feat(onboarding): Gate SCM_PROJECT_DETAILS step with feature flag

When `onboarding-scm-project-details` flag is absent, skip the project
details step and auto-create the project with defaults (platform key as
name, first admin team, default alert rules) during the platform
features Continue action.

Also update useBackActions to use useExperiment for the SCM context
preservation check, since the hardcoded step ID no longer works when
the step is removed.

Refs VDY-82

Author: jaydgoss

static/app/views/onboarding/onboarding.spec.tsx

@@ -630,7 +630,7 @@ describe('Onboarding', () => {
 
   describe('SCM onboarding flow', () => {
     const scmOrganization = OrganizationFixture({
-      features: ['onboarding-scm-experiment'],
+      features: ['onboarding-scm-experiment', 'onboarding-scm-project-details'],
     });
 
     const githubProvider = GitHubIntegrationProviderFixture({

static/app/views/onboarding/onboarding.tsx

@@ -170,7 +170,15 @@ export function OnboardingWithoutContext() {
     feature: 'onboarding-scm-experiment',
   });
 
-  const onboardingSteps = hasScmOnboarding ? scmOnboardingSteps : legacyOnboardingSteps;
+  const hasProjectDetailsStep = organization.features.includes(
+    'onboarding-scm-project-details'
+  );
+
+  const scmSteps = hasProjectDetailsStep
+    ? scmOnboardingSteps
+    : scmOnboardingSteps.filter(s => s.id !== OnboardingStepId.SCM_PROJECT_DETAILS);
+
+  const onboardingSteps = hasScmOnboarding ? scmSteps : legacyOnboardingSteps;
 
   const stepObj = onboardingSteps.find(({id}) => stepId === id);
   const stepIndex = onboardingSteps.findIndex(({id}) => stepId === id);

static/app/views/onboarding/scmPlatformFeatures.spec.tsx

@@ -10,6 +10,8 @@ import {
   OnboardingContextProvider,
   type OnboardingSessionState,
 } from 'sentry/components/onboarding/onboardingContext';
+import {ProjectsStore} from 'sentry/stores/projectsStore';
+import {TeamStore} from 'sentry/stores/teamStore';
 import * as analytics from 'sentry/utils/analytics';
 import {sessionStorageWrapper} from 'sentry/utils/sessionStorage';
 
@@ -72,6 +74,8 @@ describe('ScmPlatformFeatures', () => {
   beforeEach(() => {
     jest.clearAllMocks();
     sessionStorageWrapper.clear();
+    ProjectsStore.loadInitialData([]);
+    TeamStore.loadInitialData([]);
   });
 
   afterEach(() => {

static/app/views/onboarding/scmPlatformFeatures.tsx

@@ -1,4 +1,5 @@
 import {useCallback, useEffect, useMemo, useState} from 'react';
+import * as Sentry from '@sentry/react';
 import {LayoutGroup, motion} from 'framer-motion';
 import {PlatformIcon} from 'platformicons';
 
@@ -7,6 +8,7 @@ import {Container, Flex, Grid, Stack} from '@sentry/scraps/layout';
 import {Select} from '@sentry/scraps/select';
 import {Heading} from '@sentry/scraps/text';
 
+import {addErrorMessage} from 'sentry/actionCreators/indicator';
 import {closeModal, openConsoleModal, openModal} from 'sentry/actionCreators/modal';
 import {LoadingIndicator} from 'sentry/components/loadingIndicator';
 import {SupportedLanguages} from 'sentry/components/onboarding/frameworkSuggestionModal';
@@ -16,13 +18,17 @@ import {
   getDisabledProducts,
   platformProductAvailability,
 } from 'sentry/components/onboarding/productSelection';
+import {useCreateProject} from 'sentry/components/onboarding/useCreateProject';
 import {platforms} from 'sentry/data/platforms';
 import {t} from 'sentry/locale';
 import type {OnboardingSelectedSDK} from 'sentry/types/onboarding';
+import type {Team} from 'sentry/types/organization';
 import type {PlatformIntegration, PlatformKey} from 'sentry/types/project';
 import {trackAnalytics} from 'sentry/utils/analytics';
 import {isDisabledGamingPlatform} from 'sentry/utils/platform';
 import {useOrganization} from 'sentry/utils/useOrganization';
+import {useProjects} from 'sentry/utils/useProjects';
+import {useTeams} from 'sentry/utils/useTeams';
 import {ScmFeatureSelectionCards} from 'sentry/views/onboarding/components/scmFeatureSelectionCards';
 import {ScmPlatformCard} from 'sentry/views/onboarding/components/scmPlatformCard';
 
