diff --git a/.eslintrc.js b/.eslintrc.js
index 2c58a2aebbea3..1ec3718ec74bc 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -911,19 +911,7 @@ module.exports = {
     {
       files: [
         'x-pack/plugins/aiops/**/*.tsx',
-        'x-pack/plugins/infra/**/*.tsx',
-        'x-pack/plugins/observability_solution/apm/**/*.tsx',
-        'x-pack/plugins/observability_solution/dataset_quality/**/*.tsx',
-        'x-pack/plugins/observability_solution/exploratory_view/**/*.tsx',
-        'x-pack/plugins/observability_solution/infra/**/*.tsx',
-        'x-pack/plugins/observability_solution/observability/**/*.tsx',
-        'x-pack/plugins/observability_solution/observability_ai_assistant/**/*.tsx',
-        'x-pack/plugins/observability_solution/observability_onboarding/**/*.tsx',
-        'x-pack/plugins/observability_solution/observability_shared/**/*.tsx',
-        'x-pack/plugins/observability_solution/profiling/**/*.tsx',
-        'x-pack/plugins/observability_solution/synthetics/**/*.tsx',
-        'x-pack/plugins/observability_solution/uptime/**/*.tsx',
-        'x-pack/plugins/observability_solution/ux/**/*.tsx',
+        'x-pack/plugins/observability_solution/**/*.tsx',
         'src/plugins/ai_assistant_management/**/*.tsx',
       ],
       rules: {
@@ -932,16 +920,7 @@ module.exports = {
     },
     {
       files: [
-        'x-pack/plugins/observability_solution/apm/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/exploratory_view/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/infra/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/observability/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/observability_ai_assistant/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/observability_onboarding/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/observability_shared/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/profiling/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/synthetics/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
-        'x-pack/plugins/observability_solution/ux/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
+        'x-pack/plugins/observability_solution/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
         'src/plugins/ai_assistant_management/**/!(*.stories.tsx|*.test.tsx|*.storybook_decorator.tsx|*.mock.tsx)',
       ],
       rules: {
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index e0692ae7f398d..5f45529fb4db3 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -1543,8 +1543,6 @@ x-pack/plugins/security_solution/server/lib/security_integrations @elastic/secur
 **/*.scss @elastic/kibana-design
 
 # Observability design
-/x-pack/plugins/observability_solution/apm/**/*.scss @elastic/observability-design
-/x-pack/plugins/observability_solution/infra/**/*.scss @elastic/observability-design
 /x-pack/plugins/fleet/**/*.scss @elastic/observability-design
 /x-pack/plugins/monitoring/**/*.scss @elastic/observability-design
 
@@ -1556,7 +1554,6 @@ x-pack/plugins/security_solution/server/lib/security_integrations @elastic/secur
 /x-pack/plugins/security_solution/**/*.scss @elastic/security-design
 /x-pack/plugins/security_solution_ess/**/*.scss @elastic/security-design
 /x-pack/plugins/security_solution_serverless/**/*.scss @elastic/security-design
-/x-pack/plugins/observability_solution/logs_explorer/**/*.scss @elastic/observability-design
 
 # Logstash
 #CC# /x-pack/plugins/logstash/ @elastic/logstash
diff --git a/x-pack/plugins/observability_solution/infra/public/apps/logs_app.tsx b/x-pack/plugins/observability_solution/infra/public/apps/logs_app.tsx
index f75f6fa29efd7..ff5631872bfe8 100644
--- a/x-pack/plugins/observability_solution/infra/public/apps/logs_app.tsx
+++ b/x-pack/plugins/observability_solution/infra/public/apps/logs_app.tsx
@@ -12,7 +12,6 @@ import ReactDOM from 'react-dom';
 import { Router, Routes, Route } from '@kbn/shared-ux-router';
 import { AppMountParameters } from '@kbn/core/public';
 import { Storage } from '@kbn/kibana-utils-plugin/public';
-import '../index.scss';
 import { LinkToLogsPage } from '../pages/link_to/link_to_logs';
 import { LogsPage } from '../pages/logs';
 import { InfraClientStartDeps, InfraClientStartExports } from '../types';
diff --git a/x-pack/plugins/observability_solution/infra/public/apps/metrics_app.tsx b/x-pack/plugins/observability_solution/infra/public/apps/metrics_app.tsx
index 4bfd65cd1ac63..338f7df860a21 100644
--- a/x-pack/plugins/observability_solution/infra/public/apps/metrics_app.tsx
+++ b/x-pack/plugins/observability_solution/infra/public/apps/metrics_app.tsx
@@ -12,7 +12,6 @@ import ReactDOM from 'react-dom';
 import { Router, Routes, Route } from '@kbn/shared-ux-router';
 import { AppMountParameters } from '@kbn/core/public';
 import { Storage } from '@kbn/kibana-utils-plugin/public';
-import '../index.scss';
 import { InfraPublicConfig } from '../../common/plugin_config_types';
 import { LinkToMetricsPage } from '../pages/link_to/link_to_metrics';
 import { InfrastructurePage } from '../pages/metrics';
diff --git a/x-pack/plugins/observability_solution/infra/public/index.scss b/x-pack/plugins/observability_solution/infra/public/index.scss
deleted file mode 100644
index e69de29bb2d1d..0000000000000
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/add_data_button.tsx b/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/add_data_button.tsx
index 51e1925e82cbe..28d08aedc4a77 100644
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/add_data_button.tsx
+++ b/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/add_data_button.tsx
@@ -37,7 +37,12 @@ export const AddDataButton: React.FunctionComponent<{}> = ({}) => {
   });
 
