/js-core/util'
 import type { MockFetch } from '../../test'
 import { collectAsyncCalls, mockFetch, mockXhr, registerCleanupTask, replaceMockable, withXhr } from '../../test'
 import { Observable } from '../tools/observable'
 import { resetFetchObservable } from '../browser/fetchObservable'
 import { resetXhrObservable } from '../browser/xhrObservable'
-import { ConsoleApiName } from '../tools/display'
 import { noop } from '../tools/utils/functionUtils'
 import { resetConsoleObservable } from './console/consoleObservable'
 import type { BufferedData } from './bufferedData'

@@ -1,11 +1,11 @@
+import { ConsoleApiName } from '@datadog/js-core/util'
 import type { Observable, Subscription } from '../tools/observable'
 import { BufferedObservable } from '../tools/observable'
 import { mockable } from '../tools/mockable'
 import type { FetchContext } from '../browser/fetchObservable'
 import { initFetchObservable } from '../browser/fetchObservable'
 import type { XhrContext } from '../browser/xhrObservable'
 import { initXhrObservable } from '../browser/xhrObservable'
-import { ConsoleApiName } from '../tools/display'
 import { addTelemetryDebug } from './telemetry'
 import type { RawError } from './error/error.types'
 import { trackRuntimeError } from './error/trackRuntimeError'

@@ -1,6 +1,6 @@
 /* eslint-disable no-console */
+import { ConsoleApiName } from '@datadog/js-core/util'
 import { ignoreConsoleLogs } from '../../../test'
-import { ConsoleApiName } from '../../tools/display'
 import type { Subscription } from '../../tools/observable'
 import type { ErrorConsoleLog } from './consoleObservable'
 import { initConsoleObservable } from './consoleObservable'

@@ -1,7 +1,7 @@
 import { clocksNow } from '@datadog/js-core/time'
+import { ConsoleApiName, globalConsole } from '@datadog/js-core/util'
 import { isError, computeRawError } from '../error/error'
 import { Observable, mergeObservables } from '../../tools/observable'
-import { ConsoleApiName, globalConsole } from '../../tools/display'
 import { callMonitored } from '../../tools/monitor'
 import { sanitize } from '../../tools/serialisation/sanitize'
 import { jsonStringify } from '../../tools/serialisation/jsonStringify'

@@ -1,6 +1,6 @@
 import { clocksNow } from '@datadog/js-core/time'
+import { getDebugMode } from '@datadog/js-core/util'
 import type { Context } from '../../tools/serialisation/context'
-import { ConsoleApiName } from '../../tools/display'
 import { NO_ERROR_STACK_PRESENT_MESSAGE, isError } from '../error/error'
 import { toStackTraceString } from '../../tools/stackTrace/handlingStack'
 import { getExperimentalFeatures } from '../../tools/experimentalFeatures'
@@ -9,7 +9,8 @@ import type { Configuration } from '../configuration'
 import { buildTags } from '../tags'
 import { INTAKE_SITE_STAGING, INTAKE_SITE_US1_FED, INTAKE_SITE_US2_FED } from '../intakeSites'
 import { BufferedObservable, Observable } from '../../tools/observable'
-import { displayIfDebugEnabled, startMonitorErrorCollection } from '../../tools/monitor'
+import { startMonitorErrorCollection } from '../../tools/monitor'
+import { display } from '../../tools/display'
 import { sendToExtension } from '../../tools/sendToExtension'
 import { performDraw } from '../../tools/utils/numberUtils'
 import { jsonStringify } from '../../tools/serialisation/jsonStringify'
@@ -261,7 +262,9 @@ function isTelemetryReplicationAllowed(configuration: Configuration) {
 }
 
 export function addTelemetryDebug(message: string, context?: Context) {
-  displayIfDebugEnabled(ConsoleApiName.debug, message, context)
+  if (getDebugMode()) {
+    display.debug('[Telemetry]', message, context)
+  }
   getTelemetryObservable().notify({
     rawEvent: {
       type: TelemetryType.LOG,

@@ -48,7 +48,7 @@ export {
   addTelemetryUsage,
   addTelemetryMetrics,
 } from './domain/telemetry'
-export { monitored, monitor, callMonitored, setDebugMode, monitorError } from './tools/monitor'
+export { monitored, monitor, callMonitored, monitorError } from './tools/monitor'
 export type { Subscription } from './tools/observable'
 export { Observable, BufferedObservable } from './tools/observable'
 export type { SessionManager, SessionContext } from './domain/session/sessionManager'