@@ -84,8 +90,17 @@ export function ScmPlatformFeatures({onComplete}: StepProps) {
     setSelectedPlatform,
     selectedFeatures,
     setSelectedFeatures,
+    createdProjectSlug,
+    setCreatedProjectSlug,
   } = useOnboardingContext();
 
+  const {teams, fetching: isLoadingTeams} = useTeams();
+  const {projects, initiallyLoaded: projectsLoaded} = useProjects();
+  const createProject = useCreateProject();
+  const hasProjectDetailsStep = organization.features.includes(
+    'onboarding-scm-project-details'
+  );
+
   const [showManualPicker, setShowManualPicker] = useState(false);
 
   useEffect(() => {
@@ -306,14 +321,59 @@ export function ScmPlatformFeatures({onComplete}: StepProps) {
     }
   }
 
-  function handleContinue() {
+  const existingProject = createdProjectSlug
+    ? projects.find(p => p.slug === createdProjectSlug)
+    : undefined;
+
+  async function handleContinue() {
     // Persist derived defaults to context if user accepted them
     if (currentPlatformKey && !selectedPlatform?.key) {
       setPlatform(currentPlatformKey);
     }
     if (!selectedFeatures) {
       setSelectedFeatures(currentFeatures);
     }
+
+    if (!hasProjectDetailsStep) {
+      // Auto-create project with defaults when SCM_PROJECT_DETAILS step is skipped
+      const platform =
+        selectedPlatform ??
+        (currentPlatformKey
+          ? toSelectedSdk(getPlatformInfo(currentPlatformKey)!)
+          : undefined);
+      if (!platform) {
+        return;
+      }
+
+      // If a project was already created for this platform (e.g. the user
+      // went back after the project received its first event), reuse it.
+      // If the platform changed, abandon the old project and create a new
+      // one — matching legacy onboarding behavior.
+      if (existingProject?.platform === platform.key) {
+        onComplete(undefined, {product: currentFeatures});
+        return;
+      }
+
+      const firstAdminTeam = teams.find((team: Team) =>
+        team.access.includes('team:admin')
+      );
+
+      try {
+        const project = await createProject.mutateAsync({
+          name: platform.key,
+          platform,
+          default_rules: true,
+          firstTeamSlug: firstAdminTeam?.slug,
+        });
+        setCreatedProjectSlug(project.slug);
+        onComplete(undefined, {product: currentFeatures});
+      } catch (error) {
+        addErrorMessage(t('Failed to create project'));
+        Sentry.captureException(error);
+      }
+      return;
+    }
+
     onComplete();
   }
 
@@ -459,7 +519,12 @@ export function ScmPlatformFeatures({onComplete}: StepProps) {
                 features: currentFeatures,
               }}
               onClick={handleContinue}
-              disabled={!currentPlatformKey}
+              disabled={
+                !currentPlatformKey ||
+                createProject.isPending ||
+                (!hasProjectDetailsStep && (isLoadingTeams || !projectsLoaded))
+              }
+              busy={createProject.isPending}
             >
               {t('Continue')}
             </Button>

static/app/views/onboarding/useBackActions.tsx

@@ -10,6 +10,7 @@ import {handleXhrErrorResponse} from 'sentry/utils/handleXhrErrorResponse';
 import type {RequestError} from 'sentry/utils/requestError/requestError';
 import {normalizeUrl} from 'sentry/utils/url/normalizeUrl';
 import {useApi} from 'sentry/utils/useApi';
+import {useExperiment} from 'sentry/utils/useExperiment';
 import {useOrganization} from 'sentry/utils/useOrganization';
 import type {StepDescriptor} from 'sentry/views/onboarding/types';
 
@@ -33,6 +34,9 @@ export function useBackActions({
   const api = useApi();
   const organization = useOrganization();
   const onboardingContext = useOnboardingContext();
+  const {inExperiment: hasScmOnboarding} = useExperiment({
+    feature: 'onboarding-scm-experiment',
+  });
   const currentStep = onboardingSteps[stepIndex];
 
   const deleteRecentCreatedProject = useCallback(
@@ -118,21 +122,22 @@ export function useBackActions({
         // store data and skip project creation.
         // In the SCM flow, preserve context so the user keeps their SCM
         // connection, repo selection, and feature choices.
-        await deleteRecentCreatedProject(prevStep.id === 'scm-project-details');
+        await deleteRecentCreatedProject(hasScmOnboarding);
       }
 
       if (!browserBackButton) {
         goToStep(prevStep);
       }
     },
     [
-      goToStep,
+      currentStep,
       organization,
-      onboardingContext,
       isRecentCreatedProjectActive,
       recentCreatedProject,
-      currentStep,
+      onboardingContext,
+      goToStep,
       deleteRecentCreatedProject,
+      hasScmOnboarding,
     ]
   );