From 019169ff657e0403721f97b93982155fc7269d00 Mon Sep 17 00:00:00 2001
From: Lukas Stracke <lukas.stracke@sentry.io>
Date: Thu, 11 Sep 2025 17:00:48 +0200
Subject: [PATCH 1/2] ref(core): Simplify `linkedErrors` mechanism logic

---
 packages/core/src/utils/aggregate-errors.ts   |  9 +++------
 .../test/lib/utils/aggregate-errors.test.ts   | 20 +++++++++++++++++++
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/packages/core/src/utils/aggregate-errors.ts b/packages/core/src/utils/aggregate-errors.ts
index f472e5b9968b..ea4e181acc98 100644
--- a/packages/core/src/utils/aggregate-errors.ts
+++ b/packages/core/src/utils/aggregate-errors.ts
@@ -99,10 +99,9 @@ function aggregateExceptionsFromError(
 }
 
 function applyExceptionGroupFieldsForParentException(exception: Exception, exceptionId: number): void {
-  // Don't know if this default makes sense. The protocol requires us to set these values so we pick *some* default.
-  exception.mechanism = exception.mechanism || { type: 'generic', handled: true };
-
   exception.mechanism = {
+    handled: true,
+    type: 'auto.core.linkedErrors',
     ...exception.mechanism,
     ...(exception.type === 'AggregateError' && { is_exception_group: true }),
     exception_id: exceptionId,
@@ -115,10 +114,8 @@ function applyExceptionGroupFieldsForChildException(
   exceptionId: number,
   parentId: number | undefined,
 ): void {
-  // Don't know if this default makes sense. The protocol requires us to set these values so we pick *some* default.
-  exception.mechanism = exception.mechanism || { type: 'generic', handled: true };
-
   exception.mechanism = {
+    handled: true,
     ...exception.mechanism,
     type: 'chained',
     source,
diff --git a/packages/core/test/lib/utils/aggregate-errors.test.ts b/packages/core/test/lib/utils/aggregate-errors.test.ts
index 01ede6d9186a..5ba689b8026d 100644
--- a/packages/core/test/lib/utils/aggregate-errors.test.ts
+++ b/packages/core/test/lib/utils/aggregate-errors.test.ts
@@ -160,6 +160,26 @@ describe('applyAggregateErrorsToEvent()', () => {
     expect(event.exception?.values?.[event.exception.values.length - 1]?.mechanism?.type).toBe('instrument');
   });
 
+  test('should assign a defualt mechanism type for the root exception', () => {
+    const fakeAggregateError = new FakeAggregateError(
+      [new Error('Nested Error 1'), new Error('Nested Error 2')],
+      'Root Error',
+    );
+
+    const exceptionFromError = (_stackParser: StackParser, ex: Error): Exception => {
+      return { value: ex.message, type: ex.name };
+    };
+
+    const event: Event = { exception: { values: [exceptionFromError(stackParser, fakeAggregateError)] } };
+    const eventHint: EventHint = { originalException: fakeAggregateError };
+
+    applyAggregateErrorsToEvent(exceptionFromError, stackParser, 'cause', 100, event, eventHint);
+
+    expect(event.exception?.values?.[event.exception.values.length - 1]?.mechanism?.type).toBe(
+      'auto.core.linkedErrors',
+    );
+  });
+
   test('should recursively walk mixed errors (Aggregate errors and based on `key`)', () => {
     const chainedError: ExtendedError = new Error('Nested Error 3');
     chainedError.cause = new Error('Nested Error 4');

From 916fb20d26c7f8ec02b34ca37d1c91835fe2c48f Mon Sep 17 00:00:00 2001
From: Lukas Stracke <lukas.stracke@sentry.io>
Date: Thu, 11 Sep 2025 18:08:46 +0200
Subject: [PATCH 2/2] snake case

---
 packages/core/src/utils/aggregate-errors.ts           | 2 +-
 packages/core/test/lib/utils/aggregate-errors.test.ts | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/utils/aggregate-errors.ts b/packages/core/src/utils/aggregate-errors.ts
index ea4e181acc98..16d100d60c09 100644
--- a/packages/core/src/utils/aggregate-errors.ts
+++ b/packages/core/src/utils/aggregate-errors.ts
@@ -101,7 +101,7 @@ function aggregateExceptionsFromError(
 function applyExceptionGroupFieldsForParentException(exception: Exception, exceptionId: number): void {
   exception.mechanism = {
     handled: true,
-    type: 'auto.core.linkedErrors',
+    type: 'auto.core.linked_errors',
     ...exception.mechanism,
     ...(exception.type === 'AggregateError' && { is_exception_group: true }),
     exception_id: exceptionId,
diff --git a/packages/core/test/lib/utils/aggregate-errors.test.ts b/packages/core/test/lib/utils/aggregate-errors.test.ts
index 5ba689b8026d..fa11fd22f7c8 100644
--- a/packages/core/test/lib/utils/aggregate-errors.test.ts
+++ b/packages/core/test/lib/utils/aggregate-errors.test.ts
@@ -176,7 +176,7 @@ describe('applyAggregateErrorsToEvent()', () => {
     applyAggregateErrorsToEvent(exceptionFromError, stackParser, 'cause', 100, event, eventHint);
 
     expect(event.exception?.values?.[event.exception.values.length - 1]?.mechanism?.type).toBe(
-      'auto.core.linkedErrors',
+      'auto.core.linked_errors',
     );
   });