@@ -1,59 +1,7 @@
 /* eslint-disable local-rules/disallow-side-effects */
-/**
- * Keep references on console methods to avoid triggering patched behaviors
- *
- * NB: in some setup, console could already be patched by another SDK.
- * In this case, some display messages can be sent by the other SDK
- * but we should be safe from infinite loop nonetheless.
- */
+import { createDisplay } from '@datadog/js-core/util'
 
-export const ConsoleApiName = {
-  log: 'log',
-  debug: 'debug',
-  info: 'info',
-  warn: 'warn',
-  error: 'error',
-} as const
-
-export type ConsoleApiName = (typeof ConsoleApiName)[keyof typeof ConsoleApiName]
-
-export interface Display {
-  debug: typeof console.debug
-  log: typeof console.log
-  info: typeof console.info
-  warn: typeof console.warn
-  error: typeof console.error
-}
-
-/**
- * When building JS bundles, some users might use a plugin[1] or configuration[2] to remove
- * "console.*" references. This causes some issue as we expect `console.*` to be defined.
- * As a workaround, let's use a variable alias, so those expressions won't be taken into account by
- * simple static analysis.
- *
- * [1]: https://babeljs.io/docs/babel-plugin-transform-remove-console/
- * [2]: https://github.com/terser/terser#compress-options (look for drop_console)
- */
-export const globalConsole = console
-
-export const originalConsoleMethods = {} as Display
-Object.keys(ConsoleApiName).forEach((name) => {
-  originalConsoleMethods[name as ConsoleApiName] = globalConsole[name as ConsoleApiName]
-})
-
-const PREFIX = 'Datadog Browser SDK:'
-
-export function createDisplay(prefix: string): Display {
-  return {
-    debug: originalConsoleMethods.debug.bind(globalConsole, prefix),
-    log: originalConsoleMethods.log.bind(globalConsole, prefix),
-    info: originalConsoleMethods.info.bind(globalConsole, prefix),
-    warn: originalConsoleMethods.warn.bind(globalConsole, prefix),
-    error: originalConsoleMethods.error.bind(globalConsole, prefix),
-  }
-}
-
-export const display: Display = createDisplay(PREFIX)
+export const display = createDisplay('Datadog Browser SDK:')
 
 export const DOCS_ORIGIN = 'https://docs.datadoghq.com'
 export const DOCS_TROUBLESHOOTING = `${DOCS_ORIGIN}/real_user_monitoring/browser/troubleshooting`

@@ -1,5 +1,4 @@
-import { display } from './display'
-import { callMonitored, monitor, monitored, startMonitorErrorCollection, setDebugMode } from './monitor'
+import { callMonitored, monitored, startMonitorErrorCollection } from './monitor'
 
 describe('monitor', () => {
   let onMonitorErrorCollectedSpy: jasmine.Spy<(error: unknown) => void>
@@ -8,162 +7,23 @@ describe('monitor', () => {
     onMonitorErrorCollectedSpy = jasmine.createSpy()
   })
 