   return (
-    <EuiButtonEmpty {...onboardingLinkProps} iconType="plusInCircleFilled" size="xs">
+    <EuiButtonEmpty
+      data-test-subj="logsExplorerAddDataButtonButton"
+      {...onboardingLinkProps}
+      iconType="plusInCircleFilled"
+      size="xs"
+    >
       {addDataLabel}
     </EuiButtonEmpty>
   );
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/list_status.tsx b/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/list_status.tsx
index 3d782544b92c5..ecdffbcefcbef 100644
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/list_status.tsx
+++ b/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/list_status.tsx
@@ -60,7 +60,11 @@ export const ListStatus = ({
             }}
           />
         }
-        actions={[<EuiButton onClick={onRetry}>{noDataRetryLabel}</EuiButton>]}
+        actions={[
+          <EuiButton data-test-subj="logsExplorerListStatusButton" onClick={onRetry}>
+            {noDataRetryLabel}
+          </EuiButton>,
+        ]}
       />
     );
   }
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/search_controls.tsx b/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/search_controls.tsx
index 5864dd37e42c0..77cb5082efa26 100644
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/search_controls.tsx
+++ b/x-pack/plugins/observability_solution/logs_explorer/public/components/data_source_selector/sub_components/search_controls.tsx
@@ -42,6 +42,7 @@ export const SearchControls = ({ search, onSearch, onSort, isLoading }: SearchCo
       <EuiFlexGroup gutterSize="xs" responsive={false}>
         <EuiFlexItem>
           <EuiFieldSearch
+            data-test-subj="logsExplorerSearchControlsFieldSearch"
             compressed
             incremental
             value={search.name}
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/highlight_section.tsx b/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/highlight_section.tsx
index 13ba409927b5e..80260a6cff11c 100644
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/highlight_section.tsx
+++ b/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/highlight_section.tsx
@@ -41,6 +41,7 @@ export function HighlightSection({ title, children, columns, ...props }: Highlig
   const showMoreButtonLabel = flyoutAccordionShowMoreText(hiddenCount);
   const showMoreButton = (
     <EuiButtonEmpty
+      data-test-subj="logsExplorerHighlightSectionShowMoreButton"
       size="xs"
       flush="left"
       css={{ width: '80px' }}
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/hover_popover_action.tsx b/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/hover_popover_action.tsx
index 584fb7e273cf1..1f9855c28a86b 100644
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/hover_popover_action.tsx
+++ b/x-pack/plugins/observability_solution/logs_explorer/public/components/flyout_detail/sub_components/hover_popover_action.tsx
@@ -72,6 +72,7 @@ export const HoverActionPopover = ({
           {hoverActions.map((action) => (
             <EuiToolTip content={action.tooltipContent} key={action.id}>
               <EuiButtonIcon
+                data-test-subj="logsExplorerHoverActionPopoverButton"
                 size="xs"
                 iconType={action.iconType}
                 aria-label={action.tooltipContent as string}
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/content.tsx b/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/content.tsx
index 13ae9ce80fa09..073d18068d650 100644
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/content.tsx
+++ b/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/content.tsx
@@ -6,7 +6,9 @@
  */
 
 import React, { useMemo } from 'react';
+import { css } from '@emotion/css';
 import { EuiButtonIcon, EuiText } from '@elastic/eui';
+import { euiThemeVars } from '@kbn/ui-theme';
 import type { DataGridCellValueElementProps } from '@kbn/unified-data-table';
 import { getShouldShowFieldHandler } from '@kbn/discover-utils';
 import { i18n } from '@kbn/i18n';
@@ -16,7 +18,6 @@ import { useDocDetail, getMessageWithFallbacks } from '../../hooks/use_doc_detai
 import { LogDocument } from '../../../common/document';
 import { LogLevel } from '../common/log_level';
 import * as constants from '../../../common/constants';
-import './virtual_column.scss';
 
 const SourceDocument = dynamic(
   () => import('@kbn/unified-data-table/src/components/source_document')
@@ -26,6 +27,11 @@ const DiscoverSourcePopoverContent = dynamic(
   () => import('@kbn/unified-data-table/src/components/source_popover_content')
 );
 
