@@ -336,6 +336,7 @@ test('source authorization returns to its desktop screen and refreshes live', as
     if (path === '/api/knowledge/slack') {
       json({
         sharedAppAvailable: true,
+        memberAppKind: installed ? 'shared' : null,
         bots: [],
         installations: installed
           ? [
 
@@ -141,10 +141,10 @@ describe('Slack member accounts on the shared app without a Search bot', () => {
       },
     })
 
-  const startSetup = (credentialGroupId: string) =>
+  const startSetup = (credentialGroupId: string, app?: { appId: string; teamId: string }) =>
     startSlackCredentialGroupConfiguration.execute({
       principal: principal(),
-      input: { organizationId: ids.organization, credentialGroupId },
+      input: { organizationId: ids.organization, credentialGroupId, ...app },
     })
 
   const completeSetup = (state: string) =>
@@ -317,7 +317,24 @@ describe('Slack member accounts on the shared app without a Search bot', () => {
     await installBot(CUSTOM_APP_ID, OTHER_TEAM)
     provideSlackConsent(MEMBER_TEAM)
     await expect(completeSetup(pending.searchParams.get('state') ?? '')).rejects.toThrow(
-      'installed during authorization'
+      'installations changed during authorization'
+    )
+    expect(await accountsGroup()).toEqual(before)
+  })
+
+  it('refuses member setup when another bot joins an installed one during authorization', async () => {
+    const groupId = (await approveSlack()).memberAccounts?.groupId
+    if (!groupId) throw new Error('Approval did not provision organization accounts')
+    await installBot(SHARED_APP_ID, MEMBER_TEAM)
+    const pending = new URL(
+      (await startSetup(groupId, { appId: SHARED_APP_ID, teamId: MEMBER_TEAM })).authorizationUrl
+    )
+    expect(pending.searchParams.get('team')).toBe(MEMBER_TEAM)
+    const before = await accountsGroup()
+    await installBot(CUSTOM_APP_ID, OTHER_TEAM)
+    provideSlackConsent(MEMBER_TEAM)
+    await expect(completeSetup(pending.searchParams.get('state') ?? '')).rejects.toThrow(
+      'installations changed during authorization'
     )
     expect(await accountsGroup()).toEqual(before)
   })
@@ -354,7 +371,7 @@ describe('Slack member accounts on the shared app without a Search bot', () => {
       release.resolve()
       await install
     }
-    await expect(completion).rejects.toThrow('installed during authorization')
+    await expect(completion).rejects.toThrow('installations changed during authorization')
     expect(await accountsGroup()).toEqual(before)
   })
 
 
@@ -171,6 +171,7 @@ export const completeSlackCredentialGroupConfiguration: OperationUseCase<
       attempt.appRevision !== pending.appRevision ||
       attempt.searchApproval?.approved !== pending.searchApproval?.approved ||
       attempt.searchApproval?.updatedAt !== pending.searchApproval?.updatedAt ||
+      attempt.installationsRevision !== pending.installationsRevision ||
       attempt.clientId !== pending.clientId ||
       attempt.redirectUri !== pending.redirectUri ||
       credentialGroupScopePolicyVersion(attempt.requiredScopes) !==
 
@@ -13,6 +13,7 @@ import { sha256Hex } from '@sim/security/hash'
 import { getErrorMessage } from '@sim/utils/errors'
 import { generateId } from '@sim/utils/id'
 import { isRecordLike } from '@sim/utils/object'
+import { compareStrings } from '@sim/utils/string'
 import { and, eq, inArray, isNull, or } from 'drizzle-orm'
 import { getRedisClient } from '@/lib/core/config/redis'
 import { resourceScopeFields, resourceScopeFromOwner } from '@/lib/core/resource-scope'
@@ -80,6 +81,8 @@ interface SlackSearchApprovalSnapshot {
 type StoredSlackManagedUsersAttempt = {
   appRevision?: string
   searchApproval?: SlackSearchApprovalSnapshot
+  /** Organization attempts: the Search installations they were authorized against. */
+  installationsRevision?: string
   version: typeof SLACK_MANAGED_USERS_ATTEMPT_VERSION
   workspaceId?: string
   organizationId?: string
@@ -103,6 +106,7 @@ type StoredSlackManagedUsersAttempt = {
 export interface SlackManagedUsersAttempt {
   appRevision?: string
   searchApproval?: SlackSearchApprovalSnapshot
+  installationsRevision?: string
   workspaceId?: string
   organizationId?: string
   userId: string
@@ -183,6 +187,9 @@ function isStoredAttempt(value: unknown): value is StoredSlackManagedUsersAttemp
     typeof candidate.credentialGroupId === 'string' &&
     typeof candidate.credentialGroupUpdatedAt === 'number' &&
     (candidate.appRevision === undefined || typeof candidate.appRevision === 'string') &&
+    (candidate.installationsRevision === undefined ||
+      (typeof candidate.installationsRevision === 'string' &&
+        candidate.organizationId !== undefined)) &&
     (candidate.organizationId !== undefined
       ? isRecordLike(approval) &&
         typeof approval.approved === 'boolean' &&
@@ -487,6 +494,21 @@ export function getSlackManagedUsersRedirectUri(): string {
   return `${getBaseUrl()}${SLACK_MANAGED_USER_CONFIGURATION_CALLBACK_PATH}`
 }
 