-  describe('decorator', () => {
+  it('catches monitored errors but does not report them before startMonitorErrorCollection', () => {
     class Candidate {
       @monitored
-      monitoredThrowing() {
+      throwing() {
         throw new Error('monitored')
       }
-
-      @monitored
-      monitoredStringErrorThrowing() {
-        // eslint-disable-next-line @typescript-eslint/only-throw-error
-        throw 'string error'
-      }
-
-      @monitored
-      monitoredObjectErrorThrowing() {
-        // eslint-disable-next-line @typescript-eslint/only-throw-error
-        throw { foo: 'bar' }
-      }
-
-      @monitored
-      monitoredNotThrowing() {
-        return 1
-      }
-
-      notMonitoredThrowing() {
-        throw new Error('not monitored')
-      }
     }
-
-    let candidate: Candidate
-    beforeEach(() => {
-      candidate = new Candidate()
-    })
-
-    describe('before initialization', () => {
-      it('should not monitor', () => {
-        expect(() => candidate.notMonitoredThrowing()).toThrowError('not monitored')
-        expect(() => candidate.monitoredThrowing()).toThrowError('monitored')
-        expect(candidate.monitoredNotThrowing()).toEqual(1)
-      })
-    })
-
-    describe('after initialization', () => {
-      beforeEach(() => {
-        startMonitorErrorCollection(onMonitorErrorCollectedSpy)
-      })
-
-      it('should preserve original behavior', () => {
-        expect(candidate.monitoredNotThrowing()).toEqual(1)
-      })
-
-      it('should catch error', () => {
-        expect(() => candidate.notMonitoredThrowing()).toThrowError()
-        expect(() => candidate.monitoredThrowing()).not.toThrowError()
-      })
-
-      it('should report error', () => {
-        candidate.monitoredThrowing()
-
-        expect(onMonitorErrorCollectedSpy).toHaveBeenCalledOnceWith(new Error('monitored'))
-      })
-
-      it('should report string error', () => {
-        candidate.monitoredStringErrorThrowing()
-
-        expect(onMonitorErrorCollectedSpy).toHaveBeenCalledOnceWith('string error')
-      })
-
-      it('should report object error', () => {
-        candidate.monitoredObjectErrorThrowing()
-
-        expect(onMonitorErrorCollectedSpy).toHaveBeenCalledOnceWith({ foo: 'bar' })
-      })
-    })
+    const candidate = new Candidate()
+    expect(() => candidate.throwing()).not.toThrowError()
+    expect(onMonitorErrorCollectedSpy).not.toHaveBeenCalled()
   })
 
-  describe('function', () => {
-    const notThrowing = () => 1
-    const throwing = () => {
+  it('reports errors to the collection callback after startMonitorErrorCollection', () => {
+    startMonitorErrorCollection(onMonitorErrorCollectedSpy)
+    callMonitored(() => {
       throw new Error('error')
-    }
-
-    beforeEach(() => {
-      startMonitorErrorCollection(onMonitorErrorCollectedSpy)
-    })
-
-    describe('direct call', () => {
-      it('should preserve original behavior', () => {
-        expect(callMonitored(notThrowing)).toEqual(1)
-      })
-
-      it('should catch error', () => {
-        expect(() => callMonitored(throwing)).not.toThrowError()
-      })
-
-      it('should report error', () => {
-        callMonitored(throwing)
-
-        expect(onMonitorErrorCollectedSpy).toHaveBeenCalledOnceWith(new Error('error'))
-      })
-    })
-
-    describe('wrapper', () => {
-      it('should preserve original behavior', () => {
-        const decorated = monitor(notThrowing)
-        expect(decorated()).toEqual(1)
-      })
-
-      it('should catch error', () => {
-        const decorated = monitor(throwing)
-        expect(() => decorated()).not.toThrowError()
-      })
-
-      it('should report error', () => {
-        monitor(throwing)()
-
-        expect(onMonitorErrorCollectedSpy).toHaveBeenCalledOnceWith(new Error('error'))
-      })
-    })
-  })
-
-  describe('setDebugMode', () => {
-    let displaySpy: jasmine.Spy
-
-    beforeEach(() => {
-      displaySpy = spyOn(display, 'error')
-    })
-
-    it('when not called, should not display error', () => {
-      callMonitored(() => {
-        throw new Error('message')
-      })
-
-      expect(displaySpy).not.toHaveBeenCalled()
-    })
-
-    it('when called, should display error', () => {
-      setDebugMode(true)
-
-      callMonitored(() => {
-        throw new Error('message')
-      })
-
-      expect(displaySpy).toHaveBeenCalledOnceWith('[MONITOR]', new Error('message'))
-    })
-
-    it('displays errors thrown by the onMonitorErrorCollected callback', () => {
-      setDebugMode(true)
-      onMonitorErrorCollectedSpy.and.throwError(new Error('unexpected'))
-      startMonitorErrorCollection(onMonitorErrorCollectedSpy)
-
-      callMonitored(() => {
-        throw new Error('message')
-      })
-      expect(displaySpy).toHaveBeenCalledWith('[MONITOR]', new Error('message'))
-      expect(displaySpy).toHaveBeenCalledWith('[MONITOR]', new Error('unexpected'))
     })
+    expect(onMonitorErrorCollectedSpy).toHaveBeenCalledOnceWith(new Error('error'))
   })
 })