+const sourceDocumentClassName = css`
+  display: inline !important;
+  margin-left: ${euiThemeVars.euiSizeXS};
+`;
+
 const LogMessage = ({ field, value }: { field?: string; value: string }) => {
   const renderFieldPrefix = field && field !== constants.MESSAGE_FIELD;
   return (
@@ -115,7 +121,7 @@ export const Content = ({
           shouldShowFieldHandler={shouldShowFieldHandler}
           maxEntries={50}
           dataTestSubj="logsExplorerCellDescriptionList"
-          className="logsExplorerVirtualColumn__sourceDocument"
+          className={sourceDocumentClassName}
         />
       )}
     </span>
diff --git a/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/virtual_column.scss b/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/virtual_column.scss
deleted file mode 100644
index f4f407875d2b6..0000000000000
--- a/x-pack/plugins/observability_solution/logs_explorer/public/components/virtual_columns/virtual_column.scss
+++ /dev/null
@@ -1,4 +0,0 @@
-.logsExplorerVirtualColumn__sourceDocument {
-  display: inline !important;
-  margin-left: $euiSizeXS;
-}
diff --git a/x-pack/plugins/observability_solution/logs_shared/public/components/data_search_progress.tsx b/x-pack/plugins/observability_solution/logs_shared/public/components/data_search_progress.tsx
index 8ccc14a4d9acd..a03844fa9b2fd 100644
--- a/x-pack/plugins/observability_solution/logs_shared/public/components/data_search_progress.tsx
+++ b/x-pack/plugins/observability_solution/logs_shared/public/components/data_search_progress.tsx
@@ -29,6 +29,7 @@ export const DataSearchProgress: React.FC<{
       {onCancel ? (
         <EuiFlexItem grow={false}>
           <EuiButtonIcon
+            data-test-subj="logsSharedDataSearchProgressButton"
             color="danger"
             iconType="cross"
             onClick={onCancel}
diff --git a/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.scss b/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.scss
deleted file mode 100644
index 82b1c88dc4038..0000000000000
--- a/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.scss
+++ /dev/null
@@ -1,3 +0,0 @@
-.obsNewsFeed__itemImg {
-  @include euiBottomShadowSmall;
-}
\ No newline at end of file
diff --git a/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.tsx b/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.tsx
index 7fad8c53564e1..b0d4821d27aa3 100644
--- a/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.tsx
+++ b/x-pack/plugins/observability_solution/observability/public/pages/overview/components/news_feed/news_feed.tsx
@@ -15,17 +15,22 @@ import {
   EuiText,
   EuiTitle,
 } from '@elastic/eui';
+import { css } from '@emotion/css';
 import { i18n } from '@kbn/i18n';
 import { truncate } from 'lodash';
 import React, { useContext } from 'react';
 import { ThemeContext } from 'styled-components';
 import { NewsItem as INewsItem } from './helpers/get_news_feed';
-import './news_feed.scss';
 
 interface Props {
   items: INewsItem[];
 }
 
+const imageClassName = css`
+  box-shadow: 0 0.7px 1.4px rgba(0, 0, 0, 0.07), 0 1.9px 4px rgba(0, 0, 0, 0.05),
+    0 4.5px 10px rgba(0, 0, 0, 0.05);
+`;
+
 export function NewsFeed({ items }: Props) {
   return (
     // The news feed is manually added/edited, to prevent any errors caused by typos or missing fields,
@@ -98,7 +103,7 @@ function NewsItem({ item }: { item: INewsItem }) {
                   height={48}
                   alt={item.title.en}
                   src={item.image_url.en}
-                  className="obsNewsFeed__itemImg"
+                  className={imageClassName}
                 />
               </EuiFlexItem>
             )}
diff --git a/x-pack/plugins/observability_solution/observability_ai_assistant_app/public/components/nav_control/index.tsx b/x-pack/plugins/observability_solution/observability_ai_assistant_app/public/components/nav_control/index.tsx
index 19ee4af2be538..1366c41464241 100644
--- a/x-pack/plugins/observability_solution/observability_ai_assistant_app/public/components/nav_control/index.tsx
+++ b/x-pack/plugins/observability_solution/observability_ai_assistant_app/public/components/nav_control/index.tsx
@@ -77,6 +77,7 @@ export function NavControl({}: {}) {
   return (
     <>
       <EuiButton
+        data-test-subj="observabilityAiAssistantAppNavControlButton"
         css={buttonCss}
         onClick={() => {
           service.conversations.openNewConversation({
diff --git a/x-pack/plugins/observability_solution/observability_logs_explorer/public/components/alerts_popover.tsx b/x-pack/plugins/observability_solution/observability_logs_explorer/public/components/alerts_popover.tsx
index c5f4785712099..fc224093dfe60 100644
--- a/x-pack/plugins/observability_solution/observability_logs_explorer/public/components/alerts_popover.tsx
+++ b/x-pack/plugins/observability_solution/observability_logs_explorer/public/components/alerts_popover.tsx
@@ -228,6 +228,7 @@ export const AlertsPopover = () => {
       <EuiPopover
         button={
           <EuiButtonEmpty
+            data-test-subj="observabilityLogsExplorerAlertsPopoverAlertsButton"
             onClick={togglePopover}
             iconType="arrowDown"
             iconSide="right"