+/**
+ * Names an organization's Search installation set. Installing, rebinding, enabling, disabling,
+ * and removing a bot each rotate or drop a row's revision.
+ */
+async function organizationInstallationsRevision(executor: DbOrTx, organizationId: string) {
+  const rows = await executor
+    .select({ id: slackSearchInstallation.id, revision: slackSearchInstallation.revision })
+    .from(slackSearchInstallation)
+    .where(eq(slackSearchInstallation.organizationId, organizationId))
+    .limit(101)
+  return sha256Hex(
+    JSON.stringify(rows.map(({ id, revision }) => `${id}:${revision}`).sort(compareStrings))
+  )
+}
+
 /** An organization app the Search bot installed; its installation fixes the Slack workspace. */
 async function resolveInstalledOrganizationSlackApp(
   organizationId: string,
@@ -599,6 +621,7 @@ export async function createSlackManagedUsersAttempt(params: {
   let clientSecret = params.clientSecret
   let appRevision: string | undefined
   let searchApproval: SlackSearchApprovalSnapshot | undefined
+  let installationsRevision: string | undefined
   if (scope.kind === 'organization') {
     if (
       params.slackBotCredentialId ||
@@ -660,6 +683,7 @@ export async function createSlackManagedUsersAttempt(params: {
     }
     if (searchApproval.approved)
       requiredScopes = [...new Set([...requiredScopes, ...SLACK_SEARCH_USER_SCOPES])]
+    installationsRevision = await organizationInstallationsRevision(db, scope.organizationId)
   } else {
     if (!params.slackBotCredentialId)
       throw new SlackManagedUsersError('Select a custom Slack bot.', 'invalid_response')
@@ -701,6 +725,7 @@ export async function createSlackManagedUsersAttempt(params: {
     clientId,
     ...(appRevision ? { appRevision } : {}),
     ...(searchApproval ? { searchApproval } : {}),
+    ...(installationsRevision ? { installationsRevision } : {}),
     ...(sharedApp && scope.kind === 'organization'
       ? { credentialSource: 'environment' as const, organizationId: scope.organizationId }
       : { encryptedClientSecret: (await encryptSecret(clientSecret)).encrypted }),
@@ -779,6 +804,9 @@ async function parseSlackManagedUsersAttempt(
     clientId: parsed.clientId,
     ...(parsed.appRevision ? { appRevision: parsed.appRevision } : {}),
     ...(parsed.searchApproval ? { searchApproval: parsed.searchApproval } : {}),
+    ...(parsed.installationsRevision
+      ? { installationsRevision: parsed.installationsRevision }
+      : {}),
     clientSecret,
     redirectUri: parsed.redirectUri,
     requiredScopes: parsed.requiredScopes,
@@ -845,8 +873,9 @@ export async function exchangeAndConfigureSlackManagedUsers(params: {
 
   return db.transaction(async (tx) => {
     if (params.attempt.organizationId) {
-      await lockOrganizationSearchApproval(tx, params.attempt.organizationId)
+      /** Taken first so waiting on a bot install never holds the approval lock other writes need. */
       await lockOrganizationSlackApp(tx, params.attempt.organizationId)
+      await lockOrganizationSearchApproval(tx, params.attempt.organizationId)
       const sharedApp = getSharedSlackSearchAppConfiguration(params.attempt.expectedAppId)
       if (sharedApp) await ensureSharedSlackAppRow(tx, sharedApp)
       const [app] = await tx
@@ -930,24 +959,13 @@ export async function exchangeAndConfigureSlackManagedUsers(params: {
           'Search approval changed during authorization. Start again.',
           'invalid_state'
         )
-      /** Bot installs share the Slack organization lock, so one added meanwhile is seen here. */
-      const installations = await tx
-        .select({
-          slackAppId: slackSearchInstallation.slackAppId,
-          teamId: slackSearchInstallation.teamId,
-        })
-        .from(slackSearchInstallation)
-        .where(eq(slackSearchInstallation.organizationId, params.attempt.organizationId))
-        .limit(101)
       if (
-        installations.length > 0 &&
-        !installations.some(
-          (installation) =>
-            installation.slackAppId === grant.appId && installation.teamId === grant.teamId
-        )
+        params.attempt.installationsRevision !== undefined &&
+        (await organizationInstallationsRevision(tx, params.attempt.organizationId)) !==
+          params.attempt.installationsRevision
       )
         throw new SlackManagedUsersError(
-          'A Slack app was installed during authorization. Start again.',
+          'Slack Search installations changed during authorization. Start again.',
           'invalid_state'
         )
     }
 
@@ -86,10 +86,14 @@ export const listSlackSearchInstallations = defineAuthorizedKnowledgeUseCase({
       readSharedSlackSearchApp(context.organizationId),
       loadOrganizationSlackMemberApps(context.organizationId),
     ])
-    const memberAppId = memberApps[0]?.configuration.slack?.appId
+    const memberAppIds = memberApps.flatMap((row) =>
+      row.configuration.slack ? [row.configuration.slack.appId] : []
+    )
+    /** Any custom member app blocks the shared-app path, so it wins over a shared one. */
     let memberAppKind: 'shared' | 'custom' | null = null
-    if (memberAppId)
-      memberAppKind = getSharedSlackSearchAppConfiguration(memberAppId) ? 'shared' : 'custom'
+    if (memberAppIds.some((appId) => !getSharedSlackSearchAppConfiguration(appId)))
+      memberAppKind = 'custom'
+    else if (memberAppIds.length) memberAppKind = 'shared'
     if (installations.length > 100 || bots.length > 100)
       throw new OrchestrationError(
         'validation',