diff --git a/packages/analytics-js-plugins/__tests__/bugsnag/index.test.ts b/packages/analytics-js-plugins/__tests__/bugsnag/index.test.ts
index 4c6674bc45..0e1cb4b01a 100644
--- a/packages/analytics-js-plugins/__tests__/bugsnag/index.test.ts
+++ b/packages/analytics-js-plugins/__tests__/bugsnag/index.test.ts
@@ -22,6 +22,14 @@ describe('Plugin - Bugsnag', () => {
         installType: 'npm',
       }),
     },
+    session: {
+      sessionInfo: signal({ id: 'test-session-id' }),
+    },
+    autoTrack: {
+      pageLifecycle: {
+        visitId: signal('test-visit-id'),
+      },
+    },
   };
 
   let state: any;
diff --git a/packages/analytics-js-plugins/__tests__/bugsnag/utils.test.ts b/packages/analytics-js-plugins/__tests__/bugsnag/utils.test.ts
index 6d58890430..4891ede13c 100644
--- a/packages/analytics-js-plugins/__tests__/bugsnag/utils.test.ts
+++ b/packages/analytics-js-plugins/__tests__/bugsnag/utils.test.ts
@@ -40,6 +40,14 @@ beforeEach(() => {
     lifecycle: {
       writeKey: signal('dummy-write-key'),
     },
+    session: {
+      sessionInfo: signal({ id: 'test-session-id' }),
+    },
+    autoTrack: {
+      pageLifecycle: {
+        visitId: signal('test-visit-id'),
+      },
+    },
   };
 });
 
@@ -235,6 +243,14 @@ describe('Bugsnag utilities', () => {
               installType: 'npm',
             },
           },
+          session: {
+            sessionInfo: { id: 'test-session-id' },
+          },
+          autoTrack: {
+            pageLifecycle: {
+              visitId: 'test-visit-id',
+            },
+          },
         },
       });
 
@@ -277,6 +293,14 @@ describe('Bugsnag utilities', () => {
               installType: 'npm',
             },
           },
+          session: {
+            sessionInfo: { id: 'test-session-id' },
+          },
+          autoTrack: {
+            pageLifecycle: {
+              visitId: 'test-visit-id',
+            },
+          },
         },
       });
 
@@ -338,7 +362,7 @@ describe('Bugsnag utilities', () => {
         maxBreadcrumbs: 40,
         releaseStage: 'development',
         user: {
-          id: 'dummy-source-id',
+          id: 'dummy-source-id..test-session-id..test-visit-id',
         },
         networkBreadcrumbsEnabled: false,
         beforeSend: expect.any(Function),
@@ -377,7 +401,7 @@ describe('Bugsnag utilities', () => {
         maxBreadcrumbs: 40,
         releaseStage: 'development',
         user: {
-          id: 'dummy-write-key',
+          id: 'dummy-write-key..test-session-id..test-visit-id',
         },
         networkBreadcrumbsEnabled: false,
         beforeSend: expect.any(Function),
@@ -527,6 +551,14 @@ describe('Bugsnag utilities', () => {
             installType: 'npm',
           },
         },
+        session: {
+          sessionInfo: { id: 'test-session-id' },
+        },
+        autoTrack: {
+          pageLifecycle: {
+            visitId: 'test-visit-id',
+          },
+        },
       });
       expect(error.severity).toBe('error');
       expect(error.context).toBe('Script load failures');
diff --git a/packages/analytics-js-plugins/__tests__/errorReporting/utils.test.ts b/packages/analytics-js-plugins/__tests__/errorReporting/utils.test.ts
index df05b806d1..eee1c438e6 100644
--- a/packages/analytics-js-plugins/__tests__/errorReporting/utils.test.ts
+++ b/packages/analytics-js-plugins/__tests__/errorReporting/utils.test.ts
@@ -416,7 +416,7 @@ describe('Error Reporting utilities', () => {
               },
             },
             user: {
-              id: 'sample_source_id - test-session-id - test-visit-id',
+              id: 'sample_source_id..test-session-id..test-visit-id',
             },
           },
         ],
diff --git a/packages/analytics-js-plugins/src/bugsnag/utils.ts b/packages/analytics-js-plugins/src/bugsnag/utils.ts
index 135054ef83..e1c159dcae 100644
--- a/packages/analytics-js-plugins/src/bugsnag/utils.ts
+++ b/packages/analytics-js-plugins/src/bugsnag/utils.ts
@@ -136,7 +136,8 @@ const getNewClient = (state: ApplicationState, logger?: ILogger): BugsnagLib.Cli
     maxBreadcrumbs: 40,
     releaseStage: getReleaseStage(),
     user: {
-      id: state.source.value?.id || state.lifecycle.writeKey.value,
+      // Combination of source, session and visit ids
+      id: `${state.source.value?.id ?? (state.lifecycle.writeKey.value as string)}..${state.session.sessionInfo.value?.id ?? 'NA'}..${state.autoTrack?.pageLifecycle?.visitId?.value ?? 'NA'}`,
     },
     logger,
     networkBreadcrumbsEnabled: false,
diff --git a/packages/analytics-js-plugins/src/errorReporting/utils.ts b/packages/analytics-js-plugins/src/errorReporting/utils.ts
index fb40b8b09a..ef8fadc3bc 100644
--- a/packages/analytics-js-plugins/src/errorReporting/utils.ts
+++ b/packages/analytics-js-plugins/src/errorReporting/utils.ts
@@ -133,7 +133,7 @@ const getBugsnagErrorEvent = (
       },
       user: {
         // Combination of source, session and visit ids
-        id: `${state.source.value?.id ?? (state.lifecycle.writeKey.value as string)} - ${state.session.sessionInfo.value?.id ?? 'NA'} - ${state.autoTrack.pageLifecycle.visitId.value ?? 'NA'}`,
+        id: `${state.source.value?.id ?? (state.lifecycle.writeKey.value as string)}..${state.session.sessionInfo.value?.id ?? 'NA'}..${state.autoTrack?.pageLifecycle?.visitId?.value ?? 'NA'}`,
       },
     },
   ],
diff --git a/packages/analytics-js/.size-limit.mjs b/packages/analytics-js/.size-limit.mjs
index d55635d440..82b89e09dc 100644
--- a/packages/analytics-js/.size-limit.mjs
+++ b/packages/analytics-js/.size-limit.mjs
@@ -13,7 +13,7 @@ export default [
     name: 'Core - Legacy - NPM (CJS)',
     path: 'dist/npm/legacy/cjs/index.cjs',
     import: '*',
-    limit: '49 KiB',
+    limit: '49.1 KiB',
   },
   {
     name: 'Core - Legacy - NPM (UMD)',