[Bug]: websearch enterprise setting defaults to false and cannot be changed

[Maimikuru]

What happened?

When creating a websearch engine, if the enterprise setting is not explicitly specified, it defaults to false. I believe this is a bug. There is no way for applications to change the enterprise setting.
Expected behavior: Either make the default configurable or provide an API/interface for applications to change this setting.
Reproduction steps: When creating a new websearch engine, the enterprise setting is observed to be fixed to false. Attempts to change it from the application side fail because there is no settings UI.

 /**
 * Google Cloud Discovery Engine - Bug Reproduction Code (Without Enterprise Edition Setting)
 *
 * Issue: When searchTier is not set during engine creation, the engine is created as Standard Edition,
 * but when trying to use Enterprise Edition features (extractiveContentSpec, returnSnippet),
 * an error occurs. However, the behavior when searchTier is not explicitly set during engine creation
 * may be inconsistent.
 */

import { DataStoreServiceClient, EngineServiceClient, protos } from '@google-cloud/discoveryengine'
import { GoogleAuth } from 'google-auth-library'

// Configuration
const PROJECT_ID = 'your-project-id'
const LOCATION = 'global'
const COLLECTION_ID = 'default_collection'
const DATA_STORE_ID = 'test-datastore-bug-reproduction'
const ENGINE_ID = 'test-engine-bug-reproduction'

async function reproduceBug() {
  const auth = new GoogleAuth({
    scopes: 'https://www.googleapis.com/auth/cloud-platform',
  })

  const client = await auth.getClient()
  const credentials = await auth.getCredentials()

  const dataStoreClient = new DataStoreServiceClient({
    credentials: credentials as any,
  })

  const engineClient = new EngineServiceClient({
    credentials: credentials as any,
  })

  const parentCollection = `projects/${PROJECT_ID}/locations/${LOCATION}/collections/${COLLECTION_ID}`
  const parentDataStores = `${parentCollection}/dataStores`
  const dataStoreName = `${parentDataStores}/${DATA_STORE_ID}`
  const engineName = `${parentCollection}/engines/${ENGINE_ID}`

  try {
    // Step 1: Create DataStore
    try {
      const [op] = await dataStoreClient.createDataStore({
        dataStore: {
          contentConfig:
            protos.google.cloud.discoveryengine.v1.DataStore.ContentConfig.PUBLIC_WEBSITE,
          displayName: 'Bug Reproduction DataStore',
          industryVertical: protos.google.cloud.discoveryengine.v1.IndustryVertical.GENERIC,
          solutionTypes: [protos.google.cloud.discoveryengine.v1.SolutionType.SOLUTION_TYPE_SEARCH],
        },
        dataStoreId: DATA_STORE_ID,
        parent: parentCollection,
      })
      await op.promise()
    } catch (error: any) {
      if (error.code !== 6) {
        throw error
      }
    }

    // Step 2: Create Engine without searchTier (should default to Standard Edition)
    try {
      const [op] = await engineClient.createEngine({
        engine: {
          dataStoreIds: [DATA_STORE_ID],
          displayName: 'Bug Reproduction Engine (No Enterprise Setting)',
          // Do not explicitly set searchTier (default should be Standard Edition)
          searchEngineConfig: {},
          solutionType: protos.google.cloud.discoveryengine.v1.SolutionType.SOLUTION_TYPE_SEARCH,
        },
        engineId: ENGINE_ID,
        parent: parentCollection,
      })
      await op.promise()
    } catch (error: any) {
      if (error.code !== 6) {
        throw error
      }
    }

    // Step 3: Verify Engine Configuration
    const [engine] = await engineClient.getEngine({ name: engineName })
    const searchTier = engine.searchEngineConfig?.searchTier
    console.log('Engine searchTier:', searchTier)
    console.log('Expected: SEARCH_TIER_STANDARD (1) or SEARCH_TIER_UNSPECIFIED (0)')

    // Step 4: Execute Search with Enterprise Edition Features
    const token = await client.getAccessToken()

    // Request including Enterprise Edition features
    const searchRequest = {
      contentSearchSpec: {
        extractiveContentSpec: {
          maxExtractiveAnswerCount: 1,
        },
        snippetSpec: {
          returnSnippet: true,
        },
      },
      pageSize: 10,
      query: 'test query',
      queryExpansionSpec: {
        condition: 'AUTO',
      },
      spellCorrectionSpec: {
        mode: 'AUTO',
      },
    }

    const searchUrl = `https://discoveryengine.googleapis.com/v1alpha/projects/${PROJECT_ID}/locations/${LOCATION}/collections/${COLLECTION_ID}/engines/${ENGINE_ID}/servingConfigs/default_search:search`

    const response = await fetch(searchUrl, {
      body: JSON.stringify(searchRequest),
      headers: {
        Authorization: `Bearer ${token.token}`,
        'Content-Type': 'application/json',
      },
      method: 'POST',
    })

    const responseText = await response.text()

    if (response.ok) {
      console.log('\n=== Unexpected Behavior ===')
      console.log(
        'Enterprise Edition features were usable on an engine created as Standard Edition.',
      )
    } else {
      const errorData = JSON.parse(responseText)
      console.log('\n=== Error Occurred ===')
      console.log('Error code:', errorData.error?.code)
      console.log('Error message:', errorData.error?.message)

      if (
        errorData.error?.message?.includes('enterprise edition features') ||
        errorData.error?.message?.includes('standard edition')
      ) {
        console.log('\n=== Bug Confirmed ===')
        console.log('Issue: When searchTier is not set, the engine is created as Standard Edition,')
        console.log('but when trying to use Enterprise Edition features, an error occurs.')
      }
    }
  } catch (error) {
    console.error('Error during bug reproduction:', error)

    throw error
  }
}

// Execute
try {
  await reproduceBug()
} catch (error) {
  console.error('Failed to reproduce bug:', error)
  process.exit(1)
}

Relevant log output

Error: Vertex AI Search: Search API request failed: Vertex AI Search: Search API request failed: HTTP error! status: 400, response: {
[chatbot]   "error": {
[chatbot]     "code": 400,
[chatbot]     "message": "Cannot use enterprise edition features (website search, multi-modal search, extractive answers/segments, etc.) in a standard edition search engine. Please follow https://cloud.google.com/generative-ai-app-builder/docs/enterprise-edition#toggle-enterprise to enable Enterprise edition. Enterprise edition can be only enabled at the engine / app level. If the search request is against a data store, please update the serving config in the search request to use the engine/app ID instead, in the format of: \"projects/*/locations/*/collections/*/engines/*/servingConfigs/*\".",
[chatbot]     "status": "FAILED_PRECONDITION"
[chatbot]   }
[chatbot] }

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